Foundation Failure
One of
biggest challenges for the engineers is the foundation. It is also the simplest
problem to avoid though. The problem is caused by the process of liquefaction.
This is the idea that when the ground shakes, lose particles (i.e. soil) moves
in a fashion similar to a liquid (i.e. water). As a result one of the biggest
problems is when foundations are created by simply pouring concrete into a hole.
When the soil (which is lose) surrounding it is shaken the foundation in effect
sinks. This is often uneven and the building may topple. The picture on the
right shows an example of this. At first it may not be too obvious, however, you
will see that the building is slanted. The main superstructure is almost
unharmed yet the lowest levels have sunk at one corner. The location of the
building suggest that it's foundations have been placed directly into relatively
lose soil.
It is possible
to have other problems with the foundation too. One such problem is caused when
the building is simply shaken from the foundation. The picture on the left shows
a building which has lost the ground floor. The foundation has been moved by the
earthquake but floors above gone the opposite direction and caused the vertical
walls to fail. This house will probably have to be demolished.
Foundation failure can be avoided by planning the foundation. The key is to prevent the foundation from sinking in the event of liquefaction and as is always key to ensure that the vertical horizontal joints are strong. Both of the pictures shown here may not have posed the greatest risk to people within the houses but, they do cause a significant risk to the roads and areas surrounding. After shocks may cause the buildings to fall over.
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3: Pancake Collapse
4: Conclusions
By Paul Wittle