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Role of Foundation Consultants in optimizing time and cost in large projects – Case Studies

Engineers Day, 15.09.2015. Role of Foundation Consultants in optimizing time and cost in large projects – Case Studies. Prof . V.S.Raju ( Formerly: Director, IIT Delhi & Professor and Dean, IIT Madras) Email: rajuvs_b@yahoo.com.

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Role of Foundation Consultants in optimizing time and cost in large projects – Case Studies

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  1. Engineers Day, 15.09.2015 Role of Foundation Consultants in optimizing time and cost in large projects – Case Studies Prof. V.S.Raju (Formerly: Director, IIT Delhi & Professor and Dean, IIT Madras) Email: rajuvs_b@yahoo.com Prof. V.S. Raju

  2. Geotechnical Engineering Practice Prof. V.S. Raju

  3. Geotechnical Engineering Practice Contd… Prof. V.S. Raju

  4. Geotechnical Engineering Practice Contd… Prof. V.S. Raju

  5. Geotechnical Engineering Practice Contd… Prof. V.S. Raju

  6. Geotechnical Engineering Practice Contd… Prof. V.S. Raju

  7. QUALITY OF INVESTIGATION World Standard India • Highly sophisticated and mechanised equipment. • Continuous core sampling (in soils as well). • SPT equipment with • automatic hammer release. • Static cone test with electric cone and • piezocone (crucial for • assessment of • liquefaction) • Poor quality of the equipment. • Shell & Auger, Wash • Boring is also common • SPT Equipment -manual operation • Static cone penetration equipment • with Mechanical cone. Prof. V.S. Raju

  8. Pic.1.1. Non Standard Equipment No safety measures Pic. 1.2. Global Standard Prof. V.S. Raju

  9. Pic. 1.4. SPT with Auto Trip Hammer + Standard Rig Pic. 1.3 SPT Hammer Dropped Manually (2013) Prof. V.S. Raju

  10. Pic. 1.6 Crawler Mounted SCPT Equipment Pic.1.5 Static Cone Penetration - Reaction with Sand bags Prof. V.S. Raju

  11. CASE STUDIES Prof. V.S. Raju

  12. Delhi International Airport – Terminal T3 Prof. V.S. Raju

  13. Terminal T3 at Delhi International Airport, DIAL • Terminal T1 was on Pile Foundation • Soil Investigation report recommends pile foundation for T3 • EPC contract awarded on the basis of pile foundation. • Review by Prof. V.S. Raju Prof. V.S. Raju

  14. Terminal T3 Continued.. • Soil Strata : Sandy silt and silty sand. • SPT N value at Founding level is 22 to 33 and increases with depth • For conforming adequacy of raft, 2 footing load tests were done at Founding level. • Footing size - 1.5 m x 1.5 m • In first case, settlements (S) at 40 t/m2 is 4 mm • In second case, Sat 38 t/m2is 5.4 mm. Prof. V.S. Raju

  15. Results of Footing Load Tests for Delhi International Airport 1st Footing load test: Soil type = Sandy silt SPT N = 50 Size of footing = 1.5 m x 1.5 m Load Intensity, q = 40 t/m2, S =4 mm * 0.82 = 1119 Kg/cm2 As per Shultze and Muhs For SPT N = 50, Es = 800 Kg/cm2 Ratio = 1119/800 = 1.4 Prof. V.S. Raju

  16. 2nd Footing load test: Type of soil = Silt with fine sand SPT N = 22 Size of footing = 1.5 m x 1.5 m For Load Intensity, q = 38 t/m2, S=5.4 mm * 0.82 = 787 Kg/cm2 As per Shultze and Muhs For SPT N = 22, Es = 530 Kg/cm2 Ratio = 787/530 = 1.48 Prof. V.S. Raju

  17. Delhi Airport – T3 • Based on these results, Raft Foundation was found fully satisfactory and adopted. • 6 months of construction Time Saved – A huge advantage, on total investment of 12,000 crores. • Direct cost savings as well. • Raft settlements were monitored and were found well with in limits. Prof. V.S. Raju

  18. 3. Pile Assisted Raft for a 51 Storey Tower at Gurgaon • High rise tower with 51 storeys and 2 Basements. • Strata : Predominantly Sandy Silt with water table 25 m below Ground level • Founding Level: 12 m below Ground Level • SPT N value is 35 & above below Founding level. Prof. V.S. Raju

  19. 51 storey building for IREO at Sector 67, Gurgaon (46 storeys completed) Prof. V.S. Raju

  20. Pile Assisted Raft for 51 Storey Tower continued…. Preliminary Design proposed by a Singapore Structural Consultant: • A Large Piled Raft of size 54 m x 68 m (3672 m2) with 600 mm dia bored piles of varying length • Total number of piles = 345. • Total Settlement of the Piled Raft is restricted to 50 mm. - In Piled Raft, Raft is the main bearing element and piles are used as settlement reducers. Prof. V.S. Raju

  21. Pile Assisted Raft for 51 Storey Tower continued…. Review by Prof. V.S. Raju: • Additional Investigations were proposed by us with 2 additional boreholes, 50 m depth. • Fresh Assessment and Analysis led to a solution of reduced raft size and number of piles. Prof. V.S. Raju

  22. Pile Assisted Raft for 51 Storey Tower continued…. Revised Pile Assisted Raft Design based on Fresh Analysis: • Raft Area = 1740 m2 (reduction 50%) • Bored Piles of 600 mm diameter and 18 m long • Total number of piles = 94 (reduction 70%) • Settlements restricted to 50 mm (as desired by the client) Prof. V.S. Raju

  23. Pile Assisted Raft for 51 Storey Tower continued…. • Approximately 25 % of total load will be transferred to piles from raft. • Initially load will be predominantly transferred to the piles. • At allowable settlement of 50 mm, the ultimate capacity of the piles will be fully mobilized. • Hence Piles are designed for ultimate capacity. Prof. V.S. Raju

  24. Pile Assisted Raft for 51 Storey Tower continued…. Settlement Observations. • Settlements of the tower are monitored at 5 points on the raft. • As of July 2014, 35 floors are completed • Estimated load transferred = 47 % • The maximum observed settlement is only 10 mm. • FIRST TIME ADOPTION Of PILED RAFT IN INDIA Prof. V.S. Raju

  25. Project: Summer Palms, Sector 4A, Bahadurgarh, Haryana. 13 Blocks, G+14 Original Investigation: • 11 Boreholes • Strata- Silty sand and sandy silt layers with water table at 2 m below GL. • SPT N values – 2 to 10 up to 7 m below Ground Level • Layers up to 7 m below ground level are prone to liquefaction. • Pile Foundation recommended. Prof. V.S. Raju

  26. Summer Palms– Artistic View Prof. V.S. Raju

  27. Summer Palms continued… Review by Prof. V.S. Raju Supplementary Investigation: • 14 Static Cone penetration Tests (SCPT) • 8 SCPTs using Mechanical Cone • 6 SCPTs using Electric Cone with Pore Pressure sensors. • Confirmation of weak strata up to 7 m below ground level. Prof. V.S. Raju

  28. Summer Palms continued… Foundation Adopted: • Vibrostone columns to mitigate liquefaction and improve soil stiffness • 900 mm diameter Stone Columns installed at 2 m c/c spacing using bottom dry feed method • Raft Foundation on improved ground. • Trial with Footing load tests on vibro stone columns • 2 m x 2 m Footing (Single Column) • 4 m x 4 m Footing (4 columns) • SCPT tests between columns after installation. • Significant ground improvement Prof. V.S. Raju

  29. Settlement Monitoring Points Monitoring Points Prof. V.S. Raju

  30. Settlement observations: Predicted 67 to 75 mm Prof. V.S. Raju

  31. L&T Serene County Hyderabad Prof. V.S. Raju

  32. Extreme Issue with one of the 10 towers, 14 storeyed • Tower Dimension : 75 m x 30 m • Recommended SBC by the soil Investigation Agency 30 t/m2? 75 m Soft Clay 4 m thick 0 t/m2 30 m Hard Murrum 80 t/m2 Hard Rock SBC 400 t/m2 Tower Foot Print Prof. V.S. Raju

  33. Acknowledgements • Larsen & Toubro Limited • IREO, New Delhi • UMANG Realtech Pvt Ltd., New Delhi • M/s Keller Ground Engineering India Pvt. Ltd • Who carried out the Ground Improvement and Monitoring Settlements Prof. V.S. Raju

  34. THANK YOU Jai Hind Prof. V.S. Raju

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