低渗砂岩孔隙类别及纵波波速演化规律研究  

Study on Pore Types and P⁃Wave Velocity Evolution of Low Permeability Sandstone

作　　者：李孝晋 LI Xiaojin(China Railway Construction Kunlun Investment Group Co.Ltd.,Chengdu Sichuan 610000,China;Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering,Xi′an Shaanxi 710055,China)

机构地区：[1]中国铁建昆仑投资集团有限公司,四川成都610000 [2]陕西省岩土与地下空间工程重点实验室,陕西西安710055

出　　处：《铁道建筑技术》2023年第12期66-69,共4页Railway Construction Technology

基　　金：陕西省创新能力支撑计划-创新团队项目(2020TD⁃005);陕西省住房城乡建设科技计划项目(2019⁃K39)。

摘　　要：以岩上隧道的低渗砂岩为试验材料进行压汞试验及声发射断铅试验,研究砂岩孔隙类别占比特征及饱水过程中砂岩纵波波速演化规律,并分析水-岩作用影响机制。结果表明,大、中、小孔隙及微孔隙为低渗砂岩孔隙的主要组成成分,大孔隙和中孔隙体积百分比分别小于5%和23%,小孔隙和微孔隙体积百分比大于70%,对低渗砂岩的孔隙度及渗流特性起控制作用;孔隙体积百分比与孔隙半径具有符合指数函数的相关性。随饱水度增加,归一化纵波波速呈三次函数变化,其演化过程经历“快速增大、平缓变化、急剧增大”三个阶段,饱水度分界点为20%和70%;H1~H3砂岩波速增量随其孔隙度增大而增大,孔隙尺度、孔洞构造以及水-岩溶蚀作用差异性导致H4~H6砂岩的波速增量与孔隙度变化规律不匹配。研究成果可为低渗性岩层隧道岩体开挖提供一定参考。Mercury injection test and acoustic emission lead breaking test were carried out on the low permeability sandstone from Yanshang Tunnel.The proportion of pore types and evolution law of P⁃wave velocity of sandstone during water saturation were studied and then the influence mechanism of water⁃rock interaction was analyzed.The results show that the pore types of low permeability sandstone include large pores,medium pores,small pores and micro pores.The volume percentage of large pores and medium pores is less than 5%and 23%,respectively.The volume percentage of small pores and micro pores is more than 70%,which controls the porosity and seepage characteristics of low permeability sandstone.The volume percentage varies exponentially with increasing the pore radius.With the increase of saturation,the normalized P⁃wave velocity changes as a cubic function,which roughly experiences the evolution process of′a first rapid increase,then a gentle change and last a sharp increase′.The cut⁃off points of saturation are 20%and 70%.The P⁃wave velocity increments of H1~H3 sandstone are positively correlated with the porosity,and the higher the porosity,the greater the P⁃wave velocity increment.The difference of pore size,pore structure and water⁃rock erosion interaction results in the effect mismatch between P⁃wave velocity increment and porosity variation of H4~H6 sandstone.The research results can provide certain reference for the excavation of tunnel rock mass in low permeability rock stratum.

关 键 词：低渗砂岩 饱水试验 纵波波速 孔隙 水-岩作用 

分 类 号：TU451[建筑科学—岩土工程] U451.5[建筑科学—土工工程]