Civil Engineering | April 2010 29 Charles MacRobert Graduate Civil Engineer Anglo Technical Department CMacRobert@angloamerican.co.za Dr Denis Kalumba Senior Lecturer Geotechnical Engineering Department of Civil Engineering University of Cape Town denis.kalumba@uct.ac.za Patrick Beales Associate Geotechnical Engineer Kantey & Templer Consulting Engineers pbeales@ct.kanteys.co.za Penetration testing: test procedures and design use in South Africa INTRODUCTION Penetration testing is used to gain both a qualitative and quantitative descrip- tion of the ground to enable the design of geotechnical structures. The two penetration tests commonly used in southern Africa are the standard pen- etration test (SPT) and the dynamic probe super-heavy (DPSH) test. The SPT is carried out at specific intervals within a borehole, while the DPSH is driven continuously from ground level to refusal. Both tests apply the same drive energy to probes with similar diameters. However, the SPT recovers an “undisturbed” sample via an open- ended split spoon, whereas the DPSH simply advances a conical point. In many cases the two tests do not produce equivalent results due to differences in ground conditions, test equipment and operational methods. South Africa does not have a defined standard for conducting and analysing the tests. Consequently, various inter- national standards are adopted. This study sought to highlight the standards used and investigate how well they are followed by geotechnical practitioners. This article also shows how these practices can influence the results ob- tained from the SPT and DPSH tests. Secondly, the article seeks to examine how the results are used in geotechnical design. A major issue was to determine whether results from the tests are taken as equivalent and what precautions are taken when assuming thus. The discus- sions in this article are centred on the results from a survey. However, as the responses were limited by the time available, it is hoped that this publica- tion will facilitate further discussions on the matter. SPT TEST PROCEDURE The SPT survey investigated three things: (1) what testing standard prac- titioners followed when carrying out SPTs; (2) what borehole drilling method was used; and (3) the actual SPT testing procedures followed. Table 1 gives the SPT standards used by the geotechnical practitioners surveyed. Both the ASTM and BS standards are broadly similar, but the ASTM standard highlights some extra practices. hese include using lighter, stronger rods for holes taken to a depth of 30 m. he ASTM standard also restricts t he diameter of the borehole to between 57,2 and 162 mm, and allows the use of a cathead to pull the rope attached to the hammer. Although no great diference in eiciency can be expected from these di ferences, it has been reported that the use of a cathead can