通风条件下高原寒区隧道围岩冻胀破坏机理及其防寒保温技术研究

Cold region distributes broadly in china. In tunnel construction in west and north cold area, frost is a serious problem. In condition of ventilation, frost heaving character, freezing-thawing damage of surrounding rock in cold region tunnel and its cold-proof insulation technology are related to airflow velocity, temperature of air and surrounding rock, seepage and stress of surrounding rock. The problem is Thermal-Hydro-Mechanical (THM) coupling. To solve this problem, experiment tests, theoretical analysis, numerical simulation, in-situ monitor and inversion analysis are adopted here. Aiming to the airflow feature in tunnel, reasonable air-flowing model is established. Then, the distribution of airflow velocity and air temperature in the tunnel axial direction is studied, as well as the heat exchange between air and surrounding rock. According to the climate variation in cold region, a method on determination of thermal, hydraulic and mechanical material parameters of rock and soil medium is proposed, considering freezing-thawing. And the freezing-thawing damage on surrounding rock is studied. Then, THM coupled model is established to study the variation of stress, seepage and temperature of surrounding rock, considering phase change of water/ice and freezing-thawing damage. Combining with the measurements of temperature, seepage and stress of surrounding rock and liner in situ at different depth, inversion method on thermal, hydraulic and mechanical material parameters of surrounding rock in tunnel under ventilation is proposed. The area affected by frost heaving in Galongla tunnel is predicted. From this study, a scientific guide is provided for the determination of depth and length of cold-proof insulation layer of tunnel in cold region.

我国寒区分布面积广，冻害问题严重威胁着西部高原和北部严寒地区隧道的安全稳定。通风条件下寒区隧道的围岩冻胀特性、冻融劣化规律及其防寒保温技术涉及复杂的空气风流速度场、空气及围岩温度场(T)、围岩渗流场(H)和应力场(M)的耦合问题。为解决该技术难题，本项目拟通过室内试验，理论分析，数值模拟，现场监测和反演分析等方法。针对隧道内风流场特点，建立合理的风流场模型，揭示风速和风温随隧道进深的变化情况及其与围岩热交换规律；根据寒区气候特征，提出冻融条件下岩土介质热、水和力学参数取值方法及损伤演化规律，建立合理的温度-渗流-应力(THM)三场耦合模型，揭示冰/水相变和冻融损伤影响下的围岩温度、渗流及应力变化规律；结合现场不同深度围岩和衬砌温度、渗流及应力场在线监测结果，提出通风条件下隧道围岩热、水和力学参数的反演分析方法，预测嘎隆拉隧道的冻胀影响范围，为寒区隧道的防寒保温层厚度和长度设计提供科学指导。

我国寒区分布面积广，冻害问题严重威胁着西部高原和北部严寒地区隧道的安全稳定。通风条件下寒区隧道的围岩冻胀特性、冻融劣化规律及其防寒保温技术涉及复杂的空气风流速度场、空气及围岩温度场(T)、围岩渗流场(H)和应力场(M)的耦合问题。为解决该技术难题，本项目通过室内试验，理论分析，数值模拟，现场监测和反演分析等方法，针对隧道内风流场特点，建立合理的风流场模型，揭示风速和风温随隧道进深的变化情况及其与围岩热交换规律；根据寒区气候特征，提出冻融条件下岩土介质热、水和力学参数取值方法及损伤演化规律，建立合理的温度-渗流-应力(THM)三场耦合模型，揭示冰/水相变和冻融损伤影响下的围岩温度、渗流及应力变化规律；结合现场不同深度围岩和衬砌温度、渗流及应力场在线监测结果，提出通风条件下隧道围岩热、水和力学参数的反演分析方法，预测嘎隆拉隧道的冻胀影响范围，为寒区隧道的防寒保温层厚度和长度设计提供科学指导。从多孔随机混合介质理念出发，提出了考虑相变及未冻水影响的冻融条件下岩土类材料的导热系数计算的新方法，并根据已有的试验数据，利用多孔随机混合介质模型求出了同等条件下的导热系数。比选出9种材料作为本次高性能泡沫混凝土研制的基本原料；采用正交试验方法，研究了各种原材料对泡沫混凝土的密度、吸水率、抗压强度、劈裂抗拉强度等一系列基本性能的影响，优选出一种泡沫混凝土配方，重点对其保温性能和冻融特性进行研究，开发出兼具轻质、保温、抗冻、抗裂和抗震等功能，特别适合于寒区工程保温层及抗震层使用的泡沫混凝土。根据含低温相变岩体温度场控制方程，分析了寒区隧道围岩与二衬混凝土热量迁移传递规律，系统研究了隧道内环境温度、浇注时洞内加热温度和加温时间对二衬模筑混凝土温度变化规律的影响，并提出了一简洁、实用的加温时间计算公式。