Analytical evaluation of reducing bending moment in piles with soil cement partial improvement

The authors have developed a new code for three-dimensional nonlinear analysis based on effective stress to assess the dynamic response of structures on liquefiable ground. The object of this paper is to study using the new code the effectiveness of some remediation methods as a means to protect a group pile foundation from soil liquefaction hazard. Four types of foundation supporting a rigid structure are considered: 1) end-bearing piles in unimproved ground, 2) end-bearing piles in the ground improved with sand compaction piles, 3)end-bearing piles and a "soil cement ring", 4) end-bearing piles and a "soil cement block". The study shows that the remedial measures of Case 3 and Case 4 reduce remarkably the magnitude of the internal forces in the piles, even though the size of the soil improvement is smaller than that of the other methods.(AU)

Analytical exploration of damage to piles-structure system caused by liquefied ground motion

The object of this study is to explore the reasons resulting in the failure of pile foundations built on the soft reclaimed ground due to the 1995 Hyogo-ken Nambu Earthquake. Based on the case investigation results, at first, numerical analyses have been perfomed to examine the dynamic bahavior of the soil-pile-structure system during earthquake shaking. Then, the seismic capacity of piles was investigated when the permanent ground displacements occurred due to the softening of liquefied soils. The following main conclusions have been drawn. 1) The collapse of middle parts of piles may be caused by the lateral forces due to soil liquefaction; 2) The damage of the pile tips may be attributed to the permanent ground displacements due to post-liquefaction.(AU)