紫红色泥岩三轴蠕变力学特性试验研究

Experimental Study on Creep Mechanical Characteristics of Aubergine Mudstone under Three-dimensional Stress Conditions

为揭示泥岩在不同应力环境下的蠕变力学特性,对取自某在建工程的紫红色泥岩分别进行围压为0.5,1.0,2.0,5.0 MPa的分级加载蠕变试验。试验研究表明:围压越大,泥岩的强度越大,塑性变形能力越强,流变特性越显著;相同围压下,稳态蠕变速率随偏应力呈幂指数函数型增长;相同偏应力下,稳态蠕变速率随围压升高而降低;利用等时应力-应变曲线法,得到泥岩的长期强度分别为11,16,22.5,29 MPa,均较各自围压下短期强度值降低40%~45%;通过摩尔强度准则得到的长期内聚力和内摩擦角分别为3.09 MPa和34.8°,分别较短期参数降低20.6%和25.9%。根据研究成果给出了一种带应变触发的分数阶蠕变本构模型,理论曲线与试验曲线拟合度良好,能较好地模拟泥岩的蠕变全过程。

In the aim of obtaining the creep mechanical properties of mudstone under different stress environments,stepped loading creep test under confining pressure of 0.5 MPa,1 MPa,2 MPa,and 5 MPa was carried out on augergine mudstone from a project under construction.Results revealed that strength,plastic deformation ability and rheological properties of aubergine mudstone were greater and more significant with the increase of confining pressure;steady-state creep rate increased exponentially with the increase of deviatoric stress under the same confining pressure,and reduced with the increase of confining pressure under the same deviatoric stress.According to isochronous stress-strain curves,the long-term strength of aubergine mudstone was 11 MPa,16 MPa,22.5 MPa,and 29 MPa respectively,reduced approximately 40%~45% compared with the short-term strength under corresponding confining pressures;the long-term cohesion and internal friction angle were 3.09 MPa and 34.8° by Mohr strength criterion,decreasing by 20.6% and 25.9% compared with the short-term parameters.Furthermore,a fractional creep constitutive model with strain trigger was given to simulate the whole process of mudstone creep,and the theoretical curves fit well with experimental curves.