Dissertation

Investigation of Soil Nailed Clay Slopes in the Centrifuge

Taib, Siti Noor Linda

2005

Overview

Soil nailing is a method to stabilise existing slopes and new cuts that has been used for over 3 decades. The method is easy and flexible, mainly due to ease of construction and is adaptable to heterogeneous soil. Soil nailed structures built on clayey soil can bring complications especially if the structures are exposed to adverse environment. Studies on clay slopes behaviour and failure mechanisms reinforced with soil nails were performed here to expand our understanding on them. A large number of centrifuge tests on soil nailing were performed on sand. This investigation is to explore the nature of soil nailed clay slopes when tested in the centrifuge. Six centrifuge tests on soil nailed clay slopes and on an unreinforced clay slope for comparison were performed in this investigation. The design of the slopes was performed based on HA 68 of Department of Transport (1994) and BS 8006 (1995). Since the centrifuge models were brought to failure by gravity turn on method, the slip surface would be deep which caused the nails, intentionally designed to have insufficient embedment length. The slope configuration was maintained the same throughout the tests but the nails length, size and material were varied. Apart from that, different excavation methods were simulated in these tests to explore each method suitability and ease of application in the centrifuge. The settlement and the strain on the nail were also measured throughout the tests. In addition, a digital camera was also installed in the centrifuge and used to observe the deformation on the model slopes. The safety factor values of the models at failure were checked and the stability number of the models against failure was obtained. In general, the results show that all the models enhanced stability due to inclusion of reinforcement and failed due to pullout failure and soil slippage against reinforcement. Measurement from strain gauges on nail proved that in clay slopes, axial force was also mobilised as early as during the excavation method and the bending moment was mobilised at a later stage when approaching failure. Axial force and bending moment were also mobilised at the nails facing plate. In addition, results from digital images were processed and analysed via a method called PIV (Particle Image Velocimetry) as introduced by White (2002) for use in geotechnical engineering analysis. A program called MatPIV (Sveen, 2004) was used and results in terms of vector representation of the movement on the slopes were obtained. This is an investigation of soil nailed models built in clay and tested in the centrifuge, which has not been extensively performed. The results obtained will add to the current theoretical understanding of the mechanism of soil nailed structures in clay.

• Publisher: ProQuest Dissertations & Theses
• Subject: Civil engineering / Geotechnology
• ISBN: 9780438203938, 0438203933