Physical Model Testing of Piles in Thawing Soils Subjected to Single and Combined Loadings
Creators: name: Singh, Harshdeep
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2022
Subjects: Freezing
Thawing
Single loading
Combined loading
Freezing cycle
Thawing cycle
Pile foundation

description: The primary purpose of pile foundations is to transfer vertical loads due to the transfer of the weight of the superstructure to the deeper ground. However, many civil engineering structures, such as bridges, transmission towers, tall chimneys, and solar panels, are subjected to significant lateral loads and overturning moments in addition to axial loads. Potential sources of lateral loads (not due to earthquakes) include wind, waves, ice forces, passive earth pressure, etc. On the other hand, axial loadings can be live loads from a structure, forces developed due to ground freezing, etc. Consequently, pile foundations for these structures should be adequately designed to resist compressive loads combined with lateral and uplift loads and moments. In most cases, these forces (compressive, lateral, and uplift) and moments are often simultaneously applied on the piles. One of the key objectives for the engineer and designer is to determine the deflections and stresses in a pile in order to keep them within tolerable limits. Passive soil resistance can be very effective in proving lateral support for the pile. However, passive soil resistance is a function of the soil thermal regime (freezing, thawing, and temperature). Due to global warming, the thermal regimes of the soils in Canada and other cold regions in the world have changed in the past decades. The change in the thermal regimes of the soil may affect the geotechnical response or performance of the pile foundations. This thesis presents and discusses the results of physical model testing on model piles in unfrozen, frozen, and thawing fine sand, which are subjected to individual and combined axial (uplift) and lateral loads. The dimensions of the pile model are established by using physical scaling laws. The physical model is also equipped with various sensors and instruments (e.g., linear variable differential transformer (LVDT), and temperature sensors) to monitor the pile and soil response during and after loading. The results of the study show that the thermal regime in the soil significantly affects the performance of the pile under combined loadings (lateral and uplift). The lateral capacity of the pile under combined loads in frozen soil is increased by 648% compared to that in unfrozen ground whereas the uplift capacity under combined loadings in frozen soil is increased by 29%. Due to the effects of the freezing and thawing (F-T) cycles of the soil, a steady increase in the lateral capacity of the pile under the combined loadings is observed. On the other hand, the uplift capacity under the combined loadings in soil subjected to F-T cycles remains constant. The results will be useful in the geotechnical design of pile foundations for bridges and other structures in Canada and other cold regions in the world. The findings of this research will contribute to efficient design practices for pile foundations in cold regions with rapid changing climatic conditions.