CLOSURE OF ROCK JOINTS
CLOSURE OF ROCK JOINTS
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DOI：
10.1029/jb091ib05p04939
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发表时间：
1986-04-10
期刊：
影响因子：
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通讯作者：
SCHOLZ, CH
中科院分区：
文献类型：
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作者：
BROWN, SR;SCHOLZ, CH
之前我们通过实验验证了描述两个随机表面弹性接触的格林伍德-威廉姆森理论的广义形式可以充分预测熔融石英玻璃样品中接头的闭合。在这里，我们对岩石实验进行了类似的分析。我们通过将实验的关节闭合与理论预测的关节闭合进行比较，定量地检验了该理论。这些比较是使用闭合实验中使用的接头表面的形貌数据进行的。进行了三种类型的测试：(1) 研究了花岗岩和石英岩样品，其中接缝由用#80 和#60 砂粒研磨的表面组成。这里的表面是随机的并且彼此不相关。这些实验可以直接检验该理论。与玻璃实验一样，理论与实验相符。然而，岩石弹性常数值的不确定性导致预测节理闭合时可能存在较大误差。 (2)研究了花岗岩和石英岩样品的拉伸断裂。这里的表面彼此高度相关。相关表面的预期闭合量取决于相关程度，因为这决定了接头的有效粗糙度。这里，表面形貌被反复进行高通滤波，并将理论与每个阶段的实验进行比较，以确定表面不匹配的有效尺度。 (3) 大理石地面承受相同的荷载条件。这里弹性假设不再合适。这些实验是表面粗糙度低于给定尺寸的所有材料均达到弹性变形极限的示例。该尺寸与材料的压痕硬度有关，方解石的压痕硬度低于硅酸盐矿物。
Previously we verified experimentally that a generalized form of the Greenwood‐Williamson theory describing the elastic contact of two random surfaces adequately predicts the closure of joints in fused silica glass samples. Here we present a similar analysis for experiments on rock. We have tested the theory quantitatively by comparing joint closure from experiment with joint closure predicted by the theory. These comparisons were made using topography data from the surfaces of the joints used in the closure experiments. Three types of tests were done: (1) Granite and quartzite samples were studied where the joints consisted of surfaces ground with #80 and #60 grits. Here the surfaces were random and uncorrelated with each other. These experiments permitted a direct test of the theory. As with the experiments on glass, the theory agrees with experiment. However, uncertainty in the values of the elastic constants for rock result in larger possible errors in predicting joint closure. (2) Tension fractures in granite and quartzite samples were studied. Here the surfaces were highly correlated with each other. The amount of closure expected for correlated surfaces depends on the degree of correlation, since this determines the effective roughness of the joint. Here the surface topography was repeatedly high‐pass filtered and the theory compared with experiment at each stage to determine the effective scale over which the surfaces were mismatched. (3) Ground surfaces of marble were subjected to the same loading conditions. Here the elastic assumption was no longer appropriate. These experiments are an example that the limit of elastic deformation is reached for all materials for surface asperities below a given dimension. This dimension is related to the indentation hardness of the material, which is lower for calcite than for silicate minerals.