Method of constructing underground pile having expanded bulb and underground pile having expanded bulb constructed by the method

Abstract

Disclosed herein is a method of constructing an underground pile having an expanded bulb on a lower end or an intermediate portion thereof. In the method of the present invention, liquefied grout is charged into a hole bored in the ground, and a rapidly expanding metal compound of metal powder and a metal salt is inserted into the grout. Thereafter, the rapidly expanding metal compound is exploded in the grout before the grout is cured, so that a portion of the hole is widened and the grout is charged into the widened portion. According to the present invention, the expanded bulb which protrudes outwards can be easily formed at a predetermined position of the underground pile and, simultaneously, the soil around the pile can be hardened. Furthermore, the construction period and construction cost of the pile having the expanded bulbs are markedly reduced. As well, the underground pipe having the expanded bulb according to the present invention can exhibit superior supporting force despite having reduced length and diameter compared to the straight pile. Therefore, the present invention makes it possible to provide superior ground reinforcing ability despite using a reduced number of piles compared to the conventional art.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGS. 1 a through 1g are views showing steps of a method of constructing an underground pile having expanded bulbs, according to an embodiment of the present invention; and

FIG. 2 is a sectional view of a rapidly expanding metal compound capsule used in the underground pile constructing method according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a method of constructing an underground pile having expanded bulbs according to a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

FIGS. 1 a through 1g are views showing steps of the method of constructing the underground pile having the expanded bulbs, according to the present invention. FIG. 2 is a sectional view of a rapidly expanding metal compound capsule used in the underground pile constructing method of the present invention.

First, a rapidly expanding metal compound 101 used in the present invention and the capsule 100 containing the rapidly expanding metal compound 101 therein will be explained herein below.

The rapidly expanding metal compound 101 is a compound in which metal powder and a metal salt, which oxidizes the metal powder at a high temperature using its own oxygen atoms, are mixed at a weight ratio of 0.1:99.9 to 99.9:0.1. It is preferable that the metal salt be one selected from among a metal nitrate, a metal perchlorate, a metal peroxide, a metal oxide, a metal oxalate, a metal carbonate and a metal sulfate, or be a compound of at least two of them. Furthermore, it is preferable that the metal powder be one selected from among aluminum (Al) powder, sodium (Na) powder, potassium (K) powder, lithium (Li) powder, magnesium (Mg) powder, manganese (Mn) powder, barium (Ba) powder, chromium (Cr) powder and silicon (Si) powder, or be a compound of at least two of them.

The rapidly expanding metal compound 101 is contained in an inner casing 103, which is made of synthetic resin such as PVC (polyvinyl chloride), and is contained in an outer casing (105, 107a and 107b), which is sealed and is made of steel, fiber reinforced plastic or polycarbonate, thus forming the capsule 100. Carbon fiber reinforced plastic and glass fiber reinforced plastic are representative examples of the fiber reinforced plastic used in the present invention. Furthermore, the carbon fiber reinforced plastic and the glass fiber reinforced plastic, which are high-strength plastic, and polycarbonate have superior plasticity despite having strength similar to steel. Therefore, the outer casing is preferably made of the above high-strength material rather than steel. Furthermore, for oxidation-reduction reaction of the rapidly expanding metal compound 101, a high oxidation detonating temperature and a sealed space ensuring a predetermined pressure are required. Therefore, the above high-strength material is preferably used as the material of the outer casing. Although the outer casing is illustrated in FIG. 2 as comprising an outer casing body 105 having a pipe shape and a pair of outer casing caps 107a and 107b that closes the opposite ends of the outer casing body 105, the structure of the outer casing is not limited to this. The outer casing can have any structure as long as it has a pressure resisting and sealing structure.

Meanwhile, a resistor wire 109, which generates a spark for creating an oxidation reaction, is embedded in the rapidly expanding metal compound 101. The resistor wire 109 is connected to power supply wires 111, which extend outside the inner casing 103 and the outer casing (107a, 107b) of the capsule 100. The power supply wires 111 are connected to a contact-detonation device 113, which generates high instantaneous voltage. When high voltage is applied to the resistor wire 109 by the contact-detonation device 113, heat is supplied, and the resistor wire 109 fuses, thus inducing a high current discharge. Then, a spark is generated by the high current discharge, thereby the rapidly expanding metal compound 101 explodes.

Hereinafter, the method of constructing the underground pile having expanded bulbs using the rapidly expanding metal compound capsule 100 having the above-mentioned construction and operation will be explained with reference to FIGS. 1a through 1g.

FIG. 1 a illustrates a process of boring a hole 3 in the ground 5 using an auger 1. FIG. 1b illustrates a process of charging grout 7, such as mortar, concrete, molten glass and asphalt, into the bored hole 3. Although it is schematically shown in FIG. 1b, the grout 7 is pumped and charged into the hole 3 through a hose using a pump. This is well known to those skilled in the art.

As shown in FIG. 1c, after the grout 7 has been charged into the hole 3 until it is level with the surface of the ground, a desired number of rapidly expanding metal compound capsules 100 are connected to each other through the power supply wire 111 and are inserted into the grout 7 to the depth at which expanded bulbs are to be formed, as shown in FIG. 1d. Here, in the case where the outer casing (105, 107a and 107b) of each rapidly expanding metal compound capsule 100 is made of steel, it can be easily inserted into the liquefied grout 7 because it is relatively heavy. However, in the case where the outer casing of the rapidly expanding metal compound capsule 100 is made of fiber reinforced plastic or polycarbonate, it is inserted into the grout 7 using a tool, such as a long pole. When it is desired to form two or more expanded bulbs in the pile at different heights, a corresponding number of the rapidly expanding metal compound capsules 100 is inserted into the grout 7 such that they are disposed at the desired heights.

After the process of inserting the rapidly expanding metal compound capsules 100 into the grout 7 has been completed, the power supply wire 111 is connected to the contact-detonation device 113, and high voltage power (3,000V or more) is applied. Then, the rapidly expanding metal compounds and the capsules 100 containing them explode and expand, so that portions of the ground 5 around the rapidly expanding metal compound capsules 100 are widened and the grout 7 is instantaneously charged into the widened portions, as shown in FIG. 1f. In this process, the soil around the widened portions is firmly hardened. In addition, a space corresponding to the volume of grout 7 charged into the widened portions is formed in the upper end of the hole 3. Here, if a detonator such as an explosive is used, the grout 7 is discharged and spattered outside the hole 3 by the explosive pressure. However, in the case where the rapidly expanding metal compound 101 according to the present invention is used, because the rapidly expanding metal compound 101 contracts just after being rapidly expanded to a predetermined volume, the grout 7 is completely prevented from being discharged outside the hole 3 and is reliably charged into the widened portion.

Thereafter, as shown in FIG. 1f and FIG. 1g, additional grout is charged into the space formed in the upper end of the hole 3, and the grout is subsequently cured, thus forming an underground pile 9 having the expanded bulbs 11 at predetermined positions, for example, at the lower end or an intermediate position of the pile 9.

As described above, according to the present invention, expanded bulbs which protrude outwards can be easily formed on predetermined portions of an underground pile and, simultaneously, the soil around the pile can be hardened. Furthermore, the construction period and construction cost of the underground pile having the expanded bulbs are markedly reduced. As well, the underground pipe having the expanded bulbs according to the present invention can exhibit superior supporting force despite having reduced length and diameter compared to the straight pile. Therefore, the present invention makes it possible to provide superior ground reinforcing ability despite using a reduced number of piles compared to the conventional art.

Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A method of constructing an underground pile having an expanded bulb, comprising: charging liquefied grout into a hole bored in ground; inserting a rapidly expanding metal compound of metal powder and a metal salt into the grout; and exploding the rapidly expanding metal compound in the grout before the grout cures, so that a portion of the hole is widened and the grout is charged into the widened portion.

2. The method as set forth in claim 1, wherein the rapidly expanding metal compound is contained in an outer casing made of steel, fiber reinforced plastic or polycarbonate and is inserted into the grout.

3. The method as set forth in claim 1, wherein the rapidly expanding metal compound comprises a compound in which the metal powder and the metal salt that oxidizes the metal powder at a high temperature using oxygen atoms thereof are mixed in a weight ratio of 0.1:99.9 to 99.9:0.1.

4. The method as set forth in claim 1, wherein the metal salt is one selected from among a metal nitrate, a metal perchlorate, a metal peroxide, a metal oxide, a metal oxalate, a metal carbonate and a metal sulfate, or is a compound of at least two thereof.

5. The method as set forth in claim 1, wherein the metal powder is one selected among aluminum (Al) powder, sodium (Na) powder, potassium (K) powder, lithium (Li) powder, magnesium (Mg) powder, manganese (Mn) powder, barium (Ba) powder, chromium (Cr) powder and silicon (Si) powder, or is a compound of at least two thereof.

6. An underground pile having an exploded bulb constructed through the method according to claim 1.

7. An underground pile having an exploded bulb constructed through the method according to claim 2.

8. An underground pile having an exploded bulb constructed through the method according to claim 3.

9. An underground pile having an exploded bulb constructed through the method according to claim 4.

10. An underground pile having an exploded bulb constructed through the method according to claim 5.