Surface Loading Research Articles

Python Software Tool for Diagnostics of the Global Navigation Satellite System Station (PS-NETM)–Reviewing the New Global Navigation Satellite System Time Series Analysis Tool

The time series of GNSS coordinates contain signals caused by the age-related movement of tectonic plates, the deformation of the Earth’s surface, as well as errors at different time scales from sub-daily tidal deformation to the long-term deformation of the surface load. Depending on the nature of the signal, specific approaches are used for both the visual interpretation and pre-processing of time series and their statistical analysis. However, none of the present software analyzes the nature of the residual errors but assumes their random nature and obedience to the classical normal distribution. One of the methods for analyzing the time series of coordinates with residual, unaccounted-for systematic errors is the non-classical error theory of measurements. The result of this work is a developed software solution for analyzing the time series of GNSS coordinates to test their normality, or in other words, to test whether a particular GNSS station is subject to the influence of small, unaccounted-for errors. Conclusions: After testing our software on four reference stations in Europe, we concluded that none of the chosen stations followed the normal law of distribution; thus, it is vital to perform such tests before conducting any experiments on the time series from reference stations.

Analysis of size-dependent response of surface excited functionally graded layer with consideration of couple-stress effects

This paper focuses on a theoretical examination of the mechanical behavior of elastic layers made of functionally graded (FG) materials. It particularly highlights the impact of material microstructures by utilizing the couple stress theory to introduce FG characteristics of the coating material across the thickness direction, along with size effects. The study distinctively addresses both surface loading and contact problems, employing various indenter shapes and eccentric indentation forces. The Fourier transform is utilized to solve for displacements and stress fields resulting from surface tractions. The method for approximating the pressure distribution under the indenter is based on a collocation method with a simple discretization of the contact pressure. Brent's method is applied to determine the unknown contact region when using indenters with non-sharp edges. The results demonstrate that the shear modulus ratio and the intrinsic material length scale significantly influence the pressure intensity, highlighting a substantial dependence on the mechanical properties of materials under indentation force. The research also shows that the effect of the length scale and shear modulus ratio affects the limit eccentricity and tilt angle. The results highlight the necessity of considering both the size effect and material gradation when analyzing FG materials under mechanical stress.

Effects of Pipe Deflection and Arching on Stress Distribution and Lateral Earth Pressure Coefficient in Buried Flexible Pipes

In this study, full-scale laboratory tests were conducted on a 315 mm diameter HDPE pipe under shallow buried and localised surface loading conditions to investigate the effects of pipe deflection and arching on stress distribution and the lateral earth pressure coefficient. The tests were validated using 2D finite element software, and further analyses were carried out through parametric studies. These studies considered variations in pipe stiffness, burial depth, backfill properties and pavement stiffness to increase the reliability of the test results. For a shallowly buried HDPE pipe, a comprehensive explanation is provided regarding the evolution of the lateral earth pressure coefficient within the central soil prism. Initially set at Ko conditions, this coefficient tends to shift towards Kp with increasing arching and transitions to Ka with weakening arching. The findings suggest that stress predictions in the crown region of shallow buried flexible pipes are achievable through the application of Terzaghi’s arching theory, contingent upon an accurate estimation of the lateral earth pressure coefficient for the central soil prism. Furthermore, the horizontal deflection of the pipe at the springline results in compressive behaviour and passive effects in the surrounding backfill in this specific region. This situation demonstrates that the horizontal stresses at the springline and the lateral earth pressure coefficient can be reliably estimated by considering them as functions of the horizontal deflection of the pipe.

Impact of fully rotating steel casing bored pile on adjacent tunnels

Abstract Based on the theoretical model of a soil plug column, the stress analysis of the soil plug column during the spinning process of steel casing is carried out, and the critical depth of the soil column is determined using the stress and torsional shear ratio of the soil column. The effect of factors such as casing wall thickness, surface load, and steel casing spinning speed on the critical depth of soil columns has been explored, and more reasonable construction process parameters have been obtained quantitatively. Combined with the construction of small net distance test piles at a distance of 2.5 m from the tunnel, the impact of the construction process on the existing shield tunnel has been explored. The results indicate that during the construction process, when the wall thickness of the steel casing does not exceed 0.012 m, the surface load does not exceed 15 kPa, the spinning speed of the steel casing is maintained at 5/4/2/4 m/h or 5/3/2/3 m/h (corresponding to soil depths of 2.5/9.5/6/14 m), and the soil height of the soil column is controlled within 11 m, it is not easy to generate soil plug inside the steel casing, and the soil column has strong torsional shear resistance. According to the measured data of adjacent tunnels, it has been found that the construction method of fully rotating steel casing bored pile can effectively reduce the impact on adjacent shield tunnels, and has a good microdisturbance effect, which can control tunnel deformation not exceeding 1 mm and maintain within the warning value range.

Increased solar-driven chemical transformations through surface-induced benzoperylene aggregation in dye-sensitized photoanodes

The impact of benzo[ghi]perylenetriimide (BPTI) dye aggregation on the performance of photoelectrochemical devices was explored, through imide-substitution with either alkyl (BPTI-A, 2-ethylpropyl) or bulky aryl (BPTI-B, 2,6-diisopropylphenyl) moieties, to, respectively, enable or suppress aggregation. While both dyes demonstrated similar monomeric optoelectronic properties in solution, adsorption onto mesoporous SnO2 revealed different behavior, with BPTI-A forming aggregates via π-stacking and BPTI-B demonstrating reduced aggregation in the solid state. BPTI photoanodes were tested in dye-sensitized solar cells (DSSCs) before application to dye-sensitized photoelectrochemical cells (DSPECs) for Br2 production (a strong oxidant) coupled to H2 generation (a solar fuel). BPTI-A demonstrated a twofold higher dye loading of the SnO2 surface than BPTI-B, resulting in a fivefold enhancement to both photocurrent and Br2 production. The enhanced output of the photoelectrochemical systems (with respect to dye loading) was attributed to both J- and H- aggregation phenomena in BPTI-A photoanodes that lead to improved light harvesting. Our investigation provides a strategy to exploit self-assembly via aggregation to improve molecular light-harvesting and charge separation properties that can be directly applied to dye-sensitized photoelectrochemical devices.Graphical Increased Solar-Driven Chemical Transformations through Surface-Induced Benzoperylene Aggregation in Dye-Sensitized Photoanodes. Benzo[ghi]perylenetriimide (BPTI) dyes are investigated to reveal the effect of aggregation by π-stacking on photovoltaic parameters in dye-sensitized devices. Photoanodes with aggregating BPTIs show both J- and H- aggregation phenomena leading to enlarged visible light absorbance and increased electron injection. The use of aggregating BPTI outperforms a non-aggregation BPTI with fivefold in terms of photocurrent and product generation.

Theoretical and experimental research on tooth root bending stress of face gear

A tooth root bending stress analysis method is proposed to study the tooth surface load distribution and tooth root bending stress during the meshing process of orthogonal face gear. Firstly, the tooth surface equation, transition surface equation and tooth width constraints are derived. Then, Through the tooth contact analysis (TCA), the contact path and spots of the face gear pair are obtained. What’s more, the proposed method based on Load tooth contact analysis (LTCA) is utilized to calculate the tooth surface load distribution and root bending stress of the face gear along the mesh cycle and compared with the finite element method. Meanwhile, root bending stress tests were carried out to verify the proposed method. The comparisons indicate that the proposed method has higher computational efficiency compared with the finite element method (e.g. the finite element method takes about 5 h for a mesh cycle and the proposed method costs 40 s). The results show that the tooth surface load distribution and root bending stress of the proposed method are consistent with those obtained by the finite element method and gear root stress experiment.

Regional variations in relative sea-level changes influenced by nonlinear vertical land motion

Vertical land movements can cause regional relative sea-level changes to differ substantially from climate-driven absolute sea-level changes. Whereas absolute sea level has been accurately monitored by satellite altimetry since 1992, there are limited observations of vertical land motion. Vertical land motion is generally modelled as a linear process, despite some evidence of nonlinear motion associated with tectonic activity, changes in surface loading or groundwater extraction. As a result, the temporal evolution of vertical land motion, and its contribution to projected sea-level rise and its uncertainty, remains unresolved. Here we generate a probabilistic vertical land motion reconstruction from 1995 to 2020 to determine the impact of regional-scale and nonlinear vertical land motion on relative sea-level projections up to 2150. We show that regional variations in projected coastal sea-level changes are equally influenced by vertical land motion and climate-driven processes, with vertical land motion driving relative sea-level changes of up to 50 cm by 2150. Accounting for nonlinear vertical land motion increases the uncertainty in projections by up to 1 m on a regional scale. Our results highlight the uncertainty in future coastal impacts and demonstrate the importance of including nonlinear vertical land motions in sea-level change projections.

Detached-eddy simulation of the vortex system on the high-lift common research model

A complex vortex system exists on the high-lift transport aircraft with components of the nacelle, pylon, high-lift devices, strakes, and brackets, and the investigation of the vortex system is helpful in profoundly understanding the aerodynamic characteristics of actual high-lift aircraft. To investigate the vortex system on the high-lift transport aircraft and evaluate the simulation capacity of detached-eddy simulation (DES) for the vortex system on the high-lift aircraft configuration, a high-resolution DES numerical investigation is carried out on a standard high-lift transport aircraft configuration, the National Aeronautics and Space Administration (NASA) high-lift common research model (CRM-HL). Reynolds-averaged Navier–Stokes simulation (RANS) is also performed to investigate the differences between DES and RANS in predicting time-averaged aerodynamic data on the CRM-HL. After experimental validation of time-averaged surface load and flow patterns, three vortex identification methods are adopted to extract the vortex structures of the flow field. It is found that the Rortex-based vortex identification method can more distinctly extract the fine vortex structures. The DES method can reliably predict the time-averaged surface load while capturing the complex vortex system on the CRM-HL under the concerned case of this work with high resolution.

Effects of Spray-On Lining Rehabilitation on Behavior of Buried Corroded Metal Pipes Subjected to Surface Loading

Effects of Spray-On Lining Rehabilitation on Behavior of Buried Corroded Metal Pipes Subjected to Surface Loading

A numerical study on load effects of low-rise buildings in a wind-blown sand environment

The transportation process of wind-blown sand, represented by sandstorms, occurs frequently in arid and semi-arid regions. The combined action of wind and sand impact load in a wind-sand environment poses a serious threat to the safety of construction, transportation and other engineering structures. However, most of the current structural designs only considers the effect of wind, and there is little detailed research on the surface load distribution of structures caused by sand impact, which leads to uncertainty in the safety assessment of engineering structures in wind-sand areas. In this paper, low-rise buildings which are easily damaged in strong wind-sand environments are taken as the research object. A numerical model of coupling turbulent wind field and particle motion was then established, and the reliability of the numerical simulation results was verified through wind tunnel experiments. Finally, the wind-sand movement around the low-rise building model and the load distribution characteristics on the building surface are simulated under different wind speed and sand concentration conditions. The results show that the edges and corners of engineering structures are subject to more severe particle erosion-abrasion. As the sand concentration increases in the flow field, the wind speed and the wind load acting on the structures weakens. Whereas the sand impact load increases with the increment of wind speed and sand concentration. The increased effect of sand particles on the total load can be considered by amplifying the wind load shape coefficient on the windward side. This study is helpful to understand the mechanism of sand wind-induced damage on low-rise buildings, and provides basic tools and a theoretical basis for the wind and wind-blown sand resistance design and performance optimization of engineering structures.

Degradation mechanisms of soil arching under a localized cyclic surface loading

Soil arching causes stress redistribution in many earth structures, such as pile-supported embankments and buried structures. A localized cyclic surface load (e.g., footing and traffic load) would weaken the arching effect and cause structural safety at potential risk. This paper presents a series of trapdoor tests using transparent soil to investigate the degradation mechanisms of soil arching subjected to a localized cyclic surface load. The particle image velocimetry (PIV) technique was adopted to monitor the inner soil deformations during test. The test results show that soil arching under localized cyclic surface loading first degraded locally on the trapdoor center and then progressed from the center to the entire trapdoor. The soil arching degraded faster within a lower backfill, on a wider trapdoor, and under a higher load frequency of localized surface loading. Owing to the volumetric expansion during trapdoor movement, the average vertical stress with soil arching increased faster under localized surface loading than that without soil arching. After full degradation of soil arching, the stress increment and vertical displacement contours with and without arching effect gradually tended to be similar. Finally, an empirical method was proposed to predict the soil arching ratio under localized cyclic surface loading.

Behavior of elastohydrodynamic lubricating film point contact problems in the unsteady state of reciprocating motion

Purpose In this study a numerical analysis of the elastohydrodynamic lubrication point contact problem in the unsteady state of reciprocating motion is presented. The effects of frequency, stroke length and load on film thickness and pressure variation during one operating cycle are discussed. The general tribological behavior of elastohydrodynamic lubrication during reciprocating motion is explained. Design/methodology/approach The system of equations of Reynolds, film thickness considering surface deformation and load balance equations are solved using the Newton-Raphson technique with the Gauss-Seidel iteration method. Numerical solutions were performed with a sinusoidal contact surface velocity to simulate reciprocating elastohydrodynamics. The methodology is validated using historical experimental measurements/observations and numerical predictions from other researchers. Findings The numerical results showed that the change in oil film during a stroke is controlled by both wedge and squeeze effects. When the surface velocity is zero at the stroke end, the squeeze effect is most noticeable. As the frequency increases, the general trend of central and minimum film thickness increases. With the same entraining speed but different stroke lengths, the properties of the oil film differ from one another, with an increase in stroke length leading to a reduction in film thickness. Finally, the numerical results showed that the overall film thickness decreases with increasing load. Originality/value General tribological behaviors of elastohydrodynamic lubricating point contact, represented by pressure and film thickness variations over time and profiles, are analyzed under reciprocating motion during one working cycle to show the effects of frequency, stroke length and applied load.

Face-dependent phosphate speciation on goethite: CD-MUSIC modeling and ATR-FTIR/2D-COS study

Understanding the face-dependent phosphate adsorption mechanisms and their variations with environmental conditions is of great significance for revealing phosphate adsorption mechanisms on various goethites and predicting phosphorus speciation in iron-rich soils. In this study, micro- (MicroGoe) and nano-sized goethite (NanoGoe) were synthesized and used to investigate the face-dependent adsorption behaviors of proton and phosphate on goethite by combining the charge distribution-multisite surface complexation (CD-MUSIC) model and attenuated total reflectance Fourier transform infrared (ATR-FTIR). The results demonstrated that MicroGoe had a higher charge density and phosphate adsorption capacity than NanoGoe, which could be attributed to the higher site density of ≡FeOH−0.5 and inner-layer capacitance arising from a higher proportion of capping face and rougher surface of MicroGoe. The logKH of ≡FeOH−0.5 on the main and capping face was 8.2 and 8.9, respectively. Three types of monodentate mononuclear phosphate complexes in different protonated states were identified, along with the non-protonated bidentate complex. Protonated monodentate complexes were formed at relatively low pH and high surface loadings, whereas non-protonated complexes were the predominant species at intermediate to high pH. MicroGoe had a higher percentage of monodentate complexes than NanoGoe, and both goethites had considerably lower phosphate adsorption on the capping face than on the main face. The results provide valuable insights into the interfacial reactivity of goethite prepared with various methods and facilitate further prediction of phosphorus speciation and availability in iron-rich soils.

Analysis of axisymmetric hollow cylinder under surface loading using variational principle

In this work, a variational principle–based approach has been adopted to analyze one of the classical linear elasticity problem of the axisymmetric cylinder under surface loading. The use of variational principle results in a set of governing partial differential equations with associated boundary conditions. The equations have been solved using the separation of variable approach and the Frobenius method. A general solution has been derived and used to solve two test cases. The proposed solution is capable of meeting all the boundary conditions. The solution has been validated by comparing it with a finite element–based numerical solution and considering a special limiting condition of a solid cylinder, for which results are available in the literature. Further various studies have been carried out to understand the robustness and limitation of the presented solution.

A multi-scale roughness rock joint model considering laboratory-scale irregularities using wear theories

The shear strength of a rock fracture is influenced by surface irregularities, geometric parameters, loading conditions, and rock mechanical properties. A new shear model, derived from the energy balance equation, explicitly accounts for the contributions of shear-off component, related to the indentation of surface roughness, and the contributions of basic friction angle and asperity sliding, related to the inclined friction component, to the total shear strength. The progressive roughness degradation is considered in the model by incorporating adhesion and abrasion wear theories. Additionally, multi-scale surface roughness is integrated in the model, as various scaled asperities have different influences on shear behaviour. Due to the distinct influences of various scaled asperities on shear behaviour, their contributions during shear are also taken into account within the model utilising multi-scale roughness theory. Moreover, the model has been implemented into three-dimensional distinct element code (3DEC) using the built-in programming language FISH and verified with experimental data incorporating laboratory-scale rock fractures. The proposed model offers new insights into roughness degradation and yields good prediction performance, as demonstrated by an average error (σ‾ave) of 4.95 % ± 0.03 for the τ−us behaviour, a Normalised Objective Function (NOF) of 0.16 for the us−un behaviour.

Integrated Assessment of Coastal Subsidence in Nansha District, Guangzhou City, China: Insights from SBAS-InSAR Monitoring and Risk Evaluation

Monitoring and assessing coastal subsidence is crucial to mitigating potential disaster risks associated with rising sea levels. Nansha District in Guangzhou City, representing global coastal soft-soil urban areas, faces significant challenges related to ground subsidence. However, the current understanding of the status, causative factors, and risk (includes subsidence susceptibility and vulnerability) assessment of ground subsidence in Nansha District is unclear. To address this gap, we utilized the SBAS-InSAR technique, analyzing 49 Sentinel-1A images from December 2015 to June 2019, for systematic ground subsidence monitoring. Subsequently, we assessed subsidence risk using a comprehensive index method and a risk matrix. Our findings indicate that subsidence velocity primarily ranged from −40 to −5 mm/a, with a spatial pattern of increasing subsidence from inland to coastal areas. The cumulative subsidence process unfolded in four distinct stages. The genesis of land subsidence was linked to an endogenous geological context dominated by soft-soil deposition, influenced by external factors such as surface loading and groundwater extraction. High-risk zones were concentrated in key engineering development areas, transportation pipeline trunk lines, and densely populated regions, demanding special attention. This study provides a foundational resource for disaster prevention and control strategies in Nansha District and similar coastal cities.

Analytic solution to isotropic axisymmetric cylinder under surface loadings problem through variational principle

Analytic solution to isotropic axisymmetric cylinder under surface loadings problem through variational principle

Influence of erosion voids and traffic loads on buried large-diameter reinforced concrete pipes

Geotechnical centrifuge tests were conducted to examine the influence of invert voids and surface traffic loads on 1400 mm diameter reinforced concrete pipes buried with a shallow soil cover depth of 700 mm. Void formation beneath the pipe was simulated during centrifuge testing. The test results revealed that before void formation, the surface load directly above the middle of the pipe caused a significant increase in not only the circumferential bending moments but also the longitudinal bending moments, the latter of which was considerable and could not be ignored. Void formation beneath the middle of the pipe led to a reduction in both the circumferential bending moments and longitudinal bending moments at all measuring positions, i.e., crown, springline, and invert. The most significant reduction occurred at the invert, and there was even a reversal in the sign of the invert longitudinal bending moment. A comparison was made between centrifuge tests with erosion voids and surface loads at different horizontal positions, which had a marked influence even when the positions differed by half a pipe length. Joint rotation played an important role in relieving large bending moments of pipe barrels in a jointed pipeline when the void and surface load were located at the joint.

Numerical analysis on the factors affecting post-peak characteristics of coal under uniaxial compression

The post-peak characteristics of coal serve as a direct reflection of its failure process and are essential parameters for evaluating brittleness and bursting liability. Understanding the significant factors that influence post-peak characteristics can offer valuable insights for the prevention of coal bursts. In this study, the Synthetic Rock Mass method is employed to establish a numerical model, and the factors affecting coal post-peak characteristics are analyzed from four perspectives: coal matrix mechanical parameters, structural weak surface properties, height-to-width ratio, and loading rate. The research identifies four significant influencing factors: deformation modulus, density of discrete fracture networks, height-to-width ratio, and loading rate. The response and sensitivity of post-peak characteristics to single-factor and multi-factor interactions are assessed. The result suggested that feasible prevention and control measures for coal bursts can be formulated through four approaches: weakening the mechanical properties of coal pillars, increasing the number of structural weak surfaces in coal pillars, reducing the width of coal pillars, and optimizing mining and excavation speed. The efficacy of measures aimed at weakening the mechanical properties of coal is successfully demonstrated through a case study on coal burst prevention using large-diameter borehole drilling.

A time‐varying meshing stiffness model for gears with mixed elastohydrodynamic lubrication based on load‐sharing

AbstractIn mixed elastohydrodynamic lubrication (EHL), the load distribution between the gear meshing surfaces is shared by the oil film and the asperities of the gear's rough surface. Based on the load‐sharing concept, this paper proposes a time‐varying meshing stiffness (TVMS) model for gears with mixed EHL. The initial step involves the utilization of the Greenwood‐Williamson model to calculate the contact stiffness of surface asperities, while the lubricating film is assessed using a curve‐fitting formula to investigate the influence of gear surface morphology on TVMS. Subsequently, the incorporation of gear fillet foundation deformation and friction enables accurate TVMS determination. The proposed method is employed to examine the meshing stiffness of the gear pair under both dry lubrication and EHL conditions. Comparative analysis reveals favorable agreement between the proposed model and experimental results obtained under dry lubrication, thereby highlighting the superior performance of the proposed approach. Moreover, the time‐varying friction coefficient under EHL is computed, and the impacts of gear surface morphology parameters, temperature, speed, and load on lubrication conditions and TVMS are investigated. The findings presented in this paper contribute significantly to advancements in gear design and performance.