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BEARING CAPACITY OF BORED PILE CALCULATION AND ACTUALITY

BEARING CAPACITY OF BORED PILE CALCULATION AND ACTUALITY. Prof. PhD. Le Duc Thang; M.Sc. Pham Viet Khoa. FECON Foundation Engineering and Underground Construction JSC. Paris - November 19th, 2010. Contents. Introduction

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BEARING CAPACITY OF BORED PILE CALCULATION AND ACTUALITY

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  1. BEARING CAPACITY OF BORED PILECALCULATION AND ACTUALITY Prof. PhD. Le Duc Thang; M.Sc. Pham Viet Khoa FECON Foundation Engineering and Underground Construction JSC Paris - November 19th, 2010

  2. Contents Introduction • Statistical data on results of static load test for bored piles in Hanoi • Pile bearing capacity: from calculation to actuality 3.1 The formulas for pile bearing capacity calculation 3.2 Static load test using sensor monitoring 3.3 Comparison between calculated load components and actual result from load test using sensor monitoring • Recommendations

  3. Introduction

  4. In recent years, the most popular technology for deep foundation of high rise buildings in Vietnam is bored pile. • Since then, there were many problem in bored pile construction had been solved: concrete quality in drilling mud, inhomogeneous of pile concrete, pile toe defect… • However, there are some problem in design work of bored pile has not been concerned properly • This report aim to show one of problem in bored pile design, that is pile bearing capacity determination, and the recommendation

  5. 1. Statistical data on results of static load test for bored piles in Hanoi

  6. Statistic summary According to Vietnamese Standard TCXDVN 269:2002: Pile failed when S/D approach 10% Testing load seem to be much lower than actual ultimate pile bearing capacity ? S200%DesignLoad/Diameter

  7. 2. Pile bearing capacity: from calculation to actuality

  8. Sandy clay Clayed Sand Sand 9

  9. Popular formula for Pile bearing capacity calculation Ultimate bearing capacity: Allowable bearing capacity: or

  10. Pile bearing capacity components: Toe bearing and Skin friction

  11. Normal static load test 12

  12. Static loading test using sensor monitoring Site: HH6 An Khanh - Hanoi Project Site : Vietnam Foreign Affair Head Office Project

  13. Signal Cable Strain Gauge Reinforcement Install Data Recorder

  14. 100% 200% Skin friction component: Toe bearing component: Load distribution at testing load of 200% of design load 18% 82%

  15. 100% 200% 300% Skin friction component: Toe bearing component: At testing load = 300% of design load 12% 88%

  16. Comparison between calculated bearing capacity and testing results

  17. 3. Recommendations

  18. The gap is biggest The gap is smallest 20

  19. Recommendations So far, testing load is always much lower than actual pile ultimate bearing capacity, so that, the load test result has not been used effectively 2. In bored pile bearing capacity calculation: the estimated skin friction resistance component is always much lower than actuality 3. There would be some problem with input data of soil properties for design work ? 4. Japanese Formula [2] should be used more often than others

  20. Recommendations 5. Factor of Safety (Fs) from 2.5 to 3 for bored pile bearing capacity calculation seem to be too high 6. In pile testing requirement, the testing load should be up to ultimate bearing capacity, not limited to 200% design load as usually 7. Sensor monitoring should be applied in combination with static load test to measure distribution load along pile shaft, so that, it is possible to correct the pile bearing calculation

  21. For long term design standard update: An official research for bored pile bearing capacity determination should be implemented by Researchers, Designers, and Contractors with agreed and supported by Ministry of Construction to find the answer for following question: 1) What is the best way for soil investigation for bored pile design ? Key soil properties ? 2) Which is the best suitable calculation formula should be applied in Vietnam Soil condition ? And the Fs ? 23

  22. THANK YOU VERY MUCH FOR YOUR ATTENTION !

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