Experimental Study On Improvement Of Mechanical Properties Of Collapsible Loess By Basalt Fiber And Cement

Collapsible loess is a special kind of soil with uniform soil quality,loose structure and well-developed pores.After being exposed to water,the structure will be quickly destroyed,causing a large subsidence and a rapid decrease in strength,which will cause great harm to buildings.In the treatment of collapsible loess,cement mixing piles are often used to reinforce the soft foundation composed of weak collapsible loess with high water content.This kind of method has no vibration,no squeezing of the soil,low noise during the construction process.Widely used in foundation treatment.The solidification material of deep mixing piles is mainly cement,and its reinforcement mechanism is that after cement is mixed into loess,it will hydrolyze and hydrate with the moisture in the loess,and then generate stable crystalline compounds that are insoluble in water,so that the loess has a certain strength,so as to meet the requirements of foundation bearing capacity.Aiming at this method,in order to determine the most suitable cement ratio and additional admixtures for improving the collapsible loess in Inner Mongolia,and to improve the foundation bearing capacity of the experimental area,the collapsible loess in the surrounding areas of Hohhot and Linger County was taken as the research object.Cement was added to collapsible loess to carry out a comparative test of pressure resistance,and the optimal ratio of single-mixed cement was determined through strength analysis and material deformation characteristics.Basalt fiber is added on the basis of mixing cement,and the unconfined compressive test determines whether the mechanical properties of the basalt fiber will be further improved and the optimal ratio is determined.The stress-strain curve is used to analyze the force and deformation trend,and then by Nuclear magnetic resonance test and scanning electron microscope test study the internal microstructure.Based on the above experiments,the effect of basalt fiber content and cement content on the improvement of the compressive strength of cement-soil and the internal micro-influence mechanism of the failure form are discussed.The experimental results show that:1.Firstly,the physical properties of the undisturbed soil are determined through basic geotechnical tests,and the collapsibility grades of collapsible loess are determined through the indoor immersion load test.The plain soil is mixed with cement of different mass ratios^[1],and the unconfined compressive test and Deformation characteristics determine that the optimal ratio of single-mixed cement is 15%and 20%of the dry material mass.2.A certain amount of basalt fiber is added to the optimal ratio of cement^[2],and the mechanical properties measured by the unconfined compression test are improved.The mechanical comparison test shows that the cement content is 20%and the basalt fiber content is 0.5%～0.8%has the best mechanical properties,and further verify the optimal content of basalt fiber and cement from a microscopic point of view through nuclear magnetic resonance test and scanning electron microscope test.3.Through the analysis of the stress-strain curve and constitutive equation of the unconfined compressive test,the characteristics of the compression deformation of single cement and double cement and basalt fiber are determined.