The result derived above is applicable also for a group of pulses when the resistance in
either direction of possible motion is the same. For a situation in which the body has a
resistance to motion greater in one direction than in another, one must take into account the
cumulative effect of the displacements. A simple example where this must be considered
would be found if Fig. 16 were rotated clockwise, as in Fig. 19, so that the body has a tendency
to slide downhill. In this situation, ground motions in the direction of the downward slope
tend to move the mass downhill, but ground motions in the upward direction along the slope
leave the mass without relative additional motion except where these are extremely large in
magnitude. One may consider that this case is applicable to the dam.