深基坑地连墙支护体系协调变形规律试验研究

深基坑地连墙支护体系中局部应力集中问题，以及施工过程中的实际变形与设计值之间往往存在较大差异造成施工风险。通过设计模型试验，采用可伸缩的内支撑体系来解决上述问题。研究了内支撑体系、地连墙和墙后土体之间的协调变形特性；得出了内支撑的轴力、墙后水平土压力、基坑周围地表位移、地连墙的最大变形量等随支撑体系调节方式的变化规律；提出了地连墙支护体系协调变形智能调节方法。研究发现，相同的位移控制条件下，上部支撑伸缩引起的轴力变化量最大，底部支撑伸缩次之，4道支撑同时伸缩时影响最小；但是，支撑伸缩的位置越深，对地表竖向位移的影响范围越大，4道支撑同时伸缩对地表位移的影响范围和幅度大于单独伸缩某一道内支撑；支撑伸长可明显减小地连墙水平位移，但是会导致支撑轴力急剧增大。结果表明，实际工程中并非基坑水平位移控制越严格，支护体系就越安全，而是应合理控制内支撑伸缩长度，加强支撑轴力和位移监测。

Experimental study on compatible deformation of diaphragm wall support system for deep foundation pit

The stress concentration in diaphragm wall support system, combined with an intolerable difference between deformation of diaphragm wall occurred during the construction process and predicted by design probably result in large construction risk. The paper solved these problems by model tests in which an adjustable device was set on the support system. The compatible deformation among the support system, the diaphragm wall and the ground soil behind the diaphragm wall were investigated. The variation of the support axial force, the lateral earth pressure on the diaphragm wall, the ground surface settlement around the foundation pit and the maximum deformation of the diaphragm wall with the adjustment mode of supports were obtained. A smart regulation method for compatible deformation of the diaphragm wall support system was proposed. The results show that under a constant displacement condition, the variation of support axial force caused by the adjustment of the upper support is the largest, by the adjustment of the bottom support is secondary, and by the simultaneous adjustment of the four supports is the smallest. However, the influence range of the ground surface displacement increases with the depth of the adjusted support, but the amplitude decreases. The influence range and amplitude of the simultaneous adjustment of the four supports are larger than that of the adjustment of a single support. The lateral displacement of the diaphragm wall can be reduced by the extension of the support, but the axial force of the support will increase sharply. It can be concluded that it is not wise to strictly control the horizontal displacement of foundation pit. Instead, a reasonable adjusted displacement of support and the monitoring of the support axial force and displacement in succession are recommend.