JPH05255941A - Liquefaction countermeasure construction method for buried structure - Google Patents

Abstract

PURPOSE:To suppress the rise of the pore water pressure around and below a buried structure, prevent liquefaction, and prevent the floating of the buried structure at the time of an earthquake. CONSTITUTION:Liquefaction suppressing sheet piles 2 having the draining function for scattering the excess pore water pressure generated in the ground at the time of an earthquake are driven on both sides of an underground multi- purpose duct 1 provided as a buried structure. Drainage channels made of drainage materials 8 such as a water-permeable resin material are provided between the vicinities of both side lower ends of the underground multi-purpose duct 1 and the liquefaction suppressing sheet piles 2. The upper ends of the liquefaction suppressing sheet piles 2 are located above the underground water level, and drainage layers made of crushed stone mats 5 are provided to surround the upper ends of the liquefaction suppressing sheet piles 2. Air vent pipes 9 are provided on the crushed stone mats 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, when burying lifelines such as power lines, gas pipes, and water pipes underground, has a large sectional width for burying them all together, such as a joint groove, or a roadway. Liquefaction countermeasure method for large-scale underground buried structures or semi-underground buried structures.

[0002]

2. Description of the Related Art As a liquefaction suppressing means for a ground that may be liquefied (hereinafter, simply called liquefied ground),
The ground compaction method and the crushed stone drain method, which have been widely used from the past (Japanese Unexamined Patent Publication No. 56-100919, Shokai 56)
No. 116434), and is applied to the ground where liquefaction is expected to occur. Further, a pressure-resistant resin pipe provided with a filter on the peripheral surface of the pipe has been conventionally used for the purpose of collecting and draining pore water in the ground and as a countermeasure against liquefaction. Also, in recent years, for the purpose of draining excess pore water in the ground in the event of an earthquake, etc., a large number of holes are drilled in piles made of steel pipes, etc., and a water-permeable filter is installed in the holes to prevent the ingress of sediment. Hollow perforated piles (see Japanese Laid-Open Patent Publication No. 61-146910) and porous concrete piles (Japanese Laid-Open Publication No. 61-837), which are expected to have strength and rigidity in addition to the drainage effect.
No. 11), etc. have been developed. In addition, a steel sheet pile and a vertical pipe for drainage are attached (Japanese Patent Laid-Open No. 62-1463).
(See Japanese Patent Publication No. 15).

By the way, for buried structures such as common grooves,
The liquefaction countermeasures that have been studied or used conventionally include the following.

(1) Sheet Pile Enclosure Method As shown in FIG. 4, by enclosing the side surface of the common groove 1 with the sheet pile 31, it is possible to prevent excess pore water pressure rising outside of the common groove 1 from being transmitted to the bottom surface of the common groove 1 when an earthquake occurs. This is a system that has the effect of suppressing the liquefaction by suppressing the generation of lifting pressure and restraining the ground 7 in the sheet pile enclosure with the sheet pile 31. Therefore, it is effective as a countermeasure against liquefaction when the sectional width of the common groove 1 is small.

(2) Pile support method As shown in FIG. 5, the weight of the common groove 1 and the overlaid load on the common groove 2 are supported by the pile 32, and the pile 32 is supported against the lifting pressure generated during ground liquefaction. It is a method to counter with a pull-out resistance.

(3) Ground improvement method The ground around the common groove is improved by various ground improvement methods.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 63-107610, a group of crushed stone drain piles is intermittently laid along the longitudinal direction of the pipeline around the pipeline buried in the liquefied ground. A countermeasure method is disclosed.

[0008] A study on the effect of liquefaction countermeasure effect on the width of the Horiki road when crushed stone drain is applied to the Horiki road (Taniguchi et al .; Analysis on gravel drain method as a liquefaction measure for the Horiki road, 22nd Soil Engineering Research Presentation (Niigata), June 1987), and a study on the effect of preventing the uplifting of the Horiwari road during liquefaction by the deep mixing method (Koga, Furuseki et al .; Liquid of the Horiwari road by the deep mixing method) Model vibration test (part 2) -Consideration on dynamic external force-The 23rd Geotechnical Research Conference (Miyazaki), June 1988) has been reported.

(4) Combined method A method that combines the sheet pile enclosure method of (1) and the ground improvement method of (3), or a method that uses the pile support method of (2) and the ground improvement method of (3), etc. is there.

(5) Liquefaction-preventing sheet pile enclosing method As shown in FIG. 6, a liquefaction-preventing sheet pile is used for the sheet pile enclosing method sheet piles to suppress excessive pore water pressure in the ground around the buried structure and ensure floating prevention. System (Japanese Patent Laid-Open No. 3-2758)
(See Japanese Patent Publication No. 13). That is, in constructing the common groove 1, the liquefaction-preventing sheet pile 2 is placed as the earth retaining sheet pile, and the sheet pile 2
By laying a crushed stone mat 5 ', etc. that continues to the external drainage channel at the upper position, the underground water is crushed by the crushed stone (below the common groove 1) against an increase in excess pore water pressure of the ground 7 on the lower surface of the common groove 1. (Kuriseki) 3, Liquefaction-preventing sheet pile 2, and crushed stone mat 5'to drain to the outside drainage channel to suppress the rise of excess pore water pressure on the lower surface of the joint groove 1 and prevent the joint groove 1 from rising. You can

[0011]

The above-mentioned conventional countermeasures against liquefaction of buried structures have the following problems.

(1) Sheet Pile Enclosure Method Even if the sheet pile is simply enclosed, the dead weight of the buried structure such as a common groove and the load thereon, and the weight of the backfill soil between the sheet pile and the buried structure cause the buried structure. It acts as an overload on the ground on the bottom surface (inside the sheet pile enclosure). Therefore, when the cross-sectional width of the buried structure is large, the ground restraint effect by the sheet pile does not work effectively during an earthquake, and the ground under the buried structure is liquefied,
Moreover, a large excess pore water pressure is generated between the buried structure and the sheet pile (immediately below the backfill soil), and the lift force on the structure becomes larger than the sum of its own weight and the top load, so that it is impossible to prevent the floating.

As shown in FIG. 4, even when the sheet piles are connected to each other on the upper surface of the buried structure, pulling-out resistance is required at the portion where the sheet piles are deeper than the liquefaction layer, and the length of the sheet pile may be long. ..

Furthermore, the surface of the sheet pile and the surface of the embedded structure (mainly the side surface) are likely to form streamlines, and there is a risk that sand is blown on the ground directly above the side surface of the sheet pile and the embedded structure.

(2) Pile support method It is difficult to avoid transmission of excess pore water pressure from the liquefied ground around the buried structure to the lower ground.

Since this is a method that corresponds to the pull-out resistance of the piles, as the scale of the buried structure such as the joint groove increases,
The number of piles increases.

Further, the side surface of the buried structure and the side surface of the pile easily form streamlines, and sand is easily generated from the periphery.

(3) Ground improvement method As the scale of the buried structure increases, the improvement area increases and the construction period becomes longer than the above two methods.

Further, for example, in the liquefied ground that causes horizontal movement as a whole, in the case of the sheet pile enclosing method and the pile supporting method, the shear surface is generated on the lower surface of the buried structure due to the strength and rigidity of the members. It can be prevented, but ground improvement does not guarantee this point. In other words, liquefaction is suppressed in the improved part in order to improve the ground around the buried structure, but if excess pore water pressure is transmitted to the bottom surface of the buried structure such as a common groove for some reason, the working lift will be improved. There is a risk that the embedded structure will float above the total weight including the above. In the crushed stone drain, which is considered to be one of the ground improvement methods, the above phenomenon is unlikely to occur because the drainage effect can be expected, but there is still a possibility.

(4) Combination method of (1) or (2) and (3) For example, there are cases where ground improvement is performed by injecting a chemical solution to the lower surface of the common groove in the sheet pile enclosure, but the construction cost is high. Get higher

(5) Liquefaction-preventing sheet pile enclosing method It is considered that lifting can be almost completely prevented. However, the method of FIG. 6 is possible when the liquefaction-preventing sheet pile is used as a self-supporting earth retaining sheet pile, but when the excavation surface is deep, it takes a lot of time to remove the supports and the like.

As for the crushed stone mat for drainage, the construction cost is high when the drainage channel as an external drainage path is distant, and since it is below the water table, the resistance to running water increases and liquefaction is suppressed. The drainage effect of the sheet pile may be reduced.

The present invention is intended to solve the above problems in the prior art. In other words, when installing underground or semi-underground buried structures such as large-scale public ditches and trench roads in the liquefied ground, increase the excessive pore water pressure in the surrounding ground is suppressed and the safety of the buried structures against earthquakes is improved. At the same time, the purpose is to prevent sand and liquefaction of the ground around the structure, and to improve the workability and economy of these buried structures.

[0024]

[Means for Solving the Problems] The construction method for liquefaction of a buried structure according to the present invention is applied to both sides of a buried structure constructed underground or semi-underground such as a common ditch or a trench road, when an earthquake occurs. By installing a liquefaction prevention sheet pile of a required length that has a drainage function to dissipate excess pore water pressure generated in the ground around the object and the bottom surface, and draining underground water, It suppresses the rise in pore water pressure, suppresses liquefaction, and prevents the embedded structure from rising.

The liquefaction-preventing sheet pile is installed at a predetermined distance from the side surface of the buried structure so as not to hinder the construction or the removal of the supporting works. Install drainage material such as water-permeable resin material between
By forming a drainage channel connecting these, the effect of dissipating excess pore water pressure is locally improved.

Regarding the upper end of the liquefaction prevention sheet pile,
Instead of draining underground water to an external drainage channel through a crushed stone mat below the water table, place the upper end of the liquefaction prevention sheet pile above the water table and use drainage material such as a crushed stone mat to surround it. Installed and use this drainage material as drainage layer. That is, a drainage layer above the groundwater table is formed directly above the liquefaction prevention sheet pile, and underground water discharged from the upper end of the liquefaction prevention sheet pile due to excessive pore water pressure during an earthquake is drained to this drainage layer.

The drainage material forming the drainage channel connecting the vicinity of the lower end of the side surface of the buried structure and the liquefaction-preventing sheet pile and the drainage material forming the drainage layer at the upper end of the liquefaction-preventing sheet pile are not necessarily resin materials or crushed stone mats. There is no limitation, and any substance having water permeability or a substance forming a water permeable space in the ground may be used.

[0028]

[Operation] Operation by installing liquefaction prevention sheet piles on both sides of the buried structure Disperse excess pore water pressure in the ground around the liquefaction prevention sheet piles during an earthquake and prevent ground constituent particles from wrapping around the bottom surface of the buried structure To do.

Action by forming a drainage channel between the lower ends of both sides of the buried structure and the liquefaction-preventing sheet pile When the buried structure is wide, it is difficult to avoid liquefaction of the ground immediately below the central portion. The excess pore water pressure in the vicinity of both ends of the bottom surface of the buried structure can be set to be equal to or lower than the vicinity of the central portion. That is, the lifting pressure is set to be equal to or lower than the top loading pressure to prevent the embedded structure from rising.

Effect of forming a drainage layer above the water table so that the upper end of the liquefaction prevention sheet pile is located above the water table and surrounding the upper end of the liquefaction prevention sheet pile Excessive gap in the ground caused by an earthquake With increasing water pressure,
Underground water is drained from the upper part of the liquefaction prevention sheet pile (the upper part of the drainage member in the case where the perforated drainage member is attached to the sheet pile), but this water treatment involves crushed stone, etc. to the ground or drainage ditch or crushed stone. Although alternative methods of connecting drainage materials have been considered, these methods increase drainage resistance.

On the other hand, a drainage layer is formed above the groundwater table, and an air vent is provided as necessary to connect the drainage layer and the liquefaction prevention sheet pile to store the drainage in the drainage layer. It is possible to shorten the drainage route. Therefore, the drainage resistance can be reduced by shortening the drainage route, and the construction area can be reduced, so that the material and the construction cost can be reduced.

[0032]

EXAMPLES Next, the illustrated examples will be described.

FIG. 1 shows an embodiment of the present invention.
In constructing the joint groove 1 with cast-in-place concrete,
After using the liquefaction prevention sheet pile 2 that has a drainage function as a retaining sheet pile, shape the bottom of the joint groove 1 with crushed stones (kuriishi) 3, construct waste concrete on it, and construct the joint groove 1,
The upper part of the sheet pile 2 is cut above the water table, and a crushed stone mat 5 as a drainage layer is constructed so as to surround the upper end of the sheet pile 2 and backfilled. In the figure, 6 indicates the liquefied ground around the common groove 1, and 7 indicates the liquefied ground on the lower surface of the common groove 1.

From the vicinity of the lower end of the side surface of the common groove 1 to the liquefaction-preventing sheet pile 2, a drainage material 8 such as a water-permeable resin material is formed to a thickness of 30.
By installing the drainage channel toward the liquefaction prevention sheet pile 2 at about 50 cm, the effect of dissipating excess pore water pressure at the time of an earthquake can be localized (the lower surface position of the common groove 1, especially large lifting pressure is a problem. Be improved near the bottom edges of both sides).

Further, in the crushed stone mat 5 as a drainage layer provided on the upper end of the liquefaction-preventing sheet pile 2, a pipe 9 for bleeding air is buried at a pitch corresponding to the drainage amount to the ground or an appropriate place.

When the liquefied grounds 6 and 7 are liquefied by the earthquake, the pore water pressure in the ground rises, but regarding the excess pore water pressure of the ground 7 on the lower surface of the common groove 1, the underground water is The rise is suppressed by being discharged to the crushed stone mat 5 above the water table through the crushed stone 3, the drainage material 8 and the liquefaction prevention sheet pile 2. Therefore, it is possible to reduce the upward lift force caused by the liquefaction, as compared with the case of the conventional common groove alone installation or the case of the ordinary sheet pile enclosure method.

If the drainage material 8 is made of a hard fibrous water-permeable material, the drainage material 8 absorbs the displacement, so that the upper loading pressure between the liquefaction prevention sheet pile 2 and the common groove 1 is transmitted to the lower ground. The upward lifting pressure can be almost completely eliminated in combination with the drainage effect.

Further, since the crushed stone mat 5 at the upper end of the liquefaction prevention sheet pile 2 forms a drainage layer, the drainage route is shorter than that of the conventional sheet pile enclosing method using the liquefaction prevention sheet pile, and the liquefaction prevention sheet pile is used. The drainage effect can be expected sufficiently.

In terms of construction, it is almost the same as the ordinary sheet pile enclosing method, and in some cases, no tie rod or the like is required, which can be further simplified.

2 and 3 show examples of the liquefaction-preventing sheet pile used in the present invention.

The liquefaction-preventing sheet pile 2a shown in FIG. 2 has joints 1 at both ends.
1. A plate-shaped sheet pile having 1 is provided with a channel-shaped drain member 12 in a predetermined section along the longitudinal direction. The drain member 12 has a large number of openings 13 and ground soil from the openings 13. A filter 14 is provided to prevent the entry of

The liquefaction-preventing sheet pile 2b in FIG. 3 is a male-female joint 1
A channel-shaped drain member 12 is provided on the outer surface of a steel pipe sheet pile having 1a and 11b, and an opening 13 and a filter 14 are provided in the drain member 12 as in the case of FIG.

The above are examples of the liquefaction-preventing sheet piles. The liquefaction-preventing sheet pile used in the present invention has a sheet pile function such as soil retention and an excess pore water pressure generated in the ground during an earthquake. The form is not limited as long as it has a drainage function for scattering.

[0044]

[Effects of the Invention] By using a liquefaction suppressing sheet pile having a drainage function for dissipating excess pore water pressure as a sheet pile for constructing a buried structure, both sides of the buried structure and the bottom surface thereof are grounded during an earthquake. Liquefaction is suppressed, and it is possible to prevent the embedded structure from rising and the particles constituting the ground from wrapping around the lower surface of the embedded structure.

The liquefaction-preventing sheet pile is provided at a predetermined distance from the side surface of the buried structure so that there is no hindrance to the construction or removal of the supporting work, and the liquefaction-preventing sheet pile is located between the lower ends of both sides of the buried structure and the liquefaction-preventing sheet pile. By forming a drainage channel made of a water-permeable resin material, etc., the effect of dissipating excess pore water pressure is locally improved, and the lifting pressure in the vicinity is suppressed to prevent the floating structure from rising. It can be fully demonstrated.

By forming a drainage layer of drainage material such as a crushed stone mat above the groundwater surface and connecting the drainage layer with a liquefaction prevention sheet pile, drainage can be stored in the drainage layer and the drainage route can be shortened. it can. In addition to above the water table, it is possible to reduce drainage resistance by shortening the drainage route. Further, since the construction area of the drainage layer is small, the material and construction cost are reduced as compared with the conventional method of connecting to the external drainage channel.

In addition to the horizontal resistance (strength and rigidity) of the sheet pile itself, the reduction of the strength of the surrounding ground is suppressed, so that the horizontal resistance of the ground can be expected and the deformation (particularly lateral fluid movement).
The soundness of the buried structure and the surrounding ground can be maintained even in the possible liquefied ground.

The construction is simplified to the same level as or less than the conventional ordinary sheet pile enclosure method.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of a liquefaction-preventing sheet pile used in the present invention.

FIG. 3 is a perspective view showing another example of a liquefaction suppressing sheet pile used in the present invention.

FIG. 4 is a vertical sectional view showing a conventional example.

FIG. 5 is a vertical cross-sectional view showing another conventional example.

FIG. 6 is a vertical sectional view showing still another conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Common groove, 2 ... Liquefaction prevention sheet pile, 3 ... Crushed stone, 4 ... Tie rod, 5 ... Crushed stone mat, 6,7 ... Liquefied ground, 8 ... Drainage material, 9 ... Air vent pipe

Continued Front Page (72) Inventor Yukio Saimura Sumitomo Metal Industries, Ltd. 1-3-3 Otemachi, Chiyoda-ku, Tokyo

Claims (2)

[Claims] 1. A liquefaction-preventing sheet pile of a required length having a drainage function for dissipating an excessive pore water pressure generated in the ground at the time of an earthquake is provided on both sides of a buried structure constructed underground or semi-underground. A drainage material is installed between the two sides of the buried structure at a predetermined interval, and a drainage material is provided between the lower ends of both sides of the buried structure and the liquefaction prevention sheet pile. Liquefaction countermeasure construction method for buried structures. 2. A drainage material that forms a drainage layer above the water table is installed so that the upper end of the liquefaction prevention sheet pile is located above the water table, and the upper edge of the liquefaction sheet sheet is surrounded by the drainage material. The liquefaction countermeasure method for a buried structure according to claim 1, wherein underground water drained from the liquefaction-preventing sheet pile is discharged to the drainage layer due to excessive pore water pressure at that time.