1、 CHAPTER 4 HYDRAULIC DESIGN OF CULVERTS 2007 by the American Association of State Highway and Transportation Officials. 2007 by the American Association of State Highway and Transportation Officials.CHAPTER 4 TABLE OF CONTENTS 4.1 INTRODUCTION. 4-1 4.2 DATA COLLECTION . 4-2 4.2.1 Topographic Feature
2、s.4-2 4.2.2 Drainage Area 4-2 4.2.3 Channel Characteristics . 4-2 4.2.4 Fish Life. 4-3 4.2.5 Highwater Information. 4-3 4.2.6 Existing Structures. 4-3 4.2.7 Field Review 4-4 4.3 CULVERT LOCATION 4-4 4.3.1 Plan 4-5 4.3.2 Profile. 4-6 4.4 CULVERT TYPE . 4-8 4.4.1 Shape and Cross Section 4-8 4.4.1.1 Ci
3、rcular. 4-8 4.4.1.2 Pipe Arch and Elliptical . 4-8 4.4.1.3 Box or Rectangular. 4-8 4.4.1.4 Arches. 4-9 4.4.1.5 Multiple Barrels 4-9 4.4.2 Materials 4-9 4.4.3 End Treatments 4-10 4.4.3.1 Projecting . 4-10 4.4.3.2 Mitered . 4-10 4.4.3.3 Pipe End Sections. 4-10 4.4.3.4 Headwalls and Wingwalls 4-11 4.5
4、HYDRAULIC DESIGN 4-12 4.5.1 Design Flood Discharge. 4-12 4.5.2 Headwater Elevation 4-12 4.5.3 Tailwater 4-14 4.5.4 Outlet Velocity. 4-14 4.5.5 Culvert Hydraulics.4-14 4.5.5.1 Conditions of Flow. 4-15 4.5.5.1.1 Inlet Control. 4-15 4.5.5.1.2 Outlet Control 4-16 4.5.5.2 Performance Curves . 4-16 2007 b
5、y the American Association of State Highway and Transportation Officials.4-iv Highway Drainage Guidelines 4.5.6 Entrance Configurations.4-18 4.5.6.1 Conventional.4-18 4.5.6.2 Beveled .4-21 4.5.6.3 Side-Tapered Inlets .4-22 4.5.6.4 Slope-Tapered Inlets .4-24 4.5.7 Barrel Characteristics .4-24 4.5.8 O
6、utlet Design4-25 4.6 SPECIAL HYDRAULIC CONSIDERATIONS.4-26 4.6.1 Anchorage 4-26 4.6.2 Piping4-28 4.6.2.1 Joints .4-29 4.6.2.2 Anti-Seep Collars4-29 4.6.2.3 Weep Holes.4-29 4.6.3 Junctions and Bifurcations .4-30 4.6.4 Training Walls4-30 4.6.5 Sag Culverts .4-31 4.6.6 Irregular Alignment4-31 4.6.7 Cav
7、itation .4-31 4.6.8 Tidal Effects and Flood Protection.4-31 4.7 MULTIPLE-USE CULVERTS 4-32 4.7.1 Utilities .4-32 4.7.2 Stock and Wildlife Passage 4-32 4.7.3 Land Access4-32 4.7.4 Fish Passage .4-32 4.8 IRRIGATION4-35 4.9 DEBRIS CONTROL .4-35 4.9.1 Debris Control Structure Design 4-36 4.9.2 Maintenan
8、ce .4-36 4.10 SERVICE LIFE.4-36 4.10.1 Abrasion .4-37 4.10.2 Corrosion4-38 4.11 SAFETY .4-39 4.12 DESIGN DOCUMENTATION 4-39 4.12.1 Compilation of Data .4-39 4.12.2 Retention of Records 4-40 2007 by the American Association of State Highway and Transportation Officials.Hydraulic Design of Culverts 4-
9、v 4.13 HYDRAULIC-RELATED CONSTRUCTION CONSIDERATIONS. 4-40 4.13.1 Verification of Plans 4-40 4.13.2 Temporary Erosion Control . 4-40 4.13.3 Construction and Documentation 4-41 4.14 HYDRAULIC-RELATED MAINTENANCE CONSIDERATIONS. 4-41 4.14.1 Maintenance Inspections 4-41 4.14.2 Flood Records 4-41 4.14.3
10、 Reconstruction and Repair. 4-41 4.15 REFERENCES 4-42 2007 by the American Association of State Highway and Transportation Officials.Chapter 4 Hydraulic Design of Culverts 4.1 INTRODUCTION The function of a culvert is to convey surface water across or from the highway right-of-way. In addition to th
11、is hydraulic function, it must also carry construction and highway traffic and earth loads; therefore, culvert design involves both hydraulic and structural design. The hydraulic and structural designs must be such that risks to traffic, of property damage, and of failure from floods are consistent
12、with good engineering practice and economics. This chapter is concerned with the hydraulic aspects of culvert design and makes reference to structural aspects only as they are related to the hydraulic design. Structures measuring more than 20 ft (6.1 m) along the roadway centerline are conventionall
13、y classified as bridges. Many longer structures, however, are designed hydraulically and structurally as culverts. Culverts, as distinguished from bridges, are usually covered with embankment and are composed of structural material around the entire perimeter, although some are supported on spread f
14、ootings with the streambed serving as the bottom of the culvert. Bridges are not designed to take advantage of submergence to increase hydraulic capacity even though some are designed to be inundated under flood conditions. For economy and hydraulic efficiency, culverts should be designed to operate
15、 with the inlet submerged during flood flows, if conditions permit. At many locations, either a bridge or a culvert will fulfill both the structural and hydraulic requirements for the stream crossing. Structure choice at these locations should be based on construction and maintenance costs, risk of
16、failure, risk of property damage, traffic safety, and environmental and aesthetic considerations. Some of the advantages of culverts are better traffic safety and lower maintenance costs than bridges. Culverts do not have bridge railing, which can be a hazard, or a bridge deck, which is subject to d
17、eterioration. Culverts are usually considered minor structures, but they are of great importance to adequate drainage and the integrity of the highway facility. Although the cost of individual culverts is usually relatively small, the total cost of culvert construction constitutes a substantial shar
18、e of the total cost of highway construction. Similarly, the total cost of maintaining highway hydraulic features is substantial, and culvert maintenance may account for a large share of these costs. Improved traffic service and a reduction in the total cost of highway construction and maintenance ca
19、n be achieved by judicious choice of design criteria and careful attention to the hydraulic design of each culvert. 2007 by the American Association of State Highway and Transportation Officials.4-2 Highway Drainage Guidelines 4.2 DATA COLLECTION For purposes of this section, site information from w
20、hatever source is broadly classified as survey data. Sources of data include aerial or field survey; interviews; water resource, fish and wildlife, and planning agencies; newspapers; and floodplain zoning studies. Complete and accurate survey information is necessary to design a culvert to best serv
21、e the requirements of a site. The individual in charge of the drainage survey should have a general knowledge of drainage design and coordinate the data collection with the hydraulics engineer. The amount of survey data gathered should be commensurate with the importance and cost of the proposed str
22、ucture. 4.2.1 Topographic Features The survey should provide the designer with sufficient data for locating the culvert and may aid in determining the hydraulic design controls. All significant physical features and culture in the vicinity of the culvert site should be located by the survey, and esp
23、ecially those features that could be affected by the installation or operation of the culvert. Such features as residences, commercial buildings, croplands, roadways, and utilities can influence a culvert design; therefore, their elevation and location should be obtained. The extent of survey covera
24、ge required for culvert design is related to topography and stream slope. In streams with relatively flat slopes, the effects of structures may be reflected a considerable distance upstream and require extensive surveys to locate features that may be affected by the culvert installation. 4.2.2 Drain
25、age Area Drainage area is an important factor in estimating the flood potential; therefore, the area of the watershed should be carefully defined by means of survey, photogrammetric maps, U. S. Geological survey (USGS) topographic maps or a combination of these.1In locations where accurate definitio
26、n of drainage areas from maps is difficult, the map information should be supplemented by survey. Noncontributing areas, such as contributing to sinkholes and playa lakes, may need to be defined. The survey should note land usage, type and density of vegetation, and any constructed changes or develo
27、pments (e.g., dams) which could significantly alter runoff characteristics. 4.2.3 Channel Characteristics The physical characteristics of the existing stream channel should be described by the survey. For purposes of documentation and design analysis, sufficient channel cross sections, a streambed p
28、rofile and the horizontal alignment should be obtained to provide an accurate representation of the channel, including the floodplain area. The channel profile should extend beyond the proposed culvert location far enough to define the slope and locate any large streambed irregularities (e.g., headc
29、utting). 1Maps for all areas of the United States can be ordered from the U.S. Geological Survey, Map Distribution, Federal Center, Box 25286, Denver, CO 80225. 2007 by the American Association of State Highway and Transportation Officials.Hydraulic Design of Culverts 4-3 General characteristics hel
30、pful in making design decisions should be noted. These include the type of soil or rock in the streambed, the bank conditions, type and extent of vegetal cover, amount of drift and debris, ice conditions, and any other factors that could affect the sizing of the culvert and the durability of culvert
31、 materials. Photographs of the channel and the adjoining area can be a valuable aid to the designer and serve as excellent documentation of existing conditions. 4.2.4 Fish Life Survey data should include information regarding the value of the stream to fish life and the type of fish found in the str
32、eam. The necessity to protect fish life and to provide for fish passage can affect many decisions regarding culvert, channel change and riprap designs and construction requirements for protection of the stream environment. Data required, and criteria for design and construction, are generally availa
33、ble from State and Federal fish and wildlife agencies. A culvert designed for fish passage is discussed in more detail in Section 4.7.4. 4.2.5 Highwater Information Reliable, documented highwater data, when available, can be a valuable design aid. Often, the designer must rely upon highwater marks a
34、s the only basis on which to document past floods. Highwater marks can also be used to check results of flood-estimating procedures, establish highway grade lines and locate hydraulic controls, but considerable experience is necessary to properly evaluate highwater information. Data related to highw
35、ater should be taken in the vicinity of the proposed structure, but it is sometimes necessary to use highwater marks from upstream or downstream points. The location of the highwater mark with respect to the proposed structure should be recorded. Highwater elevations should be referenced to the proj
36、ect data. If highwater information is obtained from residents, the individuals should be identified and the length of residency indicated. Other sources for data include commercial and school bus drivers, mail carriers, law enforcement officers, highway and railroad maintenance personnel, or other p
37、ersons who have frequently traveled through the area over a long period of time. Unusual highwater elevations should be examined to ascertain whether irregularities existed during the flood, such as blockage of the channel from drift, ice, or backwater from stream confluences. 4.2.6 Existing Structu
38、res Considerable importance should be placed on the hydraulic performance of existing structures, and all information available should be gathered in the survey. The performance of structures some distance either upstream or downstream from the culvert site can be helpful in the design. Local reside
39、nts, highway maintenance personnel, or others can furnish important highwater data and dates of flood occurrences at such structures. Data at existing structures should include the following, if available: date of construction; major flood events since construction and dates of occurrence; 2007 by t
40、he American Association of State Highway and Transportation Officials.4-4 Highway Drainage Guidelines performance during past floods; scour indicated near the structure; type of material in streambeds and banks; alignment and general description of structure, including condition of structure, especi
41、ally noting abrasion, corrosion, or deterioration; alignment and general description of structure, including dimensions, shape, and material and flowline invert elevations; highwater elevations with data and dates of occurrence; location and description of overflow areas; photographs; silt and drift
42、 accumulation; evidence of headcutting in stream; appurtenant structures (e.g., energy dissipators, debris control structures, stream grade control devices); and as-built plan of structure. 4.2.7 Field Review The engineer designing drainage structures should be thoroughly familiar with the watershed
43、 site under consideration. Much can be learned from the survey notes, but the most complete survey cannot adequately depict all watershed site considerations or substitute for a personal inspection by the designer. Often, a plans-in-hand inspection by the designer and the construction engineer will
44、prove mutually beneficial by improving the drainage design and reducing construction problems. 4.3 CULVERT LOCATION Culvert location deals with the horizontal and vertical alignment of the culvert with respect to both the stream and the highway. It is important to the hydraulic performance of the cu
45、lvert, to stream stability, to construction and maintenance costs, and to the safety and integrity of the highway. The horizontal and vertical alignment are important in maintaining a sediment-free culvert. Deposition occurs in culverts because the sediment transport capacity of flow within the culv
46、ert is often less than in the stream. The following factors contribute to deposition in culverts: at moderate flow rates, the culvert cross section is larger than that of the stream, thus the flow depth and sediment transport capacity is reduced; point bars form on the inside of stream bends, and cu
47、lvert inlets placed at bends in the stream will be subjected to deposition in the same manner. This effect is most pronounced in multiple-barrel culverts with the barrel on the inside of the curve often becoming almost totally plugged with sediment deposits; and abrupt changes to a flatter grade in
48、the culvert or in the channel adjacent to the culvert will induce deposition. Gravel and cobble deposits are common downstream from the break in grade because of the reduced transport capacity in the flatter section. 2007 by the American Association of State Highway and Transportation Officials.Hydr
49、aulic Design of Culverts 4-5 Deposition usually occurs at flow rates smaller than the design flow rate. The deposits may be removed during larger floods, dependent upon the relative transport capacity of flow in the stream and in the culvert, compaction and composition of the deposits, flow duration, ponding depth above the culvert, and other factors. 4.3.1 Plan Plan location deals basically with the route the flow will take in crossing t
