以個別元素法探討岩栓束制節理面剪脹之效應暨其對力學特性之影響

Abstract

岩栓為現代隧道工法中主要使用的支撐構件，主要用途為抵抗節理面滑動及穩定懸浮岩塊。岩栓抵抗節理面滑動的原理有兩種方式，一為利用岩栓本身的材料強度抵抗作用於節理面的剪力，另一則是利用岩栓的勁度束制節理面受剪膨脹的程度，間接使節理面的破壞模式由滑動破壞轉變節瘤剪斷破壞。 基於節理面受力剪動變形實為一界面分離的現象，欲有效評估岩栓支撐效果，採用之工具需具備描述節理面界面分離與受剪膨脹的特性。故本研究應用基於顆粒力學個別元素法發展的PFC3D軟體為工具，分由微觀尺度節理面受力變形的特性與宏觀尺度岩體整體變形特性出發，探討規則節理岩體的非線性與異向性行為。 本研究首先以單軸壓縮試驗結果為比較基礎，求得FPC3D模擬完整岩石的微觀參數；繼而模擬節理面受剪特性，經深入探討顆粒力學模式模擬平滑面的幾何引致摩擦問題後，釐清各微觀參數對於節理面剪力變形與剪脹曲線的影響，掌握PFC3D模擬節理面的關鍵技術；最後整合完整岩石與節理面模擬所得，建立節理岩體PFC3D數值模式。經比較物理模型試驗結果顯示模擬所得良好，本研究透過PFC3D程式可有效考慮規則節理岩體的非線性與異向性行為。 本研究繼而設計一系列數值模擬試驗，探討岩栓的抗剪與束制的支撐功效。透過分離抗剪與束制作用對剪動與剪脹曲線的影響，數值模擬有效釐清了節理面受剪過程岩栓的作用機制。未來若能進一步確認分析所得的徵觀參數，將可更深入評估岩栓束制節理面受剪的極限強度，有利於精緻化岩體工程的分析與設計。

Rockbolt is the major support components of tunnel excavation. It is use to resist joint sliding and stable suspension rocks. There are two ways that how rockbolt resist joint sliding: resist shearing force by strength of materials, or constraining dilation of joint surface that surface behavior will change from sliding up to shearing off. Because joint sliding is an interface-separated phenomenon, The tools we use must describe the feature of joint separated and dilation if we want to evaluate support effect. So this study using distinct element method simulation software PFC3D to investigate the nonlinear and anisotropic behavior of jointed rock mass from microscopic of joint deformation and macroscopic of rock deformation. This study first analysis the mechanics of intact rock with results of uniaxial compression test to observing the effects of parameters in PFC3D. Then we simulate behavior of smooth joint to observing the effects of geometry that induce friction problem in particle mechanics to predominate. key technology of simulating joint surface in PFC3D. Finally we combine the results to building jointed rock mass numerical model in PFC3D. The results of simulation is well, and we can consider the nonlinear and anisotropic behavior of regular jointed rock mass through PFC3D. After establish the application of DEM method to jointed rock mass, this study investigate effects of rockbolt constraining joint surface dilation through separating the support effects of anti-dilate and anti-shear. We clarify the mechanism of rockbolt during joint surface shearing by numerical simulation. In the future, we can deeply analysis the limit strength of joint which is constrained by rockbolt if we can establish parameters setting, and it will improve the analysis and design of engineering.