Excavating – Beneath a body of water – Suction
Reexamination Certificate
2002-03-25
2004-11-16
Safavi, Michael (Department: 3673)
Excavating
Beneath a body of water
Suction
Reexamination Certificate
active
06817120
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a deposit discharge system and a method of discharging deposit from a water storing place, e.g., dam.
2. Description of Background Art
In a water storing places such as a dam, functions of the dam are lost when pondage of the dam is, reduced. To maintain the functions, deposits in water, e.g., sands and stones, are dredged so as to maintain enough water level. Stones included in the deposits dredged are used as aggregates of concrete, and others are used for reclamation, etc.
However, if the dam is dredged, no stones and sands are conveyed downstream. Therefore, the natural balance is lost and new environmental problems are occurred. For example, organic components made in mountains stored by the dam; no nourishment or foods of plankton are supplied to the sea, so that number of fish is reduced. Further, no stones and sands are conveyed downstream, so that a riverbed is extremely washed out and sandy beaches are disappeared.
In a huge dam, water flows little and stays there for a long time. Unlike a small dam, stones and sands are apt to precipitate and deposit therein. Almost all fine grains in water are also deposited. For example, about 10,000,000 m3 of fine grains have been deposited for 40 years. It is very difficult for a dredging boat to remove a huge amount of stones and sands, so it is also difficult to maintain effective pondage of dams.
As shown in FIG. S, a system for discharging deposits
22
from a huge dam
60
was proposed. The system directly flows flood flow and solid-liquid two-phase flow from the upstream side of the dam to the downstream side
64
via a bypass tunnel
30
. A plurality of supplementary tunnels
32
, which communicate a water storing place
20
to the bypass tunnel
30
, are formed in a coast
23
of the dam. With this structure, deposits can be discharged from a plurality of positions in the water storing place
20
.
Deposit discharging ports
62
of the supplementary tunnels
32
are opened in a bank of the dam so as to safely flow the deposits
22
. Water gates for opening and closing the discharging ports
62
and a mechanism for securely actuating the water gates are required. If the discharging ports
62
are not securely closed, water stored on the upstream side of the supplementary tunnels
32
will be leaked out therefrom.
However, it is difficult to securely open and close the water gates when a large amount of water including deposits flows. Even if the water gates are opened and closed, the open-close mechanism must be large. To discharge stones and sands deposited thicker than prescribed thickness, height of the water gates must be equal to or higher than the thickness of the deposits. The water gates must bear up against high water pressure, so that they must have large structures.
The deposits
22
must be uniformly removed from a large area of the water bottom so as to maintain proper pondage.
However, in the case of discharging the deposits to the bypass tunnel
30
via the water gates and the supplementary tunnels
32
, the deposits near the water gates can be effectively discharged, but other deposits cannot be discharged effectively. Therefore, the deposits
22
distributed in the large area cannot be fully removed.
To solve this problem, a siphonal discharge system shown in
FIG. 12
was proposed.
A discharge tube
70
has a suction port
71
opened so as to face the water bottom face
29
of the water storing place
20
and a discharge port
78
opened in a water path
80
located on the downstream side. A tube part
73
of the discharge tube
70
, which is located on the suction port side, is supported by a boat
82
; a mid part
76
is bent and routed above the water level
21
so as to get over the dam banking
25
.
The discharge tube
70
is filled with water by a high power pump
84
installed in the water, so that the siphonage can be occurred. When the siphonal action is stopped, an air valve
77
, which is provided to a top of the mid part
76
, which is bent, of the discharge tube
70
, is opened so as to introduce air into the discharge tube
70
.
A straight tube part
72
, which is close to the suction port
71
of the discharge tube
70
, is vertically arranged. The straight tube part
72
can be extended and contracted according to a distance between the water surface
21
to the water bottom
29
. For example, it is formed by an inner tube and an outer tube, which can be vertically extended and retracted with respect to the inner tube.
The discharge tube
70
has a bendable section
74
. The suction port
71
of the discharge tube
70
can be turned, in a horizontal plane, about the bendable section
74
. To horizontally turn the suction port
71
, the boat supporting the part of the tube on the suction port
71
side is moved. By moving the boat, the suction port
71
can be moved along a circular track. A float
75
makes the discharge tube
70
stay on the water surface.
TECHNICAL PROBLEMS
In the above described conventional system, the discharge tube
70
is installed to get over the dam banking
25
. With this structure, the discharge by siphonal action is limited. If speed of solid-liquid two-phase flow is equal to or lower than prescribed speed, solids begin to precipitate. For example, if volume percentage of solids is 1%, the speed is about 2.5 mlsec. At this speed, deposits close the tube. To solve this problem, the conventional system employs the high power source, e.g., the pump
84
, so as to add jet flow. Namely, the high power source maintains a filled water channel in the discharge tube
70
. Note that, the word “filled water channel” means a channel filled with water and having no free water surface.
The conventional deposit discharge system must have the high power source, e.g., the pump
84
. Therefore, the structure must be complex, and the siphonal structure is not essential. With this complex structure, initial cost and running cost of the discharge system must be increased.
Since the discharge tube
70
gets over the dam banking, the mid part of the discharge tube
70
must be bent upward. The discharge tube
70
must be bent at three points at least, so that friction loss in the tube must be greater. Deposits, which must be passed through the discharge tube
70
, are deposited in and closes the tube.
Further, the discharge tube
70
cannot be made longer due to the friction loss therein.
SUMMARY AND OBJECTS OF THE INVENTION
An object of the present invention is to provide a deposit discharge system having a simple structure and capable of easily and efficiently discharging deposits.
Another object of the present invention is to provide a deposit discharge system in which no deposits close the tube and which is capable of efficiently discharging deposits.
Further, another object of the present invention is to provide a method of efficiently discharging deposits with the deposit discharging system.
To achieve the objects, the present invention has following structure.
The deposit discharge system comprises: a discharge tube having a suction port opened so as to face a water bottom face of a water storing place on which deposits are deposited, a straight tube part vertically extending upward from the suction port, and a discharge port opened in a water path on the downstream side of the water storing place for draining the deposits from the water storing place to the water path together with water stream, characterized in: that the discharge tube is pierced through a bank hole, which is located below the water level of the water storing place, and suspended by a boat, which floats on the water, so as to locate the discharge tube under the water level of the water storing place; and that the discharge tube is vertically moved by an elevating unit, which is provided to the boat, so as to move the suction port close to and away from the water bottom face of the water storing place with prescribed cycle, whereby pulsating flow and plug flow, in which high solid-concentrated part and low solid-concentrat
Shibuya Yorikuni
Tsuchiya Yoshiaki
Japan as represented by Director General of Shinshu University
Safavi Michael
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