JPH0932004A - Structure for coping with liquefaction of ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a construction cost by providing oblique structure composed of units having a V-like cross-sectional shape, in the liquefiable ground. SOLUTION: Oblique structure 5 having a V-like cross-sectional shape is formed on the liquefiable ground with the use of a material having a modulus of deformation and a strength which are larger than those of the liquefiable ground, such as improved earth of the earth ground using a cement group solidifier. Further, Vertical structures 7 made of the same material as the oblique structure are formed on both sides of the oblique structure 7. A skin layer solidified board 7 made of the same material as that of the oblique structure 5 is laid above the latter so as to build a one unit body structure. A plurality of such unit body structures are used for a wide range countermeasure for the liquefaction. Accordingly, the horizontal shearing force exerted to the ground 6 surrounded by the structures 5, 7 and the solidified board 8 can be reduced, thereby it is possible to enhance the anti-liquefying effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground liquefaction countermeasure structure.

[0002]

2. Description of the Related Art In Japan, which is an earthquake-prone country, structural damage caused by liquefaction has been historically heavily affected by the liquefaction of sandy soil-based grounds due to the occurrence of earthquakes. Prevention of damage is one of the important issues in Japan's seismic engineering.

Even during the Hyogo-ken Nanbu Earthquake (January 1995), large-scale ground liquefaction occurs, especially in the reclaimed land in the port area, and the large-scale caisson quay, which is considered to be caused by liquefaction Great damage such as collapse and bridge girder collapse,
The importance of liquefaction countermeasure technology was recognized again.

The liquefaction countermeasure method is, depending on the function, a pore water pressure dissipation method, a drainage method such as gravel drain, a method of increasing density represented by sand compaction or a vibrating rod method, or suppression of shear deformation of underground walls. Many construction methods have been proposed to date, classified into construction methods, mixed treatment construction methods that solidify the ground, and the like.

Each of the construction methods is appropriately used in consideration of various conditions such as cost, restrictions on noise and ground displacement generated during construction, and construction workability.

[0006] The mixing treatment method for consolidating the ground is intended to solidify the entire ground so as not to generate liquefaction, which is economically relatively expensive but other methods. In comparison, it can cope with a large earthquake.

The applicant previously mentioned that one of the mixing processing methods is as follows:
As shown in FIG. 16, the solidified walls 2 in the vertical direction are constructed on the sand ground 1 at appropriate intervals, and the solidified bodies 3 in the diagonal direction are arranged in a streak pattern between the solidified walls 2 in the vertical direction. A liquefaction-suppressing ground for the above was proposed and filed as Japanese Patent Application No. 4-143250 (Japanese Patent Application Laid-Open No. 5-311638). In the figure, 4 is a ground improvement layer applied to the surface layer.

[0008]

According to the liquefaction-suppressing ground shown in FIG. 16, the vertical solidified wall body 2 is supported by the diagonal solidified body 3 and the binding force of the entire wall to the ground is restrained. Liquefaction can be completely prevented because the temperature is increased.

However, the obliquely solidified bodies 3 are considered to support the longitudinally solidified wall bodies 3 only as bracings arranged between the vertically solidified wall bodies 2 and therefore, in the figure. The X-shaped crossing arrangement as shown is adopted.

Such an obliquely solidified body 3 needs to have a large area, and even if it is formed by using a cement solidifying material, it is economically very expensive.

The object of the present invention is to solve the problems of the above-mentioned conventional examples, to expect a dramatic liquid resistance effect, and to provide a structure for countermeasures against liquefaction of the ground, which can be constructed with more partial improvement and less costly construction. To provide.

[0012]

In order to achieve the above object, the present invention firstly provides a liquefied ground with an oblique structure having a cross-sectional shape of one unit close to V. The gist is that the liquefaction of the ground is particularly suppressed. Secondly, an oblique structure close to V is combined with a vertical structure and a surface solidified plate.
The main idea is to construct each unit continuously.

According to the present invention as set forth in claim 1, a diagonal structure close to V is provided on the liquefied ground so that a part of the horizontal shearing force is shared by the diagonal structure. Liquefaction of the ground can be particularly suppressed, and liquefaction resistance performance can be enhanced. Moreover, unlike the conventional diagonally consolidating structure which is crossed in the X-shaped braces arranged between the longitudinal consolidating walls, the diagonal structure close to V is supposed to suppress the liquefaction inside. The minimum required.

Although only an oblique structure close to V may be used, according to the present invention as defined in claim 2, a more stable liquefaction resistance effect can be expected in addition to the above-mentioned action, and the invention as defined in claim 3 is expected. According to this, by constructing each unit continuously, it is possible to deal with a wide range of measures against liquefaction.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a side view showing an embodiment of a ground liquefaction countermeasure structure of the present invention.

According to the present invention, a diagonal structure 5 whose cross-sectional shape of one unit is close to V is provided on the liquefied ground, and the ground inside the V of the diagonal structure 5 is ground 6 in which liquefaction is particularly suppressed. did. α is a liquefiable ground, β is a non-liquefied ground, and the lower end of the diagonal structure 5 does not reach the non-liquefied ground β as shown in FIG. 5, and as shown in FIG. In some cases, this is determined from the scope of the target liquefaction countermeasures.

In the illustrated example, vertical structures 7 are provided on both sides of the oblique structure 5, and a surface layer solidifying plate 8 is provided on the upper side of the oblique structure 5.

The diagonal structure 5, the vertical structure 7, and the surface solidified plate 8 are all materials such as improved soil of the original ground using a cement-based solidifying material and having a larger deformation coefficient and strength than the liquefiable ground. Build with.

More specifically, the vertical structure 7
Is solidified by the in-situ ground agitation solidification method or is constructed by the underground wall, and the diagonal structure 5 is the in-situ solidification by the in-situ ground agitation solidification method or diagonal H
Use piles or steel pipe piles.

Further, the diagonal structure 5 is a case in which it is laid in a flat plate shape as shown in FIG. 2 and a case in which a columnar body is laid alternately in a continuous manner as shown in FIG. However, the interval is determined at a level where a predetermined liquefaction resistance effect can be obtained.

FIG. 4 shows a case where the unit shown in FIG. 1 is regarded as one unit and each unit is continuous, and is a case of a wide area liquefaction countermeasure.

Further, various variations are shown in FIG.
As shown in, the width V of the diagonal structure 5 is relatively wide,
Moreover, when there is no vertical structure, the width is wide as shown in FIG. 7, but when there is the vertical structure 7 as in FIG.
As shown in FIG. 8, there is a case where the vertical structure 7 is further arranged at the intersection of V.

Next, the operation of the ground liquefaction countermeasure structure of the present invention will be described. 10m thick deposited on the surface
As a countermeasure against the liquefaction of the liquefiable ground in Fig. 13, when only the vertical structure 7 is arranged in Fig. 13, Fig. 10 shows the form of Fig. 7, Fig. 11 shows the form of Fig. 8, and Fig. 12 shows The two-dimensional liquefaction analysis result when each structure is arranged in the form of FIG. 9 is shown.

In the analysis, the rigidity of the improved body and the physical property values of the ground are the same, and only the cross-sectional shape of the improved body (structure) is different. In addition, as an input wave, El Centro wave N at a depth of 30 m
A wave that extends the S component to a maximum acceleration of 200 gal is used, and a sufficiently strong wave is assumed.

FIGS. 10 to 13 show changes in the effective average stress of the ground at each point when the surrounding ground is sufficiently liquefied. In the figure, the slanted line portion (larger diagonal eyes indicate more liquefaction) indicates liquefaction, and the stippled portion (rougher stippling indicates more non-liquefaction) indicates non-liquefaction. Diagrams that can be found from these diagrams
In the case of only the vertical structure 7 in FIG. 13, the inside of the improvement body is liquefied, but in the other structures using the diagonal improvement body in FIGS. The results show that the liquefaction resistance is dramatically improved. This is because part of the horizontal shearing force is shared by the diagonal structure.

FIG. 14 further shows an application example. By properly installing the vertical improvement wall 9, the liquefaction resistance can be further enhanced. In the figure, 10 is a caisson quay, a quay such as a sheet pile quay, and 11 is its basic mound.
As described above, the present invention can be used as a liquefaction countermeasure structure for various civil engineering structures other than the case where the harbor structure is used as a liquefaction countermeasure.

[0027]

As described above, the ground liquefaction countermeasure structure of the present invention can be expected to have a drastic liquid resistance effect, and since it can be partially improved, it is economical and inexpensive construction. It is possible to suppress the decrease in the amount of social capital stock, which is an asset common to all people due to the earthquake.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing a first embodiment of a liquefaction countermeasure structure of the present invention.

FIG. 2 is a cross-sectional plan view showing a first embodiment of a liquefaction countermeasure structure of the present invention.

FIG. 3 is a cross-sectional plan view showing a second embodiment of the liquefaction countermeasure structure of the present invention.

FIG. 4 is a vertical cross-sectional side view showing a third embodiment of the liquefaction countermeasure structure of the present invention.

FIG. 5 is a vertical sectional side view showing a fourth embodiment of the liquefaction countermeasure structure of the present invention.

FIG. 6 is a vertical sectional side view showing a fifth embodiment of a liquefaction countermeasure structure of the present invention.

FIG. 7 is a vertical sectional side view showing a sixth embodiment of the liquefaction countermeasure structure of the present invention.

FIG. 8 is a vertical cross-sectional side view showing a seventh embodiment of the liquefaction countermeasure structure of the present invention.

FIG. 9 is a vertical cross-sectional side view showing an eighth embodiment of the liquefaction countermeasure structure of the present invention.

10 is an explanatory diagram showing a two-dimensional liquefaction analysis result when the structures are arranged in the form of FIG. 7.

FIG. 11 is an explanatory diagram showing a two-dimensional liquefaction analysis result when the structures are arranged in the form of FIG. 8.

FIG. 12 is an explanatory diagram showing a two-dimensional liquefaction analysis result when the structures are arranged in the form of FIG. 9.

FIG. 13 is an explanatory diagram showing a two-dimensional liquefaction analysis result when only vertical structures are arranged.

FIG. 14 is a perspective view showing an eighth embodiment of the liquefaction countermeasure structure of the present invention.

FIG. 15 is a side view when the liquefaction countermeasure structure of the present invention is used as a liquefaction countermeasure for a port structure.

FIG. 16 is a perspective view showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sand ground 2 ... Vertical solidified wall body 3 ... Diagonal solidified body 4 ... Ground improvement layer 5 ... Diagonal structure 6 ... Ground where liquefaction is particularly suppressed 7 ... Vertical structure 8 ... Surface solidified version 9… Vertical improvement wall 10… Quay 11… Basic mound

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Teruyoshi Yoshida, 19-1 Tobita, Chofu City, Tokyo Kashima Construction Co., Ltd.

Claims (3)

[Claims] 1. The cross-sectional shape of one unit is V on the liquefied ground.
A liquefaction countermeasure structure for the ground, characterized in that a diagonal structure close to the above is provided, and the liquefaction of the ground inside the V of the diagonal structure is particularly suppressed. 2. The ground liquefaction countermeasure structure according to claim 1, wherein an oblique structure close to V is combined with a vertical structure and a surface solidified plate. 3. The unit according to claim 1, wherein each unit is constructed continuously.
Alternatively, the ground liquefaction countermeasure structure according to claim 2.