Search Results (184)

Cutter soil mixing (CSM) is a widely adopted construction technique for forming waterproof diaphragm walls in underground engineering. However, cement slurry is prone to dispersion loss and performance degradation in moving water, making it difficult to meet engineering requirements. In this study, based on the characteristics of the CSM method in dynamic water environments, ordinary Portland cement is used as the main material, and hydroxypropyl methyl cellulose (HPMC), redispersible latex powder, polypropylene fiber and a polyether defoamer are added to improve it. The influence of each component on the performance of the new material is investigated, and a new CSM material suitable for dynamic water environments is developed. The material has good stability and suitable fluidity, controllable setting time, good anti-dispersion performance in dynamic water. The optimal mix ratio is as follows: water–cement ratio of 1; HPMC 1.4%; redispersible latex powder 3%; polypropylene fiber 0.4%; and polyether defoamer 0.8%. Field tests show that the new grouting material applied to CSM waterproof curtain construction results in a leak-free wall with excellent waterproofing performance, which verifies its engineering feasibility and provides a technical reference for the application of the CSM method in dynamic water environments. Full article

Sarcocystis species are apicomplexan protozoa infecting a wide range of domestic and wild animals, including cattle, in which several species are of zoonotic relevance. This study reports, for the first time, the detection and molecular identification of pathogenic and zoonotic Sarcocystis hominis in slaughtered cattle from Central Chile. A total of 200 muscle samples (100 = myocardium, 100 = diaphragm) were examined by macroscopic inspection and tissue homogenization. Selected samples were additionally analyzed by histology, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and multiplex real-time PCR targeting the 18S rDNA. No macroscopic sarcocysts were observed, nonetheless microscopic sarcocysts were detected in 56% of assessed samples, with higher infection rates in the heart (91%) than in the diaphragm (21%). SEM and TEM analyses revealed thin-walled sarcocysts with finger-like protrusions in the diaphragm, as well as flattened hair-like projections in the myocardium. Molecular analysis identified Sarcocystis cruzi in all positive samples and detected additional DNA of Sarcocystis bovifelis/Sarcocystis rommeli and for the first time the zoonotic species S. hominis. These findings confirm the coexistence of canine-, feline-, and human-transmitted Sarcocystis species in Chilean cattle and highlight potential public health implications associated with consumption of raw or undercooked S. hominis-carrying beef meat. This constitutes the first molecular evidence of S. hominis in Chile, emphasizing the need for further surveillance and control measures in the meat production chain. These novel data on human S. hominis infections in Chile confirm the importance of initiating investigations on human sarcocystosis as this enteric parasitic disease is still sparsely considered by local public health authorities. Full article

This study assessed whether electrochemical activation of mixing water can enhance autoclaved aerated concrete (AAC), in which fly ash replaces sand as the siliceous component. Mixing water was electrolyzed in a diaphragm-type “Melesta” unit to obtain the catholyte and anolyte, and fly ash was pre-exposed to the catholyte for up to 15 min. The material’s behavior was evaluated using slurry flow tests, scanning electron microscopy, Fourier-transform infrared spectroscopy, macropore-uniformity analysis, mercury intrusion porosimetry, and shrinkage and short-term durability indicators. At an approximately constant density class near 600 kg/m³, the catholyte-pretreated fly-ash AAC mixes showed a near-monotonic increase in compressive strength with increasing fly-ash replacement (relative to the sand-based reference), while fresh-mixture fluidity decreased. The pore structure became more uniform, as indicated by a decrease in the standard deviation of pore diameters from 0.175 to 0.133 mm, and porosimetry indicated a higher micro-porosity fraction in fly-ash AAC than in sand-based AAC. Capillary shrinkage remained essentially unchanged, and short-term durability indicators (durability coefficients after 25 cycles) showed a small improvement. Overall, electrochemically activated water promoted a more regular pore system and stronger interpore walls under autoclave curing, supporting higher fly-ash utilization without loss of dimensional stability. The results are limited to one fly-ash source (Ekibastuz TPP); transferability should be verified using ashes with different glass content, fineness, and carbon/LOI. Full article

Cantrell syndrome (CS) is a rare congenital disorder involving defects in the thoraco-abdominal midline, the diaphragm, the pericardium, the sternum and the heart. Since the initial description of the syndrome, 165 well-documented cases in humans have been reported, demonstrating substantial heterogeneity ranging from complete pentalogy to partial or atypical variants. A systematic review classified body wall defects and associated anomalies into nine categories, which are fully described in the manuscript. The categories include midline defects (UThAb, SUThAb, UAb, SUAb, SUICD, and UH), lateral defects (ThLAb and StLAb), and special cases. Each case was reassessed for umbilical cord status, body wall morphology, cardiac anomalies and additional malformations. Midline defects predominated (153 out of 165 cases, 92.7%), with supraumbilical variants being the most frequent. Umbilical hernias formed a distinct subgroup of ten cases. Lateral defects were uncommon (9 cases, 5.5%) and typically presented as thoracogastroschisis or lateral thoracoabdominoschisis. These defects were often associated with normal umbilical cords. Cardiac anomalies were universal, with ventricular and atrial septal defects being the most common findings. Reclassification revealed that many cases originally labeled as ‘classic pentalogy of Cantrell’ were more accurately classified as partial or atypical forms. This unified framework improves epidemiological understanding and diagnostic precision. From a One Health perspective, it underscores CS as a shared developmental vulnerability across mammalian species. Full article

Diaphragm walls are widely used for deep foundation pit support and permanent underground structures. The joints between adjacent panels are critical weak points, significantly influencing the overall deformation and stress distribution of the structure. To address the insufficient shear and tensile capacity of existing diaphragm wall joints, this study proposes a novel rigid joint incorporating retractable shear studs. The joint features a straightforward and constructible design, primarily comprising retractable shear studs, H-section steel, and shear stud pop-out limit plates. By withdrawing the limit plates inserted into the H-section steel, the retractable shear studs mounted on the web automatically extend along their axis, penetrating into the adjacent reinforcement cage to form an intrusive lap joint. This mechanism effectively enhances the integrity and load-bearing capacity at the joint. To validate its mechanical performance, large-scale specimens featuring this new joint were fabricated and subjected to shear and tensile tests. The experimental results demonstrate that, compared to traditional H-section steel joints, the peak shear and tensile strengths of the proposed joint are increased by approximately 10 times and 16 times, respectively. These findings fully verify the excellent mechanical performance of the novel diaphragm wall joint structure. Full article

This study investigates the seismic performance of reinforced concrete flat slab buildings strengthened with conventional structural elements, including drop panels, edge beams, shear walls, and coupled shear walls. Unlike previous works that examined these elements independently, this research provides an integrated comparative evaluation of several common strengthening approaches under identical modeling and seismic loading conditions, offering clear guidance for practical design optimization. A comparative finite element analysis was conducted using ETABS v20 in accordance with ACI 318-19 and ASCE 7-22 seismic design provisions. Five ten-story building models were developed to assess key response parameters such as story displacement, inter-story drift, column axial forces, diaphragm deformation, and punching shear resistance under gravity and earthquake loading. Results reveal that models incorporating coupled shear walls achieve the greatest improved seismic performance, with up to 50% reduction in story displacement compared to other configurations, while also minimizing column over-compression and lateral drift. Drop panels alone showed a localized improvement in punching resistance, but their global impact on lateral stiffness was limited. However, the combination of drop panels and edge beams produced a synergistic effect, significantly enhancing overall stiffness and controlling drift. Coupled shear walls efficiently redirected lateral forces away from critical slab–column joints, thereby mitigating the risk of punching shear failure. These findings offer practical guidance for structural engineers seeking to optimize the seismic design of flat slab buildings, emphasizing the importance of integrated strengthening strategies in achieving both stiffness and ductility in seismic regions. The findings underline the significance of systematically evaluating conventional strengthening techniques within a unified modeling framework, offering engineers practical insights for improving the seismic behavior of flat slab buildings at the early stage of design. Full article

To investigate the complex interaction in multi-structure systems, this study establishes a refined 3D numerical model based on a transportation hub project in Tianjin to analyze the asymmetric coupling deformation mechanism of a deep excavation adjacent to a shared-wall metro station and elevated bridge piles. This study highlights the transition from soil-mediated interaction mechanisms to those dominated by structures under shared-wall constraints. Results show that the existing station acts as a high-stiffness boundary, effectively suppressing lateral-wall deflection and basal heave on the proximal side. A critical finding is the reversal of the station’s deformation mode: while stations with a soil buffer typically tilt toward the excavation, the shared-wall station exhibits a clockwise rotation away from the excavation; this phenomenon is driven by excavation-induced basal rebound directly transferred through the common diaphragm wall. Furthermore, the station exerts a significant “shielding effect” on adjacent bridge piles, shifting their maximum lateral displacement from the pile head to the toe and reducing overall deformation. Parametric analyses reveal that optimizing shared-wall thickness is more effective for controlling lateral deformation, whereas increasing wall depth primarily mediates vertical heave. This study concludes that, for shared-wall systems, design priorities must shift from settlement control to anti-heave measures, and pile monitoring should extend to the deeper critical zones identified in this study. Full article

As an emerging construction method, the lateral launching technique for shield tunneling can ensure launching safety while significantly reducing disturbances to urban traffic. However, the influence of its design parameters on construction stability and economic performance has not yet been systematically investigated, thereby limiting its broader application in complex urban environments. To address this gap, this study proposes a comprehensive analytical framework integrating field monitoring, numerical modeling, orthogonal experiments, and regression-based optimization. Relying on a shield lateral launching project in a central urban district of Guangzhou, a systematic investigation is conducted. Field monitoring data are used to verify the reliability of the three-dimensional finite element model, confirming that deformations of both the retaining structures and the surrounding ground remain within a stable and controllable range. On this basis, the orthogonal experimental method is, for the first time, introduced into the parameter sensitivity analysis of the shield lateral launching technique. The analysis reveals the influence ranking of support parameters on surface settlement. Key parameters are then selected for optimization design according to the sensitivity order, followed by a comprehensive evaluation of deformation control effectiveness and economic performance of the optimized scheme. The results show that the deformation of both the retaining structures and the ground during construction remains below the control limits, indicating good structural stability. Among the supporting parameters, the sensitivity coefficients from high to low are the diaphragm wall thickness H_W, the grouting reinforcement range H_G, the initial support thickness of the lateral-shifting tunnel H₁, the initial support thickness of the advance launching tunnel H₂, and the elastic modulus of the diaphragm wall E_W. Based on the sensitivity ranking, the highly sensitive parameters are selected for optimization, and the optimal parameter combination is determined to be a diaphragm wall thickness of 1000 mm, a grouting reinforcement range of 1600 mm, and an initial support thickness of 100 mm for the lateral-shifting tunnel. This combination meets the safety requirements for surface settlement while effectively reducing material consumption and improving economic performance. The study provides technical and theoretical references for shield launching under complex conditions. Full article

With the increasing functional and geometric complexity of modern steel buildings, irregular-shaped beam-to-column joints are becoming common in engineering practice. However, their seismic behavior remains insufficiently understood, particularly for configurations with geometric asymmetry and complex stress transfer mechanisms. This study experimentally investigates the seismic performance of irregular steel-beam-to-concrete-filled steel tube (CFST) column joints incorporating inclined internal diaphragms (IIDs), taking unequal-depth beam (UDB) and staggered beam (SB) joints as representative cases. Two full-scale joint specimens were designed and tested under cyclic loading to evaluate their failure modes, load-bearing capacity, stiffness/strength degradation, energy dissipation capacity, strain distribution, and panel zone shear behavior. Both joints exhibited satisfactory strength and initial stiffness. Although diaphragm fracture occurred at approximately 3% drift, the joints retained 45–60% of their peak load capacity, based on the average strength of several loading cycles at the same drift level after diaphragm failure, and maintained stable hysteresis with average equivalent damping ratios above 0.20. Final failure was governed by successive diaphragm fracture followed by the tearing of the column wall, indicating that the adopted diaphragm thickness (equal to the beam flange thickness) was insufficient and that welding quality significantly affected joint performance. Refined finite element (FE) models were developed and validated against the test responses, reasonably capturing global strength, initial stiffness, and the stress concentration patterns prior to diaphragm fracture. The findings of this study provide a useful reference for the seismic design and further development of internal-diaphragm irregular steel-beam-to-CFST column joints. Full article

With the rapid expansion of urban transportation networks, new metro tunnels frequently cut through existing structures’ diaphragm walls by using the shield machine. Such intrusions induce dynamic disturbances that pose significant risks to adjacent structures. This study employs Suzhou Metro Line 8 as a case study to evaluate the safety of existing metro stations during shield tunneling, specifically examining deformation characteristics induced by varying tunneling parameters. A three-dimensional numerical model is developed to assess structural responses, with simulation accuracy rigorously validated against field measurements. Results reveal that the transverse influence zone of the base slab extends approximately 2.5 times the tunnel diameter. Diaphragm wall exhibits horizontal deformation opposite the tunneling direction, while the maximum lateral deformation of adjacent station walls reaches 2.49 mm. Concurrently, a slight uplift manifests at the base slab center with a peak value of 2.54 mm. All obtained structural deformations remain well below the permission value of 5 mm, with observed maxima constituting only 50% of this safety threshold. This substantial deformation margin significantly mitigates construction hazards, promoting the sustainable development of underground space. Full article

This paper addresses the seismic retrofitting of masonry churches with timber roofs by designing a ductile roof diaphragm with a new energy-based methodology. The proposed approach relies on nonlinear dynamic analyses conducted on an equivalent structural model. In this model, masonry nonlinearity is represented by rotational plastic hinges at the base of the equivalent wall elements. Roof system nonlinearity is modeled by shear plastic hinges simulating the energy dissipation of steel connections. In the equivalent model, the earthquake is implemented using a set of spectrum-compatible accelerograms. The dynamic response of the aforementioned plastic hinges is analyzed in terms of equivalent damping during the seismic events by extracting the relevant hysteresis cycles. This allows for the evaluation of both dissipated and strain energy. The estimation of the equivalent damping ratio provided by the roof diaphragm is based on multiple design configurations. After identifying the maximum achievable damping ratio, the study suggests ways to determine the corresponding roof stiffness, which defines the optimal retrofit configuration. This configuration is then implemented in a three-dimensional model that includes nonlinear properties for both masonry and connection elements, allowing a validation of the seismic response obtained from the initial equivalent model with a more complex and detailed model. Finally, a seismic response comparison is conducted between the optimized dissipated energy configuration, based on damping ratio evaluation, and an overstrength design variant determined considering the elastic behavior of the roof connections. Full article

Significant environmental temperature variations occur during the construction of large-scale underground structures, constituting one of the major factors influencing structural deformation. Parameter inversion of soil layers based solely on the causal relationship between excavation-induced loading effects and structural displacements can lead to substantial errors. To address this issue, this study aims to improve the inversion accuracy of soil parameters by considering temperature effects. A finite element model incorporating temperature effects, combined with machine learning algorithms, was employed to improve the inversion process. Based on the measured displacements and structural temperatures of diaphragm walls of the Beijing Tongzhou Integrated Transportation Hub Project, the influence of temperature effects on structural behavior was investigated to improve the inversion accuracy of soil parameters for large underground structures. Then, a finite element model of the excavation considering temperature effects is established using measured soil parameters and temperature data. According to soil classification, a training dataset is constructed through proportional scaling of soil parameters. Three machine learning algorithms—Decision Tree, Random Forest, and Gaussian Process Regression—are compared to evaluate inversion accuracy. The results indicate that the deformation of underground structures is governed by the coupled effects of temperature and earth pressure. Among the tested methods, the Random Forest algorithm demonstrates the highest accuracy in soil parameter inversion, with an average displacement error of 4.23% in the finite element model based on the inverted parameters. These findings highlight the importance of incorporating temperature effects to enhance inversion reliability for large underground structures. Full article

Deep excavation in natural structured clay causes disturbance to the surrounding soil, which damages the soil structure and results in soil strength reduction. This study investigates excavation-induced disturbance in natural clay based on a case of subway station excavation. A series of piezocone tests was performed adjacent to the diaphragm wall before and after excavation to determine the disturbance degree based on cone tip resistance. The stress and deformation variations in soil were also obtained via numerical simulations, and the mechanisms of excavation-induced disturbance were proposed based on the numerical simulation results. The results showed that excavation caused a decrease in the cone tip resistance, and the disturbance degree of soil determined by cone tip resistance ranged from 0% to 50%. At identical locations, the disturbance degree of soil increased with excavation depth. The main reason for excavation disturbance is the increase in shear stress. Therefore, shear strain can serve as an indicator of the degree of disturbance, and the relationship between disturbance degree and shear strain can be expressed by a power function. The degree of soil disturbance is affected not only by the magnitude of the diaphragm wall horizontal displacement but also by its deformation distribution pattern. Full article

The extensive development of urban underground space increases the risk of deformation to adjacent structures during deep excavations. This study investigates the response of three low-strength strip-foundation buildings (#4, #8, and #11 of the Ninggong Apartment) in Nanjing, China, affected by the excavation of an adjacent super-long, narrow subway station. The site is located in a typical soft alluvial area of the Yangtze River, characterized by highly compressible and sensitive soil, which poses substantial challenges. Pre-construction ground improvement was implemented to mitigate the impacts of diaphragm wall trenching; however, monitoring data indicated that buildings’ settlements of this stage still reached 28.2%, 24.8%, and 27.2% of their final values, with extensive influence zones. Subsequent excavation of the eastern and middle sections induced further cumulative and differential settlements, raising safety concerns and necessitating structural strengthening before adjacent western excavation. An integrated underpinning system, combining anchor static pressure steel pipe piles with a raft foundation, was adopted. Although short-term settlement increased during pile and raft installation, post-strengthening settlement rates decreased significantly. The adjacent western excavation caused only 13.3% of the settlement to be observed during the middle section’s excavation. All buildings were ultimately protected from excessive deformation. The protective strategies and lessons learned provide practical guidance for similar projects. Full article

This paper presents a case study on an ultra-deep excavation in a reclaimed area supported by servo steel struts, addressing the limited case-specific data on deformation behavior under such complex geological conditions. Comprehensive monitoring of the pit structure and surrounding environment was performed throughout construction. Results highlight significant time-dependent deformation due to the rheological behavior of artificial fill and soft soil, with metro tunnel displacement during suspension phases contributing up to 29% of the total. Servo steel struts, via active axial force compensation, reduced maximum diaphragm wall displacement by 24%, ground settlement by 29%, and pipeline settlement by 46% compared to conventional supports. Integrated measures, including bottom-sealed diaphragm walls, isolation piles, and grouting curtains, successfully confined tunnel deformation within 5.4 mm, complying with strict safety criteria. A strong linear correlation between tunnel and wall displacements was observed, enabling a predictive envelope model for deformation. This study underscores the efficacy of servo steel struts in controlling excavation-induced deformation in reclaimed areas and offers practical insights for designing and managing ultra-deep excavations in similar challenging settings. Full article