Design and Installation of Embedded Culverts

Transcription

1 Kamloops March 12, 2002 Pilot 2 Design and Installation of Embedded Culverts Part 2: Design 1

2 2 Part 2: Design 6 Main Topics 1. Evaluation of site suitability 2. Detailed streambed profile 3. Sizing the pipe 4. Design embedment 5. Embedment material 6. Design drawings

3 Culvert Terminology 3 Slope/Gradient Barrel Perching Invert Weir Jump/Rest Pool

4 4 1. Evaluation of Site Suitability Should consider the following: Fish stream Stable stream channel Stream gradient <6% Stream channel width <2.5m Depth of excavatable fill Suitable for both stream and road geometry Evaluate diversion options

5 5 2. Detailed Streambed Profile Use precise instruments Establish elevation benchmarks

6 Detailed Streambed Profile 6 Field Survey Reference Control Elevational benchmarks Spike BM in blazed tree Horizontal reference stakes

7 Detailed Streambed Profile 7 Profile Length Extended distance upstream and downstream (~50m minimum) note potential influences such as log/debris jams, bedrock, nick points

8 Detailed Streambed Profile 8 Elevation (m) Proposed Stream Bed Slope and Elevation (at low points) Existing Stream Bed Profile Length (m)

9 9 3. Sizing the Pipe Stream Channel Width Edges of rooted vegetation Definite change in vegetation and sediment texture Culvert diameter / span must span SCW at point of embedment

10 Sizing the Pipe 10 Diameter/Span Determination of Stream Channel Width with field measurements Use systematic approach to avoid skewing the results (FSCG - 6 equally spaced intervals along 100 m length)

11 Sizing the Pipe 11 Depth of Embedment Round pipes - 40% of diameter or 0.6m, whichever is greater Pipe-arch - 20% of vertical rise of the arch

12 Sizing the Pipe 12 Round Pipes Pipe Dia > Stream channel width 40% of diameter or 0.6m, whichever is greater Span the stream channel width (SCW) at embedment depth present water level 40% embeddment

13 Sizing the Pipe 13 Arch Pipes Arch Span > Stream channel width Pipe-arch 20% of vertical rise of the arch Span the stream channel width (SCW) at embedment depth Present water level 20% embedment

14 Sizing the Pipe 14 Check Q100 Check that Q100 will embedment depth Non-embedded pipe Culvert Cross Sectional Area ~ 3 x Visible Highwater Area Round pipe at 40% embedment => loss of 37% of area Arch pipe at 20% embedment => loss of 17% of area

15 Sizing the Pipe 15 Check Q100 Round pipe at 40% embedment -> loss of 37% of area Arch pipe at 20% embedment -> loss of 17% of area Round Culvert X-sectional Area Required ~ 1.37 x (3 x visible high water area) Arch Culvert X-sectional Area Required ~ 1.2 x (3 x visible high water area)

16 Sizing the Pipe 16 FPC Forest Road Regulations Require P.Eng. For : >2000mm or >6 m 3 /s

17 Sizing the Pipe 17 Factors Influencing Culvert Length Depth of fill and fill slopes Road surface width Culvert gradient Skew angle of culvert to road

18 Sizing the Pipe 18 Factors Influencing Culvert Length Include: R/W width 1 1 depth of fill gradient

19 Sizing the Pipe 19 Factors Influencing Culvert Length Include: amount of skew to road r/w C/L

20 20 4. Design Embedment Depth of Embedment Round pipes - 40% of diameter or 0.6m, whichever is greater Pipe-arch - 20% of vertical rise of the arch

21 Design Embedment 21 Elevation (m) Proposed Stream Bed Slope and Elevation (at low points) Existing Stream Bed Profile Length (m) 40% or 20 % Embedment Estimated Culvert Invert Elevation & Slope

22 22 5. Embedment Materials Objective is to emulate/simulate natural streambed Fish passage is related to Hydraulic Roughness (HR) HR related to size of bed materials Bed materials, in turn, are related to water velocities and water depth in culvert which influence fish passage

23 Velocity (m/s) Embedment Materials 23 Material Size Influence on Velocity Depth of Flow (m) Material Size 5 cm 15 cm 30 cm 60 cm

24 Embedment Materials 24 Velocity Refuge (Shadows) Roughness reduces velocity and creates shadows

25 Embedment Materials 25 Embedded pipes -modeling/simulating the natural streambed

26 Embedment Materials 26 Rule of Thumb Size similar to that found in adjacent natural streambed Natural Stream Channel Embedment Material

27 Embedment Materials 27 Range of Material Size Design should specify composition and distribution sizes of material to be used

28 Embedment Materials 28 Range of Material Size A range of substrate sizes (gradation) should be specified in the design Materials must be well graded to seal the streambed Ensure sufficient fines (sands & gravels) to seal the streambed Supplement with larger D90 material to help retain substrate D90 or greater particularly important on stream between 3 and 6% Defn. D90 is the size of which 90% of the material will be smaller than

29 Embedment Materials 29 Range of Material Size 25% 35% 25% 15% Cobble Gravel Fine Boulder Rule of thumb - aka George Robison General Size Distribution of Embedded Material

30 Embedment Materials 30 Substrate Volume Determination Round pipe embedded 40% ~ 37% of area Area (Round) = p(dia/2) 2 Arch pipe embedded 20% ~ 17% of area Area (Arch) from manufacturer info

31 Design Drawings 31 Purpose Tools to design culvert to fit site Document proposed works and final product Provides material and construction specifications Provide construction referencing

32 Design Drawings 32 Site Plan / Profiles - Plan/profiles developed for the crossing - design drawings developed from site plan / profiles - used for design and documentation purposes

33 Design Drawings 33 Site Plan - contour map of the site

34 Design Drawings 34 Fit Crossing to Site - The selected crossing structure should be suited to both the stream and road - consider road drainage to minimize potential sediment delivery to the stream - avoid vertical dips, provide for roadway drainage

35 Design Drawings 35 Culvert Profile

36 Design Drawings 36 Road profile

37 Design Drawings Plan Drawing 37

38 Design Drawings Riprap Specifications 38

39 Design Drawings Installation Measures 39

40 Design Drawings Installation Referencing 40

41 Design Drawings 41 Other Details ie. Weir Design channel widths stream bank stream bank well graded boulders, cobbles and fines leaving no gaps in matrix A downstream weir may required as part of the design to be installed within channel widths downstream of culvert outlet Assists in maintaining adequate low flow depth Helps retain substrate Prevents formation of plunge pool Particularly important where stream gradient is > 3%

42 Design Drawings 42 Weir Design Weir Plan View Flow Longitudinal View Weir

43 Design Drawings Weir Design 43

44 Design Drawings Summary 44 Design should include: Stream data Plan Profile Construction referencing (vertical / horizontal) Materials specifications Installation specifications other details (riprap, weir, etc.)