On the assumptions that the shear resistance increases linearly with increasing shear displacement between the uplift pile and surrounding soil, that the axis force is distributed as parabola along the pile length, th...On the assumptions that the shear resistance increases linearly with increasing shear displacement between the uplift pile and surrounding soil, that the axis force is distributed as parabola along the pile length, that elastic distortion occurs when the pile is loaded, that the displacement of pile is in accord with that of the soil, and that the uplift pile failure is regarded as the soil failure, a rational calculation method was proposed for calculating the deformation, ultimate displacement and shear resistance of piles. The distributions of frictional resistance and the shear displacement along the pile length were obtained with the method. The comparisons were made between the measurement results and the present results. The present theoretical results agree well with the measurement results, with the average difference being less than 12% before failure. The comparisons show that the proposed method is reasonable for uplift design and engineering construction of piles.展开更多
Pile foundations of ports, mooring systems for ocean surface or submerged platforms are subjected to amount of uplift loading, and prediction of the uplift capacity is one of the most important subjects in structure d...Pile foundations of ports, mooring systems for ocean surface or submerged platforms are subjected to amount of uplift loading, and prediction of the uplift capacity is one of the most important subjects in structure designs. The paper pertains to the development of a simplified theoretical method on prediction of the uplift capacity of pile group embedded in clay assuming a composite failure surface (inverted and tnmcated circular pyramidal and cylindrical sttrface). Various pile and soil parameters such as the arrangement of pile group, pile spacing, length, diameter of the pile and the soil properties such as unit weight, angle of internal friction and the pile-soil interface friction angle, which have direct influence on the uplift capacity of the pile group, are incorporated in the analysis. A 3D numerical model is built by FLAC3D to analyze the pile group under uplift loading for comparison, and various effect factors, such as length to diameter ratio, pile spacing and pile numbers are considered. The predicted values of uplift capacity and failure surface of pile group with different length to diameter ratio, pile spacing and soil properties are then compared with numerical analysis results and tleld test results. The predictions are found to be in good agreement with numerical analysis and measured values, which validate the correctness of the developed method. It is also found that the uplift capacity is significantly influenced by the pile-soil friction coefficient, soil shear strength, etc.展开更多
Based on the characteristics of pile-soil interaction and the Mohr-Coulomb strength theory,a new method of determining the side friction at a pile-soil interaction is proposed.Combined with the actual engineering case...Based on the characteristics of pile-soil interaction and the Mohr-Coulomb strength theory,a new method of determining the side friction at a pile-soil interaction is proposed.Combined with the actual engineering cases,the effectiveness of the analogue test method is verified by comparing it with the traditional anchor pile method and self-balanced method.Taking the self-balanced test of the bridge pile foundation in the Songhua River as an example,the conversion factor of sandy soil and weathered mudstone are confirmed by the analogue test method.The results show that the conversion factor of sandy soil and weathered mudstone in the Songhua River area should consider the geological conditions and the construction technology,etc.The standard values are relatively conservative.It is suggested that the engineering application should be properly revised.The recommended range of the conversion factor of sandy soil in this area is 0.65 to 0.85,and that of weathered mudstone is 1.0.展开更多
This paper reports in situ tension test and laboratory model test for large diameter, manually digging anchorage piles in the 2nd Luzhou Changjiang Bridge. Tension behavior, uplift bearing capacity and influenc...This paper reports in situ tension test and laboratory model test for large diameter, manually digging anchorage piles in the 2nd Luzhou Changjiang Bridge. Tension behavior, uplift bearing capacity and influence of rock characteristics on bearing capacity are discussed. Proposes are presented with respect to issues related to the construction and design of uplift piles.展开更多
Prestressed high-strength-concrete (PHC) tube-shaped pile is one of the recently used foundations for soft soil. The research on uplift resistance of PHC pile is helpful to the design of pile foundations. A field-scal...Prestressed high-strength-concrete (PHC) tube-shaped pile is one of the recently used foundations for soft soil. The research on uplift resistance of PHC pile is helpful to the design of pile foundations. A field-scale test program was conducted to study the uplift behavior and load transfer mechanism of PHC piles in soft soil. The pullout load tests were divided into two groups with different diameters, and there were three piles in each group. A detailed discussion of the axial load transfer and pile skin resistance distribution was also included. It is found from the tests that the uplift capacity increases with increasing the diameter of pile. When the diameter of piles increases from 500 to 600 mm, the uplift load is increased by 51.2%. According to the load-displacement (Q-S) curves, all the piles do not reach the ultimate state at the maximum load. The experimental results show that the piles still have uplift bearing capacity.展开更多
A laboratory setup was developed to investigate irregular wave uplift loads on exposed high-pile jetties. It is shown that the dimensionless uplift load increases to the maximum with an increasing relative clearance a...A laboratory setup was developed to investigate irregular wave uplift loads on exposed high-pile jetties. It is shown that the dimensionless uplift load increases to the maximum with an increasing relative clearance and then decreases. The relative clearance corresponding to the peak force is linked to a range from 0.4 to 0.8. When the relative clearance exceeds a certain value, the wave can not reach the underside of the deck and the force becomes zero. Distinct trends of dimensionless force with a relative width of deck show that the force tends to decrease as the relative deck width increases, and then the decrease slows down after the relative deck width increases or decreases to a certain value. The pressure distribution length associated with the maximum uplift force is equivalent to the wave contact width x. When x is larger than the width of deck B, it is taken as B. The statistical distribution of loads obeys the Weibull distribution. The results from the analyses of the real data suggest a new dimensionless prediction model on wave-in-deck uplift loads and the conversion ratio between wave loads at different exceedance probabilities. A comparison is made between the new prediction model and the existing widely used three prediction models. These results are used as useful references for structural design of the jetty.展开更多
To optimize the distance between the bells in pile design,this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space rati...To optimize the distance between the bells in pile design,this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space ratios.Finite element modelling is also performed to evaluate the range of soil failure around the piles during pile uplift displacement.Test results show that when bell space ratio is 6 or 8,the uplift capacity reaches the peak value.The upper bell bears more load than the lower one for the piles with bell space ratio less than 6,while the lower bell bears more load than the upper one for the piles with bell space ratio larger than 8.展开更多
The buoyancy of groundwater can reduce the foundation bearing capa-city and cause the metro tunnels to float as a whole,which threatens the safety of structures seriously.Therefore,uplift piles are set up to improve t...The buoyancy of groundwater can reduce the foundation bearing capa-city and cause the metro tunnels to float as a whole,which threatens the safety of structures seriously.Therefore,uplift piles are set up to improve the structural sta-bility.In this paper,FLAC3D software is used to establish the calculation models of pile foundation.The bearing failure process of uplift piles was simulated to study the influencing factors on single pile load bearing capacity as well as the cooperative work laws of pile groups.The load-displacement curves of pile top under different length-diameter ratios,pile soil interface characteristics and pile types are obtained,respectively.The results showed that,increasing the length-diameter ratio and the pile-soil interface roughness properdly can improve the bear-ing capacity of uplift piles.Besides,changing the shapes of constant pile section can also improve it,which has the most significant effect concerning of saving material cost.In the loading process of pile groups,the ultimate bearing capacity of corner pile is the biggest,the side pile is the next,and the center pile is the smallest.The de formation characteristics of pile top are as follows:the center pile is the biggest,the side pile is the next,and comer pile is the smallest.Combined with the results,the uplift resistance of group piles can be enhanced pertinently,and the conclusions provide guidance for the design and construction of up lift piles in the actual engineer.展开更多
Following the foundation failure of a building, with an aim of economical solution to strengthen other existing buildings of the same project, a new arrangement was implemented experimentally to test the adequacy of l...Following the foundation failure of a building, with an aim of economical solution to strengthen other existing buildings of the same project, a new arrangement was implemented experimentally to test the adequacy of load bearing capacity of a few selected cast-in-situ RCC (reinforced cement concrete) pile groups without demolishing the existing buildings. In this test, the column bottom of an existing building was removed by the help of scaffolding and after that a frame system consisting tension piles and hollow beam was constructed over the pile cap of the to be tested pile group. The load was tested by the help of hydraulic jack system and the constructed frame system. This paper contains the detailed plan, arrangement and method of the test with illustrations. The deflection and loading data analysis is also included which was performed to determine the outcome of the test. Through this test method the appropriate assessment of capacity of pile group of existing building could be done successfully and in result the structure could be saved by only super structure retrofitting.展开更多
基金Project(05-0686) supported by the Program for New Century Excellent Talents in UniversityProject(200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China
文摘On the assumptions that the shear resistance increases linearly with increasing shear displacement between the uplift pile and surrounding soil, that the axis force is distributed as parabola along the pile length, that elastic distortion occurs when the pile is loaded, that the displacement of pile is in accord with that of the soil, and that the uplift pile failure is regarded as the soil failure, a rational calculation method was proposed for calculating the deformation, ultimate displacement and shear resistance of piles. The distributions of frictional resistance and the shear displacement along the pile length were obtained with the method. The comparisons were made between the measurement results and the present results. The present theoretical results agree well with the measurement results, with the average difference being less than 12% before failure. The comparisons show that the proposed method is reasonable for uplift design and engineering construction of piles.
基金supported by the National Natural Science Foundation of China through the Postgraduate Visiting Scholar Plan (Grant No.1046-B08005)the National Natural Science Foundation of China(Grant No.50679015)
文摘Pile foundations of ports, mooring systems for ocean surface or submerged platforms are subjected to amount of uplift loading, and prediction of the uplift capacity is one of the most important subjects in structure designs. The paper pertains to the development of a simplified theoretical method on prediction of the uplift capacity of pile group embedded in clay assuming a composite failure surface (inverted and tnmcated circular pyramidal and cylindrical sttrface). Various pile and soil parameters such as the arrangement of pile group, pile spacing, length, diameter of the pile and the soil properties such as unit weight, angle of internal friction and the pile-soil interface friction angle, which have direct influence on the uplift capacity of the pile group, are incorporated in the analysis. A 3D numerical model is built by FLAC3D to analyze the pile group under uplift loading for comparison, and various effect factors, such as length to diameter ratio, pile spacing and pile numbers are considered. The predicted values of uplift capacity and failure surface of pile group with different length to diameter ratio, pile spacing and soil properties are then compared with numerical analysis results and tleld test results. The predictions are found to be in good agreement with numerical analysis and measured values, which validate the correctness of the developed method. It is also found that the uplift capacity is significantly influenced by the pile-soil friction coefficient, soil shear strength, etc.
基金The National Key Research and Development Program(No.2017YFC0703408)the National Natural Science Foundation of China(No.51478109,51678145,51878160)
文摘Based on the characteristics of pile-soil interaction and the Mohr-Coulomb strength theory,a new method of determining the side friction at a pile-soil interaction is proposed.Combined with the actual engineering cases,the effectiveness of the analogue test method is verified by comparing it with the traditional anchor pile method and self-balanced method.Taking the self-balanced test of the bridge pile foundation in the Songhua River as an example,the conversion factor of sandy soil and weathered mudstone are confirmed by the analogue test method.The results show that the conversion factor of sandy soil and weathered mudstone in the Songhua River area should consider the geological conditions and the construction technology,etc.The standard values are relatively conservative.It is suggested that the engineering application should be properly revised.The recommended range of the conversion factor of sandy soil in this area is 0.65 to 0.85,and that of weathered mudstone is 1.0.
文摘This paper reports in situ tension test and laboratory model test for large diameter, manually digging anchorage piles in the 2nd Luzhou Changjiang Bridge. Tension behavior, uplift bearing capacity and influence of rock characteristics on bearing capacity are discussed. Proposes are presented with respect to issues related to the construction and design of uplift piles.
基金Project(50621062) supported by the National Natural Science Foundation of China
文摘Prestressed high-strength-concrete (PHC) tube-shaped pile is one of the recently used foundations for soft soil. The research on uplift resistance of PHC pile is helpful to the design of pile foundations. A field-scale test program was conducted to study the uplift behavior and load transfer mechanism of PHC piles in soft soil. The pullout load tests were divided into two groups with different diameters, and there were three piles in each group. A detailed discussion of the axial load transfer and pile skin resistance distribution was also included. It is found from the tests that the uplift capacity increases with increasing the diameter of pile. When the diameter of piles increases from 500 to 600 mm, the uplift load is increased by 51.2%. According to the load-displacement (Q-S) curves, all the piles do not reach the ultimate state at the maximum load. The experimental results show that the piles still have uplift bearing capacity.
文摘A laboratory setup was developed to investigate irregular wave uplift loads on exposed high-pile jetties. It is shown that the dimensionless uplift load increases to the maximum with an increasing relative clearance and then decreases. The relative clearance corresponding to the peak force is linked to a range from 0.4 to 0.8. When the relative clearance exceeds a certain value, the wave can not reach the underside of the deck and the force becomes zero. Distinct trends of dimensionless force with a relative width of deck show that the force tends to decrease as the relative deck width increases, and then the decrease slows down after the relative deck width increases or decreases to a certain value. The pressure distribution length associated with the maximum uplift force is equivalent to the wave contact width x. When x is larger than the width of deck B, it is taken as B. The statistical distribution of loads obeys the Weibull distribution. The results from the analyses of the real data suggest a new dimensionless prediction model on wave-in-deck uplift loads and the conversion ratio between wave loads at different exceedance probabilities. A comparison is made between the new prediction model and the existing widely used three prediction models. These results are used as useful references for structural design of the jetty.
基金Project(51778346) supported by the National Natural Science Foundation of ChinaProject(2019GSF111007) supported by the Key Research and Development Project of Shandong Province of China+1 种基金Project(ZR201808040034) supported by the Natural Science Foundation of Shandong Province of ChinaProject(2015RCJJ010) supported by the Talent Introduction Research Start-up Fund Project of Shandong University of Science and Technology,China。
文摘To optimize the distance between the bells in pile design,this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space ratios.Finite element modelling is also performed to evaluate the range of soil failure around the piles during pile uplift displacement.Test results show that when bell space ratio is 6 or 8,the uplift capacity reaches the peak value.The upper bell bears more load than the lower one for the piles with bell space ratio less than 6,while the lower bell bears more load than the upper one for the piles with bell space ratio larger than 8.
基金This work was supported by National Key Research,Development Project of China(2016YFC0802206)Disaster Prevention and Mitigation Collaborative Innovation Center for Large Infrastructure of Hebei Province(2017),and Postgraduate Innovative Funding Projects of Hebei Province(CXZZSS2018060).
文摘The buoyancy of groundwater can reduce the foundation bearing capa-city and cause the metro tunnels to float as a whole,which threatens the safety of structures seriously.Therefore,uplift piles are set up to improve the structural sta-bility.In this paper,FLAC3D software is used to establish the calculation models of pile foundation.The bearing failure process of uplift piles was simulated to study the influencing factors on single pile load bearing capacity as well as the cooperative work laws of pile groups.The load-displacement curves of pile top under different length-diameter ratios,pile soil interface characteristics and pile types are obtained,respectively.The results showed that,increasing the length-diameter ratio and the pile-soil interface roughness properdly can improve the bear-ing capacity of uplift piles.Besides,changing the shapes of constant pile section can also improve it,which has the most significant effect concerning of saving material cost.In the loading process of pile groups,the ultimate bearing capacity of corner pile is the biggest,the side pile is the next,and the center pile is the smallest.The de formation characteristics of pile top are as follows:the center pile is the biggest,the side pile is the next,and comer pile is the smallest.Combined with the results,the uplift resistance of group piles can be enhanced pertinently,and the conclusions provide guidance for the design and construction of up lift piles in the actual engineer.
文摘Following the foundation failure of a building, with an aim of economical solution to strengthen other existing buildings of the same project, a new arrangement was implemented experimentally to test the adequacy of load bearing capacity of a few selected cast-in-situ RCC (reinforced cement concrete) pile groups without demolishing the existing buildings. In this test, the column bottom of an existing building was removed by the help of scaffolding and after that a frame system consisting tension piles and hollow beam was constructed over the pile cap of the to be tested pile group. The load was tested by the help of hydraulic jack system and the constructed frame system. This paper contains the detailed plan, arrangement and method of the test with illustrations. The deflection and loading data analysis is also included which was performed to determine the outcome of the test. Through this test method the appropriate assessment of capacity of pile group of existing building could be done successfully and in result the structure could be saved by only super structure retrofitting.