Robertson (1990) proposed a development of the Robertson et al. (1986) profiling chart, shown in Fig. 2.8, plotting a “normalized cone stress”, qcnrm, against a “normalized friction ratio”, Rfnrm, in a cone stress chart. The accompanying pore pressure ratio chart plots the “normalized cone stress” against the pore pressure ratio, Bq, defined by Eq. 2.2…
Vos (1982) suggested using the electrical cone penetrometer for Dutch soils to identify soil types from the friction ratio, as shown in Table 2.2 (Vos, 1982). The percentage values are similar but not identical to those recommended by Begemann (1965). Robertson et al. (1986) Robertson et al. (1986) and Campanella and Robertson (1988) presented a…
Schmertmann (1978) proposed the soil profiling chart shown in Fig. 2.4A. The chart is based on results from mechanical cone data in “North Central Florida” and also incorporates Begemann’s CPT data. The chart indicates envelopes of zones of common soil type. It also presents boundaries for density of sands and consistency (undrained shear strength) of…
Begemann (1965) Begemann (1965) pioneered soil profiling from the CPT, showing that, while coarse-grained soils generally demonstrate larger values of cone stress, qc, and sleeve friction, fs, as opposed to fine-grained soils, the soil type is not a strict function of either cone stress or sleeve friction, but of the combination of the these values….
Introduction Design of foundations presupposes that the soil conditions (profile and parameters) at the site have been established by a geotechnical site investigation. Site investigations employ soil sampling and in-situ sounding methods. Most methods consist of intermittent sampling, e.g., the standard penetration test with split-spoon sampling and probing for density—the N-index. Other intermittent methods are…
A small diameter footing, of about 1 metre width, can normally be assumed to distribute the contact stress evenly over the footing contact area. However, this cannot be assumed to be the case for wider footings. Both the Boussinesq and the Westergaard distributions assume ideally flexible footings (and ideally elastic soil), which is not the…
The assumption of ideally elastic response produces an exaggerated radial stress distribution near the location of the point-load. Thus, immediately below the location of a single point and to a distance radially away from the location, the Boussinesq point-load formula does not provide realistic values, as illustrated in Fig. 1.6. However, for a series of…
Load applied to the surface of a body distributes into the body over a successively wider area. The simplest way to calculate the stress distribution is by means of the 2(V):1(H) method. This method assumes that the load is distributed over an area that increases in width in proportion to the depth below the loaded…
As mentioned, effective stress is the total stress minus the pore pressure (the water pressure in the voids). Total stress at a certain depth below a level ground surface is the easiest of all values to determine as it is the summation of the total unit weight (total density times gravity constant) and depth. Where…
All languages describe “clay”, “sand”, “gravel”, etc., which are terms primarily based on grain size. In the very beginning of the 20th century, Atterberg, a Swedish scientist and agriculturalist, proposed a classification system based on specific grain sizes. With minor modifications, the Atterberg system is still used and are the basis of the International Geotechnical…