International Journal of Civil Engineering最新文献

The crisscrossed joints produced by weathering will seriously affect the mechanical parameters of a rock mass, resulting in the frequent occurrence of engineering geological disasters. Taking the paleoweathered jointed rock mass (PWJRM) in K₁/J₂ contact zone of the Ordos Basin as the research object, the shear parameters of the PWJRM were tested using large-scale in situ shear test, namely the cohesion (C) is distributed between 44.2 and 96.9 kPa, and the friction angle (φ) is distributed between 19.8° and 66.32°. A numerical model considering joint thickness, joint roughness coefficient (JRC) and joint strength was established with MatDEM software. Numerical simulations under different vertical stress conditions reveal the shear mechanical properties and progressive failure mechanism of the PWJRM from a meso-level perspective. It is concluded that the peak shear strength is positively correlated with the joint strength and JRC, as well as negatively correlated with the joint thickness. Under the premise that the joint thickness is greater than the thickness of the joint surface roughness, the cohesion is positively correlated with the joint strength, JRC, and joint thickness. The friction angle is negatively correlated with the joint thickness but has little correlation with the joint strength and JRC. As the joint strength increases, the shearing process is controlled by tension cracks, and with increasing joint thickness, the shearing process is controlled by tension cracks and gradually becomes controlled by shearing cracks.

In this study, experimental and numerical investigation were conducted on scour pits of granular flow downstream. Firstly, the flow flume experiment studied the influence of the material mass from the source area, the initial location of the material, the height of the check dam, and the length of the entrainment area. In the experiment a wedge was used to simulate the check dam. Then a numerical research of typical experiment processes was carried out using the discrete element method. The experiment results show that apparent entrainment only occurs under specific conditions of high initial energy, low wedge height, and small length of entrainment area. Based on the numerical verification, the numerical results obtained by the discrete element method were used for analysis, which show that the formation of the scour pit undergoes three main sub-stages, including downstream impact entrainment at the initial sub-stage, retrospective scraper entrainment toward the upstream at the middle sub-stage, and shear deformation zone formation in the entrainment area by friction and pushing at the later sub-stage. The damage caused by shear deformation in the entrainment area deserves special attention, as this area is difficult to observe directly. However, it can influence the stability of scour pits and surrounding structures. The results of this study may provide the basis for further research on the scour pits.

Conducting physical experiments to measure submergence ratio, limit, and head loss in flume flows can be resource-intensive and time-consuming. Consequently, there is a growing need to develop modeling techniques for such measurements. The goal of this study was to calibrate and employ the computational fluid dynamics (CFD) platform FLOW-3D^® code to implement varying downstream bottom elevation in a studied rectangular flume that enables measurement of submergence ratio, limit, and head loss under three flow rates (0.112, 0.169, and 0.320 ({m}^{3})/s) for the studied flume. Flow rates of 0.112, 0.169, and 0.320 m³/s were examined across three flows: Flow 1, Flow 2, and Flow 3. Calibration of FLOW-3D^® code was achieved by comparing its results with published experimental data (R² > 0.98 and RMSE < 1.5 cm). Variations in downstream bottom elevations were analyzed to determine the submergence limit, resulting in values of 0.21, 0.24, and 0.25 for Flow 1, Flow 2, and Flow 3, respectively. Additionally, the study observed a maximum head loss of 32.5% when the submergence ratio exceeded its limit in Flow 1.

Field load testing of bridges is often used as a reliable method for evaluating bridge performance. One of the downsides of field testing is that it usually requires a heavy instrumentation setup. This paper investigates the efficacy of using an artificial neural network (ANN) to predict a concrete slab bridge response and potentially reduce the number of instruments needed for field testing. The diagnostic test results from a single-span bridge are incorporated as the input dataset. Test truck location from the edge of the bridge, loading on the truck axles, and distance covered along the bridge by each axle are set as the input parameters, while the measured strains from 13 strain gauges are set as the target output. The neural network is then trained, tested, and validated, showing a good correlation with an acceptable average error percentage. Parametric studies are conducted next using the developed neural network to examine the influence of the number of strain gauges on the results. The network involving only three strain gauges with peak response shows a nearly similar correlation as the network with all 13 strain gauges. The developed neural networks are then used to predict the bridge response compared with the same bridge's proof load test results. The networks are found to predict the bridge response with high accuracy within a range of − 13.7 to + 18.6%, even with the reduced number of sensors. The results from this study demonstrate the potential of using ANNs to predict the bridge response and to optimize the sensor plans for on-site bridge load testing.

This paper investigates the deformation patterns of surrounding rock in the Xingzishan Tunnel Project, located in Yunnan Province, China, and a method that can respond to the deterioration pattern of the surrounding rock parameters is proposed. The surrounding rock in this project is carbonaceous slate, which possesses the characteristics of anisotropy, and it is hard to detect the mechanical parameters of the rock. A deformation back-analysis method that considers the deterioration effect of the surrounding rock is proposed by using the function approximation and pattern recognition functions of the back propagation (BP) neural network. The fitting equations for the deterioration pattern of the vertical and horizontal elastic moduli E of the surrounding rock are established. Based on the regression prediction of the back propagation (BP) neural network, it is found that the changes in the deformation parameters of the surrounding rock follow certain variation rules within 20 m from the excavation surface. Furthermore, by comparing the deterioration of the surrounding rock in the vertical and horizontal directions, it is considered that the degree of deterioration of the anisotropic surrounding rock varies in different directions. The result is a reference for studying tunnel deformation in anisotropic rocks, and provide a basis for further studies on the deformation mechanisms and control measures of rock surrounding tunnels.

Reducing residual deformations is crucial for repairing structures post-earthquake. Steel frame structures that are self-centring and equipped with disc springs show promising performance in this area. This study investigates the seismic performance of this innovative system by first correlating the friction and pre-loading force of the disc springs to their yielding stress. The parameters β (energy dissipation) and γ (secondary stiffness) were analysed. To assess these coefficients, diagonal braces with varying β and γ values were incorporated into a single-storey, single-bay frame. These models underwent quasi-static loading and were validated using experimental data. The results revealed that three braces with coefficient pairs of (β, γ) = (1, 1.2), (1, 1.6), and (1, 2) achieved maximum energy dissipation with nearly zero residual deformations. Further investigation involved designing nine structural models of 3-, 6-, and 9-storey buildings equipped with disc spring-based, self-centring bracing systems that included friction plates. Additionally, three special Chevron-braced steel frame models of 3-, 6-, and 9-storeys were designed for comparison with the self-centring frames. Utilizing OpenSees software and the TCL programming language, all twelve models were analysed through Incremental Dynamic Analysis subjected to specified ground motion records. A fragility curve for each case was derived. The results demonstrated that the self-centring frame with coefficients of β = 1.0 and γ = 1.2 showed improvements of 118% and 504% in collapse capacity and residual deformation control, respectively, compared to the equivalent Chevron-braced frame, with only a 17% increase in weight.

This study examines experimentally and numerically the thermo-mechanical behaviour of a novel Structural Insulated Panel (SIP) wall. The SIP UWall comprises of external cement boards and an internal core of expanded polystyrene and foamed concrete. Thermo-structural panels of size 600 × 2400 mm were first exposed to temperatures of up to 70 °C and flexo-compression to examine experimentally the behaviour of the novel SIP UWall vs traditional wall systems used in Southeast Asia, such as mon block walls, brick block walls, and lightweight block walls. The results indicate that the deflection of the SIP UWall was 42.0%, 23.8%, and 16.4% lower than that of traditional mon block, brick block, and lightweight block walls, respectively. To further assess the thermal performance of the above walls under real environmental conditions, four scale-down house units (1.5 × 1.5 × 2.4 m) were built in Chachoengsao province, Thailand. Results from the four scaled-down house units show that the use of SIP UWall reduced indoor temperatures by up to 5 °C compared to units constructed with mon block walls. Subsequently, the study proposes a novel approach to assess the thermo-mechanical behaviour of the panels using Fourier's law of heat transfer, Airy's stress function, and the principle of conservation of energy. The new approach explicitly considers the combined effect of applied thermal and mechanical loads. The approach is validated using the results obtained from the panel tests and the scale-down house units. It is shown that the proposed semi-empirical approach predicts well the thermo-mechanical behaviour on the wall panels tested in this study, with a Prediction/Experiment ratio of 1.06 and a Standard Deviation of 0.12. The tested wall panels and scaled-down hose units are subsequently modelled in Abaqus®. The results indicate that the SIP UWall exhibited superior thermal performance in terms of heat absorption, surpassing the mon block, brick block, and lightweight block panels by 19.4%, 15.7%, and 10.8%. The small errors in the Abaqus® predictions (always < 5%) indicate that the modelling approach adopted in this study was sufficiently accurate to simulate the thermal behaviour of the tested wall panels. This study contributes towards developing better assessment models and more energy-efficient construction materials in Southeast Asia.

The primary objective of this investigation is to assess the potential reusability of aged, dumped waste found in landfills for its application as a bulk geomaterial. Owing to the inherent heterogeneity of municipal solid waste (MSW), comprehensively understanding its behaviour—be it physical, mechanical, or dynamic—presents a significant challenge. Laboratory-based studies serve as a pivotal means to gain insight into a material's behaviour before its practical implementation. The study focuses on examining the intricate strength characteristics of MSW fines (< 4.75 mm) and fiber-reinforced MSW fines (with varying fiber content ranging from 0 to 10%) using the bender element laboratory test. The bender element analysis facilitates the determination of shear wave velocity (V_s) values by measuring the disparity in time travel between transmitted and received waves. Comprehensive scrutiny encompasses the influence of diverse parameters, notably the excitation frequency of the wave (f), applied confining pressure (σ_c), relative compaction (R_c), fiber content (FC), and the saturation state. Notably, the study identified an optimal fiber content of 1% across different excitation frequencies and applied confining pressures, where V_s or normalized G_max values exhibited higher levels. Furthermore, the study involved fitting a cubic polynomial model and devising a generalized equation that correlates the normalized small strain modulus with the normalized shear strength for fiber-reinforced MSW fines. This equation serves as a valuable tool in understanding and predicting the material behaviour concerning small strain modulus and shear strength in fiber-reinforced MSW fines.

Engineers have limited control over the process of soil formation, which can pose challenges when it comes to constructing structures such as dams, pavements, rail tracks, and foundations. To address this issue, a study was conducted to examine the mechanical properties of Hormoz Carbonate Sand and Firoozkooh Quartz Sand No 161. The goal was to predict the settlement, particle breakage, and shear strength of these sands. Tall oedometer and direct shear tests were conducted in a drained condition and the samples were prepared with the dry pluviation method in two different relative densities (30% as loose and 80% as dense) and consolidated under various confining pressures. The results revealed that in dense specimens, the particle breakage index increased as the porosity decreased. In the tall oedometer tests, it was observed that the vertical applied stress decreased with increasing height of the soil sample. Additionally, particle breakage decreased with depth in the samples, corresponding to the decreasing vertical applied stress. Furthermore, direct shear tests were performed on soil samples of different heights (0.5, 1, 1.5, 2, and 3 cm) using a direct shear apparatus. It was found that in the lower sample heights (0.5, 1, 1.5 cm), a greater amount of breakage occurred due to a higher percentage of soil volume placed in the shear zone. The results also indicated that increasing the shearing rate led to a reduction in the particle breakage index.

This paper discusses the uncertainties surrounding corrosion prompted by stray direct current (DC) and alternating current (AC) interferences. The influence of railway stray DC interference was simulated through cyclic potentiodynamic (CP) polarization in a simulated concrete pore solution. Steel fibres exhibit excellent resistance to stray DC perturbations up to 1.0 V (vs. OCP or Open Circuit Potential) in the absence of chloride. However, when the electrolyte contains 0.6 mol/L chloride, a reduced DC perturbation of 0.4 V (vs. OCP) was sufficient to initiate pitting corrosion, indicating decreased corrosion resistance. The stray AC interference was simulated by applying an AC perturbation test to the embedded steel fibres which were polarized in simulated concrete pore solution as well. This approach allows for the effect of steel fibre orientations under stray AC interferences to be assessed. Following the AC interference test, the Tafel polarisation test shows a stochastic corrosion pattern in the embedded steel fibres. Notably, there is a significant reduction in the corrosion potential (E_corr) and a corresponding increase in the corrosion current density (i_corr) observed in one of the fibres. Ongoing research is being conducted to explore the stochastic corrosion phenomena identified in this research. Boundary element modelling (BEM) results show that the maximum voltage drops between steel fibres arranged in various configurations closely correspond to experimental measurements. The computer simulation approach applied in this study has the potential to further advance the development of more valuable predictive tools in forecasting the corrosion behaviours of reinforced concrete exposed to stray currents under complex built environments.