黄土湿陷地裂缝发育特征与成因机理研究

Research on Development Characteristics and Formation Mechanisms of Collapsible Earth Fissure

通过一系列地质调查研究了黄土湿陷地裂缝的发育特征,结合浸水试验分析了地裂缝的成因机理和形成过程。研究结果表明:黄土湿陷地裂缝与浸水坑平行,兼具水平拉张和竖直位错,地裂缝发展演化过程可分为四个阶段。黄土湿陷地裂缝上宽下窄,其宽度和竖直位移均随深度增加而减小,地裂缝发育深度约等于黄土湿陷土层厚度。黄土渗透浸润线与竖直面的夹角随时间逐渐增加,导致湿陷地裂缝逐渐向外扩展。黄土湿陷产生的差异沉降和拉张应变是湿陷地裂缝形成的直接因素,当地面倾斜率达到0.6%,拉应变达到0.002%时,地裂缝出露地表。基于悬臂梁理论提出了湿陷差异沉降产生拉张应力的计算公式,根据本公式可预测黄土湿陷地裂缝的发育位置。

A serious geological investigations are used to reveal the development characteristics of collapsible earth fissure.Combined with in-situ water immersion test,the formation mechanism and process of earth fissure are analyzed.The results show that:The collapsible earth fissure posses both horizontal tension and vertical dislocation,and it is parallel to water pit.The development and evolution of collapsible earth fissure can be divided into four stages.The width and vertical dislocation of the collapsible earth fissure decrease with the increasing depth.The depth of the earth fissure is about equal to the thickness of the loess collapsible soil layer.The angle between the seepage line and the vertical plane increases gradually with time,which leads to the development position of collapsible earth fissure expanding outwards.The differential settlement and tensile strain caused by loess collapse are the direct factors of collapsible earth fissure formation.When ground inclination reaches to 0.6%and the tensile strain reaches to 0.002%,the collapsible earth fissure is generated on earth surface.Based on the theory of cantilever beam,the calculation formula of tensile stress produced by differential settlement of collapsible soil is put forward.According to the calculation formula,the development position of collapsible earth fissure can be predicted.