围压影响的盐岩压缩力学特性及非线性本构模型

Compression Mechanical Characteristics and Nonlinear Constitutive Model of Salt Rock Considering Confining Pressure Effect

为了更准确地描述盐岩的力学特性,对盐岩开展多组单轴、三轴压缩试验。根据试验结果,多组试验数据得到的莫尔包络线具有非线性特征,并且盐岩力学特征对围压有很强的相关性。单轴及低于5 MPa围压时盐岩应力应变关系曲线表现弹性、应变硬化、软化3个过程,而当高于5MPa围压时盐岩延性特征显著,应力应变曲线硬化阶段比例加大,扩容点前移,而软化过程有一定程度的减弱。基于Hoek-Brown准则的软化模型将应力应变曲线峰前阶段改进为弹性非线性弹性模型,得到一种新的非线性本构模型。结果表明这种非线性本构模型可以很好地吻合不同围压作用的盐岩应力应变曲线。

To well describe the mechanical characteristics of salt rock,many groups of uniaxial and triaxial compression tests are carried out.Based on the test results,the non-linear Mohr envelope is obtained,and confining pressure has great influence to mechanics characteristics of the salt rock.Under uniaxial pressure,when the confining pressure is less than 5 MPa,the salt rock undergoes the three stages,which are elastic,strain-hardening and strainsoftening.When the confining pressure is larger than 5 MPa,the ductility of the salt rock sample is obvious,and the hardening regime of the stress-strain curve increases,and the dilatation point moves forward and the softening degree decreases with the increase of confining pressure.Based on the results,the pre-peak stage of the stress-strain curve is replaced by an elasticity-nonlinear elasticity model.Based on the softening model of Hoek-Brown,a new nonlinear constitutive model is constructed.The results show that the nonlinear constitutive model is in good agreement with stress-strain curves of salt rock under different confining pressure.