The in-situ piston loading test is an attempt to supplement, and perhaps improve upon, the existing techniques employed to determine the shear strength of clay, particularly London clay for which a considerable scattering of results is obtained because it is heavily fissured. A circular piston closely contained by steel casing is pushed into the clay at a constant rate of penetration of normally 0.05 in/minute to failure. The method of preparing for and taking the test is fully described. Two photographs show a typical arrangement for a 20in dia piston. Failure is defined as a deformation of 20 per cent of the piston diameter or movement under constant load of 10 per cent of the plate diameter. Settlement is measured by two dial gauges reading to 0.001in and the load is measured on a direct reading pressure gauge. The bearing capacity is reduced to an equation, given and explained. A bearing capacity factor of 9, based on work by Skempton is utilised and reasons are given for its use. A typical comparison between graphs obtained from triaxial tests and piston loading tests at one site is shown and compared. The author comments on test results. The number of tests has been relatively small and with different contractors therefore the cost has been high. Once equipment and procedure is improved lower costs are anticipated.

  • Corporate Authors:

    Morgan-Grampian Limited

    30 Calderwood Street
    London SE18 6QH,   England 
  • Authors:
    • BUTLER, F G
  • Publication Date: 1965-4

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Filing Info

  • Accession Number: 00263641
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Dec 19 1974 12:00AM