Water Leakage Research Articles

Case study of bearing capacity failure in a 4-story reinforced concrete building

This case history analyzes the bearing capacity failure of a 4-story reinforced concrete building in Benghazi, Libya, constructed in Fall 2000. The building has a plan area of 65 m² and is supported by an 80 cm thick raft foundation resting on collapsible sandy loess, which can lose shear strength when wet. Several months before the building's failure, nearby construction work caused a broken pipeline, leading to significant water leakage. This moisture infiltrated the soil under the foundation, reducing its bearing capacity, particularly on the northern side. In winter 2002, the building began to tilt northward due to this reduced capacity, although inspections revealed no structural cracks, attributed to the rigidity of the raft foundation and reinforced concrete shear walls. The paper discusses the geotechnical properties of the supporting soil and uses finite element analysis to show that the bearing pressures exceeded allowable limits under wet conditions, emphasizing the importance of moisture content in assessing soil stability. This case highlights the complexities of foundation design and the critical impact of environmental factors on soil behavior, advocating for thorough geotechnical assessments and ongoing monitoring of conditions around structural foundations.

Segmentation of tunnel water leakage based on a lightweight DeepLabV3+ model

Abstract The accurate and efficient detection of water leakage with complex backgrounds is crucial for the safety of metro operations. A lightweight segmentation method for metro tunnel water leakage based on transfer learning is proposed. Firstly, this is based on the Deeplabv3+ model and adopts MobileNetv3-Large as the backbone feature extraction network, which significantly reduces the network parameters and improves the detection speed; secondly, it incorporates the efficient channel attention mechanism, which enables the model to adaptively adjust the weights of the channel features and capture the inter-channel relationships in the image, which significantly improves the model’s ability for feature extraction ability; furthermore, for the problem of severe imbalance between positive and negative samples in the dataset, the recognition accuracy of complex samples is increased by optimizing the loss function; finally, the training method of transfer learning is utilized to solve the problem of scarcity of water leakage dataset, and to improve the model’s accuracy and generalization ability. The results show that the model has more significant detection accuracy and segmentation speed advantages than today’s mainstream semantic segmentation model. With strong generalization ability in complex environments (e.g., low illumination and multiple obstructions), the model can be used for intelligent operation and maintenance in metro tunnel projects.

ОГЛЯД РЕЗУЛЬТАТІВ ДОСЛІДЖЕНЬ ЗАБРУДНЕННЯ КАХОВСЬКОГО ВОДОСХОВИЩА ЦЕЗІЄМ-137 І СТРОНЦІЄМ-90, ЯКІ ПРОВОДИЛИСЬ ПІСЛЯ АВАРІЇ НА ЧОРНОБИЛЬСЬКІЙ АЕС (1986-1921 РР.)

The available data on the state of radioactive contamination of water and bottom sediments of the Kakhovka Reservoir were analyzed in order to assess the possible deterioration of the quality of the environment based on the indicators of radioactive contamination in the zone of influence of the emergency discharge of water due to destruction of the Kakhovka NPP dam by the Russian military. Contamination of the Kakhovka Reservoir with 137Cs occurred mainly through the fallouts of this radionuclide with aerosols on the water surface in May 1986. A much smaller part of this radionuclide transported by water runoff directly from the headwaters of the Dnieper basin. Strontium-90 entered the reservoir exclusively by water pathway starting from October 1986. The steady trends of decreasing activity of both radionuclides in water has been observed since 1987. Approximately to 1996 137Cs activity concentrations had decreased to pre-accident level, 90Sr activity demonstrated a slow decrease and by 2022 remained slightly higher than pre-accidental level. The average levels of contamination of the Kakhovka reservoir bottom with 137Cs and 90Sr turned out to be the lowest compared to the other reservoirs of the Dnieper cascade. It was shown that in 1994 137Cs activity levels were 0.06 Ci/km2(2,2 kBq/m2) on 80% of the bottom surface (submerged former floodplain of the Dnieper) and were lower than on the territory adjacent to the reservoir. In the areas of silt accumulation (former channel of the Dnieper) 137Cs activity was on average three times higher. Balance calculations based on the data of radiation monitoring of water showed that the amount of 137Cs activity in the bottom sediments in the period 1987-2022 halved due to natural radioactive decay, the amount of 90Sr activity decreased by approximately 20%, since activity losses due to natural radioactive decay were partially compensated by the constant supply of this radionuclide with water runoff from the contaminated part of the catchment. After a catastrophic water leak from the reservoir, the Dnieper floodplain had exposed. According to the calculations, the average density of soil contamination of the ехposed areas with 137Cs does not exceed 0.03 Ci/km2 (1,1 kBq/m2), with 90Sr – less than 0.1 Ci/km2 (3,7 kBq/m2). Silt deposits of the former Dnieper channel, which had an increased level of 137Cs contamination, were re-suspended, probably, and carried out into the Dnipro-Bug estuary and further into the Black Sea. However, according to our assumptions, this should not have a negative effect on the radioecological state of the sea, because the 137Cs activity concentrations in the water of north-western part of the Black Sea were always 20-30 times higher than in the Dnieper water.

Water Leak Detection: A Comprehensive Review of Methods, Challenges, and Future Directions

This paper provides a comprehensive review of the methods and techniques developed for detecting leaks in water distribution systems, with a focus on highlighting their strengths, weaknesses, and areas for future research. Given the substantial economic, social, and environmental impacts of undetected leaks, timely detection and precise location of leaks are critical concerns for water authorities. This review categorizes existing methods into traditional approaches, such as manual sounding, and modern techniques involving smart water management and sensor technologies. A multidimensional bibliometric analysis was employed to systematically identify, select, and evaluate 600 scholarly articles on water leak detection, sourced from the Scopus database over a 23-year period (2000–2023). The paper evaluates each method based on leak sensitivity, burst detection, continuous monitoring, alarm accuracy, and implementation costs. Novel insights include an analysis of emerging smart water technologies and their integration into real-world water distribution networks, offering improved efficiency in leak detection. The paper also identifies key gaps in current research and suggests future directions for advancing the accuracy and cost-effectiveness of these technologies.

Image segmentation of tunnel water leakage defects in complex environments using an improved Unet model

Computer vision technology provides an intelligent means for detecting tunnel water leakage areas. However, the accuracy of defect feature extraction and segmentation is limited by factors such as insufficient lighting and environmental interference inside tunnels. To address the problem, this paper proposes a tunnel water leakage area segmentation network model called Customized Side Guided-Unet (CSG-Unet), using Unet as the baseline model. The main contributions are: (1) To improve the accuracy of water leakage area extraction, a customized side guided term is introduced to direct the net’s attention to the changes in light and shade within the image. A parallel attention network module is designed to extract internal information from the guided term. Subsequently, a strengthened channel attention module aggregates the guided term and the original information to achieve accurate segmentation of water leakage areas; (2) To address the scarcity of tunnel water leakage area datasets, a basic dataset is constructed by collecting data from open-source datasets and manually gathered data in tunnels. On this basis, perspective transformation is used to change the camera viewpoint, gaussian noise is randomly added to the images in the dataset to simulate images taken in dimly lit scenes, thereby expanding the dataset and enhancing the network’s generalization. The CSG-Unet network was trained using the constructed training set, achieving a mean Intersection over Union (mi IoU) of 85.54%, a mean Dice coefficient (mi Dice) of 85.26%, and a mean Pixel Accuracy (mi PA) of 90.85%. Compared to its baseline network, U-Net (tiny), these metrics show an improvement of over 3.2% in each indicator. Finally, a visual comparison between the improved network and the baseline network further confirms that the proposed model can effectively adapt to the segmentation of water leakage areas in complex environments.

A new tunnel drainage system using double-adhesive spray-applied membrane: key parameters and applicable scope

To address water leakage in tunnels with high water pressure, a new waterproof drainage system was proposed. The system uses a spray-applied material with double-adhesive properties as a waterproof layer, significantly reducing leakages, and incorporates a unique bottom drainage system to reduce water pressure. In order to check the effectiveness of the new drainage system and to analyze the effects of various structural measures on pressure reduction, a numerical seepage analysis was carried out under the conditions of a water head of 160 m and a surrounding rock permeability of 1 × 10−6 m/s. The results show that the maximum water pressure on the secondary lining is 0.6 MPa, which is about 60% reduction compared to a fully enclosed waterproof system and shows a significant pressure reduction. The spacing of the circumferential drainage pipe and the width of the drainage sheet significantly affect the drainage performance, while the arrangement of the drainage system and the size of the bottom drainage pipe have minimal impact. With full consideration of pressure reduction, cost efficiency and construction feasibility, it is recommended to use the following drainage scheme for iterative calculations during the design stage: “1” shaped arrangement, blind pipe diameter of 10 cm, width of drainage sheets of 0.8 m, and drainage spacing of 6 m. By combining the experimentally determined hydrostatic peel-off strength of 1.4 MPa for spray-applied membrane, the applicable scope of the new drainage system was acquired. The research results can provide valuable insights into the application of spray-applied waterproofing membrane in drainage tunnels with high water pressure.

Acoustic leak localization for water distribution network through time-delay-based deep learning approach

Water leakage within water distribution networks (WDNs) presents significant challenges, encompassing infrastructure damage, economic losses, and public health risks. Traditional methods for leak localization based on acoustic signals encounter inherent limitations due to environmental noise and signal distortions. In response to this crucial issue, this study introduces an innovative approach that utilizes deep learning-based techniques to estimate time delay for leak localization. The research findings reveal that while the Res1D-CNN model demonstrates inferior performance compared to the GCC-SCOT and BCC under high signal-to-noise ratio (SNR) conditions, it exhibits robust capabilities and higher accuracy in low SNR scenarios. The proposed method's efficacy was empirically validated through field measurements. This advancement in acoustic leak localization holds the potential to significantly improve fault diagnosis and maintenance systems, thereby enabling efficient management of WDNs.

Prototyping of vibration-sensing-actuation device which is contained high-power electrodynamic speaker for diagnosis of actual water main network

Water leakage and bursting due to deterioration of water distribution mains lead to water outages and economic losses. To prevent the accidents, we are conducting research to develop measurements and diagnostic methods for buried water mains. In this study, we focused on the shift in eigenfrequencies of in-plane bending vibration of rings because of deterioration. Therefore, we are developing the vibration-sensing-actuation device which detects the frequency changes of in-plane bending mode. The water distribution network is mainly composed from cast iron pipe. Moreover, the attached facilities for example fire hydrant and water valve are contained. Since attached facilities are fabricated from cast iron component, actual water main network is heavy facilities which have high rigidity. In order to excite the desired in-plane bending mode in heavy components, the proposed sensing-actuation device requires the high-power actuator. In this study, we introduce the high-power electromagnetic actuator more than 100W output into the proposed device. Furthermore, the fundamental operational tests were conducted under the various input signals in the laboratory situations. In addition, the field operation confirmation was performed in an actual water main network.

Experimental modal analysis of in-plane bending vibration mode using actual water main network

Accidents of water leakage and bursting due to deterioration of water pipes cause water outages and economic losses in the surrounding areas. We are conducting research to develop measurement and diagnostic methods for buried water pipes. The graphitic corrosion of water pipes in a buried environment causes a reduction in pipe thickness which leads to strength problems. For this reason, methods for detecting pipe thickness are necessary for evaluating pipe deterioration, however, there is no effective way to analyze pipe thickness today because it cannot be visually observed in a buried environment. In this study, we focused on the shift in eigenfrequencies of in-plane bending vibration of rings due to deterioration. At first, we performed an experimental modal analysis by using a water pipe network which is used in a practical water utility. In addition, we conducted a theoretical analysis based on a model of a two-dimensional ring with coupled incidental attachment. As a result, in-plane bending vibration was observed in the water pipe of actual size. Furthermore, in-plane bending vibration was observed when excited through fire hydrants and it is also observed in pipes that are different material and diameters.

Techno-economic comparison between commercial energy recovery devices in complex Water Distribution Networks

Water Distribution Networks (WDN) proved to be viable for the exploitation of throttling hydraulic energy. Researchers often focused their attention on the study of Pumps as Turbines (PaTs) for WDNs without considering other solutions. Actually, PaTs are not the only machines that can be employed. Indeed, other solutions exists, e.g. Cross-Flow Turbines, and commercially available Energy Harvesting Control Valves. The novelty of this study regards the selection, for each node, of the best technology among these machines rather than choosing only among PaTs, in order to help the water utilities in the techno-economic decision processes. Regarding PaTs, the authors have updated and integrated PaT-ID, their proprietary decision making tool. A complex real WDN has been used as a case study, characterized by 8 reservoirs and 16 Pressure Reducing Valves (PRVs) installed to balance the network and to reduce water leakages. Although all the three considered type of devices show at least 40% of recovered available energy within the WDN, the best solution form an energy point of view not always could be feasible from an economic point of view.

Characteristics of deformation and defect of shield tunnel in coastal structured soil in China

Shield tunnel is a type of linear underground structure assembled by lining segments, characterized with long joint, weak stiffness, and strict deformation control requirement. The situation of the long-term deformation and defect of the shield tunnel in soft ground in coastal area of China is severe, mainly attributed to the tunneling-induced ground consolidation, frozen cross passage, groundwater pumping, cyclic train load, and nearby construction. Shield tunnel is buried in ground, and the above factors could result in underlying ground settlement, overlying ground loading/unloading, and at-side ground unloading. As a result, the tunnel could suffer from different types of structural deformation and defect. Based upon the aforementioned different reasons, this study investigates the characteristics of the tunnel deformation and defect corresponding to the different types of ground stress change and deformation. It is found that tunneling-induced ground consolidation, frozen cross passage, groundwater pumping, and cyclic train load mainly contribute to the longitudinal differential settlement but negligible transverse convergence, associated with water leakages at circumferential joints. In comparison, surface surcharge and at-side unloading not only cause significant longitudinal differential deformation but also increase transverse lining internal forces, resulting in water leakages at circumferential joints, longitudinal lining concrete cracks and water leakages. Finally, nearby construction could strongly disturb the ground and cause the generation of excess pore-water pressure, making the shield tunnel deformation develops continuously after the nearby construction is completed.

A global approach to detecting and characterizing water leakage in a concrete bridge deck: Parametric study to validate an adapted full-waveform inversion method

The objective of this study is to address issues related to defects in waterproofing membranes through the use of Ground Penetration Radar to detect water leakage into the concrete layer of bridge decks. Given that processing radar signals based solely on temporal data introduces significant estimation errors, an advanced method optimized from Full-Waveform Inversion (FWI) is employed. This method accounts for several unknown factors, including boundary conditions, antenna positioning inaccuracies, and approximations inherent in 2D modeling during the inversion process. The method is adaptable and capable of reconstructing both the dielectric and geometric parameters of a multilayered structure with any number of layers and unknown parameters using just a few A-scans (up to 10, depending on the number of parameters and layers). In contrast, other methods typically require several hundred A-scans. This efficiency is achieved due to the two-dimensional nature of the layer system. Additionally, the simplicity of the structure facilitates a much faster and more straightforward inversion algorithm, hence making these features especially advantageous for practical applications. The optimized Full-Waveform Inversion approach allows for an accurate determination of unknown parameters within a multilayered medium. The high accuracy of this method is validated through a direct comparison with experiments, wherein the exact parameters are known. Such an approach enables the attainment of a low relative error using the currently available measurement device.

High-pressure core meltdown and hydrogen generation during In-vessel and Ex-vessel phases of VVER-1000 nuclear reactor and effect of heat structures

Following unprecedented Fukushima Daiichi severe accident, which significantly amplify the production of hydrogen and the associated risk of explosions, particularly in accidents like station blackout (SBO) that jeopardize containment integrity and reactor safety, a thorough investigation and comprehension of the phenomenon known as high-pressure melt ejection (HPME) are necessary. This study examines how the SBO accident develops without operator intervention or access to emergency diesel generators through full nuclear power plant simulation, including containment, core, primary, and secondary circuits. Accurate time step selection is crucial for the simulation to produce reliable results for high-pressure melt ejection processes. While the process is faster and easier under Low Pressure Melt Ejection (LPME) conditions, time step tuning can significantly lengthen the (HPME) simulation (approximately one month for each scenario). After thorough examinations and analysis of various simulation findings, three cases were evaluated for the ex-vessel phase, illustrating the most likely scenarios of high-pressure molten material splashing into the cavity. The findings demonstrate that during the in-vessel phase, 578 kg of hydrogen is created. Additionally, during the ex-vessel phase, there is a significant increase in the containment’s temperature and pressure due to the high-temperature hydrogen and significant water and steam leakage. The temperature and pressure inside the containment rise well above the safety criteria due to the leakage of 1529 kg of hydrogen from the cavity and lead to hydrogen explosion due to MELCOR message. The calculated amount of hydrogen gas is within the explosion limit range of 18.3% to 59% of the containment atmospheric pressure volume. Moreover, the height and diameter of the cavity alter due to the direct heating and corrosion of the cavity walls, ultimately compromising the integrity of the plant in the alpha mode. Based on the results obtained, it can be seen that if a large portion of the molten material is deposited on the concrete surface (case III) instead of dispersed in the cavity atmosphere (case I), the rate of hydrogen production and therefore the total amount of hydrogen (and its related energy) produced will be increased and could lead to deflagration to detonation situation.

Influence mechanism of initial mechanical damage on concrete permeability and tunnel lining leakage

The stress state is not effectively considered in existing studies when researching the permeability evolution of concrete with initial mechanical damages, causing ambiguity in the influence mechanism of initial mechanical damage on tunnel lining leakage. This deficiency can lead to significant uncertainty in predicting the probability and evaluating the consequences of tunnel leakage diseases, further affecting the formulation of relevant prevention strategies. Therefore, mechanical damage is induced to concrete specimens by subjecting them to certain stress levels, and triaxial compression seepage tests are subsequently conducted to study the influence of initial mechanical damage on permeability evolution and macrocracks. Furthermore, the relationship between microcrack characteristics and concrete permeability is studied, ultimately revealing the influence mechanism of initial mechanical damage on tunnel lining leakage. Research results indicate that the concrete permeability decreases first, becomes stable, and then continuously increases during testing, and is positively related to changes in horizontal deformation ratio. When the damage-inducing stress reaches 80% of the uniaxial compressive strength (UCS), the impact of initial mechanical damage on concrete permeability increases significantly. The increase in initial mechanical damage can lead to a significant rise in permeability, even when the crack volume is in a compacted state. Additionally, cracks on the surface of the specimen become clearly visible when the test terminates, once the damage-inducing stress reaches 85% UCS. Two factors contribute to the gradual increase in concrete permeability with the rise in initial damage-inducing stress. Firstly, microcracks inside the concrete gradually widen and propagate. Secondly, the microcracks resulting from the initial damage progressively enlarge due to water pressure during the triaxial compression seepage test. Influenced by the blockage of seepage channels, concrete permeability can occasionally decrease during testing. The accidental load induces the gradual propagation of microcracks inside the mechanically damaged concrete. Then, the rebound deformation of concrete after the removal of the accidental load causes the closed microcracks to reopen significantly, leading to an increase in permeability and subsequent tunnel lining water leakage.

Exploring the Effects of Fissures on Hydraulic Parameters in Subsurface Flows from the Perspective of Energy Changes

Reynolds number (Re), pore water pressure (P), and water flow shear force (τ) are primary indicators reflecting the characteristics of subsurface flow. Exploring the calculation of these parameters will facilitate the understanding of the hydrodynamic characteristics in different subsurface flows and quantify their differences. Hence, we conducted a study to monitor soil water content, matrix potential, and pore water pressure in two typical soil profiles (with and without fissures). The distribution of Re, P, and τ in both matrix flow (MF) and preferential flow (PF) were calculated with an improved calculation method, focusing on their energy changes. Results showed that these hydrologic parameters are quite different between MF and PF. Re values in MF remained below 0.1, indicating lower water flow velocities, while the Re values ranged from 0.8 to 2 in PF, indicating higher flow velocities. The P values in PF was tens to hundreds of times higher than that in MF, which is mainly due to the rapid accumulation and leakage of water within soil fissures. Additionally, the larger hydraulic radius and gradient in PF also resulted in higher τ values in PF (2~6 N m−2) than in MF (0~1.5 N m−2). In PF, the pressure potential was the significant factor for τ, while τ in MF was dominated by the matrix potential and varies with the magnitude of the matrix potential gradient. This study suggests that Re, P, and τ could be considered as the major indexes to reflect dynamic characteristics of subsurface flow.

The role of fault pathways for modern and deep recharge to a semi-confined aquifer: revised analysis of modern water leakage pathways in the Davis wellfield, Memphis, Tennessee, USA

Hydrologic tracer, borehole log and geophysical data provide new insight into recharge sources and pathways to the semi-confined Memphis aquifer in the Davis wellfield, Memphis, Tennessee, U.S.A. New data and recent studies highlight the importance of faults as potential pathways for the migration of modern water into the Memphis aquifer, an important regional public, industrial, and agricultural water supply. Geochemical and environmental tracer data collected over the past 28 years, combined with hydrologic, stratigraphic, and structural data, were used to evaluate changes in water quality and different recharge pathways to the Memphis aquifer. Assessment of stratigraphic and structural relationships argue for the wellfield being bound by a fault along the bluff line (west) and another fault or faults along the eastern and southeastern margins. Modern water recharge (< 60 years old) occurs through the fault along the western boundary of the wellfield, whereas modern water and, seasonally, deep-seated (helium-bearing) fluids recharge along the fault on the southeastern margin. Each recharge source and pathway present different vulnerabilities, suggesting that the role of faults in wellfields within active tectonic regions needs to be assessed.

Stress and deformation response of pipe jacking in upper-soft and lower-hard strata: A case study in Changsha

Constructing underground structures using the pipe jacking technique presents challenges in upper-soft and lower-hard strata. The complicated strata conditions make pipes prone to deflection, leading to problems such as cracking, pipe joints failure and water leakage. To determine the stress and jacking force characteristics of pipe jacking during the entire construction period in upper-soft and lower-hard strata, this paper presents a case study of pipe jacking passing through upper-soft and lower-hard strata in Changsha, China. Pipes stresses at two wings, and the top crest in the longitudinal directions for six different pipe sections were monitored. Then, a jacking force model is proposed to describe the additional thrust after deflection in upper-soft and lower-hard strata. The results show that the jacking force induced by upper-soft and lower-hard strata exhibits a tortuous increase and causes pipe deflection. The stress and deflection patterns in different monitoring pipes are consistent. The maximum pipe stresses during the jacking were 9.26 MPa in the longitudinal direction and 394 % increasing after deflection. Axial stress in test pipes exhibit nonlinearly transfer, with the distribution of friction resistance forms a“W”shape between pipes. An excessive alignment deflection would generate incremental jacking force, which strengthens with larger deflection. By regarding the composite formation area as a fully contact model with the surrounding rock, and uniform formation as a contact with the bottom of the surrounding rock, and the formulas were corrected for deeply buried pipe under uniform formation. Combining the calculation results and field data, the predict model is validated. The calculation method that can effectively predict the jacking force after pipe alignment deflection in upper-soft and lower-hard strata. The results of this study can provide beneficial guidance for the design and construction of pipe jacking.

A two-phase approach for leak detection and localization in water distribution systems using wavelet decomposition and machine learning

Water is a crucial resource for all forms of life, yet it is becoming increasingly scarce. A significant portion of water loss in urban and industrial areas is attributed to leaks. Addressing this issue is critical for enhancing efficiency, sustainability, and resource conservation. This paper presents a novel two-phase approach for leak detection and localization in water distribution systems using wavelet decomposition and machine learning for depth analysis of pressure signals. The first phase, Leak Detection, utilizes wavelet analysis to extract significant features from the daily pressure signal data. These features are then inputted into a Random Forest classifier, achieving a classification accuracy of 99% for distinguishing between “Leak” and “No Leak” scenarios. Following the detection, the Leak Localization phase aims to pinpoint the leak’s location using strategically placed sensors within the system. To facilitate understanding and application of our methodology, we have developed a user-friendly, web-based application designed for the detection and localization of water leaks on any given day. Extensive testing in a WDS named “L-Town” has validated our system’s ability to accurately identify leaks. The combination of wavelet-based signal analysis and the Random Forest algorithm forms an effective framework for advanced leak detection in water distribution systems. This approach holds great promise for future research and practical implementations in water management.

Study on the Rules of Ground Settlement and Pipeline Deformation Considering the Combined Effects of Pipeline Damage Leakage and Shield Tunneling Construction

A pipeline with long-term “hidden leakage” will greatly reduce the stability of the ground between the pipeline and tunnel in the process of tunneling through existing pipelines in unsaturated soil. Excessive settlement of the surrounding strata and pipelines can occur when the shield excavation face approaches below a pipeline, which can lead to engineering accidents. This study is based on a self-developed model experimental system for tunneling through an existing pipeline with a double-line tunnel shield. The ground settlement and pipeline deformation caused by shield construction with small-scale and no leakages are investigated. An experimental study is conducted and the accuracy of the results is verified through a comparison with theoretical solutions. The results demonstrate that there is a significant increase in ground settlement and pipeline deformation under the influence of leakage water. It is also determined that the displacement field generated by the excavation of a double-line tunnel is not simply a superposition of the displacement field generated by the excavation of a single-line tunnel. The repeated disturbances caused by the excavation of a double-line tunnel significantly influences the redistribution of the displacement field. Additionally, a three-dimensional (3D) model of shield construction considering the influence of pipeline leakage is established. This study discusses the ground settlement and pipeline deformation patterns caused by changes in the vertical and horizontal leakage diffusion ranges. The computational results indicate that the diffusion depth of a leakage is the primary factor controlling the extent of settlement.

Influence of reinforcement reductions on the response of reinforced concrete half-joints

Reinforced concrete half-joints are susceptible to deterioration mechanisms primarily due to the leakage of surface water, often contaminated with chlorides from de-icing salts, through the expansion joint. Due to the joint geometric form, favourable conditions can be created inside the joint for the corrosion of steel reinforcement. To this end, seven reinforced concrete half-joints were tested to failure under three-point bending to investigate the effect of reinforcement reductions that simulate common deterioration scenarios arising from the corrosion of reinforcement. The results were then compared to the predictions of nonlinear finite element analyses and the strut-and-tie method. The results demonstrated that a reduction in the amount of reinforcement close to the re-entrant corner has major influence on the load-deflection response of reinforced concrete half-joints. The largest reductions in load-carrying capacity were obtained from the half-joints with a full removal of diagonal bars and a combined removal of diagonal and U-bars, both showing reductions in load capacity of more than 50 %. The failure mode in each case of simulated deterioration scenarios involved a shear failure at the nib, except one case which displayed a shear failure in the full depth section due to the reduced anchorage of the bottom reinforcement. Furthermore, it was shown that nonlinear finite element analyses provide accurate predictions of the load-deflection response and failure crack patterns. The strut-and-tie method was found to result in overly conservative predictions, with an average observed-to-predicted load ratio of 1.48 and a coefficient of variation (COV) of 10.2 %. This is considerably higher than an average load ratio of 1.05 and a COV of only 3.1 % obtained from the nonlinear finite element analyses.