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
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
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
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
This paper describes the model test and the virtual simulation respectively for the VLCC class FPSO hookup, as well as addresses their different applications to the mating operation between the FPSO and the soft yoke ...This paper describes the model test and the virtual simulation respectively for the VLCC class FPSO hookup, as well as addresses their different applications to the mating operation between the FPSO and the soft yoke mooring system （SYMS） in extremely shallow water. The scope of the model test and the virtual simulation covers various installation stages including a series of positioning trials, positioning keeping and temporary mooring to the pre-installed SYMS mooring tower, pendulum mating, and yoke ballasting to storm-safe. The model test is to accurately verify bollard pull capacity to keep the FPSO in position and assess motion responses and mooring loads for the FPSO and installation vessels during various installation stages. The virtual simulation is to provide a virtual-reality environment, thus realistically replicating the hookup operation at the Simulation Test Center （STC） facility and identifying any deficiencies in key installation personnel, execution plan, or operation procedures. The methodologies of the model test and the virtual simulation addressed here can be easily extended to the deepwater applications such as positioning and installation operations of various floating systems.展开更多
Automatically formed roadway(AFR)by roof cutting with bolt grouting(RCBG)is a new deep coal mining technology.By using this technology,the broken roadway roof is strengthened,and roof cutting is applied to cut off str...Automatically formed roadway(AFR)by roof cutting with bolt grouting(RCBG)is a new deep coal mining technology.By using this technology,the broken roadway roof is strengthened,and roof cutting is applied to cut off stress transfer between the roadway and gob to ensure the collapse of the overlying strata.The roadway is automatically formed owing to the broken expansion characteristics of the collapsed strata and mining pressure.Taking the Suncun Coal Mine as the engineering background,the control effect of this new technology on roadways was studied.To compare the law of stress evolution and the surrounding rock control mechanisms between AFR and traditional gob-side entry driving,a comparative study of geomechanical model tests on the above methods was carried out.The results showed that the new technology of AFR by RCBG effectively reduced the stress concentration of the roadway compared with gob-side entry driving.The side abutment pressure peak of the solid coal side was reduced by 24.3%,which showed an obvious pressure-releasing effect.Moreover,the position of the side abutment pressure peak was far from the solid coal side,making it more beneficial for roadway stability.The deformation of AFR surrounding rock was also smaller than the deformation of the gob-side entry driving by the overload test.The former was more beneficial for roadway stability than the latter under higher stress conditions.Field application tests showed that the new technology can effectively control roadway deformation.Moreover,the technology reduced roadway excavation and avoided resource waste caused by reserved coal pillars.展开更多
To explore the failure mechanism of roadway in layered soft rocks,a physical model with the physically finite elemental slab assemblage(PFESA)method was established.Infrared thermography and a video camera were employ...To explore the failure mechanism of roadway in layered soft rocks,a physical model with the physically finite elemental slab assemblage(PFESA)method was established.Infrared thermography and a video camera were employed to capture thermal responses and deformation.The model results showed that layered soft roadway suffered from large deformation.A three-dimensional distinct element code(3 DEC)model with tetrahedral blocks was built to capture the characteristics of roadway deformation,stress,and cracks.The results showed two failure patterns,layer bending fracture and layer slipping after excavation.The layer bending fracture occurred at positions where the normal direction of layers pointed to the inside of the roadway and the layer slipping occurred in the ribs.Six schemes were proposed to investigate the effects of layered soft rocks.The results showed that the deformation of ribs was obviously larger than that of the roof and floor when the roadway passed through three types of strata.When the roadway was completely in a coal seam,the change of deformation in ribs was not obvious,while the deformation in the roof and floor increased obviously.These results can provide guidance for excavation and support design of roadways in layered soft rocks.展开更多
A physical model for the footwall slope of Nanfen open-pit mine, China was established using a selfdeveloped deep geological engineering disaster model test system. A thermosensitive similar material,paraffin, was sel...A physical model for the footwall slope of Nanfen open-pit mine, China was established using a selfdeveloped deep geological engineering disaster model test system. A thermosensitive similar material,paraffin, was selected to simulate a weak structural plane in the slope to reproduce the landslide process.From an experimental perspective, the variation trend of shear strength parameters of weak structural plane and the mechanical support characteristics of NPR(negative Poisson’s ratio) anchor cable under the condition of a large landslide deformation and failure were examined. The results of this model test showed that slope failure has four distinct stages:(1) soil compaction stage,(2) crack generation stage,(3) crack propagation stage, and(4) sliding plane transfixion stage. According to the test results, the rock mechanics parameters of weak surface in the footwall slope of Nanfen open-pit mine were calculated.The cohesion is approximately 1.35×10~5 Pa, and the internal friction angle is approximately 6.33°.During slope failure, the NPR anchor cable experiences a large deformation but no damage occurs, indicating that the NPR anchor cable can be continuously monitored and reinforced during the deformation and failure of landslide. The stress characteristics of NPR anchor cables during the test are consistent with the monitoring results of Newtonian force at the landslide site, proving that NPR anchor cables are effective and reasonable in landslide monitoring and early warning.展开更多
This study introduced at first the background of numerous highway widening projects that have been developed in recent years in China.Using a large ground settlement simulator and a fiber Bragg grating (FBG) strain se...This study introduced at first the background of numerous highway widening projects that have been developed in recent years in China.Using a large ground settlement simulator and a fiber Bragg grating (FBG) strain sensor network system,a large-scale model test,with a similarity ratio of 1:2,was performed to analyze the influence of differential settlement between new and old subgrades on pavement structure under loading condition.The result shows that excessive differential settlement can cause considerable tensile strain in the pavement structure of a widened road,for which a maximum value (S) of 6 cm is recommended.Under the repetitive load,the top layers of pavement structure are subjected to the alternate action of tensile and compressive strains,which would eventually lead to a fatigue failure of the pavement.However,application of geogrid to the splice between the new and the old roads can reduce differential settlement to a limited extent.The new subgrade of a widened road is vulnerable to the influence of dynamic load transferred from the above pavement structures.While for the old subgrade,due to its comparatively high stiffness,it can well spread the load on the pavement statically or dynamically.The test also shows that application of geogrid can effectively prevent or defer the failure of pavement structure.With geogrid,the modulus of resilience of the subgrade is increased and inhomogeneous deformation can be reduced;therefore,the stress/strain distribution in pavement structure under loading condition becomes uniform.The results obtained in this context are expected to provide a helpful reference for structural design and maintenance strategy for future highway widening projects.展开更多
Based on the similarity theory,a tunnel excavation simulation testing system under typical unsymmetrical loading conditions was established.Using this system,the failure mechanism of surrounding rock of shallow-bias t...Based on the similarity theory,a tunnel excavation simulation testing system under typical unsymmetrical loading conditions was established.Using this system,the failure mechanism of surrounding rock of shallow-bias tunnels with small clear distance was analyzed along with the load characteristics.The results show that:1) The failure process of surrounding rock of shallow-bias tunnels with small clear distance consists of structural and stratum deformation induced by tunnel excavation; Microfracture surfaces are formed in the tunnel surrounding rock and extend deep into the rock mass in a larger density; Tensile cracking occurs in shallow position on the deep-buried side,with shear slip in deep rock mass.In the meantime,rapid deformation and slip take place on the shallow-buried side until the surrounding rocks totally collapse.The production and development of micro-fracture surfaces in the tunnel surrounding rock and tensile cracking in the shallow position on the deep-buried side represent the key stages of failure.2) The final failure mode is featured by an inverted conical fracture with tunnel arch as its top and the slope at tunnel entrance slope as its bottom.The range of failure on the deep-buried side is significantly larger than that on the shallow-buried side.Such difference becomes more prominent with the increasing bias angle.What distinguishes it from the "linear fracture surface" model is that the model proposed has a larger fracture angle on the two sides.Moreover,the bottom of the fracture is located at the springing line of tunnel arch.3) The total vertical load increases with bias angle.Compared with the existing methods,the unsymmetrical loading effect in measurement is more prominent.At last,countermeasures are proposed according to the analysis results: during engineering process,1) The surrounding rock mass on the deep-buried side should be reinforced apart from the tunnel surrounding rock for shallow-buried tunnels with small clear distance; moreover,the scope of consolidation should go beyond the midline of tunnel(along the direction of the top of slope) by 4 excavation spans of single tunnel.2) It is necessary to modify the load value of shallow-bias tunnels with small clear distance.展开更多
Frequent soil landslide events are recorded in the Three Gorges Reservoir area,China,making it necessary to investigate the failure mode of such riverside landslides.Geotechnical centrifugal test is considered to be t...Frequent soil landslide events are recorded in the Three Gorges Reservoir area,China,making it necessary to investigate the failure mode of such riverside landslides.Geotechnical centrifugal test is considered to be the most realistic laboratory model,which can reconstruct the required geo-stress.In this study,the Liangshuijing landslide in the Three Gorgers Reservoir area is selected for a scaled centrifugal model experiment,and a water pump system is employed to retain the rainfall condition.Using the techniques of digital photography and pore water pressure transducers,water level fluctuation is controlled,and multi-physical data are thus obtained,including the pore water pressure,earth pressure,surface displacement and deep displacement.The analysis results indicate that:Three stages were set in the test(waterflooding stage,rainfall stage and drainage stage).Seven transverse cracks with wide of 1–5 mm appeared during the model test,of which 3 cracks at the toe landslide were caused by reservoir water fluctuation,and the cracks at the middle and rear part were caused by rainfall.During rainfall process,the maximum displacement of landslide model reaches 3 cm.And the maximum deformation of the model exceeds 12 cm at the drainage stage.The failure process of the slope model can be divided into four stages:microcracks appearance and propagation stage,thrust-type failure stage,retrogressive failure stage,and holistic failure stage.When the thrust-type zone caused by rainfall was connected or even overlapped with the retrogressive failure zone caused by the drainage,the landslide would start,which displayed a typical composite failure pattern.The failure mode and deformation mechanism under the coupling actions of water level fluctuation and rainfall are revealed in the model test,which could appropriately guide for the analysis and evaluation of riverside landslides.展开更多
The application of the vertical hoisting jack and wave motion compensation techniques to the salvage of an ancient sunken boat is introduced. The boat is wooden, loaded with cultural relics. It has been immersed at th...The application of the vertical hoisting jack and wave motion compensation techniques to the salvage of an ancient sunken boat is introduced. The boat is wooden, loaded with cultural relics. It has been immersed at the bottom of the South China Sea for more than 800 years. In order to protect the structure of the boat and the cultural relics inside to the largest extent, an open caisson is used to hold the sunken beat and the silts around before they are raised from the seabed all together as a whole. In the paper, first, the seakeeping model test of the system of the salvage barge and the open caisson is done to determine some important wave response parameters. And then a further experimental study of the ap- plication of the vertical hoisting jack and wave motion compensation scheme to the salvage of the sunken boat is carried out. In the model tests, the techniques of the integrative mechanic-electronic-hydraulic control, wave motion forecast and wave motion compensation are used to minimize the heave motion of the open caisson. The results of the model tests show that the heave motion of the open caisson can be reduced effectively by the use of the present method.展开更多
This paper presents the features of newly designed hydrodynamics test for the scaled model of 4500 m deepsea open-framed remotely operated vehicle （ROV）, which is being researched and developed by Shanghai Jiao Tong...This paper presents the features of newly designed hydrodynamics test for the scaled model of 4500 m deepsea open-framed remotely operated vehicle （ROV）, which is being researched and developed by Shanghai Jiao Tong University. Accurate hydrodynamics coefficients measurement and spatial modeling of ROV are significant for the maneuverability and control algorithm. The scaled model of ROV was constructed by 1：1.6. Hydrodynamics coefficients were measured through VPMM and LAHPMM towing test. And dynamics model was derived as a set of equations, describing nonlinear and coupled 5-DOF spatial motions. Rotation control motion was simulated to verify spatial model proposed. Research and application of hydrodynamics coefficients are expected to enable ROV to overcome uncertainty and disturbances of deepsea environment, and accomplish some more challengeable and practical missions.展开更多
To study ice-induced vibration of a compliant conical structure, a series of model tests were performed from 2004 to 2005. In the tests, the ice sheet before the compliant conical structure was found to fail in two-ti...To study ice-induced vibration of a compliant conical structure, a series of model tests were performed from 2004 to 2005. In the tests, the ice sheet before the compliant conical structure was found to fail in two-time breaking. From 2005 to 2006, this type of ice failure was studied through more groups of tests. The tests show that two-time breaking is the typical failure of ice before steep conical structures, and is controlled by other factors at the same time, such as ice speed and the angle of the cone.展开更多
Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under...Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.展开更多
Piles are generally an effective way to reduce the risk of slope failure.However,previous approaches for slope stability analysis did not consider the effect of the piles coupled with the decrease of the water level(d...Piles are generally an effective way to reduce the risk of slope failure.However,previous approaches for slope stability analysis did not consider the effect of the piles coupled with the decrease of the water level(drawdown).In this study,a series of centrifuge model tests was performed to understand the deformation and failure characteristics of slopes reinforced with various pile layouts.In the centrifuge model tests,the pile-reinforced slopes exhibited two typical failure modes under drawdown conditions:across-pile failure and through-pile failure.In the through-pile slope failure,a discontinuous slip surface was observed,implying that the assumption of the slip surface in previous stability analysis methods was unreasonable.The test results showed that drawdown led to instability of the piles in cohesive soil,as the saturated cohesive soil failed to provide sufficient constraint for piles.The slope exhibited progressive failure,from top to bottom,during drawdown.The deformation of the piles was reduced by increasing the embedment depth and row number of piles.In addition,the deformation of soils outside the piles was influenced by the piles and showed a similar distribution shape as the piles,and the similarity degree weakened as the distance from the piles increased.This study also found that the failure mechanism of unreinforced and pile-reinforced slopes induced by drawdown could be described by coupling between the deformation localization and local failure,and it revealed that pile-reinforced slopes could reduce slope deformation localization during drawdown.展开更多
Many landslides in reservoir areas continuously deform under cyclic water level fluctuations due to reservoir operations. In this paper,a landslide model, developed for a typical colluvial landslide in the Three Gorge...Many landslides in reservoir areas continuously deform under cyclic water level fluctuations due to reservoir operations. In this paper,a landslide model, developed for a typical colluvial landslide in the Three Gorges Reservoir area, is used to study the effect of cyclic water level fluctuations on the landslide. Five cyclic water level fluctuations were implemented in the test, and the fluctuation rate in the last two fluctuations doubled over the first three fluctuations. The pore water pressure and lateral landslide profiles were obtained during the test. A measurement of the landslide soil loss was proposed to quantitatively evaluate the influence of water level fluctuations. The test results show that the first water level rising is most negative to the landslide among the five cycles. The fourth drawdown with a higher drawdown rate caused further large landslide deformation. An increase of the water level drawdown rate is much more unfavorable to the landslide than an increase of the water level rising rate. In addition, the landslide was found to have an adaptive ability to resist subsequent water level fluctuations after undergoing large deformation during a water level fluctuation. The landslide deformation and observations in the field were found to support the test results well.展开更多
The stability of the anchorage slope on the Baiyang Yangtze River Highway Bridge in Yichang,China,was investigated under different rainfall conditions using model test,numerical simulation,and factor analysis.The resu...The stability of the anchorage slope on the Baiyang Yangtze River Highway Bridge in Yichang,China,was investigated under different rainfall conditions using model test,numerical simulation,and factor analysis.The results of the study are as follows:(1)with the increase of rainfall intensity,the change of earth pressure can be divided into three stages.However,when the rainfall intensity was larger than a certain value,the change of earth pressure of cut slope became two stages;with the increase of rainfall intensity,pore water pressure increased with the increase of rainfall time,while at a certain stage after the rainfall,the pore water pressure in the cut slope did not decrease immediately,but increased for a period of time.(2)When the rainfall stopped,the stability coefficient of the anchorage slope continued to decrease,then slowly increased,and finally tended to be gentle.Meanwhile,when the rainstorm reached a certain intensity,the main factor that restricted the rainfall infiltration rate became the geotechnical permeability coefficient of the cut slope,which was no longer the rainfall intensity.(3)Factor analysis shows that the rainfall intensity and rainfall duration were the most important factors for anchorage slope stability,while earth pressure,pore water pressure and slope displacement were much less significant.展开更多
Analyzing the dynamic response and calculating the tendon tension of the mooring system are necessary for the structural design of a tension leg platform （TLP）. The six-degree-of-freedom dynamic coupling responses a...Analyzing the dynamic response and calculating the tendon tension of the mooring system are necessary for the structural design of a tension leg platform （TLP）. The six-degree-of-freedom dynamic coupling responses and the mooring characteristics of TLP under random waves are studied by using a self-developed program. Results are verified by the 1：40 scaling factor model test conducted in the State Key Laboratory of Ocean Engineering at Shanghai JiaoTong University. The mean, range, and standard deviation of the numerical simulation and model test are compared. The influences of different sea states and wave approach angles on the dynamic response and tendon tension of the mooring system are investigated. The acceleration in the center and corner of the deck is forecasted.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.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.
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 Fund from COPC PL19-3 FPSO Project
文摘This paper describes the model test and the virtual simulation respectively for the VLCC class FPSO hookup, as well as addresses their different applications to the mating operation between the FPSO and the soft yoke mooring system （SYMS） in extremely shallow water. The scope of the model test and the virtual simulation covers various installation stages including a series of positioning trials, positioning keeping and temporary mooring to the pre-installed SYMS mooring tower, pendulum mating, and yoke ballasting to storm-safe. The model test is to accurately verify bollard pull capacity to keep the FPSO in position and assess motion responses and mooring loads for the FPSO and installation vessels during various installation stages. The virtual simulation is to provide a virtual-reality environment, thus realistically replicating the hookup operation at the Simulation Test Center （STC） facility and identifying any deficiencies in key installation personnel, execution plan, or operation procedures. The methodologies of the model test and the virtual simulation addressed here can be easily extended to the deepwater applications such as positioning and installation operations of various floating systems.
基金This work was supported by the National Natural Science Foundation of China(Nos.51874188,52074164,42077267,and 51927807)the Natural Science Foundation of Shandong Province,China(Nos.2019SDZY04 and ZR2020JQ23)the Project of Shandong Province Higher Educational Youth Innovation Science and Technology Program,China(No.2019KJG013).
文摘Automatically formed roadway(AFR)by roof cutting with bolt grouting(RCBG)is a new deep coal mining technology.By using this technology,the broken roadway roof is strengthened,and roof cutting is applied to cut off stress transfer between the roadway and gob to ensure the collapse of the overlying strata.The roadway is automatically formed owing to the broken expansion characteristics of the collapsed strata and mining pressure.Taking the Suncun Coal Mine as the engineering background,the control effect of this new technology on roadways was studied.To compare the law of stress evolution and the surrounding rock control mechanisms between AFR and traditional gob-side entry driving,a comparative study of geomechanical model tests on the above methods was carried out.The results showed that the new technology of AFR by RCBG effectively reduced the stress concentration of the roadway compared with gob-side entry driving.The side abutment pressure peak of the solid coal side was reduced by 24.3%,which showed an obvious pressure-releasing effect.Moreover,the position of the side abutment pressure peak was far from the solid coal side,making it more beneficial for roadway stability.The deformation of AFR surrounding rock was also smaller than the deformation of the gob-side entry driving by the overload test.The former was more beneficial for roadway stability than the latter under higher stress conditions.Field application tests showed that the new technology can effectively control roadway deformation.Moreover,the technology reduced roadway excavation and avoided resource waste caused by reserved coal pillars.
基金supported by the National Key Research and Development Plan of China(No.2016YFC0600901)the National Natural Science Foundation of China(No.51874311)the Natural Science Foundation of China(No.51904306)。
文摘To explore the failure mechanism of roadway in layered soft rocks,a physical model with the physically finite elemental slab assemblage(PFESA)method was established.Infrared thermography and a video camera were employed to capture thermal responses and deformation.The model results showed that layered soft roadway suffered from large deformation.A three-dimensional distinct element code(3 DEC)model with tetrahedral blocks was built to capture the characteristics of roadway deformation,stress,and cracks.The results showed two failure patterns,layer bending fracture and layer slipping after excavation.The layer bending fracture occurred at positions where the normal direction of layers pointed to the inside of the roadway and the layer slipping occurred in the ribs.Six schemes were proposed to investigate the effects of layered soft rocks.The results showed that the deformation of ribs was obviously larger than that of the roof and floor when the roadway passed through three types of strata.When the roadway was completely in a coal seam,the change of deformation in ribs was not obvious,while the deformation in the roof and floor increased obviously.These results can provide guidance for excavation and support design of roadways in layered soft rocks.
基金This study was supported by Zhejiang Collaborative Innovation Center for Prevention and Control of Mountain Geologic Hazards(Grant no.PCMGH-2016-Z-02).
文摘A physical model for the footwall slope of Nanfen open-pit mine, China was established using a selfdeveloped deep geological engineering disaster model test system. A thermosensitive similar material,paraffin, was selected to simulate a weak structural plane in the slope to reproduce the landslide process.From an experimental perspective, the variation trend of shear strength parameters of weak structural plane and the mechanical support characteristics of NPR(negative Poisson’s ratio) anchor cable under the condition of a large landslide deformation and failure were examined. The results of this model test showed that slope failure has four distinct stages:(1) soil compaction stage,(2) crack generation stage,(3) crack propagation stage, and(4) sliding plane transfixion stage. According to the test results, the rock mechanics parameters of weak surface in the footwall slope of Nanfen open-pit mine were calculated.The cohesion is approximately 1.35×10~5 Pa, and the internal friction angle is approximately 6.33°.During slope failure, the NPR anchor cable experiences a large deformation but no damage occurs, indicating that the NPR anchor cable can be continuously monitored and reinforced during the deformation and failure of landslide. The stress characteristics of NPR anchor cables during the test are consistent with the monitoring results of Newtonian force at the landslide site, proving that NPR anchor cables are effective and reasonable in landslide monitoring and early warning.
文摘This study introduced at first the background of numerous highway widening projects that have been developed in recent years in China.Using a large ground settlement simulator and a fiber Bragg grating (FBG) strain sensor network system,a large-scale model test,with a similarity ratio of 1:2,was performed to analyze the influence of differential settlement between new and old subgrades on pavement structure under loading condition.The result shows that excessive differential settlement can cause considerable tensile strain in the pavement structure of a widened road,for which a maximum value (S) of 6 cm is recommended.Under the repetitive load,the top layers of pavement structure are subjected to the alternate action of tensile and compressive strains,which would eventually lead to a fatigue failure of the pavement.However,application of geogrid to the splice between the new and the old roads can reduce differential settlement to a limited extent.The new subgrade of a widened road is vulnerable to the influence of dynamic load transferred from the above pavement structures.While for the old subgrade,due to its comparatively high stiffness,it can well spread the load on the pavement statically or dynamically.The test also shows that application of geogrid can effectively prevent or defer the failure of pavement structure.With geogrid,the modulus of resilience of the subgrade is increased and inhomogeneous deformation can be reduced;therefore,the stress/strain distribution in pavement structure under loading condition becomes uniform.The results obtained in this context are expected to provide a helpful reference for structural design and maintenance strategy for future highway widening projects.
基金Project(51508575)supported by the National Natural Science Foundation of ChinaProject(2011CB013802)supported by the National Basic Research Program of China+1 种基金Projects(2014M560652,2016T90764)supported by the China Postdoctoral Science FoundationProject(2015RS4006)supported by the Innovative Talents of Science and Technology Plan of Hunan Province,China
文摘Based on the similarity theory,a tunnel excavation simulation testing system under typical unsymmetrical loading conditions was established.Using this system,the failure mechanism of surrounding rock of shallow-bias tunnels with small clear distance was analyzed along with the load characteristics.The results show that:1) The failure process of surrounding rock of shallow-bias tunnels with small clear distance consists of structural and stratum deformation induced by tunnel excavation; Microfracture surfaces are formed in the tunnel surrounding rock and extend deep into the rock mass in a larger density; Tensile cracking occurs in shallow position on the deep-buried side,with shear slip in deep rock mass.In the meantime,rapid deformation and slip take place on the shallow-buried side until the surrounding rocks totally collapse.The production and development of micro-fracture surfaces in the tunnel surrounding rock and tensile cracking in the shallow position on the deep-buried side represent the key stages of failure.2) The final failure mode is featured by an inverted conical fracture with tunnel arch as its top and the slope at tunnel entrance slope as its bottom.The range of failure on the deep-buried side is significantly larger than that on the shallow-buried side.Such difference becomes more prominent with the increasing bias angle.What distinguishes it from the "linear fracture surface" model is that the model proposed has a larger fracture angle on the two sides.Moreover,the bottom of the fracture is located at the springing line of tunnel arch.3) The total vertical load increases with bias angle.Compared with the existing methods,the unsymmetrical loading effect in measurement is more prominent.At last,countermeasures are proposed according to the analysis results: during engineering process,1) The surrounding rock mass on the deep-buried side should be reinforced apart from the tunnel surrounding rock for shallow-buried tunnels with small clear distance; moreover,the scope of consolidation should go beyond the midline of tunnel(along the direction of the top of slope) by 4 excavation spans of single tunnel.2) It is necessary to modify the load value of shallow-bias tunnels with small clear distance.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41977244, 42007267)the National Key R&D Program of China (Grant No. 2017YFC1501301)
文摘Frequent soil landslide events are recorded in the Three Gorges Reservoir area,China,making it necessary to investigate the failure mode of such riverside landslides.Geotechnical centrifugal test is considered to be the most realistic laboratory model,which can reconstruct the required geo-stress.In this study,the Liangshuijing landslide in the Three Gorgers Reservoir area is selected for a scaled centrifugal model experiment,and a water pump system is employed to retain the rainfall condition.Using the techniques of digital photography and pore water pressure transducers,water level fluctuation is controlled,and multi-physical data are thus obtained,including the pore water pressure,earth pressure,surface displacement and deep displacement.The analysis results indicate that:Three stages were set in the test(waterflooding stage,rainfall stage and drainage stage).Seven transverse cracks with wide of 1–5 mm appeared during the model test,of which 3 cracks at the toe landslide were caused by reservoir water fluctuation,and the cracks at the middle and rear part were caused by rainfall.During rainfall process,the maximum displacement of landslide model reaches 3 cm.And the maximum deformation of the model exceeds 12 cm at the drainage stage.The failure process of the slope model can be divided into four stages:microcracks appearance and propagation stage,thrust-type failure stage,retrogressive failure stage,and holistic failure stage.When the thrust-type zone caused by rainfall was connected or even overlapped with the retrogressive failure zone caused by the drainage,the landslide would start,which displayed a typical composite failure pattern.The failure mode and deformation mechanism under the coupling actions of water level fluctuation and rainfall are revealed in the model test,which could appropriately guide for the analysis and evaluation of riverside landslides.
文摘The application of the vertical hoisting jack and wave motion compensation techniques to the salvage of an ancient sunken boat is introduced. The boat is wooden, loaded with cultural relics. It has been immersed at the bottom of the South China Sea for more than 800 years. In order to protect the structure of the boat and the cultural relics inside to the largest extent, an open caisson is used to hold the sunken beat and the silts around before they are raised from the seabed all together as a whole. In the paper, first, the seakeeping model test of the system of the salvage barge and the open caisson is done to determine some important wave response parameters. And then a further experimental study of the ap- plication of the vertical hoisting jack and wave motion compensation scheme to the salvage of the sunken boat is carried out. In the model tests, the techniques of the integrative mechanic-electronic-hydraulic control, wave motion forecast and wave motion compensation are used to minimize the heave motion of the open caisson. The results of the model tests show that the heave motion of the open caisson can be reduced effectively by the use of the present method.
基金financially supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2008AA092301)
文摘This paper presents the features of newly designed hydrodynamics test for the scaled model of 4500 m deepsea open-framed remotely operated vehicle （ROV）, which is being researched and developed by Shanghai Jiao Tong University. Accurate hydrodynamics coefficients measurement and spatial modeling of ROV are significant for the maneuverability and control algorithm. The scaled model of ROV was constructed by 1：1.6. Hydrodynamics coefficients were measured through VPMM and LAHPMM towing test. And dynamics model was derived as a set of equations, describing nonlinear and coupled 5-DOF spatial motions. Rotation control motion was simulated to verify spatial model proposed. Research and application of hydrodynamics coefficients are expected to enable ROV to overcome uncertainty and disturbances of deepsea environment, and accomplish some more challengeable and practical missions.
基金This project is financially supported by the National High Technology Research Development Program of China(863Program) by the National Natural Science Foundation of China(Grant No.50609015)
文摘To study ice-induced vibration of a compliant conical structure, a series of model tests were performed from 2004 to 2005. In the tests, the ice sheet before the compliant conical structure was found to fail in two-time breaking. From 2005 to 2006, this type of ice failure was studied through more groups of tests. The tests show that two-time breaking is the typical failure of ice before steep conical structures, and is controlled by other factors at the same time, such as ice speed and the angle of the cone.
基金National Natural Science Foundation of China under Grant Nos.51622803,51378177 and 51420105013the 111 Project under Grant No.B13024
文摘Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.
基金The study is supported by the National Key R&D Program of China(Grant No.2018YFC1508503)the Open Research Fund Program of State Key Laboratory of Hydroscience and Engineering,Tsinghua University(Grant No.sklhse-2020-D-03),which are greatly acknowledged.
文摘Piles are generally an effective way to reduce the risk of slope failure.However,previous approaches for slope stability analysis did not consider the effect of the piles coupled with the decrease of the water level(drawdown).In this study,a series of centrifuge model tests was performed to understand the deformation and failure characteristics of slopes reinforced with various pile layouts.In the centrifuge model tests,the pile-reinforced slopes exhibited two typical failure modes under drawdown conditions:across-pile failure and through-pile failure.In the through-pile slope failure,a discontinuous slip surface was observed,implying that the assumption of the slip surface in previous stability analysis methods was unreasonable.The test results showed that drawdown led to instability of the piles in cohesive soil,as the saturated cohesive soil failed to provide sufficient constraint for piles.The slope exhibited progressive failure,from top to bottom,during drawdown.The deformation of the piles was reduced by increasing the embedment depth and row number of piles.In addition,the deformation of soils outside the piles was influenced by the piles and showed a similar distribution shape as the piles,and the similarity degree weakened as the distance from the piles increased.This study also found that the failure mechanism of unreinforced and pile-reinforced slopes induced by drawdown could be described by coupling between the deformation localization and local failure,and it revealed that pile-reinforced slopes could reduce slope deformation localization during drawdown.
基金funded by the Key Program of National Natural Science Foundation of China (41630643)the National Key Research and Development Program of China (2017YFC1501302)the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) (CUGCJ1701)
文摘Many landslides in reservoir areas continuously deform under cyclic water level fluctuations due to reservoir operations. In this paper,a landslide model, developed for a typical colluvial landslide in the Three Gorges Reservoir area, is used to study the effect of cyclic water level fluctuations on the landslide. Five cyclic water level fluctuations were implemented in the test, and the fluctuation rate in the last two fluctuations doubled over the first three fluctuations. The pore water pressure and lateral landslide profiles were obtained during the test. A measurement of the landslide soil loss was proposed to quantitatively evaluate the influence of water level fluctuations. The test results show that the first water level rising is most negative to the landslide among the five cycles. The fourth drawdown with a higher drawdown rate caused further large landslide deformation. An increase of the water level drawdown rate is much more unfavorable to the landslide than an increase of the water level rising rate. In addition, the landslide was found to have an adaptive ability to resist subsequent water level fluctuations after undergoing large deformation during a water level fluctuation. The landslide deformation and observations in the field were found to support the test results well.
基金the National Natural Science Foundation of China(Nos.41807265,41972286)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(No.CUGQY1931)。
文摘The stability of the anchorage slope on the Baiyang Yangtze River Highway Bridge in Yichang,China,was investigated under different rainfall conditions using model test,numerical simulation,and factor analysis.The results of the study are as follows:(1)with the increase of rainfall intensity,the change of earth pressure can be divided into three stages.However,when the rainfall intensity was larger than a certain value,the change of earth pressure of cut slope became two stages;with the increase of rainfall intensity,pore water pressure increased with the increase of rainfall time,while at a certain stage after the rainfall,the pore water pressure in the cut slope did not decrease immediately,but increased for a period of time.(2)When the rainfall stopped,the stability coefficient of the anchorage slope continued to decrease,then slowly increased,and finally tended to be gentle.Meanwhile,when the rainstorm reached a certain intensity,the main factor that restricted the rainfall infiltration rate became the geotechnical permeability coefficient of the cut slope,which was no longer the rainfall intensity.(3)Factor analysis shows that the rainfall intensity and rainfall duration were the most important factors for anchorage slope stability,while earth pressure,pore water pressure and slope displacement were much less significant.
基金supported by the National Natural Science Foundation of China(Grant Nos.40906049 and 51309123)
文摘Analyzing the dynamic response and calculating the tendon tension of the mooring system are necessary for the structural design of a tension leg platform （TLP）. The six-degree-of-freedom dynamic coupling responses and the mooring characteristics of TLP under random waves are studied by using a self-developed program. Results are verified by the 1：40 scaling factor model test conducted in the State Key Laboratory of Ocean Engineering at Shanghai JiaoTong University. The mean, range, and standard deviation of the numerical simulation and model test are compared. The influences of different sea states and wave approach angles on the dynamic response and tendon tension of the mooring system are investigated. The acceleration in the center and corner of the deck is forecasted.
