Heat exchange characteristics of underground and pavement buried pipes for bridge deck heating conditions.

Geothermal energy is increasingly employed across diverse applications, with bridge deck snow melting emerging as a notable utilization scenario. In Jinan city, China, a project is underway to utilize ground source heat pumps (GSHPS) for heating bridges. However, essential operational parameters, including fluid medium, temperature, and heat exchange details, are currently lacking. This study addresses the thermal design challenges associated with ground heat exchangers (GHE) for bridge heating through a combination of numerical modeling and field experiments. Utilizing software Fluent, a refined three-dimensional multi-condition heat transfer numerical analysis was carried out. Field tests based on actual operating conditions were also conducted and the design parameters were verified. The results indicate that an inlet temperature of 5°C and an aqueous solution of ethylene glycol with a mass concentration of 35% as the heat exchange medium are suitable for the GSHPS in Jinan; Moreover, the influence of backfill material and operation time on the heat transfer efficiency was revealed and the suitable material with 10% bentonite and 90% SiO2 was suggested; Finally, based on the influence of the pipe spacing on the heating characteristics of bridge deck, the transition spacing of 0.2 m is given for the temperature response of the bridge deck. This comprehensive study contributes valuable insights through simulation and experimental analysis of the thermal environment variation, aiming to advance the development of GSHPS for bridge deck heating in Jinan, China.

Experimental Study on Mechanical Properties of Root-Soil Composite Reinforced by MICP.

Mechanical properties of undisturbed root-soil composites were investigated through direct shear tests under different cementation concentrations by microbially induced carbonate precipitation (MICP). The results show that MICP has a significant strengthening effect on the undisturbed root-soil composite, and the maximum shear strength increases by about 160% after grouting. The shear strength of root-soil composites increases with the increase in calcium chloride concentration, and the shear strength increases the most when the concentration is 0.75M. Calcium carbonate formed by MICP treatment has cementitious properties, which increases the cohesion and internal friction angle of the root-soil composite by about 400% and 120%, respectively. The results show that it is feasible to solidify slope and control soil erosion together with microbial and vegetation roots. The research results can serve as a scientific basis and reference for the application of MICP technology in vegetation slope protection engineering.