Study On Mechanical Properties Of Improved Expansive Soil In Hefei Area

With the continuous deepening and expansion of infrastructure in Hefei,the quality requirements of the project are getting higher and higher,and the requirements for expansive soil-based fillers for road engineering(including highways,railways,etc.),municipal engineering,water conservancy projects,and housing construction are also increasing.Come higher.Expansive soil is one of the most common diseases in engineering construction due to its water loss and shrinkage characteristics.Therefore,it is urgent to meet the needs of expansive soil projects with high efficiency,fast construction,good economy and high safety.Strategies for coping with problems.Under this background,this research topic combined with the foundation pit construction project of Huizhou Avenue Station of Line 6 of Hefei Rail Transit conducted a series of experimental studies on the basic mechanical properties,expansion and contraction properties,and pore structure properties of the improved expansive soil in Hefei City,and from Theoretical analysis of the inherent causes of its characteristics change law.The main research contents are as follows:(1)The expansive soil expansion and contraction characteristics and strength characteristics of Hefei City are theoretically described and experimentally studied.Introduced the distribution origin and expansion-shrink theory of expansive soil in Hefei City;carried out free expansion rate test,presence / absence load expansion rate test,expansive force test,etc.According to its free expansion rate,Hefei expansive soil grade can be divided into Weak expansive soil.(2)Free expansion test,expansion test with / without load,compaction test,direct shear test,etc.were carried out on the expansion and contraction characteristics and basic mechanical properties of the improved expansive soil in Hefei.According to the experimental results,as the ash-doping ratio continues to increase,the free swelling rate and maximum dry density of the improved expansive soil continue to decrease,and the optimal moisture content continues to increase;with the ash-doping ratio and the vertical net normal stress With the increase,cohesion,internal friction angle and shear strength continue to increase.With the increase of water content,cohesion,internal friction angle and shear strength continue to decrease.The improvement effect of cement is more obvious than that of lime.(3)The NMR test was carried out on the improved expansive soil in Hefei City,and the T2 distribution,pore throat distribution and porosity of the improved expansive soil under different ash mixing ratios were analyzed.The results show that with the increase of the ash-doping ratio,the number of T2 distribution peaks decreases from 3 to 2 in plain soil,and the first peak decreases;as the ash-doping ratio increases,the pore-throat distribution gradually increases;As the ash-doping ratio increases,the porosity tends to increase first and then decrease.Figure [40] Table [15] Reference [75]...