Three dimensional dynamic numerical simulations were conducted on thermal and mechanical responses of energy pile group and single energy pile to 72-hour continuous and intermittent heat rejection processes. The temperature of piles body, piles stress, additional temperature load, piles section displacement and lateral resistance of the piles were analyzed. Results show that the outlet water temperatures of the buried pipes are similar, but temperature differences of pile body between the pile group and the single pile are obvious, leading to a series of differences of mechanical responses between two pile types, such as pile body displacement and additional temperature stresses, etc. With mechanical force loaded on the top, the single pile exhibits greater stress than each pile in the pile group and the stress reaches the maximum in the lower part of the pile body. The additional temperature load is almost equal in the main part of the pile but varies dramatically near the pile tops and bottoms. With structure load exerted on the top, the settlements of the whole pile occur. But as time proceeds, the tops of the piles move upward and the bottoms move downward. The lateral resistance of the piles increases along the depth direction and reaches the maximum at the pile bottom. The outlet water temperature, pile temperature and displacement of energy piles fluctuate obviously under intermittent operational condition, and accumulative effect appears.

At present, the research on characteristics of piston wind flow in subway tunnel is mostly based on in-situ measurement or CFD simulations, but the conclusion lacks universality. A one-dimensional simulation model of ventilation network system related to one-station two-sectional tunnel was established by using the software of IDA tunnel, based on parameters of an actual subway line in practice to investigate the impact of five factors, including train length (60 m ~ 360 m), travel speed (10 m/s ~ 100 m/s), departure interval (120 s ~ 600 s), tunnel length (1000 m ~ 10000 m), and blockage ratio (0.1 ~ 0.9), on dynamic piston wind speed and ventilation rates within the tunnel. The correctness of the simulation results was verified. Finally, grey correlation analysis was conducted to reveal the influential intensity of each factor on the ventilation rates. Fitting correlation formulae of the maximum piston wind speed and of the piston wind ventilation rates of the tunnel were obtained by multiple regression analysis method. The results indicate that: The influential intensity of blockage ratio, train speed, tunnel length, train length and departure time interval on the ventilation rates decreases in order; The proposed fitting relationship has a good agreement with the simulated calculation values and previous research results, indicating that the fitting correlation is reliable.