Date of Award:

11-2011

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Advisor/Chair:

Blake P. Tullis

Abstract

Culverts are rehabilitated using a variety of techniques; the approach studied in this report focuses on the use of slip liners. Slip lining refers to installing a liner pipe inside a host pipe to extend its useful life. Slip lining reduces the diameter of the culvert; however, when a smooth-walled liner [e.g., high-density polyethylene (HDPE)] is installed in a profiled-wall pipe (e.g., corrugated metal pipe), the reduction in hydraulic roughness helps to compensate for the reduction in flow area, minimizing any reduction in discharge capacity. In some cases, the discharge capacity may increase. A smaller diameter liner, made of smoother material, will likely produce larger pipe flow velocities relative to the host culvert. High velocities can potentially create a barrier for fish passage, discouraging their use in areas sensitive to fish passage.

The objective of this research was to find ways to implement slip liners and still accommodate fish passage. A 60-ft long, 2-ft diameter, baffled slip liner was tested at seven slopes (0-3.5%) and at three flow rates per slope (1-4.6 cfs). For comparison purposes, tests were also conducted on a smooth-walled (non-baffled) liner. Baffles were found to greatly increase the potential for low-flow fish passage, allowing passage up to slopes of 3.5%. Conversely, the smooth-walled liner prohibited passage beyond a 1.0% slope.

The potential drawback to using baffles in a slip-lined culvert is the reduction in culvert flow capacity. Compared to the smooth-walled liner, the baffled culvert reduced the flow capacity of the culvert by about 74% at pressurized, full pipe flow.

Finally, velocity was measured with an acoustic Doppler velocimeter (ADV) in the baffled culvert and turbulence values were calculated using four different methods. The Energy Dissipation Factor, or EDF, values had a close relationship with percent fish passing and if more testing is done, it could be used as a scaling factor to transfer fish passage data to other sized culverts. The results of this study, suggest that baffled slip-lined culverts can aid fish passage and are useful for culvert rehabilitation as long as the culvert can still maintain appropriate flow capacity.

Comments

Publication made available electronically December 21, 2011.

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