贵州某岩溶地区结构地基基础设计研究

Study on the foundation design of the structure in a karst area in Guizhou province

由于岩溶地区地下溶洞分布复杂、形状大小不一,给建筑结构基础设计带来了困难。结合贵州岩溶强发育地区某实际工程,重点研究了在溶岩强发育地区桩端顶板厚度小于3D(D为桩径)和5m时,溶洞体积、顶板厚度、岩体临空面及应力扩散角对桩基承载力的影响,探讨了同一建筑多种基础形式的应用以及基础遇到溶洞时处理方法。得出如下结论:应保证桩端下3D和5m范围内无软弱夹层、断裂破碎带和洞穴分布,且在桩底应力扩散范围内应无岩体临空面;桩身穿越溶洞时,应将顶板厚度乘以折减系数后计入侧阻力的计算;相邻桩基的桩端有高差且距离较近(净距小于5m)时,桩端高差应小于桩净距(满足桩底竖向应力的扩散角条件);当基岩面起伏较大且都是岩石地基时,同一建筑物可以采用用多种基础形式。

Due to the complex distribution and different shapes and sizes of underground karst caves in karst area,it is difficult to design foundation of building structure.Combined with a practical engineering in strong karst developed area in Guizhou province,the focus is the influence of the volume of karst caves,roof thickness,the free surface of the rock mass and stress diffusion angleon the bearing capacity of the pile foundation when the thickness of the pile end roof thickness is less than 3D(D is the pile diameter)and 5m in the strong karst developed area.The application of multiple foundation forms in the same building and the treatment methods when the foundation encounters karst caves were discussed.The following conclusions are drawn:it should be guaranteed that there should be no weak interlayers,fractured zones and caves within the range of 3D and 5m below pile end,and there should be no rock free surface within the stress diffusion range of the pile bottom;when the pile body passes through the karst cave,the thickness of the roof should be multiplied by the reduction factor and counted into the calculation of the lateral resistance;if the pile end of adjacent pile foundations has height difference and the distance is relatively close(the net distance is less than 5m),the height difference of pile end should be less than the net distance of pile(satisfying the diffusion angle condition of vertical stress of pile bottom);when the bedrock surface fluctuates greatly and is all rock foundation,the same building can adopt mutiple foundation forms.