气体运移引起煤体变形是研究煤层气抽采、预防瓦斯突出与温室气体的地质封存的核心问题。一般认为，有效应力变化是控制岩土类材料骨架变形的关键因素。但大量测试结果表明，煤的渗透率与有效应力（或者孔隙压力）表现出非线性关系。为此，应实时观测在静孔隙压力与三轴应力状态下氦气流动导致原煤变形演化全过程。在静孔隙压力状态下煤体积经历从收缩到回弹过程。注气压力越大，煤的收缩与回弹量越大，且收缩量总是大于回弹量。在三轴应力状态下注气初期煤样迅速膨胀。随着注气达到平衡状态，煤变形过程与约束条件表现出紧密相关性，即在应力约束下煤的膨胀率相比注气初期明显减缓；在位移约束下煤由膨胀转向收缩。上述试验结果表明，仅有孔隙压力作用下，煤基质与裂隙之间孔隙压力差可以压缩煤体，随着气体扩散的进行，可恢复煤的部分压缩变形量。在三轴应力状态下，煤的总体变形是裂隙与基质两者变形共同作用的结果。在应力约束下煤基质与裂隙可以自由膨胀。而煤体在位移约束下，因气体扩散导致煤基质膨胀只能挤压裂隙。根据上述实测结果探讨注气导致煤骨架变形演化机制，为深入理解煤裂隙与基质相互作用对煤渗透率演化提供试验依据。

Coal deformation induced by gas migration is significant to investigate coal bed methane recovery and geological sequestration of greenhouse gas. Generally, the variations of effective stress result in the shrinkage of geo-materials. However, the relationship between coal permeability and effective stress or pore pressure is nonlinear from extensive experimental results. Therefore, experiments are performed to study coal deformation caused by the flow of injected pure helium gas under hydrostatic pressure and triaxial stress conditions, respectively. Experimental results show that the coal sample undergoes a transition from shrinkage to recovery under hydrostatic pressure. Although both the coal shrinkage and recovery are proportional to the pressure of injected gas, the magnitude of shrinkage is greater than that of recovery. Under triaxial stress conditions, the coal sample rapidly expands at the beginning of helium injection. As the gas injection approaches equilibrium, the coal deformation is significantly controlled by the boundary condition. The coal expansion rate changes slowly under stress controlled condition, while the coal transits from expansion to shrinkage under displacement controlled condition. The above results indicate that the gas pressure difference between coal matrices and cleats is able to compress the matrix volume, and such compressed coal also could recover due to gas diffusion. In addition, the coal deformation is controlled by the interaction between cleats and matrix. It can be explained that coal matrices and cleats expand freely under the stress controlled boundary, while the coal matrix expansion induced by gas diffusion only narrow the aperture of cleats under displacement controlled condition. In conclusion, this study demonstrates the deformation evolution of coal induced by gas injection based on experimental results, which is particularly significant for deeply understanding the coal permeability.