JP2668922B2 - Seismic structure of excavated road - Google Patents

Description

Description: [Industrial field of application] The present invention relates to a seismic retrofitting structure for an excavated road in a ground that is likely to be liquefied.

[Conventional technology]

Conventional earthquake-resistant construction methods for excavated roads, especially excavated roads close to the embankment and excavated roads on sloping land, often involve compaction methods, and in recent years, the crushed stone drain method [Taniguchi et al .; Analysis of application of gravel drain, 41st Annual Scientific Lecture Meeting of the Japan Society of Civil Engineers, November 1986] has also been tried. Against this background, the former is applied to soft ground as it is to the ground including sandy soil layer, and the latter is born from the recent earthquake damage, especially the study of liquefaction phenomenon of sandy soil and sandy soil layer. In addition, a consolidation method using cement milk or the like is also being studied.

[Problems to be solved by the invention]

These conventional methods can be expected to have a considerable seismic effect when applied to a vast area including immediately below the embankment when the adjacent part is embankment at the time of new construction, but in the case of existing excavated roads, for example, As shown in Fig. 11, the construction must be done just under the excavated road 1, and the improvement area is extremely limited. In the figure, 3 is a liquefied layer such as sand ground, and 13 is a ground improvement section by compaction or crushed stone drain.

As a result, the increase in excess pore water pressure in the surrounding liquefaction layer 3 at the time of an earthquake is transmitted to these improvement parts 13, and the whole road 1 is lifted. At the same time as the rising phenomenon, the embankment portion or the inclined portion sinks, and the liquefied layer 3
Moves in the horizontal direction by exhibiting a lateral flow behavior.

Even if the adjacent part of the excavated road 1 is a natural sloping land, the conventional method shows the same result as the above existing case, and every time an earthquake occurs, it requires a great deal of cost such as road repair and slope repair. .

The present invention has been made to solve the above problems.

[Means for solving the problem]

Hereinafter, an outline of the present invention will be described using reference numerals in the drawings corresponding to the embodiments.

The seismic-resistant structure of the excavated road according to the present invention shuts off water in the liquefied layer 3 which is a sandy soil layer by installing the sheet pile walls 2 having both waterproofing and drainage properties on both sides of the excavated road 1. ,
In addition, the excess pore water pressure in the liquefaction layer 3 that occurs during an earthquake is reduced by draining it, and the propagation of excess pore water pressure from the surrounding sandy soil layer is blocked, and the strength and rigidity of the sheet pile wall 2 close the embankment. It prevents the lateral flow behavior of the liquefied layer from the slope and sloping land, and prevents floating of the excavated road 1 and horizontal movement in the event of an earthquake.

For this reason, in the present invention, at least a part of the sheet piles constituting the sheet pile wall 2 has a hollow portion in the longitudinal direction, and a perforated section having a large number of small holes opened in the liquefaction layer 3. Is used. The perforated portion is provided only on one surface of the sheet pile wall 2 so that the water stoppage of the sheet pile wall 2 is maintained, and the perforated sheet pile 2a is cast on different sides so that the perforated portions are on different sides. Drainage of excess pore water from the water.

As shown in FIGS. 6 and 7, for example, as shown in FIGS. 6 and 7, a steel sheet 21 is welded between flanges 20b of a steel sheet pile 20 having a substantially groove-shaped cross section, and a web 20a of the steel sheet pile 20 and the steel sheet 21 are welded. To form a longitudinal gap between the steel sheet pile and
20 A body provided with a large number of small holes 22 in at least one of the body and the steel plate 21 (see Japanese Patent Application No. 62-280422), and FIGS. 8 and 9
As shown in the figure, a number of small holes 31 are formed on one side of a steel sheet pile 30.
And the like can be used.

(Operation)

The seismic-resistant structure of the excavated road according to the present invention has a sheet pile wall 2 including a perforated sheet pile 2a, or a sheet pile wall 2 including the perforated sheet pile 2a, which is placed on both sides of the excavated road 1 to form a close embankment or a close slope and a lower side of the cut road 1. Because it is installed so as to penetrate the liquefied layer 3 consisting of a sandy soil layer and a sandy ground, the groundwater can be forcibly discharged by applying vibration at the time of casting. The ground around the sheet pile 2 can be compacted, the generation of excess pore water pressure at the time of an earthquake is suppressed, and the water stopping property enables the propagation of excess pore water pressure in the liquefaction layer 3 around the excavated road 1. It is possible to cut off and prevent the excavation road 1 from rising.

Furthermore, by appropriately selecting the cross section and the embedding of the sheet pile constituting the sheet pile wall 2, the lateral flow behavior of the liquefied layer 3 can be prevented, and the horizontal movement of the cut road 1 can be prevented.

〔Example〕

 Next, the illustrated embodiment will be described.

FIG. 1 and FIG. 2 show an embodiment suitable for an existing cut road.

In the example shown in FIG. 1, perforated sheet piles 2a are installed on both sides of the cut road 1, and the rise of excess pore water pressure in the liquefied layer 3 caused when the liquefied layer 3 is liquefied by an earthquake is perforated. Sheet pile
By suppressing near 2a and blocking the propagation of water pressure by the sheet pile wall 2, it is possible to reduce the lifting pressure U _D due to the excessive pore water pressure at the time of an earthquake acting on the excavated road 1 and to remove the lifting pressure F due to the seepage hydraulic force. And the safety factor against the rise of the excavated road 1 Where: W: own weight of the cut road Q: vertical frictional force on the side wall of the cut road U _S : still water buoyancy U _D : lift force due to excess pore water pressure during earthquake F: lift force due to seepage water can be significantly increased it can.

On the other hand, since there is an embankment or a natural slope 4, the liquefaction layer 3 immediately below it is pushed toward the excavation road 1 in the event of an earthquake, and the subsidence of the embankment or the natural slope 4 and horizontal movement of the excavation road 1 in the figure. The rise of the ground on the right side of the excavated road 1 occurs, but this can be sufficiently prevented by examining the sectional rigidity of the perforated sheet pile 2a.

In the example shown in FIG. 2, as a further countermeasure against this horizontal movement, an earth anchor 5
Are installed at an appropriate pitch.

FIG. 3 and FIG. 4 show an embodiment suitable for a newly-buried road.

In the example of FIG. 3, the purpose of use of the perforated sheet pile 2a is the same as in the above case, but since it is a new construction, prior to the installation of the excavation road 1, a perforated horizontal connecting material 6 is appropriately attached to the lower side thereof. It is provided at a pitch and connects perforated sheet piles 2a separated by a cut road 1. As a result, the perforated sheet pile 2a and the perforated horizontal tie member 6 form a rigid frame structure, which exerts sufficient resistance against the above-described horizontal movement, and at the same time, the cut road 1
It can suppress the rise of excess pore water pressure directly below and almost completely prevent disasters caused by earthquakes. The perforated horizontal tie member 6 is a steel pipe, a rectangular pipe or the like having the same structure as the perforated sheet pile 2a shown in FIGS. 6 to 9.

FIG. 4 shows an example of the perforated horizontal connecting material 6 shown in FIG.
Instead of using a crushed stone mat 7 and a crushed stone column 8 that provide a drainage function, for horizontal movement prevention, as in the embodiment of FIG.
The ground anchor 5 is used.

FIG. 5 shows an example of a case where there is no embankment or natural slope 4 close to the excavated road 1. In this case, since horizontal movement does not occur on the cut road 1, the crushed stone mat 7, the crushed stone column 8, and the perforated sheet pile 2a are used in combination in order to completely prevent only the floating.

6 to 9 show an example of a perforated sheet pile 2a used in the present invention.

In the example of FIG. 6, a perforated plate 21 having a large number of small holes 22 formed so as to connect the flanges 20b of the conventional steel sheet pile 20 to each other.
Is attached, and the entire drainage area surrounded by the steel sheet pile 20 main body and the perforated sheet 21 is filled with a filter material 23 for preventing the intrusion of seismic particles and backfilled sand particles to form a perforated sheet pile 2a. It is. In a state where the perforated sheet piles 2a are connected to each other via a joint, the water in the liquefied layer 3 can be drained from both surfaces of the sheet pile wall 2 and the water stoppage of the sheet pile joint portion causes the permeated water and excess pore water pressure to be reduced. Propagation can be blocked.

Unlike the one shown in FIG. 6, the one shown in FIG. 7 has a filter 24 made of metal or synthetic resin attached to the entire back surface of the perforated plate 21. Most of the drainage area surrounded by the plate 21 is hollow, and the drainage capacity is higher than that of the one filled with the filter material 23.

6 and 7, reference numeral 20c denotes a joint portion, and reference numeral 25 denotes a welded portion.

The perforated sheet pile 2a shown in FIG. 8 and FIG. 9 is provided with a number of small holes 31 on one side with respect to the center line connecting the joints 30a and 30b of the conventionally used steel pipe sheet pile 30. A filter 32 made of metal or synthetic resin is attached to the inner surface of the filter. By connecting the steel pipe sheet piles 30 so that the surfaces having the small holes 31 are alternately arranged to configure the sheet pile wall 2, both the drainage function and the water stop function can be provided. Fitting
By filling the area surrounded by the joint 30a and the joint 30b with the bagged mortar 33, it is possible to ensure the waterproofness.

These perforated sheet piles 2a may be used discretely in the sheet pile wall 2 for every several sheet piles. These perforated sheet piles
When 2a is used on both side surfaces of the cut road 1, these can be used as earth retaining works at the time of temporary construction, and can also be used as a formwork or form support for the side wall of the cut road 1. At this time, as a countermeasure against uneven settlement of the cut road 1, as shown in FIG. 10, a bituminizing agent or a resin agent 11 for reducing friction is applied without providing a small hole at a position in contact with the cut road 1. Further, a method of constructing a joint material 10 at the position of the shade concrete 9 on the sheet pile wall 2 can be adopted. In the figure, reference numeral 12 denotes a receiving member for the bitumen or the resin 11. If the perforated sheet pile 2a is not in contact with the excavated road 1, it can be dealt with by backfilling between the sheet pile wall 2 and the excavated road 1 with crushed stone.

Also, although not shown, the discharge of water in the perforated sheet pile 2a is as follows.
This can be done by piping inside the cap concrete 9 on the top of the sheet pile wall 2 and connecting to the drainage ditch of the excavated road 1.

As described above, the water in the liquefied layer 3 is reliably stopped and drained by the perforated sheet pile 2a, thereby preventing the cut road 1 from being lifted up and preventing unequal settlement.

〔The invention's effect〕

The seismic resistant structure of the excavated road according to the present invention, which is different from the conventional seismic resistant construction method, pays attention to the behavior and action of water in the liquefied layer at the time of an earthquake, and cuts a perforated sheet pile having a water stop function and a drainage function. Since it is installed on both sides, the rise of excess pore water pressure in the liquefaction layer caused by an earthquake can be suppressed by natural drainage, and the transmission of excess pore water pressure from the outside of the cut road can be completely blocked, and Infiltration water can be prevented.

In addition, since the rigidity of the perforated sheet pile itself can be arbitrarily selected, it is possible to resist the horizontal force acting on the excavated road from the side of the embankment or the natural sloping ground by the perforated sheet pile, and the horizontal movement of the excavated road can be prevented. It also has the effect that it can be prevented.

[Brief description of the drawings]

1 to 5 are vertical sectional views showing different embodiments of the present invention, FIGS. 6 to 8 are perspective views showing different embodiments of a perforated sheet pile according to the present invention, and FIG. FIG. 8 is a plan view, FIG. 10 is a vertical cross-sectional view showing an embodiment in the case of taking measures against uneven settlement, and FIG. 11 is a vertical cross-sectional view of a conventional example. 1 ... cut road, 2 ... sheet pile wall, 2a ... perforated sheet pile, 3
Liquefaction layer, 4 embankment or natural sloping ground, 5 earth anchor, 6 perforated horizontal tie material, 7 crushed stone mat, 8 crushed stone pillar, 9 ...... concrete concrete, 10 ...... Joint material, 11: bitumen or resin, 12: receiving member, 13
…… Soil improvement part, 20 …… Steel sheet pile, 21 …… Perforated board, 22 ……
Small hole, 23 ... Filter material, 24 ... Filter, 25 ...
Welded part, 30 ... steel sheet pile, 31 ... small hole, 32 ... filter, 33 ... mortar

Claims (4)

(57) [Claims] 1. A sheet pile wall having a water blocking property made of continuous sheet piles is installed on both sides of a cut road constructed on the ground having a liquefied layer, and at least a part of the sheet piles constituting the sheet pile wall is provided. Having a hollow portion in the longitudinal direction, a perforated sheet pile having a perforated part having a plurality of small holes formed in the liquefaction layer and having a perforated part on one surface of the sheet pile wall, Earthquake-resistant structure. 2. A perforated horizontal connection between perforated sheet piles separated from each other by the perforated road having a hollow portion in the longitudinal direction and having a perforated portion formed with a large number of small holes opening in the liquefaction layer. The earthquake-resistant structure of a cut-away road according to claim 1, wherein the structure is connected by a material. 3. The seismic resistant structure for a road cut according to claim 1, wherein a crushed stone mat and a crushed stone column are installed immediately below the road cut between the perforated sheet piles separating the road cut. 4. The earthquake-resistant structure of a cut road according to claim 1, wherein a bituminous agent or a resin agent is applied to a portion of the sheet pile wall including the perforated sheet pile that contacts the cut road.