Experimental Research On Properties Of Soil Considering Its Non Continuum

With the rapid development of urbanization in China, civil engineering construction such as tunneling and pile foundation and excavation has become more and more frequent. Construction inevitably leads to the disturbance to soils, which will change the property of soils, so the physical and mechanical parameters which describe the property of soils will also be changed. The property of soil is different from metal materials which are continuous medium, and the soil is multiaperture and triphase medium. Taking into account the non-continuity of soils, the author took the relative density as the control index, and studied the effects of physical parameter on strength and deformation of soils by laboratory tests on the basis of existed achievements, and then amended the parameters of traditional Duncan-Chang model and Mohr-Coulomb criterion based on the analysis of test results. The major works and results of this thesis are as follows:(1) Taking ISO standard sands of China and intermediate sands of Fujian as the test materials, some sand samples with different relative densities were made, and then the triaxial compressed tests of dry sands and drained triaxial shear tests of saturated sands were carried out respectively under three confining pressures. It is found that the bigger the relative density is, the bigger the slope of the stress-strain curve is. It is also obtained that the bigger the relative density is, the bigger the peak value of the principal stress difference of dry sands and the peak value of the principal stress ratio is.(2) According to the triaxial compression test results of dry sands, it is found that the parameters n and Rf are independent on Dr basically, however, the parameters K, (σ1-σ3)f and (?) are sensitive to Dr. The three parameters were amended by establishing the quantitative relationship between Dr and them.(3) On the basis of test results, Mohr-Coulomb failure criterion was modified considering the relative density to make it more realistic. Taking dry sand for example, new equation of the stress state was derived considering porosity. Based on the new equation, the risk of using Mohr-Coulomb failure criterion was indicated with the introduction of egg failure envelope considering the non-continuity of soil.