CGL engineers have a wide and varied experience in undertaking the design of earth support methods, ranging from simple trench sheeted cofferdams using empirical methods such as Ciria R96, to highly engineered piled retaining walls with multi-propping levels fully coordinated with the permanent works design.

What Is Excavation Stability?

During any construction process, it is important to ensure the safety of all workers, prevent accidents, and protect adjacent developments and structures as well as the environment. 

At CGL, we undertake excavation stability services to assess and maintain the structural integrity and safety of below ground construction sites. This includes trenches, cofferdams, or excavations both during and after the excavation process. 

Our Excavation Stability Services

During our excavation stability services we offer the following investigations:

  • A review of site investigation data to establish an optimised ground model and design parameters.
  • Detailed Ground Movement Analysis for basement, perimeter walls and whole development.
  • A conceptual and detailed temporary works scheme including designs of critical sections, predicted wall deflections and waler/prop loading.
  • Outline design and detailing of temporary propping framing and reaction piles, including structural checks on retaining systems (piled wall and mass concrete underpins).
  • Recommendations for underpin construction including an assessment of groundwater infiltration rate within the gravels during underpin construction.
  • Producing a recommended groundwater control strategy and movement monitoring and contingency plan for each boundary location based upon observational methods.
  • Advising on construction sequencing for ramp removal.
  • Ground Movement Analysis during the excavation stability assessment on the impact of the development and other developments close to the site.
  • Tower crane base design, developing the detailed geostructural design on detailed sequencing drawings how to construct the base.
  • CAT II checks on the subcontractor’s pile and basement propping temporary work designs.

Below Ground Temporary Works design specialist

CGL worked closely with the structural engineer to simplify the construction approach as well as reduce the cost.

During our excavation stability services we are able to identify potential for open cut excavation supported by adoption of the observational method for slope monitoring. CGL set out inspection regimes for site staff, briefing documents, and a call out service for identified issues using the traditional traffic light graded risk response of the CIRIA Observational Method.

As part of our excavation stability process, we also provide contractor support, pre-tender outline designs, support regulatory approval for the project, then design the perimeter support systems and temporary works during excavation and basement construction. 

The process involved in excavation stability includes the following key elements:

  • Site Assessment
  • Design Of Temporary Propping And Retaining Systems
  • Soil Stabilisation
  • Monitoring And Inspection
  • Safety Procedures
  • Coordination With Permanent Works Design
  • Emergency Response Plan
  • Regulatory Compliance

Industry Leading Geotechnical and Geostructural Design Software

At CGL, our expert accredited team use the following software to conduct thorough excavation stability testing and investigations:

  • WALLAP to analyse retaining walls and underpins in the lateral condition.
  • PLAXIS 3D to model the forces in perimeter support props and reaction caps, the support piles for the tower cranes and impact on the adjacent developments.
  • CADS A3D frame analysis to inform the RC capping beam and steel walling design.

Why Choose CGL For Excavation Stability Services?

At CGL our team has wide and varied experience in designing and implementing comprehensive excavation stability services. We provide detailed investigations including a review of site investigations data and detailed ground movement analysis both in terms of the project and in relation to adjacent developments and structures. 

Our excavation stability services have been developed to ensure that our clients receive a comprehensive and industry leading service using state of the art software tools to address the safety and integrity of all below ground construction. 

Our experienced and accredited team of geotechnical and geoenvironmental specialists strive to ensure that all our clients receive an efficient and cost effective service enabling them to proceed with their projects and meet their objectives in a timely manner.