Experimental Study On California Bearing Ratio Of Fiber Reinforced Soil And Analysis Of Road Working Condition

Loess is a special type of soil with large pores and under-compacted structure,which loses its strength rapidly when exposed to water.Researchers usually use lime and cement to strengthen and improve the soil,which enhances its mechanical properties and meet the requirements of subgrade strength.In recent years,under the advocacy of the concept of "green water and green mountain is Jinshan and Yinshan",the actual project has put forward higher requirements for the environmental protection and safety of the soil improved by the curing agent.The new environmentally friendly fiber materials with excellent performance have entered the public's field of vision,and fiber reinforced soil has been favored by geotechnical engineers.The related research has achieved fruitful results.The bearing ratio test is a test that reflects the local shear strength and water stability characteristics of the soil.The CBR value is an important technical index for evaluating the strength of the subgrade soil and road materials,and is the main basis for flexible pavement design.Nowadays,there are more and more road projects built in the loess area,but the research on the fiber reinforced soil is rarely reported as the roadbed filler.In this paper,the loess in Yangling,Shaanxi was used as the raw material,and basalt fiber was mixed to conduct the compaction test of the reinforced soil.The efforts were investigated about the fiber content and fiber length on the maximum dry density and the optimal moisture content of the reinforced soil.On this basis,the bearing ratio test of basalt fiber reinforced soil was carried out by changing the initial moisture content,fiber content,fiber length,compaction times,soaking time.The law of CBR value was studied by the influence of initial moisture content,fiber parameters and test methods.At the same time,the most popular and eco-friendly polypropylene fiber,wheat straw fiber and basalt fiber are selected for comparison,and the road strength,cost performance,dispersion and durability of the three fibers were analyzed.The main research results include:(1)The heavy-duty compaction curves of basalt fiber reinforced soil and loess have the same change rule,both of which are "parabola with opening downward".The dry density increases first and then decreases with the increase of moisture content.Under different reinforcement conditions,the maximum dry density and the optimal moisture content of reinforced soil are not fixed.With the increase of fiber content and fiber length,the maximum dry density generally shows a decreasing trend.There is no obvious change in the optimal moisture content of fiber-reinforced soil,and it fluctuates around the optimal moisture content of loess.(2)The effect of initial moisture content on the CBR value of basalt fiber reinforced soil is similar to the compaction curve.With the increase of the initial moisture content,the CBR value of reinforced soil increases first and then decreases.There is an "optimal moisture content for construction" is different from the optimal moisture content in the compaction test.The difference is in the range of 1% ? 3% under different reinforcement conditions.(3)The effect of fiber content and fiber length on the CBR value of basalt fiber reinforced soil also showed a trend of increasing first and then decreasing.The optimal fiber ratio was 0.4% fiber content and 20 mm fiber length.There are four different stages of the effects of fiber content and fiber length on the one-dimensional lacing effect and the three-dimensional fiber web effect.(4)As the times of compactions increases,the CBR value of the loess and the basalt fiber reinforced soil continues to increase.The compaction times increase from 30 to 98,the CBR value increases by 273%,the CBR value increases by 327% after the fiber is added.Reinforcement makes the soil local shear strength more effective by increasing the compaction work.(5)With the increase of the immersion time,the CBR value of the loess and the basalt fiber reinforced soil gradually decreases,and the initial influence of the immersion on the sample CBR value is greater,and the final influence of the immersion on the sample CBR value is less.The sensitivity of the sample to the soaking time is further reduced by the addition of fibers.(6)Basalt fiber is suitable for expressways and first-grade highways with highest strength requirements,and is the fiber of choice in contaminated areas by acid rain.Polypropylene fiber is suitable for the second and third grade roads with higher strength requirements.It is especially suitable for lime,cement to jointly improve strength of composite.It is not recommended to use it in areas with high altitude and strong ultraviolet rays.Wheat straw fiber is suitable for temporary projects in economically underdeveloped regions and dry areas.