确定嵌岩桩下伏溶洞顶板安全厚度的局部强度折减法

摘要

以一岩溶区建筑工程为例,建立桩基-顶板-溶洞相互作用力学模型,通过不断折减溶洞顶板强度参数,直到溶洞顶板塑性区完全贯通,获取强度折减系数,进而获得溶洞顶板安全厚度和桩基极限承载力.溶洞顶板安全厚度为模型顶板厚度与强度折减系数之商;桩基极限承载力为模型桩顶加载量与强度折减系数之积.桩基静载试验表明计算结果合理.与简化理论解析法相比,局部强度折减法不受溶洞形状、顶板边界、荷载作用位置等因素制约,具有普适性.%A construction in karst area is selected for case study. A mechanics model of interaction among pile foundation-roof-karst cave is established with the reduction of karst cave roof strength parameters until the plastic zone of karst cave roof is fully penetrated.The strength reduction coefficient is obtained,and then the safe thickness of karst cave roof and the ultimate bearing capacity of the pile.The safe thickness of karst cave roof is the quotient of the roof thickness and the strength reduction coefficient.The ultimate bearing capacity of the pile is the product of the pile top load and the strength reduction coefficient.The static loading test of the pile indicates a reasonable calculation. Compared with the simplified analytical method, the local strength reduction method may be used more widely because it is not limited by the shape of the cave,the boundary of the roof and the loading position.