JP2001234532A - Pile construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely anchor a steel pipe at a predetermined depth by avoiding a jamming phenomenon in the sandy soil ground containing small water content and being homogeneous in particle size, and preventing retaining of the steel pipe at a high level, in a method of constructing soil cement composite piles by agitating and excavating the ground and settling the steel pipes. SOLUTION: Excavation of the ground is carried out by an excavator 4, and a non-ionic soluble cellulose ether compound is added to a hardening liquid discharged from the excavator 4 when the steel pipes 1 are anchored. The compound has the viscosity of 25,000 to 35,000 mPa.s measured by the Brookfield type viscometer at a temperature of 20 deg.C provided that the hardening liquid is a 2% aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solidified body formed by stirring and mixing of a solidifying material liquid such as cement milk which is poured together with excavation of a ground, and a steel pipe inserted into the solidified body. The present invention relates to a pile construction method for preventing steel pipes from staying high when constructing a soil cement composite pile.

[0002]

2. Description of the Related Art In general, a soil cement composite pile composed of a solidified body formed by excavating the ground and agitating and mixing a solidified material liquid and a steel pipe inserted therein, Patent No. 2645322, No. 2688622
No. 2887702, etc., is constructed by a digging method in which a steel pipe is sunk while excavating, stirring and mixing with the tip of a rod having a drilling claw and stirring blade at the tip protruding from the tip of the steel pipe. You.

According to this method, in the case of a steel pipe, the thickness is smaller than the thickness of a ready-made hollow concrete pile, and the resistance applied to the lower end face during laying is small. It is possible to sink the steel pipe to a predetermined depth without increasing the viscosity of the solidified body, and it is unlikely to cause a high stop.

However, in a sandy ground having a small water content and a uniform particle size, a so-called jamming phenomenon occurs, in which the resistance when rotating a rod or a steel pipe is increased and the construction becomes impossible. It is necessary to increase the excavation. As a result, the time required for excavation may be unusually long, or the work may not be possible.Since the solidification of the solidified body progresses with the lapse of time, the steel pipe may be sunk to a predetermined depth even if the rotational force is increased. It will be difficult and likely to stay high.

The so-called jamming phenomenon, in which the rotation of rods and steel pipes is restricted only in sandy ground having a small water content and a uniform particle size, occurs when the cement particles hydrate and solidify. As a result of depriving the water, it is presumed that the cause is that the water in the sandy soil decreases, and the sand particles and the hydrated cement particles are in a close-packed state.

In view of the above background, the present invention proposes a construction method for avoiding the occurrence of a jamming phenomenon in sandy ground, preventing the steel pipe from stopping at a high height, and reliably fixing the steel pipe to a predetermined depth.

[0007]

According to the present invention, the ground is excavated by an excavator, and the solidified material liquid discharged from the excavator when the steel pipe is laid is converted into a 2% aqueous solution.
Viscosity of 25,000-35,000 mP by B-type viscometer at ℃
By adding a nonionic water-soluble cellulose ether compound having the characteristics of a · s, the above-mentioned jamming phenomenon is avoided, and the steel pipe is prevented from stopping at a high level. The viscosity value is a value measured when a tachometer is rotated at 20 rpm according to a usual measuring method.

If the viscosity under the above conditions is lower than 25,000 mPa · s, the intended purpose cannot be achieved and 35,000 mPa · s
If the viscosity is higher, the rotational resistance of the rod or the like is increased by the influence of the viscosity. Therefore, the intended purpose can be achieved when the viscosity is in the range of 25,000 to 35,000 mPa · s.

By adding a nonionic water-soluble cellulose ether compound having the above-mentioned properties, the jamming phenomenon is avoided and the excavation time is not prolonged. It is possible to reliably construct a composite pile composed of columns.

As the nonionic water-soluble cellulose ether compound having the above-mentioned properties, at least one selected from the group consisting of ethylhydroxyethylcellulose, methylhydroxyethylcellulose and methylhydroxypropylcellulose is preferable.

The mixing ratio of the nonionic water-soluble cellulose ether compound to the solidified material liquid is 0.05 to 0.2 by weight.
%, Particularly preferably in the range of about 0.07 to 0.15%.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is practiced by using, for example, an excavator 4 shown in FIG. 1, and a steel pipe 1 is laid by discharging a solidified material liquid from the excavator 4 and excavating the ground by the excavator 4. B at 20 ° C when a 2% aqueous solution
This is a method of constructing a soil cement composite pile while discharging a solidifying material liquid to which a nonionic water-soluble cellulose ether compound having a characteristic of a viscosity of 25,000 to 35,000 mPa · s by a type viscometer is added.

The drilling device 4 includes a rod 5 and a leading drilling wing 6 connected to, for example, a tip thereof, a drilling stirring blade 7 mounted on the rod 5 so as to be contractable in an expanded state, and is also contractible in an expanded state. Fig. 1
The excavation and stirring are performed by rotating the rod 5 in a state where the leading excavation blade 6 to the stirring blade 8 protrude from the lower end of the steel pipe 1 as shown in FIG. The drilling rig 4 shown in FIG.
Is inserted into the steel pipe 1 by being dropped,
It will be in the construction start state as it is.

The steel pipe 1 is provided with a spiral wing, an enlarged wing, or a rib-like projection on the outer periphery of a lower end portion thereof to compensate for the sedimentation caused by the rotation, or a reinforcing bar, flat steel, etc. In some cases, a ring-shaped projection may be formed by welding the steel material. The excavation of the ground is started by rotating the rod 5 in a state where the excavating and stirring blades 7 and 8 are expanded as shown in FIG. While excavating, stirring the solidified material liquid
The steel pipe 1 is lowered, and the rod 5 is excavated until the tip of the steel pipe 1 reaches the target depth as shown in FIG.

The solidifying material liquid is fed through a rod 5 as shown in FIG. 2, for example, and is discharged from a discharge port 51 formed at the tip of the rod 5 or the like. In the ground where the steel pipes 1 were actually laid, sandy ground with a low water content and a uniform grain size existed over a considerable depth range.
-Ethylhydroxyethylcellulose in an amount of 0.15% by weight with respect to the cement content of the cement milk was added to the solidified material liquid discharged from the discharge port 51 in the step of-, no jamming phenomenon occurred, and The steel pipe 1 was sunk to a predetermined depth without stopping, and the composite pile 3 of the steel pipe 1 and the soil cement column 2 was constructed.

When a 2% aqueous solution of ethylhydroxyethylcellulose added to the solidifying material liquid was used, the viscosity at 20 ° C. measured by a B-type viscometer was 30,000 mPa · s. After the construction of the composite pile 3, the excavating stirring blade 7 and the stirring blade 8 are contracted by colliding with the lower end of the steel pipe 1 as shown in FIG.
The work is completed by pulling up the excavator 4 as it is. When the work is performed by discharging only the solidifying material liquid without adding ethylhydroxyethylcellulose, a jamming phenomenon occurs. Excavation became difficult.

FIG. 2 shows details of the excavator 4 shown in FIG. The drilling and stirring blades 7 and the stirring blades 8 and 8 are respectively pinned to a plate 10 integrated with a boss 9 and the like arranged around the rod 5.
The plate is supported rotatably around the horizontal axis by 11
The expanded state is maintained by engaging with the shear pin 12 penetrating the 10.

The rod 5 is arranged in a section surrounded by the steel pipe 1 and holds a position with respect to the steel pipe 1 at the time of excavation by a stabilizer 13 which is rotatably mounted relatively to the rod 5. After the excavation is completed, the excavator 4 is pulled up as shown in FIG.
The steel pipe 1 is caused to collide with the lower end of the steel pipe 1 so that the shear pin 12 is broken and contracted, and the drilling rig 4 is pulled up through the inside of the steel pipe 1 to complete the subsidence of the steel pipe 1 and the construction of the composite pile 3.

Although not specifically shown in the above example, the portion from the bottom of the target depth to about twice the diameter of the steel pipe is switched to cement milk containing a large amount of cement, and the cement content is increased. In some cases, the soil cement portion is formed in accordance with the present invention as a root portion. Also in that case, the soil cement column 2 is constructed in accordance with the present invention described above at the portion above the soil cement portion where the cement content is high.

[0020]

According to the present invention, the ground is excavated by the excavator,
Nonionic water-soluble cellulose having a viscosity of 25,000 to 35,000 mPa · s measured at 20 ° C by a B-type viscometer when a 2% aqueous solution is used as the solidified material liquid discharged from an excavator when laying a steel pipe. By adding an ether compound, this type of sandy material is used to suppress the rotational resistance of rods etc. while ensuring the thickening effect of the solidified material liquid on sandy ground with a low water content and a uniform particle size. Even when the ground exists in the ground over a considerable depth range, the jamming phenomenon can be avoided.

As a result, the excavation time is not prolonged, and the steel pipe is prevented from staying at a high height, so that a composite pile composed of the steel pipe and the soil cement column can be reliably constructed at a predetermined depth.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a construction procedure.

FIG. 2 is a longitudinal sectional view showing details of the excavator of FIG. 1;

FIG. 3 is a longitudinal sectional view showing a state when the excavator of FIG. 2 is pulled up.

[Explanation of symbols]

1 ... steel pipe, 2 ... soil cement column, 3 ... composite pile,
4 ... Drilling equipment, 5 ... Rod, 51 ... Discharge port, 6 ...
Preceding excavation wing, 7 ... Excavation stirring wing, 8 ... Stirring wing, 9 ...
Boss, 10 ... Plate, 11 ... Pin, 12 ... Sharpin, 13 ... Stabilizer.

Claims (2)

[Claims] While discharging solidified material liquid from a drilling device,
While excavating the ground with a drilling rig, sinking steel pipes,
In the method of constructing a soil cement composite pile, the viscosity of a 2% aqueous solution using a B-type viscometer at 20 ° C
A method for constructing a pile, comprising adding a nonionic water-soluble cellulose ether compound having a characteristic of 25,000 to 35,000 mPa · s to the solidifying material liquid and constructing the pile to prevent the steel pipe from stopping at a high level. 2. The pile construction according to claim 1, wherein the nonionic water-soluble cellulose ether compound is at least one cellulose ether compound selected from ethylhydroxyethylcellulose, methylhydroxyethylcellulose, and methylhydroxypropylcellulose. Method.