JPS63197717A - Construction work of in-situ pile - Google Patents

Abstract

PURPOSE:To exactly prevent the degradation of pile wall by a method in which bearing layer is improved to form gel blocks, the gel block is pulled up with an earth auger, a stabilizer solution is injected, and the earth auger is again inserted and pit wall is stabilized to form a pile. CONSTITUTION:An earth auger 1 is turned to improve the bearing layer 18 and pulled up with a gel block 10. A bentonite solution 11 is injected from the end of the shaft 2 of the auger 1, the auger 1 is again inserted into the pit, and the wall of the pit 8 is treated by a trowel. A reinforcing bar cage 13 is then set in the pit 8, and a tremie tube 14 is penetrated to place ready- mixed concrete 15. A good shape of concrete pile can thus be formed, and slime can also be effectively removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for constructing reinforced concrete field-prepared piles as foundation work for construction work.

[Conventional technology and its problems]

As is well known, such on-site piles are created by creating a hole in the ground using an excavator such as an auger screw, inserting a reinforcing bar cage into the hole, and then pouring concrete to form a reinforced concrete column. It is something.

Such on-site construction piles are required to maintain good bearing capacity with respect to the ground, and problems arise in handling slime and bonding the lower end of the concrete to the ground.

Additionally, if the hole wall collapses during drilling, the shape of the pile will deteriorate;
Reliability becomes poor.

Various methods have been proposed for the treatment of slime, including a method of mechanically extracting it and a method of mixing cement milk into the slime to produce soil cement. It is extremely difficult to remove it, and using fill cement reduces its strength compared to regular concrete.

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

Furthermore, if the ground is soft, the constructed concrete piles themselves may be dragged down as the ground subsides, and the reliability of the piles may be lost.

The purpose of the present invention is to eliminate the disadvantages of the conventional example, reliably prevent collapse of the hole wall, and effectively remove slime.
Furthermore, we provide a construction method for site-prepared piles that allows you to obtain highly reliable concrete piles that have a good connection with the ground at the tip of the pile, and are less susceptible to ground subsidence by cutting the edge between the desk side and the ground. It's about doing.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention uses an earth auger with a hollow rotary shaft provided with a digging blade at the tip and a kneading drum formed in the middle. After the tip has sufficiently penetrated the supporting layer such as sand and gravel, cement milk is injected into the bottom of the hole from the rotating shaft end while expanding the diameter of the hole bottom as necessary, and the tip of the earth auger is inserted into the bottom of the hole. The support layer is improved by thoroughly kneading it with the sand and gravel in the support layer, and the cement milk is made into a gel by using a hardening agent, etc., and the gel is pulled up together with the earth auger. At the same time, a highly concentrated stable liquid is added into the hole. was injected, the earth auger was inserted into the hole again, and the hole wall was pressurized and edged with a drum to form a stabilized liquid mud cake layer. Then, after erecting a reinforcing bar cage in the hole, ready-mixed concrete was poured. The gist of this is to

[Effect]

According to the present invention, since the excavated soil is kneaded into the hole wall during hole excavation, the hole wall is reinforced and its collapse can be prevented. In addition, a large amount of slide generated at the bottom of the hole can be removed by placing it on the drum and cement milk gel and pulling up the earth auger. Furthermore, the cement milk injected into the bottom of the hole improves the loosening of the supporting layer, and the stabilizer mud cake layer formed on the hole wall acts as a negative friction cut material for the concrete pile, thereby reducing the edge of the ground. This way, even if the ground is soft and subsides, it will not be affected by the negative effects.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figures 1 to 12 show the first method of constructing on-site piles of the present invention.
First, the earth auger 1 used in the construction method of the present invention will be explained using cross-sectional views showing each step of the embodiment.

The earth auger l is provided with a screw-shaped excavation blade 4 protruding from one or more parallel excavation bits 3 at the tip of a hollow rotary shaft 2, and a kneading drum 5 at an appropriate position in the middle of the shaft 2.
This is the one with the . Furthermore, between the drums 5 of the shaft 2, radially protruding stirring blades 6 or screw blades (not shown) may be provided.

The drum 5 is formed by, for example, a 90 degree fan-shaped body attached symmetrically to the axis 2 in a plane, and is provided with a lid having a planar shape substantially the same as the planar shape on the upper surface, and the drum The diameter of 5 can be changed as necessary by replacing the fan-shaped body.

Using such an earth auger 1, a hole of a predetermined diameter is excavated at the planned excavation position of the pile hole 8 (FIG. 1). in this case,
The excavated soil is carried upward by a screw-shaped excavation blade 4, and is crushed by a stirring blade 6 and the like into fine particles. Furthermore, a portion (a considerable amount, although it varies depending on the quality of the excavated soil) is troweled onto the wall of the pile hole 8 on the outer peripheral surface of the kneading drum 5 under pressure.

Incidentally, if an appropriate amount of water is squirted from the tip of the rotary shaft 2 during excavation, the excavation can be made smoother, and the excavated soil can be turned into mud, thereby making the kneading process even easier.

Furthermore, depending on the ground, it is also possible to fill the hole 8 with a stabilizing liquid such as bentonite liquid.

In this way, as shown in FIG. 2, once the earth auger 1 has excavated a pile hole 8 of a predetermined depth so that its tip sufficiently penetrates 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 interior, the cement milk 9 is filled so as to wrap around the excavation blade 4 as shown in FIG. When rotated, the cement milk 9 is mixed with sand, gravel, etc. of the support layer 18 by the excavation blades 4, and the support layer 18 loosened by the excavation is improved.

Next, or in advance, if necessary, an appropriate amount of cement hardener is injected from the two ends of the shaft. If the earth auger 1 is moved up and down and then rotated as shown in FIG. 4, the cement milk and the cement hardening agent are mixed uniformly, and the hardening agent permeates into the cement milk.

After about 10 minutes, the cement milk is gelled by the hardening agent and becomes a cylindrical lump as shown in FIG. I will take it in. This 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 mud-like cement milk gel 10, the remaining slime rides on the drum 5 and the gel 10 and is discharged out of the hole. .

During this pulling up, cement milk 9' is injected to fill the bottom of the pile hole 8, and the shaft of the auger 1 is placed in the space created by the gelled material 10 rising when the auger 1 is pulled up.
Highly concentrated bentonite liquid 11 or other stable liquid is forced in from the end.

The cement milk gel 10 is in the form of a plug inside the pile hole 8, and when the bentonite liquid 11 is injected, the rise of the gel 10 creates a negative pressure below it, which reduces the lifting load of the earth auger 1. In addition to preventing the increase of the bentonite liquid 11, the injection pressure of the bentonite liquid 11 actively pushes up the gelled material 10 and serves to assist in pulling up the earth auger 1.

Furthermore, since the hole walls are smoothed by the drum 5 as described above, the gelled material 10 can be pulled up smoothly without getting caught.

Further, the cement milk 9' filled in the bottom of the pile hole 8 exerts the effect of improving the ground of the support Ji 18 and the fit with the upper concrete.

Next, as shown in FIG. 7, the earth auger 1 or another auger 1 of the same type, which has been lifted above the ground and the gelled material 10 has been removed, is rotated and inserted into the pile hole 8 again. At this time, the high concentration bentonite liquid 11 is troweled onto the wall of the pile hole 8 on the outer peripheral surface of the kneading drum 5, and a stabilized liquid mud cake layer 12 is formed on the wall surface.

The diameter of the drum 5 used to form the stabilizer mud cake layer 12 is slightly smaller than the diameter of the drum at the time of drilling and cutting in FIGS. We took care to form this 120-layer layer of Matsudoke-Ki to the required thickness on the pressurized wall surface.

Thereafter, as shown in FIG. 8, the inside of the pile hole 8 is replaced with clean water 16 to prevent the stabilizing liquid from adhering to the reinforcing bar cage 13, which will be described later. After doing this, as shown in Figure 9, the pile hole 8
A reinforcing bar cage 13 is built inside, and a tremie pipe 14 is further inserted as shown in FIG. 1O. This tremie tube 14 uses a bottom lid type rather than a plunger set, but by filling the inside of the tremie tube 14 with cement milk or fresh concrete in advance, it is possible to prevent it from floating in the fresh water 16. Prevented the rise.

Then, as shown in FIG. 11, fresh concrete 15 is poured while being pulled up using the tremie pipe 14. By placing the ready-mixed concrete 15 under pressure at the initial stage, it is possible to prevent faults from occurring at the joints with the cement milk 9', and furthermore, a part of the cement milk 9' is poured into the ready-mixed concrete. You can also remove slime by pushing it up with the top of 15.

In addition to using the tremie pipe 14, the fresh concrete 15 can be placed by pumping before processing.

In this way, reinforced concrete field-built piles as shown in FIG. 12 are formed.

Next, the invention of claim 2 will be explained. The earth auger used is one in which an enlarged blade 17 is provided on the excavation blade 4 of the auger 1 described in the first embodiment.

13 to 24 show each process. Using the earth auger 1, the wire layer drum 5 is moved to the planned excavation position of the pile hole 8.
Then, a hole of a predetermined diameter is excavated while applying excavated soil to the wall of the pile hole 8 with a trowel (Fig. 13).

As shown in FIG. 14, once the earth auger 1 has excavated a pile hole 8 of a predetermined depth with its tip sufficiently penetrating the supporting layer 18 such as sand or gravel layer, the earth auger 1 is turned in the opposite direction. When rotated, the enlarged wing 17 as shown in FIG.
expands, and the enlarged wings 17 form an enlarged diameter portion 8a at the bottom of the pile hole 8.
is formed. Before or after that, if a predetermined amount of cement milk 9 is flowed into the bottom of the pile hole from the tip using the hollow interior of the rotating shaft 2, the cement milk 9 is mixed with the sand and gravel of the supporting layer, and as a result of excavation. Repair loose support layers.

Next, as shown in FIG. 16, the earth auger 1 is moved up and down and further rotated, and the cement milk 9 is gelatinized with a constant amount of cement hardening agent, etc., as shown in FIG. A cylindrical mass is formed, and the earth auger 1 is pulled up together with the gelled material 10 as shown in FIG. Note that the gelled product 10 of the cement milk 9 is formed in the enlarged diameter portion 8a.
Although it becomes somewhat bulbous, it is relatively soft in itself, so 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 created by the auger 1 being raised by the lifting of the auger 1 has a high height from the shaft 2 end of the auger 1. A concentrated bentonite liquid 11 is then pressurized.

Next, as shown in FIG. 19, the earth auger 1 or another auger 1 of the same type, which has been lifted above the ground and the gelled material 10 has been removed, is rotated and inserted again into the pile hole 8, and the highly concentrated bentonite liquid is poured into the pile hole 8. 11 is troweled onto the wall of the pile hole 8 on the outer peripheral surface of the kneading drum 5 to form a stabilized mud cake layer 2 on the wall surface.

Next, as shown in FIG. 20, the inside of the pile hole 8 is replaced with fresh water 16, and then the reinforcing bar cage 13 is erected as shown in FIG. 21, and the tremie is installed as shown in FIGS. 22 and 23. Fresh concrete 15 is placed under pressure using pipe 14.

The fresh concrete 15 can be placed under pressure by using a tremie pipe 13 or by pumping.

In this way, an on-site constructed reinforced concrete pile with a diameter-expanded tip and a high bearing capacity is formed as shown in FIG. 24.

〔Effect of the invention〕

As described above, the construction method for on-site piles of the present invention reliably prevents the collapse of the hole wall and provides concrete piles with a good shape, and can also effectively remove slime, which would otherwise cause a decline in bearing capacity. Furthermore, the outside of the concrete pile and the ground are separated by a layer of bentonite mud cake, so even if the ground is soft and subsides, the pile will be dragged by it and have negative effects. Instead, cement milk is injected into the bottom of the hole to improve the ground of the supporting layer, ensuring solid connection to the ground and producing highly reliable piles with large bearing capacity.

Furthermore, a series of steps can be performed with one earth auger, resulting in faster construction speed.

[Brief explanation of the drawing]

Figures 1 to 12 are cross-sectional views showing each step of the construction method for on-site piles according to the present invention, and Figures 13 to 24 are cross-sectional views showing each step of other embodiments of the present invention. It is a diagram. 1... Earth auger 2... Hollow rotating shaft 3... Drilling bit 4... Drilling blade 5... Drum for kneading
6... Stirring blade 8... Pile hole, 8a...
Expanded diameter part 9.9'... Cement milk 10... Gelled product 11... Highly concentrated bentonite liquid 12... Stable liquid mud cake layer 13... Reinforcement cage 14... Tremy tube 15.
...Ready-mixed concrete 16...Shimizu 17...Enlarged wing 18...Support layer 11 diagram
Figure 2 Figure 3 Exit

Claims (4)

[Claims] (1) Using an earth auger with a hollow rotary shaft that has a drilling blade at its tip and a kneading drum formed in the middle, the drum pressurizes the wall of the pile hole while forming a hole to form a hole at the tip. After the cement has sufficiently penetrated the support layer such as sand and gravel, cement milk is injected into the bottom of the hole from the end of the rotating shaft and thoroughly mixed with the sand and gravel in the support layer using the tip of the earth auger to improve the support layer. In addition, the cement milk is made into a gel by using a hardening agent, and the gel is pulled up with an earth auger.
At the same time, a highly concentrated stabilizing liquid is injected into the hole, the earth auger is inserted into the hole again, the hole wall is kneaded under pressure with a drum to form a stable liquid mud cake layer, and then a reinforcing bar cage is inserted into the hole. A construction method for on-site preparation piles that is characterized by pouring ready-mixed concrete after erection. (2) Using an earth auger with a hollow rotary shaft equipped with a drilling blade with enlarged wings at its tip and a kneading drum formed in the middle, the hole is formed while pressurizing and kneading the pile hole wall with the drum. After the tip has sufficiently penetrated the supporting layer such as sand and gravel, the earth auger is rotated in the opposite direction to spread the expansion blades to enlarge the diameter of the hole bottom, and cement milk is injected into the hole bottom from the end of the rotating shaft. The support layer is improved by sufficiently kneading it with the sand and gravel in the support layer at the tip of the earth auger, and the cement milk is made into a gel by using a hardening agent, etc., and the gel is pulled up with the earth auger. A highly concentrated stabilizer was injected into the hole, the earth auger was inserted into the hole again, the hole wall was kneaded under pressure with a drum to form a stabilizer mud cake layer, and then a rebar cage was built inside the hole. A construction method for on-site piles, which is characterized by pouring ready-mixed concrete afterwards. (3) The method for constructing on-site piles according to claim 1, wherein the ready-mixed concrete is cast under pressure using a tremie pipe. (4) The method for constructing on-site piles according to claim 1, wherein the ready-mixed concrete is poured under pressure by pumping.