浅埋隧道施工扰动下含空洞地层破坏演化规律试验研究

地层中隐伏空洞的存在是浅埋隧道施工安全事故的重要诱因。通过模型试验,系统研究了浅埋隧道施工扰动下隐伏空洞位置和数量变化对地层破坏的影响规律。模型试验结果表明:1浅埋隧道施工扰动下,含空洞地层较无空洞地层的破坏进程更为快速,破坏程度更为剧烈,导致的地面塌陷范围更广。2浅埋隧道邻近地层空洞施工过程中,空洞往往会成为隧道周边围岩破坏的起点,施工前对邻近的地层空洞进行有效处理是防控安全事故的基础。3地层空洞位置和数量的变化会显著改变围岩破裂面角度和破裂面对称性等几何特征,使得地层破坏的发展演化规律更为复杂。4当地层空洞位于隧道斜上方时,空洞对侧(无空洞一侧)区域地表裂缝的出现时间要早于空洞一侧区域,且空洞对侧区域地表裂缝的数量和尺寸均明显大于空洞一侧区域,这也为浅埋隧道施工过程中通过观测地表裂缝分布来推断地层空洞的位置提供了依据。

Model tests on failure laws of ground with voids induced by shallow tunnelling

The void existing in the ground is an important inducement for safety accidents in shallow tunnelling. Based on model tests, the failure laws of ground with voids at different locations and with different numbers are studied. The results show that: (1) The shallow tunnelling in the ground with voids results in more rapid failure process, more severe failure degree and larger surface collapse of the surrounding rock than that in the ground without voids. (2) When the tunneling is adjacent to the voids, the failures of the surrounding rock are more likely to start from the voids. Therefore, it’s important to take effective measures to deal with the voids before the tunnelling to prevent safety accidents. (3) The location and quantity of voids significantly change the geometrical characters of slip planes in the surrounding rock, such as the angle and the symmetry, which makes the failure laws of the ground with voids more complicated than those of the ground without voids. (4) When the void is located diagonally above the tunnel, the first ground surface crack at the opposite side of the void appears earlier than that at the other side. Moreover, the quantity and size of ground surface cracks at the opposite side of the void are obviously larger than those at the other side. It may provide significant information for deducing the location of a void by observing the distribution of ground surface cracks during shallow tunneling.