By Peggy Hagerty Duffy, P.E., ADSC Technical Advisor

Page 18 FOUNDATION DRILLING July 2014

Reality TV relies on drama and conflict for success. Drama and conflict in con-struction create not revenues and promotion, but added cost to the owner, loss of prof-its for the contractor, and poor publicity for all involved. Many projects have challengesthat produce the potential for job problems and drama worthy of its own “Keeping upwith the Kardashians” reality TV series, but numerous other complicated projectsnever travel down that road. These are the successful projects no one hears about be-cause everyone involved is…happy. Long Foundation Drilling Co., ADSC ContractorMember, Hermitage, Tennessee, recently completed such a project.Alabama State Road 13 is located in Franklin County, Alabama, in the northwest

portion of the state. The route is frequently traveled as a connector to Interstate 22 be-tween Memphis and Birmingham. The area has seen significant population increasein recent years, and the presence of the Upper Bear Creek Reservoir in the center ofthe region has presented access issues for commuters and transportation interests try-ing to traverse the county. Travel between the northern part of the county and thesouth has included a nearly 45 minute trip around the reservoir. In addition, the por-tion of State Road 13 between the towns of Phil Campbell and Haleyville has only twolanes. This geographical obstacle has become increasingly significant as area officialsattempt to optimize the local infrastructure for economic development. In the early 2000’s Alabama officials identified State Road 13 as a transportation

improvement priority. The existing alignment of State Road 13 extends to the west ofthe Bear Creek Reservoir and travels to the southeast toward Haleyville. State officialsdeveloped a plan to relocate the road to cross the Gas Branch and Bear Creek sections

of the reservoir, cutting travel timesacross the reservoir significantlyand, therefore, creating a more di-rect route to the south. The newroute includes dual bridges at GasBranch, one for southbound trafficand the other for northbound driv-ers. The bridges are approximately1,100 feet long. Planning for the project began in

2001, when initial environmentalscoping began. Construction of anyalignment crossing the reservoirwould involve work in the flood-

Cove

r Fe

ature Long Foundation’s

Hard Rock ExperienceBeneficial for Project

Special spoil handling and containment was required at the waterway locations.

plain and disturbance of threatened plantspecies. In addition, endangered bat specieswere recorded as living in the area. An Envi-ronmental Assessment was performed, and

“404-Permitting” was required, placing re-strictions on construction methodologyaround the water. The final alignment was a

(Continued on page 20)

Long Foundation Just Right for ALDOT Bridge Project

Bridge design, including foundations, was performed in-house by ALDOT engineers. Construction was delayed until sufficient funding could be obtained. Bidding forthe project took place in early 2013.

FOUNDATION DRILLING July 2014 Page 19

Sequencing work on benches along main access road while coordinating material deliveries.

Page 20 FOUNDATION DRILLING July 2014Page 20

LONG Contd.

Drilled shaft work on both sides of water-way as access preparation underway forredesigned Bent 3 South.

product of optimal topographic conditions, aswell as minimal environmental damage.Bridge design, including foundations, was per-

formed in-house by ALDOT engineers. Con-struction was delayed until sufficient fundingcould be obtained. Bidding for the project tookplace in early 2013. Wright Brothers Construc-tion, a general contractor based in Charleston,Tennessee, was awarded the project. Long Foun-dation Drilling Co., with a local office in Birm-ingham, Alabama, won the subcontract toconstruct the drilled shaft foundations.

Subsurface Conditions

In 2002, a geotechnical exploration was per-formed by Southern Earth Sciences of Mobile,Alabama. Borings were advanced where possiblealong the alignment. Heavy vegetation and steeprelief prohibited borings from being conductedat certain locations along the route. The groundsurface elevation of the overall project siteranged almost 250 feet, from 725 feet to 975 feetabove the National Geodetical Vertical Datum of1929 (NVGD). Ground surface elevations inproposed foundation locations ranged approxi-mately 120 feet from the tops of the slopes tonormal pool.Borings included standard penetration testing

and sampling. Rock coring also was performedin each boring. The project site is underlain primarily by the

lower portion of the Pottsville formation of theAppalachian Plateaus physiographic province.This formation is composed of light gray quart-zose sandstone, with interbedded dark grayshale, siltstone, and thin, discontinuous coal.Borings encountered relatively little overbur-

den, with clay, silt, and sand layers extending todepths of only 2.62 feet to 28.9 feet. Some thinshale strata were observed. Beneath refusal, lightgray, fine-grained sandstone was observed.

LONG Contd.

(Continued on page 22)

FOUNDATION DRILLING July 2014 Page 21

Sample of the quartzose sandstone with embeddedquartz gravel.

Page 22 FOUNDATION DRILLING July 2014

Layers of quartzose sandstone were encountered in some bor-ings, typically in zones 6 feet to as much as 30 feet thick. Thisrock was very hard and highly abrasive. The concentration ofquartz gravel varied significantly between the borings, but mostof the zones of heavy quartzose gravel were 6 feet thick or less.

Foundation Design

Heavy loads, shallow depth to refusal, and hard, competent rockmade drilled shafts the most suitable foundation option. Shaftswere designed to be socketed up to seven diameters into soundand continuous sandstone. This design was a function of lateralloads on the bridge. Much of the compressive loads were designed

to be resisted by side shear. The geotechnical engineer recom-mended probe holes in each shaft excavation to confirm suitablebearing conditions.

Each bridge bent was designed to be supported by four drilledshafts, 48-inch to 72-inch in diameter. Bridge abutments were sup-ported by 42-inch diameter shafts. Four of the bents were to be lo-cated to bear below normal pool elevation of Gas Branch. Thegeotechnical report indicated that casing should be used for shafts

in the waterway. Dry construction methods were thought to be vi-able for the shafts once casing was installed. In the event that wetconstruction methods were necessary, crosshole sonic logging test-ing would be required.

Construction

Construction of the bridges would involve complications in fourmajor areas: accessibility, sequencing, dewatering, and removal of

LONG Contd.

Steep hilly terrain created accessability challanges for drilling andconcreting operations.

Each bridge bent was designed to be supported by fourdrilled shafts, 48-inch to 72-inch in diameter. Bridge abutments were supported by 42-inch diameter shafts.

Heavy loads, shallow depth to refusal, and hard, competentrock made drilled shafts the most suitable foundation option.Shafts were designed to be socketed up to seven diametersinto sound and continuous sandstone.

FOUNDATION DRILLING July 2014 Page 23

large quantities of sandstone with heavyquartzose gravel concentrations. WrightBrothers and Long Foundation Drilling Co.worked with ALDOT closely from well be-fore construction began to work out potential

problems and identify the most suitable andefficient methods for dealing with each issue.

Sequencing

Slopes within the construction area wereas steep as 24%. The rough terrain combinedwith the close proximity of bent locationscreated logistical challenges. Long Founda-tion Drilling Co. and Wright Brothers met ex-tensively prior to the start of the project toestablish a very detailed sequence of work sothat access preparations, spoils removal, anddrilling would not conflict and cause workdelays.Access to the steep site was accomplished

by building a construction road to the east ofthe proposed alignment of the two bridges.Wright Brothers cleared vegetation andplaced limestone gravel to construct a roadsuitable to support drill rigs, concrete trucksand hoisting equipment, as well as dumptrucks needed to carry off spoils. Construc-tion of the access road started several monthsbefore earthwork and drilling commenced.The selection of drill rigs maneuverable

enough to navigate the steep hilly terrain yetpowerful enough to excavate the largeamounts of hard abrasive rock was para-mount to the success of the project. It was de-cided that a Watson 3110* and a Watson3100* had the right capabilities needed forthis project.Benches were cut into the steep slopes

leading down to the creek in order to provideworking platforms for drill rigs to construct drilled shaft founda-tions for the bridge bents. Wright Brothers initiated bench con-struction two months before Long mobilized to the site in order toprovide sufficient access to allow at least two rigs to operate at thesame time.Bench construction also entailed a large volume of rock re-

moval. Blasting and hoe rams were used to excavate rock to theprescribed elevations for construction. Benching operations con-tinued well after drilling began. In many cases, shaft excavationbegan in hard rock and continued to tip elevation. Some shafts re-

quired almost 50 feet of rock excavation before reaching an ap-proved bottom. Almost 2000 linear feet of rock excavation wascompleted for drilled shaft construction.Long Foundation Drilling Co. devised a very specific drilling

sequence so that one rig would not be cut off by a second rig work-ing on the same bench. The plan also accounted for the position-ing of drill rigs so that concrete placement could continue whileshaft excavation was being performed on the same bench. Spoilsfrom the drill rigs were spun off into a skip pan made from a dump

LONG Contd.

(Continued on page 24)

Redesign elevations at Bent 3 South required rock coring techniques from top of subgrade.

Wright Brothers and Long FoundationDrilling Co. worked with ALDOT closelyfrom well before construction began to work out potential problems andidentify the most suitable and efficientmethods for dealing with each issue.

truck bed. An excavator was used to transport spoils from the skippan into dump trucks. Extended operations or delays at any shaftscould have caused delays in getting to shaft locations in close prox-imity. Therefore, Long’s sequence was set up so that shafts inprogress were close enough to permit shared access but not soclose as to risk interference.The sequencing plan was complicated further by restrictions on

work in the creek due to environmental issues. Shafts in the water,(at the lowest elevation), had to be completed with very careful

erosion control measures and handling of spoils. In addition,working pads had to be built in the water to provide Long accessto the holes. As such, construction of the last sixteen shafts on theproject constituted a separate phase of work with different con-straints.Long petitioned ALDOT to allow all shafts in each bent to be

poured at the same time. The approval of this method reduced a

significant amount of downtime. Typical specifications for ALDOTbridge projects have mandated that shaft excavation cannot takeplace until after concrete has reached strength in an adjacent, com-pleted shaft excavation. Long representatives indicated that thischange positively affected the overall job progress without jeop-ardizing shaft integrity. ALDOT was aware of the additional movesand time required to place concrete for each shaft immediatelyupon completion of excavation, and they appreciated the logisti-cal benefits of Long’s plans with minimal associated risk.

Rock Removal

Although the geotechnical report identified hard, abrasive lay-ers of sandstone with quartzose gravel, it was not possible to knowin advance how thick the concentrations of quartzose gravel wouldbe when actually encountered. Long Foundation Drilling Co. uti-lized standard core barrels to perform coring operations for mostof the rock removed at the site. Shot barrels also were used whenthe very hard, abrasive zones were encountered. Long has exten-sive experience drilling rock in the area. In prior jobs they hadused a number of methods, including pilot hole drilling, to removea variety of rock types. As a result, Long came to the project well

Page 24 FOUNDATION DRILLING July 2014

LONG Contd.

In many cases, shaft excavation began in hard rock and continued to tip elevation. Some shafts required almost 50feet of rock excavation before reaching an approved bottom.Almost 2000 linear feet of rock excavation was completedfor drilled shaft construction.

Concrete pump used for areas inaccessable to truck traffic.

prepared for potential rock conditions, and they equipped them-selves accordingly.Long’s familiarity with local rock conditions and appropriate

rock removal methods proved to be critical in facilitating efficient

drilling without long delays to evaluate variations in the rock hard-ness and abrasivity.

Field Redesign

Heavy vegetation onsite prior to construction created compli-cations with regard to surveying and access for the geotechnicalexploration. It was not evident until construction began that shaftsfor Bent #3 on the southbound bridge were located at the edge ofa rock bluff. Drilling of the shafts at the original locations would have re-

quired drilling over the edge of the bluff to the ground surface over20 feet below. Bent #3 was deemed unconstructable at the originallocation, and redesign was necessary. ALDOT engineers redesignedthe bent so that the shaft elevations would be located at the baseof the bluff. All redesign was completed during construction, andno significant delays were experienced even though a large vol-ume of mass rock was removed to produce the working surfacefor shaft construction.Moving the shafts to the lower elevation affected the drilling se-

quence, which already was tightly scheduled. Redesign was com-pleted relatively quickly and early in the project so that sequencingcould be adjusted. Redesign and repositioning of Bent #3 south-bound was completed with minimum impact to scheduling, inlarge part due to the diligence and detailed cooperation of ALDOT,Wright Brothers, and Long. ALDOT engaged in several in-depthmeetings with the design team and with the contractors to makesolving this issue a priority.

Dewatering

Another unknown in the planning stages of the project involveddewatering of shafts below normal pool elevation in the creek.Geotechnical data suggested that shaft excavations could be de-watered by advancing casing into rock to seal off the holes againstwater inflow. However, discontinuities in the upper rock surfacecould provide pathways for seepage. Without specific informationabout rock conditions across the shaft cross-sectional area at eachlocation, it would not be possible to determine in advance if cas-ing alone could be used to effect dewatering.Rip rap benches were used to provide working platforms for

the shafts located in the creek. In order to avoid having to drillback through the rip rap, Long and Wright Brothers chose to ad-vance a 102-inch diameter casing approximately 10 to 12 feetlong at the start of each shaft. Rip rap was placed around the cas-ing, creating a cofferdam of sorts within the rip rap. An 84-inchdiameter casing then was twisted into the top of rock to seal thehole from water inflow. No spoils were removed from within this

or the first casing. The final 78-inch permanent casing was drilleddown through the second casing and screwed into rock, thus cre-ating a double seal against water infiltration. Excavation advancedthrough the interior casing and down into rock to complete thepermanent shaft. This method was successful in permitting con-crete placement in dry conditions. The two outer casings were ex-tracted once the concrete had cured.Extensive environmental controls were implemented to prevent

spoils from being deposited in the creek and disrupting existinghabitats. Silt bags were placed throughout the excavation area, thefloodway perimeter was defined and protected, and spoils disposalwas controlled carefully. All materials excavated from the shaftswere removed promptly and were transported off the site.

Conclusion

Construction of all drilled shaft foundations was completed inDecember of 2013, within the original schedule. A number ofcomplications were encountered during construction that couldhave created significant delays in the project. Steep topography,dense environmental conditions, hard, abrasive rock and con-struction below normal pool elevation, and little working roomall were conditions that could have delayed project progress nu-merous times and produced costly delays. However, strong com-munication between Wright Brothers, Long Foundation DrillingCo., and ALDOT encouraged intensive planning prior to the startof construction. This cooperative environment permitted rapid de-cision making when complications arose and helped to make surethat solutions met the needs of all parties.The motivation and dedication of the site crews for both Wright

Brothers and Long; prompt service by USA Readymix; and quickand professional responses by ALDOT allowed the difficult chal-lenges to be met with the best-case solutions. What could havebeen a costly, late, and inefficient project ultimately was an effi-cient, organized success that was completed in a timely fashion.

*Indicates ADSC Member.

FOUNDATION DRILLING July 2014 Page 25

LONG Contd.

PROJECT TEAM

Project Owner:Alabama Department of TransportationAdam Sandlin, Project Engineer

General Contractor:Wright Brothers ConstructionEric Samples, Project ManagerChris Brown, General Superintendent

Foundation Contractor:Long Foundation Drilling Co.*Bobby Simpson, Superintendent

*Indicates ADSC Member.

Long’s familiarity with local rock conditions and appropriaterock removal methods proved to be critical in facilitating efficient drilling without long delays to evaluate variations in the rock hardness and abrasivity.