JPH08199566A - Construction method of pile - Google Patents

Abstract

PURPOSE: To eliminate cutting work of a pile head to reduce a construction cost by floating earth and sand on the bottom of an excavated hole in foot protection liquid when the excavated hole is formed, and preventing pile height restriction when a pile is settled. CONSTITUTION: After excavation is made with the tip bit 3 of an excavation rod 1 and reaches specific ground, the excavation rod 1 is reversely rotated to widen the diameter of the bit 3, and the motion is repeated up and down to form an extended bulb section. Foot protection liquid 7 is impregnated into the extended bulb section and is stirred with the bit 3, and gravels 6 are accumulated on the bottom of an excavated hole and are floated in the foot protection liquid 7. Then, the excavation rod 1 is pulled out, the existing pile 9 having a cylindrical bag body 8 is settled to the bottom of the inside of the excavated hole, and solidifiable liquid such as cement milk, etc., is impregnated into the cylindrical bag body 8. With the expansion of the bag body on the tip of the pile caused by the impregnation, excavation liquid into which gravels 6 remain suspended is discharged from a pile hollow section to the ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing ready-made piles used as a foundation for civil engineering and building structures.

[0002]

2. Description of the Related Art Conventionally, various construction methods for ready-made piles have been developed, and low pollution construction methods are required in urban areas. The pre-boring method is a low-pollution method for such ready-made piles. In the conventional pre-boring method, a drilling rod having a bit at the tip discharges the drilling fluid to drill a drilling hole, and after reaching a predetermined depth, cement milk is injected to pull up the drilling rod, It is to insert and fix ready-made concrete piles inside.

[0003]

However, according to the above-mentioned construction method, when a large-diameter drilling hole is to be drilled, earth and sand are deposited in the drilling hole during the drilling, and especially the gravel ground is drilled. In that case, it caused a high stop when the piles were sunk. Also, a pile in which a large-diameter bag body is attached to the pile tip portion of a large-diameter pile, particularly a bag body in which the upper and lower portions of the bag body are attached to the outer peripheral surface of the pile tip portion so as to surround only the pile outer circumference. This was a cause of insufficient expansion of the bag body at the tip of the pile when constructing the expanded bulb part in the construction of the attached pile.

The present invention is intended to eliminate the drawbacks of the prior art as described above, and prevents the pile from staying high in the pre-boring method, and in the construction of the prefabricated pile with the bag body, the pile tip bag body is used. It is an object of the present invention to provide a method for constructing a ready-made pile that enables sufficient expansion and has a large tip supporting force.

[0005]

The construction method of the present invention is to excavate to a desired depth with an excavating bit to form an enlarged excavated portion on a predetermined ground at the tip, and to consolidate the enlarged excavated portion with viscosity. The method is characterized in that after pouring liquid, the gravel existing near the bottom of the excavation hole is floated, and then a ready-made pile is inserted into the excavation hole to prevent a high stop during pile digging. Alternatively,
Excavate to a desired depth with an excavating bit to form an enlarged excavated portion on a predetermined ground at the tip, and add a viscous root-hardening solution to the enlarged excavated portion to remove sand and gravel existing near the bottom of the excavation hole. After floating in the hardening liquid, a bag body whose upper and lower sides are opened is attached to the outer peripheral surface of the tip of the pile at the upper and lower parts thereof, and the ready-made pile mounted so that the bag body surrounds only the outer periphery of the pile is used for the excavation hole. The method for constructing a pile with a bag, which is characterized in that the pile is expanded into the bag body, and a solidifying fluid is injected into the bag body to form a root-consolidated bulb for expanding the pile root. Is. Alternatively, the excavation bit is excavated to a desired depth to form an enlarged excavation portion in a predetermined ground at the tip, and a viscous rooting solution is added to the enlarged excavation portion, which exists near the bottom of the excavation hole. After floating the sand and gravel, a bag body whose upper and lower sides were opened was attached to the outer peripheral surface of the pile tip part at its upper and lower parts, and the bag body was attached so as to surround only the outer periphery of the pile, and the ready-made pile with the tip open was installed. Inserted into the excavation hole to a position floating a predetermined height above the bottom surface of the enlarged excavation portion, injecting a solidifying fluid into the bag body to form an enlarged root-fixing bulb for the pile tip, and in the hollow portion of the ready-made pile, It is a method of constructing a pile with a bag, characterized in that the gravel is moved together with a rooting liquid to sufficiently expand the bag body in a lateral direction.

The present invention has solved the above-mentioned problems mainly by improving a rooting liquid used for burying a ready-made pile. In the present invention, an additive for imparting viscosity to the root-hardening solution is bentonite, magnesium carbonate, or the like. The viscosity of cement milk can be increased by using bentonite or magnesium carbonate. When bentonite is used, bentonite is roughly classified into Na-based bentonite and Ca-based bentonite, but Na-based bentonite having excellent swelling property, capable of quickly forming a mud cake, and having good waterproofness is preferable. The composition of the root-hardening liquid containing these additives varies depending on the ground. For example, in the case of gravel ground, Na-based bentonite is added to cement milk with a water-cement ratio of 50 to 70% in a weight ratio of 1.5 to 3% of water. .5
%, The water-cement ratio is 50-70 in the sand ground mixed with gravel.
% Cement milk to which 0.5 to 1.5% by weight of water is added to the Na-based bentonite. Within the above range, it is possible to add an appropriate viscosity to the rooting liquid for the purpose of floating gravel, and the silica component in the bentonite reacts with the cement, so that the strength of the cement is higher than that of the rooting liquid containing only cement milk. Will never fall below. When magnesium carbonate is used as an additive, for example, in the case of gravel ground, magnesium carbonate is added to cement milk having a water-cement ratio of 50 to 70% in an amount of 0.5 to 0.5% by weight of water.
Add 1.0%, and in the sand ground mixed with gravel, the water-cement ratio is 50.
It is desirable that the composition be prepared by adding 0.1 to 0.5% by weight of magnesium carbonate to 70% of cement milk. The viscosity of the root-setting liquid of the present invention is 4200 cP to 8,500 cP in the root-setting liquid for gravel ground as measured by a rotational viscometer, and it has been confirmed that even pebbles having a diameter of 50 mm can sufficiently float. In addition, it is 3300 cP or more with root consolidation liquid for sand ground
It is 4200 cP. Further, in consideration of the solubility of the additive, it is preferable that the root-cure solution is prepared by dissolving the additive in water with a mixer or the like and then adding cement to the solution. The waiting time from the addition of the additive to the water to the addition of the cement needs to be at least about 1 minute, and the longer the time, the better.

[0007] By using the pre-boring method with the root-setting liquid having such properties, the sand gravel is suspended in the root-setting liquid, whereby the above-mentioned pile stays at a high level and the bag body at the top of the pile is insufficiently expanded. The problem of can be solved. When creating a pile-expanded bulb by bottoming a pre-made bag pile with a closed tip on the bottom of the excavation hole, consider the sand gravel diameter of the prescribed ground and make the enlarged excavation diameter slightly larger than the expansion diameter of the bag body. It is preferable that the expansion of the bag at the tip of the pile becomes smoother. In particular, if the ready-made pile with a bag having an open tip is inserted up to about 0.5 to 2D above the bottom surface of the enlarged excavation section, the height of the pile head can be adjusted to the designed pile top height. Eliminates the work of picking up pile heads. Further, the upper and lower portions of the bag body are attached to the outer surface of the pile tip bag body, especially the pile tip portion, and the solidified fluid is injected into the bag body that surrounds only the pile outer circumference to expand the pile tip root. By adding an additive to the hollow part of the ready-made pile and moving the suspended gravel together with the viscous rooting solution, the bag body can easily reach the specified diameter without digging a large amount. It can be inflated. The ready-made pile used in the present invention has a pile diameter of 400.
It is a hollow pile of φ or more, and may be a steel pipe pile, a concrete pile, or a steel pipe concrete composite pile. The material of the bag used in the present invention is preferably nylon, polyester, polyethylene, vinylon or the like from the viewpoint of having a dehydrating effect of allowing only water in the solidified fluid to be injected to pass therethrough and strength.

[0008]

An embodiment of the present invention will be described with reference to the drawings.
GL-0 with ready-made pile with a bag diameter of 500φ with open tip
It is a soft ground with an N value of 20 or less between -11m (distance from the ground surface), but N value of 40-5 during GL-11-16m.
It was constructed on a gravel ground of 0. The pile tip penetrated the gravel ground for 3 m. The construction sequence will be described below. First, as shown in FIG. 1, while excavating liquid from the tip, the excavating rod 1 was rotated, and excavation was performed with the bit 3 at the tip. The screw 2 was spirally installed in the section 5 m from the lower end of the drill rod 1, and the diameter of the bit 3 was 550φ. The drilling fluid had a composition in which bentonite was added to water in an amount of 8% by weight and carboxymethyl cellulose was added in an amount of 0.1% by weight. During excavation, the screw 2 and the agitating arm 4 agitate the excavated soil and the excavating liquid to form slurry muddy water 5. After the excavation rod 1 reaches the predetermined ground, FIG.
Further, as shown in FIG. 3, the drill rod 1 was rotated in the reverse direction, the bit 3 was expanded to a bit diameter of 900φ, and it was repeated up and down 4 m to form an expanded bulb portion. At this time, the excavating rod has a structure capable of enlarging the bit by rotating in the reverse direction, and a known one can be used. As shown in FIG. 3, normally, when gravel ground is excavated, gravel 6 exists near the bottom of the excavation hole due to sedimentation of the excavated gravel. Next, according to the present invention, the root-cure solution 7 shown in FIG. 4 was obtained by adding bentonite to a cement milk of W / C = 60% in a weight ratio of 3% of water and a thickener in a weight ratio of 0.2% of water. It was used as a blend. The root compaction solution was poured into the enlarged bulb portion and then stirred with a bit to suspend the gravel accumulated near the bottom of the drill hole in the root compaction solution. The amount of this rooting liquid was 1300 liters, which is about 50% of the expanded excavation volume.

Next, as shown in FIG. 4, the excavation rod 1 was pulled up while rotating forward. After pulling up and collecting the excavating rod 1, as shown in FIG. 5, a ready-made pile 9 having a tubular bag body 8 woven with nylon 66 woven with a band attached to the tip 3 m of the pile with a band is suspended in the excavation hole. It was sunk to the bottom. At the time of sunk, the pile did not stop at all. Therefore, even if the pile is a ready-made pile that does not have a bag, the pile does not stay high. The tubular bag used was one that expands to 900φ at the end of the cement milk injection. As shown in FIG. 6, after the pile is once sunk to the bottom of the enlarged drill hole, the tip of the ready-made pile 9 is floated 50 cm from the bottom of the enlarged bulb, and the bag is located in the enlarged bulb where it does not solidify yet. I chose

Next, using a mortar pump, cement milk having a water-cement ratio of 60% was injected into the cylindrical bag 8 through an injection pipe as shown in FIG. Although not shown, the injection pipe is provided in the hollow portion of the ready-made pile or in the concrete thick portion of the ready-made pile, and is configured to inject a solidified fluid such as cement milk into the bag body 8 from the ground. As the bag expands at the tip of the pile due to injection, the maximum diameter from the hollow part of the pile is 130
The drilling fluid with suspended mm gravel was discharged to the ground. Whether the tubular bag was sufficiently inflated by the cement milk was judged by the pressure of the pump and the injection amount of the cement milk. In this case, the maximum injection pressure of the pump was 7.4 kg / cm ² , and the injection amount was 1320 liters. At this time, as shown in FIG. 8, the tubular bag body 8 is sufficiently expanded to a predetermined diameter and has a reliable expanded bulb of 900φ.
Even if some gravel left behind between the pile and the hole wall is suspended in the rooting solution, it is judged that the bag will not be inflated.

As a comparative example of the present invention, W / C = 60
Pile was also constructed using only% cement milk as the root consolidation solution. In this case, the pile stays at a height of 90 cm, and when the pile tip bag body 8 is expanded with cement milk under the same conditions as in the embodiment, the maximum injection pressure of the pump is 5.6.
It was kg / cm ² and the injection amount was 701 liters. The tubular bag at the tip of the pile did not expand, and only an enlarged bulb of 740φ could be created. When excavating on gravel ground, collapsed gravel accumulates near the bottom of the excavation hole, which causes the pile to remain high and hinder the sufficient expansion of the tubular bag attached to the tip of the pile. When mounting a large-diameter bag body on a large-diameter pile in this way, it is difficult to create a complete bulb without removing the gravel accumulated in the excavation hole.

[0012]

EFFECTS OF THE INVENTION According to the present invention, the pre-boring method is mainly used to prevent sedimentation existing in the vicinity of the bottom of the drilling hole by suspending the sediment existing in the vicinity of the bottom of the drilling hole in the rooting liquid when the pile is sunk. As a result, there is no need to pick up the pile head,
It is possible to significantly reduce the cost by eliminating waste of pile materials to be removed by scraping and disposal of waste materials. At the same time, especially in the construction of ready-made piles for forming pile tip enlarged bulbs, even when cement hardening material is injected into the pile tip bag body, it promotes fluidization of sand and gravel due to the root consolidation liquid to surely expand the pile tip bag body. It is possible to Therefore, a large pile (for example, diameter 400φ or more)
Even if it is a ready-made pile with a large-diameter bag attached to it, a complete expanded bulb can be created, and the surrounding ground loosened during excavation can be restored by the expansion force of the bag, so a large bearing force can be obtained. As a result, the number of piles can be reduced in terms of design, which enables economical design.

[Brief description of drawings]

FIG. 1 is an excavation process diagram showing a construction procedure of the present invention.

FIG. 2 is an enlarged excavation process diagram showing a construction procedure of the present invention.

FIG. 3 is an enlarged excavation process diagram showing a construction procedure of the present invention.

FIG. 4 is an excavation rod recovery process diagram showing a construction procedure of the present invention.

FIG. 5 is a pile laying process diagram showing a construction procedure of the present invention.

FIG. 6 is a pile sunk state diagram showing a construction procedure of the present invention.

FIG. 7 is a cement milk injection process diagram showing a construction procedure of the present invention.

FIG. 8 is a completed construction view of an enlarged root consolidation portion showing a construction procedure of the present invention.

[Explanation of symbols]

 1 Drilling rod 2 Screw 3 Bit 4 Stirring arm 5 Mud 6 Gravel 7 Rooting liquid 8 Cylindrical bag 9 Ready-made pile

Claims (3)

[Claims] 1. An excavation bit is excavated to a desired depth to form an enlarged excavation portion on a predetermined ground at the tip, and a viscous rooting solution is added to the enlarged excavation portion, and the enlarged excavation portion is provided near the bottom of the excavation hole. A method for constructing a pile, characterized in that, after suspending existing gravel, a ready-made pile is inserted into the excavation hole to prevent a high stop when the pile is sunk. 2. An excavation bit is excavated to a desired depth to form an enlarged excavation portion on a predetermined ground at the tip, and a viscous rooting solution is added to the enlarged excavation portion, and the enlarged excavation portion is provided near the bottom of the excavation hole. After suspending existing gravel in the rooting liquid, a bag body with open top and bottom is attached to the outer peripheral surface of the tip of the pile at its upper and lower parts, and the bag body is mounted so as to surround only the periphery of the pile. A bag characterized in that a pile is inserted into the excavation hole to prevent a high stop at the time of sinking the pile, and a solidifying fluid is injected into the bag body to form a pile tip enlarged root consolidation bulb. Construction method of attached pile. 3. An excavation bit is excavated to a desired depth to form an enlarged excavation portion on a predetermined ground at the tip, and a viscous rooting solution is introduced into the enlarged excavation portion, and the excavated portion is provided near the bottom of the excavation hole. After floating the existing gravel, a bag body whose upper and lower sides are opened is attached to the outer peripheral surface of the pile tip part at its upper and lower parts, and the bag body is mounted so as to surround only the outer periphery of the pile, and the tip is open. The pile is inserted into the excavation hole to a position where it floats above the bottom surface of the enlarged excavation part by a predetermined height, and a solidifying fluid is injected into the bag body to form an enlarged root-consolidating bulb at the tip of the pile. A method for constructing a pile with a bag, characterized in that the gravel is moved together with the rooting liquid to sufficiently expand the bag body laterally.