Study On The Effect And Mechanism Of Temperature On The Physical And Mechanical Properties Of SH Strengthened Site Soil

Areas in northwestern China has are generally characterized by sufficient sunlight and thermal radiation energy.Meanwhile,the drastic differences in diurnal temperature and seasonal temperature have led to significant changes in temperature field and stress field of the site soil.Furthermore,these changes and some coupled factors,such as wind and water,have also caused soil property deterioration and soil structure damage.Since rainfall in northwestern China is sparse,the damage of water to soil sites is limited.Thus,long-term temperature cycling may be the dominant factor in the weathering process.The SH,a new polymer material developed by Lanzhou University,has the advantages of non-toxicity,low price,and aging resistance.The SH has been applied to the surface weathering prevention,grouting,and support of soil sites.This material is very suitable for earthen heritage reinforcement and always exhibit satisfactory effects.There have been numerous studies on SH reinforced soil,but few of them considered the impact of temperature cycling on SH reinforced soil.Therefore,in this paper,we conducted relevant research based on the above situation.Concretely,effects of temperature cycling on physical and mechanical properties of SH reinforced soil were studied through the thermal conductivity test,compressive strength test,tensile strength test,volume and surface area change test,capillary water test,thermophysical parameter test,wave velocity test,linear expansion rate test,direct shear test and surface hardness test.Besides,scanning electron microscopy(SEM)and MIP experiments were performed to investigate the effect of temperature cycling on the microstructure of SH reinforced soil.The main conclusions were listed as follows:(1)The solid content and dry density of SH reinforced soil have a significant impact on the thermal conductivity.The thermal conductivity increases with the increase of solid content and dry density.As the dry density increases,the strengthening effect of solid content on the thermal conductivity becomes more remarkable.Moreover,there is a positive correlation between the compressive and tensile strengths of SH reinforced soil and the SH solid content,which may be due to the same mechanism of action of SH materials on the thermal conductivity,compressive and tensile strengths of SH reinforced soil.(2)Temperature cycling can have varying degrees of impact on the physical and mechanical properties of SH reinforced soil.In the early stage of temperature cycling,the volume,surface area,longitudinal wave velocity,and linear expansion rate of SH reinforced soil decreased rapidly,possibly due to the residual water evaporation in the sample caused by high temperature.During the later stage of temperature cycling,the changes in physical and mechanical properties,including volume,surface area,longitudinal wave velocity,linear expansion rate,compressive strength,tensile strength,shear strength,and surface hardness,of SH reinforced soil are relatively small.This is because with the increase of temperature cycles,the soil particle structure tends to be stable,further causing effects of thermal expansion on the soil weakened.(3)Temperature cycling will have an impact on the capillary water absorption rate of SH reinforced soil,affecting its resistance to water infiltration.Temperature cycling will have an impact on the capillary water absorption rate of SH reinforced soil,affecting its resistance to water infiltration.Temperature cycling can accelerate the rate.The higher the solid content,the smaller the impact of temperature cycling on the capillary water absorption rate.For the 0.8% SH solid content test,the capillary water absorption rate before and after temperature cycling remains almost unchanged.This indicates that temperature cycling leads to an increase in the number of pores,but the number of pores in soil with high solid content is less affected by temperature cycling.(4)Temperature cycling will have an impact on the porosity and proportion of large pores of SH reinforced soil.As the number of temperature cycles increases,the porosity and proportion of large pores increase.The changes in porosity and pore size distribution may be one of the reasons for the changes in the physical and mechanical properties of SH reinforced soil.(5)Reinforced soil with high SH solid content can effectively counteract the adverse effects of temperature cycling on its physical,mechanical properties and microstructure.Compared to remolded plain soil and samples with low solid content,after multiple temperature cycles,the physical,mechanical properties and microstructure of those with high solid content show relatively small changes,indicating that the higher the solid content,the better the thermal degradation resistance.