Abstract:
In view of the demand of the water-preserved coal mining and the safe and efficient storage of water resource in arid and semi-arid areas of northwest China,in order to give full play to the advantages of strip constructional back- fill to protect aquifer structure and to reuse underground space in coal mines,the technical conception of “ water-pre- served and water-stored” coal mining with strip constructional backfill is put forward under the guidance of the basic i- dea of constructional backfill mining. Based on the analysis of structural characteristics of overlying strata with strip constructional backfill,the finite length beam model on elastic foundation is used to analyze the “constructional strip- immediate roof” structure,and the deformation equation of immediate roof is piecewise analyzed by combining the ini- tial parameter method. At the same time,the immediate roof control principle of strip constructional backfill is put for- ward according to the functional requirements of “water-preserved and water-stored” coal mining. According to the en- gineering geological conditions of Xinyang mining area and the properties of backfill materials,the critical backfill rate and maximum backfill spacing of strip constructional backfill obtained by theoretical calculation are 51% and 11. 95 m respectively. The backfill scheme of Xinyang mine is optimized through FLAC3D numerical simulation. The results show that when the back rate changes little,with the decrease of backfill space,the self-bearing capacity of the immediate roof gradually increases,a “ constructional strip-immediate roof” structure control system is forming,and the control effect of immediate roof on overlying strata is improved significantly. The decrease of the backfill spacing relieves the stress concentration phenomenon in the backfill strip and immediate roof and reduces the range of plastic zone in back- fill strip and immediate roof significantly,which is conducive to the long-term stability of backfill strip and immediate roof,and realizes the purpose of “ water-preserved and water-stored” coal mining. According to the comprehensive a- nalysis,the optimum scheme of strip constructional backfill in Xinyang mine is spaced 2 m and backfill 2 m.