Influence Of Seawater On Engineering Properties Of Granite Residual Soil And Soil Reinforcement Mechanism

Granite is widely exposed all over the world.It is mainly distributed in the southern coastal area,Jiangxi,Shandong and Northeast China.It is a kind of granular intrusive rock.It is very easy to weathering on the surface,and can form a weathering crust of tens and even hundreds of meters thick.The physical,hydraulic and mechanical properties of granite weathered materials vary significantly with the degree of wind,so it is of great significance to study the granite with different weathering degrees,which is gradually paid attention to by the geotechnical engineering community.Generally speaking,the weathered granite has a high sand and gravel content,which presents some lithotripsy soil characteristics.In natural state,it still maintains the residual structural strength of the original rock,but its water properties are poor and easily thixotropic.After the influence of water immersion,disturbance and other factors,the original stable structure will be broken quickly,the mechanical properties are rapidly reduced and the structure will collapse.Solution.At the same time,the granite residual soil is often used as the filling material for the seaside buildings,and the sea water is rich in various ions.The long-term dry and wet circulation and contact will have a certain effect on the physical and mechanical properties of the residual soil..Therefore,it is of great practical significance to study the effects of seawater on the physical and mechanical properties of granite residual soil,the physical and mechanical properties of the modified soil,the curing effect and the curing mechanism of the modified soil after the adding of the solidifying agent.The purpose of this paper is to study the effects of curing agent and seawater on the physical and mechanical properties of granite residual soil.The residual soil was treated with different concentration of curing agent,and the indoor test was carried out.The plastic index,the maximum dry density and the maximum dry density of the modified soil were analyzed by measuring the limits of water content,density,direct shear strength,compressibility,disintegration and so on.Strength index,compressibility,dry and wet cycling ability,and combined with microscopic test,the curing mechanism of the curing agent was analyzed.The results showed that the residual soil had good compaction and high strength,and the physical and mechanical properties of the modified soil and the residual soil were compared.The main results are as follows:（1）The three kinds of granite residual soil have better compaction and shear properties,the maximum dry density is about 1.6-1.7g/cm^-3,but the three soils have a serious water softening phenomenon.Among them,the most apparent softening property of the most surface soil is water softening,and the cohesion decreases most after saturation.（2）Through the determination of the plastic index of the modified soil with different curing agents,the effect of the curing agent on the limit water content of the modified soil is analyzed.The results show that the plastic index of the modified soil with the curing agent will be improved,and the modified soil plastic index of the modified soil is up to the highest with the 5%content of the solidifying agent.（3）Through the compaction test of different types of modified soil samples,the compaction properties of the granite residual soil are analyzed and studied.The results show that the effect of seawater on the compaction property of the residual soil is not significant.The maximum dry density of the soil is reduced by the admixture,the higher the dosage of the solidifying agent is,the more the maximum dry density is.Small。（4）On the surface of saturated straight shear test and dry wet cycle saturated direct shear test of different soil samples,the cohesiveness of soil can be increased in varying degrees by sea water and curing agent.The cohesive force of the modified soil can be improved by the dry and wet process,which can increase the 30kPa.（5）Seawater has little effect on compressive properties of residual soil,and all of them belong to medium compacted soil.The curing agent can reduce the compression performance of soil sample.The higher the content of curing agent is,the lower the compressibility of soil sample is,so that residual soil can be changed from compressible soil to low compressible soil.（6）The disintegration of the original soil immersion is very rapid,there is no obvious slow period,only the rapid period,until the end of the disintegration,and the disintegration curve of the modified soil is a S curve,and the disintegration process is slow fast slow,after the admixture is added into the soil,the soil particles are formed between the soil particles and the soil is difficult to disintegrate,Thus the disintegration of soil is weakened.After drying and wetting cycles,the anti disintegration performance of modified soil has been improved.（7）The solidified soil produces a new functional group,but there is no new mineral formation.It shows that the curing agent makes a complex reaction between a new solidified substance and the soil particles,so that the solidified material connects the soil particles between the soil particles and fills the intergranular pores and forms a stereoscopic structure to improve the overall structure of the solidified soil.It improves the engineering properties of granite residual soil under water softening and improves the strength of solidified soil.（8）The change of soil mechanical properties after adding the solidifying agent can obviously improve the safety factor of the soil slope,make the most dangerous slip surface of the soil slope move to the depth of the stratum,reduce the trend of the slope sliding and increase the safety of the seawalls.The consolidation of the solidifying agent can effectively improve the stability,durability and firmness of the subgrade and sea embankment,ensure the safety of the structure,save the cost of the packing,and greatly reduce the cost of the project.