| Based on numerical analysis with special FEM(Finite Element Method) software , the observation in-situ and the special tests in lab, the author has studied the engineering and mechanical properties, characteristic of deformation of the deep and thick water bearing unconsolidated layers in Huanghuai area, the author has also studied its application in preventing the shaft wall from failure. The work involved:1) According to the test result of the soil in several coal mines, physical properties and its variation of deep and thick clay were researched The layer of deeper than 70m is named as the Deep and Thick Layer according to clay properties. And the idea of potential consolidation thickness of deep clay was proposed. Characteristic of the strength of the deep clay was also studied varying with the depth and the water content. In addition, the author proposed the concept of weak face, upper and lower strength limit of deep clay, together with the method to determine them.2) Two special tests were made. One is the high pressure seeping test of deep clay, another is triaxical compressing test with controlling two factors of tight sand. The first test testified the existence of weak face at the interface between the deep clay and the artesian aquifer. Compression area will be larger if the pore water pressure being higher in the water bearing layer. Lower strength limit of the deep and thick clay can be determined according to the strength of the shallow clay with equal effective stress and similar physical properties. Discrepancy was found between some test results with equal pressure and higher pore water pressure based on Principle of Effective Stress and that by simulation of gravity of the tight sand. These will be useful for further research on deep sand.3)Based on analysis of the structure of the deep and thick water bearing unconsolidated layers in Huanghuai area and the study of the influence of mine withdrawing water on water bearing layer, the author presented the similarity of the structure of the layers in mining field and its variability in local area The author also analyzed the relationship between mine withdrawing water and the water level of the aquifers, which is helpful for the study on the mechanism of shaft wall failure and the study on the characteristic of properties and deformation pattern of deep and thick water bearing unconsolidated layers.4)Referring to the observations in coal mine, the author analyzed the characteristic of consolidation and compression in the layers, and constitute the model to calculate the compressing on the basis of the water level, compressing time and the compressing ratio of the layers. The author also studied characteristic and mechanism of the concentrated horizontal movement first observed in China in the deep layers, together with its influence on the shaft walls. These will be useful in studying the prevention of the shaft wall from failure.5)The observation results of the stress and deformation of stress releasing notch in shaft walls were studied, which is useful for preventing shaft walls from failure by stress releasing notch. According to the surveying of cracks in buildings, the author pointed out that settlement in large scale generally does no harm to the building in mining industrial area.6)Numerical analysis with special FEM software was made to constitute the uniform model on shaft wall-soil layer-consolidation. Additional stress induced by deep unconsolidated layer's compression, mechanism and characteristic of stress releasing notch's effect on the prevention of shaft wall from failure, the optimum plan and the effect of grouting and the mechanism of the concentrated horizontal movement of the deep unconsolidated layers were also analyzed. In addition it was testified that the deflection deformation of the deep layers was one of the main factors of the concentrated horizontal movement of soil layer in mining area was made, which is important for treatment engineering in practice.7)The study presented in the paper has been us...
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