JPS6286223A - Settlement work of prefabricated pile - Google Patents

Abstract

PURPOSE:To increase the bearing capacity of a prefabricated pile by a method in which the ground is excavated to a given depth by jetting an excavating liquid at high pressures from the bit of an excavating rod, the excavating liquid is replaced with a foot-protecting liquid to form a foot-protected portion, and a pile is set into the pit. CONSTITUTION:The surface layer is excavated by an auger bit 2 to remove out obstructions, and while an excavating rod 1 is turned and also an excavating liquid K is jetted at a high pressure of 100kg/cm<2> or more form the tip of an excavating bit 5, the excavation is made to a given depth. The liquid K is then replaced with a foot-protecting liquid C to form a foot-protected portion on the bottom of the excavated pit, and the rod 1 and the bit 5 are recovered. A custom-made pile 10 is further settled into the pit.

Description

[Detailed description of the invention] (Industrial application field) The present invention is a low-pollution method for sinking ready-made piles.

This paper relates to improvements to the pre-poling method, and provides a method that allows ready-made piles to be constructed using small-scale equipment.

(Prior Art) Conventionally, as a low-pollution method for sinking ready-made piles, there is a pre-poling method represented by the cement milk method. This pre-poling method requires mechanically excavating a hole with a diameter larger than the outside diameter of the pile to be sunk, which requires large rotational torque and driving force, and requires large construction machinery.

In addition, in the case of the prebo IJ Ngué method, drilling is performed using an auger screw, etc., and a solidifying agent such as cement milk is injected into the hole to replace the hole, but due to sedimentation of slime, it is difficult to obtain sufficient support at the tip, and furthermore, the auger screw etc. The amount of soil removed by excavation machines is large, and its disposal has become a problem.

(Problems to be Solved by the Invention) The present invention aims to eliminate the drawbacks of the prior art as described above.It is a small construction machine, has a small amount of soil removed, and has a low tip support force and peripheral friction force. The purpose is to provide a method for constructing ready-made piles that can be made large.

(Means for Solving the Problems) The present invention rotates a drilling rod having a drilling bit at its tip, and pumps drilling fluid from the pit at 100 K? The drilling liquid is lowered while being injected at a high pressure higher than AD, and the soil is mixed and agitated by the jet flow to form a fluid mud-like drilling hole in the ground.After reaching a predetermined depth, the drilling fluid is poured into the ground. Switch to the foot hardening liquid and rotate, lower or pull up the drilling rod while spraying horizontally at higher pressure from the side of the bit part to form a foot hardening part with a larger diameter than the above drilling hole at the bottom of the drilling hole, and then excavation. This invention relates to a method for sinking ready-made piles, in which the rods are collected, and then the ready-made piles are inserted into the holes and then sunk.

The drilling bit used in the present invention has an injection hole that can spray drilling fluid horizontally or both horizontally and downward, and the diameter of the drilling bit is designed to ensure smooth circulation of the drilling fluid and stabilize the surrounding ground on its own. It is set within a range that maintains the same, and it is sufficient if the outer diameter is slightly larger than that of the drilling rod.

Ground excavation using high-pressure jet flow is different from mechanical excavation.
Even if the bit diameter is increased, the jet stream from the bit will stir and fluidize the ground over a wide area, resulting in extremely low excavation resistance and no need for large rotational torque or propulsive force. It is possible to drill a hole of the same diameter. The injection pressure requires a pressure of 100 Kp/cm2 or more. The injection pressure required to fluidize the soil is 1
It varies depending on the soil quality of the surrounding ground, 100 to 200 Kf/i for loose sandy soil layers and soft clayey soil layers, and 200 Kf/c for well-compacted sandy soil layers and hard clayey soil layers! An injection pressure of i or more is required.

By setting the pressure of the drilling fluid within the above range, it is possible to fluidize the area where piles can be easily deposited.

In addition, when drilling through a diluvial clay layer with poor excavability due to jet flow or a sandy gravel layer with poor hole wall stability, high drilling energy is required, making it necessary to slow down the drilling speed. In order to efficiently fluidize and stabilize such ground, installing an auxiliary stirring blade will improve the soil stirring effect, making it possible to perform construction without reducing drilling efficiency.

The drilling fluid used in the present invention is not particularly limited, and ground stabilizing fluids such as water, circulating mud or bentonite mud, or solidifying fluids containing cement milk, water glass, lime, etc. can be used.

To promote fluidization of the ground, a surfactant may be added to clayey soils, a thixotropy agent such as magnesium hydroxide or silica sol, or a water-soluble glue such as methylcellulose to sandy soils, as appropriate. good.

In the present invention, after an excavated hole is excavated and fluidized by a high-pressure jet stream to a predetermined degree of calmness, a foot protection portion with a diameter larger than that of the excavated hole is formed at the bottom of the excavated hole.

It is preferable that the diameter of the foot protection part at the bottom of the excavation hole is approximately 1.5 times the diameter of the pile, and the length thereof is at least 1.5 times the diameter of the pile.

The foot hardening section is created by rotating, lowering or lifting the excavation rod while horizontally spraying the foot hardening liquid at high pressure from the bit part t11].

The method of enlarging the foot protection area from the excavation hole is easy, as increasing the injection pressure, reducing the rotation speed of the injection hole, and slowing the rising or descending speed will increase the distance of excavation stirring by the injection flow. , a root turn portion with an expanded outer diameter as desired can be obtained.

The hardening liquid used here is a cement-based hardening liquid such as cement milk, which hardens and develops strength after completion of construction.

Piles are installed by placing ready-made piles into the fluidized holes, inserting them using their own weight, and then using press-fitting, rotary cylinder frequency vibration, or a combination of these. The pile is sunk while pushing away the fluidized upper particles. At this time, minute vibrations caused by the rotation of the pile and high-frequency vibrations are used as an auxiliary means for press-fitting. Rotation is particularly effective for press-fitting into clayey soil layers, and micro-vibration is particularly effective for press-fitting into sandy soil layers.

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

First, the excavator was moved to the pile laying position and the drilling rod was aligned with the pile core.

Next, as shown in FIG. 1, shallow excavation was carried out to a depth of 1 m using an auger bit 2 attached to the excavation port rad 1, and obstacles such as debris and wood chips in the surface layer were removed.

As shown in FIG. 2, a 500 mm diameter copper pipe was press-fitted into this excavated hole to maintain the water head and treat muddy water, thereby forming a casing 3.

This casing is equipped with a 4-metal mud pump for circulating mud water, and then a drilling bit 5 (outer diameter, 200 mA) is attached to the drilling rod 1 (outer diameter 85 + uφ), and the mud that circulates through the swivel 6 is used as drilling fluid. , from the two injection holes installed on the drilling bit, in the horizontal direction J? The excavation was carried out to a predetermined depth of 18.5 m while spraying downward.

At this time, the rotation speed of the drilling rod 1 was 40 rpm, and the digging speed was 0.5 to 2.0 @/min. The injection rate of drilling fluid is about 704/min, and the injection pressure is 100 to 200.
K? It was /-.

During the drilling, a stirring blade 9 (diameter 4
00wa)k installed.

After digging to a predetermined depth (xs, sm), the drilling fluid is switched to foot hardening fluid, and is injected from the horizontal injection hole at a high injection pressure of 230 to 250 odor/d, and the rotation speed of the drilling rod is 3.
A foot protection section with a predetermined length (t, 2 m) was created at the bottom of the excavation hole at a pulling speed of 10 cm (rpm) for 1 minute. (See Figure 3).

The root hardening solution used was a mixture of water and cement milk with a cement ratio of 60%, to which an anti-breathing agent gold to cement ratio of 1 t was added.

After creating the foot protection section, the drilling rod and drilling bit 5 were collected as shown in FIG. No drilling fluid or root hardening fluid was injected at this time.

To sink the pile, pile 10 of 400 IIJφ was inserted into the excavated pile. In this example, the pile was inserted to a depth of around 71 rL using only its own weight, and after 7, the pile was sunk to a depth of 187 rL using rotary press-in KL. (Figures 5 and 6) (Effects of the Invention) As described above, the present invention rotates a drilling rod with a large-diameter drilling bit at its tip, and pumps drilling fluid from the bit at a rate of 100 Kf/cm2 or more. The soil is excavated and mixed with the jet flow by descending while being injected with high pressure, forming a fluid mud-like hole in the ground, and after reaching a predetermined depth, the excavation fluid is turned into a root hardening solution. Then, the drilling rod is rotated downward or pulled up while horizontally injecting at higher pressure from the side of the bit part to form a foot protection part with a larger diameter than the drilling hole at the bottom of the drilling hole.Then, the drilling rod is recovered, and then The present invention relates to a method for sinking ready-made piles, which is characterized in that the ready-made piles are then inserted into the holes and then sunk.

According to the construction method of the present invention, excavated mature metal 100 Kg/ca1
Since excavation is performed while injecting at a high pressure as described above, it does not require a large torque unlike conventional methods, and the excavation torque is small, and the injected drilling fluid can be easily circulated. can easily dig over long distances.

In addition, unlike conventional methods, the method of the present invention does not require complete conversion of VCB to gold-cement milk or muddy water inside the excavation hole, and only fluidizes the ground within the area necessary for the pile to sink, making it suitable for pile construction. The amount of soil involved is small and the treatment in step 7 is economical.

Furthermore, cement milk, etc. is injected into the supporting ground to create a hardening bulb, but during this creation process, fine clay such as silt and viscosity in the ground and particles with a light specific gravity are discharged under high pressure into cement. As the slime is expelled by milk, etc. and replaced by rising up the borehole, there is little chance of slime settling at the bottom of the borehole.
Because the gaps are filled with cement milk, etc., it becomes mortar or concrete-like, so it has high strength after hardening.
The tip of the pile is anchored to the entire ground, providing strong bearing capacity.

In addition, in creating the enlarged bulbous portion, there is no need to use an expanding bit as in conventional construction methods, and there is an advantage that a bulbous material with a diameter larger than the pile diameter can be formed using a small diameter bit. Therefore, by removing the slime that does not contribute to the strength and creating a bulbous material with a large diameter, it is possible to increase the bearing capacity of the pile.

In addition, if a solidifying liquid such as cement milk is used as the drilling fluid, the stone in the excavation hole will solidify after the pile has been deposited, and the pile and the surrounding ground will be firmly connected, resulting in a large Frictional force around the pile is expressed at 0

[Brief explanation of drawings]

FIGS. 1 to 6 are explanatory diagrams showing a construction member j1 according to an embodiment of the present invention, and FIG. 6 shows a completed diagram of a pile that has been constructed according to the present invention. In the figure, 1 is a drilling rod, 2
is an auger bit, 3 is a casing, 4 is a mud circulation pump, 5 is an excavation pit, 6 is a swivel, 7 is a foot protection part, 8
is the injection hole, 9 is the stirring blade, 10 is the ready-made pile, G is the ground, C
indicates root hardening solution, and K indicates drilling fluid. Patent applicant: Asahi Kasei Industries, Ltd. Figure 6 Figure 1 Figure 2

Claims (1)

[Claims] A drilling rod with a drilling bit larger in diameter than the drilling rod at the tip is rotated, and 100 kg of drilling fluid is poured from the bit part.
Drilling liquid is lowered while being injected at a high pressure of /cm^2 or more, and the soil is excavated and mixed with the jet flow, forming a fluid mud hole in the ground. After reaching a predetermined depth, the drilling fluid is released. is switched to a foot hardening liquid, and the drilling rod is rotated while being sprayed horizontally at higher pressure from the side of the bit part, lowered or pulled up, and a foot hardening part with a larger diameter than the upper drill hole is formed at the bottom of the drill hole. A method for sinking ready-made piles, which is characterized in that the drilling rod is then retrieved, and then the ready-made piles are inserted into the hole and sunk.