碱性环境下吹填土的力学特性及微观机制分析

Analysis of mechanical properties and microscopic mechanism of dredger fill in alkaline environment

化学环境的变化对吹填土的力学性质及微观特征影响显著。利用不同掺量NaOH的吹填土试样进行室内直剪试验、三轴剪切试验和一维压缩试验,探讨碱性环境对吹填土强度和变形特性的影响,并对碱性环境下吹填土的微观结构特征进行研究。试验研究结果表明:由于碱性环境中生成的难溶物对粒间胶结强度的增强作用,抗剪强度平均提高15.1~79.3 kPa,结构屈服应力提高5~169 kPa;碱性环境中,吹填土的应力-应变关系由应变硬化型转变为应变软化型为主,压缩性大幅度降低,压缩指数的最大降低幅度达到60.3%。微观试验表明,碱性环境中吹填土的粒间胶结物发育良好,颗粒形态由粒状结构和片状结构过渡为团粒结构,粒间连接形式以面-面接触为主。

Chemical environment has a significant effect on the mechanical and microscopic characteristics of the dredger fill.In this paper,a set of laboratory tests were carried out to look into the strength,deformation as well as the microscopic structure of dredger fill with various NaOH content,including direct shear test,triaxial shear test,one-dimensional compression test and microscopic test.The experimental results show that the shear strength and structural yield stress increase by 15.1–79.3 and 5–169 kPa respectively,and the reason is that the intergranular cement strength was greatly enhanced due to the insoluble substances generated in the alkaline environment.Moreover,the stress-strain relationship of dredger fill changes from strain hardening to strain softening in the alkaline environment,meanwhile,the compressibility being greatly reduced with the maximum reduction of the compression index being 60.3%.Finally,the intergranular cement of the dredger fill in the alkaline environment develops well.The particle morphology is transformed from granular structure and flaky structure to agglomerate structure,and the surface-to-surface contact is the main form of the intergranular connection.