Numerical simulation of cooling effect for heat pipe subgrade

Based on heat pipe test engineering for the frozen soil subgrade distresses treatment of Qinghai-Tibet highway, the equivalent model of heat transmission for heat pipe subgrade was established and simulated using finite element method, the working cycle, operating condition and operating radius of heat pipe were discussed under Qinghai-Tibet highway environmental conditions, the cooling effect of heat!pipe in permafrost subgrade was compared with the two-year observation data of the subgrade.Comparison results show that heat pipe work is not continuous but fluctuant in one work cycle about five months, its actual working time is two-thirds of one work cycle, the cooling effect of heat pipe subgrade in winter is obvious, which is good for the contained cool increase of soil body and improves subgrade heat stabilization, there is a decrease for its cooling strength with the increase of horizontal distance, its effective operating radius is 2.25 m, its maximum cooling strength is in evaporation segment in depth direction, which low the thaw sensitivity of permafrost in the seasonal thaw layer about permafrost table.The results indicate that the space between heat pipes for 4.0 m is reasonable, the installation positions of heat pipes at two sides are better than at one side, pile oblique placement is better than perpendicular placement.