Ground Investigation : Replacement Road Bridge

Technics Group was commissioned to undertake a ground investigation to support a local council with the design of a replacement road bridge. 

The bridge included an embankment which had suffered subsidence due to badgers burrowing into it over a number of years. Following the safe removal of the badgers, investigation was required to confirm the thickness and details of the embankment and underlying natural ground.  

The investigation was complicated by the unstable nature of the ground following the extensive badger activity. Previous GPR surveys undertaken by Technics Group demonstrated a high degree of voiding of the underlying ground and concerns were raised regarding stability of the drilling rig and embankment during the works.  

Following extensive discussions with contractors, it was decided to undertake the four requested boreholes using a sonic rotary drilling rig, rather than more ‘traditional’ percussive techniques. Sonic drilling was chosen as the high-frequency vibration induced down the drill string to progress the borehole is limited to the soils immediately surrounding the drill string and does not dissipate through the wider soil matrix, as is the case with cable percussive drilling. This enabled the boreholes to progress with minimal disturbance to surrounding soils, avoiding the risk of destabilising of below-ground voids. A calibrated drop hammer attached to the rig enabled in-situ Standard Penetration Testing and recovery of UT100 samples for subsequent laboratory testing. 

Geotechnical and Geoenvironmental investigations are an essential starting point for the design of any construction project as the findings can be used to avoid potential problems from unforeseen ground issues. The works we carried out allowed the client’s structural engineers to design appropriate foundations for the new bridge, allowing the roadway to be reopened.

Are you looking for more information on ground investigations? Read our helpful guide on ground investigations.

If you would like to know more about how our Ground Investigation Surveys can help with your project then please do get in touch with our team of experts at our Guildford office on 01483 230080 or email enquiries@technicsgroup.com.