大地材料依時變形對隧道收斂特性之影響

Abstract

隧道施工變形控管為現代隧道施工之重要理念之一，當變形量達一穩定後方能設置二次襯砌；目前國內許多進入「中、老年期」的隧道深處於數百公尺地底以下，施工過程既無災害記錄，亦無大量變形情況，卻於完工營運後數年開始出現異狀，且逐年惡化；如何掌握營運中隧道長期穩定的影響因素，及早展開系統性的安全檢測與評估，適時進行維護與延壽，已成為隧道工程極為重要之課題。欲探討營運後結構長期穩定的特性，必先瞭解施工過程的依時變形行為，而欲瞭解施工過程的依時變形的行為，必先納入大地材料黏彈塑特性對工程行為的影響。 大地材料在承受應力達特定門檻以上常顯露依時變形行為，其特性不同於廣泛應用的彈塑性組成關係所描述者，而造成工程行為具有依時變化的現象，欲在既有的彈塑模式下納入依時變形特性，受限於分析程序的複雜性以及參數取得的困難度等因素，在工程實務上仍不多見。 因此本研究以探討隧道依時收斂變形為目的，透過：(1)隧道開挖的力學機制與長期影響因素的研究；(2)非線性黏彈塑模式的建立；(3)數值模擬與監測案例的比對進行參數反算；(4) 比較不同開挖與支撐條件之隧道周圍應力分佈與收斂特性等四方面，進行分析與探討。 數值分析方面，將柏格模式撰寫修改成阻尼參數隨應力狀態變化，改善既有黏彈模式於不同應力狀態下考慮不足的缺憾，經過測試無誤後，進而探討不同開挖與支撐方式隧道周圍的應力分佈，以及該應力狀態下周圍材料阻尼參數的變化，以至於其引致的隧道收斂變形特性，並闡述大地材料依時變形特性對隧道長期穩定性的影響。研究結果將可以提隧道長期穩定分析之參考。

The controlling of convergence deformation is an important concept in modern tunneling technique, and the second lining well be installed when deformation of rock surrounding tunnel is under control as the NATM method. In Taiwan, numbers of tunnels in middle to old ages increase with time rapidly, which deteriorate after years of performance, but there are no ruptures during construction and few numbers of deformations on rock when tunneling. So it is important to know well about the factors affecting their long-term stability. In order to know well about tunnel structure systems in long-term stability characteristics, we must understand how time-dependent deformations occur during tunneling in first. Secondly, it is necessary to consider the influences by visco-elastio-plastic mechanics behavior of geo-materials. Time-dependent deformation behaviors usually appear when geo-materials are abide by stress which is larger than creep critical stress threshold. It is different between time-dependent deformation behaviors and elasto-plastic constitutive model which is been applied extensively in tunnel convergence mechanisms. Some models combine elasto-plastic constitutive law with time-dependent characters which are too many complex procedures for analysis and the parameters are too hard to obtain, so they are difficult to use in engineering application. This research aims to know well about tunnel time-dependent convergence deformations by using: (1) the influences of long-term factors and mechanics mechanisms during tunneling; (2) a non-linear visco-elasto-plastic constitutive model; (3) numerical simulations and monitoring measurements data for parameters by back-analysis; (4) time-dependent constitutive numerical model of different excavation forms and support systems and discuss stress around tunnel and convergence behaviors. Base on the original Burgers rheological model, the model in this research modifies the viscous parameter as a function relative to different stress states. After test and verify confidentially, the model can improved the defects that classic visco-elastic model cannot consider different stress states mechanics mechanisms. The numerical results show that the model can understand the phenomena at time-dependent deformation for geo-materials and underground structures during tunneling, and it also can be used for tunnel long-term stability research.