Risks associated with slopes are an indication of how a slope would affect us should it fail. Simply put, no matter how high or steep a slope, if it were to affect no one and cause no damage, one can call it a "NO-risk slope". If the same slope near a roadway were to fail and block the road, causing some traffic disruption but causing no injury, one could call it a "LOW-risk slope". However, if there were structures below or above a slope where people live and the slope were to fail, there would not only be traffic disruption and damages but likely loss of lives. This would be considered a "HIGH- risk slope".
FOUNDATION FOR SLOPE FAILURES
We have seen what constitutes a slope. We now look at what causes slope instabilities leading to failures or landslides. Not all landslides occur due to natural causes or unforeseen factors. If we were to give this issue careful thought, we will see that a lot of slopes concerning us are manmade or in some way modified by humans. However, when a failure takes place, we blame everybody including nature and God, but we rarely blame our shortcomings for these slope failures. We suggest all sorts of reasons how failure occurred but fail to ask why these reasons were not addressed before the slope was constructed or modified. One only needs to look at news reports whenever a tragedy occurs, we display our public concerns, our righteous indignation and host of such things, always after a failure.
Before any manmade slope is created, the following essential steps have to be carefully considered:
Assessment of the surroundings, the environment, and the design parameters for the slope
Design of the slope taking the above into account
Construction of the slope
Of the above, the assessment, design, and construction of the slope are usually beyond the control of endusers who are likely to be affected by the slope since they "use" the slope only after all these steps are completed.
Given the quality of our existing site investigation (soil test) practices which provide the crucial design parameters, almost all of the design parameters become suspect. This in turn causes the design, regardless of how powerful computer software is used, to be also suspect. And when the construction consists of bad compaction, dumping, and all sorts of horrifying practices, the slope thus constructed is already bad to begin with. This mess is then grassed over and made pretty and put into service.
Under these circumstances, maintenance will not be very effective and bad maintenance will simply accelerate failure. Therefore, instead of looking for solutions after failure, it may be simpler to address our design and construction practices first, at the design and construction stage.
