水分耗散下紫色土埂坎裂隙发育及影响因素

Cracks Development in Purple Soil Bunds Under Water Evaporation and Its Influencing Factors

埂坎裂隙发育危害埂坎稳定性,进而影响埂坎水土保持作用的发挥。为揭示失水过程埂坎裂隙发育规律及其主要影响因素,以紫色土坡耕地埂坎为样地,采用模拟埂坎试验,研究不同初始含水率(25%,30%,35%)、干密度(1.3,1.4,1.5 g/cm^(3))和加筋量(0.05%,0.15%,0.25%)下裂隙发育过程,通过图像分析方法获取裂隙发育强度和复杂度指标,分析了裂隙发育与(初始)含水率、干密度、加筋量的关系。结果表明:水分耗散下裂隙开裂可分为起始阶段、迅速扩展和基本稳定3个阶段。不同初始含水率下各试样裂隙开裂强度和形态复杂度均随水分耗散快速增大,直至含水率为12%后趋于稳定。相同初始含水率情况下干密度越小,试样裂隙强度和复杂度越大。加筋量能抑制裂隙的快速发育,与裂隙开裂程度呈反比。相比而言,初始含水率对水分耗散过程中裂隙起始阶段影响较大,但裂隙开裂之后含水率影响更大,其次是干密度和加筋量。研究结果为紫色土区埂坎的设计、建设和管理维护提供参考。

The development of soil cracks endangers the stability of soil bund,further influences soil conservation.In order to reveal the law of crack development and the main influencing factors under water evaporation,a typical purple soil bund on sloping farmland in Beibei district of Chongqing was chosen to sample and test.Different levels of initial water contents(25%,30%,35%),dry densities(1.3,1.4,1.5 g/cm^(3))and reinforcements(0.05%,0.15%,0.25%)were defined to model the crack development process of purple soil bunds by using a set of simulated bunds.The crack development intensity,complexity indexes and the relationship between crack development and(initial)water content,dry density,and reinforcement were studied through image analysis.The results showed that the crack development process could be divided into three stages under water evaporation in terms of the initial stage,rapid crack expansion and stabilization.Under different initial water contents,the cracks intensity and complexity of all specimens increased rapidly with the decreasing water evaporation,and then tended to be stable at the water content of 12%.Dry density was an important factor impacting soil shrinkage and swell.Under the same initial water content,the cracks intensity and complexity increased as dry density increasing.The amount of reinforcement of polypropylene fiber was inversely proportional to the degree of cracks development.Comparatively,the initial water content had a great impact on the early stage of crack development in the process of water evaporation,but after the cracks began,the water content became a more important impacting factor,followed by the dry density and reinforcement.These results are expected to provide a basis for the design,construction,maintenance and management of soil bunds in purple soil area.