Comparative analysis of beachrock cementation mechanisms in Sri Lanka: toward biomimetic engineering solution

Abstract

Beachrocks are intertidal coastal sediments formed mainly through carbonate cementation, and these sedimentary structures can be seen along the coastlines of Sri Lanka due to the prevailing tropical climate. Beachrock occurrences and formations in Sri Lanka are underexplored, despite their potential for biomimetic ground improvement. This study investigates the formation mechanism and engineering relevance of beachrocks in Chilaw and Uswetakeiyawa, focusing on the mineralogical and elemental characteristics to support nature-based ground improvement applications. Analytical methods employed included Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), Fourier Transform Infrared Spectroscopy (FT-IR), and X-ray Diffraction (XRD). The evidence suggests that beachrocks in both the localities consist mainly of quartz grains cemented by High Magnesium Calcite (HMC) with micritic coating and scalenohedral terminations, show evidence of carbonate cementation by mixed marine and meteoric water, and biological activity. Contrasting with Aragonite-rich beachrocks in Southern Sri Lanka, these findings highlight regional variations in cementation and formation mechanisms. Further exploration is recommended with additional geochemical analysis, tests of strength, petrographic thin sections, and geochronological dating, to help establish an integrated basis for understanding beachrock formation and its application to nature-based ground improvement techniques.