Comparison between empirical, numerical and practical compression capacity of rock socketed bored and cast in-situ pile : a case study

Abstract

The development of tall structures as a rapidly developing trend in Colombo-Sri Lanka is evident during the recent past due to the high land prices. These tall structures require to be founded on strong substrata and piling is the most popular method that has been used as the foundation for these tall buildings. In Colombo area having found bed rock at shallow depth around 15m to 20m, always design engineers tend to specify the rock socketed end bearing piles without much considering the load carrying mechanism of the pile. It is evident that Sri Lankan design engineering community has a tendency to disregard the pile shaft skin friction resistance, mostly due to the existence of bentonite slurry within borehole during concreting. Therefore, load carrying capacity of such piles is determined completely based on the end bearing from the bed rock. In addition to that in most standards and codes of practice, the pile load carrying capacity correlations are given for specific soil types i.e. sand, clay, gravel. However in local context it is hard to find such conditions and almost all the soils are residual soils having both 𝑐,∅ values. In this research, different correlations for pile load capacity and its variations are evaluated. A detail comparison is conducted between the compression capacity of piles obtained from different empirical/semi-empirical methods, numerical methods such as FEM and in-situ testing i.e. MLT and HSDLT against the code of practices and local guide lines.