基于能量原理砂岩应变软化模型研究

摘要

In order to establish the nonlinear damage equation of graded sandstone rock based on the principle of energy,three axial tests were carried on the sandstone under different confining pressure conditions,and the mechanical properties of its peak were analyzed.It was concluded that the increase of confining pressure increases the stress level corresponding to the initial point of sandstone expansion and delayed the non-linear expansion of sandstone.The confining pressure increased the bearing capacity of the rock to a certain extent.At the same time,the brittle failure degree of the rock was weakened and the ductility was increased,so that the sample tended to form a single shear plane.The sample was complete after failure.Under different confining pressures,the stage of the rock peak moved and slided along the fracture surface.It still had some bearing capacity,and the deformation rate of rock decreased gradually.It was assumed that the change rule of stress-strain relationship satisfies cubic polynomial.The nonlinear damage model was established through the energy principle,which could better reflect the relationship and damage of rock stress-strain.Finally,the correctness of the model was verified by comparing the experimental curve with the high fitting degree of the fitting curve.%为了建立基于能量原理的分段砂岩非线性损伤方程,对砂岩进行不同围压条件下三轴试验,并分析其峰后力学特性,得出以下主要结论:围压增大提高了砂岩扩容起始点对应的应力水平,延缓了砂岩的非线性扩张,围压在一定程度上提升岩石承载力;同时,减弱岩石的脆性破坏程度,增强延性,使得试样趋于形成单一剪切面,破坏后试样较为完整.考虑不同围压条件下,岩石峰后阶段主要沿着断裂面移动、滑动,仍然具有一定承载力,岩石形变率逐渐非线性减小.假定应力-应变关系变化规律满足三次多项式,通过能量原理建立非线性损伤模型,可以更好地反映岩石应力-应变关系与破坏情况,最终通过对比发现试验曲线与拟合曲线拟合度较高.