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) 1 Prof. V.S. Raju Engineers Day,

Geotechnical Engineering Practice S.NoBest Practice (Mostly followed by developed world) Most Situations in India at present After Site Selection 1 Contour SurveySometimes available 2 Geology of site by expertBy the Geotechnical Agency as part of the Geotechnical Investigation 3 Preliminary Geotechnical Investigation by an accredited Agency Rarely Done 2 Prof. V.S. Raju

Geotechnical Engineering Practice Contd… 3 S.NoBest Practice (Mostly followed by developed world) Most Situations in India at present 4. Project layout with location of important structures made available to Geotechnical consultant. Generally not made available to Investigation Agency 5. Scope of Detailed Geotechnical Investigation: Geotechnical Consultant in Consultation with structural consultant and on the basis of structural details. Not the common practice. Most often a bill of quantities and a standard set of laboratory tests are given to the agency by Architect/Structural Designer. Inappropriate also because the laboratory tests are a function of the type of soil strata. Prof. V.S. Raju

Geotechnical Engineering Practice Contd… 4 S.N o Best Practice (Mostly followed by developed world) Most Situations in India at present 6. Detailed Soil Investigation by an accredited and qualified investigation agency. Investigations done under independent supervision by a qualified person. Lack of accreditation process. Most investigation agencies are not accredited.They do not have trained manpower. Mostly not supervised 7. Investigation report by the agency giving the results of field and laboratory tests only. No Foundation Recommendations. Report containing Results of Field and Laboratory Tests Recommendations for Foundations Safe Bearing Capacity and Pile Capacities without having full details of the structures Prof. V.S. Raju

Geotechnical Engineering Practice Contd… 5 S.NoBest Practice (Mostly followed by developed world) Most Situations in India at present 8. Interpretation of the results by a Specialist Foundation Consultant and recommendation for type of foundation and foundation parameters. Very rarely the case. Investigation Agency hardly has qualified and experienced Foundation Engineers. 9. Interaction between Foundation and Structural Consultant and finalisation of Foundation Design. Mostly Absent. Prof. V.S. Raju

6 S.N o Ideal/ International Practice Most Situations in India at present 10.Involvement of Foundation Consultant during execution, review of results of further tests. Ex. Pile Load Tests (Initial & Routine) Very Rare. 11.Settlement Observations and information to Foundation Consultant. Very Rare. 12.Foundation Performance assessment and report by Foundation Consultant Absent. Geotechnical Engineering Practice Contd… Prof. V.S. Raju

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

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

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

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

CASE STUDIES Prof. V.S. Raju 11

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

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 13 Terminal T3 at Delhi International Airport, DIAL Prof. V.S. Raju

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 m x 1.5 m In first case, settlements (S) at 40 t/m 2 is 4 mm In second case, S at 38 t/m 2 is 5.4 mm. 14 Prof. V.S. Raju

Results of Footing Load Tests for Delhi International Airport 15 Prof. V.S. Raju

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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. 17 Prof. V.S. Raju

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. 18 Prof. V.S. Raju

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

Preliminary Design proposed by a Singapore Structural Consultant: -A Large Piled Raft of size 54 m x 68 m (3672 m 2 ) with 600 mm dia bored piles of varying length -Total number of piles = 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. Pile Assisted Raft for 51 Storey Tower continued…. 20 Prof. V.S. Raju

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. Pile Assisted Raft for 51 Storey Tower continued…. 21 Prof. V.S. Raju

Revised Pile Assisted Raft Design based on Fresh Analysis: Raft Area = 1740 m 2 (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) Pile Assisted Raft for 51 Storey Tower continued…. 22 Prof. V.S. Raju

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. Pile Assisted Raft for 51 Storey Tower continued…. 23 Prof. V.S. Raju

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 Pile Assisted Raft for 51 Storey Tower continued…. 24 Prof. V.S. Raju

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. 25 Prof. V.S. Raju

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

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. 27 Prof. V.S. Raju 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 28 Summer Palms continued… Prof. V.S. Raju

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

Tower No.Current Updates of each Tower Settlement (Measured) (1st Week-August’15) (4 points on 4 corners) Remarks FG+14 casted and Brickwork is in progress 58 to 60 mmMonitoring started from raft construction GG+14 casted and Brickwork is in progress 49 to 50 mmMonitoring started after construction of ground floor HG+5 casted and 6 th floor is in progress 24 to 25 mmMonitoring started after construction of Raft IG+5 casted and 6 th floor is in progress 23 to 25 mmMonitoring started after construction of Raft Settlement observations: Predicted 67 to 75 mm Prof. V.S. Raju 30

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

 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/m 2 ? Hard Rock SBC 400 t/m 2 Hard Murrum 80 t/m 2 Soft Clay 4 m thick 0 t/m 2 75 m 30 m Tower Foot Print Prof. V.S. Raju 32

Acknowledgements 33 Prof. V.S. Raju  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

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