靖边Q_(3)砂质黄土湿陷特征及其微观机制研究  

Collapsibility characteristics and microscopic mechanism of Q3 sandy loess in Jingbian

作　　者：慕焕东[1,2] 何也 白逸松 邓亚虹[2,3] 郑龙浩 MU Huan-dong;HE Ye;BAI Yi-song;DENG Ya-hong;ZHENG Long-hao(Institute of Geotechnical Engineering,Xi’an University of Technology,Xi’an,Shaanxi 710048 China;School of Geological Engineering and Geomatics,Chang’an University,Xi’an,Shaanxi 710054 China;Key Laboratory of Western Mineral Resources and Geological Engineering,Ministry of Education,Chang’an University,Xi’an,Shaanxi 710054,China)

机构地区：[1]西安理工大学岩土工程研究所,陕西西安710048 [2]长安大学地质工程与测绘学院,陕西西安710054 [3]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《岩土力学》2024年第10期3024-3036,共13页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.42372336);陕西省自然科学基础研究计划一般项目(No.2022JQ-289);长安大学中央高校基本科研业务费专项资金(No.300102262505)。

摘　　要：沙漠-黄土高原过渡带的砂质黄土遇水后会产生明显的湿陷变形,广泛分布于陕北靖边的长庆油田工程遭受砂质黄土湿陷危害严重,揭示砂质黄土湿陷特性及湿陷机制是长庆油田工程建设迫切需求。为此,以陕北靖边沙漠-黄土高原过渡区Q_3砂质黄土为研究对象,通过室内基本物理性质、X射线衍射和湿陷试验,研究砂质黄土基本物理特性和物质组成,厘清湿陷特性、影响因素及其规律。在此基础上,通过扫描电子显微镜试验和孔隙及裂隙图像识别分析手段,探究砂质黄土湿陷前后的微观结构,孔隙大小分布、方向频率及丰度变化,从微观角度揭示砂质黄土湿陷机制。研究表明:靖边Q_(3)砂质黄土具有湿陷性,且湿陷系数随着轴向压力的增加先增加后减小,随着干密度、含水率的增加而逐渐减小,轴向压力为150 kPa时湿陷系数达到峰值;靖边Q_(3)砂质黄土以石英、钠长石、白云母以及方解石为主,颗粒形态多以棱角状亦或次棱角状为主,具有架空排列结构和架空孔隙,以点-点接触为主,黏粒胶结物多分布在骨架颗粒接触处。靖边Q_(3)砂质黄土的架空孔隙结构崩塌是砂质黄土湿陷变形的本质,为湿陷提供主要空间,黏粒胶结物包裹少量碎屑颗粒形成的凝块结构产生的沉降变形为砂质黄土湿陷变形提供了增量。研究成果为长庆油气田工程建设区砂质黄土湿陷性评价提供了数据依据。The sandy loess in the desert-loess Plateau transition zone exhibits obvious collapse deformation when it encounters water.The collapsibility of the sandy loess in Changqing Oilfield,widely distributed in Jingbian,northern Shaanxi province,is seriously influenced by the collapsibility of sandy loess.It is urgent to reveal the collapsibility characteristics and mechanism of the sandy loess in Changqing Oilfield construction.Therefore,taking the sandy loess of Jingbian Q_(3) in the transition area of Jingbian Desert-Loess Plateau in northern Shaanxi as the research object,the basic physical properties and material composition of the sandy loess were analyzed using laboratory basic physical properties,X-ray diffraction and collapsibility tests.The collapsibility characteristics,influencing factors and rules were clarified.On this basis,the microstructure,pore size distribution,directional frequency and abundance changes before and after the collapse of sandy loess were explored using scanning electron microscopy test and pore and fissure image recognition analysis.The collapse mechanism of the sandy loess was revealed from a microscopic perspective.The results show that the Jingbian Q_(3) sandy loess has collapsibility.The collapsibility coefficient first increases and then decreases with the increase of axial pressure,and it gradually decreases with the increase of dry density and moisture content.The collapsibility coefficient peaks at the axial pressure of 150 kPa.Jingbian Q_(3) sandy loess is mainly composed of quartz,albitite,muscovite and calcite.The grain morphology is mostly angular or subangular,with overhead arrangement structure and overhead pores,and point-to-point contact.Clay cements are mostly distributed in the contact areas of skeleton particles.The collapse of the overhead pore structure in Jingbian Q_(3) sandy loess is the essence of its collapsible deformation,providing the main space for collapse.Subsidence deformation,caused by the coagulated structure formed by a small amount of debris particl

关 键 词：靖边 Q_(3)砂质黄土 湿陷特性 微观机制 扫描电镜 

分 类 号：TU444[建筑科学—岩土工程]