加筋水泥土桩锚墙支护的基坑监测分析

Monitoring and analysis of foundation pit with braced structure of reinforced cement soil pile anchor wall

开挖深度内地基土为淤泥质黏土,基坑西侧采用加筋水泥土桩锚大放坡开挖,其余三侧采用加筋水泥土桩锚墙支护方式支护。发现,基坑坑顶水平位移随着开挖深度的增加线性增大,到地下室封顶时,施工通道处的坑顶位移,要比不施加荷载的坑顶大2倍以上。从水平位移分布来看,基坑的阴角最小,阳角最大,基坑每侧跨中也大。对于水泥土桩锚墙支护形式,墙后土体的深层水平位移分布存在位移零点,而位移零点恰好出现在水泥土墙底附近。大放坡开挖,后面的土体也存在位移零点,但零点位置明显比有墙的浅。另外,基坑到底后,如果坑顶不作用荷载,深层水平位移变化不大,作用荷载后,深层水平位移增加较大,甚至比基坑到底时的位移高一倍以上。基坑后面路面沉降随开挖深度增加而增大,但沉降速率最大出现在基坑到底后结构开始施工的期间内。基坑开挖过程中,最大沉降出现在距离基坑约8m的地方,而不是基坑坑顶,沉降分布曲线呈凹形。靠近地面的第一排桩锚受力最大,由于第一排桩锚的屏蔽作用,分散了应力,从而以下的第二、第三、第四排桩锚的抗拔力增加不显著。

On the condition of silt clay, the west wing of foundation pit has been under slope excavation by means of reinforced cement-soil pile anchors while the other three sides braced by pile anchor walls of same materials. As findings spans on the rise. On the basis of reinforced cement-soil walls, deep-layer horizontal displacement distribution of exterior soil manifests zero just around the wall base. So does hind soil in the case of slope excavation yet with apparent shallower position than that with braced walls. Furthermore, when reaching the bottom of foundation, under load upon the heading deep-layer horizontal displacement increases much and even by over one time compared with that without load. The road sedimentation worsens with excavation depth, whose maximum rate arises within the duration of foundation construction. In the process of the excavation, maximum sedimentation occurs at the distance of eight meters away the foundation pit rather than the heading with concave curves. First row of anchor piles close to the surface bear the most and thanks to such shielding effect and then dispersive stress, uplift capacity of following three piles does not increase distinctly.