Development and formation conditions of karst collapse induced by tunnel engineering in the Gele Mountain area

Abstract

In recent years, intensive tunnel construction has induced a large number of karst collapses in the Gele Mountain area. However, the distribution, scale, cause and evolution of karst collapses have not been systematically summarized. By means of data collation, drilling data analysis, monitoring data interpretation and other working methods, this study systematically analyzes the development law and formation conditions of karst collapse in the Gelle Mountain region, conducts in-depth discussion of the cave-causing mechanism and evolution process, and comes to the following conclusions. Multiple groups of karst collapse are developed in the wide karst depression, trough or dense area of tectonic fissure covered by Quaternary silty clay in the tunnel site. The multi-stage rock cave and fracture system provide a good spatial development condition for the formation of karst collapse, and the cave-inducing force mainly comes from the change of groundwater dynamic condition caused by tunnel construction. The main mechanism of karst collapse is that tunnel construction changes the local groundwater environment, and the collapse of collapsible geological structures is induced by multi-effect caving in the reconstruction process. The development and evolution of karst collapse includes three stages: incubation, formation and stability. In the incubation period the water-rich karst fissure and cave system are initially exposed during tunnel construction. Space for soil migration and collapse is formed in the surface fissure and cave zone, and the local deformation and fall of overburden occur. In the formation period water diversion and discharge measures are usually adopted in tunnel construction and operation, and karst collapse is eventually formed under the action of multi-effect collapse. In the stable period, after tunnel operation to a certain stage, groundwater environment gradually tends to a new dynamic equilibrium, the existing karst collapse gradually becomes stable, collapse group no longer expands outward. The results can be used as reference for karst collapse monitoring and warning, ecological restoration and tunnel planning.

Keywords

• gele mountain
• tunnel project
• karst collapses
• groundwater
• monitoring and forewarning