Abstract

The fluid–solid coupled with triaxial servo-controlled seepage experiments of coal containing gas was used to study coal samples from a coal mine in Sichuan Province, China. The mechanical characteristics, seepage laws, energy dissipation, and fracture evolution of raw coal under incremental tiered cyclic loading and different confining pressures were studied. The experimental results show that as the axial stress increases, the axial relative residual strain curve changes in an "N" shape, while the radial relative residual strain curve always increases. The change in the relative residual strain can be divided into three stages: compaction stage, elastic stage, and yield–failure stage. Except for in the last cycle, as the cycle number increases, the dissipated energy of coal increases linearly. With increasing cycle number, the difference in energy dissipation under different confining pressures gradually increases. During the yield–failure stage, some closed fractures inside the coal began to expand, and new fissures and cracks were generated, causing a large residual deformation and leading to a sharp increase in the dissipated energy and elastic modulus. Additionally, from the perspective of energy, a new method for calculating the elastic modulus (referred to as the equivalent elastic modulus) using the integral method was proposed.

Article Highlights

• The geomechanical behavior of gas-containing coal under incremental tiered cyclic loading is investigated.

• The failure mechanism of coal is analyzed based on dissipated energy analysis.

• The equivalent elastic modulus is calculated from the perspective of energy.

中文翻译：

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增量分层循环加载下含气煤力学特性及耗能试验研究

摘要

采用流固耦合三轴伺服控制含气煤渗流实验对四川某煤矿煤样进行研究。研究了增量分层循环荷载和不同围压条件下原煤的力学特性、渗流规律、能量耗散及裂缝演化规律。实验结果表明，随着轴向应力的增大，轴向相对残余应变曲线呈“N”形变化，而径向相对残余应变曲线始终增大。相对残余应变的变化可分为三个阶段：压实阶段、弹性阶段和屈服破坏阶段。除最后一个循环外，随着循环次数的增加，煤的耗散能量呈线性增加。随着循环次数的增加，不同围压下的能量耗散差异逐渐增大。在屈服失效阶段，煤内部的一些闭合裂缝开始扩大，产生新的裂隙和裂缝，造成较大的残余变形，导致耗散能和弹性模量急剧增加。此外，从能量的角度，提出了一种利用积分法计算弹性模量（简称等效弹性模量）的新方法。

文章亮点

• 研究了增量分层循环荷载作用下含气煤的地质力学行为。

• 基于耗散能分析分析了煤的破坏机理。

• 从能量的角度计算等效弹性模量。