FROST ACTION ON SMALL FOOTINGS

FROST HEAVE OF SMALL FOOTINGS IS A PERIODIC TROUBLE AT TRANSFORMER STATIONS OF THE ONTARIO HYDRO ELECTRIC POWER COMMISSION. WARPED TRANSFORMER PADS, OPENED SWITCHES AND DISTORTED SERVICE BOXES ARE AMONG THE DISTURBANCES ARISING DURING THE WINTER MONTHS. THIS PAPER SUMMARIZES THE RESULTS OF LABORATORY AND FIELD INVESTIGATIONS, MADE DURING THE LAST 4 YEARS, TO DETERMINE WAYS OF CONTROLLING FOOTING HEAVE. INITIAL LABORATORY TESTS INDICATED THAT THE GRIP BETWEEN FROZEN SOIL AND CONCRETE WAS OF THE ORDER OF 400 PSI. AT -10F. THESE RESULTS CONFIRMED MEASUREMENTS MADE IN SIBERIA APPROXIMATELY 18 YEARS AGO. DURING THE LAST TWO WINTERS VARIOUS PROPOSALS FOR HEAVE CONTROL WERE TRIED ON AN INSTALLATION OF SMALL FOOTINGS, PLACED IN A FROST SUSCEPTIBLE SOIL 40 MILES NORTH OF TORONTO. LOW TEMPERATURE GREASE, POLYETHYLENE COVERS, GRAVEL BACKFILL, AND SOIL TREATMENT WITH A WASTE PRODUCT OF THE PULP AND PAPER INDUSTRY WERE AMONG THE MEASURES USED TO REDUCE THE GRIP BETWEEN THE FROZEN SOIL AND CONCRETE. REACTION TO THE HEAVING FORCES WAS ALSO PROVIDED BY SUBJECTING THE FOOTINGS TO VARIOUS LOADS OR BY EQUIPPING THEM WITH ENLARGED PADS BELOW THE FROST LINE. DURING THE WINTER OF 1951-52, UNTREATED FOOTINGS HAVING A BUOYED WEIGHT OF APPROXIMATELY 150 LB. HEAVED AS MUCH AS 4 INCHES, GREASED FOOTINGS MOVED ABOUT THIS AMOUNT. FROST PENETRATION THAT YEAR WAS 12 INCHES. THE FOLLOWING WINTER WAS MILD AND THE MAXIMUM HEAVE OF UNTREATED FOOTINGS WAS LESS THAN 2 INCHES. LESS MOVEMENT WAS OBTAINED UNDER HIGHER LOADS, HOWEVER, AND FOOTINGS EQUIPPED WITH CONCRETE PADS DID NOT MOVE AT ALL. THE GREASED FOOTINGS UNDER LOADS OF 350 LB. AND ABOVE DID NOT MOVE. AN ANALYSIS OF THE FROST HEAVE PROBLEM, BASED ON THESE OBSERVATIONS, RESULTED IN THE PREPARATION OF AN APPROXIMATE CHART WHICH INDICATES THE BEARING PRESSURE REQUIRED TO OVERCOME FOOTING HEAVE. IT SUGGESTS THAT THE CROSS-SECTION OF FOOTINGS WITHIN THE ZONE OF FREEZING SHOULD BE MADE AS SMALL AS POSSIBLE, CONSISTENT WITH THE STRUCTURAL STRENGTH OF THE CONCRETE. BELOW THIS DEPTH THE FOOTINGS SHOULD BE ENLARGED TO TRANSMIT THE FOOTING LOAD TO THE SOIL SAFELY. THE USE OF LOW TEMPERATURE GREASE WAS ALSO RECOMMENDED FOR SPECIAL APPLICATIONS, SUCH AS CONDUITS, WHERE A REACTION FORCE IS NOT OBTAINABLE. FIELD OBSERVATIONS ARE CONTINUING TO ASSESS THE RESISTANCE OF THESE FOOTINGS UNDER MORE-SEVERE WINTER CONDITIONS./AUTHOR/

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    • Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved. No 100, pp 22-35, 8 FIG
  • Authors:
    • Trow, W A
  • Publication Date: 1955

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  • Accession Number: 00237741
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 22 1994 12:00AM