Experimental and Numerical Investigations of Frost Heave Characteristics of a Transmission Tower Foundation along the Lanzhou-Lintao Power Transmission Line

The Lanlin 750-kV electrical transmission line is 162.45 km long and traverses more than 3.27 km in highly frost-susceptible soil in Lintao County, China, possibly inducing several engineering problems related to frozen soil in the transmission tower foundation. To study the frost heave characteristics of a reinforced concrete foundation in a seasonally frozen alpine region, in this study, physical model tests were performed on independent reinforced concrete foundations under highly frost-susceptible soil conditions and verified via numerical simulations. The temperature field evolution, tangential frost heaving force, unfrozen water content, and frost heave of highly frost-susceptible soil in an open water-refill environment and under dead load were investigated. The influences of surface temperature, overburden loads, and the buried depth of the groundwater level on the frost heave, tangential frost heaving force, and vertical displacement of the foundation were considered in the numerical simulations. Results showed that when the soil is close to the surface, the response of the temperature field is fast and the range of temperature variations is wide. The tangential frost heaving force was the largest in the middle and upper areas of the foundation, reaching a maximum value of 2.18 kN; moreover, the frozen depth and frost heave were 210.42 and 7.20 mm, respectively. The variation curves of the unfrozen water content were similar at all depths, and the replenished water content increased linearly with time. The numerical simulation results showed that the surface temperature considerably influences the frost heave deformation of the foundation, the dead load has a substantial restraining effect on the tangential frost heaving force and vertical displacement of the foundation, and the groundwater level influences the frost heaving ratio and the increment rate of frost heaving force. The fitting degree between the experimental and simulation results was good. Finally, measures for controlling frost heave to guide engineering practices were proposed based on the experimental study and numerical calculation.