SPR 2013 Prime KTC: Pipe Inspection Criteria

The research proposed under this project will be used to develop a standardized pipe inspection technique, reporting format and acceptance limits to be used on all state projects involving storm sewer and culvert pipes. Kentucky's pipe policy requires all storm sewer and culvert pipes to be video inspected and laser/mandrel inspected for installation problems, material defects, excess deflection or other problems that may contribute to structural or hydraulic failure. This policy has been in place for almost two construction seasons and KYTC would like to refine the specification based on experience gained from the current policy, revised AASHTO guidelines, and research conducted by KTC. There are several software applications that are designed to facilitate pipe inspections for the contractor. The programs are separated into two groups: distress cataloging and deflection measurement. Distress cataloging software allows the user to note or callout distresses that are seen during a video screening of the pipe. The deflection measurement software determines the amount of deflection exhibited at any point inside the length of pipe. The reports generated by the respective software manufacturers all have different reporting formats with varying degrees of specifics in the report. KYTC uses the inspection reports to ensure the pipe was installed properly and free of critical distresses or excess deflection. If the inspections show problems then remediation and/or pay reductions may be warranted. Currently, Pay reductions and remove/replace criteria are based on deflections greater than 5%, 7.5% and 10%. Penalties for distresses identified during the inspection are up to KYTC’s Project Engineer. There are currently no defined acceptance limits for critical distresses found during inspection. Deflections greater than 7.5% but less than 10% warrant a pay reduction and require a structural analysis to be performed by an engineer based on AASHTO LRFD Bridge Design Specifications to ensure the pipe will not fail. There is interest by KYTC to investigate the possibility of creating a mechanism to efficiently determine the structural stability of a pipe that is deflected over 7.5% but less than 10%. The mandrel sizing technique used in the current specification is of concern to KYTC because in theory there could be an infinite number of mandrel sizes for the same pipe diameter. A primary concern when using a mandrel is to determine the actual diameter of the pipes as delivered to the site as this is the baseline used to determine the amount of deflection in a pipe. With manufacturing tolerances allowing the dimensions of HDPE pipe and CMP to vary as much as 6.0% and 2% respectively, determining the base size of the mandrel becomes important.