NUMERICAL ANALYSIS OF INTERNAL STABILITY OF ANCHORED SHEET PILE WALL WITH DIFFERENT BACKFILLS

Abstract

In this project the numerical investigation using the finite method is done to study the failure mechanism of anchored sheet pile wall with extensible reinforcements with different backfills models. The details of the numerical approach are given in the literature review. The high strength steel is used in the form of face of the sheet pile wall. Alternatively, we can also provide strength to the sheet pile wall by providing anchors and geogrids. It can also be shown that improvement in the capacity of the sheet pile wall can be done by change in the properties of the backfill materials. In this report more emphasis is given on the study of properties of backfill materials. The methods used in the design of anchored sheet pile walls are free earth support method and fixed earth support methods. Due to the simplicity, the free earth support is widely used method. These conventional support methods use Rankine‘s active and passive earth pressures which are related to the Mohr- coulomb failure criterion. Rankine‘s earth pressures are based on the rotation and translation of wall as a rigid body. But the anchored sheet pile walls are far from being a rigid body as they are relatively flexible walls. Also, the anchor in the sheet pile wall creates a stress concentration in the surrounding backfill soil at the anchor level which is basically due to restricted wall movements, which is not considered in the conventional methods of design. Therefore analysis of anchored sheet pile wall using FEM method is more desirable. A study by Bjerrum et al. by finite element method (FEM) also showed the stress concentration at the anchor level. Finite element models of different backfill soils models are simulated and analyzed along with variation in reinforcement spacing, reinforcement length and reinforcement stiffness. The Ø – c reduction procedure, a technique based on shear strength parameter reduction , is used to calculate or simulate the failure conditions. The results of Ø – c reduction analysis are used for design purpose of anchored sheet pile walls. In particular, shear strain is used to identify failure surfaces. Inference of the results shows that, for both the backfills i.e. cohesive and granular, the potential failure surface acts like a direct sliding mode. Analysis of both the types of backfills is done and the required failure plane and failure type is determined by the numerical method, also the type of backfill most suitable for the sheet pile wall is concluded.