岩石化学风化时效效应的离散元模拟

Discrete element simulation of aging effect of chemical weathering on rock

微观上,岩石由晶粒和晶粒之间的联接组成。在岩石的风化过程中,晶粒之间的联接会被削弱,导致岩石微观缺陷的发展,从而表现为显著的时效效应。在已有胶结模型的基础上,将岩石的化学风化过程等效为颗粒之间胶结物质不断溶蚀进而影响颗粒之间胶结强度和刚度的过程,基于此建立了考虑化学风化的微观接触模型。随后将模型植入离散元软件,运用离散元方法(DEM),模拟和对比分析了室内腐蚀试验与DEM模拟化学风化试验,结果表明:该模型可以反映岩石强度的化学风化时效效应,即随着反应时间增加,强度减小;可以反映单轴压缩试验中裂隙压密阶段以后变形的时效效应,即随着反应时间的增加,弹性模量、破坏时应变减小;粒间胶结的破坏,即微观缺陷的发育,是导致岩石化学风化时效效应的微观原因。同时DEM模拟风化与加载耦合的试验现象表明,施工过程中的施工速度会影响岩石的强度,施工应该选择合适的速率。

In the microscopic view, rock is composed of crystal grains and the contacts between them. During the chemical weathering process, the bonding materials are corroded and the connections between the particles are weakened which would lead to evident aging effect on the mechanical properties of rock. Based on the existing contact model, the chemical weathering process of rock was idealized as the solution of the bonding materials which resulted in the decay of the strength and stiffness of the bonds between the particles. In this way, the factor of chemical weathering is induced into the existing contact model. According to establishing contact model considering chemical weathering, DEM is used to simulate and analyze the corroded experiments and the discrete element simulation results. The results show that： the new model can reflect the aging effect on the strength of rock; the strength will decrease with the erosion; the new model can reflect the aging effect after the fracture pressure stage in the compression test. The elastic modulus and failure strain will decrease with the erosion; the failure of bonds between the particle, namely the growth of the microfracture, is the reason that leads to the aging effect. At the same time, the simulation results of the tests combined chemical weathering and loading show that a suitable construction speed should be chosen to ensure a safe and efficiency construction.