(1) Drop structures are used in canals to lower the water level along its course. There are several types of drop structures including vertical drops, inclined drops, piped drops, and farm drops.
(2) The main types of vertical drops discussed are the common straight drop, Sarda-type fall, and YMGT-type drop. Inclined drops include common chutes, rapid fall drops, and stepped cascades. Piped drops can be well drops or pipe falls.
(3) Each type has specific design considerations like crest shape and length, basin/stilling pool dimensions, upstream and downstream protections works, and guidelines for selection based on discharge and design head.
Canal fall- necessity and location- types of falls- Cross regulator and
distributory head regulator- their functions, Silt control devices, Canal
escapes- types of escapes.
Canal fall- necessity and location- types of falls- Cross regulator and
distributory head regulator- their functions, Silt control devices, Canal
escapes- types of escapes.
Topics:
1. Causes of Failures of Weirs on Permeable Foundations
2. Bligh’s Creep Theory
3. Lane’s Weighted Creep Theory
4. Khosla’s Theory
5. Application of Correction Factors
6. Launching Apron
Types- selection of the suitable site for the diversion headwork components
of diversion headwork- Causes of failure of structure on pervious foundation- Khosla’s theory- Design of concrete sloping
glacis weir.
Bligh’S CREEP THEORY
LIMITATIONS OF BLIGH’S THEORY
LANE’S WEIGHTED CREEP THEORY
KHOSLA’S THEORY AND CONCEPT OF FLOW NETS
COMPARISON OF BLIGH’S THEORY AND KHOSLA’S THEORY
WEIRS VERSUS BERRAGE
TYPES OF WEIRS
COMPONENT PARTS OF A WEIR
CAUSES OF FAILURE OF WEIRS & THEIR REMEDIES
DESIGN CONSIDERATIONS
DESIGN FOR SURFACE FLOW
DESIGN OF BARRAGE OR WEIR
Topics:
1. Causes of Failures of Weirs on Permeable Foundations
2. Bligh’s Creep Theory
3. Lane’s Weighted Creep Theory
4. Khosla’s Theory
5. Application of Correction Factors
6. Launching Apron
Types- selection of the suitable site for the diversion headwork components
of diversion headwork- Causes of failure of structure on pervious foundation- Khosla’s theory- Design of concrete sloping
glacis weir.
Bligh’S CREEP THEORY
LIMITATIONS OF BLIGH’S THEORY
LANE’S WEIGHTED CREEP THEORY
KHOSLA’S THEORY AND CONCEPT OF FLOW NETS
COMPARISON OF BLIGH’S THEORY AND KHOSLA’S THEORY
WEIRS VERSUS BERRAGE
TYPES OF WEIRS
COMPONENT PARTS OF A WEIR
CAUSES OF FAILURE OF WEIRS & THEIR REMEDIES
DESIGN CONSIDERATIONS
DESIGN FOR SURFACE FLOW
DESIGN OF BARRAGE OR WEIR
Design of Hydraulic Structures and Cross Drainage WorksArunSekhar18
To develop capability to perform the design of minor irrigation structures such as; cross drainage works, canal falls, regulators and prepare drawings. Also to impart knowledge on causes of failure and design criteria of hydraulic structures like dams and canal structures.
Dams , piping, uplift Pressure, Khosla’s Theory, causes of Failure of Hydraulic structure by piping and uplift pressure
what is the importance of reservoir planning and dams? Discuss multipurpose reservoir in detailed, Give Economic height of dam.
Design of water tank (RCC design) By Working Stress Method as per Indian Standards.
Useful for Practicing Civil Engineers & Students of B.Tech & B.E in civil
This study was competent studied earth dams and species and its history and the factors influencing them and the other part of a study of the most important risks that affect earth dams (seepage through earth dams) and how to calculate the leak and methods of their account and types the seepage and forms of cost and what are the ways process is treated with filters.
1. INTRODUCTION TO SEEPAGE THROGH EARTH DAM
2.METHODS CALCULATION SEEPAGE THROGH EARTH
DAM
3. ENTRANCE, DISCHARGE, AND TRANSFARE
CONDITIONSOF LINE OF SEEPAGE
4.SIMULATE THE PRESSURE ON THE EARTH DAM USING SAP 2000 PROGRAM
5.DESIGN FILTER TO CONTROLED THE SPAAGE IN EARTH DAM
The students can learn about basics of image processing using matlab.
It explains the image operations with the help of examples and Matlab codes.
Students can fine sample images and .m code from the link given in slides.
This lecture is about particle image velocimetry technique. It include discussion about the basic element of PIV setup, image capturing, laser lights, synchronize and correlation analysis.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Design and Analysis of Algorithms-DP,Backtracking,Graphs,B&B
Chapter 5 drop sturcutures
1. CHAPTER 5: DROP STRUCTURES
1
0401544 - HYDRAULIC STRUCTURES
University of Sharjah
Dept. of Civil and Env. Engg.
DR. MOHSIN SIDDIQUE
ASSISTANT PROFESSOR
2. LEARNING OUTCOME
After taking this lecture, students should be able to:
(1). Obtain in-depth knowledge on various types of drop
structures used in open channels and their design guide
lines
(2). Identify the suitable drop structure for various flow
conditions
(3). Apply the design guide lines for the design of selected
drop structure
2
References:
Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan, Hydraulic Structures, 4the Ed.
CRC Press
Santosh K. G., Irrigation Engineering and Hydraulic Structures, Khanna
Pubilshers
3. DROP STRUCTURES (CANAL DROPS)
A drop (or fall) structure is a regulating structure which lowers the
water level along its course.
The slope of a canal is usually milder than the terrain slope as a
result of which the canal in a cutting at its headworks will soon
outstrip the ground surface. In order to avoid excessive infilling
the bed level of the downstream canal is lowered, the two reaches
being connected by a suitable drop structure
3
5. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
Drops are usually provided with a low crest wall and are
subdivided into the following types:
(i) the vertical drop
(ii) the inclined drop
(iii) the piped drop and
(iv) Farm drop structures
Note: The above classification covers only a part of the broad spectrum
of drops, particularly if structures used in sewer design are included; a
comprehensive survey of various types of drops has been provided,
e.g. by Merlein, Kleinschroth and Valentin (2002); Hager (1999)
includes the treatment of drop structures in his comprehensive
coverage of wastewater structures and hydraulics.
5
6. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
(i) the vertical drop,
(a). Common (straight) drop
(b). Sarda-type fall (India)
(c). YMGT-type drop (Japan)
(d) Rectangular weir drop with raised crest (France)
6
7. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
(i.a) Common (straight) drop: The common drop structure, in which
the aerated free-falling nappe (modular flow) hits the downstream basin
floor, and with turbulent circulation in the pool beneath the nappe
contributing to energy dissipation, is shown in Fig
7
8. DROP STRUCTURES (CANAL DROPS)
The following equations fix the geometry of the structure in a suitable
form for steep slopes:
where d is the height of the drop crest above the basin floor and Lj the length of
the jump. Lj=6.9(y2-y1)
A small upward step, h (around 0.5<h/y1<14), at the end of the basin floor is
desirable in order to localize the hydraulic jump formation. Forster and Skrinde
(1950) developed design charts for the provision of such an abrupt rise.
32
/ gdqDr =
8
9. DROP STRUCTURES (CANAL DROPS)
The USBR (Kraatz and Mahajan, 1975) impact block type basin also
provides good energy dissipation under low heads, and is suitable if the
tailwater level (TWL) is greater than the sequent depth, y2.
9
h
d/s Floor
level
Crest level
yo
Tailwater
level
10. DROP STRUCTURES (CANAL DROPS)
The following are the suggested dimensions of such a structure with
impact block type basin
where yc is the critical depth.
The values of Ld can be
obtained from the following
Fig
10
11. DROP STRUCTURES (CANAL DROPS)
2
456.0185.0
228.0691.0
368.4195.3406.0
368.4195.3406.0
2
2
sf
d
c
t
c
cc
t
c
c
t
c
c
f
LL
L
y
L
y
y
d
y
L
Ls
y
y
h
L
y
y
d
L
+
=
+
−
+
=
−+−=
−+−=
Use –ve sign with d and h2
Note: sometime d is replaced with ho.
However, both are the same.
h2=RL of crest-D/S FSL
d=RL of crest-stilling basin flood level
11
12. 0.85yc
0.8yc
0.4yc
h2
h=drop height=RL of crest-D/S Floor level
h2=RL of crest-D/S FSL
d=RL of crest-stilling basin flood level
Side wall height
above tailwater
h
d/s Floor
level
Crest level
yo
DROP STRUCTURES (CANAL DROPS)
12
Tailwater
level
14. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP
STRUCTURES
(i.b) Sarda-type fall (India):
This is a raised-crest fall
with a vertical impact,
consisting of a crest wall,
upstream and downstream
wing walls, an impervious
floor and a cistern (basin),
and downstream bank and
bed protection works
14
15. DROP STRUCTURES (CANAL DROPS)
Two types of crest are used; the rectangular one for discharges up to
10m3/s** and the trapezoidal one for larger discharges (see Punmia and
Lal, 1977).
**(14m3/s) according to Santosh K. G.
15
18. DROP STRUCTURES (CANAL DROPS)
The following are the design criteria established by extensive model
studies at the Irrigation Research Institute in India.
1. Length of crest: Since fluming is not permissible in this type of fall,
the crest length is normally kept equal to the bed width of the canal
2. Shape of crest:
Rectangular
Top width, Bt=0.55d1/2(m)
Base width, B1=(H+d)/G
where Gis the relative density of the crest material (for masonry, G=2).
Trapezoidal
top width, Bt=0.55(H+d)1/2 (m).
For the base width, B1, upstream and downstream slopes of around
1 in 3 and 1 in 8 are usually recommended
18
19. DROP STRUCTURES (CANAL DROPS)
3. Design Discharge:
Rectangular : Q=1.835LH3/2(H/Bt)1/6
Trapezoidal: Q=1.99LH3/2(H/Bt)1/6
Where L is length of crest, Bt is top width, H is head of water over crest
4. Length and depth of cistern
length, Lc=5(H.HL)1/2
depth, dc=1/4(H.HL)2/3
19
Where, HL= drop
20. DROP STRUCTURES (CANAL DROPS)
5. Upstream wing walls
For trapezoidal crest, the upstream
wing walls are kept segmental with
radius equal to 5 to 6 times H and
subtending an angle of 60o at center
and then carried tangential into the
berm as shown in Figure.
The foundations are laid on the
impervious concrete floor itself
For rectangular crest, the approach
wings may be splayed straight at an
angle of 45o
20
21. DROP STRUCTURES (CANAL DROPS)
6. Upstream Protection
Brick pitching in a length equal to
upstream water depth may be laid
on upstream bed, sloping towards
the crest at a slope of 1:10.
Drain pipes should be provided at
the u/s bed level in the crest so as
to drain out the u/s bed during the
closure of channel.
Upstream curtain walls: 11/2” brick
(~35cm) thick upstream curtain
wall is provided, having a depth
equal to 1/3rd of water depth
21
Upstream curtain wall
22. DROP STRUCTURES (CANAL DROPS)
7. Impervious floor downstream of the crest
Length: Total length of impervious floor can be determined by Bligh’s
theory for small works and by Khosla’ theory for large works. The
minimum length of flood d/s of toe of crest wall should be
Lbd=2(D1+1.2)+HL
D1=U/S FSL-BL and HL= drop
Thickness: the floor thickness can be worked out for uplift pressure
(using minimum thickness of 0.4m to 0.6m) and only a nominal
thickness of 0.3m is provided on the upstream side.
Note: seepage theories play key role in calculation of length and
thickness of floor.
22
24. DROP STRUCTURES (CANAL DROPS)
8. Downstream protection:
The d/s bed may be protected with dry brick pitching, about 20cm thick
resting on 10cm thick ballast. The length of d/s pitching is given by the
values of table below or 3 times the depth of downstream water, whichever
is more. The pitching may be provided between two or three curtain walls.
The curtain walls may be 1 ½ brick (~35cm) thick and of depth equal to ½
the downstream depth; or as given in table (minimum=0.5m)
24HL= drop height
25. DROP STRUCTURES (CANAL DROPS)
9. Slope pitching:
After the return wing, the side of the channel are pitched with one brick
of edge. The pitching should rest on a toe wall 1 ½ brick thick and of
depth equal to half the downstream water depth.
The side pitching may be curtailed at angle of 45o from the end of
pitching or extended straight from the end of bed pitching
10. Downstream wings. Downstream wings are kept straight for a
length of 5 to 8 times (H.HL)1/2 and may then be gradually wrapped.
They should be taken up to the end of impervious floor.
All the wing walls must be designed as retaining walls, subjected to full
pressure of submerged soil at their back when channel is closed. Such
as wall generally has a base width equal to 1/3rd its height
25
26. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
(i.c) YMGT-type drop (Japan): This type of drop is generally used in
flumed sections suitable for small canals, field channels, etc., with
discharges up to 1m3/s. The following are the recommended design
criteria:
26
28. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
(i.d) Rectangular weir drop with raised crest (France): SOGREAH
(Kraatz and Mahajan, 1975) have developed a simple structure suitable
for vertical drops of up to 7m (for channel bed widths of 0.2–1 m with
flow depths (at FSL) of 0.1–0.7 m):
Hdr
28
29. DROP STRUCTURES (CANAL DROPS)
For the design of crest,
discharge, Q=CL(2g)1/2H3/2,
where C=0.36 for the vertical upstream face of the crest wall and 0.40
for the rounded upstream face (5–10 cm radius).
The crest length, L=LB-0.10 m for a trapezoidal channel and is B1 (the
bed width) for rectangular channels.
For the design of cistern,
Volume of basin, V=QHdr/150 (m3),
29
30. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
(ii) the inclined drop and
(a) Common chute
(b) Rapid fall type inclined drop (India)
(c) Stepped or cascade-type fall
30
31. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
(ii.a) Common chute: This type of drop has a sloping downstream
face (between 1/4 and 1/6,called a glacis) followed by any
conventional type of low-head stilling basin; e.g. SAF or USBR
type III. The schematic description of a glacis-type fall with a
USBR type III stilling basin, recommended for a wide range of
discharges and drop heights, is shown in Fig.
31
32. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
(ii.b) Rapid fall type inclined drop (India): This type of fall is cheap in
areas where stone is easily available, and is used for small discharges
of up to 0.75m3/s with falls of up to 1.5 m. It consists of a glacis sloping
between 1 in 10 and 1 in 20. Such a long glacis assists in the formation
of the hydrualic jump, and the gentle slope makes the uninterrupted
navigation of small vessels (timber traffic, for example) possible.
32
33. DROP STRUCTURES (CANAL DROPS)
TYPES OF DROP STRUCTURES
(ii.c) Stepped or cascade-type fall: This consists of stone-pitched
floors between a series of weir blocks which act as check dams and are
used in canals of small discharges; e.g. the tail of a main canal escape.
A schematic diagram of this type of fall is shown in Fig.
33
34. DROP STRUCTURES (CANAL DROPS)
TYPES OF CANAL FALLS
(iii) the piped drop.
A piped drop is the most economical structure compared with an
inclined drop for small discharges of up to 50 liter/s. It is usually
equipped with a check gate at its upstream end, and a screen (debris
barrier) is installed to prevent the fouling of the entrance.
Types:
(a) Well drop structure
(b) Pipe fall
34
35. DROP STRUCTURES (CANAL DROPS)
TYPES OF CANAL FALLS
(iii.a) Well drop structure: The well drop (Fig) consists of a
rectangular well and a pipeline followed by a downstream apron.
Most of the energy is dissipated in the well, and this type of drop is
suitable for low discharges (up to 50 L/s) and high drops (2–3 m),
and is used in tail escapes of small channels.
35
36. DROP STRUCTURES (CANAL DROPS)
TYPES OF CANAL FALLS
(iii.b) Pipe fall; This is an economical structure generally used in small
channels. It consists of a pipeline (precast concrete) which may
sometimes be inclined sharply downwards (USBR and USSR practice)
to cope with large drops. However, an appropriate energy dissipator
(e.g. a stilling basin with an end sill) must be provided at the
downstream end of the pipeline.
36
37. DROP STRUCTURES (CANAL DROPS)
TYPES OF CANAL FALLS
(iv) Farm drop structures:
Farm channel drops are basically of the same type and function as
those in distribution canals, the only differences being that they are
smaller and their construction is simpler.
The notch fall type of farm drop structure (precast concrete or timber)
consists of a (most commonly) trapezoidal notch in a crested wall
across the canal, with the provision of appropriate energy-
dissipation devices downstream of the fall. It can also be used as a
discharge measuring structure.
37
38. DROP STRUCTURES (CANAL DROPS)
The details of a concrete check drop with a rectangular opening,
widely used in the USA, are shown in Fig. Up to discharges of about
0.5m3/s, the drop in the downstream floor level (C) is recommended to
be around 0.2 m and the length of the apron (L) between 0.75 m and
1.8m over a range of drop (D) values of 0.3–0.9m.
38
39. DROP STRUCTURES (CANAL DROPS)
Solved Examples
1. Common drop structure with impact
block type basin
2. Sarda type drop structure
39
40. DROP STRUCTURES (CANAL DROPS)
Example 1: Find the dimensions for a straight drop structure with a
impact block type basin.
Given:
• Q = 250 ft3/S (7.08m3/s)
• Drop: h = 6.0 ft. (1.93m)
(Upstream and Downstream Channel -Trapezoidal)
• B = 10.0 ft. (3.2048)
• Z = 1V:3H
• So = 0.002 (after providing for drop)
• n = 0.030
40
41. 0.85yc
0.8yc
0.4yc
h2
h=drop height=RL of crest-D/S Floor bed level
h2=RL of crest-D/S FSL
d=RL of crest-stilling basin flood level
Side wall height
above tailwater
h
d/s Floor
bed level
Crest level
yo
DROP STRUCTURES (CANAL DROPS)
41
42. DROP STRUCTURES (CANAL DROPS)
Solution:
Step 1. Estimate the required approach and tailwater channel elevation
difference, h. This is estimated and given above as 6.0 ft.
Step 2. Calculate normal flow conditions approaching the drop to verify
subcritical conditions. By trial and error using Manning’s equation
Q=1.49/n(AR2/3So1/2)
yo = 3.36 ft.,
Velocity of approach, Vo=Q/A:
Vo = 3.71 ft/s,
Froude no. =Vo/(gyo)1/2= 0.36;
Therefore, flow is subcritical.
yo=?
B=10ft
1V:ZH
i.e. (Z=3)
42
43. DROP STRUCTURES (CANAL DROPS)
Solution:
Step 3. Calculate the critical depth over the weir into the drop structure.
Calculate the vertical dimensions of the stilling basin.
Start by finding the critical depth over the weir based on the unit
discharge, q = Q/B = 250/10 = 25ft.2/s
ft
g
q
yc 69.2
2.32
25
3/1
2
3/1
2
=
=
=
43
44. DROP STRUCTURES (CANAL DROPS)
Solution:
Next calculate the required tailwater depth above the floor of the stilling
basin:
y2 = 2.15yc = 2.15 (2.69) = 5.77ft.
Now the distance from the crest down to the tailwater needs to be
calculated:
h2 = (h-yo) = -(6.0-3.36) = -2.64 ft. (-ve indicate vertically downward
distance)
Finally, calculate the total drop from the crest to the stilling basin floor:
d = -(h2 + y2) = -(2.64 + 5.77) = -8.41 ft. (round to 8.4 ft. )
Since the nominal drop, h, is 6.0 ft., the floor must be depressed by
2.4 ft.
44
45. DROP STRUCTURES (CANAL DROPS)
Solution:
Step 4. Estimate the basin length.
( )( )
( )( )
ft
LL
L
ft
y
L
y
y
d
y
L
Ls
ftyyhL
ftyydL
sf
d
c
t
c
cc
t
cct
ccf
4.10
2
89.1094.9
2
89.10
69.2
26.6
456.0185.0
69.2
69.2
41.8
69.2
26.6
228.0691.0
456.0185.0
228.0691.0
26.669.2
69.2
64.2
368.4195.3406.0/368.4195.3406.0
94.969.2
69.2
41.8
368.4195.3406.0/368.4195.3406.0
22
2
=
+
=
+
=
=
+
−
−
+
=
+
−
+
=
=
−
−+−=−+−=
=
−
−+−=−+−=
ftyyLL ccdB 3.1769.2*75.169.2*8.04.1075.18.0 =++=++=
Therefore the total basin length = 17.3ft
45
46. DROP STRUCTURES (CANAL DROPS)
Solution:
Step 5. Design the basin floor blocks
and end sill.
Block height = 0.8yc = 0.8(2.69) = 2.1ft.
Block width = Block spacing = 0.4yc =
0.4(2.69) = 1.1ft.
End sill height = 0.4yc = 0.4(2.69) = 1.1ft.
Step 6. Design the basin exit and
entrance transitions.
Sidewall height above tailwater elevation
= 0.85yc = 0.85(2.69) =2.3 ft.
Armour approach channel above
headwall length = 3yc = 3(2.69) = 8.1ft.
46
48. DROP STRUCTURES (CANAL DROPS)
Solution:
1. Length of crest:
same as d/s bed width
2. Shape of crest: Rectangular
because Q<14m3/s
Top width, Bt=0.55d1/2(m)
Base width, B1=(H+d)/G
3. Crest Level: Applying Q formula:
Assume Bt=0.8m (It will be later recomputed with above formula)
48
49. DROP STRUCTURES (CANAL DROPS)
Solution:
2. Shape of crest:
Velocity of approach
Velocity head
49
50. DROP STRUCTURES (CANAL DROPS)
Solution:
2. Shape of crest:
Therefore
Top width, Bt=0.55d1/2=0.55(2.27) 1/2=0.825m
Base width, B1=(H+d)/G=(0.76+2.27)/2=1.5m
Keep 1.5m width of base
P
d
50
51. DROP STRUCTURES (CANAL DROPS)
Solution:
4. Length and depth of cistern
length, Lc=5(H.HL)1/2
depth, dc=1/4(H.HL)2/3
Depth of cistern, dc
HL is drop (fall)= 1.5m (given)
51
59. DROP STRUCTURES (CANAL DROPS)
Solution:
10. Downstream wings
Wing walls are kept straight and parallel up to the end of the floor and
joined to return walls
59
Wing walls
Plan view
61. DROP STRUCTURES (CANAL DROPS)
Problem 1: Vertical drop without blocks
The volume flow rate in a rectangular channel is 5ft3/s/ft. A vertical drop
is used to lower the channel 6.0ft. The flow is subcritical above and
below the drop structure. Determine the dimension of the drop structure
for a tailwater (d/s water) depth of 1.67ft.
Solution: q=5ft3/s/ft, d=6ft, ytw=1.67ft
Calculate Basin dimensions:
Calculate sequent depths,
Length of hydraulic jump,
61
( ) ( ) ftyyLj 0.133.018.29.69.6 12 =−=−=
ftyD
d
y
ftyD
d
y
r
r
18.2)6()106.3(66.166.1
3.0)6()106.3(54.054.0
27.03
2
27.02
425.03
1
425.01
=×=⇒=
=×=⇒=
−
−
3
106.3 −
= xDr
62. DROP STRUCTURES (CANAL DROPS)
Problem 1: Vertical drop without blocks
Basin length,
Pool depth,
End sill height,
62
( ) ftLdLD
d
L
Bjr
B
6.1866/13106.33.1/3.4
27.0327.0
=
+×=⇒+= −
ftDY rp 74.1)106.3( 22.0322.0
=×== −
( ) ftyyh tw 51.067.118.22 =−=−=