高温三轴应力下气煤蠕变特征及本构模型

采用中国矿业大学研制的“600 ℃20 MN伺服控制高温高压岩体三轴试验机”，对尺寸为 200 mm×400 mm的山东兴隆庄气煤进行了200 ℃和400 ℃两个温度点的三轴应力下的蠕变实验。实验表明：200 ℃时，气煤蠕变具有明显的第1，2阶段，但未出现加速蠕变阶段，而400 ℃时，气煤在很短时间内就进入加速蠕变阶段；在温度和应力共同作用下，气煤在加载瞬间及后续变形过程中，始终伴随着显著的塑性变形，煤体变形为典型的黏弹塑性变形。通过对不同温度下气煤的渗透率和孔隙率的分析，初步判断300 ℃是气煤蠕变特征发生变化的临界温度。根据气煤高温蠕变特征，引入一种新型的非线性黏壶，构建了气煤的高温蠕变本构模型，该本构模型轴向蠕变的理论曲线和实验曲线吻合较好，表明该本构模型能较好地模拟高温下气煤的蠕变特征。

Creep characteristics and constitutive model of gas coal mass under high temperature and triaxial stress

Utilizing the 20 MN servo controlled triaxial rock testing machine with high temperature and high pressure developed by China University of Mining and Technology，experimental study was carried out on the creep properties of large size gas coal specimens of 200 mm×400 mm under two temperature points of triaxial stress at 200 ℃ and 400 ℃ .The research results indicate that the gas coal experiences the first and second phases of creep at 200 ℃，but without acceleration of creep；and phase that creep accelerates appears after a short time at 400 ℃.In the joint action of temperature and stress，the gas coal specimens show typical sticky elastic plastic deformation；because of the moment and subsequent deformation in the loading process，coal specimens are always accompanied by significant plastic deformation.By the analysis of the permeability and porosity of gas coal under different temperatures，it was initially judged that 300 ℃ is the critical temperature of the change of creep characteristics about gas coal.On the basis of high temperature creep characteristics of gas coal，a new type of nonlinear dashpots was introduced，and a creep constitutive model under high temperature aimed at gas coal was built，which theoretical curves of axial creep could agree well with the experimental curves，which indicating that this constitutive model can preferably simulate the creep characteristics of the gas coal under high temperature.