Test and Analysis of Confined Compressive Strength and Average Elastic Modulus of Metasedimentary Rocks in the Northern Metropolis of Hong Kong

Abstract

Metasedimentary rocks are widely distributed in the Northern Metropolis of Hong Kong and exhibit pronounced variability in confined compressive strength (CCS) and average elastic modulus (Avg. E) due to well-developed foliations, fractures, and mineral fabric. To identify the controlling mechanisms and develop a practical prediction method, this study combined triaxial compression tests, pre- and post-test CT scanning, Cerchar abrasivity tests, slake durability tests, and petrographic thin-section analysis. CT results indicate that pre-existing fractures and structural integrity mainly control the lower bound of mechanical performance, whereas thin-section observations show that quartz skeleton continuity, quartz recrystallization, and the preferred orientation of platy minerals jointly affect load-bearing capacity and weak-plane development. Based on these observations, the controlling factors were classified into four physical dimensions: skeleton hardness, structural integrity and water sensitivity, loading angle, and confining pressure. Model comparisons show that the full-variable log-linear regression model improves CCS prediction over the single-variable model, and that reorganizing the variables according to mechanistic dimensions yields further improvement. The proposed framework provides a practical and interpretable approach for rapid estimation of the mechanical parameters of metasedimentary rocks in the Northern Metropolis of Hong Kong.