列车振动对岩溶区覆盖层内土洞稳定性影响机制

岩溶区覆盖层内土洞大量发育，土洞的失稳将威胁穿越该岩溶区的铁路交通正常运行，开展列车振动对既有土洞稳定性影响机制研究以提出有效监测建议对其防灾减灾有重要工程意义。依托武汉市江夏区乌龙泉岩溶塌陷实例，开展物理模型试验，探究列车振动荷载对土洞稳定性的影响机制，并用数值模拟分析其应力应变特征，据此提出有效监测建议。研究表明：覆盖层浅层的土压力动力响应较中深层更为敏感；在临界塌陷阶段，土洞背离路基侧较靠近侧具有更大的土压力波动；土洞破坏模式为：顶板弯折破坏，洞肩剪切破坏。据此提出以土洞顶板水平土压力减小和土洞背离路基侧洞肩土压力增大的重点监测部位和监测指标建议。

Influence mechanism of train vibration on stability of soil cave in overburden of Karst Area

Groundwater fluctuation in karst area results in a large number of soil caves in the upper overburden. The instability of soil caves will threaten the normal operation of railway traffic passing through the karst area. It is of great engineering significance to carry out the influence mechanism of train vibration on the stability of existing soil caves and put forward effective monitoring suggestions for disaster prevention and mitigation. Based on the case of Wulongquan karst collapse in Jiangxia District of Wuhan City, the physical model test is carried out to explore the influence mechanism of train vibration load on the stability of soil cave, and the stress-strain characteristics are analyzed by numerical simulation, so as to put forward effective monitoring suggestions. The results show that the dynamic response of earth pressure in shallow overburden is more sensitive than that in deep overburden; In the critical collapse stage, the earth pressure fluctuation on the side away from the subgrade is larger than that the side near one; The failure mode of soil cave is: bending failure of the roof, shear failure of the cave shoulder. Based on this, the key monitoring parts and indexes are put forward, which are the decrease of horizontal earth pressure on the roof of the cave and the increase of earth pressure on the shoulder of the cave away from the subgrade.