We recently took the ferry out to Rottnest Island for a geotechnical investigation. With stunning weather and light winds JDSi set sail, mobilising a CPT rig from Fremantle to investigate the site. The reporting phase now is underway and we look forward to our next Rotto trip soon!

The investigation was part of the redevelopment of the iconic Rottnest Hotel with addition multi-story buildings and swimming pools. We sent over a CPT rig and an Engineering Geologist to carry out the works and hoped they would be able to get quokka selfie!

Scope

  • Assess the subsurface soil and groundwater conditions across the site;
  • Provide construction considerations including site preparation, excavation conditions, and suitable of materials for use as structural fill;
  • Provide a site classification in accordance from AS2870-2011;
  • Provide geotechnical design parameters for the recommended foundation systems and retaining walls;
  • Provide recommended subsoil class(es) for seismic design in accordance with AS1170.4;
  • Provide recommendations for temporary and permanent slope batters;
  • Complete a desktop study to assess the presence of Acid Sulphate Soils (ASS);
  • Assess suitable foundation systems and geotechnical parameters for foundation design;
  • Provide an assessment of the allowable bearing pressures and estimates of total and differential settlements for shallow foundations;
  • Undertake pH, Sulfate and Chloride, and electrical resistivity in soil samples in order to assess exposure for concrete structures in aggressive soils;
  • Assess the permeability of in-situ material and the potential for stormwater disposal by soakage at the site; and
  • Provide a recommended subgrade CBR for flexible pavement.

Key Challenges and Solutions

Mobilising a CPT rig to a small island off the coast of Perth and carrying out an investigation within a popular tourist destination were some of the challenges of this project.