Location
Chicago, Illinois
Date
01 May 2013, 2:00 pm - 4:00 pm
Abstract
India has massive developments, urbanization, housing, communication in last decade. The optimization of cost and saving construction time to complete, are now new aspects which geotechnical engineers are facing. Till today the typical design of shallow foundations of structure-buildings, fly over and dams on non-plastic silty fine sand subsoils found in alluvial deposits of state like Uttar Pradesh, Punjab, Gujarat, Bengal and long coastal belt, were designed by age old practice based on soil mechanics of 1948. Such proven practice became BIS codes for design and construction of structural foundations in 1976-81. The common sense and observational approach of Terzaghi (1959) did not confirm such interpretation of Standard Penetration (SP) test. SP test on non – plastic silty sand at 2 to 3 m below ground surface, being loose (Rd < 15%), had permissible bearing capacity for 25 mm settlement (qa25) less than 100 kPa. This required almost double concrete in footings. Vast country with fast growth had more than million structures built/year, saving of RCC would be around 900 million cubic meter/year. The time reduced will be added advantage. Even up to 10m depth, at number of sites N recorded as 5 to 10 blows/30cm, was considered as “loose” to “medium” by the code indicating prima-facie high liquefaction potential under low seismic activity. This phobia did not spare proposed, under construction over years and existing structures from a long process of reinvestigations, consultants opinions and cost. High rise housing at Chennai, Delhi, Surat, monumental structures at Delhi, Agra, Ahmedabad, Kollkata, Panipat, Rajasthan suffered setback and perpetual suspense due to lack of proper interpretation. Some dams under construction like Ukai, Tenughat, barrages in West Bengal, Delhi, unique projects like Akshardham (Delhi) had to be stopped or delayed by suspected liquefaction. Long chain of opinions and additional tests like evaluation of Rd by alternative methods, rechecking of SPT values, blasting test as well as cross bore holes shear wave velocity tests had to be planned to remove notional interpretation. Study proposes to eliminate such decays & cost escalation by providing alternatives. Typical case studies, showing methodology are also illustrated. Authors with professionals (30 numbers) in geotechnical engineering practicing in India formed a TC-16 technical group (Year 2000-2005) to prepare a report on ground characterization by in-situ testing. The final recommendations for interpretation of SP test (N) and DCP test (NC) for non-plastic alluvial deposit, investigated as per IS code are presented in the form of a chart. It gives for observed N or NC at P0’ (effective overburden pressure) the relative density (Rd), ∅’ (angle of shear resistance), E (deformation modulus) and permissible bearing capacity for 40 mm permissible settlement. The chart also indicate likely liquefaction potential at depth for a = 0.1g for preliminary analysis. Typical case studies have been illustrated. The authors advocated bore holes to be supplemented by uncased DCPT adequate in number, to provide recommendation for an area (not point). If results are not satisfying commonsense, check by in-situ tests for Rd, plate load, even prototype test shall be used before resorting to rejection of site or adopting ground improvement. Any recommendation, for probable liquefaction for existing or under construction project, must be checked by proper reinvestigations and interpretation.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
7th Conference of the International Conference on Case Histories in Geotechnical Engineering
Publisher
Missouri University of Science and Technology
Document Version
Final Version
Rights
© 2013 Missouri University of Science and Technology, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
Desai, Mahesh D.; Patel, Jignesh B.; and Desai, Nehal H., "Application of Case Studies to Practice in Foundation Engineering in India" (2013). International Conference on Case Histories in Geotechnical Engineering. 6.
https://scholarsmine.mst.edu/icchge/7icchge/session01/6
Application of Case Studies to Practice in Foundation Engineering in India
Chicago, Illinois
India has massive developments, urbanization, housing, communication in last decade. The optimization of cost and saving construction time to complete, are now new aspects which geotechnical engineers are facing. Till today the typical design of shallow foundations of structure-buildings, fly over and dams on non-plastic silty fine sand subsoils found in alluvial deposits of state like Uttar Pradesh, Punjab, Gujarat, Bengal and long coastal belt, were designed by age old practice based on soil mechanics of 1948. Such proven practice became BIS codes for design and construction of structural foundations in 1976-81. The common sense and observational approach of Terzaghi (1959) did not confirm such interpretation of Standard Penetration (SP) test. SP test on non – plastic silty sand at 2 to 3 m below ground surface, being loose (Rd < 15%), had permissible bearing capacity for 25 mm settlement (qa25) less than 100 kPa. This required almost double concrete in footings. Vast country with fast growth had more than million structures built/year, saving of RCC would be around 900 million cubic meter/year. The time reduced will be added advantage. Even up to 10m depth, at number of sites N recorded as 5 to 10 blows/30cm, was considered as “loose” to “medium” by the code indicating prima-facie high liquefaction potential under low seismic activity. This phobia did not spare proposed, under construction over years and existing structures from a long process of reinvestigations, consultants opinions and cost. High rise housing at Chennai, Delhi, Surat, monumental structures at Delhi, Agra, Ahmedabad, Kollkata, Panipat, Rajasthan suffered setback and perpetual suspense due to lack of proper interpretation. Some dams under construction like Ukai, Tenughat, barrages in West Bengal, Delhi, unique projects like Akshardham (Delhi) had to be stopped or delayed by suspected liquefaction. Long chain of opinions and additional tests like evaluation of Rd by alternative methods, rechecking of SPT values, blasting test as well as cross bore holes shear wave velocity tests had to be planned to remove notional interpretation. Study proposes to eliminate such decays & cost escalation by providing alternatives. Typical case studies, showing methodology are also illustrated. Authors with professionals (30 numbers) in geotechnical engineering practicing in India formed a TC-16 technical group (Year 2000-2005) to prepare a report on ground characterization by in-situ testing. The final recommendations for interpretation of SP test (N) and DCP test (NC) for non-plastic alluvial deposit, investigated as per IS code are presented in the form of a chart. It gives for observed N or NC at P0’ (effective overburden pressure) the relative density (Rd), ∅’ (angle of shear resistance), E (deformation modulus) and permissible bearing capacity for 40 mm permissible settlement. The chart also indicate likely liquefaction potential at depth for a = 0.1g for preliminary analysis. Typical case studies have been illustrated. The authors advocated bore holes to be supplemented by uncased DCPT adequate in number, to provide recommendation for an area (not point). If results are not satisfying commonsense, check by in-situ tests for Rd, plate load, even prototype test shall be used before resorting to rejection of site or adopting ground improvement. Any recommendation, for probable liquefaction for existing or under construction project, must be checked by proper reinvestigations and interpretation.
