火山灰粉质黏土强度浸水劣化及机理研究  

Research on the Strength Deterioration and Mechanism of Pozzolanic Silty Clay

作　　者：张志国 ZHANG Zhiguo(China Railway Design Corporation,Tianjin 300308,China)

机构地区：[1]中国铁路设计集团有限公司,天津300308

出　　处：《铁道工程学报》2024年第12期33-39,共7页Journal of Railway Engineering Society

基　　金：国家自然科学基金项目(51978672);中国铁设科技开发课题(2021A240601)。

摘　　要：研究目的:沈白高速铁路途经长白山地区,该区域广泛分布富含火山灰的粉质黏土,其物质组成、强度浸水劣化性质及机理未知,而高铁地基基础的承载变形计算分析和控制亟待探明其特性,为此开展火山灰粉质黏土的物质组成、强度劣化和扫描电镜试验,获得其基本物理性质和物质组成,揭示抗剪强度随浸水时间的演化规律和机理。研究结论:(1)火山灰粉质黏土细粒含量多,呈硬塑,具有孔隙比大、中高压缩性的特征;(2)矿物成分主要为伊利石(含量29.5%)、石英、云母、长石等,且基本不随深度改变;(3)火山灰粉质黏土的抗剪强度随浸水饱和时间呈指数函数衰减,可分为快速衰减(0~4 d)、缓慢衰减(4~8 d)、基本稳定(8~16 d)三个阶段,内摩擦角和黏聚力的最终劣化系数分别为0.28和0.81;(4)伊利石黏土矿物含量较高,浸泡时间增加,水膜不断增厚,火山灰粉质黏土孔隙比逐渐增大,孔隙和颗粒形态变得越来越复杂和不规则,同时强度衰减;(5)本研究成果深化了对火山灰粉质黏土物理力学性质和强度浸水劣化特性的认识,可为途经火山灰粉质黏土区的高铁基础设计提供宝贵计算参数和技术支撑。Research purposes:Shenyang-Baihe high-speed railway passes the Changbai Mountain area with the thick pozzolanic silty clay,whose material composition,strength and deterioration properties and mechanism are unknown.However,the bearing deformation calculation,analysis and control of the foundation of high-speed railway urgently need to be investigated.Therefore,the material composition test,strength deterioration test and scanning electron microscopy test were performed to obtain the basic physical properties and material composition of the pozzolanic silty clay and to reveal the evolution law of the shear strength with the soaking time and its mechanism.Research conclusions:(1)Pozzolanic silty clay in the state of hard plastic contains the large fine-grained particle and has the characteristics of large void ratio and medium to high compressibility.(2)It consists of illite(29.5%),quartz,mica and feldspar,etc.,and its composition barely changes with depth.(3)The shear strength decreases exponentially with increase of the soaking time and this deterioration process consists of three stages of the rapid attenuation(0~4 d),slow attenuation(4~8 d)and basic stability(8~16 d).The final degradation coefficients of internal friction angle and cohesion stress are 0.28 and 0.81,respectively.(4)The high content of illite with strong ability to adsorb water results into thickening the layer of water,accordingly enlarging the void ratio and making particle morphology more complex and irregular with the increase of soaking time.(5)The research results deepen the understanding of the physical and mechanical properties of pozzolanic silty clay and the strength deterioration characteristics for water immersion.It can provide valuable calculation parameters and technical support for the foundation design of high-speed railway constructed on the pozzolanic silty clay stratum.

关 键 词：火山灰粉质黏土 物质成分 强度劣化 微观结构 劣化机理 

分 类 号：U24[交通运输工程—道路与铁道工程]