论文部分内容阅读
采用伺服刚性试验机对天然膏岩开展三轴压缩试验,研究了温度及围压对膏岩强度及变形特性的影响。结果表明,膏岩在不同围压下均具有良好的塑性流动特性,加载后无明显的剪切破坏面,而是出现明显的侧向膨胀。根据三轴试验结果,利用摩尔-库仑定律得到了膏岩的强度准则及抗剪强度参数。升高温度导致膏岩强度降低,且高温下石膏发生晶型转变,从二水石膏脱水转变为半水石膏,利用扫描电镜和X衍射对此过程进行了研究。脱水过程导致瞬间孔隙应力增加,膏岩破坏特性由延性转变为脆性。随着持续加载,破裂断面逐渐愈合。膏岩显著的塑性流动能力及快速的裂隙愈合能力对于天然气盖层的封闭稳定性具有重要意义。
Triaxial compression tests were carried out on natural gypsum with a servo rigid testing machine to study the effect of temperature and confining pressure on the strength and deformation characteristics of the gypsum. The results show that the gypsum has good plastic flow characteristics under different confining pressures and no obvious shear failure surface after loading, but obvious lateral expansion. According to the triaxial test results, the strength criterion and the shear strength parameter of the gypsum rock are obtained by Mohr-Coulomb’s law. The increase of temperature led to the decrease of strength of gypsum, and the transition of gypsum from high temperature to crystalline transition from gypsum to hemihydrate gypsum. The process was studied by scanning electron microscopy and X-ray diffraction. The dehydration process leads to an instantaneous increase of pore stress, and the failure characteristics of the gypsum rock change from ductility to brittleness. With continuous loading, rupture gradually healed. The significant plastic fluidity of the gypsum rock and rapid fracture healing are of great importance to the sealing stability of the gas cap.