JPH0629509B2 - Construction method of field construction pile - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for constructing a reinforced concrete field constructed pile as a foundation work for construction work.

[Conventional technology]

As is well known, such a field construction pile is one in which a hole is formed in the ground by using an excavator such as an auger screw, and a reinforcing steel basket is inserted into the hole and then concrete is poured to form a reinforced concrete pillar. Is.

[Problems to be Solved by the Invention]

In such field construction piles, it is required to maintain good bearing capacity for the ground, and treatment of slime and connection between the lower end of concrete and the ground pose problems.

Also, if the hole wall collapses during drilling, the shape of the pile will deteriorate,
It becomes less reliable.

Regarding the treatment of slime, various methods have been conventionally proposed, for example, a method of mechanically removing the slime and a method of mixing soil milk into the slime to generate soil cement. It is extremely difficult to remove it, and the method using soil cement has a lower strength than ordinary concrete.

On the other hand, it has been attempted to fill the inside of the drilled hole with a bentonite solution to prevent collapse of the hole wall, but this is not sufficient.

Further, if the ground is soft, the concrete pile itself constructed along with the subsidence of the ground may be dragged down and lose reliability as a pile.

The object of the present invention is to eliminate the disadvantages of the conventional example, and to ensure the collapse of the pore wall by adjusting the thickness of the stabilizing solution mud cake layer according to the slack of the pore wall when the ground is soft. It is possible to prevent concrete, to effectively remove slime, and to have a good connection with the ground at the tip of the pile, and to cut the edge of the pile side and the ground to obtain a highly reliable concrete pile that is not easily affected by ground subsidence. The purpose is to provide a construction method for on-site constructed piles.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention uses an earth auger with a hollow rotary shaft in which a drilling blade is provided at the tip and a kneading drum is formed in the middle of the pile, while press-kneading the pile hole wall with the drum. After forming a hole and the tip has sufficiently penetrated into the supporting layer such as sand or gravel layer, cement milk is injected into the hole bottom from the end of the rotating shaft while expanding the hole bottom if necessary, and the tip of the earth auger. To improve the support layer by sufficiently kneading with sand or gravel in the support layer, and to make the cement milk into a gelled substance with a curing agent, etc., and take in the slime generated near the bottom of the pile hole inside the gelled substance. With the earth auger, pull up this gelled product, and at the time of this pulling up, the gelled product becomes a plug state in the hole, so the remaining slime is also placed on the drum or gelled product and discharged outside the hole, while, At the same time as the pulling up, the high concentration in the hole Fill the hole with the stabilizer, and then insert the earth auger with a drum with a diameter slightly smaller than the diameter of the drum at the first drilling into the hole again, The gist of the present invention is to knead the wall under pressure to form a stable liquid mud cake layer having an appropriate thickness, and then to construct a reinforcing steel basket in the hole and then to pour ready-mixed concrete.

[Action]

According to the present invention as set forth in claim 1, since the excavated soil is kneaded into the hole wall during the hole excavation, the hole wall is reinforced and its collapse can be prevented. Also, a large amount of slime generated at the bottom of the hole can be eliminated when the earth auger is pulled up by placing it on the drum and the gelled product of cement milk. Furthermore, cement milk injected into the bottom of the hole improves the looseness of the support layer,
In addition, the stable liquid mud cake layer formed on the hole wall acts as a negative friction cut material for concrete piles to cut the edge with the ground, so that even if the ground is soft and there is subsidence, it will not be adversely affected.

Incidentally, the drum for forming the stabilizing liquid mud cake layer has a diameter slightly smaller than the diameter of the drum at the time of the first hole cutting, and the mud cake layer is initially kneaded and pressurized on the wall surface. Consideration was given so that it can be formed by adjusting the required thickness according to the looseness of the hole wall.

In addition, the gelled product of cement milk is in a plug state in the pile hole, and the injection of the mortar or cement milk is
This rise of the gelled substance prevents the lower part thereof from becoming a negative pressure to increase the pulling load of the earth auger, and rather, the injection pressure positively pushes up the gelled auger to help pull up the earth auger.

According to the present invention as set forth in claim 2, in addition to the above action, if a pile hole having a predetermined depth that sufficiently penetrates into the tip portion of the earth auger or a supporting layer such as sand or gravel layer is excavated. , Expand the expansion blade of the earth auger, and use this expansion blade to form a diameter expansion part at the bottom of the pile hole, and use the hollow inside of the rotating shaft before or after that to obtain a predetermined amount of cement milk from the tip to the bottom of the pile hole. When it flows in, the cement milk is mixed with the sand and gravel of the support layer, and improves the support layer loosened by excavation.

In addition, although the gelled product of cement milk becomes somewhat bulbous in this expanded diameter portion, it is relatively soft in itself, so there is no problem in pulling it up.

〔Example〕

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 to 12 are cross-sectional views showing respective steps of the first embodiment of the method for constructing a site constructed pile of the present invention, and the earth auger 1 used in the method of the present invention will be described first.

The earth auger 1 is provided with a screw-shaped drilling blade 4 having a plurality of parallel drilling bits 3 protruding from the end of a hollow rotating shaft 2, and a kneading drum 5 is attached at an appropriate position in the middle of the shaft 2. It is a thing. Further, between the drum 5 of the shaft 2 may be provided a stirring blade 6 or a screw blade (not shown) protruding radially.

As an example, the drum 5 is formed by attaching a fan-shaped body of 90 degrees in a plane so as to be symmetrical with respect to the axis 2, and a lid having a plane shape substantially the same as the plane shape is provided on the upper surface. The diameter of can be changed as necessary by replacing the fan shape.

Using the earth auger 1 as described above, a hole having a predetermined diameter is drilled at the planned drilling position of the pile hole 8 (Fig. 1). In this case, the excavated soil is carried upward by the screw-shaped excavating blade 4,
It is crushed by the stirring blade 6 etc. and becomes fine. Further, a part of it (a considerable amount depending on the soil quality of the excavated soil) is troweled on the wall of the pile hole 8 on the outer peripheral surface of the kneading drum 5 under pressure.

If a suitable amount of water is jetted from the tip of the rotary shaft 2 during excavation, the excavation can be made smooth and the excavated soil can be made mud to facilitate the kneading.

Further, depending on the ground, it may be possible to fill the holes 8 with a stabilizing liquid such as bentonite liquid.

In this way, as shown in FIG. 2, if the earth auger 1 is used to excavate a pile hole 8 having a predetermined depth such that the tip of the earth auger 1 sufficiently penetrates into the support layer 18 such as sand or gravel layer, the rotary shaft 2 When a predetermined amount of cement milk 9 flows into the bottom of the pile hole from the tip using the hollow inside of the cement milk 9,
As shown in the figure, it is filled so as to enclose the drilling blade 4,
When the earth auger 1 is rotated at the same time, the cement milk 9 is mixed with the sand and gravel of the support layer 18 by the excavation blade 4,
Improving the loose support layer 18 by excavation.

Then, or in advance, an appropriate amount of cement hardening agent is injected from the end of the shaft 2 as required. As shown in FIG. 4, if the earth auger 1 is moved up and down and further rotated, the cement milk and the cement hardening agent are uniformly mixed, and the permeability of the hardening agent into the cement milk is improved.

After about 10 minutes, as shown in Fig. 5, the cement milk was gelled by the hardening agent and turned into a cylindrical mass as a whole.
The gelled substance 10 entraps slime generated near the bottom of the pile hole inside. The gelled material 10 can also be formed over time without using a curing agent.

Then, as shown in FIG. 6, when the earth auger 1 is pulled up together with the gelled substance 10 of the cement milk in the form of mud, the remaining slime rides on the drum 5 and the gelled substance 10 and is discharged out of the holes. .

At the time of this pulling up, cement milk 9'is injected to fill the bottom of the pile hole 8, and in the space where the gelled substance 10 is raised by pulling up the auger 1, a space higher than the shaft 2 end of the auger 1 is formed. Bentonite solution 11 or other stable solution having a concentration is injected under pressure.

In addition, the gelled product 10 of the cement milk is plugged in the pile hole 8, and when the bentonite liquid 11 is injected, a negative pressure is applied to the lower part of the bentonite liquid 11 due to the rise of the gelled product 10 and the pulling load of the earth auger 1 is increased. To prevent the increase,
Rather, the injection pressure of the bentonite liquid 11 positively pushes up the gelled substance 10, and the earth auger 1 plays a role of helping pulling up.

Further, since the hole wall is smoothed by the drum 5 as described above, the gelled material 10 can be pulled up smoothly without being caught.

The cement milk 9'filled in the bottom of the pile hole 8 exerts the function of improving the ground of the support layer 18 and fitting with the upper concrete.

Then, as shown in FIG. 7, the earth auger 1 or another auger 1 of the same type, which has been pulled up to the ground to remove the gelled material 10, is again inserted into the pile hole 8 by rotation. At this time, the high-concentration bentonite liquid 11 is trowel-coated on the wall of the pile hole 8 on the outer peripheral surface of the kneading drum 5, and the stabilizing liquid mud cake layer 12 is formed on the wall surface.

The diameter of the drum 5 for forming the stabilizing mud cake layer 12 is set to be slightly smaller than the diameter of the drum at the time of the first hole cutting in FIGS. Consideration was made so that the mud cake layer 12 could be formed on the wall surface that was kneaded and pressed by adjusting the thickness to the required thickness according to the looseness of the hole wall.

After that, as shown in FIG. 8, the inside of the pile hole 8 is replaced with fresh water 16 to prevent the stabilizing liquid from adhering to the reinforcing bar basket 13 described later.
After this, the reinforcing bar cage 13 is installed in the pile hole 8 as shown in FIG. 9, and the tremie pipe 14 is further inserted as shown in FIG. This tremie pipe 14 uses a bottom lid type instead of a plunger type, but by injecting cement milk or fresh concrete into the inside of the tremie pipe 14 in advance and filling it, the inside of the fresh water 16 Prevented floating.

Then, as shown in FIG. 11, the tremie pipe 14 is used to pour the fresh concrete 15 while pulling it up. By placing the green concrete 15 in a pressurized state in the initial stage, it is possible to prevent a fault from occurring at the joint with the cement milk 9 ', and a part of the cement milk 9'is added to the green concrete. You can also remove slime by pushing up on the top of 15.

Further, the pouring of the ready-mixed concrete 15 in a pressurized state can be performed by using a pump instead of using the tremie pipe 14.

In this way, on-site constructed piles of reinforced concrete are formed as shown in FIG.

Next, the invention of claim 2 will be described. As the earth auger to be used, the expanding blade 17 is provided on the excavation blade 4 of the auger 1 described in the first embodiment.

13 to 24 show each process, and ground auger 1
Using the tool, a hole having a predetermined diameter is drilled while ironing the excavated soil on the wall of the pile hole 8 with the kneading drum 5 to the planned drilling position of the pile hole 8 (Fig. 13).

As shown in FIG. 14, if the earth auger 1 is used to dig a pile hole 8 having a predetermined depth such that the tip of the earth auger 1 sufficiently penetrates into the supporting layer 18 such as sand or gravel layer, the earth auger 1 is moved in the opposite direction. When rotated, the expanding blade 17 expands as shown in FIG. 14, and the expanding blade 17 forms the expanded diameter portion 8a at the bottom of the pile hole 8. Before or after that, if the cement milk 9 flows into the bottom of the pile hole from the tip of the hollow inside of the rotary shaft 2 by a predetermined amount, the cement milk 9 is kneaded with the sand or gravel of the support layer, and is excavated. Improves loose support layer.

Then, as shown in FIG. 16, the earth auger 1 is moved up and down and further rotated to gel the cement milk 9 as shown in FIG. As shown in FIG. 18, the earth auger 1 is pulled up together with the gel material 10 as shown in FIG. It should be noted that the gelled substance 10 of the cement milk 9 in the expanded diameter portion 8a becomes somewhat bulbous, but since it is relatively soft in itself, there is no problem in pulling it upward.

At the time of this pulling up, cement milk 9'is injected to fill the bottom of the pile hole 8, and the space where the agglomerate 10 is raised by pulling up the auger 1 is elevated from the end of the shaft 2 of the auger 1. Bentonite liquid 11 with a concentration is pressed in.

Next, as shown in FIG. 19, the earth auger 1 or another auger 1 of the same type, which has been pulled up to the ground to remove the gelled product 10 once, is again inserted into the pile hole 8 again, and the bentonite liquid having the high concentration described above is inserted. 11 is applied to the wall of the pile hole 8 on the outer peripheral surface of the kneading drum 5, and the stable liquid mud cake layer 12 is applied to the wall surface.
To form.

Next, as shown in FIG. 20, the inside of the pile hole 8 is replaced with fresh water 16, and then the reinforcing cage 13 is installed as shown in FIG. 21, and the tremie is shown as shown in FIGS. 22 and 23. The concrete 14 is poured under pressure using the pipe 14.

Placement of fresh concrete 15 under pressure is done by tremie pipe 13
It is also possible to use pumping instead of using.

In this way, a reinforced concrete field-constructed pile having a high bearing capacity with the diameter of the tip expanded as shown in FIG. 24 is formed.

〔The invention's effect〕

As described above, the method for constructing a field construction pile of the present invention, when the ground is soft, adjusts the thickness of the stable liquid mud cake layer according to the slack of the hole wall to form the collapse of the hole wall. The concrete pile can be surely prevented and a good shape can be obtained, and slime can be effectively removed without lowering the bearing capacity. Furthermore, since the edges of the outside of the concrete pile and the ground are cut off by the mud cake layer with a high concentration of bentonite liquid, even if the ground is soft and subsidence may occur, the pile will be adversely affected by it. Instead, cement milk is injected into the bottom of the hole to improve the ground of the support layer, so that the ground is surely connected and a highly reliable pile with a large bearing capacity can be obtained.

Moreover, a series of steps can be performed with one earth auger, which makes the construction speed fast.

[Brief description of drawings]

1 to 12 are examples of the method for constructing on-site constructed piles of the present invention, sectional views showing respective steps, and FIGS. 13 to 24 are sectional views showing respective steps of other examples of the present invention. It is a figure. 1 ... Earth auger, 2 ... Hollow rotating shaft, 3 ... Drilling bit, 4 ... Drilling blade, 5 ... Mixing drum, 6 ... Stirring blade, 8 ... Pile hole, 8a ... Expanded portion, 9 '…… Cement milk, 10 …… Gelified product 11 …… High-concentration bentonite solution 12 …… Stabilizer mud cake layer 13 …… Reinforcing bar basket, 14 …… Tremy tube 15 …… Green concrete 16 …… Shimizu 17… … Enlarged wings, 18 …… Supporting layer

Claims (4)

[Claims] 1. An earth auger with a hollow rotary shaft having a drilling blade at the tip and a kneading drum formed in the middle thereof is used to form a hole while pressure-kneading a pile hole wall with the drum. After the tip has sufficiently penetrated into the support layer such as sand and gravel layer, cement milk is injected into the hole bottom from the end of the rotating shaft and the tip of the earth auger mixes well with sand and gravel in the support layer to support layer. In addition, the cement milk is made into a gelled substance by a hardening agent, etc., and the slime generated near the bottom of the pile hole is taken into the inside of the gelled substance and the gelled substance is pulled up together with the earth auger. Since the gelled substance becomes a plug state inside, the remaining slime is also placed on the drum or the gelled substance and discharged out of the hole, while at the same time as the pulling up, a high-concentration stabilizing solution is injected into the hole. This will fill the hole, then first Insert the earth auger forming a drum with a diameter slightly smaller than the diameter at the time of drilling into the hole again, and press and knead the hole wall with this drum to form a stable liquid mud cake layer of appropriate thickness After that, after constructing a reinforced basket in the hole, the concrete is placed, and the construction method of the site pile is characterized. 2. An earth auger with a hollow rotary shaft having a drilling blade having an expanding blade at its tip and a kneading drum formed in the middle thereof is used to press and knead the pile hole wall with the drum. After the tip is fully penetrated into the support layer such as sand or gravel layer, the earth auger is rotated in the reverse direction to expand the expanding blade and expand the hole bottom, and the cement milk is added to the hole bottom from the rotary shaft end. Improving the support layer by injecting it and thoroughly kneading with sand or gravel in the support layer at the tip of the earth auger, and also making the cement milk into a gelled substance with a hardening agent etc., and near the bottom of the pile hole inside the gelled substance. The gelled substance is pulled up together with the earth auger by taking in the slime generated in 1., and the gelled substance becomes a plug state in the hole at the time of this pulling up, so the remaining slime is also placed on the drum or the gelled substance outside the hole. Discharge to
On the other hand, simultaneously with the pulling up, a high-concentration stabilizing solution is injected into the hole to fill the inside of the hole, and then an earth auger formed with a drum having a diameter slightly smaller than the diameter of the drum at the time of the first drilling. Insert it again into the hole, knead the hole wall with this drum to form a stable liquid mud cake layer with an appropriate thickness, and then build a reinforcing steel basket in the hole and then place fresh concrete. Construction method for on-site constructed piles. 3. The method for constructing a site constructed pile according to claim 1, wherein the ready-mixed concrete is placed in a pressurized state using a tremie pipe. 4. The method for constructing a site constructed pile according to claim 1, wherein the ready-mixed concrete is placed in a pressurized state by pumping.