JP3669577B2 - Construction method of cast-in-place piles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for constructing a cast-in-place pile by installing an injection bag at the tip of a reinforcing bar.
[0002]
[Prior art and problems to be solved by the invention]
A method is known in which cast-in-place piles are constructed after preloading the ground at the tip of the pile by injecting grout or the like into an injection bag installed at the tip of the reinforcing bar. This construction method has the following problems.
(1) The following phenomena (a), (b), (c) are considered to occur in the infusion bag, the base fabric of the infusion bag is cut due to them, and grout flows out of the infusion bag, The case where the required pressurization is not performed is assumed.
(A) The injection bag is sandwiched between the pile hole hole wall ground and the frame for setting the injection bag, and the base fabric of the injection bag is caught by the frame to restrain the movement.
(B) The injection bag is sandwiched between the pile hole hole wall ground and the injection bag laying frame, and the movement of the base fabric of the injection bag is restrained by the frictional force.
(C) When the injection bag is sunk at the bottom of the hole, the base of the injection bag is cut by contact with the pile hole ground or the like.
(2) When grout or the like is injected into the injection bag and pressurized, the dehydration phenomenon of the grout occurs. Excessive dehydration causes clogging such as grout in the infusion bag, and gives non-uniform pressure in the infusion bag. In order to prevent this, a separation reducing material is mixed in grout or the like, but the separation reducing material is expensive.
(3) When the base of the injection bag is cut at the time of injection and injection pressure cannot be applied, the grout that has flowed out may be washed away by underground water in the ground.
[0003]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems, and is intended to recover the injection pressure lowered by the outflow of the grout and the like and to reinforce the ground, by cutting the base fabric of the injection bag, preventing excessive dehydration. .
Therefore, the present invention is a method for constructing a cast-in-place pile in which the ground at the tip of the pile is preloaded by an injection bag attached so as to surround the frame for settling fixed to the tip of the reinforcing bar,
The injecting bag is covered with a bag that covers the protruding portion of the setting frame and that has a hole for passing through the water in the hole at the time of setting.
Further, the present invention is characterized in that the bag is made of an impermeable material.
[0004]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a diagram for explaining a method of constructing a cast-in-place pile that covers an injection bag at the tip of a reinforcing bar rod with a bag, and FIG. 2 is a diagram schematically showing a state in which the injection bag and the bag are vertically divided.
In FIG. 1, a steel injection bag laying frame 3 is attached to a tip of a reinforcing bar 2 disposed in a pile hole 1 for constructing a cast-in-place pile with a fixture 4 such as a wire. An injection bag 6 is attached so as to surround the settling frame 3, and a bag 5 is provided to cover the injection bag 6. The ground at the bottom of the pile hole is pressurized by pressure-injecting grout or the like into the injection bag 6 through an injection pipe (not shown) extending from the ground with a reinforcing bar lowered at the bottom of the pile hole 1. In addition, when the grout etc. are pressure-inject | poured into the injection | pouring bag 6, the bag 5 uses a water-impermeable raw material, such as a vinyl sheet, so that excessive dehydration such as grout does not occur.
[0005]
In FIG. 2, the upper and lower base fabrics (actually the edges thereof are stitched together) constituting the infusion bag are indicated by 6a and 6b, and the upper and lower fabrics constituting the bag around the infusion bag. Cover with 5a, 5b (actually the edges are sewn together), and fix by tying the set frame 3 with a string with the cover sheet 7 interposed. The cover sheet 7, the upper cloth 5a of the bag, and the upper base cloth 6a of the infusion bag are respectively provided with a required number and predetermined dimensions of holes 8 for passing the injection pipe and holes 10 for temporarily fixing the tape. The injection pipe 11 extends from the ground into the injection bag, and grout and the like are pressurized and injected into the injection bag, and the injection bag 6 can be temporarily fixed to the set-up frame 3 with the temporary fixing tape 12. ing. Further, the upper and lower cloths 5a and 5b and the cover sheet 7 constituting the bag are each formed with a cross-shaped cut in the center portion to form a hole 9 for passing through the water in the hole. The water resistance is reduced.
[0006]
FIG. 3 is a view showing an example in which the protrusion of the sinking frame is covered.
As described in the problem, when the injection bag is sandwiched between the hole wall ground and the frame for settling, the base fabric of the injection bag is caught on the frame, or the movement of the base fabric of the injection bag is restricted by the friction force, The base fabric of the infusion bag is cut. Therefore, as shown in the figure, the projection of the laying frame is covered with a soft material to eliminate the acute angle portion. Since the covering portion 15 formed in this way has no sharp protrusions, the movement of the base fabric of the infusion bag can be restricted and the base fabric can be prevented from being cut.
[0007]
FIG. 4 is a diagram showing a state in which the setting frame is crushed and spread at the hole bottom.
At the bottom of the hole, the frame for installation is crushed and spread by the weight of the reinforcing bar, and when the base fabric of the injection bag is cut at the time of grout pressure injection, the grout 22 flows out into the ground as shown in FIG. This is minimized by the presence of a bag covering the bag. In this case, the quick setting grout etc. 21 is inject | poured, and the outflow path | route of the grout etc. of the lower part of the pile body 20 and an injection | pouring bag is blocked, and the ground is strengthened. And after required intensity | strength expresses in the quick setting grout etc., injection | pouring pressurization of grout etc. can be performed again and a required preload can be given.
[0008]
【The invention's effect】
As described above, according to the present invention, the following effects can be achieved.
(1) By covering the infusion bag with a bag, it is possible to prevent the infusion bag from being damaged when it is laid or injected with grout or the like.
(2) By using an impermeable base fabric for the bag covering the infusion bag, the amount of separation reducing material mixed in the infusion grout can be reduced.
(3) By covering the protruding portion of the settling frame, the injection bag is not damaged when settling, and the injection bag is easily moved in the bag when pouring grout or the like, and is not easily caught by the settling frame.
(4) Even when the injection bag is torn, the outflow of the grout is minimized due to the presence of the bag. By injecting the quick-setting grout, the injection pressure can be recovered and the ground can be strengthened. .
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a method for constructing a cast-in-place pile that covers an injection bag at the tip of a reinforcing bar rod with a bag.
FIG. 2 is a diagram schematically showing a state where an injection bag and a bag are divided into upper and lower portions.
FIG. 3 is a view showing an example in which a projection of a sinking frame is covered.
FIG. 4 is a diagram showing a state in which the sunk frame is crushed and spread.
FIG. 5 is an explanatory diagram at the time of injection of quick setting grout or the like.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Pile hole, 2 ... Reinforcing bar, 3 ... Setting frame, 4 ... Fixing tool, 5 ... Bag, 6 ... Injection bag, 7 ... Cover sheet, 8 ... Hole for injection pipe passage, 9 ... Water passage through hole Hole 10 for temporary fixing tape passage, 11 injection pipe, 12 tape for temporary fixation, 20 pile body, 21 grout for quick setting, 22 underground into injection Leaked grout etc.

Claims (2)

In the construction method of cast-in-place pile that preloads the ground at the tip of the pile with an injection bag attached so as to surround the settling frame fixed to the tip of the reinforcing bar,
A cast-in-place pile construction method characterized by covering the projecting portion of the settling frame and covering the injection bag with a bag in which a hole for passage of water in the hole at the time of settling is formed .   The construction method according to claim 1, wherein the bag is made of an impermeable material.

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