This paper proposes an accurate, efficient and explainable method for the classification of the surrounding rock based on a convolutional neural network (CNN). The state-of-the-art robust CNN model (EfficientNet) is applied to tunnel wall image recognition. Gaussian filtering, data augmentation and other data pre-processing techniques are used to improve the data quality and quantity. Combined with transfer learning, the generality, accuracy and efficiency of the deep learning (DL) model are further improved, and finally we achieve 89.96% accuracy. Compared with other state-of-the-art CNN architectures, such as ResNet and Inception-ResNet-V2 (IRV2), the presented deep transfer learning model is more stable, accurate and efficient. To reveal the rock classification mechanism of the proposed model, Gradient-weight Class Activation Map (Grad-CAM) visualizations are integrated into the model to enable its explainability and accountability. The developed deep transfer learning model has been applied to support the tunneling of the Xingyi City Bypass in the high mountain area of Guizhou, China, with great results.
Double-bonded spray membrane waterproofing materials have excellent waterproofing performance and can improve the load-bearing capacity of tunnel linings, leading to an increasing global application. However, due to the double-bonded capability of spray membrane materials, traditional interlayer drainage methods cannot be applied. This limitation makes it difficult to use them in drainage-type tunnels, significantly restricting their range of applications. In this regard, a novel tunnel waterproof-drainage system based on double-bonded spray membrane materials was proposed in this paper. The proposed drainage system primarily comprises upper drainage sheets and bottom drainage blind pipes, both located in the tunnel circumferential direction, as well as longitudinal drainage pipes within the tunnel. Subsequently, numerical calculation methods are employed to analyze the seepage characteristics of this system, revealing the water pressure distribution around the tunnel. The results indicate that in the novel waterproof-drainage system, the water pressure in the secondary lining exhibits a “mushroom-shaped” distribution in the circumferential direction, while the water pressure in the longitudinal direction exhibits a “wave-like” distribution. Furthermore, comparative results with other waterproof-drainage systems indicate that under typical working conditions with a water head of 160 m and a rock permeability coefficient of 10−6 m/s, the maximum water pressure in the secondary lining of the novel waterproof-drainage system is 0.6 MPa. This represents a significant reduction compared to fully encapsulated waterproofing and traditional drainage systems, which respectively reduce the water pressure by 65% and 30%. The applicability analysis of the double-bonded waterproofing and drainage system reveals that it can reduce at least 40% of the static water pressure in any groundwater environments. The novel drainage system provides a valuable reference for the application of double-bonded spray membrane waterproofing materials in drainage-type tunnels.
In slurry shield tunneling, the stability of tunnel face is closely related to the filter cake. The cutting of the cutterhead has negative impact on the formation of filter cake. This study focuses on the formation time of dynamic filter cake considering the filtration effect and rotation of cutterhead. Filtration effect is the key factor for slurry infiltration. A multilayer slurry infiltration experiment system is designed to investigate the variation of filtrate rheological property in infiltration process. Slurry mass concentration CL, soil permeability coefficient k, the particle diameter ratio between soil equivalent grain size and representative diameter of slurry particles d10/D85 are selected as independent design variables to fit the computational formula of filtration coefficient. Based on the relative relation between the mass of deposited particles in soil pores and infiltration time, a mathematical model for calculating the formation time of dynamic filter cake is proposed by combining the formation criteria and formation rate of external filter cake. The accuracy of the proposed model is verified through existing experiment data. Analysis results show that filtration coefficient is positively correlated with slurry mass concentration, while negatively correlated with the soil permeability coefficient and the particle diameter ratio between soil and slurry. As infiltration distance increases, the adsorption capacity of soil skeleton to slurry particles gradually decreases. The formation time of external filter cake is significantly lower than internal filter cake and the ratio is approximately 3.9. Under the dynamic cutting of the cutterhead, the formation time is positively associated with the rotation speed of cutter head, while negatively with the phase angle difference between adjacent cutter arm. The formation rate of external filter cake is greater than 98% when d10/D85≤ 6.1. Properly increasing the content or decreasing the diameter size of solid-phase particles in slurry can promote the formation of filter cake.
Dynamic soil−pile−superstructure interaction is crucial for understanding pile behavior in earthquake-prone ground. Evaluating the safety of piles requires determining the seismic bending moment caused by combined inertial and kinematic interactions, which is challenging. This paper addresses this problem through numerical simulations of piles in different soil sites, considering soil nonlinearity. Results reveal that the period of the soil site significantly affects the interaction among soil, piles, and structures. Bending moments in soft and hard soil sites exceed those in medium soil sites by more than twice. Deformation modes of piles exhibit distinct characteristics between hard and soft soil sites. Soft soil sites exhibit a singular inflection point, while hard soil sites show two inflection points. In soft soil sites, pile-soil kinematic interaction gradually increases bending moment from tip to head, with minor influence from superstructure’s inertial interaction. In hard soil sites, significant inertial effects from soil, even surpassing pile-soil kinematic effects near the tip, lead to reversed superposition bending moment. Superstructure’s inertial interaction notably impacts pile head in hard soil sites. A simplified coupling method is proposed using correlation coefficient to represent inertial and kinematic interactions. These findings provide insights into complex seismic interactions among soil, piles, and structures.
A tunnel-group metro station built in rock site is composed of a group of tunnels. Different tunnels and their interconnections can show inconsistent responses during an earthquake. This study investigates the dynamic responses of such a metro station in a rock site, by shaking table tests. The lining structures of each tunnel and surrounding rock are modeled based on the similitude law; foam concrete and gypsum are used to model the ground-structure system, keeping relative stiffness consistent with that of the prototype. A series of harmonic waves are employed as excitations, input along the transverse and longitudinal direction of the shaking table. The discrepant responses caused by the structural irregularities are revealed by measurement of acceleration and strain of the model. Site characteristics are identified by the transfer function method in white noise cases. The test results show that the acceleration response and strain response of the structure are controlled by the ground. In particular, the acceleration amplification effect at the opening section of the station hall is more significant than that at the standard section under transverse excitation; the amplification effect of the structural opening is insignificant under longitudinal excitation.
On January 1, 2024, a devastating M 7.6 earthquake struck the Noto Peninsula, Ishikawa Prefecture, Japan, resulting in significant casualties and property damage. Utilizing information from the first six days after the earthquake, this article analyzes the seismic source characteristics, disaster situation, and emergency response of this earthquake. The results show: 1) The earthquake rupture was of the thrust type, with aftershock distribution showing a north-east-oriented belt-like feature of 150 km. 2) Global Navigation Satellite System (GNSS) and Interferometric synthetic aperture radar (InSAR), observations detected significant westward to north-westward co-seismic displacement near the epicenter, with the maximum horizontal displacement reaching 1.2 m and the vertical uplift displacement reaching 4 m. A two-segment fault inversion model fits the observational data well. 3) Near the epicenter, large Peak Ground Velocity (PGV) and Peak Ground Acceleration (PGA) were observed, with the maxima reaching 145 cm/s and 2681 gal, respectively, and the intensity reached the highest level 7 on the Japanese (Japan Meteorological Agency, JMA) intensity standard, which is higher than level 10 of the United States Geological Survey (USGS) Modified Mercalli Intensity (MMI) standard. 4) The observation of the very rare multiple strong pulse-like ground motion (PLGM) waveform poses a topic worthy of research in the field of earthquake engineering. 5) As of January 7, the earthquake had left 128 deaths and 560 injuries in Ishikawa Prefecture, with 1305 buildings completely or partially destroyed, and had triggered a chain of disasters including tsunamis, fires, slope failures, and road damage. Finally, this paper summarizes the emergency rescue, information dissemination, and other disaster response and management measures taken in response to this earthquake. This work provides a reference case for carrying out effective responses, and offers lessons for handling similar events in the future.
The condition of bolted connections significantly affects the structural safety. However, conventional bolt tension sensors fail to provide precise measurements due to their bulky size or inadequate stability. This study employs the piezoresistive effect of crystalline silicon material to fabricate an ultrathin sensor. The sensor exhibits a linear relationship between pressure and voltage, an exceptional stability under varying temperatures, and a superior resistance to corrosion, making it adaptable and user-friendly for applications of high-strength bolt tension monitoring. A monitoring system, incorporating the proposed sensor, has also been developed. This system provides real-time display of bolt tension and enables the assessment of sensor and structural conditions, including bolt loosening or component failure. The efficacy of the proposed sensor and monitoring system was validated through a project carried out at the Xiluodu Hydropower Plant. According to the results, the sensor and online monitoring system effectively gauged and proficiently conveyed and stored bolt tension data. In addition, correlations were created between bolt tensions and essential unit parameters, such as water head, active power, and pressures at vital points, facilitating anomaly detection and early warning.
This work uses isogeometric analysis (IGA), which is based on nonlocal hypothesis and higher-order shear beam hypothesis, to investigate the static bending and free oscillation of a magneto-electro-elastic functionally graded (MEE-FG) nanobeam subject to elastic boundary constraints (BCs). The magneto-electric boundary condition and the Maxwell equation are used to calculate the variation of electric and magnetic potentials along the thickness direction of the nanobeam. This study is innovative since it does not use the conventional boundary conditions. Rather, an elastic system of straight and torsion springs with controllable stiffness is used to support nanobeams’ beginning and end positions, creating customizable BCs. The governing equations of motion of nanobeams are established by applying Hamilton’s principle and IGA is used to determine deflections and natural frequency values. Verification studies were performed to evaluate the convergence and accuracy of the proposed method. Aside from this, the impact of the input parameters on the static bending and free oscillation of the MEE-FG nanobeam is examined in detail. These findings could be valuable for analyzing and designing innovative structures constructed of functionally graded MEE materials.
Bushfire-related building losses cause adverse economic impacts to countries prone to bushfires. Building materials and components play a vital role in reducing these impacts. However, due to high costs of experimental studies and lack of numerical studies, the heat transfer behavior of building’s external components in bushfire-prone areas has not been adequately investigated. Often large-scale heat transfer models are developed using Computational Fluid Dynamics (CFD) tools, and the availability of CFD models for heat transfer in building components improves the understanding of the behavior of systems and systems of systems. Therefore, this paper uses a numerical modeling approach to investigate the bushfire/wildfire resistance of external Light gauge Steel Framed (LSF) wall systems. Both full-scale and small-scale heat transfer models were developed for the LSF wall systems. Experimental results of six internal and external LSF wall systems with varying plasterboard thickness and cladding material were used to validate the developed models. The study was then extended to investigate the bushfire resistance of seven external wall systems under two different bushfire flame zone conditions. The results illustrate the significant effects of fire curves, LSF wall components and configuration on the heat transfer across the walls. They have shown 1) the favorable performance of steel cladding and Autoclaved Aerated Concrete (AAC) panels when used on the external side of wall systems and 2) the adequacy of thin-walled steel studs’ load-bearing capacity during bushfire exposures. This study has shown that most of the investigated external LSF walls could be reused with cost-effective retrofitting such as replacing the Fire Side (FS) steel cladding after bushfire exposures. Overall, this study has advanced the understanding of the behavior of external light steel framed walls under bushfire flame zone conditions.
Concrete is the most widely utilized material for construction purposes, second only to water, in the ever-increasing need for construction globally. Concrete is a brittle material and possesses a high risk of crack formation and consequent deterioration. Cracking, which allows chemicals to enter and can cause concrete structures to lose their physico-mechanical and durability features. Repairing and rehabilitating concrete structures involves high costs and leads to various repair methods including coating, adhesives, polymers, supplementary cementitious materials (SCMs), and fibers. One of the latest technologies is the use of microorganisms in concrete. These added microorganisms lead to calcite precipitation and thereby heal the cracks effectively. This study presents a comprehensive literature survey on bacteria-included concrete, before which a bibliographic survey is performed using VOSViewer software. In addition to regular bacterial concrete, this study focuses on also using SCMs and fibers in bacterial concrete. A detailed literature review with data representation for various mechanical properties including compressive strength (CS), split tensile strength (SS), and flexure strength (FS), along with durability properties including carbonation, water absorption, resistance against chloride ion penetration, gas permeation, and resistance against cyclic freeze-and-thaw is presented. A study on the use of X-ray computed tomography (XCT) in bacterial concrete is highlighted, and the scope for future research, along with identification of the research gap, is presented.
To improve the mechanical properties and durability of the cement-stabilized base, rubber particles of three different sizes and with three different contents were optimally selected, the evolution laws of the mechanical strength and toughness of rubber-particle cement-stabilized gravel (RCSG) under different schemes were determined, and the optimal particle size and content of rubber particles were obtained. On this basis, the durability of the RCSG base was clarified. The results show that with an increase in the rubber particle size and content, the mechanical strength of RCSG gradually decreased, whereas the toughness and transverse deformation ability gradually increased. 1% content and 2–4 mm sized RCSG can better balance the relationship between mechanical strength and toughness. The 7 d unconfined compressive strength was 17.7% higher than that of the 4–8 mm RCSG. The 28 d toughness index and ultimate splitting strain can be increased by 9.8% and 6.3 times, respectively, compared with ordinary cement-stabilized gravel (CSG). In terms of durability, compared with CSG, RCSG showed a 3.7% increase in the water stability property of cement-stabilized base with 1% content and 2–4 mm rubber particles, 5.5% increase in the frozen coefficient, and 80.6% and 37.9% increase in the fatigue life at 0.70 and 0.85 stress ratio levels, respectively.
