Concrete Pipe Association of ... shaped bedding; and, f. Zone 10, 60-degree concrete bed ding. On the

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  • www.cpaa.asn.auConcrete Pipe Association of Australasia

  • 1980 Seminar on the Bacher/Davis Investigations

    NewConceptsof Loads on Underground Structures

    ,, The history of concrete pipe

    installation in Australia is closely related to investigation and practice overseas.

    So the Australian Standard CA33- 1962 takes into account the investi- gations of M.G. Spangler and W.]. Schlick. This standard is currently under review by the Stand- ards Association.

    In furthering the understanding of soil/structure interaction of buried concrete pipelines, the American Concrete Pipe Association sponsored investigations at North Western University about which Dr. R.A. Parmelee reported at our first National Seminar.

    Another investigation of soi 1- structure interaction has been spon- sored by the American Department

    of Transport. It has been conducted by the California Department of Transportation, Division of High- ways, under the direction of two of its senior bridge engineers, A.E. Bacher and R.E. Davis.

    It is our opinion that this work gives every indication of being a major breakthrough in our under- standing of the forces acting on buried pipes under differing conditions of bedding and fill depth, and that it will be advantageous to the committee revising CA33.

    This paper is an up-to-~ate report of the Bacher/Davis field studies. It il has been reprinted with"the per- mission of the American Concrete Pipe Association from their period- ical Concrete Pipe News and forms the basis of Mr. Bacher's lecture.

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    Rigid Culvert Tests - Mountainhouse Creek Part I

    by Raymond E. Davis

    Senior Bridge Engineer California Department of Transportation

    and Alfred E. Bacher

    Senior Bridge Engineer California Department of Transportation

    Field studies of concrete pipe culvert behavior recently con-

    cluded at Mountainhouse Creek, in California, dramatically dem- onstrated the significant influence of the surrounding embankment on pipe behavior and the benefi- cial results that may be derived from soil-structure interaction, even with relatively rigid pipes.

    A dummy, 84-inch, pipe proto- type was designed for a nominal 1,0000 load rating, but three-edge bearing tests indicated a load capacity closer to 1,5000. Califor- nia specifications traditionally have barred 1,0000 pipes from highway embankments and have allowed only 16 feet of overfill in emhankments where they could

    be used. With proper construc- tion methods and inspection, the dummy culvert at Mountainhouse Creek sustained an overfill of 45 feet before the first hairline crack appeared and a total of 136 feet without significant distress. Other, less rigorous construction proce- dures resulted in gross failure of the pipe.


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    ~IO ~O 0 0;:: l LAYERS,,::1 E.lIBANK.I,lENT OF r 1 .... .... BATTER50ARO ••.• POLYSTYRENE EMBANKMENT •

    o 20Til H UNTREATED 11. T COlIMERCLI.l r • .J a.F. PLA/iK l't CRADE COtlCRETE

    Sil;no 8EDDING

    pacted (95%), well graded, con- crete aggregate. In the remaining zones, ordinary embankment ma- terial was placed by excavating machinery around the pipe and compacted with hand tampers.

    Diameter changes, measured with an extensometer and photo-

    The dummy culvert, which ter- minated within the embankment at a straw-buffered, timber bulk- head, was divided into six, 40- foot long zones, comprising five, 8-foot long pipe segments, each. A longitudinal section through the culvert and embankment is shown in Figure 1, bedding and backfilling parameters in Figure 2.

    Two installation conditions were examined: two Zones, 7 and 8 were embedded in as-foot deep, vertical sided trench ex- cavated after the embankment had been constructed and com- pacted to the proper level, the re- maining Zones, 9 through 12, were installed as "positive pro- jecting."

    The bedding condition was varied between zones and all zones were underlaid by a rock filled trench 3 to 8 feet deep to produce an essentially unyielding foundation. Shaped bedding was used in Zones 7 and 9; Zone 8 on a 6-inch layer of dry sand; Zone 10 on a 60-degree, Class C. con- crete bedding; Zone 11 on a 6-inch by 24-inch polystyrene plank; and Zone 12 on line bear- ing.

    Backfill material in Zones 7 and 8 was comprised of well com-


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  • ACKNOWLEDGEMENTS The research work described

    herein was sponsored and par- tially financed by the United States Department of Transporta- tion, Federal Highway Administra- tion. The contents of this paper reflect the views of the writers who are responsible for the facts and the accuracy of the data pre- sented herein. The contents do not necessarily reflect the official views or policies of the California Department of Transportation or the Federal Highway Administra- tion. This paper does not consti- tute a standard, specification, or regulation.

    Appendix - R~ferences 1. Davis, R. E., Bacher, A. E., and

    Obermuller, J. c. "Structural Be- havior of a Concrete Pipe Culvert -Mountainhouse Creek - (Part 1}," California Division of High- ways Report R&D 4-71, Apr., 1971.

    2. Davis, R. E., Bacher, A. E., and Obermuller, J. C. "Concrete Pipe Culvert Behavior-Part 1," Journal of the Struclural Division, ASCE, Mar., 1974 (Proceedings Separate 10404).

    3. Davis, R. E., Bacher, A. E. "Con- crete Pipe Culvert Behavior--Part 2," Journal of the Structural Divi- sion, ASCE, Mar', 1974 (Proceed- ing Separate 10405).

    mate compaction of the poly- styrene at 80 feet of overfill, after which the pipe deteriorated rap-

    idly. Effective density distributions at

    60 feet and 100 feet of overfill re- inforce the above qualitative ob- servations of distress. High aver- age densities at the upper octant points of Zones 7 through 10 at 60 feet of overfill reflect the rela- tive rigidity of the soil-pipe sys- tem, while sub-hydrostatic upper densities a1 Zones 11 and 12 dem- onstrate the arching in the soil as the pipe settled: 1. into the soft polystyrene at Zone 11; and, 2. due to invert crushing at Zone 12, respectively.

    High lateral densities at Zone 8 reilect the early buildup of pas- sive soil stress components as the pipe tried to flatten and expand horizontally against the restraint of the well-compacted backfill, fostering a uniformity of soil stress around the pipe periphery, with small consequent moments and shears in the pipe wall. Such passive components were also ultimately generated at Zones 9, 11 and 12 but only ailer sufficient extension of the horizontal diam- eter to produce severe distress.

    The decreases in several effec- tive densities at Zone 10 between the 60 feet and 100 feet overfills resulted from pipe breakage and movement of the wall away from the soil.

    The increase of densities from 60 feet to 100 feet overfill at Zone 11 occurred as the settlement of the pipe into the polystyrene plank ceased and no further soil arching occurred.

    Based on relative distress ob- served, the quality of bedding and backfill parameters may be rated from best to worst as follows:

    1. Entrenched pipe: a. Zone 7, shaped bedding; b. Zone 8, fine aggregate (unshaped) bedding (actually nearly a tie). 2. Positive projecting pipe: c. Zone 11, on 6-inch polystyrene


    plank; d. Zone 12, line bearing on hard earth; e. Zone 9, shaped bedding; and, f. Zone 10, 60-degree concrete bed- ding. On the basis of unmodified

    economics, the bedding and backfilling parameters may be listed in the follOWing order-the total cost per linear foot of trench- ing, bedding, placing pipe and backfilling is also listed for each lone:

    1. Zone 12, $11.33 2 Zone 8, $13.56 3. Zone 7, $14.01 4. Zone 9, $15.34 5. Zone 11, $16.67 6. Zone 10, $18.26 Results of the experiments

    demonstrated the potential for greatly modifying current tables of overfills for concrete pipe pro- vided that proper construction procedures, which induce soil- structure interaction, are em- ployed. Results of the Mountain- house Creek tests have been in- corporated into tests of a grossly underdesigned pipe at Cross Can- yon, in Southern California, to augment the information already obtained. Field tests at Cross Can- yon are essentially complete, and analysis of data is progressing.

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    Rigid Culvert Tests - Mountainhouse Creek Part II

    by Raymond E. Davis

    Senior Bridge Engineer California Department of Transportation

    and Alfred E. Bacher

    Senior Bridge Engineer California Department of Transportation

    This article is the second of a series on an experimental installation of precast concrete pipe by the California Department of Transport- ation. Full reports of the research are