A new model of temperature-dependent permeability coefficient and simulating of pipe leakage produced immersion of loess foundation

Temperatures (T) vary greatly in the loess region of China. T have a complex influence on the permeability coefficient (K). Existing theoretical models, however, do not fully reflect this complexity. To establish a new model of thermal effect of K, the horizontal diffusion test in soil column and the matric suction test were carried out at different T. The results show that the diffusion coefficient (D) increases with increase of T, and the growth rate is more significant at a higher temperature; the matric suction (h) is linearly positively related to T. The water volume coefficient (mw) was obtained by fitting the SWCC. A new equation of K was obtained by combining the equations of D and mw. Local saturation caused by pipeline leakage is one of the main reasons for uneven settlement of foundation in collapsible loess area. It is important to explore the humidification radius under the pipeline leakage in loess fields. In this paper, the numerical calculation model of pipeline leakage was established. Using this model and the new equation of K, the calculation under different seepage pressure (P) is carried out for loess considering the changes of void ratio (e), initial water content (wi), and T. The results show that a saturated area formed around the leaking pipeline which decreases with the expansion of humidification radius. The increases of e, wi, P, and T promote the diffusion speed and expand the diffusion radius. Once connected with groundwater, the leaked water will be drained away rapidly with the movement of groundwater. This drainage slows the horizontal humidification speed down. With an increase in T, the increase rate of humidification range continues to expand. The thermal effect on diffusion range is more obvious at high wi.