Stabilyty of Erth dam
The safety of an earth dam structure. The properties of the material of which the dam is constructed. The process of collapse of an improperly designed earth dam with slopes too steep. Stability of the hydrodynamic pressure of the penetrating water.
|Рубрика||Геология, гидрология и геодезия|
Ministers of education and since
Al - Farabi Kazakh National University
Faculty of Mechanics and Mathematics
Department of Mechanics
Specialty: 5B060300 Mechanics
IN MANUFACTURING PRACTICE ON THE TOPIC OF THE THESIS THEME: stability of an earth dam
Student: Ospanov N. M
Scientific supervisor : Alibayeva. K. A
1. STABILTY OF AN EARTH DAM
1.1 Equipment Diagrams
1.2 Equipmen setup
1.3 Experiment results
The class of problems involving flow of water through permeable media has a wide range and is of considerable importance to engineers and scientists. The Armfield Drainage and Seepage Tank, Model S1, facilitates a detailed study of the movement of water through permeable media.
The engineer is probably the one who faces such problems most frequently and whose success or failure will often depend on his knowledge and understanding of phenomena related to the movement of the water in soils. This is one of the most important aspects in the design of almost all hydraulic structures. Consider an earth or rock fill dam, for instance. Water flows directly through the engineering structure itself. Obviously, it is important to know how much water we can expect to lose from the reservoir by seepage through the dam. We also need to know whether a certainkind of soil can be used to construct the dam without running the risk that the reservoir will run dry after filling. The safety and the very existence of the dam edepends on the flow pattern of the penetrating water and on the balance of the hydraulic and static forces. Many earth dams have collapsed because of improper design with respect to the movement of water through their bodies. In fact, the conditions of seepage are vital, not only for earth dams, but for any dams having permeable materials in the foundations. A dam can collapse or be badly damaged as a result of seepage underneath its bottom, or because of hydrostatic forces exerted by the penetrating waters. These forces cannot be determined without prior determination of the flow pattern underneath the structure. Once known, they can be altered using drains, cut-offs, sheet pile walls and other means to change the flow pattern.
Similar problems arise in other engineering structures built from, or on, soil. As examples, we can mention levees, road and railway embankments, canals, navigation locks, foundations of buildings, bridges, harbour walls and similar structures 
Another engineering field where good understanding of water movement in soil is essential is water supply and drainage. In both we are concerned with extracting water from saturated strata by using wells, horizontal galleries, tile lines, or trenches.
In this type of problem, we usually deal only with the flow pattern and quantity of the water traversing the strata. The forces exerted by seepage remain of secondary importance.
Mining is an area where both seepage and ground water flow is fundamentally important. The design of an effective drainage system for a mine must be based on profound knowledge of permeability, of the degree of water saturation of the various geological layers, of seepage rates and of the effect of pumping or draining the water on the balance of forces.
Ground water hydrology and hydrogeology are the main non-engineering fields dealing with flow of water through permeable media and require the study of problems such as salt water intrusion into fresh water basins, underground movement of water towards inner channels, discharge of ground water into surface run-offs, recharge of water from rivers to underground storage, artificial recharge off all practical work areas and laboratories should be covered by local safety. regulations which must be followed at all times. If required Armfield can supply a typical set of standard laboratory safety rules.
S1 Drainage and Seepage Tank has been designed to be safe in use, when installed, operated and maintained in accordance with the instructions in this manual.
As with any piece of sophisticated equipment, dangers may exist if the equipment is misused, mishandled or badly maintained. If the equipment is used in a manner not specified by Armfield then the protection provided by the equipment may be impaired .
The S1 is a heavy piece of equipment, and should be lifted fork lift if possible. Ensure that the arms of the fork lift do not foul the sump moulding in the base of the unit. Do not attempt to lift the unit when it is full of sand or water.
The continuing safety of an earth dam structure depends on the stability of its slopes. The stability of the slope is in turn dependent on:
1. the properties of the material of which the dam is constructed;
2. whether it is 'exposed' to water or air; and
3. on conditions of seepage through the dam.
This experiment is to demonstrate the process of collapse of an improperly designed earth dam with slopes too steep for the material used. At the same time it may be noticed how the water itself adjusts a dam's surface to the steepest slope allowable for given conditions. This slope is called the critical slope.
In the laboratory, we have the advantage of being able to use homogeneous materials of known properties. This simplifies the problem and makes it possible to reduce the number of components involved. By this means significant relationships between the physical properties of the medium and characteristics of flow are found. To further simplify the problem, we usually restrict ourselves to a two-dimensional flow, investigating conditions in a vertical cross section* along the horizontal direction of the moving water mass. The Armfield Drainage and Seepage Tank, Model S1, is specifically designed to permit the simulation in the laboratory of such vertical cross sections .
1. STABILTY OF AN EARTH DAM
1.1 Equipment Diagrams
We can see front view of our experimental equipment on the figure 1.1.
Figure 1.1: Front View of S1 Drainage and Seepage Tank (Shown with impermeable baffle fitted but not filledn with sand)
2) water inlet
4) impermeable baffle plate
5) adjustable clamp
6) incorporating six tapping points
7) two independently adjustable overflows (7 & 16)
8) A drain valve
9) the frame
10) adjustable feet
11) sump tank drain
12) sump tank
13) centrifugal pump
14) flow control valve
15) electrical switch
Figure 1.2: Side View of S1 Drainage and Seepage Tank
17) aluminum back panel
18) a shelf
1.2 Equipment Set Up
dam water hydrodynamic stability
A segment of an earth dam is formed out of moist sand in the middle of the tank with slopes as steep as the material permits.
Water is poured into the lower pool and, after it has reached the top of the overflow, the input is transferred into the upper pool and maintained at a moderate rate 1.3 figure. The rising water level in the upper pool will gradually undercut the upstream slope of the dam and level it out into its "critical slope".
At the same time the increasing rate of seepage will start washing away sand
particles at the toe of the downward slope, depositing them at a critical slope. It should be noticed that the upstream and the downstream critical slopes are different, the upstream slope being steeper.
This difference is due to the variant contributions to stability of the hydrodynamic pressure of the penetrating water. Upstream the water exerts pressure on the dam
Surface and so contributes to its stability. Downstream it acts to "pull" the sand moreor- less horizontally out of the dam.
The process continues gradually until the upper part of the dam loses stability and collapses. Then the whole process starts again and proceeds upwards to the dam crest.
Figure 1.3 Front view of the equipment set up
1.3 Experiment results
1) Water is poured into the lower pool as in figure 1.4
Figure 1.4 Front view of the equipment set up after water poured in to the lower pool
2) The input is transferred into the upper pool and maintained at a modern as in figure 1.5.
Figure 1.5 The input is transferred into the upper pool and maintained at a modern
3) At the same time the increasing rate of seepage will start washing away sand particles at the toe of the downward slope, depositing them at a critical slope. It should be noticed that the upstream and the downstream critical slopes are different, the upstream slope being steeper as in figure 1.6, 1.7.
This difference is due to the variant contributions to stability of the hydrodynamic pressure of the penetrating water.
Figure 1.6 As we can see water start washing away sand particles at the toe
Figure 1.7 Top of the dam start collapsing
4) Then, in the end upper part of the dam loses stability and collapses as in figure 1.8.
Figure 1.8 - Dam is colapsed, and stabiled
I have seen the process of collapse of an improperly designed earth dam with slopes too steep for the material used.
Also I have noticed how the water itself adjusts a dam's surface to the steepest slope allowable for given conditions.
And I have learned how to find the critical slope.
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