高温变温环境下喷射混凝土–岩石界面剪切特性及温度损伤模型研究

高岩温隧道修建过程中,喷射混凝土结构实际上是在高温变温环境下水化成型并发挥支护作用。基于隧道内实测环境参数及初支混凝土温度数据,开展混凝土–岩石界面剪切力学特性试验。根据试验结果,探明隧道内初期支护混凝土的温变周期,对比分析试样剪切破坏模式、界面剪切强度、位移在不同变温条件下的发展特征。通过讨论剪切变形曲线特点,建立考虑温度损伤效应的岩石–混凝土界面剪切本构模型。结果表明:初支混凝土在5～7 d可降至洞内环境温度。随着初始养护温度的升高,剪切曲线峰前弹性增长,压密硬化及峰后弹性软化规律明显。剪切破坏模式主要为胶结面及混合剪切破坏2种。峰值剪切应力与养护温度呈负增长函数关系,峰值剪切位移与养护温度呈正增长函数关系,且法向应力水平的增加对于温度引起的力学特性损伤有一定的削弱作用。基于室内剪切力学特性试验成果,建立考虑温度损伤及法向应力修正的岩石–混凝土界面剪切本构模型。通过计算曲线与试验曲线的对比验证,表明两者拟合度较高,该本构模型可以适用于分析不同程度高温损伤下的混凝土–岩石界面剪切力学特性。研究结论可以为受高温影响的隧道及地下工程支护设计和分析提供一定理论支撑。

Experimental study on shear mechanical properties and thermal damage model of shotcrete-rock interfaces under variable high temperatures

Shotcrete structures of geothermal tunnels are molded by hydration action under variable high temperatures and play a supporting role. Based on environment parameters in the tunnel and temperatures of the initial support,shear tests of concrete-rock interfaces were carried out. According to the experimental results,the temperature change period of the initial support concrete was ascertained. The shear failure mode, the interface peak shear strength and the displacement were analyzed under different temperatures,and a concrete interface shear constitutive model of concrete-rock interfaces considering temperature damage effect was proposed. The results show that the temperature of the initial shotcrete declines to the environment temperature in the tunnel within 5–7 days. With the increase of the initial curing temperature,the shear curve shows elasticity before the peak,and compaction hardening and elastic softening after the peak. The peak shear stress is a negative growth function of the curing temperature,but the peak shear displacement has a positive relationship with the curing temperature. The normal stress has a weakening effect on the temperature damage characteristics. Based on the indoor shear test results,a rock-concrete interface shear constitutive model considering temperature damage and normal stress correction was established. Comparisons between the theory curves and the experimental curves were performed and a good agreement was observed. The constitutive model can be applied to the analysis of the shear-mechanical properties of the concrete-rock interfaces with different degrees of high-temperature damage and can provide some support for the design and analysis of tunnels and underground engineering affected by high temperatures.