Reliability Analysis of Load Bearing Capacity of Single Pile Placed Adjacent to Existing Buried Conduit or Utility Tunnel

In a congested city or urban area, the so-called “lifeline of the city”, i.e., Gas, Electricity, telecommunication, as well as other utilities or facilities are supplied or transported underground through buried pipes or utility tunnels. Sometimes these buried pipes or utility tunnels are deep underground and interfere with the foundation of the new structure. It is highly probable that a pile foundation is placed near an existing underground buried pipe or utility tunnel and may influence its load bearing capacity. Hence, the estimation of reduced load bearing capacity of the pile foundation placed near the existing buried conduit or utility tunnel is a complex soil-buried structure interaction problem. It is further complicated owing to uncertainty in the estimation of geotechnical parameters of foundation soil due to measurement and testing errors, inherent soil variability, and model translation. Under such circumstances, load bearing capacity is best assessed in the probabilistic framework or through reliability analysis. The present study demonstrates how the concept of response surface method (RSM) in conjunction with Numerical Analysis and First Order Second Moment (FOSM) methods can be combined as per the reliability analysis. The study answers the following question “reliability in reduction in the load bearing capacity of a single pile placed near the existing underground pipe or utilities tunnel”. It is demonstrated that the approach provides first-hand action on the reduction in the load bearing capacity and then estimates the reliability of that estimation in terms of an index called the Reliability Index (β). Such preliminary investigation can be useful for advocating the detailed analysis as well as in the decision-making for relocation of pile foundation.