添加秸秆后黑土力学行为特征——秸秆含量的影响

Mechanical properties of black soil after straw incorporation:Effect of straw mixing amount

为探明秸秆还田量对黑土力学特性的影响,以典型黑土区未经开垦(高有机质低黏粒含量)以及耕作40年(低有机质高黏粒含量)的土壤为研究对象,在秸秆长度为15 mm条件下,采用室内固结和三轴剪切相结合的方法,通过压缩指数、回弹指数、黏聚力及内摩擦角的测定与分析,模拟研究了黑土压缩-回弹及抗剪切行为对不同小麦秸秆还田比例(0%、25%、50%、75%、100%)的响应规律.结果表明:添加秸秆后黑土力学性能明显改善,以开垦多年有机质含量低的黑土改善效果更为显著.秸秆全量还田时,最不易被压缩且压实后恢复能力最强;秸秆50%还田时,土体抗剪强度最大;当秸秆还田比例为50%~100%时,黑土抗压与抗蚀效果较好.

Aiming to explore how mixing amount of chopped straw affects mechanical properties of black soil, in our study, two typical black soils with no tillage （high organic matter and low clay content） and with tillage for 40 years （low organic matter and high clay content） were chosen as subject samples. With the length of the chopped straw being 15 mm according to the pretrial results, compression-rebound and shearing behavior of black soil with different proportions of straw returning （0%, 25%, 50%, 75%, 100%） were determined by calculating and analyzing the compression index, rebound index, cohesion and internal friction with the methods of indoor oedometer test and triaxial test. Results showed that the mechanical properties of black soil improved after incorporation with straw, and soil with low organic matter content significantly responded to the change of straw mixing amount. The black soil showed the strongest resistance to compression and the strongest recovery capacity after compaction when the proportion of straw returning was 100%. However, shear strength of the black soil was greatest when the proportion of straw returning was 50%. In conclusion, black soil has a better potential to resist compression and erosion especially when the ratio of straw returning was 50%-100%.