地下空洞引起土质地层地陷的形成机制与预测研究

Study of formation mechanism and prediction of sinkholes in soil stratum induced by subterranean cavity

地下空洞引起的土质地层地陷是地质灾害的一种常见形式。由于地陷产生的原因非常复杂,目前相关研究还处于起步阶段。通过地陷成因和实例分析,首先确认了软土和粗粒土地层的地陷破坏模式。然后对软土地层圆柱形地陷,采用土体塑性极限平衡理论导出了计算地陷安全系数的公式,并据此分析了影响地陷的相关因素。对粗粒土地层地陷的圆形塌陷漏斗,基于散体流动理论提出了粗粒土流失判据,推导了地陷安全系数计算公式;通过分析粗粒土地层地陷形成规律,提出了基于土层厚度和地陷漏斗最大沉降的地陷预测与评估方法。最后,采用数值模拟方法分析了软土和粗粒土地层地陷时的地层变形规律,对所提地陷模型的合理性进行了说明。本文研究成果可为认识土质地层地陷的形成机制和地陷防治提供参考。

The phenomenon of sinkholes in soil stratum induced by subterranean cavity is the common geological hazards. However, there is limited research on the formation mechanisms of sinkholes due to its complicated reasons. In this paper, the formation models of sinkholes in soft and coarse-grained soil strata are firstly obtained by analyzing the formation causes and case studies. For the cylinder-shaped sinkhole in soft soil stratum, the equations of safety factor are derived using the plastic limit equilibrium theory, which are further used to characterize some relevant factors that influence the formation of sinkholes. For the funneled sinkhole in coarse-grained soil stratum, the equation of safety factor is also determined on the basis of the granular media flow theory. By analyzing the formation patterns of sinkholes, we propose a method to predict and assess the sinkhole occurrence based on the thickness of soil stratum and the maximum subsidence. Finally, the deformation characteristics of the soft and coursed-grained soil strata induced by sinkholes are analyzed by using numerical simulation, and two formation models of the sinkholes are further verified. This study is essential to understanding the formation mechanisms and prevention of sinkholes in soil stratum.