透過您的圖書館登入
IP:44.222.212.138
  • 學位論文

以PFC探討裂隙間岩橋破裂連接行為

Study on the fracture and connection behavior of rock bridge between fissures using PFC

指導教授 : 楊長義

摘要


擬利用顆粒流PFC程式來模擬岩石裂隙(fissures)間的破裂連結問題:旨在利用PFC具備分辨顆粒鍵結間之張力斷裂或剪力破裂等AE紀錄的特色,首先 (1)針對不同傾角下單一條裂隙岩石之破裂發展順序與 (張裂或剪裂) 初始破裂(crack initiation)、損傷應力(damage stress)等力學特性;(2)再安排多道不同幾何排列(共線或平行排列)條件下,探討多道裂隙間岩橋(rock bridge)之微觀破裂行為的相互影響及其連結(coalescence)發展串連行為之間破裂連接差異性問題。 本文主要獲致結論如下:(1) 由PFC數值模擬利用AE訊號抓取破裂初始應力(σ_ci),獲知σ_ci約落在0.63UCS,與一般岩石之初始破裂應力範圍(0.35 ~ 0.6UCS) 接近,可知於PFC數值模擬中可藉由AE訊號抓取之初始破裂應力(σ_ci)。(2) 從模擬含單一裂隙岩石之張裂與剪裂的AE發展順序,可知岩石之張裂破裂比剪裂破裂發展速度快,且張力裂縫的延伸是影響整體岩石之破裂行為。因此,初始張裂機制在花崗岩的破壞過程中較初始剪裂機制重要。(3) 由PFC模擬花崗岩含雙裂隙岩石之斷鍵紀錄,可觀測到於共線狀態下顯示岩橋間微觀鍵結斷鍵是由張力斷鍵與剪力斷鍵一同形成之混合式破壞。(4) 於共線、裂隙傾角(α)為45度及岩橋角(β)為45度的狀況下得知,模擬含雙裂之單軸壓縮試驗,發現岩橋長度(2b)會影響破裂順序,並可將岩橋間破裂連結順序分成三種破壞模式,分別為LTM模式(2b/2a < 0.2)、TLM模式(0.2 < 2b/2a < 0.52)及TML模式(2b/2a >0.52)。(5) 於非共線狀態下、裂隙傾角(α)為45度,當岩橋長度小於或等於裂隙長度(即2b≦2a),並改變岩橋角(β)時,可獲知:(i) 當β< 90°時,岩橋破裂連結為張裂與剪裂的混合破裂模式(mixed shear crack & tensile crack)為主控;(ii) 當β= 90°時,岩橋由裂隙內部尖端(inner crack tips)先出現剪力破裂,再產生張力破裂形成岩橋間的破裂連結;(iii) 當β> 90°時,岩橋之破裂連接為張力破裂形成主控。

關鍵字

花崗岩 破裂連接 AE PFC 岩橋 混合式破壞

並列摘要


It is planned to use the PFC program to simulate the fracture coalescence problem between rock fissures: the purpose is to use PFC to distinguish the criharactestics of AE rates such as tension fracture or shear fracture between particle bonds. First of all (1) for different inclination angles the fracture development sequence of a single fissure rock and the mechanical characteristics (tension or shear) and crack initiation, damage stress and other mechanical characteristics ; (2) Arrange multiple different geometrical arrangements (collinear or parallel arrangement) Under the conditions, discuss the mutual influence of the microscopic fissure behavior of the rock bridge between multiple fissures and the difference in fracture coalescence between the development of coalescence and the series behavior, and hope that the results of this research will be useful for future research on the fissures subject to long-term external forces. It is helpful to understand that the new fracture and its extended growth trend, which increase the serial degree of the rock fracture network and increase the liquidity. The main conclusions obtained in this paper are as follows: (1) The crack initial stress (σ_ci) is captured by the PFC numerical simulation using the AE signal, and it is found thatσ_ci falls approximately at 0.63UCS, which is close to the initial fracture stress range of ordinary rocks (0.35 ~ 0.6UCS). The crack initiation stress (σ_ci) that can be captured by the AE signal in the PFC numerical simulation. (2) From the AE development sequence of simulating the tension and shear failure of a rock with a single fracture, it can be seen that the tension fracture of the rock develops faster than the shear fracture, and the extension of the tension failure affects the fracture behavior of the whole rock. Therefore, the initial fracture mechanism is more important than the initial shear fracture mechanism in the failure process of granite. (3) Using PFC to simulate the broken bond record of granite rock with double fissures, it can be observed that the microscopic bond broken between rock bridges in the collinear state is a mixed failure formed by the tension broken bond and the shear broken bond. (4) Under the condition of collinear,fissure inclination (α) of 45 degrees and rock bridge angle (β) of 45 degrees, it is known that the uniaxial compression test with double fissures has shown that the length of the rock bridge (2b) will affect the fracture sequence , and the sequence of fracture coalescence between rock bridges can be divided into three failure modes, namely LTM mode (2b/2a <0.2), TLM mode (0.2 <2b/2a <0.52) and TML mode (2b/2a> 0.52). (5) In the non-collinear state, the fissure inclination (α) is 45 degrees, when the rock bridge distance is less than or equal to the fissure length (i.e. 2b≦2a), and the rock bridge angle (β) is changed, it can be known that: (i) When β<90°, the fracture of the rock bridge is controlled by a mixed shear failure & tensile failure; (ii) When β=90°, the rock bridge is controlled by the shear failure occurs first, followed by tension failure to form a fractured coalescence between the rock bridges; (iii) When β>90°, the fractured coalescence of the rock bridge is the main control of the tension fracture.

參考文獻


1.李宏輝(2008),砂岩力學行為之微觀機制-以個別元素法探討,國立台灣大學土木工程學博士論文。
2.吳勁頤(2017),以PFC模擬離島花崗岩處置坑道之破裂行為,淡江大學土木工程學研究所碩士論文。
3.林冠良(2019),裂隙延伸於岩楔穩定性之影響-以分離元素法探討,國立台灣大學土木工程學研究所碩士論文。
4.楊長義(2017),台灣潛在母岩破壞強度特性與處置坑到破裂關係之研析,科技部補助專題研究計畫案。
5.楊長義(2020),關鍵性裂面受地震力闢列之延伸行為研析,科技部補助專題研究計畫案。

延伸閱讀