In Situ Site Investigation were asked to complete a project for a new housing development in West Sussex. A tracked rig was required on this site due to the sticky clay surface layer, therefore CPT 012, Bob, one of our remote-controlled tracked rigs was deployed to complete the works.

Our Gamma Cone was requested for this investigation because the ground was known to be soft clay on top of chalk and our client wanted to determine the boundary between the chalk and clay to help with the planning of their foundation designs. It can be hard to tell the difference between clay infill material and weathered chalk due to its similar properties when the cone is pushed through using a standard CPT. The gamma sensor, which is mounted behind the standard CPT cone allows us to identify the high gamma readings in the clay and very low readings in the chalk therefore giving an accurate depth of the clay/ chalk divide.

A total of 73 Gamma CPTs were successfully completed over a 3 week duration and went to a maximum depth of 24.5 metres.

Project : Gamma Cone used in West Sussex

Date : November 2019

Location : West Sussex, UK

Rig : CPT012 'Bob'

Type of Testing : Gamma