| For the application of shotcrete shotcrete support in the construction of mountain tunnels with high rock temperature and high impact pressure and deep mine tunnels.In the initial support of shotcrete on high-temperature rock walls,problems such as poor early anti-cracking performance,low thermal insulation performance of the supporting body,and poor impact resistance will occur.Explore the mixing of low thermal conductivity ceramsite,high elastic modulus rubber particles and mechanically enhanced hybrid basalt and polypropylene fiber into sprayed concrete to prepare a sprayed concrete with high heat insulation and anti-disturbance.That is,Light-aggregate Rubber Fiber Shotcrete(LRFS),physical mechanics and impact performance tests were carried out,and the main conclusions were obtained:(1)The bonding performance of ceramsite and LRFS cement matrix gradually increases with time.As a result,the stress transmission mechanism of the two is different.The 7d compressive strength is weakened by the incorporation of ceramsite.When the 28d compressive strength is measured,the incorporation of ceramsite can significantly enhance it.(2)The content of ceramsite and combined rubber is the main factor that affects the evaluation indicators of LRFS.The contribution rate of ceramsite to 28d/LAFS compressive,splitting tensile,flexural strength and thermal conductivity variance is 46.38%,58.18%,76.43%and 68.51%,respectively.The maximum contribution rate of the combined rubber content to the water penetration height of LRFS is 88%.In addition,the optimal ratio of ceramsite and rubber particles is mixed,and the particle gradation interaction between the two directly affects the mechanical properties of LAFS.(3)The low thermal conductivity ceramsite and rubber particles are mixed into LRFS,which effectively prevents the heat transfer between the pore walls of the shotcrete matrix.However,if too much ceramsite is mixed with rubber particles,the surface porosity of the matrix increases significantly,and the penetration resistance of LRFS decreases and the water seepage height increases.When the optimal level of ceramsite content is 7%,the corresponding thermal conductivity and water seepage height change ranges are 31.67%and 5.11%,respectively.A variety of rubber composite particles have better thermal conductivity and water permeability performance at 3%+4%+3%,2%+5%+3%.Compared with the unblended rubber group,the optimized ranges were 18.76%and 12.42%,19.21%and 25.54%.(4)The stress-strain curve of LRFS under impact stress can be roughly divided into three stages:approximate elastic stage,plastic stage and failure stage.The incorporation of a variety of rubber composite particles can significantly improve the peak impact stress of LRFS specimens,and the appropriate and uniform mixing of ceramsite and rubber particles can effectively resist and release impact energy.Hybrid basalt and polypropylene fibers can not only increase the peak stress of LRFS to a certain extent,but also show obvious yield step/impact plasticity.Based on statistical damage theory and dissipated energy,a dynamic impact damage model of LRFS is established.The model has certain guidance and can provide reference for engineering application of LRFS.(5)The content of ceramsite is 7%;a variety of rubber composite particles:2%for rubber particles with a particle size of 3-6mm,5%for rubber particles with a particle size of 1-3mm,and 3%for rubber particles with a particle size of 20 mesh.The mixing amount of hybrid polypropylene and basalt fiber is 0.455kg/m3 and 2.8kg/m3,which can improve the physical and mechanical properties of LRFS and the dynamic mechanical properties.figure[34]table[18]reference[81]... |
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