JP3868177B2 - Pile construction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention constructs a soil cement synthetic pile in which a solidified body formed by agitation and mixing of a solidified liquid such as cement milk injected together with excavation of the ground and a steel pipe inserted therein behaves integrally. In this case, the present invention relates to a method for constructing a pile that prevents the steel pipe from staying high.
[0002]
[Prior art and problems to be solved by the invention]
Soil cement composite piles composed of a solidified body formed by excavation of the ground and agitation / mixing of the solidified material liquid and a steel pipe inserted into the solidified body are generally patents 2645322, 2688622, 2887702, etc. In this way, it is constructed by a medium excavation method in which the steel pipe is set while excavating, stirring and mixing in a state where the tip of the rod having the excavation claw and the stirring blade protrudes from the tip of the steel pipe.
[0003]
According to this method, in the case of a steel pipe, the wall thickness is smaller than the thickness of a ready-made hollow concrete pile, and the resistance to the lower end surface when set is small, so a thickener is added to the solidified liquid, and the solidified body Even without increasing the viscosity, it is possible to sink the steel pipe to a predetermined depth, and it is rare to cause a high stop.
[0004]
However, in sandy ground with a low water content and a uniform particle size, the resistance when rotating rods and steel pipes rises, causing so-called jamming phenomenon, which increases the rotational force. Drilling is required.
As a result, the time required for excavation may become abnormally long, or the construction may become impossible, and the hardening of the solidified body progresses over time, so the steel pipe can be submerged to a predetermined depth even if the rotational force is increased. It becomes difficult and likely to stay high.
[0005]
The so-called jamming phenomenon, in which the rotation of rods and steel pipes is restricted only in sandy ground with a low water content and a uniform particle size, takes away the surrounding water when cement particles hydrate and solidify. As a result, it is presumed that the cause is that the moisture in the sandy soil is reduced and the sand particles and the cement particles being hydrated are in a close packed state.
[0006]
In view of the above background, the present invention proposes a construction method that prevents the occurrence of a jamming phenomenon in sandy ground, prevents the steel pipe from stopping at a high level, and reliably fixes the steel pipe at a predetermined depth.
[0007]
[Means for Solving the Problems]
In the present invention, when the ground is excavated by the excavator and the solidified material liquid discharged from the excavator when the steel pipe is subsidized, the viscosity of the B-type viscometer at 20 ° C. when the 2% aqueous solution is obtained is 25,000 to 35,000 mPa -By adding a nonionic water-soluble cellulose ether compound having the characteristic of s, the jamming phenomenon is avoided and the steel pipe is prevented from staying high. The viscosity value refers to the value measured when the tachometer is rotated at 20 rpm according to the usual measurement method.
[0008]
If the viscosity under the above conditions is lower than 25,000 mPa · s, the intended purpose cannot be achieved, and if it is higher than 35,000 mPa · s, the rotational resistance of the rod, etc. will increase due to the influence of the viscosity. The purpose can be achieved when the viscosity is in the range of 25,000-35,000 mPa · s.
[0009]
By adding the nonionic water-soluble cellulose ether compound having the above characteristics, jamming phenomenon is avoided and the excavation time is not extended, so that the steel pipe is prevented from being stopped at a high level, and is composed of a steel pipe and a soil cement column at a predetermined depth. It becomes possible to construct a composite pile reliably.
[0010]
The nonionic water-soluble cellulose ether compound having the above characteristics is preferably at least one cellulose ether compound selected from ethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose, and methyl hydroxypropyl cellulose.
[0011]
The blending ratio of the nonionic water-soluble cellulose ether compound to the solidifying material liquid is preferably about 0.05 to 0.2%, particularly about 0.07 to 0.15% by weight.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is implemented using, for example, the excavator 4 shown in FIG. 1, and when the steel pipe 1 is submerged by discharging the solidified material liquid from the excavator 4 and excavating the ground by the excavator 4, Of soil cement composite piles while discharging a solidified material liquid containing a nonionic water-soluble cellulose ether compound having a viscosity of 25,000-35,000 mPa · s with a B-type viscometer at 20 ° C. It is.
[0013]
The excavator 4 is mounted with a rod 5, a preceding excavator blade 6 connected to the tip of the rod 5, an excavator agitator blade 7 mounted on the rod 5 in a contracted state, and a contracted blade in the expanded state. Excavation and agitation are performed by the rotation of the rod 5 in a state where the preceding excavation blade 6 to the agitation blade 8 protrude from the lower end of the steel pipe 1 as shown in FIG. The excavator 4 shown in FIG. 1 is inserted into the steel pipe 1 when the steel pipe 1 is dropped from above, and the construction starts.
[0014]
The steel pipe 1 is provided with spiral wings, enlarged wings, or rib-like projections on the outer periphery of the lower end portion to compensate for the settling with rotation, or a steel material such as a reinforcing bar or flat steel on the inner periphery of the lower end portion. A ring-shaped protrusion may be formed by welding.
In the state where the excavation stirring blade 7 and the stirring blade 8 are expanded as shown in FIG. 1- (1), the rod 5 is rotated to start excavation of the ground. In addition to the excavation by the excavation stirring blade 7, the steel pipe 1 is lowered while stirring the solidified liquid, and the rod 5 is advanced until the tip of the steel pipe 1 reaches the target depth as indicated by (3).
[0015]
For example, as shown in FIG. 2, the solidified material liquid is fed through the rod 5 and discharged from a discharge port 51 formed at the tip position of the rod 5.
In the ground where the steel pipe 1 was actually submerged, sandy ground with a small water content and a uniform particle size existed over a considerable depth range. When adding 0.15% by weight of ethylhydroxyethylcellulose to the cement content of cement milk to the solidified material liquid discharged from the discharge port 51 in the step ▼, jamming does not occur and it remains high. Without doing so, the steel pipe 1 was submerged to a predetermined depth, and the composite pile 3 of the steel pipe 1 and the soil cement column 2 was constructed.
[0016]
When a 2% aqueous solution of ethyl hydroxyethyl cellulose added to the solidifying material solution was used, the viscosity with a B-type viscometer at 20 ° C. was 30,000 mPa · s.
After the composite pile 3 is constructed, as shown in (4) and (5), the excavating agitating blade 7 and the agitating blade 8 are contracted by colliding with the lower end of the steel pipe 1, and the construction is completed by pulling up the excavating device 4 as it is. When the construction was performed by discharging only the solidifying material liquid to which no ethyl hydroxyethyl cellulose was added, it was difficult to perform excavation to a predetermined depth when a constant torque was applied to the rod 5 because a jamming phenomenon occurred.
[0017]
FIG. 2 shows details of the excavator 4 shown in FIG. The excavation stirring blade 7 and the stirring blades 8 and 8 are respectively supported by a plate 10 integrated with a boss 9 or the like disposed around the rod 5 so as to be rotatable about a horizontal axis by a pin 11, and a shear pin 12 penetrating the plate 10. The expanded state is maintained by engaging.
[0018]
The rod 5 is disposed in a section surrounded by the steel pipe 1, and maintains a position with respect to the steel pipe 1 at the time of excavation by a stabilizer 13 that is rotatably mounted relative to the rod 5.
After the excavation is completed, the excavator 4 is lifted as shown in FIG. 3, and as described above, the excavation stirring blade 7 and the stirring blades 8 and 8 collide with the lower end of the steel pipe 1, and the shear pin 12 is broken to contract the steel pipe. By pulling up the excavating device 4 through the interior of 1, the settling of the steel pipe 1 and the construction of the composite pile 3 are completed.
[0019]
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 with a large amount of cement, and the soil cement portion with a large amount of cement is used. May be formed according to the present invention as a root-hardening part. Even in that case, the soil cement pillar 2 is constructed according to the above-described present invention in the portion of the cement cement portion having a large amount of cement.
[0020]
【The invention's effect】
When the ground is excavated by the excavator and the solidified material liquid discharged from the excavator when the steel pipe is submerged, the viscosity by the B-type viscometer at 20 ° C when the 2% aqueous solution is used is 25,000-35,000 mPa · s. By adding a nonionic water-soluble cellulose ether compound with characteristics, the rotational resistance of rods, etc. can be reduced while ensuring the thickening effect of the solidified liquid on sandy ground with low water content and uniform particle size. In order to suppress it, jamming can be avoided even when this type of sandy ground exists in the ground over a considerable depth range.
[0021]
As a result, since the excavation time is not extended and the steel pipe is prevented from staying high, a synthetic pile made of a steel pipe and a soil cement column can be reliably constructed at a predetermined depth.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal sectional view showing a construction procedure.
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. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Steel pipe, 2 ... Soil cement pillar, 3 ... Synthetic pile, 4 ... Drilling device, 5 ... Rod, 51 ... Discharge port, 6 ... Pre-excavation blade, 7 ... Drilling stirring blade, 8 ... Stirring blade, 9 ... Boss, 10 ... Plate, 11 ... Pin, 12 ... Shear pin, 13 ... Stabilizer.

Claims (2)

In the method of excavating the ground with the excavator while discharging the solidified material liquid from the excavator, and substituting the steel pipe and constructing the soil cement composite pile, using a B-type viscometer at 20 ° C. when the aqueous solution is 2% A pile construction method in which a nonionic water-soluble cellulose ether compound having a viscosity of 25,000 to 35,000 mPa · s is added to the solidified material liquid and then constructed to prevent the steel pipe from being stopped at a high level. 2. The pile construction method according to claim 1, wherein the nonionic water-soluble cellulose ether compound is at least one cellulose ether compound selected from ethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose, and methyl hydroxypropyl cellulose.

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