Study On The Structure Mechanics Properties Of Deep Soils Of Mine Area In Eastern China

The deep soils of mine area in eastern China are dominated by Tertiary soil layer, which contains low water content, is compact and appears in a saturated hard or half-hard condition, and is a type of special soil transitioning from soil to soft rock. In recent years the problems of earth pressure and permeation of deep well soil layer are outstanding, whereas it is required to look into the mechanical properties of engineering geology such as geological formation, structure, mechanics, permeability etc. of the deep soils in order to thoroughly solve such technical engineering difficulty. Therefore, the study the structural mechanics of deep soils has important theoretical significance and practical value.In this paper the soils buried below 300m in the mine area are taken, on the basis of indoor tests and theoretical analysis, and the micro-structural features, high Pressure triaxial unloading mechanical properties and K0 consolidation of the deep soils are studied deeply and systematically.Firstly, the microstructure of deep soils is detected by SEM, and a simple and feasible image map processing methods which can be extracted various micro-structural elements in deep soils are explored.Mathematical statistics is adopted for determining the weight of each single-factor index of the microstructure.And a relatively reasonable composite quantification parameter S that reflects the microstructure of deep clay is established. The densityρ, water contentωand composite quantification parameter S is , tcombined and he relationship among the parameters is established.Under the condition that considers approximate simulation of natural and well-building acting stress of deep clay,MTS815 servo test apparatus are introduced to carry out high Pressure triaxial unloading tests of undisturbed and remodeling soils, And the stress - strain characteristics through the state from high Pressure unloading dense structure to a more loose structure are analyzed.GE8800CT is introduced to detect high Pressure triaxial unloading soils. It is showed that: the initial state, the densities of different soil layers are close, and the arrangement of particles and pores inside the soil layer is not uniform; under the condition of equal pressure in all directions, the particle density of each soil layer increases, the pores decrease, the arrangement of the soil particles and pores tend to be uniform with the increase of pressure.When the confining pressure unloading is carried out and the axial pressure is kept unchanged, the particle density decreases and the porosity increasesof the sandy soil on the lateral section.But the particle density of the clay on the lateral section is basically kept unchanged.The directionality of particles and pores of the soil on the lateral section will be slightly influenced.A high Pressure K0 consolidation Apparatus which consolidation pressure up to 18MPa is designed.After K0 consolidation tests.We obtained that the remarkable difference between characteristic of deep soils mass and shallow soil mass. With the increase of consolidation pressure, soil samples ordered microstructure anisotropy gradually increasing,when the consolidation pressure to reach certain values, the microstructure anisotropic growth rate is small, indicating the direction of arrangement of soil particles does not change, the basic particles highly directional, and K0 value remained unchanged.Triaxial permeability tests showed that: there is remarkable anisotropy in the permeability of undisturbed soil sample of deep clay, the permeability coefficient kT in vertical direction under equal axial stress is less than permeability coefficient kH in horizontal direction, before sudden change (i.e. they have not reached the critical stress sections, respectively).The kH/kT ranges roughly between 1.1 and 1.3, the main reason lies in that: the flat clay particles settle directionally in vertical and horizontal direction in the environment of different stresses, resulting in tat the continuity of the pores in horizontal direction is generally better than that in vertical direction.The effect of horizontal earth pressure on the stability of well wall of the shaft under construction is calculated by the high Pressure K0 so as to simulate the actual conditions better, so has certain signification for guiding construction of the pit shaft.The paper have 48 maps, 34 tables, 195 references.