Use of screw pile foundations to reduce temperature of warming permafrost: Lab tests and numerical modeling

Abstract

Steel screw piles may be a viable pile foundation type in the permafrost region of the Canadian Arctic but the effects of climate change may accelerate the creep settlement rate of the pile. Reducing the temperature around a pile is an effective way of enhancing the long-term performance of a pile. This study proposes a technique that combines the steel screw pile with the artificial ground freezing method, where liquid coolant is circulated through the hollow screw pile shaft to lower the temperature of surrounding permafrost. A series of laboratory experiments of freezing tests was conducted to verify the feasibility of the proposed technique. A finite element model was then developed to evaluate the cooling effect of this technique by analysing the duration of the permafrost freezing and the power of removing the heat from the soil. The numerical model was calibrated against laboratory freezing tests. A series of numerical analyses were performed to investigate the effects of soil properties and screw pile shaft configuration on the ground freezing process in field application. The duration required for freezing the soil at a radial distance of 450 mm to −2 °C was estimated and compared. The results showed that the proposed method was applicable in the field. Numerical results showed that the power of removing the heat from the soil was larger when using the screw segment than the smooth segment. The results are expected to guide the field application of artificial ground freezing around screw piles installed in permafrost.