JPS59170318A - Sand pile formation work - Google Patents

Abstract

PURPOSE:To pack sand into a guide pipe with high speeds by a method in which sand is supplied into a guide pipe penetrated into the ground while jetting a high-pressure fluid downwards, and then the guide pipe is drawn out. CONSTITUTION:A vibrator 5 is operated and a guide pipe 3 is penetrated to a given depth into the ground of the seabed. When a three-way valve 15 is opened and a gate 14 is opened, sand 11 in a supply hopper 12 is dropped into a packing chute 6 and slides down in the chute 6 while opening an air-tight gate 9. In this case, when a high-pressure seawater pump 10 is actuated, the jet of seawater jetting from a jet pipe 8 downwards is mixed with the sand, and thereby the sand is acceleratedly sent down and deposited in the guide pipe 3. After the packing of sand, the guide pipe 3 is drawn out to form a sand pile.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the construction of sand piles for improving the ground by inserting sand in the form of pillars into the ground on land or underwater to draw out the water contained in the ground. .

The conventional sand pile construction method involves inserting a guide pipe into the ground, filling the guide pipe with sand, and then pulling the guide pipe out leaving only the sand in the ground. However, when filling the guide pipe with sand, sometimes the sand gets stuck in the middle of the guide pipe and becomes tightly packed, causing an accident that prevents it from falling downward. If such an accident occurs, it is necessary to pull out the guide pipe, use gas flames to drill a window in the side wall of the guide pipe, and scrape out the thousands of stagnant sand from there. Work is interrupted for several hours or more.

Sand stagnation accidents in the guide tube are more likely to occur as the guide tube becomes thinner and the sand filling speed becomes faster. For this reason, conventionally, sand was filled at a low speed, and especially when the guide tube was small in diameter, the sand was filled in extremely small amounts using a belt conveyor or the like. For example, under the ground conditions of 1
It took 0 minutes, and it accounted for a large proportion of the total working time, reaching about 50 people.

The object of this invention is to fill a guide pipe with sand at high speed without causing sand stagnation.

In this invention, an inner pipe with a relatively small diameter is provided at the upper part of the guide pipe, and sand is supplied into the inner pipe while jetting high-pressure fluid downward from the upper part of the inner pipe. It accelerates and causes it to fall. Water or seawater is suitable as the fluid to be used, and the amount thereof is just enough to fill the gaps between the sand particles, that is, 20 to 40% of the volume of the sand.
), its pressure l110~40 kg/d gf
jf,,1. Next, the invention of item 4 will be explained based on the illustrated embodiment.

1 is the sea surface and 2 is the ocean floor. Reference numeral 3 denotes a guide tube, a lid 4 that can be opened and closed is provided at its lower end, and an exciter 5 is attached to its upper end. A filling chute 6 is inserted from the upper side of the guide tube 3.
It enters the pipe and bends downward to form the inner pipe 7. A jet pipe 8 for pressurized seawater supplied from the outside is introduced into the bent portion of the filling chute 6 and the inner pipe 7, and opens downward.

The jet pipe 8 is connected to a high pressure seawater pump 10 via a flexible supply pipe 9.

A supply hopper 12 containing sand 11 is located above the filling chute 6. Reference numeral 13 indicates an airtight gate provided in the middle of the filling chute 6, and reference numeral 14 indicates an opening/closing gate provided at the opening of the supply hopper 12.

Reference numeral 15 denotes a three-way valve provided at the upper part of the guide tube 3, one opening of which opens to the outside world, and the other opening connected to a pressurized air supply source 17 via a flexible tube 16.

When constructing a sand pile, first close the lid 4, airtight gate 13, and three-way valve 15 to prevent seawater and seabed sediment from entering the guide pipe 3, and then operate the exciter 5. The guide tube 3 is inserted into the seabed ground to a predetermined depth. Next, when the three-way valve 15 is opened to the outside world and the gate 14 is opened,
The sand 11 in the supply hopper 12 falls into the filling chute 6 and slides down inside the filling chute 6 while pushing open the airtight gate 9. At this time, when the high-pressure seawater pump 7'lO1 is operated, the seawater jet ejected downward from the spouting pipe 8 mixes with the sand, the sand is accelerated and descends in the inner pipe 7, and from the bottom of the guide pipe 3. Stacks upward.

After filling the guide tube 3 with a predetermined amount of sand, the gate 1
4 to stop the supply of sand and also stop the operation of the high pressure seawater pump 010. Then, close the airtight gate 13, switch the three-way valve 15 to the flexible tube 16 side, introduce the pressurized air 2 from the supply source 17 into the guide tube 3, and pull out the tube t.
Only the sand remains in a pillar shape in the seabed ground, and only the guide pipe 3 remains.
It can be pulled up.

In the above construction method, the falling flow rate of sand in the guide pipe 3 is regulated by the inner pipe 7Vc, and the falling speed of the sand is accelerated by a seawater jet. When falling sand is formed into a column, the diameter of the column is reduced by increasing the falling speed, making it extremely easy to pass through the guide tube 3. In addition, the fluidity of falling sand increases when it contains an appropriate amount of water; instead, the particles bond with each other and contain water to form high-density nodules, and these nodules form whole bodies. Since it has a large kinetic energy, even if the nodules collide with the inner wall of the guide tube, they do not stagnate and continue to fall.

As a result, by using the above-mentioned construction method, it was possible to halve the time required for sand filling to 5 minutes when constructing a sand pile to a depth of 1,577 mm using the aforementioned guide pipe with a diameter of 500 mm. As a result, the sand pile construction cycle was shortened to 15 minutes.

As described above, according to the construction method of the present invention, not only can accidents such as sand clogging in the guide pipe and requiring a long time to remove it be prevented, but also the sand pile construction cycle can be significantly shortened. Therefore, it greatly contributes to shortening the construction period and cost of constructing sand piles.

[Brief explanation of the drawing]

The figure is a schematic longitudinal cross-sectional view of one example of equipment used in the construction method of the present invention. 2...Sea bottom ground, 3...Guide pipe, 6...Sand filling, filling chute, 7...Inner pipe, 8...High pressure seawater spouting pipe, 10...High pressure seawater pump . Patent applicant: Nippon Kaiko Co., Ltd.

Claims (1)

[Claims] (1) By inserting a guide pipe into the ground and supplying sand from the upper end into the inner pipe while jetting high-pressure fluid downward from the upper end of the inner pipe installed parallel to the inner wall of the guide pipe. A sand pile construction method characterized in that the guide pipe is filled with sand, and then only the guide pipe is pulled out from the ground, leaving the filled sand behind.