Predicting the resistance profile of a spudcan penetrating sand overlying clay

Abstract

Assessment of the risk of punch-through failure of spudcan foundations on sand overlying clay requires prediction of the full penetration resistance profile, from touchdown and through punch-through to equilibrium of the vertical resistance at depth in the underlying clay layer. This study uses the Coupled Eulerian–Lagrangian approach, a large deformation finite element analysis method, to model the complete penetration resistance profile of a spudcan on sand overlying clay. The sand is modeled using the Mohr–Coulomb model, while the clay is modeled using a modified Tresca model to account for strain softening. The numerical method is then used to simulate a series of spudcan penetration tests, performed in a geotechnical centrifuge, on medium dense sand overlying clay. The punch-through behavior observed in the experiments is replicated, and the penetration resistance profiles from numerical analyses are generally a reasonable match to the experimental measurements. The influences of the sand layer height to foundation diameter ratio, sand–clay interface shear strength, and strength gradient in clay on the penetration resistance profiles are explored in a complementary parametric study. The penetration resistance in the underlying clay layer is well predicted using a simple linear expression for the bearing capacity factor for the spudcan and underlying sand plug. This expression is combined with an existing failure stress dependent model for predicting peak resistance to form a simplified method for prediction of the full penetration resistance profile. This new method provides estimates of the vertical penetration that the spudcan will run during the punch-through event. It is validated against both medium dense and dense sand centrifuge tests.

Large deformation finite element analyses in geotechnical engineering

“…In contrast to RITSS and EALE, an element in CEL may be occupied by multiple materials fully or partially, with the material interface and boundaries approximated by volume fractions of each material in the element. The CEL method has been used by a number of researchers to investigate the penetration of spudcan foundations in various soil stratigraphies [27,35,36,25,12] and uplift capacity of rectangular plates [9]. The comparatively rigid structural part (i.e.…”

“…A 'general contact' algorithm by means of an enhanced immersed boundary method describes frictional contact between Lagrangian and Eulerian materials. Advanced soil constitutive models, such as a hypoplastic model for sand, a visco-hypoplastic model for clay and a modified Tresca model considering strain softening and rate-dependency of clay, have been incorporated into the CEL [27,26,12]. To date, CEL is limited to total stress analysis, although it can be modified to obtain pore pressures under undrained conditions [50].…”

Numerical simulation of the penetration process of ship anchors in sand

“…Simulations focusing on the soil-structure interaction problems have been carried out by Tho et al [29], Qiu et al [24] [25] and Hu et al [13]. They revealed that the CEL approach is well suited to solving numerical problems involving large deformations which cannot be solved satisfactorily using the classic finite element method.…”

Failure Mode and Pullout Capacity of Anchor Piles in Clay

“…The contact pressure between Eulerian and Lagrangian materials is calculated by a penalty contact method, while the shear stress τ is calculated by the Coulomb frictional frame, i.e., τ = µ c σ. µ c is the frictional coefficient and σ is the contact pressure. The CEL method was wildly utilized to solve geotechnical problems with large deformations (Qiu et al, 2011;Tho et al, 2013;Hu et al, 2014;Liu et al, 2014;Dutta et al, 2015;Kim et al, 2015;Liu, 2015, 2016;Liu et al, 2016). More information about the CEL method can be found in (Dassault Systemes, 2010;Benson, 1992).…”