Editorial

Abstract

. The theme of the conference was 'Deep excavation and ground improvement'. There were 179 papers presented to an approximate audience of more than 500. In view of it being an important regional conference, some of the authors of the papers were invited to contribute fulllength articles to Geotechnical Research because their topics were of interest and relevance to the objectives of the journal. These articles are extended versions with new material and have been through rigorous peer review before being accepted for publication. We hope readers will find this issue interesting and useful for their research and engineering careers in academia and/or geotechnical industry.The first paper, by , describes the procedure in carrying out the design of vertically loaded piles considering the pile set-up phenomenon in cohesive soils, drawing experiences from 32 documented local case histories with detailed information on the hammer used, pile driving process, pile properties and subsurface information for wave equation analysis programme (WEAP) analyses and load and resistance factor design (LRFD) resistance factor calibration. To aid with LRFD design of driven piles, 12 step-by-step design examples were created. These examples were presented in three different tracks considering four pile types, three soil categories and four special design considerations. The design guide and examples were developed specifically for a region but its commendable concept and advantages could be emulated for other regions.In the next paper, Ng and Sullivan (2017) studied the common practice in Wyoming, USA where steel H-piles are driven to penetrate rock materials. Current static analysis methods, originally developed for soil, provided inconsistent and potentially conservative geotechnical resistance estimations for a driven pile on soft rocks. Hence, this study highlights the importance of establishing methods to distinguish rock materials for driven pile design and construction as well as of developing methods to predict better the resistances of piles driven on soft rocks.In the paper by Choo and Ong (2017) a novel method was developed by the authors to derive equivalent rock strength characteristics based on the interpretation of results obtained from direct shear testing of reconstituted tunnelling rock spoils. The established theories on power law and the generalised tangential approach were successfully used to capture the nonlinear behaviour of the reconstituted sheared rock samples. By applying the interpreted strength parameters to four pipe-jacking drives in varying geology, it was found that geology had significant effects on lubricant use and arching around the tunnel, thus affecting the accrued jacking forces in each drive. The applicability of the interpreted parameters to the back-analysed jacking forces was also validated through the use of three-dimensional finiteelement modelling. This research contribution could lead to the development of a predictive jacking force model for drives in soft and highly fractured rock f...