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Empirical approaches play a significant part in the prediction of squeezing conditions in tunnels or caverns. On analysis of collected squeezing data from published literature, no empirical squeezing equations have been found for tunnels with a depth of more than 850 m. In this paper, an attempt has been made to generate linear classifications usin...
Citations
... Tunneling through heterogeneous rock masses, particularly formations like flysch, presents a unique set of challenges that demand early identification of potential risks. Accurate predictions are crucial for tunnel designers to make informed decisions about route selection and resource allocation to address anticipated tunneling problems (Jain and Rao 2022). One prominent challenge in tunneling projects is tunnel squeezing, a phenomenon defined by the International Society for Rock Mechanics (ISRM) as the deformation around the tunnel causing stress on the tunnel liner (Jain and Rao 2022). ...
... Accurate predictions are crucial for tunnel designers to make informed decisions about route selection and resource allocation to address anticipated tunneling problems (Jain and Rao 2022). One prominent challenge in tunneling projects is tunnel squeezing, a phenomenon defined by the International Society for Rock Mechanics (ISRM) as the deformation around the tunnel causing stress on the tunnel liner (Jain and Rao 2022). Tunnel squeezing, quantified as the normalized tunnel convergence (ε), is the percentage ratio of radial tunnel wall displacement to tunnel radius. ...
Understanding tunneling-induced ground deformation, particularly squeezing behavior, is crucial for safe and efficient underground construction. This study employs Artificial Neural Networks (ANN) and Multivariate Adaptive Regression Splines (MARS) models to predict tunneling squeezing behavior using various rock classification systems, namely rock quality index (Q), rock mass rating (RMR), and geological strength index (GSI). The objective is to assess model performance, evaluate the influence of classification systems, and conduct sensitivity analyses on key parameters. The investigation reveals that both ANN and MARS models exhibit enhanced accuracy as model complexity increases, up to a critical point where overfitting occurs. Comparing model performance, ANN outperforms MARS, and the most accurate ANN model is identified as ANN50-RMR with an R2 of 0.978. This confirms the ANN’s capability to capture non-linear relationships inherent in tunneling-induced ground deformation. Choosing a rock classification system as an input parameter significantly impacts model accuracy. RMR and GSI classification systems exhibit improved performance over the conventional Q-system. In particular, GSI-based models offer more consistent and accurate predictions, emphasizing GSI’s suitability for modeling tunneling squeezing behavior. Variables’ importance analysis elucidates the dependence of parameter relevance on the chosen classification system. Sensitivity analyses on tunnel depth, diameter, and rock mass deformation modulus reveal logical correlations between these parameters and tunnel squeezing behavior, further validating model predictions. By enhancing our understanding of tunneling-induced ground deformation, these models contribute to safer and more efficient underground construction practices.
... underground spacing is an outstanding alternative and this leads to an increase in the demand for tunnel construction. Unfortunately, tunnels and associated infrastructure damages due to the 1995 Kobe earthquake in Japan, the 1999 Chi-Chi earthquake in Taiwan, the 2008 Wenchuan earthquake in China, and the 2016 Kumamoto earthquake in Japan discarded the belief in the structural safety of underground structures during seismic events (Ansari et al. 2022a;Tsinidis et al. 2020a;Wang and Li 2021;Jain and Rao 2022). Seismic risk assessment for tunnels is performed for urban planning and formulation of structural design and safety policies (Argyroudis and Pitilakis 2012a;Hu et al. 2022;Yao et al. 2019). ...
In the last few decades, Jammu and Kashmir has faced many moderate to large earthquake events that caused catastrophic damage to the physical infrastructure and significant socioeconomic loss. The growing number of infrastructure projects, as well as previous historical records of severe earthquakes in this area demand the study of the seismic vulnerability of tunnel. In this paper, an attempt has been made to develop the seismic fragility curves for circular tunnels located in four distinct zones classified based on seismic microzonation results of the Jammu Region (JR). The damage probabilities of shallow tunnels in these zones decrease fiercely as lining thickness increases. Furthermore, increasing PGA by 0.2 g increases the exceedance probabilities for minor, moderate, and extensive damage exposed to 82%, 89%, and 93%, respectively for shallow tunnels. The fragility functions proposed for Jammu and Kashmir were employed to assess seismic risk for tunnels under Udhampur Srinagar Baramulla Rail Link (USBRL) project. Most of the tunnels in Phase 3 showed more than 50% of damage probability for the region specific defined seismic environment.
The Rohtang tunnel is an important road tunnel in the Himalayas providing all weather connectivity between Manali and Keylong, headquarter of the Lahul Spiti District. Major folds and faults are present in and near the vicinity of the Rohtang tunnel indicating the complex geology of the area. The 8.8-km-long tunnel consists of uniformly dipping sequences of phyllites/schists and gneissose rocks with an average overburden of about 600 m and a maximum of 1900 m. Anataxis and migmatization of rock have led to the complexity of the area. The closed-form solution and finite element method were used for studying the phenomena of stresses and convergence in four rock types. The study includes four sections of different metamorphic rocks, excavated in very poor rock class (Q classification) with different depths and K0 conditions. Assessment of stress and displacement was carried out to determine the ground response of the tunnel and applicable support for tunnel stability. The ground response was analyzed up to a distance of 60 m from the tunnel face under different K0 conditions. Analyzed deformations were also compared with observed deformation at these sections. Squeezing was observed in a short period for K0 value almost equal to 1, whereas, time-dependent deformation was observed for K0 values greater than 3. However, no deformation was observed for K0 values less than 1 and 1.53 in very poor rock class.
