To mitigate the metro-induced vertical vibration of the indoor substation structure, this study proposes a gas-spring quasi-zero stiffness air damping isolator (AD-QZSI) with excellent low dynamic stiffness and high-static stiffness characteristics. The working principle and mechanical properties of the AD-QZSI are introduced and studied through theoretical and numerical methods. A model for substation considering soil-structure-equipment interaction is established using the software ABAQUS, its accuracy is validated based on a series of measured data from actual projects, and the AD-QZSI's simulation method and parameter design method are described in detail. The air damper's stiffness ka is integrated into the isolator's mechanical model, theoretically and numerically achieving an accurate simulation of AD-QZSI's nonlinear mechanical properties. The numerical results have an error of less than 5% with the measured data, indicating that the model is able to better capture the actual structure's dynamic characteristics and is reasonable to be employed for subsequent analysis. Numerical results show that AD-QZSI can significantly reduce the structural vertical vibration, and its control effect is better in the whole frequency band, in particular, the effect is also visible in the low-frequency band, indicating that its vibration isolation frequency band is wider than that of traditional QZS isolator. With the vibration source distance increasing, the control effect of AD-QZSI presents a tendency to decrease and then level off, and its vibration isolation gain is weakened by the continuous increase of the damping ratio greater than 0.01. Moreover, the equipment's dynamic amplification factor of the isolated structure decreases significantly. Finally, the proposed AD-QZSI can obtain ideal quasi-zero stiffness characteristics by adjusting the air pressure, and the adopted air damper belongs to the green low-carbon components, featuring great practical value and application prospects.

Corrugated steel-plate culverts, particularly in horizontal ellipse form, are commonly used in large-span projects. Despite the guidelines on plate radius ratios, the impact of these ratios on mechanical properties remains unexplored. This gap highlights the need for research to guide utility tunnel design because existing studies mainly focus on round culverts compressed into elliptical shapes. Therefore, this study conducted backfill, simulated vehicle live load, and ultimate-load tests on two horizontal-ellipse corrugated steel utility tunnel structures with different top-side plate ratios to examine their response characteristics under various load conditions. Moreover, they were compared with those of existing design methods to offer new insights for the design analysis of soil-steel structures. The results demonstrated that the ratio significantly influenced bending moment distribution, and the critical was concentrated beneath the loading pad for live loads. The ultimate capacity varied with the ratio, with the higher ratio specimen reaching approximately 92.5 % of the capacity of its counterpart. Both specimens failed via tri-plastic hinge mechanisms, with reduced capacity as corrugations flattened. The Canadian Highway Bridge Design Code, which considers thrust force and bending moment, accurately predicted bearing capacity than the other methods in this study. These findings are vital for optimising design and ensuring safety in horizontal-ellipse corrugated steel utility tunnels.

The subgrade structure of high-speed railways is an important foundation for the safe and smooth operation of high-speed trains, and the scientific design of the subgrade structure provides a fundamental guarantee of its durability and technical economy. As, in the development of high-speed railways in China, higher speeds are being pursued, more requirements have been put forward for the dynamic stability of subgrade structures. To address this issue, this article focuses on the control requirements for the long-term stability of subgrade deformation, and various design methods for high-speed railway subgrade structures are presented. Considering the energy dissipation and dynamic stability characteristics of subgrade filling materials, the dynamic performance of coarse-grained soil filling materials in the bottom layer and graded crushed stones in the surface layer are revealed. The methods for determining the values of dynamic parameters such as the dynamic modulus and damping ratio are provided. Based on the dynamic shakedown theory, the stress-strain hysteresis characteristics of fillers and the variation law of dissipated energy are revealed. The correlation between unit volume dissipated energy and shakedown state under cyclic loading conditions is identified. A criterion for determining the critical shakedown state of high-speed railway subgrade structures based on equivalent unit volume dissipated energy is proposed, and a method for determining the design threshold of dynamic stress and dynamic strain is also proposed. The results show that the shakedown design critical values of equivalent unit volume dissipated energy in the bottom and surface layers of the foundation were between 0.0103 similar to 0.0133 kJ/m(3) and 0.0121 similar to 0.0149 kJ/m(3) , respectively. The critical dynamic strain range was 0.8 x 10(-3)similar to 1.3 x 10(-3). On this basis, a high-speed railway subgrade design method based on energy dissipation and dynamic shakedown characteristics was developed. The results can provide theoretical support for the design of high-speed railway subgrade structures with different filling material alternatives and control standards.

To decrease the environmental impact and increase the high-quality resource utilization of construction spoil (CS), the alkali-activated slag (AAS) was selected to solidify CS and prepare solidified construction spoil (SCS). SCS with certain working and mechanical properties can be used as building materials, such as unsintered bricks. However, the preparation of SCS is inefficient, mainly because the properties of SCS are affected by various factors, and the formula is difficult to determine. This study intensively investigated the effects of the liquid-solid ratio (W/ (B + S)), clay content of CS, and binder-soil ratio (B/S) on the flowability and compressive strength of SCS. It was found that W/(B + S) was the main factor controlling compressive strength, and both W/(B + S) and clay content significantly affected the flowability of SCS. Based on an assumption for the flowability prediction method and the relationship between flowability and liquid-solid ratio of CS, AAS, and SCS, a method to predict the flowability of SCS was proposed and validated. Additionally, the extended Abrams' law was applied to fit the compressive strength variation of SCS. Combining the flowability prediction method and the extended Abrams' law, a novel formula design method for SCS was proposed and proven effective in validation experiments.

Agricultural production is facing challenges such as water scarcity, declining soil quality, and excessive use of chemical fertilisers and pesticides, and there is an urgent need to find sustainable solutions. Hydrogel, as a novel functional polymer material, is considered as a potential agro-material to solve these problems due to its excellent water retention, swelling, slow release, biocompatibility and biodegradability. However, there are still challenges in designing efficient agrohydrogels, such as sustainability of the materials, environmental impacts of cross-linking methods, adaptability of the network structure to the crop growing environment, as well as the cost of the materials and the effectiveness of the practical applications. Therefore, a systematic review of the design, properties and applications of agrohydrogels is of great theoretical and practical significance. This paper reviews the design methods of agricultural hydrogels, including network structure design, material source selection, crosslinking technology and its mechanism research. Then, the key properties of agricultural hydrogels, such as water retention, swelling, slow release, biocompatibility and biodegradability, are discussed in detail. Finally, the applications of hydrogels in the fields of soilless cultivation, soil improvement and smart agriculture are presented. This paper concludes that with the continuous progress of technology, agricultural hydrogels will play an important role in future agricultural production.