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 tunnel-type anchorage(TTA)is one of the main components in suspension bridges:the bearing mechanism is a key problem.Investigating the deformation characteristics,development law,and failure phenomenon of a TTA unde...A tunnel-type anchorage(TTA)is one of the main components in suspension bridges:the bearing mechanism is a key problem.Investigating the deformation characteristics,development law,and failure phenomenon of a TTA under load can provide the theoretical basis for a robust design.Utilizing the TTA of the Jinsha River suspension bridge at Lijiang Shangri-La railway as a prototype,a laboratory model test of the TTA was carried out for three different contact conditions between the anchorage body and the surrounding rock.The stress and deformation distribution law of the anchorage body and its surrounding rock were studied,and the ultimate bearing capacity and failure mode of the TTA were analyzed.The test results show that the compressive stress level is highest at the rear part of the anchorage body.Moving away from the rear portion of the body,the stress decays in a negative exponential function.Based on the load transfer curve,the calculation formula for the shear stress on the contact surface between the anchorage body and the surrounding rock was derived,which shows that the distribution of the shear stress along the axial direction of the anchorage body is not uniform.The distance from the maximum value to the loading surface is approximately 1/3 of the length of the anchorage body,and the stress decreases as the distance from the loading surface increases.Furthermore,the contact condition between the anchorage body and surrounding rock has a great influence on the bearing capacity of the TTA.The increase in the anti-skid tooth ridge and radial anchor bolt can improve the cooperative working capacity of the anchorage body and the surrounding rock,which is approximately 50%higher than that of the flat contact condition.The main function of the anchor bolt is to increase the overall rigidity of the TTA.The contact condition between the anchorage body and the surrounding rock will lead to a change in the failure mode of the TTA.With an increase in the degree of contact,the failure mode will change from shear sliding along the interface to trumpet-shaped inverted cone-shaped failure extending into the surrounding rock.展开更多
Offshore platforms are always subjected to wave action which is random variable amplitude cyclic loading. In order to simulate the stressing condition at the 'hot spot' of the tubular joints and the marine env...Offshore platforms are always subjected to wave action which is random variable amplitude cyclic loading. In order to simulate the stressing condition at the 'hot spot' of the tubular joints and the marine environment, random variable amplitude fatigue tests have been carried out on welded plate joints in sea water. The tests have been conducted under the conditions of loading frequency of 0.2 Hz/, stress ratio of -1, seawater temperature of about 20°C and cathodic protection with the potential about -850 mV, SCE. The test results have been compared with the seawater corrosion fatigue life under constant amplitude loading. Miner's linear cumulative damage summation rule has been used to predict the corrosion fatigue life under variable amplitude loading. The predicted life is in good agreement with the test data.展开更多
To overcome the deficiencies of conventional geosynthetic-reinforced and pile-supported (GRPS) embankment, a new improvement technique, fixed geosynthetic technique of GRPS embankment (FGT embankment), was developed a...To overcome the deficiencies of conventional geosynthetic-reinforced and pile-supported (GRPS) embankment, a new improvement technique, fixed geosynthetic technique of GRPS embankment (FGT embankment), was developed and introduced. Based on the discussion about the load transfer mechanism of FGT embankment, a simplified check method of the requirement of geosynthetic tensile strength and a mechanical model of the FGT embankment were proposed. Two conditions, the pile cap and pile beam conditions are considered in the mechanical model. The finite difference method is used to solve the mechanical model owing to the complexity of the differential equations and the soil strata. Then, the numerical procedure is programmed. Finally, a field test is conducted to verify the mechanical model and the calculated results are in good agreement with field measured data.展开更多
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.
基金supported by the National Natural Science Foundation (Grant No. 51408495)Key R & D projects in Sichuan Province (2020YFG0123)
文摘A tunnel-type anchorage(TTA)is one of the main components in suspension bridges:the bearing mechanism is a key problem.Investigating the deformation characteristics,development law,and failure phenomenon of a TTA under load can provide the theoretical basis for a robust design.Utilizing the TTA of the Jinsha River suspension bridge at Lijiang Shangri-La railway as a prototype,a laboratory model test of the TTA was carried out for three different contact conditions between the anchorage body and the surrounding rock.The stress and deformation distribution law of the anchorage body and its surrounding rock were studied,and the ultimate bearing capacity and failure mode of the TTA were analyzed.The test results show that the compressive stress level is highest at the rear part of the anchorage body.Moving away from the rear portion of the body,the stress decays in a negative exponential function.Based on the load transfer curve,the calculation formula for the shear stress on the contact surface between the anchorage body and the surrounding rock was derived,which shows that the distribution of the shear stress along the axial direction of the anchorage body is not uniform.The distance from the maximum value to the loading surface is approximately 1/3 of the length of the anchorage body,and the stress decreases as the distance from the loading surface increases.Furthermore,the contact condition between the anchorage body and surrounding rock has a great influence on the bearing capacity of the TTA.The increase in the anti-skid tooth ridge and radial anchor bolt can improve the cooperative working capacity of the anchorage body and the surrounding rock,which is approximately 50%higher than that of the flat contact condition.The main function of the anchor bolt is to increase the overall rigidity of the TTA.The contact condition between the anchorage body and the surrounding rock will lead to a change in the failure mode of the TTA.With an increase in the degree of contact,the failure mode will change from shear sliding along the interface to trumpet-shaped inverted cone-shaped failure extending into the surrounding rock.
文摘Offshore platforms are always subjected to wave action which is random variable amplitude cyclic loading. In order to simulate the stressing condition at the 'hot spot' of the tubular joints and the marine environment, random variable amplitude fatigue tests have been carried out on welded plate joints in sea water. The tests have been conducted under the conditions of loading frequency of 0.2 Hz/, stress ratio of -1, seawater temperature of about 20°C and cathodic protection with the potential about -850 mV, SCE. The test results have been compared with the seawater corrosion fatigue life under constant amplitude loading. Miner's linear cumulative damage summation rule has been used to predict the corrosion fatigue life under variable amplitude loading. The predicted life is in good agreement with the test data.
基金Project(51278216) supported by the National Natural Science Foundation of ChinaProject(20091341) supported by the Scientific Research Foundation for Returned Overseas Chinese Scholars,Ministry of Education,ChinaProject(HF-08-01-2011-240) supported by the Graduates’ Innovation Fund of Huazhong University of Science and Technology,China
文摘To overcome the deficiencies of conventional geosynthetic-reinforced and pile-supported (GRPS) embankment, a new improvement technique, fixed geosynthetic technique of GRPS embankment (FGT embankment), was developed and introduced. Based on the discussion about the load transfer mechanism of FGT embankment, a simplified check method of the requirement of geosynthetic tensile strength and a mechanical model of the FGT embankment were proposed. Two conditions, the pile cap and pile beam conditions are considered in the mechanical model. The finite difference method is used to solve the mechanical model owing to the complexity of the differential equations and the soil strata. Then, the numerical procedure is programmed. Finally, a field test is conducted to verify the mechanical model and the calculated results are in good agreement with field measured data.
