We have evaluated a field test in the city of Singapore to assess the feasibility of the passive seismic survey for bedrock depth determination and to further investigate the optimal acquisition parameters. The ambient noise field, dominated by urban traffic noise, is recorded passively for the application of seismic interferometry. Spectral analysis indicates that the traffic-induced noise by local roads is concentrated between 3 and 25 Hz. We use multiple signal classification beamforming for wavefield direction of propagation analysis. We apply seismic interferometry to retrieve the surface-wave part of the Green’s functions, based on which surface-wave dispersion relations are extracted and further inverted for 1D S-wave velocity profiles. Subsequently, we compare the inversion results from seismic interferometry with borehole logs at multiple sites in Singapore and establish that the bedrock depths are well-determined using passive seismic methods within a maximum error of 3 m. By investigating the convergence of the crosscorrelograms, we ascertain that the best compromise of cost, efficiency, and accuracy for a passive site investigation in Singapore can be achieved in 15 min in the morning of a working day using an array as short as 30 m with six vertical geophones, although these parameters should be reinvestigated at other sites and other times. The success of this case study demonstrates that accurate near-surface site investigation can be achieved with faster acquisition, fewer receivers, and a smaller acquisition footprint compared with conventional methods, all of which improve the efficiency particularly in a highly developed urban environment.

Naturally available sands are always found with finer particles of varying sizes and proportions which are generally not accounted for in the geotechnical design of a cemented soil system. This paper explores the behavior of cemented sand with fine particles in smaller proportions. Two types of cements: (1) ordinary portland cement (OPC), (2) calcium sulfoaluminate cement (CSA); three cement contents: 3%, 5%, 7% and four fine (kaolin powder) contents: 0%, 1%, 3%, 5% are considered in this study. The ultrasonic pulse velocity (UPV), shear wave velocity ( $$V_{s}$$Vs ) and unconfined compressive strength (UCS) are measured to investigate the effects of fine particles on the cemented sand. The results show that fine particles do affect quite significantly the mechanical properties of cement-treated sand, even at negligent proportions. The strength and stiffness increase with fine content in both types of cement. The increase in strength and stiffness with increasing fine contents is attributed to the increased density with kaolin acting as a filler material facilitating more contact points among the particles. The results also show that the effect of fine particles on cemented sand depends not only on their relative volume and mineralogy but also on the type of the binding material.