Tunnel Intersection Research Articles

Seismic response of tunnel intersections in jointed rock mass within underground research laboratory: A coupled DEM–DFN approach

Seismic response of tunnel intersections in jointed rock mass within underground research laboratory: A coupled DEM–DFN approach

Seepage interaction mechanism of crossing tunnels and existing tunnels: Model test and numerical analysis

High-density urban tunnel engineering produces strong spatial seepage and stability interactions of newly built and existing operational tunnels, which is critical to the safety and resilience of transport infrastructure. Previous research mainly focused on the mechanical response of adjacent tunnel construction and the active deformation control of surrounding rock, while little consideration is given to the influence of spatial intersecting tunnels on the seepage field distribution, especially in water-rich regions. This paper investigates the seepage interaction of crossing tunnels and existing tunnels using dedicated seepage tests and corresponding numerical analysis under different hydrodynamic head heights and spatial crossing forms. The schemes are designed based on the Kexuecheng Tunnel in Chongqing City, China, which is a typical small spacing highway tunnel that crosses five existing railway tunnels in complex hydrogeological environment. According to the results, the seepage funnels generated by intersecting tunnels will overlap each other in space, causing significant changes in the seepage field within the impact area. When the newly built tunnel above-crossing the existing tunnels, the water pressure on lining structure of the small interval tunnel can be reduced by 20 ∼ 30 %. While the impact of the existing tunnel on the seepage field of the new tunnel is mainly reflected in its upper part. The construction of new tunnels is equivalent to adding seepage paths to the upper or bottom of an existing tunnel, reducing its water pressure by 10 ∼ 30 %. The spatial overlap effect will significantly reduce the water pressure at the intersection of tunnels, but also exacerbates the asymmetric distribution of water pressure in small spacing tunnel. According to the W-shaped spatial distribution of the seepage field in small spacing tunnels, the predicted seepage influence range may exceed 80 ∼ 100 m. When the newly built tunnel above-crossing or under-crossing the existing railway tunnels, the water inflow of the small interval tunnel and the overlying tunnel can be decreased by 10 ∼ 30 % compared to the situation without crossing. However, the overall groundwater discharge further increases by 53.9 %. The seepage interactions of newly built tunnels and existing tunnels could provide support for both alignment design and construction of newly built tunnel, and service performance improvement of existing tunnels.

A multi-scale model for longitudinal seismic design of prefabricated utility tunnel based on multi-point constraints

A multi-scale model for the longitudinal seismic analysis of underground prefabricated utility tunnel was proposed. In this multi-scale model, beam elements were used to model the utility tunnel segments, shell elements were used to model the weak parts, e.g., tunnel intersections, and node frames with multiple springs were used to simulated the behavior of the tunnel joint. The node frames, whose form are the same as that of the prefabricated joint, were established on a basis of the cross-sectional size and the joint form of the tunnel. By arranging multiple sets of nonlinear springs to connect adjacent node frames, the refined model of the utility tunnel joint was established. Based on the multi-point constraint method, the multi-point constraint equations between the structure model and the refined joint model were given. Finally, a specific straight utility tunnel as well as a specific cross-type utility tunnel were taken as the examples to verify the accuracy and applicability of the proposed model. The results indicate that the proposed model is suitable for the longitudinal seismic analysis of the utility tunnels with asymmetric cross-section and intersections, and may provide reference for the longitudinal seismic design of large-scale utility tunnels.

Exploring the role of loop tunnels in enhancing termite food transport efficiency: A simulation approach

Subterranean termites construct a network of tunnels beneath the ground, comprising a main tunnel and branch tunnels. While termites do not construct tunnels that turn back in a “U” shape, the intersection of main and branch tunnels often forms closed curved structures (a loop). The loop structure can have either a positive or negative effect on the transport efficiency of termites in food transportation. However, little research has been conducted on the impact of loop tunnels on transport efficiency (E) due to the technical difficulties associated with direct observation. In this study, we used an individual-based model to simulate termite behavior during food transportation within a tunnel composed of a main tunnel and a loop tunnel. The model incorporates four control variables: the number of introduced simulated termites (k1), the probability of a simulated termite using a loop tunnel when walking towards a food or nest site (k2 or k3), and the length of the loop tunnel (k4). The simulation results reveal that the E value is high for (k2, k3) = (high, high), (low, low), (high, low), and (low, high) when the length of the loop tunnel is relatively short. However, when the length of the loop tunnel is relatively long, E is high only for (k2, k3) = (high, low) and (low, high). We found that these results are primarily influenced by the frequency of traffic jams. Therefore, termites would benefit from adopting strategies that reduce the occurrence of traffic jams during food transportation. In the Discussion section, we briefly touch on the strategy from an ecological perspective.

3D numerical investigation of the interaction between interchange tunnels at different angles

The development of subway and highway tunnels has led to the spatial intersection of tunnels, significantly impacting tunnel deformation, lining stress, and ground settlement during construction. To study the influence of critical parameters such as the cross angle and centre-to-centre distance on the tunnel performance, a series of numerical simulations were carried out. The influence range and magnitude of stress in the spatial cross tunnel under different cross angles were determined. The results indicated that as the crossing angle increased, the stress on the lining decreased, and the vault displacement increased. Meanwhile, the parallel tunnels showed opposite tendencies. Based on these results, the crossing angle of the cross tunnels was suggested to be greater than 45°. Parallel tunnels should be considered individually because the loading is symmetrically distributed. Considering the vault displacement and von Mises stress of the lining, it is recommended that the tunnel spacing be greater than 2D. The numerical model was validated against field data, and the findings of this study can be useful in designing cross tunnels.

Shaking table tests on the seismic performance of prefabricated T-shaped cross utility tunnel

The seismic performance of the intersection of a T-shaped cross utility tunnel is weak under earthquake excitation. This study is the first to perform 1/20 scaled shaking table tests on the seismic performance of prefabricated T-shaped cross utility tunnel based on an actual utility tunnel project. Micro-concrete was used to create prefabricated utility tunnel models, and a prefabricated T-shaped cross utility tunnel was assembled by a T-shaped intersection and prefabricated utility tunnel segments using bolts. The laminar shear model box was used in the tests, and earthquake excitations along the two principal axes of the prefabricated T-shaped cross utility tunnel were inputted respectively at the bottom of shear box. The model soil acceleration, prefabricated utility tunnel strains, and opening and dislocation of joints were tested and analysed. Numerical simulation was conducted on the test cases, the test and numerical results were in good agreement. The results showed that the significant strain concentration on the T-shaped intersection or its adjacent utility tunnel was found under earthquake excitations along the two principal axes of the T-shaped utility tunnel, owing to incompatible deformation caused by the difference in lateral stiffness between two intersecting utility tunnels. The amplification of the axial strain at the T-shaped intersection or its adjacent utility was up to 5.2–6.4 times. Under earthquake excitations along the two principal axes of the T-shaped utility tunnel, the significant opening or dislocation of joint between the T-shaped intersection and prefabricated utility tunnel was found. The closer the joint was to the T-shaped intersection, the larger the opening or dislocation of joint. The amplification of the dislocation or opening of joint between the T-shaped intersection and prefabricated utility tunnel was 5.7–10 times. This study provides a certain reference for the seismic design of T-shaped cross utility tunnel.

Numerical Simulation Analysis of Construction Support of Intersection Section in Extra-long Water Diversion Project Tunnels

The selected Middle Yellow River Diversion Project is an important backbone project of the planning and construction of the modern water network in Shanxi Province. The project is composed of water source project and water transmission project, the water transmission project is about 400 kilometers long, there are about 200 kilometers of total dry, about 100 kilometers of East Dry and West Dry each, with an average depth of about 400 meters. The intersection section studied in this paper is located under the ridgeline of Lvliang Mountain with a burial depth of more than 600 meters. Whether to support the excavation of the tunnel intersection section was simulated by three-dimensional numerical simulation analysis of different sections. The stress field of surrounding rock and liner and the distribution of plastic zones in surrounding rock were simulated and calculated. The research results provide a technical reference for the design of tunnel support and the formulation of construction schemes, which is of great significance for the construction safety and operation management of water diversion tunnels.

Response Monitoring and Analysis in Deep Foundation Pit Excavation: A Case Study in Soft Soil at Subway Tunnel Intersections

With the rapid development of urban rail transit and underground space development, the occurrence of excavation near existing tunnels is becoming more common. This excavation and unloading will inevitably cause soil deformation outside the pit and the tunnel buried therein. This paper presents an investigation into the entire excavation process and the deformation effects on the adjacent subway structure under complex construction environments, including soft soil foundations and adjacent subway intersections, based on measured data of pit construction. The horizontal and vertical displacements of deep soils in two pits were analyzed along with safety management measures to determine the horizontal displacement curve pattern and the lateral displacement development distribution law of deep soils. The analysis of subway deformation data shows that after excavation, the subway tunnel undergoes “lateral expansion” and “vertical compression” type deformation, accompanied by “in-pit” horizontal displacement and “settlement” vertical displacement. Furthermore, a correlation analysis reveals a clear linear relationship between pit deformation and subway structure deformation, which can be used as a prediction method for adjacent structure deformation. Finally, a comparative analysis of existing relevant influence zone models and tunnel deformation prediction formulas is carried out based on the monitoring. The results of this study have significant guiding implications for the excavation construction of soft soil foundations in the vicinity of subway crossings.

Influence of Underground Excavation Expansion on Surrounding Rock Characteristics at Intersection of Ventilation Shaft and Tunnel: A Case Study

Existing railways can no longer meet transportation requirements, and it is an urgent need to expand old tunnels. However, the existence of ventilations shaft makes expansions face greater risks. This study analyzed the tangential stress change trend during the expansion process through field monitoring, and numerical simulation was used to analyze the changes in stress and displacement under different shaft depths and width–span ratios. The results show that as one approaches the tunnel face, the tangential stress in the arch foot and side wall of the J-2 and J-3 sections gradually increased, and the tangential stress in the arch foot and side wall of the J-1 section gradually decreased. The distance of the tunnel expansion’s influence on tangential stress is about 0.91 to 1.45 times the tunnel span. The largest value of vertical displacement had a linear relationship with shaft depth, and the largest value of horizontal displacement had a quadratic relationship with shaft depth. Changes in the width–span ratio only had a greater impact on the ventilation shaft section. These results can provide a reference for similar in situ expansion projects.

A Methodology for the Analysis of Tunnel Intersections Using Two-dimensional Numerical Modeling

Intersections of tunnels are an integral component of most underground applications. The design and construction of tunnel intersections can be the most technically challenging element of a tunnel project. Yet, there are relatively few publications and methods regarding tunnel intersection design. Tunnel intersections are essentially a three-dimensional problem. However, 3D models require significantly longer time for solving and interpreting, greater computer resources, and higher user expertise. Hence, there is a great incentive to develop simpler and quicker analysis methods for tunnel intersections. In this paper, a methodology is developed so that a 3D tunnel intersection problem can be modelled using an equivalent 2D numerical model. For this purpose, it is proposed that the main tunnel cross section is modelled with an additional horizontal expansion component that represents the cross tunnel. Multiple 3D and 2D models were computed for the purpose of finding the expansion distances in the 2D models that yield similar deformations to the 3D models. Based on the results, regression analysis was employed to derive a formula relating the ratio of equivalent diameters of the main to cross tunnel to the proper expansion distance. This formula provides a useful and practical tool for preliminary tunnel intersection design. The current work relies on a number of assumptions, mainly that the rock mass is elastic. More work can be carried out to extend and modify the proposed method for more complex conditions.

Study on heat allocation and temperature profile in a T-shaped branched tunnel fire with different branch slopes under natural ventilation

Reduced scale experiments in a T-shaped branched tunnel with different branch slopes (0%, 6% and 9%) were carried out to study the variation of temperature profile beneath the ceiling under natural ventilation. Numerical simulation with branch slopes of 0%, 3%, 6% and 9% was also executed. A methodology to estimate the mass and heat flux into the branch was proposed. The results show that the branch slope has limited influence on the maximum temperature beneath the ceiling in the main tunnel when fire locates at the intersection of main tunnel. A correlation for maximum temperature beneath the ceiling in the main tunnel is proposed and agrees well with others’ experiments (in full scale and reduced scale). Higher branch slope could transport more hot smoke and heat into the branch. When the branch slope is within 0–9%, about 28–35% of the total released heat enters the branch. When the branch slope is 0%, maximum ceiling temperature in the branch can be well-estimated by Li’s model, if the heat flux into the branch is treated as the heat release rate of ‘virtual fire source’. The longitudinal temperature decay factor in the branch can be estimated based on the mass flux into the branch. This work could help to understand the flow characteristics of hot smoke of branched tunnels scientically.

Numerical Study on the Effect of Large Deep Foundation Excavation on Underlying Complex Intersecting Tunnels

The effect of large deep foundation excavations on the surrounding existing tunnels is a problem that cannot be avoided in the current construction background. This effect is difficult to assess precisely, especially when the geometry of the tunnels and pits is complex. In this paper, a three-dimensional (3D) finite element model has been developed based on a case containing four complex intersecting tunnels and a large deep foundation pit. The model used the hardening soil model with small-strain stiffness (HSS) and the Hoek–Brown (HB) model to describe the mechanical properties of the soil and rock, and various methods including the standard penetration test (SPT) and heavy dynamic penetration test (HDPT) were used to determine the model parameters. The results of the analysis are as follows: the excavation of the foundation pit caused the tunnels to heave and the heave deformation conforms to the normal distribution; the maximum heave of numerical simulation is 3.1 mm which is consistent with the field data; the horizontal displacement, horizontal convergence, and vertical convergence of the tunnels caused by the excavation of the pits are small, and all kinds of deformations meet the control requirements; the intersection of multiple tunnels shows obvious stress concentration when the tunnels were constructed, and the lining stress slightly decreases as excavation progresses.

Structural Stability Analysis of Concrete Lining in the Shaft–Tunnel Intersection Area of the Long-Distance Tunnel

Structural Stability Analysis of Concrete Lining in the Shaft–Tunnel Intersection Area of the Long-Distance Tunnel

The anatomical relationship of the common peroneal nerve to the proximal fibula and its clinical significance when performing fibular-based posterolateral reconstructions.

The common peroneal nerve (CPN) can be injured during fibular-based posterolateral reconstructions due to its close relationship to the neck of the fibula. Therefore, the purpose of this study was to observe the course of the CPN and its branches around the fibular head and neck and quantify the position in relation to relevant bony landmarks and observe the relation between tunnel drilling for posterolateral corner reconstruction and both the tunnel entry and exit at the proximal fibula and the CPN and its branches was observed. In 101 (mean age = 70.6 ± 16years) embalmed cadaver knees, the relationship between bony landmarks (tibial tuberosity, styloid process of fibula (APR)) and the CPN and its branches were established and 8 (M1-M8) distances from these landmarks measured; mean, SD and 95% CI were recorded. In 21 of these knees, a fibula tunnel was drilled as in PLC reconstruction and the association of the CPN and its branches to the tunnel entry and exit were judged by two independent observers. Fisher's exact test of independence was used to determine significant differences between genders. Tunnel intersection was analysed in a binary yes/no fashion and was described in frequencies and percentages. The mean distance from the APR to where the CPN reaches the fibula neck (M1) was 31.4 ± 8.9mm (CI:29.8-33.0); from the apex of the styloid process (APR) to where the CPN passes posterior to the broadest point of the fibular head (M3) was 21.7 ± 12.6mm (CI:19.4-24.0); from the apex of the APR to the most proximal point of the CPN/CPN first branch in the midline of the fibular head (M2) was 37.0 ± 6.7mm (CI: 35.4-37.7). Out of the 21 randomly selected knees for drilling, the first branch of the CPN was damaged at the tunnel entry point in 7 (33%), and in 5 knees (24%), the CPN was damaged at the tunnel exit. In one knee, at both the tunnel entry and exit, the first branch of the CPN and the CPN were intersected, respectively. The results of this study strongly suggest that the CPN is at risk when drilling the fibula tunnel performing fibula-based posterolateral corner reconstructions. The total injury rate was 57% with a 33% incidence of injury to the first branch of the nerve at the tunnel entry and 24% to the CPN at the tunnel exit. Due to the high incidence of injury, percutaneous placement of guide pins and tunnel drilling is not recommended. The nerve should be visualized and protected by either a traditional open approach or minimally invasive techniques. With a minimally invasive approach, the nerve should be identified at the fibula neck and then followed ante- and retrograde.

Numerical approach for structural analysis of Metro tunnel station

In this paper is presented the results of calculations of reinforced concrete structure of metro station in the form of cupola located at the intersection of interstation tunnels. The constructive solution of station is economical, allows diversifying its architecture and using the internal space for placing objects of the national economy. One of the important design stages is the assessment of the stress-strain state of structure with different boundary conditions when it is exposed to external loads. It is assumed that deformable environment surrounding the tunnel station is elastic and is modeled by discrete bearing reaction located in contact with the station. The structure is modeled by finite shell elements. As the result of calculation the principal stresses and moments in its sections are determined. The obtained data can be made by designers in determining of structural solution, dimensions and initial sections selection of reinforcement elements.

A special support design for a large-span tunnel crossing an active fault (T9 Tunnel, Ankara–Sivas High-Speed Railway Project, Turkey)

Throughout construction process of a tunnel in an active tectonic region, it may be impossible to avoid active faults. Active faults create two adverse effects on the tunnels which are sudden fault displacement and weak ground conditions in fault zone. If a tunnel crossed by an active fault, the tunnel might be damaged by sudden movement of the fault. However, the main goal is to localize this damage without complete loss of tunnel. In this study, a special design developed for a wide span tunnel cut by an active fault is presented and the performance of the design is verified by numerical analyses. T9 tunnel was constructed within the scope of Ankara–Sivas High-Speed Train Project, Turkey, and the special design at the intersection of T9 tunnel with the Akdagmadeni active fault is the main subject of this study. T9 tunnel predominantly passes through agglomerate, basalt, marble and gneiss units and the tunnel route crosses the Akdagmadeni fault at around Km: 327 + 915. At this location, major deformations occurred in the tunnel and the tunnel excavation had to stop for a certain period. After the re-design phase, a special tunnel support system for this location were developed and proposed design was analyzed with numerical analyses. In addition, the possible displacement of the Akdagmadeni fault was estimated and the inner lining was re-designed considering the seismic parameters (i.e. peak ground acceleration and maximum displacement during a large earthquake). Consequently, in the present study, the effects of active fault crossing on the tunnel were explained and a special inner lining design was proposed to localize the possible damages, which are originated from the sudden displacement of the active fault.

How to reduce the risk of tibial osseous tunnel intersection when reconstructing posterior cruciate ligament and posterior oblique ligament simultaneously: using a 3-dimensional finite element model

How to reduce the risk of tibial osseous tunnel intersection when reconstructing posterior cruciate ligament and posterior oblique ligament simultaneously: using a 3-dimensional finite element model

Using PAVER Software to Evaluate Pavement Condition Index of Highway Segment in the North Sector of Najaf City (Case Study)

Current paper present part of comprehensive case study for urban highway networks of north sector of Najaf city located 161 km Southwest of Baghdad the capital of Iraq. The main goals of current paper are to evaluation pavement condition index denoted as (PCI). Values of PCI acting a main factor on depending maintenance of pavement, selecting economic alternative, increasing development of engineers and technician’s capabilities, in order to reach the best maintenance management process and achieve the best riding level with lowest costs and the shortest travel time. PAVER software uses surveying data to calculate pavement condition index which should be within rating from zero, which mean pavement in failed condition, to 100, that mean excellent pavement condition. Pavement’s condition is providing predicting its maintenance and Rehabilitation requirements. Free issue of PAVER 5.2 software was used to calculate values of PCI for a minor arterial urban highway in north sector of Najaf city, that is the Najaf-Karbala highway located from Al-Askarain Tunnel intersection to the end of Al-Nidaa district, with length (8011m). Manual geometric and types of distresses survey was depended instead of using assessment technologies to consider the type, degree of severity, of distresses for sample unites along the highway. As a results of implementing PAVER 5.2 software depending on field survey data collection, PCI value is equal to 80. That’s mean this part of the selected study section was in good situation.

Concomitantly combined ACL and PLC reconstruction: Case report and literature review

Abstract Introduction: : Injuries involving the posterolateral ligamentous system occur in approximately 7 - 16% of knee ligament injuries. However, only 28% of all posterolateral corner (PLC) injuries are alone and usually combined with cruciate ligament injury (posterior cruciate ligament-PCL > anterior cruciate ligament-ACL). Combined ACL and PLC tears account for 10% of complex knee injuries. An unaddressed posterolateral corner injury may be a leading cause of ACL reconstruction failure. Case presentation: A 26 year old male patient with combined ACL and PLC injury. He was concurrently reconstructed by both ACL and PLC. We used 2 semitendinosi (1 in each knee) and 1 gracilis tendon (in the injured knee). The ACL was reconstructed by one stranded semitendinosus with all-inside technique and Tightrops fixation. The PLC reconstruction utilized one femoral tunnel at the isometric point, graft fixation at the femoral tunnel by tightrope, and at the tibial tunnel by absorbable screw. At the 9 months follow-up, the Cincinnati score was 70/100 and the IKDC score was B type. Conclusions: Concomitantly combined ACL and PLC reconstruction has good results in remaining knee functions and decreasing ACL reconstruction failure. However, femoral tunnel creation needs to avoid femoral tunnel intersection.

Numerical Simulation of Dynamic Response Law of Intersecting Metro Tunnels in Upper and Lower Strata

With the acceleration of urbanization process, more and more urban subway construction, inevitably space intersection of subway tunnels has been formed. Based on practical engineering cases, a three-dimensional model is established by using MIDAS-GTS/NX numerical software. The dynamic response of metro tunnel under seismic wave is analyzed. The effect of tunnel intersection angle on the dynamic response law is discussed. The results show that: (1) Acceleration amplification factor, internal force and displacement of intersecting tunnels increase first and then decrease along the measuring points. The dynamic response of the area where the upper and lower tunnels intersect is the strongest. (2) The dynamic response of the tunnel in the upper soil is stronger than that in the lower rock. The difference of dynamic response between two tunnels in the same stratum is small. (3) With the increase of the intersection angle between the upper and lower tunnels, the acceleration and shear force decrease gradually. There is a negative correlation. The exponential function is established to describe the functional relationship between the dynamic response and the angle. The research results can provide references for earthquake resistance and shock absorption of urban metro.