Abstract:
This presentation will cover the slope stabilization attempts at the HAM-275-7.02 roadway embankment which is part of the ramp connecting I-275 and eastbound I-74 in Cincinnati, Ohio. The embankment is approximately 70 feet high with a 2H:1V side slope and was built in 1974.
The embankment showed signs of distress in the late 1980’s. The Ohio Department of Transportation (ODOT) installed piezometers and inclinometers to monitor the embankment and investigate the cause of the observed movement. Based on the inclinometer data collected up until 2006, it was established that the movement was at the interface between soil and bedrock and the attempts of stabilization are not effective due the sloping bedrock. A decision was made to contract the slope stabilization and the restoration to 2H:1V slope to a design-build (DB) team.
The proposed design utilized rock socketed drilled shafts to stabilize the embankment and mitigate slope movement. The design was optimized using a single row of 48-inch diameter drilled shafts socketed into bedrock and spaced at 7 feet center to center. Slope stability analyses were conducted using limit equilibrium method using Slope/W and UASLOPE (a program developed by the university of Akron for ODOT that can calculate the factor of safety and the force on the drilled shafts installed in the slope to stabilize it). The drilled shaft reinforcement was concentrated on the tension side to maximize the capacity of the reinforced section. Three stabilization shafts were instrumented with inclinometers to monitor the lateral movement with depth, in addition to several inclinometers in the embankment upslope and downslope of the row of drilled shafts to capture any movement and verify the effectiveness of the drilled shafts in stabilizing the embankment. Details of the analysis, design, and long-term monitoring will be discussed in detail in the presentation.