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为了使工业副产品木质素在粉土路基中得到更好的应用,采用室内无侧限抗压强度试验、三轴压缩试验和扫描电镜试验,研究木质素改良粉土的剪切强度特性和微观结构,分析木质素掺量、养护龄期对改良土强度和破坏特征的影响,探讨不同围压和排水剪切条件下改良土的应力-应变关系,阐述木质素产生的胶结作用对土体剪切特性的影响,并研究临界状态下改良土的剪切强度特征。试验结果表明:改良土体无侧限抗压强度随木质素掺量增加而增加,过高掺量会造成强度降低,木质素的添加可增强粉土的韧性特征,对于江苏粉土的木质素最优掺入质量分数为12%;终值偏应力随围压和掺量增加而增大,其增量随围压增加呈降低趋势;低围压条件下,剪切过程会产生吸力,改良土孔隙水压力在各围压下均小于素土;低围压排水剪切条件下,改良土体积应变存在先“剪缩”后“剪胀”的变化特征,高围压条件下则完全表现为“剪缩”;木质素产生的胶结物质填充孔隙并增强土颗粒间联结,土体形成更为致密、稳定的微观结构;改良土临界状态线相对于素土仅发生平移,黏聚力可用来表征木质素对土体临界状态强度特性的影响;临界状态下木质素改良土剪切特性的研究可为其本构模型建立提供一定的基础。
In order to make the industrial byproduct lignin better applied in the silt subgrade, the indoor unconfined compressive strength test, triaxial compression test and scanning electron microscope test were used to study the shear strength characteristics and microstructure of the modified silt , The influence of lignin content and curing age on strength and failure characteristics of improved soil was analyzed. The stress-strain relationship of modified soil under different confining pressures and drainage shear conditions was discussed. The effects of cementing effect of lignin on soil shear Characteristics of the impact, and study the shear strength characteristics of modified soil under critical conditions. The experimental results show that the unconfined compressive strength of the improved soil increases with the increase of the content of lignin. If the content of lignin is too high, the strength will decrease, and the addition of lignin will enhance the ductile characteristics of the silt. The optimal incorporation mass fraction is 12%; the final value partial stress increases with the increase of confining pressure and dosage, and the increment decreases with the increase of confining pressure; under low confining pressure, the shearing process produces suction and improves Soil pore water pressure is less than that of plain soil under each confining pressure; under the condition of low confining pressure drainage shear, the change of volumetric strain of the soil after the first “shearing” and “dilation” Under the complete performance of “Scission ”; cement produced by lignin to fill the pores and enhance the inter-particle bonding, soil formation of a more dense and stable microstructure; improved soil critical state line relative to plain soil only occurred The translational and cohesive forces can be used to characterize the influence of lignin on the strength characteristics of the soil in critical condition. The study on the shear properties of the modified lignin soil in the critical condition may provide a basis for the establishment of its constitutive model.