Study On Deformation And Strength Properties Of Red Clay Under Drying And Wetting Circulation

This paper takes Guizhou Kaili red clay as the research material.The main research bases on the strength and deformation characteristics under the drying and wetting circulation effect, through swell-shrink deformation test、fissure observation test direct shear test and direct shear test of the reshape red clay in the laboratory,we can comprehensively reveal the variation of swell-shrink properties、strength properties and fissure under the research.The main contents are as follows:1.Through the basic physical properties test in the laboratory, we can get the soil’s moisture content, natural density and the specific density.It is concluded that natural soil moisture content is 39.4%, natural dry density is 1.16 g/cm3, the specific density is2.676.Using the screening test and moisture test method to get the soil’s particle size gradation composition,it turns out that clay content in the soil as high as 65%;Measuring the limit moisture content,the results are the liquid limit is 61.1%,plastic limit is 36.8%;Analysis of soil’s compaction characteristics, to calculate the optimal moisture content is 32.09% and maximum dry density is 1.412 g/cm3 by lagrange interpolation method; Judging the state of the soil is hard plastic, category is MH and determine its hydrophilic ability is not strong, it is not activated clay.2.Acquisition the Free expansion rate、No load inflation rate、Inflation rate under load application、Expansion forces and The vertical shrinkage through conventional swell-shrink property test. Points out that the essential difference between the red clay and expansive soil,we can find that the red clay’s main characteristics is shrinkage.Setting up drying-wetting cycle conditions to discuss the relationship between shrinkage indexes and moisture content、circular times and the order to dry or wet.After the research we get the moisture content and contraction cycles will significantly influence the results, but the order to dry or wet failed to cause the obvious difference.3.Observe the fissure in the laboratory,comparing the effect of moisture content on the fissure development.Discussion on the changing rule of the fissure with the growth of the number of cycles,Try to describe the quantitative of fissure.Test shows that crack along with the growth of cycle times first will gradually development and after several times will to stable. Surface is easy to form a grid tension fracture when samples under low moisture content, and high moisture content of sample is easy produce the circular direction cracks due to shrinkage.The higher of the moisture content, the bigger of the crack.In the process of evaporation the crack will first expand outward and then shrink back.4.Setting up the initial conditions of reshape red clay samples(The initial water content,dry density, the temperature),setting up the cycle times,the diachronic of the cycle and the degree of the drying and wetting circulation to conduct direct shear test in the laboratory.Researching the rule of strength variation under repeated wetting and drying cycles.Explore the fitting formula of descending strength under various water content,Analysis of therelationship between the strength and water content and number of cycles.Results show that under the influence of dry-wet cycles, 0 to 2 cycle, for high moisture content of specimens,the internal friction angle and cohesive force has the obvious change, but low moisture content sample under dry-wet circulation only make the cohesive force to rapid attenuate. The sample near optimal moisture content will produce cohesive force and Angle of internal friction peak point under 0 cycle, after this cycle, the moisture content influence almost can be ignored.