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Abstract On the basis of strip mining characteristics，the exchanging technology of gangue backfill was described briefly firstly according to subject of strata movement and quadratic stability of coal-pillar under three circumstances exchanged by gangue backfill，mining process of coal-pillar. Mechanism and characteristics of quadratic strata movement were also analyzed. It is considered that the main mechanism is compression of the gangue filling support body and bearing rock strata，and curving belt of overlying strata show the wavy type sinking curved layer. Then，some analytic formulae of the bearing body of“bearing rock strata + gangue filling support body”were deduced by means of the elastoplastic theory and based on the actual force and ultimate strength of the gangue filling support body，these analytic formulae includes the quadratic stability condition，the safety factor，the width of plastic area under limit state and the width of bearing core area. Calculation formulae of the compression amount of gangue filling support body(w1) and the quadratic compression amount of bearing rock strata(w2) were got；and the sinking total amount calculation method of quadratic strata movement was put forward too. Theoretical calculation results of Baoyuan Coal Mine indicate that the safety factor of the bearing body of “bearing rock strata + gangue filling support body”Fs = 1.36，and placed in stable state. The sinking total amount w is 0.833 m，the bearing bodies resist against high stress，and maintain quadratic stable of overlying strata. Numerical analysis results show that there is a saddle distribution for above vertical stress of the gangue filling support body；the average value of maximum subsidence displacements of bearing rock strata is about 0.801m，which closes to the theoretical value.
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Received: 24 May 2010
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2011, Vol. 30 
