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simplified method for free ground site and of the cone model concept well developed by Meek
and Wolf in dynamics for scattered field. Their conclusion showed the reasonableness and
tendency in good accord with results of small model tests and of finite element analyses.
In this paper based on Men's simplified method and considering the nonlinear constitutive
relationship of soil and Martin's model of pore water pressure, another method is suggested for
evaluating pore water pressure of subsoil of building. The method is more suitable for evaluating
seismic liquefaction potential of subsoil of buildings in engineering
Men's simplified method for evaluation of seismic liquefaction of subsoil of building
Men et al adopted following assumptions in their method proposed.
1. The building is rigid as a whole.
2. The building is situated on the ground surface and represented only by a footing
3. The soils may be regarded as elastic under dead and seismic loading condition.
4. The rocking component of building motion is neglected in evaluation of liquefaction
potential because only shear stress is important to induce residual pore water pressure.
5. A plane shearing body wave SH is propagated vertically upward from the source of
earthquake.
Based on the above assumptions and the substructure method to deal with the structure reaction
to seismic input, Men's simplified method can be summed up as consisted of the following
procedures.
For given displacement, the wave field in subsoil can be written as following
u~u f +u^ (1)
where u^ is the free field ground motion and « 4 is the scattered field motion induced by
building, and u is the total motion of subsoil of building. If the input motion from the
earthquake source is u t = u ia f (t-z/c) then the free field motion of homogeneous elastic media
will be
(2)
where / (t) is an input function, c s is a shear wave velocity, z is a vertical ordinate downward.
For given stress, the dynamic stress in subsoil of building can be written as following
where r^o^are the total dynamic shear stress and total normal stress in subsoil of building,
respectively, T / ,a / are the dynamic stresses in free ground, T 4 ,cr, are the additional dynamic
stresses due to existing building.
In the simplified method proposed by Men et al, the dynamic stress in free ground can be