Abstract
The deep patch repair technique has been widely used in the western U.S.A. to address subsidence and shallow slope failures mainly within poorly performing side-cast embankments and natural slopes consisting of weak soils overlying stronger soils. This project was a multi-phase effort to examine, refine, update, and verify the design procedure associated with this repair method. An experimental design was developed to examine the performance of various deep patch repair configurations and to validate the design technique developed using FLAC (Fast Lagrangian Analysis of Continua) modeling results during Phase I. A series of unreinforced and reinforced slope configurations were tested using a large centrifuge to study their behavior and document their performance. Fourteen centrifuge models (seven unreinforced and seven deep patch reinforced) were run to verify the design chart for a 39-degree slope angle and having one-foot thick deep patch layer spacing (one of four design charts developed during Phase I). Performance of the deep patch models was evaluated based on a serviceability criterion limiting movement in the road bench atop the reinforced zone. Models reinforced with deep patches helped stabilize slope failures by acting as a cantilever and redirecting the failure path to the face of the slope beneath the slope crest, thereby reducing distresses near the top surface of the deep patch. Overall, results from this analysis indicated that the design tool created during Phase I sufficiently predicts the depth of the deep patch necessary to achieve good performance.
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