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| MECHANICAL PROPERTIES OF HARD ROOF BASED ON ASSUMPTIONS OF SOFTEN FOUNDATION AND ELASTIC FOUNDATION |
| PAN Yue1，GU Shitan2，3 |
| (1. School of Civil Engineering，Qingdao Technological University，Qingdao，Shandong 266520，China；2. State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology，Shandong University of Science and Technology，Qingdao，Shandong 266590，China；3. College of Mining and Safety Engineering，Shandong University of Science and Technology，Qingdao，Shandong 266590，China) |
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Abstract In traditional ground control theory，supporting action of soft rock under hard roof was often simplified as the Winkler elastic foundation. To accurately analyze the mechanical characteristics and activity of overlying strata，this simplification cannot be contented with the actual requirements. In view of peak of abutment pressure in front of the coal wall，mechanics properties of hard roof model that was thought as soften foundation between coal wall and the peak of abutment pressure and elastic foundation ahead of the peak of abutment pressure were analyzed before the periodic weighting. Methods for determinating peak value of the abutment force were presented. Examples were given to illustrate how to calculate the peak value of the abutment and verify the accuracy using the development approaches. Analysis results were compared with mechanics properties of roof based on full elastic foundation. The research results are shown as follows：Reaction force near the coal wall to the roof obtained by full elastic foundation is 4 times as big as that of the roof calculated by the soften foundation in the depths of 200–300 m. Bending degree of roof，scope of the bend，the distance between peak of bending moment and the coal wall，storage area of strain energy and storage capacity become small near the coal wall，which result from the powerful reaction near coal wall. Reaction near the coal wall to the roof，which is caused by the soften foundation is a fourth as big as that of the former. Owning to the small reaction near coal wall，bending degree of roof and scope of the bend become increase for resisting on overly roof，which lead to the peak of bending moment and the distance between peak of bending moment and the coal wall increase remarkably. Meanwhile，storage area of strain energy and storage capacity outstanding aggrandize in front of coal wall. Then the roof?s deflection increase overall and remarkably when compared with the roof supported by full elastic foundation. Position of peak of bending moment in front of coal wall is related to the location of roof fracture. Position of roof fracture that calculated based on the assumption of soften foundation and elastic foundation is closer to the actual，and the corresponding internal force，strain energy and deflection are closer to the actual when compared to full elastic foundation.
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2015, Vol. 34 
