Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 2411 An introduction to pipe jacking and microtunnelling 3 SITE INVESTIGATION AND INFORMATION REQUIRED ON SOIL CONDITIONS FIELD STUDY The field exploratory techniques selected should be appropriate to the type of ground and the planned depth of tunnelling. Geo-physical testing, trial pitting, static cone penetration testing and percussive or rotary-drilled boreholes may be used where appropriate. The laboratory testing programme should include tests relevant to the ground conditions and the tunnelling techniques likely to be employed. Table 3b suggests parameters to be considered in relation to each soil type. INFORMATION PROVISION All historical and site investigation information should be provided to the pipe jacking contractor in AGS Format* to enable an accurate assessment of the techniques required to execute the work. If the route of the tunnel is varied after the completion of the site investigation, then the need for further boreholes must be reviewed to ensure that the information provided is still relevant to the revised route. Additional information may also be required as a result of the findings from the initial investigation. * AGS Format is the standard electronic format for the transfer of geotechnical and geoenvironmental data as recommended by the Association of Geotechnical and Geoenvironmental Specialists. 3b) Parameters to be considered in relation to each soil type BOREHOLE POSITIONS In no circumstances should boreholes be sunk on the line of the tunnel. Exploratory hole positions should be chosen to provide information on the nature of the ground that will be encountered by the tunnel. All boreholes should be properly backfilled and sealed. Piezometers should be installed where recommended. Boreholes should always extend to the tunnel horizon and sufficiently far below the invert level to identify changes in the strata below that could affect the tunnel’s construction. Boreholes should be sunk adjacent to shaft locations. Additional boreholes should be considered to identify the location of significant changes in geology or to resolve other geotechnical uncertainties. TEST Non-cohesive Cohesive Mixed Soils Fill Material Rock Unit weight and moisture content • • • • • Angle of friction • • • Particle size distribution • • • • Abrasivity • • • • • Cohesion • • • Types and proportions of minerals • • • • • Standard penetration tests • • • • Permeability and nature of ground water flows (seasonal/tidal changes) • • • • Toxic/hazardous constituents in the ground/groundwater • • • • • Frequency and physical properties of boulders, cobbles or flints • • • • • Pump down tests • • • • Presence of gases • • Compressive strength • Rock quality designation (RQD) • Core logging (TCR, SCR, FI) • Tensile strength • Specific energy (excavatability) • Slake durability • Geological description • • • • Plasticity indicees (SL, PL, PI) • • Disaggregation mixing test* • • RF (x-ray fluorescence) mixing test • • *See N. S. Phillips 2016 on