Study On The Stress-strain Characteristics Of Soil With Adulteration

Tri-axial test is one of the most common soil tests, which determines the soil constitute model parameters through the measurement of stress-strain relationship. The application of digital image processing technique for local deformation measurement in tri-axial test leads to much advantages comparing to traditional measuring method . It improves the accuracy of deformation measurement, and provides a new, more reasonable and effective method in specimen deformation measurement. By taking the advantage of digital image processing technique, the stress-strain characteristics of soil with adulteration are studied.The sheet-film-mixed sandy is studied through the tri-axial compression tests. Laboratory tri-axial tests are carried out in order to understand the stress-strain relationship and shear strength property of sheet-film-mixed sandy soil. The laboratory test results show that :(1) the strength and the capacity for resisting the deformation of sheet-film-mixed sandy soil are better than those of pure sandy soil;(2) as to the shear strength indexes of sheet-film-mixed sandy soil, the change of internal friction angle is smaller compared to that of pure sandy soil, but the cohesion is more larger than that of pure sandy soil, related to the location of sheet-film;(3) sheet-films restrict radial strain greatly. When specimens deform to a degree, radial strain is linearly increased with axial strain; (4) the Duncan-Chang model's parameters are described. Results show that sheet-film-mixed sandy soil mainly has an influence on D (Poisson' Ratio coefficient).The mixed-grassroots sandy soil is studied through the tri-axial compression tests. The research is propitious to understanding the mechanism of vegetation protection for slopes and determining the shear strength of mixed-grassroots sandy soils. From a large of contrast tests, the stress-strain curves of mixed-grassroots sandy soil are analyzed, The laboratory test results show that :(1) the grassroots bring into effect only after the strain to some extent. (2) the deviatoric stress of mixed-grassroots sandy soil is larger than pure sandy soil, but it is influenced by the cell pressure, and the cell pressure is more larger ,the improvement is more smaller. (3)They are the same tendency of deformation between mixed-grassroots sandy soil and pure sandy. They all show strain-softening. It can obtain a very high correlation coefficient utilizing Mohr-Coulomb relation to fit the measured results of mixed-grassroots sandy soil. This means that the strength envelope of mixed-grassroots sandy soil follows Mohr-Coulomb criterion. In addition, the paper takes use of fictitious cohesion to calculate side-binding force and the degree of side-binding deformation.