JPS6225815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for constructing underground structures such as cast-in-place piles, underground continuous walls, and underground water-stop walls.

Conventional technology When constructing cast-in-place piles, underground continuous walls, underground water-stop walls, etc. using ready-made prestressed concrete members such as PC piles and AC piles, the problems are noise during driving and transportation. It is the difficulty of the work.

For this purpose, a hole is drilled in the ground using muddy water,
A conceivable method is to place underwater concrete into the muddy water and tension the prestressed steel material inserted vertically into the drilled hole to apply prestress, but the following problems arise.

Mud water such as bentonite solution is injected into the ground excavation hole to maintain the excavated surface, so when concrete is poured into the hole, the mud water and concrete mix, making the quality of the concrete unstable and causing prestress. It is not possible to obtain high enough strength to introduce

Concrete members formed by replacing mud with water using the cast-in-place method are in direct contact with the surrounding soil, so even if prestress is introduced, it is not possible to apply uniform tension due to the friction between the concrete and the surrounding soil. Can not.

If pre-stressing is to be introduced, the post-tension method will be used, but in the case of foundation structures, grouting is difficult because the distance from the sheath tip to the basement is 10 to several tens of meters.

Although mud drilling is economical, slime precipitates at the bottom of the drilled hole, causing subsidence of underground structures.

Furthermore, in terms of earthquake-resistant structures, underground structures such as piles are increasingly required to have a high pull-out capacity.

Purpose of the Invention The present invention was made to solve the above-mentioned problems, and its purpose is to provide a method for constructing an underground structure as described below.

A method for constructing underground structures that does not cause problems such as noise and difficulty in carrying in work.

A method of constructing underground structures that can be expected to have sufficient strength to introduce prestress.

A construction method for underground structures that allows uniform prestress to be introduced over the entire length of the underground structure.

A construction method for underground structures that can minimize the subsidence of underground structures.

A method of constructing underground structures that can provide tensile strength.

Composition of the Invention The method for constructing an underground structure according to the present invention is to fix the end of a prestressed steel material to the bottom of a ground borehole excavated with muddy water, integrate a plurality of concrete blocks through which the prestressed steel material has been inserted, and place the concrete blocks inside the borehole. The above objective is achieved by injecting grouting material.

Embodiment Hereinafter, the present invention will be explained in detail based on an embodiment shown in the drawings.

<1> Concrete Block The concrete block used in this invention can have various shapes, and in this embodiment, the concrete block 1 shown in FIG. 2 can be used.

That is, the concrete block 1 has a PC steel insertion hole 2 penetrating the center of both the upper and lower surfaces, a spherical concave surface 3 is formed on the upper surface, and a spherical convex surface 4 is formed on the lower surface.
is formed. The concave surface 3 and the convex surface 4 are formed to be able to fit into each other. concrete block 1
is formed into a regular hexagonal cross section having six planes 5 parallel to the longitudinal direction of the PC steel insertion hole 2.

<2> Excavation of Hole Below, a case will be described in which the method for constructing an underground structure according to the present invention is implemented using the concrete block 1 as described above.

First, a hole 6 is drilled in the ground.

The borehole 6 is formed by mud drilling. An anchor hole 7 having a smaller diameter than the drilled hole 6 is drilled in the center of the bottom of the drilled hole 6.

<3> Fixing of PC steel material Use a PC strand as the PC steel material 8 and fix it in the drilled hole 6. The PC strand is inserted into a sheath 10 having an irregularly shaped sheath portion 9 having an uneven outer periphery at its lower end. The lower end of the PC strand located inside the irregularly shaped sheath part 9 is fixed with a hardening agent 11 such as cement, epoxy, polyester, etc. so as to be integrated with the irregularly shaped sheath part 9.

The PC steel material 8 has the irregularly shaped sheath part 9 side connected to the anchor hole 7.
and fixed with grout material 12.

<4> Subsidence of concrete block PC steel insertion hole 2 of concrete block 1
Insert the fixed PC steel material 8 into the drilled hole 6,
Let it sink into the muddy water in drill hole 6.

Before the concrete block 1 sinks, a fixing member 1 made of precast concrete and having a PC steel insertion hole in the center and a spherical concave surface on the upper surface is installed.
7 is inserted through the PC steel material 8 and allowed to sink.

After that, a plurality of concrete blocks 1 are stacked with the convex surface 4 facing downward by inserting the PC steel material 8 and letting them sink in order.

Incidentally, the inner circumferential surface of the PC steel insertion hole 2 of one or more concrete blocks 1 located below among the plurality of concrete blocks 1 is formed as an uneven surface 13.

Furthermore, the concrete block 1 located below among the plurality of concrete blocks 1 is provided with a grout flow hole 14 penetrating from the PC steel insertion hole 2 to the outer circumferential surface.

<5> Tensioning of PC steel The plurality of concrete blocks 1 are integrated by tensioning the PC steel 8, and fixed with wedges 15.

Slime 1 by tensioning PC steel material 8
6 is compressed from above, it is possible to significantly reduce the amount of subsidence of the underground structure.

<6> Injection of grout material Inject the grout material 12 from the ground into the drilled hole 6 using the PC steel insertion hole 2. After the grout 12 reaches the lower end of the drilled hole 6, it passes through the grout distribution hole 14 of the concrete block 1 and fills the space between the concrete block 1 and the ground of the drilled hole 6.

The uneven surface 13 of the prestressed steel material insertion hole 2 of the lower concrete block 1 and the irregularly shaped sheath portion 9 of the prestressed steel material 8
When the grout material 12 fills between the outer peripheries and hardens, the upper end of the PC steel material 8 is fixed by the wedge 15, and the lower end is bonded to the concrete block 1 by the grout material 12, so that the concrete block 1 may be slightly Even if the concrete blocks 1 sink, they maintain their initial prestress and are integrated, so a highly reliable underground structure can be constructed.

An underground structure is constructed as described above, but when constructing an underground continuous wall or the like, the above operations may be repeated to construct the underground structure continuously underground.

Effects of the Invention Since the present invention has the above configuration, it is possible to obtain the following effects.

Since the concrete blocks are simply lowered into the borehole, there are no noise problems and the work can be carried in easily.

Since concrete blocks are used, it is expected to be strong enough to introduce prestress.

Since there is no friction between concrete blocks and the excavated ground, uniform prestress can be applied over the entire length of the underground structure.

Since the slime at the bottom of the borehole is compressed when prestress is introduced, the subsidence of underground structures can be significantly reduced.

Since the PC steel material was fixed at the bottom of the drilled hole, it was possible to obtain the pull-out strength of the underground structure.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention in a construction state, FIG. 2 is a half-cut perspective view of a concrete block, and FIGS. 3 to 7 are illustrations of the construction sequence. 1...Concrete block, 2...PC steel material insertion hole, 3...Concave surface, 4...Convex surface, 5...Flat surface,
6... Hole drilling, 7... Anchor hole, 8... PC steel material, 9... Irregular sheath part, 10... Sheath, 11
... hardening agent, 12 ... grout material, 13 ... uneven surface, 14 ... grout material distribution hole, 15 ... wedge, 16 ... slime, 17 ... fixing member.

Claims (1)

[Scope of Claims] 1. Fixing the end of the PC steel material to the bottom of the ground hole drilled with muddy water, passing the PC steel material through the PC steel through hole of the concrete block and sinking into the hole, and stacking the concrete blocks. A method of constructing an underground structure, in which a plurality of concrete blocks are integrated by tensioning prestressed steel, and grout is injected into the hole. 2. The method for constructing an underground structure according to claim 1, wherein the inner circumferential surface of the PC steel insertion hole of the lower concrete block among the plurality of concrete blocks is made into an uneven surface.