Study On Ground Pressure Characteristic Of Shallow Coal Seam Longwall Mining And Its Safe Exploitation Demarcation

Based on theory of ground pressure and its control, functionally graded material, granular dynamic and so on, in view of the questions of shallow coal seam mining, through a large number substantial work such as laboratory physical analogue experimental techniques and in situ observation method and numerical simulation, shallow coal seam exploitation demarcation, mechanization of primary weighting and periodic weighting, dynamic load cause of working face weighting, the condition named safe exploitation demarcation of guarantee sand and water against coming into shallow coal seam longwall working face and theory of ground pressure control, etc are studied deeply in this paper, those have important theory significance and practice value for making up and improving the theory system of ground pressure and its control and make clear ground pressure characteristic of shallow coal seam and its safe mining technology.The main conclusion and innovation in thesis as following:1) The three defining index of shallow coal seam mining are brought forward: The coal bed overburden composition is made up of the thin bedrock and the loose loading layer, bedrock thickness is smaller than 50m; The surrounding rock activity law of longwall working face namely the single key seam, the loose loading layer is moved with bedrock seam, the roof pressure fiercely and the dynamic pressure phenomenon is obvious; The coal bed burial depth is smaller than 100m.2) Established overburden mechanics model of the shallow coal seam longwall working face, namely gradient compound board which formed elastic foundation is made of bedrock seam and uniform load gradient which formed by the loose loading layer; the working face first pressure go through three processes: the key rock layer broken bring pressure load and key rock layer above rock layer broke down falls bring the first pressure load, the loose loading layer broke down fall bring the second pressure load.3) The model of the bearing pressure bricklaying after key layer broken is constructed, the cycle pressure mechanism of the shallow coal seam mining working face is expounded, the overburden rock cannot form relatively stably "bricklaying beam" structure is obtained. This is one of the main characteristics shallow coal seam mining ground pressure. 4) The dynamic laws of shallow coal seam overburden loose loading layer are analyzed, the process for the first time pressure of working face consist of above bedrock loose load body separate from bedrock and pressed the bedrock violently bring working face violent dynamic load phenomenon are brought forward.5) The coal seam and hydrology geological condition of guarantee sand and water against pouring shallow coal seam longwall working face is get and the definite method of the working surface support reasonable working resistance is given simultaneously, the strong support and the short bricklaying working surface roof safety control principle are presented.