JPH09195258A - Liquefaction preventing crushed stone drain, and its constructing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crushed stone drain capable of ensuring satisfactory water permeability over a long term and a constructing method thereof. SOLUTION: A liquefaction preventing crushed stone drain is arranged in a littoral area where underground level is fluctuated according to ebb and flow to bore a drain hole 3 in the ground 1 from the ground surface 2 and fill crushed stones 4 therein. A communicating pipe 10 is passed in the crushed stones 4 within the drain hole 3 so as to penetrate through a tide sensitive part 5 within the drain hole 3 where the level is fluctuated, the lower end 11 of the communicating pipe 10 is situated in the water on the lower side from the tide sensitive part 5 in the drain hole 3, and the upper end is situated in the air at least on the upper side from the tide sensitive part 5, whereby the water part is allowed to communicate with the air part by the communicating pipe 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquefaction-preventing crushed stone drain provided in soil that may be liquefied in a coastal area such as a landfill.

[0002]

2. Description of the Related Art Conventionally, as a method for preventing liquefaction during an earthquake,
A crushed stone drain is used to dissipate the pore water pressure in the soil. As shown in FIG. 2, the crushed stone drain has a drain hole 3 drilled from the ground surface 2 in a stratum (soil) 1 which is likely to be liquefied, and forms innumerable gaps therein for water pressure dissipation. A crushed stone 4 is filled and a crushed stone mat 6 is laid on the ground surface 2.

[0003]

By the way, when a crushed stone drain is installed on the back of the seawall, the tide section 5 is also provided in the drain hole 3 in response to the vertical fluctuation (upper H and lower L) of the groundwater level due to the tide. Appears. Therefore, if a long time elapses from the time of construction to the occurrence of an earthquake, repeated movements of the water surface of the tidal section 5 will cause clogging of the tidal section 5 due to oxidized slag and propagated microorganisms, thus increasing the permeability of the drain. There was a possibility of damage. Especially for this kind of crushed stone drain,
Since the diameter is limited, if there is a part where the water permeability decreases, there is a risk that the original function of dissipating the water pressure during an earthquake may not be achieved.

In view of the above circumstances, it is an object of the present invention to provide a liquefaction-preventing crushed stone drain capable of ensuring good water permeability for a long period of time and a method for constructing the drainage.

[0005]

The invention according to claim 1 is arranged in a seaside area where the groundwater level changes according to the tide, and a drain hole is bored in the soil from the ground surface to crush stones therein. In the packed liquefaction prevention crushed stone drain, pass a communication pipe through the crushed stone in the drain hole so that it penetrates the tidal part where the water level in the drain hole changes depending on the tide, and the lower end of this communication pipe is in the drain hole. Is located in the water below the tide section, and the upper end is located at least in the air above the tide section, whereby the water and the air are connected by a communication pipe.

According to a second aspect of the present invention, in the first aspect, filters for preventing intrusion of earth and sand are attached to the upper end and the lower end of the communication pipe.

According to the method for constructing a crushed stone drain for liquefaction prevention according to the invention of claim 3, a drain hole is bored from the ground surface in the soil of a seaside area where the groundwater level changes according to the tide,
Fill the inside with crushed stone and arrange a communication pipe in the crushed stone in the drain hole so that it penetrates the tidal part where the water level in the drain hole changes depending on the tide. It is characterized in that it is located in the water below the tide section and the upper end is located at least above the tide section in the air.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a crushed stone drain of the present invention. This crushed stone drain is located in a seaside area where the groundwater level changes according to the tide, and a drain hole 3 is bored in the stratum (under the ground) 1 where liquefaction is expected from the ground surface 2 Is filled with crushed stone 4. 6 is a crushed stone mat.

In this crushed stone drain, the crushed stone 4 in the drain hole 3 is connected to the crushed stone 4 so as to penetrate through the tidal section 5 in which the water level changes in the drain hole 3 depending on the tide. The pipe 10 is passed vertically. The lower end 11 of the communication pipe 10 is located in the water below the tide section 5 in the drain hole 3, and the upper end 12 is located in the crushed stone mat 6 above the tide section 5, that is, in the air. As a result, the underwater and the air are communicated by the communication pipe 10, and the tide section 5 is bypassed by the communication pipe 10. The diameter of the communication pipe 10 in this case is 2 when the diameter of the drain hole 3 is, for example, 500 mm.
It is set to about 00 mm to 250 mm.

Further, the upper end 12 of the communication pipe 10 is bent in the horizontal direction so that the earth and sand do not enter, and the upper end 12 and the lower end 11 are provided with filters (not shown) for preventing the invasion of earth and sand. Has been.

When constructing this crushed stone drain, first, a drain hole 3 is made in the soil 1 from the ground surface 2 and the crushed stone 4 is filled to a certain height inside. Next, the communication pipe 10 is arranged at a position penetrating the tidal section 5 where the water level changes according to the tide, and the crushed stone 4 is provided outside the communication pipe 10.
Fill with. Then, the lower end 11 of the communication pipe 10 is positioned in the water below the tide section 10, the upper end 12 is exposed from the ground surface 2, and a crushed stone mat 6 layer is formed on the ground surface 2 to form the communication pipe 10. The upper end 12 of the is placed in the crushed stone mat 6.

According to the crushed stone drain configured as described above, since there is the communication pipe 10 that bypasses the tidal section 5, even if the tidal section 5 is clogged, good water permeability can be ensured for a long period of time. You can As a result, the groundwater pressure dissipation function during an earthquake can be fully fulfilled.

[0013]

As described above, according to the inventions of claims 1 and 3, since the communication pipe for bypassing the tidal portion is provided in the drain hole, even if the tidal portion is clogged. Also, good water permeability can be maintained for a long time, groundwater pressure can be released by the communication pipe even during an earthquake, and liquefaction of the ground can be effectively prevented.

Particularly, if filters are provided at the upper and lower ends of the communication pipe as in claim 2, it is possible to prevent the intrusion of earth and sand into the communication pipe, so that the function of the communication pipe may be impaired for a long period of time. Absent.

[Brief description of the drawings]

FIG. 1 is a sectional view of a crushed stone drain as an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional crushed stone drain.

[Explanation of symbols]

 1 Stratum (underground) 2 Ground surface 3 Drain hole 4 Crushed stone 5 Tidal part 6 Crushed stone mat 10 Communication pipe 11 Lower end 12 Upper end H Groundwater level (upper) L Groundwater level (lower)

Claims (3)

[Claims] 1. A liquefaction-preventing crushed stone drain, which is disposed in a seaside area where the groundwater level fluctuates according to the tide, has a drain hole formed in the soil from the ground surface, and is filled with crushed stone in the tide. Depending on the location, the communication pipe is passed through the crushed stone in the drain hole so that it passes through the tidal part where the water level changes, and the lower end of this communication pipe is located in the water below the tidal part in the drain hole. A liquefaction-preventing crushed stone drain characterized in that the upper end is located at least in the air above the tidal portion, and thereby water and the air are connected by a communication pipe. 2. The crushed stone drainage for preventing liquefaction according to claim 1, wherein filters for preventing intrusion of earth and sand are attached to upper and lower ends of the communication pipe. 3. A drain hole is drilled from the ground surface in the soil in a seaside area where the groundwater level changes according to the tidal level, and crushed stones are filled inside the hole, and the water level in the drain hole changes according to the tidal level. A communication pipe is placed in the crushed stone in the drain hole so as to pass through the tide section that fluctuates, and the lower end of this communication pipe is located in the water below the tide section in the drain hole, and the upper end is at least A method for constructing a crushed stone drain for preventing liquefaction, which is characterized in that it is located in the air above the tidal part.