CHAPTER 6ROAD CONSTRUCTION TECHNIQUES6.1 Road Construction Techniques6.1.1 Construction StakingPrior to the construction activity the design information has to be moved from the plan to the ground.Thisisaccomplishedbystaking. Slopestakesareaneffectivewaytoinsurecompliancewiththedesign standards and to keep soil disturbance to an absolute minimum. Various staking methods canbe employed. (Dietz et al. !"#$% Pearce !"&'( The method discussed here is but one e)ample.Stakes marking various road design points are typically obliterated during the clearing and grubbingphase. *n order to relocate the stakes (centerline slope stakes( it is helpful to establish reference pointsoutside theclearinglimits.+eference pointsshouldbeset atleast ,to-meters behind theuphillclearinglimits. .ntheaverage referencepoints(or+P/s(shouldbeset at least every0'to!''meters. Typically reference points are placed at points where the center line alignment can be easily re1established such as points of curvature. 2igure !'3 shows the necessary stakes and stake notationneeded by the e4uipment operator to construct a road.Stakes are used by the e4uipment operator in locating where to begin cutting. *f the selected startingpoint is too high considerably more material has to be cut in order to construct the proper subgrade(2igure !',(. 2or e)ample if the cut results in a 3' percent wider subgrade appro)imately -' percentmore volume has to be e)cavated. (See Section ,.3.3.( *f the cut is placed too low an overstepped cutslope or e)tra side casting may result both of which are undesirable.Starting the cut at the proper point becomes more important as the side slope increases. 5s a ruleslope stakes should be set when sideslopes e)ceed $' to $- percent depending on the sensitivity of thearea and the operator/s e)perience.The use of +P/s (+eference Points( or slope stakes for proper e)cavation is shown in 2igure !'$. 6erethe engineer stands on the preliminary centerline of the construction grade and sights for the +P. 5slope reading of ,' percent and a slope distance of -.-, m is recorded. 7onverting the slope distanceof -.-, m to a horizontal distance of -.,' m and to a vertical distance of !.-" m allows the engineer todetermine how much the 8present8 or preliminary centerline has to be shifted to conform with the designcenterline. The +P tag re4uires &.-' m horizontal distance to centerline with a vertical drop of $.#' m.2rom that information it can be seen that an additional !.-& m 9$.#' 1 (!.-" : !.&-( ; !.-&< has to becut and the present location has to be shifted by !.3 m (&.-' 1 -.,' ; !.3'(. 6eight of instrument or eye1level is assumed to be !.&- m.i!ure 1"#. +oad cross section showing possible construction information.i!ure 1"$. The effect of improperly starting the cut as marked by the slope stake. Starting the cut toohigh results in e)cess e)cavation and side cast. Starting the cut too low leaves an overstepped cutbank.i!ure 1"%. 7onstruction grade check. =ngineer stands on center of construction grade and sights to+P tag. >easured distance and slope allow for determination of additional cut.6.1.2. Clearing and Grubbing of the Road Construction AreaPreparing the road right1of1way or construction area is referred to as clearing and grubbing. During theclearing phase trees are felled. ?rubbing refers to the clearing and removalof stumps and organicdebris. Trees should be felled and cleared a minimum of ! to , m from the top of the cut or toe of the fill(2igure !'-(. The logs can be decked outside the construction area (2igure !'- @ to =( or skiddedaway.i!ure 1"&. 7learing limits in relation to road bed widths. Significant 4uantities of organic materials areremoved between @ and =. Stumps are removed between @ and D. Stumps may be left between D and=. .rganic debris and removed stumps are placed in windrows at 2 to serve as filter strips (see Section&.,.!(.This additionalwidth between construction width and forest edge ensures that space is available todeposit organic debris outside the road construction width and that there is no overlap between forestedge and construction area.5 good construction practice to follow is to remove stumps that are within the construction width (2igure!'- @ to =(. Trees should be felled to leave a stump '.# to !.3 m high. This helps bulldozers in stumpremoval by providing added leverage..rganic overburden or topsoil typically has to be removed over the full construction width (2igure !'-@ to D(. This is especially true where organic layers are deep or considerable sidecast embankment orfillsareplanned. .rganicmaterial will decomposeandresult inunevensettlement andpotentialsidecast failure. .rganic material should be deposited at the lower edge of the road (2igure !'- = to2(. This material can serve as a sediment filter strip and catch wall (see Section &.,.!( however careshould be taken that this material is not incorporated into the base of the fill. Past road failures showthat fill slope failures have been much more fre4uent than cut slope failures (0' percent and ,' percentrespectively(. *n most cases poorly constructed fills over organic side cast debris was the reason forthe failures.Duringthegrubbingphase or preparationphase apioneer roadisoftenconstructedtofacilitatee4uipment access logginge4uipment movement anddeliveryof constructionmaterials suchasculverts. Thisisoftenthecasewhenconstructionactivitiesareunder wayat several locations. *fpioneer roads are constructed they are often built at the top of the construction width and are usuallynothing more than a bull dozer trail. Ahen considerable side hill fill construction is planned howeverthe dozer trail should be located at the toe or base of the proposed fill. The trail will serve as a benchand provide a catch for the fill to hold on (2igure !'&(.i!ure 1"6. Pioneer road location at bottom of proposed fill provides a bench for holding fill material ofcompleted road.6.# 'enera( Equi)*ent ConsiderationsThe method and e4uipment used in road construction is an important economic and design factor inroad location and subse4uent design. 5 road to be built by an operator whose only e4uipment is abulldozer re4uires a different design than a road to be built by a contractor e4uipped with hydraulice)cavator scrapers andbulldozer. Table,#listscommonroadconstructione4uipment andtheirsuitability for the different phases of road construction. 5 bulldozer can be used in all phases of roadconstruction from e)cavation and drainage installation to final grading. The front end loader performswell in soft material. 2ront end log loaders can be fitted with a bucket e)tending their usefulness underthe correct conditions.6.2.1 Bulldozer in Road ConstructionProbably the most common piece of e4uipment in forest road construction is the bulldozer e4uippedwithstraightor B1type blades. These are probablythe mosteconomicalpieces of e4uipmentwhenmaterial has to be moved a short distance. The economic haul or push distance for a bulldozer with astraight blade is from !0 to "' meters depending on grade. The road design should attempt to keep themass balance points within these constraints.Theroaddesignshouldconsider thefollowingpointswhenbulldozers aretobeusedfor roadconstruction.!. +oads should be full benched. =arth is side cast and then wasted rather than used to build up sidecast fills.3. =arth is moved down1grade with the aid of gravity not up1grade.,. 2ill material is borrowed rather than pushed or hauled farther than the economic limit of the bulldozer.$. +ock outcrops should be bypassed. Bnless substantial rock blasting is specified re4uiring drilling andblastinge4uipmentsolidrockfaces shouldbeavoided(Thishowever isprimarilyaroadlocator/sresponsibility.(Ta+(e $,. +oad construction e4uipment characteristics. (from .SB =)tension Service !"#,(.Criteria -u((do.erront end /oaderH0drau(ice1ca2atorDu*)truc3s or scra)ersar* tractors=)cavationmode (levelof control ofe)cavatedmaterials(Digs andpushes%ade4uatecontrol(dependson bladetype(>inordigging ofsoftmaterial%lifts Ccarries%good controlDigsswings Cdeposits%e)cellentcontrol% canavoidmi)ingmaterialslong1distancematerialmovement%e)cellentcontrolScraperscan loadthemselves%/top down/subgradee)cavation%used forsmall4uantities>inor diggingand carrying%good controlbecause ithandles.peratingdistance formaterialsmovement"! m%pushingdownhillpreferred"! m ongoodtractionsurfaces3, m(limited toswingdistance(Do limite)cept byeconomics%trucks mustbe loaded,! m(appro)imately(Suitabilityfor fillconstruction5de4uate ?ood Eimited tosmaller fills?ood forlarger fillsDot suitable7learingandgrubbing(capacity tohandle logsand debris?ood 5de4uate =)cellent Dot suitable 6andles onlysmall materials5bility toinstalldrainagefeatures5de4uate Digginglimited to softmaterials=)cellent Dot suitable 5de4uate forsmall tasks.peratingcost perhour>oderatedependingon machinesize+elativelylow>oderate tohigh butproductivitye)cellentVery high EowSpeciallimitations oradvantagesAidelyavailable%can matchsize to Fob%can do allre4uiredwith goodoperator7annot dighardmaterial%may betractionlimited?ood forroads onsteephillsides%can do allre4uirede)ceptspread rockfor rocksurfacingEimited tomovingmateriallongdistances%can haulrock rip rapetc.Very dependenton siteconditions andoperatorskillAhen using bulldozers the practice of balancing cut and fill sections should be used only whenG1 sideslopes do not e)ceed $- to -- percent1 proper compaction e4uipment is available such as a 8grid roller8 or vibrating or tamping roller1 fills have a sufficient width to allowpassage of either compaction e4uipment or constructione4uipment such as dump trucks.5de4uate compaction cannot be achieved with bulldozers alone. The degree of compaction e)erted bya piece of e4uipment is directly related to its compactive energy or ground pressure. =ffective groundpressure is calculated as the weight of the vehicle divided by the total ground contact area or the areaof tiresor tracksincontact withthesurface. @ulldozersarealow1groundpressuremachineandtherefore are unsuitable for this process. ?round pressure of a !$" kA (3'' hp( 3, tonne bulldozer(7at D0? for e)ample( is '.0 bar (!'.3 lb H in3(. @y comparison a loaded dump truck (, a)les !' m,bo) capacity( generates a ground pressure of - to & bar (03.- to #0.! lb H in3(.7omparative production rates for various size bulldozers are shown in 2igure !'0. .ne should note thatproduction curves are based onG!. !'' I efficiency (&' minutesHhour(3. power shift machine with '.'- minute fi)ed time,. machine cuts for !- m then drifts blade load to dump over a high wall$. soil density of !,0' kgHm, (#-.& *bHft,( loose or !0"' kgH m, (!!!." *bHft,( bank-. coefficient of traction J '.- and&. hydraulic controlled blades are used.i!ure 1"4. >a)imum production rates for different bulldozers e4uipped with straight blade in relationto haul distance. (from 7aterpillar 6andbook !"#$(.Thegraphprovidestheuncorrected ma)imumproduction. *norder toadFust tovariousconditionswhich affect production correction factors are given in Table ,". 5dFustment factors for grade (pushinguphill or downhill( are given in 2igure !'#.Ta+(e$5. Kobconditioncorrectionfactorsfor estimatingbulldozer earthmovingproductionrates.Values are for track1type tractor e4uipped straight (S( blade. (7aterpillar 6andbook !"#$( TRAC6 T7PETRACTOR8HEE/ T7PETRACTOR.P=+5T.+=)cellent !.'' !.''5verage '.0- '.&'Poor '.&' '.-'>5T=+*5EEoose stockpile !.3' !.3'6art to cut% frozen11with tilt cylinder '.#' '.0-without tilt cylinder '.0' 1cable controlled blade '.&' 16ard to drift% 8dead8 (drynon1cohesive material( orvery sticky material'.#' '.#'SE.T D.L*D? '.&' 1 '.#' 1S*D= @M S*D= D.L*D? !.!- 1 !.3- !.!- 1 !.3-V*S*@*E*TM 11Dust rain snow fogdarkness'.#' '.0'K.@ =22*7*=D7M 11-' minHhr '.#$ '.#$$' minHhr '.&0 '.&0D*+=7T D+*V=T+5DS>*SS*.D ('.! min. fi)ed time( '.#' 1@BEED.L=+N5ngling (5( blade '.-' 1 '.0- 17ushioned (7( blade '.-' 1 '.0- '.-' 1 '.0-D- narrow gauge '."' 1Eight material B1blade (coal( !.3' !.3'N DoteG 5ngling blades and cushion blades are not consideredproduction dozing tools. Depending on Fob conditions the 51bladeand71blade will average-'10-Iof straight bladeproduction.i!ure 1",. 5dFustment factors for bulldozer production rates in relation to grade. (7aterpillarPerformance 6andbook !"#$(.E9A:P/E;Determine the average hourly production of a 3'' hp bulldozer (D0( e4uipped with a straight blade andtilt cylinder. Thesoil isahardpackedclaythegradeis!-percent favorable andaslot dozingtechni4ue is used. The average haul or push distance is ,' m. The soil weight is estimated at !3''kgHm, loose with a load factor of '.0&" (,' I swell(. 5n ine)perienced operated is used. Kob efficiencyis -' minHhour.The uncorrected ma)imum production is $,' m, looseHhour (from 2igure !'0( bulldozer curve D0S.5pplicable correction factors areGKob efficiency (-'minHhr('.#$Poor operator '.&'6ard to cut soil '.#'Slot dozingtechni4ue!.3'Aeight correction '.#0Production ; >a)imum Production N 7orrection 2actor; ($,' m, looseHhr( ('.#$( ('.&'( ('.#'( (!.3'( ('.#0( ; !#! m, looseHhourProduction (bank m,( ; (!#! m, looseHhr( ('.0&"( ; !," bank m,HhrProduction rates for bulldozers are also influenced by grade and side slopes. Percent change in hauldistance with respect to changes in grade are shown in Table $'. 5s side slope increases productionrate decreases. Typical production rates for a medium sized bulldozer in the !3 to !& tonne range (fore)ample 7at D&( are shown in Table $!.Ta+(e %". 5ppro)imate economicalhaullimit for a !#- hp bulldozer in relation to grade. (Productionratesachievedaree)pressedinpercent of productionona!'percent favorablegradewith,'mhaul(. (Pearce !"0#(.Hau(distance(meter('rade (I(aterial is wasted as loose side cast material readilyavailable for erosion. *n the latter case it has been incorporated into the fill properly compacted andpresumably unavailable for erosion.The key to a stable balanced road design is proper compaction of fill material. 6aber and Ooch (!"#3(4uantified costs for erosion and compaction for several types of sediment control treatments on roads insouthwest *daho. This study represents an e)cellent e)ample of applying uniform criteria to e)aminedifferences between standard and non1standard construction techni4ues.7ostswereinitially determinedfor eachactivity usingtwomethodsG (!( local (@oise( labor ande4uipment rates ta)es insurance and servicing (repair and maintenance( including !' percent profitand risk margin and (3( +egional =4uipment @lue @ook ?uidebook which include margins for profit andrisk fuel oil lubrication repairs maintenance insurance and incidental e)penses. 5fter actual costsfor each activity were calculated average cost per unit and average crew cost was determined basedon design 4uantities. 5 comparison was then made between actual costs for 8non1standard8 treatmentsand actual costs of standard treatments.5verage observed production rates for all activities were calculated for use in predicting time and costsassociatedwith8non1standard8 constructiontechni4ues. 2igure!!&illustratesane)ampleof theirresults in determining the cost of three different methods of embankment placement. These methodsareG (!( side cast embankments with no compactive effort (3( layer placed (less than ,' cm (!3 in(thick(embankmentsinwhicheachlayerisleveledandsmoothedbeforeeachsubse4uent layerisplaced(some compaction is obtainedduring thelevelingprocessasthebulldozerpassesoverthematerial( and (,( controlled compaction in which embankments are placed in layers (less than 3' cm (#in( thick( followedbycompactionwithwater andvibratoryroller toachieverelativedensityof "-percent.5s e)pected side cast embankment construction per volume costs the least and controlled compactionthe most. (+oad !'&0#! was shorter and only a small 4uantity of earth was moved resulting in a higherunit cost.( Total cost however for a road e)pressed in cost per unit length may be very similar for sidecast embankment and layered placement considering the fact that total e)cavation volume may be upto ,- percent less for the lattercase. 5s mentioned before most of this e)cavated materialis nowconsolidated rather than loose. 7ombined with proper fill slope surface treatment and filter windrowsvery little erosion can be e)pected.*t is worth noting that production rates of manual labor for e)cavation work are generally ,.# to $ m, (-yd.,( of dirt during eight hours of work (Sheng !"00(. 6owever these rates will vary widely dependingon terrain soil environmental and psychological conditions of the work crew.i!ure 116. =)cavation cost comparison for three different embankment construction techni4ues ( !cu.yd. ; '." m,(. (after 6aber and Ooch !"#,(.6.#.( Subgrade Construction $ith !ca"ator=)cavatorsarebecomingmoreandmorecommoninroadconstruction. @ecauseof theire)cellentplacement control of e)cavatedmaterial theyareideal machinesfor constructionunder difficultconditions. Thebackhoeore)cavator shouldbethepreferredmachineonsteepsideslopes. Theconstruction se4uence differs from the bulldozer approach and is e)plained below.The e)cavator works from a platform or pioneer road at the lower end of the finished road.1st )ass; Pioneering of log and stump removal accomplished in the fist pass. Kust enough overburdenis moved toprovide astableworking platform (2igure !!0(. Eogs are piledat the lower side oftheclearing limit.#nd )ass; 5fter completion of the first pass the operator begins retracing its path. During this passunsuitable material is stripped and placed below the toe of the fill (2igure !!#(.$rd )ass; During the third pass now working forward again the e)posed mineral soil is dug up for theembankment construction. 5t thesametimeaditchispreparedandthecut slopesmoothedandrounded. The portion of pioneer road or platform which consist of organic debris is outside the loadbearing road surface fill (2igure !!"(..n steep side slopes the e)cavator is able to place large boulders at the toe of the fill (in a ditch line(and place e)cavated materialagainst it (2igure -- and !'"(. Totale)cavation and e)posed surfacearea can be kept to a minimum.i!ure114. 2irst pass with e)cavator clearinglogs andstumps fromconstructionsite. Aorkingplatform or pioneer road Fust outside of planned road surface width.i!ure 11,. Second pass with e)cavator removing or stripping overburden or unsuitable material andplacing it below pioneer road.i!ure 115. Third pass finishing subgrade and embankment fill over pioneer road. +oad side ditch isfinished at the same time.6.#.) %ilter *indro$ Construction=rosion from newly built fill slopes can effectively be trapped through filter strips or windrows made ofslash and placed at the toe of the fills. This measure is particularly important and effective where theroad crosses a draw or creek. The effect of such filter strips on soil loss from new fill slopes is shown inTable $,. 2ill erosion from newly built slopes can be reduced by more than "- percent over a , yearperiod (7ook and Oing !"#,(. This time period is sufficient in most cases to allow for other measuressuch as surface seeding mulching or wattling to become established.Ta+(e %$. 2illslope erosion volume for windrowed and nonwindrowed slopes during a , year periodfollowing construction (7ook and Oing !"#,(.S(o)eC(assNi(ter 8indro> (nowindrow(Un)rotectedm, H !''' m! '.,' ,,.3"3 '.&- &$.,'Nclass !G vertical fill height Q ,meterclass3G vertical fill height ,to&meterConstruction o? ?i(ter stri)s;!. Suitable material from the clearing and pioneering activity should be stockpiled at designated areaseitheraboveorbelowtheclearinglimits. Slashshouldconsist of tops limbsandbranches not toe)ceed !- cm in diameter and ,- m in length. Stumps and root wads are not suitable material andshould be e)cluded.3. Aindrowsareconstructedbyplacingacull log(reasonablysound(onthefill slopeimmediatelyabove and parallel to the toe of the fill (2igure !3'( for the fill material to catch against. The log shouldbe appro)imately $' cm in diameter and should be firmly anchored against undisturbed stumps rocksor trees.,. Slash should be placed on the fill above the cull log. The resulting windrow should be compacted fore)ample bytampingit withthebucket of ane)cavator. *t isimportant that part of theslashbeembedded in the top !- cm of the fill. 2ilter strips are built during subgrade construction in order toma)imize their effectiveness. 7are should be taken so as not to block drainage structures (outlets ( orstream channels.i!ure 1#". Typicalfilter windrow dimensions built of slash and placed on the fillslope immediatelyabove the toe. The windrow should be compressed and the bottom part embedded !- cm in the fillslope. (after 7ook and Oing !"#,(./ITERATURE CITED7aterpillar. !"#$. 7aterpillar Performance 6andbook Do. !$. Peoria *llinois.7ook >.K. and K.?. Oing!"#,. 7onstruction cost and erosion control effectiveness of filter windrowson fill slopes. BSD5 2orest Service +esearch Dote *DT1,,- Dovember !"#,.Dietz P. A. Onigge and 6. Eoeffler. !"#$. Aalderschliessung. Verlag Paul Parey 6amburg and @erlin?ermany.6aber D. and T. Ooch. !"#,. 7osts of erosion control construction measures used on a forest road inthe Silver 7reek watershed in *daho. B.S. 2orest Service +egion ! and Bniversity of *daho >oscow*daho.Dagygyor S.5. !"#$. 7onstruction of environmentally sound forest roads in the Pacific Dorthwest. *n(ed 7orcoran and ?ill( 7...2.=.HB.2.+... Proceedings Bniversity of >aine .rono and Bniversity ofDew @runswick 2redericton 5pril !"#$ p.!$, 1 !$0..regon State Bniversity. !"#,. +oad construction on woodland properties. .r. St. Bniv. =)t. 7ir. !!,-.7orvallis .regon. 3$ p.Pearce K. O. !"&'. 2orest =ngineering 6andbook. BS Dept. of *nterior. @ureau of Eand >anagement.33' p.