温湿循环条件下圆环花岗岩径向压缩力学特征试验研究

Experimental study on mechanical characteristics of radial compression of circular granite under the condition of temperature-humidity cycling

采用加热处理圆环花岗岩,降温并浸入不同温度水中养护,模拟地热能开采时井筒围岩经历的环境变化,开展温湿循环条件下圆环花岗岩的径向压缩试验研究。研究结果表明:圆环花岗岩的变形特征受内径、加热温度、养护水温、采热循环次数的影响,其荷载–位移曲线常出现上凹段–直线段–平台段和断崖下降段。大内径、高温加热、高水温养护、采热循环次数增多都弱化了圆环花岗岩承受径向荷载的能力。圆环花岗岩是在拉伸应力效应下产生破坏的,且最先起裂的位置是沿加载方向的圆环内壁,然后扩展至圆环外壁,导致整个结构失稳破坏。基于圆环花岗岩的变形破坏特征,发现最大拉伸应变可作为圆环花岗岩破坏判定的参量,进而在一定假设条件的基础上建立圆环花岗岩的破坏判据,并以不同内径圆环岩样在径向荷载作用下发生破坏时的内壁、外壁应变进行了验证。

For simulating the environmental changes experienced by wellbore surrounding rocks during the exploitation of geothermal energy,circular granite was heated and cooled and immersed in water at different temperatures for curing,thus the experimental study on the radial compression of circular granite under the condition of temperature-humidity cycling has been carried out. The results show that the deformation characteristics of circular granite are affected by inner diameter,heating temperature,curing water temperature and cycles of thermal energy exploitation,and there appear concave section,straight section,platform section and cliff descending section on load-displacement curve. The larger inner diameter,the higher temperature heating,the higher curing water temperature and more cycles of thermal energy exploitation weaken the ability of circular granite to bear radial load. In addition,the circular granite was destroyed under the effect of tensile stress,and it cracked along the circular inner wall of loading direction firstly,and then the cracks extended to the circular outer wall,resulting in buckling failure of the whole structure. Based on the deformation and failure characteristics of circular granite,it is indicated that the maximum tensile strain can be used as a parameter to determine whether the specimen is damaged. Furthermore,the failure criterion of circular granite is established with certain assumptions,and it is verified by the inner and outer wall strains of circular granite with different inner diameters under radial load.