In-situ physical properties of reclaimed lands in Singapore

Abstract

Reclaimed land construction is crucial for sustainable development of the land-scarce city-state of Singapore. To characterize the physical properties of two different types of reclaimed lands — one with well-sorted sands and the other with municipal solid waste — we conduct both active and passive seismic surveys at the sites and compare them with natural geologic formations. From the multichannel surface wave analysis, we observe more complex features related to mode kissing, mode jump, and mode loss on the dispersion spectra of the reclaimed lands, indicating complex subsurface structures. To utilize multiple orders of Rayleigh waves for inversion, we design a quantitative procedure to optimize the mode-order assignment. Seismic data and inverted results show that an older municipal solid waste landfill is more heterogeneous and stronger in its shear strength compared to the younger landfill. The reclaimed land filled with sand is more homogeneous and weaker in shear strength than the natural sedimentary rock formation. The contrast of physical properties at the four sites suggest a significant acceleration in soil hardening when landfill materials are chemically reactive with each other and with the environment. These in-situ measurements are crucial for civil engineering constructions and redevelopment of reclaimed lands in the future.