弱胶结西域砾岩组构特征及其力学性能演化规律研究  

Study on the fabric characteristics and evolution mechanism of the mechanical behavior of weakly cemented Xiyu conglomerate

作　　者：范雷[1] 胡伟[1] 张宜虎[1] FAN Lei;HU Wei;ZHANG Yihu(Key Laboratory of Geotechnical Mechanics and Engineering of the Ministry of Water Resources,Changjiang River Scientific Research Institute,Wuhan,Hubei 430010,China)

机构地区：[1]长江科学院水利部岩土力学与工程重点实验室,湖北武汉430010

出　　处：《岩石力学与工程学报》2024年第8期1893-1908,共16页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(51927815,42277186)。

摘　　要：弱胶结西域砾岩在新疆天山南北两麓分布广泛,物质组成复杂,力学性质较差。为科学认识弱胶结西域砾岩力学特性的演化规律,采用室内测试与现场大尺寸真三轴试验方法对西域砾岩的颗粒组构特征与宏观力学特性进行系统研究。研究结果表明:(1)弱胶结西域砾岩物质组成中碎石、粗砾、中砾3个粒组占比较高,且颗粒级配不良,碎石、砾粒等巨粒、粗粒间接触关系为颗粒悬浮和颗粒支撑结构,颗粒间胶结型式主要为孔隙式胶结;(2)受颗粒排列特征影响,弱胶结西域砾岩表现出明显的各向异性变形特征,其中铅直方向变形模量最大,颗粒长轴方向(近垂直于天山走向)变形模量最小,中轴方向(近平行于天山走向)变形模量居中,但是随着应力水平提高,弱胶结西域砾岩逐渐趋向于各向同性;(3)在三轴应力状态下弱胶结西域砾岩在屈服阶段表现出应变硬化特征,当达到峰值后表现出典型的塑性流动特征;(4)弱胶结西域砾岩的抗剪强度具有明显的非线性特征、加卸载应力路径效应以及中间主应力效应,其中应力水平越高,抗剪强度参数内摩擦角越小,黏聚力越大;卸载条件下西域砾岩的内摩擦角高于加载条件下的内摩擦角,而卸载条件下的黏聚力则低于加载条件下的黏聚力;真三轴加载条件下,其峰值强度随着中间主应力的增加而有所提高,并且中间主应力对抗剪强度参数黏聚力的影响更加明显;(5)弱胶结西域砾岩在三轴应力状态下的破坏以压剪破坏为主,破坏后形成陡倾的主破裂带,主破裂带之间有拉裂纹连接贯通。试验结果为系统了解弱胶结西域砾岩的宏观力学特性及其演化规律提供了重要依据。The weakly cemented Xiyu conglomerates are widely distributed in the northern and southern foothills of Tianshan Mountains in Xinjiang.The material composition of Xiyu conglomerates is complex,and their mechanical properties are poor.In order to scientifically understand the evolution laws of mechanical properties of weakly cemented Xiyu conglomerate,its grain fabric characteristics and macro mechanical properties were systematically studied by means of laboratory test and in-situ large-scale true triaxial test.The results indicate that:(1)The material composition of weakly cemented Xiyu conglomerate is relatively high in the three particle groups of crushed stones,coarse gravels,and medium gravels.And the particle size distribution of weakly cemented Xiyu conglomerate is poor.The inter-granular contact between large and coarse particles such as crushed stones and gravels involves either particle suspension or particle support.The inter-granular cementation is mainly pore-type cementation.(2)Due to the influence of particle arrangement,weakly cemented Xiyu conglomerates exhibit obvious anisotropic deformation characteristics.The deformation modulus is highest in the vertical direction,lowest in the direction of the particle's major axis(nearly perpendicular to the Tianshan Mountain),and moderate in the direction of the particle's mid axis(nearly parallel to the Tianshan Mountain).However,with the increase of stress level,the weakly cemented Xiyu conglomerates tend to be isotropic.(3)Under triaxial stress state,weakly cemented Xiyu conglomerate shows strain hardening characteristics in the yield stage.After reaching peak strength,it shows typical plastic flow characteristics.(4)The shear strength of weakly cemented Xiyu conglomerates have obvious nonlinear characteristics,loading and unloading stress path effects and intermediate principal stress effects.The higher the stress level,the smaller the internal friction angle and the greater the cohesion.The internal friction angle of Xiyu conglomerate under unloading

关 键 词：岩石力学 弱胶结西域砾岩 现场真三轴试验 颗粒组构 力学性能 演化机制 

分 类 号：TU45[建筑科学—岩土工程]