Abstract

The extreme hydroclimatic events like heavy rainfall and drought affect the behavior of deep foundations that support critical infrastructures. These extreme events can cause significant variations in the strength and deformation properties of the soil resulting in significant variations in skin resistance and end bearing capacity capacities of deep foundations resulting in failure of foundations. However, the current design methods are based on static hydrologic soil conditions and forecasts indicate that extreme hydroclimatic events will become increasingly common in the future. Therefore, it is important to understand and quantify the impacts of extreme hydroclimatic events on the behavior of deep foundation for updating the existing design procedures.

In this study, an experimental study was conducted to evaluate the effect of extreme hydroclimatic events on the behavior of drilled shaft in sand, silt, and clayey sand. The experiment was conducted in a 1.5 m x 1.5 m x 2.24 m wooden soil testing pit with a 76 mm diameter and 1.83 m length drilled shaft. The drilled shaft was subjected to mechanical and hydrological loads. The mechanical loading of 1.14 kN equal to the total ultimate axial capacity of the drilled shaft was applied using a hydraulic jack and reaction frame system and measured by a load cell. A spray nozzle setup and a heater simulated heavy rainfall and drought. In order to record the temporal and spatial variations of the moisture content, temperature, displacement, and strain in the surrounding soil and drilled shaft, moisture sensors, temperature sensors, LVDT's, and Fiber Bragg Grating (FBG) sensors were used. The temperature and moisture sensors were placed in the soil near the drilled shaft and ground surface to capture the hydrological load's maximum effect. One LVDT was placed on top of the drilled shaft, and two separate LVDT were away from the drilled shaft on the ground surface to measure drilled shaft and ground displacement. The FBG sensors were inscribed into acrylate optical fibers and embedded in the rebar and surface of the drilled shaft longitudinally. The optical fibers with FBG sensors were installed on a bias-ply ribbon and placed vertically in the soil. The temperature-induced strains were separated from the total strains (temperature and displacement induced) obtained from the FBG sensors using thermistors paired alongside the FBG sensors.

The results show the variation of skin resistance and end bearing resistance of the drilled shaft as a function of heavy rainfall and draught level. Finally, the results were compared with the base case of the fully saturated condition.