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9.2 Overview of nonvented drift with preventable failure features
FIGURE 9.2
Overview of nonvented drift with preventable failure features
Drift failure mechanism
Unstable fill materials Insufficient or unsuitable material results in damage of top slab due to traffic loading
Under-scouring Lack of apron/inadequate apron results in under- scouring of the drift foundation
End failure P eak floods rise above level of concrete road surface and erode drift road approaches Road approach Lack of robustness Lack of rigidity results in damage by floodwater when it enters int o the stru ct ure
Apron
Concrete road su rf ace Seasonal sandy river
Top slab failure Poor construction method and poor materials result in cracks to head wall or drift slab
Direction of flow
Road approach Unprotected river bank River bank erosion due to lack of tion by riprap or vegetation protec
Source: MetaMeta ( www.roadsforwater.com ).
