複合岩體之岩塊體積比量測及其力學行為; The measurement of block volumetric fraction and the mechanical behaviors of composite rock mass

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题名:	複合岩體之岩塊體積比量測及其力學行為;The measurement of block volumetric fraction and the mechanical behaviors of composite rock mass
作者:	郭明傳;Ming-Chuan Kuo
贡献者:	土木工程研究所
关键词:	複合岩體;岩塊體積比;掃瞄線法;人造複合岩體;微觀力學模式;破壞準則;破壞模態;micromechanics model;artificial composite rock mass;scanline;volumetric fraction;composite rock mass;failure criterion;failure mode
日期:	2005-07-19
上传时间:	2009-09-18 17:08:51 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	「複合岩體」係由工程性質不同的粗顆粒岩塊及細粒基質材料或由兩種不同強、勁度的層狀岩石材料相互交錯所構成的混合岩體。由於複合岩體之異質性、異向性及其複雜的特性，此類地質之大地工程性質相當難以評估與掌握。而複合岩體之工程性質與力學行為主要受到組成材料之力學性質、內部岩塊體積比、岩塊排列方向或強度及變形異向性所影響。其中，岩塊體積比則是最常用以評估複合岩體整體工程性質的參數，因此，本文利用數值模擬方式，藉由分析一代表性表徵單元內掃瞄線長度與岩塊顆粒相交長度，來探討掃瞄線長度、岩塊粒徑、岩塊體積比、岩塊長短軸比及岩塊排列方向對掃瞄線所求取之面積比的影響，建立各影響因素相互間的關係，並以統計學上「信心度」及「信賴區間」的觀念，給予掃瞄線法所求得之面積比一定性且定量的描述。針對複合岩體之強度、變形性及其力學行為，採用試驗與理論併行方式來探討。利用人造方式製作具有「巨觀等向性」及「巨觀橫向等向性」之複合岩體，並進行一系列三軸試驗，以探討岩塊體積比、圍壓及層面傾角對複合岩體強度及變形性之影響。複合岩體破壞模態部分，利用改良型的旋轉式掃瞄器擷取試體破壞過程及破壞後之表面影像，以探討橫向等向性複合岩體的破壞過程及破壞機制，並就等向性及橫向等向性複合岩體的破壞模態進行分類及比較。理論分析部分，利用等值均質化觀念，以五種不同之微觀力學模式預測不同岩塊體積比之等向性複合岩體的楊氏係數與柏松比，結果顯示，利用微觀力學模式來預測等向性複合岩體之力學性質相當可行。並以異向性線彈性材料組成律模式，配合最大軸向應變理論及Jaeger(1960)之單一弱面理論，建立一個適合橫向等向性岩石的破壞準則。以此破壞準則針對不同類型之橫向等向性岩體及橫向等向性複合岩體在不同圍壓及傾角進行破壞強度預測，由理論預測與試驗數據比較，兩者相當吻合，足證此破壞準則之正確性、適用性與廣泛性。 Composite rock mass is a mixture of rocks, composed of geotechnically significant blocks with a bonded matrix of finer texture or rock materials with two kinds of distinct strength and stiffiness. Because of the heterogeneity, anisotropy and complex nature, composite rock mass is a kind of difficult geotechnical material with which to deal in geotechnical engineering. The engineering properties and mechanical behaviors of composite rock mass are mainly influenced by the mechanical properties of composite materials, volumetric fraction of block, preferred block orientation and the anisotropic behaviors of deformation and strength. The volumetric fraction of block is a general parameter for assessing the overall engineering properties of composite rock mass. By analyzing the crossing length between the block and scanline in representative volume element (RVE), this research represented the discussion on the influence of total length of scanline, diameter of block, volumetric fraction of block, the aspect ratio of block and the preferred block orientation on the volumetric fraction of block measured by scanline. Using the concept of confidence level and confidence interval offers a qualitative and quantitative description of the volumetric fraction. Furthermore, the main purpose of this research is to investigate the failure strength, deformation properties and mechanical behaviors of composite rock mass from both theorectical and experimental approaches. The preparation technique for artificial composite rock mass which overall mechanical properties are macroscopically isotropic and transversely isotropic is developed. A series of triaxial tests are conducted to investigate the influence of the volumetric fraction, confining pressure, the orientation angle on the composite rock mass. In the experiment carried out, a procedure using a rotary scanner to obtain the “unrolled” images of rock specimens at different stress level during the uniaxial compressive tests is employed. Based on the experimental results, the failure modes of isotropic rock mass and transversely isotropic rock mass are classified. For theoretical prediction, five micromechanical models are used to predict the Young’s modulus and Poisson’s ratio of isotropic composite rock mass with different block proportions. Comparing the theoretical predictions with test results, the feasibility of using the micromechanical models to predict the mechanical properties of isotropic composite rock mass was investigated. A new failure criterion for the transversely isotropic rocks has been developed and presented. The criterion is based on the maximum axial strain criterion, the constitutive laws of linearly elastic of anisotropic materials and the theory of single plane of weakness. The predictions of the failure strength of various types of transversely isotropic rock masses with different orientation angles and under various confining pressures agree well with experimental data. The accuracy and the versatility of the criterion are demonstrated.
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