Estimation of soil liquefaction potential in Colombo Port City (Sri Lanka) using several design earthquakes

Considering the limited land area in the Colombo Business District, the development of reclaimed land in the Colombo coastline was initiated. Colombo Port City is the first-ever mega-reclaimed land project in Sri Lanka. Land reclamations in coastal areas very often have liquefaction-related issues. Liquefaction is a process which occurs mainly due to natural seismic events. Even though Sri Lanka is located in an earthquake-free geological region, events like the 2004 Tsunami and recent studies confirmed that seismic events cannot be ignored and should be considered in the design stages of structures. Therefore, the determination of the effects of seismic events on the port city project is of prime importance. The primary purpose of this paper is to present the assessment of liquefaction triggering potential and the post-liquefaction vertical settlement. Seismic soil liquefaction was evaluated for the port city in terms of the Factor of Safety against liquefaction along with the depth of the soil profiles under the seismic demand of five earthquake scenarios that could be anticipated. The analysis process was done for 142 locations using a Cone Penetration Test-based simplified empirical procedure. The results showed that the Factor of Safety against liquefaction resistance decreases with the depth, and post-liquefaction vertical settlement is considerably high in Phase 2 land plots at the site. An earthquake with a magnitude of 6.0 and a peak ground acceleration of 0.2 has been identified as the most critical combination among the selected design seismic scenarios.