Numerical investigation of spudcan penetration in multi-layer deposits with an interbedded sand layer

J Zheng,D Wang,M S Hossain

doi:10.1680/jgeot.16.p.110

Abstract

For calculating spudcan penetration resistance in an interbedded sand layer between two clay layers, the recently developed mechanism-based design methods for surface sand-over-clay deposits are extended to account for the influence of the overlying clay layer. A series of large-deformation finite-element (LDFE) analyses were carried out, varying layer geometries and strength parameters. The numerical results and existing centrifuge test data are used to calibrate the extended design methods. The performance of the modified design methods and those suggested in the ISO standard 19905-1 is compared, confirming the accuracy of the former methods in estimating the peak penetration resistance in the sand layer. LDFE analyses were also carried out adding a strong fourth layer, with the corresponding effects on the increasing peak resistance in the second (sand) layer and squeezing behaviour (or limiting squeezing depth) in the third (soft clay) layer discussed. Design formulas are also developed to estimate th...

Highlights

For spudcan penetration in a sand-over-clay soil layering system, a reduction in penetration resistance may occur, forming a local peak in the sand layer
This study focuses on spudcan penetration in an interbedded sand-over-clay layering system through large-deformation finite-element (LDFE) analyses, together with centrifuge test data reported by Hossain (2014)
This study has considered a circular spudcan penetrating into a clay–sand–clay deposit with and without a fourth layer of stiff clay, as illustrated schematically in Fig. 2, where the second layer sand with effective unit weight γ2′ = γs′ has a thickness of t2 = Hs and a relative density ID

Summary

Introduction

For spudcan penetration in a sand-over-clay soil layering system, a reduction in penetration resistance may occur, forming a local peak in the sand layer. New mechanism-based design methods (Lee et al, 2013a, 2013b; Hu et al, 2014a, 2014b, 2015) have recently been proposed for estimating the peak bearing capacity in the surface sand layer and the bearing capacity in the underlying clay layer. Their applicability in multi-layer soils with an overlying clay layer (i.e. clay–sand–clay deposit) is yet to be examined. The aim is to extend the existing design methods for two-layer sand-over-clay deposits to be applicable for assessing spudcan penetration in three- (weak– strong–weak) and four-layer (weak–strong–weak–strong) seabed profiles within the depth of interest

Methods

Results

Conclusion