| Filling the underground space is the development direction of the mine,but the coverage rate is not high in the filling of mines.In order to study the feasibility of using the bentonite in the filling material to expand the filling body and increase the coverage ratio,the fluidity of the filling slurry mixed with bentonite and the swelling and strength characteristics of the filling body were studied.Specifically,slurry concentration(65%,70%,75%,80%),bentonite content(0,5%,10%,15%),lime-sand ratio(1:4,1:6,1:8,1:10)Three-factor and four-level orthogonal test,XRD diffraction,SEM scanning,nuclear magnetic resonance scanning and other experiments on the physicochemical properties of filling materials,slurry fluidity,bleeding rate and gas content,filling body expansion rate,Porosity,strength characteristics and microstructure have been studied to provide basis for bentonite to expand the filling body and improve the quality of the roof.The specific research content is as follows:(1)Study on Bleeding Characteristics,Flow Characteristics,Early Hydration Law of Bentonite-Mixed Filler Pulp.Slurry bleeding can be divided into two stages:rapid bleeding and stable bleeding.Bleeding rate decreases as the amount of bentonite increases.The slump of the filling slurry decreases with the increase of bentonite addition,but the slump of 15%bentonite is still 24.5cm,which is less than 25.5cm when bentonite is not added,and the fluidity is good;the main body of the filling slurry is water.The reaction took place within the first 30 minutes,during which time the physically bound water rapidly decreased.(2)Research on Filling Body Expansion Laws.The swelling rate of the backfilling body is mainly affected by the amount of bentonite,and the swelling rate of the backfilling body increases with the increase of bentonite content.The ratio of sand and sand and slurry concentration have little effect on it;when the amount of bentonite is increased from 0 to 15%,The expansion rate increased from-1.89%to 3.47%,and the negative sign represents sinking.The swelling of the filling body can be divided into two stages.One is the stage where the bleeding is shown to resist,and the other is the further active swelling after the bleeding.The resistance is the main source of the swelling rate.(3)Study on the strength characteristics of backfills.The filling body strength increases with increasing bentonite content.Within 30 days of compressive strength in the 0-15%bentonite dosage range,the strength increases from 1.68 MPa to 2.68 MPa.In high-concentration(greater than 75%)high-bentonite(greater than 10%)backfills,the damage pattern tends to be less common for tensile failure.Bentonite improves the macroscopic structure of the filling body.Bentonite absorbs stored water and continuously supplies water required for later hydration.The combination of the two increases the strength of the filling body as the amount of bentonite increases.(4)A Study on the Regularity of the Porosity and the Intensity of the Backfilled Body Filled with Bentonite.The bubbles produced by hydration of bentonite are stable,and all of them are small bubbles.Therefore,the porosity increases with the increase of the amount of bentonite.The compressive strength and porosity of the backfill are not significantly positive and negative.Because the compressive strength of the backfill is also affected by the size and shape of the pores,and is more dependent on the pore size,the larger the pore size,the lower the strength.(5)Study on the swelling mechanism and strength mechanism of filling body There are more ettringite produced by bentonite backfills,and the pores inside the backfill are filled with bentonite particles and ettringite,and expand outwards,so the expansion rate is greater.Bentonite-containing bentonite fills the body to increase the compressive strength of the backfill by generating a large number of gel groups that have cementation ability and generating ettringite that fills pores and improves the macroscopic structure of the backfill. |
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