JPH0645944B2 - Liquefaction countermeasure construction method for buried structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a large cross-sectional width for burying lifelines such as power transmission lines, gas pipes, water pipes, etc. all at once when they are buried underground. The present invention relates to a liquefaction countermeasure construction method for large-scale underground buried structures or semi-underground buried structures such as common ditches or horizon roads.

[Conventional technology]

As a means for suppressing liquefaction against a ground that may be liquefied (hereinafter, simply referred to as liquefied ground), a ground compaction method and a crushed stone drainage method that have been widely used in the past (Japanese Patent Application Laid-Open No. Sho
56-100919 and Japanese Utility Model Laid-Open No. 56-116434), 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 filter with water permeability is installed in the holes to prevent the ingress of sediment. , A hollow perforated pile that is expected to have strength and rigidity in addition to the drainage effect (JP-A-61
-146910), and porous concrete piles (see Japanese Patent Laid-Open No. 61-83711). In addition, a steel sheet pile with a vertical pipe for drainage attached (Japanese Patent Laid-Open No. 62-1
(See Japanese Patent No. 46315)).

By the way, there are the following liquefaction measures that have been conventionally studied or used for buried structures such as common grooves.

(1) Sheet pile enclosing method By enclosing the side surface of the joint groove 1 with the sheet pile 31 as shown in FIG. 7, it is possible to prevent excess pore water pressure rising outside of the joint groove 1 at the time of an earthquake from being transmitted to the bottom surface of the joint groove 1. This is a system that has the effect of suppressing the liquefaction by suppressing the generation of pressure and restraining the ground 5 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. 8, the pile 32 supports the self-weight of the common groove 1 and the overlaid load on the common groove 2, and the pull-out resistance of the pile 32 against the lifting pressure generated during ground liquefaction. It is a method to compete with.

(3) Ground improvement method Various ground improvement methods are used to improve the ground around the common ditch.

For example, Japanese Patent Laid-Open No. 63-107610 discloses a liquefaction countermeasure construction method in which a group of crushed stone drain piles is intermittently placed along the length of the pipeline around the pipeline buried in the liquefaction ground. It is disclosed.

Also, a study on the effect of liquefaction countermeasure effect by the width of the digging road when crushed stone drain is applied to the digging road (Taniguchi et al .; Analysis of gravel drain method as liquefaction countermeasure of the digging road, 22nd Geotechnical Research Presentation (Niigata), June 1987) and research on the effect of preventing the lift-up of the Horiwari road during liquefaction using the deep mixing method (Koga, Furuseki et al .; Liquefaction countermeasures for the Horiwari road using the deep mixing method) Model vibration experiment (Part 2) -Study on dynamic external force-The 23rd Geotechnical Engineering Research Presentation (Miyazaki), 63
(See June of the year).

(4) Combination method A method that uses the sheet pile enclosure method of (1) and the ground improvement method of (3) together, or a method that uses the pile support method of (2) and the ground improvement method of (3).

[Problems to be Solved by the Invention]

The above-mentioned conventional measures against liquefaction of the buried structure have the following problems.

(1) Sheet pile enclosing method Even if the sheet pile is simply enclosed, the self-weight of the buried structure such as the common groove and its load, and the weight of the backfill soil between the sheet pile and the buried structure cause the bottom surface of the buried structure (the sheet pile enclosure). Inside)
It acts as a pressure on the ground. Therefore, if the cross-sectional width of the buried structure is large, the ground restraint effect by the sheet pile will not work effectively during an earthquake, and the ground on the lower surface of the buried structure will be liquefied, and the lifting pressure will be greater than the sum of its own weight and the overlaid load. However, it cannot prevent rising.

As shown in FIG. 7, even when the sheet piles are connected to each other on the upper surface of the buried structure, pull-out resistance may be required at the portion where the sheet piles are deeper than the liquefaction layer, and the length of the rooting 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 possibility that sand is generated on the ground just 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 it is a method that corresponds to the pull-out resistance of piles, the number of piles will increase as the scale of the buried structure such as common grooves increases.

In addition, the side surface of the buried structure and the side surface of the pile easily form streamlines, and sand is easily generated from the surrounding area.

(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 strength and rigidity of the member can prevent the occurrence of a shear surface on the lower surface of the buried structure. However, it is not clear that the ground improvement will guarantee this point. That is, 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. 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 is a case where the ground is improved by injecting a chemical solution into the lower surface of the common groove in the sheet pile enclosure, but the construction cost becomes high.

The present invention aims to solve the above-mentioned problems in the prior art. In other words, when installing underground or semi-underground buried structures such as large-scale joint trenches and trench roads in the liquefied ground, it is possible to suppress the increase of excess pore water pressure in the surrounding ground and improve the safety of the buried structures against earthquakes. 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.

[Means for Solving the Problems]

The liquefaction countermeasure method of the buried structure described in each claim of the present application is a method for liquefaction of a buried structure, such as a common ditch or a trench road, on the bottom surface of the buried structure constructed in the ground or semi-underground And a liquefaction prevention pile with a required length that has a drainage function to dissipate excess pore water pressure generated in the ground on the lower surface and the ground, and the upper part of the liquefaction prevention pile and the ground subject to liquefaction A drainage route that connects the outside,
The groundwater is drained during an earthquake and the buried structure is supported by liquefaction prevention piles, and the rise of pore water pressure around and below the buried structure is suppressed to prevent liquefaction.

In the invention according to claim 1, with respect to the drainage path, a drainage material that rises from the upper portion of the liquefaction prevention pile along the side wall of the buried structure, and a crushed stone for drainage from the upper portion of the drainage material to the outside of the liquefaction countermeasure target ground It was decided that the mat would form part or all of the drainage route.

In the invention according to claim 2, regarding the drainage route, a pipe is provided from the upper part of the liquefaction prevention pile toward the inside of the buried structure, and a part or all of the drainage route is formed in the buried structure by this pipe. And

Further, in the invention according to claim 3, with respect to the drainage path,
Pipes are pierced from the upper part of the liquefaction prevention piles into the side wall of the buried structure, and further, a crushed stone mat for drainage is constructed from the upper part of this pipe to the outside of the ground subject to liquefaction countermeasures. It was decided to form part or all of the drainage route.

In addition, in the construction method according to claim 1 or 3, when the construction range of the drainage path of the portion connecting the upper part of the drainage material or pipe and the outside of the ground targeted for liquefaction is too wide with only the crushed stone mat for drainage, Alternatively, a culvert may be used together.

Further, such a drainage route may be a drainage route in which water is returned to the ground outside the liquefaction countermeasure target ground, or a drainage route to a river through a gutter or the like.

〔Example〕

 Next, the illustrated embodiment will be described.

5 and 6 show an example of the liquefaction prevention pile used in the present invention.

The liquefaction prevention pile 2a of FIG. 5 has a large number of openings 21 formed in a predetermined section of the steel pipe, that is, in the thickness direction of the liquefaction ground.
Filter 2 for preventing the intrusion of earth and sand into the opening 21
2 is provided so that the inside of the steel pipe serves as a drainage space.

The liquefaction prevention pile 2b of FIG. 6 is provided with a drainage member 23 in a predetermined longitudinal section of the outer surface of the steel pipe. The drainage member 23 has a large number of openings 24 and intrusion of soil from the ground through the openings 24. A filter 25 for preventing the above is provided.

The above is each an example of a liquefaction prevention pile. As the liquefaction prevention pile used in the present invention, the support function as a pile and the excessive pore water pressure generated in the ground during an earthquake are dissipated. As long as it has a drainage function for that purpose, its form does not matter.

FIG. 1 shows a joint groove 1 according to the invention described in each claim of the present application.
2 schematically shows the positional relationship between the common groove 1 and the liquefaction prevention pile 2 when applied to. In this figure, the drainage route from the liquefaction prevention pile 2 due to the increase in excess pore water pressure during an earthquake is omitted. In construction, liquefaction prevention pile 2 with drainage function after construction of a dome sheet pile (not shown)
And the bottom surface of the joint groove 1 is shaped with crushed stones 3
Construct joint groove 1 with cast-in-place concrete. Dome sheet pile will be removed after construction. The head of the liquefaction prevention pile 2 and the joint groove 1 are rigidly connected to each other, and the joint groove 1 and the load thereon are supported by the liquefaction prevention pile 2. In the figure, 4 indicates the liquefied ground around the common groove 1, and 5 indicates the liquefied ground on the lower surface of the common groove 1.

FIG. 2 shows a concrete drainage path of an embodiment corresponding to the invention described in claim 1 of the present application, and the drainage member 23 of the liquefaction prevention pile 2 (the inside of the steel pipe is used as a drainage space). In the form, the opening 21) near the pile head is provided up to the inside of the crushed stone 3, and the drainage material 6 made of resin or the like is raised from the upper surface along the side wall 1b (only one side is shown) of the common groove 1, It is connected to a blind underdrain 8 provided in a crushed stone mat 7 for drainage. By forming the drainage path by the drainage material 6 and the crushed stone mat 7 for drainage, it is possible to suppress the increase in pore water pressure during an earthquake by draining underground water.

Furthermore, in order to completely support the joint groove 1 and the load on it, the excess pore water pressure at the bottom surface of the joint groove 1 at the bottom surface of the joint groove 1 shows a value close to zero. The groove 1 is prevented from rising, and no sinking occurs.

The pitch of the liquefaction prevention piles 2 in the direction perpendicular to the paper surface is set so that the excess pore water pressure dissipation effect of the single liquefaction prevention piles 2 overlaps that of the adjacent liquefaction prevention piles 2 so that the common groove 1 It is possible to prevent the large excess pore water pressure generated in the outer liquefied ground 4 from being transmitted to the liquefied ground 5 on the lower surface of the common groove 1.

FIG. 3 shows a concrete drainage path of an embodiment corresponding to the invention described in claim 2 of the present application, in which the drainage member 23 of the liquefaction prevention pile 2 is extended to the bottom plate 1 a of the common groove 1. It is embedded and piped in the common groove 1 with a flexible resin pipe 9 or the like. This eliminates the need for drainage measures such as the crushed stone mat 7 for drainage on the upper surface of the common groove 1 in FIG. According to this method, it is difficult to prevent the formation of a water groove on the surface of the side wall 1b of the common groove 1, and there is a possibility that a sand blowing phenomenon may occur on the ground just above the side surface of the common groove 1 at the time of an earthquake, but the construction speed is extremely fast.

FIG. 4 shows a concrete drainage path of an embodiment corresponding to the invention described in claim 3 of the present application.
It shows a case where a part of the drainage path is provided in the side wall 1b of the common groove 1 in order to provide the drainage function to itself. In this example, the pipe 10 is provided in the side wall 1b of the common groove 1 to secure the drainage route from the liquefaction prevention pile 2, and the drainage crushed stone mat 7 and the same as in the case of FIG. A drainage measure is provided by a blind culvert 8. In addition, pipes 11 with a filter that communicate with the pipes 10 are also provided on the side surface of the common groove 1 at an appropriate pitch to prevent the liquefaction of the surrounding liquefied ground 4.

Also in the case of FIG. 3 and FIG. 4, the liquefaction prevention pile 2 sufficiently functions against the lifting pressure acting on the common groove 1 at the time of an earthquake, and the safety against floating is significantly improved.

Although the joint groove 1 in the above-mentioned embodiment is made of cast-in-place concrete, there is no problem even when the precast concrete joint groove is used, for example, mortar or concrete is used between the liquefaction prevention pile and the joint groove. A filling structure is sufficient. Further, these liquefaction measures are not limited to the common ditch, and can be similarly applied as the liquefaction measures for the Horikiri road.

Further, the invention described in each claim of the present application, the strength of the liquefaction prevention pile itself, when the liquefaction ground is inclined or when sand is generated, when the entire liquefaction ground is going to move to the side, The rigidity and the liquefaction prevention piles prevent the lowering of the surrounding ground strength to prevent lateral movement of the ground, and not only prevent the embedded structures such as joint grooves from rising, but also prevent ground deformation. It is extremely effective as a liquefaction measure in terms of deterrent.

[Effects of the Invention] By using a liquefaction prevention pile having a drainage function to dissipate excess pore water pressure as a support pile for a buried structure such as a common groove, the ground around the buried structure and the bottom surface during an earthquake can be used. Liquefaction is suppressed.

Due to the presence of the liquefaction prevention pile and the drainage path continuous to it, it is possible to solve the problem of the formation of water channels on the surface of the buried structure or the pile, and to suppress the generation of sand sand around the buried structure.

In addition to the strength and rigidity of the 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 buried structure even in the liquefied ground that can be greatly deformed (especially lateral fluid movement). And, the soundness of the ground around it can be maintained.

The liquefaction-preventing pile as a pile sufficiently functions even with respect to the lifting pressure generated on the lower surface of the buried structure due to the excessive pore water pressure, and the floating of the buried structure can be suppressed.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing the positional relationship between a common groove and a liquefaction suppressing pile when the invention described in each claim of the present application is applied to the common groove as an embedded structure, Figure ~
FIG. 4 is a vertical sectional view showing an example of a concrete drainage path in the invention described in each claim of the present application, FIG. 5 and FIG.
The drawings are perspective views showing an example of a liquefaction-preventing pile used in the inventions described in each claim of the present application, FIG. 7 and FIG.
The figure is a vertical sectional view showing a conventional example. 1 …… Common groove, 2 …… Liquefaction prevention pile, 3 …… Crushed stone, 4,
5 ... Liquefied ground, 6 ... Drainage material, 7 ... Drained stone mat, 8 ... Blind culvert, 9 ... Resin pipe, 10 ... Piping, 11 ... Piping with filter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Saimura 1-3-3 Otemachi, Chiyoda-ku, Tokyo Sumitomo Metal Industries, Ltd. (56) Reference JP-A-3-212515 (JP, A)

Claims (3)

[Claims] 1. A drainage function is required on the lower surface of an underground structure constructed underground or semi-underground to dissipate excess pore water pressure generated around the underground structure and in the ground on the lower surface during an earthquake. A liquefaction prevention pile of a length is provided, and a drainage path connecting the upper part of the liquefaction prevention pile and the outside of the liquefaction countermeasure target ground is provided, and from the upper part of the liquefaction prevention pile to the side wall of the buried structure. Drainage material that stands up along
A method for liquefaction countermeasures for a buried structure, characterized in that a part or all of the drainage path is formed by a crushed stone mat for drainage from the upper part of the drainage material to the outside of the liquefaction countermeasure target ground. 2. A drainage function is required on the lower surface of the buried structure constructed underground or semi-underground to dissipate excess pore water pressure generated around the buried structure and in the ground on the lower surface during an earthquake. A liquefaction prevention pile with a length is provided, and a drainage path that connects the upper part of the liquefaction prevention pile and the outside of the liquefaction countermeasure target ground is provided, and from the upper part of the liquefaction prevention pile to the inside of the buried structure. A liquefaction countermeasure method for an embedded structure, characterized in that part or all of the drainage path is formed in the embedded structure by the pipe. 3. A drainage function is required to dissipate excess pore water pressure generated in the ground around the buried structure and in the ground on the lower surface at the time of an earthquake on the lower surface of the buried structure constructed underground or semi-underground. A liquefaction prevention pile with a length is provided, and a drainage path connecting the upper part of the liquefaction prevention pile and the outside of the liquefaction countermeasure target ground is provided, and from the upper part of the liquefaction prevention pile to the side wall of the buried structure. A pipe that penetrates through the pipe, further constructs a crushed stone mat for drainage from the upper part of the pipe to the outside of the liquefaction countermeasure target ground, and forms a part or all of the drainage route by the pipe and the crushed stone mat for drainage. Liquefaction countermeasure method for buried structures, which is characterized by