JPS6245834A - Earthquake insulating pile and its construction - Google Patents

Abstract

PURPOSE:To enhance the durability of an earthquake insulating pile by a method in which the lower end of a pile inserted concentrically into a cylindrical casing is provided with an expanded pile bottom of a larger diameter than that of the pile, and concrete is packed into a steel tube to form an unbonded type packed steel tube which makes up the pile. CONSTITUTION:A pile 12 is concentrically inserted into the shape 11 of a casing 10 buried under the ground S. The pile 12 is made up of an unbonded type packed steel tube-concrete composite formed by packing concrete 14 into a steel tube 13 whose inner surface is coated with a releasing agent 15. The lower end of the body 12 projected from the casing 10 is provided with integrally formed expanded bottom 16 of a greater diameter than that of the pile body 12. A soft (at ordinary temperature) viscous material 17 is packed into the space 11 and the bottom 16 is closely connected with the ground S.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pile that is used as a pile having a rigid structure such as a reinforced concrete structure on the upper part, and which is immune to earthquake forces etc. Concerning seismic isolation piles with seismic function and their construction methods.

[Prior art]

There are various types of seismic isolation structures that are equipped with various types of seismic isolation devices, but all of them are designed to lengthen the natural period of the structure (1 J of the earth's period) and thicken it (shift it, etc.). It is based on the principle of increasing the damping constant by dissipating energy using dampers, dashpots, etc., and is an application of these principles.

[Problem that the invention seeks to solve]

However, since conventional seismic isolation devices are made of materials such as rubber, oil, and iron, they suffer from bacterial rot and corrosion, resulting in a lack of durability, and frictional parts that are difficult to maintain between the ground and the structure. There were drawbacks such as large relative deformation occurring during the process and lack of reliability against changes over time.

This invention was made in view of the above circumstances, and the constituent materials have durability and reliability against rot, corrosion, aging, etc., and it is also possible to obtain a stronger seismic isolation effect. The purpose of this project is to provide seismic isolation piles for creating seismic isolation structures.

[Failure to solve the problem]

In order to solve the above-mentioned problems, the seismic isolation pile of the present invention includes a cylindrical casing that is buried in the ground to a predetermined depth from the ground surface and has a hollow interior, and an inner surface of the casing inside the casing. The pile body is inserted concentrically with a space in between, and the lower end is inserted into the ground below the lower end of the casing. It has a pile expansion bottom that is in close contact with the ground,
The pile body is characterized in that it is made of unbonded steel pipe concrete in which the pipe and the concrete filled inside the steel pipe are in a non-adhesive state.

In addition, the method of constructing such seismic isolation piles is as follows (1)
It is characterized in that the piles are made according to the process order of ~(IV).

(:) The process of drilling a hole to a predetermined depth from the ground surface and fitting a cylindrical casing into the top of the hole.

(++t aii The pile body is composed of unbonded filled steel pipe concrete in which the pipe and the concrete filled inside the steel pipe are in a non-layered state, and the outer diameter is smaller than the inner diameter of the casing and the length is longer than the depth of the hole. , the pile body is set in the hole by inserting it into the hole concentrically with the casing.Alternatively, a steel pipe whose outer diameter is smaller than the inner diameter of the casing is inserted into the hole concentrically with the casing. The step of setting a pile body made of unbonded filled steel pipe concrete in the hole by inserting the steel pipe into the hole and then filling the inside of the steel pipe with concrete so that the steel pipe and concrete are not attached.

(lIl) A step of pouring concrete into the gap between the lower end of the pile body and the inner surface of the hole to form the expanded bottom portion of the pile.

−ψ Process of pouring viscous material between the casing and the pile body.

[Principle of this invention]

Firat-sOf-
The idea of "8tory theory" is advocated.

The idea is that by making only the lowest layer of the structure partially flexible in the horizontal direction, the natural period of the entire structure is lengthened and a seismic isolation effect is achieved. If we replace this with the ground, a natural escape structure would be a ground that has a very soft stratum (clay layer, sandy layer) superimposed on top of a hard stratum (rock, etc.).

Here, r First-3or replaced with the above ground
I will briefly touch on the ``t-8tory theory'' with reference to Figures 3 and 4. As shown in Fig. 6, the ground has a seismic isolation structure, and has a structure in which piles 3 are driven into hard soil 112 from the ground surface through a soft stratum 1, and a structure 4 is installed on top of the piles 3. Try setting the object to -ID. Figure 4 shows that 44
This is a partial model of the pile 3 of the vibration system subjected to DZ.

When the Itil wave arrives late on the structure built on the above ground, the following phenomenon occurs.

(1) Simply think, if! The length resting on the hard stratum 2 (possibly).

(ii) The energy returning from the superstructure 4 is dissipated in the soft stratum 1.

This invention is based on the above, f) r First-8of-
This is an attempt to take 8tory G a step further and artificially create a ground with a natural seismic isolation structure.
The aim is to reduce the seismic input to the building itself, and at the same time attempt to dissipate energy using viscous materials, thereby simplifying the structural design of the upper building.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In the figure, S indicates the ground, and a cylindrical casing 10 is embedded in the ground to a predetermined depth from the surface of the ground S. The inside of this casing 10 is hollow, and a space 1 is formed between the inside of this casing 10 and the inner surface of the casing 10.
1 and the pile body 12 is inserted concentrically.

The pile body 12 includes a steel pipe 13 having an outer diameter smaller than the inside of the casing 10 and concrete 1 filled inside the steel pipe 13.
4 is constructed of unbonded filled steel pipe concrete in a non-adhesive state.

In order to make the steel pipe 13 non-adhesive, for example, paraffin, grease, oil, vaseline, etc. may be applied as a separation material 15 to the inner surface of the steel pipe 13, and the concrete 14 may be filled therein.

The lower end of the pile body 12 is inserted into the ground S below the lower end of the casing 10, and at the lower end there is a wiped bottom part 16 that has a larger diameter than the pile body 12 and is in close contact with the surrounding ground S. It is provided integrally with 12. and,
A space 11 between the pile body 12 and the casing 10 is filled with a viscous material 17 such as asphalt that is soft at room temperature.

To construct such seismic isolation piles, proceed as follows.

That is, first, a hole of a predetermined depth is excavated from the surface of the ground S using an auger, and the cylindrical casing 10 is inserted into the upper part of the hole.

Next, a pile body 12 is formed of unbonded filled steel pipe concrete and has an outer diameter smaller than the inner diameter of the casing 10 and a length substantially equal to the depth of the hole.
is inserted concentrically into the hole overflowing the casing 10.

When constructing the pile body 12 on site, first prepare a steel pipe 13 whose outer diameter is smaller than the inner diameter of the casing 10,
This steel pipe 13 is inserted into the hole concentrically with the casing. Inside this steel pipe 13, a separation material 15 is placed in advance.
is applied to the pile body 12, and then, by driving concrete +J-) 14 inside this steel pipe 13, the pile body 12
Complete 0 set.

Thereafter, concrete is placed between the inner surface of the hole and the lower end of the pile body 12 from above the space 11 between the casing 10 and the pile body 120 to form the wiped bottom portion 16. Then, by filling the space 11 with the viscous material 17, the illustrated seismic isolation pile can be obtained.

Note that the wiped bottom portion 16 can also be formed at the same time as the filling concrete 14 of the pile body 12 is cast.

The seismic isolation pile constructed in this way is [First-3o
It is an artificially created natural seismic isolation structure that follows the "ft-8tory theory" and has a seismic isolation function. Therefore,
Even if an earthquake occurs and seismic waves reach the ground in this area,
Because the natural period of the structure deviates significantly from the earthquake period, only a small amount of seismic force is input, and
The energy returned from the upper structure will also be dissipated by the viscous body 17.

Therefore, when a superstructure is supported on top of a seismic isolation pile, the superstructure is not affected by earthquakes (and its structure can be easily designed).

Moreover, in this foundation structure, unbonded type filled steel pipe concrete is used as the pile body 12.

The unbonded type filled steel pipe concrete structure was patented in 1986.
As shown in the specification of No. 42979, the function is different from the conventional filled steel pipe concrete structure in which a steel pipe is simply filled with concrete as follows.

In other words, in the conventional method, the steel pipe and concrete are integrated, so when the compressive force in the axial direction increases, the steel pipe is distorted as one with the concrete, and if it is greatly distorted,
Steel pipes may exceed the Mises yield condition or experience local buckling. Therefore, although it is expected that the confining effect of the tensile force in the circumferential direction of the steel pipe will sufficiently increase the yield strength of concrete, in reality, conventional filled steel pipe concrete structures have limited axial strength due to the limited axial strength of the steel pipe. We cannot expect sufficient results, and the yield strength is too high.

On the other hand, in an unbonded type filled steel pipe concrete structure, when the axial compressive force acts only on the filled concrete and the axial compressive force exceeds the predetermined compressive strength and causes transverse strain in the concrete, the steel pipe It behaves as a confining effect that resists transverse strain. Therefore, unbonded filled steel pipe concrete is guaranteed to have high axial yield strength.

As explained above, this seismic isolation pile uses unbonded filled steel pipe concrete with high compressive strength as the pile main body 12, and also has a wiped bottom part 16 at the lower end of the pile main body 12, so it can be used for emergency purposes. It can exhibit high axial support force.

In addition, as the viscous body 17, bentonite liquid, oil, and air can be used in addition to asphalt. Further, instead of the viscous material 170, it may be filled with a granular material that dissipates energy by slipping or breaking itself. Suitable granules include lightweight aggregate and pumice.

〔Effect of the invention〕

Since this invention has the above-mentioned configuration, it is possible to obtain a greater seismic isolation effect than conventional seismic isolation devices, and it also has durability against rot, corrosion, aging, etc.
The structure can be designed as a reliable structure.

In addition, the pile body is made of unbonded filled steel pipe concrete with high compressive strength, and a wiped bottom is provided at the bottom of the pile body, so the axial strength of the pile is extremely high. It can also be connected to the columns of the superstructure.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of one embodiment of this invention, Fig. 2 is a 7J
Fig. 6 is a cross-sectional view taken along the line nn of Fig. be. 10...Casing, 11...2M,
12...Pile wood, 13...m pipe, 14
... Concrete, 15 ... Separation material,
16... Wipe bottom, 17. River... Viscous body, S...
·····ground.

Claims (2)

[Claims] (1) A cylindrical casing that is buried in the ground to a predetermined depth from the ground surface and has a hollow interior; has a pile main body inserted into the ground below the lower end of the casing, and a pile enlarged bottom part that is integrally provided at the lower end of the pile main body, has a diameter larger than the pile main body, and is in close contact with the surrounding ground; A seismic isolation pile characterized in that the main body is composed of unbonded type filled steel pipe concrete in which the steel pipe and the concrete filled inside the steel pipe are in a non-adhesive state. (2) A construction method for seismic isolation piles, characterized by making the piles according to the following steps (i) to (iv). (i) A step of excavating a hole to a predetermined depth from the ground surface and fitting a cylindrical casing into the upper part of the hole. (ii) a pile body composed of unbonded steel pipe concrete in which the steel pipe and the concrete filled inside the steel pipe are in a non-adhesive state, and whose outer diameter is smaller than the inner diameter of the casing and whose length is longer than the depth of the hole; The pile body is set in the hole by inserting the pile body into the hole concentrically with the casing. Alternatively, a steel pipe whose outer diameter is smaller than the inner diameter of the casing is inserted into the hole concentrically with the casing, and then concrete is filled into the steel pipe so that the steel pipe and the concrete do not adhere to each other. A step of setting a pile body made of unbonded filled steel pipe concrete in the hole. (iii) A step of pouring concrete into the space between the lower end of the pile body and the inner surface of the hole to form a pile expanded bottom portion. (iv) A step of pouring a viscous material between the casing and the pile body.