JP7244332B2 - Multi-stage pipe, multi-stage drainage pipe, construction method of multi-stage drainage pipe, and drainage structure of multi-stage drainage pipe - Google Patents

Description

The present invention provides a multistage pipe, a multistage drain pipe, and a multistage pipe that includes a plurality of tubular bodies having different diameters, and the outer tube having the largest diameter among the plurality of tubular bodies can accommodate the other tubular bodies. The present invention relates to a construction method of a multi-stage drainage pipe and a drainage structure of a multi-stage drainage pipe.

2. Description of the Related Art Conventionally, a multistage pipe is known which has a plurality of tubular bodies with different diameters and in which an outer tube having the largest diameter among the plurality of tubular bodies can accommodate other tubular bodies. Such multi-tiered pipes are used as ground reinforcement piles, as well as in a wide variety of other applications such as soil improvement, liquefaction countermeasures, landslide countermeasures, and groundwater drainage.

For example, in Patent Document 1, a pre-boring hole is formed by excavating the ground in advance, a multi-stage pipe that is contractably combined from a plurality of water-permeable pipe bodies is inserted into the pre-boring hole, and the surroundings are covered with soil. A ground improvement method for forming a drainage pipe by backfilling with is described (see the claims of Patent Document 1, FIGS. 1 to 3 of the drawings, etc.).

However, the multi-stage drainage pipe described in Patent Document 1 is such that rubber foam or cloth is wrapped around the inner pipe peripheral side of the connecting portion of the pipe bodies so that the drain pipe can contract according to the load. rice field. For this reason, the multi-stage drainage pipe described in Patent Document 1 cannot resist the compressive force when the compressive force acts in the direction of compressing the tubular bodies along the pipe axis direction, and the ground subsides. or when a load is applied to the tubular body, the multi-stage pipe shrinks unexpectedly and unnecessarily.

Further, in Patent Document 2, a telescopic hollow pile 1 composed of an inner pipe 1a, a middle pipe 1b, and an outer pipe 1c is installed in a piled state at a foundation pile erection position, and a granular material such as sand is used with a rammer 5. 4, the inner pipe 1a having a smaller diameter is driven into the ground in order, and concrete is placed inside the pipe to create a foundation pile (claim 1 of the scope of claim of Patent Document 2, drawing (See Fig. 1, etc.).

However, in the telescopic hollow pile 1 of Patent Document 2, an outward flange is formed at the upper end of each pipe and an inward flange is formed at the lower end. The structure is such that the piles extend. For this reason, when concrete is not placed, similar to the multi-stage drainage pipe of Patent Document 1, when a compressive force acts in the direction of compressing the pipe bodies along the pipe axis direction, the compressive force It was not something that could be competed (see paragraph [0018] of the specification of Patent Document 2, FIG. 1 of the drawings, etc.).

JP-A-52-132510 JP-A-11-256625

SUMMARY OF THE INVENTION Accordingly, the present invention has been devised in view of the above-mentioned problems, and its object is to provide a multi-stage pipe, a multi-stage drainage pipe, and a multi-stage drainage pipe that can withstand compression force. The object is to provide a construction method and a drainage structure for a multistage drainage pipe.

A multi-stage pipe according to a first aspect of the present invention is a multi-stage pipe that includes a plurality of tubular bodies having different diameters, and an outer tube having the largest diameter among the plurality of tubular bodies can accommodate the other tubular bodies. A locking mechanism is provided between the plurality of tubular bodies for locking the tubular bodies against a compressive force acting in a direction of contracting and compressing the tubular bodies when stretched. The locking mechanism is formed by fitting a locking projection formed on one of the outer tubular body and the inner tubular body with a locking hole formed on the other. It is characterized by being a mechanism for locking each other .

A multi-stage pipe according to a second invention is characterized in that, in the first invention, the plurality of tubular bodies consist of three or more tubular bodies.

A multi-stage drainage pipe according to a third aspect of the present invention comprises a plurality of pipe bodies having different pipe diameters, and a multi-stage pipe in which other pipe bodies can be accommodated in an outer pipe having the largest diameter among the plurality of pipe bodies. A locking mechanism is provided between the plurality of tubular bodies for locking the tubular bodies against a compressive force acting in a direction of contracting and compressing the tubular bodies when stretched. A drainage hole for draining groundwater is formed in a part of the plurality of tubular bodies.

A multistage drain pipe according to a fourth invention is characterized in that, in the third invention, at least the drain holes are not formed in the outer tube.
A multi-stage drain pipe according to a fifth aspect of the invention is the third aspect of the invention or the fourth aspect of the invention, wherein the locking mechanism is such that the locking claw formed on the inner tubular body and the lower end surface of the outer tubular body It is characterized by being a mechanism that locks the tubular bodies to each other by abutting each other.
A multi-stage pipe according to a sixth aspect of the invention is the third aspect of the invention or the fourth aspect of the invention, wherein the locking mechanism comprises a projection formed on one of the outer tubular body and the inner tubular body, and a It is characterized in that it is a mechanism that engages the tubular bodies with each other by fitting the formed recesses.
A multistage pipe according to a seventh invention is the multistage pipe according to the third invention or the fourth invention, wherein the locking mechanism is such that projections formed on the outer tubular body and the inner tubular body abut and engage with each other. Thus, it is characterized by a mechanism for locking the tubular bodies to each other.
A multi-stage drain pipe according to an eighth invention is characterized in that, in the third invention or the fourth invention, the plurality of tubular bodies consist of three or more tubular bodies.

A multistage drainage pipe construction method according to a ninth aspect of the present invention is a multistage drainage pipe construction method in which the multistage drainage pipe according to claim 3 or 4 is pushed into the ground in the axial direction of the pipe and penetrates, It is characterized by penetrating into the ground with other tubular bodies housed in the pipe.

A method for constructing a multi-stage drainage pipe according to a tenth aspect of the invention is characterized in that, in the ninth aspect of the invention, the pipes are penetrated into the ground in order from the pipe having the largest pipe diameter.

A multi-stage drainage pipe drainage structure according to an eleventh aspect of the present invention is a multi-stage drainage pipe structure in which the multi-stage drainage pipe according to claim 3 or 4 is penetrated into the ground and drains water from the surrounding ground to the inside of the tubular body. In the structure, the inner pipe having the smallest diameter among the plurality of pipe bodies penetrates to a level below the groundwater level in the surrounding ground, and collects groundwater inside the inner pipe from the drain hole. It is characterized by reducing the excessive pore water pressure of the ground.

According to the first invention and the second invention, even if a compressive force acts in the direction in which the tubular bodies are contracted and stored, it can be opposed, and when the ground subsides or a load acts on the tubular bodies However, the multistage pipe can be prevented from shrinking unnecessarily. Therefore, according to the first and second inventions, the multi-stage pipe can be used as a countermeasure against soil improvement and liquefaction, and the multi-stage pipe can be used for various purposes.

In particular, according to the fifth invention, it is sufficient to form the locking claws on the inner tubular body in order to provide the locking mechanism. Therefore, the manufacturing cost of the multistage drain pipe can be reduced.

In particular, according to the fifth invention, even if force acts not only in the compression direction of the multi-stage drainage pipe but also in the pull-out direction, it can be used as a pile that requires pull-out resistance such as a ground reinforcement pile. This allows multistage pipes to be used in a wider variety of applications.

In particular, according to the second and eighth inventions , the multi-stage pipe or multi-stage drainage pipe can be penetrated deeper into the ground even in a place where there is a headspace limit, and furthermore, the multi-stage pipe or multi-stage drainage pipe can be penetrated. Applications can be expanded. Therefore, according to the second and eighth inventions , the multi-stage pipe or the multi-stage drainage pipe can be used as a drainage pipe or the like even in areas where soft ground is thickly deposited.

According to the third invention and the fourth invention, since the drain hole for draining groundwater is formed in the pipe, the multistage pipe can be used as a drain pipe. In addition, according to the third and fourth inventions, since the drainage pipe is multi-staged, the time to vibrate the drainage pipe at the time of penetration is shorter than that of a single drainage pipe with the same overall length. Therefore, it is possible to further reduce the amount of earth and sand that flows in through the drainage holes and the like during penetration.

In particular, according to the fourth invention, since the outer tube is not formed with drainage holes, the torsional resistance of the outer tube is high, and the penetration resistance is maximized due to the large diameter and the high peripheral friction resistance. It is possible to reduce the risk of twisting even if press-fitting while rotating at the time of insertion. Therefore, the thickness of the outer tube can be reduced, and the product cost can be reduced. Moreover, according to the fourth invention, it is possible to reduce the amount of groundwater and earth and sand that flow into the tubular body when the outer pipe is penetrated, and it is possible to easily construct the drainage pipe in a short period of time.

According to the ninth and tenth inventions, when penetrating the outer pipe with the highest penetration resistance, it is possible to penetrate into the ground while another tubular body is accommodated in the outer pipe. For this reason, it is possible to reduce the plate thickness of each pipe such as the outer pipe, and reduce the penetration resistance by reducing the peripheral friction of the drainage pipe with the ground at the time of penetration, and the penetration work of the drainage pipe with small force. It can be performed.

In particular, according to the tenth invention, the penetration depth of the drainage pipe can be divided into a swinging type (multi-stage type) to the desired ground depth, and peripheral friction is generated only in the pipes that are pushed out sequentially. Penetration resistance can be reduced as a whole. For this reason, it is possible to further reduce the plate thickness of each pipe body, reduce the penetration resistance by reducing the peripheral surface friction of the drainage pipe with the ground at the time of penetration, and perform the penetration work of the drainage pipe with a small force. can be done. For this reason, it is possible to carry out construction with a hydraulic pile driver or a small excavator on hand, and it is possible to reduce the construction cost of the drainage pipe by eliminating the transportation and assembly costs of the dedicated machine.

According to the eleventh invention, since groundwater is collected inside the inner pipe from the drain hole to reduce excessive pore water pressure in the ground, it can be suitably used as a drainage structure against liquefaction. In addition, since the drain pipe is provided with a locking mechanism, even when the ground subsides or a load is applied to the pipe body, the multistage drain pipe can be prevented from shrinking unnecessarily. can be done.

1 is a side view showing a multi-stage drainage pipe according to a first embodiment of the present invention with the middle omitted; FIG. Fig. 4 is a cross-sectional view taken along the pipe axis direction, showing a state in which the multi-stage drain pipe is accommodated; Fig. 3 is a partial cross-sectional view showing a locking mechanism between an outer pipe and an inner pipe of the same multi-stage drainage pipe, showing the outer pipe in cross section and the inner pipe in side view; Fig. 3 is a partially enlarged cross-sectional view showing a state in which the tip portion of the same multistage drain pipe is cut along the pipe axis direction; FIG. 11 is a partial cross-sectional view showing a first modification of a locking mechanism between the outer tube and the inner tube of the multistage drainage pipe; It is a fragmentary sectional view which shows the 2nd modification of a locking mechanism same as the above. It is a fragmentary sectional view which shows the 3rd modification of a locking mechanism same as the above. It is a fragmentary sectional view which shows the 4th modification of a locking mechanism same as the above. It is a partial cross-sectional view which shows the 5th modification of a locking mechanism same as the above. FIG. 4 is a process explanatory diagram showing a first penetration process of the construction method of the multi-stage drainage pipe according to the embodiment of the present invention; It is process explanatory drawing which shows the 2nd intrusion process of the construction method of a multistage drainage pipe same as the above. FIG. 5 is a view showing a ground drainage structure in which a multistage drainage pipe penetrates into soft ground according to the second embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION A multi-stage drainage pipe, a drainage structure for a multi-stage drainage pipe, and a construction method for a multi-stage drainage pipe according to embodiments of the present invention will now be described in detail with reference to the drawings.

<Multistage drainage pipe>
[First embodiment]
First, a multistage drain pipe 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. The multistage drainage pipe 1 according to the embodiment of the present invention is assumed to be used as a drainage pipe for countermeasures against liquefaction by penetrating into the ground having strata that may liquefy. FIG. 1 is a side view showing a multi-stage drainage pipe 1 according to an embodiment of the present invention with the middle omitted, and FIG. 2 is a cut along the pipe axis direction showing the storage state of the multi-stage drainage pipe 1. It is a sectional view. FIG. 3 is a partially cut cross-sectional view showing the locking mechanism 6 between the outer pipe 2 and the inner pipe 3 of the multi-stage drain pipe 1, showing the outer pipe 2 in cross section and the inner pipe 3 in side view. FIG. 4 is a partially enlarged cross-sectional view showing a state in which the tip portion of the multi-stage drain pipe 1 is cut along the pipe axis direction.

The multi-stage drain pipe 1 according to this embodiment is a highly corrosion-resistant plated steel pipe with a predetermined thickness, and has two large and small pipe bodies with different pipe diameters of a predetermined length according to the depth of the ground to be penetrated. However, the drainage pipe according to the present invention is provided with a plurality of tubular bodies having different diameters, and the outer tube having the largest diameter among the plurality of tubular bodies can accommodate the other tubular bodies. It is not limited to the one consisting of two large and small tubular bodies.

As shown in FIGS. 1 and 2, this multi-stage drainage pipe 1 has an outer tube 2 having a large diameter and an inner tube 3 having a small diameter. A convex end cap 4 is fitted to the end of the inner tube 3 (see also FIG. 4). Note that the front end refers to the tube end on the penetration direction X side of the tube body shown in FIG. 1, and the rear end refers to the tube end on the opposite side (the same applies hereinafter).

Between the outer tube 2 and the inner tube 3, the compression force acting in the direction of contracting and compressing the outer tube 2 and the inner tube 3 when the both are extended is provided, so that the outer tube 2 and the inner tube 3 are in contact with each other. A locking mechanism 6 is provided for locking the tubular bodies together so that the foreign matter does not enter.

(outer tube)
As shown in FIGS. 1 and 2, the outer tube 2 is mainly composed of a cylindrical outer tube body 20 made of steel. The outer pipe main body 20 is a straight straight pipe whose diameter is substantially the same from the front end portion 21 to the rear end portion 22, and is a non-porous pipe in which no drainage hole H1 is formed. .

(inner tube)
The inner tube 3 is mainly composed of an inner tube main body 30 made of a cylindrical steel tube having an outer diameter smaller than the inner diameter of the outer tube 2 . In the vicinity of the tube end on the tip side of the inner tube main body 30, a tip portion 31 having a smaller diameter than the other portion is formed. It has a straight tubular body.

Further, as shown in FIG. 1, the outer peripheral surface of the inner pipe main body 30 is provided with a large number of drainage holes H1 having a predetermined diameter (for example, 5 mm in diameter) through which groundwater and excess pore water pass, at a predetermined pitch (for example, 10 mm). perforated. Therefore, when the multi-stage drainage pipe 1 penetrates into a stratum that may be liquefied, it can collect groundwater inside the inner pipe 3 through the drainage hole H1 and drain it, thereby reducing excess pore water pressure. You can escape from the ground. Drainage refers to passing groundwater or the like in the ground to the inside of the inner pipe 3, and does not necessarily refer to pumping up from the multi-stage drainage pipe 1 to the ground surface.

As mentioned above, the inner tube 3 has an outer diameter smaller than the inner diameter of the outer tube 2 . Therefore, as shown in FIG. 2, the inner tube 3, which is another tubular body, can be accommodated in the outer tube 2. As shown in FIG. Therefore, the inner tube 3 can be transported in a state in which the outer tube 2 is accommodated, and the transport efficiency is good.

(tip cap)
As shown in FIG. 4, a conical end cap 4 is fitted to the end portion 31 of the inner pipe 3 in order to reduce earth pressure resistance when the multi-stage drain pipe 1 penetrates. This tip cap 4 is made of polypropylene. Of course, the material of the end cap 4 is not particularly limited as long as it has a shape with little resistance, and is not limited to resin such as polypropylene, and may be made of metal such as ductile cast iron.

(locking mechanism)
Next, the locking mechanism 6 according to the first embodiment of the present invention will be described using FIG. As shown in FIG. 3, at the rear end portion 32 of the inner tube 3, a plurality of triangular wedge-shaped locking claws 33 made of metal, which are thin on the tip end side and thick on the rear end side, are elastic. They are formed to project radially from the surface of the cylindrical body at a constant pitch. The locking claw 33 and the end face (lower end face) of the tip portion 21 of the outer tube 2 contact to form the locking mechanism 6 that locks the outer tube 2 and the inner tube 3 against the compressive force. Configure.

The locking claw 33 may be formed by deforming the same material as the steel pipe of the inner pipe main body 30, or may be retrofitted from a different material mechanically by screwing or the like, or by welding or the like. . Also, the shape of the locking claw 33 is not limited to a triangular wedge shape, and a structure in which a plate spring or the like is attached may be employed. In short, the locking claw 33 may be any projection that can be locked to the end face of the distal end portion 21 of the outer tube 2 .

According to the locking mechanism 6 described above, the locking mechanism can be configured simply by forming the locking claws 33 on the inner tube 3 which is the inner tubular body. Therefore, the manufacturing cost of the multistage drainage pipe 1 can be reduced.

Next, a locking mechanism 7, which is a first modified example of the locking mechanism described above, will be described with reference to FIG. FIG. 5 is a partial cross-sectional view taken along the pipe axis direction showing a locking mechanism 7 according to a first modified example of the multistage drain pipe 1. As shown in FIG. As shown in FIG. 5, the locking mechanism 7 includes a concave portion 23 formed in the inner peripheral surface of the outer tube 2 along the circumferential direction, and a concave portion 23 formed in the outer peripheral surface of the inner tube 3 along the circumferential direction. and a convex portion 34 . The locking mechanism 7 has a function of restraining the relative movement between the outer tube 2 and the inner tube 3 by fitting the protrusions 34 into the recesses 23 .

It should be noted that neither the concave portion 23 nor the convex portion 34 need to be provided over the entire circumference in the circumferential direction, and may be provided at regular intervals.

According to the locking mechanism 7 described above, unlike the locking mechanism 6, it is possible to counter even if force acts not only in the direction of compression of the multi-stage drain pipe 1 but also in the direction of pulling it out, and the ground reinforcement pile It can also be used as a pile that requires pull-out resistance such as. Therefore, the multistage drainage pipe 1 can be used for various purposes.

Next, a locking mechanism 8, which is a second modified example of the locking mechanism described above, will be described with reference to FIG. FIG. 6 is a partial cross-sectional view taken along the pipe axis direction showing a locking mechanism 8 according to a second modification of the multi-stage drain pipe 1. As shown in FIG. As shown in FIG. 6, the locking mechanism 8 includes a protrusion 24 formed on the inner peripheral surface of the outer tube 2 along the circumferential direction, and a protrusion 24 formed on the outer peripheral surface of the inner tube 3 along the circumferential direction. and a concave portion 35 . The locking mechanism 8 has a function of restraining the relative movement between the outer tube 2 and the inner tube 3 by fitting the protrusions 24 into the recesses 35 .

It should be noted that neither the convex portion 24 nor the concave portion 35 need to be provided over the entire circumference in the circumferential direction, and may be provided at regular intervals.

According to the locking mechanism 8 described above, as with the locking mechanism 7, it is possible to resist even if a force acts not only in the compression direction of the multi-stage drainage pipe 1 but also in the extraction direction, and the ground reinforcement pile or the like can be opposed. It can also be used as a pile that requires a pull-out resistance of Therefore, the multistage drainage pipe 1 can be used for various purposes.

Next, a locking mechanism 9, which is a third modified example of the locking mechanism described above, will be described with reference to FIG. FIG. 7 is a partial cross-sectional view taken along the pipe axis direction showing a locking mechanism 9 according to a third modified example of the multi-stage drain pipe 1. As shown in FIG. As shown in FIG. 7, the locking mechanism 9 includes a rib-like convex portion 25 having a rectangular cross section formed along the circumferential direction on the inner peripheral surface of the outer tube 2 and a circumferential and triangular wedge-shaped locking claws 36 which are projections formed at predetermined intervals along the direction. Therefore, the locking mechanism 9 has a function of resisting compressive force compressing the outer tube 2 and the inner tube 3 in the axial direction by contacting the locking claw 36 with the convex portion 25 .

The projections 25 are also provided only at positions corresponding to the locking claws 36, and need not be provided over the entire circumferential direction. Conversely, the locking claw 36 may be formed in a triangular rib shape along the entire circumference.

Like the locking mechanism 6, the locking mechanism 9 described above cannot withstand the stress acting in the pull-out direction. However, it is also possible to adopt a mechanism in which the protrusions 25 are provided in duplicate and the locking claws 36 are sandwiched between them for locking.

Next, a locking mechanism 10, which is a fourth modified example of the locking mechanism described above, will be described with reference to FIG. FIG. 8 is a partial cross-sectional view taken along the pipe axis direction showing a locking mechanism 10 according to a fourth modification of the multistage drain pipe 1. As shown in FIG. As shown in FIG. 8, the locking mechanism 10 is composed of locking holes 26 formed in the inner peripheral surface of the outer tube 2 and locking projections 37 formed in the outer peripheral surface of the inner tube 3. ing. The locking mechanism 10 has a function of restraining the relative movement between the outer tube 2 and the inner tube 3 by fitting the locking protrusions 37 into the locking holes 26 . Note that the locking hole 26 and the locking projection 37 are both provided at regular intervals.

According to the locking mechanism 10 described above, as with the locking mechanisms 7 and 8, even if a force acts not only in the compression direction of the multi-stage drain pipe 1 but also in the extraction direction, it can resist the force, thereby reinforcing the ground. It can also be used as a pile that requires pull-out resistance, such as a pile. Therefore, the multistage drainage pipe 1 can be used for various purposes.

Next, a locking mechanism 11, which is a fifth modified example of the locking mechanism described above, will be described with reference to FIG. FIG. 9 is a partial cross-sectional view taken along the pipe axis direction showing a locking mechanism 11 according to a fifth modification of the multistage drain pipe 1. As shown in FIG. As shown in FIG. 9, the locking mechanism 11 has a locking hole 27 formed on the inner peripheral surface of the outer tube 2 and the aforementioned locking claw 36 formed on the outer peripheral surface of the inner tube 3, which are turned upside down. and a locking claw 38 that The locking mechanism 11 has a function of restraining relative movement between the outer tube 2 and the inner tube 3 by fitting the locking claws 38 into the locking holes 27 . The locking holes 27 and the locking claws 38 are both provided at regular intervals.

According to the locking mechanism 11 described above, as with the locking mechanisms 7, 8, and 10, even if a force acts not only in the compression direction of the multi-stage drain pipe 1 but also in the pull-out direction, it can resist it. It can also be used as a pile that requires pull-out resistance, such as a ground reinforcement pile. In addition, in the locking mechanism 11, the locking claw 38 becomes thinner as it goes upwards and the lower end is flat against the compressive force. It is higher than the stopping mechanism.

<Construction method for multistage drainage pipe>
Next, a method for constructing a multistage drain pipe according to an embodiment of the present invention will be described with reference to FIGS. 10 and 11. FIG. A case where the multi-stage drainage pipe 1 described above is penetrated into the ground G having a stratum G1 that is likely to liquefy deep underground and a ground drainage structure 12 is constructed as a countermeasure against liquefaction will be described as an example.

(First penetration process)
FIG. 10 is a process explanatory view showing the first penetration process of the construction method of the multistage drainage pipe according to the embodiment of the present invention. In the construction method of the multi-stage drainage pipe according to the present embodiment, as shown in FIG. 10, first, a first penetration step is performed in which the multi-stage drainage pipe 1 is directly penetrated into the ground without pre-boring.

Specifically, using a 0.2 m ³ class small heavy machine with a breaker attached to the tip of a hydraulic excavator or a hand-held pile driver, while applying vibration, the multistage drainage pipe 1 is pushed down to the ground. penetrate into. At this time, the inner pipe 3 is housed in the outer pipe 2, and the tip cap 4 is fitted to the tip of the inner pipe 3, and the multistage drain pipe 1 is penetrated into the ground.

In this step, the inner pipe 3 is penetrated into the ground while being accommodated in the outer pipe 2 . At this time, the penetration resistance when the multi-stage drainage pipe 1 is penetrated into the ground is only the press-fit resistance of the tip acting through the tip cap 4 and the circumferential frictional resistance of the outer pipe 2 with the ground. Therefore, as compared with the conventional construction method, the peripheral surface frictional resistance is applied to only about half of the total length of the multistage drain pipe 1 . Therefore, the peripheral surface friction of the multi-stage drainage pipe 1 with the ground during penetration is reduced, the penetration resistance is reduced, and the drainage pipe can be penetrated with a small force.

In addition, in this step, as shown in FIG. 10, the tip cap 4 is attached to the tip of the multi-stage drain pipe 1, so that the tip cap 4 is convex to reduce the penetration resistance. can do.

In the multi-stage drain pipe 1 described above, the length of the outer pipe 2 is set according to the depth of the stratum G1 that is likely to liquefy, and the outer pipe 2 shown in FIG. 10 is provided with a drain hole H1. Although not shown, a number of drain holes H1 may be provided.

However, by making the outer tube 2 a non-porous tube, the torsion resistance of the outer tube 2 is increased, and since the diameter is large and the frictional resistance of the peripheral surface is high, the penetration resistance is maximized. It is possible to reduce the risk of twisting. Therefore, the thickness of the outer tube 2 can be reduced, and the product cost can be reduced. In addition, if the outer pipe 2 is a non-porous pipe, it is possible to reduce the amount of groundwater and sand that flow into the pipe body when the outer pipe 2 penetrates, and the construction of the multistage drain pipe 1 can be easily performed in a short time. can.

(Second penetration process)
Next, in the construction method of the multi-stage drainage pipe according to the present embodiment, as shown in FIG. 11, a second penetration step is performed in which the inner pipe 3 is further penetrated into the ground from the outer pipe 2 penetrated in the previous step. .

In this process as well, a small heavy machine or a hand-held pile driver is used to push down the inner pipe 3 of the multistage drainage pipe 1 while applying vibrations to penetrate the ground.

Completion of this step completes the construction of the ground drainage structure according to the first embodiment of the present invention. As a result, the inner pipe 3 can be penetrated into the stratum G1 that is likely to liquefy, and groundwater flows into the inner pipe 3 from the stratum G1 that is likely to be liquefied through the drain hole H1 of the inner pipe 3. can be made Therefore, it is possible to reduce and dissipate the excess pore water pressure in the stratum G1, which is likely to liquefy, and to take measures against liquefaction.

<Ground drainage structure>
Next, with reference to FIG. 11, the ground drainage structure 12 constructed by the construction method of the multi-stage drainage pipe according to the present embodiment described above will be briefly described. The ground drainage structure 12 is a drainage structure for the ground G that is located below the groundwater level and has a stratum G1 that is likely to liquefy deep underground. A multi-stage drainage pipe 1 is driven into the ground G and drains from the ground G to the inside of the multi-stage drainage pipe 1. - 特許庁Here, the term "drainage" refers to the passage of groundwater or the like in the ground G to the inside of the inner pipe 3, as described above, and does not necessarily refer to pumping up from the multi-stage drainage pipe 1 to the ground surface. do not have. However, it goes without saying that the ground drainage structure 12 may have a structure that pumps up the groundwater accumulated in the multi-stage drainage pipe 1 to the ground surface.

Further, in the ground drainage structure 12, as described above, the inner pipe 3 penetrates to the stratum G1, which is likely to liquefy, and allows groundwater to flow into the inner pipe 3 to release excess pore water pressure. is. Therefore, the liquefaction countermeasure work becomes durable, and the stratum G1, which is likely to liquefy, can be maintained as sound ground capable of supporting structures without liquefying over a long period of time.

[Second embodiment]
Next, a multi-stage drain pipe 1' according to a second embodiment of the present invention will be described with reference to FIG. FIG. 12 is a view showing a ground drainage structure in which a multistage drainage pipe 1' according to the second embodiment of the present invention penetrates to a stratum (soft stratum) G1 that may be liquefied. The main difference between the multi-stage drainage pipe 1' according to the second embodiment and the multi-stage drainage pipe 1 described above is that, in addition to the outer tube 2 and the inner tube 3, the tube diameter is exactly intermediate between these tube bodies. The point is that it has a certain middle tube 13 . In other respects, the configuration is substantially the same as that of the multi-stage drainage pipe 1 .

As shown in FIG. 12, the middle pipe 13 is a straight tubular body having substantially the same pipe diameter from the front end to the rear end like the outer pipe 2, and is also formed with a drainage hole H1. It is a non-perforated pipe.

Further, between the outer tube 2 and the intermediate tube 13 and between the intermediate tube 13 and the inner tube 3, the locking mechanism 6 described above is provided. Therefore, it is possible to resist the compressive force acting on the multistage drain pipe 1'. Needless to say, any one of the locking mechanisms 6 to 11 may be provided between the tubular bodies.

In addition, the multi-stage drainage pipe 1 ′ penetrates into the ground G in a state where the other pipes (the middle pipe 13 and the inner pipe 3) are accommodated in the outer pipe 2, and the outer pipe 2, the middle pipe The pipe 13 and the inner pipe 3 are penetrated into the ground G in order. Therefore, it is possible to reduce the penetration resistance by reducing the circumferential friction of the multistage drainage pipe 1' with the ground G at the time of penetration, and to carry out the penetration work with a small force.

However, as in Patent Document 2, the multi-stage drainage pipe 1 ′ is penetrated into the ground G in order from the inner pipe 3, the middle pipe 13, and the outer pipe 2 with a small pipe diameter using some kind of jig. It is also possible to continue However, when penetrating into the ground G sequentially from the small pipe diameter, when the outer pipe 2 penetrates into the ground G, the peripheral friction of the entire peripheral surface of the multistage drainage pipe 1 ′ acts as penetration resistance. Since it acts, it is disadvantageous in terms of construction.

According to this multi-stage drainage pipe 1 ′, it is possible to penetrate the ground G while the multi-stage drainage pipe 1 ′, which is finally lengthened, is accommodated in the outer pipe 2 . Therefore, the multi-stage drainage pipe 1' can be penetrated deep into the ground even in a place where there is a headspace restriction such as the ground under a bridge or overhead wires. Therefore, even if there is a stratum G1 that is likely to liquefy deep underground in the ground G, the inner pipe 3, which is a perforated pipe, is penetrated to that depth, and the multistage drainage pipe 1' is installed as a countermeasure against liquefaction. Can be used as a pipe.

According to the multistage drainage pipes 1, 1', the construction method of the multistage drainage pipe 1, and the ground drainage structure 12 according to the present embodiment described above, the penetration depth of the multistage drainage pipe 1 is set to the first penetration step. And like the second penetration step, it can be penetrated by dividing it into multiple stages in a swing-out type (multi-stage type). Therefore, the peripheral surface friction of the multi-stage drainage pipe 1 with the ground G during penetration is reduced, the penetration resistance is reduced, and the penetration work can be performed with a small force. For this reason, as described above, it is possible to carry out construction with a hydraulic pile driver or a small excavator on hand, and it is possible to reduce the construction cost of the drainage pipe by eliminating the transportation and assembly costs of the dedicated machine.

Further, according to the multistage drainage pipes 1, 1', the construction method of the multistage drainage pipe 1, and the ground drainage structure 12 according to the present embodiment, any one of the locking mechanisms 6 to 11 is provided, Even if a compressive force acts in the direction in which the tubular bodies are contracted and accommodated, it can be opposed. Therefore, even when the ground subsides or a load acts on the tubular body, it is possible to prevent the multistage drain pipe 1 from shrinking unnecessarily. Therefore, the multi-stage drainage pipe 1 can be used as a ground improvement countermeasure or a liquefaction countermeasure, and the multi-stage drainage pipe 1 can be used for various purposes.

In addition, according to the multistage drainage pipes 1, 1', the construction method of the multistage drainage pipe 1, and the ground drainage structure 12 according to the present embodiment, the multistage drainage pipes 1, 1' vibrate during penetration. The time to apply is shorter than that of a normal single drainage pipe. Therefore, it is possible to further reduce the amount of earth and sand that flows in from the drain hole H1 of the multi-stage drain pipe 1 and the like at the time of penetration.

Also, the multi-stage drainage pipes 1, 1' can be transported in a compact state in which the inner pipe 3 is housed in the outer pipe 2 (see FIG. 2). Therefore, the transportation efficiency is good, and in this respect as well, the construction cost of the multi-stage drainage pipes 1, 1' can be reduced.

The multistage drainage pipes 1, 1', the construction method of the multistage drainage pipe 1, and the ground drainage structure 12 according to the embodiments have been described in detail above. It is merely a representation of one specific embodiment for implementation. Therefore, the technical scope of the present invention should not be construed to be limited by the illustrated embodiments.

1, 1': Multi-stage drainage pipe (multi-stage pipe)
2: Outer tube (tubular body)
20: Outer tube main body 21: Tip part 22: Rear end part 23: Concave parts 24, 25: Convex parts 26, 27: Locking hole 3: Inner tube (tubular body)
30: inner pipe main body 31: tip portion 32: rear end portions 33, 38: locking claw 34: convex portion 35: concave portion 36: locking claw 37: engaging convex portion H1: drain hole 4: tip caps 7-11 : Locking mechanism 12: Ground drainage structure (drainage pipe drainage structure)
13: Middle pipe (pipe body)
G: Ground G1: Stratum with risk of liquefaction (stratum below the groundwater level)
X: Penetration direction

Claims (11)

A multistage pipe comprising a plurality of tubular bodies with different diameters, wherein the outer tube having the largest diameter among the plurality of tubular bodies can accommodate other tubular bodies,
A locking mechanism is provided between the plurality of tubular bodies for locking the tubular bodies against a compressive force acting in a direction of contracting and compressing the tubular bodies when the tubular bodies are stretched. ,
In the locking mechanism, the tubular bodies are engaged with each other by fitting a locking projection formed in one of the outer tubular body and the inner tubular body into a locking hole formed in the other. A multi-stage pipe characterized by a mechanism for stopping . 2. The multistage pipe of claim 1 , wherein said plurality of tubes comprises three or more tubes. A multistage pipe comprising a plurality of tubular bodies with different diameters, wherein the outer tube having the largest diameter among the plurality of tubular bodies can accommodate other tubular bodies,
A locking mechanism is provided between the plurality of tubular bodies for locking the tubular bodies against a compressive force acting in a direction of contracting and compressing the tubular bodies when stretched,
A multistage drainage pipe, wherein a part of the plurality of tubular bodies is formed with a drainage hole for draining groundwater inside the pipe. 4. The multistage drain pipe according to claim 3 , wherein at least the drain holes are not formed in the outer pipe. 3. The locking mechanism is a mechanism for locking the tubular bodies to each other by contact between a locking pawl formed on the inner tubular body and a lower end surface of the outer tubular body. 4. Multi-stage drainage pipe according to 3 or 4 . The locking mechanism is a mechanism for locking the tubular bodies to each other by fitting a projection formed on one of the outer tubular body and the inner tubular body with a recessed part formed on the other. 5. A multistage pipe according to claim 3 or 4, characterized in that 3. The locking mechanism is a mechanism for locking the tubular bodies to each other by abutting and engaging projections formed on the outer tubular body and the inner tubular body. Or the multi-stage drainage pipe according to 4. 8. The multi-stage drain pipe according to any one of claims 3 to 7 , wherein the plurality of tubular bodies consist of three or more tubular bodies. A method for constructing a multi-stage drainage pipe, wherein the multi-stage drainage pipe according to claim 3 or 4 is pushed into the ground in the axial direction of the pipe and penetrates,
A method for constructing a multi-stage drainage pipe, characterized in that the outer pipe contains another pipe body and penetrates into the ground. 10. The construction method of the multi-stage drainage pipe according to claim 9 , wherein the pipe body is penetrated into the ground in order from the pipe body having a large pipe diameter. 5. A multi-stage drainage pipe drainage structure in which the multi-stage drainage pipe according to claim 3 or 4 is penetrated into the ground and drains from the surrounding ground to the inside of the tubular body,
The inner pipe with the smallest diameter among the plurality of pipes penetrates below the groundwater level in the surrounding ground, and collects groundwater inside the inner pipe from the drain hole to create an excess gap in the ground. A multistage drain pipe drainage structure characterized by reducing water pressure.

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