JP3753876B2 - Drain material construction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for constructing a drain material that is installed in a columnar shape in the ground for the purpose of ground improvement for suppressing liquefaction and promoting consolidation. In addition, it can be used to increase the bearing capacity of piles by consolidating drainage materials while constructing joint piles and other prefabricated piles in the ground with low vibration and low noise.
[0002]
[Prior art]
A method of suppressing liquefaction of the ground by creating a column of gravel drain material in the ground and suppressing an increase in excess pore water pressure in the ground during an earthquake or the like is well known (for example, Japanese Patent Laid-Open No. Sho 55- No. 142815, Japanese Patent Laid-Open No. 56-1000091 etc.). Sand drains for promoting consolidation in viscous ground and the like are also well known.
[0003]
Japanese Patent Application Laid-Open No. 60-250122, which is filed by the applicant of the present application, shows a liquefaction-preventing basic pile structure in which a joint pile is filled with a drain material around the joint pile.
[0004]
In addition, in Japanese Examined Patent Publication No. 61-58615, when placing a hollow preformed pile such as a steel pipe pile into the ground, the lower part of the pile is filled with a granular material made of sand, slag or gravel, A method is described in which a granular material is struck from the inside to cause a dilatancy phenomenon in the granular material, the lower end of the pile is blocked, and the pile is driven into the ground as it is.
[0005]
Furthermore, the present applicant has previously developed a method capable of constructing a prefabricated pile filled with a drain material with low vibration and low noise (Japanese Patent Application No. 10-15434, Japanese Patent Application No. 10- 15435), as one of the methods for efficiently and surely filling the drain material, a double-pipe structure casing having an inner pipe and an outer pipe is used, and when the casing is pulled up, the inner pipe is moved up and down to Discloses a method for tamping the remaining drain material.
[0006]
In this case, the drain material around the buried pile is sufficiently compacted, so that the pile's original peripheral surface bearing force can be obtained even in soft ground. The pore water pressure is dissipated and liquefaction is suppressed.
[0007]
[Problems to be solved by the invention]
The drain material that is formed in the ground or the drain material that is left in the ground so as to surround the pile together with the pile, if the compaction is sufficient, the water drain is not interrupted and the gravel drain or sand When it is effective as a drain and filled around the pile, it is possible to secure the peripheral surface support force, but when the compaction is insufficient, the expected effect cannot be obtained.
[0008]
As in Japanese Patent Application No. 10-15434 and Japanese Patent Application No. 10-15435, it is considered that one of the efficient methods is to use a double-pipe structure casing and raise and lower the inner pipe to compact the drain material. However, when the inner pipe is moved up and down in the axial direction, there is a problem of interference with the outer pipe, and it is not always easy mechanically to move the inner pipe up and down with a large stroke, even if it is not as strong as the striking method. Problems with vibration and noise may occur.
[0009]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has an object to provide a drain material construction method capable of efficiently compacting a drain material with a simpler structure. .
[0010]
[Means for Solving the Problems]
In the construction method of the drain material according to claim 1 of the present application, the casing in which one or a plurality of serrated pressing portions having a predetermined gradient in the circumferential direction of the tip is rotated around the axis by a rotary press-fitting device. While being press-fitted into the casing, the drain material is filled in the casing, and when the predetermined depth is reached, the casing is rotated around the axis so that the gradient of the sawtooth pressing portion is a downward gradient with respect to the rotation direction, The casing is pulled up while the drain material is compacted by the serrated pressing portion at the tip of the casing, and a column made of the drain material is formed in the ground.
[0011]
Incidentally, the downward gradient with respect to the rotation direction means that the position of the sawtooth pressing portion in a certain vertical plane continuously changes from the upper side to the lower side when the casing rotates about its axis. The reverse case is assumed to be an upward gradient.
[0012]
As the drain material, sand, crushed stone, gravel and the like are generally used, but other materials such as artificial lightweight aggregate for concrete may be used.
When the casing is rotated so that the serrated pressing portion has a downward gradient with respect to the rotation direction, the downward pressing force acts on the drain material filled from the serrated pressing portion, so that the drain material is compacted. It will be.
[0013]
In addition, when the casing is rotated about its axis, vibration and noise are hardly generated as compared with the case where the casing and the like are moved up and down to be solidified. Further, with rotation, not only the casing tip but also the drain material filled upward can be guided downward without being greatly disturbed.
[0014]
Furthermore, even if the casing has a double-pipe structure as in claims 3 and 4 to be described later, there is almost no problem of interference between the inner pipe and the outer pipe, and a simple rotating mechanism makes it smooth. The drain material can be compacted.
[0015]
Regarding the rotational press-fitting into the ground of the casing, the resistance against the rotational press-fitting is less when the sawtooth-shaped pressing portion is rotated so that the gradient of the sawtooth pressing portion is an upward gradient with respect to the rotational direction. When input is obtained, press-fitting can be performed while rotating in the reverse direction. In addition, when the casing has a double-pipe structure, there may be a case where only the outer tube is rotated and the inner tube formed with the sawtooth pressing portion is not rotated.
[0016]
Further, the compaction force by the sawtooth pressing portion is directly transmitted to the range corresponding to the tube thickness at the casing tip, but the tube thickness is increased only at the casing tip or the sawtooth pressing portion at the casing tip It is also possible to provide an inclination also in the tube diameter direction to increase the pressing area or adjust the pressing direction.
[0017]
The rotation direction is set so that the gradient of the sawtooth pressing portion is a downward gradient. Usually, it is set in the direction opposite to that during rotational press-fitting, but it is possible even if it is not the reverse.
A second aspect of the present invention is the case where the spiral blade or the spiral projection is provided on the outer peripheral surface of the casing in the drain material construction method according to the first aspect.
[0018]
These are mainly for reducing the resistance when the casing is rotationally press-fitted, but the protrusion may be a spot welded by winding a steel wire or the like.
[0019]
A third aspect of the present invention is the construction method of the drain material according to the first or second aspect, wherein the casing is a double pipe composed of an inner pipe and an outer pipe, and the sawtooth pressing portion is formed on the inner pipe.
[0020]
Although the construction method of the drain material of the present invention can be constructed with a single pipe having a sawtooth-shaped pressing portion, if it has a double pipe structure, it is necessary to consider much the resistance of the ground to the rotation of the inner pipe, etc. In addition, by providing spiral wings or spiral projections on the outer tube, rotational press-fitting into the ground becomes easy. In addition, it is also possible to make a double tube structure only at the tip of the casing.
[0021]
Claim 4 is the construction method of the drain material according to claim 1, 2, or 3, in which the pre-made pile surrounded by the drain material is inserted inside the casing together with the drain material, and the pre-made pile is underground with the drain material. It is a case to leave it in.
[0022]
The present invention can also be applied to construction of a gravel drain for liquefaction countermeasures or a sand drain for promoting consolidation, but the inventions of the inventions described in Japanese Patent Application Nos. 10-15434 and 10-15435 described above. As described above, it is useful as a method to increase the peripheral surface support force of the pile by sufficiently compacting the drain material while constructing the existing pile filled with the drain material with low vibration and low noise. .
[0023]
Embodiment
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The embodiment of FIG. 1 corresponds to claims 1 to 3 and aims to suppress liquefaction and the like by press-fitting a casing 1 having a double-pipe structure composed of an inner pipe 1a and an outer pipe 1b into the ground. The column of the drain material 7 is formed in the ground.
[0024]
The construction procedure in this case is as follows.
(1) A double-pipe structure casing 1 is set on the construction ground 10, and a drain material 7 such as crushed stone is introduced into the tip of the casing 1 (see FIG. 1 (a)). A tip bit 2 for excavation is attached to the tip of the outer tube 1b constituting the casing 1.
[0025]
The drain material 7 thrown into the tip of the casing 1 causes a dilatancy phenomenon due to the ground reaction force at the time of rotary press-fitting, and the lower end of the casing 1 is closed, thereby serving as a lid during excavation. Become.
[0026]
Alternatively, when the casing 1 is rotationally press-fitted into the ground, a lid is installed at the lower end, the lid is rotationally press-fitted together, and the casing 1 is pulled up together with the drain material 7 filled with the lid. A method of leaving in the ground 10 is also possible.
[0027]
It is also effective to provide a spiral projection or the like on the outer peripheral surface of the outer tube 1b in order to cut friction and facilitate press-fitting. Depending on the ground, there may be a case where rotation press-fitting is possible even if there is no protrusion. However, by providing a spiral-shaped protrusion to the extent that a steel wire is spot-welded, rotation press-fitting becomes easy. When the ground is relatively hard, a spiral blade is provided, and the press-fitting is facilitated by rotational press-fitting while pushing up the earth and sand.
[0028]
{Circle around (2)} The outer tube 1b of the casing 1 is rotated forward about the axis (in the direction of the right-hand screw in the figure) and press-fitted to a predetermined depth (see FIG. 1 (b)).
(3) When the depth reaches a predetermined depth, the drain material 7 is put inside the inner tube 1a, the inner tube 1a is reversed, and the drain material 7 is compacted by the serrated pressing portion 4 at the tip of the inner tube 1a. Then, the casing 1 is pulled out (see FIG. 1 (c)).
[0029]
The drain material 7 can be introduced at an arbitrary stage even during or after the press-fitting.
(4) The column of the drainage material 7 that has been compacted is left and the construction is completed (see FIG. 1 (d)).
[0030]
The embodiment of FIG. 2 corresponds to claims 3 and 4, and a casing 1 having a double pipe structure comprising an inner pipe 1a and an outer pipe 1b provided with a spiral blade 3 is press-fitted into the ground, and a drain material is provided. In the filling process of No. 7, a pile pile as a foundation pile is buried in the drain material 7, and the peripheral surface support force is secured through the compacted drain material 7, and the liquefaction suppression function by the drain material 7 is provided. It is what I expected.
[0031]
The construction procedure in this case is as follows.
(1) A casing 1 having a double-pipe structure is set on the construction ground 10, and a drain material 7 such as crushed stone is introduced into the tip of the casing 1 (see FIG. 2 (a)).
[0032]
The drain material 7 thrown into the tip of the casing 1 causes a dilatancy phenomenon due to the ground reaction force at the time of rotary press-fitting, and the lower end of the casing 1 is closed, thereby serving as a lid during excavation. Become.
[0033]
In addition, the above-mentioned Japanese Patent Application No. 10-15434 similarly closes the lower end of the casing opened by utilizing the dilatancy phenomenon, whereas in Japanese Patent Application No. 10-15435, At the time of rotational press-fitting into the ground, a lid is installed at the lower end, and the lid is rotationally press-fitted together. When the casing is pulled up, the lid is left in the ground together with the filler.
[0034]
In the case of the present invention, construction can also be performed using the lid without using the dilatancy phenomenon.
In this example, a tip bit 2 for excavation is attached to the tip of the outer tube 1b constituting the casing 1, and a spiral blade 3 for facilitating press-fitting is provided.
[0035]
{Circle around (2)} The outer tube 1b of the casing 1 is rotated forward about the axis in the direction of the spiral blade 3 (in the direction of the right screw in the figure) and press-fitted to a predetermined depth (see FIG. 2 (b)).
(3) When the depth reaches a predetermined depth, the pile 11 is built inside the inner pipe 1a (see FIG. 2 (c)), and the drain material 7 is further introduced (see FIG. 2 (d)).
[0036]
{Circle around (4)} The inner tube 1a or the inner tube 1a and the outer tube 1b are simultaneously reversed, and the casing 1 is pulled out while the drain material 7 is compacted by the serrated pressing portion 4 at the tip of the inner tube 1a (see FIG. 2 (e)), the pile 11 surrounded by the compacted drain material 7 is left, and the construction is completed (see FIG. 2 (f)).
[0037]
The embodiment of FIG. 3 shows the outline of the construction procedure in another embodiment of the present invention. In FIG. 2, a double pipe is used for the casing 1 whereas in this example, the example of FIG. A casing 1 made of a single pipe corresponding to the inner pipe 1a is used.
[0038]
That is, depending on the ground conditions, construction scale (column length by the drain material 7, etc.), performance of the construction device for rotary press-fitting, etc., the casing 1 made of a single pipe may be sufficient, and the construction cost can be reduced. .
[0039]
The construction procedure in this case is as follows.
(1) A casing 1 made of a single pipe is set on the construction ground, and the tip of the casing 1 is filled with a drain material 7 in an amount that will become a lid during excavation (see FIG. 3 (a)). In this example, the drain material 7 at the front end is filled from the lower end of the casing 1.
[0040]
A tip bit 2 is provided at the tip of a casing 1 made of a single tube, and a spiral projection 3b is provided above the tip bit.
{Circle around (2)} The casing 1 is rotated forward about the axis in the direction of the spiral projection 3b (in the direction of the right screw in the figure) and press-fitted to a predetermined depth (see FIG. 3 (b)).
[0041]
(3) When a predetermined depth is reached, the pile 11 is built inside the casing 1 (see FIG. 3 (c)), and the drain material 7 is further introduced (see FIG. 3 (d)).
{Circle around (4)} The casing 1 is reversely rotated and the casing 1 is pulled out while the drain material 7 is compacted by the serrated pressing portion 4 at the tip of the casing 1 (see FIG. 3 (e)), and the compacted drain material 7 The pile 11 surrounded by is left, and the construction is completed (see FIG. 3 (f)).
[0042]
In addition, although embodiment of FIG. 2, FIG. 3 described above is a case where a node pile is embed | buried in the drain material 7, the pile 11 is not only a node pile but a steel pipe pile and a normal round pile. It may be a concrete pile or a steel-concrete composite pile.
[0043]
FIG. 4 shows a front view and a developed view of the tip portion of the sawtooth pressing portion 4 at the tip of the casing 1 used in the present invention, and shows a case where the tooth of the sawtooth pressing portion 4 is one. is there.
[0044]
FIGS. 5 (a) to 5 (d) are examples in the case where there are a plurality of serrated pressing parts 4, and a case where the length L of the casing 1 is 7 m, the diameter D is 609 mm, and the tube thickness t is about 16 mm is assumed. ing. Further, the diameter of the drain material 7 to be compacted is assumed to be about 2.5 to 10 mm.
[0045]
In addition, about the diameter of the drain material 7 in this invention, and the dimension of the casing 1, it is not limited to these, Rather, it is relative in the relationship between the diameter of the drain material 7, the material, and the dimension of the casing 1, etc. Tend to be.
[0046]
FIG. 5 (a) shows two teeth of the serrated pressing part 4 and its height h = D. FIG. 5 (b) shows two teeth of the serrated pressing part 4 and its height. In the case of h = D / 2, FIG. 5 (c) shows the case where the number of teeth of the serrated pressing portion 4 is four and its height is h = D / 2.
[0047]
FIG. 5 (d) shows a case in which a short steel pipe 5 is put on the outer periphery of the sawtooth pressing portion 4 of the casing 1 of FIG. 5 (a), and the steel pipe 5 is sawtooth when excavated or when the drain material 7 is compacted. It has a function of preventing the shape pressing portion 4 from being deformed or worn.
[0048]
Further, the above is a case where the casing 1 is a single pipe, but the inner pipe in the case where the casing 1 has a double pipe structure can be considered similarly.
FIG. 6 shows variations in the cross-sectional shape of the sawtooth pressing portion 4, which is not limited to the case where the front end surface is horizontal as shown in FIG. 6 (a), but as shown in FIGS. A case where a taper is formed toward the inside or the outside of the casing 1 or a case where a mountain-shaped groove is formed as shown in FIG. In addition, for example, a cross section that protrudes downward in a chevron shape in reverse to FIG.
[0049]
【The invention's effect】
(1) In the present invention, since the drain material is compacted by rotating the casing, it can be compacted with a small force compared to the case where the casing is moved up and down and compacted, or when using a stick or the like. There are few problems of noise and vibration.
(2) Since the compaction can be performed continuously by rotation, the efficiency is high, and the rotation speed is adjusted according to the ground conditions and other construction conditions, and the number and shape of the serrated pressing parts It can be dealt with by selection.
{Circle around (3)} The drive device for compaction is economical because it can also be used as a rotary press-fitting device for press-fitting the casing into the ground.
(4) In the invention according to claim 4, by sufficiently compacting the drain material surrounding the periphery of the pile, the frictional force between the pile and the drain material can be used even in soft ground, compared to other embedded pile methods. A circumferential support force can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an outline of a construction procedure in an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an outline of a construction procedure in another embodiment of the present invention.
FIG. 3 is a cross-sectional view showing an outline of a construction procedure in still another embodiment of the present invention.
FIGS. 4A and 4B show an embodiment of a serrated pressing portion at the front end of a casing used in the present invention, in which FIG. 4A is a front view and FIG. 4B is a development view.
FIGS. 5A to 5D are front views showing another embodiment of a casing formed with a sawtooth pressing portion used in the present invention. FIG.
FIG. 6 is a view showing variations in the cross-sectional shape of the serrated pressing portion at the front end of the casing used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Casing (double pipe or single pipe), 1a ... Inner pipe, 1b ... Outer pipe, 2 ... Tip bit, 3 ... Spiral wing, 3b ... Spiral-shaped protrusion, 4 ... Sawtooth-shaped press part, 5 ... Steel pipe, 6 ... Input port, 7 ... Drain material, 10 ... Ground, 11 ... Pile

Claims (4)

The casing formed with one or a plurality of serrated pressing portions having a predetermined gradient in the tip circumferential direction is pressed into the ground while being rotated around the axis by a rotary press-fitting device, and the casing is filled with a drain material. When the predetermined depth is reached, the casing is rotated about its axis so that the slope of the serrated pressing portion is downwardly inclined with respect to the rotation direction, and the drain material is tightened by the serrated pressing portion at the front end of the casing. A drain material construction method, wherein the casing is pulled up while being solidified to form a column of drain material in the ground. The drain material construction method according to claim 1, wherein spiral wings or spiral projections are provided on an outer peripheral surface of the casing. The drain material construction method according to claim 1 or 2, wherein the casing is a double pipe composed of an inner pipe and an outer pipe, and the serrated pressing portion is formed on the inner pipe. The drain according to claim 1, 2, or 3, wherein a preformed pile surrounded by the drain material is inserted into the casing together with the drain material, and the preformed pile is left in the ground together with the drain material. Material construction method.

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