Environmental Engineering Reference
In-Depth Information
Accn. of
Soil Block
k
y
1
k
y
2
k
y
3
t
t
1
t
2
Velocity of
Soil Block
t
t
1
t
3
Disp. of
Soil Block
Toward
Bluff
t
t
1
t
3
Figure 12.36.
Double integration method for determination of the permanent deformation period of an
embankment (Newmark, 1965).
Pells and Fell (2003) had limited data to indicate the ratio of transverse crack depth to
crack width at the surface is about 15 to 100, averaging about 40.
12.6.3.3
The Newmark approach
In 1965, Newmark introduced the basic elements of a procedure for evaluating the poten-
tial deformations of an embankment under earthquake loading (Newmark, 1965). In this
contribution, sliding of a soil mass along a failure surface was likened to slipping of a
block on an inclined plane. He envisaged that failure would initiate and movements
would begin when the inertia forces exceed the yield resistance, and that movements
would stop when the inertia forces were reversed. Thus, he proposed that once the yield
acceleration and the acceleration time history of a slipping mass are determined the per-
manent displacements can be calculated by double integrating the acceleration history
above the yield acceleration as shown in Figure 12.36.
According to this approach, the permanent deformation in a sliding mass is a function of:
- The amplitude of the average acceleration time history of the sliding mass, which in
turn is a function of the base motion, the amplifying factor of the embankment and the
location of the sliding mass within the embankment;
- The duration of the earthquake, which is a function of the magnitude of the earthquake;
- The acceleration of the potential sliding mass.
The validity of the basic principles of Newmark's approach has been demonstrated by
many investigators (e.g. Goodman and Seed (1966), Ambraseys (1973), Sarma (1975)
