JP2009167752A - Steel pipe for ground reinforcement and method of ground reinforcement using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel pipe for ground reinforcement which is suitable for use in a prelining construction method for tunnel work or the like and for use as a reinforcement of a tunnel to be excavated, which can improve adhesion between a filling material and the steel pipe, and which can firmly fix the steel pipe to the ground or a concrete foundation. <P>SOLUTION: The steel pipe used for natural ground reinforcement has a concavity in its peripheral direction, and is provided with a plurality of through-holes in the concavity or on the other peripheral surfaces of the steel pipe. The plurality of through-holes are used for making the filling material leak to the outside of the steel pipe, and are connected to the inside and the outside of the steel pipe. The outer diameter (D) of the steel pipe is 50 mm or more. The depth of the concavity is 0.005D to 0.2D, and the width of the concavity is 0.015D to 2D. When the width and the depth of the concavity are made (B) and (H) respectively, it is preferable that B/H=3-20 when the cross section of the concavity is triangular (1), that B/H=4-20 when the cross section of the concavity is rectangular (2), and that B/H=3-20 when the cross section of the concavity is semicircular or trapezoidal (3). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steel pipe for ground reinforcement suitable for use in a receiving method in tunnel construction or the like, a reinforcement method for excavation wall surfaces, a ground reinforcement method using the same, and a method for reinforcing a structure such as a concrete foundation. Is.

For example, in a tunnel construction in a soft ground, in order to reinforce the ground, a receiving construction method in which a steel pipe is buried is often adopted. In this method, a steel pipe is externally fitted to a drill rod with a bit attached to the tip. After drilling at a predetermined depth, the drill rod is pulled out while leaving the steel pipe as it is, and a reinforcing material such as mortar is injected into the steel pipe. A large number of through-holes leading to the inside and outside are drilled in the body of the steel pipe, and the reinforcing material injected inside penetrates into the natural ground through the through-hole and solidifies, so that a soft natural ground is formed. Strengthened. A number of patent applications have been filed for the prior construction method (see, for example, Patent Document 1 and Patent Document 2).
Since the steel pipe used for the above-mentioned prior receiving method is buried in the natural ground, a steel pipe made of a material that is relatively inexpensive and has high strength is used. When injecting the injection material, it is necessary that the injection material flowing out through the through hole sufficiently penetrates into the natural ground and is tightly filled in the gap between the natural mountain and the steel pipe. Further, in order to firmly fix the embedded steel pipe, it is desirable that the steel pipe and the layer of the injecting material on the outer periphery thereof are firmly integrated.

However, since the conventional steel pipe is formed with a smooth outer surface, it cannot be said that both are firmly fixed without being caught by an external injection material layer. In order to improve this, sandblasting etc. was applied to the outer surface of the steel pipe to roughen the surface, and a certain effect was obtained, but it is still satisfactory in terms of firmly fixing the steel pipe to the ground It was not a thing.
Further, in Patent Document 3, as a steel pipe for ground reinforcement, a plurality of spiral ridges are formed on the outer peripheral portion, and the gaps between the spiral ridges are connected to the inside and outside for allowing an injection material to flow out of the steel pipe. A steel pipe for ground reinforcement provided with a through hole is disclosed.
JP 2000-204870 A JP 2001-020657 A JP 2006-022501 A

However, in the steel pipe disclosed in Patent Document 3, since there is a convex portion on the outer peripheral surface of the steel pipe, it becomes an obstacle at the time of placing the steel pipe and disturbs discharge of earth and sand from the outer surface side. It is difficult to ensure sufficient adhesion. Moreover, since giving a convex part to a steel pipe outer peripheral surface requires the process which provides a convex-shaped thing by another process after steel pipe manufacture, there exists a problem that productivity is inferior and cost becomes high.
The present invention solves the above problems, and when embedded in the ground without increasing the manufacturing cost, the resistance is small, and when the reinforcing material is poured, the steel pipe and its periphery are firmly and firmly fixed. It aims at providing the steel pipe for ground reinforcement which adheres, the ground reinforcement method using the same, and the reinforcement method of a structure.

In order to solve the above problems, the present invention has the following configuration.
(1) A steel pipe for ground reinforcement for placing in the ground and injecting a reinforcing material into the ground,
The steel pipe has a concave portion on the outer peripheral surface, and the concave portion or other smooth portion is provided with a plurality of through-holes through which the injected material flows into and out of the steel pipe for allowing the injected material to flow out of the steel pipe. Steel pipe for ground strengthening.
(2) When the cross-sectional shape of the recess is a steel pipe outer diameter (D), the depth of the recess is 0.005D to 0.2D, the width of the recess is 0.015D to 2D, and the width of the recess is (B ), When the depth of the recess is (H) (1) When the concave cross-sectional shape is triangular, B / H = 3-20
(2) When the concave cross-sectional shape is a square shape, B / H = 4 to 20
(3) When the concave cross-sectional shape is semicircular or trapezoidal, B / H = 3-20
(1) The steel pipe for ground reinforcement according to (1).
(3) The ground reinforcing steel pipe according to (1) or (2), wherein a plurality of the concave portions are provided on the same circumference of the steel pipe.
(4) The ground reinforcing steel pipe according to claim 1 or 2, wherein a plurality of the concave portions are provided in a circumferential direction, and at least the facing concave portions do not exist on the same circumference.
(5) The steel pipe for ground reinforcement according to (1) or (2), wherein a plurality of the concave portions are provided obliquely with respect to the steel pipe shaft.
(6) The ground reinforcing steel pipe according to (1) or (2), wherein a plurality of the recesses are provided in parallel to the steel pipe axis.
(7) The ground reinforcing steel pipe according to (1) or (2), wherein a plurality of the concave portions are provided in a spot shape.
(8) The steel pipe for ground reinforcement according to any one of (1) and (7), wherein the surface of the steel pipe is plated or resin-coated.
(9) During ground strengthening, the steel pipe for ground reinforcement described in (1) to (8) is placed while excavating the ground, and after placing the steel pipe, the steel pipe A ground strengthening method characterized by injecting a reinforcing material outside.
(10) The ground strengthening method according to (8), wherein a minimum inner diameter of the ground reinforcing steel pipe is larger than an outer diameter of an inner bit used when excavating the ground.
(11) The ground reinforcing method according to (8), wherein a maximum outer diameter of the ground reinforcing steel pipe is smaller than an outer diameter of an outer bit used for excavation of the ground.
(12) In the ground strengthening method according to any one of (9) to (11), a structure strengthening method characterized by strengthening a structure such as concrete or cement such as a foundation of a building instead of the ground.

By using the steel pipe for ground reinforcement according to the present invention, since the concave portion is formed on the outer peripheral surface of the steel pipe, it does not become resistance when buried in the ground, and when the reinforcing material is poured into the outer peripheral surface of the steel pipe, The concave portion is also filled with a reinforcing material, and adhesion with the ground is improved. As a result, it is possible to reduce the number of burials at the time of construction, and it is possible to shorten the construction cost and the construction period.
Moreover, since the steel pipe according to the present invention is only provided with a concave portion on the outer peripheral surface, for example, after forming the steel pipe, it can be produced simply by passing between the rolls having the convex portion as it is, without reducing the production efficiency. The manufacturing cost can also be reduced as compared with the conventional method.
Moreover, if the steel pipe for ground reinforcement | strengthening of this invention is used, it can apply similarly to reinforcement of structures, such as a concrete foundation of a building, for example, and a strong reinforcement is possible at low cost.

Hereinafter, the present invention will be specifically described with reference to the drawings.
FIG. 1 illustrates a steel pipe 1 for ground reinforcement according to the present invention, and this steel pipe is provided with recesses 2 in a circumferential shape at regular intervals on an outer peripheral portion.
In the steel pipe of FIG. 1, there are a plurality of through holes 3 that have recesses at a plurality of locations in the circumference and that pass through the inside and outside of the steel pipe 1 on the entire circumferential surface, and the reinforcing material is provided on the outer surface of the steel pipe through these through holes 3. When injecting, the concave portion of the steel pipe can increase the frictional force between the steel pipe and the ground or concrete. 4 indicates an outer bit.
In addition, this steel pipe manufacturing method is such that, after the pipe is formed in the steel pipe manufacturing line, the steel pipe surface is simply provided with a concave portion by a pressing means either hot or warm, and the productivity is almost the same as a normal pipe forming process.

2A to 2K show specific examples showing other concave shapes.
2 (a), 2 (b), and 2 (c) have a recess 2 in the circumferential direction of any steel pipe 1A, and a plurality of the recesses 2 are formed at regular intervals in the axial direction. 2A is an example in which a plurality of recesses 2 are provided on the same circumference of the steel pipe 1A (two in opposition to each other in the figure), and FIG. 2B is a steel pipe instead of a rolling roll. 1A is formed by a reciprocating pressing device that can approach and retract, and the recess 2 has substantially the same depth on the circumference. In the steel pipe of (c), a plurality of concave portions 2 are provided in the circumferential direction of the steel pipe 1A, and at least the concave portions facing each other are not present on the same circumference.
The staggered arrangement so that the concavities 2 facing each other do not exist on the same circumference as in the steel pipe of FIG. 2 (c) is to improve the strength of the concavity position compared to the steel pipe of (a), In particular, this portion is suitable for adaptation when the strength of the portion is required to be higher. Note that, in the example of the staggered arrangement of the recesses 2, it is desirable that the entire width of the opposing recesses is not wrapped.

2 (d) to (g) are views showing a steel pipe in which a recess 2 having a long side in an oblique direction with respect to the steel pipe axis is shown, and (h) and (i) are long in a direction parallel to the steel pipe axis. The figure which showed the steel pipe which formed the recessed part which has a side, (j) and (k) are the figures which showed the steel pipe which formed the round spot-shaped recessed part. The spot-like recess shape can be freely selected from an ellipse, a polygon, and the like for ease of formation. It is also possible to freely select whether the concave portions are arranged on the same circumference or alternately arranged in a staggered manner.
Here, the concave shape is limited only by the height, and it is sufficient to secure a space that allows the excavation bid to pass through the inner surface of the pipe.

As will be described later, the steel pipe of the present invention forms a recess hot or warm, so that it can be easily manufactured even if the thickness of the steel pipe is 2 mm or more, for example. At that time, the torsional force acts on the steel pipe, and it is not bent or the tip is crushed. Also, a steel pipe having an outer diameter of 50 mm or more that can be practically used as a steel pipe can be easily manufactured.
In addition, when the steel pipe according to the present invention is used for an application in which corrosion resistance is particularly required, the surface of the steel pipe configured as described above may be plated or resin-coated to exhibit good corrosion resistance. desirable.

  Concerning the concave portion of the steel pipe, as shown in FIGS. 3A, 3B, 3C, and 3D, there are basically a case where the cross-sectional shape is a triangular shape and a case where the cross-sectional shape is a square shape. In the case of a semicircular shape and a trapezoidal shape, it may be considered to be substantially equal to a triangle. In either case, the depth H of the recess (which indicates the depth of the deepest portion) is 0.005D (where D is the outer diameter of the steel pipe) in order to obtain a frictional force between the steel pipe peripheral surface and the ground or concrete. The above is necessary. However, since the effect of improving the frictional force is saturated at more than 0.2D, the recess depth is set to 0.005D to 0.2D. Further, the width B of the concave portion needs to be 0.015D or more in order to obtain the above frictional force, but if it exceeds 2D, the effect of improving the frictional force is small, so it is necessary to make it 2D or less.

Furthermore, it is important to define the following matters in order to optimize the concave shape under the above assumption. That is,
(1) When the concave cross-sectional shape is triangular, B / H = 3-20
(2) When the concave cross-sectional shape is a square shape, B / H = 4 to 20
(3) When the concave cross-sectional shape is semicircular or trapezoidal, B / H = 3-20
It is.
Hereinafter, the process of deriving the B / H relationship will be described with reference to FIG. As a premise, the fracture mode at the recess is determined by either the shear strength of the soil cement at the outside of the recess, the bottom of the triangle in the figure, or the bearing strength of the soil cement inside the recess. And At this time, if any one of the destruction modes clearly precedes the other, the strength is determined by the destruction mode, and thus the strength is considered to decrease. Therefore, in considering the optimum shape of the recess, it is necessary to find a shape in which the above two destruction modes occur simultaneously.

As a result, in the optimum shape, the support pressure P that gives the support strength and the shear force S that gives the shear strength are required to satisfy the balance condition formula of the following formula (1).
S = P cos θ (1)
However, θ: an angle formed between the steel pipe surface and the recessed entry side surface Here, the shearing force S is defined by the area where the shearing force acts × shearing force, and thus is formulated by the following equation (2). Here, it is assumed that the concave portion is disposed around the entire circumference of the steel pipe, and the shear area is represented by the product of the circumferential length πD of the steel pipe and the width B (the bottom portion of the triangle) of the concave portion.
S = τ ・ B ・ π ・ D (2)
On the other hand, the support pressure is formulated as follows assuming that the area acting on the support stress is multiplied.
P = H · σb · cosθ · π · D (3)
τ: shear stress, D: steel pipe outer diameter, σb: bearing pressure (bearing stress, force / area dimension)
Substituting the formulas (2) and (3) into the formula (1) and rearranging leads to the following formula.
τ · B = (H · σb · cosθ) cosθ (4)
∴B / H = σb · cos ² θ / τ (4 ′)
Expression (4 ′) is a modification of the force balance conditional expression (1) for giving the optimum shape. Here, the side surface of the concave shape, that is, the angle (θ) formed by the slope of the triangle in FIG. 4 with the steel pipe surface is 45 degrees (hereinafter referred to as a triangular shape) and 90 degrees (this is referred to as the following). , A square shape).
If θ = 90 ° (the concave portion is a square),
B / H = σb / τ (5)
For example, if the bearing strength σb = 1 N / mm ² and the shear strength τ = 0.1 N / mm ² of soil cement are substituted into the equation (5), B / H = 10 (the width of the recess is 10 times the height) Thus, the concave shape is a rectangle having a long side 10H and a height H.

On the other hand, if the final concave shape is a triangle and the triangle is an isosceles triangle, the following relational expression is established for B, H, and θ.
tan θ = 2 · H / B (6)
Substituting this into equation (4 ')
2 / (sin θ · cos θ) = σb / τ (7)
Substituting the bearing strength σb = 1 N / mm ² and the shear strength τ = 0.1 N / mm ² of the soil cement into this,
sinθ · cosθ = 1/5 (8)
sin2θ = 2/5 = 0.4 (8 ′)
∴θ = 11.8
The relation between bearing strength σb and shear strength τ of soil cement (concrete) is 1/20 ≦ τ / σb ≦ 2/9
(Usually τ / σb = 1/10)
(A) When the concave shape is a quadrangle, the relationship between the width B and the depth H of the concave portion is 4.5 ≦ B / H ≦ 20.0 according to the equation (5).
(B) When the concave shape is a triangle, an appropriate range of θ is 5.8 ≦ θ ≦ 31.4 according to Equation (7).
At this time, the relationship between the width B and the depth H of the concave portion is 3.3 ≦ B / H ≦ 19.8 according to the equation (6).
It becomes.
Here, also in the case of a concave, concave, or oblique spot shape in the steel pipe axial direction as shown in FIGS. 2 (d) to (k), the cross section AA in (d), B in (h) What is necessary is just to apply the said formula about CC cross section of -B cross section and (j).
From the above, in the present invention, B / H is defined as follows.
(1) When the concave cross-sectional shape is triangular, B / H = 3-20
(2) When the concave cross-sectional shape is a square shape, B / H = 4 to 20
(3) When the concave cross-sectional shape is semicircular or trapezoidal, B / H = 3-20

Next, the manufacturing method of the steel pipe which concerns on this invention is demonstrated.
Although the present invention can be applied to any of the following steps a), b), c), and d), the present invention will be described using a forged steel pipe production line as a representative example.
a) In an ERW steel pipe production line, after ERW welding, the steel pipe is heated and its surface is pressed by pressing means.
b) In a hot or warm welded steel pipe production line, the surface is pressed by pressing means after welding.
c) In the forged steel pipe production line, after the collision, the surface is pressed by pressing means.
d) In the seamless steel pipe production line, after pipe making, the surface is pressed by pressing means.

FIG. 5 is a view showing a production line of a normal forged pipe.
A steel strip slit to a desired width is formed into a circular cross section with a # 1 roll, and both ends thereof are heated to high heat with a # 2 roll, pressed, and abutted. A forged welded tube is manufactured by reducing the diameter of the abutted pipe to a predetermined size by a subsequent roll, cutting it to a predetermined length with a cutting machine, and adjusting the shape with the subsequent roll.

FIG. 6 is an example of a forged pipe manufacturing line.
Only the final roll of the squeeze roll before the cutting machine is changed with respect to the conventional production line. As shown in FIG. 7, the roll is provided with convex portions at one or a plurality of locations in the roll axial direction on the roll peripheral surface, and this is used as a pressing means. The roll provided with this convex part is used both up and down or one side. In the figure, the upper and lower two rolls are shown, but one set may be three or more rolls. Since pressure is applied to a high-temperature (about 1200 to 1300 ° C.) forged pipe with a roll having such a convex portion, a concave portion is easily formed in the portion of the steel pipe that the convex portion hits. Moreover, since the recess shape is formed in a shape conforming to the convex shape of the roll as compared with the cold processing, it is possible to obtain a more acute recess. Then, it is cut into a predetermined length, shaped, and a forged steel pipe with a recess is completed.
Here, when it is desired to change the height, width, and pitch of the concave portion on the steel pipe, the shape and pitch of the convex portion of the roll may be changed. Also, if both the upper and lower rolls are provided with convex portions and the concave portions on the steel pipe are to be formed at the same position, the convex portions of the upper and lower rolls are aligned at the initial stage. And the upper and lower rolls may be driven in synchronization with each other.

  Next, as shown in the lower diagram of FIG. 7, the shape of the convex portion formed on the roll is desirably made higher at the roll center and lower toward the roll end. The reason is that the peripheral speed is different between the center and the end of the roll, and the peripheral speed is large because the end has a larger diameter. Therefore, in order to advance faster than the passing pipe, an unnecessary force is applied to the steel pipe, and an unnecessary deformation or distortion is given to the steel pipe.

FIG. 8 is an example of another forged pipe manufacturing line according to the present invention.
In this example, a pressurizing device (pressing means) for a dedicated steel pipe is provided between the drawing roll and the cutting machine. The pressurizing device may be a roll having the above-mentioned convex portions, or may be a type that pressurizes the steel pipe by sandwiching from above and below. And it is desirable for this pressurizing device to have a mechanism capable of moving back and forth with respect to the steel pipe or moving back and forth in the moving direction of the steel pipe.
By being close to and retractable from the steel pipe, a concave portion can be formed at an arbitrary position of the steel pipe, and even when it is desired to change the pitch of the concave portion, it is not necessary to replace the roll. Furthermore, with this function, it is also possible for the control unit to recognize the cutting position of the steel pipe in advance, and to control so that the concave portion is not positioned at this cutting position. This is because if the concave portion comes to the end of the steel pipe, the diameter and shape of the end face are different for each steel pipe, for example, it becomes difficult to connect the steel pipes.
Further, by enabling movement in the traveling direction of the steel pipe, it is possible to move the reduced diameter portion forming apparatus in synchronization with the progress of the steel pipe, and as a result, the peripheral speeds of the center portion and the end portion of the roll as described above. The shape of the concave portion can be freely formed without causing unnecessary distortion to the steel pipe due to the difference between the two.
As described above, the dedicated device has been described. Of course, these functions may be applied to a roll in which a convex portion is provided on the existing final drawing roll.

Thus, the pipe making method may be any of a pipe making method by electric sewing, a pipe making method for hot or warm welding, a pipe making method by forging, and a seamless pipe making method. What is necessary is just to press the surface where the pipe was made by the pressing means in the warm or hot state as it is or after heating, and it is possible to manufacture a steel pipe with a recess online.
And the forged steel pipe manufactured by these manufacturing methods forms a recess hot, so it can be easily manufactured even if the thickness of the steel pipe is 2 mm or more, for example, while being rotated to the ground as a steel pipe pile because it is thick At the time of driving, a torsional force acts on the steel pipe, and it does not bend or crush the tip. In addition, a steel pipe having an outer diameter of 50 mm or more that can be practically used as a steel pipe for ground reinforcement can be easily manufactured. Moreover, the production efficiency is the same as when producing a normal forged steel pipe.

  By manufacturing a steel pipe with a dedicated roll provided with protrusions in a normal steel pipe manufacturing line by the steel pipe manufacturing method as described above, a concave shape can be continuously given simultaneously with the steel pipe manufacturing. By changing the shape of the protrusion, it is possible to give a concave shape with any shape, spacing, and arrangement, and there is no need for processing in a separate process, providing a steel pipe with a concave shape at a very low cost. can do.

In the steel pipe according to the present invention, by providing a concave shape not on the outer surface side of the steel pipe but on the inner surface side in this way, the steel pipe has a large concave portion that can ensure sufficient adhesion without interfering with the steel pipe. The steel pipe for ground reinforcement can be manufactured at low cost without reducing productivity.
And a several through-hole is drilled in the steel pipe which provided the recessed part. The through hole may be a concave portion on the circumference of the steel pipe, or may be provided in a smooth portion other than the concave portion. Or you may provide in either. The diameter and arrangement of the through-holes are not particularly limited as long as the injection material spreads over the entire length, and may be arbitrarily determined depending on the properties of the reinforcing agent to be injected and the state of the ground to be injected.

FIG. 9 is a diagram showing the positions of the excavation bit and the steel pipe. The outer bit excavates the ground in front while rotating by the power transmitted from the rod and the inner bit, and the ground reinforcing steel pipe of the present invention is disposed behind the outer bit. Therefore, the outer diameter of the steel pipe for ground reinforcement should just be smaller than the outer diameter of an outer side bit.
Further, since the rod and the inner bit pass inside the steel pipe, the minimum inner diameter of the steel pipe needs to be larger than the maximum outer diameter of the inner bit. As long as the above conditions are satisfied, the depth of the recess on the periphery of the steel pipe can be increased.

When using this steel pipe for ground reinforcement, as shown in FIG. 9, a drill rod with an inner bit attached to the tip is inserted into the steel pipe, and the inner bit at the tip protrudes beyond the outer bit of the steel pipe. In this manner, the drill rod and the rear end of the steel pipe are connected to a drilling machine (not shown). Then, drilling is performed while hitting, rotating, and thrusting from the drilling machine to the drill rod and steel pipe. During drilling, water or compressed air is supplied from the rock drill and discharged from the tip of the bit. Most of the flour produced by drilling is discharged through the inside of the steel pipe, but a part is discharged backward through the outside of the steel pipe.
When drilling of a predetermined depth is completed and the steel pipe is buried in the natural ground, the drill rod is pulled back together with the inner bit from the steel pipe, and an injection device (not shown) is attached to the rear end of the steel pipe. Is pressed into the steel pipe. The injected material fills the steel pipe, flows out through a large number of through holes provided in the steel pipe, flows along the outer surface of the steel pipe, and penetrates into the ground and solidifies. As a result, the natural ground is strengthened.

  Since this steel pipe has a recess formed in the outer peripheral portion thereof, the recess is embedded in the solidified injection material layer, and both are firmly integrated. For this reason, even if axial force acts on the steel pipe, the engagement between the concave portion and the injecting material layer causes a catching resistance and prevents the steel pipe from moving. In this way, the steel pipe is firmly fixed in the natural ground. Since the recess has a predetermined cross-sectional shape, it is possible to improve both the fluidity of the pouring material and flour and the catching resistance for preventing deviation.

  The concave portion is usually formed by a rolling roll, and has a gentle shape with no edge or corner in the cross-sectional shape, so that the flour and the injected material smoothly flow, and partially clogged or voided. Does not occur. For this reason, not only the discharge state of the flour is good, but also the adhesion between the injection material and the steel pipe is improved, and excellent ground reinforcement can be achieved. In the above description, a combination of a ring-shaped outer bit fixed to the tip of the steel pipe and an inner bit attached to the tip of the drill rod is used as the bit. Using a bit, when drilling, expand the diameter so that it is larger than the outer diameter of the steel pipe, and at the end of drilling, shrink the diameter so that it is smaller than the inner diameter of the steel pipe and pull it backward. May be. In this case, it is not necessary to fix the ring bit to the tip of the steel pipe.

[Example 1]
Next, since the adhesion strength was compared at the following levels, it will be described. The levels are the three levels shown in Table 1. Size: 76.3mmφ × 3.2mmt × 6mL, standard STK

For the evaluation method of adhesion, a steel pipe was embedded in soil cement, and a load was applied from the top as shown in FIG. (Evaluation of adhesion at maximum load)
In addition, soil cement
・ Mixed soil and solidifying agent ・ Soil is implemented in two cases: viscous soil and sandy soil Cohesive soil: particle size 0.001 to 0.005 mm
Sandy soil: particle size 0.074-2mm
As a result, as shown in FIG. 11, it was confirmed that the present invention has a larger push-through load, that is, a higher adhesion force than the other comparative examples.

  In addition, although the manufacturing cost of the stepped steel pipe of the present invention is substantially the same level as the manufacturing cost of the straight pipe of the comparative example 1, the convex steel pipe of the comparative example 2 forms a convex part in the pipe making cost. Since the overlay welding cost of the steel is added, the cost becomes high. Thus, it can be seen that the present invention is superior in terms of cost.

  As is apparent from the above description, the steel pipe for ground reinforcement according to the present invention has a concave portion formed on the outer peripheral surface of a conventional steel pipe, which reduces ground reinforcement in tunnel construction or the strengthening of structures such as concrete foundations. It can be done effectively at a cost.

The front view which shows an example of the steel pipe for ground reinforcement of this invention. (A)-(c) is a figure which shows the embodiment example of the steel pipe for ground reinforcement with a recessed part of this invention. (D)-(g) is a figure which shows the embodiment example of the steel pipe for ground reinforcement with a recessed part of this invention. (H)-(k) is a figure which shows the embodiment example of the steel pipe for ground reinforcement with a recessed part of this invention. The figure which shows the specific example of the recessed part of this invention steel pipe. The figure which shows the relationship between the width | variety and depth of the recessed part of this invention steel pipe. The figure which shows the manufacturing line of a normal forge-welded steel pipe. The figure which shows one Example of the manufacturing line of the forge welded steel pipe which manufactures this invention steel pipe. The conceptual diagram of the roll used for manufacture of this invention steel pipe. The figure which shows the other Example of the manufacturing line of the forge welded steel pipe which manufactures this invention steel pipe. The partial cross section figure of the front-end | tip part of the steel pipe which inserted the drill rod with a bit. The figure which shows the evaluation method of the adhesive force in an Example. The figure which compared the effect in Example 1. FIG.

Explanation of symbols

1: Steel pipe for ground reinforcement 2: Concave part 3: Through hole 4: Outer bit

Claims (12)

  A steel pipe for ground reinforcement for placing in the ground and injecting a reinforcing material into the ground, the steel pipe having a recess on the outer peripheral surface, and an injection material in the recess or other smooth part A ground reinforcing steel pipe, wherein a plurality of through holes are provided to allow the inside and outside of the steel pipe to flow out to the outside of the steel pipe. When the outer diameter of the steel pipe is (D), the depth of the recess is 0.005D to 0.2D, the width of the recess is 0.015D to 2D, and the width of the recess is (B). (1) When the concave cross-sectional shape is triangular, B / H = 3-20
(2) When the concave cross-sectional shape is a square shape, B / H = 4 to 20
(3) When the concave cross-sectional shape is semicircular or trapezoidal, B / H = 3-20
The steel pipe for ground reinforcement according to claim 1, wherein the steel pipe is for ground reinforcement.   The ground reinforcing steel pipe according to claim 1 or 2, wherein a plurality of the concave portions are provided on the same circumference of the steel pipe.   The ground reinforcing steel pipe according to claim 1 or 2, wherein a plurality of the concave portions are provided in a circumferential direction, and at least the concave portions facing each other do not exist on the same circumference.   The steel pipe for ground reinforcement according to claim 1 or 2, wherein a plurality of the concave portions are provided in an oblique direction with respect to the steel pipe shaft.   The steel pipe for ground reinforcement according to claim 1 or 2, wherein a plurality of said concave parts are provided in parallel to the steel pipe axis.   The ground reinforcing steel pipe according to claim 1 or 2, wherein a plurality of the concave portions are provided in a spot shape.   The steel pipe for ground reinforcement according to any one of claims 1 to 7, wherein the surface of the steel pipe is plated or coated with a resin.   When the ground is reinforced, the ground reinforcing steel pipe according to any one of claims 1 to 8 is placed while excavating the ground, and after the steel pipe is placed, the steel pipe is inserted from the inside of the steel pipe through the plurality of through holes. A ground strengthening method characterized by injecting a reinforcing material outside.   The ground reinforcement method according to claim 8, wherein a minimum inner diameter of the steel pipe for ground reinforcement is larger than an outer diameter of an inner bit used when excavating the ground.   9. The ground strengthening method according to claim 8, wherein a maximum outer diameter of the steel pipe for ground reinforcement is smaller than an outer diameter of an outer bit used for excavation of the ground.   The ground reinforcement method according to any one of claims 9 to 11, wherein a structure such as a concrete such as a foundation of a building or a cement is reinforced in place of the ground.

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