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The batter rock-socketed pile (BRSP) groups have been gradually introduced in practice to support not only the vertical load caused by overlying infrastructures but also the horizontal loads caused by waves and wind. A series of laboratory model tests were conducted to investigate the bearing capacities of the BRSP groups installed with their batter piles ranging from 0° to 20° under combined vertical and horizontal loads. It is found that the vertical ultimate bearing capacities nonlinearly increase with the increase of the batter angle with its optimum batter angle of 10°. The normalized vertical loads and horizontal ultimate loads are nonlinearly related to their relationship in an ellipse function. The plumb rock-socketed pile groups develop primarily a pair of shear forces and secondary bending moments due to the clockwise rotation under the pure horizontal loads. The BRSP group may fail due to the pile fracture near the pile cap in the form of the plastic hinge or compression failure at the base of the front pile. The corresponding load-displacement curves mostly have no peak or sudden downward trend. [ABSTRACT FROM AUTHOR]

The monopile-supported offshore wind turbines (OWTs) are subjected to the wave and current loadings. Affected by currents and waves, monopile-supported OWTs are also vulnerable to scour. However, the effect of scour and currents on the dynamic behavior of the monopile are not fully appreciated. This study conducted the model tests to evaluate the effect of scour depth and flow velocity on the lateral responses of support structure. Furthermore, the two-way (T-W) coupling fluid–structure interaction (FSI) method was proposed to evaluate the dynamic responses of piles in sand. The support structure is modeled using ABAQUS, a finite-element models software package, by considering the nonlinear soil–structure interaction effects, STAR-CCM + tools has been employed to model the FSI which are fed into ABAQUS to predict the structure's dynamic response. Using the proposed method, a parametric study has been conducted to evaluate the effects of scour depths, flow velocities on the dynamic responses of OWTs. The results indicate that scour altered the fundamental frequency of OWT, causing resonance. An increase in scour depth and flow velocity increased the dynamic responses of support structure, which are detrimental for the safety and stability of the OWT system. [ABSTRACT FROM AUTHOR]

The reactivation events of old landslides in the Three Gorges Reservoir area occur frequently, making it imperative to study the water softening characteristics and reactivation mechanism. An old clay landslide was selected as the focus of the research, and a segmented water injection permeable sliding surface was designed to simulate the formation and evolution of the old sliding zone during the process of groundwater rise. Volumetric water content sensors, pore water pressure gauges, high-speed camera devices, and Geopiv-RG digital image processing technology were used to obtain data on multiple physical fields. The analysis results indicated that the decrease in shear strength of the sliding zone soil and the sudden increase in pore water pressure on the sliding surface were important factors in the reactivation of old landslides. The surface deformation exhibited prominent zoning characteristics, primarily categorized into zones of strong deformation, weak deformation, and traction deformation. The failure mechanism involved shear sliding at the front edge, tensile cracking and failure at the trailing edge, and shear creep in the middle section. The development of multi-stage secondary sliding zones in old landslides can be categorized into three types: parallel to the original old sliding zone, partially overlapping with the original sliding zone to form a layered landslide, and completely overlapping with the original sliding zone, indicating overall reactivated deformation. [ABSTRACT FROM AUTHOR]

Traditional medium-low speed Maglev track separated beam structures have drawbacks such as large structural height and neglect of F-type rail stiffness. This study proposes a new integrated track beam for medium-low speed maglev transportation. Finite element analysis is employed to compare the strength, stiffness, and natural frequencies of the integrated track beam with the existing separated track beam. The influence of beam height on the overall mechanical performance of the integrated track beam is analyzed. The ultimate bearing capacity of the steel-concrete composite joint in the integrated track beam is investigated through full-scale model testing. The results demonstrate that the proposed integrated track beam exhibits a 28% increase in flexural stiffness. The mid-span deflection is reduced by 19.9% under static and live loads. The first-order vertical natural frequency increases by 13.6%. The main factor governing the minimum beam height of the integrated track beam is the deflection limit under static and live loads. The beam height can be optimized from 2.1 m to 1.6 m. The model testing reveals that the F-type rail is controlled by torsional stiffness and can withstand 1.3 times the design load. The ultimate bearing capacity of the steel-concrete composite joint is 4.5 times the design load, providing sufficient load reserves. [ABSTRACT FROM AUTHOR]

This article presents a composite tunnel rockfall protection structure (CPRC) employing galvanized corrugated steel plates as the inner formwork for reinforced concrete structures. It addresses the threats posed by frequent rockfall disasters in mountainous regions with complex geology. The research investigates impact damage from various rockfall shapes through numerical simulations and experiments on five representative forms, comparing traditional reinforced concrete structures RC with CPRC. The study highlights both structures' dynamic responses and damage characteristics across different impact scenarios, introducing the Residual Resistance Index RRI as a measure of post-impact safety performance. Results show that the numerical simulations align with laboratory tests, with discrepancies within 10%, validating the simulation method's accuracy in predicting impact resistance. Following impacts, both structures primarily displayed brittle concrete damage; however, the CPRC structure demonstrated a 79.46% reduction in concrete damage and an 86.31% decrease in reinforcement damage. The energy-dissipating properties of the corrugated plates significantly lowered rockfall penetration depth and impact energy transfer ratio, with an RRI exceeding 0.88 post-event. Additionally, the study reveals varying damage effects from different rockfall shapes, further supporting the CPRC structure's superior impact resistance and its effectiveness in preventing secondary disasters in tunnel engineering within mountainous terrains. [ABSTRACT FROM AUTHOR]

The prefabricated assembled cover arch reinforcement method offers rapid construction and high quality, effectively addressing the challenges of cast-in-place cover arch reinforcement used in tunnel linings in mountainous areas of China. This study investigated the mechanical performance of prefabricated assembled arches in tunnels through model tests and numerical simulations. The results indicate that joint opening and deflection, as well as their change rates, increase with eccentric distance. There is a roughly linear relationship between joint opening and deflection with increasing load. At an eccentric distance of + 0.2 m, the peak stress appears on the outside of the joint, with a valley on the inside, and stress concentration at bolt holes. The application of bolt preloading enhances the joint's stress performance. Furthermore, the stiffness of the lining and soil significantly impacts the mechanical response of the cover arch, with peak stress mainly observed at the foot of the cover arch and the handhole of the joint. [ABSTRACT FROM AUTHOR]

The pipe-soil interaction force is a crucial load that ensures the on-bottom stability of submarine pipelines and acts as a vital input parameter for the design of controlled pipeline buckling. It is necessary to precise prediction of soil lateral resistance and sensitivity to environmental parameters. This study developed a numerical simulation technique based on the coupled Euler-Lagrange (CEL) method to systematically analyse the deformation of the pipeline and the soil-pipeline forces on the seabed foundation during service. To validate the numerical method for large lateral displacement of pipe-soil interaction, an experimental approach employing parameter variation was utilized to conduct sensitivity analysis on the environmental parameters. The key parameters affecting soil-pipeline interaction were determined through an analysis of relative variation factors. The research findings demonstrate a satisfactory agreement, with an amplitude difference range of within 15 %, between the numerical simulation technique using the CEL method and the experimental results. This method resolves the issue of non-convergence due to grid distortion under conditions of large displacement, thereby enhancing computational accuracy. Sensitivity analysis shows that the relative variation factors for soil friction angle, initial burial depth, and soil density exceed 50 %, which is notably higher than the elastic modulus, friction coefficient, and Poisson's ratio of the soil. The results of this study enable the prediction of lateral forces in pipe-soil interaction and identification of environmentally sensitive parameters. This study establishes a foundation for calculating pipeline buckling strength in complex environments and holds paramount importance for the design and construction of pipelines to ensure on-bottom stability. [ABSTRACT FROM AUTHOR]

The long-line abalone culture system in the bottom waters outside the bay is a new type of aquaculture facility that utilizes the underwater attenuation effect of waves to achieve better wind and wave resistance. Currently, most of the research on long-line aquaculture systems is aimed at the sea surface, and the research on the seabed is still pending. Therefore, to ensure the abalone culture system’ s survival rate and structural safety, it is of great significance to study the dynamic characteristics of the long-line abalone culture system in the bottom waters. Based on the similarity criterion, a model test was carried out in the wave-current flume laboratory; a numerical simulation method of the dynamic response of the long-line abalone culture system in the bottom waters was established based on the centralized mass model, and the accuracy of the numerical simulation method was verified. In view of the actual sea conditions off Luoyuan Bay, Fujian Province, the dynamic characteristics of the long-line abalone culture system in the bottom waters were numerically simulated under the action of different waves and currents to analyze the effects of the wave heights, current velocities and flow directions on the stresses on the abalone culture system and the structural safety of the system. The effects of wave height, current speed, and flow direction on the force and trajectory of the system were analyzed. The results show that the numerical model is consistent with the model test results: the maximum relative error of the maximum cable tension measured against the waves is 8. 33%, the minimum relative error is 4. 84%, and the average relative error of the peak horizontal and vertical motions of the float A is 5. 23% and 8. 92% respectively, which proves that the numerical simulation method used in this paper is accurate and reliable; there is a significant difference in the distribution of the force of the long-line and the anchor rope, and the force curve of the long-line shows an arch of the force. The force distribution of the long-line and the anchor rope has obvious differences; the force curve of the long-line shows an arch shape and a sawtooth shape, and the maximum force section is not on the anchor rope but located in the middle region of the long-line; the wave height has a linear relationship with the maximum force of the system and the motion amplitude of the abalone cage, i. e., the higher the wave height is, the larger the transverse and vertical motion amplitude of the system is, and the larger the maximum tension in the middle part of the long-line, the supporting rope and the anchor rope is, and the peak tension curve of the supporting rope shows a sawtooth shape; the maximum tension of the anchor rope in the headward side appears nonlinearly when the velocity of the current is increasing, the maximum tension of the anchor rope in the headward side appears nonlinearly. When the flow velocity increases, the maximum tension of the anchor rope on the headwater side shows a nonlinear steep increase. The maximum tension of the long-line on the headwater side increases slowly, and the maximum tension of the anchor rope and the long-line on the backwater side decreases significantly. In contrast, the maximum tension of the branch ropes does not increase significantly with the flow velocity, and the maximum tension of each branch rope is the same; when the flow direction increases, the maximum tension of the system’s anterior part of the longline and the anchor rope decreases. The posterior part of the long-line and the anchor rope increases, and the branch ropes’ tensions remain relatively stable. The results of this study can provide a reference for the structural design of similar long-line abalone culture systems in the bottom waters. [ABSTRACT FROM AUTHOR]

This study aims to provide substantial theoretical support for employing vacuum preloading‐airbag pressurization (VP‐AP) to enhance soft soil foundations. By integrating the airbags and prefabricated vertical drains (PVDs) within the analytical framework, the consolidation models are developed to accommodate double smear zones and well resistance. Analytical solutions for various airbag pressurization scenarios are derived under the equal‐strain assumption. A model test is subsequently conducted to investigate the settlement process of soft soil using the VP‐AP method. The validity of the proposed theoretical model is corroborated through comparison with existing analytical solutions and experimental data. The accuracy of the predictive model is further substantiated by the model test results. Lastly, this research offers an in‐depth analysis of soil consolidation behavior under diverse influencing factors. The findings indicate that the VP‐AP method demonstrates superior efficacy over conventional vacuum‐surcharge preloading when the airbag pressure matches the external load pressure. Additionally, an increase in the radius of airbags enhances the soil consolidation efficiency. The analytical model presented in this study elucidates the consolidation mechanisms of the VP‐AP method, with experimental research confirming the efficacy of this approach and the predictive model established herein. [ABSTRACT FROM AUTHOR]

Energy dissipation of water flow is an important factor in the planning of structures such as stilling basins. One of the standards set by the USBR (United States Bureau of Reclamation) that must be considered in the planning of the stilling basin is the Froude number (F1) at the toe of the spillway. Various forms of planning can be used to meet these standards, one of which is by using a double-sill downstream of the chute channel with a certain distance and height. However, as an alternative to planning, this study aims to evaluate the level of attenuation of flow energy in a stilling basin by using a double-sill. Because this sill is more effective in breaking down and reducing the strength of the water flow. Hydraulic physical model tests were carried out in the laboratory by placing double sills in a fixed position and varying the height of the sills. Because several previous studies have shown that the shape and size of sills affect the level of energy dissipation. It is expected that the results of the hydraulic model test can provide better information about the flow behavior in the overflow system in terms of energy dissipation. [ABSTRACT FROM AUTHOR]

Dynamic compaction (DC) represents a cost-effective method for reinforcing subgrade and is particularly suited to treating large-scale building subgrade. Nevertheless, the effect of DC reinforcement on high groundwater level (HGL) subgrade remains uncertain due to the lack of clarity surrounding the energy transfer mechanism of DC in HGL subgrade. In this paper, an outdoor model test of HGL subgrade was conducted based on the DC method. The temporal evolution of the internal transverse and vertical dynamic stresses in soil under different water levels, energy levels, and tamper weight conditions was monitored, and the DC mechanism of HGL subgrade was described from the perspectives of the dynamic stress waveform, peak development, and attenuation. On this basis, a novel methodology for assessing the extent of subgrade reinforcement through the utilization of impulses was put forth, thereby facilitating a more precise evaluation. The results showed that the HGL is obstructive in DC energy transfer. The peak dynamic stress, depth of impact and maximum impulse per unit area were markedly diminished when tamping the water surface. The study results also recommend that construction could expand the application range of the DC method and provide engineering suggestions for the selection of construction parameters and subsequent building construction. [ABSTRACT FROM AUTHOR]

The increasing demand to harness offshore wind resources has pushed offshore wind turbines into deeper waters, making floating platforms more economically feasible than bottom-fixed ones. When the incident wind and wave forces act on the floating wind turbine, the floating platform will experience oscillations around its equilibrium position in six degrees of freedom (DOFs). Significant floater motions can affect the aerodynamic power output, increase the failure risk, and even shorten the operational lifetime, especially under a harsh offshore environment. To improve the dynamic behavior of the floating platform, this research designed a heave plate for an OC4-Deepcwind wind turbine. The dynamic performance of the wind turbine was specifically investigated based on a series of wave-basin model tests, including free decay tests, regular wave tests, and irregular wave with steady wind tests. The results show that the heave plate increases damping in heave and pitch motions. The weakening effect on the heave and pitch motion is obvious in the wave period of 15–20 s and 20–27 s, respectively. However, the arrangement of the heave plate may exacerbate the fluctuation of the force and moment at the bottom of the tower. [ABSTRACT FROM AUTHOR]

Hinged multi-body systems are gaining popularity in the field of ocean engineering. Their performance is commonly evaluated using numerical simulations, but comparisons with experimental data are required to ensure the accuracy of the computational tools. However, there is a dearth of experimental studies on the motion performance of hinged multi-body systems, particularly those involving more than two hinged floating bodies. This study aims to fill this gap in experimental data for hinged multi-body systems beyond two bodies. The rectangular box was chosen as the test model due to its stable hydrodynamic properties and ease of numerical modelling. Five identical boxes were prefabricated and subsequently tested in the pool in a sequence ranging from one to five boxes to capture the motion performance. Additionally, a numerical programme based on potential flow theory was developed for mutual validation with the experimental data. Firstly, the physical properties of each box were determined through equations calculation and a free decay test, enabling the acquisition of all parameters for conducting numerical simulations. Then, the response amplitude operator (RAO) curves for the heave and pitch motion of a single box were depicted, and the results indicated that the resonant frequency in pitch direction obtained from the regular wave test was consistent with that obtained from the free decay test. Finally, the motion RAO curves of hinged multi-body systems were presented and analysed. The agreement between the measured and computed results confirms the suitability of the experimental data presented in this study as benchmark data for validating numerical simulations. [ABSTRACT FROM AUTHOR]

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The earth pressure of slope retaining structure is one of the problems that are often encountered in geotechnical engineering but have not yet been fully understood and well solved. At present, there are still a lot of problems that need to be solved. For complex conditions such as stratified soil or containing ground water, the distribution law of earth pressure and the displacement mode of retaining structure need to be further studied. This paper summarizes the existing research on earth pressure of slope retain structures. According to the research methods, it is divided into three categories: research on the theoretical calculation method of earth pressure, research on earth pressure by model test, and research on earth pressure by numerical simulation. Focused discussions are carried out respectively, and the previous research results are summarized. At present, there are still a lot of problems that need to be solved in the research of earth pressure of slope retaining structure, and the calculation formula of earth pressure and the assumed fracture surface of earth are lack of experimental verification and engineering measurement. [ABSTRACT FROM AUTHOR]

Longitudinal joints are the most vulnerable parts of prefabricated utility tunnels, susceptible to damage from external forces and foundation settlement. Currently, the shear mechanical properties of prefabricated double-cabin utility tunnel joints are unclear, preventing the evaluation of the structural or joint safety of utility tunnels. The shear mechanical response and failure characteristics of the joints of prefabricated double-cabin utility tunnels are investigated by combining model testing with numerical simulation. The results indicate that the shear deformation of utility tunnel joints can be categorized into elastic, crack propagation, and damage stages. In the course of joint-shear deformation, the middle utility tunnel sustains centrosymmetric failure. The degree of deformation of the large cabin is greater than that of the small cabin, while the damage to the small cabin is more severe. When the utility tunnel is subjected to the same load, the joint dislocation under the gravelly sand foundation is the smallest, but the damage range is the largest and the cracks are the most. Local strengthening and protection are needed at the chamfer, near the bolt hole, and the top and bottom. The stratum conditions have little effect on the shear stiffness of the joint during the elastic stage, but they have a significant impact during the crack propagation and damage stages. Finally, the joint damage area is approximately 15% of the total utility tunnel, and the deformation region of the longitudinal connectors is approximately 16% of its length. [ABSTRACT FROM AUTHOR]

As basic structural components of the ship hull, stiffened plates suffer both thrust and shear loads while ships sail in rough sea environments. In order to guide the scaled model design effectively, the similarity law is investigated in this paper. The parameters that determine the nonlinear behaviour of the stiffened plate under compression and shear loading are defined and the nonlinear similarity method is improved. This method is applied to design a scaled model under combined bending and torsional moment, and the collapse test is conducted to research the collapse characteristics. The collapse behaviour of actual ship structures under combined loads predicted by the model test is compared with that obtained by the nonlinear finite element analysis. The good agreement represents the capability of the newly improved nonlinear similarity law. The present research provides a proper way to investigate the collapse characteristics of actual ship structures through a model test. [ABSTRACT FROM AUTHOR]

Engineering slope stability issues typically exhibit the impact of deteriorating durability on the susceptibility of slopes to failure. A thorough investigation was essential to explore theoretical and experimental aspects of slope durability degradation and its implications on long-term stability. Hence, a durability model was developed to accommodate slope stabilization using reinforced concrete (RC) support structures. This model was grounded in classical durability principles for RC structures. Subsequently, a model test was conducted to compare the responses of a standard slope model with a weakened counterpart subjected to environmental impacts. According to the proposed methodology for slope durability and stability, a case study involving future durability and stability predictions was performed. It was found that the theoretical solutions for the carbonation or neutralization (CN) velocity, depth, and penetration time agreed well with model test results. The slope surface displacements of the weakened slope with deteriorating coefficients between 0.6 and 0.9 were 4 to 8 times those of the standard slope, demonstrating significant degradation in stability. The case study indicated a steady reduction in the safety factor, at a rate of 2.3 to 2.4‰ per year throughout the slope's service life. Finite-element-based predictions also suggested the potential for corrosion of slope anchor bolts within 20 years and breakage within 30 years, at an average rate of 7.5‰ per year in the ultimate bearing capacity. These findings highlight the need for timely maintenance and reinforcement interventions to ensure the long-term durability of operational slopes. [ABSTRACT FROM AUTHOR]

Ground fissures, as a typical geohazard, pose potential georisks to the construction and maintenance of urban transportation infrastructure. Under the influence of ground fissures, the segmented tunnel structure used in subway systems complicates the propagation of subway train vibrations. In this study, the soil acceleration, earth pressure and contact pressure of a three-section subway tunnel under dynamic loading of a subway train in a ground fissure environment were observed and analyzed by physical modeling tests, and the effects of the presence and activity of the ground fissure and tunnel segmentation were discussed. The results show that the vibration generated by the subway traveling will have different degrees of attenuation when propagating in all directions in the soil layer, and the ground fissure has a damping effect on the subway vibration. The attenuation and enhancement of acceleration by ground fissure is affected by the activity and propagation direction of ground fissure. The distribution of additional earth pressure is affected by the ground fissure, soil contact state, which is related to the ground fissure activity state. The ground fissure activity on the contact additional pressure mainly focuses on the bottom and top of the tunnel and there are differences in the location of the hanging wall and footwall. Three-section tunnels have a stronger vibration response and vibration attenuation than monolithic tunnels due to the influence of segmentation. Based on the consideration of the effects of ground fissure and tunnel segmentation, the tunnel design mainly takes into account the amount of ground fissure activity and determines the structural measures, the tunnel structure at the location of the ground fissure is strengthened, in addition to the vibration attenuation measures for the segmented tunnels when crossing the ground fissure. The discussion of mechanical response and design measures in this study helps to reduce the georisk of ground fissures on urban underground transportation infrastructure. [ABSTRACT FROM AUTHOR]

A comprehensive study was conducted at three coal mines with thin bedrock zones to understand the occurrence of water–sand inrush accidents in overlying rock strata induced by the combined effects of ground stress generated by the loading of a thick loose layer, secondary mining-induced stress, and bottom aquifer pressure. This study involved field sampling at the Yangcun, Xinglongzhuang, and Baodian coal mines through underground drilling, as well as particle size and microscopic analysis, laboratory model experiments, and numerical simulations. The clay and sandy gravel layers in the lower group of the Quaternary strata in the study area were found to be interlaced. Particle size analysis and microscopic testing of the soil samples had consistent patterns, revealing the compositional structure of the soil samples. The composition structure of the bottom aquifer of the three sampling boreholes differed; using a self-designed experimental device, water–sand inrush tests were conducted with different crack widths. The critical hydraulic gradient decreased with increasing crack width, while it increases with increasing clay content, showing a good correlation; The PFC3D software was used to simulate the process of water–sand inrush under the influence of mining. The simulation and model testing indicate that water–sand inrush is more likely to occur, the process of water–sand inrush will be more intense, and the duration will be shorter when the inclination angle and crack widths are larger. [ABSTRACT FROM AUTHOR]

The mechanism of surface subsidence induced by shallow buried excavation construction and the failure mode under ultimate state were not unclear. In view of this situation, a scaled model experiment based on particle image velocimetry(PIV)was conducted to simulate the construction process of shallow buried tunnels in sandy soil and Ⅴ-grade surrounding rock. PIV technology was used to analyze the deformation images of the surrounding rock during the construction process of the tunnel, and to obtain displacement cloud maps of geological deformation induced by construction disturbance. By analyzing the characteristics and gradual evolution of surface deformation induced by underground excavation construction disturbance, the shape and range of the failure surface and collapse induced by underground excavation tunnel construction in different strata under the limit state were summarized. The equation of the failure surface induced by the collapse of the arch top strata during underground excavation construction was derived by using the upper limit theorem of limit analysis and variational principle, and the collapse surface graph was drawn. The validity of the model test results was verified by comparing the range of collapse induced by underground excavation construction in the arch crown strata obtained from the model test with the theoretical calculation results. [ABSTRACT FROM AUTHOR]

In this article, the influence of soil condition on the dynamic response of a tunnel and the surrounding soil was studied by both experimental model tests and numerical simulations. We tested a 1/20‐scale tunnel model with three different soil conditions: upper soft soil and lower hard soil, homogeneous soft soil and homogeneous hard soil. We also applied dynamic loads, sweep loads and train loads on the model tunnel for time domain and frequency domain analysis. The experimental and numerical results revealed that the interface between the soft and hard soil strata has an obvious amplification effect on the vibration wave. With the propagation of the vibration wave to the surface, the damping effect of the soil above the tunnel becomes the main factor affecting the dynamic response of soil. The internal force response of the tunnel structure is for the most part concentrated in the section under the excitation load, which is mainly affected by the soil properties beneath the tunnel. [ABSTRACT FROM AUTHOR]

In order to study the crystallization blockage law and crystallization mechanism of dolomite tunnel drainage system, based on the indoor model test, the simulated crystal blockage and growth process were simulated. The phase composition and microstructure of the crystal were analyzed by energy‐dispersive X‐ray spectroscopy (EDS), scanning electron microscopy (SEM), and X‐ray diffraction (XRD). Combined with the pipeline crystal weighing, the crystal growth law and the internal cause of pipeline blockage were analyzed. The results show that the pipeline crystallization mechanism is divided into the first mechanism, the second mechanism, and the third mechanism. The crystallization blockage of the longitudinal and horizontal pipes are more serious, while the crystallization blockage of the ring pipes are less harmful. The crystallization is positively correlated with ion concentration, crystalline ions having a great influence on the blockage of pipeline crystallization, while noncrystalline ions having little influence. The crystal growth law is fast first and then slow, the crystallization affected by the coupling concentration of Cl−‐K+‐Na + ions, and positively correlated with the coupling concentration of CO32−‐SO42−‐Ca2+‐Mg2+‐Al3+ ions. Compared with the longitudinal pipes and the ring pipes, the horizontal pipes have more crystallization and higher degree of crystallization blockage per meter, while the crystallization degree of the longitudinal pipes are between the horizontal pipes and the ring pipes. [ABSTRACT FROM AUTHOR]

To investigate the impact of the geometric parameters of periodic pile barriers on bandgap characteristics in passive vibration isolation, a two-dimensional, three-component unit cell was developed using the finite element method (FEM). This study analyzed the bandgap properties of periodic pile barriers and validated the effectiveness of the FEM through model testing. The FEM was then methodically applied to evaluate the effects of pipe pile thickness, periodic constant, arrangement pattern, and cross-sectional shape on the bandgap characteristics, culminating in the proposition of a novel H-shaped cross-section for the piles. The results demonstrated that the FEM-calculated bandgap frequency range, featuring steel piles arranged in a square pattern, closely aligned with the attenuation zone in the model tests. The lower band frequency (LBF) was primarily influenced by the pipe pile's inner radius, while the upper band frequency (UBF) was predominantly affected by its outer radius. As the periodic constant increased, the LBF, UBF, and the width of band gap (WBG) all decreased. Conversely, changing the arrangement pattern from square to hexagonal led to increases in UBF and WBG, while the LBF diminished. Notably, the WBG of the H-section steel piles, possessing the same cross-sectional area, was 1.31 times greater than that of the steel pipe piles, indicating an enhanced vibration isolation performance. Additionally, the impact of transverse and vertical characteristic dimensions of the H-shaped pile on the band gap distribution was assessed, revealing that the transverse characteristic dimensions exerted a more significant influence than the vertical dimensions. [ABSTRACT FROM AUTHOR]

After the May 12 earthquake in Wenchuan, numerous debris flow disasters occurred due to heavy rainfall. After the earthquake, disaster prevention and mitigation projects, such as the sand dam, played an essential role in safety. However, when the outflow of solid material exceeds the designed storage capacity of the sand dam, the debris flow overtopping the dam intensifies the scraping effect on the source material of the gully channel. This paper takes the "8.20" debris flow in the Chutou gully as the research object. A transport mode of the debris flow after dam overtopping is studied through comprehensive field investigation, theoretical analysis, and indoor model tests. A quantitative evaluation model is established for the scraping depth and scraping volume of dam-overtopping debris flow. The study results showed that once the debris flow overtops a dam, the loose source carried by the channel is involved in the entire migration process, enlarging the fluid scale and intensifying the damage along the channel. The results agree with the measurements and observations, with maximum relative errors of 5.81% and 14.70%, respectively. This shows model validity. Furthermore, the test results show that the debris flow scarping phenomenon in the γ=[1.4 t/m3, 1.6 t/m3] interval is the most significant. Overall, this study will help improve future engineering decisions, design strategies, and finding the best design solutions to minimize the risk of dam-overtopping debris flow disasters. [ABSTRACT FROM AUTHOR]

As the main component of the anchorage system in marine aquaculture facilities, the anchor pile is key to ensuring safety and stability. However, conventional monopiles have limited capacity to withstand uplift forces, thus rendering them susceptible to deviations and potentially causing damage to facility structures. Hence, a new winged monopile is proposed to improve and optimize the anchor pile. In this study, laboratory experiments are conducted to investigate the effect of load inclination angle (θ = 0°, 30°, 45°, and 60°), wing length (L = 30, 50, and 70 mm), and wing width (W = 10, and 20 mm) on the uplift resistance capacity of anchor piles in silty clay. The results show that: the winged monopile exhibits at least a 15% improvement in uplift performance compared with the conventional monopile (without wings) when the smallest wing plate parameters are selected (W = 10 mm, L = 30 mm). Additionally, the effect of the wing width on the uplift resistance under an oblique load is more evident than that of the wing plate length. As the area of the wing plate increases, the range of improved wing plate efficiency first increases, and then gradually decreases. This study can be used as a reference for the design optimization of uplift piles and the construction of marine aquaculture. [ABSTRACT FROM AUTHOR]

Collapsibility significantly impacts the bearing capacity of pile foundations in loess areas. To improve the load-bearing capacity of piles, the pile-base postgrouting technique is widely used worldwide. However, there are still several related issues to be solved: the impact of loess collapsibility on the bearing capacity; the effectiveness of the pile-base postgrouting technique in enhancing the bearing capacity; and the diffusion pattern of the grout during the grouting process. To investigate these issues, this experiment utilizes a visual static pressure device combined with numerical simulation. According to the experiment, the maximum axial force and neutral point appeared to shift downward after grouting, resulting in a 17.5% increase in the bearing capacity of the pile foundation. Additionally, an increase in grouting pressure leads to a rise in both the number of shear cracks and the diffusion radius. As the permeability of the grout improves, the number of shear cracks and diffusion radii tend to stabilize after an initial increase. These discoveries enable a thorough analysis of the changes in side friction and base resistance of postgrouted piles in collapsible loess. Furthermore, they provide valuable references and guidance for the implementation of the pile-base postgrouting technique in loess areas. [ABSTRACT FROM AUTHOR]

A model test device is developed to simulate water seepage and ice formation on tunnel linings in cold regions based on surface water supply conditions. This device allows real-time monitoring of the surrounding rock's temperature and the ice formation process on leak sections. Furthermore, Image-J software measures the cross-sectional area of ice, and linear regression analysis is used to analyze the ice development process. The authors examine distribution of temperature of the surrounding rock at the leakage point and the evolution of ice blockage rate under different wind speeds and initial rock temperatures. Following are the findings from the study: (1) At the beginning of ice formation on the lining, increased wind speed and initial rock temperature leads to higher critical temperature at the leakage point. The temperature of the surrounding rock at this point gradually decreases with cooling time, following a logarithmic distribution. Low wind speeds and high initial temperatures result in slow average cooling rate and prolonged ice formation. At wind speeds of 0.6 and 1.2 m/s, the frozen circles form in the surrounding rock, and the inner wall ice eventually seals the leakage section, respectively, halting further ice development. (2) The ice blockage rate on the lining correlates linearly with time. Low wind speeds and high initial temperatures delay the onset of ice formation, increase frost damage severity, and reduce urgency. [ABSTRACT FROM AUTHOR]

A novel three-dimensional printed refined scale model for tunnels in cold regions is developed using a model test method to explore the freezing response patterns of railway tunnel drainage systems in such regions and clarify key points regarding the cold and frost resistances of such tunnels. This model provides a complete and transparent drainage structure, enabling a visual representation of the freezing process in tunnel drainage systems in cold regions. Based on this model, a series of freezing response tests is conducted for drainage systems under various temperature conditions. The following results are drawn from this study. (1) The temperature field varies considerably above the tunnel arch foot, with the maximum variation being observed at the widest span of tunnel. By contrast, the temperature field below the tunnel arch foot shows small variation, highlighting the important role of the deep-buried central ditch. (2) Under all temperature conditions, the freezing of the tunnel drainage system begins at the side ditch, followed by the circumferential blind pipe. The transverse guide pipe and central ditch do not freeze during tests. Furthermore, the connection between the side ditch and circumferential blind pipe is identified as a critical weak point for frost resistance; hence, insulation measures for this area should be strengthened. [ABSTRACT FROM AUTHOR]

The purpose of ship optimization is to reduce the resistance of the ship and improve the propulsive efficiency of the propeller. Taking the design of the hull, propeller and rudder as an example, the integration optimization of ship speed performance based on the fully-parametric model was described in detail. Based on the parent hull, stock propeller and flat plate rudder, the fully-parametric coupling models of ship, propeller and rudder were established. The fully-parametric optimization method was used to optimize the optimal combination of hull, propeller and rudder with low resistance, high efficiency and appropriate propeller light running margin. The models were tested in the towing tank to verify the speed performance of the two sets of hulls, propellers and rudders. It was found that the ship integration optimization method based on the fully-parametric model excavated the improvement space of the ship's speed performance from the overall level and realized the integration optimization of the fully-parametric model. The design of hull, propeller and rudder achieved the best speed performance. Compared with the initial design, the speed performance was greatly improved. By analyzing the effects of the hull, propeller and rudder separately, it was found that these parts have different effects on speed performance improvement, and ultimately can maximize the overall comprehensive income; CFD calculation and model test results had a good agreement. [ABSTRACT FROM AUTHOR]

The prediction of the wave load on a hovercraft is essential for the design of the hull structure and safety. However, theoretical methods for the prediction of wave loads are still not mature enough due to the unique and complex nature of the air cushion structure, and numerical modeling and simulation are challenging due to the complexity of the gas-solid-liquid three-phase coupling, so the study of wave loads on hovercrafts still relies on experimentation. In this study, we aim to analyze the wave load response characteristics of a four-chamber hovercraft by conducting a wave load model test under medium/low sea states. The load components and amplitude-frequency response characteristics were thoroughly analyzed based on the acquired data of the cushion pressure, acceleration, and bending moment. The main characteristics of the wave-induced response of the hovercraft were described in detail, and an analytical relationship between the cushion pressure and hull acceleration was derived. The reliability of the experimental results was confirmed through a comparison with the derived results. The relationship between the cushion pressure and cushion volume was investigated in terms of the observed geometric volume of the air chamber, and the relationship between the cushion pressure and flow rate was analyzed to validate the derivation of the theory of wave loads on hovercrafts. [ABSTRACT FROM AUTHOR]

Due to the thin bedrock, typical geological characteristics, and the high-intensity underground mining in western China, the water and sand inrush pour into the panels through the broken rock fragmentations in the caving zone, which could result in serious financial losses or even casualties. This paper investigated the influence of the height of the caving zone and the size of sand particles on the speed of water and sand inrush by the methods of laboratory tests and numerical simulation. The test results reveal that the speed of sand flow decreases with an increase in the height of the caving zone until the height of the caving zone approaches a certain value, and the speed of sand flow decreases with the increase in sand particles. The particle flow (PFC3D) method was used to simulate the experiment to study the dynamic changes in the force chain during the process of water and sand inrush. The simulation results show that the process of water and sand inrush is a continuous and variable process of force chain formation and break. Sand particles only flow through the gap between the caving zones, and during this process, some sand particles remain, which makes the force chain gradually become stable and the speed of water and sand inrush slow. [ABSTRACT FROM AUTHOR]

There has been a frequent occurrence of tailing dam failures in recent years, leading to severe repercussions. Flood overtopping is an important element contributing to these failures. Nevertheless, there is a scarcity of studies about the evolutionary mechanisms of dam breaches resulting from flood overtopping. In order to fill this knowledge vacuum, this study focused on the evolutionary characteristics and triggering mechanisms of overtopping failures, utilizing the Heshangyu tailings pond as a prototype. The process of overtopping breach evolution was revealed by the conduction of small-scale model testing. A scaled-down replica of the tailings pond was constructed at a ratio of 1:150, and a controlled experiment was conducted to simulate a breach in the dam caused by water overflowing. Based on the results, the following conclusions were drawn: (1) The rise in water level in the pond caused the tailings to become saturated, leading to liquefaction flow and local slope sliding at the initial dam. If the sediment-carrying capacity of the overflowing water exceeded the shear strength of the tailings, water erosion would accelerate landslides on the slope, generating a sand-laden water flow. (2) The breach was primarily influenced by water erosion, which subsequently resulted in both laterally widened and longitudinally deepened breach. As the breach expanded, the sand-carrying capacity of the water flow increased, leading to a faster rate of failure. The breach process of overtopping can be categorized into four distinct stages: gully formation stage, lateral broadening stage of gully, cracks and collapse on the slope surface, and stable stage of collapse. (3) The tailings from the outflow spread downstream in a radial pattern, forming an alluvial fan. Additionally, the depth of the deposited mud first increased and subsequently declined as the distance from the breach grew. The findings of this research provide an important basis for the prevention and control of tailings dam breach disasters due to overtopping. [ABSTRACT FROM AUTHOR]

Shield tunnels' structural stability is challenged due to the fact that they are often built under rivers, lakes, and oceans. It is crucial to execute the structural deformation perception of the shield tunnel. Fiber Bragg grating (FBG) sensing technology is sensitive to deformation information, making it one of the greatest options for shield tunnels to perceive structural deformation. In this study, a 1:20 scale model test was carried out to investigate the deformation perception of the shield tunnel structure under three different layouts of surface-mounted FBG sensors. The deformation law of the tunnel is discussed, under the condition of two-factor cross fusion and especially under the condition of constant water pressure and soil pressure change. The results indicate that, under the combined action of water and soil pressure, the uniform water pressure of 0.33 MPa has a stabilizing effect on the segment strain under the vertical load of 0.4 MPa. The traditional four-point layout and the 18° uniform layout are more effective in detecting changes in local tunnel curvature and strain, respectively, compared to the 36° uniform layout mode. It is advised that the traditional four-point layout be used to collect information for other sections' monitoring and that the 18° uniform layout is for harsh terrain conditions. [ABSTRACT FROM AUTHOR]

Offshore carbon capture, utilization, and storage (OCCUS) is regarded as a crucial technology for mitigating greenhouse gas emissions. Quantitative monitoring maps of sealed carbon dioxide are necessary in a comprehensive OCCUS project. A potential high-resolution method for the aforementioned purpose lies in the full-waveform inversion (FWI) of time-lapse seismic data. However, practical applications of FWI are severely restricted by the well-known cycle-skipping problem. A new time-lapse FWI method using cross-correlation-based dynamic time warping (CDTW) is proposed to detect changes in the subsurface property due to carbon dioxide (CO2) injection and address the aforementioned issue. The proposed method, namely CDTW, which combines the advantages of cross-correlation and dynamic time warping, is employed in the automatic estimation of the discrepancy between the seismic signals simulated using the baseline/initial model and those acquired. The proposed FWI method can then back-project the estimated discrepancy to the subsurface space domain, thereby facilitating retrieval of the induced subsurface property change by taking the difference between the inverted baseline and monitor models. Numerical results on pairs of signals prove that CDTW can obtain reliable shifts under amplitude modulation and noise contamination conditions. The performance of CDTW substantially outperforms that of the conventional dynamic time warping method. The proposed time-lapse full-waveform inversion (FWI) method is applied to the Frio-2 CO2 storage model. The baseline and monitor models are inverted from the corresponding time-lapse seismic data. The changes in velocity due to CO2 injection are reconstructed by the difference between the baseline and the monitor models. [ABSTRACT FROM AUTHOR]

This study aims at addressing the face failure of earth pressure balance (EPB) shield tunnels in dry dense sand by model tests and discrete element method (DEM) models. The model tests incorporated a miniature EPB shield which could fully reproduce the real tunnel construction of excavation and support. DEM models simulating the model tests were developed to capture the underlying face failure mechanism. Results show that both the limit support pressure obtained at chamber board and tunnel face increase with increasing C/D (C is tunnel cover depth, and D is tunnel diameter). The ratio of the former to the latter approximates 0.60 due to the soil retaining of cutter head panel, and it is independent of C/D. The local face failure initializes around tunnel face and develops directly to the global failure outcropping the ground surface in one phase with C/D ≤ 1.0, while the local failure develops to the global failure in three phases with C/D = 2.0 due to the soil arching evolution. The soil arching gets weaker when it propagates upward, and the horizontal stress concentration in the longitudinal direction is stronger than the transverse direction due to the difference of arch foot. [ABSTRACT FROM AUTHOR]

Abstract This article presents a composite tunnel rockfall protection structure (CPRC) employing galvanized corrugated steel plates as the inner formwork for reinforced concrete structures. It addresses the threats posed by frequent rockfall disasters in mountainous regions with complex geology. The research investigates impact damage from various rockfall shapes through numerical simulations and experiments on five representative forms, comparing traditional reinforced concrete structures RC with CPRC. The study highlights both structures’ dynamic responses and damage characteristics across different impact scenarios, introducing the Residual Resistance Index RRI as a measure of post-impact safety performance. Results show that the numerical simulations align with laboratory tests, with discrepancies within 10%, validating the simulation method’s accuracy in predicting impact resistance. Following impacts, both structures primarily displayed brittle concrete damage; however, the CPRC structure demonstrated a 79.46% reduction in concrete damage and an 86.31% decrease in reinforcement damage. The energy-dissipating properties of the corrugated plates significantly lowered rockfall penetration depth and impact energy transfer ratio, with an RRI exceeding 0.88 post-event. Additionally, the study reveals varying damage effects from different rockfall shapes, further supporting the CPRC structure’s superior impact resistance and its effectiveness in preventing secondary disasters in tunnel engineering within mountainous terrains.

Abstract The prefabricated assembled cover arch reinforcement method offers rapid construction and high quality, effectively addressing the challenges of cast-in-place cover arch reinforcement used in tunnel linings in mountainous areas of China. This study investigated the mechanical performance of prefabricated assembled arches in tunnels through model tests and numerical simulations. The results indicate that joint opening and deflection, as well as their change rates, increase with eccentric distance. There is a roughly linear relationship between joint opening and deflection with increasing load. At an eccentric distance of + 0.2 m, the peak stress appears on the outside of the joint, with a valley on the inside, and stress concentration at bolt holes. The application of bolt preloading enhances the joint’s stress performance. Furthermore, the stiffness of the lining and soil significantly impacts the mechanical response of the cover arch, with peak stress mainly observed at the foot of the cover arch and the handhole of the joint.

The pipe-soil interaction force is a crucial load that ensures the on-bottom stability of submarine pipelines and acts as a vital input parameter for the design of controlled pipeline buckling. It is necessary to precise prediction of soil lateral resistance and sensitivity to environmental parameters. This study developed a numerical simulation technique based on the coupled Euler-Lagrange (CEL) method to systematically analyse the deformation of the pipeline and the soil-pipeline forces on the seabed foundation during service. To validate the numerical method for large lateral displacement of pipe-soil interaction, an experimental approach employing parameter variation was utilized to conduct sensitivity analysis on the environmental parameters. The key parameters affecting soil-pipeline interaction were determined through an analysis of relative variation factors. The research findings demonstrate a satisfactory agreement, with an amplitude difference range of within 15 %, between the numerical simulation technique using the CEL method and the experimental results. This method resolves the issue of non-convergence due to grid distortion under conditions of large displacement, thereby enhancing computational accuracy. Sensitivity analysis shows that the relative variation factors for soil friction angle, initial burial depth, and soil density exceed 50 %, which is notably higher than the elastic modulus, friction coefficient, and Poisson's ratio of the soil. The results of this study enable the prediction of lateral forces in pipe-soil interaction and identification of environmentally sensitive parameters. This study establishes a foundation for calculating pipeline buckling strength in complex environments and holds paramount importance for the design and construction of pipelines to ensure on-bottom stability.

Purposes To investigate the influence of different tamping methods on the reinforcement effect of sand dynamic compaction, this research has been done from the perspective of soil stress distribution characteristics. Methods The dynamic compaction model test was carried out in the outdoor field to monitor the vertical and radial soil pressures in the soil and falling weight acceleration during tamping process, and the displacements in the soil were analyzed by numerical simulation method. Findings It is concluded that in the construction of dynamic compaction method, the vertical soil pressure waveform is the shock wave waveform or the vibration attenuation wave shape, and the radial earth pressure waveform is the impact waveform; There are two reinforcement modes in the process of dynamic compaction, the soil under tamping point is mainly vertically compacted, while the soil side of tamping point also has significant radial compaction; At the same level of dynamic compaction, heavy falling weight is suitable for deep soil and radial soil reinforcement, while light falling weight is suitable for rapid reinforcement of shallow soil. Conclusions The research results have a certain guiding significance for the selection of tamping methods of the same energy level dynamic compaction.

To develop an efficient internal force calculation model for double row anti-slide piles with connecting beams, the finite difference method was used to calculate the internal force of all piles at the load section and embedded end of double row piles. The structure of double row anti-slide pile with connecting beam was simplified to two single piles disconnected at the zero bending moment of the connecting beam at the pile top; the bending moments and shear forces at the top of the front and back piles were obtained by superposition of the forces on the double row piles. The structural model tests were carried out to check the effectiveness of the calculation model based on the finite difference method. The results show that the model test results are consistent with the data of pile top displacement and pile body bending moment obtained from the calculation model, indicating that the simplified calculation model is effective. There is a slight deviation between the positions where the maximum bending moment calculation is for the rear pile. The calculated maximum bending moment position is close to the real pile failure position, further proving the reliability of the entire pile internal force calculation model based on the finite difference method. The finite difference calculation model avoids the complex calculation process of iterating the loaded and embedded sections using continuous conditions, and provides a fast and efficient method for calculating the internal forces of double row piles with connecting beams in practical engineering.

Abstract Engineering slope stability issues typically exhibit the impact of deteriorating durability on the susceptibility of slopes to failure. A thorough investigation was essential to explore theoretical and experimental aspects of slope durability degradation and its implications on long-term stability. Hence, a durability model was developed to accommodate slope stabilization using reinforced concrete (RC) support structures. This model was grounded in classical durability principles for RC structures. Subsequently, a model test was conducted to compare the responses of a standard slope model with a weakened counterpart subjected to environmental impacts. According to the proposed methodology for slope durability and stability, a case study involving future durability and stability predictions was performed. It was found that the theoretical solutions for the carbonation or neutralization (CN) velocity, depth, and penetration time agreed well with model test results. The slope surface displacements of the weakened slope with deteriorating coefficients between 0.6 and 0.9 were 4 to 8 times those of the standard slope, demonstrating significant degradation in stability. The case study indicated a steady reduction in the safety factor, at a rate of 2.3 to 2.4‰ per year throughout the slope’s service life. Finite-element-based predictions also suggested the potential for corrosion of slope anchor bolts within 20 years and breakage within 30 years, at an average rate of 7.5‰ per year in the ultimate bearing capacity. These findings highlight the need for timely maintenance and reinforcement interventions to ensure the long-term durability of operational slopes.

This study aims to develop a rational theoretical model for cutterhead-soil interaction. The cutterhead-soil interaction mechanism is divided into two components: the cutting action of the cutter on the soil and the extrusion of the cutterhead on the soil. By enhancing the Mckyes–Ali model, we analyze and deduce the force state of the cutter during shield tunneling, obtaining a calculation method for determining the force on the cutter. Additionally, we conduct an in-depth analysis of the extrusion effect of the cutterhead on the soil during shield tunneling, utilizing the fundamental solution of the Kelvin problem. Based on these theoretical calculations, we validate the tunneling thrust and cutterhead torque of the shield using our self-developed multi-functional large-scale shield tunneling test platform. The test results demonstrate that the tunneling thrust and cutterhead torque derived from the established cutterhead-soil interaction model in this paper are relatively close to the experimental monitoring values. This provides a theoretical foundation for establishing reasonable shield tunneling loads.

Groundwater is one of the key problems that must be faced and solved in underground engineering. Under special conditions, large-scale water damage accidents will occur. Therefore, it is of great engineering significance to study the stability of the surrounding rock of water-inrush roadways. In this paper, a laboratory model test is used to simulate the actual project. First, similar material and the similarity ratio of the test are determined, and the relationship between the ratio of the similar material and its physical parameters is analyzed through an orthogonal test, the multiple linear regression equation of the two is established, and the optimal ratio of the model similar material is determined. Then, the model test of tunnel water inrush is carried out. Through the orthogonal test, the influence of roadway depth, water-inrush height and water-inrush time on the stability of surrounding rock during and after tunnel water inrush is analyzed, and the numerical simulation is used to verify and extend the conclusion. The test results show that the sensitivity of each factor to roadway stability is as follows: water-inrush height > water-inrush time > roadway depth. In the test within 24 h after water inrush (7 days in actual engineering), the sensitivity of each factor to roadway stability is also water-inrush height > water-inrush time > roadway depth. This conclusion can provide an important basis for the rescue work after tunnel water inrush and enrich the relevant test simulation after tunnel water inrush. Practical Applications: In this paper, a laboratory modeling test is used to emulate the actual project where groundwater exists. Similar materials used in the model test and their optimal ratios are determined by similarity ratios and multiple linear regression equations. The effects of roadway depth, water-inrush height, and water-inrush time on the stability of the tunnel's surrounding rock are investigated by orthogonal tests, and finally the results are verified by numerical simulation. The test results show that the sensitivity of each factor to the stability of the roadbed is as follows: water-inrush height > water-inrush time > roadway depth. In the test within 24 h after water influx (7 days in the actual project), the sensitivity of each factor to the stability of the tunnel is also water-inrush height > water-inrush time > roadway depth. This conclusion can provide an important basis for the rescue work after the tunnel water influx and can provide suggestions for the early reinforcement support of the project in the presence of groundwater. [ABSTRACT FROM AUTHOR]

Laboratory model tests were conducted on artificially structured clays using self-developed equipment to better understand the penetration mechanism of jacked piles in structured clays. Two artificially structured clays with the same initial void ratio but different structured strengths, along with one unstructured clay, served as foundation soils for model tests. Cement and salt were selected to simulate the bonding force and macroporous fabric between soil particles in artificially structured clays. The microstructure and mechanical behavior of artificially structured clay samples were analyzed using a scanning electron microscope and a triaxial apparatus. This analysis aimed to evaluate the efficacy of the current method utilized in preparing structured clays and elucidate the evolution mechanism of pile response in structured clays in relation to soil cells. The findings showed that increased confining pressures lead to a more pronounced impact of soil structure on pile jacking force. Unlike the pile shaft, soil structure played a more crucial role in influencing the pile end during jacking, primarily due to the shear-induced structure degradation of clays close to the pile shaft. The axial force and shaft resistance of piles significantly increased with higher cement content. Simultaneously, the mobilization of the increased pile shaft resistance enhanced the nonlinearity in the distribution of axial force along the pile shaft. The pore-water pressure and total radial stress at the pile–soil interface, located 150 mm from the pile toe, experienced respective increases of 1.27 and 1.38 times as the cement content of model soils increased from 0% to 4%. [ABSTRACT FROM AUTHOR]

A thorough study was conducted to assess the performance of the strip footing reinforced with geocells in sand, focusing on understanding the enhancement effects and geocell reinforcement mechanisms. Critical factors such as geocell modulus, height, soil relative density and load eccentricity were examined through fully instrumented model tests. Measurements included surface displacement profiles, strains on the geocell layer, subsurface pressure distribution and other relevant parameters. Results revealed that the strip footing on geocell-reinforced sand beds exhibited better performance compared to those on unreinforced soil, characterized by increased load-carrying capacity and reduced settlements. Notably, stiffer geocells improved performance significantly, with a 40% higher modulus enhancing the bearing pressure by up to 25%, due to better confinement and anchorage effects. Conversely, geocells with a lower modulus demonstrated more effective vertical stress distribution. Furthermore, increased geocell height moderately enhanced footing performance by improving confinement, although wall buckling under eccentric loading limited major gains. Dense soils under centric loading exhibited up to a 20% better improvement in bearing pressure than loose soils due to higher strain mobilization within the geocell layer. These findings highlight the crucial role of geocell and soil properties, as well as loading conditions, in optimizing reinforcement effects for strip footings. • Assessed geocell-reinforced strip footings with fully instrumented tests. • Geocell footings outperform unreinforced soils, improving key non-dimensional factors. • Stiffer geocells notably enhance performance due to better confinement and anchorage. • Lower modulus geocells benefit from enhanced vertical stress distribution. • Increased geocell height moderately increased footing performance. [ABSTRACT FROM AUTHOR]

Abstract Background Loess is prone to large deformation and flow slide due to natural and artificial interfaces inside. The strength of these interfaces controls the mechanical properties of loess. Obtaining their mechanical parameters through in-situ testing is essential for evaluating the mechanical stability in loess engineering with interfaces. Methods By developing a borehole micro static cone penetration system and creating various types of loess with interfaces, extensive borehole penetration model tests were conducted to observe changes in cone tip resistance during penetration. The response surface method was used to analyze the impact of various test conditions on the calculated resistance. A three-dimensional surface fitting method was employed to establish the relationship between penetration parameters and shear strength parameters, which was validated through in-situ testing. Results The developed borehole micro static cone penetration system achieves overall miniaturization while providing significant penetration power and ensuring an effective penetration distance. Cone tip resistance development during penetration can be divided into three stages: initial, rapid increase, and slow increase. The transition times between these stages vary for different soils. Calculated resistance is positively correlated with dry density and normal stress and negatively correlated with water content. A quadratic positive correlation was established between calculated resistance and shear strength parameters during penetration. In composite soils, the interaction between water content and normal stress is strong. Compared to intact soil samples, the shear strength parameters of composite soils are more prominently influenced by water content. Conclusion A system for testing interface mechanical parameters was innovatively developed, fulfilling the need to obtain interface shear strength parameters for deep soil. This study can provide support for ensuring the long-term stability of the loess slope or subgrade with interfaces.

Ground penetrating radar (GPR) is a vital non-destructive testing (NDT) technology that can be employed for detecting the backfill grouting of shield tunnels. To achieve intelligent analysis of GPR data and overcome the subjectivity of traditional data processing methods, the CatBoost & BO-TPE model was constructed for regressing the grouting thickness based on GPR waveforms. A full-scale model test and corresponding numerical simulations were carried out to collect GPR data at 400 and 900 MHz, with known backfill grouting thickness. The model test helps address the limitation of not knowing the grout body condition in actual field detection. The data were then used to create machine learning datasets. The method of feature selection was proposed based on the analysis of feature importance and the electromagnetic (EM) propagation law in mediums. The research shows that: (1) the CatBoost & BO-TPE model exhibited outstanding performance in both experimental and numerical data, achieving R2 values of 0.9760, 0.8971, 0.8808, and 0.5437 for numerical data and test data at 400 and 900 MHz. It outperformed extreme gradient boosting (XGBoost) and random forest (RF) in terms of performance in the backfill grouting thickness regression; (2) compared with the full-waveform GPR data, the feature selection method proposed in this paper can promote the performance of the model. The selected features within the 5–30 ns of the A-scan can yield the best performance for the model; (3) compared to GPR data at 900 MHz, GPR data at 400 MHz exhibited better performance in the CatBoost & BO-TPE model. This indicates that the results of the machine learning model can provide feedback for the selection of GPR parameters; (4) the application results of the trained CatBoost & BO-TPE model in engineering are in line with the patterns observed through traditional processing methods, yet they demonstrate a more quantitative and objective nature compared to the traditional method.

The use of prestressing anchor active support technology in tunnel engineering is becoming morecommon.However, the support characteristics and mechanism of action have not been fully understood for shallow, large-span rocky tunnels.In order to investigate the bearing characteristics of the surrounding rock under the prestressed anchor support system, a concealed excavation station of Qingdao Metro Line 6 was used as the engineering background, and based on the similarity principle of formulating experimental materials for stratum and support structure modelling, the bearing characteristics of the anchors under the prestressed anchor and ordinary anchor support were investigated by hydraulic loading tests.The results indicate that: ① The interaction between prestressed anchors and the surrounding rock creates a load-bearing anchor solid that can effectively support most of the overlying loads.The application of prestressed anchors during the overburden loading process increased the warning load value of tunnel instability damage by 42.8% and the ultimate load value by 41.2%.② The overburden loading process involved the prestressing anchors going through the tight anchorage load holding stage and the de-anchorage unloading stage.Simultaneously, the lining underwent the strain accumulation stage, strain surge stage, and strain release stage during the overlay loading process.③ The prestressed anchor under active support has better force synergy with the rock body than an ordinary anchor, without the axial force mutation phenomenon.This allows the support performance of the anchor to be fully utilized.Additionally, the prestressed active support effectively inhibits the development of fissures and significantly improves the overall stability of the tunnel.

Abstract Deep-buried tunnels with weak surrounding rock are frequently encountered issues in traffic engineering. It plays an important role in the excavation process and the project operation. This paper applies the theoretical analysis and laboratory test related to four different conditions in terms of their thickness to determine the mechanical response of deep-buried tunnel lining. Then, the energy dissipative structure theory is employed to explain the experimental results. This paper has made the following achievements: firstly, it is found that the toughness of the secondary lining was found to be often the most important indicator of tunnel safety, with better-toughness linings having higher tensile strength and crack resistance. Secondly, it suggests that the inclusion of steel reinforcement in the concrete lining can effectively improve the secondary lining toughness. Finally, it proves that the more ductile liner had more energy, higher load-carrying capacity, and was better able to maintain the overall stability of the structure.