振冲碎石桩加固某高土石坝深厚软弱地基变形特性数值模拟

Numerical simulation of deformation characteristics of deep soft foundation of a high earth-rock dam strengthened by vibro-flotation gravel columns

为准确预测碎石桩加固深厚软弱坝基后的变形特点,基于某大型水电站工程,根据坝体不同的高度范围,将其下软弱地基按不同置换率进行振冲碎石桩加固,并利用PLAXIS有限元软件建模分析全施工阶段地基加固后的变形.建模过程考虑采用复合模量法及桩墙法两种地基等效处理方法对照分析.研究结果表明,碎石桩加固大坝软弱地基方案具有可行性,两种等效方法模拟碎石桩复合地基反映的变形趋势基本吻合;采用不同置换率分区加固软土地基可以有效控制地基的水平位移和大坝的不均匀沉降;回填弃渣底部需要碎石桩对软土地基进行置换加固,控制坡脚部位的位移变形,避免坡脚隆起;碎石桩加固地基可以加快地基超孔压消散,在大坝堆载结束时,地基沉降变形已基本完成.

In order to accurately predict the deformation characteristics of the deep and weak dam foundation reinforced with gravel columns,this study reinforced the weak foundation under the dam with vibro-flotation gravel columns at different replacement rates according to the height range of the dam of a large hydropower station project.The deformation of the foundation after reinforcement during the entire construction stage was analyzed using PLAXIS finite element software modeling,where two equivalent foundation treatment methods,including composite modulus method and pile wall method,were applied so as to compare and analyze the results.The research results indicate that the scheme of using gravel columns to reinforce the weak foundation of the dam is feasible,and the two equivalent methods used for simulating the deformation trend reflected by the gravel column composite foundation are basically consistent with each other.It can effectively control the horizontal displacement of the foundation and the uneven settlement of the dam by using different replacement rates to reinforce soft soil foundation.In backfilling the bottom of the abandoned slag,it requires using the gravel columns to replace and reinforce the soft soil foundation,control the displacement and deformation at the foot of the slope,and avoid uplift at the foot of the slope.It can accelerate the dissipation of excess pore pressure in the foundation by strengthening the foundation with gravel columns.By the end of the dam's loading,the settlement and deformation of the foundation have been basically completed.