Show EARTH ROAD GRADE Stability of Embankments Is of Great Importance CAREFUL SCRUTINY IS URGED To Prevent Damage amage by Shrinkage Material Material Ma Ma- Used Must Be Free From Vegetable Matter and Uniformly Uniformly Uni Compacted Prepared by the United States Department Department Department Depart Depart- ment of or Agriculture One of the most Important considerations considerations consid consid- connected with the grading of an earth road Is the stability of the embankments Where a road Is situated situated situ situ- In a cut and Is well drained it Is not likely to be affected seriously by such agencies as shrinkage settlement and slipping any one of which may in injure injure In in- jure or destro destroy a road situated on a n poorly constructed embankment In grading a road therefore the methods employed In building the embankments are deserving of much more careful scrutiny than those employed In making mak mak- making ing excavations To prevent pre a road over oyer an embankment embankment embank embank- m ment nt from rain being damaged damaged- b by shrinkage shrinkage shrink shrink- age of the material forming the embankment embankment em em- the material must be free from vegetable matter and uniformly compacted as It is deposited Where the road surface Is to be of earth the embankment usually be ma may compacted compact compact- ed sufficiently to prevent nt injury from shrinkage by spreading the material In relatively thin horizontal layers and letting ea each h layer be compacted by the grading teams as the succeeding layer Is being spread Layers of ordinary earth not more than 12 inches thick can be Compacted fairly well In this way ny provided prO that the grading teams are made to travel over the entire surface surface sur sur- face of each ench layer and amI that the material material material mate mate- rial Is spread uniformly Where the road surface Is to be of some highly Improved ed type trpe each la layer er of the embankment embankment em em- should be rolled thoroughly with a power roller weighing not less th than n about t ten n tens f t i embankments aside from tint that due l to shrinkage may b be by the sr gradual dual flattening 9 91 the s- s s1 ur 1 By ty f Tack li of t stability s of theo the ground Y o nd surface 8 rf c over Iner which the the- embankment embankment embank embank- ment is constructed The question of ground surface ace stability u usually does not ot arise as a k grading problem except where an embankment Is being con- con over very marshy land If i proper oper pre precautions aution ar are not yot of observed the embankment material fua may be abe ab- ab jed e l gradually by by tho tle h m l r until the roadbed ht has dI disappeared 4 lliPi lured F d ail un oc occurrence which Is pot not infrequent t r Where drainage of the marsh Is impracticable im Impracticable Im- Im practicable the lower portion of the embankment which would come In contact contact contact con con- tact with the marsh water should be bc formed of some material that will cement together and distribute distribute dis dis- tribute the weight of the embankment over the entire bottom area Some varieties of ot gravelly clay arc excellent excellent excel excel- excellent lent for this purpose Where the marshy matter Is Iser er very soft and deep It ma may be necessary to lay a wide foundation bed of logs or upon which to construct the thc embankment embankment embankment embank embank- ment but such a foundation bed would not obviate the necessity for using a anon non material In the lower portion portion portion por por- tion of the embankment Where embankments are ure constructed on an vcr very sloping ground or where old embankments are to be bc widened there always Is n a tendency for the new material mate mate- rial to slip along the thc plane of tion In such cases the thc old surface should be roughened before the new material Is deposited Where the thc old surface Is earth It usually can be I roughened by plowing a series of rather deep furrows about two feet apart Old rock surfaces ordinarily ordinarily ordinarily or or- I are fairly rough to begin with but hut to prevent present slipping it may be necessary necessary I sary In some cases to blast steps Into such surfaces before betor depositing embankment embankment embankment em em- material No matter how the grading of an earth road may be accomplished It usually Is economical to bring the road surface to Its final shape by means of ofa a grading machine In making excavations excavations excavations It Is 18 not generally generall considered practicable to form the crown and und side ditches with scrapers or hand tools alone and the cross section Is therefore therefore there there- fore frequently left approximately flat Hat The grading machine Is then used In Inthe Inthe inthe the manner already described to produce produce produce pro pro- duce the required cross section After the road has been finished with the grading machine It should be given frequent attention until the embankments embank embank- ments menIs have e finished settling and the surface has become thoroughly compacted compacted compacted com com- b by the action of traffic Usually a period of ot severn several I months should elapse after a road rond Is graded before itis Itis It ItIs Is considered complete and such settlements settlements settlements settle settle- ments and Irregularities as develop during this period should be corrected b by the use of either cither a grading machine or a road drag Construction Costs Aside from drainage structures the principal item of cost attached to the construction of an earth road Is for the grading The Thc cost of grading varies greatly according to the condition of the weather the nature of the material to be excavated the efficiency of labor teams and machinery etc and seldom can be estimated In advance with any great de degree ree of accuracy On this account account account ac ac- ac- ac count average costs based on past experience experience ex ex- ma may be very misleading when applied to n u particular project The first step in estimating the cost of grading a given road Is to ascertain the he quantities of work to be done clone After the he quantities have been determined the he cost ma may be estimated in either of ot two wo wa ways s First the thc organization for carr carrying on the work ma may be planned In n detail and the estimate arrived at ati by considering the thc cost of maintaining such an organization together with the rate ate at fit which it may reasonably be expected ex ex- expected to accomplish the thc work Second Sec 1 oud onel the cost cubic ard for per yard excavation excavation and the cost per mile for shaping the roadway may be estimated at flat rates The first method Is the most accurate though the latter Is theone tho the one employed ed most frequently |