不同温度下砂岩三点弯曲破坏的特征参量研究

RESEARCH ON CHARACTERISTIC PARAMETERS OF SANDSTONE THREE-POINT BENDING FAILURE UNDER DIFFERENT TEMPERATURES

基于三点弯曲试验研究不同温度影响后平顶山砂岩的特征参量,重点探讨热处理后砂岩破坏的弹性模量、损伤参量及延性比的变化。提出一种新的分析岩石材料性能的参数,即数值弹性模量,这大大方便通过试验方法来获取弹性模量。基于不同温度下弹性模量的变化及Lemaitre损伤理论,定义热损伤,并发现分段的四次多项式能较好拟合岩石等脆性材料热损伤与温度的关系,并由此把热损伤分为4个阶段,即不稳定热损伤阶段、初始热损伤阶段、稳定热损伤阶段和快速热损伤阶段。最后,借用混凝土结构工程的概念,采用延性比来判别热处理后砂岩的脆-延转变特性,该值大于2时砂岩开始具有延性性质。

Based on three-point bending tests,the characteristic parameters of Pingdingshan sandstone under different temperatures have been investigated.The variation of three characteristic parameters with thermal effects is focused on,namely,elastic modulus,damage parameter and ductility ratio.Based on numerical statistical method,a new parameter has been put forward to characterize rock material property,namely,numerical elastic modulus.The method is convenient for experimental methods to determinate elastic modulus for brittle materials.Thermal damage has been defined according to the variation of elastic modulus at different temperatures with Lemaitre＇s damage theory.A piecewise four-order polynomial has been used to fit the nonlinear relationship between the thermal damage and temperatures.And the fitting results agree well with experimental results.The thermal damage under different temperatures can be divided into four stages,namely,instable stage of thermal damage,initial thermal damage stage,stable thermal damage stage and fast thermal damage stage.At last,based on concrete structure theory,ductility ratio to characterize the ductility property of sandstone at different temperatures is employed;and the ductility ratio value of two may be approximately as the point of brittle-ductile transition.