JPH02176014A - Structural steel for constructing continuous retaining wall and method of withdrawing structural steel therefrom - Google Patents

Abstract

PURPOSE:To withdraw structural steels safely and surely with small force by inserting the structural steels, adherently covered at their surfaces with sulphur mortar sprayed thereon, into cement material that is to harden later, and by detaching the structural steels from a retaining wall by heating the mortar for melting the same. CONSTITUTION:At construction of a continuous retaining wall, structural steels 3, after being covered adherently at their surfaces with sulphur mortar 7 made of sulphur as its principal material, are inserted into cement material 2 that is to harden later. After performing a function as the continuous retaining wall, the sulphur mortar 7 is heated and melted by a method such as of supplying electric current to electric heating wires 5, and the structural steels 3 are pulled out thence. The sulphur mortar 7 hardens at a temperature of 110 deg.C or below becoming to have the strength same as or above the cement mortar, and softens at a temperature of 110 deg.C or above becoming liquid substance rich in fluidity. Therefore it does not do any harm to the structural steels 3 during the use and recovery of the structural steels 3 after the use of the structural steels can be easily carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present application relates to a construction method for pulling out the steel members of a continuous earth retaining wall constructed in architecture and civil engineering work after its function has been completed.

[Prior Art] Generally, continuous earth retaining walls are constructed by constructing a continuous wall of cement-based hardened material while drilling and excavating the ground, and then inserting steel materials at appropriate intervals while the wall is still unhardened. It is something that

The steel material bears the external forces such as soil pressure and water pressure on the back of the wall, but after its function as an earth retaining wall has ended, it becomes useless, and in the past, it was buried inside the wall. This is what I was looking for.

However, from the viewpoint of resource conservation, the reuse of resources, and from the viewpoint of recent underground space utilization concepts, the removal of used buried materials such as steel materials is required using this construction method.

Therefore, it has been considered that the steel material of a continuous earth retaining wall can be pulled out after its function has been completed, and the following methods have been proposed one after another.

That is, A. A method of directly pulling out using a hydraulic or floating-type drawing bottle.

For example, B (Japanese Patent Publication No. 61-33094, etc.) is a method in which various lubricating materials are interposed in advance around the steel material as edges to weaken the pulling force and then the material is pulled out.

For example (Japanese Patent Publication No. 58-57574 No. 61-32452, Japanese Patent Publication No. 59-88536, 60
-242218, 61-290118, 62-41
No. 1319, No. 63-185615, etc.) A method using a C0 crushing agent.

For example, (Japanese Patent Publication No. 59-12809) [Problems to be Solved by the Invention] The prior art described in the prior art had the following problems.

Method A requires a huge amount of pulling force because it involves pulling out something that is strongly integrated. This means that even if there is a machine that can produce that pulling force, it will have a significant impact on the surrounding ground and nearby buildings.

Also, even if you pull it out little by little, the initial force will not change,
It takes a long time.

Furthermore, drilling a large number of holes in a steel material as a guide for pulling it out also reduces the value of the steel material.

In any case, it goes without saying that as the depth of the retaining wall increases (as the length of the steel material increases), it becomes more difficult to pull it out.

From the above, method A is not preferred in practice.

Method C is less reliable and has risks.

Therefore, currently B
Although this method seems to be commonly used, there are factors that are fundamentally incompatible with this method.

That is, it is the coating thickness of the lubricant (edge cutting material).

Originally, the cement-based hardened materials and steel materials that form earth retaining walls are
The premise is that they are strongly integrated.

However, the strength of lubricants is extremely low compared to cement-based hardened materials and steel materials.

This means that the presence of a lubricant inhibits strong integration between the cement-based cured product and the steel material.

Therefore, first, from the mechanical viewpoint of the earth retaining wall, it is desirable that the lubricant be as thin as possible and have a uniform thickness.

This is because if the lubricant is thick and there are variations in thickness, there is a risk that external forces (earth pressure, water pressure, etc.) exerted on the cement-based hardened material will not be accurately transmitted to the steel material.

This has a negative impact on the earth retaining wall and may eventually lead to its failure.

Second, from the perspective of pulling out steel materials, it is desirable that the lubricant be thicker, considering the amount of pulling force and the reliability of pulling out.

This is because there is a risk that the lubricant may peel off or be scraped off when the steel material is inserted, and the lubricant may be partially lost.

In addition, steel materials and cement-based hardened materials that bear external forces always undergo displacement (deformation) in the direction of the external force (horizontal direction), so if the thickness of the tsukuda material is thinner than the amount of displacement, the steel material must be pulled out with some residual displacement remaining.

This means that when pulling out the steel, it must be pulled out in the vertical direction, and that when the steel is pulled out, some steel tends to return to its original state fi (the state without any displacement when inserted or erected), while others remain displaced. This is because a horizontal pressing force is generated between the hardened cement material and the resultant frictional force is increased, and the lubrication (Xi cutting) effect is lost.

These things increase as the retaining wall gets deeper.

In short, the advantage of method B is that it uses the same machine as method A, but the pulling force is slightly weaker.

The present application has been made to solve the above-mentioned problems inherent in the conventional technology, and its purpose is to provide a construction method having the following functions.

In this invention, after the steel in the earth retaining wall is fully worked,
This method has a simple structure and allows steel materials to be pulled out safely and reliably with extremely low pulling force.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following means.

That is, in this construction method, when inserting a steel material into a cement-based hardened material, sulfur mortar is fixed around the steel material in advance and then inserted.

When pulling out the steel material, the fixed sulfur mortar is heated and melted to separate the steel material from the retaining wall.

Here, sulfur mortar is manufactured from elemental sulfur, fine aggregate, and various admixtures.

Its properties include that it begins to soften around 110°C, and at higher temperatures it becomes a very fluid liquid;
It solidifies at temperatures below around °C and has a strength equal to or greater than cement mortar, and its strength develops very quickly, reaching 80% of its final strength within a few hours after pouring.

In addition, since hardening progresses only by cooling the sulfur mortar, no special curing is required. Unlike cement mortar, no water is used, so there is no need to worry about freezing even if the outside temperature is below freezing. Good strength can be obtained in a short time even during construction in cold weather.

In the present invention, the cement-based hardened material of the earth retaining wall is in contact with the steel material,
The cement-based hardened material is replaced with sulfur amortar at an appropriate thickness in the part where they are integrated.

[Action Co. Explain along with the effects.

[Embodiments of the Invention] A case in which the embodiments are applied to a pillar type underground continuous earth retaining wall, which is an example of the object, will be described with reference to the accompanying drawings.

The construction procedure is shown in Figure 1.

Referring to FIG. 1A, the auger 1 is set at a predetermined position and a hole is drilled, and when a predetermined depth is reached, the auger 1 is pulled out by rotating in the opposite direction.

At this point, the cement-based cured material 2 is injected from the tip of the auger 1.

FIG. 1B shows the column filled with hardened cement material 2 after drilling has been completed and the auger 1 has been removed.

Referring to FIG. 1C, next, before the cement-based cured material 2 hardens, a steel material 3 is inserted and installed.

FIG. 1E represents the state of the plane in FIG. 1C.

In this way, one cycle is completed, and the cycle is repeated to form columns.

FIG. io shows a state in which a column type underground continuous earth retaining wall 4 is formed.

Note that this case is an example in which the steel materials 3 are arranged in a staggered manner.

FIG. 1F represents the state of the plane in FIG. 1D.

After the earth retaining wall 4 of a predetermined depth and width is completed in this way, underground excavation on the inner surface side of the earth retaining wall 4 starts and underground construction is carried out. The function of the wall 4 is completed and the steel material 3 is no longer needed.

Therefore, the present invention is designed to pull out steel material as shown in FIGS. 2 and 3.

The electric heating Is5 is attached to the steel material 3 in advance, but in this case, it is only necessary to fix it here and there with the adhesive tape 6.

This is because the heating wire 5 is reliably fixed to the steel material 3 by fixing the sulfur mortar 7 to the steel material 3 after the heating wire 5 is attached.

In this way, a steel material for constructing a continuous earth retaining wall is a material in which sulfur mortar is fixed to the surface of the steel material to a predetermined thickness.

Further, the number and arrangement of the heating wires 5 are not limited to this example.

The point is that it is sufficient that enough heat is conducted to melt the sulfur mortar 7 in contact with the steel material 3.

Note that depending on the number and arrangement of the heating wires 5, the temperature may reach such a high temperature that the sulfur mortar around the heating wires 5 burns by the time the entire sulfur mortar 7 in contact with the steel material 3 melts. Since there is no sulfur mortar 7, it will not burn.

The end of the heating wire 5 is exposed above the ground.

Referring to Figure N4, the steel material 3, on which the heating wire 5 is attached in advance and is sprayed with sulfur mortarf by the spraying machine 8 and fixed, is inserted into the cement-based hardened material and built.

Note that the construction period is located between FIG. 1B and FIG. 1C.

In this case, it is better to spray the sulfur mortar 7 to a thickness that is slightly larger than the amount of displacement of the steel material.

Further, there may be some variation in thickness.

Figure 5 is a plan view after construction is completed.

In addition, as shown in Fig. 6, when suspending the steel material 3 using something like a portable hoist 9 and inserting it into the cement-based hardened material, spray the sulfur mortar around the steel material with the machine 8 while inserting it. You may also do so.

As shown in FIG. 7, when pulling out the steel material 3, electricity is applied to the heating wire 5 led to the ground to generate heat.

As the temperature of the heating wire 5 rises, the sulfur mortarf in contact with the surface of the steel material 3 starts to melt, rapidly softening, and becoming viscous.

Therefore, the adhesion force between the sulfur mortar 7 and the steel material 3 becomes extremely small.

In addition, if the fixed thickness of the sulfur mortar 7 is greater than the amount of displacement of the steel material 3, the sulfur mortar becomes like a liquid with no viscosity when melted, so the cement-based hardening that is displaced in the horizontal direction It deforms freely between the material 2 and the steel material 3, there is no horizontal restraint between the cement-based hardened material 2 and the steel material 3, and since the steel material 3 is an elastic body, it returns to its original shape 7.
! ! (It will return to its original state without any displacement when it was inserted and installed.At this time, the portable erected
By applying a pulling force with something like the machine 9, the steel material 3 can be pulled out easily and quickly.

This is the end of the example, but the heating method does not necessarily have to be a heating wire, but any method that heats sulfur mortar may be used.

For example, a method can be considered in which electrodes are attached to the steel material and electricity is applied when the steel material is pulled out, causing the steel material itself to generate heat and melting the stuck sulfur mortar.

Also, regarding the fixing method, it is not strictly a matter of spraying, but by pouring sulfur mortar onto the steel material in advance.
It can also be fixed.

The above-mentioned sulfur mortar is made by mixing appropriate amounts of sulfur, fine aggregate, and other admixtures, and kneading the mixture by utilizing the thermoplasticity of sulfur.

[Effects of the Invention] Since the present invention is configured as described above, it produces the following effects.

1) Since sulfur mortar has a strength equal to or higher than that of the cement-based hardened material forming the retaining wall at room temperature, the above-mentioned mechanical problem can be ignored.

In other words, it is sufficient to fix the steel material to an appropriate thickness depending on the displacement of the steel material.

Moreover, there is no problem even if there is variation in thickness.

This means that pulling out is reliable and construction is easy.

2) Sulfur mortar instantly solidifies at temperatures below around 110°C, so it will not peel off or be scraped off.

This means certainty of extraction.

3) Sulfur mortar melts at a heating temperature of around 115℃,
Since it is extremely fluid like water, the pulling force is very small due to the weight of the steel itself and the weight of some attached sulfur mortar.

In other words, even if the space is narrow or the surrounding ground is soft, it can be done easily and quickly using a small portable hoist m.

This means that it can be pulled out anywhere and economically.

4) In the case of the embodiment, in order to prevent the melting of sulfur, heating wires are simply attached around the steel material, so the material is extremely cheap and the work is simple, resulting in low construction costs.

Since sulfur is an extremely stable substance, there is usually no problem even if it remains underground (oxygen must be supplied to destabilize it, and at high temperatures -20
0°C or higher is required).

Although sulfur exists naturally, it is generally used as residue from the crude oil refining process, which leads to the reuse of resources.

From the above, the present invention is a novel construction method that allows for simple pulling means and easy pulling out by fixing sulfur mortar to the steel material of a continuous earth retaining wall.

[Brief explanation of the drawing]

Figures 1A, 1B, 1C, and 1D are schematic longitudinal sectional views showing the construction procedure, Figure 1E is a plan view of Figure 1C, Figure 1F is a plan view of Figure 1D, and Figure 1D is a plan view of Figure 1D. The figure is a perspective view with a part of the steel part cut away, Figure 3 is an end view of the same as above, Figure 4 is a schematic vertical cross-sectional view showing the state of the steel being pulled out, Figure 5 is a plan view after construction is completed, FIG. 6 is a schematic longitudinal sectional view showing a state in which the steel material is inserted while spraying sulfur mortar around the periphery thereof, and FIG. 2@7 is a schematic longitudinal sectional view showing the state in which the steel material is inserted into the insertion chamber. Auger cement-based hardened material 1, steel material 1, earth retaining wall 1, heating wire 1, adhesive tape, sulfur mortar 1, spraying machine 1, portable hoist. Procedural amendment February 7, 1999 Display of the case Patent application No. 330085 of 1988 Name of the invention Steel materials for constructing continuous earth retaining walls and steel material drawing method for continuous earth retaining walls Relationship with the case Person who amends the case Patent applicant Name: Iwata Construction Co., Ltd. Tsutomu 060 Address: 7 Kita 1-jo Nishi 3-chome, Chuo-ku, Sapporo Correct to.

Claims (1)

[Claims] 1. Continuous earth retaining characterized by fixing mortar containing sulfur as a main material (hereinafter referred to as sulfur mortar) to a predetermined thickness on the surface of a steel material (H-type steel, I-type steel, etc.) Steel materials for wall construction. 2. The steel material for constructing continuous earth retaining walls according to claim 1, wherein the fixed thickness of the sulfur mortar is greater than the amount of displacement of the steel material. 3. When inserting steel into a cement-based hardened material (concrete, cement milk, cement and bentonite) in forming a continuous earth retaining wall, spray sulfur mortar around the steel material while inserting it, or A steel material pulling method for a continuous earth retaining wall, characterized in that the steel material is inserted, and after the function of the continuous earth retaining wall is completed, the sulfur mortar is heated and melted, and the steel material is pulled out. 4. The method of drawing out steel material for a continuous earth retaining wall according to claim 3, wherein the sulfur mortar fixed to the steel material is heated and melted using a heating wire.