橫向等向性岩石之變形性研究

Abstract

岩石之異向性對岩體內應力分佈具有甚大影響，是故於從事異向性岩體應 力分析（例如，隧道應力分析，現地應力量測分析等）前，應詳細探究異 向性岩石之異向變形特性，企求得到更合理的應力值。本研究利用傳統之 單軸壓力試驗以二個不同傾角圓柱試體（其中之一為90度傾角，即作用力 方向與劈理面平行），求取具橫向等向性之乾溝層硬頁岩及廬山層板岩之 五個靜動彈性常數 E，E'，v，v'，G'，並以超音波試驗求取未受壓下硬 頁岩之五個動態彈性常數。經由一系列試驗，乾溝層硬頁岩之五個平均彈 性常數為E=51000 MPa，E'=32000 MPa，v=0.19，v'=0.18，G'=13000 MPa ，其E/E'=1.6，G/G'=1.6，v/v'=1.05，除v/v'外皆具異向性，其動彈性 常數皆略大於靜彈性常數，但異向性程度較小。廬山層板岩之五個彈性常 數則分別為E=54000 MPa，E'=22000 MPa，v=0.19，v'=0.12， G'=15000 MPa，上述結果之E/E'=2.5，G/G'=1.5，v/v'=1.65，可見其異向性程度較 硬頁岩為高。 The stress distribution in anisotropic rock masses is strongly dependent on the degree of rock anisotropy which can be represented by the elastic contants of the rock．In order to evaluate the stress components in anisotropic rocks，the elastic contants have to be obtained． The five elastic constants of two types of transversely isotropic rocks， argillite of Ken-Guo formation and slate of Lu-Shan formation in central Taiwan and northern Taiwan， respectively，are obtained by conventional uniaxial compressive testing on cylindrical samples at laboratory in this experimental reseach． The results show that the five static elastic constants of argillite are E=51000 MPa，E'=32000 MPa，v=0.19，v'=0.18， G'=13000 MPa， and those of slate are E=54000 MPa，E'=22000 MPa ，v=0.19， v'=0.12$，G'=15000 MPa．It is found that the degree of anisotropy of slate samples is larger than that of argillite samples．This phenomenon shows the difference of metamorphism degree of the two diffenerce types of rocks．