Show I GRAVEL ROAD WORK Construction Is Usually Divided Into Two Entire Distinct Classes I SUB GRADE FOR T THE E SURFACE Some of Most Important Details Requiring Requiring Requiring Re Re- quiring Careful Attention Arc Frequently Frequently Fre Fre- Overlooked Some Precautions to Observe Fi Figure ure 1 shows show s a typical cross section section section sec sec- tion for a u road gravel surface and In Indicates Indicates Indicates In- In the customary steps involved in the construction of such a surface The limiting shown on this cross section are b by no means followed universally but are believed to represent represent represent sent the best current practice The minimum thickness shown Is supposed to be employed where the traffic is light mal aril the Is uniformly stable while the maximum thickness Is IN adapted for opposite conditions Perhaps the most usual compacted thickness of surface Is eight Inches at nt atthe atthe the center and six itches inches at nt the edges The difference in thickness between the ed edges es and center is effected by making the crown of the flatter flat flat- tor tr than that of the surface The construction of a gravel road usually Is divided Into two entirely distinct distinct distinct dis dis- classes of work worl The he work of grading and preparing the exclusion of vegetable matter from fills 8 provision for tor draining wet wet wet- weather springs which occur In thes the tho s and 4 the matter of thoroughly thoroughly thor thor- thoroughly loosening and distributing the tho materials contained In old road crusts After Aftel the roadbed has been graded and drained properly and the details mentioned above have received proper attention the work worl of preparing the consists simply In forming a trench sis UR shown In figure 1 1 to receive the gravel surface The trench ma may he be formed lar largely ely with a grading machine machine ma mn- I chine but hut the final shaping should be effected b by means ot of picks and shovels and rolling It Is customary to provide grade stakes at nt Intervals of about 50 feet to serve ser as a n guide for the pick and shovel work and where extreme accuracy Is desired cords may be stretched between the stakes that the line conforms to the required grade throughout The rolling rollIng rollIng roll- roll Ing is done ordinarily with a power roller weighing about ten tons In order that the may be bewell bewell well drained du during ing the process of spreading and compacting the gravel it Is frequently necessary to provide I shoulder drains at comparatively short short intervals Such drains are constructed by opening small ditches through the shoulders and partially filling them with gravel s w s r r 6 to S J l h S N oM w ws Gross Cross section read rudy ready to th the surtax surfacing 1 r s- s tv s- s 1 to 5 n the first course of travel cavil spread and rolled Broken line line shows the ne finished road sections section s W tr S H et I I r n I it vj 6 to b J AV J i SU v r Cross section of completed road TYPICAL CROSS SECTIONS SHOWING METHOD OF CC CONSTRUCTING A R C-R GRAVEL C VEL I JOO CAD b be at least 10 feet for single track r roadway w ly and s not I less IMS ss than 5 S feet for double track frat be x not l s 14 19 f feet and not andS Snot less than 3 feet H crown varies from j i j inch per foot for level grade to I inch loch per foot for a gr grade je of 5 Tic 1 l falls alls Into one class and that of hauling hauling hauling haul haul- ing spreading and compacting the gravel gra Into the other The first class of work has hns been discussed at nt considerable consid erable length In connection with earth and sand-clay sand roads but since It Is desired to emphasize certain features Df f preparation that are of Increased Importance In connection with road gravel-road construction both classes of work will be considered In Inthe Inthe inthe the following discussion Preparation of the In grading the roadbed and preparing preparing ing the for a gravel surface surface It should be borne In mind also that the more expensive a B road surface the greater grenter should be the care exercised to prevent pre it t from being damaged through though settlement or upheaval of the and the greater reater should be bethe bethe bethe the accuracy with which the tile Is constructed so that no unnecessary surfacing material mn may be required to correct Irregularities In grade nn and cross section No matter what the soil conditions may be the for a gravel road rond surface when completed should conform closel closely In gra grade e and cross section with the requirements of the plans and should present an even uniform appearance Also It should be he as firm and unyielding as ns the conditions will permit Some of the most Important details requiring careful attention In III preparing preparing ing the subi nn and which are perhaps perhaps perhaps per per- haps most frequently overlooked are 1 backfilling cuI culvert vert trenches so as ns asto asto I to prevent subsequent settlement 2 |