高地温喷射混凝土宏细观损伤特征试验分析

高地温是我国深部地下工程开发中普遍存在的现象之一,高地温喷射混凝土的损伤问题已成为国内外研究的热点与难点问题。在现有研究成果的基础上,通过喷射混凝土试件单轴压缩、巴西劈裂、超声波测试以及CT扫描试验,采用波速定义相对损伤量,采用抗压强度、拉压比、孔隙比作为喷射混凝土损伤的宏细观表征参数,分析不同围岩温度条件下喷射混凝土的抗压强度、拉压比、孔隙比、相对损伤量的演化规律。结果表明：喷射混凝土的拉压强度均随着温度的升高逐渐弱化,抗压强度对温度的变化更加敏感；波速与温度呈现线性负相关,而相对损伤变量与温度呈现非线性正相关；温度升高导致喷射混凝土内部孔隙分布密集化,空隙之间贯通,形成初始缺陷,引发温度损伤加剧。相关研究成果可望为我国高地温环境下隧洞安全施工与运营提供理论依据。

Experimental analysis on macro-meso damage characteristics of high ground temperature shotcrete

I High ground temperature is one of the common phenomena in the development of deep underground engineering in China. The damage problem of high ground temperature shotcrete has become a hot and difficult problem at home and abroad. Based on the existing research results, through uniaxial compression test, Brazilian splitting test, ultrasonic test and CT scanning test of shotcrete specimens, the relative damage is defined by wave velocity, and the compressive strength, tensile-compression ratio and void ratio are used as macro and micro characterization parameters of shotcrete damage to analyze the evolution law of compressive strength, tensile-compression ratio, void ratio and relative damage of shotcrete under different surrounding rock temperatures. The results show that the tensile and compressive strength of shotcrete gradually decreases with the increase of temperature, and the compressive strength is more sensitive to the change of temperature. Wave velocity has a linear negative correlation with temperature, while the relative damage variable has a nonlinear positive correlation with temperature. The increase of temperature leads to the dense distribution of pores in shotcrete, the coalescence of pores, the formation of initial defects, and the aggravation of temperature damage. The relevant research results are expected to provide a theoretical basis for the safe construction and operation of tunnels under high geothermal environment in China.