| The construction of roads,railways,tunnels and other infrastructure in our country is booming,and its scale ranks first in the world.Fire disaster is a catastrophic accident in underground engineering with great hazards and a wide range of disasters,which has attracted the attention of the engineering field.This article takes the Wuhuang highway tunnel project in Anhui Province as the background,takes the rock-concrete interface specimens as the research object,and comprehensively uses laboratory tests and numerical simulation methods to study the degradation characteristics of interface between tunnel surrounding rock and concrete after high temperature fire.The main research contents and conclusions are as follows:(1)Based on three-dimensional carving technology and three-dimensional scanning technology,the preparation of sandstone-concrete interface specimens with different interface roughness has been realized.Through physical and mechanical experiments,the physical and mechanical characteristic parameters of sandstone and concrete materials after high temperature treatment were measured respectively,and the change laws of the mechanical properties of sandstone and concrete with temperature was summarized.(2)The effects of temperature and interface JRC on the mechanical properties of sandstone-concrete interface specimens were studied by uniaxial compression and Brazilian splitting tests.With the increase of temperature,the peak strength,elastic modulus,secant modulus and tensile strength of sandstone-concrete interface specimens show a significant downward trend.With the increase of JRC,the mechanical properties of sandstone-concrete interface specimens first decline and then improve.Compared with interface JRC,temperature plays a dominant role to a certain extent,which has a more profound impact on the mechanical properties of sandstone-concrete interface specimens.(3)Based on digital photography and acoustic emission measurement technology,the crack evolution processes and failure characteristics of sandstone-concrete interfaces under uniaxial compression and Brazilian splitting were studied quantitatively.Under uniaxial compression,with the increase of temperature,the main crack form of sandstone-concrete interface specimens gradually changes from tensile crack to shear crack,and the failure mode changes from tensile failure to mixed tensile shear failure to shear failure.With the increase of interface JRC,the crack form changes from tensile crack to mixed tensile shear crack,and the failure mode gradually changes to mixed tensile shear failure.(4)The three-dimensional particle flow model of the rock-concrete interface specimen in the form of "Ball+Clump" particles was established using PFC3 D.The crack evolution laws and failure mode of the rock-concrete interface specimens under uniaxial compression and Brazilian splitting conditions were reproduced.And the influences of temperature and interface JRC on the total number of cracks,the types and corresponding proportions of cracks,the spatial distribution of cracks,the characteristics of crack inclination and the failure mode of specimens are analyzed.(5)Based on the actual characteristic parameters of Wuhuang Expressway Tunnel Engineering in Anhui Province,the PFC3 D numerical simulation method is used to explore the deformation and fracture evolution laws of tunnel surrounding rock-concrete structure after different temperature fire disasters.In general,the deformation of the tunnel vault is the largest,followed by the two sides.The main form of cracks in surrounding rock is shear cracks,which are distributed uniformly.A few tensile cracks are concentrated in the vault and the middle of two sides.There are 97 figures,12 tables and 110 references in this thesis. |
