论文部分内容阅读
基于室内模型试验对不同溶洞顶板厚度和位置偏移量下桩端基岩极限承载力及破坏模式进行了研究。试验结果表明:基岩承载力随着溶洞顶板厚度的增加呈线性增长,到5D(D为桩径)时达到完整基岩极限承载力;随着位置偏移量的增大,基岩极限承载力也随之增大;当位置偏移溶洞轴线1.0l(l为洞跨)时,基岩承载力达到完整基岩极限承载力;顶板厚度达到5D时,位置偏移对基岩承载力无影响。溶洞顶板厚度在1D~3D时,在中心荷载作用下破坏模式为冲切破坏,破坏体为一旋转体;随着荷载位置偏移量的增加,破坏模式转变为扇形冲切破坏;当位置偏移量为1.0l时,破坏模式由冲切破坏过渡到桩端基岩塑性区发展破坏;溶洞顶板厚度为4D时,在中心荷载下呈现撕裂和冲切复合的破坏模式;溶洞顶板厚度为5D时,沿溶洞轴线方向发生撕裂破坏并伴随桩端基岩塑性区发展。最后结合规范给出了完整顶板不同厚度时的安全系数。
Based on the indoor model test, the ultimate bearing capacity and failure mode of the bedrock at different karst roof thickness and position offset were studied. The results show that the bearing capacity of bedrock increases linearly with the increase of the thickness of the roof of karst cave, and the ultimate bearing capacity of intact bedrock reaches to 5D (D is the pile diameter). With the increase of the position deviation, the bedrock ultimate bearing capacity When the displacement of the cave is 1.0l (l is a hole span), the bearing capacity of bedrock reaches the ultimate bearing capacity of complete bedrock. When the thickness of the roof reaches 5D, the position deviation has no effect on the bearing capacity of bedrock . When the roof thickness of the cave is between 1D and 3D, the failure mode is punching failure and the failure body is a rotating body under the central load. As the load displacement increases, the failure mode changes to fan-shaped cutting failure. When the position deviation When the displacement is 1.0l, the failure mode changes from blanking failure to the development of plastic zone in the bedrock. When the thickness of cave roof is 4D, the failure mode of tearing and die-cutting compound is presented under the center load. The thickness of cave roof is 5D, tearing and fracture along the axis of the cave accompanied with the development of the plastic zone of bedrock. At last, the safety coefficient of the complete roof with different thickness is given in combination with the specification.