Experimental Study On The Improvement Of Hefei Expansive Soil By EPS-basalt Fiber

Expansive soil is a special soil composed of hydrophilic montmorillonite and illite,with many cracks,strong swelling and repeated deformation of engineering characteristics,the distribution of it in different forms widely in various regions in China;with the reform and opening up,China vigorously carry out economic construction,in the construction of railways,roads,bridges and other large infrastructure,often involving the expansive soil to the construction conditions,it has brought great difficulties,slightly mishandled it easily affect the engineering quality and economic benefits.So for the special soil of expansive soil,a lot of researches have been done in academic field.It is expected to solve the problems encountered in practical engineering by reducing its expansibility and improving its strength.In view of the characteristics of swelling and shrinkage and repeated change of expansive soil,the soil is often improved in actual construction,and then applied to the actual project.The main research and conclusion of this paper are as follows:(1)firstly,undisturbed soil compaction test,the curves of undisturbed soil moisture content and dry density,maximum dry density and optimum water content can also be undisturbed,as the maximum dry density and optimum water content of the experiment provided the basis of expansive soil based on the latter.(2)0%,3%,6% and 9% phosphorus tailings were added into the expansive soil with the mass ratio,and the expansive soil was subjected to no load expansion test,unconfined compressive strength test and consolidated undrained three axis shear test.The test results show that the improvement effect of the modified expansive soil with phosphorus tailings is the best when the amount of phosphorous tailings is 6%.(3)based on the optimal amount of phosphate tailings is 6%,ensure the water content and dry density under the same conditions,will be 0,0.1%,0.3% basalt fiber,0.5% according to the quality ratio of mixing expansive soil,and the free swelling rate test and unconfined compressive strength test,consolidation and non drainage three triaxial shear test of expansive soil improved.The experimental results show that the Xuan Wuyan fiber on expansive deformation to a certain extent,and improves the ductility of expansive soil,delayed expansive soil shear failure,the strength played a good reinforcing effect;but Xuan Wuyan fiber content is not possible,the experimental study shows that,when Xuan Wuyan fiber content is 0.3%,the best effect of improved expansive soil.(4)based on the optimal dosage of phosphorus tailings is 6%,and the moisture content and dry density remain unchanged,EPS is mixed into expansive soil at mass ratio of 0%,0.25%,0.5%,0.75% and 1%,and no swelling test and unconfined compressive strength test are carried out for the improved expansive soil.The test results show that the EPS density is small,lightweight and high degree of compression,the incorporation of expansive soil,the expansion has a good inhibitory effect,the dosage of EPS and the final expansion rate decreased linearly approximate,the mixing amount is larger,smaller expansion rate of soil,but the incorporation will lead to EPS the modified soil strength decreased.Therefore,the improved effect coefficient is defined,and the different dosage of EPS,the absolute strength reduction rate and the absolute rate of expansion reduction rate were analyzed,the different dosage of EPS modified effect coefficient curve,when the dosage of EPS is 0.25%,the modified effect coefficient is the biggest improvement effect of the best.Compared with plain soil,expansive soil phosphorus tailings-EPS modified to shrink the inhibitory effects of good swelling,significantly enhance the effect of the compressive strength,weight reduction of modified soil,in order to reduce the post construction settlement,phosphate tailings,optimal amount of EPS was 6%,0.25%.