Dynamic Response of the Entrance Structure of an Elliptical Mountain Tunnel under the Action of SH Waves

Generally, the surrounding rock at the entrance of a mountain tunnel is loose, and the entrance has more slopes due to topography, which causes the tunnel entrance section to be easily destroyed under an earthquake. Based on the established slope model with a single free surface, this paper adopted the elastic wave theory to derive the analytical solution of the strain at the entrance of the mountain tunnel when the SH wave is incident perpendicularly to the bottom of the tunnel; besides, the factors affecting strain were also analyzed. The tangential strain curve at each point of the entrance section takes the centre of the elliptical tunnel as the centre of symmetry, forming symmetry between the left and right sides and mirror symmetry between the top and bottom sides. Then, large-scale shaking table model experiments were conducted to model the actual working conditions, and the correctness of the analytical solution was verified. The research can provide a theoretical reference for the seismic design of the entrance section of the high-speed railway tunnel and greatly improve the understanding of its seismic response.

Analysis on Leakage Characteristics of Labyrinth Piston Clearance in Reciprocating Labyrinth Compressor

In this paper, the piston clearance leakage model in reciprocating labyrinth compressor is established, and the leakage characteristics of labyrinth piston are analysed. The results show that in the labyrinth entrance section, the gas velocity decreases greatly, and the throttling effect is the most obvious. In the middle section of the labyrinth, the flow velocity descending gradient decreases. In the exit section, the flow rate begins to increase. When the labyrinth clearance is less than or equal to 0.1 mm, the clearance changes has little effect on the leakage. When the clearance is greater than 0.1 mm, the leakage increases rapidly with the clearance increasing. When the piston operates eccentrically, the leakage will increase by 1.5 ∼ 2 times compared with the non-eccentric operation. Therefore, the eccentric operation of the piston should be avoided as much as possible and the clearance should be reduced.

Study on temperature field of entrance section at high altitude tunnel considering water supply from snowmelt

To explore the influence of snowmelt supply at the entrance section at high altitude tunnel on tunnel engineering, several indoor model tests were carried out by setting a water-supply system above the model device for simulating the actual snowmelt supply environment. The model tests were based on a project at high altitude tunnel in Qinghai. The varied characteristics of temperature field in typical cross-sections of tunnel entrances with and without water-supply condition under freeze-thaw cycles were analyzed accurately by the model. This study shows that the external water supply has a great influence on the tunnel entrance. When the surrounding rock freezes at the tunnel entrance, it first freezes from the arch, then develops to the side wall, and then spreads to the inverted arch to form a freezing circle. The faster the freezing development rate is, the greater the thickness of the freezing ring is under the water-supply condition. The development of temperature field under water-supply condition is obviously faster than that under normal condition. The distribution characteristics of freezing depth in both conditions are the arch is the largest, the side wall is the second, and the inverted arch is the smallest. This study can provide a reference for analyzing the process of freezing injury caused by high altitude snowmelt water supply into tunnel entrances in western Sichuan.

Numerical Study on Discharging Characteristics of Pebble Cluster Flow in Pebble Bed

To better understand the flow features of pebble cluster in pebble bed, discharging of the pebble cluster were simulated by DEM. The pebble entangled cluster was composed of eight particles connected by rigid bonds and the simulated cluster models are divided into two types: axisymmetric u-particle and distorted z-particle. The simulation starts with the closed discharge outlet and the bonded clusters with different ID are randomly added from the entrance section. The pebbles fall freely and accumulate freely in the pebble bed. The discharge hole opens after all the pebbles being stationary for a period. Then the pebbles are discharged from the pebble bed under gravity. The discharging process is time-dependent bulk-movement behavior. There is not much mixing between layers on the boundary. The vertical end makes the packing loose, but also intensifies the interaction between particles due to entanglement. Consequently, the discharge features of pebble clusters of different included angles were quantified. The results show that the pebble discharging speeds depend on entanglement angle (α of u-particle and η of z-particle) and discharging outlet diameter. A large included angle may play the role of retarding or inhibiting the discharging flowrate. Therefore, the entanglement of particles component also always plays the key role of retarding the discharge.

Design and implementation of LED lighting intelligent control system for expressway tunnel entrance based on Internet of things and fuzzy control

Due to the special characteristics of highway tunnels and vehicles, the interior of the tunnel is required to provide appropriate lighting to ensure the safety of driving vehicles, especially at the entrance section of the tunnel. At present, most of the tunnel entrance lighting control system only considers one single factor, the brightness outside the tunnel. However, in practice, the required lighting brightness in the tunnel is also related to traffic flow, speed, and other factors. Comprehensively utilizing these factors to improve the control strategy is urgently needed. To deal with this problem, this article has designed a multi-source information acquisition system for tunnel lighting based on the Internet of things technology, which combined with fuzzy control theory in order to develop an intelligent control system for LED lighting at the entrance section of the tunnel. The designed system was implemented and long-term tested in a real highway tunnel. The experimental results have shown that the system designed in this article can automatically control the brightness of the lighting inside the tunnel according to the real-time measurements of the brightness outside the tunnel, traffic flow, speed, and so on. Furthermore, the utilizations of the system can minimize the human and power consumption of tunnel lighting while ensuring the safety of tunnel traffic.