In April, 1957, under Circular Memorandum 22-40, the Bureau of Public Roads issued a rational criterion covering beddings of reinforced concrete pipe, construction methods, and simplified methods for determining the allowable heights of fill over pipe having given D-load strengths. The states were urged to adopt the criterion; and, accordingly, the Kentucky Department of Highways issued Amendments No. 15 and 16 (Feb, 28, 1958) to its 1956 edition of Standard Specifications for Road and Bridge Construction and Standard Drawings Nos. 11.22 and 11.23. These amendments and standard drawings were patterned after the criterion of the Bureau of Public Roads but contained some practical modifications from the original criterion. Amendment No. 15 was later revised and superseded by Amendment No. l5a (Dec. 1961).

The two bedding conditions thus permitted under the revised Department of Highways Specifications are the B (Standard Bedding) and the B1 (Imperfect Trench High-Fill Bedding); each is similar to the same respective designation as outlined in the Bureau's Circular Memorandum 22-40, The required strengths and bedding conditions for various heights of fill were thus established and are set forth in "Table for Safe Fill Cover Heights and Classes for Reinforced Concrete Circular Pipe" on the Department's Standard Drawing No. 11.23. Installation procedures are also shown and outlined on Standard Drawing No. 11.22.

In order to evaluate the effectiveness of the design and construction criterion, the Bureau of Public Roads requested that a number of reinforced concrete pipe installations so constructed be selected for periodic inspections. A group of 113 reinforced concrete pipe culverts installed in accordance with new criteria was selected early in 1960. The culverts so selected are located on Interstate Routes I-64 in Jefferson, Shelby, Franklin, Clark and Montgomery Counties, and on I-75 in Scott, Grant and Kenton Counties. Each culvert was inspected during the summers of 1960, 1961 and 1962.

Report Date


Report Number

No. 197

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