Bristol Temple Meads Platform Strengthening

The roof structure at Bristol Temple Meads Station was due for refurbishment/repair, this work was to be carried out from scaffolds spanning across platforms and live tracks.   However, the existing platform structure was not able to support the load from the scaffold support legs and required strengthening prior to the scaffold being erected.

The client approached Geobear to establish if we could provide a solution that would enable them to carry out the work over 13 days during a Christmas blockade of the station platforms and associated rail tracks.

Innovative design to overcome a significant geotechnical challenge

Geobear’s engineering team designed a solution that would increase the bearing capacity of the ground below the main scaffold towers in 16 locations across the station platforms together with stabilising the pedestrian subway below the platforms.

From the award of the contract, Gebear carried out the design from the F001 stage to construction in 3 weeks including Network rail approvals.

By modelling the existing soils under the platform and the loading requirements from the scaffold we were able to create a bespoke solution for the station works which could be installed in the blockade.

The Geobear solution also overcame the key risk associated with cementitious grouting on railway projects, trackbed and drainage contamination.  Our bespoke design and engineered curing periods enabled us to determine the exact spread of the material removing the risk to platform walling and track when using traditional grout methods.

The geopolymer injection solution we designed enabled us to guarantee that the platform surface could carry the required 100kN/m2. loading

Delivery of value and quality for the client

The speed of installation of Geobear geopolymer solutions made it ideal for railway possessions such as Bristol Temple Meads. 

The rapid curing of the product meant that as soon as we had finished the injection process the client could begin the erection of the scaffold.  Curing times of 15 minutes for our geopolymer material saved hours of possession time at each scaffold support location compared to the traditional alternatives.   The geopolymer curing speed also enabled complete control of the product ensuring that only the required areas were treated and ensured no pressure on the platform walling.

Each location was individually designed to ensure that the solution addressed all location-specific requirements.

Geopolymer was injected at 3 levels from 0.5m to a depth of 2.5m below formation using groups of three 12mm injection pipes to precisely place the geopolymer at the correct levels.  The drilled holes and subsequently injected pipes were angled at 15° from the vertical to increase the volume of the strengthened soil block further increasing the available bearing pressure capability. 

Heavyweight deflectometer testing was then conducted to establish the design criteria had been met.