岩溶地区隐伏溶洞顶板稳定性及变形分析

溶洞顶板以及溶洞本身的变形是评价含隐伏溶洞岩溶地基稳定性最为直观的技术指标，在岩土自重和桩基的外附荷载作用下，确定桥基隐伏溶洞顶板安全厚度为8.0 m能够满足稳定性要求，突破了设计规范中对溶洞厚跨比必须大于0.8的要求。利用有限元计算，预测了桥基下溶洞及顶板的变形规律，采用钻孔多点位移计实现了在施工荷载施加过程中对溶洞及顶板岩体的变形的实时监测，有效验证了数值计算结果的合理性。监测结果表明：溶洞顶板不同岩层及溶洞本身的变形在荷载施加初期发展较快，相同施工荷载作用下洞体本身的应变最大，而顶板表层的应变又高于洞体上部岩层应变。

Analysis on roof stability and deformation of concealed cave in karst regions

The deformation of karst cave and its roof are the audio-visual qualification to evaluate the stability of karst cave foundation. The thickness of karst cave roof more than 8.0 m was determined which can ensure stability of karst cave roof under roof rock weight and pile foundation loading. It breaks the survey and design code about that the ratio of thickness to span of karst cave should be larger than 0.8. Based on finite element analysis, the deformation characteristic of the karst cave and its roof were forecasted. The multiple-point borehole extensometer was inbuilted in karst rock, so deformation of karst cave and cave roof rock mass under construction loading were monitored on-site. The results of monitoring show that 8.0 m thickness of karst cave roof is safe, and rationality of comprehensive evaluation was confirmed. The monitoring results show that the deformation of the karst cave and its roof are faster at the begin of construction loading application. The strain of the karst cave is larger than that of the superficial rock, and the strain of the cave roof rock mass is the smallest.