冻融条件下东北地区3种土壤抗剪强度差异性分析

Difference Analysis of Shear Strength of Three Soils in Northeast China under Freeze-thaw Conditio

为明确引起冻融条件下不同土壤抗剪强度差异性产生的原因,以东北地区常见的棕壤、白浆土和黑土为研究对象,采用野外取样和室内模拟冻融循环环境等方法,对不同冻融循环次数和含水量条件下的3种土壤抗剪强度进行比较分析,进而阐明引起不同土壤类型抗剪强度差异性的原因。结果表明:3种土壤黏聚力均随冻融循环次数的增加逐渐减小,最后趋于稳定。冻融循环作用对3种土壤黏聚力的影响大小为黑土>白浆土>棕壤,与未经冻融作用时相比,3种土壤黏聚力平均减小54.29%,35.19%,31.77%。3种土壤对于含水量的响应存在较大差异,随着初始含水量的升高,白浆土和棕壤的黏聚力呈下降趋势,平均减小88.99%和76.67%,而黑土的黏聚力呈现出先降低25.73%后升高144.75%的特点。土壤质地和含水量是导致冻融过程中棕壤和白浆土黏聚力差异的主要因素,而独特的团粒结构和孔隙特征是引起黑土黏聚力变化的重要原因。高含水条件导致春季解冻期东北地区3种土壤内摩擦角变化远不如黏聚力剧烈,3种土壤内摩擦角的减小范围均在1°~2°。研究结果将为解冻期土壤侵蚀机理研究,解冻期土壤侵蚀预测模型构建,以及东北地区耕地保护与地力提升等奠定理论基础。

In order to clarify the reasons for the differences in shear strength of different soils in Northeast China under freeze-thaw condition,the brown earth,albic soil and black soil,were used as research objects,and methods such as field sampling and indoor simulated freeze-thaw cycle environments were used.The soil shear strength of three kinds of soil under different freeze-thaw cycles and moisture content were compared and analyzed,then clarified the reasons for the differences in shear strength of different soil types.The results showed that the cohesion of the three soils decreased gradually with the increase of freeze-thaw cycles,and finally tended to be stable.The effects of freeze-thaw cycles on soil cohesion of the three soils are:black soil>albic soil>brown earth.Compared with the non-freeze-thaw cycle,the cohesive forces of three soils were reduced by 54.29%,35.19%,and 31.77%on average.The responses of the three soils to moisture contents were quite different.With the increase of initial moisture content,the cohesive forces of albic soil and brown earth showed a downward trend,decreasing by 88.99%and 76.67%on average,while that of black earth showed the characteristics of first decreasing by 25.73%and then increasing by 144.75%.The main factors that led to the difference in cohesion between brown earth and albic soil during the freeze-thaw cycle were soil texture and water content,while the unique agglomerate structure and pore characteristics were responsible for the change of black soil cohesion.The changes of internal friction angle of three soils in Northeast China were much less than that of cohesive force due to high moistureduring thawing in spring.The reduction range of the three soil internal friction angles was 1°-2°.The research results could lay a theoretical foundation for the study of soil erosion mechanism and the construction of soil erosion prediction models during the thawing period,and the protection of cultivated land and the improvement of soil fertility in Northeast China.