Fluid Mechanics Dams Problems And Solutions Pdf Page
Solving dam problems requires:
These principles are essential for dam design and are a standard application of fluid statics in civil engineering.
End of PDF excerpt
The analysis of dams in fluid mechanics primarily involves calculating hydrostatic forces and evaluating structural stability against overturning and sliding. Comprehensive resources for these problems include the 2500 Solved Problems in Fluid Mechanics and specialized Dam Analysis Problem Sets Core Concepts and Problem Types
If you are looking for fluid mechanics dam problems and solutions in PDF format, there are several high-quality academic and professional resources available. These documents typically focus on hydrostatic forces, stability analysis (sliding and overturning), and uplift pressure. Top PDF Resources for Dam Problems Comprehensive Problem Sets: The 2500 Solved Problems in Fluid Mechanics
on Scribd includes a massive section dedicated to dam solutions, covering virtually all types of scenarios encountered in study and practice. Hydrostatic Force Exercises: A detailed set of Fluid Mechanics Exercises
from Istanbul University provides step-by-step calculations for finding resultant forces on unit lengths of dams and determining minimum friction coefficients. Stability Analysis Cases: Scribd's Dam Analysis: Hydrostatic Uplift Cases
outlines five critical cases, including overflowing dams and those with water on both sides, providing essential formulas for moments and safety factors.
Lecture Notes & Solutions: For foundational theory combined with practice, the MIT OpenCourseWare Problem Set on MIT OCW features specific design problems, such as determining the critical water depth before a dam topples. Key Concepts Covered in These PDFs Hydrostatic Force (
): Calculating the magnitude and location of the resultant force on both vertical and inclined dam faces.
Overturning Stability: Evaluating the moments about the "toe" of the dam to ensure it won't rotate.
Sliding Stability: Determining if the friction between the dam base and foundation is enough to resist horizontal water pressure.
Hydrostatic Uplift: Analyzing the upward pressure exerted by water seeping under the dam, which reduces its effective weight.
Before diving into the PDFs, it is crucial to understand the fundamental principles that govern dam stability. Most textbook problems focus on Gravity Dams, which rely on their own weight to resist the force of water.
Fluid mechanics problems regarding dams primarily focus on hydrostatic forces stability analysis
. To solve these, you must account for the dam's weight, the pressure exerted by the water, and potential uplift forces at the base. Core Principles for Dam Analysis Dams are typically analyzed using a one-meter strip (unit width) to simplify calculations. Hydrostatic Force ( cap F sub h The horizontal force exerted by water. is the specific weight of water ( is the depth to the centroid, and is the submerged area. Line of Action: Acts at a height of from the base. Weight of the Dam ( The vertical force providing stability. Hydrostatic Uplift ( Upward pressure from water seeping under the foundation. Factors of Safety (FS): Against Sliding: is the friction coefficient. Against Overturning: Sample Problem: Gravity Dam Stability A concrete gravity dam has a height of and a rectangular cross-section
wide. Water is filled to the top. Determine the factor of safety against sliding if the friction coefficient and concrete density is Royal Academy of Engineering 1. Calculate Dam Weight ( 2. Calculate Hydrostatic Force ( cap F sub h 3. Calculate Factor of Safety Against Sliding ( cap F cap S sub s The resisting force is friction: İstanbul Üniversitesi Conclusion: The dam is against sliding ( ) and requires a wider base or higher friction to be safe. Recommended PDF Resources
For more detailed examples and comprehensive problem sets, refer to these authoritative collections:
In the quiet mountain town of Oakhaven, the old Silver Creek Dam
wasn't just a slab of concrete; it was a ticking clock. For Leo, a young engineer with a dog-eared Fluid Mechanics
textbook and a caffeine habit, the dam was a giant physics problem waiting to be solved.
One rainy Tuesday, the reservoir levels hit a critical mark. Leo’s mentor, a grizzled veteran named Elias, handed him a tablet. "The hydrostatic force on the gate is spiking, Leo. If the center of pressure shifts another six inches, the hinges won't hold."
Leo scrambled to his desk, his mind racing through the equations he’d practiced hundreds of times. He visualized the water not as a lake, but as a series of pressure gradients . He calculated the resultant force
acting on the submerged vertical surface, knowing that as the depth ( ) increased, the pressure increased linearly ( moment of inertia
for the gate's shape is the bottleneck," Leo muttered, scribbling formulas to find the exact point where the water's weight would overpower the steel. He realized the solution wasn't just in venting the water, but in managing the flow velocity through the spillways to prevent cavitation —bubbles that could eat through the concrete like acid.
With the town sleeping below, Leo adjusted the spillway gates based on his Bernoulli’s Equation
derivations. He watched the sensors. Slowly, the turbulent energy dissipated, the pressure stabilized, and the "problem" on his screen finally matched the "solution" in the real world.
He didn't need a PDF to tell him he’d passed the ultimate exam; the dry streets of Oakhaven were proof enough. break down a specific type of dam problem (like hydrostatic force or gate stability) or find a real-world practice set
For comprehensive problems and solutions related to fluid mechanics in dams, you can access several high-quality academic resources and textbooks in PDF format. These materials typically cover hydrostatic forces dam stability (overturning and sliding), and uplift pressure Top PDF Resources for Dam Problems 2500 Solved Problems in Fluid Mechanics and Hydraulics
: This classic text by Jack Evett and Cheng Liu contains an extensive collection of worked-out problems specifically focused on dams and hydraulics. You can find it on Fluid Mechanics Exercises (Istanbul University)
: A detailed set of exercises that includes step-by-step solutions for calculating the resultant force of water on unit lengths of dams and determining friction coefficients for stability. Accessible via Istanbul University Dam Analysis & Hydrostatic Uplift Cases
: This presentation-style document outlines five critical cases for analyzing dams, including scenarios with and without hydrostatic uplift and overflowing conditions. View it on Fluid Mechanics: Hydrostatics Review : Includes fundamental formulas for the resultant hydrostatic force hydrostatic uplift
) which is vital for calculating stability against sliding. Available on Key Concepts in Dam Fluid Mechanics When solving these problems, textbooks like White's Fluid Mechanics suggest following these steps: Universidade Federal do Paraná Calculate Hydrostatic Forces : Identify the horizontal ( cap F sub cap H ) and vertical ( cap F sub cap V ) components acting on the dam face. Determine Uplift Pressure
: Use "Creep Theory" or pressure distributions to find the upward force acting on the base of the dam. Analyze Stability Factor of Safety against Overturning
: Ratio of resisting moments (dam weight) to overturning moments (water pressure). Factor of Safety against Sliding
: Ratio of resisting frictional forces to the horizontal driving force of the water. İstanbul Üniversitesi
For a visual walkthrough of a specific exam-level problem, you might also find the Solved Gravity Dam Problem on YouTube helpful. for the forces acting on a gravity dam? Fluid Mechanics - UFPR
Introduction
Fluid mechanics is a crucial branch of physics that deals with the study of fluids and their behavior under various forces and conditions. Dams are structures that are built across rivers or streams to impound water, and they play a vital role in water resources management, hydroelectric power generation, and flood control. However, designing and constructing dams requires a deep understanding of fluid mechanics principles to ensure their stability and safety.
Common Problems in Fluid Mechanics related to Dams
Solutions to Fluid Mechanics Problems in Dams
Key Concepts and Formulas
Benefits of Understanding Fluid Mechanics in Dams
PDF Resources
For those looking for a comprehensive resource on fluid mechanics dams problems and solutions, here are a few PDF resources:
Conclusion
In conclusion, understanding fluid mechanics is crucial for designing and operating safe and efficient dams. By grasping the fundamental principles of fluid mechanics, engineers can mitigate common problems associated with dams, such as water pressure, flow over spillways, sedimentation, and hydraulic loading. With the help of PDF resources and practical applications, engineers and students can develop a deeper understanding of fluid mechanics in dams and contribute to the development of more efficient and sustainable water resources systems.
For students and engineers, mastering fluid mechanics in the context of dam engineering is essential for ensuring structural integrity and public safety. This field focuses on how water interacts with large barriers, primarily dealing with hydrostatic pressure, uplift forces, and flow control.
Below is a structured overview of the core concepts, common problem types, and the typical logic found in comprehensive study PDFs. 1. Fundamental Concepts
When analyzing dams, fluid mechanics principles are applied to determine the forces acting on the structure:
Hydrostatic Pressure: The pressure exerted by a fluid at rest due to the force of gravity. It increases linearly with depth (
Center of Pressure: The specific point on the submerged surface where the total sum of a pressure field acts. For a rectangular dam face, this is usually at the height from the base.
Uplift Pressure: Water seeping under the dam creates an upward force that can destabilize the structure.
Resultant Force: The single force that represents the combined effect of all water pressure on the dam face. 2. Common Problem Types
Study materials typically categorize problems into these three areas: A. Static Analysis of Gravity Dams
The Goal: Calculate the horizontal force of the reservoir and the vertical weight of the dam to ensure it doesn’t slide or tip over. Typical Question: "Given a concrete gravity dam of height
, determine the factor of safety against overturning when the reservoir is full." B. Uplift and Seepage
The Goal: Use flow nets or empirical formulas to calculate the pressure underneath the dam.
Typical Question: "Calculate the total uplift force on the base of the dam assuming a linear pressure distribution from the heel to the toe." C. Spillway and Outlet Hydraulics
The Goal: Analyze fluid in motion (dynamics) to design spillways that can handle flood events without eroding the dam's foundation.
Typical Question: "Using Bernoulli’s equation, find the velocity of water at the base of an ogee spillway." 3. Step-by-Step Solution Strategy
Most "problems and solutions" guides follow this methodology:
Sketch the Free Body Diagram (FBD): Identify all forces—hydrostatic (horizontal), uplift (vertical), and the dam’s weight (vertical). Calculate Force Magnitudes: Use for the dam face.
Locate the Lines of Action: Determine where these forces act (the "moment arm").
Sum Moments: Take moments about the "toe" (the downstream bottom corner) to check for stability.
Check for Sliding: Ensure the frictional resistance of the base is greater than the horizontal water pressure. 4. Recommended Resources for PDFs
If you are looking for downloadable practice sets, search for these specific terms:
"Fluid Mechanics: Hydrostatic Forces on Submerged Surfaces PDF"
"Civil Engineering: Stability Analysis of Gravity Dams Solved Examples" "NPTEL Fluid Mechanics Assignment Solutions"
Dams are among the most massive structures built by humans, and their safety hinges on correct application of fluid mechanics. Whether you are calculating the horizontal thrust of 30 meters of water or modeling seepage through a clay core, having a curated fluid mechanics dams problems and solutions pdf is not a luxury—it is a necessity.
Start by building your own binder from the reliable sources listed above, or download a university-tested problem set. Practice the three major problem types—overturning with uplift, sliding resistance, and seepage via flow nets. Within a few hours of focused work, you will master this high-yield topic.
If you want, I can:
Which would you prefer?
Analyzing fluid mechanics problems in dam design involves calculating the forces exerted by water (hydrostatic) and the weight of the structure (gravity) to ensure stability against failure modes like sliding or overturning. Core Concepts & Formulas
The primary challenge in dam problems is determining the magnitude and location of the resultant force. Hydrostatic Force ( cap F sub cap H
The force exerted by the water on a vertical or inclined surface. = Specific weight of water (
= Vertical distance from the surface to the centroid of the area. = Area of the submerged surface. Center of Pressure ( y sub c p end-sub
The point where the total hydrostatic force is assumed to act. For a rectangular vertical surface: Acts at the depth from the surface. Gravity Force ( The stabilizing weight of the concrete. Hydrostatic Uplift (
Upward pressure caused by water seeping under the dam foundation.
Usually modeled as a triangular or trapezoidal pressure distribution from the (upstream) to the (downstream). Standard Stability Problems
Most textbook and exam problems focus on three critical safety checks: 1. Factor of Safety against Overturning ( cap F cap S sub cap O The dam must not "tip" over its downstream edge (the toe). Stabilizing Moments: Produced by the weight of the dam ( Overturning Moments: Produced by hydrostatic pressure ( cap F sub cap H ) and uplift ( 2. Factor of Safety against Sliding ( cap F cap S sub cap S The dam must not slide horizontally along its base. = Coefficient of friction between the dam and foundation. cap R sub y = Net vertical force (Weight - Uplift). 3. Foundation Pressure (Eccentricity) Ensuring the dam doesn't crack the soil or foundation. The resultant force should ideally fall within the middle third of the base ( ) to prevent tension at the heel. Solved Example Snippet A concrete dam (
wide at the base (triangular section). If water is at the top, find the factor of safety against overturning. Water Force ( cap F sub cap H Overturning Moment ( cap M sub cap O Dam Weight ( Resisting Moment ( cap M sub cap R (Likely unsafe, as it is below the typical threshold). Recommended PDF Resources For comprehensive problem sets and step-by-step solutions: Schaum's 2500 Solved Problems in Fluid Mechanics
: The industry standard for practice problems across all fluid topics, including dams. Istanbul University Fluid Mechanics Exercises
: Contains detailed worked examples for gravity dam stability and friction. ITU Water Resources Lecture Notes
: Offers a theoretical breakdown of forces like uplift and ice pressure. USBR Design of Gravity Dams
: A technical manual for professional engineering standards. Internet Archive
To help you find the right level of difficulty, are you preparing for a basic undergraduate exam professional engineering license (PE/FE) ? I can provide more complex cases like curved surfaces seepage analysis if needed. FLUID MECHANICS EXERCISES fluid mechanics dams problems and solutions pdf
Comprehensive reports and solved problem sets for fluid mechanics in dam analysis focus on hydrostatic forces, stability (factors of safety), and uplift pressure. Essential Solved Problem Resources
Comprehensive Problem Sets: The 2500 Solved Problems in Fluid Mechanics & Hydraulics by Evett and Liu includes a dedicated "Dams Solution" section covering virtually all standard exam and practice scenarios.
Gravity Dam Stability: This Dam Problem Set provides structured exercises on calculating factors of safety against sliding and overturning, plus pressure intensity at the base.
Uplift and Overflow Cases: A specialized report on Dam Analysis: Hydrostatic Uplift Cases details five specific scenarios, including dams with water on both sides and overflowing conditions. Core Concepts and Problem Types Problem Category Key Calculation/Principle Hydrostatic Force is specific weight, is depth to centroid, and Overturning Stability
Ratio of Righting Moments (weight of dam) to Overturning Moments (hydrostatic force). Sliding Stability Factor of safety determined by is the friction coefficient. Uplift Pressure
Accounts for water seeping under the dam, typically modeled as a triangular or trapezoidal pressure distribution. Example Walkthrough: Resultant Force on a Dam
A common exam problem involves finding the resultant force on a sloped dam face. Find the Geometry: Determine the angle of the slope using
Calculate Hydrostatic Force: Use the depth of the centroid and the wetted area of the slope. Locate Center of Pressure: Use the formula to find where the resultant force actually acts.
Need a specific problem solved? Drop the details in the comments below, and we can walk through the solution step-by-step!
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Introduction
Fluid mechanics is a branch of physics that deals with the study of fluids and their behavior under various forces and conditions. Dams are structures built across rivers or streams to impound water, and they play a crucial role in water resource management, hydroelectric power generation, and flood control. However, dams also pose significant challenges in terms of fluid mechanics, as they interact with water and must withstand various hydraulic forces.
Common Fluid Mechanics Problems Associated with Dams
Solutions to Fluid Mechanics Problems in Dams
PDF Resources for Fluid Mechanics Dams Problems and Solutions
For those seeking to learn more about fluid mechanics dams problems and solutions, several PDF resources are available online. These resources often provide detailed explanations, examples, and case studies of fluid mechanics problems in dams, as well as solutions and best practices. Some examples of PDF resources include:
Conclusion
In conclusion, fluid mechanics plays a critical role in the design, construction, and operation of dams. By understanding and addressing common fluid mechanics problems, engineers can ensure the safety, stability, and efficiency of dams. The availability of PDF resources provides valuable support for those seeking to learn more about fluid mechanics dams problems and solutions. By leveraging these resources and applying fundamental principles of fluid mechanics, engineers can develop innovative solutions to the complex challenges posed by dams.
Fluid mechanics problems regarding dams typically focus on hydrostatic forces, stability analysis (sliding and overturning), and uplift pressure. Below is a report on key problem types and resources for solutions in PDF format. Key Problem Categories in Dam Analysis Dam Analysis: Hydrostatic Uplift Cases | PDF - Scribd
Fluid Mechanics Dams Problems and Solutions PDF: A Comprehensive Guide
Fluid mechanics is a fundamental branch of physics that deals with the study of fluids and their interactions with other objects. One of the critical applications of fluid mechanics is in the design and construction of dams, which are crucial infrastructure projects that provide hydroelectric power, irrigation, and flood control. However, designing and operating dams requires a deep understanding of fluid mechanics, as dams are subjected to various forces and pressures exerted by water. In this article, we will explore some common problems and solutions related to fluid mechanics in dams, providing a comprehensive guide for students, engineers, and professionals seeking to understand and tackle these challenges.
Introduction to Fluid Mechanics in Dams
Dams are massive structures that impound water, creating a reservoir behind the dam. The pressure exerted by the water on the dam is a critical consideration in dam design. The pressure varies with depth, and its calculation is essential to ensure the dam's stability. Fluid mechanics plays a vital role in understanding the behavior of water and its interactions with the dam.
Common Problems in Fluid Mechanics of Dams
Solutions to Fluid Mechanics Problems in Dams
To solve these problems, engineers and designers use various techniques, including:
Examples and Case Studies
Several examples and case studies illustrate the application of fluid mechanics in dam design and operation:
Best Practices and Recommendations
To ensure safe and efficient design and operation of dams, engineers and designers should:
Conclusion
In conclusion, fluid mechanics plays a critical role in the design and operation of dams. Understanding the behavior of water and its interactions with the dam is essential to ensure safe and efficient operation. By applying fluid mechanics principles and techniques, engineers and designers can tackle common problems and ensure the stability and performance of dams. This article provides a comprehensive guide to fluid mechanics dams problems and solutions, serving as a valuable resource for students, engineers, and professionals.
Download Fluid Mechanics Dams Problems and Solutions PDF
For those seeking a more in-depth understanding of fluid mechanics dams problems and solutions, a comprehensive PDF guide is available for download. This guide provides detailed explanations, examples, and case studies, covering topics such as:
The PDF guide also includes:
Download the fluid mechanics dams problems and solutions PDF guide today to enhance your understanding of fluid mechanics in dams and improve your skills in designing and operating these critical infrastructure projects.
Understanding Fluid Mechanics in Dam Engineering: Common Problems and Solutions
Dams are among the most impressive feats of civil engineering, acting as vital infrastructure for water supply, flood control, and hydroelectric power. However, managing millions of cubic meters of water requires a deep mastery of fluid mechanics.
When engineers search for resources like a "fluid mechanics dams problems and solutions PDF," they are usually looking to solve specific challenges related to pressure, flow, and stability. This article breaks down the core fluid mechanics principles applied to dams and the standard solutions used to ensure their safety. 1. Hydrostatic Pressure and Resultant Force Solving dam problems requires:
The most fundamental problem in dam design is calculating the horizontal force exerted by the reservoir. The Problem: Water pressure increases linearly with depth (
). For a massive gravity dam, this creates a staggering amount of force that attempts to slide or tip the structure. The Solution: Engineers calculate the Resultant Force (
) and its Center of Pressure. By ensuring the dam’s weight (vertical force) is sufficient to keep the resultant force within the "middle third" of the dam’s base, they prevent overturning and sliding. 2. Seepage and Uplift Pressure
Water doesn't just push against the face of a dam; it also tries to go under it.
The Problem: Seepage through the soil foundation creates uplift pressure. This upward force effectively "lightens" the dam, reducing its friction against the ground and increasing the risk of a blowout or sliding. The Solution:
Grout Curtains: Injecting cement into the foundation to create an impermeable barrier.
Drainage Galleries: Internal tunnels that collect seepage and pipe it away safely, relieving the internal pressure.
Flow Nets: Using graphical solutions (Laplace equations) to map the path of water and calculate the exact uplift pressure at any point. 3. Spillway Hydraulics and Energy Dissipation
During heavy rains, excess water must be released. Moving water carries immense kinetic energy.
The Problem: As water rushes down a spillway, it reaches high velocities. If this energy isn't managed, it will erode the "toe" (bottom) of the dam, leading to structural failure. The Solution:
The Hydraulic Jump: Engineers design "stilling basins" that force the water to undergo a hydraulic jump—a phenomenon where high-velocity (supercritical) flow transitions to low-velocity (subcritical) flow, dissipating energy through turbulence.
Baffle Blocks: Concrete Obstacles in the basin that break up the water’s force. 4. Cavitation in Outlet Works
The Problem: When water flows at high speeds over irregular surfaces or through valves, local pressure can drop below the vapor pressure. This forms bubbles that collapse with enough force to pit and destroy solid concrete and steel.
The Solution: Using aerators to introduce air into the flow. The air bubbles act as a cushion, absorbing the shock of collapsing vapor bubbles and protecting the dam’s surface. 5. Sedimentation and Fluid Density
The Problem: Over time, silt collects at the bottom of the reservoir. This "sludge" has a higher density than pure water, increasing the hydrostatic pressure on the lower portion of the dam beyond original design specs.
The Solution: Frequent modeling of sediment transport and the installation of low-level outlets (sluiceways) to "flush" the silt out before it settles. Summary for Students and Engineers
If you are preparing a PDF or study guide on this topic, focus your "Problems and Solutions" section on these three calculation types:
Stability Analysis: Summing moments about the "toe" to check for overturning.
Bernoulli’s Equation: Applying it to spillway flow to find discharge velocities.
Seepage Discharge: Using Darcy’s Law to find the volume of water lost through the foundation.
Problem:
A dam has a vertical downstream face and an inclined upstream face with slope 1H:4V (i.e., for every 4 m vertical, it projects 1 m horizontally). Height ( H = 30 , \textm ), base width ( B = 20 , \textm ). Water depth = 30 m. Compute the horizontal and vertical components of hydrostatic force on the upstream face per meter width. Use ( \rho_w = 1000 , \textkg/m^3 ).
Solution:
The upstream face is a plane inclined at angle ( \theta ) to horizontal, where ( \tan \theta = 4/1 )?? Wait – slope 1H:4V means horizontal projection 1 m per 4 m vertical rise. So the angle from vertical: ( \tan(\phi) = 1/4 = 0.25 ) → ( \phi = 14.04^\circ ) from vertical. But easier: horizontal projection length = ( H \times (1/4) = 30 \times 0.25 = 7.5 , \textm ).
Length of inclined face ( L = \sqrtH^2 + (7.5)^2 = \sqrt900 + 56.25 = \sqrt956.25 \approx 30.92 , \textm ).
Area of inclined face per unit width: ( A = L \times 1 = 30.92 , \textm^2 ).
Centroid depth: The centroid of the inclined rectangular surface is at mid-length. But vertical depth to centroid = ( H/2 = 15 , \textm ) (since top at 0, bottom at 30 m depth, centroid at 15 m depth vertically). Yes, that's correct – for any plane surface with top at free surface, the vertical depth to centroid = ( H/2 ).
Total hydrostatic force normal to surface:
[
F = \rho g \barh A = 1000 \times 9.81 \times 15 \times 30.92
]
[
F = 1000 \times 9.81 \times 463.8 = 4,548,000 , \textN \approx 4.548 , \textMN
]
Now resolve into horizontal and vertical components.
Horizontal component = ( F \times \sin \phi )? Let’s be careful: The normal force is perpendicular to the inclined face. The horizontal component of that normal force is ( F \cos(\textangle from vertical) ) or ( F \sin(\textangle from horizontal) ). Better: Angle of face from vertical = ( \phi = \arctan(1/4) = 14.04^\circ ). So horizontal component ( F_h = F \sin \phi )? Wait – if force is normal to face, and face is tilted away from vertical by ( \phi ), then the normal vector is horizontal component = ( F \sin \phi ) and vertical component = ( F \cos \phi ). Check: If face were vertical (( \phi=0 )), horizontal = F, vertical = 0 – correct. If face horizontal (( \phi=90^\circ )), horizontal = 0, vertical = F – correct.
Thus:
[
F_h = F \sin 14.04^\circ = 4.548 \times 0.2425 \approx 1.103 , \textMN
]
[
F_v = F \cos 14.04^\circ = 4.548 \times 0.9701 \approx 4.412 , \textMN
]
Check: The vertical component should also equal the weight of water above the inclined face (imaginary water column). Volume of water above the face per meter width = triangular area = ( 0.5 \times \texthorizontal projection \times H = 0.5 \times 7.5 \times 30 = 112.5 , \textm^3 ). Weight = ( 1000 \times 9.81 \times 112.5 = 1,103,625 , \textN = 1.104 , \textMN ) – That matches ( F_h )?? Wait, that’s wrong: The vertical component should equal weight of water above – but here I got 1.104 MN, which equals my ( F_h ) earlier. That indicates a mix-up.
Actually, known principle: On an inclined plane,
Horizontal force = force on vertical projection of the surface = ( \frac12 \rho g H^2 \times \textwidth ) = ( 0.5 \times 1000 \times 9.81 \times 30^2 = 4.4145 , \textMN ).
Vertical force = weight of water directly above the surface = ( \rho g \times \textvolume = 1000 \times 9.81 \times (0.5 \times 7.5 \times 30) = 1.1036 , \textMN ).
So I swapped them earlier! Correct values:
[
F_h = 4.4145 , \textMN, \quad F_v = 1.1036 , \textMN
]
Final answer:
Horizontal component = 4.41 MN, Vertical component = 1.10 MN.
Problem:
A concrete dam (( \rho_c = 2400 , \textkg/m^3 )) has a vertical upstream face. Height ( H = 20 , \textm ), width ( b = 1 , \textm ) (unit length into page). Base width ( B = 15 , \textm ). Water depth = ( H ).
Find:
(a) Total hydrostatic force on the dam.
(b) Overturning moment about the toe.
(c) Factor of safety against overturning (ignore uplift).
Solution:
(a) Hydrostatic force
[
F_h = \frac12 \rho_w g H^2 \times b = 0.5 \times 1000 \times 9.81 \times 20^2 \times 1
]
[
F_h = 0.5 \times 1000 \times 9.81 \times 400 = 1,962,000 , \textN = 1.962 , \textMN
]
(b) Overturning moment about toe
The hydrostatic force acts at ( H/3 = 20/3 \approx 6.667 , \textm ) above the toe.
[
M_\textoverturning = F_h \times \fracH3 = 1.962 \times 10^6 \times 6.667 = 13.08 \times 10^6 , \textN·m = 13.08 , \textMN·m
]
(c) Resisting moment from dam weight
Dam cross-section area = ( H \times B = 20 \times 15 = 300 , \textm^2 ) per meter length.
Weight per meter length:
[
W = \rho_c g \times \textarea = 2400 \times 9.81 \times 300 = 7.0632 \times 10^6 , \textN = 7.063 , \textMN
]
Center of gravity of rectangular section from heel (upstream face) = ( B/2 = 7.5 , \textm ).
Distance from toe = ( 15 - 7.5 = 7.5 , \textm ). Wait – careful: Heel is upstream, toe is downstream. For rectangular dam, CG is at B/2 from heel. So moment arm about toe = ( B - B/2 = B/2 = 7.5 , \textm ). Yes.
[ M_\textresisting = W \times 7.5 = 7.063 \times 7.5 = 52.97 , \textMN·m ]
Factor of safety against overturning:
[
\textFS = \fracM_\textresistingM_\textoverturning = \frac52.9713.08 \approx 4.05
]
Since ( 4.05 > 2 ), the dam is safe against overturning.
Answer:
(a) 1.962 MN, (b) 13.08 MN·m, (c) 4.05.