双层地基基坑降水-防渗-回灌耦合模型沉降控制研究

Settlement Control of Excavation Dewatering-seepage Control-recharging in Coupling Model of Double-layered Ground

针对双层复合地基基坑降水过程中极易引发地基渗透破坏和基坑周边建筑物沉降等问题,为真实模拟现场双层地基三维渗流条件,自行研制了室内大型渗流试验装置,开展了双层地基基坑降水-防渗墙防渗-回灌井回灌的耦合模型试验.试验表明,相对于降水-防渗条件,增设回灌后,基坑外上排测压管水头抬升近10.7%,下排测压管水位抬升约3.1%;各测压管外侧水头比内侧平均高出约2.75%,说明在基坑降水-防渗的同时进行坑外回灌可以有效地提高基坑外回灌井底端土层以上区域的水头高度,减小基坑外建筑物的沉降.运用FLAC3D软件对坑外沉降进行数值计算,进一步印证了模型试验中降水-防渗-回灌耦合模型对沉降控制的效果.相关研究成果对复合地基降水过程中的渗透变形及地基沉降控制有一定的参考价值。

Aiming at the problems of ground seepage failure and foundation settlement around the foundation pit during the dewatering process of the double- layer composite foundation pit,the three- dimensional seepage conditions of the double-layer foundation on the site were simulated. The test device of large-scale indoor seepage was developed and double-layered. Coupling model test of foundation pit in dewatering-anti-seepage wall antiseepage- recharge well recharge was developed. The test showed that,compared with the precipitation-anti-seepage condition,after the additional recharge,the upper head of the pressure tube outside the pit is uplifted by 10.7%. The water level in the lower row of pressure measuring tubes was about 3.1%. The outer head of each pressure measuring tube was about 2.75% higher than the inner side,which indicated that it was effective to carry out the extra-pit recharge while the foundation pit was subjected to precipitation-anti-seepage. The height of the head above the soil layer at the bottom end of the recharge well outside the foundation pit was increased,and the settlement of the building outside the foundation pit was reduced. The numerical method was used to calculate the settlement,which confirmed the effect of the precipitation-anti seepage and recharge coupling model on the settlement control. The related research results had the certain reference value for the control of seepage deformation and foundation settlement composite foundation.