内支撑局部失效对基坑支护体系影响的试验研究

Experimental Study on the Influences of Brace Local Failure on Excavation Supporting System

中外内支撑排桩支护体系的基坑坍塌事故时有发生,针对内支撑局部失效所引发的结构安全性问题,采用室内模型试验和数值模拟结合的研究方法,通过对比构件失效前后基坑变形及结构内力变化情况,初步揭示内支撑局部失效对整体基坑的影响。结果表明:支撑失效后引发的墙体变形在开挖面以上的中下部位最为明显,加载对地表沉降造成的影响要大于支撑破坏,与上部支撑相比下部支撑失效对支护体系更不利。支撑失效后墙体变形以该位置为中心向四周扩散至邻近支撑附近,邻近支撑会限制这种位移影响进一步扩散。最下层支撑失效后对垂直方向未失效支撑的影响大于对水平方向,随着失效支撑的深度降低,其对垂直方向的支撑影响逐渐降低而对水平方向支撑的影响逐渐增加。内支撑局部失效后荷载传递具有明显的就近现象,且随着失效支撑根数的增加,荷载传递系数也随之增大。

Excavation collapses of brace-row pile supporting system occur frequently,aiming at the structural safety problems caused by the brace local failure,using the method of indoor model test and numerical simulation,the influences on excavation was revealed by comparing the changes of excavation deformation and structural internal force before and after component failure.The results show that the wall deformation caused by brace failure is most obvious in the middle and lower parts above the excavation surface.The impact of load on surface settlement is greater than brace failure.Compared with the upper brace,the lower brace failure is more unfavorable to the supporting system.After the brace failure,the wall deformation diffused around the position to the vicinity of the adjacent brace,which will limit the further diffusion of this displacement.After the failure of the lowest brace,the impact on the intact brace in the vertical direction is greater than that on the horizontal direction.With the decrease of the depth of the failed brace,the impact in the vertical direction gradually decreases and the impact in the horizontal direction gradually increases.After the local failure of brace,the load transfer has an obviously nearby phenomenon,and the load transfer coefficient increases with the increase of the failed brace number.