Study On Tunnel Toughness Layer Of Improved Rubberized Concrete And Its Shock Absorption Performance

Tunnel engineering is complicated by the geological environment,which is influenced by uncertain factors such as fault zones and seismic belts.Once a highintensity earthquake occurs,it will cause irreversible damage to the tunnel.The tunnel lining is a rigid support with weak tensile strength and poor toughness.When subjected to seismic loads,it is prone to cracking and even collapse.Therefore,how to improve the toughness of concrete has become a hot research topic.Considering the excellent deformation ability and impact resistance of rubber concrete,rubber concrete is applied as a toughening and shock absorption layer material in tunnel construction.This not only solves the problem of "black pollution" caused by a large number of waste tires but also improves the seismic performance of tunnels.However,the addition of rubber reduces the strength of concrete,making it unable to meet the requirements for application in tunnels.To improve this situation,this thesis explores an improved plan for enhancing the mechanical strength of rubber concrete while also considering its toughness.Using numerical simulation and model testing methods,we verify that the improved rubber concrete toughening layer can enhance the seismic performance and toughness of the tunnel lining structure,with the main content as follows:(1)Summarizing the current research status of rubberized concrete and tunnel seismic mitigation technologies,exploring the effects of Na OH rubber interfacial modification,PE fiber content,and kaolin clay content on compressive and splitting tensile strength using material experiments.Combining SEM microscopic observation of the microstructure,the impact mechanisms of each factor are analyzed: Na OH improves the bond between rubber and cementitious materials by removing zinc stearate from the surface of rubber and increasing surface roughness;PE fiber forms a three-dimensional network within the cementitious matrix,playing a bridging effect and the addition of bentonite through physical filling and reaction with volcanic ash enhances the strength of rubber concrete.(2)Designing a three-factor,three-level orthogonal improvement plan and conducting notch beam three-point bending tests and Hopkinson bar impact tests to obtain stress-strain curves of rubberized concrete with different improvement measures.Using fracture toughness and impact toughness as evaluation indices,the study identifies 1% Na OH interfacial modification,6% PE fiber content,and 10% kaolin clay content as the optimal processing method for rubberized concrete,which improves fracture and impact toughness by 10.9% and 85.4%,respectively.(3)Based on the improved mechanical properties of rubberized concrete material,using finite difference software to compare and analyze the effects of different toughness layer thicknesses on the seismic performance of tunnel lining structures.The dynamic response laws of displacement,acceleration,and stress when applying earthquake loads at positions with fractured zones are analyzed for a variety of structures with 10 cm,15 cm,and 20 cm layers respectively.The research reveals that there is a significant amplification effect of acceleration caused by fractured zones;lining displacement is larger at fault locations,leading to concentrated stress.In conclusion,the addition of rubber composite toughness layer reduces dynamic response,improves the seismic performance of tunnel structures,and reduces maximum acceleration by 29.0%.(4)Based on the Shantou Bay Tunnel project,we carry out research on rubber concrete toughening layer materials and their seismic performance in tunnels.Based on the principle of similarity,the study selects a 1:20 scaled-down model to conduct tunnel lining structure model tests,evaluating the effectiveness of improved rubberized concrete in enhancing the toughness properties of tunnel lining structures via ultimate load,failure deflection,and acoustic emission parameters.The research finds that the maximum increase in ultimate load is 153.7%,the maximum increase in failure deflection is 94.6%,and the maximum increase in acoustic emission energy parameter is 860.92%,while the maximum reduction in acoustic emission ringing count parameter is 47.14%.(5)Utilizing a combined method of numerical simulation and model testing,the study analyzes the seismic response and toughness performance of tunnel lining structures with improved rubberized concrete toughness layers.Results indicate that incorporating improved rubberized concrete as a toughness layer significantly improves the seismic performance of tunnel linings.