以數值模擬層狀岩石巴西試驗; Numerical simulation for layered rock under Brazilian test

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题名:	以數值模擬層狀岩石巴西試驗;Numerical simulation for layered rock under Brazilian test
作者:	劉文智;Liu,Wen-Chih
贡献者:	土木工程學系
关键词:	層狀岩石;巴西試驗;破壞模態;張力強度;layered rock;Brazilian test;failure mode;tensile strength
日期:	2013-07-25
上传时间:	2013-08-22 11:36:30 (UTC+8)
出版者:	國立中央大學
摘要:	本文以顆粒流程式PFC2D(Particle Flow Code2D)模擬層狀岩石在巴西試驗(Brazilian test)下之張力強度(tensile strength)、破壞過程及破壞模態(failure modes)，並探討在材料層厚比與強度比變化對各巴西試驗之影響。進行層狀岩石模擬前，本文亦針對等向性岩石巴西試驗進行相關參數研究(包括：微觀參數敏感性分析、尺寸效應、位移速率與原生異向性等)。數值模擬結果顯示：層面傾角(θ)、材料強度比與層厚比皆會影響張力強度。隨著層面傾角增加，使張力強度遞減。隨材料強度比增加，在各傾角狀況下，張力強度皆有大幅遞增之趨勢。此外，改變材料層厚比所對應之張力強度則受到傾角所影響，於低傾角狀況下張力強度隨層厚比增加而遞增，而高傾角則不因層厚比影響張力強度。層狀岩石受力達尖峰強度前，僅在受力點附近有少數微裂隙生成，試體其餘處並無任何裂縫生成。過尖峰強度後，受力點附近之微裂隙迅速向試體中心處延伸。裂縫之發展亦受傾角影響甚鉅，形成不同的破壞模態，可分為四類：(1)穿層劈裂模態(Split across layer mode) (2)層間滑動模態(Sliding along layer mode) (3)混合模態(Mixed mode)與(4)層間劈裂模態(Split along layer mode)。最後，本文數值模擬結果亦與Cho et al. (2012)實驗結果進行比較，無論在強度、破壞模態與彈性常數部分結果相符。This paper employs 2-D Particle Flow Code (PFC2D) to simulate layered rocks and focuses on the tensile strength, failure process, and failure modes under Brazilian test. Besides, this paper presents the effect of layer thickness ratio and strength ratio on tensile strength and failure modes. Before simulating layered rocks, this paper also performs the parametric studies (including the sensitive analysis of micro-parameters, size effect, displacement rate, and inherent anisotropy) of isotropic rocks under Brazilian test. Based on the numerical simulation results, the inclination angle (θ), layer thickness ratio, and strength ratio all have significant effects on Brazilian tensile strength. The tensile strength of layered rocks decrease with the increase of inclination angle, and the tensile strength would increase with the increase of strength ratio. The tensile strength of layered rock would also increase with the increase of layer thickness ratio when the low inclination angle however, there is no significant effect when the layered rock with high inclination angle. During Brazilian test, the micro-crack of layered rock initiate at pre-peak. Besides, the micro-cracks are limited around the edge of specimen and propagate slowly until the peak is reached. After post-peak, the crack propagate rapidly and we observe four major failure modes in these numerical simulations:(1)Split across layers mode (2)Sliding along layer mode (3)Mixed mode (4)Split along layer mode. In this paper, we also verify our simulation result to experimental results from Cho et al.(2012). The strength anisotropy, elastic constants and failure modes almost agree with experimental results.
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