Trial Pits and Trial Trenches
Subject to access and other constraints, trial pits and trial trenches are a relatively rapid and low-cost method for the investigation of shallow soil strata typically to depths of around 3-4m. The pits/trenches are generally dug using a mechanical excavator with hand tool excavation being reserved for special situations (e.g. where underground services are anticipated and to examine existing foundations or other substructures).
Dynamic Sampling and Dynamic Probing
This method of percussive boring can be used for shallow-depth investigation of soil strata, typical depths of investigation being around 5m. It provides for in-situ standard penetration testing and the installation of instrumentation such as gas/groundwater observation wells. Hole diameters are typically about 100mm and the rig's compact size makes it well suited for investigations where access and other constraints preclude or otherwise impede the use of trial pits and larger drilling/boring rigs. The rig can also be used to undertake dynamic probe soundings which provide a continuous record of the ground's penetration resistance. We have successfully used this type of rig to probe to depths in excess of 20m.
Cable Percussion Boring
Also known as shell and auger boring, this traditional method of percussinve boring uses a trailer-mounted tripod rig to bore thorough soil strata to depths in excess of 20m at hole diameters of 150mm or 200mm. A range of in-situ tests can be performed in these boreholes (e.g. standard penetration tests, vane tests and rising/falling/constant head tests) and disturbed or undisturbed soil samples can be recovered. Instrumentation such as gas/groundwater observation wells, piezometers, inclinometers and settlement gauges can also be installed.
Rotary drillling techniques are required to investigate competent rock strata.
When detailed information is required rotary core drilling is used to bring rock cores to the surface for examination and logging by one of our Engineering Geologists or Geotechnical Engineers. In some situations, such as probe drilling to investigate the possibility of old coal mine workings, openhole drilling (without core recovery) will often suffice. Hole and core diameters typically range from about 70mm to about 140mm.
Static Cone Penetration Testing
Static cone pentration testing involves pushing a small diameter cone with a short friction sleve into the ground at a constant speed of 20mm/s and recording the penetration resistance on the cone tip and on the friction sleve. Pore water pressures during penetratioin may also be recorded. The data obtained provides a continuous record of the soil's penetration resistance and pore water pressure response and, in the right ground, can be successfully used to derive estimates of many commonly used geotechnical strength, stiffness and hydraulic parameters.
Soil Infiltration and Percolation Testing
We undertake infiltration tests in accordance with BRE Digest 565 to provide infiltration rates for usein feasibility studies and detialed design of soakaways.
We also undertake percolation tests in accordance with Building Regulations Approved Document H to provide percolatioin rates for use in feasibility studies and detialed design of sceptic tanks and drainage fields.