JPH0657942B2 - Construction method for ready-made piles - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a pre-boring method among low pollution pollution laying methods for ready-made piles, and a method for constructing ready-made piles with a small-scale facility. It is provided.

(Prior Art) Conventionally, there is a pre-boring method represented by a cement milk method as a low-pollution depositing method for ready-made piles. In this pre-boring method, it is necessary to mechanically excavate a hole having a diameter larger than the outer diameter of the pile to be sunk, which requires a large rotational torque and propulsion force and a large construction machine.
In the case of the pre-boring method, excavating with an auger screw etc. and injecting a cementing agent such as cement milk into the hole to replace it, but due to sedimentation of slime, it is difficult to obtain sufficient tip support force, and further Since the amount of soil discharged by excavating machines is large, its disposal is a problem.

(Problems to be Solved by the Invention) The present invention is intended to solve the above-mentioned drawbacks of the prior art, and is a small construction machine, which has a small amount of earth removal, a tip supporting force, and a peripheral friction force. The purpose is to provide a construction method for ready-made piles that can be taken large.

(Means for Solving Problems) The present invention is to rotate a cutting rod having an excavation bit at its tip to lower the excavation liquid from the bit portion while injecting it at a high pressure of 100 kg / cm ² or more to inject the soil. Mixing and stirring by excavation to form a mud-like excavation hole with fluidity in the ground, and after reaching a predetermined depth, switch the excavating liquid to a rooting liquid and level it further at a higher pressure than the side of the bit section. While spraying, the drill rod is rotated, lowered or pulled up to form a root consolidation part having a diameter larger than the above drill hole at the bottom of the drill hole,
After that, the excavation rod is collected, and then a prefabricated pile is inserted into this hole, and the precast pile is sunk.

The excavating bit used in the present invention has an injection hole capable of injecting the excavating liquid horizontally or horizontally and downward, and the diameter of the excavating bit makes the circulation of the excavating liquid smooth and the self-sustaining stability of the surrounding ground. Is set within a range that keeps the above value, and it is sufficient if the outer diameter is slightly larger than that of the excavation rod.

Excavation of the ground by high pressure jet flow is different from mechanical digging
Even if the bit diameter is increased, the jet flow from the bit agitates and fluidizes the ground extensively, so excavation resistance is extremely small and large rotating torque and propulsion force are not required, so it is easy to use on a small machine. Large diameter holes can be drilled. The injection pressure requires a pressure of 100 kg / cm ² or more. The injection pressure required to fluidize the soil varies depending on the soil properties of the surrounding ground, and is 100 to 200 Kg / cm ^{2 for} loose sandy soil layers and soft cohesive soil layers, and for tightly sandy soil layers and hard cohesive soil layers. Injection pressure of 200Kg / cm ² or more is required.

If the pressure of the drilling fluid is set in the above range, it is possible to easily fluidize the area where the pile can be sunk.

In addition, when drilling a diluvial cohesive soil layer that has poor excavability due to a jet flow or a gravel layer that has poor hole wall stability, high excavation energy is required, so it may be necessary to slow down the excavation speed. In order to efficiently fluidize and stabilize such a ground, if a stirring blade is additionally installed, the stirring effect of soil is improved, and it becomes possible to carry out construction without lowering the drilling efficiency.

The drilling liquid used in the present invention is not particularly limited, and a ground stabilizing liquid such as water / circulating mud or bentonite mud, or a solidifying liquid containing cement milk, water glass, lime or the like is used. In order to promote fluidization of the ground, if necessary, for clay soil, surfactant for sandy soil,
A thixotropy-imparting agent such as magnesium hydroxide or silica sol, and a water-soluble sizing agent such as methyl cellulose may be appropriately blended.

In the present invention, after excavating and fluidizing an excavation hole by a high-pressure jet flow to a predetermined depth, a root consolidation portion having a diameter larger than that of the excavation hole is formed at the bottom thereof.

It is preferable that the diameter of the root consolidation portion at the bottom of the excavation hole is approximately 1.5 times the pile diameter and the length is at least 1.5 times the pile diameter.

The formation of the root consolidation section is carried out by rotating, lowering or pulling up the excavation rod while horizontally injecting the root consolidation solution at a high pressure from the side of the bit section.

The method of enlarging the root consolidation part from the drill hole is to increase the injection pressure or reduce the rotation speed of the injection hole and slow the rising or lowering speed, because the excavation stirring distance due to the jet flow becomes longer, so easily. A targeted consolidation portion having an enlarged outer diameter can be obtained.

As the root-hardening liquid used here, a cement-based hardening liquid such as cement milk that hardens after the completion of construction to develop strength is used.

The piles are set by placing ready-made piles in the fluidized holes, inserting them using their own weight, and then press-fitting / rotating high-frequency vibration or a combination thereof. The pile is sunk while pushing away the fluidized upper particles. At that time, the rotation of the pile and the slight vibration due to the high frequency vibration are used as an auxiliary means for press-fitting. Rotation is particularly effective for press-fitting into a cohesive soil layer, and micro-vibration is particularly effective for press-fitting into a sandy soil layer.

Embodiment An embodiment of the present invention will be described with reference to the drawings.

First, the excavator body was moved to the pile sunk position, and the excavation rod was aligned with the pile core.

Next, as shown in FIG. 1, surface layer excavation was carried out at a depth of 1 m by an auger bit 2 attached to an excavation rod 1 to remove obstacles such as surface debris and wood chips.

As shown in FIG. 2, a steel pipe having a diameter of 500 mm was press-fitted into this excavation hole to hold the head of the water and to treat the muddy water to form a casing 3.
A muddy water pump 4 for circulating muddy water was attached to this casing, then an excavation bit 5 (outer diameter 200 mm) was attached to the excavating rod 1 (outer diameter 85 mmφ), and the muddy water circulated through the swivel 6 was used as the excavating liquid. Drilling was carried out to a predetermined depth of 18.5 m while spraying horizontally and downward from the two spray holes installed in the drill bit.

At this time, the rotation speed of the excavation rod 1 is 40 rpm, and the excavation speed is 0.5.
It was performed at ~ 2.0 m / min. The injection amount of the drilling fluid was about 70 / min, and the injection pressure was 100 to 200 Kg / cm ² .

In order to enhance the fluidization of soil particles in the hole and facilitate the sinking of the pile, the stirring blade 9 (diameter 4
00 mm) was attached.

After excavating to a predetermined depth (18.5 m), the excavating liquid was switched to the root compacting liquid, and the injection pressure was injected from the horizontal injection hole at a high pressure of 230 to 250 Kg / cm ² , and the rotation speed of the excavating rod was 3 rp.
At a m pulling speed of 10 cm / min, a rooted portion was formed at the bottom of the drill hole for a predetermined length (1.2 m). (See Figure 3).

As the root-hardening liquid, water and cement milk having a cement ratio of 60% and a bleeding inhibitor to a cement ratio of 1% were used.

After forming the rooting part, the excavating rod and the excavating bit 5 were collected as shown in FIG. At this time, the drilling fluid and the root consolidation fluid were not sprayed.

The pile 10 was inserted by inserting the pile 10 having a diameter of 400 mm into the excavated pile. In this example, the pile is inserted only up to 7m by its own weight,
After that, the pile was sunk to a depth of 18 m by rotary press-fitting. (FIGS. 5 and 6) (Effects of the Invention) The present invention rotates the excavating rod having the excavating rod having a diameter larger than that of the excavating rod at the tip thereof as described above, and the excavating liquid from the bit portion is 100 kg / cm ² or more. While spraying at a high pressure, the soil is excavated and mixed with the jet stream to form a mud-like hole with fluidity in the ground, and after reaching a predetermined depth, the excavating solution is consolidated. The pressure is further increased from the side of the bit part, and the excavation rod is rotated downward or raised while horizontally injecting to form a rooted part having a diameter larger than that of the excavation hole at the bottom of the excavation hole, and then the excavation rod is recovered, After that, the present invention relates to a method for laying down prefabricated piles, which comprises inserting prefabricated piles into the holes and burying them.

According to the construction method of the present invention, since the drilling fluid is drilled while being jetted at a high pressure of 100 kg / cm ² or more, a large torque is not required unlike the conventional construction method, the drilling torque is small, and the jetted drilling fluid is also used. Since it can be easily circulated, it is possible to easily excavate a long distance with a small machine as in a normal boring.

Further, the construction method of the present invention does not need to completely replace the inside of the excavation hole with cement milk or muddy water as in the conventional construction method, and since the pile only fluidizes the ground in the range necessary for sunk, it is suitable for pile construction. The amount of soil that accompanies it is small and the treatment is economical.

Furthermore, cement milk is sprayed into the supporting ground to form root-hardening bulbs. In this building process, fine clay such as silt and viscosity in the ground and particles with low specific gravity are discharged at high pressure. Since it is expelled by milk etc. and rises up the excavation hole and is replaced, slime is unlikely to settle at the bottom of the hole, and the expanded root solidification part is filled with cement milk etc. in the voids of sand and gravel in the ground. Since it becomes mortar or concrete shape, it has high strength after hardening,
By fixing the tip of the pile to the ground, it exerts a strong supporting force.

Further, in forming the enlarged bulb portion, there is an advantage that unlike the conventional method, it is not necessary to use an expanding blade but a small diameter bit can form a bulb-shaped object having a diameter larger than the pile diameter. Therefore, by removing the slime that does not contribute to the strength and creating a bulb having a large diameter, the bearing capacity of the pile can be greatly exerted.

In addition, if a congealing liquid such as cement milk is used as the drilling liquid, it solidifies in the excavated hole fluidized after the pile is laid down, and the pile and the surrounding ground are firmly connected to each other. Friction force around the pile is developed.

[Brief description of drawings]

1 to 6 are explanatory views showing a construction procedure in one embodiment of the present invention, and FIG. 6 shows a completed view of a pile constructed according to the present invention. In the figure, 1 is an excavation rod, 2 is an auger bit, 3 is a casing, 4 is a mud circulation pump, 5 is an excavation bit, 6 is a swivel, 7 is a rooting part, 8
Is an injection hole, 9 is a stirring blade, 10 is a ready-made pile, G is the ground, C is a rooting liquid, and K is a drilling liquid.

Claims (1)

[Claims] 1. A drilling rod having a drilling bit having a diameter larger than that of the drilling rod is rotated, and the drilling fluid is jetted from the bite portion while being jetted at a high pressure of 100 kg / cm ² or more, and the soil is jetted and mixed by jet flow. After being stirred, a mud-like hole with fluidity is formed in the ground, and after reaching a predetermined depth, the drilling liquid is switched to the rooting liquid, and horizontal drilling is performed at a higher pressure from the side of the bit section. Rotate, descend or pull up, form a root consolidation part with a diameter larger than the upper drill hole at the bottom of the drill hole, then collect the drill rod, then insert a ready-made pile into this hole and set it down. Construction method for prefabricated piles characterized by