Study On Physical And Mechanical Characteristics Of Paste Filling Material With Swelling Properties

Goaf paste filling is one of the most efficient solutions of mining subsidence and surface damage at present. Paste filling can not only improve the influence of environmental pollution caused by coal gangue and fly ash disordered stacking from the source but also to solve the problem of mining under the villages and buildings. The mechanical characteristics of filling body, filling cost and effect of ground control by backfilling mining were determined by paste filling material, which was the kernel of paste filling technology. Therefore, paste filling materials with swelling properties were researched systemically through slurry palpability and mechanical properties in thesis.Main investigation and study results as below:(1)According to the distortion and destroy law or theory of roof strata in goaf, The early strength of the filling body should be above0.15MPa to meet their stable self-sustaining and roof support effectively; Through calculation methods of coal pillar carrying capacity in strip extraction, one can draw a conclusion that the late strength of the backfill should match its overlying rock in goaf area, which use the long wall interval strip filling method. In order to meet the pumping demand of filling slurry, the slump of the filling material should be more than12cm, And the bleeding rate should be controlled between1.4%-3.2%.the maximum allowable size of aggregate for coal gangue should be smaller than25mm, where the proportion of particles smaller than5mm no less than40%of either grading requirements.(2) A new type of paste filling material with swelling properties which mainly made up of coal gangue, fly ash, cement, bentonite and part of chemical activator was invented, Through chemistry analysis methods, such as XRD and SEM, micro hydration mechanism research of paste specimens under various curing ages (8h、7d、1d、28d) were carried out. The variation relationship between different bentonite mixing ratio varying with time was analyzed as well as the rate of expansion and mechanical properties of paste materials.(3) The coal gangue, fly ash, cement, auxiliary materials and bentonite proportioning test were been designed to achieve the optimal proportion of paste filling materials with swelling properties through systematic mechanics experiment. The experiment results show that cement is the key material influencing the strength of filling materials, the influence of fly ash is limited on concrete strength in different ages. The expansion rate of paste filling material increased with the mixing amount of bentonite, the mechanical strength and flowing property of paste filling materials will be greatly effected when the mixing amount of bentonite is more than60%.(4) Analyzed the impact of vertical stress and vertical displacement and damage range of the plastic zone by different filling parameters of filling body by using numerical simulation software of FLAC3D, vertical stress of gob roof increase with the filling ratio of paste material, while vertical displacement of gob roof is gradually decrease.