EFFECTS OF CULVERT SHAPES ON POTENTIAL RISK OF HYDRAULIC FRACTURING ADJACENT TO CULVERTS IN EMBANKMENT DAMS

Abstract

Hydraulic fracturing is generally considered as one of the most probable causes of dam failures
and concentrated leakage occurring adjacent to the outlet conduits in embankment dams. It is thought that
hydraulic fracturing will occur in a fill dam when the stress in the dam is reduced to levels that are lower than
the water pressure, causing the subsequent propagation of cracks in the dam body. This phenomenon might be
closely related to the arching action which occurs around the culverts due to the effects of the culvert
configurations. The aim of this study is to investigate the effects of culvert shapes on the potential for hydraulic
fracturing close to culverts in fill dams using the finite element method. Many numerical analyses are taken
here to determine the stress distributions around culverts with various shapes. The possibility of hydraulic
fracturing is then predicted by comparing the values of normal stress and water pressure. The results reveal
that there is a probable risk of hydraulic fracturing occurring adjacent to box-shaped culverts in embankments.
In addition, box-shaped culverts with inclining chamfers or arc-chamfers on the culvert top also have a similar
potential for hydraulic fracturing because the chamfers have a negligible effect on the stress on the sides of the
culverts. However, in culverts with slanted walls, that have a gradient for the slanted walls equal to 0.4 or
greater, the risk of hydraulic fracturing might be reduced.