SHAFT EXCAVATION AND CLEANING

Transcription

1 Lesson 6 SHAFT EXCAVATION AND CLEANING 6-1 Version 1-1/15 6-1

2 Learning Outcomes Perform inspection of drilled shaft excavations for compliance to plans, tolerances and cleanliness. Perform visual field verification of soil/rock material for comparison to supplied soil boring data/logs. Sample and test slurry and fluid in the excavation. Calculate Elevations & Extra Shaft Lengths. Identify the applicable 455 Specifications 6-2 Version 1-1/15 6-2

3 Checklist 6-3 Version 1-1/15 6-3

4 Vibrations Placed Concrete Vibrations on Freshly Placed Concrete (Drilled Shafts and Piers): Ensure that freshly placed concrete is not subjected to vibrations greater than 1.5 in/sec from pile driving and/or drilled shaft casing installation sources located within the greater dimension of three shaft diameters (measured from the perimeter of the shaft closest to the vibration source) or 30 feet (from the nearest outside edge of freshly placed concrete to the vibration source) until that concrete has attained its final set as defined by ASTM C-403 except as required to remove temporary casings before the drilled shaft elapsed time has expired. 6-4 Version 1-1/15 6-4

5 Templates General Requirements: Templates: Provide a fixed template, adequate to maintain shaft position and alignment during all excavation and concreting operations, when drilling from a barge. Do not use floating templates (attached to a barge). The Engineer will not require a template for shafts drilled on land provided the Contractor demonstrates satisfactorily to the Engineer that shaft position and alignment can be properly maintained. The Engineer will require a fixed template, adequate to maintain shaft position and alignment during all excavation and concreting operations, for shafts drilled on land when the Contractor fails to demonstrate satisfactorily that he can properly maintain shaft position and alignment without use of a template. 6-5 Version 1-1/15 6-5

6 Test Holes Test Holes The Engineer will use the construction of test holes to determine if the methods and equipment used by the Contractor are sufficient to produce a shaft excavation meeting the requirements of the Contract Documents. During test hole excavations, the Engineer will evaluate the ability to control dimensions and alignment of excavations within tolerances; to seal the casing into impervious materials; to control the size of the excavation under caving conditions by the use of mineral slurry or by other means; to properly clean the completed shaft excavation; to construct excavations in open water areas. 6-6 Version 1-1/15 6-6

7 Test Holes Test Holes. Continued. To determine the elevation of ground water; to place reinforcing steel and concrete meeting the requirements of these Specifications within the prescribed time frame; and to execute any other necessary construction operation. Revise the methods and equipment as necessary at any time during the construction of the test hole when unable to satisfactorily carry out any of the necessary operations described above or when unable to control the dimensions and alignment of the shaft excavation within tolerances. 6-7 Version 1-1/15 6-7

8 Test Holes Test Holes. Continued.Drill test holes out of permanent position at the location shown in the plans or as directed by the Engineer. Ensure the diameter and depth of the test hole or holes are the same diameter and maximum depth as the production drilled shafts. Reinforce the test hole unless otherwise directed in the Contract Documents. Fill the test hole with concrete in the same manner production drilled shafts will be constructed. Backfill test holes which are not filled with concrete with suitable soil in a manner satisfactory to the Engineer. Leave concreted test holes in place, except remove the top of the shaft to a depth of 2 feet below the ground line. 6-8 Version 1-1/15 6-8

9 Leave concreted test holes in place, except remove the top of the shaft to a depth of 2 feet below the ground line 6-9 Version 1-1/15 6-9

10 Test Holes Test Holes. Continued. Use the same procedure for shafts constructed in water. Restore the disturbed areas at the sites of test holes drilled out of position as nearly as practical to their original condition. When the Contractor fails to demonstrate to the Engineer the adequacy of his methods or equipment, and alterations are required, make appropriate modifications and provide additional test holes at no expense to the Department. Include the cost of all test holes in the cost of the Drilled Shafts. Make no changes in methods or equipment after initial approval without the consent of the Engineer Version 1-1/

11 Test Holes Test Holes. Continued A separate test hole is not required for drilled shafts installed under mast arms, cantilever signs, overhead truss signs, high mast light poles or other miscellaneous structures. The first production shaft will serve as a test hole for determining acceptability of the installation method Version 1-1/

12 Checklist 6-12 Version 1-1/

13 General General: All shaft excavation is Unclassified Shaft Excavation. The Engineer will require Drilled Shaft Sidewall Overreaming when inspections show it to be necessary. These terms are defined in , , and , respectively. Use excavation and drilling equipment having adequate capacity, including power, torque, and crowd (downthrust), and excavation and overreaming tools of adequate design, size, and strength to perform the work shown in the plans or described herein Version 1-1/

14 General General:Continued When the material encountered cannot be drilled using conventional earth augers and/or underreaming tools, provide special drilling equipment, including but not limited to rock augers, core barrels, rock tools, air tools, blasting materials, and other equipment as necessary to continue the shaft excavation to the size and depth required. In the event blasting is necessary, obtain all necessary permits. The Contractor is responsible for the effects of blasting on already completed work and adjacent structures. The Engineer must approve all blasting Version 1-1/

15 Unclassified Shaft Exca Unclassified Shaft Excavation: Unclassified Shaft Excavation is defined as all processes required to excavate a drilled shaft of the dimensions shown in the Contract Documents to the depth indicated in the plans plus 15 feet or plus 3 shaft diameters, whichever is deeper, completed and accepted. Include in the work all shaft excavation, whether the material encountered is soil, rock, weathered rock, stone, natural or man-made obstructions, or materials of other descriptions Version 1-1/

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17 Unclass. Extra Depth Ex Unclassified Extra Depth Excavation: Unclassified Extra Depth Excavation is defined as all processes required to excavate a drilled shaft of plan dimensions which is deeper than the limits defined as Unclassified Shaft Excavation Version 1-1/

18 D. S. Sidewall Overreaming Drilled Shaft Sidewall Overreaming: Drilled Shaft Sidewall Overreaming is defined as the unclassified excavation required to roughen its surface or to enlarge the drilled shaft diameter due to softening of the sidewalls or to remove excessive buildup of slurry cake when slurry is used. Increase the shaft radius a minimum of 1/2 inch and a maximum of 3 inches by overreaming. The Contractor may accomplish overreaming with a grooving tool, overreaming bucket, or other approved equipment Version 1-1/

19 Casing Casings: The Engineer will allow the Contractor to supply casing with an outside diameter equal to the specified shaft diameter (O.D. casing) provided he supplies additional shaft length at the shaft tip. Determine the additional length of shaft required by the following relationship: 6-19 Version 1-1/

20 Casing Casings: Continued Additional Length = (D 1 D 2 ) L D 2 where: D1 = casing inside diameter specified = shaft diameter specified D2 = casing inside diameter provided (D2 = D1 minus twice the wall thickness). L = authorized shaft length below ground for temporary casing methods or below casing for permanent casing methods. Bear all costs relating to this additional length including but not limited to the cost of extra excavation, extra concrete, and extra reinforcing steel If the contractor brings the proper size ID casing no correction to the length is required. Version 1-1/

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23 Method of Measurement Drilled Shafts: The quantity to be paid for will be the length, in feet, of the reinforced concrete drilled shaft of the diameter shown in the plans, completed and accepted. The length will be determined as the difference between the top of shaft elevation as shown in the plans and the final bottom of shaft elevation as authorized and accepted. When the Contractor elects to provide outside diameter (O.D.) sized casing rather than inside diameter (I.D.) sized casing as allowed in , the pay quantity measured as described above will be multiplied by a factor (F) determined as follows: 6-23 Version 1-1/

24 Method of Measurement F = 2D 2 D 1 D 2 where: F = factor to adjust pay quantities to compensate for smaller shafts D 1 = casing inside diameter specified = shaft diameter specified D 2 = casing inside diameter provided (D 2 = D 1 minus twice the wall thickness) 6-24 Note that there is no length involved; only diameters in this calculation This factor can never be greater than 1.0. Version 1-1/

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26 Inspection of Excavations Dimensions and Alignment: Provide equipment for checking the dimensions and alignment of each permanent shaft excavation. Determine the dimensions and alignment of the shaft excavation under the observation and direction of the Department. Generally check the alignment and dimensions by any of the following methods as necessary: (a) Check the dimensions and alignment of dry shaft excavations using reference stakes and a plumb bob. (b) Check the dimensions and alignment of casing when inserted in the excavation Version 1-1/

27 Inspection of Excavations Dimensions and Alignment: Continued (c) Insert a casing in shaft excavations temporarily for alignment and dimension checks. (d) Insert a rigid rod or pipe assembly with several 90- degree offsets equal to the shaft diameter into the shaft excavation for alignment and dimension checks. Insert any casing, rod or pipe assembly, or other device used to check dimensions and alignment into the excavation to full depth The depth of the shaft during drilling is usually referenced to appropriate marks on the Kelly bar or other suitable methods. Version 1-1/

28 Vertical Alignment ¼ Version 1-1/

29 Check for Vertical Alignment Casing 4 ft. Level positioned on reference Reference Version 1-1/

30 Check for Vertical Alignment Casing Tolerance Tolerance A Depth A Section A-A Plumb bob 6-30 Version 1-1/

31 Check for Vertical Alignment Casing Tolerance=12.5 A Depth =50 A Depth = 50 ft Tolerance; ¼ per ft., therefore, 0.25 x 50 ft. = 12.5 Plumb bob 6-31 Example: let s assume the shaft in the illustration is 50 ft. in depth. Determine Tolerance; ¼ per ft., therefore, 0.25 x 50 ft. = 12.5 Measure in from casing towards center of shaft lower plumb bob When plumb bob makes contact, note measurement. Do this at several locations around shaft. In our scenario, any measurement less than 50 ft. would indicate an out of alignment shaft. Note- we are assuming the shaft is clean and there is no significant accumulation of sediment or cuttings on the bottom. Version 1-1/

32 Inspector Duties for Test Hole The Inspector s responsibilities are the same during the Test Shaft Installation as in the Production Shaft installation Version 1-1/

33 Elevations Was this an English or Metric job? 6-33 Version 1-1/

34 Elevations What does Linear Measurement mean? + 20 When working with elevations, what must you keep your eye on? + Reference and - Reference Length ELEVATION IN FEET Version 1-1/

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38 Slurry Sampling and Testing 6-38 Version 1-1/

39 Slurry. Provide CTQP qualified Drilled Shaft qualified Inspector to perform control tests using suitable apparatus on the mineral slurry mixture to determine the following parameters: (a) Freshly mixed mineral slurry: Measure the density of the freshly mixed mineral slurry regularly as a check on the quality of the suspension being formed using a measuring device calibrated to read within ±0.5 lb/ft3. (b) Mineral slurry supplied to the drilled shaft excavation: Perform the following tests on the mineral slurry supplied to the shaft excavation and ensure that the results are within the ranges stated in the table below: 6-39 Version 1-1/

40 Slurry Slurry Tests Item to be measured Range of Results at 68 0 F Test Method Density 64 to 73 lb/ft 3 (in fresh water env.) 66 to 75 lb/ft 3 (in salt water env.) Mud density balance FM 8-RP13B-1 Viscosity 30 to 40 seconds Marsh Cone Method FM 8-RP13B-2 ph 8 to 11 Electric ph meter or ph indicator paper strips FM 8-RP13B-4 Sand Content 4% or less FM 8-RP13B Version 1-1/

41 Viscosity Test Also known as Marsh Funnel Test Measures the flow rate (i.e. consistency) FM 8-RP13B The viscosity test is also known as the Marsh Funnel. It measures the flow rate. This tests must be performed in accordance with the Florida Method FM 8-RP13B-2. This test is performed on the fluid and consists basically of measuring the time required for a prescribe d amount of slurr y, one q uarter of a gal lon, to p ass through a plastic funnel with a standar d size orifi ce. The fu nnel is hel d in an upright position with th e outlet sealed by one s hand or finger. The test sample is poured through the screen at the top of the funnel until the mud level just reaches the underside of the screen. A stop watch is used t o measure the time for a prescribed amount of mud to e xit the funnel with the results measured in seconds. As a comp arative number, clear wat er would generally have a test result of 26 seconds, which is a good check on the equipment. Version 1-1/

42 Mud Balance Test Also known as Mud Density Test Measures the density (i.e. unit weight) FM 8-RP13B The second test prescribed for the pre-mixed slurry, and a test that may also be used for testing samples from the actual excavation, is the density test or mud balance. This device is st andardized such th at a prescribed amount of mud can be added to a cup attached to a balance arm which rests across a fulcrum. Readings can be taken directly on the scale depending on the weight of mud contained in the cup. The procedures for this test are as follows: 1. Fill the cup with mud to be weighed. 2. Place the lid on the cup and seat it fir mly but slowly with a sliding motion. Be sure some mud runs out of the hole in the cap. 3. With the hole in the cap covered with a fi nger, wash or wipe do wn all mud from the outside of the cup and arm. 4. Move the sliding weight along the graduated arm until the cup and arm are balanced. 5. Read the density of the mud at the left hand edge of the sliding weight. Note; generally the equipment comes with a mark on the scale representing the weight of water (62.4 pcf). Also, you may use the specific gravity scale. For water the specific gravity is 1.0. A way to check that the scale is calibra ted is to te st clean water. You should get 62.4 pcf or a specific gravity of 1.0. Version 1-1/

43 For determining the acidity and alkalinity content of the slurry mix Reported as number value (1-14) FM 8-RP13B-4 ph Test 6-43 ph is a test to determine determining the acidity and alkalinity content of the slurry mix It is reported as number value (1-14) ph strips may be used to estimate this value. Version 1-1/

44 Sand Content Test For determining the sand content of the slurry mix Reported in volume percent FM 8-RP13B A more co mplex test is requir ed when the sand co ntent must be d etermined. Th e equipment required for this test consists of a 200 mesh sieve, a small funnel and a sand content tube. The test procedure is prescribed as follows: 1. Fill the sand content tube to the indicated mark with mud. Add wat er to next mark. Close mouth of the tube and shake vigorously. 2. Pour the mixture onto the clean, wet screen. Discard the liquid passing through the screen. Add more water to the tube, shake, and again pour onto the screen. Repeat until the wash water passes through clear. Wash the sand retained on the screen to free it of any remaining mud. 3. Fit the funnel upside down over the top of the screen. Slowly invert the assembly and insert the tip of the funnel into the mouth of the tube. Wash the sand int o the tube by spraying a fi ne spray of w ater through the screen. (Tappi ng on th e side of th e screen with a spa tula handle, may facilitate this process). Allow the sand to settle. From the gradations on the tube, read the volume percent of the sand. 4. Report the sand content of the mud in volume percent. Version 1-1/

45 Pre-mixed vs Fluid in Excavation Fluid in the excavation Slurry 6-45 Slurry refers to the pre-mixed slurry or the slurry that has not been introduced into the hole. Fluid in the excavation refers to the slurry or fluid in the shaft excavation. Version 1-1/

46 Pre-mixed Slurry , Slurry: Continued The Contractor may adjust the limits in the above table when field conditions warrant as successfully demonstrated in a Test Hole or with other methods approved by the Engineer. The Engineer must approve all changes in writing before the Contractor can continue to use them Version 1-1/

47 Slurry , Slurry: Continued Perform tests to determine density, viscosity, and ph value to establish a consistent working pattern, taking into account the mixing process and blending of freshly mixed mineral slurry and previously used mineral slurry. Perform a minimum of four sets of tests to determine density, viscosity, and ph value during the first 8 hours mineral slurry is in use Version 1-1/

48 Slurry , Slurry: Continued When the results show consistent behavior, discontinue the tests for ph value, and only carry out tests to determine density and viscosity during each four hours mineral slurry is in use. If the consistent working pattern changes, reintroduce the additional tests for ph value for the time required to establish consistency of the test values within the required parameters Version 1-1/

49 Slurry , Slurry: Continued (c) The Department may perform comparison tests as determined necessary during the mineral slurry operations Version 1-1/

50 Slurry , Slurry: Continued During construction, maintain the level of mineral slurry in the shaft excavation within the excavation and at a level not less than 4 feet above the highest expected piezometric water pressure along the depth of a shaft. At any time the wet construction method of stabilizing excavations fails, in the opinion of the Engineer, to produce the desired final result, discontinue this method of construction, and propose modifications in procedure or alternate means of construction for approval Piezometric level refers in the water level that would be observed in an open well or in a piezometer. In an artesian aquifer the water level may be significantly higher than the water level even higher than the ground level. In a typical normal unconfined aquifer the water table is the piezometric level Version 1-1/

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52 Polymer Slurry Misc. Struc Polymer Slurry For Shafts For Miscellaneous Structures:. Perform the following tests on the polymer slurry in the shaft excavation and ensure that the results are maintained within the ranges stated in the table below: 6-52 Polymer Slurry For Shafts For Miscellaneous Structures: The Department allows polymers that meet certain conditions to be used in shafts for miscellaneous structures only. The same tests performed for mineral slurry are performed. Version 1-1/

53 Polymer Slurry Misc. Struc. Mixed Polymer Slurry Properties Item to be measured Range of Results at 68 0 F Test Method Density Viscosity 62 to 64 lb/ft 3 (fresh water) 64 to 66 lb/ft 3 (salt water) Range published by the Manufacturer For Materials Excavated Mud density balance FM 8-RP13B-1 Marsh Cone Method FM 8-RP13B-2 ph Sand Content Range published by the Manufacturer For Materials Excavated 0.5% or less Electric ph meter or ph indicator paper strips FM 8-RP13B-4 FM 8-RP13B Version 1-1/

54 Polymer Slurry Misc. Struc Polymer Slurry For Shafts For Miscellaneous Structures: Continued..During construction, maintain the level of the slurry at a height sufficient to prevent caving of the hole. At any time the wet construction method of stabilizing excavations fails, in the opinion of the Engineer, to produce the desired final result, discontinue this method of construction, and propose modifications in procedure or alternate means of construction for approval Version 1-1/

55 Fluid in Excavation Fluid In Excavation At Time Of Concrete Placement: When any fluid is present in any drilled shaft excavation, including shafts to support miscellaneous structures, the applicable test methods and reporting requirements described in apply to tests of fluid in the shaft prior to placing the concrete 6-55 Version 1-1/

56 Fluid in Excavation Fluid In Excavation At Time Of Concrete Placement: Continued. Take samples of the fluid in the shaft from within 1 inch of the base of the shaft and at intervals not exceeding 30 feet up the shaft, using an approved sampling tool designed to sample over a depth range of 12 inches or less. Take whatever action is necessary prior to placing the concrete to bring the fluid within the specification and reporting requirements, outlined in the tables in , except as follows: The Engineer will not require tests for ph or viscosity when slurry has not been introduced into the shaft excavation Version 1-1/

57 Fluid in Excavation 6-57 Version 1-1/

58 Fluid in Excavation Fluid In Excavation At Time Of Concrete Placement: Continued When using polymer slurry to support the excavation for drilled shafts installed to support mast arms, cantilever signs, overhead truss signs, high mast light poles or other miscellaneous structures, take whatever action is necessary prior to placing the concrete to bring the properties of the fluid within the ranges in Section Version 1-1/

59 Fluid in Excavation Fluid In Excavation At Time Of Concrete Placement: Continued Provide a CTQP qualified Drilled Shaft Inspector to perform testing. The Department may also perform comparison tests. Provide equipment for such comparison tests when requested by the Engineer Version 1-1/

60 Down-hole Slurry Sampler 6-60 This is a Slurry Sampler designed for sampling slurry from a drilled shaft. A cable is attached to the bottom cap and runs through the sampling tube to the top cap. The lower cap is placed to the desired depth. The tube is then lowered to that depth. The top cap is allowed to slide down the cable, trapping slurry from the sample depth. Remember that the sampler should be designed to take fluid sample for a length not greater than 12 inches. Samples longer than that may provide diluted results particularly in the bottom sample. Version 1-1/

61 Drilled Shaft Fluid/Slurry Testing Log This could be filled in advance These data could be filled in advance Enter here results for premix condition Enter measurements Enter depths of samples 6-61 There is a form to be filled by the technician performing the slurry tests. Testing is performed at two instances: prior to introduce to the shaft (premix) and just prior to place concrete. This form is used to document both cases. Fill in every blank on the form. If it does not apply, put an N/A or a long dash. Use pencil -- but never erase. If you need to change something, strike a single line through the item and insert the correct information above it. If there is insufficient room to make a note, footnote the item and go to the bottom of the page, or use a separate page. Version 1-1/

62 Learning Outcome How many sets of tests are to be performed within the first 8 hours of mineral slurry use? Slurry samples are to be obtained at what intervals up the slurry column for testing? 6-62 Version 1-1/

63 Learning Outcome Which slurry tests are not required if neither mineral nor polymer slurry is being used? True or False Testing of the slurry prior to introduction into the shaft excavation is not required for drilled shafts to support mast arms, cantilever signs, overhead truss signs, high mast light poles or other miscellaneous structures Version 1-1/

64 Depth Depth: Generally reference the depth of the shaft during drilling to appropriate marks on the Kelly bar or other suitable methods. Measure final shaft depths with a suitable weighted tape or other approved methods after final cleaning The Inspector will know the approximate depth of the shaft from the kelly bar marks and a reference point, which is generally the top of the casing. Version 1-1/

65 Weighted Tape for Bottom Measurements 6-65 Version 1-1/

66 Shaft Inspection Generally determined and verified by lowering a weighted tape down to the bottom of the shaft after cleaning, or Contractor s marks on the kelly. Typically measured and recorded to the nearest 0.01 foot from the supplied reference. Check specifications for degree of accuracy, 6-66 Version 1-1/

67 Weighted Tape for Bottom Measurements 6-67 Version 1-1/

68 Bottom Sounding Device 6-68 Pictured here at the left side is a shaft sounding device called by the manufacturer as DID, an acronym for Ding Inspection Device. This device measures the thickness of sediments at local points using a strain gage. The measurements appear digitally in an electronic transducer. At the right side a technician is taking the sediment thickness readings with this device. The Department is currently testing this device and considering its use statewide in the near future. Version 1-1/

69 Shaft Cleanliness Reqrmt Shaft Cleanliness Requirements: Adjust cleaning operations so a minimum of 50% of the bottom of each shaft will have less than 1/2 inch of sediment at the time of placement of the concrete. Ensure the maximum depth of sedimentary deposits or any other debris at any place on the bottom of the shaft excavation does not exceed 1 1/2 inches. The Engineer will determine shaft cleanliness by visual inspection for dry shafts, using divers or an inspection device or other methods the Engineer deems appropriate for wet shafts. When using slurry, meet the requirements of at the time of concrete placement Version 1-1/

70 Checking Shaft Bottom for Cleanliness Weighted tape A-A A A < ½ for 50% of base Max. 1 ½ on base Sounding location 6-70 One of the most common methods to measure sediment on the bottom of the shaft is through the use of a weighted tape. Following removal of the drilling tool, lower a weighted tape sl owly down the hole until encountering the sediment or bottom. Take and record the measurement. Compare that measurement with the depth of the tape when it encounters a firm bottom which would be the depth of the shaft. The difference between these measurements is the thickness of sediment on the shaft bottom. Repeat this at five locations or more around the shaft. By doing 5 (or m ore) soundings around the shaft, the Inspector has accumu lated sufficient data to document compliance with both of the specified dimensions. Larger shafts may require more locations. Version 1-1/

71 Exceptions Misc. Shafts Exceptions for Shafts for Miscellaneous Structures: Ensure the depth of sedimentary deposits or other debris does not exceed 1 inch over the bottom of the shaft when installing drilled shafts to support mast arms, cantilever signs, overhead truss signs, high mast light poles or other miscellaneous structures Version 1-1/

72 Time of Excavation Time of Excavation: Any unclassified excavation work lasting more than 36 hours (measured from the beginning of excavation for all methods except the Permanent Casing Method, which begins at the time excavation begins below the casing) before placement of the concrete requires overreaming the sidewalls to the depth of softening or removing excessive slurry cake buildup. Ensure that the minimum depth of overreaming the shaft sidewall is 1/2 inch and the maximum depth is 3 inches Version 1-1/

73 Time of Excavation 6-73 Here is a Contractor- made overreaming bucket. In this case it consists of a piece of casing with holes burned through to allow sticking steel cable through. As the tool is turned the steel cable cleans the sides of the shaft. Note: the Contractor must still clean the bottom of the shaft. Remember that all shafts require cleanliness of the bottom and need to meet the cleanliness requirements of the specifications Version 1-1/

74 Time of Excavation Time of Excavation: Continued. Provide any overreaming required at no expense to the Department when exceeding the 36-hour limit unless the time limit is exceeded solely to accomplish excavating deeper than the elevation shown in the plans as ordered by the Engineer. The Department will pay the Contractor for authorized overreaming resulting from softening or excessive filtercake buildup which is indicated by sidewall samples or other test methods employed by the Engineer during the initial 36-hour time period Version 1-1/

75 Time of Excavation Time of Excavation: Continued...The Department will pay the Contractor for authorized overreaming when excavating deeper than the elevation shown in the plans as ordered by the Engineer exceeds the 36 hour limit. When using mineral slurry, adjust excavation operations so that the maximum time that slurry is in contact with the bottom 5 feet of the shaft (from time of drilling to concreting) does not exceed 12 hours. If exceeding the 12-hour time limit, overream the bottom 5 feet of shaft at no additional expense to the Department prior to performing other operations in the shaft Version 1-1/

76 Shaft Inspection Devices (SID) 6-76 This photograph shows a mini-sids which are currently used in our projects. These are much smaller and easier to mobilize and use than the previous large FDOT device. In addition the camera has a better resolution. Version 1-1/

77 Mini-SID 6-77 Version 1-1/

78 Shaft Inspection Device Shaft Inspection Device (SID): When shown in the plans, furnish all power and equipment necessary for the Engineer to inspect the bottom conditions of a drilled shaft excavation and the measure the thickness of bottom sediment or any other debris using a SID. Provide a means to position and lower the SID into the shaft excavation to enable the bell housing to rest vertically on the bottom of the excavation. Include all cost related to the inspection device in the cost of drilled shaft items Version 1-1/

79 Learning Outcome Question: What if Contractor wants to extend shaft due to debris in bottom at planned tip elevation? Is cleaning still required? (Ex: Shaft is to be 30 ft. Because there is 2 feet of debris, Contractor wants to drill down to 32 ft.) Answer: 6-79 Version 1-1/

80 Typical Problem Folded-in debris- insufficient cleaning of the shaft, excessive cuttings suspended in slurry. Soft shaft bottom- incomplete bottom cleaning, side sloughing or sedimentation of cuttings from slurry column. Reduced concrete section at the bottom of shaftbullet shaped tip Version 1-1/

81 Learning Outcome The maximum depth of sediment or debris permitted anywhere on the bottom of a bridge foundation shaft is? Describe a common non-intrusive method of determining shaft cleanliness Version 1-1/

82 Drilled Shaft Log Form The Drilled Shaft Log form, Form number is used to record the events observed during the excavation process. The log consists of two pages. They are available in pdf and excel formats. In the pdf formats the inspector needs to compute the data of the field highlighted in yellow. In the excel format these fields are compute automatically. Version 1-1/

83 Drilled Shaft Log Form Page 1 Page The form contains two pages. These can be accessed in the spreadsheet by clicking the tabs at the bottom. Version 1-1/

84 1 Drilled Shaft Log We will go to the page 1 first. For our explanation we will divide this page in sections 1 through 10 as shown in the slide Version 1-1/

85 Drilled Shaft Log Section 1 consists of the heading with the following basic information: Project name, Financial project number, Contractor s name, Inspector s name, dates, pier number, shaft n umber, stations and offsets and t he bridge or structure number. This information may be filled before drilling starts. Be sure to print your name & the start date of drilling or casing installation. The Project Administrator or permit manager will sign approval line. Version 1-1/

86 Drilled Shaft Log-Page 1 Section We will use this slide now to illustrate the section 2 of the form, in which detailed casing information is input. The form allows the input of up to two casings (one outside and one inside). The inside casing may be segmental. The form allows the use of up to 5 segmental sections in the interior casing. The figure at the right side illustrates the casing sections for the input of this part of the form. When using the excel spreadsheet, the yellow fields are formulas and you cannot enter anything on them. Type could be either permanent or temporary. ID, OD are the inside and outside diameters of the casings For the outside casing you input the total length of the casing used. For the i nterior segmental casing you enter the i ndividual segment lengths. The spreadsheet will compute the total length of the segments of the interior casing, and the bottom elevation of both casings. If there is no segments but only one section just enter one section under the top section column. Do not enter it under the collar column as it produces redundant information. Even though the information shown is correct it may be confusing for a reader. Version 1-1/

87 Drilled Shaft Log-Page This is the right part of page 1 of the form. We will cover now the different sections of this area. Section 3: Enter Da tes of casing i nstallation, dates of e xcavation and the date of pouring. Section 4: Enter in itial reference elevations. Indicate ground surface elevation, water table and the shaft top elevations, both per plans and the as built elevation. The drilled shaft bottom elevation is deter mined after the aver age shaft bottom elevation is calculated in page 2. We will look into page 2 in a moment. Section 5: Enter auger diameter used in inches. Enter rock socket diameter, rock socket length achieved in the shaft, and actual shaft diameters. Indicate whether the shaft was overreamed. The constructed shaft length is calculated from th e actual shaf t top elevation and th e drilled shaft bottom elevation input in section 4. Section 6 Enter the computed theoretical volume and actual volume of concrete placed and the ratio Actual over theoretical volumes A over T. This will be input after concrete is completed. Version 1-1/

88 Drilled Shaft Log-Page This is the main body of the log where you will document the materials encountered. We will cover the sections of this area: Section 7: Enter Depth. Depth can be measured by either: Contractor Kelly bar marks or The use of a Weighted tape Section 8: Enter times whenever tools go in and come out of hole. Be sure to input the AM and PM after the hour, or use military times based on 24 hours. Section 9: Enter reference elevation. In the spreadsheet, if th ere are no ch anges you can just copy and paste the input down the column. This input is used to compute t he elevations of the bottom of the shaft as the excavation progresses. Elevations in the yellow column, are calculated based on the reference elevation and the depth. In the spreadsheet this occurs automatically. Section 10: Accurately describe soil and rock materials observed from the drilled shaft excavation. Enter any pertinent Notes regarding events observed during the excavation (example: loss of slurry, setting more casing, etc.) Version 1-1/

89 Drilled Shaft Log -Page This is page 2 of the form. In the left side, it contains a continuation of the sections 7 to 10 already covered when we saw the fir st page. We use th ese columns to keep inputting deeper information of the materials observed during excavation and pertinent notes of events observed. In deep shafts it may be required to use this p age 2 more than once until completing the full depth of the shaft. We also use this page to record the bottom cleanliness and depth information. We will cover now the sections at the right side of this page. Section 11: This is a quick checklist to document whether the rebar det ails were checked. Section 12: Indicate here what tools were used in the clean out operation. Section 13: Enter here the date and time of the clean out completion. Section 14: Indicate here the method used to perform the bottom cleanliness inspection. Enter also the reference elevation to be used to compute the final tip elevation. Section 15: Enter the sediment thickness and depth of the shaft at each of the points indicated. The next slide illustrates a detail of this section. Enter also the starting and finishing times of the bottom inspection. Version 1-1/

90 Drilled Shaft Log -Page 2 Depth Sediment 6-90 Here we see a detail of a sample of section 15 of page 2. Input the information measured at each point. Depth is input at the top of the line in ft. Sediment thickness is in put below the line in inches. For example, in point 5 of the example, the depth is 90.2 feet and the sediment is 0.3 inches thick. The yellow fields are for t he average shaft bottom elevation and the average shaft depth. These are computed based on the 5 points measured above and the reference elevation entered here. In the spreadsheet these are automatically computed and you cannot input data on them. The average shaft bottom elevation is also used in part 4 of page 1 as we saw earlier (click twice to show right table with arrow) This is the end of the instructions for the Drilled Shaft log. Version 1-1/

91 Shaft Inspection Device Log % Area <1/2 sediments Max. Sediment in inches Average of % Area <1/2 sediments 6-91 When a Shaft Inspection Device SID or mineshaft Inspection device is used th e Department has a separate f orm to fill. Use form to document the details of the shaft inspection device. The camera has to be placed on a minimum of f ive locations as indicated in t he log. Large diameter shafts may require additional points. Discuss with the PA regarding the number of points required. At each camera location observe and record the largest thickness of the se diments. If the sediment at o ne location already exceeds 1.5, t he shaft ca nnot be a pproved for pouring and the contractor must perform additional cleaning. At each camera location observe and estimate the percentage of the view area that has less than ½ inch sediments. After all the locations have be en observed and r ecorded determine the average percentage of the sha ft with less than ½ in ch of sedi ments. This is done simply by performing an arithmetic average of the individual locations. If the average of the five (or more) readings is les s than 50%, the shaft is n ot acceptable for p ouring and the contractor needs to perform additional cleaning. Version 1-1/

92 Shaft Inspection Device Log 10.6 Shaft Inspection Device (SID).. The Shaft Inspection Device uses pressurized nitrogen to overcome the static head of the drilling fluids, purge the fluids from the camera bell, and provide an unobstructed view of the shaft. A small reduction in air pressure would allow drilling fluid to slowly enter the bell. When the shaft bottom is flat (as required in Specifications) and the bell is plumb, a layer of water or drilling fluid in the bell can be used measure the thickness of sediments mounds "away" from the sediment depth gauge. When the fluid rises to the 1/2" pin on the gauge, the percentage of the view covered with sediment deposits thicker than 1/2" may be estimated; these sediments are above the fluid level. When the1/2"depthpinismissingthefirstmark(1.0cm)depthmustbeused. Thesame procedure may also be used to determine whether any portion of the view contains sediments in excess of 1-1/2" [4.0 cm] thick. Special care must be used to ensure the fluid does not erode the sediment as it enters the bell, especially if the operator attempts to fill the bell with water using the water jets intended for flushing these sediments, instead of filling the bell with drilling fluid as described above. (FROM SOILS AND FOUNDATION HANDBOOK 2015) 6-92 Version 1-1/

93 Learning Outcomes Perform inspection of drilled shaft excavations for compliance to plans, tolerances and cleanliness. Perform visual field verification of soil/rock material for comparison to supplied soil boring data/logs. Sample and test slurry and fluid in the excavation. Calculate Elevations & Extra Shaft Lengths. Identify the applicable 455 Specifications 6-93 Version 1-1/

94 Questions? ANY QUESTIONS? 6-94 Version 1-1/

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99 Project Name: FIN Project No: Contractor: Inspected By: xxxxxx xxxxxx xxxxxx xxxxxx STATE OF FLORIDA DEPARTMENT OF TRANSPORTATION SHAFT INSPECTION DEVICE LOG VISUAL INSPECTION REPORT Date: xx/xx/xx CONSTRUCTION Shaft No: Depth: Diameter: Clean out method xx ft 48 " air lift and clean out bucket Inspection No: Date: Time: xx xx/xx/xx xx:xx % Area < 1/2" sediments 100 % Max. Sediment: 0.5 in % Area % Area % Area < 1/2" < 1/2" < 1/2" sediments: sediments: sediments: 33 % 33 % 100 % Max. Sediment: Max. Sediment: Max. Sediment: 1 in 1.25 in 0.5 in % Area < 1/2" sediments: 100 % Max. Sediment: % Area <1/2" 0.5 in sediments: 73.2 % Comments More than 50% has less than 1/2" sediments. Pass Approval for pouring x Yes No Given to By Time xxxxxx xxxxxx xx:xx Date xx/xx/xx NOTE: Referring to Specification

100 STATE OF FLORIDA DEPARTMENT OF TRANSPORTATION DRILLED SHAFT FLUID/SLURRY TESTING LOG CONSTRUCTION 10/13 Page 1 Project Name: xxxxx Pier No. xxxx FIN Project No. xxxxx Shaft I.D. or # 1 QC Testing Technician xxxxx TIN Date: Station Testing Witnessed by: xxxxx TIN Date: Offset Bridge/Structure # xxxxxxxxx Slurry/fluid type: water/natural slurry Was this slurry/fluid included in the DSIP? Yes x No ` NOTE: Fill-in the acceptable values for the particular fluid being used, soil and water environmental conditions Passing Density (pcf): NA to 73 Passing ph: NA to NA Passing Visc. (sec): NA to NA Passing Sand cont.: < 4 % a) Premix Condition (Tank) Sand Viscosity Time Density ph Content Pass Fail (lb/ft3) (sec) (%) * Comments NA no mineral slurry used Note * If recycled slurry is introduced b) Before Placing Concrete (Bottom and at max. intervals of 30 ft) ** Sampling tool length: 12 (in) Sampling tool diameter: 2 (in) Sand Depths Density ph Viscosity Content Pass Fail Comments (ft) (lb/ft3) (sec) (%) NA NA 0.5 x NA NA 0.25 x NA NA 0.25 x 0 63 NA NA 0.25 x Note** For projects let before January 1/14, max. interval= 10 ft. For projects let after January 1/14 max. interval= 30 ft.