What is the purpose of the cutoff wall?
Cutoff walls are a type of seepage barrier structure designed to reduce the flow of water through or around a dam.
What is cut off wall in Bridge?
Cutoff Walls. CUTOFF WALLS. A cement-bentonite or soil-bentonite Cut-Off Wall’s (COW) primary purpose is to mitigate the flow of groundwater. The COW is constructed using a trench cutter and can be installed in almost any soil conditions. The trench cutter makes ‘bites’ to excavate rectangular panels in the earth.
How does the location of the cut off wall affect the exit hydraulic gradient Why is this important?
The placing position of the cut off in the dam length has no significant effect on the exit hydraulic gradient changes and always is less than 1. With increase of the cut off depth, the exit hydraulic gradient reduces.
What is impervious cut off?
Impervious Cutoff : Cutoff is a core in the foundation. The cutoff into the rock is useful for creating a seal between the dam core and foundation when the rock is relatively soft with decrease in permeability with depth below the surface. The type of cutoff depends on the geological conditions of the foundation.
How does the cut off wall affect the uplift pressure distribution?
Results of this study showed that minimum uplift pressure happens when cut off wall is in the heel (upstream) of the dam. With fixing of longitudinal cut off wall placement, inclination of cutoff wall respect to the vertical position, results in reducing of uplift pressure.
What is a cut-off trench?
Sample 2. Cutoff Trench means an excavation under a dam to be later filled with impervious material to prevent or reduce the seepage of water through the foundation of a dam.
What is cutoff in earthen dam?
The main function of cutoff trench in earth fill dam is to reduce the loss of stored water in the reservoir, from the seepage flow through foundation and its abutment. The cut off shall be located such that its centre line should be within the base of impervious core and should be upstream of centre line of dam.
What is cutoff wall in civil engineering?
Cut-off wall is a device use to reduce or prevent the seepage of water through the pervious foundation. It is always provid below the upper surface of the foundation. If the cut-off wall extends through the foundation to impervious material below, it is called complete cut-off wall.
What is a weir in construction?
What is a weir? A weir is a concrete or masonry structure which is constructed across the open channel (such as a river) to change its water flow characteristics. Weirs are constructed as an obstruction to flow of water.
What is an example of a cut off wall?
Cutoff walls are often used in combination with other remediation and containment techniques such as pumping wells and gravity drains. Figure 4 shows an example of a hanging, downgradient cutoff wall being used to stop the flow of a floating contaminant and a pumping well being utilized to remove the contaminant from the soil.
Why are slurry trench cutoff walls used for vertical cut off walls?
The main reasons why slurry trench cutoff walls are so commonly used for vertical cutoff walls are: 1. The depth of the trench may be checked to confirm penetration to the desired depth, and excavated materials may be examined to confirm penetration into a particular stratum;
How can we improve the efficiency of a weir?
We could improve the geometry of the weir to increase its efficiency. Different shapes of weirs can pass flow more efficiently and thus have a higher discharge coefficient, but this has a practical limit. The most efficient shape for a weir is to match the curve that the water would take off of a sharp crest.