CPT and SPT as Complementary Tests for the Formulation of Geotechnical Design Profiles

Standard Penetration Test (SPT) is the most commonly used field test in any geotechnical investigation campaign. Although SPT provides quite useful information on the nature and type of the subsurface strata, owing to its inherent operating mechanism, SPT incorporates several limitations. During the dynamic impact of the SPT hammer during the testing/sampling, there is a tendency of the breakage of the cementation and disturbance of the structure in the partially-cemented soils. Breakage of cementation and similar disturbance to the soil structure may mask some of the essential information required for the choice of geotechnical design parameters for the in-situ strata. Such partially-cemented soils are prevalent in the semi-arid regions of the world such as eastern Saudi Arabia. Cone Penetration Test (CPT) is another penetration-based field test employed, usually, deployed as a secondary test for the geotechnical explorations. Due to the pseudo-static penetration mechanism of the cone during CPT testing, this test is capable of quite closely recording the information pertinent to the undisturbed structure of the soil. Therefore, CPT can be classed as an essential complementary test to SPT for the development of the representative in-situ design subsurface profile. This paper discusses several case studies from eastern Saudi Arabia, in which the precise interpretation of the CPT provided the essential complementary information that augmented the results from the SPT in developing the accurate and field representative subsurface design profiles.