Study On Engineering Characteristics Of Improved Weak Expansive Soil Of Silty Sand Along The Yellow Rive

Due to its special engineering characteristics and extensive regional distribution charact-erristics,expansive soil is well known to the engineering and academic circles.In the construction of areas where the expansive soil is widely distributed,the expansive soil will be treated to reduce the damage of the expansive soil to the extent acceptable.In this paper,based on the consideration of reducing the impact on the surrounding environment and cost saving,a new method for physical improvement of weak expansive soil is proposed for the expansive soil and silt soil distributed in Xinxiang of Henan Province:the expansive soil can be improved by using silty sandy soils.Through the laboratory physical,mechanical,expansion properties test and FLAC3D numerical analysis software,the numerical simulation analysis of weak expansive soil and silty sand improved weak expansive soil in this area is carried out,The main work and conclusions are as follows:(1)The silty soil with the mass ratio of 0%,10%,20%,30%,40%and 50%was added to the weakly expansive soil,through the experiment of basic physical properties such as liquid plastic limit and compaction found that:Silty soil can improve the hydrophilic property and compactness of expansive soil.With the increase of silt content,the hydrophilic property of the improved soil gradually decreases,and the maximum dry density first increases and then decreases,among which the silt content is increased.The maximum dry density at 30%is the largest,1.865g/cm~3?(2)Through the experimental study on the expansion characteristics such as free expansion rate,no-load expansion ratio,load expansion ratio and expansion force,it is found that silty soil can improve the expansion characteristics of weak expansive soil and reduce the expansion potential of expansive soil.The expansion potential of the improved soil decreases with the increase of the amount of silty soil.Especially when the amount of silt is 20%and30%,the rate of expansion and contraction of the improved soil is the fastest.Silty soil has the best effect on the improvement of expansive soil;When the amount of silt is 20%,the free expansion rate of the improved soil is 39.6%,and when the amount of silt is 30%,the free expansion rate of the modified soil is 33.5%.(3)Through the tests of mechanical properties such as direct shear and unconfined compressive strength,it is found that silty soil can improve the compressive strength of weak expansive soil and has a great influence on the shear strength of improved soil.With the increase of silt content,cohesion of improved soil increases first and then decreases.When the amount of silt is 10%,the cohesive force of the modified soil is the largest.With the increase of the amount of silty soil,the unconfined compressive strength of the improved soil increases first and then decreases with the increase of the amount of silty soil.The compressive strength is the highest when the dosage is 20%,and the compressive strength is still greater than the expansive soil when the content is 30%.(4)Through the comprehensive research and analysis of the physical,mechanical and expansion characteristics test results and the construction control requirements of the actual project,the optimum silt content suitable for the improvement of Xinxiang weak expansive soil was determined to be 30%,and it also provides a reference for weak expansive soil improvement in other areas.(5)Through the FLAC3D software,numerical simulation analysis of embankment settlement deformation of weak expansive soil subgrade and 30%silt soil is carried out.By using the temperature field instead of the humidity field,considering the influence of expansion force on the embankment when the expansive soil in saturated state,studying the settlement characteristics of the weak expansive soil embankment and the improved soil embankment.It is found that the settlement deformation of the improved soil subgrade is much smaller than that of the weak expansive soil subgrade,which further indicates that the silt of 30%is applied to the weak expansive soil have a good improvement effect.