Overview of underpinning and caisson shaft-sinking techniques

Abstract

The paper discusses four traditional, soft ground, shaft-sinking techniques, namely: underpinning in free air; dry and wet open caisson-sinking; pneumatic caisson-sinking; and underpinning in compressed air. Each technique has been developed to suit a range of ground conditions that can be categorised by strength, stability and the influence of groundwater. Selecting the most advantageous sinking technique to mitigate design and construction risk must be based upon the results of a project-specific, comprehensive, ground investigation and infrastructure survey. Guidance is given on a suitable shaft borehole configuration and ground investigation content both in the field and the laboratory. Recently there has been a greater emphasis on reducing the risk to the workforce from falling objects by minimising man entry in shafts of 6 m diameter or less during shaft sinking. This favours open caisson-sinking, which allows the caisson lining to be erected as a surface activity and the caisson floor to be excavated using surface-mounted excavation equipment.

Surface settlements arising from elliptical shaft excavation in clay

“…Construction of a shaft in clay can be carried using a number of methods dependent on the strength of the clay. Allenby & Kilburn (2015) discuss shaft-sinking techniques divided into two general categories; underpinning and caisson sinking however Schwamb (2014) also highlights the use of piling and diaphragm walling as viable construction techniques. In an urban environment where there are limitations on available space, noise and vibrations, shafts are usually constructed by underpinning (e.g.…”

“…Morrison et al, 2004). Underpinning is a construction technique which incrementally excavates the shaft followed by installation of a pre-cast concrete segmental lining and grouting behind the annulus (Allenby & Kilburn, 2015). There are also recent examples of shaft construction in stiff clays using a sprayed concrete lining (e.g.…”

The analysis of shaft sinking progress as a function of technical and organizational parameters

“…The progress achieved by them is unsatisfactory in comparison to the one assumed. The main obstacle to achieving the right progress is a series of activities resulting from the shaft lining technology , Allenby & Kilburn, 2015, Schmah, 2007, Casteel, 2009 and the failure rate, in particular of new solutions (Sitko et al, 2018). In connection with this, a new, unique solution for the mechanized shaft complex was developed or cabins of minings machines operators (Tokarczyk, 2015).…”

Editorial

“…This issue contains eight excellent papers, from both practitioners and academics, all of which have current practical relevance. The first paper, by Allenby and Kilburn (2015), presents a very readable and comprehensive overview of four techniques used for sinking caisson shafts. The authors explore the issues involved in each technique and identify the most favourable, considering the ground and groundwater conditions.…”