石膏矿岩三轴压缩蠕变特性试验研究

石膏矿开采多采用房柱法，其蠕变特性对采空区稳定性有重要影响。以荆花石膏矿为背景，利用RC-2000微机控制岩石三轴蠕变试验机，结合具体工程情况，对荆花石膏矿岩进行围压分别为0、2.5、5.0、7.5 MPa的蠕变试验。分析了所得的蠕变试验数据，选取合适的模型对试验曲线进行拟合，利用等时应力-应变曲线簇法求得在不同围压下的长期强度。分析可知，荆花石膏矿蠕变包含衰减蠕变和等速蠕变2个阶段，轴向应力较小时只出现衰减蠕变，轴向应变增大到一定程度时将出现衰减蠕变和等速蠕变2个阶段。选择西原模型对试验曲线进行拟合结果表明,西原模型能较好地描述石膏矿的蠕变力学特性，拟合相关系数R均大于0.9；在不同围压情况下长期强度与蠕变强度的比值为0.89～0.95，即围压对长期强度的影响不大。研究结论能为石膏矿采空区的稳定性分析提供依据。

Experimental study of creep characteristics of gypsum mine rock in triaxial compression

Gypsum minings use room and pillar method frequently; the creep characteristics of gypsum mine have an important impact on the stability of mined-out area. In this paper, Jinghua gypsum mine is taken as the background, using RC-2000 microcomputer to control triaxial creep test machine to carry out experiments with Jinghua gypsum mine rock under confining pressures of 0, 2.5, 5.0, 7.5 MPa respectively. Creep test data obtained are analyzed, selecting the appropriate model for the test curve, and utilize the stress-strain curves method to obtain long-term strength under different confining pressures. The analytical results elaborate that the gypsum mine rock creep contains attenuation creep and constant creep; attenuation creep appears when the axial stress is small; constant creep and attenuation creep appear when the axial stress is big enough; using Nishihara model to fit the test curve. Results show that Nishihara model can describe the creep mechanical properties of gypsum mine rock nicely; the correlation coefficient R is more than 0.9. The ratio of long-term strength to creep strength is within 0.89-0.95 under different confining pressures, which means that the confining pressure has little effect on the long-term strength. The results findings will provide a basis for studying stability of gypsum mine mined out areas.