Status quo of Standard Penetration Test in India: A Review of Field Practices and Suggestions to Incorporate in IS 2131
By: Panjamani, Anbazhagan P
.
Contributor(s): Ingale, Sagar G.
Publisher: Germany Springer 2021Edition: Vol.51(2), April.Description: 421-434p.Subject(s): Civil EngineeringOnline resources: Click here
In:
Indian geotechnical journalSummary: SPT (Standard Penetration Test) being the most widely used field test has not been effectively regulated in India. Guidelines regarding hammer weight, the height of fall and use of liner are not followed correctly in the field, and guidelines for energy transfer efficiency and hammer blow rate are not addressed in the BIS (Bureau of Indian Standards) code for SPT. In this paper, some standard provisions on SPT in India and other countries are compared, and few observations on field SPT tests are presented. Operational and equipment-related variables, such as weights and dimensions of hammer, anvil, and drill rod, were noted in the field. Furthermore, hammer blow rate and inclination of guide rods during the field tests were also observed and are presented. It is found that IS 2131 (1981) does not provide standard dimensions of components of SPT set-up, and hence, there is a large variation in SPT set-up in practice and the whole set-up is usually an ensemble of locally manufactured components. This is a major defect in the SPT code and needs to be addressed. Sixteen different SPT set-ups were observed, which were employed on field SPT tests on 30 boreholes. Thirteen of the observed set-ups were used for the soil investigation for a large infrastructure project. Hammer blow rates are found to be very low as compared to those stated in IS 1893 (2016), DSO-98-17 (1999) and ASTM D6066 (2011). The inclination of guide rods in field was observed to be more than 5°, which causes friction between guide rod and drive weight and, hence, reduces the free fall velocity. These variables affect N values and international studies have reported correction factors to account for these. Because of the fact that large variety of set-up was observed, it will be prudent to standardise the dimensions of hammer and anvil, and hammer release mechanism to bring uniformity in SPT operations. Furthermore, normalising field N values to a standard energy ratio of 60% as per the international practice will facilitate reliability of N values obtained from different set-ups.
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School of Engineering & Technology (PG) Archieval Section | Not for loan | 2021-2022223 |
SPT (Standard Penetration Test) being the most widely used field test has not been effectively regulated in India. Guidelines regarding hammer weight, the height of fall and use of liner are not followed correctly in the field, and guidelines for energy transfer efficiency and hammer blow rate are not addressed in the BIS (Bureau of Indian Standards) code for SPT. In this paper, some standard provisions on SPT in India and other countries are compared, and few observations on field SPT tests are presented. Operational and equipment-related variables, such as weights and dimensions of hammer, anvil, and drill rod, were noted in the field. Furthermore, hammer blow rate and inclination of guide rods during the field tests were also observed and are presented. It is found that IS 2131 (1981) does not provide standard dimensions of components of SPT set-up, and hence, there is a large variation in SPT set-up in practice and the whole set-up is usually an ensemble of locally manufactured components. This is a major defect in the SPT code and needs to be addressed. Sixteen different SPT set-ups were observed, which were employed on field SPT tests on 30 boreholes. Thirteen of the observed set-ups were used for the soil investigation for a large infrastructure project. Hammer blow rates are found to be very low as compared to those stated in IS 1893 (2016), DSO-98-17 (1999) and ASTM D6066 (2011). The inclination of guide rods in field was observed to be more than 5°, which causes friction between guide rod and drive weight and, hence, reduces the free fall velocity. These variables affect N values and international studies have reported correction factors to account for these. Because of the fact that large variety of set-up was observed, it will be prudent to standardise the dimensions of hammer and anvil, and hammer release mechanism to bring uniformity in SPT operations. Furthermore, normalising field N values to a standard energy ratio of 60% as per the international practice will facilitate reliability of N values obtained from different set-ups.
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