Tunnel Segments Research Articles

Experimental and analytical investigation of the mechanical behavior of deformed segmental tunnel linings strengthened by stainless steel corrugated plate

Experimental and analytical investigation of the mechanical behavior of deformed segmental tunnel linings strengthened by stainless steel corrugated plate

A Novel Approach to Repositioning Peritoneal Dialysis Catheters.

Peritoneal dialysis (PD) is a crucial kidney replacement therapy for patients with end-stage kidney disease. Despite its advantages over hemodialysis (HD), long-term success can be hindered by catheter dysfunction, which often necessitates revision. Currently, surgical treatment methods for PD catheter malfunction include fluoroscopy-guided procedures and laparoscopic or open surgery to salvage or replace the catheter. Here, we introduce the first novel, minimally invasive surgery for repositioning PD catheters. From November 2021 to May 2024, 8 patients with PD catheter dysfunction underwent this innovative procedure at the Department of Nephrology, Sichuan Provincial People's Hospital. Surgical Procedure: On the side of the original abdominal incision, blunt separation was used to find the PD catheter tunnel segment. The anterior rectus abdominal muscle sheath was incised, followed by separation of the deep polyester sleeve. The original catheter was exposed in the abdominal port or purse-string suture, and the intra-abdominal segment of the dialysis catheter was pulled out. Blunt cleaning around the periphery was performed to ensure that the PD catheter was smooth, and a rigid guidewire was placed through the intra-abdominal segment of the proximal end of the catheter of the first lateral hole. The intra-abdominal segment of the PD catheter was placed into the pelvis via the original catheter in the abdominal port. Clinical data were retrospectively collected, and patients were followed up for safety and efficacy assessment. In a study involving 8 patients, no significant complications were observed, with an immediate imaging success rate of 100% and a clinical PD catheter reset success rate of 75%. The catheter remained patent until the end of the study, with a mean follow-up time of 17.25 ± 9.25 months. This new method for resetting dysfunctional PD catheters demonstrates technical feasibility, simplicity, cost-effectiveness, and safety. It has the potential to emerge as an alternative, particularly suitable for resource-limited settings.

The Vibration Response Characteristics of Neighboring Tunnels Induced by Shield Construction

With the increasing complexity of engineering environments in tunnel construction, the vibrations generated by shield tunneling in hard rock strata pose significant challenges to the operation and maintenance of adjacent tunnels. This study investigates the vibration characteristics induced by shield tunneling and provides an in-depth analysis of the propagation behavior of these vibrations within tunnel segments and surrounding soil layers. Through a combination of theoretical derivations, on-site monitoring, and numerical simulations, the research examines the distribution of vibration energy and its attenuation patterns with increasing propagation distance. The findings reveal that vibration energy is primarily concentrated in the low-frequency range (3–4 Hz) and follows an exponential decay trend as distance increases. Furthermore, the vibration response of neighboring tunnels is heavily influenced by the construction vibration source, with rapid energy attenuation observed over short distances. Numerical simulations conducted using PFC3D6.0 (Particle Flow Code) software validate the theoretical model and emphasize the critical roles of soil-damping properties and tunnel segment material characteristics in vibration attenuation. This study offers a robust theoretical framework and valuable data to support the control of tunnel vibrations and the optimization of construction practices.

Innovative Insights into Fatigue Damage Evolution of Shield Tunnel Segments by Introducing Stable Damage Limit and Memory Effect.

In this study, an experimental equipment is designed to simulate the mechanical boundary conditions of shield tunnels and test samples that exhibit varying degrees of initial damage fabricated through low-energy impact experiments. The fatigue damage characteristics of the initially damaged segments are examined under multistage cyclic loading. A comprehensive analysis of dynamic strain, mean strain, and strain amplitude time-history curves is conducted to derive damage evolution curves based on the degradation of elastic modulus. The average damage evolution rate is evaluated from these curves. The findings reveal that both initial damage and load level significantly influence segment performance evolution, potentially increasing the damage evolution rate by tenfold or more. Importantly, the results highlight a "memory effect" in damage evolution and identify a critical threshold that distinguishes between "stable" and "accelerating" damage evolution stages. Exceeding this threshold results in a substantial acceleration of the damage evolution rate, ultimately leading to failure. This research introduces the innovative concept of a stable damage limit and underscores the crucial role of initial damage in the nonlinear strain development of segmented concrete, providing valuable insights for improving fatigue design strategies in structural concrete elements.

Deformation and Reinforcement of the Existing Tunnel Affected by New Shield Tunnel Construction with Small Clearance

In recent years, the rapid expansion of subway construction has brought increasing challenges related to the crossing of new and existing subway lines. This study focuses on the Nanjing Metro line 11 project, where the new line crosses the existing line 3. A numerical simulation analysis of the tunnel intersection area is conducted using ABAQUS software to investigate the deformation mechanism of shield segments when a new tunnel is constructed at a close distance and oblique angle to an existing tunnel. During the construction of a new tunnel, the existing tunnel segments experience the greatest settlement at the intersection point, with the deformation pattern gradually evolving from a V-shape to a W-shape. The majority of the deformation in the existing tunnel occurs during the close-crossing stage of the new tunnel. An ultra-high-performance grouting (UHPG) material is proposed, and the optimal reinforcement material ratio is determined through tests. The UHPG material is applied to the underside of the existing tunnels in the crossover section for local reinforcement. The results demonstrated the effectiveness of the proposed reinforcement method. Specifically, the deformation of the left line and right line of the existing tunnel is reduced by 35.0% and 33.1%, respectively, the segmental stress decreased by 10.1%, and the ground subsidence was reduced by 13.2%.

Performance optimisation of alkali-activated slag ultra-low carbon concrete (AAS-ULCC) for shield tunnel segments by steel fibres

Performance optimisation of alkali-activated slag ultra-low carbon concrete (AAS-ULCC) for shield tunnel segments by steel fibres

Experimental investigation of mechanical behavior of horseshoe-shaped segmental tunnel linings

The fully mechanized tunnelling method using an earth pressure balance tunnel boring machine (EPB-TBM) with a horseshoe-shaped cross section was first developed and applied to a loess mountain tunnel, along with the application of a horseshoe-shaped segmental tunnel lining. The mechanical behavior of this novel type of segmental tunnel lining still contained uncertainties, and full-scale ring tests were conducted for further investigation. During the loading process, the ring deformation, joint opening, and concrete strain were measured, and the occurrence and progression of structural damage were observed and documented. The experimental results demonstrate that the structural failure of the horseshoe-shaped segmental ring mainly occurred in the arch area, while the invert did not prove to be a weak area. The deformation and failure mechanisms of the horseshoe-shaped segmental ring were found to be similar to those of circular ones. Significantly, the specific characteristics of the ring convergence deformation and bending moment distribution were significantly affected by the distribution positions of segment joints. In addition, during the initial stages of TBM advancement, frequent segment damage was observed at inferior joints, and the elaboration on the causes and corresponding measures was provided. This study provides significant evidence for the design and optimization of horseshoe-shaped segmental tunnel linings.

A Study on the Bending Stiffness of Reinforced Concrete Tunnel Segments with Added Steel Fibers.

In recent years, steel-fiber-reinforced concrete (SFRC) has been increasingly applied in shield tunnel engineering. However, most research on SFRC segments focuses on the load-bearing capacity, while the tunnel deformation is an equally critical indicator that decides if the tunnel can operate safely during service conditions. Therefore, it is essential to also study the stiffness variations in SFRC segments, which is closely connected to the serviceability limit state (SLS). To investigate the influence of SFRC on segment stiffness, full-scale four-point bending tests and analytical calculations are carried out on both traditional reinforced concrete (RC) segments and SFRC segments with rebars. A C55 plain concrete is used in the RC segment, and for SFRC, 30 kg/m3 steel fibers are added. The segment stiffnesses are calculated and analyzed, and compared between test and analytical results. This study shows that the addition of steel fibers to traditional reinforced concrete segments can enhance the bending stiffness. This effect becomes apparent only after the segments crack. Initially, the effect is strong but then becomes weaker, with increasing load. The added 30 kg/m3 steel fibers generate a maximum of 33% in stiffness increment for a segment with 2.1% reinforcement. Further analysis indicates that the transfer of stresses in the cracked SFRC results in a stiffness improvement, but after cracking, the contribution of the reinforcement to the flexural resistance increases while the contribution of the SFRC gradually decreases. Thus, the effect is weak at high load levels. This paper contributes to a better understanding of the effect of SFRC on the stiffness of segments, as relevant for SLS requirements.

Influence of a Frame Structure Building Demolition on an Adjacent Subway Tunnel: Monitoring and Analysis

In a complex urban environment, the impact of building demolitions by blasting on the structural integrity of nearby metro tunnels is critical. This study systematically analyzed the blasting and demolition process of a building adjacent to a metro tunnel using various monitoring methods, including blasting vibration, dynamic strain, deformation and settlement, pore water pressure, and displacement. The results indicate that the metro tunnel’s vibration response can be divided into four stages: notch blasting, notch closure, overall collapse impact, and auxiliary notch blasting. The most significant impact on the tunnel segments occurred during the building’s ground impact phase, with a peak particle velocity of 0.57 cm/s. The maximum tensile and compressive stresses induced in the tunnel segments did not exceed 0.4 MPa, well within the safety limits. Displacement and settlement changes in the tunnel structure were less than 1 mm, far below the warning threshold. Additionally, blasting vibrations significantly affected the pore water pressure in the surrounding soil. However, fluctuations caused by ground impact vibrations were minimal, and the pore water pressure quickly returned to its initial level after the blasting concluded. Throughout the process, no adverse effects on the metro tunnel structure were observed.

Steel Fiber Reinforced Concrete: A Systematic Review of Usage in Shield Tunnel Segment

With the advancement of tunnel construction, the load-bearing capacity of shield tunnel segments is diminishing, while issues of deformation and fissuring are becoming more conspicuous, posing direct threats to structural integrity and functionality. Steel fiber reinforced concrete (SFRC) is considered a prevalent material, endowed with high strength, excellent crack control, fracture toughness, and remarkable economic advantages. This paper surveys the state-of-the-art research on SFRC, systematically encapsulating key aspects regarding its composition, attributes, methods of segment reinforcement, constitutive models for SFRC segments, and performance enhancements of SFRC segments. By optimizing steel fiber content, aggregate preparation, and selection of chemical admixtures, the mechanical performance of SFRC can be augmented, among which the aspect ratio (l/d) and volume fraction (Vf) of steel fibers exert the most significant influence. Compared with conventional reinforcing materials, SFRC possesses benefits of low cost, uncomplicated fabrication, and superior durability. As a heterogeneous multiphase composite, SFRC exhibits high strength, stiffness, and excellent crack resistance, which can amplify the load-bearing capacity and deformation resistance of the segments, defer damage inception, and thereby enhance the safety and durability of tunnel-lining segments. This study assists in redressing the deficiencies of current shield tunnel segment reinforcement technologies and further facilitates the extensive employment of SFRC in tunnel segment strengthening and restoration.

Effects of the physico-mechanical properties on water tightness performance of ethylene propylene diene monomer-based tunnel segment gasket

Effects of the physico-mechanical properties on water tightness performance of ethylene propylene diene monomer-based tunnel segment gasket

Median nerve impairment in leprosy: how does it differ from the classic carpal tunnel syndrome?

Carpal tunnel syndrome (CTS) has already been described as a possible form of neural leprosy presentation. However, the median nerve can be involved in this neuropathy in proximal segments and, sometimes, with an asymmetric impairment of the digital branches. To detail the pattern of median nerve impairment through nerve conduction study (NCS) and ultrasound evaluation. This cross-sectional study comprises 15 primary neural leprosy (PNL) patients and 14 patients with CTS who underwent peripheral nerve ultrasonography and NCS evaluation. From the total, 92.8% of patients with CTS and 80% with PNL had bilateral impairment of the median nerve, with 27 nerves in each group. Considering the cross-sectional area (CSA) of the tunnel (Mt) segment, 63% of the nerves in the CTS and 74.1% in the PNL groups were found to be thickened, with an average CSA of 13.4 ± 4.4 and 12.4 ± 4.6, respectively (p = 0.18). The CSA of the proximal tunnel (Mpt) segment showed thickening in only 3.7% in the CTS group and 96.3% in the PNL (p < 0.0001), with an average of 6.6 ± 1.3 and 17.0 ± 6.7, respectively (p < 0.001). Finally, 88.9% of the nerves in the PNL group and only 7.4% in the CSA (p < 0.0001) showed a reduction in conduction velocity in the distal forearm, with an average of 41.0 ± 6.3 and 53.2 ± 5.2, respectively (p < 0.0001). The presence of neural thickening and demyelinating impairment in the segments proximal to the carpal tunnel favors the diagnosis of leprosy.

Experimental Research on the Structural Performance of Shield Tunnel Segments Subjected to Different Fire Temperatures

Experimental Research on the Structural Performance of Shield Tunnel Segments Subjected to Different Fire Temperatures

Waterproofing performance of longitudinal segmental tunnel joints under external loads: a full-scale experimental investigation

Waterproofing performance of longitudinal segmental tunnel joints under external loads: a full-scale experimental investigation

EVALUASI SISTEM PENGAMANAN BERDASARKAN NILAI ROCK MASS RATING (RMR) PADA TEROWONG PENGAMBILAN BENDUNGAN DI LOMBOK BARAT, NUSA TENGGARA BARAT

The construction of the dam in West Lombok is one of the National Projects of the Ministry of Public Works and Public Housing (Kemen PUPR) located in West Nusa Tenggara. The tunnel excavation process for this dam entails blasting and digging, which could potentially disrupt the stability of the surrounding area and lead to rock mass movement, including rock falls. The aim of this study is to analyze the quality of the rock mass related to the design of the support system in the tunnel segments. The results of this study show that the tunnel segment STA 0+290.704 - 292.804 exhibits good rock mass quality (RMR 61-80), where, based on the support recommendations (Bieniawski, 1989), the use of rock bolts on the roof with a length of 3m, spacing of 2.5m, and combined with wire mesh, is advised. Additionally, shotcrete with a thickness of 50mm should be applied to the roof. For the segments STA 0+285.309 - 288.104, STA 0+288.104 - 290.704, STA 0+416.068 - 414.864, and STA 0+417.134 - 416.068, which exhibit fair rock mass quality (RMR 41-60), the recommended support system (Bieniawski, 1989) includes the use of rock bolts on both the walls and roof with a length of 4m, spacing of 1.5–2m, combined with wiremesh, and shotcrete application with thicknesses of 50-100mm on the roof and 100 mm on the walls. For the segment STA 0+420.144 - 417.134, which has poor rock mass quality (RMR 21-40), the support system recommendations (Bieniawski, 1989) suggest using rock bolts on both the walls and roof with a length of 4m, spacing of 1.5–2m, combined with wiremesh, and shotcrete with a thickness of 100-150mm on the roof and 100mm on the walls. Additionally, the installation of steel ribs/steel sets is recommended.

Influence of Water Ingress at the Shield Tunnel Portal on Tunnel Deformation and Load Capacity Weakening

Abstract. During the construction of shield tunnels, adverse geological conditions can lead to tunnel segment settlement and damage. This study investigates the deformation patterns and changes in load capacity of shield tunnels under water ingress conditions at the portal, using a segment of the Jinan Metro as a case study. Through field measurements and numerical simulations, we analyzed the structural deformation and weakening of load capacity caused by water ingress. The results indicate that significant settlement occurs at both the tunnel crown and invert after water ingress, with a maximum settlement of 181.2 mm compared to the original design axis. The deformation profile of the tunnel primarily resembles a transverse "duck egg" shape, while the segments near the portal exhibit vertical "duck egg" deformations due to grouting and other factors. Multiple cracks and damages were observed in the segments, with up to 16 cracks found in a single ring. Compared to the original design conditions, the bending moment in the tunnel lining increased by approximately 7%, and the axial force increased by about 9%, leading to an 11% reduction in tunnel resistance effects. The findings of this study regarding tunnel lining deformation and load capacity weakening provide valuable insights for similar engineering projects.

Research on the Construction Mechanics and Stability Control Technology of Expressway Tunnel Based on Numerical Analysis

As an effective structural form, connecting arch tunnel has been widely used in practical engineering because of its smooth linear shape, small footprint and good bridge and tunnel connection. With the increase of domestic traffic volume year by year, the width of the even arch tunnel is gradually changed from two-way four lanes to two-way six lanes. I20 I-steel, spacing 0.75∼1 m, anchor length 3∼4 m, ring spacing 0.5∼1 m, the side ring spacing of the middle wall is 0.75 m, the side ring spacing of the side wall is 1 m, and the shotcrete thickness is 0.25∼0.3 m. The excavation span of a two-way six-lane continuous-arch tunnel is considerable, leading to complex stress characteristics, thereby posing risks to construction safety and structural stability. Following the construction of the initial tunnel, disturbance to the surrounding rock occurs, affecting subsequent excavation phases. The initial support requirements for subsequent excavations are more intricate, with increased internal forces compared to the initial tunnel segment. As the rear tunnel progresses, the surrounding rock near the middle wall shifts towards the rear tunnel, reducing internal forces in the concrete and steel arch frame. However, as the rear tunnel distance increases, concrete stress and axial forces on the middle wall side of the initial tunnel begin to rise. Throughout the construction, the steel arch frame’s internal forces and spray concrete stress on the middle wall side’s arch waist and foot are the highest, making them susceptible to disruption from construction on the opposite side, thus constituting critical tunnel components. Numerical simulations effectively capture surrounding rock and structural stress dynamics during large-span arch tunnel construction. Simulation outcomes align closely with field measurements, particularly in three-dimensional simulations, enhancing construction understanding and management.

Failure analysis and deformation characteristics of shield tunnel obliquely crossing ground fissure under earthquake

Failure analysis and deformation characteristics of shield tunnel obliquely crossing ground fissure under earthquake

Mechanical‐performance deterioration of RC segment of shield tunnel under high corrosion degree and the transformation of eccentric‐failure mode

AbstractReinforcement corrosion in shield tunnel segments has an important impact on the structure's bearing capacity and failure mode. Generally, a shield tunnel structure is under small eccentric compression, but if the reinforcement corrosion develops sufficiently, then a transition occurs from small to large eccentric load state, thereby lowering the structural bearing capacity and endangering the safety of tunnel operation. In the study reported here, based on the compressive bending load characteristics of the shield lining structure, corrosion test columns with small eccentric loading were designed to simulate the actual force state of the tunnel lining, and the whole evolution process of their mid‐span strain, ultimate bearing capacity, and cracks under different corrosion degrees was analyzed. With increasing corrosion, the bearing capacity, concrete strain, and depth of the compressive zone of a test column decrease more and more rapidly, and at the maximum corrosion degree of 68.32%, the maximum reduction of bearing capacity is 53.23%. The tests show that the failure mode of a test column with high corrosion degree (≥46.25%) is transformed from small to large eccentric failure. Based on theoretical analysis of the normal section bearing capacity of reinforced concrete flexural members, a theoretical method is proposed for calculating the critical corrosion degree for the tunnel lining structure to transform from small to large eccentric failure. The theoretical calculation method is verified against finite‐element calculations, and the present research results offer theoretical support for the durability design and safety evaluation of shield tunnel lining structures.

Experimental study on mechanical behavior and countermeasures of mountain tunnels under strike-slip fault movement

Experimental study on mechanical behavior and countermeasures of mountain tunnels under strike-slip fault movement