Study On Mechanical Properties Of Graded Crushed Stones Road Base Materials

In the pavement structure with semi-rigid base course is influenced greatly by temperature and humidity,destroyd quickly after overload and is easy to produce reflection crack and so on.This researcher focused on the graded crushed stone flexible base which can drain better and can effectively control the reflection cracks.The CBR test,triaxial test and permanent deformation test of 7 kinds of graded crushed stones were carried out in order to research the stress distribution,CBR strength and its influencing factors,the shear strength and deformation characteristics.In this paper,crushed limestone was chosen as the test materials.On the premise of verifying the basic performance of the material to meet the requirements,seven gradations were designed,and the optimum water content and maximum dry density of the material were determined by compaction test.Secondly,The semi-rigid base and the flexible base are calculated by using ABAQUS finite element software,and the differences in the mechanical characteristics are analyzed.Then combined the current domestic and international research results and the mechanics experience design method,34 kinds of common pavement structures were designed.Three dimensional finite element models were built to simulate 34 kinds of pavement structures.The third principal stress distribution law and distribution range of flexible base and base were calculated.According to the calculation results the stress level of the permanent deformation test is determined.And then CBR tests were carried out.Through the CBR value,4 kinds of gradation which were used in the basic level and the base level of all grades of road were screened out.The relationship between CBR and gradation of graded crashed stones were studied.The results shows that CBR has a certain relationship with the gradation curve,fineness modulus and average particle size.The grading crushed stones can be designed with reference to the above parameters in order to meet the requirements of CBR.Statical triaxial tests of 7 kinds of graded crashed stones under the optimum water content were carried out,and the relationship between the parameters of the triaxial tests and the CBR was studied.Statical triaxial tests of 4 kinds of graded crashed stones under different moisture content and compaction degree were carried out.Failure criterions were determined based on Mohr-Coulomb strength theory.The relationship between the parameters of the Mohr-Coulomb strength theory and the moisture content and compaction degree were analysed.The permanent deformation tests of graded crushed stone were carried out on the basis of the above simulation calculation and tests.Through the tests,the elastic deformation was the characteristic of graded crushed stone,water content has a influence on elastic deformation.The moisture content,confining pressure and the partial stress have remarkable influence on the plastic deformation of the graded crushed stone.Strict control of moisture content and overload condition in grass roots is an effective way to prevent the destruction of graded crushed stones in practical engineering.