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Soil Finite Element Modeling

The engNoveX team has extensive experience modeling soil using the latest commercial finite element software. The background below showcases some of the three-dimensional models that the engNoveX team has created for past projects.

Modeling of Piles in Soil

The engNoveX team has subject matter experts experienced in the field of performing soil-pile interaction analysis to estimate the dynamic stiffness and damping of piles under machine induced dynamic loading. The team uses state-of-the-art techniques to model the soil-pile interaction effects and has developed several automation tools to model the soil bounded domain.

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Vertical Displacement Distribution for Pile Group 2x2 and Spacing = 3.0 ft

Vertical Displacement Distribution for Pile Group 2x2 and Spacing = 3.0 ft

Soil-03.png

Background

The dynamic performance of a machine foundation system is very sensitive to the supporting soil, and in a case of poor soil conditions machine foundations are commonly supported on piles. Introducing piles under machine foundation pedestals in many cases will reduce the vertical induced vibrations in the soil continuum, and will limit the vertical dynamic amplitude response, thus achieving acceptable foundation dynamic performance.

Vertical dynamic   f  orces in all piles


Vertical dynamic forces in all piles

In some cases, additional piles are added for the purpose of increasing the natural frequency of the machine foundation system, and consequently avoiding the resonance conditions under the steady-state operation of the machine and during machine ramp-up and coast-down periods. Soil-pile interactions under dynamic loading modify the pile stiffness, making it frequency dependent, as well as generating geometric damping. In addition, the effect of the soil conditions, pile length, pile compressive strength, pile spacing and pile tip condition will influence the dynamic stiffness and damping of pile.

Additional complexity of the soil-pile interaction problem is modeling the soil domain, since the soil unbounded domain has to be truncated to a finite size. In static analysis, simple boundary conditions are introduced at a sufficient distance from the structure, usually in the range of 3 to 5 times the soil depth. Thus, the unbounded soil system is converted into a bounded system. This truncation process is not applicable in a soil dynamic application, since the elastic waves produced by the dynamic excitation of the system will be reflected back to the foundation pile system from the truncated rigid boundary. In reality, waves emitted from the dynamic excitation should pass through the boundary toward infinity without reflecting back into the dynamic system.

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