Study On Pressure Relief Of Reserved Deformed Layers Of Foamed Concrete In Tunnel Support

How to better play the role of tunnel support,and then release the surrounding rock pressure to control the surrounding rock deformation,which is of great significance to the stability and safety of tunnel engineering.In this thesis,the Tongzi tunnel support project is taken as the background.Through the combination of indoor axial compression test,similar material model test and numerical simulation,the pressure relief rule of the foam concrete deformation layer on the tunnel surrounding rock is studied.The main contents are as follows:?1?Prepare carbon nanotubes?CNTs?reinforced foamed concrete,use response surface method to optimize the proportion of the experimental plan,and study the factors such as the amount of carbon CNTs,bone cement ratio and fly-ash content on the compressive strength of the sample influences.The results show that the ratio of bone glue to single factor has a great influence on the strength of the sample.The compressive strength of the sample is the largest when the amount of CNTs is 0.10%.?2?Analyze the action mechanism of carbon nanotubes to improve the compressive strength of specimens by means of SEM and EDS test methods,and analyze the failure rule of specimens using digital speckle cloud images.The ultimate strain can reach 0.045,which meets the requirements of surrounding rock pressure relief material.?3?Analyze the decompression effect of the reserved foamed concrete deformation layer on the surrounding rock of the tunnel by the method of comparative similar model test,and analyze the change law of the strain field and stress field of the surrounding rock.The results show that the reserved deformation layer has a certain pressure relief effect on the surrounding rock of the tunnel.The concept of"pressure relief efficiency"is proposed to describe the pressure relief effect of the material of the deformation layer,and the function of different stress loads and pressure relief efficiency is fitted by a quadratic function relationship.?4?Use FLAC^3D software for numerical simulation.The results show that setting the reserved foamed concrete deformation layer can effectively control the vertical displacement and horizontal displacement of the surrounding rock of the tunnel after loading.The overall change trend of the pressure relief efficiency obtained is consistent with the results of similar simulation tests while is slightly lower in numerical size,and make suggestions for the modification of the material thickness of the deformed layer during engineering application.There are 61 pictures,12 tables,and 54 references in this thesis.