Quantcast SEQUENCE  OF  CONSTRUCTION - 14070_69

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drawing.  Refer  to  the  example  in  figure  3-5,  and  read the  following  explanation: 1. STATION NUMBERS. The station numbers are lettered horizontally below the profile and grade line and are centered on the appropriate vertical grid line. 2. ELEVATIONS. At the bottom of the sheet, the profile and grade-line elevations for each station are lettered vertically. The grade-line elevations are lettered just  above  the  profile  elevations.  Any  station  numbers other  than  full  stations  are  noted  as  plus  stations, vertically,  just  outside  the  bottom  border. 3. CUTS  AND  FILLS.  Above  the  profile  and grade-line elevations are lettered the cuts and fills. They are also in a vertical position. The grade points, or points where the profile crosses the grade line, are also noted in this row. They are designated by the word GRADE  lettered  vertically  above  the  grade-point station. 4. DITCHES.  The  procedure  for  dimensioning ditches has two steps as follows: a. First, draw extension lines from the ends of a ditch or any point in the ditch where the ditch grade changes. These lines should be extended downward, and dimension lines (with heavy arrowheads) should be drawn  between  them.  These  extension  and  dimension lines should be drawn heavier than normal so they may be distinguished from grid lines. b. Next, above the dimension line, letter the information  necessary  to  describe  the  ditch.  If  the lettering is crowded, you may also use the space below the line. You should furnish the following information: percent of grade of the ditch, depth relative to center line, type of ditch, and width of ditch. Give the elevation and station at the ends of the ditches and at changes of grade. 5. VERTICAL CURVES. Each vertical curve on the grade line is also dimensioned. Draw extension lines upward from the PVC and PVT. Then draw a dimension line between the extension lines and letter the length of the curve above. Letter the station and elevation of the PVC, PVI, and PVT vertically over these points and above the dimension line. 6. CORRELATION WITH PLAN. All points on the  profile  and  grade  line  coincide  with  center-line points  on  the  plan.  For  example,  you  should  show  the beginning and ending of construction on the plan view and also on the profile and grade line. Also, note the elevations  at  these  points. 7. DRAINAGE  STRUCTURES.  Dimension all drainage structures, such as pipes and culverts, by notes. Note the station number, size of opening, length of pipe, and  flow-line  elevation. 8. TITLE. In this example, the title, “PROFILE AND   GRADE   LINE   is   lettered   below   the   ditch dimensions. Below this are noted the horizontal and vertical  scales. SEQUENCE  OF  CONSTRUCTION In  constructing  a  road,  the  construction  crews should follow a specific sequence. First, they clear the area through which the road must pass of trees, stumps, brush, boulders, and other debris. The width of the clearing varies greatly but is always at least 12 feet greater than the roadway width; that is, the crew should clear at least 6 feet behind the construction limit on both sides  of  the  road. The next step is the grading operations and the laying of cross-drain pipes, or culverts. The grading operations are carried on by the Equipment Operators until the subgrade is completed. In fill areas, the grading is brought up in layers and compacted. In cuts, the excavation is carried on until the subgrade elevation is reached, and then the earth is compacted. Throughout this step of the road construction, workers place the culverts when and where required. These culverts are placed in their appropriate positions and at the required slopes according to the roadway plans. After   the   subgrade   is   completed,   Equipment Operators place abase course on the subgrade. The base course material can be gravel, sand, crushed stone, or more expensive and permanent materials. Finally, the Equipment  Operators  place  a  surface  course  over  the base. This material can be sand, asphalt, blacktop, concrete,  or  similar  materials. In some cases, traffic may be allowed to travel over the subgrade itself. In others, traffic may require only a gravel or stone surface. A high-speed road, however, requires abase and a hard, durable surface. SECTIONS As you should recall from your study of the EA3 TRAMAN, a section is a view of an object that has been cut by a plane that is perpendicular to the line of sight. For road sections, the line of sight is perpendicular to the  roadway  center  line. Sections are used for a variety of purposes during the various phases of road design and construction. One purpose is to define what the materials and design 3-7

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