三峡库区紫色土干缩裂隙形态几何尺寸效应  

Geometrical size effect of desiccation cracks in purple soil in the Three Gorges Reservoir areas

作　　者：黎桉君[1,2] 汪时机 李贤[1,2] 张起勇 肖雪[1] 张静 向阳 刘川 LI Anjun;WANG Shiji;LI Xian;ZHANG Qiyong;XIAO Xue;ZHANG Jing;XIANG Yang;LIU Chuan(College of Engineering and Technology,Southwest University,Chongqing 400715,China;Chongqing Key Laboratory of Agricultural Equipment in Hilly Area,Chongqing 400715,China;School of Geographical Sciences,Southwest University,Chongqing 400715,China)

机构地区：[1]西南大学工程技术学院,重庆400715 [2]丘陵山区农业装备重庆市重点实验室,重庆400715 [3]西南大学地理科学学院,重庆400715

出　　处：《农业工程学报》2023年第24期117-126,共10页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金项目(11972311);重庆市自然科学基金项目(2022NSCQ-MSX2206);西南大学创新研究2035先导计划项目(SWU-XDPY22003);西南大学大学生创新创业训练计划项目(X202310635332)。

摘　　要：紫色土是一种广泛分布于三峡库区的农业土壤,易在降雨-蒸发循环作用下产生干缩裂隙,严重影响土壤的水力和力学性能,并加剧水土流失等自然灾害的发生。几何尺寸是影响紫色土裂隙发育的主要因素,基于响应面设计对13组不同厚度和直径的紫色土泥浆试样开展室内干燥试验,利用数字图像处理技术和形态学算法进行裂隙形态参数的定量表征。结果表明:1)几何尺寸对干缩裂隙的面积率、长度密度、平均宽度密度和分形维数影响极显著。厚度是影响裂隙面积和形态不规则性的主要因素,而直径对裂隙长度和宽度发育的影响较厚度更加明显。并且直径和厚度对裂隙率、平均宽度密度及分形维数存在交互影响作用;2)裂隙形态主要呈“T”型,含少量“I”和“Y”型,厚度越小,裂隙分布越密集,裂隙网络越不规则。直径越小,裂隙网络越单一,裂隙朝着土体边缘分布。单根裂隙面积占比的概率密度随着裂隙面积的增大呈指数型衰减,频率分布符合Expdec函数曲线形式;3)裂隙发育存在明显的几何尺寸效应,其平均开裂应力随着直径的增大以幂函数曲线形式减少,厚度的增大将削弱直径对平均开裂应力的几何尺寸效应。研究结果对三峡库区紫色土裂隙形态和发育机制的认识具有一定参考意义。Purple soil is one kind of agricultural soil that is widely distributed in the Three Gorges Reservoir area.The drying desiccation cracks in the purple soil can be easy to form under the rainfall-evaporation cycle.Hydraulic and mechanical properties of the soil can also be significantly exacerbated by natural disasters,such as soil erosion.Three Gorges Reservoir area also shares the complex topographical characteristics.Geometric size has been the most common environmental factor in the development of desiccation cracks in purple soil.Additionally,the recurrent persistent heavy rainfall often leads to severe hydraulic erosion in the purple soil,leasing to the dispersion of soil aggregates,the migration of fine particle runoff,and significant soil structural damage.The soil saturation can be localized,due to waterlogging.This study aims to investigate the geometric size effect of desiccation cracking under hydraulic erosion using the response surface method(RSM).A series of indoor drying experiments were conducted on 13 groups of purple soil mud samples with different thicknesses(10,20,and 30 mm)and diameters(100,200,and 300 mm).The crack morphologies were quantitatively characterized using digital image processing.The results show that:1)Geometry posed an outstanding effect on the crack ratio,length density,average width density,and fractal dimension of desiccation cracks.Thickness was the main influencing factor on crack ratio and fractal dimension,while there was a more pronounced effect of the diameter on the crack length and width development.All crack ratio,average width density,and fractal dimension showed linear growth with an increase in thickness,whereas,ρl decreased linearly.length density decreased linearly with an increase in diameter,while average width density,and fractal dimension decreased nonlinearly,and crack ratio increased linearly.There was an interaction effect of diameter and thickness on crack ratio,average width density,and fractal dimension;2)The cracks mainly presented in three forms of

关 键 词：土壤 裂隙 应力 紫色土 响应面法 几何尺寸效应 平均开裂应力 

分 类 号：TU443[建筑科学—岩土工程]