Study of scale effect on intact rock strength using particle flow modeling
Study of scale effect on intact rock strength using particle flow modeling
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DOI：
10.1016/j.ijrmms.2011.09.016
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发表时间：
2011-12
影响因子：
7.2
通讯作者：
Qi Zhang;Hehua Zhu;Lianyang Zhang;Xiaobin Ding
中科院分区：
文献类型：
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作者：
Qi Zhang;Hehua Zhu;Lianyang Zhang;Xiaobin Ding
基于对单抗强度与试样尺寸测试数据的广泛回顾，以及单抗强度与试样尺寸之间的各种经验关系，提出了一个新的表达式来描述单抗强度与试样体积的依赖关系。所提出的新关系式可以很好地拟合不同岩石的单轴载荷与试样尺寸的试验数据。在此基础上，建立了以接触点上相互结合的颗粒为代表的完整岩石的数值模型，该模型同时具有法向强度和抗剪强度分量，对单轴单轴抗剪强度的尺度效应进行了数值研究。当法向或剪切接触应力超过相应的粘结强度时，粘结就会断裂。为了模拟岩石中的初始微破裂（缺陷或裂纹），采用了光滑节理接触模型。骨折被认为是随机定向和定位的椎间盘。裂缝的大小和数量由分形理论导出的指数表达式来描述。利用80mm×40mm×40mm棱柱山口大理岩试样的试验应力-应变曲线对数值模型进行了标定。然后，利用校正后的模型对不同尺寸山口大理石试样的单轴剪切强度进行了预测。预测的UCS值与实验值吻合较好。数值模拟结果表明，为了捕捉完整岩石单轴破碎的尺度效应，在建模时必须考虑初始裂缝尺寸随试样尺寸增大而增大的情况。
Based on the extensive review of the UCS versus specimen size test data and the various empirical relations between the UCS and the specimen size, a new expression is proposed to describe the dependence of the UCS on specimen volume. The proposed new relation can fit the UCS versus specimen size test data of different rocks very well. Then, a numerical study of the scale effect on UCS is conducted using a numerical model in which the intact rock is represented by particles bonded to each other at contact points, with the contact bonds having both normal and shear strength components. The bond can break if the normal or shear contact stress exceeds the corresponding bond strength. To simulate the initial micro-fractures (flaws or cracks) in the rock, the smooth-joint contact model is used. The fractures are considered to be randomly orientated and located disks. The size and number of fractures are described by an exponential expression derived using fractal theory. The numerical model is calibrated using the test stress–strain curves of 80mm×40mm×40mm prism Yamaguchi marble samples. Then, the calibrated model is used to predict the UCS of Yamaguchi marble samples at different sizes. The predicted UCS values are in good agreement with the experimental values. The numerical simulations show that to capture the scale effect on UCS of intact rock, initial fractures with sizes increasing faster with the specimen size must be considered in the modeling.