冻融循环作用下泥质白云岩力学特性及损伤演化规律研究

针对饱水状态下的泥质白云岩，采用BCD–218 C低温数控恒温箱、WDW3100型微机控制电子万能试验机进行不同冻融循环状态下的单轴压缩试验，对其在单轴状态下应力-应变曲线变化特征以及抗压强度、峰值应变、弹性模量、泊松比的变化规律进行了分析。在现有的损伤力学理论基础上，引入斜率增大趋势系数，建立了以冻融循环次数和应变为控制变量的本构模型。结果表明，在冻融循环过程中，单轴抗压强度、峰值应变、弹性模量参数呈指数下降趋势，泊松比呈线性增加的趋势；受冻融循环的影响，应力-应变全过程曲线在第一阶段后出现短暂的线形平缓阶段，具有岩石局部滑移现象；岩石破坏形态从脆性向延性转化，具有峰前塑性硬化和峰后应变软化等行为特征。理论本构模型与试验结果相符合。

Research on mechanical properties and damage evolution law of argillaceous dolomite under freeze-thaw cycles

Mechanical characteristics of saturated argillaceous dolomite under freezing–thawing cycles were tested by low temperature numerical control incubator BCD-218 C and computer-controlled electronic versatile testing machine WDW3100. In uniaxial compressive state, characteristics of stress–strain curves and law of peak stress, peak strain, elastic modulus and Poisson's ratio varying with freezing-thawing cycles were analyzed. Base on existing theory of damage mechanics, damage constitutive model of taking freeze-thaw cycle times and strain as control variables were established by introducing slope increase trend coefficient (correction coefficient). The results show that peak stress, peak strain and elastic modulus decrease exponentially; while Poisson's ratio increases linearly with increase of freezing-thawing cycles. For the effects of freezing and thawing cycles, the short line shape gentle stage appears after the first stage (compaction stage) in complete stress-strain curves, during this period, the rock shows partial slippage phenomenon. In addition, failure mode of the rock transforms from brittleness to ductility, which has pre-peak plastic hardening and post peak strain softening behavior. Theoretical constitutive model coincides with experimental results.