CPTs, Dissipations And Magnetometer Tests In Greater London

In Situ Site Investigation were asked to complete a selection of tests around an existing reservoir in the Greater London area. The purpose of the ground investigation was to assess the engineering characteristics of the embankment fill and foundation soils to better understand deformations (soft spots) occurring within the structure of the embankment.

CPT 010, ‘Walter’, one of our wheeled CPT rigs was ideal for this site due to its compact size where access was restricted. Furthermore, Walter’s height, only 3.5metres and rear steering axle enabled us to manoeuvre it into more awkward areas of testing around the embankment of the reservoir.

For this project, we used one of our combined cones to complete CPTs and Magnetometer tests simultaneously because the area was deemed high risk, UXO clearance was essential. CPTs were ideal for this particular project because of their ‘real time’ results. Our operator was able to work alongside the client, analysing results as they occurred and steering the investigation on a daily basis in order to identify if and where the soft spots in the embankment were occurring by providing a profile of the strength of the material. After analysing these results with our client, we were able to identify where best to do dissipation tests in order to establish if there was any under draining happening in the embankment.

A combination of standard U2 and U1 filters were used on this project. The U1 filter was used to give us better pore pressure results because the U2 filter was being infected by the embankment material dilating around the U2 filter.