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Excavation & Grading Handbook Revised This new trusted reference has been completely updated to keep excavation contractors, operating engineers, and those learning the trade current with state-of-the-art equipment usage and the most efficient excavating and grading techniques. You'll learn how to read topo maps, set crows feet, install water drain and sewer pipes, lay or remove asphaltic concrete, use a laser level, cut drainage channels, and use GPS and sonar for absolute precision. Includes a CD-ROM with an interactive study center to help anyone brush up their skills or study for the license exam. Filled with hundreds of tips, pictures, and diagrams and tables every excavation contractor can use. 1. Understanding Road Survey Stakes, 5 Highway plans and cross sections, 37 Checking grade with swedes, 55 4. Setting Grade Stakes Using a Contour Plan, 83 5. Grading with Lasers, GPS and Other Specialized Equipment, 93 Using a laser level for parking lots, 94 Using a laser level for pads, 95 Using a laser level for road projects, 96 Using a laser level for trench work, 98 Laser receivers on equipment, 101 Other on-board control systems, 103 6. Road Building Equipment, 117 Other specialty equipment, 126 7. Planning for Excavation, 133 Cutting slopes in rocky soil, 146 Ripping and excavating rock, 148 Compacting fill with rock, 150 9. Excavating Subdivisions, 155 Selecting the right equipment, 156 Fine trimming the subgrade, 177 10. Excavating Commercial Sites, 183 Excavating an apartment or office complex, 185 11. Highway Grading and Excavation, 199 Minimize the inconvenience, 220 13. Building Narrow Embankments, 233 Making space for the equipment, 234 Bringing in fill from above, 237 Testing for unsuitable soil, 254 Excavating unsuitable material, 254 Remedies for unsuitable soil problems, 260 Unsuitable soil around utility lines, 264 Meeting embankment standards, 276 Meeting subgrade standards, 277 Selecting the right equipment, 281 17. Curb and Sidewalk Grading, 285 18. Preparing Subgrade for Aggregate, 297 Rough trimming street sub grade, 298 Fine trimming the subgrade, 299 Trimming highway subgrade, 303 Placing aggregate in parking lots, 313 Placing aggregate base on highways, 320 Placing aggregate on subdivision roads, 325 Using lime to bridge unsuitable soil, 341 Using cement instead of lime, 343 Removing asphalt pavement, 347 Placing asphalt with a paver, 364 Paving with a spreader box, 376 Scheduling asphalt trucks, 377 Patch paving and trench paving, 384 22. Trenching and Pipe Laying, 393 Pressure testing sewer pipe, 411 Repairing broken sewer pipe, 416 23. Trench Shoring, Shields and Sloping, 433 24. Constructing Manholes, 443 25. Underdrains, Culverts and Downdrains, 459 A. Equipment operating tips, 467 Answers to Chapter Questions, 499 UNDERSTANDING ROAD SURVEY STAKES Since the mid 1970s, when my first grading and excavation book was published, there have been many changes in construction methods and equipment. Adapting lasers, sonar, and GPS to control the equipment to carry grade is by far the biggest change I've dealt with in this field. Using sonar and slope control on graders to fine trim has greatly increased production in the last few years. The operator using a GPS has the precise location where he is working right on his screen, showing the parameters of the lot pad and the elevation needed. G PS is now used on dozers, scrapers and compactors, and is also used for surveying. I'll be covering G PS in detail in a later chapter in the book. In the trenching department, the biggest change is that backhoes have replaced most trenchers, and hoes with compaction wheels have eliminated most trench jetting. So let's start at the beginning - with surveying and staking. Everyone - the inspector, superintendent, foremen and grading equipment operator, needs a good understanding of how surveyors stake the job. Not under-standing the stakes is like having the specifications and not being able to read. Today, most large jobs and many small ones are excavated using GPS to guide equipment. And even fewer stakes will be used in the future, making the stakes that are set more important than ever to read. The basic information on the stakes has changed little in the last few years. However, the way the surveyors compute that information has changed. Excavation for roads, buildings and pipelines begins with a survey of the area where the excavation will be done. A survey crew working for the engineering firm that's designing the project will set out stakes and hubs that identify points on the construction plans. When a precise distance or elevation is needed, a surveyor's tack on top of the hub establishes the point from which elevations and distances are measured. Beside each hub there will be an information stake marked in surveyor's code. It explains the grades at various distances from the hub or other reference stake or point. It's essential; that you know how to read the markings on these information stakes and follow the instructions they provide. The surveyor may write on one or all sides of the stake. The stakes are usually called cut, fill or slope stakes, depending on the type of excavation required. Figure 1-1 shows the kind of markings you'll find on an information stake. In this case, we're looking at a cut stake for a road excavation. The front, back and both sides of a cut stake are shown in the figure. Below the stake there's a cross section drawing of the existing grade and final road grades that are described on the stake. Refer to the drawing as I explain the markings on the information stake in the figure. Look first at the stake labeled front in the upper left of Figure 1-1. That's the front of the information stake. The RS at the top of the stake means that there's a reference stake to be established, and that reference stake is the point from which measurements and elevations are taken. The location of the reference stake is the point that the projected cut slope meets or catches original ground, also referred to as a catch point. Find the reference stake in the drawing. It's labeled RS and it's in the upper left-hand corner of the drawing. Below the letters RS on the information stake you see C-1Q. Below that you see a diagonal line and 5Q. These markings above and below the diagonal line identify the amount of cut and distance needed to establish the ,correct grade at the reference stake. The number above the diagonal line is the elevation and the number below the diagonal line is the distance. In this case, the information stake shows a cut of 1.0 foot (below the level of the surveyor's hub) to be made 5.0 feet from the hub for the RS point. Some surveyors may use RP instead of RS. RP means reference point. Treat it exactly the same as the RS. Notice that distances and elevations are measured in feet and tenths (or hundredths) of a foot, not feet and inches. The small number above the small horizontal line shows decimals of a foot. That's a little different from what you're probably used to, but you'll appreciate the difference when adding and subtracting feet and decimals of a foot rather than feet inches and fractions of an inch. I'll explain more about this measuring system, called engineer's measure, later in this chapter. The two horizontal lines below the first set of measurements are very important. All measurements above the double horizontal line are taken from the hub beside the information stake. The double horizontal line means and then, indicating that all measurements and elevations from that point down on the stake are taken from the RS point and not the surveyor's hub. Note this very carefully: If the double horizontal line was replaced with a single horizontal line, all measurements and elevations would be taken from the surveyor's hub rather than reference stake or hub established by the grade setter. On the other hand, if the surveyor uses a double line after each grade, then each cut becomes the reference for the next. We'll look at this last method shortly. The next information on this stake shows the elevation and location of the ditch cut (C-10o /20o). It's to be 10 feet lower than the RS point and 20 feet from it. The grade falls 10 feet over a horizontal distance of 20 feet, thus creating a 2:1 slope. You can see this indicated on the drawing (about lower middle). For every foot of cut, the grade line moves horizontally 2 feet. Notice that all measurements are made from the reference stake. The ditch is cut 10 feet below the reference stake and 20 feet from that stake. Also note that the 20-foot distance is measured horizontally, not diagonally, from the reference stake. Look again at the drawing to be sure you understand how the 20-foot distance to the ditch is measured. Remember, each square on the survey drawing represents 1 horizontal and 1 vertical foot. The next reading is the hinge point (HP) grade and distance. Note the hinge point on Figure 1-1. It's 2 feet above the ditch cut. The HP information on the stake shows an 8-foot cut at 24 feet, indicating the grade must come up 2 feet and move out 4 feet. By computing the amount the HP rises from the ditch and the distance it moves towards the center of the road, you can see that it's again a 2:1 slope. Reading down the information stake, the next grade and distance is the edge-of-pavement (EP) point. The grade will be 7.9 feet below the reference stake hub. Notice the cut at EP is 0.10-foot less than the HP cut. The reason for this is that the road grade rises 2 percent in the 5 feet from HP to EP. Multiplying 5 feet by 2 percent gives the amount the shoulder rises in that distance (5.00 x 0.02 = 0.10). The next markings give the centerline cut. You can see that the cut is again less than the previous cut at EP. Subtracting the 29 feet at EP from the 49 feet to the centerline leaves 20 feet. So the centerline is 49 feet from RS and 20 feet from EP. The cut at the centerline is 0.40 foot less than EP cut, making the centerline 0.40 foot higher than EP. Again, we have a 2 percent slope from the centerline to EP. You can check this by multiplying the 20 feet by 2 percent (20.00 x 0.02 = 0.40). These are all finished grades so the grade setter must add the thickness of the road section to the EP and centerline grade to get the correct subgrade elevation that must be excavated. Look at the back of the cut stake. It's marked 3+50, indicating that this station is 350 feet from station 0+00, the point from which the survey began. Below the station number is the distance from the surveyor's hub to the center of the road. This includes 5 feet to the RS and 49 feet from the RS to the centerline, a total of 54 feet (54o). Now let's look at the sides of the stakes. Note the first drawing of the stake labeled side. This side of the stake identifies the percentage of slope from the centerline to HP. The minus sign indicates that the centerline slopes down to the HP. If it were a plus sign instead, the centerline would be sloping up to the HP. The second side stake drawing shows the rate the cut slope falls from RS to the ditch. In this case, it's 2 feet out for every foot downward. The second group of numbers is the elevation of the surveyor's hub above sea level. Here's another method a surveyor might use to indicate measurements and elevations. I mentioned earlier that the line between each grade on the surveyor's information stake was very important. A double horizontal line means and then. So, if the surveyor uses a double line after each grade on the information stake, then each cut becomes the reference for the next. The information stake in Figure 1-2 shows the same information as the one in Figure 1-1, except it's written with a double line between each grade. Notice that by adding the double line, the last three distances change. In Figure 1-2, if you add the distances on the stake to centerline together (the distances indicated under the diagonal lines), you'll get 54 feet from the surveyor's hub to centerline. Now look at the back of the stake in Figure 1-~ It also reads 54 feet to centerline from the surveyor's hub. By using the double lines between grades, the last three cuts in Figure 1-1 become fills in Figure 1-2. The reason is because the HP grade must now be computed from the ditch grade, which is 2 feet lower, creating a fill of 2 feet. This method is also used to determine the centerline grade. The EP grade is 0.10 foot higher than the HP, and the centerline is 0.40 foot higher than EP. If you encounter a stake marked like the one shown in Figure 1-2, for better control and accuracy you should set a hub at each point as a reference to shoot your next grade from. If you study Figures 1-1 and 1-2 carefully, you'll notice each distance and elevation are exactly the same. Only the methods for computing them are different. Comparison of Inches and Decimals of a Foot Setting grades requires many additions and subtractions. Using decimals speeds the work and makes errors less likely. Figure 1-3 compares inches with decimals of a foot. If you're uncomfortable reading distances in tenths and hundredths of a foot, think of one foot as being like a dollar bill. One dollar is the same value as 100 pennies; one foot is the same distance as 100 hundredths of a foot. One dollar is the same value as 10 dimes; a foot is the same distance as 10 tenths of a foot. Pennies are hundredths. Dimes are tenths. We've looked at a cut stake where material must be excavated to reduce the existing grade to the finish grade (Figure 1-1). Figure 1-4 shows a typical fill situation where soil has to be deposited to build up the existing grade. Again, the illustration shows four sides of the stake and the road cross section. The RS at the top of the stake means that the reference stake (to the right of the hub) is the starting point and the place from which all measurements and grades are measured. Cut or fill information given for the RS point will be measured from the surveyor's hub. Here, the RS is located 1.8 feet above the hub and 3 feet from it. T grade setter will have to set the reference stake at the indicated horizontal distance from the hub and draw a horizontal line on the stake at the elevation given on the surveyor's information stake. If the ground hasn't been disturbed at that point, his line will match the existing ground. The grade setter should add a boot to his stake with a horizontal line foot above his RS grade. Because this is a fill, if the fill is made correct] the overfill will cover his finished grade line. By placing a I-foot boot above his finished mark, he'll save the time it would take him to dig it later. So when the grade setter returns to set a second slope stake at HP, he can use the 1-foot boot to compute the next vertical grade needed. He'll just subtract his 1-foot boot from the vertical grade he wants. Reading down the surveyor's stake, the two horizontal lines mean and then, indicating that the grade setter must measure from the RS point for the next fill and distance, instead of measuring or shooting grades from the original surveyor's hub. For the hinge point (HPJ, measure 10 feet from the RS hub or lath. At this point, a fill of 5 feet must be made to obtain the required grade. The hinge point is the place where the fill slope stops and the road grade begins. A stake won't be set at HP until the fill reaches that point. It would be in the way. The operator will get that grade from the RS stake set by the grade setter. It'll show the fill needed 10 feet out, and that the fill slope should be 2: 1 for the HP grade. If the fill were to be 20 feet high (rather than 5 feet), the grade setter would set slope stakes every 5 feet the fill rises to HP. There are times when the grade setter must offset the reference stake. Let's look at how he would do this. We'll say that the grade setter set his reference stake 5 feet out from the surveyor's hub. It often happens that the ground level is disturbed during clearing. What if, during the clearing operation, 1 foot of the existing ground is removed and the grade at the RS no longer matches the surveyor's information stake? When there is a 1 foot difference in grade, the grade setter working a 2:1 fill should move the reference stake back 2 feet. He must then mark his RS lath to reflect the change. His new fill and distance to HP will be F-6/ 12o. By moving the RS 2 feet back, once the fill is made 1 foot high at a 2:1 slope, it will match the grade and distance on the original RS set at 5 feet. If he didn't do this, the slope would be off line with the remaining RS points that were not undercut during clearing. On a cut slope, you may have to offset the RS for the equipment. You'd again move the RS back 2 feet to provide clearance for the grader's blade. This will keep the grader operator from having to slow down and adjust his cutting edge in from its normal grading position to avoid the stake. The grader would use the same cut and fill given for the 5-foot RS distance, but the grade setter would mark a 2 in a circle at the top of his lath to indicate the actual RS point is offset 2 feet. He should also mark the actual RS point with a paint line for the grader operator to follow. It's very important to set the RS point precisely because it controls the entire cut or fill elevation and alignment. Let's return to reading the information stake in Figure 1-4. The next point referenced is the EP. This is the edge of the pavement and it shows a fill of 5.12 feet (F-512) at 14.0 feet from RS. Below the EP data is the centerline, represented by a C and an L (one overlapping the other). From the RS, you measure 32 feet and fill 5.66 feet. This will put the centerline 18 feet from the EP and 0.54 foot higher. The back of the stake has 25+00. That signifies that this stake is 2,500 feet up the line from the point where the measurements started (the beginning of the road construction in this instance). The point the surveyors start from is most likely marked 0+00. These are station numbers. The number 35.0 below means that the center of the road is 35 feet out from the surveyor's hub (not RS). Look again at the front of the stake and notice that when the RS distance of 3 feet is added to the distance of 32 feet, the total is 35 feet, the same distance as that marked on the back of the stake. The first stake labeled side is marked SE -3%. This is the percentage that the roadbed slopes from the centerline to the hinge point. On the right-hand stake marked side, the first reading is 2:1 (2 to 1). This is the rate the fill slope will rise from RS to HP. Notice that the front of the stake shows HP with a 5-foot fill over a 10-foot distance. This is what the 2:1 indicates. The next item on the side stake is EL 9660. This is the elevation of the hub at the surveyor information stake. The surveyors computed all cuts or fills from that hub. What I've described so far in this chapter is more or less standard procedure for indicating elevations and distances on road stakes. However, surveyors in some counties and cities follow slightly different procedures. Some surveyors provide more information on the stakes and some less. The surveyor stake in Figure 1-5 shows what you might see on some county or city road stakes. The front of the stake begins with a 2 with a circle around it. This indicates that the first cut starts 2 feet out. The next markings indicate tha1 the ditch cut is 4 feet at a distance of 10 feet from the stake. The slope will again be 2: 1 because the first 2 feet aren't cut and the cut over the next 8 feet is 4 feet. Look at the figure again. Notice that there's no double and then line. This means that you must take all measurements and grade shots from the hub set by the surveyors rather than from an RS or RP point, as on the previous stakes we've looked at. Reading down the stake, we find a second group of numbers that show the top of the shoulder cut (Sho). This is the HP, or hinge point, referred to on previous stakes. Notice there's no EP distance or elevation on this stake. You must look at the plans for the distance from the shoulder to the edge-of-pavement, and the elevation. Notice that there's only 13 feet from the shoulder to the centerline, which indicates a possible aggregate shoulder. In this case the shoulder would be brought up to subgrade and not finished grade. Engineering companies follow different conventions when marking their stakes. But the plans should clarify what's intended and which points are actually indicated. If something isn't clear, don't guess. Call the engineering company that created the drawing and marked the stakes. They should be eager to help. The second drawing in Figure 1-5 is the back of the stake. It shows the rate of fall of the cut slope (2:1) and the station number (8+00). It doesn't have the centerline distance because all the front measurements are from the hub and not an RS or RP point. Many stakes have just the details required to allow you to set the grades. Even though other information may be absent, they always have the station number on theback. The side of the stake is shown in the right-hand illustration. It gives the elevation above sea level (EL 8256). In some cases the hub elevation won't be on the stake at all. It may be replaced with the percentage of slope for the road, or both may be omitted entirely. Miscellaneous Information Stakes Curb stake - Now look at Figure 1-6. The stake at the left is what you expect the surveyor to set for cutting and setting curb grades. From the hub at the base of this information stake, you'd move out 5 feet and down 1.50 feet to the top-back-of-curb (TBC) to set the curb forms or for the top of the concrete pour. In some cases, the surveyors may also give the front lip grade or even the flow line grade. If not, you'll have to determine the distance from the back of the curb to the lip. This information is available in the plans or specifications. When setting curb subgrade, determine the thickness of curb plus any aggregate base, if it's called for under the curb. The thickness of one or both must be added to the cuts and subtracted from the fills to find the subgrade rather than the finished grade level. Notice that there's a tack in the hub in front of the curb stake. The tack marks the exact spot from which the surveyor took his measurements. Without this marker, the measurements could be as much as 1-1/2 inches off (using a 2 x 2-inch hub). The tack provides greater accuracy. Street stake - The center stake in Figure 1-6 is a street stake you'd expect to find on a rural road first cut. The front of the stake indicates the centerline of the street and the cut or fill to the finished grade. In this case, there's a 2-foot cut to the finished grade (FG). The plans should show the road width, percentage of slope or crown, and the thickness of the road section. Remember to add the thickness of the road to this cut. The station number may be on the back or front of the street stake. Surveyors rarely stake the street centerline. The stakes are usually offset behind the back of the curb or a roadside ditch and will carry enough information for the grade setter to establish a centerline grade. Those are the common methods for staking roads. Ditch channel stake - The stake at the far right in Figure 1-6 is a grade stake for a ditch or small channel. The 3 in the circle (read 3-foot offset) is the distance from the hub where the first cut starts (which would be the catch point or top-of-slope). The west toe grade indicates the first slope and the bottom of that slope. The east toe is the bottom of the slope on the opposite side of the ditch. Both toe cuts are the same, so the bottom is flat. The east top cut is where the cut will be started on the opposite side. Subtracting the 3-foot offset from the 23-foot distance to the east top cut gives the distance across the top of the ditch, 20 feet. Subtract the small toe distance from the larger. This gives the width of the ditch bottom, 4 feet. To find the rate of slope from the top cut to the toe of the channel, subtract the distance given to the top cut from the distance given to the toe cut. The 3-foot offset must be subtracted from the west side distance of 11 feet. This will make the distance 8 feet from top cut to toe on each side. Dividing the cut of 8 feet into the 8-foot horizontal distance gives an answer of 1. This indicates that for every foot cut vertic,ally, the slope moves out 1 foot horizontally. That's a 1:1 slope. A stake with only a few markings will usually provide all the information you need to do the excavation. If something is still unclear, the plans should have the answer you're looking for. In this chapter we've described grades by either a ratio of run to rise or as a percent above the horizontal. Most grades in excavation work c expressed as a ratio of horizontal distance (run) to vertical distance (rise), or run to rise (run:rise). Figure 1-7 illustrates the four most common slope ratios, and should help you visualize most of the slopes you work with in excavation. If you're still confused about the work required after reading the surveyor's stakes and checking the plans, ask the survey crew about it they're still on the job. If they've left, call the engineer and have him clarify the problem or send the survey crew out for a field meeting. Be sure you know what's required before beginning the work. Earthmoving is far too time-consuming and expensive for you to be taking your best guess and hoping you're right! (please look at our rules and privacy policy) |
M_arnold@machine--tools.com (Marietta Arnold) for additional information. This email is used for forwarding to newsgroup user.
