Tunnel Route Research Articles

Pushing boundaries in slurry microtunneling: Innovations in microtunnel boring machine design for hard rock conditions

AbstractFor microtunneling in hard rock, as it is encountered very often in alpine tunneling, the continuous further development of technologies plays a key role to overcome the limitations in drive length and to improve performance. During the last decades, the application range of slurry microtunneling has been considerably extended and more demanding projects have been designed for underground utilities installations worldwide, including many sewage tunnels and hydropower plants. The prevailing ground conditions still play a key role and determine the limits for alignment design and the possible use of trenchless construction methods. In hard rock conditions with high rock strength and/or abrasivity, the applicability of slurry microtunneling has been especially limited in the non‐accessible diameter range in the past. With the new AVN 800 HR for hard rock microtunneling, Herrenknecht has developed a machine concept, enabling drives of up to 200 m, with precise steering of the MTBM. Longer drives, even through hard rock, make microtunneling a more economic, flexible, and more environmentally friendly construction method. New opportunities for clients and consultants in the planning of tunnel routes in alpine environments for different infrastructure installations can be considered, making trenchless installations even more cost‐effective, while improving public acceptance.

Hydraulic impact of pressure transients from water conveyance tunnel on the complex hydrogeological system: A case study HPP Pirot, Serbia

Hydraulic tunnels, integral components of hydropower plant (HPP) systems, traversing diverse rock masses, pose challenges for long-term operation. The study’s main goal was to investigate how hydraulic transients originating from the headrace tunnel transfer through the concrete lining and manifest in surrounding aquifer systems. In this experimental study at the water pressure tunnel of HPP Pirot (Serbia), a novel monitoring approach was employed. The internal piezometers with highly sensitive probes are distributed strategically along the tunnel in different geological environments. This approach involved monitoring of water pressure in the surrounding rock masses and observing the impact of hydraulic transients generated by HPP operation. A comprehensive analysis of monitoring data, incorporating ordinal and partial correlations and considering geological features, provides a profound understanding of groundwater dynamics, pressure transient phenomena, and hydrogeological characterization during HPP operation. The study highlights the complex and spatially diverse hydrogeological environment, emphasizing the varying reactivity of pore pressure during HPP operation, particularly concerning Water Mass Oscillations (WMO). Reactive piezometers near the surge tank demonstrate significant pressure variations, while those located further away display synchronous pressure changes with reduced amplitudes. Schematic hydrogeological models have been created based on the hydraulic impacts of HPPs in different geological environments along the tunnel route. The water pressure response enabled aquifer characterization of (1) a thin-layered, low-fissured aquifer closely related to the reservoir, with low influence on WMO transients; (2) a low-fissured, compartment aquifer or non-aquifer with minimal to no influence on WMO transients; (3) a well-structured karst aquifer system influenced by WMO transients; (4) a fault-controlled zone of deep hypogene karst aquifer discharge highly influenced by WMO transients; and (5) an aquifer with a dominant development of the karst conduit system highly influenced by WMO transients. The study highlights the significance of monitoring water pressure within the rock mass as a fundamental element in analyzing the interaction between water pressure tunnels and the hydrogeological environment. Applying the presented instrumentation and methodology facilitates effective monitoring in research areas where pressure tunnels are constructed.

Construction control technology for cutting historical anchor cables along the path of shield tunnels crossing existing tunnels at close proximity

In Dongguan Metro Line 1, the new shield tunnel crosses above the existing metro tunnel at a close proximity, necessitating strict control over the displacement of the existing tunnel caused by shield construction. In addition, on the left route of the new shield tunnel, anchor cables used to strengthen the stratum during the construction of the existing tunnel remain embedded in the soil. These anchor cables must be cut off to avoid damaging the shield machine. However, cutting these anchor cables may influence the stress states of the soil and existing tunnel, resulting in additional displacements. To address these challenges, an innovative cutting method for anchor cables was employed in this project. To strictly control the induced settlements of the existing tunnel during shield tunneling, the following measures were implemented: pregrouting reinforcement of the soil above the new tunnel, numerical simulation, and displacement monitoring. The construction of the new tunnel through shield tunneling was successfully completed. The monitoring data indicated minimal displacement of the existing tunnel, demonstrating effective construction control. The control technologies introduced in this study for constructing new shield tunnels crossing an existing tunnel serve as valuable reference for similar projects in the future.

Long-range magnon transfer across a bridging ferromagnetic chain via sequential and tunnel routes

A theoretical study of the mechanism of magnon transfer through a ferromagnetic chain (F) has been carried out from magnetically ordered contact A to similar contact B (AFB system). The regime of spin excitation transport is considered, when the inner section of the chain with identical paramagnetic units acts as a bridge for magnon transfer and thereby is poorly populated by magnons. In this case, the magnon transfer can be carried out by sequential hopping the localized magnon across all units of the chain or/and tunneling the magnon between the terminal units of the chain by a “superexchange” mechanism. The latter involves in the tunneling route the virtual delocalized magnons. The analytical dependence of the corresponding transfer rates on the number of paramagnetic bridge units is found and the magnon analog of the Seebeck and Peltier effects is predicted.

Enhancing tunnel stability in the Himalayas: Empirical design support through numerical modelling

AbstractThis study focuses on assessing the effectiveness of an empirically recommended support design through numerical modelling. Numerical techniques are utilized to accurately evaluate tunnel stability under various geological conditions. Numerical analysis is conducted on two different rock types along the tunnel route, employing the recommended support design based on the existing rock mass rating (RMR) and Q‐system. Furthermore, support recommendations are made using the modified RMR and Q‐system, considering the impact of stress. The numerical analysis indicates that the support recommended by the existing RMR may not substantially impact the total displacement and vertical stresses around the tunnel crown in the “Fair” to “Poor” rock mass of the study area. However, extending the bolt length by modifying the RMR to incorporate stress effects results in a reduction of total displacement and vertical stresses, ultimately achieving a stable level. These results underline the importance of considering stress effects and utilizing modified support designs to enhance tunnel stability.

Establishing Long-Term Haemodialysis Vascular Access with Permcath in Children with Chronic Kidney Disease: A Single-Centre Retrospective Analysis

Background: In some regions, the types and sizes of tunneled central venous catheters (CVCs) are limited. Objective: The objective of this study was to review our experience with 10F Quinton Permcath catheters used for long-term vascular access in children of various ages and weights with chronic renal failure. Methods: Children with renal failure on maintenance hemodialysis who underwent placement of the 10F Quinton Permcath between June 2017 and June 2023 at the First Affiliated Hospital of Jinan University were included. We collected clinical data from children with the Permcath, including patients' gender, age, weight, and height. Additionally, data on catheter-related complications were gathered. Imaging data of the patients were obtained to compare the catheter route on imaging and the position of the catheter tip in each case. This enabled an analysis of the characteristics of vascular access establishment and its correlation with catheter-related complications in 11 children implanted with 10F Quinton Permcath. Results: Among the 11 children on maintenance hemodialysis with catheters, five were male, and six were female, with a median age of 9 years (range 8 - 10). The median body weight of the included patients was 23.00 kg (range: 19.95 - 24.30 kg). Eight cases involved placement in the right internal jugular vein (IJV), with the catheter tip located at the level of T8 in two cases, T5 in one case, and T7 in the remaining cases, with no early catheter dysfunction. Three patients underwent catheter placement in the left IJV, with the catheter tip located at the level of T5, T4, and the T7/T8 intervertebral space, respectively, and two cases of early catheter dysfunction occurred in two patients. There were no acute complications in the 11 cases following catheter insertion. Conclusions: Whenever feasible, the right IJV should be the preferred choice for establishing vascular access for the 10F Quinton Permcath in children with chronic kidney disease, regardless of age and weight. The tunnel route and catheter length within the tunnel can be adjusted to ensure the appropriate placement of double-lumen tunnelled cuffed catheters (TCC).

Tunneling problems in weak rock conditions under shallow overburden and comparison between full-face excavation and sequence excavation methods

ABSTRACT The T8 tunnel was constructed within the scope of the Ankara – Sivas High-Speed Railway project. The tunnel route is formed completely by very weak and weak lithological units. The overburden decreases to 10 m, and the highest overburden thickness reaches up to 60 m. The tunnel is large with a 150 m2 excavation area and 14 m diameter. During the excavations in the section with an overburden thickness of 12 m, the supports failed, and the tunnel was completely collapsed. The purposes of the present study are to discuss the causes of the failure and engineering measures and to compare NATM and ADECO-RS methods with three-dimensional (3D) numerical analyses. Considering the mechanism of failure, extra engineering measures were proposed and the T8 tunnel was completed successfully. For the purpose of the study, a series of 3D numerical analyses were performed, and the results are discussed. The results obtained from the 3D numerical analyses showed that the ADECO-RS method yielded higher performance than the NATM method, for very weak and weak ground conditions (Category C).

Hydrogeological and hydrochemical condition in planned tunnel B route of the Yogyakarta-Bawen toll road

The Yogyakarta-Bawen toll road tunnel, located in Magelang Regency, Central Java Province, is a national strategic project that connects Central Java and the Special Region of Yogyakarta. It has geology resulting from volcanic processes, resulting in rocks with moderate aquifer properties and low to moderate permeability. The study covers 24 observation points, with 11 locations sampling groundwater for chemical analysis. The analysis results of hydrochemical facies are Na-K-HCO3. Water table depth varies from 623 m to 704 m above sea level, with the water table along the tunnel route at depths of 13-40 m above mean sea level, generally above the tunnel’s elevation. The groundwater flow pattern tends to move from southeast to northwest, perpendicular to the tunnel’s direction. Groundwater quality testing indicates that water in the research area falls under the category of fresh groundwater, based on electrical conductivity and total dissolved solids values. The overall acidity level is generally acidic, except at specific points. In general, the interaction of groundwater with concrete results in weak erosion. It can be concluded that the groundwater at the research location is shallow, situated above the planned tunnel elevation, exhibits hydrochemical facies variations, and has the potential to weakly erode concrete.

Potenential for thermal energy from Tunnels beneath Manchester and Crewe: a case study

potenential for thermal energy from Tunnels beneath Manchester and Crewe: a case study

TBM performance prediction using LSTM-based hybrid neural network model: Case study of Baimang River tunnel project in Shenzhen, China

Accurately predicting tunnel boring machine (TBM) performance is beneficial for excavation efficiency enhancement and risk mitigation of TBM tunneling. In this paper, we develop a long short-term memory (LSTM) based hybrid intelligent model to predict two key TBM performance parameters (advance rate and cutterhead torque). The model combines the LSTM, BN, Dropout and Dense layers to process the raw data and improve the fitting quality. The features, including the ground formation properties, tunnel route curvature, tunnel location and TBM operational parameters, are divided into historical/real-time time-varying parameters, time-invariant parameters and historical/real-time output prediction data. The effectiveness of the proposed model is verified based on a large monitoring database of the Baimang River Tunnel Project in Shenzhen, south China. We then discuss the influence of the prediction mode, neural network structure and time division interval length of historical data on the prediction accuracy. The significance evaluation of input features shows that the historical output prediction has the largest influence on the prediction accuracy, and the influence of ground properties is secondary. It is also found that the correlations between input features and the output prediction are coincident with their interrelationships with the ground properties and ease of TBM excavation. Finally, it is found that the prediction results are most affected by the total propulsion force followed by the rotation speed of the cutterhead. The established model can provide useful guidance for construction personnel to roughly grasp the possible TBM status from the prediction results when adjusting the operational parameters.

Study on the Response of Tunnel Lining under Fault Dislocation

In order to clarify the influence of fault dislocation on tunnel lining, the FEM and single factor variable methods were used to explore the influence of the degree of fault dislocation, dip angle, width, the intersection angle between the strike and the tunnel axis, and the fault dislocation form on the lining structure response, based on which length of the lining anti-dislocation set-up for engineering design was obtained. The research shows that the maximum displacement of the lining is basically consistent with the fault displacement; with the increase of the fault width, the overall fortification range of the tunnel increases. Among the three types of fault dislocation, the axial force of the lining caused by reverse fault dislocation is the largest, the level of normal fault is the moderate, and the strike-slip fault is the smallest. With the increase of the intersection angle between the fault strike and the tunnel axis, the lining gradually changes from tension-shear failure to shear failure. It is suggested that the tunnel should cross the fault at a large angle as far as possible. If it is unavoidable to cross the fault when selecting the tunnel route in the project, the tunnel axis should be selected to cross the fault vertically as far as possible.

Application of Autoregressive Model in the Construction Management of Tunnels

The unknown subsurface conditions in tunnelling projects have led to their management with many uncertainties. From these uncertainties, we can mention the geological condition of the tunnel route and the time and costs required for construction. In order to significantly reduce these uncertainties, techniques that have a high predictive power must be used. For this purpose, in this study, an autoregressive model was used to reduce the uncertainties related to geology and construction time and cost in tunnelling projects. A comparison between the predicted results and the actual values through several statistical indices showed the high-performance prediction of the autoregressive model in the prediction of tunnel resources. Also, three input parameters affecting tunnel construction time and costs, such as RQD, groundwater, and RMR, were considered. The sensitivity analysis of these parameters on the time and cost of tunnelling projects was investigated through mutual information test (MIT). The groundwater was the most effective parameter on the tunnel's time and cost.

The Relation of the Method Used in Tunneling Operations with the Geological Structure Example of the Black Sea Coastal Road

Transportation tunnels are the most preferred method to facilitate transportation in mountainous and rough terrains. The excavation method and the choice of fortification tools in tunnel construction depend on the geological structure of the tunnel route. Correct formation determination and determination will reduce the cost and eliminate many risks. The Black Sea region has a very mountainous and rugged terrain. The most obvious method used to overcome rough terrain is road tunnels. The rock classification of the tunnel route and the support to be formed accordingly are very important in the selection of the method to be applied in the highway tunnel constructions. Within the scope of this study, Trabzon-Akyazi region, which is an important part of the Black Sea coastal road, was studied. The geological formations on the route of the 3-lane and double-tube tunnel with a length of approximately 2476 meters, which is planned to be built within the highway passing through this region, were examined and the method used in the tunnel construction was determined. As a result of the analyzes and calculations, it has been determined that the dominant unit along the tunnel routes is the agglomerate of the Besirli formation and the New Austrian Tunneling (NATM) method is applicable. The rock classes found were determined to be B3 and C2 classes according to NATM. Excavations in the tunnel were carried out by drilling and blasting method in the form of the upper half and the lower half.

A Geotechnical Perspective on a Complex Geological Environment in a High-Speed Railway Tunnel Excavation (A Case Study from Türkiye)

The T26 tunnel was designed within the scope of the Ankara-Istanbul high-speed railway in accordance with the speed of 250 km/h. Some serious problems and excessive deformations were encountered during the excavation works. The deformations in the tunnel caused subsidence on the surface and the Tunnel Boring Machine (TBM) became stuck; therefore, tunnel excavation works were suspended. Design works for re-excavation in the T26 tunnel and extracting of the TBM were carried out and the tunnel was re-designed by the New Austrian Tunneling Method (NATM) system. The main purposes of the present study are to describe the problems encountered during the T26 tunnel and to discuss the sources of the problems. The advantages and disadvantages of TBM and NATM methods for the tunnel having difficult ground conditions were discussed. Critical points needing to be considered for the tunnels excavated with TBM through weak ground conditions and the effect of the TBM selection process were discussed. Considering the complex geological and geotechnical structure of the tunnel route, it is possible to say that the T26 case is an interesting case for tunnel engineering. Along the tunnel route, landslides, high seismic activity, groundwater conditions, and extremely weak rock mass features coexist. Therefore, the tunnel route is a very complex environment. However, due to the geometric limitations of the high-speed railways, relocation of the route is not possible. The experiences gained from tunnel excavations under difficult conditions are capable of bringing new horizons to future tunneling studies.

A new method for subsea tunnel site selection based on environmental bearing capacity.

Engineering site selection is an essential and systematic work in the early engineering construction stage. At present, the subsea tunnel site selection mainly depends on manual experience. There is still a lack of subsea tunnel site selection systems based on environmental impact. This study develops a comprehensive site selection evaluation system based on the analytic hierarchy process (AHP) and fuzzy evaluation method for the subsea tunnel site selection. It is a multi-indicator mathematical model evaluation system. On this basis, the ecological site selection method of the subsea tunnel is further studied, an indicator system for evaluating the environmental carrying capacity of the island is established, and the site selection results of the subsea tunnel based on the environmental indicators are obtained. We compared the site selection results of the two methods. The results show that the conventional method and the ecological site selection method based on environmental indicators can well carry out the site selection of subsea tunnels. The two methods take into account both the overall and local optimum of the subsea tunnel route and organically combine the overall and local objectives. This way provides a reference for the design and construction of the subsea tunnel in the future and points out the direction for the site selection of other large-scale projects with significant environmental impact.

Zayıf zeminlerde açılan büyük çaplı çift tüp tünellerde tünellerin birbirine olan etkisinin 3 boyutlu sayısal analizler ile incelenmesine bir örnek, Bolu Tüneli destek sistemlerinin değerlendirilmesi

Bolu Tüneli Ankara İstanbul Otoyolu üzerinde yer almaktadır. Bolu Tüneli proje çalışmalarına 1993 yılında başlanmış olup 2007 yılında trafiğe açılmıştır. 3 şeritli çift tünel olarak inşa edilmiştir. Tünel uzunlukları sağ tünel 2788 m sol tünel ise 2954 m’dir. Bolu Tüneli inşası sırasında 2 kez sel ve 2 kez depreme maruz kalmış ve tünelin Ankara girişinde yeralan Elmalık kesiminde 12 Kasım 1999 Düzce Depremi sonrası göçük yaşanmıştır. Bu göçük sonrasında tünel güzergahı değiştirilmiştir. Bolu Tüneli jeolojik olarak Kuzey Anadolu Fay Hattı ana kolu ile Düzce Fayı arasındaki tektonik bloktan geçmektedir. Tünelin İstanbul tarafı (Asarsuyu girişi) metakristalin temel kayaları içerisinde yer almakta iken Ankara tarafı (Elmalık girişi) sedimanter kayaçlar içerisinde bulınmaktadır. Tünel bu iki birimi Bakacak fayı ile kesilmektedir. Tünelde kazı aşamasında en büyük sorunların meydana geldiği Elmalık girişinde Elmalık fayı bulunmakta olup, tünelin bu bölümlerinde 1.2 m’ye varan deformasyonlar ile karşılaşılmıştır. Ayrıca Elmalık sağ tünelde fay geçişi sırasında 1996 yılında göçük meydana gelmiş, 12 Kasım 1999 Düzce Depreminde ise Elmalık sol tünel tamamen kapanarak göçük oluşmuştur. Yeni Avusturya Tünelcilik Yöntemi ile projelendirilen Bolu Tünellerinde yaşanan sorunlar ve geliştirilen destek sistemleri tünelcilik açısından çok değerli bilgiler içermektedir. Bu çalışma kapsamında Bolu Tünel destek sistemleri Flac3d programı ile 3 boyutlu olarak incelenmiş, iki tünelin birbirine olan etkisi, üst yarı, alt yarı ve invert kazılarında meydana gelen değişimler ortaya konmuştur.

Analysis of Blasting Vibration Effect of Railway Tunnel and Determination of Reasonable Burial Depth

Based on specific examples of underpass tunnel blasting, field measurements, and numerical simulation studies are carried out. According to the results of the blasting vibration data measured on-site, a regression model of the blasting vibration velocity is established. Based on the wavelet packet energy spectrum analysis method, the effect of frequency on the vibration response intensity is studied. In addition, the maximum charge per delay allowed for tunnel blasting is obtained by formula inversion. Relying on ANSYS/LS-DYNA to establish a three-dimensional numerical model, the accuracy of numerical simulation can be checked by the measured vibration data. The results show that the numerical simulation has high precision and can meet the subsequent analysis needs. Using numerical simulation, the variation law of the vibration response characteristics of ground blasting under different tunnel burial depths is studied. The analysis results show that with increasing tunnel burial depth, the ground blasting vibration velocity decays exponentially. According to the corresponding specification of blasting vibration, a reasonable value range of the buried depth of the underpass tunnel can be obtained. The research ideas and methods introduced can be used for reference for similar railway tunnel blasting control and railway tunnel route selection.

Over-The-Top Technique for Revision ACL Reconstruction with Achilles Allograft and Associated Lateral Extra-articular Tenodesis

Revision anterior cruciate ligament reconstruction (ACL-R) is made challenging by the frequent presence of rotatory instability, tunnel malpositioning and widening, and limited autograft options. Lateral extra-articular tenodesis (LET), alternative tunnel routing, and the use of allograft tissue can be used to manage these challenges. This Technical Note describes revision ACL-R using the over-the-top (OTT) technique with Achilles tendon allograft with concomitant LET. The surgical approach involves routing the graft around the posterior aspect of the lateral femoral condyle, and then deep to the iliotibial band to a site just medial to Gerdy’s tubercle, with staple fixation on the lateral femur for the ACL-R and anterolateral tibia for the LET. The OTT technique with LET provides a versatile approach for the management of failed ACL-R by circumventing challenges in revision ACL-R and addressing rotatory instability, a contributing factor to prior graft failure.

Numerical Analysis of Mechanical Response Characteristics of Jointed Tunnel Surrounding Rock under Dynamic Loading

The jointed rock mass is widely distributed in nature, which has certain impact on the stability of the underground tunnel. In order to study the response characteristics of jointed tunnel surrounding rock mass under dynamic loading such as earthquake and explosion, the tunnel surrounding rocks with different distributed joints are simulated and studied by RFPA numerical analysis method, and the failure process of tunnel surrounding rock is obtained. The numerical results show that under the action of dynamic loading, the tunnel surface reflects the stress wave and form a tensile failure zone, resulting in serious instability and failure in the zone; The stability of tunnel surrounding rock is closely related to the distribution of joints; The interaction between tunnels increases the failure of surrounding rock mass, so a safe distance should be maintained between tunnels. The research results of this paper provide guidance for tunnel route selection and surrounding rock reinforcement design.

Numerical Modelling of Blasting Dust Concentration and Particle Size Distribution during Tunnel Construction by Drilling and Blasting

In order to reduce the blasting dust concentration in the tunnel during the drilling and blasting, accelerate the tunnel excavation process, and improve the working environment for the construction workers, a three-dimensional geometric model of dust transport was established based on the gas-solid two-phase flow model using the DesginModeler software, and the discrete phase model (DPM) in the FLUENT software was used to simulate the variation of dust concentration and the distribution of dust particle size at different locations along the tunnel route within 1200 s after tunnel blasting. The results showed that the concentration of blasting dust gradually decreased over time, with the fastest decrease in the range of 2 s to 120 s, and after 900 s, the dust concentration stabilized. The overall spatial distribution of the dust concentration showed a trend of decreasing from the palm face to the tunnel entrance and from the bottom plate to the upper part. The distribution pattern of dust with different particle sizes was not the same along the length of the tunnel. The large particles settled in the area of 25 m from the palm face under the action of gravity. With the increases of distance, the mass flow rate decreased, and the dust particle size became smaller, but the proportion of small particles gradually increased, while the R-R distribution index increased. The results in this study were confirmed to be reliable by comparing the measured data to provide guidance for the dust reduction technology in tunnel blasting, so as to quickly remove the dust generated during the blasting process and improve the engineering construction efficiency.