富水粉砂地层深基坑底部注浆加固数值模拟分析

Numerical simulation analysis of grouting reinforcement at bottom of a deep foundation pit in water-rich silt stratum

以太原某地铁车站试验段的富水粉砂地层深基坑为依托,利用三维数值计算软件FLAC^(3D)对该工程坑底加固、坑内降水及开挖进行模拟,并将数值计算结果与现场实测数据进行对比分析。结果表明:采用高压旋喷注浆联合双液注浆加固富水软弱地层基底,能够有效阻止坑外地下水向坑内渗流,基坑周边的地下水位在整个施工过程中变化很小。基坑开挖过程中,周边地表出现最大沉降的点距离地下连续墙5~10 m,而且地表沉降最大影响范围未超过2倍开挖深度;地下连续墙变形在各开挖阶段均呈现中间大两端小的抛物线形式,最终产生的最大侧向位移为22.1 mm,位于距离地表开挖深度的1/2~2/3处。提高土体的弹性模量能够显著地抑制坑底隆起变形,然而对坑外的地表沉降及地下连续墙水平位移影响并不大,因此在实际施工过程中,不能盲目增大水泥掺入量,以免造成浪费。

Based on a deep foundation pit in water-rich silt stratum inside a subway station test section of Taiyuan,the numerical calculation software FLAC^(3D) was adopted to simulate the bottom reinforcement,pit precipitation and excavation.The calculation results were compared and validated with the field measured data.It shows that the high-pressure jet grouting combined with double liquid grouting can effectively prevent groundwater from seepage into the pit,and the groundwater level around the foundation pit varies little during the whole construction process.During foundation pit excavation,the maximum settlement point nearby is located at about 5 m to 10 m away from the underground diaphragm wall,and the maximum influence range is less than twice of the excavation depth.In each excavation stage,the deformation of diaphragm wall presents a parabolic form of high in the middle and low on both ends and the maximum lateral displacement is 22.1 mm,located at 1/2 to 2/3 of the excavation depth.Increasing the elastic modulus of soil can significantly suppress the uplift deformation at the bottom of the pit,but has little influence on the surface settlement around the foundation pit and the horizontal displacement of the diaphragm wall.Therefore,it is not advisable to blindly increase the cement content to avoid waste in actual construction.