JP4476230B2 - Steel pipe pile rooting method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a steel pipe pile rooting method, and more particularly, to a rotary tunneling type steel pipe pile rooting method in which a cutting bit is fixed at a tip and is rotationally press-fitted into a ground by a rotary press-fitting device.

  For example, when constructing an artificial ground over the track, the foundation pile is constructed between narrow tracks. In general, the necessary space is secured by moving the track, but if the track cannot be switched, the construction will be performed in the middle of stopping the Kiden, so the pile construction takes a lot of days. In many cases, cast-in-place piles are used as the foundation pile, and in this case, securing the stability of the hole wall is a problem. As countermeasures, a method of directly protecting the train with a construction girder and an auxiliary method of protecting the hole wall by improving the ground are applied.

  In the case of cast-in-place piles, the ground where the piles are constructed is generally reinforced by ground improvement work such as chemical injection, and TBH (reverse circulation excavation method) or BH (forward circulation method) excavation methods are used. It is constructing. As a result, it is possible to cope with construction for a long time, and construction is performed while preventing collapse of the hole wall due to train vibration.

  As a pile construction method for stabilizing the hole wall, there is a construction method using a steel pipe pile with a cutting bit attached to the tip. In this case, the steel pipe pile is pressed into the ground while rotating, but the pile driving machine that can be carried into a narrow place such as the inside of a railway line is limited to a small one. For this reason, the pipe diameter of the steel pipe pile that can be placed must be small, and the required pile length becomes long, which is problematic in terms of cost and construction period. For these reasons, it has been desired to develop a method for constructing a steel pipe pile that can secure a required bearing capacity with a small pile driving machine.

  By the way, as a method of improving the frictional force of the outer peripheral surface of the steel pipe, conventionally, a rotary stirring rod with a stirring blade attached to the tip is placed in the steel pipe, and the soil and solidified material near the tip of the pile are stirred and mixed. There are known methods to improve and attach the rib attached to the outer peripheral surface of the pile at the improved part to secure the support force, and to pre-construct the soil mortar pile and then sink the ribbed steel pipe Yes. However, these methods require pulling out the stirring rod in the steel pipe and attaching a rotating mechanism to the upper part, and the work is a two-step process. It cannot be applied to construction between tracks.

In addition, about the steel pipe pile of the system which fixes a cutting bit to the front-end | tip and carries out rotation press-fit in the ground, it is described in patent document 1, for example. Further, the present applicant has already proposed a steel pipe pile rotary press-fitting device for low head suitable for construction between tracks (Patent Document 2 and Patent Document 3).
JP 2003-261940 A Japanese Patent No. 3218202 Japanese Patent No. 3255278

The present invention has been made based on the technical background as described above, and achieves the following object.
An object of the present invention is to provide a steel pipe pile consolidation method capable of increasing the peripheral frictional force of a steel pipe and expressing a predetermined supporting force under low-heading, narrow and short-time construction conditions. is there.

The present invention employs the following means in order to achieve the above object.
That is, according to the present invention, the cutting bit is fixed to the tip, and a feed pipe for feeding the drilling fluid during excavation and the solidification material during the rooting process is disposed in the cutting bit. A steel pipe pile connected to the bit so as to communicate with an injection port provided in the bit and rotationally press-fitted into the ground, and solidified on the outer periphery of the steel pipe at the bottom wall of the steel pipe during the rooting treatment Using a steel pipe pile provided with an injection hole for discharging the solidified material and provided with an injection pipe for the solidified material communicating with the injection hole inside,
Supplying the drilling fluid to the feed pipe, excavating the ground while discharging the drilling fluid from the inlet of the cutting bit, and rotating press-fitting the steel pipe pile;
After reaching a predetermined depth that requires root consolidation, the drilling fluid is switched to the solidified material, the solidified material is discharged from the inlet of the cutting bit through the feed pipe, and the steel pipe pile is rotated while the predetermined depth range is reached. The process of raising and lowering the steel pipe pile with,
And a step of discharging the solidification material from the injection hole to the outer periphery of the steel pipe pile through the injection pipe while rotating the steel pipe pile at the lowered position of the steel pipe pile. is there.

  More specifically, the rib is provided in the outer periphery of the steel pipe containing the part in which the said injection hole exists. This rib can be spiral. Further, a branch joint is provided on the upper part of the feed pipe, the injection pipe is connected to the branch joint, and a solidifying material can be selectively supplied to the feed pipe and the injection pipe. You can also

  According to this invention, since the injection hole for the solidification material is provided in the peripheral wall of the lower end portion of the steel pipe and the injection pipe communicating with the injection hole is provided inside the steel pipe, the solidification material is provided from the injection hole to the outer periphery of the steel pipe during the rooting treatment. Is discharged, a hardened layer of solidified material integrated with the steel pipe is formed on the outer periphery of the steel pipe pile. For this reason, the vertical load which acts on a steel pipe pile will be transmitted to the ground through a hardened layer, and it can increase a circumferential frictional force.

  Embodiments of the present invention will be described below with reference to the drawings. 1 is an axial cross-sectional view of a steel pipe pile showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG. The steel pipe pile is rotationally press-fitted into the ground while sequentially connecting a plurality of steel pipes having a predetermined length by welding or screw joints. The steel pipe pile 1 shown by FIG. 1 is a steel pipe part of the head (lowermost end part). A cutting bit 2 is fixed to the tip of the steel pipe pile 1.

  The cutting bit 2 includes a tube shaft 3 and a plurality of excavation blades 4 fixed to the outer periphery of the tube shaft 3, and the outer edge of each excavation blade 4 is fixed to the steel pipe pile 1. At the tip of the tube shaft 3 is provided an inlet 5 for drilling fluid and solidified material. The inlet 5 is normally closed by a valve 6 and is opened by the injection pressure. Inside the steel pipe pile 1, a feed pipe 7 for the drilling fluid and the solidified material is disposed at the axial center position, and the lower end of the feed pipe 7 is connected to the pipe shaft 3 of the cutting bit 2. The stabilizer 8 provided in the upper part of the steel pipe pile 1 is a member for holding the feed pipe 7 at the axial center position of the steel pipe pile 1.

  According to the present invention, a plurality of solidified material injection holes 9 are provided in the peripheral wall of the steel pipe pile 1. In this embodiment, two injection holes 9 are provided at an interval in the length direction of the steel pipe pile and at an angular interval of 180 degrees. A plurality of injection pipes 10 are provided in the steel pipe pile 1 corresponding to the injection holes 9. Each injection pipe 10 is disposed so as to extend downward along the inner circumference of the steel pipe pile 1, and is fixed to the inner circumference of the steel pipe pile 1 by a stopper 11 such as a U bolt. An elbow 13 having a check valve 12 is provided at the tip of each injection tube 10, and the tip of the elbow 13 communicates with the injection hole 9.

  Ribs (projections) 14 are provided on the outer periphery of the steel pipe pile 1 including the portion where the injection holes 9 exist. In this embodiment, the rib 14 has a spiral shape. In addition to the ribs 14 having a spiral shape, a plurality of ribs 14 formed of a flat steel, an angle, a round steel, a modified steel bar, or the like to a predetermined length may be attached to the outer periphery of the steel pipe pile 1. Moreover, you may make it provide the ring-shaped rib surrounding the outer periphery of the steel pipe pile 1 single or multiple.

  A branch joint 16 is provided at the upper end of the feed pipe 7 via a valve 15 a, and a hose 18 is connected to the branch joint 16 via a swivel 17. Moreover, the hose 19 is connected to the upper end of each injection pipe 10, and each hose 19 is connected to the branch pipe 16 via the valve 15b.

Next, the construction procedure of the above steel pipe pile will be described with reference to FIG.
1. The steel pipe pile 1 is press-fitted into the ground while being rotated by a rotary press-fitting device (not shown). As the steel pipe pile 1 rotates, the cutting bit 2 at the tip rotates to excavate the ground, and at the same time, the steel pipe pile 1 is press-fitted into the ground. At that time, the drilling fluid in which an additive such as bentonite is added to the water is sent to the cutting bit 2 through the feed pipe 7 in accordance with the properties of the soil. This drilling fluid opens the valve 6 by pressure and is discharged from the inlet 5 to the bottom of the drilling hole (FIG. 3A). In FIG. 3, only the leading steel pipe pile 1 is shown, but the steel pipe pile 1, the feed pipe 7 and the injection pipe 10 are added one by one until reaching a predetermined depth for solidification.

2. When the depth position that requires root consolidation is reached, the press fitting of the steel pipe pile 1 is completed (FIG. 3B).
3. After completion of press-fitting, supply of drilling fluid is stopped and switched to supply of solidified material such as cement milk. Then, the cement milk is discharged from the inlet 5 and the steel pipe pile 1 is rotated, and is raised by a predetermined depth range d (for example, 500 mm) (FIG. 3 (c)).

4). When the steel pipe pile 1 reaches the ascending position, the steel pipe pile 1 is lowered by the ascending amount (d) while continuing the discharge of the cement milk from the inlet 5 and the rotation of the steel pipe pile 1 (FIG. 3 (d)).
5). After the steel pipe pile 1 is lowered, the cement milk is discharged while reversing this, and the rising and lowering in the depth range d is repeated (about two reciprocations, FIG. 3 (e)). As described above, as the steel pipe pile 1 is moved up and down with forward and reverse rotation, a soil cement formed by mixing and mixing the excavated sediment and cement milk is formed near the tip of the steel pipe pile 1, and a part of the steel pipe pile 1 is formed. 1 is taken in. Thereby, the root of the steel pipe pile is made.

  6). In this invention, in order to increase the peripheral friction force of the outer peripheral surface of the steel pipe pile 1, the following process is further performed. That is, this is rotated at the lowered position of the steel pipe pile 1, and the opening and closing of the valve 15a and the valve 15b is switched to discharge cement milk from the injection hole 9 to the outer periphery of the steel pipe pile 1 through the injection pipe 10 (FIG. 3 (f)). ). Although the construction is completed as described above, the cutting bit 2, the feed pipe 7 and the injection pipe 10 in the steel pipe pile are buried. Therefore, it is not necessary to pull out these after completion of construction.

  According to the above construction method, when the steel pipe pile 1 is rooted, cement milk is discharged to the outer periphery thereof, so that the outer periphery of the steel pipe pile 1 is filled with cement milk as shown in FIG. And when this cement milk hardens | cures, the hardening layer 20 united with this is formed in the outer periphery of the steel pipe pile 1. FIG. For this reason, the vertical load which acts on the steel pipe pile 1 will be transmitted to the ground through the hardened layer 20, and it can increase a circumferential frictional force.

  Moreover, since the rib 14 was provided in the outer periphery of the steel pipe pile 1, the adhesive force with the hardened layer 20 can be improved. Furthermore, by making the rib 14 into a spiral shape, the cement milk discharged to the outer periphery of the steel pipe pile will rise with the rotation of the steel pipe pile, and the cement milk is filled in a wide range with respect to the length direction of the steel pipe pile. Can do.

  The above embodiment is merely an example, and various modifications can be made to the present invention. For example, in the above embodiment, the solidified material injection hole for increasing the peripheral frictional force is provided only in the leading steel pipe portion, but the injection hole is also provided in the steel pipe portion added to this, so that the filling range of the solidified material is increased. You may make it extend in a length direction.

  In the above embodiment, the injection pipe is branched from the supply pipe, but the injection pipe may be an independent solidification material supply path. Further, in the above-described embodiment, a plurality of injection holes and injection pipes are provided, but the present invention includes a single injection hole and a single injection pipe.

It is an axial sectional view of a steel pipe pile showing an embodiment of this invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. It is sectional drawing which shows the construction procedure of a steel pipe pile. It is sectional drawing which expands and shows the hardened layer formed in a steel pipe pile outer periphery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel pipe pile 2 Cutting bit 3 Pipe shaft 4 Excavation blade 5 Inlet 6 Valve 7 Feeding pipe 9 Injection hole 10 Injection pipe 12 Check valve 13 Elbow 14 Rib 15a, 15b Valve 16 Branch joint

Claims (4)

The cutting bit is provided on the cutting bit and is provided with a feed pipe for feeding the drilling fluid during excavation and the solidification material during the rooting process. A steel pipe pile that is connected to the bit so as to communicate with the inlet and is rotationally press-fitted into the ground, and is injected to discharge the solidified material to the outer periphery of the steel pipe at the lower end peripheral wall of the steel pipe during the consolidation process Using a steel pipe pile in which a hole is provided and an injection pipe for the solidified material communicating with the injection hole is provided inside,
Supplying the drilling fluid to the feed pipe, excavating the ground while discharging the drilling fluid from the inlet of the cutting bit, and rotating press-fitting the steel pipe pile;
After reaching a predetermined depth that requires root consolidation, the drilling fluid is switched to the solidified material, the solidified material is discharged from the inlet of the cutting bit through the feed pipe, and the steel pipe pile is rotated while the predetermined depth range is reached. The process of raising and lowering the steel pipe pile with,
And a step of discharging the solidification material from the injection hole to the outer periphery of the steel pipe pile through the injection pipe while rotating the steel pipe pile at the lowered position of the steel pipe pile.   The steel pipe pile rooting method according to claim 1, wherein a rib is provided on an outer periphery of the steel pipe including a portion where the injection hole exists.   The steel pipe pile rooting method according to claim 2, wherein the ribs are spiral.   A branch joint is provided in an upper part of the feed pipe, the injection pipe is connected to the branch joint, and a solidifying material can be selectively supplied to the feed pipe and the injection pipe. The steel pipe pile rooting method according to claim 1, 2 or 3.

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