Study On Mechanical Properties Of Basalt Fiber Reinforced Microbially Modified Red Clay

As a special soil in the southern region of China,red clay soil often induces engineeri ng problems such as slope instability and uneven foundation settlement due to its poor engi neering properties.Therefore,in this paper,microbial curing is used to improve the red cla y soil,and basalt fibers are incorporated into the soil to improve its toughness while enhanc ing its performance in response to the characteristic that the soil is prone to brittle damage after microbial curing.Based on fiber reinforcement and microbial curing technology,the r ed clay soil in Loudi,Hunan Province was improved.The effects of fiber dosing and maint enance time on the physical and mechanical properties of fiber-reinforced,microbially enh anced red clay soil were investigated through a range of physical and mechanical tests.The differences in the red clay soil’s microscopic properties before and after improvement wer e compared and analyzed by microscopic tests.The Duncan-Zhang model is used to exami ne how fiber dosage and ambient pressure affect the model’s parameters,and it is modified depending on how naturally occurring structural soil deforms.Through the above experime nts and theoretical analysis,the following main conclusions were obtained:1.the key factor affecting the microbial improvement of red clay is the concentration r atio of the cementing solution,the secondary factor is the number of injections,the general factor is the curing time and PH value.The optimal values of each factor are:cement conc entration 0.75:0.5:0.5,injection times 3 times,curing time 12h,PH value 8.2.After fiber reinforcement and microbial improvement,the red clay underwent tests for water absorption,calcium carbonate content,and compaction.The results showed that a s calcium carbonate content increased,the red clay’s water absorption decreased,its water s tability clearly improved,and its maximum dry density was somewhat impacted.3.It was found that the shear strength and compressive strength of the red clay were si gnificantly increased after fiber reinforcement and microbial curing by straight shear and u nconfined compressive strength.The shear and compressive strength of the red clay impro ved soil showed a trend of increasing and then decreasing with the increase in basalt fiber c ontent under the same maintenance time conditions,and under the same maintenance time conditions with the addition of fiber,the red clay improved soil showed a monotonic increa sing trend.By using a triaxial compression test,it was discovered that the modified red cla y’s stress-strain curve had been weakened,and that the peak of each specimen’s main stress difference had a tendency to rise and then fall as basalt fiber concentration increased.4.The microstructure of the unmodified red clay was found to have a large number of mineral particles in the form of fish scale flakes with large pores,and the microstructure of the modified red clay had fewer fish scale flake mineral particles,and the calcium carbonat e cemented clay particles formed agglomerates with fewer inter-particle pores and tighter c onnections by SEM test.Fibers exist in the microstructure of modified red clay in two way s:fiber-soil embedded structure and fiber-soil reticulated space structure,respectively.It w as found by X-ray diffraction tests that fiber incorporation did not affect the change of min eral composition of the red clay,while microbial incorporation resulted in a small amount of calcite production in the red clay.5.Based on the deformation mechanism of natural structural soil,the Duncan-Thang model was modified by using segmental function to obtain the model parameters initial tan gential modulus Ei,damage ratio Rf,parameters K and n.The Duncan-Thang model of fib er reinforced microbial modified red clay was established to obtain the tangential deformati on modulus Et of the modified red clay.