被动区土体加固范围对整个深基坑的影响

摘要

Based on numerical simulation method, the influence of soil mass reinforcement scope in passive zone (the bottom of deep excavation) on whole deep excavation was studied. The correlativity curves (the maximum of ground settlement, the maximum of heave value of bottom, the horizontal displacement of wall top and the stability safety factor of whole deep excavation versus the reinforcement depth and the reinforcement width) were established. The study results show that with the enlargement of soil mass reinforcement scope (the reinforcement depth or the reinforcement width) , the displacement of the whole deep excavation decreases and tends to uniformity, the force of the construction becomes rational. The heave of bottom reduces as a whole, the settlement of ground, the bending moment (or shearing force or axial force) of the supporting wall and the horizontal displacement of supporting wall (except for the top of the wall whose horizontal displacement increase slightly) decrease obviously and tend to steady values; when the reinforcement width is 7. 5 m (the half of whole reinforcement width) , the heave curves of the bottom of deep excavation with different reinforcement depths are almost parallel step-like pencil of curves, and when the reinforcement width is 15 m, the heave curves of the bottom of deep excavation with different reinforcement depths are almost parallel gently pencil of curves; with the stepwise increase of reinforcement width ( here the reinforcement depth value is constant), the heave value of pit bottom reduces obviously, the scope of higher heave zone dwindles gradually, especially, the scope of higher heave zone is zero when the reinforcement width is 15 m; the stability safety factor of whole deep excavation increases with the increase of the reinforcement scope. The soil mass reinforcement in passive zone is favorable to deep excavation; there exists appropriate reinforcement depth, and the wider the reinforcement width is, the better is.%基于数值模拟方法探讨了被动区土体(坑底土体)加固范围对整个基坑的影响;建立了地面沉降最大值、坑底隆起最大值、支护墙顶水平向位移和基坑整体稳定性安全系数分别与加固深度、加固宽度的关系曲线.研究结果表明:随着加固范围(加固深度或加固宽度)的扩大,整个基坑的变形减小且趋向均匀,结构的受力变得合理,主要表现为坑底隆起总体减小,地面沉降、支护墙弯矩(或剪力或轴力)、支护墙水平向位移(除支护墙顶水平向位移稍有增加外)明显减小,且趋于某一稳定值;当加固宽度为整个宽度的一半(即为7.5m)时,不同加固深度的坑底隆起曲线为近于平行的台阶型曲线束,而当加固宽度为15m时,坑底隆起曲线为近于平行的平缓型曲线束;当加固深度不变而加固宽度逐渐增大时,靠近坑壁的坑底隆起值明显减小,高隆起区范围逐渐缩小,特别是全宽度加固时,已无高隆起区;随着加固范围的增大,整个基坑的稳定性安全系数增大;坑底土体的加固对基坑是有利的;加固范围中存在适当的加固深度,而加固宽度越大越好.