Experimental Research On Properties Of Slurry Used For Isolated Overburden Grout Injection

Isolated overburden grout injection makes the adjacent working faces are in nonfull mining by controlling the width of the working face and the isolated coal pillar,and before the key stratum is broken,the filling slurry was injected into the separation layer under the high pressure by drilling,to avoid surface subsidence.With the wide application of the isolated overburden grout injection,the filling slurry--fly ash is in short supply,which limits the development of the technology.In this regard,This dissertation introduces the experimental research on the characteristics of the filling slurry and explores key parameters and its range applied in slurry.The verification in whether the loess can be used for isolated overburden grout injection is based on this.The research results are as follows:10 ideal properties of the isolated overburden grout injection are obtained from the practice.By analyzing,the stability of the slurry,the diffusion radius,the viscosity,the compaction rate and the solid strength are chosen to confirm properties of slurry used for isolated overburden grout injection.The stability of the slurry is mainly measured by the speeds of particle sinking in slurry.When the density and velocity of the medium are the same,the speeds of particle sinking in slurry is only influenced by the diameter and density of the particles,and the speeds of particle sinking in slurry is same under both static condition and flow state.At the same time,the plastic viscosity can reflect the diffusion radius of the slurry.The compaction rate is the volume of the compacted slurry injected divided by the volume of the slurry before injecting.To some extent,the strength of the compacted body is on behalf to the long-term stability of both the filling slurry and subsidence control.The uniaxial compressive strength is used to represent it in the experiment.Therefore,the speeds of particle sinking in slurry,plastic viscosity,compaction rate and compressive uniaxial compressive strength are needed to measured.The experimental scheme is based on the physical meaning and engineering significance of these 4 properties,and as close as possible to the actual working conditions of grouting.The speeds of particle sinking in slurry decreases with the increase of water-liberating rates,and the overall process can be divided into 3 stages,and the main precipitation occurs in the second stage.According to the data of the six speed rotating viscometer,the plastic viscosity increases with the increase of the waterliberating rates,and the curve generally appears exponentially,and the turning point is about 0.6 ~ 0.7.The compaction rate of the slurry that is analyzed by the data obtained from the self-designed pressure vessel,which consisting of 3 stages,has been decreasing with the increase of the threshold pressure,and the decline speed is gradually decreasing.The overall logarithmic generally appears exponentially.The experiments conclude 8 kinds of parameters of 4 kinds of properties of the fly ash slurry,so to define the range of whether the paste can be injected.The loess is tested in the same way,and its properties are in this range.This shows it can be used for isolated overburden grout injection.This experiment also applies in guiding the reasonable proportioning of filling slurry in engineering.The relation between the weight of fly ash and the volume of compacted fly ash slurry obtained by the experiment is established under different grouting depth,and the formula of filling ratio is improved,the formula for the limit value of fly ash used for grouting is obtained,and the engineering verification is carried out,which provides a reasonable basis for the design of weight of fly ash in grout injection engineering.