Influence of grain size on strength of polymineralic crystalline rock: New insights from DEM grain-based modeling

作     者：Jun Peng Louis Ngai Yuen Wong Cee Ing Teh Jun Peng;Louis Ngai Yuen Wong;Cee Ing Teh

作者机构：Department of Earth SciencesThe University of Hong KongHong KongChina School of Civil and Environmental EngineeringNanyang Technological UniversitySingapore Shenzhen Institute of Research and InnovationThe University of Hong KongShenzhenChina 

出 版 物：《Journal of Rock Mechanics and Geotechnical Engineering》 (岩石力学与岩土工程学报（英文版）)

年 卷 期：2021年第13卷第4期

页      面：755-766页

核心收录：

学科分类：08[工学] 080104[工学-工程力学] 0818[工学-地质资源与地质工程] 0815[工学-水利工程] 0813[工学-建筑学] 0814[工学-土木工程] 0801[工学-力学（可授工学、理学学位）] 

基　　金：in part supported by the National Natural Science Foundation of China(Grant Nos.41877217 and 51609178) the General Research Fund of the Research Grants Council(Hong Kong,China)(Grant No.17303917) the Singapore Academic Research Fund Tier 1 Grant(RG112/14). 

主　　题：Grain size Rock strength Grain-based modeling(GBM)approach Grain boundary Micro-cracking behavior 

摘      要：Grain size effect on rock strength is a topic of great interest in geotechnical engineering.A consensus obtained from earlier laboratory tests is that rock strength generally decreases with the increase of grain size for both silicate and carbonate rocks;however,some recent numerical results conflict with such laboratory test results.To address this intriguing issue,the effect of grain size on strength of polymineralic crystalline rock with low porosity is investigated numerically using the grain-based modeling(GBM)approach in discrete element method(DEM)by interpreting micro-cracking process in response to loading.In agreement with some previous DEM simulation results,the simulated rock strength is found to increase with increasing grain size for both homogeneous and heterogeneous models,even when the number of assembled disks in one mineral grain changes.The mechanism of strength increase with increasing grain size is mainly associated with the number of assembled smooth-joint contacts along grain interfaces and the generation of grain boundary cracks in response to loading.The grain interfaces significantly weaken the integrity of the rock model,which is similar to effects of inherent defects in real rock.As the grain size increases,fewer grain interfaces are built in the model and the rock strength becomes much higher.Hence,by solely changing the mineral grain size in a model,the mechanism of grain size effect as observed in laboratory tests cannot be replicated.To address this issue,a method of degradation of grain boundary strength parameters is used to mimic the possible mechanism of grain size effect.The simulated strength using the method becomes comparable with those obtained from laboratory tests when the heterogeneity in the rock is considered.Degradation of grain boundary parameters with increasing grain size provides a plausible explanation for the grain size effect on rock strength.