The Installation of Hollow Bars Joe Patterson TEI

The Installation of Hollow Bars Joe Patterson TEI Rock Drills

Hollow Bars - Advantages • • It works in any soil condition, without casing One-step process Less equipment Simple

Hollow Bars – Materials and Equipment The equipment, as well as the installation, of hollow bars is relatively simple. Hollow bars, nuts, bits etc. Drill Rig Grout Plant

Hollow Bars - Sizes • Continuously threaded to allow cutting & coupling at any length • Req’d size determined in design • 30 mm to 130 mm diameter bars • Grades vary: 60 - over 90 ksi • Amount of steel determines capacity (30 kips to 500+ kips)

Hollow Bars – Drill Bits

Hollow Bars - Applications Micropiles for earth retention Anchors for Excavation Repairing an underpass

Hollow Bars – Applications Increasing the Capacity of Cell Towers Lifting a Structure

Drill Rig Requirements • Mast or Feed System in a Basket or on a Rig

Drill Rig Requirements • Mast or Feed System in a Basket or on a Rig • Kinematics to reach the hole

Drill Rig Requirements • Mast or Feed System in a Basket or on a Rig • Kinematics to reach the hole • Drifter with Rotary AND Percussion

Drill Rig Requirements • Mast or Feed System in a Basket or on a Rig • Kinematics to reach the hole • Drifter with Rotary AND Percussion • Clamp and Breaker

Drill Rig Requirements • Mast or Feed System in a Basket or on a Rig • Kinematics to reach the hole • Drifter with Rotary AND Percussion • Clamp and Breaker • Grout Swivel 100 bar (1450 PSI)

Hollow Bars – Grout Mixers • As important as the drill • Cuts soil as much as the bit • Most difficult piece of equipment Paddle Mixer 80 -100 RPM High Shear/Colloidal Mixer 1200 RPM

Hollow Bars – Grout Pumps • Supply constant flow/pressure of grout to the bit • High pressure to penetrate the soil & unplug the bit • Twin plunger pump is required for hollow bars Single Piston Twin Plunger Progressive Cavity Screw Pump Moyno

Grout Plant Operation • Spray it down first! • Keep all safety panels in place • Protect your eyes with goggles • Protect your ears with plugs • Protect your lungs with a respirator • Protect your skin with clothing, long sleeves and gloves

Water • Should be potable water • No organic particles in the water! • Ensure sufficient supply for Grouting and Cleaning

Water / Cement Ratio for Final Grout • Imperial Units • 94 lbs bag with 5 gallons of water: w/c = 0. 44 • Metric units • 40 kg bag with 18 liters of water: w/c = 0. 45 • Specific Gravity • Measured with a mud balance: SG ≈ 1. 8

Water / Cement Ratio • Using Imperial Units for a Flushing Grout Mix with a w/c = 0. 8 Mixer Working Volume 3 bags of cement @ 94 lb/ea Cement volume = 282 lbs/26. 2 lbs/gal Water weight = 0. 8 x 282 lbs 45 gallons 282 lbs 10. 8 gallons 225. 6 lbs Water volume = 225. 6 lbs / 8. 33 lbs/gal 27. 1 gallons Total volume 37. 9 gallons

Water / Cement Ratio • Using Imperial Units for a Final Grout Mix with a w/c = 0. 45 Mixer Working Volume 5 bags of cement @ 94 lb/ea Cement volume = 470 lbs/26. 2 lbs/gal Water weight = 0. 45 x 470 lbs 46 gallons 470 lbs 17. 9 gallons 211. 5 lbs Water volume = 211. 5 lbs / 8. 33 lbs/gal 25. 4 gallons Total volume 43. 3 gallons

Quality Control – Methods of Grout Testing • Marsh Cone • • Principal: Flow time is proportional to viscosity Measured flow time is compared with predicted flow time • Mud Balance • • Accurate determination of specific gravity Immediate results during grouting • Cube samples • • • 50 x 50 mm (2 x 2 x 2“) Grout compressive strength at 3, 7, 14 and 28 days Too late to change procedures on job site

Quality Control – Grout Strength • Grout Strength Gain • • • Day 1 – 45% Day 7 – 75% Day 28 – 90% • Effect of Adding Water • A 25% increase in water will decrease grout strength by 50%

Hollow Bars - Drilling • • • Drill hole using designed bar & bit size Thin grout is used to flush the hole When design depth is reached, stop advancing Thick grout is used to finish the hole Flush with finish grout 5 -10 times or until the thick grout returns to the surface Exhumed hollow bars next to cased micropiles, for FHWA testing in Montrose, Colorado

Steps for the installation of Hollow Bars • • • Review drill control functions Review grout plant operation Assemble the drill string Clamp and centralizer Rotation/Feed/Hammer Down pressure on the bit Grout returns, plunging the hole Adding another hollow bar Grout permeation of the soil What’s happening at the bit Finishing the installation

Assembling the Drill String • Connect the grout plant and the drifter with a hose 1” diameter • Use bit grease on the shank and coupling but not the bit • Run drill to the top of the mast • Helper holds the drill steel/coupling WATCH HELPERS HANDS • Rotate slowly onto the coupling • Clamp the hollow bar above the bit • Think from grout plant to bit • Communicate with helper and grout plant operator.

Drilling Progression Grout flow is on (good, even flow) Rotation is on (at 60 -80 RPM) Slowly feed bit into the hole “Collar” the top of the hole Ensure grout return is constant Consider percussion as assistance with the rotation • Back off every 2 -3 feet (clear drill cuttings at the bit and ensure even grout flow) • Rotation is always on • • •

Down Pressure on Bit • Adjustable 0 psi to 2500 psi • Adjustable from the radio control or drill control panel • Adjusts only the down pressure • Out of hole is full pressure • Watch and listen for correct pressure • Too much pressure – Bar is bowing and lifting the drill off the ground • Too little pressure – Bar is “ringy” • Generally around 700 -1000 psi

Grouting and Grout Return • Drill the hole using thin grout • This permeates the surrounding soil and acts as drilling fluid • Constantly watch for grout returns • Helper should be clearing the top of the hole of drill cutting and excess grout using a shovel • If grout return stops, stop drilling • If drilling in rock switch to only water while drilling rock then back to grout in soils • Before adding a new hollow bar, plunge the hole 3 -5 times of the full bar

Grouting and Grout Return Don’t let this be your job site. Construct good products!

Grouting and Grout Return What to do if you lose grout return 1. Stop advancing the drill, continue to rotate, wait for grout to return, plunge hole to increase flow and pressure of grout to clear the hole. 2. Drill quickly through the void, stop advancing, wait for grout to return. Always have a grout clause in your contract to cover extra grout. 3. Change your grout to a specialized quick setting grout as the final option. Hollow Bar Drill School

Adding Hollow Bars • Drill below the clamp as deep as the feed will go • Plunge the hole 3 -5 times • Grab the coupling with the clamp • Reverse the rotation slowly • Pull drifter back slowly • Run drifter to the top of the feed • Thread another bar and coupling • Open the clamp • Grout flow and rotation on • Resume drilling when you have grout flow coming from the hole

Finishing the Hole • Plunge the hole 5 -10 times using the thick grout mixture • Rattle/Unthread the last coupling off the hollow bar • Push casing over bar if required • Extend/Crowd off of the hole • Swing the boom away from the hole avoiding clamp • Center the bar in the hole

Things to Consider while Drilling… • What is happening at the bit? • Is the grout permeating the soil? • Am I going to hit a void? • What will I do if I lose grout flow? • Am I constructing a good product You are basically waiting for something to go wrong!

Grouting Equipment – Clean Up Watch out, this is a sore point: • Run water through mixer and pump until clear water comes out • Blow through pipes and hoses with compressed air • Use pressure washer to clean mixer and holding tank • Check suction and pressure valves for grout deposits • Use hand brush to remove grout from difficult spots • Remove gates from mixers and flush remaining cement deposits out • Grease entire machine and pump

Drilling Equipment – Clean Up • Flush grout line until clear water comes out of the shank • Remove all grout from drill rig with pressure washer and brush • Remove grout swivel, clean and grease the seals, replace if needed • Grease the drifter, feed, rig • Inspect for loose or missing bolts, nuts or washers

Additional Technical Resources List of recommended web sites for information on designing and installing hollow bars • Federal Highway Administration (FHWA) site for all soil nail and earth retention documents: http: //www. fhwa. dot. gov/engineering/geotech/library_sub. cfm? keyword=020 • ADSC and DFI site for books, design and construction manuals, private and public research, etc. : www. adsc-iafd. com www. dfi. org • TEI site for all brochures, specifications, and pictures: www. teirockdrills. com

Thank You for Your Attention! 2015 TEI Hollow Bar Installation School