寒区隧道内气温分布特征及影响因素

Longitudinal distribution characteristics of air temperature and influence factors in cold region tunnels

受严寒气候影响,寒冷地区的隧道工程普遍面临不同程度的衬砌挂冰、冻融损伤甚至开裂、路面结冰、排水系统冻结失效等一系列冻害问题,给隧道工程的建设和运营带来了极大的挑战。负温环境是隧道冻害产生的必要条件,掌握隧道内气温沿进深方向的分布是寒区隧道冻害研究和工程防治措施采取的基础和前提。然而,不同寒区隧道工程的隧址区环境气象、工程结构和交通情况等因素各不相同,导致不同隧道内气温的分布特征存在显著差异。因此,准确地预测和获取寒区隧道内气温纵向分布仍是亟待解决的问题。为得到寒区隧道内气温分布特征及其影响因素,本文采用文献调研和数据统计与分析的方法,收集整理了我国52座寒区隧道内气温的现场监测数据以及相关影响因素数据。依据寒区隧道内气温分布特征,将其划分为对称型、非对称型和贯通型三类,并对各类型寒区隧道的长度和埋深情况进行了统计分析。在此基础上,探讨了隧址区气温和隧道围岩地热以及洞内通风对隧道内气温分布的影响机制,之后针对引起隧道内空气流动的自然风、工程建设、机械通风和交通情况四类因素进行了分析,并指出各类因素的主次影响顺序。研究表明,当隧道两端洞口自然环境要素基本相同且两端洞口高差不大时,隧道内气温往往呈对称型分布;当隧道内存在较大纵坡坡度或受洞外盛行风向影响时,隧道内气温多呈非对称型分布;而当隧道长度较短、埋深小且盛行单向风时,隧道内气温分布常为贯通型。隧址区(隧道进出口)环境气温对隧道内气温分布起决定性作用,隧道埋深状况决定了地热作用从而对洞内气温产生重要影响。通风是影响隧道内气温的关键因素,其中自然风、工程中纵坡设计因素分别为进出口高差较小、长度较短的隧道和进出口高差较大、长度较长的隧道内气温分布的主导因素,工程附属结构、机械通风、交通情况为相对次要因素。本研究工作可为寒区隧道冻害问题研究和保温设防设计以及运营维护提供参考。

Affected by the severely cold climate,cold region tunnels are often faced with a series of frost damage problems,such as lining ice hanging,freeze-thaw damage or cracking,road icing and drainage system freezing failure,which pose great challenges to the construction and operation of tunnels.The sub-zero temperature environment is the necessary condition for frost damage in tunnels,thus mastering the longitudinal distribution of air temperature in tunnels is the basis and premise of frost damage research and engineering control measures in cold regions.However,various tunnels differ in environmental meteorology,engineering structure and traffic conditions significantly,resulting in obvious discrepancies in the longitudinal distribution characteristics of air temperature,causing many difficulties in accurately predicting and obtaining the longitudinal distribution of air temperature inside cold region tunnels.Therefore,in order to obtain the distribution characteristics and influence factors of air temperature in cold region tunnels,literature research and statistics and analysis methods were used to collect and sort the field measuring data and related influence factors of air temperature inside 52 cold region tunnels in China.According to the distribution characteristics of air temperature inside tunnels in cold regions,they are divided into three types:symmetric,asymmetric and cut-through type,and then the length and burial depth of each type of cold region tunnels are statistically analyzed.On this basis,the influential mechanism of temperature in tunnel site area,geothermal heat of surrounding rock and ventilation in tunnel on air temperature in the tunnels is discussed.Subsequently,the natural wind,engineering construction,mechanical ventilation and traffic factors that cause air flow inside the tunnel were analyzed,and then the primary and secondary influence order of each factor was pointed out.The research results indicate that when the natural environmental factors at both ends of the tunnel portal are basically the same and the elevation difference between the two ends of the entrance is not significant,the air temperature inside the tunnel usually shows a symmetrical distribution.When there is a significant slope inside the tunnel or it is affected by the prevailing wind direction outside the tunnel,the air temperature inside the tunnel often shows an asymmetric distribution.When the tunnel length is short,the burial depth is small and unidirectional wind is prevalent,the air temperature distribution inside the tunnel often presents a cut-through type.In addition,in terms of the primary and secondary factors affecting the temperature distribution inside cold region tunnels,the environmental temperature in the tunnel site area(tunnel entrance and exit)plays a decisive role in the distribution of temperature inside the tunnel,the burial depth of the tunnel determining the geothermal effect has an important impact on the temperature inside the tunnel,and ventilation is the key factor affecting the temperature inside the tunnel.Among the various factors affecting ventilation,natural wind and longitudinal slope design are the main factors influencing the longitudinal distribution of air temperature inside tunnels with slight entrance and exit elevation differences and short lengths and tunnels with significant entrance and exit elevation differences and long lengths respectively,while engineering ancillary structures,mechanical ventilation and traffic factors are relatively secondary.This research will provide reference for the study of frost damage,insulation laying design and operation and maintenance of cold region tunnels.