With the development of urban rail transit, the subway inevitably needs to run through the main channel of the South-to-North Water Diversion. With the subway being put into operation, the deformation during the construction period has been gradually stabilized, and the cyclic vibration load of the train during the operation period has gradually affected the channel structure. Therefore, in order to further investigate the effect of vibration load on the structure of the Middle Route of the South-to-North Water Diversion Project during the operation period, this paper, based on the actual cases of undercrossing projects in different regions, established a tunnel-soil-channel finite element model considering silty clay and fine sand under different burial depths by using ANSYS. The vertical vibration levels of the roadbed, tunnel wall and channel bottom are extracted and compared with the measured vibration acceleration levels. The dynamic displacement and maximum tensile (compressive) stress under different working conditions are analysed, and the fatigue life of the canal concrete structure is predicted using the obtained maximum tensile (compressive) stress. The results show that under the condition of fine sand, 1 times the hole diameter is the most unfavourable condition. In the prediction of concrete fatigue life by S-N equation, the number of trains that can pass under the most unfavourable condition is about 6.68 x 1010, which is far more than the number of trains that can pass within the service life of the tunnel.

In recent years, the increasing use of mulching in agricultural practices has been driven by its benefits in weed suppression, soil moisture retention, and improved soil structure. However, Korean farms typically perform mulching and soil covering separately, leading to excessive labor requirements. To address this issue, this study analyzes the safety of a newly developed mulching and soil covering machine. To evaluate its structural safety, strain gauges were attached to critical points of the machine, and strain data were collected under various Power Take-Off (PTO) and engine speed conditions. The measured strain was converted into von Mises stress and maximum shear stress, and the safety factor was calculated using the maximum shear stress theory and the strain energy theory. Additionally, fatigue life was predicted using the rainflow counting method, the Goodman equation, and Palmgren-Miner's rule. The results indicate that the safety factor ranged from 1.65 to 16.54 based on the maximum shear stress theory and 2.42 to 19.83 based on the strain energy theory, confirming that the machine can withstand operational loads without failure. Furthermore, fatigue life prediction revealed that the lowest estimated fatigue life is 14,575 h, equivalent to approximately 607 years of continuous use. These findings demonstrate that the developed machine possesses high safety, making it a viable solution for improving efficiency in mulching and soil covering operations.

In this study, the potential use of industrial waste materials, namely, copper slag (CS), iron ore tailings (IOT), and red mud (RM), as stabilizing agents for black cotton (BC) soil in pavement construction applications was evaluated. Laboratory tests were conducted to assess the performance of the stabilized BC soil, including Atterberg limits, compaction characteristics, California bearing ratio (CBR), unconfined compressive strength (UCS), permeability, and fatigue tests. Additionally, microstructural analysis was performed to further investigate the changes in the soil properties. The results indicated that BC soil mixed with CS, IOT, and RM exhibited enhanced plasticity, strength (UCS and CBR), permeability, and fatigue properties compared to untreated BC soil, regardless of the mix percentage. Notably, BC soil with 30% CS demonstrated comparable results to BC soil stabilized with 5% cement, significantly improving its properties. This study addressed a gap in pavement engineering research by evaluating the fatigue behavior of stabilized subgrade soils. It was concluded that incorporating 30% CS into BC soil not only enhanced its performance but also provided a sustainable alternative to traditional stabilizers such as cement and lime.

Insufficient understanding of the stress-strain behavior of pavements built over backfilled trenches, particularly with recycled aggregates, often leads to overdesign or overcompaction, raising costs and project delays. This research investigates how compaction levels during backfilling impact the pavement performance over these trenches. Various recycled material mixtures, both unbound and cement-treated, are compared with conventional crushed rock. Investigations included repeated load triaxial (RLT) tests, microstructural analysis with scanning electron microscopy, environmental assessments, and modeling with FlexPAVETM, a pavement response and performance analysis software. RLT test results were incorporated into the FlexPAVETM models by utilizing established constitutive resilient modulus models. Stress-strain responses of pavements over recycled aggregate backfill, compacted with standard and modified Proctor efforts, were compared with those over crushed rock and natural clay subgrades. Outcomes revealed that the standard compaction energy was sufficient for the desired performance. Fatigue and rutting strains with recycled mixtures closely resembled those with crushed rock, making them viable green alternatives. Pavements over backfilled trenches exhibited 1.5 and 1.8 times longer fatigue and rutting lives, respectively, than those over natural clay subgrades.

The double wellhead system equipped with a suction anchor is subject to alternating loads, such as shear forces and bending moments, which can lead to fatigue failure. Considering the impact of the suction anchor on the subsea wellhead, an equivalent theory has been derived, and a refined equivalent model established to determine the fatigue hot spot moment-stress transfer function. To address the challenges of high computational complexity and convergence difficulties in the dynamic analysis of the refined equivalent model, a simplified theory of global coupling analysis has been derived, and a corresponding simplified subsea wellhead model established. Utilizing the environmental conditions of X gas field in China south sea, the fatigue life of the double wellhead system with suction anchor is evaluated. The results were compared with those of a conventional subsea wellhead, demonstrating that the double wellhead system with suction anchor can significantly improve fatigue life of the subsea wellhead. The fatigue life of high and low pressure welds in conventional subsea wellheads under drilling conditions has been extended from 17.77 years to 1.20 years-186.16 years and 25.62 years, respectively.

Today, the construction sector experiences significant pressure to use green and sustainable materials. In this framework, using biological components derived from agricultural products is the most interesting topic for the stability of asphalt pavement construction materials. Furthermore, the escalation in demand for transportation infrastructure has resulted in a rapid surge in the volume of traffic and premature degradation of asphalt pavements. The primary objective of this study is to assess the efficacy of olive kernel ash (OKA) obtained from olive canning factories in modifying the characteristics of asphalt. The investigation of this function has not been explored in prior research. To this end, a comprehensive analysis of morphological, Thermogravimetric, chemical, and phase separation was conducted, in addition to physical and rheological testing, over three distinct temperature ranges: high, intermediate, and low. The results showed that OKA is thermally stable and has a slow decomposition. Also, using OKA, compared to most biomass employed in bitumen, exhibits a satisfactory amount of phase separation. Despite the enhanced shear strength, the modified samples incorporating OKA do not encounter any operational challenges regarding transportation and pumping. The findings from the rheological experiments indicate that incorporating 20 % OKA in bitumen can increase the shear modulus up to 71 % and recovery percentage up to 20 %. Therefore, it significantly enhances the resistance to permanent deformation under high temperatures. The increase in molecular weight and asphaltene phase creates a resistant binder against high temperatures. Meanwhile, the fatigue life of modified samples containing 20 % OKA decreased to 59 %. However, applying the highest shear stress to the sample containing OKA experiences demonstrates its ability to resist this stress for longer. Also, it was found that regulating the OKA dosage in bitumen can maintain its acceptable resistance level to cracking at low temperatures. This phenomenon is due to the positive effect of OKA on the viscoelastic characteristics of bitumen. Based on our assessments, it has been observed that incorporating OKA up to 20 % in bitumen consistently enhances its performance capabilities at high temperatures. Nevertheless, while using this modified bitumen in cold regions, limiting its utilization to a maximum of 5 % is advisable.

The current study identifies the critical design considerations for the universal joint of a cutter suction dredger. The cutter suction dredger is modelled as a hybrid two subsystems consisting of hardware-in-the-loop (HIL) and Software-in-the-loop (SIL). HIL, consisting of Dredge hull, spud and soil embedment, is modelled experimentally. System identification is carried out, and a single degree of freedom (SDOF) system is determined for HIL. The identified dynamic parameters are interfaced with the SIL. SIL consisting of the cutter shaft is modelled numerically. The primary and secondary shaft of the cutter shaft is coupled using springs to emulate the universal joint. A sensitivity analysis of the acceleration amplification based on the spud location relative to the hull is carried out. It is observed that the spud position relative to the hull has less influence on the acceleration amplification. A soft universal joint produces a higher response transmitted to the Dredge hull. Further, the influence of the universal joint on the fatigue life of the shaft is analyzed. The results from the fatigue analysis indicate that higher coupling stiffness reduces the fatigue life of the cutter shaft. Therefore, while designing the universal joint, both the impulsive and the fatigue loading must be considered.

The agricultural front-end loader is an implement attached to the front of tractors to transport various agricultural materials, including soil. Since they are subjected to various loads due to the working environment, their safety analysis in consideration of actual working conditions is required. However, there are no official standardized test codes to consider various actual working environments currently. In this study, the structural safety of a front-end loader for static and fatigue failures was evaluated using new test code reflecting actual working environments. Thirty-four measurement locations were determined as the stress concentration spots of each component of the front-end loader derived through multibody dynamic simulation. The total testing time was set to 1 h, and the test time for each task was determined considering the duty percentage of the actual loader work. The measurement results showed that the maximum stress that exceeds the material's yield strength occurred at two locations of the mount, which is the connection to the tractor body, resulting in static yielding. For tasks, the pulling and dumping exhibited the highest stress. The task that had the largest impact on fatigue damage was the dumping. The static safety factor was found to be over 1.93 and the fatigue life met the required lifespan at all measurement locations except for those exhibiting static yielding. Therefore, the most vulnerable part of the front-end loader is the mount, and it is necessary to secure the overall structural integrity by robust design for the mount.

A set of large-scale physical model tests were performed to investigate the performance of unreinforced and glass fibre geogrid-reinforced asphalt pavement under the development of a void in the subgrade. Traffic loadings were simulated with repeated sinusoidal loadings of different amplitudes. The formation of the void was simulated using a novel displacement control device between loading cycles. The accumulative permanent deformation of the asphalt pavement, the composite resilient modulus and dissipated energy were presented and analysed. It was found that the inclusion of geogrid greatly improved the fatigue life of asphalt pavement, and the stronger the geogrid, the greater the improvement if a void was formed below the asphalt layer. After forming the void, the composite moduli of the pavements increased compared with that during the first cyclic loading stage (without the void) and seemed to be not much affected by the geogrid type. The effect of cyclic loading level on the composite modulus was not significant. The inclusion of geogrid in asphalt had a limited effect on the dissipated energy in the pavements with and without voids. The dissipated energy increased with the cyclic loading amplitude.

For wind farms situated in resonance-prone environments, exemplified by the Xiangshan wind farm in China, where wave-induced resonance impacts most of the operating time, designing offshore wind turbines (OWT) is an urgent engineering challenge. Given the scarcity of solutions lowering resonance response while balancing power generation, this study provides a hybrid control strategy to facilitate OWT operation for optimal power capture at low wind speeds and safeguard structural integrity by mitigating fatigue loads at high speeds. This is achieved through the integration of a maximum power point tracking (MPPT) generator torque controller and a PID-based blade pitch controller, which incorporate wind speed feedforward and tower acceleration feedback. The tangible effects of hybrid control are demonstrated through the simulation of the Xiangshan wind farm employing an integral OWT model within the aero-hydro-servo-elastic-soil framework. The results show that the hybrid controller achieves a trade -off between energy capture efficiency and long-term structural stabilization. The hybrid control strategy presents effective regulation under varying environmental conditions and significantly extends the lifetime of OWT foundation while incurring minimal power production reductions. Enabling to satisfy power generation and load reduction, this research signals a promising potential for the OWT design in wave resonance-prone areas.