Fully Coupled Computational Simulations of Pile Foundations in Improved and Unimproved Soft Clays: Fid-Bau Portal

Fully Coupled Computational Simulations of Pile Foundations in Improved and Unimproved Soft Clays

Kirupakaran, Karrthik / Muraleetharan, Kanthasamy K.

Pile foundations are integral parts of many civil engineering structures and pile foundations are routinely constructed in soft clays. The seismic behavior of pile foundations is a very complex problem with interactions between soils (solid skeleton, pore water, and pore air), piles, and superstructure. This complexity is further increased when weak soils, such as soft clays, surround the pile foundation. Seismic behavior of pile foundations in soft clays may be improved using ground improvement techniques such as Cement Deep Soil Mixing (CDSM). The seismic behavior of pile foundations in improved ground is, however, poorly understood. A fully coupled finite element computer code, TeraDysac, is used to study the influence of CDSM ground improvement around pile foundations in saturated soft clays during earthquakes. TeraDysac considers the coupled differential equations governing the behavior of the solid skeleton, pore water, and piles. Bounding surface elastoplastic constitutive models are used to simulate the stress-strain behavior of soils in TeraDysac. TeraDysac simulations of a centrifuge model test involving pile foundations in unimproved and CDSM improved soft clays are presented. The prototype of the centrifuge model test consisted of 10 m of soft clay underlain by 8 m of dense sand with single piles and various extents of CDSM ground improvement around the piles. TeraDysac simulations show that improving the ground around the piles is an effective way to reduce displacements, accelerations, and bending moments in piles during an earthquake. The dimensions of the ground improvement, however, have to be sufficiently large for these reductions to be realized.