The deformation of coal during the injection of sorptive gases can be classified into two types: deformation due to the pore pressure and the swelling deformation of the coal matrix induced by adsorption. These types of deformation have not been investigated separately in the previous researches. The main reason is that measuring the radial strain of the coal core directly and accurately is extremely difficult under triaxial stress. This paper demonstrates that by injecting both sorptive and non-sorptive gases into a coal sample with different pore pressures, while measuring the radial deformation of the coal sample with a high precision instrument (± 0.227 mm³), deformations due to the pore pressure and deformations induced by adsorption were separated from each other. The adsorption-induced deformations have an important influence on the effective stress. We studied the relationship between Biot coefficient and the swelling deformation due to the adsorption based on the Biot effective stress theory. The experimental results show that the Biot coefficient is the bilinear function in terms of the volumetric stress and pore pressure, shown as \(\alpha = a + b\Theta + cp + d\Theta p\). The data and results obtained in this experiment played a fundamental role in the applications of gas extraction, coal and gas outburst prevention and control, displacement of coalbed methane with CO₂, and the establishment of the solid–fluid coupling model.

注入吸附性气体期间煤的变形可分为两种类型：孔隙压力引起的变形和吸附引起的煤基质的溶胀变形。这些类型的变形在以前的研究中还没有单独研究过。主要原因是在三轴应力下直接，准确地测量煤芯的径向应变非常困难。本文证明了通过将吸附性气体和非吸附性气体同时注入具有不同孔隙压力的煤样品中，同时使用高精度仪器（±0.227 mm ³），由于孔隙压力引起的变形和由吸附引起的变形相互分离。吸附引起的变形对有效应力有重要影响。基于Biot有效应力理论，研究了Biot系数与吸附引起的溶胀变形之间的关系。实验结果表明，根据体积应力和孔隙压力，毕奥系数是双线性函数，表示为\（\ alpha = a + b \ Theta + cp + d \ Theta p \）。该实验获得的数据和结果在瓦斯抽采，煤与瓦斯突出的预防和控制，CO ₂置换煤层气以及建立固-液耦合模型方面发挥了重要作用。