JP2001152439A - Construction method for well point and well point device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device, by which displacement per well point device is set at a large value and the intervals of the arrangement of the devices are set at a large value, while the drainage efficiency of the device can be improved by preventing the clogging of the suction hole of a water absorption section. SOLUTION: The well point device 1 is constituted in such a manner that a pipe having a large diameter is driven and the well point 3 configuring the pipe having the large diameter and a riser pipe 2 are laid in a pit and openings in the pit are filled with sand, and a sand filter 12 is formed and the pipe having the large diameter is removed. In the well point 3, a water absorption section 5 in which holes 6, etc., are formed is arranged in the fixed range of the lower section of the pipe having the large diameter, a space is arranged and the whole pipe is covered with a wire gauze member, the generation of clogging in the water absorption section 5 is prevented, and a large amount of water can be drained through the filter 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a well point device capable of setting a large amount of water absorption per unit well point, and more particularly to a well point device capable of easily installing a large diameter well point.

[0002]

2. Description of the Related Art When digging a ground with a high groundwater level or a ground sandwiching a soft clay layer to construct a foundation of a building,
In order to lower the water level in the ground to be excavated, a well point method is used in which deep wells are constructed at predetermined intervals around the construction ground and the like, and groundwater is pumped up. When the well point method is used, for example, FIG.
The well point device 20 as shown in FIG. 1 is constructed, and the ground for construction is an upper sand layer 25 and a lower sand layer 25.
b, when a soft clay layer 25a is interposed,
A vertical hole 23 having a predetermined diameter is excavated from the ground surface GL, a riser pipe 22 is disposed in the vertical hole 23, sand is filled in the hole 23, a sand filter 24 is formed, and pumping of the well point device 20 is performed. Make up the route. Also, well points 21 disposed below the riser pipe 22 are provided.
Is positioned at the bottom of the vertical hole 23 by locating it in the lower clay layer 25c. An upper clay packing is provided on the upper portion of the vertical hole 23 to perform processing for preventing air from entering. I have.

In the well point method, as shown in FIG. 7, a number of well point devices 20 are arranged so as to surround a construction section, and each well point device is connected to a header pipe 31 by a swing joint 32. Ground device 30 connected through a line and provided with a negative pressure generation mechanism and a drainage mechanism
Connected to In the ground device 30, a negative pressure is generated by connecting the vacuum pump 35 and the separator tank 34. Further, in the separator tank 34, a path is provided for separating water and air through a water shield plate and discharging the water and air through a drain pipe 37 by a drain pump 36.

In the case of using the conventional well point method, it is necessary to arrange a number of vertical holes 23 for pumping groundwater, and the well point device is provided with a distance W1 of about 1 m closely. Then, as shown in FIG. 8, by absorbing water between the well points 21, 21a,...
6 is lowered to the working water level 17 which is a position lower than the construction surface 15 so that the ground excavation work can be performed. In constructing the well point device, a means for sinking the well point into the ground while ejecting a water jet from an opening provided at the lower end of the well point is used. It can be easily constructed.

[0005]

In the conventional well point device, the riser pipe 22 has a diameter of 50 mm.
Use well-sized pipes and fit well points 21 with a diameter of 75
A pump having a capacity of about 50 liters per minute is used for a unit of the well point device by using a material of about mm. Then, as shown in FIGS. 7 and 8, the well points 20 are provided so as to be close to each other at a distance W1 of about 1 m, and are arranged so as to surround the construction site.
The excavation work is performed so that 7 can be made lower than the construction surface 15. The well point 21 is configured to have a length of about 70 cm. The well point 21 covers the periphery of the well point, and a wire mesh member is disposed so that sand, gravel, soil, and the like are not sucked from the well point hole, and only water is discharged. I can do it.

However, in the conventional well point device, when the well point is installed while excavating the vertical hole, the soil of the ground is not completely removed from the inside of the vertical hole, so that the performance of the sand filter is improved. However, there is a problem that the water collecting hole at the well point is clogged and the water collecting efficiency is easily lowered. In addition, depending on the properties of the ground, excavation by a water jet is often not performed well, and particularly in the case of ground such as gravel, it is often difficult to excavate a vertical hole. Furthermore, since the number of well point devices installed is large, the configuration of the ground equipment is complicated, and there are still many points that require many solutions, such as troublesome maintenance of each well point device. The present invention solves the above-mentioned problems of the conventional well point device, and uses a large-diameter pipe, sets a large pumping amount of the unit of the well point device, and sets the installation interval of the well point device. It is an object of the present invention to provide a device capable of simplifying the configuration of the device by increasing the size.

[0007]

The present invention relates to a method of constructing a well point, and the invention of claim 1 comprises a step of casting a casing pipe in a construction ground to construct a large-diameter vertical hole; A step of arranging a well point connected to a riser pipe inside the casing pipe, a step of filling a gap inside the casing pipe with sand to form a permeable layer, and pulling out the casing pipe,
And constructing a vertical hole in which a well point and a riser pipe are arranged at the center. The invention of claim 2 is characterized in that the well points are arranged at intervals of 3 to 5 m so as to surround a construction site, and each well point is connected to a drainage device on the ground. Therefore, when installing a well point, it is only necessary to cast a large-diameter casing first and insert it into the hole, and to fill the hole with sand and collect water, so a large-diameter pipe A large amount of groundwater can be easily collected by using the method. Further, even if the interval between the vertical holes is set to be large, the effect of lowering the water level of the groundwater can be favorably exhibited, and the overall configuration of the device can be simplified.

[0008] The invention according to claim 3 of the present invention relates to a well point device which is disposed in a vertical hole formed in a construction ground and is used for lowering a groundwater level. A well point arranged at the bottom of the vertical hole to be formed, a riser pipe connected to the ground equipment and a well point are formed by a large diameter pipe member, and a plurality of holes are provided in a predetermined range at the lower end of the well point. And a wire mesh member disposed around the well point via a spacer member. According to a fourth aspect of the present invention, the relationship between the diameter of the vertical hole and the well point is set to have a ratio of 2: 1 to 2.5: 1, and the distance between the vertical hole and the well point and the well point are defined. A sand filter is formed in a gap between the riser pipe and the vertical hole arranged at the upper part. And, by the configuration as described above, it is possible to collect a large amount of groundwater toward the water absorbing portion provided at the bottom of the vertical hole, and the holes in the water absorbing portion are not clogged with foreign substances, and maintenance is performed. It can be simplified. In addition, a large-diameter well point allows a large amount of groundwater to be sucked out.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The well point device of the present invention will be described with reference to the illustrated example. FIGS. 1 to 3 show the structure of a well point device, in which a main pipe 4 is provided at the bottom of a vertical hole 10 formed by excavating underground.
Is provided with a water absorbing portion 5 in which a number of water absorbing holes 6 are arranged. In the well point device 1, the inner diameter D is 17
The well point 3 to be installed inside the large-diameter vertical hole 10 formed to about 20 cm is constituted by a large-diameter main pipe 4 having a diameter D1 of about 10 cm and a length L of about 3 m. A portion of about L1 = 1 m is configured as a water absorbing section 5, and the water absorbing section 5 is provided with a large number of water absorbing holes 6 having a size of about 2 cm with an interval L2 = 5 cm. The riser pipe 2 provided above the well point 3 has an inner diameter D
2 uses a thick pipe of about 7.5 cm to increase the amount of drainage. The inside of the vertical hole 10 is filled with sand or the like so as to fill the gap between the riser pipe 2 and the well point 3. A sand filter 12 is provided.

The well point 3 is configured as described in detail with reference to FIGS. 2 and 3. A wire mesh member 7 is arranged around a main body pipe 4 via a spacer member 8. A layer of a sand filter 12 is provided between the wire mesh member 7 and the hole wall of the vertical hole 10. The spacer member 8 disposed on the outer peripheral surface of the main body pipe 4 is attached to the periphery of the main body pipe 4 by using a fixing means such as welding at a predetermined interval using a reinforcing bar having a thickness of about 8 mm. A predetermined gap can be formed on the inner surface of the.
The water absorption holes 6 configured as the water absorption portions 5 of the main body pipe 4 can be provided at intervals as shown in the figure, but the size and the number of the holes can be arbitrarily provided. . Then, toward the well point 3,
Water flowing through the sand filter 12 in the vertical hole 10 flows,
The groundwater is sucked from the water suction hole 6 of the main body pipe 4 by the negative pressure applied from the ground apparatus via the riser pipe 2,
It can be discharged through the riser pipe 2.

When the well point device 1 is constructed, it can be formed through steps (a) to (d) of FIG. First, as shown in FIG. 4A, a casing pipe 11 is penetrated from the ground using a drilling device to form a vertical hole for installing a well point device. In that case, in order to place a pipe with an outer diameter of about 20 cm, a device that blows out pressurized water and air is attached to the tip of the pipe, as in the conventional method, and a water jet is installed from the pipe tip. In order to discharge the excavated earth and sand, the air is blown out from the bottom of the hole to discharge the excavated earth and sand. Further, when the soil is hard or on the ground of gravel, a vibration device is arranged on the casing pipe 11 and a means for improving the excavation efficiency by applying vibration is used.

As described above, the casing pipe 1
1 is immersed to a predetermined depth, the soil and sand are discharged from the inside of the casing pipe 11 by an air lift to perform a cleaning operation, and as shown in FIG. The well point device provided with the well points 3 is disposed below the riser pipe 2 such that the gap between the well points 3 and the inner surface of the casing pipe 11 is kept constant. When the well point device is installed, an appropriate spacer may be arranged around the well point 3 so that the gap can be maintained constant. Next, as shown in FIG. 1C, sand is charged into the casing pipe 11 to form a sand filter 12 in a gap on the inner surface of the casing pipe. After that, pull out the casing pipe 11,
The well point device 1 in which the well points 3 are disposed inside the vertical holes 10 via the casing pipe 12 is constructed.

As described above, by constructing the well point device 1, it is possible to construct a sand filter 12 having a predetermined thickness inside the vertical hole 10, and the water absorbing portion 5 of the well point 3 is formed. The water passing through the sand filter 12 can be sucked through the wire mesh member 7 into the holes provided in the. The collapse of the hole wall of the vertical hole 10 is prevented by the sand filter 12, and only water can be guided toward the well point 3 by the sand filter 12 and the wire mesh member 7. Can be blocked. Further, the vertical hole 10 is configured as a large-diameter one,
Since the amount of flowing water can be set large, even when the amount of water discharged to the ground equipment is large, drainage can be easily performed.
In this embodiment, the ground device for connecting and draining above the riser pipe 2 can use the ground device 30 shown in FIG. 7 as it is, and therefore the description of the ground device 30 is omitted. .

The well point device 1 can cope with, for example, a case where the amount of drainage is 300 to 400 liters per minute, and as shown in FIG. It can be arranged to surround.
Then, the natural water level 16 is reduced to the working water level 1 lower than the construction level 15.
7 and can be used for ground excavation work. As described above, even in the well point device 1 in which the arrangement interval W is set to be large, since the drainage amount per one of the well point devices is large, it is easy to set the working water level 17.
The working water level 17 can be formed in the same manner as in the case of using a large number of well point devices constituted by conventional thin pipes. Therefore, in the ground apparatus 30 arranged on the ground with respect to the well point apparatus 1, the number of connection points of the riser pipe 2 to the header pipe 31 is reduced, and other materials can be significantly reduced.
Naturally, maintenance on the ground equipment and well point equipment becomes easier.

In the well point device 1, the diameters of the vertical hole, the riser pipe and the well point are set according to the height of the groundwater level and the amount of spring water on the construction ground. Are also set according to the amount of spring water and the geology of the ground. Conditions such as the size of the mesh of the wire mesh member 7 arranged with respect to the well point 3 and the size of the sand particles of the sand filter 12 are set according to the geology of the construction site.

[0016]

According to the apparatus of the present invention, when a well point is set, a large-diameter casing is first cast and inserted into the hole, and the hole is filled with sand and collected. Since water is supplied, a large amount of groundwater can be easily collected using a large-diameter pipe. Further, even if the interval between the vertical holes is set to be large, the effect of lowering the water level of the groundwater can be favorably exhibited, and the overall configuration of the device can be simplified. Furthermore, by configuring as described above, it is possible to collect a large amount of groundwater toward the water absorbing portion provided at the bottom of the vertical hole, and it is possible to perform maintenance without foreign substances clogging the hole of the water absorbing portion. It can be simplified. The large-diameter well point not only enables a large amount of groundwater to be sucked out, but also simplifies equipment and improves construction efficiency.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a well point device.

FIG. 2 is an explanatory diagram showing a configuration of a well point.

FIG. 3 is a sectional view of FIG. 2;

FIG. 4 is an explanatory view showing a step of forming a well point according to steps (a) to (d).

FIG. 5 is an explanatory diagram of a state in which a water level is lowered by a well point device at a construction site.

FIG. 6 is an explanatory view of the structure of a conventional well point device.

FIG. 7 is an explanatory diagram of the entire structure when a well point method is applied.

FIG. 8 is an explanatory diagram of a conventional water level lowering state.

[Explanation of symbols]

1 well point device, 2 riser pipe,
3 well points, 4 body pipes, 5
Water absorption part, 6 Water absorption hole, 7 Wire mesh member, 8 Spacer member, 10 Vertical hole, 11 Casing pipe, 12 Sand filter, 15 Construction surface,
16 Natural water level, 17 Working water level, 20 well point device, 21 well point, 22
Riser pipe, 23 vertical hole, 24 sand filter, 25 formation, 30 ground equipment, 31
Header pipe, 32 swing joint,
33 valve, 34 separator tank, 35
Vacuum pump, 36 drain pump, 37 drain pipe.

Claims (4)

[Claims] 1. A step of casting a casing pipe on a construction ground to form a large-diameter vertical hole; a step of arranging a well point to which a riser pipe is connected inside the casing pipe; Filling the gaps with sand to form a water-permeable layer; and withdrawing the casing pipe to form a vertical hole in which a well point and a riser pipe are arranged in the center. Well point construction method. 2. The well point construction method according to claim 1, wherein the well points are arranged at intervals of 3 to 5 m so as to surround a construction site, and each well point is connected to a drainage device on the ground. . 3. A well point device disposed in a vertical hole formed by excavating in a construction ground and used for lowering a groundwater level, comprising: a well point disposed in a lowermost part of a vertical hole formed by excavating in the ground. A riser pipe and a well point to be connected to the ground apparatus are formed by a large-diameter pipe member; a predetermined range at the lower end of the well point is formed as a water-absorbing section provided with a large number of holes; A wire netting member is disposed on the wire point member via a spacer member. 4. The relationship between the diameter of the vertical hole and the well point is set so as to have a ratio of 2: 1 to 2.5: 1, and the diameter of the vertical hole and the well point is set between the vertical hole and the well point and above the well point. 4. The well point device according to claim 3, wherein a sand filter is formed in a gap between the riser pipe to be disposed and the vertical hole.