JP3524074B2 - Construction method of pile - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a pile including a step of drilling with an earth auger and injecting a cement milk mixture liquid under pressure.

[0002]

2. Description of the Related Art This conventional method is carried out by the following procedure. In other words, the earth auger drills to the required depth according to the length of the pile material, stops the rotation and progress of the earth auger, or stops the progress while continuing the rotation,
Next, the cement milk mixture is pressurized and supplied to the passage in the screw from the mortar plant on the ground through a hose that is connected in advance to the upper end of the screw, and the o, located at the bottom of the drilling hole, is ejected from the head. Start the injection into the drilling hole, and after the cement milk mixture has been filled sufficiently above the auger head position, continue the injection and pull up the screw to the predetermined height position to stop the injection, and The screw is pulled out, and then H steel, a steel pipe, or a concrete pile, which is a pile material, is built in the drilled hole into which the cement milk mixed liquid is injected.

At the start of injecting the cement milk mixture, the reason why the screw is started to be lifted after the mixture is filled to a position sufficiently higher than the auger head is that the cement milk mixture to be injected into the lower part of the drilling hole. In addition, if soil blocks are mixed and hardened as it is, the root consolidation strength becomes insufficient. That is, if the screw is pulled up while injecting the mixed liquid in a state where the mixed liquid of cement milk does not reach the upper side of the auger head, the screw pulling speed becomes too fast and the injection of the mixed liquid cannot catch up. When this happens, the inside of the drilled hole on the lower side of the auger head becomes lower than the surrounding earth pressure, causing the collapse of the inner surface of the drilled hole and the depression of the excavated mass on the upper side of the auger head. The soil clod easily mixes in, resulting in insufficient consolidation strength.

[0004]

In the conventional method for constructing H steel piles, the auger head has an outlet for the cement milk mixed liquid supplied through the passage inside the screw, and the check outlet is provided at the outlet. A valve is provided, and at the position of the check valve, the cement milk mixed liquid may be clogged in a state where it does not spout. For example, foreign matter such as stones or lumps of sand may be caught in the check valve protection portion of the auger head depending on the soil quality of the portion to be drilled so that the check valve does not open. In such a case, the supply pressure of the cement milk mixture liquid pressurized and supplied from the mortar plant by the mortar pump rises to the high pressure set by the safety valve of the mortar plant.

Even when the check valve is open,
When filling the upper part of the auger head with the liquid mixture during the injection of the liquid mixture of cement milk, the supply pressure of the liquid mixture of cement milk usually rises to the set pressure set by the safety valve. In other words, a considerably high pressure is required to fill the formulation liquid on the upper side of the auger head.

The set pressure of the safety valve is, of course, within the allowable pressure range of the hose, but the hose may be damaged due to use and may leak at a pressure lower than that at which the safety valve operates, or rarely burst. . If the hose bursts during construction in an urban area, the cement milk liquid mixture will be scattered and fall on passersby, causing a problem. That is,
Although there is no danger of personal injury due to a shield wall or the like in preparation for the fall of foreign matter, there is a problem that the scattering of mud liquid will almost certainly damage clothes.

In the conventional construction method, the outlet of the auger head may be clogged, or the cement milk mixture may not be filled in the upper side of the auger head at the initial feeding stage. Since the supply of the cement milk mixed liquid is started and the supply pressure rises, the hose is often subjected to a high pressure higher than the normal injection pressure. Therefore, there are many opportunities for the hose to burst.
If the outlet of the auger head is found to be clogged, the cement milk mixture cannot be injected, so the screw must be pulled out to remove foreign substances before it is inserted, and injection will be restarted. There is also a problem that the construction will be delayed by that amount because it will take another measure, which is troublesome and requires extra time for the work. An object of the present invention is to solve the problems that the outlet of the auger head is clogged and the cement milk mixture is hard to be filled on the upper side of the auger head.

[0008]

[Means for Solving the Problems] The means of the present invention is to mix a cement milk from an auger head through a hose connecting a mortar plant to the upper part of a screw and a passage in the screw by boring a ground auger to a predetermined depth. Withdrawing the screw while injecting the liquid into the hole under pressure,
Then, in the method of constructing a pile to build a pile material in the cement milk mixture liquid in the drilling hole, by supplying pressurized air into the hose prior to pressure injection of the cement milk mixture liquid from the auger head, The feature is that air outflow from the surface opening of the drilled hole is confirmed.

By this means, it is possible to confirm that there is no clogging in the vicinity of the cement milk mixture outlet of the auger head by supplying pressurized air and confirming the air outflow before the pressurized injection of the cement milk mixture. That is, when there is no clogging, the supplied pressurized air is jetted into the drilling hole and rises in the drilling hole to reach the ground surface so that it can be seen, so if the cement milk mixture is supplied after that,
The cement milk liquid mixture is surely injected from the auger head into the drilling hole and rises to the pressure required for injection, but it rarely rises to the maximum pressure like when the outlet is clogged, so careless Bursting of the hose by injecting cement milk formulation into the is greatly reduced. Also,
When it is found that the outlet is clogged, the screw is pulled out to remove the foreign matter, but since the passage in the screw is not filled with the cement milk formulation liquid, the foreign matter can be relatively easily removed. .

In the above-mentioned means, it is preferable to supply pressurized air into the hose while continuing the drilling while the drilling is in progress to eject the air from the cement milk mixture outlet of the auger head. Item 2). By this means,
Usually, multiple piles are constructed one after another, so it is almost clear at the first construction whether or not the auger head outlet is soil that is likely to be clogged, so this method is applied when it is determined that clogging is likely to occur. . When air is blown from the middle of drilling, if air is blown from the beginning, dust easily scatters, but if excavation progresses to a certain extent, the scattering is prevented, and clogging occurs at shallow positions. Even if it occurs, since the soil pressure is low, it is likely to be released by the air pressure when the air is jetted, and it hardly remains stuck. And when drilling while continuing air injection,
The soil near the auger head is agitated and turned into a mud-like state containing air. The air also floats, and clogging at the outlet is greatly reduced. As a result, even at the stage where the drilling has proceeded to a predetermined depth corresponding to the length of the pile, the auger head outlet is not clogged in most cases. Therefore, it is possible to save the trouble of pulling out the screw from the drilling hole, cleaning and re-inserting it in order to remove the foreign matter from the vicinity of the outlet of the auger head.
Further, since the hole is drilled while continuing the air injection, the excavated soil mudized into the above-mentioned air is being discharged upward by the screw, so the discharging action is when air injection is not performed. It is performed smoothly compared to the above, there is mud-like excavated soil containing air on the upper side of the auger head, and during the injection of the cement milk mixed solution, when filling the mixed solution on the upper side of the auger head, Since the excavated soil is pushed up, and the excavated soil is discharged smoothly, it is easily filled, and the supply pressure of the mixed solution does not rise extremely.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an apparatus used for this pile construction method, 1 is an earth auger, 2 is a rough terrain crane supporting the earth auger, 3 is a mortar plant, 4 is a high pressure compressor, and 5 is power generation. It is a machine. The earth auger 1 includes a screw 11 having a head 10 at the lower end and an upper end portion of a screw 11 for rotating the motor 1 by a motor.
2 is connected to the screw 11. There is a fluid passage inside the screw 11, and one end of a hose 13 for supplying a cement milk mixture is connected to the upper end of this fluid passage through a swivel joint. It is possible to discharge the cement milk formulation liquid that is pressurized and supplied through the stop valve. Further, the other end of the hose 13 is connected to a mortar plant 3 equipped with a grout mixer and a mortar pump, whereby a cement milk mixed liquid can be supplied under pressure, and the hose 13 is pressurized from a high pressure compressor 4. Air can be supplied by appropriate valve operation.

Piles are built using this apparatus in the order shown in FIG. That is, first, the auger head 10 at the lower end of the screw is accurately set at the pile core position (see FIGS. 1 and 2).
(See (a)), after confirming the verticality of the screw 11,
Drilling is started (see FIG. 2B). When the drilling progresses to a predetermined depth and finishes drilling (see FIG. 2 (c)), the earth auger 1 continues to rotate and the auger head 10 is drilled without applying a vertical load during drilling. Pressurized air is supplied through the hose 13 in a state of being suspended inside 14. It is difficult to make this air pressure higher than the maximum supply pressure of the cement milk formulation liquid, but it should be as high as possible. As a result, when the outflow of air from the surface opening of the drilled hole 14 is recognized, the outlet of the auger head 10 is not clogged, so the cement milk mixture liquid is injected. When the auger head 10 is rotated at a fixed position in the early stage of supplying the cement milk mixture, the auger head 10 is driven by the discharging action of the screw and the supply pressure of the cement milk mixture.
The cement milk mixture is filled on the upper side of. This filled state can be determined by the amount of the cement milk mixed liquid fed while the auger head 10 is rotating at a fixed position.
When this filling is done properly, ground auger 1
While continuing the rotation, it is pulled up according to the rise of the liquid level of the cement milk mixed liquid (see Fig. 2 (d)), and when the required amount of the cement milk mixed liquid is supplied, the supply is stopped and the liquid is completely drawn. Pull out. Next, pile material, for example H steel 15, is drilled 14
Installed in the cement milk mixture 16 in the
After the state of (e), the building is completed as shown in FIG. 2 (f). Incidentally, when showing an example of a cement milk liquid combination, cement 600kg during compounding solution 1 m ^3, bentonite 25 kg, the rest is water 0.79 m ^3.

At the stage where the high-pressure air is supplied from the hose 13, if no air jet is observed at the surface opening of the drilled hole 14, the outlet of the auger head 10 is blocked. In this case, the earth auger 1 is once pulled out from the drilled hole 14, the foreign matter is removed, and the earth auger 1 is reinserted. Then, pressurized air is supplied to confirm that there is no clogging, and then the cement milk mixed liquid 16 is supplied to build the pile. Then, in the next drilling, for example, as shown in FIG.
The high-pressure air is started to be supplied to the hose 13 from the stage where the drilling shown in (1) is slightly advanced, and the high-pressure air is continuously supplied from the auger head 10 until the drilling is completed. At the stage where the predetermined drilling depth is reached and the progress of the drilling is stopped, if air is ejected from the surface opening of the drilling hole 14, the mortar mixture is supplied in the same manner as described above, and the screw 11 is turned on. Pull out and insert pile material. In addition, in the dozens of on-site tests in which holes were drilled while supplying high-pressure air from the midway, there has been no case so far in which the outlet of the auger head 10 is blocked. In addition, in the test of filling the cement milk mixed liquid on the upper side of the auger head following the similar drilling test, there is no case where the filling becomes difficult.

In the method of constructing such a pile, the cement milk mixture is injected by the auger head 1 of the earth auger 1.
Since it is performed after confirming that the 0 outlet is not clogged, the pressure is set so as to oppose the earth pressure near the auger head. That is, the cement milk formulation liquid is supplied at a pressure slightly higher than the supplied air pressure. This is a much lower pressure than if the outlet of the auger head 10 is blocked and the hose 13 is very unlikely to burst. When the outlet of the auger head is clogged, the pressure rises to the maximum supply pressure set in the mortar plant 3 that supplies the cement milk mixture, so that the possibility of the hose bursting increases.

Further, in the construction method in which air is jetted from the outlet of the auger head 10 during drilling, clogging of the outlet of the auger head 10 can be prevented and the auger head 1 can be formed at the end of drilling.
It is possible to confirm that there is no clogging at the outlet of 0, and the excavated soil is agitated by air and becomes a mud containing air, so that the adhesive force to the screw is weakened and the discharge is performed smoothly, and the cement milk It becomes easy to fill the upper side of the auger head with the mixed solution at the initial stage of supplying the mixed solution. Therefore, the maximum preset pressure is less likely to act on the hose 13, and the hose 13 can be prevented from bursting. Also, because cleaning due to clogging can be almost eliminated,
The work efficiency is improved, and the rupture of the hose 13 is almost eliminated, so that the clothes of a passerby can be prevented from being damaged.

[0016]

According to the invention of claim 1, the hose can be prevented from bursting while the cement milk mixture is being supplied by the hose. Therefore, the cement milk mixture is scattered in the air in the urban area and the clothes of passersby are obtained. In addition, since the clogging of the outlet is detected by air, the inside of the screw passage is air, and when the clogging is detected, the foreign matter removal work is completed with the cement milk mixture liquid. There is an effect that is easier than when there is. According to the second aspect of the present invention, since the outlet of the auger head can be prevented from being clogged, it is possible to save the trouble of taking the screw and the auger head in and out of the drilled hole for cleaning, and further to the upper side of the auger head. This has the effect of easily filling the cement milk liquid mixture.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an apparatus used in the method of the present invention.

2A to 2F are cross-sectional views of a holed portion showing sequentially different states for explaining an embodiment.

[Explanation of symbols]

1 earth auger 2 rough terrain crane 3 Mortar plant 4 High pressure compressor 5 generator 10 auger head 11 screw 12 Rotation drive 13 hose 14 Drilling 15 H steel 16 Cement milk liquid mixture

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) E02D 7/00 E02D 3/12

Claims (2)

(57) [Claims] 1. A ground milk auger is drilled to a predetermined depth, and then a cement milk mixture is pressure-injected into the drilled hole from an auger head through a hose connected from the mortar plant to the upper part of the screw and a passage in the screw. While pulling out the screw, after that, in the method of constructing the pile in which the pile material is built in the cement milk mixture liquid in the drilling hole, pressurizing the hose prior to pressure injection of the cement milk mixture liquid from the auger head. A method for constructing a pile, characterized in that air is supplied to confirm the outflow of air from the surface opening of the drilled hole. 2. The method for constructing a pile according to claim 1, wherein pressurized air is supplied into the hose while continuing the drilling while the drilling progresses, and the cement milk mixture outlet of the auger head is provided. A method for constructing a pile, characterized in that air is ejected from the pile.