KR101455327B1 - Seismic isolation foundation for marine bridge and construction method thereof - Google Patents

Abstract

The present invention relates to a pile (10) embedded in a seabed ground; An earthquake-resistant layer 100 formed by laying steel-making slag on the bottom of the seabed so that the upper end of a plurality of piles 10 is embedded; And a foundation caisson 40 installed above the seismic isolation layer 100 to support the lower end of the bridge pier 41. The seismic isolation layer 100 normally supports the foundation caisson 40, , The seismic load of the seabed ground is prevented from being transmitted to the foundation caisson (40) due to the occurrence of sliding in the seismic isolation layer (100) , It is possible to effectively resist a large-scale earthquake, to secure the material easily, and to ensure excellent structural stability.

Description

TECHNICAL FIELD [0001] The present invention relates to a foundation structure of a marine bridge using seismic isolation layers and a method of constructing the bridge structure.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a civil engineering field, and more particularly, to a structure of a marine bridge.

Recently, with the development of civil engineering technology, there have been more and more cases of construction of marine bridges for passing through land, islands, or between islands and islands by land transportation.

These maritime bridges are not only more emphasized in terms of structural stability than general land bridges, but also have difficulty in construction due to their poor accessibility.

In addition, various structures for earthquake resistance have been developed in the case of onshore bridges. However, in case of marine bridges, the development and construction of seismic structures have not been properly performed due to the above difficulties.

1 and 2 relate to an invention which is registered and filed by the applicant of the present invention with No. 10-2011-0008831.

As shown in FIGS. 1 and 2, it comprises a plurality of piles 10 buried in the seabed ground; A sliding layer 20 formed by laying a sliding aggregate having a smooth and curved surface on an upper portion of a submarine ground so that the upper end of a plurality of piles 10 is embedded; A supporting layer 30 formed by laying a supporting aggregate having a rough surface on an upper portion of the sliding layer 20 so as to be supported by the upper end of the plurality of piles 10; And a foundation caisson 40 installed on the support layer 30 to support the lower end of the bridge pier.

In this case, since the support layer 30 slides on the sliding layer 20 during the earthquake, the seismic load of the seabed ground can be prevented from being transmitted to the foundation caisson 40 (seismic isolation) Thereby reducing the risk of damage to the marine bridge.

Specifically, the sliding layer 20 should be formed so that sliding can occur at the interface between the sliding layer 20 and the supporting layer 30 during the earthquake, and further, .

For this purpose, the sliding layer 20 should be formed by laying a sliding aggregate having a smooth and curved surface, and slag processed into a strong granule or a similar shape is used as the sliding aggregate (FIG. 2).

Since the support layer 30 is supported by the upper ends of the plurality of piles 10 to support the foundation caisson 40 during normal and earthquake, Should be made of roughly formed support aggregate, such slag being processed into crushed stone or similar shape.

However, these conventional techniques have pointed out the following problems.

First, in the structure according to the prior art, the sliding layer 20 and the support layer 30 are made of separate materials, and when they are subjected to an earthquake, they play different roles as described above to perform seismic isolation functions. In the case of large earthquakes with maximum ground acceleration of 0.5g, stratification was not significant.

Second, materials such as hard rock and crushed stone require excessive cost for securing them, and there are many cases where the secured materials do not have the properties required by the present method.

Third, the blast furnace slag was found to be inadequate because of the occurrence of flaking during loading of the blast furnace slag.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a seismic isolation structure capable of effectively restraining a large-scale earthquake, securing materials easily, And a method for constructing the same.

In order to solve the above problems, the present invention provides a pile comprising: a plurality of piles (10) buried in a seabed ground; A seismic isolation layer 100 formed by laying the steel making slag on the bottom of the seabed so that the upper ends of the plurality of piles 10 are embedded; And a foundation caisson 40 installed above the seismic isolation layer 100 to support the lower end of the bridge pier 41. The seismic isolation layer 100 normally supports the foundation caisson 40 And the seismic load of the seabed ground is prevented from being transmitted to the foundation caisson (40) due to occurrence of sliding in the seismic isolation layer (100) at the time of an earthquake. Present basic structure.

The internal friction angle of the steelmaking slag is preferably 35 ° to 42 °.

It is preferable that the shear strain rate-shear elastic modulus curve of the steel making slag exists in a region between the Sand curve and the Graval curve.

The shear strain-damping ratio curve of the steelmaking slag is preferably present between the Sand curve and the Graval curve.

A slab layer 50 is formed on both ends of the foundation caisson 40 as an upper portion of the seismic isolation layer 100 so as to prevent the foundation caisson 40 from sliding on the upper surface of the seismic isolation layer 100 desirable.

A method of constructing a foundation structure of a marine bridge using the seismic isolation layer, the method comprising: piling a plurality of piles (10) in a seabed ground; A sand layer forming step of forming a sand layer (60) on the upper surface of the sea floor to planarize; Forming the seismic isolation layer (100) on the upper surface of the sand layer (60); And placing the foundation caisson (40) on an upper surface of the seismic isolation layer (100). The present invention also provides a method of constructing a foundation structure of a marine bridge using the seismic isolation layer.

It is further preferable that the upper portion of the bottom of the seabed so that the upper end of the pile 10 is exposed is inserted between the pile-embedding step and the sand layer forming step.

A method of constructing a foundation structure of a marine bridge using the seismic isolation layer, comprising: embedding the plurality of piles (10) in a seabed ground; Forming a sand layer (60) on the upper surface of the sea floor to planarize; Forming the seismic isolation layer (100) on the upper surface of the sand layer (60); Disposing the foundation caisson (40) on an upper surface of the seismic isolation layer (100); And forming a slag layer (50) on both ends of the foundation caisson (40) as an upper portion of the seismic isolation layer (100). Together.

It is further preferable that the upper portion of the bottom of the seabed so that the upper end of the pile 10 is exposed is inserted between the pile-embedding step and the sand layer forming step.

The present invention proposes a foundation structure of a marine bridge using a seismic isolation layer which can resist effectively against a large-scale earthquake, secures materials easily and secures excellent structural stability, and a construction method thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an earthquake-proof foundation structure of a marine bridge according to a conventional method; FIG.
2 is an enlarged view of a main part of Fig.
3 shows the embodiment of the present invention,
3 is a cross-sectional view of a foundation structure of a marine bridge using an earthquake-resistant layer.
4 is an enlarged view of a main part of Fig.
5 to 8 are process drawings of a method of constructing a foundation structure of a marine bridge using an earthquake-resistant layer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3, the basic structure of a marine bridge using the seismic isolation layer according to the present invention basically comprises a plurality of piles 10 buried in the seabed ground; An earthquake-resistant layer 100 formed by laying steel-making slag on the bottom of the seabed so that the upper end of a plurality of piles 10 is embedded; And a foundation caisson 40 installed above the seismic isolation layer 100 to support the lower end of the bridge pier.

In such a configuration, the seismic isolation layer 100 supports the foundation caisson 40 at normal times, and sliding occurs inside the seismic isolation layer 100 at the time of an earthquake, (40).

Therefore, there is an effect that the risk of damage to the marine bridge due to the seafloor earthquake can be reduced.

In the conventional structure, the multi-layer structure of the sliding layer 20 and the support layer 30 is adopted. However, in the structure according to the present invention, the seismic isolation layer 100 formed by the steelmaking slag performs all of these functions. have.

The supporting isolation structure is basically required to 1) to support the foundation caisson 40 stably, and 2) to prevent the seismic load from being transmitted to the upper part by sliding.

In order to fulfill the former role, the internal friction angle must fall within a certain range (35 ° ~ 42 °).

In order to perform the latter role, shear-shear modulus curves and shear strain-damping ratio curves should be in the area between Sand (Seed & Idriss, 1970) and Graval (Seed et al.) Curves.

Hereinafter, experiments conducted as to whether the steel making slag material satisfies the above requirements will be described.

First, in order to estimate the friction coefficient between the foundation caisson 40 and the seismic isolation layer 100, an experiment was conducted in which a concrete block was placed on a steel slag layer and a vertical load and a horizontal force were applied (FIG. 9).

Table 1 shows the shear stress-displacement behavior at the interface between the concrete block and steel slag in the above test.

The strain softening gradually progressed after reaching the maximum shear stress and the expansion behavior at the contact surface was small.

Table 2 is a graph for estimating the friction coefficient at the contact surface between the concrete block and the steelmaking slag.

The coefficient of friction at the interface between the concrete block and steel slag was 0.645 and the friction angle at the interface was 32.81 °.

From this, it can be estimated that the internal friction angle of the steelmaking slag is 42 °. Therefore, it can be confirmed that the seismic isolation layer 100 formed by the steelmaking slag can sufficiently perform the role of stably supporting the foundation caisson 40.

Tables 3 and 4 show the shear strain-shear modulus curves and the shear strain-damping ratio curves of the steel slag, respectively, compared with the Sand curve and the Graval curve.

As shown in Tables 3 and 4, the shear strain-shear elastic modulus curve and the shear strain-damping ratio curve of the steelmaking slag exist in the region between the Sand curve and the Graval curve. Therefore, when applied to the seismic isolation layer 100, It is possible to sufficiently perform the role of preventing the earthquake load from being transmitted to the upper part by sliding.

In addition, the uniaxial compressive strength of steel slag is 42.75 Pa compared to 30 MPa of crushed stone, the steel slag is 2.48 t / m 3 compared to 2.33 to 2.40 t / m 3 for unit weight, Steel slag was less than 20% compared to 35 ~ 40% of crushed stone, and steel slag was 0.645 compared to 0.57 for contact friction coefficient.

Therefore, the seismic isolation structure according to the present invention forms the seismic isolation layer 100 by steelmaking slag having the above-mentioned excellent physical properties, so that the following effect is obtained.

First, in the prior art, the sliding layer 20 and the support layer 30 form an isolation structure by a separate material, whereas in the present invention, an isolation structure is formed by one seismic isolation layer 100 made of steelmaking slag , The workability can be improved, and the labor and cost required for the construction can be reduced.

As can be seen from the above experimental results, the seismic isolation layer 100 formed by the steelmaking slag can simultaneously perform the role of stably supporting the upper structure and isolating the seismic load during the earthquake, It is expected that seismic isolation performance can be obtained by one layer even in case of a large earthquake with a maximum ground acceleration of 0.5 g.

Secondly, the reclaimed slag has a lower cost for securing it than steel balls and crushed stone, and has the effect of having stable properties required in the present method.

Third, steel slag installed in the water is not corroded, so it can be said to be environmentally friendly in that it efficiently utilizes industrial waste.

The base caisson 40 is not slid on the upper surface of the seismic isolation layer 100 but must be firmly supported. To this end, the base caisson 40 is provided on both ends of the foundation caisson 40 as an upper portion of the seismic isolation layer 100, (Fig. 4).

Hereinafter, a method of constructing a foundation structure of a marine bridge using the seismic isolation layer according to the present invention will be described.

First, a plurality of piles 10 are buried in the seabed ground. It is preferable to use the steel pipe 11 as the pile 10 in view of structural stability and workability of seabed work (FIG. 5).

The upper part of the bottom of the pile 10 is exposed so as to secure the area where the seismic isolation layer 100 is to be formed and a sand layer 60 is formed on the upper surface thereof for planarization (Fig. 6).

The seismic isolation layer 100 is formed on the upper surface of the flattened sand layer 60.

The seismic isolation layer 100 is advantageous in that it can be easily installed even at the seabed since the steel slag can be constructed only by laying it with equipment such as a hopper.

It is preferable for the foundation caisson 40 to be manufactured by pre-casting in the ground, then lifting and transporting the foundation caisson 40 on the upper surface of the seismic isolation layer 100 for convenience of construction.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It is to be understood that both the technical idea and the technical spirit of the invention are included in the scope of the present invention.

10: Pile 100: Seismic isolation layer
40: Foundation caisson 41: Pier
50: slag layer 60: sand layer

Claims (9)

A method of constructing a foundation structure of a marine bridge using an earthquake-isolating layer,
A step of piling a plurality of piles 10 in the seabed ground;
A crushing step of crushing the upper part of the bottom sole so that the upper end of the pile 10 is exposed;
A sand layer forming step of forming a sand layer (60) on the upper surface of the sea floor to planarize;
Forming an earthquake-resistant layer (100) by laying steel-making slag on the upper surface of the sand layer (60);
A slab layer 50 is formed at both ends of the foundation caisson 40 so as to prevent the foundation caisson 40 supporting the lower end of the bridge pier 41 from sliding on the upper surface of the seismic isolation layer 100. [ Forming step; And
And placing the base caisson (40) on an upper surface of the seismic isolation layer (100)
The seismic isolation layer 100 supports the foundation caisson 40 and slides inside the seismic isolation layer 100 at the time of an earthquake so that an earthquake load of the seabed foundation is transmitted to the foundation caisson 40 , ≪ / RTI >
The internal friction angle of the steel making slag is set to a value of 35 ° to 42 ° so that the steel making slag can support the foundation caisson 40 at normal times,
Shear elastic modulus curve of the steelmaking slag is present between the Sand curve and the Graval curve so that sliding can be generated in the seismic isolation layer 100 at the time of an earthquake, Wherein the strain-damping ratio curve is in a region between the Sand curve and the Graval curve.
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