Experimental Study On The Characteristic Of Improved Expansive Soil With Phosphorus Tailings-Basalt Fiber

Expansive soil is a very special unsaturated clay,with water swelling,water shrinkage,multi-fracture,high plasticity and other significant features.Expansive soil widely distributed in different forms,different depths and different layers throughout the country,brought a lot of inconvenience to the construction project,seriously affected the project safety and economic benefits.With the rapid growth of China's economic level,the rapid development of highway and railway construction.Highways,railways will inevitably cross the bad engineering geology.Some areas short of land resources will use the expansive soil to fill the roadbed,but in view of water swelling,loss of water shrinkage of the salient features of the expansive soil,it is necessary to improve the soil before they can be applied to the actual project.The main work of this paper and the conclusions are as follows:(1)Through the compaction test of expansive soil,the relationship between moisture content and dry density of the soil was obtained,and the maximum dry density and the optimal water content of soil were obtained,and then lay the important foundation of the followed experiment in the basis of the optimum water content and the biggest dry density.(2)0%,5%,10%,15% of the phosphorus tailings in the proportion of mass was mixed with expansive soil,and the unconfined compressive strength test and the undrained triaxial compression test was carried out on the modified expansive soil.The results show that,when the dosage is 10% phosphate tailings,the phosphate tailings modified expansive soil is optimal.(3)0%,0.1%,0.3%,0.5% basalt fiber in the proportion of mass was mixed with expansive soil,and the consolidation test,free expansion test,expansion force test was carried out on the modified expansive soil.The results show that basalt fiber can not improve the consolidation performance of soil;can effectively inhibit the free expansion of expansive soil;can restrain the swelling force of expansive soil.But not more dosage of basalt fiber is better,basalt fiber obtained by the test dosage of 0.3%,the effect of improved soil best,When the content of basalt fiber is 0.3%,the effect of modified soil is the best.(4)The phosphorus tailings and basalt fibers were added to the soil with dry density of 1.7g/cm3(maximum dry density)and 17% water content(optimum watercontent),conduct confining pressure of 100 kPa for consolidation undisturbed triaxial compression test,the results show that the strength of the modified expansive soil is the best when the content of the phosphorus tailings is 10% and the basalt fiber content is 0.3%,and the ductility of the soil is also increased.The phosphorus tailings and basalt fibers were co-added into soils with a dry density of 1.6g/cm3 and a water content of 19%,and the consolidation undisturbed three-axis compression test with confining pressure of 100 kPa was carried out.By comparing the experimental results,it is concluded that the improved soil is better when the dry density is bigger.