干湿循环作用下炭质泥岩孔隙演化及本构模型研究

Study on pore evolution and constitutive model of carbonaceous mudstone under dry-wet cycles

【目的】建立干湿循环作用下炭质泥岩的损伤本构方程。【方法】对0、5、10和15次干湿循环作用下的炭质泥岩进行核磁共振试验,探讨炭质泥岩孔隙演变规律,并对干湿损伤的炭质泥岩进行单轴压缩试验,研究干湿循环对岩石力学特性的影响。在此基础上,利用Weibull分布函数表征岩石损伤演化,考虑干湿损伤炭质泥岩的孔隙变形,建立炭质泥岩的损伤本构方程。【结果】随干湿循环作用次数的增加,炭质泥岩孔隙增多、尺寸增大,小孔汇合、贯通形成中孔。干湿循环加剧炭质泥岩力学性质劣化,干湿损伤后的炭质泥岩峰值应力和弹性模量减小、延性增强。损伤本构方程可以较好地描述炭质泥岩应力应变发展的全过程,特别是可以较好地反映岩石压密阶段的非线性变形。【结论】该损伤本构模型有较高的适用性,可为干湿环境下炭质泥岩边坡工程的建设提供参考。

[Purposes]This study aims to establish the damage constitutive equation of carbonaceous mudstone under dry-wet cycles.[Methods]Nuclear magnetic resonance tests are carried out on carbonaceous mudstones undergoing 0,5,10,and 15 dry-wet cycles,so as to explore the pore evolution law of carbonaceous mudstone.Uniaxial compression tests are carried out on carbonaceous mudstone with dry-wet damage,so as to study the influence of dry-wet cycles on the mechanical properties of rock.On this basis,the Weibull distribution function is used to characterize the damage evolution of rock,and the damage constitutive equation of carbonaceous mudstone is established by considering the pore deformation of carbonaceous mudstone with drywet damage.[Findings]With the increase in the number of dry-wet cycles,the pores of carbonaceous mudstone increase,and the size enlarges.The small pores merge and penetrate to form mesopores.Dry-wet cycles aggravate the deterioration of the mechanical properties of carbonaceous mudstone.The peak stress and elastic modulus of carbonaceous mudstone with drywet damage decrease,and the ductility increases.The damage constitutive equation can describe the whole process of stress and strain development of carbonaceous mudstone and reflect the nonlinear deformation of rock in the compaction stage.[Conclusions]The damage constitutive model has high applicability and can provide a reference for the construction of carbonaceous mudstone slopes under dry and wet environments.