Abstract

Fracking for shale gas extraction has been the subject of intense debate. Many myths, mistruths and misunderstandings abound – frequently fuelled by the media – but there are also understandable concerns. Most of these concerns have arisen from experiences in the USA where more than 30,000 shale gas wells have been drilled in recent years, resulting in their ‘shale gas revolution’. The key questions are (a) what are the risks of earthquakes? (b) what are the environmental risks, particularly in relation to possible groundwater contamination? The lecture will address these and other issues considered in the report for the UK Government by the Royal Society and the Royal Academy of Engineering.

The technique of fracking – better known as hydraulic fracturing – is also used for controlling settlements in soils induced by tunnelling and excavations, particularly in relation to limiting damage to potentially affected buildings. The lecture will describe the technique of compensation grouting, which involves controlled hydraulic fracturing of the ground; this is achieved by injection of liquid grout from tubes installed between the tunnel and building foundations to compensate for ground loss and stress relief caused by the tunnel excavation. The technique was used very successfully to protect the Big Ben during construction of the Jubilee Line Extension and is now widely adopted around the world; it has been used extensively to protect many buildings during the recent construction of Crossrail in London.