THE SELF-DRILLING PRESSUREMETER

In situ measurement of soil properties by the expansion of a cylindrical probe (pressuremeter test) is widely employed in soil engineering practice; nevertheless, at its present development stage, it suffers severe limitations due to theoretical difficulties in the interpretation of the test and to disturbance to the ground around the instrument arising from either preboring a hole or forcing the instrument into the ground. The authors report substantial improvements in both respects. They have developed a self-drilling pressuremeter, consisting of a hollow cylindrical probe which is steadily inserted into the ground while the soil is excavated by a rotating internal cutter. The soil cuttings are washed out by a drilling fluid circulating inside the hollow cylinder. The instrument may be used to measure the horizontal soil pressure and hence the coefficient of earth pressure at rest; furthermore a cylindrical expansion test may be conducted in either an undrained or a drained condition. Stress or strain control and pore pressure measurement are provided. From the viewpoint of the test interpretation, a rigorous theory of the undrained pressuremeter test is furnished with no assumptions being made on stress-strain properties of the soil. Results obtained at several sites in fine grained soils are reported; experimental factors such as testing rate, cyclical loading, creep, and influence of a disturbed area are analyzed and discussed. Soil properties (undrained cohesion, undrained modulus, shear strength characteristics in terms of effective stress) measured by the new instrument are consistently higher than corresponding values measured by conventional techniques (van test, laboratory tests on undisturbed samples). The authors claim that these higher values are probably a better measure of true in situ soil properties; they warn against an uncritical use of such values in conventional design analysis which fails to take into account factors as, for instance, the occurrence of progressive failure.

  • Authors:
    • Baguelin, F
    • Jezequel, J F
  • Publication Date: 1973

Language

  • French

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00265338
  • Record Type: Publication
  • Source Agency: Applied Mechanics Reviews
  • Report/Paper Numbers: Nos. 307/308
  • Files: TRIS
  • Created Date: Jan 16 1975 12:00AM