1. Stability analysis of embankment dams
Hana shehu
ZEKIRIJA IDRIZI

2. Introduction – Dams and their purpose
The importance of Dams as structures
water supply,
flood control,
irrigation,
navigation,
sedimentation control, and
hydropower.
The Design and Construction
“trial and error” vs. “computations”
THE SINGLE PURPOSE DAMS

3. The history of building dams
“Sadd-el-Kafara” Dam – Egypt
Dams of the mining industries – Harz Mountains - Germany
11m high rockfill dam – earth core
2600 BC (flood control)
Destroyed during construction - overtopping
Old method of Construction
New method of Construction

4. Water resources and dams in Kosova
Kosova has 5 artificial lakes which are the main form of water supply:
BATLLAVA
BADOVCI
RADONIQI
UJMANI (Gazivoda)
PËRLEPNICA
“UJMAN” lake and embankment dam
Height:107.5 meters

5. Embankment dams – types and characteristics
Embankment dams – Earth fill and Earth - Rockfill materials
75% of all world dams
The prevailing of embankments in the modern dam construction is mainly because of:
The climate, topography, and geology conditions
Construction materials are principally supplied near the dam site
Economical advantage
The development of rock and soil mechanics
The advanced construction equipments (heavy vibrating roller, hydraulic vibrating plate, laser- oriented gradall, etc.)

6. STABILITY ANALYSIS OF EMBANKMENT DAMS
LOADS ON EMBANKMENT DAMS
The stability of dams and their foundation – different conditions and load cases and combinations
Construction
Exploitation period.
Loads can be:
Static loads (dead load and impounding)
Dynamic loads (seismic forces)
hydrostatic forces, dead load, filtration counter pressure and filtration forces appearing in the body of the dam
Primary loads
wave pressure, ice pressure
Secondary loads
inertial seismic forces on horizontal and vertical directions and inertial water mass forces)
Special loads

7. STATIC LOADS
DEAD LOAD
Deformation of the dam body – dam zoning and material properties
Dead load – during construction
Dam construction (individual layers) - settlements of the previous dumped layers and of the foundation.
Pore water pressure - all fine grained materials, construction materials, the foundation.
Kinda Dam – settlements after construction
Measured – 130cm and Computed – 180 cm

8. Static loads IMPOUNDING
The stress and strain conditions - change under the effect of the water load.
Change is in principle different for dams with an internal sealing and dams with a face sealing.
This follows from the different locations of the resultant of the hydrostatic pressure.
Kinda Dam - Computed lines of equal horizontal displacements after impounding to 0.7H

9. Failure of embankment dams
Failures of embankment dams can generally be grouped into three classifications:
HYDRAULIC
from the uncontrolled flow of water due to the erosive action of water on the embankment slopes
1)Overtopping
2)Wave and Top Erosion
3)Gullying
SEEPAGE
Seepage failures account for approximately 40 percent of all embankments or dike failures. Seepage can also cause slope failures by saturating the slope material
STRUCTURAL
separation (rupture) of the embankment material and/or its foundation. It is more prominent in large embankment dams.

10. Slope stability analysis
Slope stability analysis – practical importance
Stability is determined by the balance of shear stress and shear strength.
“If the forces available to resist movement are greater than the forces driving movement, the slope is considered stable.”
Factor of safety
Different slope sliding surfaces
“To determine the surface of sliding, with the smallest factor of safety - we need to examine quite a number of surfaces of sliding in different positions”

11. METHODS OF STABILITY ANALYSIS
Development of methods for determination of the static stability - make possible the design of a safe and economical dam structure.
The methods for calculating the stability of embankment dams are divided into:
Classical
Infinite Slope Analysis
Limit Equilibrium methods
Modern
Finite Element Method

12. Limit Equilibrium methods
METHODS OF SLICES
Swedish Slip Circle Method of Analysis
Oldest method - This method gives lower values for the safety factor, as compared to the more accurate methods by 5–20%.
Ordinary Method of Slices
Modified Bishop’s Method of Analysis
suitable for programming, more accurate than the Swedish one, while the disregard of the safety factor does not exceed 7%.
Lorimar’s Method of Analysis
Spencer’s Method of Analysis
𝐹𝑠= 𝑐 ′ + σ ′ tan 𝜑′ 𝐺 · sin α = 𝑐 ′ 𝐿ₐ+ tan 𝜑′ 𝑁 𝐺 · sin α

13. Limit Equilibrium Methods Finite Element Method
Simplicity and accuracy.
Must search for critical surface by using geometry.
The method of slices is based purely on the principles of statics; the summation of moments, vertical and horizontal forces
It requires only a simple Mohr - Coulomb soil model.
It cannot compute displacement.
It cannot model progressive failure.
Computer performance has improved application of FE in geotechnical analysis.
The critical surface is automatically fond out by various software’s.
Better visualizes the deformation of soil in place.
It must have complete stress- strain model for soil.
It can compute displacement.
It can model progressive failure.

14. Conclusions
Dams - high economic and political importance, critical role in agriculture, development of urban and rural areas, water supply, generation of hydroelectric energy, control and regulation of water current velocity.
Slope stability analysis is very important to ascertain the stability of the structure. It depends on its geometry, its components, materials, properties of each component and the forces to which it is subjected.
A failure of earth dam is attributed to the following: hydraulic failure, seepage failure, piping through dam body and structural failure due to earthquake.

15. conclusions
There are several applicable methodologies that have been put forward for analyzing the overall stability of a dam, from classical methods to modern ones;
The infinite slope model is more suitable and convenient for the surficial slope stability analysis
The limit equilibrium models are professional for the circular slip surface analysis in the deep slope and could provide a much higher accuracy but with much more complicated calculation process.

16. THANK YOU FOR YOUR ATTENTION!