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volume and residual pore pressure within one load cycle, respectively. t r is the tangent rebound
modulus of sand skeleton, y is the shear stain, c { ~~ c 4 are the test constants.
Note that t r is relates to the effective confined pressure and can be expressed by an empirical
formula, for example of the form (Martin et al 1975)
E= (7)
Where a v0 is the vertical effective normal stress at the beginning of unloading, a v is the
residual normal stress after unloading, & 2 , m,n are the test constants, respectively.
Using Massing' s model, the non-linear relationship of the shear stress and strain can be
expressed as follows
Therefore
T==(e7,)'"-- (8)
a + by
1—
where a,b are test constants, respectively.
Substituting formula (9) into formula (5), the pore water pressure can be approximately
calculated with formula (4) in terms of r after Nth cyclic loading which the dynamic shear
stress T can be calculated with the simplified method proposed by Men et al
Evaluating seismic liquefaction potential of subsoil of building
After obtaining pore water pressure, based on the initial liquefaction criterion, the estimation of
liquefaction can be made with the pore pressure ratio. The pore pressure ratio is defined as a
ratio of the pore pressure to the vertical confined stress. According to the cone model, the ratio of
pore pressure in the three zones of subsoil is as follows, respectively
Zone I R(Z,N)= - - - (10)
zone nan
where a£ is the pore water pressure after Nth cyclic shear loading.