Cohesive Soil Infiltration Model And Elastoplastic Damage Model

The permeability coefficient, permeability model and strength damage model of cohesive soil were researched and problems in this field were determined in this thesis by comprehensively analysis of soil mass' permeability, constitutive relationship and strength damage characteristic based on microstructure theory, fractal geometry theory and damage mechanics.In the research it was carried out that cohesive soil's permeability does not obey sands' Darcy law because of initial hydraulic gradient when water seeps in cohesive soil that is caused by the resistance among the soil grains and so that cohesive soil's Darcy law was proposed. Simultaneously the micro-mechanism of cohesive soil's permeability was expatiated as the overlapping of bound water film in gaps of soil. A permeability coefficient formula, in which the initial hydraulic gradient considered, was given according to cohesive soil's Darcy law and continuity of water flow, and then error analytical methods were given. The fact cases show that the permeability coefficient calculated by the new formula is greater than that calculated by formula in specification in which the initial hydraulic gradient was not considered but error indexes are less. It shows that new formula with initial hydraulic gradient indexed is more suitable for the actual state of the cohesive soil's permeability.Ulteriorly, permeability of cohesive coefficient can be modeled by fractal geometry theory. In this field, soil grains were supposed as spherical and their sizes behave as self-similarity of distribution so that the grain size distribution function was determined by fractal dimensions of the grain size distribution. At first, the total number of grains and surface area in a unit soil can be calculated by grain size distribution function, and then the surface area of the soil pores and surface-to-volume ratio of pores can be determined according to the coherence between the boundary of pores and the surface of soil grains. At last, the permeability model was built according to Poiseiulle Law based on the principle that the surface-to-volume ratio of equivalent capillary is equal to that of pore and the method determining the parameters of the model was given. The analytic result of example indicates that there is an apparent relation between permeability and surface-to-volume ratio in which the...