Mineral Weathering and Bedrock Weakening: Modeling Microscale Bedrock Damage Under Biotite Weathering
Mineral Weathering and Bedrock Weakening: Modeling Microscale Bedrock Damage Under Biotite Weathering
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DOI：
10.1029/2019jf005068
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发表时间：
2019-11
期刊：
影响因子：
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通讯作者：
Xianda Shen;C. Arson;K. Ferrier;N. West;S. Dai
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文献类型：
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作者：
Xianda Shen;C. Arson;K. Ferrier;N. West;S. Dai
基岩弱化是广泛的兴趣，因为它影响景观演变，化学风化，地下水文。一个长期存在的假说认为，基岩的弱化是由黑云母等矿物的化学风化作用造成的，黑云母在风化过程中会膨胀，并产生足以使岩石断裂的应力。我们建立在岩石损伤力学的最新进展，开发一个模型的多矿物化学风化对基岩损伤的影响，这被定义为减少基岩刚度。我们使用黑云母化学风化作为该模型的一个示例应用，以探索丰度、纵横比和方向如何影响黑云母化学风化过程中基岩损伤的时间依赖性演化。我们的模拟表明，黑云母丰度和纵横比有一个深刻的影响，在黑云母化学风化过程中的基岩破坏的演变。这些特点施加特别强烈的影响的时间开始的损害，这发生在较高的黑云母丰度和较小的黑云母纵横比。相比之下，黑云母方向对损伤的影响相对较弱。我们的模拟结果进一步表明，损伤发展的边界条件的强烈影响，与损伤开始较早的横向约束的边界下比无约束的边界。这些模拟表明，相对较小的差异，黑云母人口可以驱动显着差异的进展，岩石弱化。这突出了黑云母丰度，纵横比和方向的矿物和字段规模的观测的必要性，并促使努力扩大这种微观模型，以调查宏观断裂网络的演变。
Bedrock weakening is of wide interest because it influences landscape evolution, chemical weathering, and subsurface hydrology. A longstanding hypothesis states that bedrock weakening is driven by chemical weathering of minerals like biotite, which expand as they weather and create stresses sufficient to fracture rock. We build on recent advances in rock damage mechanics to develop a model for the influence of multimineral chemical weathering on bedrock damage, which is defined as the reduction in bedrock stiffness. We use biotite chemical weathering as an example application of this model to explore how the abundance, aspect ratio, and orientation affect the time‐dependent evolution of bedrock damage during biotite chemical weathering. Our simulations suggest that biotite abundance and aspect ratio have a profound effect on the evolution of bedrock damage during biotite chemical weathering. These characteristics exert particularly strong influences on the timing of the onset of damage, which occurs earlier under higher biotite abundances and smaller biotite aspect ratios. Biotite orientation, by contrast, exerts a relatively weak influence on damage. Our simulations further show that damage development is strongly influenced by the boundary conditions, with damage initiating earlier under laterally confined boundaries than under unconfined boundaries. These simulations suggest that relatively minor differences in biotite populations can drive significant differences in the progression of rock weakening. This highlights the need for observations of biotite abundance, aspect ratio, and orientation at the mineral and field scales and motivates efforts to upscale this microscale model to investigate the evolution of the macroscale fracture network.