JPH0115752Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a structure for preventing backflow when removing a casing for inserting a strainer that has penetrated into the ground in a drainage construction method or the like.

<Prior art> (Figures 5 and 6) The following operations are performed as a drainage method for a compressed sand layer, etc.

First, a casing C with a disposable bit D attached to the tip is driven in, and the casing C is penetrated into the ground.

Next, the strainer B is inserted into the casing C.

Finally, only the outer casing C is removed, and the strainer B is left in the ground to drain water.

<Problems to be solved by the present invention> The above-mentioned drainage construction method has the following problems.

(1) There is no problem if the ground is hard, but if the ground is difficult to stand on its own, such as a sandy layer, and there is spring water, when removing the casing C, remove the casing C and the strainer from the opening at the tip of the casing C. B
Earth and sand enters into the space E between the circumferential surfaces.
(Fig. 5) The inflowing earth and sand becomes clogged between the casing C and the strainer B, and as a result, as the casing C is pulled out, the strainer B, which has reached the depths of the hole, is pulled out all at once. (Fig. 6) <Purpose of the present invention> The present invention was made to solve these problems, and even on ground that is difficult to stand on its own, it is possible to We have developed a backflow prevention structure in a double pipe, etc. consisting of a strainer and casing, which prevents the inflow of earth and sand, actively drains water, reduces the resistance to pulling out the casing, and allows the strainer to remain in the hole reliably. The purpose is to provide.

<Means for solving the problem> The present invention is a double pipe in which a strainer is inserted into the casing, and a ring-shaped pipe that allows only water to pass through the entire front inner peripheral surface of the casing with the front end open. Install a check valve.

The inner circumferential surface of the check valve is lightly pressed against the outer circumferential surface of the strainer to define a space between the inner circumferential surface and the outer circumferential surface of the strainer.

The present invention also relates to a technical means for solving the above-mentioned problem by blocking the front part of the casing with a check valve provided at the front part of the casing to prevent the inflow of earth and sand when only the casing is removed. be.

<Example> Next, an example of the present invention will be described with reference to the drawings.

(1) Double pipe (FIG. 1) The double pipe 1 used in the present invention is composed of a well-known example, such as a casing 2 and a strainer 3 inserted into the casing 2.

A collar 21 is provided to protrude in the circumferential direction on the inner circumferential surface of the front end of the casing 2 with both ends open.

The strainer 3 is, for example, a hollow tube for the purpose of draining water.

Furthermore, a disposable punching bit 4 is attached to the tip of the casing 2.

The drilling method is performed by, for example, independently imparting rotational motion and axial reciprocating motion to the casing 2.

In addition to the above-described combinations, any combination of pipes that has a double pipe structure in which two pipes are combined and that allows the inserted pipe to remain underground can of course be used.

(2) Non-return valve (FIGS. 1 and 2) The anti-return valve 5 is a water-permeable shielding material that is located at the opening at the tip of the casing 2 and closes the pipe space A with the outer periphery of the strainer 3.

For example, the check valve 5 includes a rubber ring 51,
It consists of a ring stopper 52 for holding and attaching the rubber ring 51 from both sides.

The rubber ring 51 has a through hole 53 having a diameter equal to or slightly smaller than the outer periphery of the strainer 3 in the center of a thin circular plate made of, for example, hard rubber.

In this ring-shaped plate, short notches 54 are formed radially from the through hole 53 in the circumferential direction.

The width of the notches 54 is set to an interval that allows water to pass through when the casing 2 is pulled out, but prevents earth and sand from entering.

In other words, theoretically, it is sufficient to set the width to be narrower than the average diameter of the excavated stone particles.

However, in reality, the amount of deflection of the rubber ring 51 varies greatly depending on the material of the rubber ring 51, its thickness, the length of the cut, the distance between adjacent cuts 54, and other factors.

Therefore, even if the width of the notch 54 is hardly visible in a stationary state, when the casing 2 is pulled out, the width of the notch 54 may be widened due to large bending, or vice versa.

For this reason, it is not possible to specify specific dimensions, but I would venture to say that the width should be set so that the width is no wider than the average diameter of the rock particles when the casing is pulled out.

Further, the diameter of the through hole 53 of the rubber ring 51 is such that the inner circumferential surface of the through hole 53 lightly presses against the outer circumferential surface of the strainer 3.

Furthermore, an attachment hole 55 is formed near the periphery of the ring-shaped plate body by penetrating the plate surface.

<How to use> Next, a method for preventing backflow using the double pipe described above will be explained.

(1) Installing the check valve Attach the rubber ring 51 to the front opening of the casing 2.
Insert the ring stopper 52 and fix it integrally to the collar 21 with bolts or the like.

(2) Drilling of a bore hole Next, a predetermined movement is given to the casing 2 having the drilling bit 4 to advance the drilling and to drill the bore hole B.

The cut rock particles are turned into slime and discharged by pumping water or the like from inside the casing 2 and using the space between the outer peripheral surface of the casing 2 and the hole wall as an ejection path.

At this time, since the tip of the casing 2 is closed by the perforation bit 4, sand does not enter into the pipe space A.

(3) Removal of the casing (Figures 1 and 4) After opening the bore hole B, insert the strainer 3 into the casing 2, then push the strainer 3 forward slightly with the punch bit 4, and close it with the punch bit 4. Open the front end of the casing 2 that had been closed.

Even if the front end of the casing 2 is opened, the pipe space A is closed by the check valve 5 provided inside the front part of the casing 2, so only the casing 2 is blocked from entering the outside earth and sand. can be removed easily.

That is, in the past, when the casing was pulled out, earth and sand often entered the space formed between the circumferential surfaces of the casing and the strainer and engaged with each other, resulting in the strainer being pulled out together with the casing.

However, in the structure of the present invention, the ground in the borehole B that collapsed due to the retreat of the casing 2 presses against the exposed outer circumferential surface of the strainer 3, and thus acts as resistance to the strainer 3 being pulled out. Further, spring water around the casing 2 passes through the rubber ring 51 and is actively discharged out of the hole.

When the spring water is discharged, the pressure of the spring water decreases, and as a result, the clamping force between the casing 2 and the earth is relaxed, and the frictional resistance between the rubber ring 51 and the strainer 3 is reduced.

In this way, the casing 2 can be extracted with a small extraction force while preventing earth and sand from entering into the pipe space A.

(4) Other Embodiment 1 It is also possible to employ a check valve 5a as shown in FIG. 3.

The non-return valve 5 of the above embodiment has a rubber ring 51.
In contrast, the backflow prevention valve 5a of this embodiment blocks the pipe space A with a group of needle bodies 56.

That is, the base end of a needle body 56 made of, for example, ultra-fat or metal is implanted inside the front part of the casing 2 to form the backflow prevention valve 5a.

Since this check valve 5a is made up of needle bodies 56, there is some space between the needle bodies 56.

The spacing of this space is also determined by the rubber ring 51 described above.
Similarly to the notch 54, the width is set to be narrower than the average particle diameter of the rock when the casing is pulled out.

Further, even if water enters through the check valve 5a, it will not have any adverse effect on the removal of the casing 2, and the removal work can be carried out smoothly.

Further, this check valve may be formed of a layered net, etc., as long as it is a member capable of preventing the intrusion of earth and sand.

(5) Other Embodiment 2 In addition to the embodiments described above, it is also possible to adopt a check valve structure as shown in FIG. 7.

In the above embodiment, the case where the check valve 5 is directly fixed to the casing 2 with bolts or the like has been described.

In this embodiment, a casing head 6, which is a short tube with both ends open and threaded at both ends, is interposed between the casing 2 and the punch bit 4.

It is also possible to provide steps with different wall thicknesses on the inner periphery of the casing head 6, and install the check valve 5 sandwiched therebetween.

<Embodiments of the present invention> Since the present invention is as described above, the following effects can be expected.

(1) A check valve is installed inside the front of the casing.

Therefore, when the strainer is inserted into the casing and only the casing is removed, the non-return valve reliably blocks the space generated between the circumferential surfaces of both pipes, thereby preventing the entry of external earth and sand.

(2) The outer surface of the strainer exposed by removing the casing is compacted by surrounding earth and sand.
This tightening force acts as pull-out resistance.

As a result, there is no need to worry about the strainer being removed from the casing as in the past.
The casing can be removed smoothly.

(3) Since the non-return valve has water permeability, spring water can be actively drained and the spring water pressure acting on the outer periphery of the casing can be alleviated.

Furthermore, due to the reduction in spring water pressure, the frictional resistance at the sliding portion between the check valve and the strainer is also reduced, so the force required to remove the casing can be reduced.

[Brief explanation of the drawing]

Figure 1...Explanatory diagram of one embodiment of the present invention, Figure 2...
An explanatory diagram of the check valve, Fig. 3... An explanatory diagram of other embodiments, Fig. 4... An explanatory diagram when the casing is removed, Figs. 5 and 6... An explanatory diagram of the conventional casing removal, Fig. 7... Explanatory diagrams of other embodiments.

Claims (1)

[Scope of Claim for Utility Model Registration] In a double pipe consisting of a strainer and a casing into which the strainer is inserted so as to be able to move in and out, the entire front inner circumferential surface of the casing with its front end open, and between it and the outer circumferential surface of the strainer. A ring-shaped check valve is installed to partition the space formed in the check valve, a gap narrower in width than the average diameter of the excavated particles is formed in the check valve, and the inner peripheral surface of the check valve is fitted with a strainer. A double-pipe backflow prevention structure consisting of a strainer and casing that is lightly pressed against the outer circumferential surface.