| Research on hybrid fiber reinforced soil is rarely reported and its mechanical mechanism is unclear.Basalt fiber,polypropylene fiber and sisal fiber were selected as soil reinforcement materials.The shear characteristics,microscopic characteristics and theoretical mechanism of hybrid fiber reinforced soil were studied by means of laboratory shear test,scanning electron microscope test and theoretical deduction,which can provide application guidance for the design and construction of soil reinforcement engineering.Shear tests were carried out on reinforced soil with different moisture content,and the optimum moisture content of natural soil was taken as the benchmark of shear test moisture content.Direct shear tests were carried out on reinforced soil with different fiber content.The results show that the stress-strain curves of the three kinds of fiber reinforced soils are strain hardening,and the optimal content of basalt fiber,polypropylene fiber and sisal fiber is 0.3%,0.3% and 0.4% respectively;Comparing with natural soil,the shear strength increases by 25.8%-33.3%,50.0%-70.7% and 38.7%-52.9%,respectively,The cohesion and internal friction Angle of the three fiber reinforced soils increase by 31.4%-50.3% and21.1%-61.7%,respectively.Direct shear tests were carried out for the three kinds of fiber pairings mixed with reinforcement.The results show that there is a peak shear strength of hybrid fiber reinforced silty clay,and the optimal fiber content is 0.1% basalt and 0.3% polypropylene,0.3% basalt and 0.1% sisal,0.2% polypropylene and 0.2% sisal;Comparing with the natural soil,the increase ratio of the optimal shear strength of the reinforced soil mixed with basalt and polypropylene,basalt and sisal,and polypropylene and sisal hybrid fiber is 39.12%-50.00%,24.93%-44.44%,44.44%-51.83%;respectively.The maximum increasing proportions of internal friction Angle are 89.73%,12.90% and 47.05%,and the maximum increasing proportions of cohesion are 34.61%,107.59% and 50.33%;respectively.Comparing with the single fiber reinforced soil,the shear strength of pairwise hybrid fiber is between the two kinds of single fiber reinforced soil.The microscopic properties of fiber and fiber soil were observed by scanning electron microscopy.The effects of different fiber characteristics on reinforcement performance were analyzed from the aspects of fiber diameter,softness,surface roughness and dispersion.Based on the results of shear test and the research path of weighted combination,the prediction formula of shear strength of hybrid fiber reinforced soil was given.Comparing with the measured data,the prediction accuracy of this method can be controlled within 5%. |
