Study On Soil-water Characteristic Curve Of Remolded Expansive Soil In Hefei Area

Expansive soil is a kind of clay formed under special geological conditions with internal fissures,rich hydrophilic minerals and remarkable dilatation and shrinkage characteristics.Because of its special engineering properties,if it is not fully considered in engineering practice,it will seriously cause deformation or destruction of buildings.So we should pay much attention to the study of the mechanical properties of expansive soil.There are pore gas pressure and pore water pressure between expansive soil particles,the difference between them is expressed by matrix suction.So to study the mechanical properties of expansive soil,we should first study the effect of matrix suction.There is a great relationship between the matrix suction and the water content and saturation of the soil,so determining the characteristic curve of soil water is an important problem to study the mechanical properties of expansive soil.As a kind of unsaturated soil,expansive soil has a long time to measure its mechanical parameters and the process is more troublesome.From the beginning of the study of unsaturated soil to now,most of them remain in the stage of theoretical research,and few of them really carry out experimental research.The experimental measurement of soil-water characteristic curve not only provides the basis for the study of mechanical parameters,but also provides a reference for the actual engineering design and construction,which is of practical significance.Based on the foundation pit of Xiyou Road Station of Hefei Metro Line 3,this paper takes the soil mass during the excavation of the foundation pit as the research object,and finds that the soil is medium expansive soil.Soil properties were studied by means of soil water characteristic curve test system,automatic residual strength tester and laser diffraction particle size analyzer.The relative parameters such as strength,moisture content,volume change of pore water,particle size and distribution were measured.Taking the characteristic curve of soil and water as the main line of study,the influence of water content,density,consolidation pressure and particle size on the characteristic curve of soil and water is analyzed with the aid of strength and particle test,and several models are selected to fit the experimentalresults.The equation suitable for the expansive soil in Hefei area is selected.The specific research contents are as follows:(1)Summing up the theoretical concept and measurement method of soil-water characteristic curve,in which saturated salt solution and filter paper are the most commonly used methods.The principle,application conditions,advantages and disadvantages of various measuring methods are analyzed.The influence of internal and external factors on soil and water characteristic curve is discussed,in which water content,particle size,stress history and dry density are the main reasons.(2)Summing up and discussing the establishment and derivation of the characteristic curve equation of soil and water in the general discussion.Classifing them according to the parameters.The application,advantages and disadvantages of all kinds of equations are introduced in detail,and the fitting effect of four parameter equation is the best.The influence of parameter selection on fitting effect is discussed.(3)The concrete operation process and method of soil water characteristic curve experiment,soil strength test and particle test are described in detail.The preparation and preparation process of the sample are introduced in detail,and the problems needing attention and the situation are also briefly explained.The experimental data obtained are simply analyzed.(4)The influence of water content,density,consolidation pressure and particle size on soil water characteristic curve is analyzed.Through the experimental data collation and analysis to draw a conclusion;the experimental data are fitted with a variety of models to compare and select the model equation suitable for Hefei area.