A Study On Static Characteristics Of Lignin Modified Silt

Powdered soil roadbed treatment is a technical problem frequently encountered in construction projects in the coastal areas of southeast China.Currently,one of the pressing issues in the geotechnical engineering community in China is the investigation of cost-effective and efficient technologies to improve dusty soils.Lignin,as an important source of bioenergy and byproduct of the paper industry,has not yet been fully explored.This paper presents a comprehensive study of lignin-based improved soils,systematically analyzing their main physical properties,stability characteristics and improvement mechanism,with the aim of providing a scientific basis for the promotion and use of lignin.In this paper,the mechanical properties,durability properties and consolidation mechanism of lignin-amended chalk soils were investigated using a combination of indoor tests and theoretical analysis as follows:(1)The current status of the use of lignin is summarised,and the results of research on its application in soil improvement,strength properties,erosion resistance and reinforcement mechanisms are analysed.(2)The effects of lignin incorporation(LC)on the basic physical properties of the amended powder soils were revealed.The specific gravity(G_s)and plasticity index(I_p is the difference between liquid limit and plastic limit)were negatively correlated with LC.The capillary water action of the amended powder soil was improved to some extent by the incorporation of lignin,and reached the optimum when LC was 8%.(3)The characteristics of lignin-amended powder soils in terms of unconfined compressive strength and shear strength were investigated.The effects of LC and curing age(t)on the unconfined compressive strength and shear strength of the improved soils were analyzed by indoor tests,and the results showed that the incorporation of lignin could effectively improve the unconfined compressive strength and shear strength of the powdered soils,and the strength both showed the law of increasing and then decreasing with the increase of LC.The optimal LC was 8%.(4)The durability performance of lignin-amended powder soils was studied.The effects of soaking and wet and dry cycles on the unconfined compressive strength and shear strength of the improved soils were investigated through indoor tests.The results showed that the incorporation of lignin could significantly improve the mechanical strength properties of the powdered soils after soaking and wet and dry cycles,and the strengths both showed the law of increasing first and then decreasing with the increase of LC.The optimal LC was 8%.(5)The reinforcement mechanism of lignin-amended chalk soil was discussed.The lignin was incorporated to produce a cement that effectively filled the pores of the chalk soil and enhanced the cementation strength between the particles of the chalk soil,resulting in a change in the pore structure of the chalk soil.The results showed that the porosity(n)and the average pore area(S_a)of the improved chalk soil were significantly reduced after the incorporation of lignin,while the main mineral composition did not change,but the quartz content had a certain degree of increase and the sodium feldspar content had a certain degree of decrease.