Research On Swelling And Strength Properties Of Whole Mill Sulfur-content Tailings Cemented Backfill

Whole mill sulfur-content cemented tailings backfill will be significant swelling phenomenon with curing period extending.Sometimes these samples appear loose or disintegrating.This problem result in the sharp decline of strength and instability of filling body.Finally,it lead to enormous risks of deep and efficient resource extraction.In this paper,the core is a sulfur-content cemented tailings backfill to explore swelling and strength characteristics about different levels of sulfur-content tailings backfill specimens.Analyzing the chemical mechanism of its swelling and the damage constitutive model of backfill provide a theoretical basis for the swelling of disaster control.Specific contents are as follows:(1)Analysis of the tailing physical properties and chemical composition were carried out.The tailings is fine,well graded,poor permeability and tailings containing a sulfur content of about 4%.After researching on the mechanism of hydration of Portland cement,cement-based materials sulfate attack mechanism.I compared similarities and differences between sulfur-content backfill erosion with them.Then acquire the chemical mechanism of swelling,cracking and disintegration and failure modes of sulfur-content backfill.(2)With the four influencing factors of sulfur content,concentration of slurry,cement content,curing age,and setting five levels orthogonal test scheme is adopted.Backfill swelling and uniaxial compressive strength under standard curing conditions are judging indexes.(3)Using range analysis the priority of swelling factors were obtained:the amount of cement>slurry concentration>sulfur content in 14d;he amount of cement>sulfur content>slurry concentration after 28d.Multivariate linear regression prediction model of sulfur-content backfill described the swelling of the law backfill.And then I tried support vector machine(SVM)method and implement an effective forecast of swelling for the filling body.(4)Using the X-ray diffraction analysis(XRD)with different sulfur content,cement content,sulfur content and curing age of filling powder were analyzed.Gypsum,ettringite,calcium silicate hydrate crystal of each comparison group have different significantly about diffraction characteristics summit.It reveals the chemistry of sulfur backfill swelling:because of sulfur(compound)converted to sulfate and the corrosion effect generated,gypsum,ettringite crystals and other swelling result in internal stress generation inside the filling body,and consuming some calcium silicate hydrate reduce the degree of adhesion between the aggregate.After that these reasons result in cracks backfill disintegration.(5)Compressive strength of backfill is low at 14d.The amount of cement,slurry concentration with strength were positively correlated.With sulfur content increasing strength was adding after reduction the first.After conservation 28d,part of the filling body specimen have surface cracks and other obvious defects,compressive strength data obtained by test of the same group specimen were very discrete.Has been unable to obtain effective compressive strength by experimental means.(6)Take the uniaxial compressive specimens complete stress-strain curves from regular and surface no obvious defects specimen for the study.I deviated damage constitutive model based on Weibull strength theory and made revise.To make the model more in line with the sulfur-containing filling body deformation and failure law under uniaxial loading.