Full-scale pile tests in sand and development of a computer program for predicting load capacity

An interactive computer program GLAMPILE has been developed for predicting the static load capacity of single piles formed in any soil profile. A variety of well-known prediction methods have been incorporated into the program, including (i) soil mechanics based formulae; (ii) direct and indirect cone penetration test (CPT) based methods with and without accounting for scale effects of the cone on pile base capacity; and (iii) a new CPT-based method that considers the effects of “critical depth” and shaft resistance distribution, although the method has only been calibrated for relatively short piles. GLAMPILE can cope with different pile types installed with or without a permanent casing. The program has been applied to predict the axial capacities of 11 piles that were recently installed in sand and statically loaded to failure. Results from the soil mechanics procedures indicate increases, on the in situ value, of the earth pressure coefficient by up to 37%, which lies within the range 0%–100% recommended in the literature. The best CPT-based prediction method applied yields a mean (µ) and coefficient of variation (COV) of predicted to measured pile head capacity (Puh(p)/Puh(m)) of 0.83 and 0.12, respectively. Scale effects are shown to be nominal for the cases analysed. An improved method is recommended, which yields µ = 1.00 and COV = 0.10, implying higher accuracy and reliability compared with the other methods.Key words: piles, cone penetration test, static and dynamic load test, modular program.