Standard Test Method for Field Vane Shear Test in Saturated Fine-Grained Soils

Importancia y uso:

5.1 This test method provides an indication of in-situ undrained shear strength of saturated fine-grained soils (clays and silts) or other saturated fine-grained geomaterials, such as mine tailings and organic muck. The test is applicable to soils with undrained strengths of less than 200 kPa [2 tsf]. Very sensitive soils can be remolded during vane insertion.

5.2 This test method is used extensively in a variety of geotechnical explorations to evaluate rapid loading strength for total stress analysis of saturated fine-grained clays and silts. Since vane shear strength values are most always higher than field strengths for analyses (5.3) they often are checked or compared with other methods of measuring undrained shear strength. Cone Penetrometer Tests (Test Method D5778) and Unconsolidated Undrained Triaxial Compression (D2850) tests are most often performed for direct comparison to the vane shear strength data. Unconfined Compression (D2166/D2166M) testing could also be performed, but suffers from many possible errors from disturbance especially in fissured clays, and should only be performed with experience. For more information on how these tests are used for soft ground site exploration refer to Ladd and DeGroot.(1)4

5.3 The peak undrained shear resistance of the vane test is commonly corrected to determine the undrained shear strength for geotechnical analysis. The agency requesting the testing must interpret these data to determine applicability for strength analysis. It is beyond the scope of this standard to recommend applicability of vane testing for geotechnical analysis. For information on the general use of these correction factors, consult Appendix X1.

5.4 This method is not applicable in unsaturated soils or in non-plastic silts, sands, gravels, or other high permeability soils. With the shearing rates described in this standard, sand lenses, if present, will allow total or partial drainage. Unsaturated soils and soils with higher permeability, in rapid shear, can dilate or collapse and generate negative or positive pore pressures which may, or may not, dissipate in the shearing process. It is important to check the soil type being tested. It is very beneficial to sample the soil either before or after testing, to understand the drainage conditions (permeability) of the soil tested.

5.5 This method also applies to hand held vane shear tests performed at shallow depths, however, hand held equipment may be less accurate, because it may be more difficult to maintain vane/rod stability and verticality.

Note 2: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Standard Practice D3740 provides a means of evaluating some of those factors.

Subcomité:

D18.02

Referida por:

D6286_D6286M-20, D0420-18, D1586_D1586M-18E01, D4648_D4648M-24

Volúmen:

04.08

Número ICS:

93.020 (Earth works. Excavations. Foundation construction. Underground works)

Palabras clave:

clay; exploration; in-situ test; sensitivity; shear strength; undrained strength; vane shear;