Study On Mechanical Properties Of Shotcrete Under High Rock Temperature Based On Pore Structure Characteristics

High geothermal is one of the common environment and phenomenon in deep geotechnical engineering,which seriously affects the overall stability of concrete lining structure and restricts the implementation of "deep ground strategy",and has become a current research hotspot.This thesis is based on the Xinjiang Qirehatar diversion tunnel project to study the effects of high rock temperature and environmental humidity on the mechanical properties and pore structure of shotcrete.Analyze the correlation between the mechanical properties and the pore structure characteristics by establishing the gray correlation analysis model.Draw the following conclusion:(1)The mechanical properties and pore structure of sprayed concrete under different test conditions are quite different.In a low-humidity environment,as the temperature of the surrounding rock increases,the mechanical performance of the sprayed concrete decreases,and the pore structure gradually deteriorates;In a high-humidity environment,the temperature of the surrounding rock increases,the mechanical properties of shotcrete increase first and then weaken,60℃ is the critical temperature,and the pore structure generally deteriorates with the increase of the surrounding rock temperature.(2)The grey relational analysis model is used to analyze the correlation between the pore structure parameters and mechanical characteristic parameters of shotcrete.The results show that there is a strong correlation between the pore structure parameters and the parameters of different mechanical properties.the order of correlation degree is as follows: fractal dimension of pore volume > average pore diameter > pore roundness >porosity.(3)The prediction model of unconfined compressive strength of shotcrete considering the influence coefficient of relative humidity was established,the comparative analysis proves the scientific rationality of the new forecasting model.