In Situ Soil Stabilisation

  • Client:  KierMG
  • Depth: 330mm
  • Surfacing: 60mm Dense Binder Course with 10mm Close Graded Surface Course
  • Site: Sovereign Harbour Cycle Route – Eastbourne
  • Works Type:  In Situ Soil Stabilisation
  • Material:  Soil Treated with Lime and OPC
  • Specification: Specification for Highway Works

As part of the joint collaborative venture between Hampshire County Council, Amey and Allasso Recycling a programme of haunching utilising Hydraulically Bound Material was undertaken. The material selected was a CBGM incorporating Pulverised Fly Ash (PFA) with the source aggregate being road planings containing coal tar.

Stabilisation of the insitu soil became the preferred choice due to the performance, speed and quality. A site investigation, laboratory testing and pavement design service was provided offering a design life equal to the initial design.

The pavement design was for a 250mm lime and OPC stabilised layer with 60mm binder course and 40mm wearing course, significantly reducing the construction thickness of the initial design yet exceeding its performance. The site had significant hazards to manage including a high pressure gas main, additional services, reptile protection requirements, potential unexploded ordinance and an adjacent watercourse. The use of a soil stabilisation reduced the construction depths and therefore reduced the risk of these hazards. The topsoil stripped on the works was used to provide reptile habitat on the site.

Key Benefits

  • Sustainable construction using site won materials
  • Significantly reduced programme – 12 to 30 days
  • Significantly reduced vehicle movements – Approximately 180 movements
  • Reduced cost
  • Enhanced performance

Process Overview

  1. Strip Topsoil
  2. Initial Pulverisation
  3. Lime Addition
  4. Conditioned OPC addition
  5. Grading and Compaction
  6. Application of Curing membrane
  7. Surfacing

The 2 stage process (Lime and PFA) was completed in 9 days with a further 3 days surfacing, significantly shorter than the original 6 week programme. Quality was monitored by an onsite technician to ensure compliance with the mix design. The works were completed to the extreme satisfaction of all parties involved, on time and on budget. 2 years on the performance of the site has proved to be excellent