Ten days after the Newcastle, Australia earthquake of 28 December, 1989, the UK-based Earthquake Engineering Field Investigation Team (EEFIT) mounted a five day mission to the affected area. This paper presents the findings of the EEFIT investigation and subsequent follow up studies in relation to the extent of building damage and its distribution within the City of Newcastle and the surrounding urban area. Results are based on both detailed street surveys and general damage surveys, the former carried out in two areas, namely the heavily damaged suburban district of Hamilton (3km west of the city centre) and the Newcastle central business district. The findings of these surveys have provided valuable information on the vulnerability of building stock of types common to other parts of Australia, the UK and elsewhere, and hence form an important database for the accurate assessment of seismic risk to buildings in regions of low seismicity. This information will assist the development of realistic, economical seismic code provisions for building design and construction in low-risk areas. An important feature arising from the surveys and subsequent analytical studies of site response in the heavily damaged districts within the Hunter River alluvial basin is that, contrary to reports published by the Institution of Engineers, Australia amongst others, the areas of deep alluvial soil and fill do not correlate strongly with the more heavily damaged districts determined from post-earthquake assessments. Hence, suggestions that this form of site soil amplification effect played a major part in the distribution and extent of heavy damage in this earthquake are somewhat misleading for the future development of planning and design regulations. Furthermore, the results of site response analyses show that it is more likely to be the shallower soils near the border of the alluvial basin which tend to amplify bedrock ground motions generated by this type of earthquake.

To advance the understanding of the rainfall-induced landslide triggering mechanism, a comprehensive field monitoring programme was implemented in a saprolitic hillslope in Hong Kong. The instrumentation covered the measurements of the two stress-state variables (i.e., net normal stress and matric suction) and their effects. The monitoring results, including pore-water pressure (PWP), volumetric water content, subsurface total horizontal stress, horizontal displacement, and rainfall intensity, are reported. Most instruments recorded reliable and good quality data, which have strong correlation among each other. The site-specific infiltration and deformation characteristics of the hillslope subjected to heavy rainstorms are investigated. Shallow transient perched groundwater tables were believed to be developed at colluvial deposits on the top 3 m, where PWPs up to 20 kPa were typically measured. The main groundwater table probably rose by 6 m when the hillslope was subjected to rainfall intensity of 133.5 mm/h. It is possible that cross-slope groundwater flowed along a shallow, dipped decomposed rock stratum at the central portion of the landslide body. Besides, two distinct types of slope movements were generally observed, namely the “cantilever” and the “deep-seated” mode. Rupture surfaces have possibly been developed at 5 m below ground or deeper, resulting in a multiple translational- and rotational-slide type of failure.

It is well recognised that field measurements of stressdependent soil-water characteristic curves (SDSWCCs) and the permeability function (coefficient of permeability with respect to the water phase) are vital for assessing transient seepage, pore water pressure changes and the stability of unsaturated soil slopes. In this study, SDSWCCs and the permeability function were measured by using the instantaneous profile method on a saprolitic hillside in Tung Chung, Hong Kong. The ground profile comprises colluvium and completely decomposed tuff (CDT). A 3 m diameter circular plot was instrumented and subjected to two wetting-drying cycles. Throughout a 48-day monitoring period, variations of volumetric water content and matrix suction in the uppermost 3 m of soil were measured continuously using time-domain reflectometry moisture probes and jet-fill tensiometers, respectively. The field observations reveal that there is a clear trend of decreasing sizes of hysteretic loops of SDSWCCs with depth. In a comparison of the field-and laboratory-measured SDSWCCs, general agreement can be seen in the first wetting-drying cycle but not in the second cycle. The field-observed unsaturated permeability function is highly dependent on suction history (wettingdrying cycles). The field-measured permeability ranges from 4 3 10 27 m/s to 3 3 10 24 m/s in the colluvium, whereas the corresponding measured values vary from 4 3 10 27 m/s to 1 3 10 24 m/s in the CDT. Predictions of SWCC and permeability function using existing empirical approaches based on particle size distributions (PSDs) should be treated with caution. There is a clear qualitative and quantitative inconsistency between predictions of permeability function from PSD and field measurements.

Results are presented for 3 soft clay sites forming part of a larger response study of 11 soil sites subjected to earthquakes of varying intensity and frequency content. The results are presented in the form of spectral ratios (surface to rock), base shear coefficients, and foundation factors. They indicate that large amplifications can be expected at structural periods close to the site period. Comparisons are made with the National Building Code of Canada (NBCC) 1990 provisions for base shear coefficients and foundation factors. These show that the NBCC provisions are adequate when the excitation is low or medium period in nature. For high-period excitation of low intensity, high amplifications that exceed the code provisions are produced. Key words: seismic, design, clay, soft, site, response, spectra, amplification, base, shear.