Study On Strength Characteristics Of Wheat Straw And Lime Improved Silt

Our country is rich in wheat straw resources,but its utilization rate is low,the rate of waste and incineration is high.Wheat straw has a certain tensile strength,and can be used in soil reinforcement and improvement.With the increase of highway and railway construction projects,a large number of projects pass through the silt area.The silt has poor gradation,low plasticity index,low strength and poor stability.The subgrade filled with silt is prone to seepage deformation,slope erosion,uneven settlement and other diseases.Therefore,this paper first carried out the anti-corrosion research of wheat straw,and on this basis,the wheat straw as the first choise of reinforcement and improvement material,through the triaxial compression test of its strength characteristics were studied.In oeder to facilitate the comparative analysis,the related strength characteristics of lime silt and wheat straw reinforced lime silt were studied,and the effects of the three improvement methods were compared and analyzed.The main research contents and achievements are as follows:(1)Through comparative analysis,polyvinyl alcohol solution was selected as preservative of wheat straw,and the best concentration of preservative was determined to be10% and the best soaking time was 4 days.After soaking in water,the ultimate tensile force of wheat straw decreased,while the ultimate tensile force of wheat straw soaked in preservative was increased.After the anti-corrosion treatment of wheat straw buried in the soil,the effects of burial time and precipitation are very small,and the strength of the wheat straw is not much loss,can meet the long-term use of wheat straw in soil improvement,polyvinyl alcohol solution has a good anti-corrosion effect on wheat straw.(2)Through triaxial compression test,the strength variation rule of lime improved silt was obtained.In the range of mixing ratio,the cohesion and internal friction angle of the improved silt increased with the increasing of mixing ratio of lime.Compared with silt,the deformation resistance of lime improved silt is improved to some extent.(3)Adding wheat straw into silt can significantly improve the cohesive force of soil.And the cohesion of wheat straw reinforced silt is the largest when the reinforcement ratio is 0.4%and the fiber length is 15 mm,which is increased by 229.5% compared with the original silt.From the perspective of improving the cohesion of wheat straw to silt,the optimal reinforcemnet ratio of wheat straw to silt is 0.37%～0.43%,and the optimal fiber length is13.5mm～16.5mm.The internal friction angle of the reinforced soil has little difference under the reinforcement ratio and the fiber length.With the addition of wheat straw,the deformation resistance of silt is significantly improved.The stress-strain relationship at low and high confining pressures can be described by hump-shaped cubic curve and Duncan-Chang model.(4)The triaxial compression test of wheat straw reinforced lime silt shows that when lime and wheat straw are used together as silt improvement materials,the improvement effect on soil strength is "one plus one less than two".Through the comparative analysis of different improvement methods,it is concluded that wheat straw is better than lime in improving soil strength when it is used as silt improvement material,and generally using wheat straw as silt improvement material is a soil improvement method with good improvement effect,energy saving,economic and environmental protection.