不同溶液环境下砂岩干湿循环损伤特性试验研究

Experimental study on dry-wet cycle damage characteristics of sandstone under different solution environments

为研究不同溶液环境下长石砂岩干湿循环损伤特性,对长石砂岩分别进行水和Na2SO4溶液两种环境下的干湿循环试验。对不同干湿循环次数后的长石砂岩进行纵波波速测定、XRD衍射试验、单轴抗压试验以及数字散斑试验(DSCM)。结果表明:Na2SO4溶液环境下干湿循环长石砂岩纵波波速、抗压强度、弹性模量等物理力学参数下降严重。干湿循环过程中水主要起溶解砂岩内部长石等矿物作用,盐分结晶产生结晶应力是长石砂岩损伤的主要原因。将应变局部化阶段初始点损伤状态确定为基准损伤,基于侧面应变标准差定义了长石砂岩损伤度,该损伤度演化方程能较好地反映长石砂岩干湿循环损伤过程。

In order to study the characteristics of dry-wet cycle damage of feldspar sandstone under different solution environments,dry and wet cycle experiments of feldspar sandstone are carried out under water and Na2SO4 solutions,respectively.Longitudinal wave velocity measurement,XRD diffraction experiment,uniaxial compression test and digital speckle correlation method(DSCM)experiment are performed on feldspar sandstone after different wet and dry cycles.The results show that the physical mechanics parameters such as the longitudinal wave velocity,compressive strength and elastic modulus of the dry-wet feldspar sandstone decline seriously in the Na2SO4 solution environment.The mineral such as feldspar in the sandstone is dissolved by water during the dry-wet cycle and the crystallized stress generated by salt crystallization is the main cause of the damage of feldspar sandstone.The initial point damage state of strain localization stage is determined as the reference damage.The feldspar sandstone damage degree is defined based on the lateral strain standard deviation.The dry and wet cycle damage process of feldspar sandstone can be well predicted by the damage degree evolution equation.