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为研究冻结岩石在卸围压条件下强度特性、变形特性以及宏观破坏形态,以鄂尔多斯梅林庙矿风井冻结施工500~600 m处饱水红砂岩为研究对象,分别对其进行不同温度(10,-5,-10,-15℃)、不同围压(4,8,12 MPa)条件下的三轴压缩试验和三轴峰前、峰后卸围压试验。结果表明:1)饱水红砂岩峰前卸围压峰值强度大于单轴压缩强度,小于三轴压缩强度;峰后卸围压峰值强度近似等于三轴压缩强度,其值受人为因素和试验方案影响显著。2)峰前卸围压时,温度越低,试件变形对围压越不敏感,抗扰动性越强;初始围压越大,试件变形对围压越不敏感,抗扰动性越差;峰后卸围压时,温度对试件强度影响甚微,峰后强度大小取决于实时围压值。3)峰前卸围压破坏不同于三轴加载破坏和峰后卸围压破坏;峰前卸围压破坏实质为拉破坏,破坏形态取决于卸围压过程中裂隙的发育状态,峰后卸围压破坏形态取决于前期加载历程,与卸围压无关。
In order to study the strength characteristics, deformation characteristics and macroscopic failure modes of frozen rock under unloading confining pressure, taking red water sandstone of 500-600 m frozen in Ordos Merlin Mine shaft as research object, , -5, -10, -15 ℃), triaxial compression tests under different confining pressure (4, 8, 12 MPa) and unconfining confining pressure tests before and after triaxial peak. The results show that: 1) the peak pre-peak unloading confining pressure of saturated red sandstone is greater than the uniaxial compressive strength and less than the triaxial compressive strength; the peak compressive strength after unloading is approximately equal to the triaxial compressive strength, Significant impact. 2) When the pre-peak unloading confining pressure, the lower the temperature, the less deformation of the specimen becomes less sensitive to the confining pressure and the stronger the anti-disturbance; the larger the initial confining pressure, the less deformation the specimen is to the confining pressure and the worse the anti-disturbance After the peak unloading confining pressure, the temperature has little effect on the strength of the specimen. The intensity after the peak depends on the real-time confining pressure. 3) The unloading failure before peak is different from that under triaxial loading failure and unloading confining pressure after peak; the de-confining pressure before de-peaking is essentially tensile failure, and the failure morphology depends on the development state of cracks during unloading confining pressure, The confining pressure damage mode depends on the previous loading process, and has nothing to do with the unloading confining pressure.