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.

To solve the problem of large sowing amount and poor sowing uniformity for millet, according to the physical characteristics of the millet seed and its sowing agronomic requirements, an electromagnetic vibration type fine and small-amount seeder was designed, and the main technical parameters of the seeder were determined, in order to realize the functions of furrow opening, electronically controlled seed metering, soil covering and pressing. Based on the principle of electromagnetic vibration, an electromagnetic vibration type seed metering device was designed to achieve uniform seeding of the millet seed with a small sowing amount; a seeding amount electronic control device was designed using an STM32 microcontroller, which realized the switching to sowing agronomic mode and the adjustment of the seeding amount with sowing operation speed; a vibration experimental bench was set up to simulate the vibration state of field operation, and studies on the seeding performance and vibration damping of the seed metering device by the isolation spring were carried out, as well as field sowing tests for verification. When the working voltage of the seed metering device is 80-160 V, the coefficients of variation for seeding uniformity per row and for total seeding uniformity are not greater than 3.57% and 2.39%, respectively, and the seed damage rate is less than 0.5%. The installation of isolation springs can increase the maximum vibration acceleration of the seed metering device by 10.61-28.20%, significantly reducing the impact of external vibrations on the seed metering device. Within the range of suitable sowing operation speeds, the electronic control device can meet the seeding amounts along with sowing operation speed in the 6, 7.5 and 9 kg/hm2 sowing agronomic modes, and the coefficient of variation for seeding uniformity per row, for total seeding uniformity and for sowing uniformity are not greater than 4.63%, 2.48% and 23.38%, respectively. This study provides a reference for the development of sowing machinery for millet crop.

Rayleigh waves are vertically elliptical surface waves traveling along the ground surface, which have been demonstrated to pose potential damage to buildings. However, traditional seismic barriers have limitations of high-frequency narrow bandgap or larger volume, which have constraints on the application in practical infrastructures. Thus, a new type seismic metamaterial needs to be further investigated to generate wide low-frequency bandgaps. Firstly, a resonator with a three-vibrator is proposed to effectively attenuate the Rayleigh waves. The attenuation characteristics of the resonator are investigated through theoretical and finite element methods, respectively. The theoretical formulas of the three-vibrator resonator are established based on the local resonance and mass-spring theories, which can generate wide low-frequency bandgaps. Subsequently, the frequency bandgaps of the resonator are calculated by the finite element software COMSOL5.6 based on the theoretical model and Floquet-Bloch theory with a wide ultra-low-frequency bandgap in 4.68-22.01 Hz. Finally, the transmission spectrum and time history analysis are used to analyze the influences of soil and material damping on the attenuation effect of resonators. The results indicate that the resonator can generate wide low-frequency bandgaps from 4.68 Hz to 22.01 Hz and the 10-cycle resonators could effectively attenuate Raleigh waves. Furthermore, the soil damping can effectively attenuate seismic waves in a band from 1.96 Hz to 20 Hz, whereas the material of the resonator has little effect on the propagation of the seismic waves. These results show that this resonator can be used to mitigate Rayleigh waves and provide a reference for the design of surface waves barrier structures.

A buried utility tunnel can effectively protect internal pipes by preventing or mitigating corrosion, external damage, and facilitating maintenance. During an earthquake, the energy from seismic waves is transmitted through the soil to the utility tunnel, then to the support structure, and ultimately to the pipe, making the support's interaction with the pipe crucial. In this study, scaled utility tunnel system undergoes shaking table tests at a horizontally non-homogeneous site. Various supports within the tunnel are modeled dynamic elements to assess energy dissipation. The attenuated seismic waves are then applied directly to the pipe to evaluate its response and validate the results against the tests. The study reveals that greater sliding between the tunnel and pipe leads to more energy dissipation and reduces the likelihood of significant pipe deformation. Situations with increased sliding of the side-wall angle steel support exhibit smaller strain peaks. Longitudinal sliding becomes more pronounced only when peak ground acceleration exceeds 0.8 g in longitudinal loading. The transverse sliding response under longitudinal loading is not influenced by the input acceleration peak. Additionally, modeling the internal pipe's interaction with the support as a simplified dynamic element yields more accurate responses, offering a foundational calculation for the design of shock absorption and vibration isolation in utility tunnel supports.

In order to solve the problem of subgrade and foundation vibration damage induced by the railway train, a new type of rubber particle-flowable fly ash (FAR) subgrade was designed based on the principle of damping energy dissipation. The FAR material was prepared to meet the requirements of the working performance by the laboratory test, and the mechanical properties were investigated. The damping ratio characteristics of the FAR material were studied by the transient excitation method, the influence of the rubber particle content on the damping characteristics of the FAR material was analyzed and the vibration isolation mechanism of the FAR material was revealed. A 3D numerical model of track-subgrade-foundation was established by the finite element software, and the vibration isolation performance of the FAR subgrade was analyzed based on the coupled model. The results show that the rubber particles reduce the strength and dry density of the FAR subgrade. And the basic mechanical properties of the subgrade can meet the requirements of railway engineering application when the rubber particle content does not exceed 15% of the mass of solid mixture. The damping ratio of the FAR subgrade increases linearly with the increase of the rubber particle content. And the smaller the rubber particle size is, the larger the damping ratio of the FAR subgrade will be. On this basis, it is recommended to use the rubber particles with particle size of 150 mesh and particle content no more than 15%. The new subgrade is recommended for subgrade filling below the surface layer of the subgrade bed. Compared with the ordinary subgrade, the dynamic stresses of the subgrade bed bottom layer, subgrade soil and foundation soil of the FAR subgrade are reduced by 10%- 30%. In the main frequency range of the FAR subgrade vibration, the ground vibration acceleration level is generally reduced by 2-6 dB and the reduction is up to 83 dB, which verifies the good vibration isolation performance of the new FAR subgrade.