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BU3102 CONSTRUCTION TECHNOLOGY III

BU3102 CONSTRUCTION TECHNOLOGY III. With case studies, discuss construction in excavations supported by sheet piling. MY SITE. Typical steel sheet piles that are used in Singapore. TYPES OF SHEET PILING. Timber Piles Concrete Sheet Piles Steel Sheet Piles A) Tapered Piles

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BU3102 CONSTRUCTION TECHNOLOGY III

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  1. BU3102CONSTRUCTION TECHNOLOGY III With case studies, discuss construction in excavations supported by sheet piling

  2. MY SITE

  3. Typical steel sheet piles that are used in Singapore.

  4. TYPES OF SHEET PILING • Timber Piles • Concrete Sheet Piles • Steel Sheet Piles • A) Tapered Piles • B) High Modulus Piles • Vinyl Sheet Piles

  5. 3. Steel Sheet Piles A) Tapered Piles The alignment of the piles can be corrected by using tapered piles. When a small amount of taper is sufficient, taper piles can be conveniently fabricated on-site

  6. 3. Steel Sheet Piles B) High Modulus Piles This type of section has been developed to meet the demand for sheet piling capable of supporting bending moments which are in excess of the capacity of conventional sheet pile sections

  7. 4. Vinyl Sheet Piles

  8. FACTORS AFFECTING CHOICE OF SHEET PILES • Soil Condition • Depth of Excavation • Time • Cost • Level of Water Table

  9. SITE CONDITIONS • Confined site along Upper Paya Lebar Road, surrounded by multi-storey factories and office buildings • Restrictions as to the height of equipment (e.g. cranes) due to site’s close proximity to Paya Lebar Military Airport • Poor soil condition as according to the boring records, soil at the surface (to 2.5m below ground) consists of loose sand with some clay and shell fragments

  10. SITE CONDITIONS • Further down, the soil composition consists of mainly light bluish grey marine clay and clayey silt • Site set on marine clay which is low in shear strength and is high in compressibility

  11. DECISION The PM decided to use steel sheet piles because…..

  12. TYPES OF DRIVING METHODS Modern installation systems may be divided into 4 categories:       1. Impact driving        2. Vibratory driving        3. Pressing        4. Other special driving systems

  13. 1. Impact Driving A) Drop Hammer This hammer is easily adopted to drive any of the pile sections for all ground conditions. The weight of the hammer is lifted by cable operation, by steam or by hydraulic pressure

  14. 1. Impact Driving B) Diesel Hammers

  15. 1. Impact Driving C) Hydraulic Hammers

  16. 2. Vibratory Driving • The principle of vibratory driving is the reduction of friction between the pile and the soil • The vibrations will temporarily disturb the soil around the pile, causing minor liquefaction, which results in a noticeable decrease in resistance between soil and pile

  17. 3. Pressing

  18. 3. Pressing

  19. 4. Special Driving Systems • Impact hammers incorporating a special cushion system formed out of steel springs or inert gas to transmit the driving energy to the pile more smoothly and over a longer period of time • A driving system which vibrates and presses on sheet piles simultaneously

  20. SEQUENCE OF DRIVING • Pitch and Drive • Panel Driving • Staggered Driving

  21. DRIVING ASSISTANCE 1. Blasting 2. Drilling

  22. 1. Blasting A) Normal blasting - explosives are used to create a V-shaped trench along the proposed line of the wall B) Shock blasting - uses very low powdered explosive to reduce solid rock to fine granular material

  23. 2. Drilling Pre-drilling allows easier driving, vibrating and pressing • Soils including hard rock layers can be made suitable for driving by this method • the soil may be sufficiently loosened by auger

  24. FACTORS AFFECTING DRIVING METHODS 1. Soil Conditions 2. Noise and Vibration

  25. 1. Soil Condition A) Granular Soil

  26. 1. Soil Condition B) Cohesive Soil

  27. 2. Noise and Vibration

  28. Decision After considering through the factors, PM decided to used the vibratory driving method to install the steel sheets piles.

  29. CONSTRUCTION PROCEDURE • Sheet piles and king posts driven using vibro-hammer mounted on excavator • Installation of sheet piles parallel to the intended basement wall for the purpose of confining soil • Installation of instruments for monitoring the movement of soil, including inclinometers and piezometers

  30. CONSTRUCTION PROCEDURE • Top soil of depth 1.5m excavated to expose upper portion of the embedded sheet piles to facilitate the installations of brackets, runners and struts • Excavation continued until the desired depth was reached • Concreting of basement wall, pilecaps and slabs

  31. CONSTRUCTION PROCEDURE • Some parts of struts would be left in the basement wall as they would be cut and left in the wall upon the completion of construction of basement • Backfilling was done after the construction of basement wall • Removal of sheet piles using vibro-hammer mounted on excavator

  32. Close proximity to surrounding buildings. • Stretch of steel piles and the basement wall

  33. Struttings extending into the basement wall. The Struts would be sawn off and left within the wall upon the completion. Grouting would be done to prevent rusting.

  34. MONITORING EQUIPMENTS • Inclinometers • Piezometers • Settlement Markers

  35. INCLINOMETERS • Inclinometer casing • Inclinometer probe • Data logger • Computer software

  36. PIEZOMETERS • Standpipe piezometers • Pneumatic piezometers • Vibrating wire piezometers

  37. Locations of the Soil Monitoring Equipment

  38. PROBLEMS ENCOUNTERED • In cases when sheet piles are slanted during the course of piling, they may have to take out the piles again and redo the piling.

  39. Excessive vibration may result in cracks to the structure of adjacent buildings • To prevent settlement of the adjacent buildings, the piles are left behind as means of support.

  40. Rocks may cause obstructions which prevent sheet piles from being driven into the required level in the soil

  41. Levelled sheet piles when there is no obstructions.

  42. DRIVING ASSISTANCE Jetting • Prevents damage to piles and reduces ground vibrations • Involves the use of a high pressure water jet situated at the toe of the pile • Toe resistance of the pile is reduced and the rising water reduces surface and interlock friction

  43. DRIVING ASSISTANCE Two Methods of Jetting • Low pressure jetting - used in non-cohesive soils • High pressure jetting - used for driving in extremely dense soils

  44. Vibrating vs. Pressing

  45. LOCAL CASE STUDY West Mall Shopping Centre • Site soil comprises of firm to hard silts that posed technical challenge to construction work • Near to Bukit Batok MRT station, hence vibration constrain. Thus, conventional vibro method not suitable. Using water pressure, it’s less vibration

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