tops are driven so that the top of the hub is setat the required grade elevation.7. GUARD STAKES are used to identify andprotect hubs. The face of the stake is markedwith station identification and is placed sothat the stake faces the hub it identifies.Sometimes more than one guard stake will beused to protect a hub.8. OFFSET STAKES may be additionalstakes that are offset a known distance from otherstakes that will likely be disturbed duringconstruction. The offset stake is marked with thesame information as the stake it offsets, and itis also marked to show the offset distance. Often,stakes will themselves be offset a known distancefrom their true location. This eliminates therequirement for additional stakes.CENTER-LINE LAYOUT.— The first majorstep in highway construction is usually the roughgrading; that is, the earthmoving that is requiredto bring the surface up to, or down to, theapproximate elevation prescribed for thesubgrade. The SUBGRADE is the surface ofnatural soil, or the place where the pavement willbe laid. The subgrade elevation, therefore, equalsgrade (finished surface) elevation minus thethickness of the pavement.In rough grading, the equipment operators areusually guided by grade stakes that are set alongthe center line by the transit-tape survey party atcenter-line stations. The center-line stations(stakes) are usually set at intervals of 100 ft ormore on straight-line stretches and intervals of50 ft or less on roads with horizontal and verticalcurvatures. On a small-radius, street-cornercurve, a center-line hub or stake might be setat the center of the circle of which the curveis a part. This is done so the constructioncrew may outline the curve by swinging theradius with the tape. Reference stakes or hubsare also set on one or both sides of the centerline to permit reestablishment of the center lineat any time.Each center-line stake is marked with thevertical depth of cut or fill required to bring thesurface to grade elevation. The surveyor mustindicate the station markings and the cut and filldirections on stakes. Let’s look at the stakes onthe center line of the road-building job. Thestarting point is the first station in the survey;Figure 14-32.-Station markings.this station is numbered 0 + 00. The next stationis normally 100 ft farther and is marked 1 + 00;the third station is another 100 ft farther and ismarked 2 + 00; and so on. On sharp curves onrough ground, the stakes may be closer together.(See fig. 14-32.) Generally, the station markingsface the starting point. The mark ~, which isalso on the side facing the starting point, isused to indicate that the stake is a center-linestake.A cut is designated by the letter C, and thefill is indicated by the letter F. Numerals followthe letters to indicate the amount that the groundshould be cut or filled. The symbol C– 13 indicatesthat the existing ground should be cut 1.5 ft, asmeasured from the reference mark. Duringrough grading, the cut and fill are generallycarried just up to the nearest half foot; exact gradeelevations are later marked with hubs (blue tops).The mark Y is called a crowfoot. The apex ofthe V indicates the direction of the requiredchange in elevation; so a cut is indicated by Y ,and a fill is indicated by fi . In some cases,surveyors mark the grade stake only with anegative or a positive number and the crowfoot,indicating the cut or fill.14-35
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