Influence Of Freeze-thaw Cycle On Dispersibility Of Saline Soil In Western Jilin Province And Dispersibility Improvement Methods

Dispersive soil is a kind of special cohesive soil,in which the repulsive force between soil particles is greater than the attractive force due to the thickening of weak binding water film around the soil particles in pure water or low concentration water with very low hydraulic gradient,so that the soil is dispersed and destroyed.Because the dispersive soil is easy to be eroded by water,it causes engineering accidents such as subgrade instability,dam piping and so on.Therefore,many experts and scholars have paid attention to the dispersive soil since its discovery.Located in the hinterland of Songnen Plain,the western part of Jilin Province is one of the three typical soda saline soil distribution areas in the world,belonging to the temperate continental monsoon climate arid zone.In order to improve the local crop yield by water diversion irrigation,the irrigation areas from Nenjiang to Baicheng city,Da'an and Hadashan water control project have been built successively.However,erosion damage was found along the canal slope of the water diversion project from Nenjiang to Baicheng and Da'an irrigation area,which seriously affected the smooth implementation of the project.Further investigation found that the soil in this area showed a certain degree of dispersion.At the same time,because this area is a seasonal frozen soil area,it experienced freeze-thaw cycles under natural conditions,resulting in the deterioration of soil properties.Therefore,it is necessary to study the effect of freeze-thaw cycle on soil dispersion,and explore effective soil dispersion improvement scheme,so as to provide certain theoretical guidance and practical basis for the treatment of dispersive soil in seasonal frozen area.This paper combines the Key Program of International(Regional)Cooperation and Exchange of National Natural Science Foundation of China named “Mechanism and prevention of carbonate saline soil slope disaster in Alpine Songyuan irrigation area” and Jilin Science and Technology of Development Plan Projects named “the Micro-mechanism study of the influence of freeze-thaw cycles on the dispersion characteristics of seasonal frozen soil in Western Jilin Province”,taking the soil samples in Qian'an area of Jilin Province as the research object,according to the results of various dispersion identification tests,a comprehensive identification method of soil dispersion is proposed.The influence of freeze-thaw cycles on the dispersion of alum modified soil samples and untreated soil samples is discussed,and the mechanism of the change of soil dispersion is explained from the micro perspective.Alum + lignin is used as a mixed modifier to evaluate the dispersion and strength of soil comprehensive improvement.The main research contents are as follows:1.In view of the fact that each dispersion identification test has different criteria for soil dispersion grade,the test results are not necessarily the same yet,we divided the dispersibility identification tests into four grades: non dispersibility,transitional,dispersibility and high dispersibility.2.Take the alum treatment soil and untreated soil as test soil samples,and the freeze-thaw cycles of 0,1,3,5,7,9,10,15 and 20 times were set.After the test,the dispersion and mechanical properties of the soil samples were tested,and the mechanism of the change of the dispersion of the soil samples was explained from the micro point of view.3.Due to alum has a good modification on soil dispersion,but the effect on the mechanical strength is poor,take alum + lignin as the mixed modifier to treat the soil sample,and the influence mechanism of the mixed modifier on the dispersion and mechanical properties of the sample is analyzed.