Experimental Study On Special Engineering Properties Of Soil Disturbance

At present, the coarse-grained soil is widely made into use in engineeringconstructions such as roadbed, airfield and earth-rock dam, etc. due to its widedistribution，good compaction and high filling density. And the coarse-grained soil isdivided into viscosity coarse-grained soil and no viscosity coarse-grained soil. So far, theresearches on coarse-grained soil mainly focus on the effect of gradation for itscompaction density.While researches on the changes of gradation after compaction areinadequate carried out. This paper expands a succession of researches on the influences ofgradation through moisture content and compaction, which can help us achieve the patternof the change of gradation.This paper researches the change of gradation after compacting by the experience andtest such as compaction, sieving and test of A densitometer. Specific researches are asfollows:1The modified compaction test was carried out on the same continuous gradation ofviscosity coarse-grained soil by three different hit experiments （98,128,158） to get thecompaction curve, maximum dry density and the optimum water content. Analyzing theresults of these experiments, the compaction can optimize the gradation of viscositycoarse-grained soil, based on comparing changes between the grading curve of threegroups test with water content, changes of maximum dry density and the optimum watercontent with compaction, and changes of three groups test’s grading curve of the optimumwater content, we can easily know that compaction can make the distribution range（Cu） forparticle size and the ratio of curvature（Cc） of viscosity coarse-grained soil bigger.2The modified compaction test was carried out on the same discontinuous gradationof viscosity coarse-grained soil by different hit experiments （98,128,158） to get thecompaction curve, maximum dry density and the optimum water content. Throughcomparing changes between the changes of maximum dry density and the optimum watercontent with compaction, and changes of three groups test’s grading curve of the optimumwater content,and analyzing the results of these experiments, we can easily know that compaction can make the distribution range（Cu） for particle size of viscositycoarse-grained soil, but it can’t improve the grain loss（Cc）.3Verified by the test, the compaction curve of viscosity coarse-grained soil is similarto the clay’s. The maximum dry density will be increased with the increasing compaction,the optimum water content will be decreased with the increasing compaction. This resultcan provide a reasonable basis for engineering construction.Undisturbed soil is the soil mass which forms under natural conditions withoutdisturbance. The microstructure which makes undisturbed soil’s mechanical propertiesdifferent from reconstituted soil is taking shape in the long-term deposition process. Thethixotropy of soil is one performance of the differences of mechanical properties betweenthe undisturbed soil and reconstituted soil, which is caused by the change ofmicrostructure. And the macroeconomic performance is followed that the mechanicalproperties change as time goes on by comparing the mechanical properties of silty clay.This paper researches the performance of Yantai silty clay by carrying out kinds ofphysical indicators, quick shear test and regular consolidation test for undisturbed soil aswell as reconstituted soil made according to standard, and combining with the pattern ofmechanical properties changing with time. Mainly include the following contents:1It is surveyed by soil test which are indexes of physical such as water content,density, etc. And the parameters of mechanical properties are also surveyed by quick sheartest and regular consolidation. According to the standard, prepare the remolded samples insame water content and same density, place different time to research its parameters ofmechanical properties, and record changes with standing time including internal frictionangle（φ）, cohesion（c）, coefficient of compressibility(α_1-2) and confined constrainedmodulus （Es）.2Analyze the pattern of the reconstituted soil with standing time such as internalfriction angle（φ）, cohesion（c）, coefficient of compressibility(α_1-2) and confinedconstrained modulus （Es）, to get the recovering rule of the parameters of mechanicalproperties of the reconstituted soil. It provides referenced basis to quantitative research theinfluence of time for the structure of soil.3Curve-fitting through software named Origin can be performed to compared the reconstituted soil’s mechanical properties including internal friction angle（φ）, cohesion（c）,coefficient of compressibility(α_1-2) and confined constrained modulus （Es）, thecorresponding equation and the indicator to describing the thixotropy is also received. Byanalyzing the average and deviation of the ratio of solution of equation and test data, it isshowed that the equation can describe the changing rule of the mechanical properties ofthe reconstituted soil.