JP3726991B2 - Construction method of bearing capacity improvement pile - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for constructing a pile that can improve the bearing capacity of the driven pile and cast-in-place pile.
[0002]
[Background Art and Problems to be Solved by the Invention]
Conventionally, open-ended piles such as H-shaped steel are placed on the foundations of temporary structures, etc., or driven by the vibration method to secure the support force with the soil. Since an actual cross-sectional area such as H-shaped steel is used, there is a limit to increasing the allowable bearing force. In order to obtain a large bearing capacity, the pile length must be long in order to expect the circumferential bearing capacity.
[0003]
It is conceivable to increase the supporting force by setting the area for calculating the bearing capacity to a closed section such as H-shaped steel. As a method for generating the closed section in that case, a boring machine that has been used as a conventional ground improvement method is used. It is conceivable to divert the method of drilling and using cement milk with high-pressure jet stirring.
[0004]
The ground improvement method using a boring machine will be described with reference to FIG. 6. First, drilling is performed with a boring machine while pouring water (FIG. 6A), and water injection is stopped when drilling to the planned depth (FIG. 6 ( b)) Next, the hardened material is jetted from the rod under high pressure and stirred (FIG. 6 (c)), and after constructing a cylindrical rooting body in which the hardened material and soil are mixed at the tip, the rod is pulled up. (FIG. 6 (d)).
[0005]
However, since this method performs boring, it is necessary to apply a reaction force for drilling from the ground side, which increases the size of the device and reduces the time and cost for drilling from the ground surface to the pile tip. It will take.
[0006]
Also, in the case of cast-in-place piles such as reverse piles, the problem of soil loosening and slime treatment due to excavation, and the load acting on the support ground is the first load, so it is quite Because it is after the settlement has occurred, a large bearing capacity and a large ground spring value cannot be expected.
[0007]
This invention is for solving the said subject, and it aims at providing the construction method of the pile which can obtain big supporting force, without making pile length long and without requiring a special apparatus. .
[0008]
[Means for Solving the Problems]
In the present invention, an open-ended pile with a guide tube extending to the vicinity of the tip is driven or pushed into the ground by vibration, the soil in the guide tube is removed, a rod is inserted into the guide tube, and the hardened material is passed through the rod with high pressure. It is characterized by spraying and stirring to create a solidified body at the tip of the pile.
In addition, the present invention digs a hole for cast-in-place piles, builds a reinforcing bar with a plurality of guide pipes extending to the vicinity of the tip, places concrete and hardens, then inserts the rod into the guide pipe The hardened material is jetted with high pressure through the rod and stirred to form a solidified body at the tip.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
Although the example applied to H-shaped steel is demonstrated with FIGS. 1-3, this invention may be applied not only to H-shaped steel but to other open end piles.
1A and 1B are diagrams showing an example of an embodiment of the present invention. FIG. 1A is a perspective view and FIG. 1B is a cross-sectional view.
As shown in the drawing, a guide tube 3 is attached to a web 2 of an H-shaped steel 1 along the length direction by welding or the like. The guide tube 3 has a tube diameter in which a rod 4 for high-pressure jet agitation with a small diameter can sufficiently enter.
The H-shaped steel 1 with the guide pipe is pushed into the ground by driving or vibration, and the soil clogged in the guide pipe 3 is removed by rotating the rod and spraying water to remove muddy water, and then inserting the rod 4. . Next, a hardener such as cement milk is jetted through the rod 4 at high pressure and stirred to solidify the tip of the H-shaped steel 1. As a result, when the width of the H-shaped steel 1 is a and the length of the web 2 is b, the support force can be increased by setting the area of approximately a × b as a closed section.
[0010]
FIG. 2 is a diagram showing an example in which the shape of the tip of the H-shaped steel is devised.
The guide tube attached to the H-shaped steel does not extend to the tip of the H-shaped steel. Therefore, when the hardened material is jetted from the front end of the guide tube at a high pressure, it may not sufficiently wrap around the ground on the back side of the web. Therefore, in FIG. 2 (a), a rectangular opening 5 is formed in the tip web, and the hardened material that has been agitated by high-pressure injection is sufficiently wound around the back ground through this opening to firmly solidify the tip of the H-shaped steel. The body is formed and adhesion between the formed solidified body and the H-shaped steel is ensured.
[0011]
In FIG. 2 (b), a notch 6 is formed in a trapezoidal shape that spreads at the tip end web, and the hardened material is sufficiently wound around the back ground through this notch to form a solidified body at the tip of the H-shaped steel. Adhesion with mold steel is ensured.
[0012]
In FIG. 2 (c), a rectangular rectangular cutout 7 is formed on the tip web, and a reinforcing steel plate 8 is attached to the tip flange in order to ensure strength when pushed into the ground. Also in this case, the hardened material is sufficiently passed through the notch 7 to the backside ground, and a solidified body is formed at the tip of the H-shaped steel to ensure adhesion with the H-shaped steel.
[0013]
Fig. 2 (d) shows that an elliptical (or circular) opening 9 is formed in the tip web, and the hardened material is sufficiently wrapped around the back ground through this opening to form a solidified body at the tip of the H-shaped steel. In this way, adhesion with the H-shaped steel is ensured.
[0014]
FIG. 3 is a diagram illustrating a small high-pressure jet stirring machine used in the present invention.
When trying to make a solidified body at the tip of the pile by the conventional method, it is necessary to drill from the ground surface to the tip of the pile by a boring machine, which requires the torque and reaction force required for drilling. Since a large rotational torque is transmitted to the rod through a transmission device such as a belt, a large number of gears, and a clutch, the high-pressure jet agitating machine device is large and has a large machine weight.
[0015]
On the other hand, in the present invention, since drilling from the ground surface to the tip of the pile such as H-shaped steel is not required, the required rotational torque and required reaction force for drilling can be reduced. From this, the small high-pressure jet agitating machine used in the present invention has a motor (not shown) with a small transmission device in the rod 4 inserted through the guide tube 3 attached to the H-shaped steel 1 as shown in FIG. ) Rotation to the rod. In the example shown in FIG. 3, the rod fixing method is a center grip type gripped by the center hole portion of the rotary table 12, the upper end is supported by the swivel 11, and the rotational force transmission method is a center hole type which is a rotary table type. Yes, it is small and lightweight. High-pressure injection through the rod is performed through the ultrahigh-pressure pump 13.
[0016]
Next, an example in which the present invention is applied to a cast-in-place pile will be described with reference to FIGS. Below, although the example of a reverse pile is demonstrated, it cannot be overemphasized that this invention is applicable also to another cast-in-place pile.
FIG. 4 is a diagram showing a reinforcing bar with a guide pipe attached, and FIG. 5 is a construction example of a cast-in-place pile by the reverse method, and is a diagram for explaining the construction sequence.
As shown in FIG. 4, a plurality of guide tubes 21 are attached to the reinforcing bar rod 20 and are used for high-pressure injection through the rod inside as described above.
In Fig. 5, a stand pipe is first built, and a hammer club is drilled (Fig. 5 (a)), a reverse machine is installed and water is supplied, and the pit water level is set to 2 m or more with respect to the groundwater level WL by hydrostatic pressure. The wall is protected (FIG. 5B). Next, excavation is performed with a rotating bit at the tip of the reverse machine, and the earth and sand are discharged to the ground sedimentation tank by reverse reflux of the circulating water (FIG. 5 (c)). After the excavation, the reinforcing bar shown in FIG. 4 is installed (FIG. 5 (d)), and then the tremy pipe is inserted into the reinforcing bar to perform slime treatment (excluding the slime by the water replacement method) (FIG. 5). 5 (e)). Next, concrete is cast through the tremy pipe (FIG. 5 (f)), the stand pipe is pulled out, and the construction is completed (FIG. 5 (g)). After the concrete is hardened, the hardened material is high-pressure jetted and stirred through a rod through a guide tube, and is wound around a surrounding natural ground to form a solidified body. Since a solidified body is formed at the tip of the pile, a large tip support force and a large tip ground spring value can be obtained.
[0017]
【The invention's effect】
As described above, according to the present invention, the guide tube is attached to the H-shaped steel or the like before being driven, and is driven together with the H-shaped steel or the like, and then a small-diameter high-pressure jet stirring rod is inserted into the guide tube. Since the pile tip is solidified by a small high-pressure jet stirring machine after being lowered, the following effects (1) to (3) are obtained.
(1) Improvement of bearing capacity and ground spring value (1) Open-ended piles The area for calculating the bearing capacity of the tip after driving is not the actual cross-sectional area but can be a closed section of H-shaped steel, etc. Values can also be calculated on the occlusion cross section.
(2) In the case of a cast-in-place pile A cast-in-place pile such as a reverse pile can be expected to have a large tip supporting force and a large tip ground spring value.
(2) Shortening of construction time Since it is only necessary to lower the small diameter high pressure jet stirring rod into the guide pipe from the ground surface to the tip of the pile, no drilling by boring is required, and the high pressure jet stirring machine can be downsized. The installation time can be shortened by shortening the installation and movement time of the machine.
[0018]
(3) Reduction of construction costs (1) Since drilling time by boring is not required, construction costs can be reduced.
(2) Mechanical loss due to downsizing of the high-pressure jet agitating machine can be reduced.
(3) The installation cost can be reduced by reducing the size of the high-pressure jet agitating machine, and the construction cost can be reduced by reducing the travel time.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an embodiment of the present invention.
FIG. 2 is a diagram showing an example in which the shape of the tip of the H-shaped steel is devised.
FIG. 3 is a diagram illustrating a small high-pressure jet stirring machine used in the present invention.
FIG. 4 is a view showing a reinforcing bar rod to which a guide pipe is attached.
FIG. 5 is a diagram for explaining the reverse construction method execution order;
FIG. 6 is a diagram illustrating a ground improvement method using a boring machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... H-shaped steel, 2 ... Web, 3 ... Guide pipe, 4 ... Rod, 5 ... Rectangular opening, 6 ... Trapezoidal notch, 7 ... Rectangular notch, 8 ... Reinforcement plate (or steel plate), 9 ... Ellipse ( (Or circular) opening, 11 ... swivel, 12 ... rotary table, 13 ... super high pressure pump, 20 ... rebar rod, 21 ... guide tube.

Claims (2)

  After driving the open-ended pile with a guide pipe extending to the vicinity of the tip into the ground by vibration or vibration, the soil in the guide pipe is removed, a rod is inserted into the guide pipe, and the hardened material is injected through the rod with high pressure and stirred. And the construction method of the bearing capacity improvement pile characterized by creating a solidified body in the pile front-end | tip part.   After excavating the hole for cast-in-place piles, build a reinforcing bar with multiple guide pipes extending to the vicinity of the tip, place concrete and harden it, insert the rod into the guide pipe, and pass the hardening material through the rod. A method for constructing a pile for improving bearing capacity, characterized in that a high-pressure jet is stirred to form a solidified body at the tip.

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