Similar experimental study on retaining waterproof coal pillar in composite strata mining

Abstract

Numerous field examples of coal seam mining show that when coal seams under confined water are mined close to faults, water inrush effects on complex mining surfaces occur. Obeying similarity rules, physical similarity models consisting of sand, lime, and plaster were used to investigate the water conducting process, along with stress and displacement measured by a combination of mechanical senor, total station, and video camera-. Comparing the physical model tests with the calculation results of elastoplastic limit equilibrium theory, the rationality of the model has been verified. Besides, a safe width of the waterproof coal pillar has been obtained. It can be demonstrated from the model observations that the coal seam in front of the mining can be divided into three areas with different characteristics of stress and displacement, namely, which are the fault-affected area, the elastic area, and the plastic yield crack area. A closed-loop water inlet and outlet pipeline composed of a water control platform that can provide stable water pressure, and water bags pre-buried in the fault was used to simulate the water conduction in the fracture zone. Integrate the development law of stress, displacement, and water conduction coming from the upper and lower walls of the fault to further determine the reasonable width of the waterproof coal pillar.

Characteristics of waterproof failure and optimal width of narrow coal pillars under the coupled effects of mining, excavation and seepage

“…The presence of water inrush accidents poses a tremendous threat to the safety of coal mining operations (Maiti et al 2009;Bukowski 2015;Ma et al 2019;Wang et al 2022b;Liu et al 2023a). During the excavation of roadways, various water inrush problems are frequently encountered (Gui and Lin 2016;Polak et al 2016).…”

Failure Characteristics of the Water-Resisting Coal Pillar under Stress-Seepage Coupling and Determination of Reasonable Coal Pillar Width

“…This study provides a theoretical basis for determining the width of the water-resisting coal pillar. Wang et al [23] determined the safe width of the water-resisting coal pillar by combining the physical model test results with the elastic-plastic limit equilibrium theory, and concluded that the coal seam before mining can be divided into fault-affected zone, elastic zone, and plastic yield fracture zone according to the stress and displacement characteristics. Based on field experience and numerical model studies, Mathey et al [24] proposed another South African squat coal pillar strength formula.…”