A Novel Approach for Simulating Soil and Pipe Response to Seasonal, Environmental and Field Conditions

Abstract

Climate change related problems are increasing in occurence and severity leading to significant econocmic losses in many places of the world. In semi-arid environments, like Saskatchewan, the main phenomenon involved in pipe breakages is the volume change behavior of unsaturated clay deposits. Underground pipelines are typically buried within the upper zone of soil deposits, and therefore, are highly affected by soil nature and the different environmental conditions present on the ground surface. To accurately model field conditions, a mathematical formulation of native soil conditions was developed based on a bimodal soil water characteristic curve (SWCC) and other constitutive relationships. In order to simulate the response of soil and pipe to various mateorological conditions, a numerical framework was developed and validated. The strength of the developed numerical framework lays in the use of bimodal SWCC and modeling the hydraulic characteristics of a cracked soil structure. This research study also utilized, as a database, the results of a filed instrumentation program conducted in the City of Regina. A hydro-mechanical analysis was implemented to model the volume change due to variations in mechanical loading conditions and moisture content. Modeling scenarios were also studied based on variations in pipe diameter, pipe depth and soil elasticity. The developed numerical framework provided insight into the sensitivity of pipe deformation to possible changes in input parameters of the soil-pipe system. The model was able to capture the transient water flow through Saturated-unsaturated soils. The results of the modeling of weather conditions applied on the soil-pipe system were in agreement with the field measurements. Specific relationships between the soil-pipe interaction and seasonal changes in the local meteorological conditions were established. The model was also used to provide some insight into the real flux transferred through the pavement structure to the backfill material surrounding the pipe. Finally, soil and pipe reactions (i.e. soil and pipe displacements, soil volumetric water content and soil temperature) to applied surface boundary conditions were predicted based on validated numerical approach