| Ice-containing cemented paste backfill(ICPB)is a new backfill material with the advantages of traditional cemented paste backfill(CPB)and the cooling function of goaf.The flow characteristics of ICPB materials are the key factors affecting the working performance and long-term strength of the backfill body.In this study,the rheological properties and the flow characteristics of pipe transportation of the ICPB slurry are studied by combining the experimental and numerical methods.The key technologies of ICPB,such as the flow settlement and stratification rules of ICPB in the stop are studied by using the flume experimental platform based on the similar theory and the nuclear magnetic resonance(NMR)technology.And a visual monitoring method of electrical resistivity tomography(ERT)is introduced,which is suitable for mine backfill pipeline transportation.The main conclusions are as follows:(1)The results indicate that the ICPB behaved as a Binghanm fluid.The yield stress,plastic viscosity,and thixotropy increased with an increase in the ice/water ratio(I/WR)and concentration,while the cylindrical slump decreased under the same variation.The simulation results of the cylindrical slump were compatible with the experimental results.Furthermore,the numerical study indicates the slump increased when the test temperature was increased from 11.85? to 31.85?.The results found in this study can be used as a reference for the pipe design of ICPB.(2)Based on CFD method,the flow characteristics of different I/WR and different ice particle size in pipeline transportation were studied.The results show that due to the deposition of coarse tailings and the suspension of fine tailings,three areas are formed in the process of pipeline transportation.The velocity of ICPB in the pipeline is arched along the pipeline section,with the highest velocity in the middle of the pipeline and the lowest velocity near the pipe wall.In addition,the I/WR and ice particle size have an important influence on the transport characteristics of ICPB pipeline.The results are of guiding significance to the design of pipe network system in mine backfill industry.(3)With the increase of curing time,the electrical conductivity of ICPB with different I/WR and concentration increased first and then decreased.According to the principle of geometric similarity,four groups of measured models were built to simulate four different degrees of blockage of filling pipeline.The boundary voltage was measured by 16 electrode ERT experimental platform and the image was reconstructed by one step linear Gauss-Newton algorithm.The experimental results show that the reconstructed image can accurately reflect the degree and position of agglomeration.The research lays a foundation for the application of electrical resistance tomography technology in the visual detection of liquid-solid two-phase flow in filling pipeline,which can greatly reduce the cost of pipeline blockage detection and avoid blind excavation.(4)The pore structure characteristics of ICPB samples in similar stopes were characterized by NMR and SEM.The strength distribution of ICPB in similar stopes along the vertical and flow directions and the flow settlement geometry of the ICPB were studied.The results show that the strength distribution and the micro pore structure distribution of the ICPB in the stope are not uniform.And the strength and pore structure of the ICPB are different from those of the laboratory specimens.The reason of the strength inhomogeneity after the settlement of the ICPB is explained from the microscopic point of view by using the microstructure parameters measured by NMR.It provides a theoretical basis for the uneven distribution of the strength of ICPB in the stope.The research provides guidance for the optimization of the ratio of ICPB,the design of backfill pipe network system,and the visual monitoring of pipeline.And lays a theoretical foundation for the improvement of production safety issues such as the pipeline transportation of ICPB and the stability of goaf. |
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