Study on the effect of dredging on existing sheet pile retaining structures

Abstract

Sheet pile retaining structures are widely used in many purposes in engineering designs. Most common applications are shoring, stabilize excavations, harbor quay wall structures, canal bank protection structures.. etc. This research is mainly focused on the issue of stability of harbor quay wall structure when deepening the harbor basin to cater larger vessels. Most of the quay wall structures in Srilanka are anchored sheet pile walls. So the effect of dredging on the sheet pile structure is studied. If the same method can be applied for the cantilever sheet pile walls which could be used in drainage improving projects. The study is extended to both anchored and cantilever sheet pile structures to increase the stability while reducing the depth of embedment. Another improvement sheet pile wall is proposed from the passive side of the existing sheet pile structure to provide an additional support to the main structure. The finite element analysis is used to estimate the effect of the improvement wall on the stability and the deflection of the wall in cohesion less soils. The effect of the distance between the existing structure and the improvement wall and the effect of increasing the depth of embedment of the improvement structure are analyzed through the finite element models. The models are tested for 22 to 38 degrees wide range of friction angles of cohesion less soils The results of the finite element model are verified by a physical model conducted in a laboratory. The results of the analysis shows that the improvement wall can significantly increase the stability of the existing structure. Compared to anchored sheet pile walls higher improvement can be achieved for cantilever sheet pile walls from this method. Rather than replacing the entire structure , applying a this sort of improvement method will be highly economical as well as less damages to the other structures close to the existing sheet pile wall.