JPS5932639B2 - Method of constructing underground concrete structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of constructing a concrete structure by directly press-fitting concrete columns into the ground in parallel, such as under an existing building, road, or railway.

Instead of corroding steel pipes, prefabricated concrete columns with the required strength that do not corrode are directly press-fitted into the ground in parallel via special-shaped lead pipes, and are used as protection works at the same time. The construction method for obtaining a structure that can be used permanently as an underground structure is disclosed in Patent Application No. 6 in 1978.
It is disclosed in No. 8399 (Japanese Unexamined Patent Publication No. 54-4419).

This invention has the following problems.

(1) Cracks occur in the concrete column due to large bending and tensile stress during press-fitting.

(2) Reinforced concrete Precast concrete columns tend to crack during transportation.

(3) The beam height of concrete columns is often restricted.

(4) Columns with high dimensions and precision are required for fitting.

In order to solve the above-mentioned problems, this invention introduces prestress into the concrete column in advance using the pretension method, and then directly inserts the column, which does not corrode, into the ground through a specially shaped pipe. The purpose of this is to press-fit the column and bridge in parallel with the girder (main girder).

The invention will be explained with reference to embodiments of the accompanying drawings.

In Figures 1 to 3, reference numeral 1 denotes a steel drilling tip pipe formed into a cylindrical shape to correspond to a concrete cylinder, with the front end having a cutting edge 1a and the rear end having a perforated partition. wall 1
The fitting part 1b for connecting the concrete column by the interposition of c.
A guide surface 1d is formed on the inside so as to curve and converge from the front toward the center hole of the rear partition wall 1C.

2 is a concrete column of the required size to be buried, and pretensioned PC steel 10 is installed in the longitudinal direction by the pretension method in advance to have the required strength, and a screw auger 5 is installed in the longitudinal direction of the center of the column. A hole 2a for insertion is provided, and a sheath tube 3 made of a suitable material such as a thin iron plate is provided in the hole 2a, and a J-TL 4 for inserting a prestressing steel material is provided in the part that receives tension. A plurality of them are provided in the longitudinal direction.

5 is a screw auger, and a digging blade 5a at the front end
In the part following , there is a screw 5b formed so that the diameter gradually decreases and the pitch gradually increases from the front to the rear.
This enables efficient loading and unloading of excavated earth and sand when press-fitting concrete columns.

Therefore, when press-fitting the above-mentioned concrete column 2 into the ground, the above-mentioned leading pipe 1 is fitted and set on the front end of the concrete pillar 2 as shown in Fig. A screw auger 5 is installed through the inside of the sheath pipe 3 of the concrete column body 2, and this is attached to a propulsion device J set in advance in the shaft as shown in Fig. 4. The pipe 1 and the concrete column 2 are horizontally press-fitted into the destination ground A by the propulsion device J.

At this time, the rotary cutter 5a at the front end of the screw auger 5 excavates the earth and sand in front, while the digging pipe 1 sinks into the ground. 5b and the curved guiding surface 1d of the backward convergence formed inside the excavation lead pipe 1, the concrete column body 2 is smoothly carried into the lead pipe 1.
The soil is fed intensively toward the center hole 2a, and then, in the center hole 2a, the excavated soil is continuously transported without stagnation due to the relationship between the sheath pipe 3 and the screw 5C, which has a small diameter and gradually increases the pitch. During this time, the concrete column 2 is pressed and propelled from behind by the propulsion device J, and the concrete column 2, which is originally thick and difficult to press into, is also guided to the leading pipe 1, without much resistance. (It is easily press-fitted into the ground A.

When one concrete column 2 is completely press-fitted into the ground and reaches the shaft on the reaching side, the leading pipe 1 is removed and the screw auger 5 is pulled out, and the next concrete column 2 is press-fitted. Will use again.

Repeating this operation, a large number of concrete columns 2 are
As shown in the figure, the post-tension PC steel members 6 are press-fitted sequentially in parallel in the vertical and horizontal directions along the outline of the structure to be constructed, and are inserted through each of the plurality of small holes 4 prepared in advance in each concrete column 2. do.

When introducing prestressing, as shown in Figure 6, prestressing is applied to the concrete column 2 in advance using prestressed steel 10, and then the main girders 7 and footrests 8 assembled at both side entrances of the construction site are jacked ( (not shown) to tension the boss tension PC steel material 6 to integrate the whole, and both ends thereof are fixed to the fixing material 9.

Once a concrete column structure is constructed in this way, the earth and sand inside it is excavated and removed, the inner surface is covered with some concrete soil, and it can be used directly as an underground passage, tunnel, or conduit. .

In addition, as mentioned above, when press-fitting each concrete column,
It is desirable to construct the concrete column 2 as a single unit as described above from the viewpoint of construction period and construction, but if it is difficult to secure exclusive construction land due to the conditions of the construction site, the concrete column 2 may be constructed in advance by approximately 5 TrL. The pieces are cut into lengths of about 10 meters and then press-fitted into pieces one after another at the work site.

In this case, as shown in FIG. 1, a protrusion 2b is formed on one end surface of each concrete column 2, and an engaging recess 2C is formed on the other end surface, so that the four parts 2 of the front one are refilled.
C is engaged with the protruding portion 2b of the rear one to prevent mutual displacement.

At that time, if an adhesive such as synthetic resin or mortar is applied to the joint portion of the can, the mutual integration of the concrete columns 2 will be more effective.

Also in this case, each concrete column 2 has a hole 2a in the center for insertion of a screw auger, a sheath pipe 3 for protecting the inner surface is installed therein, and a pretensioned PC steel material 10 is installed using the pretension method. It has a small hole 4 for inserting a prestressed steel material on the periphery that receives tension.
The earth and sand excavated during press-fitting is smoothly discharged backward through the sheath pipe 3, and the PC steel material 6 is inserted into the small hole 4 after burying.
Inserting the wire is no different from the previous example.

Furthermore, Fig. 8 shows an example in which a square cross-section is used as the concrete column 2. In this case, the external shape of the excavation leading pipe 1' is the same as the cross-sectional shape of the rear concrete column, and the inner guide The surface 1d' has a square shape at the cutting edge portion 1a', a circular shape in the middle, and continues to converge toward the center hole of the rear partition wall 10'.

A prestress is applied to the concrete body τ using a prestressing steel material 10 in advance.

The other configurations are the same as in FIG. 3.

By appropriately changing the inner guide surface to match the external shape of the concrete column, it is possible to press-fit concrete columns of other shapes, not just those with circular or square cross sections.

The present invention has the above-mentioned configuration, has a cutting edge portion at the front end, has a fitting portion matching the outer shape of the concrete column at the rear end,
The precast concrete column is connected to a special excavated tip pipe with a guiding surface formed on the inside that converges from the front end toward the rear center hole, and a screw is inserted between the excavated tip tube and the center hole of the concrete column. Since we installed an auger to press-fit the concrete columns into the ground one after another, we were able to bury concrete columns, which would normally be thick and difficult to press-in, directly into the ground without any problems. Since steel pipes are not used as in the past, there is no need to worry about strength loss due to corrosion, and the structure is extremely robust and can be used not only as a protection structure but also as a permanent underground structure.

In addition, prestress is introduced into the concrete column using the pretension method, and a sheath for the post tension cable is provided, so even if the column is subjected to large bending and tensile stress during press-fitting, the column will remain intact even during transportation. No cracks appear on the body.

Also, by using prestressed concrete columns rather than reinforced concrete columns, the beam height can be made considerably smaller.

Further, since the columns have the same shape and are made of prestressed concrete using a pretension method, they can be produced in a factory and a highly accurate product can be obtained.

Also, if the pre-tension method is used for the column, the PC steel material 10
This has many effects, such as being able to apply sufficient prestress.

[Brief explanation of drawings]

Figure 1 is a perspective view of an example of an excavation pipe, Figure 2 is a cross-sectional view of the excavation pipe connected to a concrete column, and a screw auger is installed inside it. Figure 1-1
A cross-sectional view along the line, Figure 4 is an explanatory diagram of the state in which concrete columns are press-fitted into the ground, Figure 5 is a front view of concrete columns after parallel press-fitting, and Figure 6 is a concrete column and main column. FIG. 7 is a cross-sectional view of a short concrete column, and FIG. 8 is a partial perspective view of another example of a concrete column and a leading pipe. 1.1'・・・Excavation pipe, 1 a t 1 a
'...Blade mouth, 1 b, 1 b'...
...Fitting part, 1d, i d'...Guiding surface,
2.2'... Concrete column, 2aj2a'
...The center hole, 3, 3'... Sheath pipe, 4, 4'... For inserting the PC steel material/'' Dimension L, 5
...Screw auger, 6...Bost tension PC steel material, 7...Main girder, 10...
...Pretensioned PC steel material.

Claims (1)

[Claims] 1. A pre-stressed pipe made using a pre-tension method is used to construct a leading pipe that has a fitting part for the concrete column at the rear end and a guide surface formed on the inside that converges toward the center hole rearward from the front end. It is connected to the front end of a precast concrete column made of concrete, and a screw auger is installed across the excavation tip pipe and the longitudinal center hole of the concrete column, and the precast concrete column is ground along the outline of the planned structure. It is characterized by excavating a large number of concrete columns in parallel and press-fitting them in parallel, inserting prestressing steel into each concrete column, adding prestress to the precast concrete column using the boss tension method, and integrating it into the main girder. Method of constructing underground concrete structures.