Experimental study on strength and deformation failure characteristics of crushed stone cement filling in Xiaojiahe Phosphate Mine

In order to realize the large-scale crushed stone cement filling of Xiaojiahe Phosphate Mine in Yichang City,the uniaxial compressive test of crushed stone cement filling has been carried out to study the compressive strength of the backfill,deformation properties and destruction properties under different lime-sand ratio,slurry mass concentration and curing age in this paper.The research results show that at the same curing age,the cementation effect between gravel particles is better and the compressive strength of backfill is also higher with the increase of cement sand ratio and slurry mass concentration.When the cement-sand ratios remain unchanged,the elastic modulus of the backfill sample increases,the strain rate corresponding to the peak stress decreases and the anti-deformation ability of the backfill is enhanced with the increase of slurry mass concentration.When the slurry mass concentration remains unchanged,the cementing effect is weakened and the shape variable of backfill increases with the decrease of cement-sand ratio.With the increase of curing age,the failure mode of backfill samples gradually changes from tensile failure to shear failure.The number of cracks on the surface of backfill and the area of block exfoliation decrease when the curing age increases,so the failure degree is smaller.Through experimental study,the optimum scheme about filling material has been determined as that the same lime-sand ratio is 1∶8,the slurry mass concentration is 86%,and the curing age is 28 d,which meets the technical and economic requirements of backfill scheme in Xiaojiahe Phosphate Mine.