FROST PENETRATION IN SOIL WITH AN INCLUSION OF SAND - DEPENDENCE ON SOIL MOISTURE CONTENT AND WINTER SEVERITY

摘要

An innovative numerical method was developed for calculating multidimensional heat conduction with phase change. The method is simple and robust, and can easily be included in standard finite element and finite difference heat transfer programs. Simulations of one- and two-dimensional heat transfer in soil with an inclusion of sand were done to investigate the disruption in frost and thaw penetration due to the presence of a dry, low thermal conductivity sand The thermal properties of the surrounding material were assumed to be those of a silty soil at various moisture contents. The dependence of frost depth on weather conditions was investigated by using four different (coldest, cold, warm, warmest) winter-long temperature histories for the soil surface boundary condition; these were derived from measured soil temperatures at a Vermont site. With derails depending an the moisture content of the soil, significant effects ts on the time history of frost penetration were observed when a wide sand inclusion is present. Frost penetration actually proceeds more rapidly through the sand at first because it is dry and, therefore, has a lower latent hear and heat capacity; initial frost depth is greater when a sand inclusion is present. Freezing of the soil below the sand inclusion is subsequently impeded by the slow removal of hear at the base of the sand as a consequence of its lower thermal conductivity; thus, the maximum frost depth is greater in soil without a sand inclusion. The influence of the width of the sand inclusion and its effective lateral range are also considered. [References: 15]