Site Investigation Services
In addition to our design and construction verification services, Foundation Specialists Group also provides site investigation (SI). Key points of difference unique to FSG and not typically carried out by other SI consultants are:
Site Investigation Manual
The FSG Site Investigation (SI) manual (2014 edition) provides a reference document for our QA procedures which goes beyond Australian Standard AS 1726 by including relevant content from the following reference documents:
- Australian Standards (AS 1726-1993), Geotechnical Site Investigations, Australia, 40 pages.
- New Zealand Geotechnical Society 2005 Field Description of Soil and Rock – Guideline for the Field Classification of Soil and Rock for Engineering Purposes, 39 pages.
- Look, B. (2014). Handbook of Geotechnical Investigation and Design Tables. 2nd Edition, United Kingdom: Taylor and Francis Publishers.
Various British (BS) and American (ASTM) standards are also mentioned as appropriate where Australian Standard AS 1726 lacks sufficient technical detail. Dr Look’s book (2nd edition) which is used by many geotechnical consultants extends on value adding and interpretation of test data from the site investigation.
There are various areas where Australian Standards are lacking or provide no guidance and it is useful to consult the international literature. These include
- ASTM D4633 – 10, “Standard Test Method for Energy Measurement for Dynamic Penetrometers”
- BS EN ISO 22476-3:2005+A1:2011 “Geotechnical investigation and testing —Field testing — Part 3: Standard penetration test
The SPT Standard in Australia is for soil and not rock (or residual soil profiles common in Australia) although used in that material. The BS and USA standards provide a higher and more meaningful blow count termination value at the soil – rock interface.
The borehole logging software used by FSG is Core-GS. This is also an integrated data base system, which also allows geospatial data reporting with Import/export from common file types (AGS 4 and gINT compatible, with easy export to Excel for spreadsheet analysis). Geotechnical cross sections can also be produced directly from the logs
FSG is one of the few (if not the only) consultant in Australia, who can measure the Standard Penetration Test (SPT) energy. Any field SPT N – value measured should not be used in design unless corrected for energy. FSG has both
- PDM which has been shown to improve the set- energy measurements of SPTs.
- The SPT analyzer. This is the current ASTM “standard” for SPT energy measurements
FSG currently carries energy measurements for other consultants and government bodies to calibrate the energy measurements, where critical or where multiple drilling rigs are being used. However this energy measurements are routinely applied in FSG site investigations where SPTs are used as this is standard practice in Europe in USA and Europe, but seldom used in Australia
Rock Modulus Testing
FSG also have a PUNDIT (Portable Ultrasonic Non-destructive Digital Indicating Tester) device to measure modulus and calibrate rock strength measurements. The Pundit equipment measures both primary and shear wave velocity, which can then be converted to a modulus value. FSG has independently assessed its reliability (with the default correlations), and to establish correlations between the PUNDIT measured velocities and other laboratory-tested properties using rock cores from south east Queensland.
Small strain rock shear modulus is increasingly being used in routine design by applying a reduction factor applicable to foundations under normal serviceability conditions. The PUNDIT velocity measurement provides a reliable means of determining the small strain modulus, but this represents only an upper bound, and an appropriate modulus degradation factor is required. FSG’s database of various rock types provides this degradation factor.
Subgrade Modulus Assessment
The Light Falling Weight Deflectometer (LFWD) can be used for subgrade assessment and quality control. FSG’s David Lacey has introduced the use of LFWD technology to many Queensland projects. David’s PhD thesis is based around the use of this equipment in residual soils.
The LFWD is a surface based, dynamic plate load test that provides quick and direct measurement of a composite insitu modulus parameter of the near-surface. The direct measurement of modulus by the LFWD negates the need to indirectly estimate the parameter using Dynamic Cone Penetrometers (DCPs) or density testing, both of which have transformation errors associated when “universal”