Advances in Design and Construction of Deep Excavations and Foundations in Sri Lanka

Sri Lanka is an island nation located Indian ocean occupying an area of nearly 65,000 square kilometers, stretching 435 km from north to south and 224 km from west to east. Sri Lankan geomorphology is featured with three distinct plains of denudation, and the country is composed almost entirely of crystalline high-grade metamorphic rocks of pre-Cambrian age. Sri Lankan history boasts of an efficient hydraulic civilisation for a period of about thousand years from 200 BC to 1200 AD. Construction of large dams and tall stupas and temples has been significant features in this civilisation. The foundations adopted for these structures are still serving their intended purposes. This water resource-based development has been continued slowly both before and after the independence era of Sri Lanka with use of contemporary construction techniques and materials involving deep excavations and foundations. A significant level of modern infrastructure development could be considered to have taken root in the early 1980’s, with the application of the field of geotechnical engineering notably in the water resources sector. Essentially with sound bedrock conditions, serious geotechnical problems were not encountered when founding large dams and their ancillary structures. However, deep rock and earth excavations were carried out in all these project sites requiring different kinds of retaining structures and systems to establish the deep excavation faces. Apart from the water resources sector, other infrastructure development activities were centred at and around the capital city, Colombo. Since then, and specifically during the last two decades, the country has been seen to achieve considerable economic and social reforms with the construction industry playing an important role. A number of high-rise buildings, expressway transportation networks and other underground structures have been built during this period. Most of the high-rise building construction involved deep excavations for basements and deep foundations. As a result, considerable advancement is seen in the areas of design and construction of deep excavations and as well as foundation systems and this paper whilst giving an account of the historical development on deep excavation and foundations in the country presents also the recent developments on the same discussing the different tools techniques, monitoring and QA/QC methods.