层理白云岩力学特性及隧道围岩位移特征研究

为探究贵阳地区层理白云岩力学特性及受层理影响的白云岩隧道围岩位移特征规律,对取自贵阳某隧道工程施工现场的层理白云岩试件进行了单轴压缩、巴西劈裂和电镜扫描(SEM)试验,并对5种层理倾角下的白云岩隧道工况进行了数值模拟分析。研究结果表明:层理白云岩抗压强度较高,随着层理角度增大,抗压强度呈先减小后增大趋势;试件破坏形态分为劈裂破坏、压剪滑移破坏及压碎破坏三种,且抗压强度大小为压碎破坏>劈裂破坏>压剪滑移破坏;层理白云岩抗拉强度具有一定的离散性,随着层理角度增大,抗拉强度整体呈下降趋势;层理白云岩岩质处微观结构排列有序,形状多呈规则的多面体,整体结构面较平滑完整,颗粒间的紧密程度较高;夹层处微观结构排列杂乱无规律,微观颗粒形状大小不一且不规则,颗粒间的结合较松散;白云岩隧道受层理影响,22.5°层理隧道围岩位移最大,隧道最大位移发生于隧道与层理交界区域,设计时可对该区域加强支护,从而达到有效控制围岩位移的目的。

Study on mechanical properties of bedded dolomite and displacement characteristics of tunnel surrounding rock

In order to explore the mechanical properties of the bedded dolomite in the area of Guiyang and the law of the displacement characteristics of the tunnel surrounding rock of dolomite under the impact of the bedding，the relevant uniaxial compression，Brazilian splitting and scanning electron microscopy ( SEM) tests are carried out on the bedded dolomite samples taken from a tunnel construction site in Guiyang，while numerical simulation analysis is made on the working conditions of the tunnel under the conditions of five bedding dips． The study result shows that the compressive strength of the bedded dolomite is higher and the compressive strength exhibits a trend of decreasing at first and then increasing along with the increase of the bedding dip． The sample failure patterns are divided into three kinds，i． e． splitting failure，compression-shear failure and crushing failure，of which the magnitudes of the compressive strengths are crushing failure＞splitting failure＞compression-shear failure in turn． The tensile strength of the bedded dolomite has a certain discreteness and the tensile strength generally presents a decreasing trend along with the increase of the bedding dip． The microstructures at the rocky positions of the bedded dolomite are orderly arranged with most of the shapes of regular polyhedron，while the overall structural plane is smooth and intact with higher compactness among the particles． The microstructures at the interlayers are disorderly and irregularly arranged with various shapes and sizes of the microscopic particles and looser jointing among the particles． The tunnel with dolomite surrounding rock is impacted by the bedding and the displacement of the tunnel surrounding rock with the bedding dip of 22. 5° is the largest． The maximum displacement of the tunnel occurs at the area of the interface between the tunnel and the bedding，thus the reinforced support for the area can be considered during the design，so as to get the target of the effective control of the surrounding rock displacement。