| Geomaterials are basic media for all creatures of nature, they are also closely related to the human engineering activities. As one of the basic characteristics of the geomaterials, the inhomogeneity characteristic affects the mechanical properties of geomaterials and further affects the human geotechnical engineering activities. Inhomogeneity characteristic of geomaterials is mainly reflected as geomaterial parameters inhomogeneity. The effective inhomogeneity modeling method of geomaterials should have three basic characteristics: firstly, it can simplely and reasonably describe the randomness and the structure of geomaterial parameters. Secondly, it can combine well with physical tests to verify the validity and accuracy of the modeling method. Finally, it can be easily applied to practical geotechnical engineering analysis and provide correct guidance of the actual geotechnical problems. Currently, there are many limitations in inhomogeneity modeling method of geomaterials. In order to better study the characteristics of the geomaterial inhomogeneity and further understand the mechanical properties of geomaterials. This paper carries out inhomogeneity modeling method, numerical simulation experiments of the mechanical properties, model test and engineering applications research that based on the material composition of geomaterials. The main contents and conclusions are as follows.(1) Inhomogeneity modeling method of geomaterials composition is proposed according to randomness and structure characteristics of geomaterials’s mechanics parameters. The modeling method considers the sorts and contents of geomaterials as the basis for the establishment of geomaterials cell unit judgment rule and structural factors. It also considers geotechnical parameters’randomness by the combination of the Monte Carlo method. The inhomogeneous geomaterial model is completed by judgment of all cell units. When the modeling method is used to descirbe inhomogeneity of geomaterials, the content of each material component equal to the true content of the geotechnical materials and it is not depended on the shape and size of the grid cells, therefor, this modeling method is well adapted to grid cells. In addition, the modeling method is applicable to homogeneous geotechnical materials and inhomogeneous geomaterial.(2) The randomness and structure characteristics of inhomogeneity modeling method of geomaterials composition are studied by numerical simulation experiments. While the random distribution of material component cell unit in numerical model has little effect on geomaterials macro-mechanical parameters, sort of components (the difference of mechanical parameters) and content on the the geomaterials have a great influence on macro-mechanic of geomaterials. If mechanical parameters of the material compositions are different, so is the macro-mechanical parameter. And if material composition content is not at the same time, niether is the macro-mechanical parameter. It has a significant linear relationship between the model macroscopic elastic modulus and the material composition cells mesoscopic elastic modulus and content. The macroscopic elastic modulus of model can be expressed by mathematical expectation of all the materials of composition cells elastic modulus.(3) Inhomogeneity modeling method of geomaterials composition is used to establish Brazilian disc specimen model of inhomogeneous rock material and uniaxial compression specimen model. Stress characteristic of the inhomogeneous rock material is simulated by finite element method. Due to inhomogeneity of geomaterials, there is the redistribution of stress inside the geomaterials under load. Therefore, inhomogeneity has an important impact on the redistribution of stress inside the geomaterials. Macro-mechanical property of inhomogeneous rock material is determined by the deformation characteristics of the material component cells and inhomogeneity characteristic of geomaterials.(4) According to the randomness nature of geomaterial parameters, coefficient of variation of material parameters which is a dimensionless quantity is defined as the degree of inhomogeneity of geomaterials. By studying the relationship between coefficient of variation and shape parameter of the inhomogeneity numerical modeling methods in random probability (Weibull distribution), it proves that using the coefficient of variation of the geotechnical parameters to describe inhomogeneity of geomaterials is reasonable. For inhomogeneous geomaterial, macro-elastic modulus gradually decreases with the increase of inhomogeneity degree. When degree of inhomogeneity is small, the change of elastic modulus is gentler with change of degree of inhomogeneity. When degree of inhomogeneity is large, change of elastic modulus is obvious with change of the degree of inhomogeneity. The macro-ultimate strength of the geotechnical materials gradually reduces with degree of inhomogeneity increases and ultimate strength and degree of inhomogeneity have a significant linear relationship.(5) A model test program about inhomogeneous geomaterials is put forward and inhomogeneous rock material model is made according to the basic idea of the inhomogeneity modeling method of geomaterials composition. The deformation and failure characteristics of the inhomogeneous rock material and the influence of inhomogeneous characteristics of the rock material on physico-mechanical properties are studied by the uniaxial compression test. Experimental results show that firstly, deformation characteristics of inhomogeneous rock material model specimen is similar to the homogeneous rock material model specimen but different in mechanical parameters of elastic modulus and ultimate strength; secondly, sort and content of material composition both have an impact on the mechanical properties of the specimen of inhomogeneous rock material model, which reflects the structure characteristics of the material composition; then, the elasticity modulus and the ultimate strength of test model of rock material are governed by the degree of inhomogeneity. At the same time, the law of influence that the inhomogeneity makes to mechanical parameters of the material obtained by the model test is consistent with the law of numerical simulation experiments. In the state of uniaxial compression, damage of inhomogeneious rock material model specimen is mainly in the form of tensile failure and shear failure, failure mode of inhomogeneious rock material model specimen is also affected by material compositions.(6) With inhomogeneity modeling method of geomaterials composition applied to slope engineering, the random meso-structure model of inhomogeneous geotechnical slope has been established. This model has the basic characteristics of the inhomogeneity modeling method of geomaterials composition. At the same time, the modeling method can be applied to establish a numerical model of the three-dimensional inhomogeneous geotechnical slope. Through the combination of the random meso-structure model of inhomogeneous geotechnical slope and strength reduction method, the influence which the inhomogeneity of geomaterials made to slope stability has been simple analysised. The results show that in the case of all other parameters are constants, safety factor of slope stability gradually decreases with increasing inhomogeneity degree of cohesion. So if inhomogeneity of geomaterials is not considered in the analysis of slope stability, there are security risks in slope engineering. |
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