Betley WwTW Deep Dry Soil Mixing | Piling Contractors | Keller UK

Betley WwTW Deep Dry Soil Mixing

For this £500,000 scheme Keller installed around 1800 Deep Dry Soil Mixed (DDSM) columns to stabilise very soft clay and organic soil to support the safe construction of a 1.0m diameter waste water pipe the Betley WwTW project, Betley. The DDSM columns treated the in-situ materials to a depth of upto 10.0m, to achieve an unconfined compressive strength of 50kPa. The works were completed using one rig and shuttle.

CPT Plot showing strength gain with depth
CPT Plot showing strength gain with depth

Deep Dry Soil Mixing (DDSM) treated the in-situ very soft alluvium and organic soil to give an unconfined compressive strength (UCS) of the columns of 50kPa. Nearly 1800 No. DDSM columns—upto 10.0m in length, were formed to enhance the properties of the existing ground to provide the required bearing capacity and settlement control to support a 1.0m diameter water water pipe

Under the supervision of the Principal Contractor, GCA. Keller undertook an up-front programme of soil sampling and laboratory testing to enable optimisation of the column binder content and predict as-built properties of the treated soil. These tests confirmed a CEM II binder content of 220kg/m3 of mixed ground.

An extensive program of insitu testing, which included 20No. winged CPT validated the finished product . Works were completed close to a natural water course and Keller were commended on their management of this environmental risk.

The setting out of the columns were completed using GPS receptors on the rig. This provided a safe system of work by reducing the workforce requirement around the working rig and providing an accurate as-built position of the columns. The specially adapted DDSM rigs are fitted with onboard compter control that ensures a consistent product is delivered while recording detailed construction records providing a robust QA process.


  • 1760No. DDSM Columns installed—800mm diameter
  • 20No. CPT/Winged CPT completed to validate strength requirement for the scheme.

Client: United Utilities

Contractor:  Costain/Galiford Try/Atkins (GCA) JV

Engineer: Atkins

Year of execution: 2014

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