This paper describes the improvement effect and mechanism of strengthening a liquefied sand foundation using the cross-vibration wing resonance method,through an indoor model test and numerical simulation.The results ...This paper describes the improvement effect and mechanism of strengthening a liquefied sand foundation using the cross-vibration wing resonance method,through an indoor model test and numerical simulation.The results obtained from the model test showed that a vertical drainage tube was formed during vibration compaction,and finally a crater with a depth of 40 mm and a radius of 150 mm was formed with sloping sides.The sand layer obtained a good improvement effect after resonance vibration,especially in the middle-lower sand deposit.The variation in excess pore water pressure showed different behavior in three stages of the vibration process,and the value after treatment was less than before with a decrease of 18.81%.The vibration energy in the horizontal direction gradually decreased to zero,however the absorption of vibration energy of the soil presented obvious nonuniformity along the depth direction.The results of the numerical simulation were similar to the model test results,including the scope and variation of pore water pressure,and the ground settlement after treatment.展开更多
Based on the variational approach for pile groups embedded in soil modeled using a load-transfer curve method, a practical method was conducted to estimate the settlement of symmetric pile group supported embankments....Based on the variational approach for pile groups embedded in soil modeled using a load-transfer curve method, a practical method was conducted to estimate the settlement of symmetric pile group supported embankments. The working mechanism of composite foundations improved by rigid or semi-rigid columns is analyzed by this method. Under equivalent strain conditions, the pile-soil stress ratio approaches the pile-soil modulus ratio up to a limited value of pile stiffness （Rm〈10）; in the subsequent stages of high pile stiffness （Rm〉10）, a further increase in the pile-soil modulus ratio cannot lead to a significant increase of stress transferred to the columns in composite foundations. The major influencing factor of the stress concentration from soil to pile in a high pile-soil modulus ratio is the padding stiffness. For the composite foundation improved by cement mixing columns, the effective column length is about 15 to 20 m and it is a more economical and effective design when the column length is less than 15 m.展开更多
The fundamental solution to dynamic elastic differential equation after the Laplace transformation, which was obtained by Cruse and Rizzo, has been utilized to solve the boundary integral equation formulated by the we...The fundamental solution to dynamic elastic differential equation after the Laplace transformation, which was obtained by Cruse and Rizzo, has been utilized to solve the boundary integral equation formulated by the weighted residual method. The boundary element method has been applied to dealing with the heavy tamping problem. As the elasticity modulus of soil is gradually increased after each tamping, and the loading modulus and unloading modulus are quite different, residual deformations can be finally obtained for each tamping. This is a method of nonlinear elastic analysis. The relationship of hammer velocity and falling distance for heavy tamping within liquid has been derived, so providing a theoretical background for heavy tamping under water.展开更多
基金National Natural Science Foundation of People′s Republic of China under Grant No.41977241the Scientific Research Foundation of Graduate School of Southeast University under Grant No.YBPY1981。
文摘This paper describes the improvement effect and mechanism of strengthening a liquefied sand foundation using the cross-vibration wing resonance method,through an indoor model test and numerical simulation.The results obtained from the model test showed that a vertical drainage tube was formed during vibration compaction,and finally a crater with a depth of 40 mm and a radius of 150 mm was formed with sloping sides.The sand layer obtained a good improvement effect after resonance vibration,especially in the middle-lower sand deposit.The variation in excess pore water pressure showed different behavior in three stages of the vibration process,and the value after treatment was less than before with a decrease of 18.81%.The vibration energy in the horizontal direction gradually decreased to zero,however the absorption of vibration energy of the soil presented obvious nonuniformity along the depth direction.The results of the numerical simulation were similar to the model test results,including the scope and variation of pore water pressure,and the ground settlement after treatment.
文摘Based on the variational approach for pile groups embedded in soil modeled using a load-transfer curve method, a practical method was conducted to estimate the settlement of symmetric pile group supported embankments. The working mechanism of composite foundations improved by rigid or semi-rigid columns is analyzed by this method. Under equivalent strain conditions, the pile-soil stress ratio approaches the pile-soil modulus ratio up to a limited value of pile stiffness （Rm〈10）; in the subsequent stages of high pile stiffness （Rm〉10）, a further increase in the pile-soil modulus ratio cannot lead to a significant increase of stress transferred to the columns in composite foundations. The major influencing factor of the stress concentration from soil to pile in a high pile-soil modulus ratio is the padding stiffness. For the composite foundation improved by cement mixing columns, the effective column length is about 15 to 20 m and it is a more economical and effective design when the column length is less than 15 m.
文摘The fundamental solution to dynamic elastic differential equation after the Laplace transformation, which was obtained by Cruse and Rizzo, has been utilized to solve the boundary integral equation formulated by the weighted residual method. The boundary element method has been applied to dealing with the heavy tamping problem. As the elasticity modulus of soil is gradually increased after each tamping, and the loading modulus and unloading modulus are quite different, residual deformations can be finally obtained for each tamping. This is a method of nonlinear elastic analysis. The relationship of hammer velocity and falling distance for heavy tamping within liquid has been derived, so providing a theoretical background for heavy tamping under water.
