Rectification of the Tilt and Shift of Well Foundation: A Numerical and Analytical Solution

Well foundation is a common type of foundation normally used in bridge construction to transfer heavy load from superstructure and moving vehicles. During construction, sinking of well at the site poses a lot of challenges due to several reasons, such as heavy mass of well, properties of soil, location of ground water table and velocity of water in river or canal. During sinking, the well may tilt and shift from its original vertical position and thereby affecting its functionality. In the current investigation, the force required to rectify the shift and tilt of a reinforced concrete well of 40.8 m deep located near the bank of river Gandak in the state of Bihar, India was determined by numerical and analytical method based on finite element simulation and earth pressure theory (conventional method), respectively. The outer and inner diameter of the well was 8.0 m and 4.9 m, respectively. In numerical study, a straight well was built and the force required to shift the well equal to the amount observed at site was determined by trial and error method. In the conventional method, the force required for rectification of the tilt and shift of the well was calculated. For both numerical and analytical study, three different depths of soil layer surrounding the well were considered for the study. By comparing the results of numerical and analytical method, the best possible condition was chosen. The soil condition was further modified, and the required force was calculated by conventional method. Further, kentledge load was applied to investigate its effect on rectification of shift and tilt of well foundation. In conventional method, by removing the top two soil layers and entire depth of soil from the surrounding of well, the inclined force was noted to decease about 79 and 99%, respectively. It was also noted that with 10 MN increase in kentledge load, the inclined force decreased by 0.82 MN. Therefore, the application of inclined force is more effective than the kentledge load for well straightening. Hence, greater effort is required for the restoration of tilt and shift due to the overburden pressure and self-weight of the well after sinking of well to a considerably deeper soil stratum. Therefore, rectifying measures should be taken immediately at the site as soon as tilt and shift is observed.