Shotcrete is one of the common solutions for shallow sliding.It works by forming a protective layer with high strength and cementing the loose soil particles on the slope surface to prevent shallow sliding.However,the...Shotcrete is one of the common solutions for shallow sliding.It works by forming a protective layer with high strength and cementing the loose soil particles on the slope surface to prevent shallow sliding.However,the solidification time of conventional cement paste is long when shotcrete is used to treat cohesionless soil landslide.The idea of reinforcing slope with polyurethane solidified soil(i.e.,mixture of polyurethane and sand)was proposed.Model tests and finite element analysis were carried out to study the effectiveness of the proposed new method on the emergency treatment of cohesionless soil landslide.Surcharge loading on the crest of the slope was applied step by step until landslide was triggered so as to test and compare the stability and bearing capacity of slope models with different conditions.The simulated slope displacements were relatively close to the measured results,and the simulated slope deformation characteristics were in good agreement with the observed phenomena,which verifies the accuracy of the numerical method.Under the condition of surcharge loading on the crest of the slope,the unreinforced slope slid when the surcharge loading exceeded 30 k Pa,which presented a failure mode of local instability and collapse at the shallow layer of slope top.The reinforced slope remained stable even when the surcharge loading reached 48 k Pa.The displacement of the reinforced slope was reduced by more than 95%.Overall,this study verifies the effectiveness of polyurethane in the emergency treatment of cohesionless soil landslide and should have broad application prospects in the field of geological disasters concerning the safety of people's live.展开更多
In the physical model test of landslides,the selection of analogous materials is the key,and it is difficult to consider the similarity of mechanical properties and seepage performance at the same time.To develop a mo...In the physical model test of landslides,the selection of analogous materials is the key,and it is difficult to consider the similarity of mechanical properties and seepage performance at the same time.To develop a model material suitable for analysing the deformation and failure of reservoir landslides,based on the existing research foundation of analogous materials,5 materials and 5 physical-mechanical parameters were selected to design an orthogonal test.The factor sensitivity of each component ratio and its influence on the physical-mechanical indices were studied by range analysis and stepwise regression analysis,and the proportioning method was determined.Finally,the model material was developed,and a model test was carried out considering Huangtupo as the prototype application.The results showed that(1)the model material composed of sand,barite powder,glass beads,clay,and bentonite had a wide distribution of physical-mechanical parameters,which could be applied to model tests under different conditions;(2)the physical-mechanical parameters of analogous materials matched the application prototype;and(3)the mechanical properties and seepage performance of the model material sample met the requirements of reservoir landslide model tests,which could be used to simulate landslide evolution and analyse the deformation process.展开更多
To ensure the operational safety of railways in the landslide-prone areas of mountainous regions,a large-scale model test and numerical simulation were conducted to study the bending moment distribution,internal force...To ensure the operational safety of railways in the landslide-prone areas of mountainous regions,a large-scale model test and numerical simulation were conducted to study the bending moment distribution,internal force distribution,deformation development,and crack propagation characteristics of a framed anti-sliding structure(FAS)under landslide thrust up to the point of failure.Results show that the maximum bending moment and its increase rate in the fore pile are greater than those in the rear pile,with the maximum bending moment of the fore pile approximately 1.1 times that of the rear pile.When the FAS fails,the displacement at the top of the fore pile is significantly greater,about 1.27 times that of the rear pile in the experiment.Major cracks develop at locations corresponding to the peak bending moments.Small transverse cracks initially appear on the upper surface at the intersection between the primary beam and rear pile and then spread to the side of the structure.At the failure stage,major cracks are observed at the pil-beam intersections and near the anchor points.Strengthening flexural stiffness at intersections where major cracks occur can improve the overall thrust-deformation coordination of the FAS,thereby maximizing its performance.展开更多
This paper presents a dynamic modeling method to test and examine the minimum mass of pressurized pore-gas for triggering landslides in stable gentle soil slopes.A stable gentle soil slope model is constructed with a ...This paper presents a dynamic modeling method to test and examine the minimum mass of pressurized pore-gas for triggering landslides in stable gentle soil slopes.A stable gentle soil slope model is constructed with a dry cement powder core,a saturated clay middle layer,and a dry sand upper layer.The test injects H_(2)O_(2)solution into the cement core to produce new pore-gas.The model test includes three identical H_(2)O_(2)injections.The small mass of generated oxygen gas(0.07%of slope soil mass and landslide body)from the first injection can build sufficient pore-gas pressure to cause soil upheaval and slide.Meanwhile,despite the first injection causing leak paths in the clay layer,the generated small mass of gas from the second and third injections can further trigger the landslide.A dynamic theoretical analysis of the slope failure is carried out and the required minimum pore-gas pressure for the landslide is calculated.The mass and pressure of generated gas in the model test are also estimated based on the calibration test for oxygen generation from H_(2)O_(2)solution in cement powder.The results indicate that the minimum mass of the generated gas for triggering the landslide is 2 ppm to 0.07%of the landslide body.Furthermore,the small mass of gas can provide sufficient pressure to cause soil upheaval and soil sliding in dynamic analysis.展开更多
Structure-type rockbursts frequently occur in deep tunnels,with structural planes and stress conditions being critical factors in their formation.In this study,we utilized specially developed analogous materials that ...Structure-type rockbursts frequently occur in deep tunnels,with structural planes and stress conditions being critical factors in their formation.In this study,we utilized specially developed analogous materials that exhibit the high brittleness and strength characteristics of deep hard rock to construct physical models representing different types of structural planes,including composite,exposed,non-exposed,and throughgoing structural planes.Physical simulation experiments were conducted on structuretype rockbursts in deep horseshoe-shaped tunnels,focusing on strain differentiation characteristics,critical triggering conditions,critical crack opening displacement,the incubation process,the reduction effects of structural planes on failure intensity,and formation mechanisms.These experiments were complemented by acoustic and optical monitoring,as well as discrete element numerical simulations,to provide a comprehensive analysis.The results revealed that the most significant strain heterogeneity in the surrounding rock occurs at the tip of the structural plane along the tunnel's minimum principal stress direction,driven by the combined effects of tensile and shear forces.We quantitatively determined the critical stress and strain conditions for structure-type rockbursts and evaluated the intensity of rockbursts induced by different structural planes using critical crack opening displacement(COD)values,the uniformity coefficient,and the curvature coefficient.Analysis of acoustic emission events,including frequency,amplitude,and b-value,indicated that the macro-fracture process is governed by both the principal stress differential and the characteristics of the structural plane.Furthermore,using the bearing capacity reduction coefficient,we found that exposed structural planes have the most significant weakening effect on rock mass strength,followed by non-exposed and throughgoing structural planes.The analysis of average frequency(AF)and rise angle(RA)parameters revealed a close correlation between the failure modes of structure-type rockbursts,the rock mass structure,and the stress levels.These findings provide critical theoretical support for the prediction and prevention of structure-type rockburst disasters.展开更多
Captive model tests are one of the most common methods to calculate the maneuvering hydrodynamic coefficients and characteristics of surface and underwater vehicles.Considerable attention must be paid to selecting and...Captive model tests are one of the most common methods to calculate the maneuvering hydrodynamic coefficients and characteristics of surface and underwater vehicles.Considerable attention must be paid to selecting and designing the most suitable laboratory equipment for towing tanks.A computational fluid dynamics(CFD)-based method is implemented to determine the loads acting on the towing facility of the submarine model.A reversed topology is also used to ensure the appropriateness of the load cells in the developed method.In this study,the numerical simulations were evaluated using the experimental results of the SUBOFF benchmark submarine model of the Defence Advanced Research Projects Agency.The maximum and minimum loads acting on the 2.5-meter submarine model were measured by determining the body’s lightest and heaviest maneuvering test scenarios.In addition to having sufficient endurance against high loads,the precision in measuring the light load was also investigated.The horizontal planar motion mechanism(HPMM)facilities in the National Iranian Marine Laboratory were developed by locating the load cells inside the submarine model.The results were presented as a case study.A numerical-based method was developed to obtain the appropriate load measurement facilities.Load cells of HPMM test basins can be selected by following the two-way procedure presented in this study.展开更多
Seismicity resulting from the near-or in-field fault activation significantly affects the stability of large-scale underground caverns that are operating under high-stress conditions.A comprehensive scientific assessm...Seismicity resulting from the near-or in-field fault activation significantly affects the stability of large-scale underground caverns that are operating under high-stress conditions.A comprehensive scientific assessment of the operational safety of such caverns requires an in-depth understanding of the response characteristics of the rock mass subjected to dynamic disturbances.To address this issue,we conducted true triaxial modeling tests and dynamic numerical simulations on large underground caverns to investigate the impact of static stress levels,dynamic load parameters,and input directions on the response characteristics of the surrounding rock mass.The findings reveal that:(1)When subjected to identical incident stress waves and static loads,the surrounding rock mass exhibits the greatest stress response during horizontal incidence.When the incident direction is fixed,the mechanical response is more pronounced at the cavern wall parallel to the direction of dynamic loading.(2)A high initial static stress level specifically enhances the impact of dynamic loading.(3)The response of the surrounding rock mass is directly linked to the amplitude of the incident stress wave.High amplitude results in tensile damage in regions experiencing tensile stress concentration under static loading and shear damage in regions experiencing compressive stress concentration.These results have significant implications for the evaluation and prevention of dynamic disasters in the surrounding rock of underground caverns experiencing dynamic disturbances.展开更多
Understanding the stress distribution derived from monitoring the principal stress(PS)in slopes is of great importance.In this study,a miniature sensor for quantifying the two-dimensional(2D)PS in landslide model test...Understanding the stress distribution derived from monitoring the principal stress(PS)in slopes is of great importance.In this study,a miniature sensor for quantifying the two-dimensional(2D)PS in landslide model tests is proposed.The fundamental principle and design of the sensor are demonstrated.The sensor comprises three earth pressure gages and one gyroscope,with the utilization of three-dimensional(3D)printing technology.The difficulties of installation location during model preparation and sensor rotation during testing can be effectively overcome using this sensor.Two different arrangements of the sensors are tested in verification tests.Additionally,the application of the sensor in an excavated-induced slope model is tested.The results demonstrate that the sensor exhibits commendable performance and achieves a desirable level of accuracy,with a principal stress angle error of±5°in the verification tests.The stress transformation of the slope model,generated by excavation,is demonstrated in the application test by monitoring the two miniature principal stress(MPS)sensors.The sensor has a significant potential for measuring primary stress in landslide model tests and other geotechnical model experiments.展开更多
The Sichuan-Xizang transportation corridor is prone to numerous active faults and frequent strong earthquakes.While extensive studies have individually explored the effect of active faults and strong earthquakes on di...The Sichuan-Xizang transportation corridor is prone to numerous active faults and frequent strong earthquakes.While extensive studies have individually explored the effect of active faults and strong earthquakes on different engineering structures,their combined effect remains unclear.This research employed multiple physical model tests to investigate the dynamic response of various engineering structures,including tunnels,bridges,and embankments,under the simultaneous influence of cumulative earthquakes and stick-slip misalignment of an active fault.The prototype selected for this study was the Kanding No.2 tunnel,which crosses the Yunongxi fault zone within the Sichuan-Xizang transportation corridor.The results demonstrated that the tunnel,bridge,and embankment exhibited amplification in response to the input seismic wave,with the amplification effect gradually decreasing as the input peak ground acceleration(PGA)increased.The PGAs of different engineering structures were weakened by the fault rupture zone.Nevertheless,the misalignment of the active fault may decrease the overall stiffness of the engineering structure,leading to more severe damage,with a small contribution from seismic vibration.Additionally,the seismic vibration effect might be enlarged with the height of the engineering structure,and the tunnel is supposed to have a smaller PGA and lower dynamic earth pressure compared to bridges and embankments in strong earthquake zones crossing active faults.The findings contribute valuable insights for evaluating the dynamic response of various engineering structures crossing an active fault and provide an experimental reference for secure engineering design in the challenging conditions of the Sichuan-Xizang transportation corridor.展开更多
The vacuum-assisted prefabricated horizontal drain offers a promising method for strengthening soil slurry,allowing simultaneous filling and vacuum-dewatering via staged construction.However,there is limited research ...The vacuum-assisted prefabricated horizontal drain offers a promising method for strengthening soil slurry,allowing simultaneous filling and vacuum-dewatering via staged construction.However,there is limited research on the unique characteristics of staged filling.This study aims to investigate the vacuum consolidation process of staged-filled soil slurry through laboratory model tests and numerical simulations,also assessing the impact of anionic polyacrylamide.Comparative analyses are conducted between vacuum consolidation with and without anionic polyacrylamide,as well as self-weight consolidation without anionic polyacrylamide.Results reveal contour lines of excess pore pressure,water content,and soil strength forming an ellipse around the prefabricated horizontal drain board.During the consolidation process,a higher degree of consolidation,lower water content,and higher soil strength were observed closer to the prefabricated horizontal drain board.After treatment,the uppermost filling layer exhibits an average water content that was approximately 40%higher than the lower filling layer,and its average strength was about 60%lower.This discrepancy is primarily due to the absence of sealing on the top surface and the relatively short vacuum consolidation time caused by staged filling.The introduction of anionic polyacrylamide-induced flocculation significantly improves the initial consolidation rate but minimally affects the dewatering capacity of vacuum preloading.Using flocculant can enhance both the staged filling rate and soil strength(by 1e2 times).Additionally,employing a staggered arrangement between different prefabricated horizontal drain layers is advisable to prevent top-down penetration in areas with low soil strength.展开更多
Testing of large-sized specimens is becoming increasingly important in deep underground rock mechanics and engineering.In traditional mechanical loading,stresses on large-sized specimens are achieved by large host fra...Testing of large-sized specimens is becoming increasingly important in deep underground rock mechanics and engineering.In traditional mechanical loading,stresses on large-sized specimens are achieved by large host frames and hydraulic pumps,which could lead to great investment.Low-cost testing machines clearly always have great appeal.In this study,a new approach is proposed using thermal expansion stress to load rock specimens,which may be particularly suitable for tests of deep hot dry rock with high temperatures.This is a different technical route from traditional mechanical loading through hydraulic pressure.For the rock mechanics test system of hot dry rock that already has an investment in heating systems,this technology may reduce the cost of the loading subsystem by fully utilizing the temperature changes.This paper presents the basic principle and a typical design of this technical solution.Preliminary feasibility analysis is then conducted based on numerical simulations.Although some technical details still need to be resolved,the feasibility of this loading approach has been preliminarily confirmed.展开更多
In this paper, cold simulation experiments and numerical calculations are conducted to predict 3 D flow field aerodynamics for an oil furnace after being retrofitted due to its fuel variation. K ε model and SIMPLE ...In this paper, cold simulation experiments and numerical calculations are conducted to predict 3 D flow field aerodynamics for an oil furnace after being retrofitted due to its fuel variation. K ε model and SIMPLE program under body fit coordination (BFC) system, in which TTM non orthogonal method is used to control the irregular geometric boundary, are adopted to solve the control equations. Model tests are conducted to check the calculation results, showing that they are in agreement with each other. Three different alternatives with different side window locations are also calculated to optimize the designs. The field retrofitting results show that the combination of cold tests with numerical calculations has prosperous application in retrofitting or renewing medium and small boilers.展开更多
Ice load on underwater vehicles breaking through ice covers from underneath is a significant concern for researchers in polar exploration,and the research on this problem is still in its early stages.Both mechanical e...Ice load on underwater vehicles breaking through ice covers from underneath is a significant concern for researchers in polar exploration,and the research on this problem is still in its early stages.Both mechanical experimental measurement and numerical simulation pose research challenges.This study focuses on the ice load of a cylinder structure breaking upward through the ice sheet form underneath in the Small Ice Model Basin of China Ship Scientific Research Center(CSSRC SIMB).A high-speed camera system was employed to observe the ice sheet failure during the tests,in which,with the loading position as center,local radial cracks and circumferential cracks were generated.A load sensor was used to measure the overall ice load during this process.Meanwhile,a numerical model was developed using LS-DYNA for validation and comparison.With this model,numerical simulation was conducted under various ice thicknesses and upgoing speeds to analyze the instantaneous curves of ice load.The calculation results were statistically analyzed under different working conditions to determine the influence of the factors on the ice load of the cylinder.The study explores the measurement method about ice load of objects vertically breaking through model ice sheet and is expected to provide some fundamental insights into the safety design of underwater structures operating in ice waters.展开更多
Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of...Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of CFST truss arch bridges.The effects of antisymmetric defect on the ultimate bearing capacity,failure mode,structural response,and steel–concrete confinement effect of CFST truss arch bridges under quarter-point loading were analyzed.On this basis,numerical simulations were conducted to investigate the in-plane bearing capacity of CFST truss arch bridges further under different scenarios.The initial defect formof the archwas obtained by using theoretical deduction,and the theoretical basis for the weakening of the ultimate bearing capacity of the arch bridge caused by geometric defects was clarified.Results indicate that the antisymmetric defect does not change the four-hinge failure mode of the model arch under quarter-point loading but increases the local cracking area and crack density of the concrete inside the pipe.The sine geometric defect with an amplitude of L/250 resulted in a 44.4%decrease in the yield load of the single hinge of the model arch,a 10.5%decrease in the failure load of the four hinges,and a 40.9%increase in themaximum vertical deformation during failure.At the initial stage of loading,the steel pipe and the concrete inside the pipe were subjected to relatively independent forces.After reaching 67%of the ultimate load,the catenary arch ribs began to produce a steel pipe concrete constraint effect.The initial geometric defects resulted in a decrease in the load when the constraint effect occurred.The antisymmetric defects with the same amplitude have a greater impact on the in-plane bearing capacity of the CFST arch bridge than the initial geometric defects with symmetry.The linear deviation at L/4 caused by constructionmust be controlled to be less than L/600 to ensure that the internal bearing capacity of the CFST arch bridge reaches 95%of the design bearing capacity.The structural deformation caused by geometric initial defects increases linearly with the increase in defect amplitude.The bearing capacity is weakened because the structural deflection and bending moment are amplified by initial defects.展开更多
On the basis of the model tests,this paper explores the coupled hydrodynamic performance of the moonpool and the hull.This study aims to compare and analyze the variation in the hull heave response between the piston ...On the basis of the model tests,this paper explores the coupled hydrodynamic performance of the moonpool and the hull.This study aims to compare and analyze the variation in the hull heave response between the piston resonance state of the moonpool under wave excitation and the non-resonance state of the moonpool under wave-current excitation.A novel damping device specifically designed and fabricated for stepped moonpools has been developed.Before and after the installation of the damping device,the free surface response characteristics of the moonpool and heave motion response characteristics of the hull are compared.The findings show a clear correlation between the current speed and heave response characteristics of the hull.During the seakeeping design phase of the drilling vessel,the current speed is an additional critical factor that cannot be disregarded,alongside the moonpool effect.A correlation exists between the fluid dynamics occurring within the moonpool and the heave motion of the vessel hull.A reduction in the amplitude of the motion of the moonpool water results in a decrease in the heave motion of the hull.This study provides a reference for alleviating the seakeeping of a drill ship’s heave response and enhancing the safety and efficiency of the operation.展开更多
To investigate the fracture propagation characteristics and failure mechanism of anti-dip rock slope induced by underground mining,the Jiguanling landslide in Wulong,Chongqing,China is taken as the prototype,and physi...To investigate the fracture propagation characteristics and failure mechanism of anti-dip rock slope induced by underground mining,the Jiguanling landslide in Wulong,Chongqing,China is taken as the prototype,and physical model test is utilized to study the fracture evolution process,deformation characteristics and failure mechanism of anti-dip rock slope.In this study,the digital image correlation(DIC)technique and pressure acquisition system are combined to analyze the displacement and stress field of rock slope during underground mining stages.The results show that the anti-dip rock slope experiences four stages during underground coal mining:tensile fracture propagation in upper toppling zone,shallow damage in the lower shear zone,coal seam roof caving,failure of the whole slope.There is a phenomenon of local tensile and compressive stress conversion in upper toppling zone after roof caving.The appearance of coal seam roof caving increases the compressive area and pressure of the shear zone,leading to the failure of the shear blocks at the front edge,and ultimately causing failure of the whole slope.Mining with retained coal pillar before shallow failure in the shear zone can effectively block the impact of lower mining on the upper toppling zone,achieve a 16%contraction in toppling zone,and improve the stability of the slope.The failure mode of slope can be summarized as shear–slip–toppling collapse failure.This paper improves the understanding on the failure mechanism of anti-dip rock slope caused by underground mining.展开更多
When the expressway crosses the goafs inevitably,the design is generally to build the road on coal pillars as much as possible.However,the existing coal pillars are often unable to meet relevant requirements of highwa...When the expressway crosses the goafs inevitably,the design is generally to build the road on coal pillars as much as possible.However,the existing coal pillars are often unable to meet relevant requirements of highway construction.Combining three-dimensional physical model tests,numerical simulations and field monitoring,with the Urumqi East Second Ring Road passing through acute inclined goafs as a background,the deformation and failure mechanism of the overlying rock and coal pillars in acute inclined goafs under expressway load were studied.And in accordance with construction requirements of subgrade,comprehensive consideration of the deformation and instability mechanism of acute inclined goafs,the treatment measures and suggestions for this type of geological disasters were put forward.The research results confirmed the rationality of coal pillars in acute inclined goafs under the expressway through grouting.According to the ratio of diff erent overlying rock thickness to coal pillar height,the change trend and value of the required grouting range were summarized,which can provide reference for similar projects.展开更多
The mineralization process of microbial-induced calcium carbonate precipitation(MICP)is influenced by many factors,and the uniformity of the calcium carbonate precipitation has become the main focus and challenge for ...The mineralization process of microbial-induced calcium carbonate precipitation(MICP)is influenced by many factors,and the uniformity of the calcium carbonate precipitation has become the main focus and challenge for MICP technology.In this study,the uniformity of the saturated calcareous sand treated with MICP was in-vestigated through one-dimensional calcareous sand column tests and model tests.The coefficient of variation was employed in one-dimensional sand column tests to investigate the impact of injection rate,cementation solution concentration,and number of injection cycles on the uniformity of the MICP treatment.Additionally,model tests were conducted to investigate the impact of injection pressure and methods on the treatment range and uniformity under three-dimensional seepage conditions.Test results demonstrate that the reinforcement strength and uniformity are significantly influenced by the injection rate of the cementation solution,with a rate of 3 mL/min,yielding a favorable treatment effect.Excessive concentration of the cementation solution can lead to significant non-uniformity and a reduction in the compressive strength of MICP-treated samples.Conversely,excessively low concentrations may result in decreased bonding efficiency.Among the four considered con-centrations,0.5 mol/L and 1 mol/L exhibit superior reinforcing effects.The morphological development of calcareous sandy foundation reinforcement is associated with the spatial distribution pattern of the bacterial solution,exhibiting a relatively larger reinforcement area in proximity to the lower region of the model and a gradually decreasing range towards the upper part.Under three-dimensional seepage conditions,in addition to the non-uniform radial cementation along the injection pipe,there is also vertical heterogeneity of cementation along the length of the injection pipe due to gravitational effects,resulting in preferential deposition of calcium carbonate at the lower section,The application of injection pressure and a double-pipe circulation injection method can mitigate the accumulation of bacterial solution and cementation solution at the bottom,thereby improving the reinforcement range and uniformity.展开更多
As an important part of offshore wind turbine support and fixed units, the multibucket jacket foundation bears large loads and a complex marine environment. In this paper, the horizontal bearing characteristics of the...As an important part of offshore wind turbine support and fixed units, the multibucket jacket foundation bears large loads and a complex marine environment. In this paper, the horizontal bearing characteristics of the four-bucket jacket foundation of offshore wind power in sandy soil are studied. Through model tests and numerical simulations, the influence of bucket foundation sealing properties, load application speed, and loading direction on foundation-bearing capacity are discussed. The results show that the horizontal ultimate bearing capacity of the foundation in the nonsealing condition is decreased by 51.3% compared with the sealing condition;therefore, after the foundation penetration construction is completed, the bucket sealing must be ensured to increase the load-bearing performance of the structure. At a loading speed of 3.25 mm/s, the horizontal ultimate bearing capacity of the foundation is increased by 9.4% over the working condition of 1.85 mm/s. The bearing capacity of the foundation is maximized in the loading direction α =45° and is the smallest when α =0°. That is, the foundation can maximize its loadbearing performance under the condition of single-bucket compression/tension. During the design process, the main load of the structure should be loaded in the 45° direction. The contrast error of the experiment and numerical simulation does not exceed 10%. The research results have important guiding importance for designing and constructing the jacket foundation and can be used as a reference for the stable operation and sustainable development of offshore wind power systems.展开更多
During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When t...During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When the roof eventually collapses,the accumulated energy is released instantaneously,exerting a strong impact on the roadway.To address this issue,we proposed the synergistic control method of directional comprehensive pressure relief and energy-absorbing support(PREA)for roadways with hard roofs.In this study,we developed a three-dimensional physical model test apparatus for roof cutting and pressure relief.The 122108 ventilation roadway at the Caojiatan Coal Mine,which has a thick and hard roof,was taken as the engineering example.We analyzed the evolution patterns of stress and displacement in both the stope and the roadway surrounding rocks under different schemes.The PREA reinforcement mechanism for the roadway was investigated through comparative model tests between the new and original methods.The results showed that,compared to the original method,the new method reduced surrounding rock stress by up to 60.4%,and the roadway convergence decreased by up to 52.1%.Based on these results,we proposed corresponding engineering recommendations,which can guide fieldreinforcement design and application.The results demonstrate that the PREA method effectively reduces stress and ensures the safety and stability of the roadway.展开更多
基金the financial support from the Fujian Science Foundation for Outstanding Youth(2023J06039)the National Natural Science Foundation of China(Grant No.41977259,U2005205,41972268)the Independent Research Project of Technology Innovation Center for Monitoring and Restoration Engineering of Ecological Fragile Zone in Southeast China(KY-090000-04-2022-019)。
文摘Shotcrete is one of the common solutions for shallow sliding.It works by forming a protective layer with high strength and cementing the loose soil particles on the slope surface to prevent shallow sliding.However,the solidification time of conventional cement paste is long when shotcrete is used to treat cohesionless soil landslide.The idea of reinforcing slope with polyurethane solidified soil(i.e.,mixture of polyurethane and sand)was proposed.Model tests and finite element analysis were carried out to study the effectiveness of the proposed new method on the emergency treatment of cohesionless soil landslide.Surcharge loading on the crest of the slope was applied step by step until landslide was triggered so as to test and compare the stability and bearing capacity of slope models with different conditions.The simulated slope displacements were relatively close to the measured results,and the simulated slope deformation characteristics were in good agreement with the observed phenomena,which verifies the accuracy of the numerical method.Under the condition of surcharge loading on the crest of the slope,the unreinforced slope slid when the surcharge loading exceeded 30 k Pa,which presented a failure mode of local instability and collapse at the shallow layer of slope top.The reinforced slope remained stable even when the surcharge loading reached 48 k Pa.The displacement of the reinforced slope was reduced by more than 95%.Overall,this study verifies the effectiveness of polyurethane in the emergency treatment of cohesionless soil landslide and should have broad application prospects in the field of geological disasters concerning the safety of people's live.
基金supported by the Major Program of the National Natural Science Foundation of China(No.42090054)the National Key Scientific Instrument and Equipment Development Projects of China(No.41827808)+1 种基金the Major Program of the National Natural Science Foundation of China(No.42090055)the National Science Foundation of China(No.42107194)。
文摘In the physical model test of landslides,the selection of analogous materials is the key,and it is difficult to consider the similarity of mechanical properties and seepage performance at the same time.To develop a model material suitable for analysing the deformation and failure of reservoir landslides,based on the existing research foundation of analogous materials,5 materials and 5 physical-mechanical parameters were selected to design an orthogonal test.The factor sensitivity of each component ratio and its influence on the physical-mechanical indices were studied by range analysis and stepwise regression analysis,and the proportioning method was determined.Finally,the model material was developed,and a model test was carried out considering Huangtupo as the prototype application.The results showed that(1)the model material composed of sand,barite powder,glass beads,clay,and bentonite had a wide distribution of physical-mechanical parameters,which could be applied to model tests under different conditions;(2)the physical-mechanical parameters of analogous materials matched the application prototype;and(3)the mechanical properties and seepage performance of the model material sample met the requirements of reservoir landslide model tests,which could be used to simulate landslide evolution and analyse the deformation process.
基金The National Natural Science Foundation of China(No.52078427).
文摘To ensure the operational safety of railways in the landslide-prone areas of mountainous regions,a large-scale model test and numerical simulation were conducted to study the bending moment distribution,internal force distribution,deformation development,and crack propagation characteristics of a framed anti-sliding structure(FAS)under landslide thrust up to the point of failure.Results show that the maximum bending moment and its increase rate in the fore pile are greater than those in the rear pile,with the maximum bending moment of the fore pile approximately 1.1 times that of the rear pile.When the FAS fails,the displacement at the top of the fore pile is significantly greater,about 1.27 times that of the rear pile in the experiment.Major cracks develop at locations corresponding to the peak bending moments.Small transverse cracks initially appear on the upper surface at the intersection between the primary beam and rear pile and then spread to the side of the structure.At the failure stage,major cracks are observed at the pil-beam intersections and near the anchor points.Strengthening flexural stiffness at intersections where major cracks occur can improve the overall thrust-deformation coordination of the FAS,thereby maximizing its performance.
基金supported by grants from the Research Grant Council of the Hong Kong Special Administrative Region,China(Project No.HKU 17207518).
文摘This paper presents a dynamic modeling method to test and examine the minimum mass of pressurized pore-gas for triggering landslides in stable gentle soil slopes.A stable gentle soil slope model is constructed with a dry cement powder core,a saturated clay middle layer,and a dry sand upper layer.The test injects H_(2)O_(2)solution into the cement core to produce new pore-gas.The model test includes three identical H_(2)O_(2)injections.The small mass of generated oxygen gas(0.07%of slope soil mass and landslide body)from the first injection can build sufficient pore-gas pressure to cause soil upheaval and slide.Meanwhile,despite the first injection causing leak paths in the clay layer,the generated small mass of gas from the second and third injections can further trigger the landslide.A dynamic theoretical analysis of the slope failure is carried out and the required minimum pore-gas pressure for the landslide is calculated.The mass and pressure of generated gas in the model test are also estimated based on the calibration test for oxygen generation from H_(2)O_(2)solution in cement powder.The results indicate that the minimum mass of the generated gas for triggering the landslide is 2 ppm to 0.07%of the landslide body.Furthermore,the small mass of gas can provide sufficient pressure to cause soil upheaval and soil sliding in dynamic analysis.
基金supported by the National Natural Science Foundation of China(Grant Nos.42307241 and 42107211)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Grant No.SKLGP2022Z008).
文摘Structure-type rockbursts frequently occur in deep tunnels,with structural planes and stress conditions being critical factors in their formation.In this study,we utilized specially developed analogous materials that exhibit the high brittleness and strength characteristics of deep hard rock to construct physical models representing different types of structural planes,including composite,exposed,non-exposed,and throughgoing structural planes.Physical simulation experiments were conducted on structuretype rockbursts in deep horseshoe-shaped tunnels,focusing on strain differentiation characteristics,critical triggering conditions,critical crack opening displacement,the incubation process,the reduction effects of structural planes on failure intensity,and formation mechanisms.These experiments were complemented by acoustic and optical monitoring,as well as discrete element numerical simulations,to provide a comprehensive analysis.The results revealed that the most significant strain heterogeneity in the surrounding rock occurs at the tip of the structural plane along the tunnel's minimum principal stress direction,driven by the combined effects of tensile and shear forces.We quantitatively determined the critical stress and strain conditions for structure-type rockbursts and evaluated the intensity of rockbursts induced by different structural planes using critical crack opening displacement(COD)values,the uniformity coefficient,and the curvature coefficient.Analysis of acoustic emission events,including frequency,amplitude,and b-value,indicated that the macro-fracture process is governed by both the principal stress differential and the characteristics of the structural plane.Furthermore,using the bearing capacity reduction coefficient,we found that exposed structural planes have the most significant weakening effect on rock mass strength,followed by non-exposed and throughgoing structural planes.The analysis of average frequency(AF)and rise angle(RA)parameters revealed a close correlation between the failure modes of structure-type rockbursts,the rock mass structure,and the stress levels.These findings provide critical theoretical support for the prediction and prevention of structure-type rockburst disasters.
文摘Captive model tests are one of the most common methods to calculate the maneuvering hydrodynamic coefficients and characteristics of surface and underwater vehicles.Considerable attention must be paid to selecting and designing the most suitable laboratory equipment for towing tanks.A computational fluid dynamics(CFD)-based method is implemented to determine the loads acting on the towing facility of the submarine model.A reversed topology is also used to ensure the appropriateness of the load cells in the developed method.In this study,the numerical simulations were evaluated using the experimental results of the SUBOFF benchmark submarine model of the Defence Advanced Research Projects Agency.The maximum and minimum loads acting on the 2.5-meter submarine model were measured by determining the body’s lightest and heaviest maneuvering test scenarios.In addition to having sufficient endurance against high loads,the precision in measuring the light load was also investigated.The horizontal planar motion mechanism(HPMM)facilities in the National Iranian Marine Laboratory were developed by locating the load cells inside the submarine model.The results were presented as a case study.A numerical-based method was developed to obtain the appropriate load measurement facilities.Load cells of HPMM test basins can be selected by following the two-way procedure presented in this study.
基金supported by the National Natural Science Foundation of China (Grant No.52279116)the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of China (Grant No.U1865203).
文摘Seismicity resulting from the near-or in-field fault activation significantly affects the stability of large-scale underground caverns that are operating under high-stress conditions.A comprehensive scientific assessment of the operational safety of such caverns requires an in-depth understanding of the response characteristics of the rock mass subjected to dynamic disturbances.To address this issue,we conducted true triaxial modeling tests and dynamic numerical simulations on large underground caverns to investigate the impact of static stress levels,dynamic load parameters,and input directions on the response characteristics of the surrounding rock mass.The findings reveal that:(1)When subjected to identical incident stress waves and static loads,the surrounding rock mass exhibits the greatest stress response during horizontal incidence.When the incident direction is fixed,the mechanical response is more pronounced at the cavern wall parallel to the direction of dynamic loading.(2)A high initial static stress level specifically enhances the impact of dynamic loading.(3)The response of the surrounding rock mass is directly linked to the amplitude of the incident stress wave.High amplitude results in tensile damage in regions experiencing tensile stress concentration under static loading and shear damage in regions experiencing compressive stress concentration.These results have significant implications for the evaluation and prevention of dynamic disasters in the surrounding rock of underground caverns experiencing dynamic disturbances.
基金supported by the National Nature Science Foundation of China(Grant No.42207216)the Major Program of the National Natural Science Foundation of China(Grant No.42090055)the National Nature Science Foundation of China(Grant No.42377182).
文摘Understanding the stress distribution derived from monitoring the principal stress(PS)in slopes is of great importance.In this study,a miniature sensor for quantifying the two-dimensional(2D)PS in landslide model tests is proposed.The fundamental principle and design of the sensor are demonstrated.The sensor comprises three earth pressure gages and one gyroscope,with the utilization of three-dimensional(3D)printing technology.The difficulties of installation location during model preparation and sensor rotation during testing can be effectively overcome using this sensor.Two different arrangements of the sensors are tested in verification tests.Additionally,the application of the sensor in an excavated-induced slope model is tested.The results demonstrate that the sensor exhibits commendable performance and achieves a desirable level of accuracy,with a principal stress angle error of±5°in the verification tests.The stress transformation of the slope model,generated by excavation,is demonstrated in the application test by monitoring the two miniature principal stress(MPS)sensors.The sensor has a significant potential for measuring primary stress in landslide model tests and other geotechnical model experiments.
基金supported by the National Natural Science Foundation of China(Grant Nos.41825018,41977248,42207219)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0904)。
文摘The Sichuan-Xizang transportation corridor is prone to numerous active faults and frequent strong earthquakes.While extensive studies have individually explored the effect of active faults and strong earthquakes on different engineering structures,their combined effect remains unclear.This research employed multiple physical model tests to investigate the dynamic response of various engineering structures,including tunnels,bridges,and embankments,under the simultaneous influence of cumulative earthquakes and stick-slip misalignment of an active fault.The prototype selected for this study was the Kanding No.2 tunnel,which crosses the Yunongxi fault zone within the Sichuan-Xizang transportation corridor.The results demonstrated that the tunnel,bridge,and embankment exhibited amplification in response to the input seismic wave,with the amplification effect gradually decreasing as the input peak ground acceleration(PGA)increased.The PGAs of different engineering structures were weakened by the fault rupture zone.Nevertheless,the misalignment of the active fault may decrease the overall stiffness of the engineering structure,leading to more severe damage,with a small contribution from seismic vibration.Additionally,the seismic vibration effect might be enlarged with the height of the engineering structure,and the tunnel is supposed to have a smaller PGA and lower dynamic earth pressure compared to bridges and embankments in strong earthquake zones crossing active faults.The findings contribute valuable insights for evaluating the dynamic response of various engineering structures crossing an active fault and provide an experimental reference for secure engineering design in the challenging conditions of the Sichuan-Xizang transportation corridor.
基金supported by the Research Grants Council of Hong Kong Special Administrative Region Government of China(Grant Nos.15210322 and R5037-18)the financial support(Grant No.86902-00000240)from Shenzhen University.
文摘The vacuum-assisted prefabricated horizontal drain offers a promising method for strengthening soil slurry,allowing simultaneous filling and vacuum-dewatering via staged construction.However,there is limited research on the unique characteristics of staged filling.This study aims to investigate the vacuum consolidation process of staged-filled soil slurry through laboratory model tests and numerical simulations,also assessing the impact of anionic polyacrylamide.Comparative analyses are conducted between vacuum consolidation with and without anionic polyacrylamide,as well as self-weight consolidation without anionic polyacrylamide.Results reveal contour lines of excess pore pressure,water content,and soil strength forming an ellipse around the prefabricated horizontal drain board.During the consolidation process,a higher degree of consolidation,lower water content,and higher soil strength were observed closer to the prefabricated horizontal drain board.After treatment,the uppermost filling layer exhibits an average water content that was approximately 40%higher than the lower filling layer,and its average strength was about 60%lower.This discrepancy is primarily due to the absence of sealing on the top surface and the relatively short vacuum consolidation time caused by staged filling.The introduction of anionic polyacrylamide-induced flocculation significantly improves the initial consolidation rate but minimally affects the dewatering capacity of vacuum preloading.Using flocculant can enhance both the staged filling rate and soil strength(by 1e2 times).Additionally,employing a staggered arrangement between different prefabricated horizontal drain layers is advisable to prevent top-down penetration in areas with low soil strength.
基金National Natural Science Foundation of ChinaGrant/Award Number:41972316+3 种基金Sichuan Science&Technology FoundationGrant/Award Number:2022YFSY0007Joint Funds of the National Natural Science Foundation of ChinaGrant/Award Number:U2344226。
文摘Testing of large-sized specimens is becoming increasingly important in deep underground rock mechanics and engineering.In traditional mechanical loading,stresses on large-sized specimens are achieved by large host frames and hydraulic pumps,which could lead to great investment.Low-cost testing machines clearly always have great appeal.In this study,a new approach is proposed using thermal expansion stress to load rock specimens,which may be particularly suitable for tests of deep hot dry rock with high temperatures.This is a different technical route from traditional mechanical loading through hydraulic pressure.For the rock mechanics test system of hot dry rock that already has an investment in heating systems,this technology may reduce the cost of the loading subsystem by fully utilizing the temperature changes.This paper presents the basic principle and a typical design of this technical solution.Preliminary feasibility analysis is then conducted based on numerical simulations.Although some technical details still need to be resolved,the feasibility of this loading approach has been preliminarily confirmed.
文摘In this paper, cold simulation experiments and numerical calculations are conducted to predict 3 D flow field aerodynamics for an oil furnace after being retrofitted due to its fuel variation. K ε model and SIMPLE program under body fit coordination (BFC) system, in which TTM non orthogonal method is used to control the irregular geometric boundary, are adopted to solve the control equations. Model tests are conducted to check the calculation results, showing that they are in agreement with each other. Three different alternatives with different side window locations are also calculated to optimize the designs. The field retrofitting results show that the combination of cold tests with numerical calculations has prosperous application in retrofitting or renewing medium and small boilers.
文摘Ice load on underwater vehicles breaking through ice covers from underneath is a significant concern for researchers in polar exploration,and the research on this problem is still in its early stages.Both mechanical experimental measurement and numerical simulation pose research challenges.This study focuses on the ice load of a cylinder structure breaking upward through the ice sheet form underneath in the Small Ice Model Basin of China Ship Scientific Research Center(CSSRC SIMB).A high-speed camera system was employed to observe the ice sheet failure during the tests,in which,with the loading position as center,local radial cracks and circumferential cracks were generated.A load sensor was used to measure the overall ice load during this process.Meanwhile,a numerical model was developed using LS-DYNA for validation and comparison.With this model,numerical simulation was conducted under various ice thicknesses and upgoing speeds to analyze the instantaneous curves of ice load.The calculation results were statistically analyzed under different working conditions to determine the influence of the factors on the ice load of the cylinder.The study explores the measurement method about ice load of objects vertically breaking through model ice sheet and is expected to provide some fundamental insights into the safety design of underwater structures operating in ice waters.
基金National Natural Science Foundation of China(Grant No.52408314)Science and Technology Project of Sichuan Provincial TransportationDepartment(GrantNo.2023-ZL-03)Science and Technology Project of Guizhou Provincial Transportation Department(Grant No.2024-122-018).
文摘Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of CFST truss arch bridges.The effects of antisymmetric defect on the ultimate bearing capacity,failure mode,structural response,and steel–concrete confinement effect of CFST truss arch bridges under quarter-point loading were analyzed.On this basis,numerical simulations were conducted to investigate the in-plane bearing capacity of CFST truss arch bridges further under different scenarios.The initial defect formof the archwas obtained by using theoretical deduction,and the theoretical basis for the weakening of the ultimate bearing capacity of the arch bridge caused by geometric defects was clarified.Results indicate that the antisymmetric defect does not change the four-hinge failure mode of the model arch under quarter-point loading but increases the local cracking area and crack density of the concrete inside the pipe.The sine geometric defect with an amplitude of L/250 resulted in a 44.4%decrease in the yield load of the single hinge of the model arch,a 10.5%decrease in the failure load of the four hinges,and a 40.9%increase in themaximum vertical deformation during failure.At the initial stage of loading,the steel pipe and the concrete inside the pipe were subjected to relatively independent forces.After reaching 67%of the ultimate load,the catenary arch ribs began to produce a steel pipe concrete constraint effect.The initial geometric defects resulted in a decrease in the load when the constraint effect occurred.The antisymmetric defects with the same amplitude have a greater impact on the in-plane bearing capacity of the CFST arch bridge than the initial geometric defects with symmetry.The linear deviation at L/4 caused by constructionmust be controlled to be less than L/600 to ensure that the internal bearing capacity of the CFST arch bridge reaches 95%of the design bearing capacity.The structural deformation caused by geometric initial defects increases linearly with the increase in defect amplitude.The bearing capacity is weakened because the structural deflection and bending moment are amplified by initial defects.
基金supported by the National Natural Science Foundation of Jiangsu Province,China(Grant No.BK20231255).
文摘On the basis of the model tests,this paper explores the coupled hydrodynamic performance of the moonpool and the hull.This study aims to compare and analyze the variation in the hull heave response between the piston resonance state of the moonpool under wave excitation and the non-resonance state of the moonpool under wave-current excitation.A novel damping device specifically designed and fabricated for stepped moonpools has been developed.Before and after the installation of the damping device,the free surface response characteristics of the moonpool and heave motion response characteristics of the hull are compared.The findings show a clear correlation between the current speed and heave response characteristics of the hull.During the seakeeping design phase of the drilling vessel,the current speed is an additional critical factor that cannot be disregarded,alongside the moonpool effect.A correlation exists between the fluid dynamics occurring within the moonpool and the heave motion of the vessel hull.A reduction in the amplitude of the motion of the moonpool water results in a decrease in the heave motion of the hull.This study provides a reference for alleviating the seakeeping of a drill ship’s heave response and enhancing the safety and efficiency of the operation.
基金supported by the National Natural Science Foundation of China(52474092 and 52074042).
文摘To investigate the fracture propagation characteristics and failure mechanism of anti-dip rock slope induced by underground mining,the Jiguanling landslide in Wulong,Chongqing,China is taken as the prototype,and physical model test is utilized to study the fracture evolution process,deformation characteristics and failure mechanism of anti-dip rock slope.In this study,the digital image correlation(DIC)technique and pressure acquisition system are combined to analyze the displacement and stress field of rock slope during underground mining stages.The results show that the anti-dip rock slope experiences four stages during underground coal mining:tensile fracture propagation in upper toppling zone,shallow damage in the lower shear zone,coal seam roof caving,failure of the whole slope.There is a phenomenon of local tensile and compressive stress conversion in upper toppling zone after roof caving.The appearance of coal seam roof caving increases the compressive area and pressure of the shear zone,leading to the failure of the shear blocks at the front edge,and ultimately causing failure of the whole slope.Mining with retained coal pillar before shallow failure in the shear zone can effectively block the impact of lower mining on the upper toppling zone,achieve a 16%contraction in toppling zone,and improve the stability of the slope.The failure mode of slope can be summarized as shear–slip–toppling collapse failure.This paper improves the understanding on the failure mechanism of anti-dip rock slope caused by underground mining.
基金Science and Technology Major Project of Xinjiang Uygur Autonomous Region(2020A03003-7)Fundamental Research on Natural Science Program of Shaanxi Province(2021JM-180)+2 种基金Fundamental Research Funds for the Central Universities,CHD(Project for Leading Talents)(300102211302)Tianshan Cedar Plan of Science and Technology Department of Xinjiang Uygur Autonomous Region(2017XS13)Shaanxi Province Young Talent Lifting Program(CLGC202219).
文摘When the expressway crosses the goafs inevitably,the design is generally to build the road on coal pillars as much as possible.However,the existing coal pillars are often unable to meet relevant requirements of highway construction.Combining three-dimensional physical model tests,numerical simulations and field monitoring,with the Urumqi East Second Ring Road passing through acute inclined goafs as a background,the deformation and failure mechanism of the overlying rock and coal pillars in acute inclined goafs under expressway load were studied.And in accordance with construction requirements of subgrade,comprehensive consideration of the deformation and instability mechanism of acute inclined goafs,the treatment measures and suggestions for this type of geological disasters were put forward.The research results confirmed the rationality of coal pillars in acute inclined goafs under the expressway through grouting.According to the ratio of diff erent overlying rock thickness to coal pillar height,the change trend and value of the required grouting range were summarized,which can provide reference for similar projects.
基金support of Natural Science Foundation of China(Grant No.52108324,No.52008207,and No.52108298)for conducting this study.
文摘The mineralization process of microbial-induced calcium carbonate precipitation(MICP)is influenced by many factors,and the uniformity of the calcium carbonate precipitation has become the main focus and challenge for MICP technology.In this study,the uniformity of the saturated calcareous sand treated with MICP was in-vestigated through one-dimensional calcareous sand column tests and model tests.The coefficient of variation was employed in one-dimensional sand column tests to investigate the impact of injection rate,cementation solution concentration,and number of injection cycles on the uniformity of the MICP treatment.Additionally,model tests were conducted to investigate the impact of injection pressure and methods on the treatment range and uniformity under three-dimensional seepage conditions.Test results demonstrate that the reinforcement strength and uniformity are significantly influenced by the injection rate of the cementation solution,with a rate of 3 mL/min,yielding a favorable treatment effect.Excessive concentration of the cementation solution can lead to significant non-uniformity and a reduction in the compressive strength of MICP-treated samples.Conversely,excessively low concentrations may result in decreased bonding efficiency.Among the four considered con-centrations,0.5 mol/L and 1 mol/L exhibit superior reinforcing effects.The morphological development of calcareous sandy foundation reinforcement is associated with the spatial distribution pattern of the bacterial solution,exhibiting a relatively larger reinforcement area in proximity to the lower region of the model and a gradually decreasing range towards the upper part.Under three-dimensional seepage conditions,in addition to the non-uniform radial cementation along the injection pipe,there is also vertical heterogeneity of cementation along the length of the injection pipe due to gravitational effects,resulting in preferential deposition of calcium carbonate at the lower section,The application of injection pressure and a double-pipe circulation injection method can mitigate the accumulation of bacterial solution and cementation solution at the bottom,thereby improving the reinforcement range and uniformity.
文摘As an important part of offshore wind turbine support and fixed units, the multibucket jacket foundation bears large loads and a complex marine environment. In this paper, the horizontal bearing characteristics of the four-bucket jacket foundation of offshore wind power in sandy soil are studied. Through model tests and numerical simulations, the influence of bucket foundation sealing properties, load application speed, and loading direction on foundation-bearing capacity are discussed. The results show that the horizontal ultimate bearing capacity of the foundation in the nonsealing condition is decreased by 51.3% compared with the sealing condition;therefore, after the foundation penetration construction is completed, the bucket sealing must be ensured to increase the load-bearing performance of the structure. At a loading speed of 3.25 mm/s, the horizontal ultimate bearing capacity of the foundation is increased by 9.4% over the working condition of 1.85 mm/s. The bearing capacity of the foundation is maximized in the loading direction α =45° and is the smallest when α =0°. That is, the foundation can maximize its loadbearing performance under the condition of single-bucket compression/tension. During the design process, the main load of the structure should be loaded in the 45° direction. The contrast error of the experiment and numerical simulation does not exceed 10%. The research results have important guiding importance for designing and constructing the jacket foundation and can be used as a reference for the stable operation and sustainable development of offshore wind power systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.U24A2088 and 42277174)the Fundamental Research Funds for the Central Universities,China(Grant No.2024JCCXSB01).
文摘During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When the roof eventually collapses,the accumulated energy is released instantaneously,exerting a strong impact on the roadway.To address this issue,we proposed the synergistic control method of directional comprehensive pressure relief and energy-absorbing support(PREA)for roadways with hard roofs.In this study,we developed a three-dimensional physical model test apparatus for roof cutting and pressure relief.The 122108 ventilation roadway at the Caojiatan Coal Mine,which has a thick and hard roof,was taken as the engineering example.We analyzed the evolution patterns of stress and displacement in both the stope and the roadway surrounding rocks under different schemes.The PREA reinforcement mechanism for the roadway was investigated through comparative model tests between the new and original methods.The results showed that,compared to the original method,the new method reduced surrounding rock stress by up to 60.4%,and the roadway convergence decreased by up to 52.1%.Based on these results,we proposed corresponding engineering recommendations,which can guide fieldreinforcement design and application.The results demonstrate that the PREA method effectively reduces stress and ensures the safety and stability of the roadway.
