Settlements And Pore Pressure Generation In
Sand During Earthquakes – Physical Phenomena
And Their 1-D Description
Author(s)
A. Niemunis, T. Wichtmann & Th. Triantafyllidis
Abstract
This paper discusses the pore water pressure generation due to earthquake
shaking. Moreover a method of settlement prediction during the reconsolidation
phase is presented. The cumulative effects are calculated with an explicit (N-type)
constitutive model.
Keywords: liquefaction, earthquake, non-linear wave, explicit accumulation
model, dissipation.
1 Introduction and notation
Even in a simple 1-D case the liquefaction of a sand layer, Fig. 1, due to an earth-quake
is a relatively complex phenomenon. The sand layer of the thickness H is
harmonically excited in the horizontal direction at the rock bed level (=0). In
the horizontal direction the phenomena are homogeneous over a large area. This
allows for a 1-D approach. The excitation at the rock bed causes a shear wave that
propagates vertically upwards, possibly with a reflection at the top (= H ). The
propagation of the shear wave with an energy dissipation D (ampl ,σ ) and with
a nonlinear shear modulus G (ampl ,σ ) is not a straightforward problem. Addi-tionally
a considerable accumulation of strain ˙ acc and of cyclic relaxation ˙ σ acc
appears as a side effect. This is accompanied by the generation of excess pore
water pressure and its subsequent dissipation.
The phenomena mentioned above are interrelated. For example, the shear stiff-ness
G and the damping ratio D depend on the shear strain amplitude γ ampl (which
requires a rate type description ˙ τ = G ˙ γ ) and on the mean effective stress p ,which
Keywords
liquefaction, earthquake, non-linear wave, explicit accumulation
model, dissipation.
Related Book
Other papers in this volume
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