Study on the Stability of the Coal Seam Floor above a Confined Aquifer Using the Structural System Reliability Method

Abstract

A quantitative method of structural system reliability was proposed to study the influence of random rock mechanical parameters and loads on the stability of the coal seam floor above confined aquifers. To obtain the reliability probability of the floor, two modes of water-resistant floor failure were suggested as follows: (1) mining completely removed the water-resistant key strata of the floor. In this case, the failure modes were of three main types: mining failure, confined water intrusion, and combined mining failure and intrusion.(2) Failure modes included shear and tensile failures when the thickness of the key strata was greater than 0. On the basis of the elastic thin plate theory, the performance function that calculates the reliability probability of all modes could be obtained. The failure modes were regarded as the series system. The Monte Carlo method was employed to calculate the reliability probability of each failure mode and series system. The results showed that the random rock mechanical parameters and loads of the key strata significantly influence the antiwater inrush capacity of the floor. In addition, the water inrush coefficient and reliability probability can be simultaneously used as the evaluation indexes of water inrush risk. Both these indexes could improve the assessment of the reliability of the floor.

Analysis on Water Inrush Prevention Mechanism of Paste-Filled Floor above Confined Water

“…Some researchers have analyzed the influencing factors of floor failure in paste-filling face from the perspective of filling strength and filling rate [27,28]. Many researchers analyzed the relationship between floor failure depth and mining height [29][30][31]. Previous studies have established the evaluation formula of paste-filling floor and the relationship between safety factor and filling parameters [32,33].…”

Fracture Propagation and Hydraulic Properties of a Coal Floor Subjected to Thick-Seam Longwalling above a Highly Confined Aquifer

“…In recent years, the failure mechanism of a longwall panel floor above a confined aquifer attracted great concerns [6][7][8][9]. For example, Liu et al [10] conducted mathematical modelling to describe the failure of an inclined coal seam floor above confined water and calculated the failure depth after mining based on semi-infinite element theory.…”

Effect of Strain-Dependent Hydraulic Conductivity of Coal Rock on Groundwater Inrush in Mining

“…Accurate prediction of the water inflow is important in designing the coal mine drainage system, as well as enhancing coal production efficiency, and hence, was widely studied in previous researches. The methods to predict water inflow from working face include engineering analogy [2], empirical formulas [3,4], hydrokinetic analysis [5,6], analytical modeling [7][8][9], and numerical simulation [10][11][12][13]. The analogy and empirical formula methods are simple and easy to operate.…”