Study On Strength Degradation And Mechanism Of Cotton Straw Fiber Reinforced Saline Soil Under Different Engineering Conditions

The foundation soil in the coastal area is soft soil,and the salt soil widely distributed on the surface has the problems of salt swelling,dissolution,corrosion,moisture absorption and softening,etc.,which cannot meet the requirements of practical engineering construction without curing or strengthening treatment.The solidification of soft soil foundation is always an important problem in geotechnical engineering.Straw fiber,as an excellent reinforcement material,has been applied in geotechnical engineering.However,due to the easily degradable property of straw fibers,the deterioration of engineering properties when applied to practical projects hinders the application and promotion of straw fiber reinforcement engineering to a certain extent.In recent years,some experts and technicians used preservatives on the surface of straw fibers to delay their degradation,improve the physical and mechanical properties of straw fibers,and promote the application of straw fibers in reinforcement engineering.And anticorrosive cause new problems,however,the effectiveness of the corrosion,preservatives pollution problem that nots allow to ignore,and project cost,although in recent years,many experts and scholars to study the straw fiber and reinforced soil intensity attenuation laws,but research mostly limited to the environment of different PH value of solution,this has to do with the actual engineering environment exist certain differences.Under the conditions of freeze-thaw and dry-wet cycle,the study on the law and mechanism of the strength attenuation of straw fiber reinforced soil is still weak.This paper saline soil in yancheng dongtai Jiang port area as the research object,using cotton straw fiber as reinforcement materials,of saline soil and cement saline soil reinforcement curing of two types of soils,analyze and contrast the cotton straw fiber reinforced this two types of soil reinforcement effect.At the same time,the variation rules and mechanism of compressive strength,flexural strength,compressive coefficient and permeability coefficient of the two kinds of reinforced soil were studied by applying a certain number of dry and wet cycles and freeze-thaw cycles to the two kinds of reinforced soil,providing a theoretical basis for promoting the application of straw fiber in the reinforcement engineering.The main research contents and results of this paper are as follows:(1)The unconfined compression test of saline soil and cement saline soil with different cotton straw fiber content was carried out.the optimal reinforcement rate of cotton straw fiber reinforced cement saline soil was 0.4%,the corresponding compressive strength is 0.66Mpa,the compressive strength of cement saline soil was 34.69%higher than that of cotton straw fiber;The optimal reinforcement rate of cotton straw fiber reinforced saline soil was 0.3%,the compressive strength value of the reinforced soil is 0.94Mpa,the compressive strength of unreinforced saline soil increased by 32.39%.(2)The changes of compressive and flexural strength of reinforced saline soil of cotton straw under wet and dry cycle were studied.The results show that the compressive and flexural strength of reinforced soil increases first and then decreases with the increase of the number of cycles,After 20 cycles,the compressive and flexural strength of reinforced soil were degraded to some extent.(3)By cotton straw fiber reinforced saline soil under the condition of freezing and thawing cycle of compressibility and permeability test,the reinforced the deteriorating law of the compressibility and permeability is determined.The results show that the compressibility and permeability of reinforced soil increase under freezing-thawing cycle.(4)By means of sem,the microscopic mechanism of reinforced salt-soil of cotton straw fiber was analyzed,and the reasons for the deterioration of reinforced soil strength under the conditions of wet and dry,freeze-thaw cycle were further interpreted.It enriches the theoretical basis of the application of cotton straw fiber reinforcement engineering and has a technical guiding significance for the engineering construction in saline soil area.