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|Title:||Field tests of the Cucaracha formation, Panama Canal, 1942-1946|
|Authors:||Panama Canal Company.|
Smith, Carneal K.
Lutton, R. J.
Pedro Miguel Locks
Third Locks Project
|Publisher:||Soils and Pavements Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: This report describes and presents the results of field studies of shales of the Cucaracha formation conducted during 1942-1946 by the Special Engineering Division of The Panama Canal Company in connection with the design of the Third Locks Project. Geology of the area in the vicinity of the then-proposed New Pedro Miguel Lock where the field studies were made, as presented in this report, was based on a review of geological studies available at the time of the tests supplemented by more recent studies and exploration of the Cucaracha formation by geologists of The Panama Canal Company and the U. S. Army Engineer Waterways Experiment Station. The two principal field studies discussed in the report are : (A.) Pedro Miguel Test Pit No. 3. The pit was excavated in 1942. Field shear and bearing tests were performed in a drift on Cucaracha clay shale, and laboratory shear and bearing tests were made for comparison, and (B.) Cucaracha Foundation Test. This test, which was initiated in early 1944, consisted of a large-scale bearing test of a concrete base 40 by 50 ft in plan and 10 ft thick. The base, which simulated that of a lock wall monolith, was loaded in stages over a period of about 9 months with steel plate and concrete to produce maximum pressures of 12.5 tsf at the toe and 7.5 tsf at the heel. Maximum pressures were maintained for about 5 months and then reduced to an average pressure of 6 tsf; which was maintained for 300 days before concluding the program in April 1946. Measurements were made of structure settlements, settlements adjacent to the structure up to 40 ft away, and pressures immediately beneath the base of the structure. Attempts to measure pressures induced at various depths beneath the structure were not successful. Recommendations made by a board of consultants in February 1945 following review of the test results are included in this report. The data indicate that settlement of large structures on Cucaracha clay shales could be higher than anticipated in 1945. It is recommended that analyses be made of the test data using present-day analytical methods.
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