城区地表塌陷土洞发育破坏特征

为了研究城区塌陷土洞的发育致塌机制,通过建立三维模型试验研究土洞的发育破坏过程,分析了试验过程中地表变形数据以及土洞的最终破坏形状,同时通过土压力量测试验分析土洞发展过程中覆土应力的变化.以此试验为基础建立了计算土洞极限半径的有限元模型,通过正交试验分析了弹性模量、泊松比、黏聚力、内摩擦角对极限半径的影响.结果表明:对于发育的土层空洞,破坏区内土压力显著降低;土洞发生破坏时,洞顶沉降速率发生突变;土洞内部破坏的高度与土洞直径间的规律与普氏理论提出的几何规律吻合良好;对于埋深不同的土洞,其破坏形式主要分为坛形和直筒形塌陷.

Study on Development and Failure Characteristics of Soil Caves in Urban Surface Subsidence

In order to study the development and collapse mechanism of the collapsed soil cave in the urban area, the development and failure process of the soil cave were studied through the establishment of a three-dimensional model test. The surface deformation data during the test and the final failure shape of the soil cave were analyzed. Changes in the stress of the covering soil during the development of the cave was also analyzed through the measurement tests of earth pressure. Based on this experiment, a finite element model for calculating the limit radius of the soil cave was established, and the influence of elastic modulus, Poisson''s ratio, cohesion and internal friction angle on the limit radius was analyzed through orthogonal experiments. The results show that: for the developed soil cavity, the earth pressure in the failure area is significantly reduced; when the soil cave is damaged, the settlement velocity of the cave top changes suddenly; the law between the height of the damage inside the soil cave and the diameter of the soil cave is consistent with that proposed by Platts theory. The geometric rules are in good agreement; for soil caves with different burial depths, the damage modes are mainly divided into altar-shaped and straight-tube-shaped collapses.