隧道循环进尺及台阶长度与浅埋下穿段结构变形特性关系  

The relationship between cyclic penetration and step length of tunnel and structural deformation characteristics of shallow buried section

作　　者：刘广发 Liu Guangfa(China Railway 24th Bureau Group Fujian Railway Construction Co.,Ltd.,Fuzhou Fujian 350000,China)

机构地区：[1]中铁二十四局集团福建铁路建设有限公司,福建福州350000

出　　处：《山西建筑》2024年第16期162-166,共5页Shanxi Architecture

摘　　要：依托福建某城市主干道大跨径隧道浅埋下穿高速公路工程,基于新奥法,结合大跨径隧道浅埋下穿既有高速公路工程实际特点,应用Midas有限元分析软件分别建立3 m,2 m,1 m,0.5 m不同循环进尺以及20 m,15 m,10 m,6 m不同台阶长度的三台阶开挖有限元模型,分析了在同条件支护情况下采用不同开挖方式对下穿高速公路深挖路堑路面及围岩变形关系。并与工程实际监测值进行比对分析,结果表明,在15 m相同台阶长度下,采用不同循环进尺进行开挖时,3 m循环进尺水平收敛最大值为9.66 mm,0.5 m循环进尺水平收敛最大值为8.63 mm,减小循环进尺可降低10%水平收敛值,但是在路面沉降、拱顶沉降以及隧底隆起变形中4种工况结果相近,无明显变化。在下穿深挖路堑段施工过程中,路面最大变形位置发生在路肩与坡脚交汇处,该结论与工程实测结果相一致,验证了计算分析的合理性;在3 m相同循环进尺下,采用6 m~20 m不同台阶长度开挖时,路面及围岩变形随着台阶长度的减小而降低,其中路面沉降变形降低最为明显达到24.7%;在三台阶法中,路面沉降变形增量主要发生在第二台阶开挖过程中,占比最大可达59.9%,但它随着台阶长度的减小而降低,最后各阶段增量趋于平衡;随着最后一级台阶开挖完成后,隧道水平收敛值会突然减小,而且这个转变会随着台阶长度的增加而越为明显。结合研究分析结果,提出合理的台阶循环进尺和开挖步距,以指导现场施工,对关键部位和关键工序增加必要的变形控制措施,经实践证明计算研究结果是合理的,提出的开挖方法是可行的。Based on the new Austrian Method and combined with the actual characteristics of existing expressway engineering,this paper relies on the shallow buried expressway project of long-span tunnel in a city of Fujian.Midas finite element analysis software was used to establish three step excavation finite element models with different cyclic penetration rates of 3 m,2 m,1 m and 0.5 m and different step lengths of 20 m,15 m,10 m and 6 m,respectively,and to analyze the relationship between the deformation characteristics of the pavement and surrounding rock in deep cutting of the underpass expressway under the same supporting conditions by using different excavation methods.Compared with the actual monitoring value of the project,the results show that under the same step length of 15 m,when the excavation is carried out with different circular footage,the maximum horizontal convergence of 3 m circular footage is 9.66 mm,and the maximum horizontal convergence of 0.5 m circular footage is 8.63 mm.Reducing the circular footage can reduce the horizontal convergence value by 10%.However,the results of the four working conditions are similar in road settlement,arch settlement and tunnel bottom uplift deformation,and there is no significant change.During the construction of the deep cut section,the maximum deformation of the road surface occurs at the intersection of the shoulder and the foot of the slope.The conclusion is consistent with the measured results,which verifies the rationality of the calculation and analysis.Under the same circular footage of 3 m,when the length of step is 6 m~20 m,the deformation of pavement and surrounding rock decreases with the decrease of step length,and the settlement deformation of pavement decreases most obviously by 24.7%;In the three-step method,the increment of pavement settlement deformation mainly occurs in the process of the second step excavation,accounting for the largest proportion of 59.9%,but it decreases with the decrease of step length,and the increment of each stage tends to

关 键 词：大跨径隧道 浅埋下穿 循环进尺 台阶长度 变形特性 

分 类 号：TU997[建筑科学—市政工程] U455[建筑科学—桥梁与隧道工程]