中深层煤炭地下气化腔围岩热变形破坏机制

doi:10.3724/1000-6915.jrme.2024.0082

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Abstract To investigate the thermal deformation and failure mechanisms of surrounding rock in medium-deep gasification cavities，the influence of high temperature and thermal stress on the thermal damage of the rock is identified on the basis of the testing of rock samples in the profile of the spontaneous combustion coal seam and the analysis of numerical simulation，the mechanical model of the gasification cavity roof was established based on the structural characteristics of medium-deep UCG cavities. Based on the results of multi-physical field coupling numerical simulation of the surrounding rock，the stress-deformation patterns of the surrounding rock is proposed. Finally，the thermal deformation damage process of surrounding rock is systematically described from three dimensions(rock，roof and surrounding rock). The research results show that：(1) temperature affects the microstructure and permeability of rock，when the temperature is 25 ℃–400 ℃，the percentage of micropores in muddy siltstone increases，when the temperature is 400 ℃–1 000 ℃，the percentage of micropores decreases，the percentage of mesopores increases and macropores begin to appear，when the temperature is more than 1 200 ℃，the percentage of macropores is the largest，and 600 ℃ is the threshold for the increase of permeability. The difference in thermal expansion coefficients of mineral components positively contributes to the tensile thermal stress. Under the joint action of rock thermal physicochemical reaction and thermal stress，the rock thermal damage shows the change rule of slow growth，rapid development and tends to be stable. In the stage of slow growth and stabilization phase，the thermophysical-chemical reaction is dominant，and in the stage of rapid development，the thermophysical-chemical reaction and thermal stress play a joint role. (2) Compared with the assumption of the beam model，the thin plate model of the gasification cavity roof is more consistent with the characteristics of the gasification cavity of medium-deep coal. After the roof meets the instability condition，the roof will have the destructive process of small-scale collapse of solid support model，large-scale collapse of simply support model, and the arch structure tends to be stabilized in sequence. (3) The surrounding rock in the gasification cavity shows a stress deformation pattern of“three deformation characteristic zones and five stress characteristic zones”，and the multi-field coupling effect leads to the increase of the scope of the“butterfly-shaped”shear plastic zone. The tensile damage mainly occurs around the gasification cavity，the top and bottom of the cavity are deformed downward and upward respectively，and the vertical stress of the surrounding rock on both sides of the gasification cavity increases by 30 %. The development height of the shear plastic zone in the overlying rock of the gasification cavity is generally 2–5 times of the coal thickness，and it should be ensured that the water barrier in the upper part of the coal seam meets the thickness requirement when selecting the site. The research results are of theoretical significance for the safe site selection of underground gasification of medium-deep coal.

Key words： rock mechanics underground coal gasification thermal damage thin plate model thermal deformation failure

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	DONG Zhen1
	2
	3
	CHEN Yanpeng1
	2
	3
	XU Hao4
	ZHAO Yufeng1
	2
	3
	REN Bo5
	CHEN Hao1
	2
	3
	WANG Fei6

Cite this article:

DONG Zhen1,2,3, et al. Thermal deformation and failure mechanism of surrounding rock in underground gasification cavity of medium-deep coal[J]. , 2025, 44(S1): 74-88.

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https://rockmech.whrsm.ac.cn/EN/10.3724/1000-6915.jrme.2024.0082 OR https://rockmech.whrsm.ac.cn/EN/Y2025/V44/IS1/74

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