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Experimental test and numerical simulation of the effect of brittleness on the microfracturing of sandstone
Bulletin of Engineering Geology and the Environment ( IF 4.2 ) Pub Date : 2022-07-11 , DOI: 10.1007/s10064-022-02776-y
Mehran Noori, Gholamreza Khanlari, Vahab Sarfarazi, Behrouz Rafiei, Hamid Reza Nejati, Wulf Schubert

The micro-cracks are one of the main causes of rock materials heterogeneity and significantly affect the rock strength and deformation behavior. A detailed study of the micro-cracking process is difficult experimentally due to the complexity of the texture in rock materials. In this study, the flat-jointed model (FJM) was used as a numerical approach based on discrete element method (DEM) in two-dimensional particle flow code (PFC2D) to the quantitative analysis of the effect of brittleness on the micro-cracking behavior of different types of sandstone samples with different brittleness degrees. For this purpose, initially, cylindrical and disc-shaped specimens were made to produce numerical models. Then, the micro-parameters were calibrated based on the macro-parameters of the intact rock specimens obtained from the compression (UCS) and tensile (BTS) tests in laboratory conditions. The stress–strain curves, peak strength, and axial strain values, elasticity modulus, and failure modes as features of numerical simulation are in well agreement with laboratory results. The results showed that the crack initiation, propagation, and coalescence process as sequences of crack evolution are significantly related to the degree of brittleness. The index of the obtained crack growth rate (CGR), for each of the stages of crack development, was increased with brittleness. The period’s length of the linear and nonlinear behavior of the stress–strain curve based on the cumulative micro-crack number curves was found to play a vital role in the variations of the degree of brittleness.



中文翻译:

脆性对砂岩微压裂影响的试验试验与数值模拟

微裂纹是岩石材料非均质性的主要原因之一,显着影响岩石强度和变形行为。由于岩石材料质地的复杂性,很难通过实验对微裂纹过程进行详细研究。在这项研究中,平面连接模型(FJM)被用作二维粒子流代码(PFC 2D )中基于离散元法(DEM)的数值方法) 定量分析脆性对不同脆性不同类型砂岩样品微裂行为的影响。为此,最初制作了圆柱形和圆盘形样品来生成数值模型。然后,根据在实验室条件下通过压缩(UCS)和拉伸(BTS)试验获得的完整岩石试样的宏观参数来校准微观参数。作为数值模拟的特征的应力-应变曲线、峰值强度和轴向应变值、弹性模量和失效模式与实验室结果非常吻合。结果表明,作为裂纹演化序列的裂纹萌生、扩展和聚结过程与脆性程度显着相关。对于裂纹发展的每个阶段,所获得的裂纹扩展速率(CGR)的指数随着脆性而增加。发现基于累积微裂纹数曲线的应力-应变曲线的线性和非线性行为的周期长度对脆性程度的变化起着至关重要的作用。

更新日期:2022-07-12
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