季节冻土区黄土湿陷变形及微观机理  

Collapsible Deformation and Microscopic Mechanism ofLoess in Seasonally Frozen Soil Region

作　　者：高英 马艳霞[2] 杨丰华 李华[1] GAO Ying;MA Yan-xia;YANG Feng-hua;LI Hua(City College,Xi'an Jiaotong University,Xi'an 710018,China;College of Civil Engineering,Qinghai University,Xining 810016,China)

机构地区：[1]西安交通大学城市学院,西安710018 [2]青海大学土木工程学院,西宁810016

出　　处：《科学技术与工程》2024年第34期14778-14786,共9页Science Technology and Engineering

基　　金：陕西省自然科学基础研究计划(2021JQ-892);陕西省教育厅计划(23JK0524,23JK0526);陕西省青年科技新星(2024ZC-KJXX-011);绿色生态赋能城镇防灾韧性创新团队(037010)。

摘　　要：黄土地区受季节性气候变化和昼夜交替引起冻融循环效应,导致黄土的结构和物理性质发生变化,从而影响黄土的湿陷变形特性。通过室内湿陷试验和微观结构试验,分析了冻结温度对微观结构损伤规律与宏观湿陷变形的响应是否一致。研究结果表明:控制水分场不变情况下,发现不同冻结温度在相同冻融次数条件下,湿陷变形量随冻结温度的降低逐渐减小,说明冻结温度决定冻结速率,冻结速率的快慢变化影响黄土湿陷量的大小;通过对冻融循环10次黄土进行微观结构试验,定性分析发现随冻结温度的降低,土体内部水分发生水-冰循环相变及冷生结构的生成,使土团粒之间胶结力弱化,骨架颗粒发生偏转、滑移,土体内部的颗粒形态、连接方式及分布排列方式均发生变化并形成新的稳定结构;定量分析发现概率熵、平均形状系数、分布分维、孔隙面积比例及孔径变化范围均呈现出规律性变化与定性分析结果一致。由此表明土体内部团粒、孔隙结构的变化规律印证了冻结温度的降低与黄土表现的宏观湿陷变形量逐渐减小的变化规律具有相关性。Seasonal changes and the alternation of day and night produces freeze-thaw cycle effects,which lead to changes in the structure and physical properties of soil in loess areas,and also affected the collapse and deformation characteristics of loess.Indoor collapse tests and microstructure tests were used to analyzed whether the influence of freezing temperature on microstructure was consistent with the response rules of macroscopic collapse deformation.The research results show that:the moisture field and the number of freeze-thaw cycles remain unchange,the collapsing deformation of loess gradually decrease as the freezing temperature decreases.This phenomenon showes that the freezing temperature determines the freezing rate,and the speed of the freezing rate affects the collapsing deformation of loess.As a result,the cementation force between soil aggregates weaken,the skeleton particles deflecte,the particle shape,connection method and distribution arrangement within the soil body changes,and a new stable structure is formed.Quantitative analysis finds that the probability entropy,average shape coefficient,distribution fractal dimension,pore area ratio and pore diameter change range all showed regular changes,which is consistent with the qualitative analysis results.This shows that is a good correlation between the change pattern of pore structure inside the soil and the collapsibility pattern of loess causes by the reduction of freezing temperature.

关 键 词：黄土 冻结温度 湿陷变形 微观结构 

分 类 号：TU444[建筑科学—岩土工程]