Quality Control of Cast in Situ Piling

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cast in situ pile

Quality Control of Cast In Situ Piling

এই ফ্রি কোর্সটিতে অধ্যাপক জাহাঙ্গীর স্যার বাংলাদেশে পাইলিং এর ভুলগুলো চিহ্নিত করে সেগুলোর সমাধান দিয়েছেন । যে সমস্ত সিভিল ইঞ্জিনিয়ার কন্সট্রাকশন বা ডিজাইন এর সাথে জড়িত আছেন তাদের জন্য এই ফ্রি শর্ট কোর্সটি অনেক উপকারে আসবে । পাইলিং কন্ট্রাক্টরদের চাঁপা বাজি থামাতে সিভিল ইঞ্জিনিয়ারদের জন্য এই কোর্সটি দরকার।

In this free course, Professor Jahangir Sir has identified the mistakes of piling in Bangladesh and solved them. This free short course will be very useful for all civil engineers who are involved in construction or design. This course is needed for civil engineers to stop the pressure of piling contractors.

What you'll learn

  • Quality control of cast in situ piling
  • Driven pile concrete casting
  • Concrete of cast in situ pile
  • Bentonite slurry
  • Sequence of piling
  • Compaction of tremie concrete
  • Slump of concrete

Prerequisite / Eligibility

  • BSc, MSc or PhD in Civil Engineering
  • Level 4 or 4th year student of bachelor’s in civil engineering

Course Teacher

Professor Dr. Jahangir Alam, Department of Civil Engineering, BUET, Dhaka, Bangladesh

Brief Biography of Course Teacher

Education

  • PhD in Geotechnical Earthquake Engineering, the University of Tokyo, Japan, 2005
  • MSc in Civil and Geotechnical Engineering, BUET, Dhaka, Bangladesh, 2002
  • BSc in Civil Engineering, BUET, Dhaka, Bangladesh, 1998

Biography

Professor Dr. Engr. Md. Jahangir Alam is faculty member at the Department of Civil Engineering, BUET, Dhaka-1000, since 1999. He completed his PhD from University of Tokyo in Geotechnical Earthquake Engineering in 2005 as a Monbu-Kagaku-sho Scholar. He was research fellow in Ecole Centrale Paris in 2008. Professor Jahangir did his BSc in Civil Engg with major in Structure and MSc in Civil and Geotechnical Engineering from BUET.

Professor Jahangir has multidisciplinary research interests and has publications in international journals and conferences. His current research topics are “Risk Sensitive Land Use Planning of Mega City”, Physical and Numerical Modeling of Liquefaction Hazard, Mitigation against Seismic Liquefaction, Cyclic Behavior of Non-plastic silt, Reinforced Earth, Earthquake Resistant Foundation in Soft Soil, Climate Resilient Concrete, Climate Resilient Road.

Professor Jahangir was involved in many consultancy projects where he designed/checked high rise RCC buildings, Communication towers, Jetty, Shore Pile, Embankment, Container Terminal, Ground Improvement, Bridge Foundation etc. He supervised many MSc and PhD students. He was involved in pile load testing, pile integrity testing, concrete mix design and development of laboratory and field-testing equipment.

Professor Jahangir actively involved in National and International professional bodies. He is life member and was Treasurer of Bangladesh Society for Geotechnical Engineering (BSGE), which is Bangladesh Chapter of ISSMGE. He is life fellow of Institute of Engineers Bangladesh (IEB). He is life member of Bangladesh Earthquake Society (BES). He was Treasurer of Bangladesh Earthquake Society (BES).

Certificate of Attendance

Certificate of attendance will be awarded after completion of all video lessons and quizzes

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Frequently Asked Questions (FAQ)

Detail Course Outline

Quality control of cast in situ piling

  • Comparison between precast and bored RCC pile
  • Mix ratio
  • Method of construction
  • Steps of cast-in-situ piling
  • Use of casing
  • Temporary casing necessary
  • Precautions for temporary casing
  • Drilling Slurry
  • Slurry types
  • Problems of Cast in situ piling
  • Pile reinforcement
  • Installation of concrete rollers
  • Pile Cap Casting
  • Placement of concrete in drilled shaft
  • Use of retarder in tremie concrete
  • Precautions during concreting
  • Influence of construction on soil properties of clay

1
Quality Control, Part-1

QUALITY CONTROL OF CAST IN SITU PILING




Compare between precast and bored RCC pile

Precast pile

1. Slump value 50-100 mm

2. Retarder and plasticizer is not needed in general

3. Compaction by vibration is necessary

4. Clear cover > 50 mm

5. Durability should be considered

 

Bore pile

1. Slump value 150 – 200 mm

2. Retarder and plasticizer should be used

3. Compaction is prohibited

4. Clear cover > 75 mm

5. Durability should be considered



Mix ratio

Mix ratio of cast in situ piling concrete (Without plasticizer):

Cement = CEM-II, FA = Coarse Sand, CA = Stone chips or Shingles

•            1:1.25:2.0

•            Minimum fc’ = 28 Mpa (4000 psi)


Mix ratio of cast in situ piling concrete (Without plasticizer):

Cement = CEM-II, FA = Coarse Sand, CA = Stone chips or Shingles

•            1:1.5:2.5



Wet method of construction or Slurry method of construction

Excavation of bore hole can be done by:

1. Percussion method of drilling

 a. Usually done in Bangladesh

 b. Good for dia 20” – 24” and L = 90’

2. Rotary method of drilling

 a. Expensive

 b. Now used in big projects

 c. Any dia and length ok

 d. Economic for large dia



Steps of cast-in-situ piling

·        Boring

·        Insertion of rebar cage

·        Concreting through tremie pipe



Temporary casing necessary

·        when caving soil (loose sand and silt) exist at top layer

·        To maintain the piling location

·        To maintain the slurry above the ground level

·        Length of casing depends of soil layers



Precautions for temporary casing 

Cleaning after each use

Must be as smooth as possible

Casing with bonded concrete should not be allowed

Slurry column should extend well above the level of the piezometric surface so that any fluid flow is from the excavation outward



Drilling Slurry

·        Bentonite or polymer slurry may be used

·        Drilling fluid serves to put soil particles in suspension and will form a membrane or a filter cake at the walls of the borehole.

·        The membrane acts to prevent caving or collapse of the borehole.

·        Also called as drilling mud



Drilling slurry is essential

·        For piling into caving soil

·        Caving soil types

o  Loose sand and gravel

o  Nonplastic Silt


·        Important note: avoid drilling slurry if only water is enough, because

o  Bentonite slurry is expensive

o  Reduces skin friction of pile



Slurry types

·        Bentonite slurry

·        Polymer slurry



Pile reinforcement (cage)

The cage is designed to meet two requirements

·        The structural requirement for bending and for column action (sometimes slender column)

·        Stability requirements of the rebar cage during its placing, during the placing of concrete and during



Minimum longitudinal reinforcement

If the pile has sufficient axial strength using only half the gross concrete area, Ag/2, the longitudinal reinforcement ratio can be reduced to 0.5 percent of the gross concrete area, Ag.



Longitudinal bar in the cage

Maximum longitudinal reinforcement at the top if no drag load

Symmetrical arrangement of longitudinal rebar is recommended unless there is compelling reasons

Minimum 5 or preferably 6 longitudinal bars are needed

16mm dia bar is the minimum size of longitudinal bar

Clear spacing between bars is 3-5 times maximum size of CA

If a very large amount of rebar is needed, concentric multiple cages or bundled bars may be used.



Centering Devices

Two purposes:

1. Clear cover 3”

2. To flow concrete


 Rebar’s should not be used for centering devices unless they are epoxy-coated. Better solution is to use concrete roller



Pile Cap Casting

·        Break 3 ft weak concrete at top of drilled shaft / bored pile before casting pile cap

·        Use top, bottom and side reinforcements in pile cap even it is not needed by calculation

·        Use thick pile cap to ensure rigid action of pile cap to distribute column load to individual piles uniformly

·        Take care of basement construction at pile cap level



Placement of concrete in drilled shaft

Basic characteristics of concrete for drilled shafts

·        Excellent fluidity

·        SCC (Self Compacting Concrete) Compaction under self-weight

·        Resistance to segregation

·        Controlled setting



Use of retarder in tremie concrete

If the required time of pouring concrete is more than initial setting time, retarder must be used

Initial setting time >= 45 minute

Final setting time <= 420 minute

Usually initial setting time = 2 hours



Precautions for tremie concrete

·        The concrete shall contain at least 10 per cent more cement than that required for the same mix placed in the dry.

·        Slump = 150 mm to 200 mm

·        Successful placement of concrete under water requires preventing flow of water across or through the concrete.

·        The first concrete placed is physically separated from the water by using a “rabbit” or go-devil or plug in the pipe, or by having the pipe mouth capped or sealed and the pipe dewatered.

·        Once filled with concrete, the pipe is raised slightly to allow the “rabbit” to escape or to break the end seal. Concrete will then flow out and develop a mound around the mouth of the pipe. This is termed as “establishing a seal”.

·        Once the seal is established, fresh concrete is injected into the mass of existing concrete.



Precautions during concreting

·        In the “rabbit” plug approach, open tremie pipe should be set on the bottom, the “rabbit” plug inserted at the top and then concrete should be added to the tremie slowly to force the “rabbit” downward separating the concrete from the water. Once the tremie pipe is fully charged and the “rabbit” reaches the mouth of the tremie, the tremie pipe should be lifted a maximum of 150 mm (6 inch) off the bottom to allow the “rabbit” to escape and to start the concrete flowing. After this, a tremie pipe should not be lifted again until a sufficient mound is established around the mouth of the tremie.

·        Tremies should be embedded in the fresh concrete a minimum of 1.0 to 1.5 m (3 to 5 ft) and maintained at that depth throughout concreting to prevent entry of water into the pipe.

·        Rapid raising or lowering of the tremie pipe should not be allowed. All vertical movements of the tremie pipe must be done slowly and carefully to prevent “loss of seal”.

·        Underwater concrete shall be placed continuously for the whole of a pour to its full depth approved by the Engineer, without interruption by meal breaks, change of shift, movements of placing positions, and the like. Delays in placement may allow the concrete to stiffen and resist flow once placement resumes.

·        The volume of concrete in place should be monitored throughout the placement. Under runs are indicative of loss of tremie seal since the washed and segregated aggregates will occupy a greater volume. Over runs are indicative of loss of concrete.


·        Tremie pipe dia > 6 times of maximum size of CA

·        Plug of cement paste is recommended as low cost solution of initial charge



Minimum c/c spacing of piles

Drilling and extraction of casing during construction of a pile can cause upward directed shear stresses to develop on the perimeter of adjacent piles that were installed earlier, possibly damaging those shafts

So minimum c/c spacing = 3D

If closer spacing is required, sequence of shaft installation must be mentioned



Load distribution in pile

·        Initial loads are taken almost completely by skin friction at very small displacement

·        as loading continues, some load is transferred to the base of the drilled shaft

·        At the ultimate load, a sizeable portion of load is carried by end bearing but at significant amount of downward displacement



Influence of construction on soil properties of clay

·        Stress released during excavation. The placing of concrete will reimpose a stress in the clay surrounding the drilled shaft that can be greater than the in situ stress. The magnitude of the concrete stress is dependent on the slump of the concrete, and high-slump concrete is highly recommended.

·        Some chemical bond occur between clay and cement, so skin friction increases. So, Shear failure does not occur at interface but a short distance from interface



Influence of construction on soil properties of sand

A membrane of bentonite is created at the wall of the borehole

Stress released during excavation. The placing of concrete will reimpose a stress in the sand surrounding the drilled shaft that can be greater than the in situ stress. The magnitude of the concrete stress is dependent on the slump of the concrete, and high-slump concrete is highly recommended.

Some chemical bond occur between sand and cement, so skin friction increases. So, Shear failure does not occur at interface but a short distance far from interface



Quality Assurance

·        Pile integrity test – length and integrity

·        Pile load test on test piles and service piles

o  Static load test – takes time

o  Dynamic load test (PDA) - rapid



Summary of quality control of pile

·        Ensuring length

·        Cross checking the soil test bore log with drilling bored pile

·        Slump and mix ratio of concrete

·        Outlet of tremie pipe into concrete all the time

·        Maintaining clear cover

·        Prevention of caving by using bentonite slurry or any other mud

·        Cleaning the bore hole properly to ensure end bearing

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Quality Control, Part-2
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Quality Control, Part-3
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Quality Control, Part-4
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Quality Control, Part-5
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Quality Control, Part-6
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Quality Control, Part-7
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Quality Control, Part-8
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Quality Control, Part-9
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Quality Control, Part-10
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Enrolled: 835 students
Duration: 3 hours
Lectures: 10
Video: 3 hours
Quality Control of Cast in Situ Piling
Category:
4.2 out of 5
4.2
5 reviews
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