A practical numerical approach for large deformation problems in soil

Abstract

SUMMARYA practical method is presented for numerical analysis of problems in solid (in particular soil) mechanics which involve large strains or deformations. The method is similar to what is referred to as 'arbitrary Lagrangian-Eulerian', with simple infinitesimal strain incremental analysis combined with regular updating of co-ordinates, remeshing of the domain and interpolation of material and stress parameters. The technique thus differs from the Lagrangian or Eulerian methods more commonly used. Remeshing is accomplished using a fully automatic remeshing technique based on normal offsetting, Delaunay triangulation and Laplacian smoothing. This technique is efficient and robust. It ensures good quality shape and distribution of elements for boundary regions of irregular shape, and is very quick computationally. With remeshing and interpolation, small fluctuations appeared initially in the load-deformation results. In order to minimize these, different increment sizes and remeshing frequencies were explored. Also, various planar linear interpolation techniques were compared, and the unique element method found to work best.Application of the technique is focused on the widespread problem of penetration of surface foundations into soft soil, including deep penetration of foundations where soil flows back over the upper surface of the foundation. Numerical results are presented for a plane strain footing and an axisymmetric jack-up (spudcan) foundation, penetrating deeply into soil which has been modelled as a simple Tresca or Von Mises material, but allowing for increase of the soil strength with depth. The computed results are compared with plasticity solutions for bearing capacity. The numerical method is shown to work extremely well, with potential application to a wide range of soil-structure interaction problems.

Numeric Analysis of Large Penetration of the Cone in Undrained Soil Using Fem

“…A few examples of application of remeshing to geotechnical problems have been also found in references [40][41][42], but direct applications to simulation of CPT have been not found. In the present study, the FE remeshing technique for simulating the large penetration of cone is developed and analysis of the cone penetration in undrained soil is provided.…”

Three-dimensional RITSS large displacement finite element method for penetration of foundations into soil

“…3 and Table 2. The bearing capacity factor of circular footing with Hex20US elements is 6.21 using the exact radius of the footing, which is 2.6% higher than the exact solution of 6.05, and the effective footing width is taken to extend half an element beyond the displacement-controlled nodes representing the foundation (a common adjustment mentioned [11]). As shown in Fig.…”

“…Hu and Randolph [11,12] had also proposed RITSS (Remeshing and Interpolation Technique with Small Strain) method to deal with geotechnical problems, which falls within ALE category, with frequent remeshing of the entire domain, followed by interpolation of all the stress values and material properties from the old mesh to the new mesh. This method had been successfully used in 2-D geotechnical problems, such as penetration of strip and circular footings [13][14][15], penetration of spudcan foundations [16,17], penetration of cones [18], the uplift of plate anchors [19], etc.…”

Undrained bearing capacity of spudcan under combined loading

“…The available published works of numerical analysis on spudcan have been mostly confined to the vertical bearing capacity or the installation behavior (Hu and Randolph, 1998;Hossain et al, 2004;Hossain, 2004), while little attention has been paid to its capacity under combined loading. In addition, the marine sediment is commonly non-homogeneous with the shear strength increasing with depth.…”