高应力泥质粉砂岩蠕变特性及长期强度研究

Study on creep behavior and long-term strength of argillaceous siltstone under high stresses

岩石在高应力状态下呈现蠕变特性是深埋硐室稳定性研究的热点问题之一。为研究高应力泥质粉砂岩蠕变特性及长期强度,采用分级增量加载方式,对泥质粉砂岩试样进行三轴压缩流变试验,试验表明:泥质粉砂岩在低应力状态下表现为黏弹性蠕变特征,高应力状态下呈现黏弹塑性蠕变特征。通过将高应力岩石蠕变的瞬弹、黏弹、黏塑性蠕变进行分离,建立稳态黏塑性蠕变速率与应力的函数关系,提出以稳态黏塑性蠕变速率的阈值应力作为高应力泥质粉砂岩的长期强度。研究表明,基于稳态黏塑性蠕变速率与应力的函数关系确定的高应力泥质粉砂岩的长期强度为单轴抗压强度的70.5%,该方法可以较好地解决高应力岩石长期强度求解的问题。

Creep behavior of rocks under high stresses is one of the hot issues in the study of deep buried chamber stability. To study creep characteristics and long-term strength of argillaceous siltstone under high stresses, triaxial compression rheological tests were carried out on argillaceous siltstone specimens under graded incremental loading. The experiment results show that the creep of argillaceous siltstone has viscoelastic characteristics under low stresses and elastoviscoplastic characteristics under high stresses. Based on separating instantaneous elastic strain,viscoelastic creep and viscoplastic creep from the total creep of argillaceous siltstone under high stresses,the functional relationship between the steady viscoplastic creep rate and the stress was established. It is suggested that the threshold stress corresponding to the steady-state viscoplastic creep rate can be regarded as the long-term strength of argillaceous siltstone under high stresses. It is also shown that the long-term strength of argillaceous siltstones under high stresses,determined by the developed function between the steady viscoplastic creep rate and the stress,is 70.5% of the uniaxial compressive strength. The research provides a reasonable method for determining the long-term strength of rocks under high stresses.