长、短桩及长短组合桩加固地基特性分析

 在典型工程的地基加固方案优化设计中，采用有限元分析法，对天然地基上的筏板基础、短桩加固、长短组合桩加固、长桩加固等方案进行系统计算与分析。作用相同荷载时，短桩加固地基的荷载水平–变形曲线接近天然地基，长短组合桩加固地基的荷载水平–沉降曲线接近长桩加固地基。基础中心剖面上土体的沉降分布及5 m深处平面上的沉降分布也是短桩加固地基接近于天然地基，长短组合桩加固地基接近于长桩加固地基。短桩加固地基与天然地基具有相似的塑性开展强度及范围，且集中在上部土层。长短组合桩加固地基则与长桩加固地基相似，塑性点往深部传递到桩端持力层。长短组合桩与长桩加固地基的反力分布及大小接近。

CHARACTERISTICS ANALYSIS OF FOUNDATIONS REINFORCED BY LONG AND SHORT PILES AND LONG-SHORT COMPOSITE PILES

In the process of optimal design of foundation reinforcement for the typical project，by means of finite element analytical method，systematic calculation and analysis have been conducted aiming at raft foundation and foundations reinforced by short pile，long pile，and long-short composite pile respectively. Under the same loading condition，the load-deformation curve of foundation reinforced by short piles approximates to that of natural foundation；and the load-deformation curve of foundation reinforced by long-short composite piles is similar with that of foundation reinforced by long piles. The changing rules of settlement distribution at central cross-section of foundations and at depth of 5 m are same as those of load level-settlement curves. The intensity and range of extensive area of plastic points，which centralizes in the upper soil layers，of foundation reinforced by short piles is similar with those of natural foundation. For the foundations reinforced by long-short composite piles and long piles respectively，the plastic point develops further down to bearing layer；and the distribution and magnitude of the foundation counterforce in the two cases are similar.