JPS6215687B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in radial wells installed underground for the purpose of collecting groundwater.

Conventionally, among well construction methods for the purpose of collecting groundwater, a radial well construction method is used, in which a large number of water absorption strainer pipes 2 are radially punched out horizontally at the lower end of a well frame 1, as shown in Figures 1 and 2.・The well construction method has been widely used. The feature is that the absorption area is much larger than that of ordinary concrete pipes that are simply connected and installed underground, and therefore the amount of water pumped per well is so large that it is not a problem compared to ordinary wells. It's about capacity. A well for home use is small in diameter, around 1 meter in diameter, and a slightly larger hole is dug manually.
Short concrete pipes are inserted into the well to form a vertically connected well frame, and spring water is collected from the open part at the bottom, but such a structure is not suitable for commercial use. is of no use because the amount of water pumped is small. Therefore, large wells with a diameter of 5 to 6 meters are installed to increase the amount of water pumped, but groundwater passes through the voids between soil particles in the aquifer layer made of deep sand and gravel. Since it is something that collects, there is considerable resistance to collecting water, and it gradually comes out. In short, it is determined by the permeability coefficient of the aquifer that is the target of water intake, and from the groundwater catchment characteristics,
Capillary collection is the most efficient method of collecting water. Due to the above-mentioned properties of groundwater, just by drilling a large hole in the ground, a large amount of water will not come out. There is no other way than to expand the surface area of the absorption area. For these reasons, the radial well construction method has been used heavily, but the radial well construction method
When comparing the case with a well and the case without one, there is clearly a large difference in the amount of water collected. In other words, for example, when collecting water only from the outside of a well with an outside diameter of 5 m, the amount of water collected per 1 m ² is 0.8
/sec, the thickness of the aqueous layer is 3 m, and the rate at which the collected water can pass through the well frame, that is, the water intake coefficient, is 0.4 in the case of a well frame, then the possible water extraction amount Q = 5.
π×3m×0.8/sec×0.4=5×3.14×3×0.8
×0.4≒1.5/sec, so 5.4 in 1 hour
m ³ , 129.6 m ³ in 24 hours, which is poor efficiency. On the other hand, in the case of radial wells of the same diameter, the amount of water absorbed per 1 m of strainer is 1.2/sec, and when 24 strainers are inserted with a length of 3 m,
1.2/sec x 3m x 24 lines = 86.4/sec,
311m ³ in 1 hour, 7464m ³ in 24 hours,
In fact, the number is 57 times that of the old well mentioned above, so it is not a problem. Here, it is difficult and unreasonable to directly compare the two numerically because the underground water collection characteristics are completely different, but in any case, the numerical value when using a radial well and when not using a radial well is difficult and unreasonable. There is no doubt that there is a huge difference of 10 times.

Although radial wells like this, which have high water intake efficiency, have generally been very important, the problem is that the installation of the well frame itself is quite difficult and requires quite advanced civil engineering technology. In order to install a large well frame underground, usually with a diameter exceeding 5 to 6 m, the well frame is sunk using its own weight while removing the soil inside the well frame, which is called the submersion method. One method is to increase the length of the concrete frame at the ground surface depending on the subsidence each time, and reach a predetermined depth.The other method is to seal air pressure inside the well frame, which is called the pressurized air infiltration method. There is a method in which workers are placed inside and excavated with internal water removed. Of these, the latter is safe, but the equipment is large and expensive, so it is rarely used as a water intake well. The former method has many achievements, but it is by no means an easy construction method, and of course belongs to the category of large-scale civil engineering construction methods. The method for installing a well frame is as shown in Fig. 3, where the first concrete rod 3 of the well frame 1 is built on the ground in step a, and the inside is excavated with a drilling machine 4 such as a clam shell. As shown in b, the well frame sinks due to its own weight. Once the first rod has finished sinking, concrete for the second rod 5 is poured as shown in c of the same figure. As the sedimentation is continued in this way, the lowest end becomes the water retention layer S, as shown in figure d.
, the bottom concrete 6 is poured underwater to complete the well sinking work, and then the strainer pipe 2 is successively hammered out horizontally.

The problems with this type of well drilling method are:
This means that the surface resistance of the well frame during sinking is so large that the well frame cannot easily sink under its own weight alone. For this reason, the lower end has to be excavated considerably, but no matter how much the excavation is done, the soil above often collapses and is held up by the ground on the sides, preventing it from sinking. In times like this,
The deeper the well is dug, the more the ground 10 meters away from the well frame installation point sinks, causing more and more damage to the surrounding area. In addition, the excavation costs will increase accordingly. In this way, the method of sinking wells involves too many uncertainties in construction, such as those that cannot be determined until digging due to the geology. Things may even happen that force you to give up on your progress.

Also, even if the well is completely sunken, there are problems when installing the strainer. The strainer is connected to a thick-walled pipe, usually about 20 mm thick, and is hammered out horizontally from a hole 7 that penetrates the well frame, using something like a diesel hammer. The problem is that workers enter the well with the inside of the well frame completely drained, so the well frame itself may float to the surface. Although the well frame has considerable dead weight, the underground water pressure is also high, so there is a high possibility that it will float to the surface. For example, outer diameter 6m, thickness 40cm, depth
The weight of a 20m well frame is 141m ³ × 2.3t/m ³ = 324t
becomes. However, in the case of buoyancy, the groundwater level is -1m.
Even if a simple hydrostatic pressure is applied, 3 ² ×
Since π x (20-1) x 1t/m ³ = 565t, the weight is insufficient by buoyancy - dead weight = 565t - 324t = 241t, and with this alone, it will float up quickly. When the friction coefficient around the well frame is set to 0.6,
6×π×20m×0.6t/m ³ = 236t, still 241t above
However, in this condition, it will float without any problem, so as a countermeasure, the thickness of the concrete wall of the well frame itself is increased. In other words, with the above-mentioned 6m outer diameter and 20m depth, 40cm is not enough, so we set it to 60cm to 80cm, so we have no choice but to increase the thickness of concrete to prevent floating even if it is unnecessary. be. Therefore, the construction cost increased proportionately, which was uneconomical. As a way to compensate for these drawbacks, by making the outside diameter of the well frame as small as possible, the specific surface area will increase and the buoyancy will also decrease, so there is no need to worry about floating. The biggest drawback is that it becomes difficult to follow. In short, in the conventional well-sinking method, the problems of workability during the well-sinking work and stability against buoyancy after the well has been sunk are contradictory elements, and if one is favorable, the other becomes difficult. , taking into consideration such relationships,
There was an inconvenience in that a skilled person with many years of experience needed to carry out everything from design to construction. Furthermore, since it was classified as a large-scale civil engineering method, the cost per unit was high and the construction required a considerable amount of time.

The conventional methods have many drawbacks as described above, but the present invention aims to compensate for these drawbacks of the conventional construction methods and provide a quick and economical construction method.

Embodiments of the present invention will be described below with reference to the drawings.

That is, as shown in FIG. 4, a schematic process is shown in FIG. A first rod 9 of a casing pipe C having a diameter of about 1 m is erected on the coaxial center of the body V so as to communicate with the housing body, and its connection point 10 is welded. Subsequently, a digging device M for digging earth and sand is inserted from above the casing pipe. The excavation device M includes a slurry pump 11 for excavating earth and sand disposed in the lower excavation section,
A cap 1 which integrates a sludge draining pipe 12 directly connected to the upper part of the pump, an outlet of the sludge draining pipe and a water injection hole 13 at the top, and is equipped with a driving device 14 above.
It consists of 5. When the preparation is completed in this way, as shown in Figure b, water is injected from the water injection hole 13 while applying driving force from above, and at the same time, the soil and sand inside the case are removed together with water by operating the slurry pump. As it progresses, the whole thing will go underground. At this time, a void 16 is created above the casing around the casing pipe, so gravel or sand that easily flows down is thrown in to fill this void. As shown in Figure c, when the casing reaches its final depth, underwater concrete is placed to close the bottom 17, the area around the casing is filled with gravel 18, and then internal water is removed. In Fig. d, the strainer pipe F is connected horizontally into the enclosure from which internal water has been removed, and if the press-fitting is completed to the specified distance, the result will be as shown in Fig. 5. The pump 19 is attached to the lower end of the pump pipe 20 and fixed in a hanging position to start pumping water.

Regarding the digging device M, in addition to the method described above, a digging device such as a reverse circulation can be considered, but it is preferable to use a device that can be easily extended as the casing is extended. . Regarding the structure of cap 15, it is necessary to remove and install it every time the casing is connected and extended, so it is essential that such work is easy, but it is necessary to apply driving force while pouring water and draining mud. Therefore, it must have a fairly durable structure.

During the above construction process, the problems are the press-fitting of the strainer pipe and the prevention of water leakage in the press-fitting hole. Since a large number of holes are drilled through the wall of the enclosure from the beginning, when the enclosure penetrates the impermeable layer 21 and enters the permeable layer 22, it will be ejected due to groundwater pressure. It becomes difficult to work inside the shelter. Therefore, during the submersion work,
The numerous holes drilled into the wall of the housing must all be kept closed.

For this reason, in the present invention, as shown in FIG. 6, a screw 24 is cut into a hole drilled in the wall portion 23 of the housing, and a blind screw 25 is screwed in to close this hole. In this way, when the case enters the permeable layer and reaches a predetermined depth, the bottom is closed and the strainer tube is press-fitted, as shown in Figure 7a, the hole in which the screw 24 is cut is permanently sealed in the center. The steel bushing 27 to which the rubber packing 26 having the through hole P is attached is attached to the blind screw 25.
Remove it and screw it into the screw hole 24. In this state, the through hole in the center of the rubber packing 26 is always in close contact, so there is no fear of water leakage. To insert the strainer tube, it is sufficient to simply push the strainer tube F into the through hole P in the center of the rubber packing, as shown in FIG. Due to the elasticity of the rubber packing, it is inserted into the strainer tube in close contact with the strainer, so no water leaks from this part during press-fitting. Once the press-fitting is completed, you can leave it as is, but as shown in Figure c, remove the bushing 27 with the rubber packing and fix the end of the strainer pipe F with the fixing bushing 28. Bye.

As for the strainer pipe F, as shown in Figs. 8 and 9, several water suction pipes 31 each having a number of strainer holes 30 with cones 29 attached to their tips are connected and extruded to a predetermined distance. That's why. The groundwater flows through this strainer hole 30.
Since we want to minimize the infiltration of mud, we set the width of the hole to 2 mm and the length to 50 mm.
mm, and provide as many as possible without reducing the strength of the tube. Since each water suction pipe is press-fitted into the internal space of the case, it is required that the pipe be smaller than the inner diameter of the case. Therefore, if the inner diameter of the housing is 1.95 m, it is necessary to set the diameter to about 1.80 m, taking into account the installation of the press-fitting device, etc. In addition, from the strainer tube that has been press-fitted,
If work is difficult due to underground water gushing out, a valve can be installed where the strainer pipe enters the enclosure.

When press-fitting, it is possible to use a device that uses driving force such as a weight or a diesel hammer, but since the inside of the box is narrow, in order to improve efficiency as much as possible, it is necessary to press two pieces symmetrically at the same time. It is a good idea to press fit. That is, when one strainer tube is press-fitted by itself, a reaction force that is exactly equivalent to the press-fitting force must be expected from the opposite wall. In that case, the body itself would be at most 5 to 9
Since they are made from relatively thin steel pipes with a thickness of about mm, a considerable amount of reinforcing material is required, which not only increases costs but also makes it difficult to use space effectively. The pressure force varies depending on the strength of the permeable layer, but assuming that the penetration resistance at the tip is about 200 kg, the surface friction resistance is 0.08 m x 3.14 x 10 m x 1.2 t/ for a pipe with an outer diameter of 80 mm and a length of 10 m. m ² ≒ 3t/piece, so in addition to the tip penetration resistance mentioned above, it is approximately 3.2t.
This requires a pressing force of If this force were to be applied by reinforcing the walls of the enclosure, the reinforcement structure would be quite large, and it would be virtually impossible if the inner diameter of the enclosure was about 2 meters. For this reason, in the method of using such a narrow housing as in this invention, it is a necessary condition that two pairs of strainer tubes are press-fitted symmetrically and simultaneously using mutual reaction force. By doing so, no unreasonable stress is applied to the housing itself, so there is no need for any special reinforcing structure, and the internal space can be utilized to its full potential.

As shown in Fig. 10, the press-fitting method is 2.
In order to horizontally press-fit the strainer pipes F and F' in a symmetrical manner, a simultaneous press-in device K with a hydraulic mechanism that can push out both sides is supported horizontally in the case, and press-fits on both sides. The press-fitting device is fixed as a whole by aligning the direction toward the insertion hole of the strainer tube previously provided in the wall of the housing.

Here, the structure of the press-fitting device K is as shown in the figure, hydraulic cylinders 32 and 3 for press-fitting in the left and right direction.
2', pressing fittings 34, 34' that directly press the strainer pipe heads attached to the tips of the piston rods 33, 33' that are directly connected to the pistons of the hydraulic cylinder, and these two hydraulic devices integrated. Once it is fixed in place in the case, open the hydraulic cylinder as far as it will go, load the first rod with a water suction pipe approximately 1.8m long, and attach the rubber packing. The second rod is then pressed into the through-hole in the center, and when the press-fit is complete, the second rod is connected and the press-fit is continued at the same time. At this time, since the press-fitting stroke is only about 1/2 of the total length of the press-fitting device, it is necessary to use a push-in assisting rod called ``Yatsutoko''. In this manner, when the predetermined length of press-fitting is completed, the head of the strainer tube is fixed as shown in FIG. 7c, and the next strainer is press-fitted. Once all the strainers have been press-fitted, the press-fitting device K is removed and removed to the surface, completing all work on the radial well according to the present invention.

In the above embodiment, it is considered that a hard layer may be present before the case reaches the water-permeable layer.
The upper part of the casing was opened so that only the central part connected to the casing pipe C was open, and the other parts were completely closed. In order to increase the construction speed when the pipe is soft, an alternative embodiment is shown in which, as shown in Figs. A box body tube 37 with a diameter of 2 to 3 m is installed, and the two tubes are rigidly connected by a connecting plate 38 to achieve integration.
It is driven directly with a hammer in the same way as ordinary steel pipe piles. When the casing pipe reaches a predetermined depth while connecting the casing pipe, the earth and sand inside the casing pipe are removed from the ground surface using something like a bucket. When all the earth and sand inside the casing tube has been removed in this way, the space 39 between the casing tube and the casing tube is removed using a patch plate 40 at the lower end of the casing tube at the position shown by the dotted line in the same figure.
The upper part is closed by welding, and the bottom of the tube is closed with concrete or the like as in the previous embodiment. In this way, the internal water can be removed in the closed state, and then the strainer pipe can be press-fitted. In short, the advantage of this method is that the casing tube can easily reach the permeable layer through the driving process widely used in general civil engineering, and then only the soil that has entered the casing tube can be removed from the surrounding area. The method involves easy digging while protected from earth pressure by a casing pipe, but the ground strength must be relatively soft enough for driving with normal driving equipment.

In both of the above two embodiments, the lower part has a large casing part, and the upper part is a casing with a small diameter.
Even in places where the groundwater is quite high and the buoyancy is strong, the shell part is underground and acts as an anchor, so it will never float to the surface. In addition, even if the surrounding ground is a little soft and cannot function as an anchor strongly, the specific surface area of the casing pipe is relatively large and the volume of the internal space is small, so the frictional resistance against buoyancy is large. There is no need to worry about uplifting, which is the case with conventional well frame sinking methods.

However, if the groundwater level is very low and only slightly above the top of the permeable layer, there is no need to worry about buoyancy, so as shown in Figure 13,
1 may be the same as the diameter of the upper casing pipe 42; in fact, in such a case, there is no need to forcefully change the diameter. In such a case, the construction method is easy and does not require any special explanation.

As described above, this invention provides a lower casing having an inner diameter that allows the strainer tube to be press-fitted and extruded, and the upper casing tube has a smaller diameter than the casing in places where stability against buoyancy is a problem. The container is installed and sunk into the ground to a predetermined depth, and the upper and lower parts of the enclosure that contact the ground are closed and drained, and then a press-in device is used that can simultaneously press horizontally symmetrically in both directions into the enclosure. Then, the strainer pipes are connected and press-fitted, and once all the strainer pipes have been press-fitted up to a predetermined distance, the head of the strainer pipe is fixed and the whole work is completed. It has the advantage of being safe and far cheaper to install.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional radial well. FIG. 2 is a plan view of the strainer section. FIG. 3 is a process diagram of the conventional radial well construction method. FIG. 4 is a diagram showing an implementation process according to the present invention when the ground is relatively hard. FIG. 5 is a longitudinal sectional view of the completed installation. FIG. 6 is a partial vertical cross-sectional view showing how the strainer tube insertion hole in the housing wall is closed during driving. FIG. 7 is a longitudinal cross-sectional process diagram showing the situation when inserting and fixing the strainer into the insertion hole.
FIG. 8 is a longitudinal sectional view showing the structure near the tip of the strainer tube. FIG. 9 is a cross-sectional view taken along the line L to L and seen in the direction of the arrow. FIG. 10 is a plan view showing the structure of a simultaneous strainer press-in device. FIG. 11 is a vertical sectional view of another plan showing the structure of the enclosure used when the upper layer is on relatively soft ground. FIG. 12 is a horizontal sectional view taken along the line N to N in the direction of the arrow. FIG. 13 is a longitudinal sectional view showing the overall structure when the groundwater level is low. The codes and names of the main parts are: well frame...1, strainer pipe...2, first rod...3, drilling machine...
...4, Second rod...5, Water retaining layer...S, Bottom concrete...6, Hole...7, Full cross-section opening...
8. Body...V, Ground...G, Casing pipe...
C, 1st rod...9, Connection point...10, Drilling device...M, Slurry pump...11, Sludge drain pipe...
12, Water injection hole...13, Driving device...14, Cap...15, Gap...16, Bottom...17, Gravel filling...18, Strainer pipe...F, Lifting pump...19, Lifting pipe ...20, Impermeable layer...2
1, Permeable layer...22, Wall part...23, Screw...2
4, Blind screw...25, Through hole...P, Rubber packing...26, Butching...27, Fixing bushing...28, Cone...29, Strainer hole...30, Water suction pipe...31, 2 Strainer...F/F', Press-in device...K, Hydraulic cylinder...32, 32', Piston rod...3
3, 33', Pressing fitting...34, 34', Frame...
35, Casing tube...36, Cap tube...37,
Connecting plate...38, space part...39, patch plate...4
0, the housing part...41, the casing pipe...42, etc.

Claims (1)

[Claims] 1. Within 4 m in diameter with a strainer tube insertion hole.
A small diameter steel case of 1.5 m or more is placed at the bottom end, and when the upper layer of the ground is hard, digging and driving inside the case are used together, and when the upper layer is soft, driving is performed without both, and the driving progresses. By connecting a casing pipe with the same diameter or smaller than the above-mentioned case on the upper coaxial center, the case reaches a permeable layer of a predetermined depth, and after reaching the part where the ground is directly exposed when viewed from inside the case. This is an improved radial well construction method that is characterized by minimizing buoyancy by completely closing off the water, removing internal water, and press-fitting a strainer pipe. 2. In the case that has been completely submerged, strainer tubes are press-fitted simultaneously and in opposite directions into insertion holes that are symmetrical to the strainer tube insertion holes provided on the wall of the case. Press-in construction method described. 3. A small steel case with a diameter of 1.5 to 4.0 m with a strainer tube insertion hole previously provided, a casing pipe with a diameter of about 0.5 to 1.5 m rigidly connected on the upper coaxial center of the case, and the above case. It consists of a number of strainer tubes that are radially ejected from the center of the can in a closed state and whose heads are fixed to the can wall from the inside, minimizing buoyancy when internal water is removed. An improved radial well device characterized by: 4. Hydraulic or hydraulic cylinders arranged side by side in opposite directions, and a pressing device provided at the tip of the piston rod of the hydraulic or hydraulic cylinder;
Claim 3, characterized in that the device comprises a connecting device that integrally connects the two hydraulic devices installed together, and is capable of extruding the strainer pipe in a symmetrical direction at the same time. Press-fit device.