- Civil Engineering Water-shielding Materials
Manmade reservoirs and regulating ponds
Manmade agricultural ponds hold water for agricultural use and the water inside the ponds should not leak out.
Mitsuboshi Belting's high-quality surface water-shielding materials produced mainly from synthetic rubber, contribute to preventing water leakage from reservoirs.
Excellent performance against earthquakes
When the great earthquakes hit the Hanshin, Awaji and Chuetsu districts, MIZUSHEET proved its maximum flexibility that the synthetic rubber sheet had.
A pond lined with MIZUSHEET sitting above a fault leaked no water even though the soil base slipped greatly. Thus, the pond maintained its safety.
Design key points
With its high elongation percentage, MIZUSHEET is excellently flexible against settlement due to consolidation compared with such materials as concrete and asphalt panels. For the base construction, remove projectiles such as stones, pieces of wood and tree roots. Thoroughly compact the base to have the base produce sufficient bearing force. If it is not practical to finish the base flat and smooth, consider the use of a protection mat, sand layer soil cement or a similar measure.
Where the base is soft and a significant ground subsidence is expected, improve and stabilize it by using a method such as replacement construction, sand drain construction and pre-load construction, while considering the soil condition and the scale of construction.
Thoroughly compact the areas such as the interface of cut and fill, a portion with a large tree root removed and the peripheral of concrete structures to prevent local settlement or depression.
Embankment dams (gradient of slope)
The standard dimensions of embankment dams are as follows. Standard dimensions for water reservoirs.
|Height to water reservoir water level||H1(m)||-3.3||3.3-7.8||7.8-12.2|
|Design spillway depth||h1(m)||0.3-0.5||0.5-0.8||0.8-1.2||Depending on position and structure of spillway|
|Margin for height||h2(m)||1.0-1.2||1.2-1.4||1.4-1.6||In principle, 0.05H + wind wave height (max. 1.0 m).|
|Embankment top width||B(m)||2.0-3.0||3.0-4.0||4.0-5.0||In principle, 0.2H + 2.0 m (min. 3.0 m)|
|Front slope Gradient||n (%)||1.5-1.8||1.8-2.1||2.1-3.0||15% - 30%|
|Front slope Middle stage width||b(m)||0-1.5||1.5||2.0||Min. 1 m if small step is provided.|
Provision of a small step is preferable if the embankment height exceeds 10 m.
The gradient of slope is to be a stable gradient depending on the soil condition and scale of construction. (15% or more)
The following cases require special attention to ensure stability.
- The fill-up is high.
- The underground water level is high or spring water is present much.
- Soft, weak soil base.
- Unstable soil bases in a region of possible landslides.
- A fill-up on steep slope.
Securing the crown of embankment
Figure① shows how to secure the edges of the sheets over the crown of the embankment.
First, dig up a ditch at a horizontal distance of 500 mm from the shoulder of the slope.
Place the portion of the sheet along the ditch in the shape of letter "L".
Fill back the ditch in a manner not to contain water or air.
Compact the ditch thoroughly. To finish the shoulder of the slope esthetically, form the portion with concrete as shown in Figure②and Figure③.
From the viewpoint of maintenance and control, provide measures such as fences to ensure safety.
Interface with structures
Compact the areas around the structures carefully and thoroughly since settlement of the back filled soil is likely to occur in these areas. In addition, chamfer the corner of the structure. Secure a bonding width of 300 mm or more.
At pipe structure
At retaining wall Seal the joint between the concrete blocks with a piece of MIZUSHEET 400 mm wide.
Measures against pressure from below
Underground water, spring water management (under drain)
Measures against underground water and spring water (Under drain) To relieve the structure of the pressures from below caused by underground water or spring water, be sure to install an under drain. Wrap around the under drain with filtering material to avoid poor water discharge due to pipe plugging or to prevent the piping from settlement due to suction forces.
Measures against underground water and spring water
(Under drain) To relieve the structure of the pressures from below caused by underground water or spring water, be sure to install an under drain. Wrap around the under drain with filtering material to avoid poor water discharge due to pipe plugging or to prevent the piping from settlement due to suction forces.
To remove residual air from under the MIZUSHEET and air and various gases generated in the base soil, install, as necessary, pieces of air vent pipe under the slope. Install pieces of perforated pipe under the slope from the bottom of the slope up to the crown of the embankment at a distance of 20 m to 30 m from the adjacent pipe to remove air from the shoulder of the slope. This is the standard method. On some occasions, the bottom may be sloped at a gradient of 1/500 to 1/200.
Detailed specifications and drawings for various constructions
(1) Fixed blocks
Determine the concrete foundation based on the height of embankment, length of slope, soil condition and other parameters.
(2) Structure around pipe
End of slope (Blanket construction)
The depth of the sheet end to be buried at the end of the slope lining is determined based on the soil condition and other parameters. Calculate the depth separately based on such parameters.
Method of simple repair
Reinforcing the repair area by taping (1)
After processing with a primer, prepare a piece of EJ TAPE cut off to fit the size of repair area. Remove the released paper from the tape.Tape it on the repair area in a manner not to trap air.
Reinforcing the repair area by taping (2)
Cut out patch-up sheet to a size slightly bigger than the repair area. Patch it up on the repair area. Treat the area with a primer.
Then, tape a piece of EJ TAPE on it in a manner not to trap air.