季冻区隧道衬砌渐进劣化规律及工程影响

Progressive deterioration of tunnel lining in seasonal freezing zone and its engineering influence

为研究季节性冰冻区隧道服役数年后衬砌混凝土劣化对隧道结构的影响,以隧道温度场测试结果为基础,建立隧道衬砌渐进劣化模型,通过数值模拟研究了隧道结构发生劣化后的工程影响。对甘肃省乌鞘岭隧道群3座不同长度的隧道,采用智能温度记录仪并以小时为监测频率对隧道温度场进行了测试,揭示了季冻区温度日周期正负温交替引起隧道衬砌混凝土经受非饱和冻融循环的现象。基于隧道纵向和横断面冻融循环次数的分布规律,建立衬砌渐进劣化荷载结构模型,分析其对隧道结构的影响。研究结果表明:隧道衬砌结构经历的日周期冻融循环次数随距洞口的距离增加而减少,且1个年周期内隧道洞口段可经历上百次冻融循环作用;衬砌结构经历的冻融循环次数随隧道径向深度增加而减少,在衬砌表面经历138次冻融循环时,径向深度5 cm处可经历77次冻融循环;衬砌混凝土的劣化程度与其经受的非饱和冻融循环次数相关,呈现从衬砌表面到衬砌内部逐渐减弱的分布,从隧道洞口到隧道中部逐渐减弱的分布规律;衬砌混凝土随服役年限逐渐劣化改变了结构的受力状态,随服役年限增加,截面安全系数由混凝土抗压强度控制变为混凝土抗拉控制,拱顶截面的安全系数明显减小,拱顶受拉区宽度逐渐增大。

To study the influence of deterioration of concrete on secondary lining structure after several years of service in the seasonally frozen zone,based on the results of temperature field test in the tunnel,the progressive deterioration model of tunnel lining was established,and the effects of tunnel structure degradation were studied by numerical simulation.Relying on 3 tunnels with different lengths in Wushaoling Tunnel group,Gansu Province,the temperature field of the tunnels was tested by using intelligent temperature recorder and hourly monitoring frequency.The test results revealed that the tunnel lining concrete was subjected to unsaturated freeze-thaw cycle due to the daily alternation of positive and negative temperatures.Based on the distribution rules of freeze-thaw cycles in the tunnel,a calculation model was established by using the load-structure method,in which the lining structure was progressively deteriorated,and the impact of degradation on the lining structure was analyzed.The results show that the number of daily freeze-thaw cycles experienced by the tunnel lining decreases with the increase of the distance from the tunnel portal,and the lining near the portal can experience hundreds of freeze-thaw cycles in a year,the number of freeze-thaw cycles experienced by lining structure decreases from lining surface in the cross section.When the lining surface experiences 138 freeze-thaw cycles,the lining at the radial depth of 5 cm can experience 77 freeze-thaw cycles.The deterioration degree of lining concrete is related to the number of unsaturated freeze-thaw cycles,and presents a gradually weakening distribution from the lining surface to the lining interior,and from the tunnel portal to the middle of the tunnel.With the increase of service life,the progressive deterioration of concrete changes the stress state of the structure,the control principle of the safety factor of lining changes from concrete compressive strength to concrete tensile strength.The safety factor of lining in vault decreases obviously,and the width of tensile zone in vault increases gradually.1 tab,16 figs,22 refs.