模擬岩石裂隙延伸行為之初探

Preliminary study of fracture propagation using model rock

張來福(Lai-Fu Chang)

指導教授 ： 鄭富書

共同指導教授 ： 黃燦輝(Tsan-Hwei Huang)

國立臺灣大學/工學院/土木工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.01502

摘要

台灣地體位在歐亞板塊與太平洋板塊聚合帶上，地質構造年輕且破碎，佈有多條斷層破裂線分佈全台。鑒於人口聚落座落在斷層破裂線之周圍趨勢增加，歷次地震事件發現破裂線延伸災害更加的加深其對破裂延伸行為研究之必要性，不僅可用於對未來斷層破裂線延伸之模擬，也可應用於岩石邊坡節理面互相影響發展之進一步研究，提供都市計畫人員與大地工程相關從業人員基礎研究的參考。
本研究對象為簡化之斷層面垂直地表面模擬材料的物理模型，並將三維問題簡化為二維問題進行討論。研究方法採用破裂力學理論與物理試驗、顆粒影像速度儀(Particle Image Velocimetry, PIV)影像分析與顆粒力學(Particle Flow Code, PFC2D)為基礎之數值工具。主要目的為釐清及探討下列各點：(1)初始主要裂隙與次生裂隙的破裂發展與破裂型態；(2)模擬不同傾角的裂隙延伸與破裂韌度的關係；(3)模擬材料的裂隙長度對破裂韌度的影響；(4)材料表面的位移場現象；(5)運用PFC模型模擬材料的位移場運動現象。
本研究成果顯示，物理模型的CSTBD不同裂隙傾角的破裂型態與前人研究的趨勢相同，同時補足前人研究中的不足。對於單壓斜裂隙矩形試體的物理模型指出，傾角30°的破裂型態以張裂為主，破裂韌度KIc明顯大於KIIc，整體上屬於進張裂的混合模式(Mixed mode I-II)；傾角45°的破裂型態則屬於張-剪裂混合模式為主，整體上以半張半剪裂模式(Mixed mode I-II)。對於影像分析，CSTBD與單壓斜裂縫的矩形試體分析結果，可看出PIV在模擬材料破裂研究的適用性，向量位移場的相對橫移與轉動位移場皆可描繪出裂隙的發生位置，可以比對前人DIC研究的破裂位置的預測方式。

關鍵字

模擬材料 ； 二維裂隙延伸 ； 破裂模式 ； 破裂韌度 ； 顆粒影像速度儀(PIV) ； 顆粒力學數值模擬(PFC2D) ； 裂隙預測

並列摘要

Taiwan terrain, located at the convergence belt between the Eurasian plate and Pacific plate, has smashed body and many faults overspreading its surface. With the incensement of space required, based on the fact that the tendency living near the fault or surface fracture becomes more popular and the disasters induced from the cracks, extending bring more catastrophic lost in the historic seismic records, it is the more and more important subjects of crack extending for human society today . It can not only be useful for the fault research but also support the cited plans or geotechnical engineering reference for designing, due to aim to reducing the calamity happening and promoting life.
The main fracture spacing distribution studied in this thesis is orthogonal to the body surface, and this research will simplify the three-dimension problem to the two-dimension one basically. The three tools will be applied to examine the behavior for fracture propagation, including physical experiments applying Fracture mechanics, digital image analysis and numerical simulation(Particle Flow Code, PFC2D). It focus on the several phenomenon list as: the fracture propagation, traditional fracture classification, relationship between the different dip angle defined by this study and Fracture toughness, the influence of pre-cracked length to the fracture development, and the investigation for surface displacement field.
As initial experiments showing, the CSTBD tests with variant dip angle will have the diverse fracture prorogations, similar with the former research, compensating the deficit part and the proving the fracture-mode transition. We also execute the single compassed rectangle sample to compare the influence of crack length and dip angle. Owning to the physical test, the crack mode for the dip angle, 30 degree, reveal the mixed mode I-II, but more belong to mode I. On the other hand, the crack mode for the dip angle, 45°degree, more agree with the mixed mode I-II, meaning that the crack tension and shear will appear together. The digital image correlation analysis, with the help through PIV, also adequately show the crack entrenching and spreading during the crack happening. We also observe and compare the rotation-concentrating characteristics with the DIC result during crack formulation and propagation, and we get the similar properties to attest to the applicability for the crack investigation using PIV tool.

並列關鍵字

mode-rock material ； two-dimension fracture propagation ； crack mode ； Fracture toughness ； Particle Image Velocimetry (PIV) ； Particle Flow Code (PFC) ； crack prediction

參考文獻

張家銓，「分離元素法於擬脆性岩材微觀破裂機制之初探」，國立台北科技大學土木與防災研究所碩士論文（2007）。

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