To efficiently link the continuum mechanics for rocks with the structural statistics of rock masses,a theoretical and methodological system called the statistical mechanics of rock masses(SMRM)was developed in the pas...To efficiently link the continuum mechanics for rocks with the structural statistics of rock masses,a theoretical and methodological system called the statistical mechanics of rock masses(SMRM)was developed in the past three decades.In SMRM,equivalent continuum models of stressestrain relationship,strength and failure probability for jointed rock masses were established,which were based on the geometric probability models characterising the rock mass structure.This follows the statistical physics,the continuum mechanics,the fracture mechanics and the weakest link hypothesis.A general constitutive model and complete stressestrain models under compressive and shear conditions were also developed as the derivatives of the SMRM theory.An SMRM calculation system was then developed to provide fast and precise solutions for parameter estimations of rock masses,such as full-direction rock quality designation(RQD),elastic modulus,Coulomb compressive strength,rock mass quality rating,and Poisson’s ratio and shear strength.The constitutive equations involved in SMRM were integrated into a FLAC3D based numerical module to apply for engineering rock masses.It is also capable of analysing the complete deformation of rock masses and active reinforcement of engineering rock masses.Examples of engineering applications of SMRM were presented,including a rock mass at QBT hydropower station in northwestern China,a dam slope of Zongo II hydropower station in D.R.Congo,an open-pit mine in Dexing,China,an underground powerhouse of Jinping I hydropower station in southwestern China,and a typical circular tunnel in Lanzhou-Chongqing railway,China.These applications verified the reliability of the SMRM and demonstrated its applicability to broad engineering issues associated with jointed rock masses.展开更多
Clayey soils in Syria cover a total area of more than 20,000 km2 of the country,most of which are located in the southwestern region.In many places of the country,the clayey soils caused severe damage to infrastructur...Clayey soils in Syria cover a total area of more than 20,000 km2 of the country,most of which are located in the southwestern region.In many places of the country,the clayey soils caused severe damage to infrastructures.Extensive studies have been carried out on the stabilization of clayey soils using lime.Syria is rich in both lime and natural pozzolana.However,few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils.The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils.Natural pozzolana and lime are added to soil within the range of 0%–20%and 0%–8%,respectively.Consistency,compaction,California bearing ratio(CBR)and linear shrinkage properties are particularly investigated.The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent.Analysis results of scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDX)show significant changes in the microstructure of the treated clayey soil.A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed.展开更多
Lime concrete and lime treatment are two attractive techniques for geotechnical engineers.However,researches have rarely been carried out to study the effects of moisture and capillary action due to increasing groundw...Lime concrete and lime treatment are two attractive techniques for geotechnical engineers.However,researches have rarely been carried out to study the effects of moisture and capillary action due to increasing groundwater level on geotechnical properties of lime concrete.The aim of this study is to investigate the effects of curing time and degree of saturation on some of geotechnical properties of lime concrete such as unconfined compressive strength(UCS),secant modulus(ES),failure strain,brittleness index(IB),and deformability index(ID) using unconfined compression tests.First of all,geotechnical and chemical properties of used materials were determined.After curing times of 14 d,28 d,45 d,and 60 d in laboratory condition,the specimens were exposed to saturation levels ranging from 0 to 100%.The results showed that the moisture and curing time have significant effects on the properties of lime concrete.Based on the results of scanning electron micrograph(SEM) test,it was observed that the specimen was characterized by a rather well-structured matrix since both the filling of a large proportion of the coarse-grained soil voids by clay and the pozzolanic activity of lime led to retaining less pore water in the specimen,increasing the UCS and ES,and consequently resisting against swelling and shrinkage of the clay soil.Moreover,due to the pozzolanic reactions and reduction of water,by increasing the curing time and decreasing the degrees of saturation,UCS,ES,and IBincreased,and IDdecreased.Based on the experimental results,a phenomenological model was used to develop equations for predicting the properties in relation to the ratio of degree of saturation/curing time.The results showed that there was a good correlation(almost R2> 90%) between the measured parameters and the estimated ones given by the predicted equations.展开更多
In recent years, there are growing demands of representing rock mechanics and rock engineering in a digital format that can be easily managed, manipulated, analyzed and shared. The objective of this paper is to give a...In recent years, there are growing demands of representing rock mechanics and rock engineering in a digital format that can be easily managed, manipulated, analyzed and shared. The objective of this paper is to give a comprehensive review of the status quo and future trends of digitization in rock mechanics and rock engineering. Research topics essential to the process of digitization are firstly discussed, including data acquisition, data standardization, geological modeling, visualization and digital-numerical integration. New techniques that will play an important role in digitization process but require further improvement are then briefly proposed. Finally, achievements of present methods and techniques for digitization in substantial rock mechanics and rock engineering are presented.展开更多
This paper explores the 12 aspects of geo-environment and construction engineering, including the earth evolution, the structure of geological bodies, the comprehensive utilization of resources, the geo-environmental ...This paper explores the 12 aspects of geo-environment and construction engineering, including the earth evolution, the structure of geological bodies, the comprehensive utilization of resources, the geo-environmental effect, the engineering construction, the sustainable development and, etc. This paper presents that the good environment could only be created through the conservation and efficient utilization of resources, the joint efforts of disaster prevention and mitigation, as well as the avoidance of adverse environmental effect caused by human activities. This paper concludes that, to build a scientific and ecological earth, the development laws of geo-science must be learnt.展开更多
Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,an...Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,and defects behind the structure.To address the need for rapid detection of different defect types,the current state of rapid detection technologies and equipment,both domestically and internationally,is systematically reviewed.The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years.Notably,the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy,achieving crack detection precision of up to 0.1 mm.However,the non-contact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations,with traditional detection remaining dominant.Nevertheless,phased array radar,ultrasonic,and acoustic vibration detection technologies have become research hotspots in recent years,offering promising directions for detecting these challenging defect types.Additionally,the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities.Devices such as cameras,3D laser scanners,infrared thermal imagers,and radar demonstrate significant advantages in rapid detection.Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects.Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures.Furthermore,progress in fully automated,intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.展开更多
Microbial geoengineering technology,as a new eco-friendly rock and soil improvement and reinforcement technology,has a wide application prospect.However,this technology still has many deficiencies and is difficult to ...Microbial geoengineering technology,as a new eco-friendly rock and soil improvement and reinforcement technology,has a wide application prospect.However,this technology still has many deficiencies and is difficult to achieve efficient curing,which has become the bottleneck of large-scale field application.This paper reviews the research status,hot spots,difficulties and future development direction microbial induced calcium carbonate precipitation(MICP)technology.The principle of solidification and the physical and mechanical properties of improved rock and soil are systematically summarized.The solidification efficiency is mainly affected by the reactant itself and the external environment.At present,the MICP technology has been preliminarily applied in the fields of soil solidification,crack repair,anti-seepage treatment,pollution repair and microbial cement.However,the technology is currently mainly limited to the laboratory level due to the difficulty of homogeneous mineralization,uneconomical reactants,short microbial activity period and large environmental interference,incidental toxicity of metabolites and poor field application.Future directions include improving the uniformity of mineralization by improving grouting methods,improving urease persistence by improving urease activity,and improving the adaptability of bacteria to the environment by optimizing bacterial species.Finally,the authors point out the economic advantages of combining soybean peptone,soybean meal and cottonseed as carbon source with phosphogypsum as calcium source to induce CaCO3.展开更多
This study investigates the mechanical response of an underground cavern subjected to cyclic high gas pressure,aiming to establish a theoretical foundation for the design of lined rock caverns(LRCs)for energy storage ...This study investigates the mechanical response of an underground cavern subjected to cyclic high gas pressure,aiming to establish a theoretical foundation for the design of lined rock caverns(LRCs)for energy storage with high internal pressure,e.g.compressed air energy storage(CAES)underground caverns or hydrogen storage caverns.Initially,the stress paths of the surrounding rock during the excavation,pressurization,and depressurization processes are delineated.Analytical expressions for the stress and deformation of the surrounding rock are derived based on the MohreCoulomb criterion.These expressions are then employed to evaluate the displacement of cavern walls under varying qualities of surrounding rock,the contact pressure between the steel lining and the surrounding rock subject to different gas storage pressures,the load-bearing ratio of the surrounding rock,and the impact of lining thickness on the critical gas pressure.Furthermore,the deformation paths of the surrounding rock are evaluated,along with the effects of tunnel depth and diameter on residual deformation of the surrounding rock,and the critical minimum gas pressure at which the surrounding rock and the lining do not detach.The results indicate that residual deformation of the surrounding rock occurs after depressurization under higher internal pressure for higher-quality rock masses,leading to detachment between the surrounding rock and the steel lining.The findings indicate that thicker linings correspond to higher critical minimum gas pressures.However,for lower-quality surrounding rock,thicker linings correspond to lower critical minimum gas pressures.These findings will provide invaluable insights for the design of LRCs for underground energy storage caverns.展开更多
A glacier hazard chain can form a long-runout mass flow and generate a large flood,affecting downstream areas hundreds of kilometers away from the initiating hazard site.This study focuses on the Yarlung Zangbo Daxiag...A glacier hazard chain can form a long-runout mass flow and generate a large flood,affecting downstream areas hundreds of kilometers away from the initiating hazard site.This study focuses on the Yarlung Zangbo Daxiagu.The objective is to address two key unresolved issues:the evolution of detached glacier materials into debris flows or debris floods and the amplification of the impact range and threats.A comprehensive framework is developed that considers the impacts of near-field and far-field hazards.Numerical modeling,remote sensing,and field investigations were integrated to understand the interactions,transformations,and amplifications of hazards in the glacier hazard chain.The results indicate that extensive,nearly saturated sediments on the glacier valley floor,when entrained,amplify the magnitude of the mass flow.The topography plays a crucial role.When the valley outlet is perpendicular to the river course,topographic obstacles cause immediate halting,resulting in the formation of high barrier dams.Conversely,when the glacier valley aligns nearly parallel to the river course,the mass flow can travel a much longer distance upon entering the river,causing an enlarged affected area.The barrier dams can breach rapidly,causing breaching floods that amplify the downstream impact from several kilometers to hundreds of kilometers.Our analysis reveals that the overall impacts remain spatially limited.Specifically,downstream areas along the Yarlung Zangbo-Brahmaputra River are unlikely to face greater threats from the upstream floods than local monsoon floods.Our findings provide the foundation for the management of glacier hazard chains.展开更多
This article proposes Styrene-Butadiene Rubber(SBR)and Chem-lite CR Powder(CCP)as a sustainable solution for dispersive clays,which cause infrastructure damage due to high sodium ions.Traditionally utilized stabilizer...This article proposes Styrene-Butadiene Rubber(SBR)and Chem-lite CR Powder(CCP)as a sustainable solution for dispersive clays,which cause infrastructure damage due to high sodium ions.Traditionally utilized stabilizers like lime/cement raise environmental concerns due to their high carbon footprints.Regarding this,SBR/CCP has been used in concrete technology for several functions;nevertheless,its effectiveness for stabilizing dispersive clay remains uncertain.Therefore,this study investigated how SBR/CCP improved sodium-rich dispersive soil's dispersion,index,mechanical characteristics,and associated mechanism.Multiple tests,including double hydrometer,cation analysis,compression strength(UCS),physio-chemical,Atterberg's limits,California Bearing Ratio(CBR),X-Ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive X-Ray spectroscopy(EDS)were performed at different mixing ratios up to curing of 60-d.The results showed a significant reduction in dispersion(61.7%),sodium(38%),and plasticity(50.4%)with an optimal 1.5%SBR-3%CCP mix after 28-d,converting the clay to a non-dispersive type.UCS and soaked CBR improved by 283%and 579%,respectively.Micro analyses revealed soil enhancement through CCP's flocculation,ion exchange,and pozzolanic reactions,while SBR-coated particles and filled pores formed reticulated membrane systems.SBR/CCP offers a sustainable/eco-friendly alternative for stabilizing dispersive clays with a lower carbon footprint.展开更多
In the deep geological disposal repository of high-level radioactive waste,buffer/backfill materials typically consist of compacted bentonite block and granular bentonite.As these materials undergo a long-term hydrati...In the deep geological disposal repository of high-level radioactive waste,buffer/backfill materials typically consist of compacted bentonite block and granular bentonite.As these materials undergo a long-term hydration,it is anticipated that the two forms of bentonite materials(i.e.compacted bentonite powder(CBP)and granular bentonite(GB))are expected to exhibit differing hydro-mechanical behaviors due to the differences in their structures.This work aims to investigate the differences in swelling pressure and compressibility through a series of swelling pressure tests,compression tests and mercury intrusion porosimetry(MIP)tests.The experimental results demonstrated that swelling pressure curves of the CBP specimens showed higher first peak values and more pronounced collapse than those of the GB specimens at a given dry density,regardless of vapor-water hydration or liquid-water hydration.The final swelling pressures of the two materials were similar at the same dry density,suggesting an independent correlation between swelling pressure and dry density.At the high suction range,the compression curves exhibited an obvious bi-linear pattern for the CBP specimens and a significant nonlinearity for the GB specimens.Meanwhile,the CBP specimens presented higher pre-consolidation pressures and larger compression indices than the GB specimens at a given suction.As suction decreased,the compression curves of the two materials gradually approached each other and their differences were reduced accordingly.After reaching saturation,a good consistency between them was observed whether for final swelling pressure or compressibility.Pore structure analysis revealed that the two materials both presented an initially double structure,and their differences were primarily manifested at the macrostructural level.Eventually,the differences in swelling pressure or compression curves of the two materials were well interpreted by combining microstructural evolutions.展开更多
Currently,there is a lack of research on the impact of excavation damage on the stability of underground compressed air energy storage(CAES)chambers.This study presents a comprehensive analytical framework for evaluat...Currently,there is a lack of research on the impact of excavation damage on the stability of underground compressed air energy storage(CAES)chambers.This study presents a comprehensive analytical framework for evaluating the elastic and elastoplastic stress fields in CAES chambers surrounding rock,incorporating excavation-induced centripetal reduction of rock stiffness and strength.A proposed model introduces exponential reduction functions for the deformation modulus and cohesion within the excavation disturbed zone(EDZ),deriving analytical solutions for both elastic and elastoplastic stress distributions.A case study of a practical engineering project validates the theoretical formulations through comparative analysis with numerical simulations,demonstrating strong consistency in stress field predictions.The main findings indicate that the EDZ causes a significant non-monotonic variation in the elastic hoop stress distribution.While it does not significantly affect the range of the plastic zone,it reduces the permeability and bearing capacity of the surrounding rock,highlighting the necessity of integrating the centripetal reduction of mechanical properties and strictly controlling excavation-induced damage in the design practice.Furthermore,this study provides a new approach for the selection of lining materials and structural design for CAES chambers:the radial stiffness smoothly increases to match the EDZ surrounding rock stiffness,and the cohesion exceeds that of the surrounding rock,which can significantly optimize the overall system's stress distribution.This study provides valuable insights and references for the selection of excavation methods,stability assessment,and support structure design for CAES engineering,and holds significant importance for improving the CAES technology system.展开更多
The increasing atmospheric CO_(2)concentration linked to human activity results in global warming by the greenhouse effect.This anthropogenic CO_(2)may be sequestrated into geological formations,e.g.,porous basalts,sa...The increasing atmospheric CO_(2)concentration linked to human activity results in global warming by the greenhouse effect.This anthropogenic CO_(2)may be sequestrated into geological formations,e.g.,porous basalts,saline aquifers,depleted oil or gas reservoirs,and unmineable coal seams.Furthermore,carbon capture,utilization,and storage(CCUS)methods are an acceptable and sustainable technology to meet the goals of the Paris Agreement,in which Kazakhstan is expected to reduce greenhouse gas emissions by 25%compared with the 1990 level.Unmineable coal seams are an attractive option among all geostorage solutions,as CO_(2)sequestration in coal comes with an income stream via enhanced coalbed methane(ECBM)recovery.This paper identifies four carboniferous coal formations,namely Karagandy,Teniz-Korzhinkol,Ekibustuz,and Chu coal basins of Kazakhstan,as CO_(2)geostorage solutions for their unmineable coal seams.The ideal depth of CO_(2)storage is identified as 800 m to ensure the supercritical state of CO_(2).However,the Ekibustuz coal basin fails to meet the required depth of 800 m in its unmineable coal seams.The conventional formula for calculating CO_(2)storage in coal basins has been modified,and a new formula has been proposed for assessing the CO_(2)storage potential in a coal seam.The CO_(2)storage capacities of unmineable coal seam of these coal basins are 24.60 Bt,0.61 Bt,14.02 Bt,and 5.42 Bt,respectively.The Langmuir volume of the coal fields was calculated using the proximate analysis of coalfields and found to vary between 36.42 and 98.90 m3/ton.This paper is the first to outline CO_(2)storage potential in Kazakhstani coal basins,albeit with limited data,along with a detailed geological and paleographic review of the carboniferous coalfields of Kazakhstan.A short overview of the CO_(2)-ECBM process was also included in the paper.Instead of any experimental work for CO_(2)storage,this paper attempts to present the CO_(2)storage capacity of carboniferous coal formation using the modified version of previously determined formulas for CO_(2)storage.展开更多
Shield attitudes,essentially governed by intricate mechanisms,impact the segment assembly quality and tunnel axis deviation.In data-driven prediction,however,existing methods using the original driving parameters fail...Shield attitudes,essentially governed by intricate mechanisms,impact the segment assembly quality and tunnel axis deviation.In data-driven prediction,however,existing methods using the original driving parameters fail to present convincing performance due to insufficient consideration of complicated interactions among the parameters.Therefore,a multi-dimensional feature synthesizing and screening method is proposed to explore the optimal features that can better reflect the physical mechanism in predicting shield tunneling attitudes.Features embedded with physical knowledge were synthesized from seven dimensions,which were validated by the clustering quality of Shapley Additive Explanations(SHAP)values.Subsequently,a novel index,Expected Impact Index(EII),has been proposed for screening the optimal features reliably.Finally,a Bayesian-optimized deep learning model was established to validate the proposed method in a case study.Results show that the proposed method effectively identifies the optimal parameters for shield attitude prediction,with an average Mean Squared Error(MSE)deduction of 27.3%.The proposed method realized effective assimilation of shield driving data with physical mechanism,providing a valuable reference for shield deviation control.展开更多
Shallow-buried thick sand strata present considerable local instability risks during diaphragm wall trenching construction.However,this critical issue has not been extensively studied,despite its serious safety conseq...Shallow-buried thick sand strata present considerable local instability risks during diaphragm wall trenching construction.However,this critical issue has not been extensively studied,despite its serious safety consequences.This paper proposes an automatic identification model for shallow-buried thick sand strata,integrating three-dimensional limit equilibrium theory with a genetic algorithm to precisely identify the most potentially dangerous local instability mass and determine its minimum safety factor.The model establishes three undetermined parameters:failure angle,upper boundary,and thickness of the local instability mass.These parameters define the search space for the local instability mass.The effectiveness of this approach was confirmed through a diaphragm wall engineering case near the Rhine River in France,where the predicted instability location closely aligned with field observations.A systematic analysis of the model indicated that the difference in slurry-groundwater levels and the friction angle are the most significant factors affecting local instability in shallow-buried thick sand strata.The model indicated that the location of the most potentially dangerous instability mass changes depending on geological conditions,and larger instability masses do not always relate to lower safety factors.Additionally,exploratory experiments revealed that support pressure losses caused by slurry infiltration significantly influence local instability calculations in sand strata.This points out the importance of considering these support pressure losses in the stability evaluations of high permeable sand strata.The results improve the evaluation of safety and the optimization of design for diaphragm wall construction in shallow-buried thick sand strata.展开更多
Reliability analysis of soil slopes under rainfall is an important task for landslide risk assessment.Previous studies rarely contribute to the probabilistic analysis of slope stability under rainfall with reinforceme...Reliability analysis of soil slopes under rainfall is an important task for landslide risk assessment.Previous studies rarely contribute to the probabilistic analysis of slope stability under rainfall with reinforcement.A new method is suggested for reliability analysis of soil slopes stabilized with piles under rainfall.First,an efficient numerical model is exploited for slope stability analysis,where two types of slope failure modes,i.e.,plastic flow and local failure are considered.To address the blocking effect of piles during seepage analysis,the equivalent hydraulic conductivity of the pile area is estimated according to the effective medium theory.The stabilizing force of piles is investigated by an analytical approach.For saving computational effort,the response surface is established based on a multi-class classification model to predict two types of slope failure modes.Finally,uncertainties in soil parameters and rainfall events are both modelled,and the failure probability of soil slopes within a given time period is assessed through Monte Carlo simulation.An illustrative example is used to demonstrate the performance of the suggested method.It is found that the slope is mainly controlled by local failure.As the pile spacing increases,the likelihood of plastic flow significantly increases.As the piles are located near the slope crest,plastic flow is effectively prevented and the slope is better stabilized against rainfall.If rainfall uncertainties are not considered,the slope failure probability is significantly overestimated.Overall,this study can provide a useful guidance for the design of pile-stabilized slopes against rainfall infiltration.展开更多
Tunnel face ground loss(TFGL)emerging in shield tunnelling can trigger ground movement and impose threats to surrounding structures.However,the impact of cutterhead vibration on TFGL in sandy soils with varying degree...Tunnel face ground loss(TFGL)emerging in shield tunnelling can trigger ground movement and impose threats to surrounding structures.However,the impact of cutterhead vibration on TFGL in sandy soils with varying degrees of saturation has been largely unexplored.To fill this gap,an innovative numerical model based on computational fluid dynamics-discrete element method(CFD-DEM)and adhesive rolling resistance linear contact algorithm is established for the simulation of TFGL.Meanwhile,algorithms are proposed to account for the effects of cutterhead vibration and support pressure.Results from the validated model reveal that the TFGL can be exacerbated by seepage and opening enlargement,but mitigated by apparent cohesion.The cutterhead vibration can merely exacerbate the relatively small TFGL,which implies the unjamming effect of the particle at the opening.The balanced support pressure(BSP)required for TFGL prevention rises remarkably with the increases in opening ratio,vibration amplitude,and frequency.The maximum BSP in unsaturated sandy ground reaches up to 0.18γD,which is significantly less than that of 1.62γD observed in saturated sandy ground.The tangential and radial intervals with the largest TFGL are located within the ranges of 82.5°-97.5°,and 0.3D≤r_(loss)≤0.45D,respectively.The increase in support pressure can alter the time-dependent development of TFGL from linear to stepwise,leading to convergence.The support pressure required for convergence is increased by cutterhead vibration and seepage,but decreased by apparent cohesion.Lastly,the prospects of the numerical study on TFGL under cutterhead vibration are also discussed.展开更多
Deep geological repository is typically situated at depths ranging from several hundred to 1000 m below ground,making bentonite engineered barrier potentially vulnerable to high water pressure and even inducing hydrau...Deep geological repository is typically situated at depths ranging from several hundred to 1000 m below ground,making bentonite engineered barrier potentially vulnerable to high water pressure and even inducing hydraulic fracturing.This study conducted injection tests on compacted GMZ(Gaomiaozi)bentonite with a self-developed visualization set-up.The objective was to unveil the roles of dry density,water content,and pressurization rate in hydraulic fracturing from the perspective of fracturing macromorphological dynamics and breakthrough characteristics.Moreover,the relationships between breakthrough characteristics and microstructure were examined by MIP(mercury intrusion porosimetry)analysis.Results showed that the fracturing dynamics were characterized by three stages:hydration,cracking,and fracturing stages.Compared to water content and pressurization rate,dry density exerted more pronounced effects on these stages.Increasing dry density can lead to an expansion of circular hydration zone,a more complex cracking network,and a change in fracturing patterns from long and clear to short and fuzzy.In terms of breakthrough characteristics,the breakthrough pressure was positively correlated with dry density and negatively correlated with water content.Interestingly,there is a good and unique logarithmic correlation between the breakthrough pressure and the ratio eM/em of inter-aggregate void ratio and intra-aggregate void ratio,regardless of dry density and water content.Within a certain range(i.e.200-50 kPa/min),breakthrough pressure showed slight dependency on pressurization rate.Nevertheless,an extremely low pressurization rate of 20 kPa/min caused a transition for the specimen from quasi-brittle to plastic state owning to more water infiltration,thereby hindering fracture initiation and propagation.展开更多
Calcareous sands are widely distributed on the coral reefs,continental shelf,and seashores between 30north and south latitude and are commonly utilized as filling materials for the construction of artificial islands a...Calcareous sands are widely distributed on the coral reefs,continental shelf,and seashores between 30north and south latitude and are commonly utilized as filling materials for the construction of artificial islands and infrastructure foundations.In this study,calcareous sands were cemented by enzymatically induced carbonate precipitation(EICP)technique.Drained triaxial tests were conducted on the EICPtreated calcareous sands.Results showed that the specimens with different cementation levels exhibited different responses in mechanical behavior.The differences in the sand fabric after consolidation under a relatively high confining pressure resulted in the untreated specimen exhibiting a higher peak strength compared to the lightly cemented specimen.High confining pressures exhibited a strongly inhibiting effect on dilatancy,which could be counteracted by increasing the cementation level.The EICP-treated specimen could have one or two yield points(smaller-strain and larger-strain yields).For lightly cemented specimens,the smaller-strain yield stress decreased under high confining pressures due to the partial carbonate bonding degradation during consolidation.The stress line of untreated particle breakage(UPB)was a critical boundary to distinguish failure mode in the p′-q space.For the EICP-treated specimens,the yield stress located above or below the UPB stress line indicates the simultaneous or sequential breakage of the carbonate bonds and sand particles,respectively.Accordingly,the EICPtreated specimen exhibited brittle or ductile properties.Failure mode transformation could be triggered by increasing cementation level or confining pressure.展开更多
Geotechnical engineering usually produces drillholes in the ground for investigation and construction.Drilling is a rock-breaking process by applying normal(thrust)and shear(torque)force from the drill bit to the rock...Geotechnical engineering usually produces drillholes in the ground for investigation and construction.Drilling is a rock-breaking process by applying normal(thrust)and shear(torque)force from the drill bit to the rock below the bit.These rock-breaking data can be obtained by digital monitoring and recording the drilling parameters through an instrumented drilling machine.However,there is no mature and standard method to determine rock strength properties(such as unconfined compressive strength,UCS,or tensile strength)from real-time monitored drilling parameter(such as thrust force,torque,rotation speed,drilling speed and specific energy).This paper presents a complete procedure to accurately determine each drilling parameter.More importantly,the specific energy develops nonlinearly with change of the thrust force,which is related to the UCS and tensile strength of the rock.This finding provides an insight into determining the UCS and tensile strength of the rock based on real-time monitored drilling parameters.In addition,novel test setups are demonstrated to determine the thrust force and torque from hydraulics pressures and rotation speeds.These setups can significantly reduce the sophisticated instrumentation cost for drilling monitoring studies.Three type rocks including granite,limestone and sandstone are used for the testing.The findings from this study provide supporting theories to upgrade drilling monitoring technique to a standard geotechnical testing method.展开更多
基金The authors are grateful to the financial support from the National Natural Science Foundation of China(Grant No.41831290)the Key R&D Project from Zhejiang Province,China(Grant No.2020C03092).
文摘To efficiently link the continuum mechanics for rocks with the structural statistics of rock masses,a theoretical and methodological system called the statistical mechanics of rock masses(SMRM)was developed in the past three decades.In SMRM,equivalent continuum models of stressestrain relationship,strength and failure probability for jointed rock masses were established,which were based on the geometric probability models characterising the rock mass structure.This follows the statistical physics,the continuum mechanics,the fracture mechanics and the weakest link hypothesis.A general constitutive model and complete stressestrain models under compressive and shear conditions were also developed as the derivatives of the SMRM theory.An SMRM calculation system was then developed to provide fast and precise solutions for parameter estimations of rock masses,such as full-direction rock quality designation(RQD),elastic modulus,Coulomb compressive strength,rock mass quality rating,and Poisson’s ratio and shear strength.The constitutive equations involved in SMRM were integrated into a FLAC3D based numerical module to apply for engineering rock masses.It is also capable of analysing the complete deformation of rock masses and active reinforcement of engineering rock masses.Examples of engineering applications of SMRM were presented,including a rock mass at QBT hydropower station in northwestern China,a dam slope of Zongo II hydropower station in D.R.Congo,an open-pit mine in Dexing,China,an underground powerhouse of Jinping I hydropower station in southwestern China,and a typical circular tunnel in Lanzhou-Chongqing railway,China.These applications verified the reliability of the SMRM and demonstrated its applicability to broad engineering issues associated with jointed rock masses.
基金financial support of this research from Damascus University
文摘Clayey soils in Syria cover a total area of more than 20,000 km2 of the country,most of which are located in the southwestern region.In many places of the country,the clayey soils caused severe damage to infrastructures.Extensive studies have been carried out on the stabilization of clayey soils using lime.Syria is rich in both lime and natural pozzolana.However,few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils.The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils.Natural pozzolana and lime are added to soil within the range of 0%–20%and 0%–8%,respectively.Consistency,compaction,California bearing ratio(CBR)and linear shrinkage properties are particularly investigated.The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent.Analysis results of scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDX)show significant changes in the microstructure of the treated clayey soil.A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed.
基金supported by the laboratory of soil mechanics of Abadgaran Negin Jonoobshargh Company
文摘Lime concrete and lime treatment are two attractive techniques for geotechnical engineers.However,researches have rarely been carried out to study the effects of moisture and capillary action due to increasing groundwater level on geotechnical properties of lime concrete.The aim of this study is to investigate the effects of curing time and degree of saturation on some of geotechnical properties of lime concrete such as unconfined compressive strength(UCS),secant modulus(ES),failure strain,brittleness index(IB),and deformability index(ID) using unconfined compression tests.First of all,geotechnical and chemical properties of used materials were determined.After curing times of 14 d,28 d,45 d,and 60 d in laboratory condition,the specimens were exposed to saturation levels ranging from 0 to 100%.The results showed that the moisture and curing time have significant effects on the properties of lime concrete.Based on the results of scanning electron micrograph(SEM) test,it was observed that the specimen was characterized by a rather well-structured matrix since both the filling of a large proportion of the coarse-grained soil voids by clay and the pozzolanic activity of lime led to retaining less pore water in the specimen,increasing the UCS and ES,and consequently resisting against swelling and shrinkage of the clay soil.Moreover,due to the pozzolanic reactions and reduction of water,by increasing the curing time and decreasing the degrees of saturation,UCS,ES,and IBincreased,and IDdecreased.Based on the experimental results,a phenomenological model was used to develop equations for predicting the properties in relation to the ratio of degree of saturation/curing time.The results showed that there was a good correlation(almost R2> 90%) between the measured parameters and the estimated ones given by the predicted equations.
文摘In recent years, there are growing demands of representing rock mechanics and rock engineering in a digital format that can be easily managed, manipulated, analyzed and shared. The objective of this paper is to give a comprehensive review of the status quo and future trends of digitization in rock mechanics and rock engineering. Research topics essential to the process of digitization are firstly discussed, including data acquisition, data standardization, geological modeling, visualization and digital-numerical integration. New techniques that will play an important role in digitization process but require further improvement are then briefly proposed. Finally, achievements of present methods and techniques for digitization in substantial rock mechanics and rock engineering are presented.
文摘This paper explores the 12 aspects of geo-environment and construction engineering, including the earth evolution, the structure of geological bodies, the comprehensive utilization of resources, the geo-environmental effect, the engineering construction, the sustainable development and, etc. This paper presents that the good environment could only be created through the conservation and efficient utilization of resources, the joint efforts of disaster prevention and mitigation, as well as the avoidance of adverse environmental effect caused by human activities. This paper concludes that, to build a scientific and ecological earth, the development laws of geo-science must be learnt.
文摘Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,and defects behind the structure.To address the need for rapid detection of different defect types,the current state of rapid detection technologies and equipment,both domestically and internationally,is systematically reviewed.The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years.Notably,the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy,achieving crack detection precision of up to 0.1 mm.However,the non-contact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations,with traditional detection remaining dominant.Nevertheless,phased array radar,ultrasonic,and acoustic vibration detection technologies have become research hotspots in recent years,offering promising directions for detecting these challenging defect types.Additionally,the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities.Devices such as cameras,3D laser scanners,infrared thermal imagers,and radar demonstrate significant advantages in rapid detection.Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects.Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures.Furthermore,progress in fully automated,intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.
基金This work was financed by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0904)the Key Research and Development Plan of Yunnan Province(Grant No.202103AA080013).
文摘Microbial geoengineering technology,as a new eco-friendly rock and soil improvement and reinforcement technology,has a wide application prospect.However,this technology still has many deficiencies and is difficult to achieve efficient curing,which has become the bottleneck of large-scale field application.This paper reviews the research status,hot spots,difficulties and future development direction microbial induced calcium carbonate precipitation(MICP)technology.The principle of solidification and the physical and mechanical properties of improved rock and soil are systematically summarized.The solidification efficiency is mainly affected by the reactant itself and the external environment.At present,the MICP technology has been preliminarily applied in the fields of soil solidification,crack repair,anti-seepage treatment,pollution repair and microbial cement.However,the technology is currently mainly limited to the laboratory level due to the difficulty of homogeneous mineralization,uneconomical reactants,short microbial activity period and large environmental interference,incidental toxicity of metabolites and poor field application.Future directions include improving the uniformity of mineralization by improving grouting methods,improving urease persistence by improving urease activity,and improving the adaptability of bacteria to the environment by optimizing bacterial species.Finally,the authors point out the economic advantages of combining soybean peptone,soybean meal and cottonseed as carbon source with phosphogypsum as calcium source to induce CaCO3.
基金supported by the State Key Laboratory of Disaster Reduction in Civil Engineering(Grant No.SLDRCE23-02)Ningbo PublicWelfare Fund Project(Grant No.2023S100)the National Key Research and Development Program of China(Grant No.2024YFE0105800).
文摘This study investigates the mechanical response of an underground cavern subjected to cyclic high gas pressure,aiming to establish a theoretical foundation for the design of lined rock caverns(LRCs)for energy storage with high internal pressure,e.g.compressed air energy storage(CAES)underground caverns or hydrogen storage caverns.Initially,the stress paths of the surrounding rock during the excavation,pressurization,and depressurization processes are delineated.Analytical expressions for the stress and deformation of the surrounding rock are derived based on the MohreCoulomb criterion.These expressions are then employed to evaluate the displacement of cavern walls under varying qualities of surrounding rock,the contact pressure between the steel lining and the surrounding rock subject to different gas storage pressures,the load-bearing ratio of the surrounding rock,and the impact of lining thickness on the critical gas pressure.Furthermore,the deformation paths of the surrounding rock are evaluated,along with the effects of tunnel depth and diameter on residual deformation of the surrounding rock,and the critical minimum gas pressure at which the surrounding rock and the lining do not detach.The results indicate that residual deformation of the surrounding rock occurs after depressurization under higher internal pressure for higher-quality rock masses,leading to detachment between the surrounding rock and the steel lining.The findings indicate that thicker linings correspond to higher critical minimum gas pressures.However,for lower-quality surrounding rock,thicker linings correspond to lower critical minimum gas pressures.These findings will provide invaluable insights for the design of LRCs for underground energy storage caverns.
基金support from the National Natural Science Foundation of China(U20A20112,42061160480,42377196,and 52479095)the NSFC/RGC Joint Research Scheme(42061160480 and N_HKUST620/20)+1 种基金the Research Grants Council of the Hong Kong SAR Government(16203720,T22-606/23-R,and JRFS25266S09)the Project of Hetao Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone(HZQB-KCZYB-2020083)。
文摘A glacier hazard chain can form a long-runout mass flow and generate a large flood,affecting downstream areas hundreds of kilometers away from the initiating hazard site.This study focuses on the Yarlung Zangbo Daxiagu.The objective is to address two key unresolved issues:the evolution of detached glacier materials into debris flows or debris floods and the amplification of the impact range and threats.A comprehensive framework is developed that considers the impacts of near-field and far-field hazards.Numerical modeling,remote sensing,and field investigations were integrated to understand the interactions,transformations,and amplifications of hazards in the glacier hazard chain.The results indicate that extensive,nearly saturated sediments on the glacier valley floor,when entrained,amplify the magnitude of the mass flow.The topography plays a crucial role.When the valley outlet is perpendicular to the river course,topographic obstacles cause immediate halting,resulting in the formation of high barrier dams.Conversely,when the glacier valley aligns nearly parallel to the river course,the mass flow can travel a much longer distance upon entering the river,causing an enlarged affected area.The barrier dams can breach rapidly,causing breaching floods that amplify the downstream impact from several kilometers to hundreds of kilometers.Our analysis reveals that the overall impacts remain spatially limited.Specifically,downstream areas along the Yarlung Zangbo-Brahmaputra River are unlikely to face greater threats from the upstream floods than local monsoon floods.Our findings provide the foundation for the management of glacier hazard chains.
文摘This article proposes Styrene-Butadiene Rubber(SBR)and Chem-lite CR Powder(CCP)as a sustainable solution for dispersive clays,which cause infrastructure damage due to high sodium ions.Traditionally utilized stabilizers like lime/cement raise environmental concerns due to their high carbon footprints.Regarding this,SBR/CCP has been used in concrete technology for several functions;nevertheless,its effectiveness for stabilizing dispersive clay remains uncertain.Therefore,this study investigated how SBR/CCP improved sodium-rich dispersive soil's dispersion,index,mechanical characteristics,and associated mechanism.Multiple tests,including double hydrometer,cation analysis,compression strength(UCS),physio-chemical,Atterberg's limits,California Bearing Ratio(CBR),X-Ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive X-Ray spectroscopy(EDS)were performed at different mixing ratios up to curing of 60-d.The results showed a significant reduction in dispersion(61.7%),sodium(38%),and plasticity(50.4%)with an optimal 1.5%SBR-3%CCP mix after 28-d,converting the clay to a non-dispersive type.UCS and soaked CBR improved by 283%and 579%,respectively.Micro analyses revealed soil enhancement through CCP's flocculation,ion exchange,and pozzolanic reactions,while SBR-coated particles and filled pores formed reticulated membrane systems.SBR/CCP offers a sustainable/eco-friendly alternative for stabilizing dispersive clays with a lower carbon footprint.
基金funded by the National Natural Science Foundation of China(Grant Nos.42207227)the Natural Science Foundation of Hunan Province,China(Grant No.2022JJ40586)The authors also thank the China Postdoctoral Science Foundation(Grant Nos.2022M722428).
文摘In the deep geological disposal repository of high-level radioactive waste,buffer/backfill materials typically consist of compacted bentonite block and granular bentonite.As these materials undergo a long-term hydration,it is anticipated that the two forms of bentonite materials(i.e.compacted bentonite powder(CBP)and granular bentonite(GB))are expected to exhibit differing hydro-mechanical behaviors due to the differences in their structures.This work aims to investigate the differences in swelling pressure and compressibility through a series of swelling pressure tests,compression tests and mercury intrusion porosimetry(MIP)tests.The experimental results demonstrated that swelling pressure curves of the CBP specimens showed higher first peak values and more pronounced collapse than those of the GB specimens at a given dry density,regardless of vapor-water hydration or liquid-water hydration.The final swelling pressures of the two materials were similar at the same dry density,suggesting an independent correlation between swelling pressure and dry density.At the high suction range,the compression curves exhibited an obvious bi-linear pattern for the CBP specimens and a significant nonlinearity for the GB specimens.Meanwhile,the CBP specimens presented higher pre-consolidation pressures and larger compression indices than the GB specimens at a given suction.As suction decreased,the compression curves of the two materials gradually approached each other and their differences were reduced accordingly.After reaching saturation,a good consistency between them was observed whether for final swelling pressure or compressibility.Pore structure analysis revealed that the two materials both presented an initially double structure,and their differences were primarily manifested at the macrostructural level.Eventually,the differences in swelling pressure or compression curves of the two materials were well interpreted by combining microstructural evolutions.
基金Science and Technology Commission of Shanghai Municipality,Grant/Award Number:22dz1205300。
文摘Currently,there is a lack of research on the impact of excavation damage on the stability of underground compressed air energy storage(CAES)chambers.This study presents a comprehensive analytical framework for evaluating the elastic and elastoplastic stress fields in CAES chambers surrounding rock,incorporating excavation-induced centripetal reduction of rock stiffness and strength.A proposed model introduces exponential reduction functions for the deformation modulus and cohesion within the excavation disturbed zone(EDZ),deriving analytical solutions for both elastic and elastoplastic stress distributions.A case study of a practical engineering project validates the theoretical formulations through comparative analysis with numerical simulations,demonstrating strong consistency in stress field predictions.The main findings indicate that the EDZ causes a significant non-monotonic variation in the elastic hoop stress distribution.While it does not significantly affect the range of the plastic zone,it reduces the permeability and bearing capacity of the surrounding rock,highlighting the necessity of integrating the centripetal reduction of mechanical properties and strictly controlling excavation-induced damage in the design practice.Furthermore,this study provides a new approach for the selection of lining materials and structural design for CAES chambers:the radial stiffness smoothly increases to match the EDZ surrounding rock stiffness,and the cohesion exceeds that of the surrounding rock,which can significantly optimize the overall system's stress distribution.This study provides valuable insights and references for the selection of excavation methods,stability assessment,and support structure design for CAES engineering,and holds significant importance for improving the CAES technology system.
文摘The increasing atmospheric CO_(2)concentration linked to human activity results in global warming by the greenhouse effect.This anthropogenic CO_(2)may be sequestrated into geological formations,e.g.,porous basalts,saline aquifers,depleted oil or gas reservoirs,and unmineable coal seams.Furthermore,carbon capture,utilization,and storage(CCUS)methods are an acceptable and sustainable technology to meet the goals of the Paris Agreement,in which Kazakhstan is expected to reduce greenhouse gas emissions by 25%compared with the 1990 level.Unmineable coal seams are an attractive option among all geostorage solutions,as CO_(2)sequestration in coal comes with an income stream via enhanced coalbed methane(ECBM)recovery.This paper identifies four carboniferous coal formations,namely Karagandy,Teniz-Korzhinkol,Ekibustuz,and Chu coal basins of Kazakhstan,as CO_(2)geostorage solutions for their unmineable coal seams.The ideal depth of CO_(2)storage is identified as 800 m to ensure the supercritical state of CO_(2).However,the Ekibustuz coal basin fails to meet the required depth of 800 m in its unmineable coal seams.The conventional formula for calculating CO_(2)storage in coal basins has been modified,and a new formula has been proposed for assessing the CO_(2)storage potential in a coal seam.The CO_(2)storage capacities of unmineable coal seam of these coal basins are 24.60 Bt,0.61 Bt,14.02 Bt,and 5.42 Bt,respectively.The Langmuir volume of the coal fields was calculated using the proximate analysis of coalfields and found to vary between 36.42 and 98.90 m3/ton.This paper is the first to outline CO_(2)storage potential in Kazakhstani coal basins,albeit with limited data,along with a detailed geological and paleographic review of the carboniferous coalfields of Kazakhstan.A short overview of the CO_(2)-ECBM process was also included in the paper.Instead of any experimental work for CO_(2)storage,this paper attempts to present the CO_(2)storage capacity of carboniferous coal formation using the modified version of previously determined formulas for CO_(2)storage.
文摘Shield attitudes,essentially governed by intricate mechanisms,impact the segment assembly quality and tunnel axis deviation.In data-driven prediction,however,existing methods using the original driving parameters fail to present convincing performance due to insufficient consideration of complicated interactions among the parameters.Therefore,a multi-dimensional feature synthesizing and screening method is proposed to explore the optimal features that can better reflect the physical mechanism in predicting shield tunneling attitudes.Features embedded with physical knowledge were synthesized from seven dimensions,which were validated by the clustering quality of Shapley Additive Explanations(SHAP)values.Subsequently,a novel index,Expected Impact Index(EII),has been proposed for screening the optimal features reliably.Finally,a Bayesian-optimized deep learning model was established to validate the proposed method in a case study.Results show that the proposed method effectively identifies the optimal parameters for shield attitude prediction,with an average Mean Squared Error(MSE)deduction of 27.3%.The proposed method realized effective assimilation of shield driving data with physical mechanism,providing a valuable reference for shield deviation control.
基金supported by the Fundamental Research Funds for the Central Universities(No.02302350113).
文摘Shallow-buried thick sand strata present considerable local instability risks during diaphragm wall trenching construction.However,this critical issue has not been extensively studied,despite its serious safety consequences.This paper proposes an automatic identification model for shallow-buried thick sand strata,integrating three-dimensional limit equilibrium theory with a genetic algorithm to precisely identify the most potentially dangerous local instability mass and determine its minimum safety factor.The model establishes three undetermined parameters:failure angle,upper boundary,and thickness of the local instability mass.These parameters define the search space for the local instability mass.The effectiveness of this approach was confirmed through a diaphragm wall engineering case near the Rhine River in France,where the predicted instability location closely aligned with field observations.A systematic analysis of the model indicated that the difference in slurry-groundwater levels and the friction angle are the most significant factors affecting local instability in shallow-buried thick sand strata.The model indicated that the location of the most potentially dangerous instability mass changes depending on geological conditions,and larger instability masses do not always relate to lower safety factors.Additionally,exploratory experiments revealed that support pressure losses caused by slurry infiltration significantly influence local instability calculations in sand strata.This points out the importance of considering these support pressure losses in the stability evaluations of high permeable sand strata.The results improve the evaluation of safety and the optimization of design for diaphragm wall construction in shallow-buried thick sand strata.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB2600504)the National Natural Science Foundation of China(Grant No.42072302)the Postdoctoral Fellowship Program of CPSF(Grant No.GZB20240533).
文摘Reliability analysis of soil slopes under rainfall is an important task for landslide risk assessment.Previous studies rarely contribute to the probabilistic analysis of slope stability under rainfall with reinforcement.A new method is suggested for reliability analysis of soil slopes stabilized with piles under rainfall.First,an efficient numerical model is exploited for slope stability analysis,where two types of slope failure modes,i.e.,plastic flow and local failure are considered.To address the blocking effect of piles during seepage analysis,the equivalent hydraulic conductivity of the pile area is estimated according to the effective medium theory.The stabilizing force of piles is investigated by an analytical approach.For saving computational effort,the response surface is established based on a multi-class classification model to predict two types of slope failure modes.Finally,uncertainties in soil parameters and rainfall events are both modelled,and the failure probability of soil slopes within a given time period is assessed through Monte Carlo simulation.An illustrative example is used to demonstrate the performance of the suggested method.It is found that the slope is mainly controlled by local failure.As the pile spacing increases,the likelihood of plastic flow significantly increases.As the piles are located near the slope crest,plastic flow is effectively prevented and the slope is better stabilized against rainfall.If rainfall uncertainties are not considered,the slope failure probability is significantly overestimated.Overall,this study can provide a useful guidance for the design of pile-stabilized slopes against rainfall infiltration.
基金the National Natural Science Foundation of China(Grant Nos.52178385 and 52020105002)the Natural Science Foundation of Guangdong Province,China(Grant No.2024B1515040017)for their financial support.
文摘Tunnel face ground loss(TFGL)emerging in shield tunnelling can trigger ground movement and impose threats to surrounding structures.However,the impact of cutterhead vibration on TFGL in sandy soils with varying degrees of saturation has been largely unexplored.To fill this gap,an innovative numerical model based on computational fluid dynamics-discrete element method(CFD-DEM)and adhesive rolling resistance linear contact algorithm is established for the simulation of TFGL.Meanwhile,algorithms are proposed to account for the effects of cutterhead vibration and support pressure.Results from the validated model reveal that the TFGL can be exacerbated by seepage and opening enlargement,but mitigated by apparent cohesion.The cutterhead vibration can merely exacerbate the relatively small TFGL,which implies the unjamming effect of the particle at the opening.The balanced support pressure(BSP)required for TFGL prevention rises remarkably with the increases in opening ratio,vibration amplitude,and frequency.The maximum BSP in unsaturated sandy ground reaches up to 0.18γD,which is significantly less than that of 1.62γD observed in saturated sandy ground.The tangential and radial intervals with the largest TFGL are located within the ranges of 82.5°-97.5°,and 0.3D≤r_(loss)≤0.45D,respectively.The increase in support pressure can alter the time-dependent development of TFGL from linear to stepwise,leading to convergence.The support pressure required for convergence is increased by cutterhead vibration and seepage,but decreased by apparent cohesion.Lastly,the prospects of the numerical study on TFGL under cutterhead vibration are also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.42430713 and 42125701)Innovation Program of Shanghai Municipal Education Commission(Grant No.2023ZKZD26)。
文摘Deep geological repository is typically situated at depths ranging from several hundred to 1000 m below ground,making bentonite engineered barrier potentially vulnerable to high water pressure and even inducing hydraulic fracturing.This study conducted injection tests on compacted GMZ(Gaomiaozi)bentonite with a self-developed visualization set-up.The objective was to unveil the roles of dry density,water content,and pressurization rate in hydraulic fracturing from the perspective of fracturing macromorphological dynamics and breakthrough characteristics.Moreover,the relationships between breakthrough characteristics and microstructure were examined by MIP(mercury intrusion porosimetry)analysis.Results showed that the fracturing dynamics were characterized by three stages:hydration,cracking,and fracturing stages.Compared to water content and pressurization rate,dry density exerted more pronounced effects on these stages.Increasing dry density can lead to an expansion of circular hydration zone,a more complex cracking network,and a change in fracturing patterns from long and clear to short and fuzzy.In terms of breakthrough characteristics,the breakthrough pressure was positively correlated with dry density and negatively correlated with water content.Interestingly,there is a good and unique logarithmic correlation between the breakthrough pressure and the ratio eM/em of inter-aggregate void ratio and intra-aggregate void ratio,regardless of dry density and water content.Within a certain range(i.e.200-50 kPa/min),breakthrough pressure showed slight dependency on pressurization rate.Nevertheless,an extremely low pressurization rate of 20 kPa/min caused a transition for the specimen from quasi-brittle to plastic state owning to more water infiltration,thereby hindering fracture initiation and propagation.
基金funding support from the National Nature Science Foundation of China(Grant No.42030714).
文摘Calcareous sands are widely distributed on the coral reefs,continental shelf,and seashores between 30north and south latitude and are commonly utilized as filling materials for the construction of artificial islands and infrastructure foundations.In this study,calcareous sands were cemented by enzymatically induced carbonate precipitation(EICP)technique.Drained triaxial tests were conducted on the EICPtreated calcareous sands.Results showed that the specimens with different cementation levels exhibited different responses in mechanical behavior.The differences in the sand fabric after consolidation under a relatively high confining pressure resulted in the untreated specimen exhibiting a higher peak strength compared to the lightly cemented specimen.High confining pressures exhibited a strongly inhibiting effect on dilatancy,which could be counteracted by increasing the cementation level.The EICP-treated specimen could have one or two yield points(smaller-strain and larger-strain yields).For lightly cemented specimens,the smaller-strain yield stress decreased under high confining pressures due to the partial carbonate bonding degradation during consolidation.The stress line of untreated particle breakage(UPB)was a critical boundary to distinguish failure mode in the p′-q space.For the EICP-treated specimens,the yield stress located above or below the UPB stress line indicates the simultaneous or sequential breakage of the carbonate bonds and sand particles,respectively.Accordingly,the EICPtreated specimen exhibited brittle or ductile properties.Failure mode transformation could be triggered by increasing cementation level or confining pressure.
基金supported by the National Natural Science Foundation of China(Grant Nos.42272338,41902275)the Sichuan Transportation Science and Technology Program(Grant No.2018-ZL-02).
文摘Geotechnical engineering usually produces drillholes in the ground for investigation and construction.Drilling is a rock-breaking process by applying normal(thrust)and shear(torque)force from the drill bit to the rock below the bit.These rock-breaking data can be obtained by digital monitoring and recording the drilling parameters through an instrumented drilling machine.However,there is no mature and standard method to determine rock strength properties(such as unconfined compressive strength,UCS,or tensile strength)from real-time monitored drilling parameter(such as thrust force,torque,rotation speed,drilling speed and specific energy).This paper presents a complete procedure to accurately determine each drilling parameter.More importantly,the specific energy develops nonlinearly with change of the thrust force,which is related to the UCS and tensile strength of the rock.This finding provides an insight into determining the UCS and tensile strength of the rock based on real-time monitored drilling parameters.In addition,novel test setups are demonstrated to determine the thrust force and torque from hydraulics pressures and rotation speeds.These setups can significantly reduce the sophisticated instrumentation cost for drilling monitoring studies.Three type rocks including granite,limestone and sandstone are used for the testing.The findings from this study provide supporting theories to upgrade drilling monitoring technique to a standard geotechnical testing method.
