考慮隧道開挖對裂隙岩體滲透特性影響之近場地下水流模擬

Abstract

滲水為山岳隧道常見的現象，而地下水作為影響山岳隧道安全性及服務性的重要環境因子之一，並且其影響可從施工階段至營運階段，對於隧道的結構穩定及功能性帶來挑戰。因此從設計乃至營運階段皆不易掌握隧道襯砌外的地下水水壓與匯集至隧道的流量。儘管現代隧道仍有設置排防水系統，但營運中隧道仍存在滲水、湧水的風險，相關營運中山岳隧道湧水的案例發生雖為罕見，但也凸顯出當實際考量地下水影響隧道時仍有精進的空間。。 本研究旨在建置考量標準隧道斷面及真實隧道排防水系統建立地下水滲流與山岳隧道互制關係的三維模擬數值技術。同時，實際山岳隧道環境中，圍岩往往為節理發達之岩體，其滲透特性隨應力變化與節理變形而變動，特別在隧道開挖過程中更為明顯。故本研究首先基於等值節理岩體組成律模式建立隧道開挖模型，分析節理內寬變化，據以評估山岳隧道開挖後圍岩水力特性的變化，繼而探討隧道開挖後近場的地下水流。 本研究探討情境分為無裂隙與裂隙位態(走向/傾角)為 N0E/0˚E、N0E/22.5˚、EN0E/45˚E、N0E/67˚E及N0E/90˚E，模擬結果顯示，節理傾角影響隧道圍岩水壓與入流量的分佈特徵。當節理發生顯著開張時，將從原本裂隙內寬1mm變化至最大裂隙內寬4.5mm。隧道支撐承受水壓力在考量節理時將相比無考量節理大0.13MPa，並且當考量節理因開挖擾動後開張也較無考量大0.15MPa左右。隧道導水層之入流量在考量節理時將相比無考量節理大10倍，並且當考量節理因開挖擾動後開張也較無考量大3倍。顯示節理變形與入流量具有高度相關性。 本研究為營運中山岳隧道應對地下水影響上提供更科學的建議。期望作為未來隧道排水與防水系統設計及營運管理之參考，進而提升山岳隧道工程於全生命週期中的韌性與使用安全。

Seepage is a common phenomenon in mountain tunnels, with groundwater recognized as a critical environmental factor affecting both the safety and serviceability of such tunnels. Its influence spans from the construction phase to the operational phase, posing significant challenges to the structural stability and functional performance of tunnels. However, it remains difficult to accurately assess the external groundwater pressure on tunnel linings and the associated inflow throughout the tunnel’s life cycle. Although modern tunnels are equipped with drainage and waterproofing systems, the risks of seepage and water ingress persist during operation. Even though water inrushes in operating mountain tunnels don’t happen often, they show why it’s important to better understand and manage groundwater issues.". This study aims to develop a three-dimensional numerical simulation framework that consider standard tunnel cross-sections and actual drainage and waterproofing systems to investigate the interaction between groundwater seepage and mountain tunnels. In real-world scenarios, surrounding rock masses are typically composed of jointed rock, whose hydraulic properties vary with stress and joint deformation. Especially tunnel excavation. Therefore, the tunnel excavation model based on the equivalent jointed rock mass constitutive framework is established, and uses it to analyze joint aperture variations and evaluate the hydraulic behavior of the surrounding rock post-excavation. This enables detailed exploration of near-field groundwater flow characteristics around tunnels. The study examines four scenarios: intact rock mass (no joints), and three joint orientations with strike/dips o configuration f N0E/0˚E,N0E/90˚E,N0E/22.5˚,EN0E/45˚E,N0E/67˚E. Simulation results demonstrate that joint dip angles significantly influence the distribution of groundwater pressure and inflow around the tunnel. When joints experience opening, preferential flow paths may develop, resulting in localized concentration of groundwater pressure and inflow. These findings reveal a strong correlation between joint deformation and inflow behavior. The outcomes of this study provide scientific insights into managing groundwater impacts in operating mountain tunnels. The proposed methodology serves as a reference for future drainage and waterproofing system designs and operational strategies.