JPH11280087A - Ground solidifying construction method for damping and preventing liquefaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground solidifying construction method for damping and preventing liquefaction by means of a columnlike solidifying body capable of preventing the vibration of each solidifying body singly when the vibration is applied to the ground while a ratio of improved volume is reduced. SOLUTION: Each solidifying body 3 constituting a solidified ground 2 is connected with an adjacent solidifying body to make them continuous mutually. The connection of adjacent solidifying bodies is done by connecting at least a part thereof in the horizontal direction or vertical direction, bringing it into contact, and connecting it using a connection member. Consequently, the solidifying body is not vibrated singly, the rigidity thereof as the solidifying ground is increased, and the effects of damping for the vibration of the ground and prevention of liquefaction are increased. Moreover, an increase of ground support force and the prevention of unequal sinking become possible because an upper load is received by the whole solidifying ground. Furthermore, this construction is done while a ratio of improved volume is reduced so that cost can be reduced and construction term can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the propagation of vibrations to the surrounding ground surface such as a foundation structure or a railway structure on which a press machine or the like is installed, and a building installed on the foundation structure due to the propagation of vibrations. The present invention relates to a construction method for suppressing vibration of a structure such as the like and preventing liquefaction of the ground.

[0002]

2. Description of the Related Art In recent years, vibrations around a structure have frequently occurred due to mechanical vibrations and traffic vibrations, and measures to prevent the vibrations have been strongly desired. Especially in the case of pile foundations on soft ground, the vibration is propagated into the soft layer, and the influence on the surrounding ground surface is large, and predominant vibration of the surface ground may be induced. In addition, soft ground may be liquefied by earthquakes or other vibrations, causing serious damage to structures, and measures to prevent liquefaction are also required.

One method of preventing vibration disturbances is to provide a trench around a substructure that generates vibration. However, in this method, it is practically impossible to maintain a complete trench, so it is necessary to install soil retaining and supporting members. There is a disadvantage that it cannot be done.

[0004] There is also a method of installing a rigid underground vertical wall around a substructure that generates vibration. However, this method also has drawbacks such as the need for countermeasures against underground objects such as water pipes and the increase in cost.

The applicant of the present invention has previously filed a patent application entitled "Vibration Suppression Method Using Buried Flat Blocks" in order to solve the above-mentioned drawbacks of the conventional method (Japanese Patent Laid-Open No. 7-382).
9). The feature is that "a flat plate block having higher rigidity than the surrounding ground is provided directly under the substructure that emits or receives vibration or under the periphery of the substructure." From the analysis results and the test results, it was found that the flat plate block had a higher damping effect than the vertical wall.

However, in the above method, when the high-pressure injection stirring method is used, the upper part is disturbed by the injection pressure due to little soil cover, and when the mechanical stirring method is used, the upper part is also disturbed because stirring is performed from the ground surface. In any case, the overburden is disturbed. As a result, there has been a problem that land subsidence has occurred, and it has been difficult to secure trafficability, resulting in poor workability.

When only one flat block is installed,
In particular, when the soft layer is deep, there is little effect of suppressing the vibration with respect to the lower layer portion, that is, the vibration of the lower layer portion becomes large, and liquefaction may occur.

In order to solve the above-mentioned drawbacks, the present applicant has filed a patent application entitled "Method of ground consolidation for damping and preventing liquefaction" (Japanese Patent Application No. Hei 8-74281). The present invention provides a method of forming a consolidated ground having a higher strength than the surrounding ground by a ground consolidation method below or around a substructure that emits or receives vibration, and forms an upper layer of the consolidated ground. The overburden is improved with lower strength than the consolidated ground. "

According to this consolidation method, it is possible to prevent the ground surface settlement and secure the trafficability without impairing the vibration damping effect by improving the strength of the overburden, thereby reducing the cost,
The construction period was shortened.

[0010] However, in the above-mentioned consolidation method, the improved volume ratio is made as small as possible, and the respective consolidated bodies constituting the consolidated ground, for example, the columnar consolidated bodies are formed at intervals without being in contact with each other. When vibration is applied to the ground, each columnar consolidated body vibrates independently. For this reason, the cost is high, but the vibration damping effect is inferior to that of a completely continuous flat plate block with an improvement rate of 100%, and the ground support force is weak, and there is a risk that uneven settlement may occur.

[0011]

An object of the present invention is to prevent each columnar compact from vibrating alone when the ground is vibrated while the improved volume ratio is kept small. In addition, an object of the present invention is to increase the ground support force and prevent uneven settlement of structures and ground.

[0012]

The present invention has the following features. That is, a ground consolidation that forms a consolidated ground with higher strength than the surrounding ground in the ground below the substructure that emits or receives vibration, or in the ground around the substructure, or inside the substructure. In the consolidation method, the individual columnar consolidated bodies constituting the consolidated ground are connected to adjacent consolidated bodies and are continuous with each other.

First, the consolidated ground can be formed by ground improvement by a mechanical stirring method, or can also be formed by a cement-based mixed ground improvement high-pressure injection stirring method or a chemical liquid injection method. The term “high strength” means that the consolidation strength is 10 kgf / cm ² or more, and the shear wave velocity is 3 to 5 times or more that of the surrounding ground. The low strength means that the consolidation strength is 10 kgf / cm ² or less, which is almost the same as the surrounding ground strength.

The columnar consolidated body constituting the consolidated ground may be formed inclined or vertical depending on the properties of the target ground. As a method for connecting adjacent consolidated bodies, there is a method in which at least a part of the consolidated bodies is connected, abutted, or connected by a connecting member that is another member. Coupling means that portions of the consolidated body overlap with each other and become integral.

The inclined compacts are joined or abutted at the upper end and / or lower end of adjacent compacts to be continuous with each other. When connecting the consolidated body with a connecting member such as a concrete slab or a section steel, a connecting member is provided on the upper end surface of the consolidated body for easy installation, and joints such as reinforcing bars and steel bars embedded in the consolidated body are provided. The connecting member is connected and fixed.

[0016]

1 to 3 show a substructure 1 according to the present invention.
An example in which the solidified ground 2 is formed below the ground is shown. In this case, four columnar consolidated bodies 3 constituting the consolidated ground 2
As a set, the upper end (shown by a solid line in FIG. 3) is connected and inclined, and the lower end (shown by an imaginary line in FIG. 3) is located at each vertex of the square. The upper end of each pair is also located at the top of the square,
The lower ends of the adjacent consolidated bodies 3 are also connected to each other. Accordingly, the upper ends and the lower ends of the respective consolidated bodies 3 are connected to each other in the horizontal direction. The upper end of each consolidated body 3 may be located at the vertex of the honeycomb shape.

If the consolidated ground 2 has a rectangular shape out of a large number of sets of the consolidated bodies 3, for example, the set located at the top is extended downward and fixed to the base layer 4. The vibration suppression effect is higher, and the ground support force can be increased to prevent land subsidence. 5 is an earth covering part.

FIG. 4 shows a configuration in which the consolidated bodies 3 provided in the vertical direction are arranged in a honeycomb shape, and adjacent consolidated bodies 3 abut each other. A part of the consolidated body 3 extends downward and is fixed to a base layer (not shown).

FIGS. 5 and 6 show an example in which a set of two consolidated bodies 3 is formed in a V-shape and the lower ends thereof are joined. in this case,
A combination in which a set spacing is provided between a set of consolidated bodies 3 and a set of laterally adjacent consolidated bodies is defined as one row, and a plurality of rows arranged in the vertical direction are shifted horizontally by one row at a time. , Make adjacent rows abut. In the illustrated example, the consolidated ground 2 is constituted by arranging a plurality of stages in the vertical direction, with three lines of A, B, and C being one stage.

According to the above configuration, the contact portions of the consolidated bodies 3 arranged in the vertical direction can be regarded as consolidated bodies arranged on one horizontal plane, so that the vibration suppressing effect is enhanced. In addition, for example, vibrations obliquely incident from below, such as vibrations emitted from the lower end of a pile foundation (not shown), are more effectively suppressed.

FIG. 7 and FIG. 8 show that a joint 6 of a reinforcing bar is buried at the upper end of a columnar consolidated body 3 formed at equal intervals in the vertical direction to form a consolidated ground 2, 2 shows an example in which a concrete slab is cast as the connecting member 7. Also in this case, a part of the consolidated body 3 extends downward and is fixed to the base layer 4. Instead, a sectional steel, for example, a grooved steel, is assembled into the connecting member 7 in a cross-girder shape, and the angle steel and the grooved steel of the joint 6 embedded in the upper end of each consolidated body 3 are connected and fixed by bolts and nuts. Can also.

FIGS. 9 and 10 show a case where the substructure 1 is an embankment on which a track or the like is installed. In order to form the consolidated ground 2, the columnar consolidated body 3 is inclined down at an angle of 10 ° from the left and right side surfaces of the embankment, and the adjacent consolidated bodies 3 are brought into contact.
At the upper end of the consolidated body 3, a consolidated body formed by angle iron and groove steel embedded in the consolidated body 3 is connected, and the embedded body is buried and a finishing concrete 8 is cast. Note that the consolidated body 3 may be provided vertically.

An experimental example showing the vibration damping effect of the present invention will be described. In the experimental site, buried soil is disposed in a range of 0.7 to 0.8 m below the ground surface, and soft cohesive soil with an N value of 0 is distributed below the ground.
Gravel with an N value of 50 or more is present from around -12.0 m. Then, as shown in FIG. 1 to FIG.
A consolidated ground 2 having a height of 1.5 m, a length of 5.60 m and a width of 4.40 m is formed by a mechanical stirring method. Also, at a position 50 m away from the consolidated ground 2, a height of GL-1.0 m and a height of 1.
A non-continuous consolidation ground having a length of 50 m, a length of 5.60 m and a width of 4.40 m is formed by 18 columnar consolidated bodies (by a mechanical stirring method) having a diameter of 0.80 m.

The vibration is generated by a hinged arm (approximately 7
(0 cm), a shock was applied by a weight (approximately 40 kg) attached to the tip, and a servo type speedometer was used. The measurement of wave propagation was performed when the footing installed just above the center of the consolidation ground 2 and the control consolidation ground was vibrated, and when the midpoint between both consolidation grounds was vibrated. The velocity response of the ground surface directly above the ground was measured.

FIGS. 11 and 12 show the results of vibration suppression. FIG.
1 shows a vertical response result immediately above both consolidated grounds by vertical excitation directly above both consolidated grounds, and FIG. 12 shows a vertical response result immediately above both consolidated grounds by midpoint vertical excitation of both consolidated grounds. In both figures, the vertical axis represents the Fourier spectrum ratio (the Fourier spectrum after the consolidated ground was formed / the Fourier spectrum before the consolidated ground was formed), and the horizontal axis represents the frequency (Hz). In the figure, a shows the measurement results directly above the consolidated ground 2 of the present invention, and b shows the measurement results directly above the consolidated ground, respectively. From both figures, the vibration damping effect of the consolidated ground 2 of the present invention is clear at a frequency of 20 Hz or less at which a person easily feels vibration.

According to the present invention, by forming the consolidated ground according to the present invention directly below and in contact with a foundation structure without providing an overburden, an increase in the ground support force for the foundation structure and uneven settlement can be achieved. Can also be used to control

[0027]

According to the present invention, since the improvement in the volume ratio is performed with a small amount, the cost and the construction period can be reduced, and the rigidity of the consolidated ground can be increased.
In addition, the effect of preventing ground liquefaction is enhanced.

By connecting the consolidated bodies, the upper load is applied to the entire consolidated ground, thereby dispersing the load and preventing an increase in ground support force and uneven settlement.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an example in which a set of four consolidated bodies is connected.

FIG. 2 is a perspective view of FIG.

FIG. 3 is a plan view of a main part of FIG. 1;

FIG. 4 is a perspective view in which consolidated bodies provided in a vertical direction are arranged in a honeycomb shape.

FIG. 5 is a plan view of an example in which two consolidated bodies are connected in a V-shape.

FIG. 6 is a side view of FIG. 5;

FIG. 7 is a side view of an example in which solidified bodies provided in the vertical direction are connected by a connecting member.

FIG. 8 is a plan view of FIG. 7;

FIG. 9 is a side view when the consolidated ground is embankment.

FIG. 10 is a plan view of FIG. 9;

FIG. 11 is a diagram showing the relationship between the Fourier spectrum ratio and the vibration frequency immediately above both the consolidated grounds of the consolidated ground and the comparative consolidated ground, respectively, obtained by vertical excitation above the ground.

FIG. 12 is a graph showing the relationship between the frequency and the Fourier spectrum ratio immediately above the consolidated ground due to vertical excitation at the midpoint between the consolidated ground of the present invention and the control consolidated ground.

[Explanation of symbols]

 Reference Signs List 1 foundation structure 2 consolidated ground 3 consolidated body 7 connecting member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Ryuichiro Naruse, 136-1, Sozume, Okayama, Okayama Prefecture (72) Mitsunori Hashimoto

Claims (6)

[Claims] 1. A consolidated ground having a higher strength than the surrounding ground is formed in the ground below a substructure that emits or receives vibration, in the ground around the substructure, or inside the substructure. In the method of soil consolidation, the individual columnar consolidated bodies constituting the consolidated ground are connected to adjacent consolidated bodies and are continuous with each other. For ground consolidation. 2. The method of consolidating ground for vibration suppression and liquefaction prevention according to claim 1, wherein at least a part of adjacent consolidated bodies is joined or abutted in a horizontal direction. 3. The ground consolidation method for damping and preventing liquefaction according to claim 1, wherein at least a part of the adjacent consolidated bodies is joined or abutted in a vertical direction. 4. The method of consolidating ground for vibration suppression and liquefaction prevention according to claim 1, wherein a part of the consolidated body extends downward and is fixed to the base layer. 5. The ground consolidation method for vibration suppression and liquefaction prevention according to claim 1, wherein adjacent consolidated bodies are connected by a connecting member. 6. The method of consolidating ground for vibration suppression and liquefaction prevention according to claim 1, wherein the consolidated ground is in contact with at least a part of the substructure.