THE PROJECT

Intrusive ground investigation techniques were required to provide a detailed investigation of the geotechnical & the hydrological characteristics of the underlying material to inform the design and construction of a new large diameter water pipe installation and monitoring of the slope stability during construction.

THE CHALLENGE

Boreholes were located on steep sides of the River Severn Valley with the Severn Valley Railway running directly below the works area. Access to the location for the drill rigs was across numerous sloping fields.

THE SOLUTION

The P60 drilling rig enabled safe access across the fields and then down the valley slopes via radio remote control with the self-levelling support platform creating a safe working area adjacent to the borehole location. The instrumentation was moved to the borehole locations on the slope using the P60 “mule” self-levelling support platform.

Window samples were also required at locations on the slope, our modular rig was transported to each location on the “mule” and set up on level areas along the valley sides.

Installation of the ShapeArray™ monitoring instrumentation was undertaken with support from the supplier. A remote solar power supply and data transmitting point was installed at the top of the slope to send live information on the slope condition.

In total three exploratory boreholes were completed using a P60 slope rig, 2 boreholes using a Comacchio GEO 305 (Pioneer) multipurpose drilling rig. Two window sample holes with the modular window sample rig and two machine excavated trial pits.  A range of drilling techniques including dynamic sampling, and rotary coring with biodegradable polymer flush media were utilised. The boreholes were advanced to the target depths of up to a maximum 40m depth. Geotechnical Laboratory testing (geotechnical and geoenvironmental) was undertaken by GEL and incorporated within a factual report along with the borehole and trial pit logs.