A Cascade Disaster Caused by Geological and Coupled Hydro-Mechanical Factors—Water Inrush Mechanism from Karst Collapse Column under Confining Pressure

Hao Li,Haibo Bai,Yabo Du,Shixin He,Jianjun Wu,Zhanguo Ma,Guangming Wu,Kai Ma

doi:10.3390/en10121938

Abstract

The water inrush from karst collapse column (KCC) is a cascading, vicious cycle disaster caused by geological and mining activities, that can cause serious casualties and property losses. The key to preventing this risk is to study the mechanism of water inrush under confining pressure. Aiming at the investigationg the characteristics of the KCC named X1 in Chensilou mine, a series of methods, including connectivity experiments, water pressure monitoring tests in two side-walls, and numerical simulations based on plastic damage-seepage (PD-S) theory have been developed. The methods are used to test the security of the 2519 mining area, the damage thickness, pore water pressure, and seepage vector in the X1. The results indicate that the X1 has a certain water blocking capacity. In addition, with the decrease of confining pressure and increase of shear stress, deviatoric stress could cause the increase of permeability, the reduction of strength, and the reduction of pore water pressure in KCC. Therefore the increased effective stress in the rock will force the rock to become more fractured. Conversely, the broken rock could cause the change of stress, and further initiate new plastic strains, damage and pore water pressure until a new equilibrium is reached. This cascading water inrush mechanism will contribute to the exploitation of deep coal resources in complex geological and hydrogeological conditions.

Highlights

Mine water inrush and consequent secondary disasters have caused huge losses in many countries, including USA [1], Russia [2], Hungary [3], Germany [4], Australia [5] and China [6]
We take Chensilou mine as an example, and study the mechanism of water inrush from karst collapse column (KCC) in complicated geological conditions by a series of methods, including connectivity experiments, water pressure monitoring tests in two side-walls, and numerical simulations based on the plastic damage-seepage (PD-S) model
The KCC’s damage zone, distribution of pore water pressure and seepage vector were obtained by numerical simulation based on the PD-S model, and verified by water pressure monitoring tests in two side-walls

Summary

Introduction

Mine water inrush and consequent secondary disasters have caused huge losses in many countries, including USA [1], Russia [2], Hungary [3], Germany [4], Australia [5] and China [6]. As a unique geological phenomenon in north China, karst collapse column (KCC), which is caused by the karst subsidence that occurs in Ordovician limestone caves, forms cone, barrel, inclined tower or irregular shapes [7], connects coal seams and aquifers (Figure 1), and may cause serious groundwater inrush disasters under the influence of the confined water pressure and the ground pressure, including axial pressure and confining pressure [8].

Results

Discussion

Conclusion