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DRILLED SHAFT INSPECTOR’S GUIDELINES

GEOTECHNICAL ENGINEERING MANUAL

GEM-18

Revision #1

GEOTECHNICAL ENGINEERING BUREAU

APRIL 2007

GEOTECHNICAL ENGINEERING MANUAL:

DRILLED SHAFT INSPECTOR’S GUIDELINES

GEM-18

Revision #1

STATE OF NEW YORK

DEPARTMENT OF TRANSPORTATION

GEOTECHNICAL ENGINEERING BUREAU

APRIL 2007

TABLE OF CONTENTS

1. INTRODUCTION3

1.1Purpose3

1.2Role and Responsibilities of the Inspector3

1.3Definition of Terms4

2. CONTRACT REQUIREMENTS6

2.1Specifications6

2.2Plans6

3. PRECONSTRUCTION MEETING7

4. DRILLING9

5. CONCRETING10

6. INTEGRITY TESTING12

7. CONSTRUCTION MONITORING15

7.1Monitoring Aids15

7.2Guidelines for Filling Out Drilled Shaft Monitoring Forms20

7.2.1Drilled Shaft In Rock - Field Record Page 120

7.2.2Drilled Shaft In Soil - Field Record Page 125

7.2.3Drilled Shaft In Rock or Soil - Field Record Page 225

REFERENCES29

APPENDIX30

ADrilled Shaft In Rock - Field Record Page 1A-1

BDrilled Shaft In Soil - Field Record Page 1B-1

CDrilled Shaft In Rock or Soil - Field Record Page 2C-1

1. INTRODUCTION

1.1 Purpose

These guidelines along with the Drilled Shaft Inspector’s Manual, prepared by ADSC: The International Association of Foundation Drilling and DFI: Deep Foundation Institute, provides the inspector or Engineer-In-Charge (EIC) with a working knowledge of drilled shaft construction techniques. To become familiar with drilled shaft installation techniques, a working knowledge of the tools used by contractors is also essential. The Drilled Shaft Inspector’s Manual will provide the individual with a working knowledge of drilled shaft installation equipment in addition to familiarity with actual construction techniques. Lastly, these guidelines will provide the individual with monitoring aids to facilitate the inspection procedures and enhance the transfer of information from the inspector to the designer. The monitoring aids consist of methods to obtain necessary field data as well as inspection forms on which to record this data.

There is no substitute for direct contact between the inspector and the geotechnical engineer who designed the drilled shaft foundation. Contact with the geotechnical engineer will give the inspector access to information he/she may not have possessed otherwise, as well as insight into why drilled shafts were utilized on this project. The geotechnical engineer will be responsible for reviewing the construction information recorded by the inspector, as well as, evaluating the foundation for acceptability. For this reason alone, it is prudent that the inspector/EIC and the geotechnical engineer have a good working relationship. At the very least, the geotechnical engineer should sit down with the inspector/EIC before construction begins and discuss any concerns either have.

1.2 Role and Responsibilities of the Inspector

The primary role of the inspector is to make sure that construction is done in accordance with the plans and specifications contained on the project. Thus it is imperative that the inspector is familiar with the plans and specifications of the project. Any deviation from the plans or specifications should be promptly noted and reported to the proper authorities, who will determine what actions to take.

The inspector’s secondary function is to record and transmit information. The drilled shaft inspector is there to observe and document the contractor’s installation of the drilled shaft. In this regard he/she should also try to be as complete and as concise as possible when recording and transmitting this information to the proper authorities. The quality of this information must be very high as it will be used to make important decisions such as the approval or rejection of the drilled shaft.

1.3 Definition of Terms

Casing Method -A method of shaft construction, consisting of advancing and cleaning a cased hole, placing the reinforcing cage, and concreting the shaft while extracting temporary casing (if used).

Casing (Shell) - A steel shell used to construct the drilled shaft. The casing can help advance the hole, and supports the sides of the hole. Casing may be permanent or temporary.

Drilling Mud - A slurry made using bentonite or polymers (see Slurry).

Drilled Shaft - A cylindrical structural column transmitting loads to soil and/or rock. The drilled shaft is constructed in a hole with a circular cross section. The hole is filled with concrete and may be reinforced with steel.

Dry ConstructionA method of shaft construction consisting of drilling the shaft, removing

Method -the water and material from the excavation, placing the reinforcing cage, and concreting the shaft in a relatively dry condition.

Permanent Casing -A casing that acts as a form, but remains in place permanently. It is usually not designed to carry structural loads.

Quality Assurance -A test or procedure that acts to verify the quality of the work or product. Quality Assurance procedures would include static load testing, Osterberg Cell testing, coring, cross hole sonic logging, and other non-destructive testing.

Rock -

Rock is identified in the boring logs. Rock may also be defined at the shaft installation site by a Departmental Engineering Geologist. Keep in mind that the state defines rock by its load bearing capacity and often, the contractor will define rock by the effort or tools required to progress the excavation through the material. These conflicting criteria will often result in different definitions of rock at a site. Refer to the Contract Plans for guidance on how rock is defined for the project.

Seat - The act of placing the tip of a casing in intimate contact on rock for its entire circumference.

Slurry -A mixture of water and bentonite, or water and polymers, which provides hydrostatic pressure that supports the sides and bottom of the hole, lubricates and cools the drill tools, and aids clean out. Slurry cannot be made from native materials, or material from the excavation.

Sound Rock -

Competent, massive, and unweathered rock, typically with a Rock Quality Designation (RQD) of at least 70%. Elevation of sound rock is always determined by a Departmental Engineering Geologist. Be aware that sound rock is not always required for a drilled shaft rock socket.

Surface Casing -Temporary casing installed to prevent sloughing of the surrounding soil near the surface of the shaft excavation.

Temporary Casing -A casing that serves its function during construction of the drilled shafts. It serves no permanent structural function, and is extracted during concreting.

Top of Socket -The highest location of the rock socket that is capable of resisting axial and lateral design loads. At any given location, the top of socket elevation is usually below the top of rock elevation. This distance depends on the type and quality of rock, and the Contractor’s drilling methods and equipment.

Tremie -

A method to place concrete under water. Refer to Section 555 - Structural Concrete of the NYSDOT Standard Specifications.

Trial Shaft -

A hole for a drilled shaft constructed on the project site, but outside the proposed footing limits. It is not to be incorporated into a structure or foundation. A trial shaft is constructed prior to installing production drilled shafts, according to the methods detailed in the Contractor’s submittals. Its function is to verify the proposed excavation methods, and permit the Inspectors to become familiar with the excavation procedure. Upon inspection and acceptance, the trial shaft is backfilled with unreinforced concrete.

Wet

A method of shaft construction consisting of using slurry to maintain

Construction

stability of the hole while advancing the excavation to the final depth,

Method -

placing the reinforcing cage, and concreting the shaft.

2. CONTRACT REQUIREMENTS

2.1 Specifications

The inspector should be familiar with the drilled shaft specification. The specification contains the following information that will be essential for the inspector to consult during construction:

Construction Tolerances - The specification contains all the allowable shaft tolerances, such as location, verticality (plumbness), cutoff elevation, rebar stick up, and diameter. Failing to meet these tolerances will result in a rejected shaft.

Drilling and Excavation Methods - The specification contains the allowable procedures for the different shaft drilling methods. They also provide the requirements of each procedure. The contractor must adhere to these requirements or once again the shaft could be rejected.

Rebar, Concrete Placement, and Temporary Casing Removal - The specification contains the allowable procedures and requirements for the above operations. Again, the contractor must adhere to these requirements or risk rejection of the shaft.

The specification also contains additional miscellaneous information on shaft requirements that the inspector should become familiar with. A good working knowledge of the specification is essential in proper drilled shaft construction monitoring.

2.2 Plans

The contract plans are another important source of information for the inspector. The contract plans contain all of the specific requirements of that particular project as opposed to the specification which covers only general requirements. The specifications refer to the contract plans many times (for example: ....as shown on the contract plans....). The plans also refer back to the specification for direction where applicable (for example: ....as per Item xxx.xx...). The inspector should be familiar with the contract plans and know where to find information in them. The contract plans contain the actual shaft design and any and all requirements not covered in the specification. These requirements are what the contractor bid on, and what he/she must construct. Any unauthorized deviation from the contract plans should be reported immediately through the proper channels.

3. PRECONSTRUCTION MEETING

Since the acceptance or rejection of a drilled shaft is usually based solely on results of integrity tests and inspection records of the shaft’s installation, a preconstruction meeting is essential. This meeting will be in addition to the usual preconstruction meeting which is standard on all DOT projects. The primary focus of this meeting is to go over the contractor’s submittals to determine if there are any concerns. This meeting should be between the Engineer-In-Charge (EIC), the inspector(s), the Regional Geotechnical Engineer, and the designer of the shaft.

This meeting will allow the EIC and his inspector and the design engineer to go over the contractor’s submittals to see if there are any concerns on either side. It will also alert the inspector as to what aspects of the construction submittal could potentially affect the performance of the shaft. The designer should have reviewed (and commented back to the contractor, if necessary) these submittals prior to the meeting. As per the current drilled shaft specification, here is what the contractor must submit to the designer before construction can begin:

a.Method describing how the Contractor will progress through obstructions and rock.

b.Details and method describing how the Contractor will keep the hole for the drilled shaft open.

c.Drawings showing and details describing the proposed sequence of drilled shaft installation. Include the sequence for each shaft, the overall construction sequence, and the sequence of shaft construction in bents or groups.

d.Information describing the type of equipment to be used, including drill rig, cranes, drilling tools, final cleaning equipment, desanding equipment, slurry pumps, sampling equipment, tremies or concrete pumps, casing(including: casing dimensions, material and splice details), etc.

e.Proposed method for cleaning out the shaft excavations. Include a description of how the Contractor will perform spoil removal and disposal.

f.Information that shows that the Contractor, Driller, and Foreman meet the pre-qualification requirements stated previously. Include the name and telephone number of someone for each project cited who can be contacted as a reference.

g.Shaft excavation methods, and final shaft dimensions.

h.If slurry is to be used, indicate the method proposed to mix, circulate, and desand slurry. Include methods of slurry disposal in the submittal.

i.Method of reinforcement placement, including support and centralization type and methods.

j.Details and method of concrete placement, curing, and protection.

k.If the concrete mix is modified (i.e., retarders), include the new mix design, and test results of cylinder breaks from an independent laboratory. Also, include test results that demonstrate a slump loss versus time relationship.

l.A description and details of the slurry sampling tool to be used. Provide a tool capable of taking a slurry sample at a specific depth, without being contaminated by slurry from another depth.

m.When slurry is used, include an alternate procedure to be used which will secure the shaft in the event of slurry loss.

n.A description of the type of feet to be used to support the rebar cage in the drilled shaft.

o.An emergency construction joint procedure, to be used in the event when concrete placement for the drilled shaft is unexpectedly interrupted.

p.A procedure for filling voids between permanent casing and the soil.

q.A description of equipment and methods to be used for drilled shaft inspection. The Inspector will use these methods and equipment to inspect the drilled shafts. The inspection program must be thorough enough to assure the Department that each drilled shaft meets the requirements contained in this specification.

Each one of these items should be gone over in detail, so that all concerned parties will know what to except and what to look for during construction. Deviation from the approved submittals by the contractor must not be tolerated, and will result in rejection of the shaft. Depending on the design, different portions of these submittals will be critical. The designer should make the inspector aware of which operations/equipment are crucial for the acceptance of the shaft.

The meeting will also open the channels of communication between the EIC and the designer. This too is essential as information (such as the inspection forms and integrity test reports) will be transmitted from the EIC to the designer for approval. Also in the case of problems during construction, a solution can be more easily achieved if everyone is on the same page.

4. DRILLING

Most drilled shaft excavations are done using rotary drilling machines. These machines come in many different sizes and designs. The capacity of a drill rig is expressed in terms of the maximum torque that can be applied to the drilling tool, as well as the downward force, or “crowd”, that the rig can apply to the drilling tool. Torque and “crowd” are transmitted from the rig to the drilling tool by a shaft of steel, known as a Kelly bar. Most Kelly bars are square in cross section, but do not have to be. Kelly bars start off as a set length but can be telescoped to drill at greater depths. The Kelly bar passes through a rotary table that is turned by a power unit. Drill rigs can be mounted on trucks, cranes, or crawlers.

Refer to Chapter 3 of the Drilled Shaft Inspector’s Manual for in-depth information on drilling tools, techniques, and what to be looking for during inspection of the drilling procedure.

5. CONCRETING

Concrete for drilled shafts must be designed and placed in a manner that is unique to drilled shafts. The basic characteristics of concrete for drilled shafts are (from “Drilled Shafts: Construction Procedures and Design Methods”):

· Excellent Workability - It is essential that the concrete have the ability to flow readily through the tremie, to flow laterally through the rebar cage, and to impose a high lateral stress against the sides of the borehole. From a geotechnical perspective, the objective of placing concrete is to reestablish the lateral stresses in the ground around the drilled shaft that existed before the borehole was excavated. This objective can best be met by using concrete that is highly fluid.

· Self-Weight Compaction - Vibration of concrete in a borehole is impractical, except very near the surface. In some cases this will lead to defects in the completed shaft by causing ground water, drilling fluid, or soil to mix with the concrete.

· Resistance to Segregation - The concrete mix should have a high degree of cohesion and should be free of large-sized aggregate; otherwise, it may segregate during placement, particularly if free fall is allowed, resulting in inferior concrete.

· Resistance to Leaching - In some instances flowing ground water could cause a weakening of the concrete after it is placed. A properly designed mix should be resistant to such flow. However, if the rate of flow is substantial, a permanent casing or liner will be necessary. Furthermore, when concrete is placed under a drilling fluid (slurry or water), there is inevitable contact between the concrete and the fluid, which is a condition that also requires the mix to be resistant to leaching.

· Controlled Setting - Drilled shaft concrete should retain its fluidity throughout the depth of the borehole during the full time required for complete placement of the concrete in the borehole to maximize the lateral pressures that are imposed by the fluid concrete. Slow setting is also required to allow for inevitable delays that may occur during concreting, such as: interrupted concrete supply, difficulties in extracting casing, etc. At the same time, it should attain an appropriate strength within a reasonable time after placement.

· Good Durability - If the subsurface environment is potentially corrosive or can become corrosive during the life of the foundation, the concrete should be designed to have high density and low permeability so that the concrete is able to resist the negative effects of the environment.

· Appropriate Strength and Stiffness - The size of most drilled shafts will be controlled by the peripheral area and base area that are needed to develop the required axial load resistance. Therefore, high-performance concrete is usually not needed. The mechanical properties of the hardened concrete can be satisfied in such instances without difficulty. However, provision of appropriate compressive strength where high levels of combined bending and axial stress occur must be dealt with in some cases.

· Low Heat of Hydration for Large Volumes of Concrete - Careful attention must be given to the design of concrete for bells and for large-diameter drilled shafts so that excessive heat does not produce thermal tensile cracking.

Refer to Chapter 4 of the Drilled Shaft Inspector’s Manual for in-depth information on concrete placement techniques and what to be looking for during inspection of the concreting procedure.

6. INTEGRITY TESTING

The most common types of integrity tests performed on completed drilled shafts are the following:

Sonic Echo Test

This test consists of striking the head of the drill shaft with a hand-held hammer. A sonic wave is generated that travels down the shaft, is reflected from the shaft base or from a defect in the shaft, and is picked up by an accelerometer. This is a very crude test which can only detect major defects such as a major soil inclusion or bases of shafts that were drilled to the wrong depth.

Impulse-Response Test

This test is similar to Sonic-Echo testing except that a more sophisticated method of processing the data is used. In addition to recording the motion at the head of the shaft versus time, the force applied by the hammer is also recorded versus time. The same limitations that apply to Sonic Echo testing apply to Impulse-Response testing, but the data is usually easier to interpret.

Impedance Log

Further computer processing of data from a Sonic Echo/Impulse-Response test can be performed to produce a graph of the cross-sectional area of the shaft as a function of depth. The result of this processing is an impedance log, which will provide a clear indication of average shaft diameter versus depth. Impedance Log testing has the same general limitations of the previous two tests, but is less prone to false positive results.

Parallel Seismic Test

A water filled tube is installed parallel to the shaft, then a piezo-electric receiver is lowered down the tube, and lastly, the shaft is struck with a hand-held hammer. The receiver can be moved up and down the tube to test the shaft at any point. The shaft does not have to be struck on its top, so the test is useful when the top of a shaft is not accessible. A change in arrival rate from the hammer blow indicates the presence of a major defect. The base of the shaft can also be determined in this way. As with the previous small-strain tests, small defects are not likely to be detected.

Internal Stress Wave Test

This test is the same concept as Sonic Echo, except that the receivers are embedded in the shaft at varying depths. This test will give clearer results as the noise level is much reduced when compared to Sonic Echo testing. The test has the same general limitations as Sonic Echo testing, and since the receivers are embedded in the shaft, the decision to use the test must be made before construction.

Crosshole Acoustic (Sonic and Ultrasonic) Test

Crosshole Acoustic testing or Crosshole Sonic Log testing consists of installing several metal or plastic tubes attached to the rebar cage of the drilled shaft. The tubes have sufficient diameter to admit probes and are filled with water (to better transmit energy from the wall of the tube to the probe). To perform the test, an acoustic transmitter is lowered into one of the fluid filled tubes, and a receiver is lowered to the same depth, in another tube. The transmitter emits an acoustic signal which is picked up by the receiver. The test is repeated at many depths along the entire length of the shaft. The travel time of the signal is measured. If there is a defect in the shaft, the travel time increases. By testing all combinations of tubes, a defect, its magnitude, and its location in the shaft can be mapped out. The two limitations of the test are that the access tubes are installed during construction of the shaft, so the decision to use the test must be made before construction, and the test cannot detect defects outside of the rebar cage, as only concrete between tubes can be tested.

Gamma-Gamma Testing

As with Crosshole Sonic Log testing, access tubes are installed in the shaft during construction. A source of ionizing radiation is lowered down the tubes. The tubes cannot be made of steel as this would prevent the gamma rays from penetrating the concrete. The instrument containing the radioactive source also contains a gamma ray detector. The gamma rays emitted are reflected back by the surrounding concrete. The reflected gamma ray count per unit time is calibrated to the concrete density. If the density measured falls below the expected density of normal concrete, a defect in the concrete is indicated. The access tubes must be installed during construction of the shaft, so the decision to use the test must be made in design. The only other limitation of the test is that the area of concrete tested is relatively small, no more than 4 in. (100 mm) from the edge of the access tube. So even with several access tubes, most of the concrete area of a shaft cannot be tested. Note that the area outside of the rebar can however, be tested with this method.

Coring

If a shaft is suspected of having a major defect, it can be cored and the concrete sampled along its entire length. Coring is expensive and time consuming. Since the area cored is small when compared to the shaft area, small defects will not be detected.

New York State DOT Practice

The New York State DOT practice is to specify Crosshole Sonic Log testing on all production drilled shafts. If the testing indicates a major defect, the shaft is then cored at various locations to determine the nature and extent of the defect.

As Crosshole Sonic Log testing is our primary method of determining a shaft’s integrity, the inspector should pay close attention to the installation of the access tubes. The tubes should be undamaged and should comply with our specifications. They should be attached to the rebar cage securely at the designed locations. During lowering of the rebar cage into the hole, care should be taken to avoid damage to the tubes (such as crushing them against the sides of the shaft or bending them at the bottom). Access tubes that are not attached correctly or damaged during installation will often result in the testing indicating a defect in the concrete when there is none.

Keep in mind that the test assumes a constant distance between access tubes. If these distances change due to improper installation or damage, the distance between tubes will vary. This will result in a different wave speed through the concrete at different depths. This differing wave speed will be interpreted as a defect in the shaft, resulting in the subsequent expensive and time consuming coring of the shaft.

7. CONSTRUCTION MONITORING

7.1 Monitoring Aids

The next four pages provide the following drilled shaft construction monitoring aids:

1) Suggested Method to Check Shaft Plumbness if Horizontal Tolerance is Known - describes a quick procedure to determine if the shaft is out of “plumb” (required verticality). As specified in the specification the allowable tolerance from the required verticality is 2% for vertical shafts, 3% for battered shafts. This procedure assumes that the actual tolerance for the shaft has been computed, based on the allowable tolerance from the required verticality (either 2% or 3%) and the total shaft length. This test should be performed when the shaft excavation is completed.

2) Suggested Method to Check Shaft Plumbness - describes a procedure to determine a shaft’s plumbness at any point during construction. It is essentially the same procedure as above. The figure shows three measurements for each check. Keep in mind that if the casing is continuous (i.e. one piece) or no casing is used, only one measurement is required for a plumbness check. This procedure should be performed periodically as the shaft is progressed to maintain correct shaft verticality.

3) Suggested Method to Check Concrete Level - describes a procedure to determine the concrete level during pouring. Determining the correct concrete level during the pour is essential for the completion of the concrete curve (a key part of the inspection forms). Basically a tape measure with its end attached to something that will sink in water and other drilling fluids, but will float on the wet concrete is used for this procedure. This will allow the inspector to determine the level of concrete in the shaft at any point during the pour, even if the shaft is filled with water or drilling fluid.

4) Shaft Areas and Volumes Table - Is a self explanatory table that aids the inspector in determining the shaft’s volume.

Shaft Areas and Volumes

Per Linear Foot

Per Linear Meter

Shaft Diameter

(in.)

Volume (yd3)

Side Shear Area

(ft2)

Bearing Area

(ft2)

Shaft Diameter

(cm)

Volume (m3)

Side Shear Area

(m2)

Bearing Area

(m2)

12

0.03

3.14

0.79

30

0.07

0.94

0.07

14

0.04

3.67

1.07

35

0.10

1.10

0.10

16

0.05

4.19

1.40

40

0.13

1.26

0.13

18

0.07

4.71

1.77

45

0.16

1.41

0.16

20

0.08

5.24

2.18

50

0.20

1.57

0.20

22

0.10

5.76

2.64

55

0.24

1.73

0.24

24

0.12

6.28

3.14

60

0.28

1.88

0.28

26

0.14

6.81

3.69

65

0.33

2.04

0.33

28

0.16

7.33

4.28

70

0.38

2.20

0.38

30

0.18

7.85

4.91

75

0.44

2.36

0.44

32

0.21

8.38

5.59

80

0.50

2.51

0.50

34

0.23

8.90

6.31

85

0.57

2.67

0.57

36

0.26

9.42

7.07

90

0.64

2.83

0.64

38

0.29

9.95

7.88

95

0.71

2.98

0.71

40

0.32

10.47

8.73

100

0.79

3.14

0.79

42

0.36

11.00

9.62

105

0.87

3.30

0.87

44

0.39

11.52

10.56

110

0.95

3.46

0.95

46

0.43

12.04

11.54

115

1.04

3.61

1.04

48

0.47

12.57

12.57

120

1.13

3.77

1.13

50

0.51

13.09

13.64

125

1.23

3.93

1.23

52

0.55

13.61

14.75

130

1.33

4.08

1.33

54

0.59

14.14

15.90

135

1.43

4.24

1.43

56

0.63

14.66

17.10

140

1.54

4.40

1.54

58

0.68

15.18

18.35

145

1.65

4.56

1.65

60

0.73

15.71

19.63

150

1.77

4.71

1.77

62

0.78

16.23

20.97

155

1.89

4.87

1.89

64

0.83

16.76

22.34

160

2.01

5.03

2.01

66

0.88

17.28

23.76

165

2.14

5.18

2.14

68

0.93

17.80

25.22

170

2.27

5.34

2.27

70

0.99

18.33

26.73

175

2.41

5.50

2.41

72

1.05

18.85

28.27

180

2.54

5.65

2.54

74

1.11

19.37

29.87

185

2.69

5.81

2.69

76

1.17

19.90

31.50

190

2.84

5.97

2.84

78

1.23

20.42

33.18

195

2.99

6.13

2.99

84

1.43

21.99

38.48

210

3.46

6.60

3.46

90

1.64

23.56

44.18

225

3.98

7.07

3.98

96

1.86

25.13

50.27

240

4.52

7.54

4.52

102

2.10

26.70

56.75

255

5.11

8.01

5.11

108

2.36

28.27

63.62

270

5.73

8.48

5.73

114

2.63

29.85

70.88

285

6.38

8.95

6.38

120

2.91

31.42

78.54

300

7.07

9.42

7.07

126

3.21

32.99

86.59

315

7.79

9.90

7.79

132

3.52

34.56

95.03

330

8.55

10.37

8.5

7.2 Guidelines for Filling Out Drilled Shaft Monitoring Forms

7.2.1 DRILLED SHAFT IN ROCK- FIELD RECORD Page 1

TITLE BLOCK/JOB STAMP

Project Stamp - This area should contain the Project Stamp. The Project Stamp contains the project name, the PIN, the BIN, the Contract Number, the town or city, and the county.

Structure - Structure refers to the specific substructure this particular shaft will support. For example: Bridge 2, North Abutment.

Shaft Number - The shaft’s number as designated in the Contract Plans.

Date - Date form was initiated.

GENERAL SHAFT INFORMATION

Date Excavation-The date and the time the shaft was begun. Preliminary work such as

Started staking out the shaft’s location does not constitute the beginning of the shaft. Installing a temporary surface casing or actual drilling usually constitutes the beginning of a shaft.

Date Bottom -The date when the bottom of the shaft was cleaned out and checked,

Cleaned usually right before the concrete is poured.

Date Concrete - The date and the time the shaft was concreted.

Placed

DESIGN - The appropriate value as it appears in the Contract Plans.

AS-BUILT - The appropriate value as it was installed in the field.

Station - The center of the shaft’s station as referenced to a specified station line.

Offset - The center of the shaft’s offset from the station line.

Top Elevation - The top elevation of the shaft as referenced in the Contract Plans. By this we mean however the top of the shaft is defined in the Contract Plans is the way it should be defined in the field. For example if the Contract Plans define the top of the shaft as the top of a permanent casing, it should be defined in the field as such, not by some other means, such as the top of a temporary casing.

Bottom - The bottom elevation of the shaft as referenced in the Contract Plans

Elevation (see Top Elevation).

Shaft Diameter - Diameter of the shaft, not including temporary casings.

Shaft Length - Total length of shaft from defined top elevation to defined bottom elevation.

Rock Socket - The diameter of the rock socket (if applicable). The rock socket is

Diameter typically smaller (usually 6 in. (150 mm)) than the overall shaft diameter.

Rock Socket - The length of the socket measured from the top of sound rock to the

Length bottom of the shaft.

Plumbness - The overall plumbness of the shaft. This should be calculated using a plumb bob as described in the manual (Suggested Method to Check Shaft Plumbness).

Design Capacity-This is copied right from the Contract Plans. It is on the form as a reference for the inspector.

Observed - This is the observed groundwater elevation in the shaft during drilling.

Groundwater

Elevation

Remarks - Any remarks the inspector wishes to make should be placed here.

SHAFT SCHEMATIC (Casing Information)

OGS Elevation - The original ground surface elevation at the shaft site prior to drilling.

Top of Rock - The elevation of the top of the rock socket as determined by the plans.

Socket Elev. Keep in mind that this is not necessarily the top of rock elevation.

Shaft Bottom - The bottom of the shaft as measured in the field (the same as the table

Elev. entry As-Built Bottom Elevation).

Surface Casing - A temporary casing used to start the hole. It is usually only a few feet or meters deep.

Permanent or -If a casing is used, circle which type. This casing is used to progress

Temporarythe shaft through the soils.

Casing

Top Elev. - The top elevation of the casing in question. This should be referenced to the top of the shaft elevation.

Bottom Elev. – The bottom elevation of the casing in question. Again referenced to the top of the shaft elevation.

Length - Length of casing, top to bottom elevation.

Thickness - Thickness of casing.

O.D. - Outside diameter of casing.

DR - Diameter of rock socket (same as As-Built Rock Socket Diameter).

LR - Length of rock socket (same as As-Built Rock Socket Length).

Plumbness - By using the Suggested Method to Check Shaft Plumbness with a

Measurements plumb bob you would get an average horizontal distance from the plumb bob to the reference edge of the casing, this distance would be “X”. The distance from the top elevation of the shaft to the plumb bob would be “Y”. Using these measurements you can calculate the plumbness and enter it in the General Shaft Information Table. Alternatively, if you calculated the horizontal distance tolerance using the specifications, your “X” would be this tolerance while your “Y” would have to be the entire shaft length for the shaft to be within horizontal tolerance (refer to section of the manual entitled “Suggested Method to Check Shaft Plumbness if Horizontal Tolerance is Known”).

DRILLING INFORMATION

Date and Time - Date and time specific strata was drilled through.

Depth - Depth measured from the top of OGS to the top of the strata documented in this entry.

Soil or Rock - The NYS Geotechnical Engineering Bureau soil/rock description for

Description the strata encountered (refer to STP-2 - An Engineering Description of Soils Visual-Manual Procedure). For example: Silty SAND, LIMESTONE, Sandy GRAVEL, etc. It is especially important to note unexpected soil types and problematic soil types (such as clays, organics, or miscellaneous fills).

Tool - The tool used to progress the shaft through the material being noted (i.e. auger, muck bucket, core barrel, etc.).

Observations - Any unexpected occurrences, such as encountering obstructions, breakdowns of the rig, loss of water or drilling fluids, or caving of the hole should be noted with as much detail as possible. This can aid in evaluating the shaft after installation.

CONTRACTOR/ENGINEER RECORD

General Contractor-The General Contractor of the project.

Drilling Contractor-The drilling subcontractor who actually installs the drilled shaft.

Engineer-in-Charge-The EIC of the project.

Inspector - The construction inspector filling out these forms.

7.2.2 DRILLED SHAFT IN SOIL- FIELD RECORD Page 1

This form is filled out identically to the Drilled Shaft in Rock - Field Record Page 1. Instead of rock socket information entries this form contains the following bell information entries:

Bell Diameter - The diameter of the bell as appears on the plans for the Design entry and as installed for the As-Built entry.

Bell Height - The height of the bell, as designed and as installed. Bell height should also be labeled on the schematic in its appropriate space.

7.2.3 DRILLED SHAFT IN ROCK OR SOIL- FIELD RECORD Page 2

CONCRETE PLACEMENT INFORMATION

Concrete - The general method by which the concrete is placed into the drilled

Placement shaft. Three methods are listed: Air - pouring or dropping concrete

Techniques directly into shaft, no water can be present in shaft; Tremie - placement of concrete under water, either poured or pumped; Pump - concrete is pumped into drilled shaft. When concrete is tremie pumped into shaft, both the tremie and the pump boxes should be checked.

Type of Priming-Describes the specific method by which the concrete is transported

Plug from the mixer to the shaft.

CONCRETING CURVE

This section contains space for a concrete curve. This allows the inspector to compare theoretical shaft concrete volume with actual measured shaft concrete volume. Using the Shaft Volume chart contained in the manual, the inspector should first graph the theoretical concrete volume curve on the chart. This curve represents the volume of concrete by depth if the shaft were installed perfectly (concrete volume equals theoretical shaft volume). As the concrete is being poured the inspector should carefully keep track of the poured volume. The level of concrete can be measured using the Suggested Method to Check Concrete Level contained in Section 7 of these guidelines. The actual measured concrete volume should then be placed on the chart. Comparing the two curves will tell the inspector if concrete was lost or gained. Lost concrete would be obvious as the measured concrete volume curve would be greater than the theoretical concrete volume curve. Concrete gain caused by soil squeezing or hole collapse would also be obvious as the measured volume would be less than the theoretical volume. Gains and losses from soil caving could also be detected (soil caving would at first lower the measured volume by displacing concrete with soil, then increase the measured volume as the concrete level gets to the area of the shaft that caved).

SHAFT CROSS SECTION SKETCH

This section allows the inspector to document the shaft reinforcement and any integrity test access tubes that were incorporated into the shaft. The cross section of the shaft should be sketched in by the inspector. The cross section should show any reinforcement as it is placed. The position of integrity test access tubes is especially important, as it would be useful in evaluating the tests later, and they should be noted carefully.

REINFORCEMENT PROFILE

Rebar Cage Information

Bar Size - The size designation of the rebar in the cage.

Number of Bars-The total number of bars in the cage.

Top Elev. - The top elevation of the rebar cage in question.

Bottom Elev. - The bottom elevation of the cage in question.

Cage Diameter - The outside diameter of the rebar cage.

(O.D.)

Integrity Testing Access Tubes Information

Tube Size (O.D.)-The outside diameter of the access tubes.

Number of - The total number of access tubes in the shaft.

Tubes

Top Elev. - The top elevation of the access tubes.

Bottom Elev. - The bottom elevation of the access tubes.

If the shaft has any secondary reinforcement, or even a second rebar cage, it can be noted by sketching it in the profile schematic.

CONCRETE TEST DATA SECTION

Class - The class of the concrete used in the shaft from the Standard Specifications (class A or G typically).

Slump - The measured slump of the concrete.

Air - The measured air content of the concrete.

Date Tested - The date the concrete was tested.

Cylinder - The test cylinder designation number.

Number

Usually the concrete of each drilled shaft is sampled and tested.

OBSERVATIONS SECTION

This section gives the inspector a place to note any irregularities which might have occurred during the shaft installation. Types of irregularities which should be noted are listed in the title block of the section. These irregularities should be noted with as much detail as possible, as it will help the engineers in evaluating the shaft later.

REFERENCES

1. FHWA-IF-99-025 Drilled Shafts: Construction Procedures and Design Methods, by Michael W. O’Neil and Lymon C. Reese, 1999.

2. Drilled Shaft Inspector’s Manual, prepared by the Joint Caisson - Drilled Shaft Committee of the ADSC: The International Association of Foundation Drilling and DFI: Deep Foundation Institute, 1989.

APPENDIX

Monitoring Forms

The following three pages are the actual monitoring forms. The inspector should make enough copies for all the drilled shafts on the project. Note that only one of the first two forms (Drilled Shaft in Rock or Drilled Shaft in Soil) are required for each shaft, depending on the project. The third form is required for all drilled shafts. Therefore, construction of each drilled shaft should be documented by two inspection forms.

NEW YORK STATE DEPARTMENT OF TRANSPORTATION