以非破壞光學干涉術研探岩材於斜剪過程之破壞演化

On the Evolution of Failure in Rocks Under Inclined Shear Test in Conjunction with Nondestructive Technique of ESPI

買冠誠(Guan-Cheng Mai)

指導教授 ： 陳立憲

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00248

摘要

囿於一般岩石直剪使用之封閉式剪切盒，僅能估求巨觀受剪行為及其強度參數c、ψ，而對微觀剪力破壞特徵如變形連續之叢聚與變形不連續之初裂和裂衍，則無法深入探究。本研究以自行研發斜剪試驗儀，採可視化剪力盒設計，並以非破壞檢測之電子斑紋干涉術（ESPI）進行開盒式試體表面之變形量測為主；並輔以聲射技術（AE）進行試體微裂震源之監測，冀能進一步研探岩材之微、巨觀破壞機制。
基於平面應變之受剪狀態下，藉由三大變數之訂定：(1) 岩材(天然岩材與人造類岩)；(2) 斜剪角度(β= 65°、70°、80°)；(3) 預裂縫之幾何形狀與方位(無預裂縫、版狀預裂縫及不同方位之版狀預裂縫、圓孔型、雙側預裂縫)；並以裂縫開口位移作為施剪設備之回饋控制訊號，求得岩材峰前、峰後之完整加載歷程。
因電子斑紋干涉術具高精度(微米)且非接觸式之即時、全域性觀測等優點，並配合另一聲射技術比對材料破壞過程中之微震裂源定位。本研究計可研探: (1) 岩材之巨觀完整受剪歷程，亦即剪應力-剪變形曲線之峰前勁度、尖峰強度及峰後韌度之求算；(2) 研探岩材之三項微觀破壞演化特徵: 叢聚、初裂與裂衍。而本研究得知岩材之叢聚與初裂時機均發生於峰前，以剪角70度而言，叢聚時機約略於LL= 60~70%，初裂時機為70~80%之間，而峰後行為之裂衍中可發現水膠比高與圓狀顆粒偏向於穩定破壞(Class I)，水膠比低與角狀顆粒偏向於不穩定破壞(Class II)。
最後利用聲射法研判其叢聚發生時機與位置，與電子斑紋干涉術所觀察之初裂及裂衍位置比對，發現兩者監測之破壞演化特徵頗為一致，證明可視化斜剪試驗建置之可行與適確。

關鍵字

電子斑紋干涉術(ESPI) ； 非破壞檢測 ； 斜向剪切試驗儀 ； 預裂縫

並列摘要

Traditional direct shear test for rock can only obtain the macroscopic strength parameters since the closed-box design is unable to investigate the evolution of failure as well as the three main microscopic characterizations such as the localization during the stage of deformation continuity and crack initiation/propagation during deformation discontinuity. Therefore, a setup of a opened-box inclined shear test device with COD (crack opening displacement) control was designed and built to couple two nondestructive techniques simultaneously: ESPI (electronic speckle pattern interferometry) and AE (acoustic emission). The external and internal in-plane fracture behavior of rock materials subjected to shear can be probed by ESPI and AE, respectively.
In this study, the failure evolution of rocks under inclined shear test was studied mainly by ESPI, and was assisted by AE. Several key factors were also studied: rock types (natural and artificial rocks), inclined shear angle (β = 65°, 70°, 80°), pre-existing crack (location, shape, orientation).
ESPI has advantage with high precision (Micron), non-contact, and whole-field monitoring. In addition, AE is able to verify microseismic activities and their source locations. This study presents crucial functionalities: (1) A macroscopic complete loading curve including pre- and post-peak stiffness, shear strength at peak, and post-peak toughness of rock was obtained quantitatively. (2) Three main microscopic characteristics for the evolution of fracture in stressed rock can be evaluated. That is, localization, crack initiation and propagation were examined respectively. Experimental results also show that both localization and crack initiation occurred prior to the peak. Localization takes place at about 60 to 70 % of load level while crack initiation at about 70 to 80 % for the case of shear angle 70°. Moreover, “class I” post peak behavior can be found in higher water-to-binder ratio and rounded particles whereas the low water-to-binder ratio and angular particles tend to “class II” unstable response posterior to peak.
By comparing the results of nondestructive techniques of ESPI and AE, the evidence of damaged development from ESPI was consistent with the measurement of AE. The feasibility and correctness of the inclined shear device was approved.

並列關鍵字

Electronic speckle pattern interferometry (ESPI) ； Nondestructive technique (NDT) ； Inclined shear test

參考文獻

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