JP2013014962A - Structure for reinforcing levee - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for reinforcing a levee, which is costwise advantageous by virtue of a small amount of steel usage while having performance required for the levee.SOLUTION: A structure for reinforcing a levee 1 is used to reinforce the levee 1 for a river k and the like. A steel wall 3, which continues in the extension direction of the levee 1 and the lower end of which reaches a ground bearing layer 12, is provided in the vicinity of a top 1c of slope on the bank outside O (the river k side) of the levee 1. Additionally, discretely-disposed stay works 4 are provided in the vicinity of the top 1c of slope on the bank inside I (the bank inside opposite to the river k). The steel wall 3 and the stay works 4 are connected to each other in the top end vicinity of the levee 1 by means of a tie rod 5.

Description

  The present invention relates to a reinforcement structure for embankments such as rivers.

  In recent years, large earthquakes have frequently occurred in Japan, and several major earthquakes are predicted to arrive in the near future, and there are concerns about damages such as cracks and subsidence of embankments in rivers and other dikes. .

  As countermeasures against earthquakes on the levee, the embankment method bottom (slope lower end) is often applied with ground improvement or steel sheet piles, but the water level rises sharply due to unexpected heavy rains. For the purpose of preventing osmotic breakage due to water and bank breakage due to overflowing water, research is being conducted on a composite structure by installing steel sheet piles inside the levee body.

As such a composite structure, double steel sheet piles are formed by driving steel sheet piles to the support layer along the continuous direction of the bank bodies on the right and left shoulders (upper end of the slope) in the bank body. There has been proposed a structure in which a wall is installed and the heads of the left and right steel sheet pile walls are joined by tie rods (see, for example, Patent Document 1).
According to this structure, subsidence of the levee body is suppressed during an earthquake, and furthermore, the steel sheet pile with excellent water-imperviousness ensures the height of the dam body. It is an effective structure for reinforcing the embankment.

  However, in the above-mentioned levee reinforcement structure, the water on the river side penetrates inside the levee so as to go around the lower end of the double steel sheet pile wall, but the water flowing into the double steel sheet pile wall such as rainwater is not There is concern about storing without draining. Then, the embankment reinforcement structure which makes it possible to always drain the water in a double steel sheet pile wall by giving water permeability to at least one steel sheet pile of a double steel sheet pile wall is proposed. (For example, refer to Patent Document 2).

JP 2003-13451 A JP 2010-24745 A

  By the way, the structure in which both double steel sheet pile walls as in Patent Documents 1 and 2 are driven to the support layer over the entire length of the wall body requires a large amount of steel material to be used, which in turn increases the steel material cost and the man-hour for placing. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dike reinforcement structure that is advantageous in terms of cost because it requires a small amount of steel material while providing performance required as a dike.

  One of the performance requirements of the dike is that when an earthquake occurs, the top sinking due to the earthquake is small, the height of the dike is maintained, and damage to private houses inside the dike due to overflow or high water is suppressed. To do. As a structure of the levee having this performance, it is not necessary to drive two rows of continuous wall bodies to the support layer, and the inside of the levee may be a structure that is discretely arranged instead of a continuous wall shape, for example. In addition, the present inventors have found that the penetration depth does not have to reach the support layer, and have come to the present invention.

  In other words, the embankment reinforcement structure according to one aspect of the present invention is a reinforcement structure of a bank or the like of a river or the like, near the shoulder outside the embankment of the embankment, is continuous in the extending direction of the embankment, and the lower end is the ground. A steel wall that reaches the support layer is provided near the shoulder on the inner side of the levee.Discretely arranged guards are provided, and the steel wall and the guard are near the top of the levee. They are connected to each other by a connecting material.

In this aspect of the invention, the amount of settlement at the top of the levee body can be kept small during an earthquake, the height of the levee can be maintained, and damage to private houses and the like inside the dam due to overflow / high water can be suppressed. Further, in the present invention, when the steelwork is provided in a double row, that is, when the steel wall reaching the ground support layer is provided in two rows by arranging the laying work in a discrete manner inside the bank, Compared to the above, the amount of steel material can be reduced. Thereby, reduction of steel material cost and reduction of the man-hour at the time of steel wall construction can be aimed at.
Moreover, since the laying work is dispersedly arranged inside the levee body, it is possible to prevent rainwater and the like from being stored in the dam body.

  In the present invention, the preliminary work is made of, for example, a steel sheet pile, a steel pipe sheet pile, a steel pipe pile, or an H-shaped steel. In this case, each one piece (one piece) may be a single backup work, or a combination of several steel sheet piles or steel pipe sheet piles may be a single backup work.

A dike reinforcement structure according to another aspect of the present invention is a dike reinforcement structure such as a river,
Near the shoulder on the outside of the dike, there is a first steel wall that extends in the extension direction of the dike and whose lower end reaches the ground support layer. A second steel wall that is continuous in the direction and has a lower end located substantially at the same height as the bottom of the levee, and the first steel wall and the second steel wall are connected near the top of the levee. It is characterized by being connected to each other by a material.

In this aspect of the invention, the amount of settlement at the top of the levee body can be kept small during an earthquake, the height of the levee can be maintained, and damage to private houses and the like inside the dam due to overflow / high water can be suppressed. Moreover, in this invention, the 2nd steel wall is not rooted in the support layer of the ground, but the 2nd steel wall is made into the 1st steel wall by being rooted in the substantially same height position as the bottom part of the levee inside the bank. The amount of steel material can be reduced. Moreover, since the vertical length of the second steel wall is short, the number of man-hours during construction can be reduced.
From the above, this dyke reinforcement structure can substantially maintain the function as a dyke even after an earthquake, and is excellent in economy and workability.
Moreover, since the 2nd steel wall inside the bank of a bank body has only the depth (rooting length) to the bottom part of a bank body, it can suppress that rainwater etc. accumulate in a bank body.

  In this invention, the said 1st and 2nd steel wall is a steel sheet pile and a steel pipe sheet pile, for example.

  According to the embankment reinforcement structure of the present invention, even if an earthquake occurs, the amount of subsidence at the top of the embankment is small even when an earthquake occurs. A reasonable embankment reinforcement structure that can maintain the length and suppress damage inside the bank due to the bank breakage is obtained.

(A) is a schematic sectional drawing which shows the reinforcement structure of the embankment which concerns on 1st Embodiment of this invention, (b) is arrangement | positioning of the steel wall in the reinforcement structure of a embankment, 1st embodiment, and a tie rod. FIG. (A) is a schematic sectional drawing which shows the reinforcement structure of the embankment of the modification of the said 1st Embodiment, (b) shows the arrangement | positioning of the steel wall in the reinforcement structure of the said modification, a construction work, and a tie rod. FIG. (A) is a schematic sectional drawing which shows the reinforcement structure of the dike of another modification of the said 1st Embodiment, (b) is arrangement | positioning of the steel wall in the dike reinforcement structure of the said modification, a construction work, and a tie rod FIG. (A) is a schematic sectional drawing which shows the reinforcement structure of the dike of another modification of the said 1st Embodiment, (b) is the steel wall in the reinforcement structure of the said dike, the construction of a tie rod, It is the schematic which shows arrangement | positioning. (A) is schematic sectional drawing which shows the reinforcement structure of the embankment concerning 2nd Embodiment of this invention, (b) is the schematic which shows arrangement | positioning of the steel wall in the reinforcement structure of the embankment of 2nd Embodiment, and a tie rod It is. It is a schematic plan view which shows the model of the embankment used in the experiment as an Example. It is a schematic sectional drawing which shows the model of the embankment used in the said experiment. It is a figure which shows the measurement result of the maximum response acceleration of each part of a model at the time of applying a vibration to the bank of a model as an experimental result of the comparative example of the said experiment. It is a figure which shows the measurement result of the maximum response acceleration of each part of a model at the time of applying a vibration to the bank of a model as an experimental result of the Example of the said experiment. It is a graph which shows the amount of settlement of a dike when vibration is added to the dike of each model which is a comparative example, a conventional example, and an example as an experimental result of the above-mentioned experiment. It is a graph which shows the deformation | transformation of an embankment when a vibration is added to the embankment of each model which is a comparative example, a prior art example, and an example as an experimental result of the said experiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the embankment reinforcement structure of the first embodiment of the present invention is for reinforcing a bank 1 of a river k made of embankment, for example.
The embankment 1 is a top end 1a having a horizontal upper surface at the highest portion in the center. Inclined slopes 1b are formed on the left and right of the top end 1a, respectively, and the upper end side of the slope 1b is a shoulder 1c and the lower end is a slope 1d.

  In the reinforcement structure of the levee 1, a steel wall 3 in which a steel sheet pile 2 is connected in the extension direction (extension direction) of the levee in the vicinity of the shoulder 1 c of the outer shore (river k side) O is provided. Is provided. Moreover, in this reinforcement structure, the preparatory work 4 which consists of the steel sheet pile 2 is discretely laid in the vicinity of the shoulder 1c of the bank inner side (opposite side of the river k) I. That is, for example, as shown in FIG. 1, the laying work 4 is arranged side by side along the extending direction of the levee 1 at intervals.

  The steel wall 3 is embedded from the height position of the top end 1a as the vicinity of the shoulder 1c of the bank outside O of the bank 1 made of embankment to the support layer 12 below the foundation ground 11 from a little below. Moreover, as a sheet pile which comprises the steel wall 3, the sheet pile which has a cross-sectional performance not to collapse even if earth pressure and water pressure by an earthquake act on a sheet pile (steel sheet pile 2 or a steel pipe sheet pile) is applied.

  The upper work 4 is arranged with its upper end slightly below the height position of the top end 1a as the vicinity of the shoulder 1c on the inside I of the bank. The steel wall 3 and the preparatory work 4 are connected (connected) by a tie rod 5 as a connecting material (tie material) at a height near the top end (slightly below the top end).

  The preparatory work 4 (steel sheet pile 2 on the dam inner side I) has a role of suppressing the outflow of earth and sand from the dam body of the levee 1 during an earthquake. When the foundation ground liquefies and the effective stress of the ground decreases, the levee body sinks to spread sideways. Therefore, by providing the steel wall 3 and the preparatory work 4 on the slope shoulder 1c of the levee body, the settlement of the levee body portion including the top edge between the outside of the levee and the shoulder in the levee is suppressed. At this time, as shown in FIG. 1, the lower construction 4 may be in the liquefied ground (foundation ground 11) without the lower end reaching the support layer, and only needs to be able to suppress the outflow of earth and sand from the dam body. .

  Thereby, compared with the deadline structure by the sheet pile double wall described in the above-mentioned patent document 1, the length of the base construction 4 can be shortened and it leads to cost reduction. As a guideline for the length of the laying work 4, it is only necessary to have a length up to the bottom of the levee body (bottom of the levee). Moreover, in consideration of scouring at the time of overflowing water, the length assumed to be scoured may be incorporated.

When the steel sheet pile 2 and the steel pipe sheet pile are applied to the backup work 4, each backup work 4 is composed of one steel sheet pile as shown in FIG. 1, and a plurality of them are connected as shown in FIG. It may be a thing. When connecting sheet piles (steel sheet piles 2 or steel pipe sheet piles), the greater the number of sheet piles, the greater the amount of steel used, but the more the function of suppressing the outflow of earth and sand improves.
After the excess pore water pressure in the ground liquefied before or after the earthquake disappears, the liquefied ground (foundation ground 11) also functions as a ground that resists deformation of the sheet pile. Therefore, even if the laying work 4 is not penetrated to the support layer 12 and the bottom end of the sheet pile stays in the liquefied ground, the laying work 4 can also resist the earth pressure and the water pressure as long as the laying length is sufficient.

  In addition, as shown in FIG. 3, a part of the steel sheet pile 2 of the preparatory work 4 is embedded into the support layer 12, and the other steel sheet piles 2 connected to the steel sheet pile 2 are separated from the dam body. It is also possible to adopt a structure in which the rooting length is limited to a level that can suppress the outflow of earth and sand. For example, it is good also considering the lower end of the remaining other steel sheet pile 2 as the height position about the bottom part of the levee 1.

  As the steel sheet pile 2 constituting the steel wall 3, various steel sheet piles 2 such as a U-shaped steel sheet pile and a hat-shaped steel sheet pile that are usually used can be used. Moreover, it replaces with the steel sheet pile 2, and the steel wall 3 is good also as what is provided by connecting and driving a steel pipe sheet pile similarly to the case of the above-mentioned steel sheet pile 2. FIG. Furthermore, the steel wall 3 can use the combination steel sheet pile etc. which stiffened with steel materials, such as H-section steel, to various steel sheet piles 2 and a steel pipe sheet pile. The steel wall 3 can be provided in the ground by driving these various sheet piles while being connected to each other at the joint.

There is no limitation also in the shape of the steel sheet pile 2 as the preparatory work 4, For example, various steel sheet piles 2, such as a U-shaped steel sheet pile normally used and a hat-shaped steel sheet pile, can be used. Further, the steel sheet pile 2 used for the laying work 4 may be a steel sheet pile or steel material having a shape different from that of the steel sheet pile 2 constituting the steel wall 3. Moreover, as shown in FIG. 4 instead of the steel sheet pile 2, the steel pipe pile 6 and the steel pipe sheet pile may be used as the laying work 4. Moreover, you may connect and use several steel sheet piles 2 and several steel pipe sheet piles as the preparatory work 4 as mentioned above.
In addition, since the steel pipe sheet pile or the steel pipe pile 6 is used as the preparatory work 4 and the steel sheet pile 2 is used as the preparatory work 4, higher rigidity can be obtained. As a result, the amount of steel used for the entire reinforcing structure is reduced.

  The distance between the laying works 4 should be small in order to suppress the sinking of the top due to an earthquake or the like. Even if the dike inner side I is not a continuous wall (that is, the distance between the preparatory works is zero over the entire length in the extension direction of the levee) as in the experimental example described later, there is no countermeasure for the amount of settlement at the top (providing a steel wall etc. It can be much smaller than the dike. It is preferable that the distance between the layers 4 is preferably about 5 m or less, and the total length of the layers 4 installed in a predetermined length in the extending direction of the levee is 25% or more. On the other hand, if the interval between the laying works 4 is reduced and brought closer to the continuous wall, the amount of steel used will inevitably increase. As long as the amount of sinking at the top is allowed, it may be determined as appropriate by the balance of the amount of steel used. For example, the sum of the lengths in which the laying work 4 is installed in a predetermined length in the extending direction of the levee If it is 75% or less, it is economical.

  In addition, since the preparatory work 4 is provided at intervals, rainwater is drained from the dam body immediately below the top end 1a to the inside of the dam when it rains, so that the dam body just below the top end 1a It is difficult to loosen, and it is thought that it can work advantageously for subsidence of the top end 1a or deformation of the levee 1 during an earthquake or the like.

  Of course, the position of the lower end of the preparatory work 4 (the placement depth) may be embedded up to the support layer 12, but it is liquid as described above as long as the sinking amount of the top end 1 a due to an earthquake or the like is allowed. It may be the height of the chemical ground (foundation ground 11). As in the experimental example described later, even if the lower end of the preparatory work 4 is at the height of the liquefied ground, the amount of settlement at the top end is markedly lower than that of a countermeasure (no steel wall etc.). Can be small. Further, in the preparatory work 4 in which a plurality of steel sheet piles 2 are connected as described above, a part of the steel sheet piles 2 are rooted to the support layer 12 and the remaining steel sheet piles 2 are rooted to the bottom of the levee body. It is good also as what to put.

  The connecting material is not limited to a tie rod, and any material that can be expected to have a tensile strength such as a tie wire or a geotextile may be used.

Next, a second embodiment of the present invention will be described.
FIG. 5 shows a dike reinforcement structure according to the second embodiment of the present invention in a river dike.
In this embodiment, steel walls 3 and 7 in which steel sheet piles 2 are connected in the extending direction of the dike 1 are provided in the vicinity of the shoulder 1 c on the dike outer side O and the dike inner side I. Among these, the 1st steel wall 3 of the bank outer side O is rooted to the support layer 12 of the ground like the steel wall 3 of 1st Embodiment, and the 2nd steel wall 7 of the bank inner side I is It is almost the same height as levee 1. That is, the second steel wall 7 is embedded from the height position in the vicinity of the shoulder 1 c on the inside I of the bank 1 to the bottom of the bank 1. The 1st steel wall 3 and the 2nd steel wall 7 are couple | bonded by the tie rod 5 as a connection material by the height of the top end 1a vicinity.

About the shape etc. of the sheet pile (steel sheet pile 2, steel pipe sheet pile, combination steel sheet pile) which comprise the 1st and 2nd steel walls 3 and 7, using the thing similar to the steel wall 3 of 1st Embodiment is used. it can.
The lower end of the second steel wall 7 is almost the same height as the bottom of the embankment 1 embankment, and even if it reaches the liquefied ground (foundation ground 11), it does not reach that land It may be in a height position.

  Also in the reinforcement structure of the embankment 1 of 2nd Embodiment, there can exist an effect similar to the reinforcement structure of the embankment 1 of 1st Embodiment. In the second embodiment, the dam inner side I of the levee 1 is not the preparatory work 4 that is discretely arranged, but is a continuous second steel wall 7. Since the depth of the bottom of the sheet pile constituting the second steel wall 7 is short, the amount of steel used compared to the conventional reinforcing structure using two rows of steel walls Can be reduced, and the construction time for placing each steel sheet pile 2 can also be shortened as compared with the prior art. That is, it is possible to satisfy the above-mentioned performance as a bank with a rational structure capable of reducing the cost.

Hereinafter, the performance of the reinforcing structure of the embankment 1 of the present invention will be further described using an experimental example using a model.
First, a model simulating the levee 1 was prepared in a rigid earthen tank (width 1210 × height 580 × depth 390 mm) installed on a vibration table. Silica sand No. 5 was used as the ground material, and the ground conditions were as shown in Table 1.

In addition, the lower ground in Table 1 is below the ground line in the schematic diagram of Table 2, and the upper ground is above the ground line in the schematic diagram. The height of the ground combining the lower ground and the upper ground is 300 mm.
The structures to be investigated in this experiment were three types of reinforcing structures (cases 2 to 4) as shown in Table 2, and a structure that was not reinforced with steel for comparison (case 1). Case 2 is a conventional example corresponding to a conventional levee reinforcement structure in which steel walls that are embedded up to the ground support layer 12 are provided on both the outer side of the levee and the shoulder on the inner side of the levee. It is an Example corresponding to 1st Embodiment, Case 4 is an Example corresponding to 2nd Embodiment, and Case 1 is a comparative example which is not reinforced. In the description of this experiment, cases 1 to 4 may be referred to as described in the column of construction method in Table 2, respectively. Moreover, in the model used by experiment, the below-mentioned steel plate is used as a 1st and 2nd steel wall and the sheet pile used as a laying work.

FIG. 6 is a schematic plan view of a model that is the case 3 and the case 4, and FIG. 7 is a schematic cross-sectional view of the model of the case 3 and the case 4.
In cases 2 to 4, one shoulder (corresponding to the outside of the levee) has a vertical length of 408 mm (the length reaching the bottom of the earth tub from the top of the levee and below the embankment (108 mm). Is 300 mm) × 128 mm in width × 1.6 mm in thickness, and three steel plates are arranged side by side so as to be substantially in contact with each other in the width direction. Moreover, the lower end of the steel plate was pinned to the earth tub side.

  On the other shoulder (corresponding to the inner side of the bank), in the case 2, as in the outer side of the bank, steel plates having a vertical length of 408 mm, a width of 128 mm, and a plate thickness of 1.6 mm were provided side by side. Moreover, it was set as pin fixation supposing that the lower end of the steel plate was rooted in the support layer of the ground.

  In case 3, except for the steel plate arranged in the center inside the bank in case 2, the other two left and right vertical lengths of 258 mm (the depth of penetration below the bank is 150 mm) × width 128 mm × sheet thickness 1 A 6 mm steel plate was provided discretely. That is, two steel plates on the left and right sides were provided with an interval of one steel plate between them. Moreover, the lower end of the steel plate was arranged without being fixed in the upper ground (soft ground).

  In case 4, three steel plates each having a length of 108 mm (the same length as the embankment height) × a width of 128 mm × a plate thickness of 1.6 mm were arranged so as to be substantially in contact with each other in the width direction. Moreover, the lower end of the steel plate was arranged without being fixed near the boundary between the embankment and the upper ground.

Further, in these cases 2 to 4, the steel plate outside the bank and the steel plate inside the bank were connected by tie rods. The positional relationship between the ground of each case, the steel plate and the tie rod is as shown in FIGS.
Regarding the structure of each case, the shaking table on which the above-mentioned earth tub was placed was vibrated with 20 sine waves of 3 Hz. The acceleration of the shaking table was 100, 200, 400, 600, 800 gal. In each case, a winding displacement meter, an accelerometer, and a strain meter are attached to the positions indicated by “CH... (... is a number)” in FIGS. 6 and 7, and the displacement, acceleration, and the like at that position are measured. did.

The main experimental results are shown in FIGS.
FIG. 8 and FIG. 9 show the measurement results of the maximum response acceleration at each position in the model when 800 gal vibration is applied in case 1 (FIG. 8) and case 3 (FIG. 9). The maximum response acceleration at the top of the embankment (the top of the embankment) was about 1.7 times the acceleration of the shaking table in Case 1, whereas it was about 2.3 times in Case 3. In cases 2 and 4 as well, the maximum response acceleration at the top of the embankment was higher than in case 1. This is considered to be because the structures such as cases 2 to 4 have higher soundness as a bank than the structure of case 1 that is not reinforced.

  FIG. 10 shows the relationship between the acceleration of the shaking table and the amount of settlement at the top after vibration in each case. In any structure, subsidence was hardly observed up to 400 gal, and subsidence was observed at 600 gal or more. Furthermore, after 800 gal vibrations were applied, in Case 1, the amount of subsidence was about 40 mm, whereas in Case 2, it was about 1/8, Case 3 was about 1/4, Case 4 was about 1 / It was 5.

  FIG. 11 shows the deformation state of the embankment after 800 gal vibration is applied in each case. In Case 1, both the embankment top and the slope inside slope collapsed almost completely. In Cases 2 and 4, the slope inside the bank was greatly collapsed and the steel plate was exposed, but the height of the embankment top was almost maintained. In Case 3, the embankment partly collapsed in the center where no steel plate was installed, but the embankment top edge height was almost maintained. In addition, in FIG. 11, sheet pile + preparatory work (center) (case 3) indicates a deformation amount in a portion where there is no steel plate between the left and right steel plates in the shoulder on the inside of the bank in case 3, (Sheet + preparatory work (side surface) (case 3) indicates the amount of deformation in the case 3 where the above-described steel plate is present.

  That is, the structures of the cases 3 and 4 are substantially close to the structure of the case 2 in terms of suppressing the settlement of the top of the dike, and have a significant improvement effect with respect to the case 1. The amount of steel used in this model is about 0.7 in case 3 and about 0.6 in case 4 when the amount used in case 2 is 1, so case 3 and case 4 are economical and simple. Considering the characteristics, it can be said that this is a balanced and rational reinforcement structure.

k River 1 Embankment 1c Leg shoulder 2 Steel sheet pile 3 Steel wall (1st steel wall)
4 Preliminary work 5 Tie rod (tie material)
6 Steel pipe pile 7 Second steel wall

Claims (4)

Reinforcement structure of embankments such as rivers,
Near the shoulder on the outside of the levee, a steel wall that extends in the extension direction of the levee and whose lower end reaches the support layer of the ground is provided. An embankment reinforcement structure, wherein the steel wall and the obstruction are connected to each other by a connecting material near the top end of the embankment.   The reinforced structure for a levee according to claim 1, wherein the steel wall is formed by continuously placing steel sheet piles, and the preliminary work is a steel sheet pile, a steel pipe sheet pile, or a steel pipe pile. . Reinforcement structure of embankments such as rivers,
Near the shoulder on the outside of the dike, there is a first steel wall that extends in the extension direction of the dike and whose lower end reaches the ground support layer. A second steel wall that is continuous in the direction and has a lower end located substantially at the same height as the bottom of the levee, and the first steel wall and the second steel wall are connected near the top of the levee. An embankment reinforcement structure characterized by being connected to each other by a material.   The levee reinforcing structure according to claim 3, wherein the first and second steel walls are formed by continuously placing steel sheet piles.

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