高围压炭质板岩流变力学试验与硬化损伤模型研究

Rheological Test and Hardening Damage Model of High Confining Pressure Carbonaceous Slate

为了研究炭质板岩在高围压条件下的流变力学特性,进行了不同围压条件下的炭质板岩加卸载流变试验,试验结果表明,炭质板岩存在明显的流变下限,约为抗压强度应力水平的50%~60%,低于流变下限时仅有瞬时弹性应变和不可恢复的压密应变,其中压密应变在应力水平较低时已经趋于稳定值,应力水平为抗压强度的60%~70%时仅出现衰减蠕变或等速蠕变,应力水平超过抗压强度80%时才发生加速蠕变。根据传统强度理论,建立了包含压密应变、硬化塑性应变和损伤塑性应变的蠕变模型,对各阶段模型参数进行辨识,依据稳定蠕变阶段参数辨识结果拟定加速蠕变阶段部分参数的合理初始值,达到了较好的拟合度,表明模型对于反映高围压炭质板岩流变特性具有较好的适用性。

In order to study the rheological mechanical properties of carbonaceous slate under high confining pressure,the rheological tests of carbonaceous slate under different confining pressure were carried out. The experimental results show that the carbonaceous slate has obvious rheological lower limit,which is about 50% ~ 60%of the compressive strength stress level. There are only instantaneous elastic strains and irrecoverable compressive strains below the creep limit,and the compressive strains tend to be stable at a low stress level. When the stress level is 60% ~ 70% of the compressive strength,only attenuated creep or isovelocity creep occurs,and accelerated creep occurs when the stress level exceeds 80% of the compressive strength. According to the traditional strength theory,a rheological model including compressive strains,hardening plastic strain,and damage plastic strain is established.Identify the parameters of each stage model and draw up the reasonable initial values of some accelerated creep stage parameters according to the fitting results of the stable creep stage parameters,and the fitting degree is better. The model has good applicability to reflect the rheological properties of high confining pressure carbonaceous slate.