The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculat...The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculation. The test results indicate that the power function is a suitable form for describing the relationship between the ratio of the maximum dynamic shear modulus due to anisotropic and isotropic consolidations and the increment of the consolidation ratio. When compared to sand, the increment of the maximum dynamic shear modulus for undisturbed soil due to anisotropic consolidation is much larger. Using a one-dimensional equivalent linearization method, the earthquake influence factor and the characteristic period of the surface acceleration are calculated for two soil layers subjected to several typical earthquake waves. The calculated results show that the difference in nonlinear properties due to different consolidation ratios is generally not very notable, but the degree of its influence on the surface acceleration spectrum is remarkable for the occurrence of strong earthquakes. When compared to isotropic consolidation, the consideration of actual anisotropic consolidation causes the characteristic period to decrease and the earthquake influence factor to increase.展开更多
A series of triaxial compression tests were arried out by means of composite-reinforced soil samples to simulate the interaction between soil and pile. The samples are made of gravel or lime-soil with different length...A series of triaxial compression tests were arried out by means of composite-reinforced soil samples to simulate the interaction between soil and pile. The samples are made of gravel or lime-soil with different length at the center. The experiment indicates that the strength of the composite samples can not be obtained by superimposure of reinforcing pile and soil simply according to their replacement proportion. It also indicates the law for stress ratio of reinforcing column to soil. The stress ratio of reinforcing column to soil increases and reaches peak rapidly while load and strain is small. Then the ratio decreases. This law is in accordance with the measuring resuits in construction site.展开更多
To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior a...To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior and its effect factors were discussed in detail. Then, the unified strength theory was introduced to set up the elastoplastic equilibrium differential equation of the subsoil under the limit equilibrium state. And from the equation, the solutions were derived with the corresponding formulas presented to calculate the earth pressure over and beneath the horizontal reinforced cushion or pillow, the stress of inter-pile subsoil and the pile-soil stress ratio. Based on the obtained solutions and measured data from an engineering project, the influence rules by the soil property parameters (i.e., the cohesion c and internal friction angle φ) and pile spacing on the pile-soil stress ratio n were discussed respectively. The results show that to improve the load sharing ratio by the piles, the more effective means for filling materials with a larger value of φ is to increase the ratio of pile cap size to spacing, while to reduce the pile spacing properly and increase the value of cohesion c is advisable for those filling materials with a smaller value of φ.展开更多
This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccen...This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, (e is the lateral load eccentricity and d is the diameter of pile) of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand.展开更多
<span style="font-family:Verdana;">This paper proposes a numerical simulation of the mechanical behavior of a reinforced concrete pile foundation under an axial load. In fact, the foundation of a struc...<span style="font-family:Verdana;">This paper proposes a numerical simulation of the mechanical behavior of a reinforced concrete pile foundation under an axial load. In fact, the foundation of a structure represents the essential structural part of it, because it ensures its bearing capacity. Among the types of foundation, </span><span style="font-family:Verdana;">deep</span><span style="font-family:Verdana;"> foundation is the one for which from a mechanical point of view, the justification takes into account the isolated or combined effects of base resistance offered by the soil bed and lateral friction at the soil-pile interface;the latter being the consequence of a large contact surface with the surrounding soil;hence the need to study the interaction between the soil and the pile in service, in order to highlight the characteristics of soil which influence the mechanical behavior of pile and therefore the stability of the structure. In this study,</span><span><span><span style="font-family:""> </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">the reinforced concrete pile is supposed to be </span><span style="font-family:Verdana;">elastic,</span><span style="font-family:Verdana;"> and characterized by a young’s modulus (</span><i><span style="font-family:Verdana;">E</span></i><span style="font-family:Verdana;">) and a Poisson’s ratio (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">ν</span></i></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">). The soil obeys to a Camclay model characterized by </span><span style="font-family:Verdana;">a cohesion</span><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">c</span></i><span style="font-family:Verdana;">), an initial voids ratio (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">e</span></i></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><sub><span style="font-family:Verdana;">0</span></sub></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">), shearing resistance angle (</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">φ</span></i></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">) </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> a pre-consolidation pressure (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">P</span></i></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><sub><span style="font-family:Verdana;">0</span></sub></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">). A joint model with a </span><span style="font-family:Verdana;">Mohr Coulomb</span><span style="font-family:Verdana;"> behavior characterizes the soil-pile interface. The loading is carrying out by imposing a vertical monotonic displacement at the head of </span><span style="font-family:Verdana;">pile</span><span style="font-family:Verdana;">. The results in terms of stress and displacement show that the bearing capacity of the pile is influenced by various soils characteristics, it appears that the vertical stress and the force mobilized at rupture increase when the initial pre_consolidation pressure, the cohesion </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> the internal friction angle of soil increase;and when the initial soil voids index decreases.</span></span></span></span>展开更多
In order to improve the design level of partially embedded single piles under simultaneous axial and lateral loads, the differential solutions were deduced, in which the soil was treated as an ideal, elastic, homogene...In order to improve the design level of partially embedded single piles under simultaneous axial and lateral loads, the differential solutions were deduced, in which the soil was treated as an ideal, elastic, homogeneous, semi-infinite isotropic medium. A comparison was made between model test results and the obtained solutions to show their validity. The calculation results indicate that the horizontal displacement and bending moment of the pile increase with increases of the axial and lateral loads. The maximum horizontal displacement and bending moment decrease by 37.9% and 13.9%, respectively, when the elastic modulus of soil increases from 4 MPa to 20 MPa. The Poisson ratio of soil plays a marginal role in pile responses. There is a critical pile length under the ground, beyond which the pile behaves as though it was infinitely long. The presented solutions can make allowance for the continuous nature of soil, and if condition permits, they can approach exact ones.展开更多
CFG pile (i.e., pile constructed by granular materials of cement, fly-ash and gravel) composite foundation is applied in subsoil treatment widely and successfully. In order to have a further study of this kind of subs...CFG pile (i.e., pile constructed by granular materials of cement, fly-ash and gravel) composite foundation is applied in subsoil treatment widely and successfully. In order to have a further study of this kind of subsoil treatment technology, the influencing factors and calculation methods of the vertical bearing capacity of single CFG pile and the CFG pile composite foundation were discussed respectively. And based on the obtained solutions, effects by the cushion and measurements to reduce negative friction area were analyzed. Moreover, the developing law of settlement and bearing capacity eigenvalue controlled by the material strength with the increase of load were given for the CFG composite foundation. The in-situ static load test was tested for CFG pile. The results of test show that the maximum test load or half of the ultimate load is used from all the points of test, the average bearing capacity eigenvalue of single pile is 390 kN, and slightly greater than the design value of bearing capacity. The bearing capacity eigenvalues of composite foundation for 3 piles are greater than 300 kPa, and the mechanical properties of CFG pile composite foundation are almost identical in the case of the same load and cushion thickness. The pile-soil stress ratio and the load-sharing ratio can be adjusted through setting up cushion thickness.展开更多
The nonlinear large deflection differential equation, based on the assumption that the subsoil coefficient is the 2nd root of the depth, was established by energy method. The perturbation parameter was introduced to t...The nonlinear large deflection differential equation, based on the assumption that the subsoil coefficient is the 2nd root of the depth, was established by energy method. The perturbation parameter was introduced to transform the equation to a series of linear differential equations to be solved, and the deflection function according with the boundary condition was considered. Then, the nonlinear higher-order asymptotic solution of post-buckling behavior of a pile was obtained by parameter-substituting. The influencing factors such as bury-depth ratio and stiffness ratio of soil to pile, slenderness ratio on the post-buckling behavior of a pile were analyzed. The results show that the pile is more unstable when the bury-depth ratio and stiffness ratio of soil to pile increase, and although the buckling load increases with the stiffness of soil, the pile may ruin for its brittleness. Thus, in the region where buckling behavior of pile must be taken into account, the high grade concrete is supposed to be applied, and the dynamic buckling behavior of pile needs to be further studied.展开更多
A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing charact...A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element Composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.展开更多
基金National Natural Science Foundation of China under Grant No.51108163Natural Science Foundation of Heilongjiang Province under Grant No.E201104
文摘The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculation. The test results indicate that the power function is a suitable form for describing the relationship between the ratio of the maximum dynamic shear modulus due to anisotropic and isotropic consolidations and the increment of the consolidation ratio. When compared to sand, the increment of the maximum dynamic shear modulus for undisturbed soil due to anisotropic consolidation is much larger. Using a one-dimensional equivalent linearization method, the earthquake influence factor and the characteristic period of the surface acceleration are calculated for two soil layers subjected to several typical earthquake waves. The calculated results show that the difference in nonlinear properties due to different consolidation ratios is generally not very notable, but the degree of its influence on the surface acceleration spectrum is remarkable for the occurrence of strong earthquakes. When compared to isotropic consolidation, the consideration of actual anisotropic consolidation causes the characteristic period to decrease and the earthquake influence factor to increase.
文摘A series of triaxial compression tests were arried out by means of composite-reinforced soil samples to simulate the interaction between soil and pile. The samples are made of gravel or lime-soil with different length at the center. The experiment indicates that the strength of the composite samples can not be obtained by superimposure of reinforcing pile and soil simply according to their replacement proportion. It also indicates the law for stress ratio of reinforcing column to soil. The stress ratio of reinforcing column to soil increases and reaches peak rapidly while load and strain is small. Then the ratio decreases. This law is in accordance with the measuring resuits in construction site.
基金Project (07JJ4015) supported by the Natural Science Foundation of Hunan Province, China
文摘To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior and its effect factors were discussed in detail. Then, the unified strength theory was introduced to set up the elastoplastic equilibrium differential equation of the subsoil under the limit equilibrium state. And from the equation, the solutions were derived with the corresponding formulas presented to calculate the earth pressure over and beneath the horizontal reinforced cushion or pillow, the stress of inter-pile subsoil and the pile-soil stress ratio. Based on the obtained solutions and measured data from an engineering project, the influence rules by the soil property parameters (i.e., the cohesion c and internal friction angle φ) and pile spacing on the pile-soil stress ratio n were discussed respectively. The results show that to improve the load sharing ratio by the piles, the more effective means for filling materials with a larger value of φ is to increase the ratio of pile cap size to spacing, while to reduce the pile spacing properly and increase the value of cohesion c is advisable for those filling materials with a smaller value of φ.
基金Thailand Research Fund and Commission on Higher Education,Ministry of Education,Thailand Under Grant No.MRG5180268
文摘This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, (e is the lateral load eccentricity and d is the diameter of pile) of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand.
文摘<span style="font-family:Verdana;">This paper proposes a numerical simulation of the mechanical behavior of a reinforced concrete pile foundation under an axial load. In fact, the foundation of a structure represents the essential structural part of it, because it ensures its bearing capacity. Among the types of foundation, </span><span style="font-family:Verdana;">deep</span><span style="font-family:Verdana;"> foundation is the one for which from a mechanical point of view, the justification takes into account the isolated or combined effects of base resistance offered by the soil bed and lateral friction at the soil-pile interface;the latter being the consequence of a large contact surface with the surrounding soil;hence the need to study the interaction between the soil and the pile in service, in order to highlight the characteristics of soil which influence the mechanical behavior of pile and therefore the stability of the structure. In this study,</span><span><span><span style="font-family:""> </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">the reinforced concrete pile is supposed to be </span><span style="font-family:Verdana;">elastic,</span><span style="font-family:Verdana;"> and characterized by a young’s modulus (</span><i><span style="font-family:Verdana;">E</span></i><span style="font-family:Verdana;">) and a Poisson’s ratio (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">ν</span></i></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">). The soil obeys to a Camclay model characterized by </span><span style="font-family:Verdana;">a cohesion</span><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">c</span></i><span style="font-family:Verdana;">), an initial voids ratio (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">e</span></i></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><sub><span style="font-family:Verdana;">0</span></sub></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">), shearing resistance angle (</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">φ</span></i></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">) </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> a pre-consolidation pressure (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">P</span></i></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><sub><span style="font-family:Verdana;">0</span></sub></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">). A joint model with a </span><span style="font-family:Verdana;">Mohr Coulomb</span><span style="font-family:Verdana;"> behavior characterizes the soil-pile interface. The loading is carrying out by imposing a vertical monotonic displacement at the head of </span><span style="font-family:Verdana;">pile</span><span style="font-family:Verdana;">. The results in terms of stress and displacement show that the bearing capacity of the pile is influenced by various soils characteristics, it appears that the vertical stress and the force mobilized at rupture increase when the initial pre_consolidation pressure, the cohesion </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> the internal friction angle of soil increase;and when the initial soil voids index decreases.</span></span></span></span>
基金Projects(50708093,51208409)supported by the National Natural Science Foundation of ChinaProject(DB01129)supported by the Talent Foundation of Xi’an University of Architecture and Technology,China
文摘In order to improve the design level of partially embedded single piles under simultaneous axial and lateral loads, the differential solutions were deduced, in which the soil was treated as an ideal, elastic, homogeneous, semi-infinite isotropic medium. A comparison was made between model test results and the obtained solutions to show their validity. The calculation results indicate that the horizontal displacement and bending moment of the pile increase with increases of the axial and lateral loads. The maximum horizontal displacement and bending moment decrease by 37.9% and 13.9%, respectively, when the elastic modulus of soil increases from 4 MPa to 20 MPa. The Poisson ratio of soil plays a marginal role in pile responses. There is a critical pile length under the ground, beyond which the pile behaves as though it was infinitely long. The presented solutions can make allowance for the continuous nature of soil, and if condition permits, they can approach exact ones.
基金Project(08JJ3111) supported by the Natural Science Foundation of Hunan ProvinceProject(08B025) supported by Scientific Research Fund of Hunan Provincial Education DepartmentProject(2006AA11Z104) supported by the National High-Tech Research and Development Program of China
文摘CFG pile (i.e., pile constructed by granular materials of cement, fly-ash and gravel) composite foundation is applied in subsoil treatment widely and successfully. In order to have a further study of this kind of subsoil treatment technology, the influencing factors and calculation methods of the vertical bearing capacity of single CFG pile and the CFG pile composite foundation were discussed respectively. And based on the obtained solutions, effects by the cushion and measurements to reduce negative friction area were analyzed. Moreover, the developing law of settlement and bearing capacity eigenvalue controlled by the material strength with the increase of load were given for the CFG composite foundation. The in-situ static load test was tested for CFG pile. The results of test show that the maximum test load or half of the ultimate load is used from all the points of test, the average bearing capacity eigenvalue of single pile is 390 kN, and slightly greater than the design value of bearing capacity. The bearing capacity eigenvalues of composite foundation for 3 piles are greater than 300 kPa, and the mechanical properties of CFG pile composite foundation are almost identical in the case of the same load and cushion thickness. The pile-soil stress ratio and the load-sharing ratio can be adjusted through setting up cushion thickness.
基金Project (50378036) supported by the National Natural Science Foundation of China
文摘The nonlinear large deflection differential equation, based on the assumption that the subsoil coefficient is the 2nd root of the depth, was established by energy method. The perturbation parameter was introduced to transform the equation to a series of linear differential equations to be solved, and the deflection function according with the boundary condition was considered. Then, the nonlinear higher-order asymptotic solution of post-buckling behavior of a pile was obtained by parameter-substituting. The influencing factors such as bury-depth ratio and stiffness ratio of soil to pile, slenderness ratio on the post-buckling behavior of a pile were analyzed. The results show that the pile is more unstable when the bury-depth ratio and stiffness ratio of soil to pile increase, and although the buckling load increases with the stiffness of soil, the pile may ruin for its brittleness. Thus, in the region where buckling behavior of pile must be taken into account, the high grade concrete is supposed to be applied, and the dynamic buckling behavior of pile needs to be further studied.
基金The National Natural Science Foundation of China (No.50478090)
文摘A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element Composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.