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Water leaking from damaged water supply pipes can cause suffosion effects
occurring in soil. Their consequences can be very onerous and threatening
the safety of both water supply systems and human’s health or even lives. The most
extreme examples of suffosion effects are swallow holes, hollows or depressions,
especially dangerous in urban areas. One of propositions of minimalizing effects of
this kind is the design of protection zones around water supply pipes. Dimensions
of protection zones marks the secure distance between water supply pipe and other
objects of infrastructure in order to ensure their stability. Depending on suffosion
conditions, flowing out water can create holes of different size and form on the soil
surface – called suffosion holes. Due to a possible extensive longitudinal shape of
suffosion holes, they can strongly influence the size of protection zones.
The purpose of this paper is to present statistically elaborated research’s results
concerning dimensions of a suffosion holes in dependence on two parameters –
leak’s area and hydraulic pressure head in a pipe. It is a part of more comprehensive
investigations aiming in the determination of a protection zone near water supply
pipes. The research was pursued in laboratory setup (scale 1:10) reflecting natural
conditions of an operating water supply pipe. Obtained results revealed that
pressure head only influences the size of suffosion holes. The dimensions of holes
ranged from 1.00 to 9.50 cm (length) and from 0.30 to 6.46 cm (width).
As expected, both the length and the width increased with the pressure head rise.
The outflow of leakage water did never occur on the soil surface directly above
the leaking pipe and it cannot be claimed that water always creates only one
suffosion hole (with statistical significance equal to 0.05). The obtained results
should be perceive as preliminary and further examinations should be continued,
including previous conclusions. Additionally, it is highly recommended to verify
the laboratory results by in-situ examinations in real conditions.
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