硬頁岩之強度與變形行為

Abstract

本研究嘗試利用傳統的單軸壓力試驗和三軸壓力試驗，企圖對具有橫向等 向特性之硬頁岩的力學性質(強度特性、變形特性)做一探討；從一系列之 試驗結果顯示，硬頁岩的三軸強度特性隨著彈性對稱面與最大主應力間之 夾角而有所變化，在層面角度=30度附近有最小之強度。硬頁岩之變形性 深受圍壓所影響，當圍壓增高，促使變形異向性降低。對於硬頁岩之三軸 尖峰強度，本研究透過一些學者所提出的強度準則與實驗結果作比較，以 Donath及McLamore的強度準則最為貼切使用 ，為使強度破壞準則能適用 於異向性岩體，本研究提出Hoek-Brown準則之修正式，本式考慮岩石之單 壓強度和強度參數m隨不連續面傾角而變，而s則為定值，代表岩體之破碎 度，經與硬頁岩試驗值比較，其能詳細預測硬頁岩之三軸強度值。由實驗 結果得知，硬頁岩之三軸殘餘強度亦隨劈理面角度變化而變化，進一步以 Mohr-Coulomb準則分析得到其殘餘之凝聚性強度c，隨層面傾角變化，而 摩擦角度則變化不大。對於硬頁岩之張力強度而言，本文嘗試以傳統的巴 西試驗以及改良型之巴西試驗，都無法得到一合理的結果，由於受到劈理 面之影響，對於異向性岩石而言，應該利用理論或數學解析來求得其張力 強度。 In order to investigate the mechanical properties of transversely isotropic rocks, a series of laboratory experiments including uniaxial compression tests, triaxial compression tests, and indirect tensile tests are performed on core samples of argillite. Based on the series of testing, the results show that the peak and residual triaxial compression strength and indirect tensile strength strongly depend on the inclination of the cleavage with respect to the direction of major applied force, the degree of deformability anisotropy decrease with the increase of the confining pressure. Based on the testing results, a modified Hoek-Brown failure criterion is proposed for the peak triaxial compression strength of transversely isotropic rock. In the criterion, the uniaxial compression strength and strength parameter m change with the inclination angle between the cleavage plane and maximum principal stress direction, then, parameter s is independent of the inclination of cleavage and only depends on the fracture properties of rock mass. For the residual triaxial compression strength ,Mohr -Coulomb theory is adopted to analyze the experimental data. It was found that the strength parameter c depends on the cleavage angle, and the strength parameter is not influence by the change of the inclination of cleavage with respect to maximum principal stress direction.