對於工程地質而言，岩體邊坡穩定性受到不連續面與岩體材料性質影響，不連續面不僅會降低岩體強度，亦可能造成顯著力學異向性。不連續面包含岩體內部之節理、層理或其他構造，使得岩體力學特性隨著不連續面位態而有所改變。然而，岩體巨觀行為受到微觀結構控制，小尺度岩體變形行為與邊坡破壞特徵相互關聯。因此，本研究採用以離散元素法為計算基礎之顆粒流軟體(Particle Flow Code3D， PFC3D)，以國立陽明交通大學陽明校區之岩體特性建立三維岩體模型，進行單軸抗壓強度試驗模擬。研究中設計八組岩體體積，藉由計算單壓強度以評估完整岩體之代表性單元體積(Representative Elementary Volume， REV)，決定適當的完整岩體模型尺寸。而後，以此岩體體積作為基準，建立含節理之岩體模型，考慮三組不同直徑節理與不同角度進行力學分析，透過計算彈性參數並建立組成律以定量節理幾何特性對於岩體強度與變形行為之影響。 根據模擬結果以及統計分析顯示，完整岩體之代表性單元體積為直徑3.5公尺、高度為7公尺的圓柱型岩體。加入節理後，岩體強度隨節理角度呈顯著變化，當最大主應力與節理夾角約為45°時，強度達最小值，顯示當節理於該方向時，岩體最容易破壞。此外，隨著節理尺寸增加，岩體強度呈現明顯異向性，表示不連續面大小對於岩體在不同方向上的力學性質影響顯著；在岩體變形行為方面，軸向應力與應變關係顯示，當節理與受力方向夾角介於45°~60°時，岩體相對較容易發生變形；且隨著節理尺寸增加，應力與應變之異向性特徵趨於明顯，說明岩體變形行為受節理尺寸影響顯著。本研究經由REV分析確定具有代表性力學特性之完整岩體尺寸，可作為後續連續體數值模擬模型設計之基準；加入平行層面節理後，藉由計算岩體強度與彈性參數量化節理幾何特性對岩體力學異向性之影響，釐清其對岩體強度與變形行為之機制，辨識岩體潛在破壞條件；研究成果有助於連結邊坡穩定分析與工程設計之應用。;For engineering geology， the stability of rock slopes is governed by both the mechanical properties of the intact rock and the characteristics of discontinuities. Discontinuities not only reduce the strength of the rock mass but also induce significant mechanical anisotropy. These discontinuities， including joints， bedding planes， and other geological structures， cause the mechanical behavior of the rock mass to vary with their orientation. Because the macroscopic behavior of a rock mass is controlled by its microscopic structure， the deformation behavior of small-scale rock masses is closely related to the failure characteristics of rock slopes. Therefore， this study employed the three-dimensional Particle Flow Code (PFC3D)， a discrete element method (DEM) based numerical simulation software， to establish three-dimensional rock mass models based on the geological characteristics of the National Yang Ming Chiao Tung University Yangming Campus and to perform uniaxial compressive strength test simulations. Eight rock mass model sizes were designed to evaluate the Representative Elementary Volume (REV) of the intact rock mass by analyzing the uniaxial compressive strength (UCS)， thereby determining an appropriate model size for the intact rock mass. Using the identified REV as the reference model， jointed rock mass models were subsequently established by incorporating three different joint diameters and various joint orientations. Mechanical analyses were then conducted by calculating the elastic parameters and constructing the constitutive law to quantitatively evaluate the influence of joint geometry on the strength and deformation behavior of the rock mass. The simulation results and statistical analyses indicate that the REV of the intact rock mass is a cylindrical specimen with a diameter of 3.5 m and a height of 7 m. After introducing joints， the rock mass strength exhibited significant variation with joint orientation. The minimum strength occurred when the angle between the maximum principal stress and the bedding parallel joint was approximately 45°， indicating that the rock mass was most susceptible to failure under this orientation. Furthermore， as the joint diameter increased， the strength anisotropy of the rock mass became more pronounced， demonstrating that joint size has a significant influence on the directional mechanical properties of the rock mass. In terms of deformation behavior， the axial stress–strain relationship showed that the rock mass deformed more readily when the angle between the loading direction and the bedding parallel joint ranged from 45° to 60°. Moreover， the anisotropic characteristics of the stress–strain response became increasingly pronounced with increasing joint diameter， indicating that the deformation behavior of the rock mass is strongly affected by joint size. Through REV analysis， this study determined a representative intact rock mass size with stable mechanical properties， which can serve as a reference for the design of subsequent continuum numerical models. By incorporating bedding parallel joints and evaluating the rock mass strength and elastic parameters， the influence of joint geometry on the mechanical anisotropy of the rock mass was quantitatively assessed， providing insight into the mechanisms controlling rock mass strength and deformation behavior as well as identifying potential failure conditions. The findings of this study contribute to bridging the gap between rock slope stability analysis and practical engineering design.
