淤泥地层中压入式沉井挤土效应的有限元分析

针对淤泥地层中压入式沉井下沉所产生的挤土效应及其环境影响问题,结合某超深地下车库工程,分析沉井压入挤土引起 的土体变形机制,并采用耦合欧拉-拉格朗日(CEL)法对下沉过程进行模拟,重点研究压入式下沉所引起的挤土效应。 研究结果表 明: 1)从土体位移来看,压入式沉井下沉挤土将引起地层发生4种典型变形,分别为井内土塞区的土体上拱、井边沉降区的土体被 带动下沉、稍远的主要隆起区的土体受挤压向上隆起及再远处的次要隆起区的土体隆起幅度逐渐减小; 2)下沉速度越快,竖向挤 土效应越大而水平挤土效应越小,刃脚挤压应力也越大,而当下沉速度为0.2~0.3 m/d时挤土效应最小; 3)土体压缩模量增大,竖 向和水平的挤土效应都会增大,且压缩模量小于2.03 MPa时挤土效应较小; 4)隔离桩可以较好地限制挤土效应引起的土体位移, 但相应地也会使挤压应力增大; 5)为控制挤土效应,建议沉井压入下沉过程中遇到高压缩性的软弱地层时以压入为主,而在遇到 相对较坚硬的地层时则应更多进行井内取土辅助压入。

Finite Element Analysis of Soil Squeezing Effect Induced by Press-in Caisson in Muddy Ground

In order to investigate the soil squeezing effect induced by press-in caisson sinking in muddy ground, the mechanism of soil displacement caused by soil squeezing is analyzed, and then the coupled Eulerian-Lagrangian (CEL) method is used to simulate the process of caisson sinking based on an ultra-deep underground garage project. In this way, the soil squeezing effect of press-in caisson and its influencing factors are studied. The study results show that: (1) The ground deformation caused by sinking can be classified into 4 types, i.e. soil plug, settlement, major heave and minor heave. (2) The faster the sinking speed, the greater the vertical squeezing effect, the smaller the horizontal squeezing effect and the larger the press stress; and the soil squeezing effect is the smallest when the sinking speed is 0.2-0.3 m/d. (3) The increase in compressive modulus of soil will lead to the growth of both vertical and horizontal squeezing effects; and the soil squeezing effect is rather small when the compressive modulus is less than 2.03 MPa. (4) The isolation piles can greatly limit the soil displacement caused by soil squeezing effect, but the press stress will also increase significantly as a result. (5) To control the soil squeezing effect, it is suggested to gently press-in caisson in soft ground with high compressibility and take digging inside caisson as an auxiliary measure in harder ground.