Stability analysis of hyperbolic coal pillars with peeling and high temperature effects

Youyou Xu,Huaizhan Li,Xiaopeng Liu,Guangli Guo

doi:10.1177/0144598720933515

Youyou Xu, Huaizhan Li + Show 2 more

Open Access

https://doi.org/10.1177/0144598720933515

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Abstract

In this present study, a twice-peeling model was established to analyze the hyperbolic coal pillars stability in underground coal gasification and then propose the concept of stripping degree to show model details for numerical simulation. The data shows that hyperbolic coal pillars stability can be analyzed through the twice-peeling model. Considering the coal pillars peeling and high temperature effects, one side of coal pillars will decrease 3 m, and the stability coefficient is 1.6 which has enough bearing capacity. When the arch depth ratio is 0.6, the critical condition for the coal pillar instability is reached. In this paper, underground coal gasification industrial test area still had strong bearing capacity after twice stripping, and there was no sudden instability. The research results can provide reference for the gasifier design and the stability of non-uniform coal pillars in the future.

Highlights

IntroductionThe r3 value can be substituted into equation (2), and the result is as follows cH þ
Underground coal gasification (UCG) is a clean, comprehensive utilization technology that converts coal into syngas through in-situ thermochemical reactions, while combustion generates waste
The combination of UCG and other technology is the direction of clean source utilization, such as Underground coal gasification (UCG)–Integrated Gasification Combined Cycle (IGCC) (Khadse et al, 2007), Underground coal gasification (UCG)– Carbon Dioxide Capture and Storage (CCS) (Friedmann et al, 2009; Michael et al, 2005; Yang et al, 2008), Underground coal gasification (UCG)–Hydrogen Underground Gasification (HUG), and Underground coal gasification (UCG)–Alkali Cells Fuel (ACF)

Summary

Introduction

The r3 value can be substituted into equation (2), and the result is as follows cH þ It can be seen from the above formula that in the case of a certain depth of mining, and the maximum vertical principal stress carried by the coal pillar is related to the cohesion and the internal friction angle, which can be determined by the coal physical properties. Due to the special process of UCG, the shape of the isolated coal pillar is “hyperbolic.” Under the stress of the overlying rock layer, it is believed that the curved pillar at the top part will be the first to peel off: the top part of the coal pillar is directly subjected to the load pressure of the overlying rock layer, the bending part is subjected to the load, and the horizontal expansion deformation occurs, while the coal pillar yielding zone is stripped off the coal pillar under the action of the overlying load and the horizontal thrust inside the coal pillar. By combining the above formulas, the relationship between d0 and d1 can be attained as d1 1⁄4 d0

À p ðk þ 1Þ À 1 2

À b1 0:6H

Conclusion