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In-Situ Classification Methods

In CPT, a rod-shaped, 35.7 mm diameter (10 cm cross section) cone with 60° apex is either mechanically, or hydraulically pushed into the soil at a constant penetration rate, usually 2 cm/sec. The penetration resistance of the cone (cone bearing), as well as the shaft friction resistance along a 150 cm friction sleeve, placed just behind the cone, are continuously measured by a load cell and a strain gauge, respectively, and the results are processed and plotted automatically. An inclinometer incorporated into the cone tip assembly continuously monitors the deviations of the CPT tip from the vertical. Details of the test is described in detail in Chapter 4. The penetration resistance is affected by the particle size, relative density, gradation, compressibility, degree of saturation, and organic/ carbonate content of the soil, as well as the shape and the compressive strength of the soil particles (Broms and Foldin, 1988). [Pg.243]

Development of specific penetration devices, either incorporated into the CPT or individually used, have further expanded the capabilities of penetration tests, resulting in subsequent refinement of soil profiling. They include the dilatometer (DMT [Marchetti, 1975,1980 Marchetti and Crapps, 1981 Lutenegger, 1988]), seismic cone (Campanella and Robertson, 1984 Campanella et al., 1986 Baldi et al., 1988), acoustic cone (Villet et al., 1981, Massarch, 1986), lateral stress cone and lateral stress cell (measurement of lateral stress on the cone shaft—Morrisson, 1984 Huntsman, 1985 Huntsman et al., 1986 Baligh et al., 1988), vibratory cone (evaluation of susceptibility of cohesionless soils to liquefaction— Sasaki et al., 1984), and pressure-cone (Jezequel et al., 1982 Hughes and Robertson, 1985 Whiters et al., 1986). [Pg.243]

A flat dilatometer measures the pressure required to lift a flexible membrane against the soil (Marchetti, 1975,1980). The standard instrument consists of a 14 mm thick, 95 mm wide, 220 mm long, flat plate with a flexible stainless steel membrane 60 mm in diameter on one [Pg.243]

Soil behavior type charts from CPTU data. Note indicates overconsolidated or cemented. (Data from Robertson, P.K. et al., Use of piezometer cone data. Proceedings of In-Situ, Blacksburg, VA, ASCE, Specialty Conference, 1263-1280,1986. Reproduced with permission of ASCE.) [Pg.244]

The charts resulting from penetration tests are used to classify soil types based on soil behavior. They are not grain size classification charts. For this reason, some overlap exists between different types of soils that have entirely different consistencies, for example, loose sands and highly overconsolidated clays. Therefore, fhe interpretation of penetration testing data must be supported by intelligent assessment of the data, and additional data provided by use of specific fools and experience. [Pg.245]


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