锦屏层状大理岩断裂特征的微细观分析

Meso-experimental analysis on fracture characteristics of Jinping bedded marble

锦屏二级地下洞室群围岩处于埋深大、高地应力状态,开挖卸荷后围岩变形破坏引起的工程问题十分突出。根据锦屏二级交通辅助洞所取得盐塘组大理岩的层状及白山组大理岩均质的特性,利用SEM高温疲劳试验系统,开展了对盐塘组大理岩不同层理方向受力及白山组大理岩的变形破坏特征及断裂机理的三点弯曲试验。试验过程中,将岩样加工成盐塘组大理岩平行层理、垂直层理及白山组大理岩3组试件。研究结果表明:盐塘组大理岩的层状特性是由于其矿物成分的方解石矿物颗粒及白云石矿物颗粒呈条带状相间分布所致,而矿物颗粒单一的白山组大理岩试件则较为均质;层状大理岩的断裂机理取决于对层理的作用力方向及矿物组成,并且表现出力学参数上的差异,而受矿物颗粒间的胶结能力及颗粒大小的影响,白山组试件强度则最小;盐塘组大理岩两组试件变形破坏过程表现出明显的3个阶段,而白山组试件变形破坏特征则划分为峰前及峰后阶段,受不同断裂机理的影响盐塘组荷载平行层理方向较之垂直方向试件的塑性变形特征明显,且白山组试件峰后阶段较为完整的表现出了其变形破坏过程。

Abstract： The project problem because of wall rock＇s deformation fracture in deep-buried and high geostress conditions is very prominent at Jinping hydropower Ⅱ station underground engineering. According to the characteristics of the bedded marble collected from Jinpiing Ⅱ hydropower station auxiliary traffic tunnel in deep-buried area, three-point bending experiment on different bedded direction specimens with SEM high temperature testing system is carried out to test the stress of bedded marble in different directions and the failure mechanism and deformation features of homogeneous marble. In the test, there are 3 groups of specimens, include parallel bedded specimen, vertical bedded specimen and homogeneous marble specimen. The results show that： bedded marble＇s bedded feature is because of the banded structure feature between dolomite mineral particles and calcite mineral particles; the fracture mechanism and strength parameter of bedded marble depend on different force directions and mineral composition. Because of the cement capacity between dolomite minerals and particles size, homogeneous marble specimen has the lowest strength. The marble specimens＇ deformation shows 3 stages, and because of different fracture mechanisms, the plastic deformation of parallel bedded specimens is more obvious than that of vertical bedded specimen. While the deformation of homogeneous marble can be divided into 2 stages, i. e. before and after peak stage, and the after peak stage shows the complete deformation development process.