Displaying Items By Tag: Site Characterization

A draft method of soil description was produced by a working group of the New Zealand Geomechanics Society (now the New Zealand Geotechnical Society) in 1980. Members of the working Group were:

- Dr S A L Read  - New Zealand Geological Survey (now GNS Science)

- Mr P J Millar  - Tonkin & Taylor Ltd

- Mr N S Luxford  - Babbage Consultants Ltd

- Mr A J Olsen  -Worley Consultants Ltd (now Maunsell Ltd)

The draft was expanded to include a method for the description of rock in 1985, and published in 1988 as “Guidelines for the Field Description of Soils and Rocks in Engineering Use”.

This 2005 revision has been prepared with the objectives of keeping pace with international practice, defining terms used in communicating soil and rock properties in New Zealand and giving emphasis to describing properties that are of engineering significance.

In particular, the soil description part of the Guideline has been revised to emphasize the distinction between classification and description. One notable change from the 1988 Guideline is the omission of Table 2.7 (USBR Unified Soil Classification Chart). This is in keeping with the 3rd edition of the USBR Earth Manual and changes to presentation of the Unified Soil Classification System in ASTM standards.

The rock description part of the Guideline has been simplified, and the section on weathering revised to make it more relevant to the range of rock types normally met in New Zealand. A more complete set of terms is provided to allow description of rock in both core and outcrop.

Contributors to the 2005 revision are:

- David Burns  - Maunsell Ltd

- Steve Crawford  - Tonkin & Taylor Ltd

- Geoffrey Farquhar - Maunsell Ltd

- Doug Johnson - Tonkin & Taylor Ltd

- Dr Laurie Wesley - University of Auckland

- Ann Williams - Beca Infrastructure Ltd

It is envisaged that in future the Guideline be reviewed and updated on a regular basis. To this end, all submissions on the Guideline should be registered with www.nzgeotechsoc.org.nz.

Guideline for the Field Classification and Description of Soil and Rock for Engineering Purposes

A 30-m long railroad embankment failure that occurred on May 25 2011 in the city of Ann Arbor, Michigan, is presented. Emphasis is given on the field observations of the failure, the characterization of the site conditions and the seepage and slope stability analyses, all of which represent important components of the training and practice of a geotechnical engineer. The failure occurred following a record wet season that resulted in ponding water against the embankment and high enough water pressures and exit gradients that resulted in instability of the railroad embankment. Detailed background material and the methodology for using the case history in geotechnical engineering education are presented.

Macroseismic observations in the meizoseismal area of the Achaia-Ilia, Greece, Mw 6.4 earthquake of 8 June, 2008, have shown that soil liquefaction occurred at a number of sites up to distances of 25 km from the causative fault. In one of these sites (SITE-I at coastal zone of Kato Achaia) the occurrence of liquefaction was extensive and was followed by lateral spreading. In another nearby site (SITE-II) only marginal liquefaction (or nonliquefaction) was observed. Following the macroseismic observations, a geotechnical investigation was carried out at SITE-I and SITE-II which included exploratory boreholes with continuous sampling, SPT measurements, CPT soundings, surface wave measurements (SASW, MASW, ReMi) and laboratory testing. Based on the results of geotechnical investigation, the soil stratigraphy and pertinent soil properties were evaluated in the liquefaction/nonliquefaction locations. The assessment of peak ground acceleration at the area of SITE-I and SITE-II was based on attenuation relations and shaking table tests performed to simulate the observed behavior of an overturned (during the main shock), barrel-shaped, plastic, water filled container sitting on the ground surface at SITE-I. It is believed that the data presented in this paper can be used to 1) check the validity of current liquefaction susceptibility criteria/liquefaction triggering relationships, and 2) establish a well documented liquefaction case history that can be part of future liquefaction databases.

In 1997 the Minnesota Department of Transportation (Mn/DOT) began operating fully automated computer controlled geotechnical testing equipment, replacing many existing systems. Existing systems required active technician oversight particularly for consolidation and triaxial testing. An increase in the number of projects requiring testing, shorter project time-lines, rapid advances in computer technologies, a decrease in the number of skilled technicians, and a desire to reduce project costs, made automated systems especially attractive. As a result of the effectiveness of the automated systems, today, the geotechnical section routinely conducts specialized tests previously available only to academic institutions and research labs. Automated laboratory testing combined with automated in-situ cone penetration testing (CPT) has dramatically improved overall site characterization quality while reducing both cost and time associated with geotechnical investigation. Test reliability, repeatability, accuracy, and confidence in the test results has improved, while decreasing subjectivity and operator error. Measurable cost savings, both in field costs and lab costs, and increases in efficiency have been realized, even after the relatively large investment cost of the new equipment.