| Based on high concentration cementing backfilling technology in Xinyang coal mine,this paper is to develop a new backfilling cementing material.Aimed to make full use of solid wastes around the mine area and power plant,further reduce the amount of cement based on the high concentration cementing backfilling material,a new cementing material is developed by lab tests.On this basis,by optimizing aggregate gradation,a new backfilling cementing material is developed and its strength and pipeline transportation characteristics are studied.The development of new backfilling cementing material raises the utilization ratio of solid waste.Meanwhile,it also can provide the reference for Xinyang coal mine to further reduce the backfilling cost and improve the economic benefit.By the research of lab tests,theoretical analysis,numerical simulation and the industrial tests,the conclusions of this paper are as follows:(1)According to the geological conditions of 10203 working face in Xinyang coal mine,the theoretical calculation formulas of filling body's early and later strength are deduced to meet the mine by the empirical formula of the early strength of cemented backfill and the key stratum theory.The result is that: In order to make the smooth transition between mining and backfilling and control the surface subsidence effectively,the filling body must be stable and its early strength(4h)can't be less than 0.16 MPa.The later strength(28d)shall not be less than 4 MPa.(2)Through lab tests and analysis of different materials ratio and hydration mechanism for the new cementing material,it is concluded that: Without adding activators,the optimal proportion of the new cementing material is that cement: lime: desulfurization gypsum: fly ash = 20%: 1.8%: 9%: 69.2%.Through the single test of activator,the excitation effect of various types of activator is obtained: Na2SiO3>NaOH,Na2SO4>CaSO4·2H2O,CaCl2>NaCl.Choosing Na2SiO3?Na2SO4 and CaCl2 for the complex mixed tests with orthogonal experiment,the optimum mix amount of three kinds of activators is 1.0%,1.5% and 1.5%.Under this condition,the new cementing material's mortar strength is 17.20 Mpa,26.49 Mpa and 42.03 Mpa on 3d,7d and 28 d.The cemented effect of the new cementing material is better than high concentration cementing material.(3)From x-ray diffraction spectrum seen,the main hydration products of the new cementing material are: C-S-H gel,ettringite(AFt)and hydration chlorine aluminum acid calcium.As the new cementing material mixes with activators,the activity of fly ash is fully stimulated,more gel products are generated in the hydration reaction.By microstructure analysis of scanning electron microscopy(SEM)for two kinds of cementing materials,it is concluded that: When the curing age is 3d,both cementing materials have C-S-H gel(clouds)and ettringite(needle)generated.But in the new cementing material,the macrostructure of needle products is bolder,in other words,it is more like the needle bar.Besides,hydration products in the new cementing material are more than those in the high concentration cementing material and the structure is more closely.When the curing age is 7d,the hydration products of both cementing materials gradually increase,the C-S-H gel cloud particles increase gradually and the gap decreases.But the spherical particles of fly ash are still clearly seen in the high concentration cementing material.In the new cementing material,ettringite and hydration chlorine aluminum acid calcium further grow up in C-S-H gel gaps and make the structure more compact.When the curing age is 28 d,there are a large amount of C-S-H gel generated in the new cementing material and it becomes a net-like stable structure.Hydration chlorine aluminum acid calcium further develops and its shape has changed flaky.The microstructure of the new cementing material keeps more closely.By analyzing the cost of new cementing material and contrasting to the high concentration cementing material used by Xinyang coal mine currently,it is concluded that the new cementing material cost is 127.7 yuan per ton.The cost per ton of new cementing material is 17.5 yuan lower than that of high concentration cementing material.The backfilling cost can be greatly reduced if the new cementing material is adopted.(4)By single factor experiment method,the new backfilling cementing material is studied from three factors: aggregate gradation,mass concentration and dosage of cementing material.The new backfilling cementing material's slump,exudation rate,and uniaxial compressive strength are tested under different conditions,the results are as follows: According to the graded theory of variable i,the best aggregate size of new cementing filling material is particle size of coal gangue less than 5 mm(40%),5 ~ 10 mm(31%),10 ~ 15 mm(29%);The optimum mass concentration and dosage of cementing material are 78% and 30% respectively.(5)By rheological test and analysis of the test data,the new cementing backfilling slurry belongs to the Bingham plastic fluid flow pattern,the formula of its flow pattern can be unified regression as:0?(28)?+??.The data of the frictional resistance loss and the local resistance loss are obtained by theoretical calculation,numerical simulation and pumping looping pipe experiment.The results from above three kinds of research methods are less than 3% and the coincidence is very high.The theoretical calculation,numerical simulation and pumping looping pipe experiment all can be the methods of studying the characteristics of slurry transportation and provide a reference for the design of backfilling system before engineering practice.(6)The new cementing backfilling material is applied in engineering practice.It is concluded that the backfilling system runs stably,the work at the working face goes smoothly and the result of backfilling is fine.The transportation performance of new cementing backfilling material is good and the strength of filling body on 3d,7d,28 d are respectively 1.17 MPa,2.13 MPa,4.92 MPa,which meet the requirements of the backfilling mining in Xinyang coal mine. |
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