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BU3102 Construction Technology

BU3102 Construction Technology. Discuss testing of piles with case studies. Introduction. There are mainly 2 types of piles Displacement Piles Replacement Piles. Problems in Pile Construction. A specialist activity Problem reduces the performance of the piles

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BU3102 Construction Technology

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  1. BU3102Construction Technology Discuss testing of piles with case studies

  2. Introduction There are mainly 2 types of piles • Displacement Piles • Replacement Piles

  3. Problems in Pile Construction A specialist activity Problem reduces the performance of the piles Pile load tests to ensure the completed piles are adequately constructed to carry the designed load. If the load tests failed, expensive remedial works have to be done. Hence it is impt for the contractor to be aware of such problems and minimised them.

  4. Problems in Pile Construction Driven Piles Design Concrete (cracks, handling, joints) Steel (driving conditions, stresses) Timber (brooming during driving) Installation pile driving (spalling, boulders, deviations) Associated Ground Movements Heave reduce bearing capacity

  5. Problems in Pile Construction Bored Piles Excavation of Boreholes (Formation of cavities/overbreak, Base of Boreholes,Water in Boreholes) Concreting the piles (quality, placing, extracting casing, design of reinforcement)

  6. Problems in Pile Construction Separation of pile shaft caused by extraction of casing The effect of a large water- filled cavity after extraction of casing

  7. Types of Test Ultimate Load Test Test piles are tested to confirm design assumptions, and therefore tested to ultimate load. It provides an indication of settlement of a contract pile in isolation and under specified load conditions.

  8. Types of Test Working Load Test This is a test load applied to a selected working pile to confirm that is suitable for the load specified and that it is in conformity with the contract requirements. The test load is normally stipulated to be some multiple of the design load, usually 150%.

  9. Methods of pile testing • Compression Pile Load Test • Uplift Test • Lateral Pile load Test • Integrity Test

  10. Compression Load Test Compression load test is carried out to assess the load carrying capacity of the pile. - It is carried out by simulating the loads - Method selected depends to some extent - on soil conditions - the size of the site - Number of piles to be tested - haulage costs for the kentledge

  11. Uplift test Uplift or pull out test on piles is used to determine the negative skin friction of the soil. - critical where basement or underground construction is involved - can be made at a continuous rate of uplift (CRU), or an incremental loading basis (ML)

  12. Uplift test

  13. Lateral pile load test Lateral pile load test is to determine the behavior of piles under lateral loading which come from a variety of sources including wind, earthquakes, waves, and ship impacts.

  14. Lateral pile load test A field test carried out to determine the lateral resistance of pile caps.

  15. Lateral pile load test

  16. Integrity test Integrity testing is a tool in appraising quality of piling carried on site and would ideally reveal the nature and extent of all defects

  17. Load test procedures Maintained Load Test This test is convenient for testing end-bearing piles and for determining the load/settlement characteristics in clay soils Constant Rate of Penetration Test The prime objective of the test is usually to determine the ultimate load capacity the loading is strain-controlled and a set rate of penetration of the pile load is specified Method of Equilibrium This procedure is primarily designed to determine the ultimate load capacity, although it also appears to provide reasonable settlement data

  18. PILE LOAD TEST

  19. Compression load test Kentledge- usually comprises either concrete blocks or pig iron blocks Procedure: • The test load is applied by means of a hydraulic jack reacting against dead weights known as kentledge • incremental load method is employed for the testing of the piles • The load at each stage is maintained for a period of one to two hours until the settlement of the pile has substantially ceased or its rate has become negligible • The worker then proceeds to start jacking so as to increase load on pile • After the addition of the final increment (working load is reached), the test load is left on the pile for about two to three days before the load is released

  20. Compression load test Tension Pile Reaction Systems- are almost invariably specially installed to provide reaction Procedure: • a sufficient number of reaction piles are inserted in the ground with the test pile at the centre • connect the piles using test beam(s) with the jack at the centre • Jack up the whole arrangement • Measure settlement of the test pile • Plot time-settlement curve and find out rate of decrease of movement

  21. Tension Pile Reaction Systems One effect of too close spacing between test pile and reaction piles

  22. Tension Pile Reaction Systems

  23. Compression load test Ground Anchor Tension System- Use ground or rock anchors to provide uplift resistance Procedure: • install a sufficient number of anchor piles or suitable anchoring devices so as to provide adequate reactive capacity • test beam of sufficient size and strength is used to avoid excessive deflection under load • Anchor pile test is seldom applied in Singapore due to the popularity of Kentledge pile test

  24. Ground Anchor Tension System Testing rig for compressive test on pile using cable anchors for reaction

  25. Ground Anchor Tension System Example of a multiple ground anchor reaction for raking piles Pile load test set up with steel traps over test beam bolted to anchor piles

  26. Ground Anchor Tension System Two test beams "doubled" with only two anchor piles Two test beams "crisscrossed" using four anchor piles

  27. Methods of Settlement Measurement • Optical methods • Dial gauge extensometers • Stretched wire over a scale • Electrical methods

  28. Methods of Settlement Measurement

  29. Load measurement Load Measurement is preferably carried out using a load cell, and several types are readily available. Commonly adopted load measuring devices are:

  30. Load measurement Hydraulic load capsule Load columns

  31. Load measurement Proving rings Load Cell

  32. INTEGRITY TESTS

  33. Integrity Testing There are basically 9 types of tests that are generally recognized as “integrity tests” and they are as follows: - Acoustic tests - Radiometric tests - Seismic (sonic echo) tests - Stress-wave tests - Dynamic response tests - Electrical tests - Excavation - Exploratory boring and drilling - Closed circuit television methods

  34. Integrity Testing Acoustic tests

  35. Integrity Testing Acoustic tests A display of results for acoustic test (Photograph courtesy of Testconsult Ltd., Lymm)

  36. Integrity Testing Acoustic tests General arrangement of equipment for twin tube acoustic test (Diagram courtesy of Testconsult Ltd.)

  37. Integrity Testing Seismic (Sonic echo) tests A synthetic pile and the reflectogram

  38. Integrity Testing Seismic (Sonic echo) tests In the Sonic test, the top of the pile is hit with a plastic hammer and the reflected wave is recorded by suitable computerized equipment. From the resulting signal, or reflectogram, one can determine both length and continuity of the pile

  39. Integrity Testing Seismic (Sonic echo) tests Schematic diagram for seismic (sonic echo) tests

  40. Integrity Testing Seismic (sonic echo) tests .

  41. KENTLEDGE TESTCASE STUDY

  42. Case Study: Kentledge Load Test • Location: Toa Payoh RC30 project Toa Payoh Lorong 2 • Working load test was conducted on 1 number of 1400mm diameter bored pile (Pile Ref: SLT 2 Blk 147 – G20/3)

  43. Toa Payoh HDB RC30

  44. Purpose : • To proof load the bored pile to 2 times the designed working load, • i.e. 1600 tons to verify the working load of bored piles • Working load = 800 tons

  45. Prior to the load test…

  46. Pile head is prepared… • Cut and leveled • Receive a 50mm thick mild steel plate

  47. Loading Blocks are delivered and stored on site prior to setting up

  48. Kentledge blocks would be supported on a crib work comprising of I-beams

  49. The whole crib is position such that its center of gravity is on the axis of the pile

  50. Bearing pressure under the supporting cribs shall be such as to ensure stability of the kentledge stack Kentledge shall not be carried directly on the pile head

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