| 摘要: | 本文以PFC3D（Particle Flow Code3D）結合FracMan模擬不同裂隙傾角之橫向等向性合成岩體，在單軸或三軸壓縮試驗下之破壞模態（failure modes）、單壓強度（UCS）、楊氏模數（E50）與變異性（CV），並與過往理論進行驗證。同時探討裂隙直徑（D）、費雪常數（κ）、裂隙程度（P32）等裂隙參數以及取樣體積變化對裂隙岩體力學行為及其變異性的影響，且整合一異向性指標，可用來表示為橫向等向性岩體之異向性程度。
本文研究結果顯示為：（1）橫向等向性岩體之力學性質與傾角呈U型關係；然而，力學性質之變異係數與傾角呈一倒U型關係。（2）此外，裂縫發展受裂隙傾角之影響，在單壓試驗下之破壞模態共可歸納為四類，分別為穿層破壞模態（Sliding or split across inherent fracture mode）、滑動破壞模態（Sliding along inherent fracture mode）、劈裂破壞模態（Split along inherent fracture mode）、混合模態（Mixed mode）。（3）橫向等向性岩體之單壓強度及楊氏模數之變異係數與取樣體積開根號成反比，符合統計學中央極限定理（central limit theorem）。與等向性結果相同（田永銘等，2017）。（4）三軸試驗中當圍壓越大，其力學性質與變異性之異向性皆越低，呈負相關。並與Tien and Kuo ( 2001 )的破壞準則進行比較，其結果高度吻合。（5）D、κ、P32等裂隙參數，對力學行為及其變異性影響甚鉅，隨著D、κ、P32提升，其力學性質與變異性的異向性越顯著，呈正相關。同時本文提出一量化之異向性指標「異向性比，AR（anisotropic ratio）」，並建立AR與D、κ、P32之關係。
;This paper employs 3-D Particle Flow Code and FracMan to simulate synthetic transversely isotropic rocks masses with different dip angles (β) and focuses on the uniaxial compressive strength (UCS), Young’s modulus (E50), failure modes, and coefficient of variance (CV) under unconfined compression test and triaxial test. And we verify our simulation results to criterion. This paper also presents the effect of sampling volume and fracture parameters such as fracture intensity (P32), fracture diameter (D), and Fisher constant (κ) on the mechanical behavior and variation of fractured rock. Furthermore, a new anisotropic index for the anisotropic degree of transversely isotropic rocks has been developed and presented.
Based on the numerical simulation results:(1) The relationship between the mechanical properties of transversely isotropic rocks and β presents the U-typed relation. However, the relationship between CVs of the mechanical properties and β presents the inverted U-typed relation. (2) In addition, the crack development is affected by dip angle of fracture, and we generalize four failure modes under unconfined compression test. The failure modes are sliding or split across inherent fracture mode, sliding along inherent fracture mode, split along inherent fracture mode, and mixed mode, respectively. (3) The coefficient of variations (CV) of uniaxial compressive strength and Young’s modulus are inversely proportional to the squared root of sampling volume, which conforms the central limit theorem. The result is the same as isotropic. (Tien et al., 2017) (4) The anisotropic of mechanical properties and variations decrease with increase of confining pressures under triaxial test, which shows the negeative relation. The simulation results almost agree with results of Tien and Kuo Criterion (2001). (5) The fracture diameter (D), fracture intensity (P32), and the Fisher constant (κ) all have significant effects on the mechanical behavior and variation. The anisotropic of mechanical properties and variations increase with the increase of D, κ, and P32, which shows the positive relation. This paper also proposed a anisotropic ratio (AR) and established the relationship among AR, D, κ, and P32 of transversely isotropic rocks. |
