Tail Escape - PowerPoint PPT Presentation

About This Presentation
Title:

Tail Escape

Description:

Tail Escape Road Waterway Water Body Tail escape is a structure constructed at the end of a waterway to evacuate the water to a water body. Tail escape consists of a ... – PowerPoint PPT presentation

Number of Views:99
Avg rating:3.0/5.0
Slides: 18
Provided by: Prof8267
Category:
Tags: escape | tail | velocity

less

Transcript and Presenter's Notes

Title: Tail Escape


1
Tail Escape
2
  • Tail escape is a structure constructed at the end
    of a waterway to evacuate the water to a water
    body.
  • Tail escape consists of a well where its crest
    level at the high water level. It is also
    equipped with an orifice at its bottom to
    evacuate all the water in 24 hrs if necessary.
  • A pipe evacuates the water to the water body
    under the road.

3
Tail Escape
4
Hydraulic Design
  • Hydraulic design of the tail escape consists of
    three parts
  • 1. Automatic evacuation (Weir)
  • 2. Controlled evacuation (Orifice)
  • 3. Discharging to Sea (Pipe)

5
  • Automatic Evacuation
  • The excess water is evacuated over the weir's
    crest.
  • The maximum acceptable rise in water level is 25
    cm.
  • the discharge of water over the weir can be
    calculated as follows
  • Qw Ts . h . Vs

6
  • Where
  • Qw is the weirs discharge in m3/sec,
  • Ts is the top width of the water
  • surface in m,
  • h is the rise in water level 0.25 m,
  • Vs is the surface water velocity in
  • m/sec.
  • Vs 1.17 vw

7
  • Where vw is the mean water velocity of the water
    way.

Ts
25 cm
H.W.L.
8
  • To design the size of the well, the weir equation
    is used,
  • Where
  • Cd is the discharge coefficient 0.55,
  • B is the crest length, and

9
  • 2. Controlled Evacuation
  • Orifice is designed to evacuate the waterway
    in 24 hrs. The following equation is used to
    determine the size of the orifice,
  • Where
  • T is the time to empty the waterway
  • 24 . 60 .60 sec

10
  • L is the waterway length in m,
  • be is the waterway average width in m,
  • y is the depth of the waterway,
  • Cd is the discharge coefficient 0.6

Ts
H.W.L.
be
y
b
11
  • a is the area of the orifice in m2 and,
  • Notice The orifice is equipped with a gate so
    the water in the waterway can be used for any
    purpose. The gate is open to evacuate the water
    if needed.

12
  • 3. Pipe
  • The pipe is designed to the maximum discharge
    for emergency as
  • Where
  • Qp is the pipe discharge,
  • Qo is the orifice discharge

13
  • Where
  • And,
  • Where Vp is the pipe velocity (2.0 m/sec) and D
    is the pipe diameter.

14
  • Example
  • A tail escape is required to be constructed at
    the end of a waterway according to the following
    data
  • Q 4.6 m3/sec, Waterway length 3000 m,
    Vc0.45 m/sec

7.6 m
1.8 m
5.8 m
4 m
15
  • Sol.
  • a. Automatic evacuation
  • Qw 7.6 0.15 (1.170.45)
  • 0.6 m3/sec
  • 0.6 (2/3)0.55B(v29.81)(0.15)1.5
  • B 6.36 m
  • D 2.7 m
  • b. Controlled Evacuation
  • T 246060

16
  • a 0.2 m2
  • do 0.5 m
  • c. Pipe
  • QpQwQo
  • Qo0.60.2(v29.812.05)
  • 0.76 m3/sec
  • Qp 1.36 m3/sec
  • Assume Vp 2 m/sec

17
  • 1.36 2 Ap
  • D 0.93 m take D 1.0 m
  • Vp 1.73 m/sec
Write a Comment
User Comments (0)
About PowerShow.com