中文摘要：

为了研究桩基下伏溶洞顶板的稳定性以及破坏模式,利用有限元软件DIANA进行阶段分析,模拟地基土体在溶洞不断扩大过程中渐进塑性变形及位移场特性,并以无溶洞时地基极限承载力为标准设置5个不同桩端载荷等级,对比分析荷载等级和溶洞发育对于围岩稳定性的耦合影响,并总结出溶洞发育过程中顶板的破坏模式和机理.得出如下结论：溶洞发育和桩端荷载等级均存在临界安全值.在荷载等级较小时,溶洞对地基起主要影响作用,溶洞不断发育使塑性应变沿桩基下方斜向下不断扩展.当荷载等级较大时,相同发育阶段溶洞顶板塑性应变显著增大,即使溶洞发育处于安全阶段,也可能使临界安全阶段提前,发生破坏.数值模拟较好地反应实际中溶洞随时间不断扩大演化过程中围岩的受力特点,对于岩溶顶板稳定性研究具有重要参考价值.

英文摘要：

This paper studies the stability and failure mode of cave-roof under pile foundation. It uses the finite element software DIANA＇s phase analysis to simulate the plastic deformation and displacement field characteristics of foundation soil in the process of karst cave expanding gradually. Also it sets up five different load levels in contrast. It takes the uhimate bearing capacity with no cave as a benchmark to analyze the coupled effects of cave development and load level on the stability of surrounding rock and summarizes cave failure mode and mechanism. The following conclusions are draw ： cave development and pile load both exist critical safe value. When the load is small, cave plays a role of main influence to foundation. The development of cave unceasingly makes plastic strain expanding downward along pile. When load level is higher, the plastic strain of same cave developmental stage increases significantly, even within the safe cave development can lead to ahead of security phase and early damage. Finally this paper simulates practice mechanical characteristics of surrounding rock better as karst growing with time in the evolution process, which has important reference value for stability study of karst-roof.