JP2012007394A - Embankment reinforcement structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an embankment reinforcement structure, when an embankment is used for a dike, capable of making cost for steel member more reasonable than a conventional structure while maintaining such a function of the dike as to prevent water from flowing inside the dike when subjected to an action of an earthquake and a high flood water level as well as overflow due to concentrated heavy rain.SOLUTION: An embankment reinforcement structure of the present invention has at least one or more rows of an underground steel wall body 14 made of sheet piles 13 along a continuous embankment 1 within a range of an approximate levee crown 6 thereof. The underground steel wall body 14 is constructed with an embedded depth which is shallower than a bearing layer 9 and protects the underground steel wall body from being collapsed at times of an earthquake and overflow. Upper sections of the sheet piles 13 are fixed each other by welding or the like.

Description

  The present invention relates to a reinforcement structure for embankments extending long along rivers, rivers such as rivers, railway embankments, roads, railways, and the like.

  In recent years, large earthquakes have frequently occurred in Japan, and several major earthquakes are predicted to arrive in the near future. In embankment structures such as river embankments, the basement due to liquefaction of the foundation ground due to the earthquake There are concerns about damage such as cracks and subsidence. As an earthquake countermeasure for the embankment structure, as shown in FIG. 13, as shown in FIG. 13, in the embankment 1, a reinforcement construction method in which the embankment method bottom (lower end portion of the slope 7) 2 is tightened with an underground steel wall body 4 made of steel sheet piles 3. In many cases, a reinforcement method for improving the ground of the butt 2 is applied.

In addition, a steel sheet pile 3 is installed in the embankment (bank 1) to create a composite structure in order to prevent seepage failure due to sudden rise of water level due to unexpected heavy rain, etc. (For example, refer to Patent Document 1). As a construction method as described in Patent Document 1, as shown in FIG. 14, the steel sheet pile 3 is continuously connected to the left and right shoulder portions (upper end portion of the slope 7) 5 in the embankment (fill 1). By placing the steel wall body 4 or by placing the underground steel wall body 4 in which the steel sheet pile 3 is continuous at the center of the top edge 6 of the embankment 1, the underground steel wall body even at the time of flooding 4 ensures the height of the top 6 and prevents the water from flowing all at once from the outside of the bank (river side) to the inside of the bank (side where private houses exist) due to the bank breakage. It is effective as a reinforcement.
13 and 14 showing the outline of the conventional embankment reinforcement structure, the embankment 1 is a river bank as described above, and the left side of the embankment 1 is a river 10 in the figure. Moreover, in the ground where the embankment 1 is installed, the lower side of the liquefied layer 8 which may be liquefied at the time of an earthquake is the support layer 9.

By the way, measures to reinforce the embankment structure such as a river dike with the steel sheet pile 3 and / or the steel pipe sheet pile (hereinafter, the steel sheet pile 3 and the steel pipe sheet pile may be collectively referred to as “sheet pile”). Therefore, it is necessary to secure a sufficient length of the sheet pile so that the sheet pile is not collapsed, slid, or rotated (see, for example, Non-Patent Document 1).
Non-Patent Document 1 includes “Calculation Method by“ Free Earth Support Method ”” and “Reference Sheet 1 of“ Steel Sheet Pile Double Deadline Design Manual ”as a calculation method of the penetration length as a countermeasure for liquefaction. Two ways of "method by" are shown.

The former ignores the passive resistance of the outer liquefied layer 8 partitioned by the underground steel wall body 4 of the steel sheet pile 3 in order to verify that the bottom end of the penetration does not move plastically. Only the passive resistance in the non-liquefaction layer (support layer 9) is considered, and a method for determining the penetration length by balancing with the earth pressure acting on the steel sheet pile 3 from the inside of the bank (bank 1) is shown.
In the latter case as well, a method in which only the non-liquefied layer is considered as the resistance on the passive side is shown. In these two methods, it is assumed that the steel sheet pile 3 is embedded in the non-liquefied layer (support layer 9).

JP 2003-13451 A

Edited by the Levee Reinforcement Research Committee “River dike reinforcement method using steel sheet piles, steel sheet pile design guide (draft)” Steel Pipe Pile Association, Levee Reinforcement Research Committee (2002.23) pp. 23-27

However, in order to penetrate the sheet pile to the support layer, a sufficient length of the sheet pile is required to reach the support layer. Also, during an earthquake, acceleration is transmitted from the support layer to the wall body, which can cause large distortions in the steel sheet pile, so the sheet pile also requires a cross section (strength, rigidity) that can withstand the distortion. Becomes larger. Therefore, the construction requires a cost (steel material cost) depending on the above-mentioned length of the sheet pile and the type (cross section) of the sheet pile.
It is necessary to take countermeasures against earthquakes in many embankments, and there is a demand for cost reduction for embankment reinforcement.

  The present invention has been made in view of the above circumstances. For example, when embankment is used for a dike, when it is subjected to an action such as an earthquake, or when it is high or overflowed by heavy rain, It aims at providing the reinforcement structure of the embankment which can rationalize steel materials cost than before, maintaining the function of the embankment which prevents water from flowing in.

  As a result of the study, the inventors have studied that the liquefied layer functions as a layer that supports the wall body in a high water state even if the sheet pile constituting the underground steel wall body does not reach the support layer. It was confirmed that no collapse occurred. In addition, when the liquefaction layer liquefies during an earthquake, the liquefaction layer existing between the steel sheet pile bottom and the support layer has a seismic isolation effect, and the transmission acceleration to the underground steel wall body is It has been found that the bending strain generated in the underground steel wall is reduced. Therefore, compared with the case where the support layer is embedded, the necessary sheet pile cross-section is small, and the cost of the steel material to be used may be reduced.

Therefore, the embankment reinforcing structure according to claim 1 is configured such that an underground steel wall body made of steel sheet piles and / or steel pipe sheet piles extends in a continuous direction of the embankment within a range of a substantially top end of continuous embankments. More than one row,
The underground steel wall body has a depth shallower than that of the support layer, and is deeply embedded to a depth at which the underground steel wall body does not collapse during an earthquake or water overflow.

In invention of Claim 1, even if the penetration depth of an underground steel wall body (sheet pile) is shallower than a support layer, the depth which an underground steel wall body does not collapse can be calculated | required by experiment or simulation. Is possible. Therefore, the embankment can be reinforced by placing the sheet piles that make up the underground steel wall body, which is shallower than the ground support layer and deeper than the depth that collapses during an earthquake or water overflow. .
The sheet pile rooted to such a depth is shorter than the sheet pile rooted to the support layer. In addition, as described above, the liquefied layer existing between the lower end of the steel sheet pile and the support layer plays a seismic isolation effect, and the bending strain generated in the underground steel wall body is reduced. It is possible to reduce. From these things, the steel material cost concerning construction of an underground steel wall body can be reduced.

In addition, when the support layer is, for example, a liquefied layer, the liquefied layer is generally more permeable than the support layer, so the depth of the sheet pile does not reach the support layer, and the lower end of the sheet pile Under the condition that there is a liquefied layer between the support layer and the underground layer, the underground steel wall does not block the flow of the permeated water and leads to the embankment between the support layer and the lower end of the underground steel wall. The embankment can be reinforced while ensuring sufficient infiltration flow.
Therefore, in a structure in which the wall body is not rooted up to the support layer, there is a high possibility that the embankment can be reinforced while ensuring the flow of groundwater. Therefore, in order to ensure the flow of groundwater, it is not necessary to provide a water-permeable hole or the like in the sheet pile, and the processing cost related to the opening can be reduced.

The embankment reinforcement structure according to claim 2 is the invention according to claim 1, wherein the underground steel wall body is provided in a row along a continuous direction of the embankment,
When the underground steel wall body is assumed to have no embankment on one side partitioned by the underground steel wall body, earth pressure and water pressure acting from both sides of the underground steel wall body, respectively. The depth is equal to or less than the depth at which the horizontal force is balanced, and is embedded to a position above the support layer.

In the invention according to claim 2, when the underground steel wall body is provided in a row in the embankment, and the embankment is used as a bank of a water area such as a river, it is made of underground steel. The earth and sand on one side of the wall (inner side of the bank) will be washed away by the overflowed water, and there is a risk that the embankment on one side (inner side of the bank) partitioned by the underground steel wall will be lost.
In this state, in order to prevent the underground steel wall body from collapsing, the underground steel wall body is configured to a depth below which the horizontal force due to earth pressure and water pressure acting from both sides of the underground steel wall body is balanced. It is necessary to put in a sheet pile.
Such depth can be obtained through ground surveys and simulations and experiments based thereon.
Even if the underground steel wall body is embedded to the depth, the steel material cost can be reduced as described above because the root depth is higher than the support layer.

The reinforcing structure for embankment according to claim 3, wherein the underground steel wall body made of steel sheet piles and / or steel pipe sheet piles is arranged in a line along the continuous direction of the embankment within the range of the approximate top end of the continuous embankment. Provided
The underground steel wall has a depth that is shallower than the support layer and is deeply embedded to a depth at which the underground steel wall does not collapse during an earthquake or a flood, and the support layer And second regions that are rooted in are alternately formed,
The length in the extending direction of the embankment in each first region is longer than the length in the extending direction of the embankment in each second region.

  In the third aspect of the present invention, the first region having a depth deeper than that of the support layer is changed to the second region of the depth of penetration reaching the support layer while providing the same effect as the first aspect of the invention. It is supported and can prevent the underground steel wall from sinking during an earthquake.

The embankment reinforcing structure according to claim 4 is the invention according to claim 3,
The underground steel wall body is provided in a row along the continuous direction of the embankment,
The first region of the underground steel wall body acts from both sides of the underground steel wall body, assuming that there is no embankment on one side partitioned by the underground steel wall body. The depth is equal to or less than the depth at which the horizontal force due to the earth pressure and the water pressure is balanced, and is rooted to a position above the support layer.

  In the invention described in claim 4, as in the invention described in claim 2, it is assumed that the underground steel wall bodies are arranged in a row, and there is no embankment on one side partitioned by the underground steel wall bodies. In this case, the depth is equal to or less than the depth at which the horizontal force due to earth pressure and water pressure acting from both sides of the underground steel wall body is balanced, and is rooted to a position above the support layer. The collapse of the area is suppressed, and embankment can be reinforced.

  The embankment reinforcing structure according to claim 5 is the invention according to any one of claims 1 to 4, wherein the underground steel wall body is normally in the ground as a position in the width direction of the embankment. It is arrange | positioned in the position where the earth pressure concerning both sides of a steel wall body balances.

  In invention of Claim 5, a sheet pile cross section can be suppressed compared with the case where the earth pressure which arises in a sheet pile on both sides of underground steel wall bodies is unbalanced, and also reduction of steel material cost can be aimed at.

  The embankment reinforcement structure according to claim 6 is the invention according to any one of claims 1 to 5, wherein an upper end portion of the adjacent steel sheet pile and / or the steel pipe sheet pile or the vicinity of the upper end portion is provided. It is characterized by being fixed to each other.

The underground steel wall body (or the first region of them) that is not rooted up to the support layer will not collapse when the earthquake occurs, but the liquefied layer liquefies. If the sheet piles are not fixed at that time, the amount of settlement may be different for each sheet pile.
In the invention of claim 6, by fixing each other at the upper end portion of each sheet pile or in the vicinity thereof, each sheet pile does not sink to different depths but sinks substantially uniformly. Moreover, if it fixes to the sheet pile of the 2nd area | region which has reached the support layer, it will hardly sink. Therefore, for example, it is easy to use the top of the embankment as a road during restoration work after an earthquake.

  The embankment reinforcement structure according to claim 7 is the invention according to any one of claims 1 to 6, wherein an underground steel wall body is provided on at least one of the bottom edges of the embankment. It is characterized by being.

  In the invention according to claim 7, since the settlement of the underground steel wall body at the time of the earthquake can be suppressed, it is possible to suppress the settlement at the top of the embankment at the time of the earthquake and at the time of high water or overflow. It is an effective measure.

  ADVANTAGE OF THE INVENTION According to this invention, it can be set as the embankment reinforcement structure more advantageous in terms of steel materials than before, although it is a structure which does not cause collapse of the underground steel wall body used for reinforcement of embankments, such as embankments. .

It is a schematic sectional drawing which shows the reinforcement structure of the embankment which concerns on embodiment of this invention. It is a schematic sectional drawing which shows the reinforcement structure of the embankment as a comparative example in experiment. It is a schematic sectional drawing which shows the reinforcement structure of the embankment as an Example in experiment. It is a figure which shows an excitation waveform in the excitation experiment of the reinforcement structure of a banking. It is the figure which showed the measurement result of the response acceleration of the underground steel wall body at the time of the vibration test of the reinforcement structure of embankment. It is the figure which showed the measurement result of the response bending distortion of the underground steel wall body at the time of the vibration test of the reinforcement structure of embankment. (A) And (b) is a figure which shows the idea of the penetration depth of a sheet pile in the reinforcement structure of a banking. (A) And (b) is a figure which shows the idea of the penetration depth of a sheet pile in the reinforcement structure of a banking. It is a schematic sectional drawing which shows the modification of the reinforcement structure of a banking. It is a schematic sectional drawing which shows another modification of the reinforcement structure of a banking. It is a schematic sectional drawing which shows another modification of the reinforcement structure of a banking. It is a schematic sectional drawing which shows another modification of the reinforcement structure of a banking. It is a figure which shows an example of the reinforcement structure of the conventional embankment. It is a figure which shows another example of the reinforcement structure of the conventional embankment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the embankment reinforcement structure of this embodiment is for reinforcing a bank embankment such as a river embankment or a road / railway embankment, and will be described by taking a river embankment as an example. .
The structure of the embankment 1 is the same as the embankment in the above-described conventional embankment reinforcement structure. The embankment 1 has a slope 7 whose lower end is the slope 2 and whose upper end is the shoulder 5, and the left and right slopes 7. The upper end between the two is the top end 6. Moreover, the drain material 15 may be provided in the slope 2 of the embankment 1 inside the bank in order to prevent a seepage failure.

In this embankment reinforcement structure, an underground steel wall body 14 composed of a sheet pile wall in which sheet piles 13 (steel sheet piles and / or steel pipe sheet piles) are connected in the range of the approximate top end 6 of the fill 1 is installed. It should be noted that the shoulder 5 portion slightly outside the top end 6 is also included in the range of the approximate top end 6.
Moreover, in this embodiment, the underground steel wall bodies 14 provided in a row in the embankment 1 are the central part in the width direction of the embankment 1 (the horizontal direction orthogonal to the longitudinal direction of the embankment 1), that is, the ceiling. The end 6 is disposed at the center in the width direction.

A sheet pile 13 constituting the underground steel wall body 14 penetrates the embankment 1 and is placed in a liquefied layer 8 which may be liquefied at the time of an earthquake. Moreover, the underground steel wall body 14 is continuously installed along the continuous direction (length direction) of the embankment 1.
The head (upper end) of the underground steel wall 14 is located at the same height as the top edge 6 of the embankment 1 or slightly below it.

  A liquefied layer 8 is formed below the foundation portion on the lower side of the embankment 1 as described above, and a support layer 9 is formed on the lower side thereof, but the underground steel wall body of this embodiment The lower end of 14 does not reach the support layer 9. That is, the underground steel wall body 14 (the sheet pile 13) is not embedded in the support layer 9, and the depth of installation is shallower than that of the support layer 9. That is, the lower end of the sheet pile 13 is disposed above the support layer 9. Therefore, there is a space between the lower end of the underground steel wall body 14 and the support layer 9.

The depth of penetration of the underground steel wall body 14 is set to a depth shallower than the support layer 9 as described above, and to a depth at which the underground steel wall body does not collapse at the time of an earthquake or water overflow. Yes.
The inset depth that does not collapse, for example, changes depending on the state of the foundation ground of the embankment, that is, the state of the liquefied layer 8, but is determined based on, for example, simulations or experiments based on the results of the ground investigation can do.

  Moreover, when the underground steel wall body 14 is provided in a row on the embankment 1 used as a bank as described above, the depth at which the underground steel wall body 14 does not collapse is the underground steel wall body 14. When it is assumed that there is no banking on one side of the partition, it is the depth at which the horizontal force due to earth pressure and water pressure acting from both sides of the underground steel wall body is balanced. In addition, at the time of overflowing, there is a possibility that the earth and sand inside the embankment of the embankment 1 may be washed away by overwater, and it is necessary to assume a state where there is no soil on one side partitioned by the underground steel wall body 14 of the embankment 1. is there.

In order to verify the effect of the embankment reinforcement structure, the following experiment was conducted.
1. Experimental Model The model used in the experiment corresponds to a compact earth layer 11 (shown in FIGS. 2 and 3) having a width of 2800 mm, a height of 900 mm, and a depth of 695 mm, and a compaction layer 12 (support layer 9) as a model ground. ), 3 layers of liquefied layer 8 and embankment layer (embankment 1) were produced. Furthermore, a hole with a valve that can be opened and closed is provided at a predetermined position on the side wall of the soil tank 11, and the water level can be adjusted on the left and right sides of the embankment 1.

  The compacted layer 12 was made by Kashima Kei sand No. 7 (Gs = 2.64, D50 = 0.13 mm) by the underwater dropping method, and then compacted by using a water absorption vibrator. The layer thickness of the compaction layer 12 was 250 mm, and the target relative density was about Dr = 90%.

  The liquefied layer 8 was produced by the underwater dropping method using Kashima Kei sand No. 5 (Gs = 2.53, D50 = 0.34 mm). The layer thickness of the liquefied layer was 250 mm, and the target relative density was about Dr = 30 to 35%. In order to confirm the behavior of the ground through the acrylic plate on the side of the soil tank during the vibration experiment, silica sand No. 5 colored in black was arranged in a grid pattern.

  The embankment layer was constructed using a material prepared by mixing kaolin clay with No. 7 Kashima sand used in the compaction layer 12 at a dry mass ratio of 5: 1 and adjusting the water content to 15%. The embankment shape was 300 mm in the top edge, 1200 mm in the lower edge, 250 mm in height, and a slope of 1: 1.8 in all cases.

  Furthermore, in the actual structure such as a river dike, as described above, the drain material 15 may be installed on the slope 2 of the embankment 1 inside the dike to prevent seepage breakage. A gravel 16 having a high water permeability of about 5 to 10 mm and a width of about 50 mm was installed on the bottom of the embankment method.

  Furthermore, iron plates 17 and 18 for simulating underground steel wall bodies (sheet piles) were installed on this model ground. There are two installation positions, Case 1 in FIG. 2 and Case 2 in FIG. In Case 1, an iron plate 17 having a thickness of 2.3 mm was embedded in the compaction layer 12 by 150 mm in the center in the width direction of the embankment 1. The upper end of the iron plate 17 was the ground surface of the top edge 6 of the embankment 1. In Case 2, similarly, an iron plate 18 having a thickness of 1.6 mm was embedded in the central portion of the embankment 1 in the width direction into the liquefied layer 8 30 mm above the upper end of the compaction layer 12. The upper end of the iron plate 18 was 50 mm below the top end 6 of the embankment 1.

2. Experimental procedure The following three types of experiments were performed.
Experiment 1; Excitation test Assuming an earthquake, horizontal excitation was conducted assuming level 2 ground motion with the water levels on both sides of the embankment kept on the ground surface, and the behavior of the embankment was investigated. An excitation waveform is shown in FIG. This excitation waveform uses acceleration records (NS component) observed at the Kobe Ocean Meteorological Observatory during the 1995 Hyogoken-Nanbu Earthquake, but considering that the model dimensions are smaller than actual, the dominant frequency is The duration was adjusted to be about 5 Hz, which is higher than the actual level.

Experiment 2: Overflow experiment and post-overflow vibration experiment This scenario assumes a case where the river water level has risen above the planned water level due to unexpected torrential rain. The overflow level is increased by raising the water level on one side of the embankment 1 The behavior of the embankment 1 was investigated. Furthermore, assuming the most severe conditions in which aftershocks occur in the high water state after overtopping, we conducted an excitation test under the above-described excitation conditions while maintaining the water level after overtopping experiment, and investigated the behavior of embankment 1.

Experiment 3: Infiltration experiment First, assuming a high water condition that is not affected by an earthquake, the water level on the opposite side rises at a speed of 10 mm / min from the ground surface while keeping one water level at the ground surface position of the horizontal ground part. The osmotic flow rate in a steady flow state was measured. Next, assuming a case where high water is generated immediately after the impact of the earthquake, the infiltration experiment before excitation to the extent that overflow does not occur while the embankment is damaged in the aforementioned excitation experiment Similarly, the water level on one side was increased at a speed of 10 mm per minute, and the osmotic flow rate in a steady flow state was measured.

3. Experimental Results Experiment 1; Excitation Experiment In Case 2, the top edge 6 of the central portion of the embankment 1 was settled by about 50 mm. On the other hand, the iron plate 18 simulating the underground steel wall body 14 sunk about 10 mm but did not cause instability such as collapse, and maintained the height at the top.

  Moreover, in Case 1 and Case 2, the comparison of the response acceleration in the 300 mm position from the lower end of the earth tub 11 (position 50 mm above the lower end of the liquefaction layer 8) is shown in FIG. Moreover, the comparison of the response bending strain of the iron plate 17 (Case 1) and the iron plate 18 (Case 2) in the boundary part of the embankment layer (embankment 1) and the liquefaction layer 8 is shown in FIG. In Case 2, the response acceleration of the iron plate 18 was reduced. Moreover, although the plate | board thickness of the iron plate 18 used by Case2 was thinner, the bending strain which generate | occur | produced in the iron plate 18 was reduced compared with Case1. As these causes, since the liquefied layer 8 exists between the lower end of the iron plate 18 and the compaction layer 12, the ground is liquefied by the vibration, so that the seismic isolation effect is obtained and the compaction transmitted to the iron plate 18 is obtained. This is probably because the acceleration from the layer 12 was reduced.

  From this result, by making the sheet pile 13 into the structure not rooted in the support layer 9, in addition to shortening the root insertion length of the sheet pile 13, it is possible to reduce the necessary cross section, leading to rationalization of the structure. Indicated.

Experiment 2: Overflow experiment and post-overflow vibration experiment Next, in Case 2, when the water level on one side of the embankment was raised to cause overflow, the overflow water was on the high water level side where the water level was raised. From the bottom, the water overflows (from left to right in Fig. 3). If a river embankment is assumed, water will flow from the outside of the bank to the inside of the bank.

  The overflow water gradually eroded the embankment 1 inside the bank. However, since the iron plate 18 was arranged in the central portion of the embankment 1, the bank did not break, and water stored on the outside of the bank was prevented from flowing into the bank at once. Also, the iron plate 18 did not collapse even under conditions where the embankment inside the bank was exposed to erosion and was subject to uneven water pressure in a high water state.

Furthermore, for Case 2, an excitation experiment was performed with the water level maintained after the overflow experiment, assuming the most severe conditions in which aftershocks occur in the high water state after overflow.
The state at the time of excitation is in a state where there is a difference in the water level on both sides and the state of unbalanced load, and the embankment 1 inside the levee has collapsed due to the overtopping experiment, so passive resistance at the embankment 1 part cannot be expected. It has become. Therefore, although the conditions were very severe for the iron plate 18, the iron plate 18 did not collapse although the head of the iron plate 18 was displaced about 100 mm in the horizontal direction. Moreover, by ensuring the height of the upper end of the iron plate 18, the water stored on the outside of the bank was prevented from flowing into the bank. This is considered to be because after the excess pore water pressure raised by the vibration was dissipated, the liquefied layer also recovered as the ground rigidity and functioned as a layer supporting the sheet pile 13.

  From these results, even if the sheet pile 13 (underground steel wall body 14) has a structure that is not embedded in the support layer 9, the underground steel wall body 14 does not collapse, and the underground steel wall body. It was shown that the upper end height of 14 was secured and the dike function could be maintained.

Experiment 3; Penetration Experiment Table 1 shows a list of permeation flow rates before and after excitation in Case 1 and Case 2.

  In Case 1 in which the lower end of the iron plate 17 was rooted to the support layer 9 (consolidation layer 12), the permeation behavior was shown to go around the lower end of the iron plate 17 in the support layer 9 both before and after excitation. The permeation flow rate was about 0.3 (l / min) both before and after vibration, and the permeation characteristics did not change even after receiving the vibration history.

  On the other hand, Case 2 shows a permeation behavior that surrounds the liquefied layer 8 between the lower end of the iron plate 18 and the upper end of the support layer 9 (consolidation layer 12) both before and after vibration. Was about 1.1 (l / min), and after excitation was about 0.7 (l / min). The permeation flow rate of Case 2 was larger than that of Case 1 even after vibration. That is, the structure of Case 2 was able to reinforce the embankment 1 while ensuring a sufficient flow of permeation leading to the periphery of the embankment 1 without blocking the flow of permeate water than the structure of Case 1.

From this result, if it is set as the structure where the underground steel wall body 14 is not rooted to the support layer 9, the embankment 1 can be reinforced, ensuring the flow of groundwater. Therefore, it is not necessary to provide a water permeable hole etc. in the sheet pile 13, and the processing cost concerning opening can be reduced.
In addition, it is thought that the reason why the permeation flow rate decreased after the vibration in Case 2 was that the iron plate 18, which was fixed in the liquefied layer 8 by the vibration, sank about 10 mm. This is because, before vibration, there is a clearance of 30 mm between the lower end of the iron plate 18 and the support layer 9, and the water passage area penetrating the lower end of the iron plate 18 is about 2 at the initial stage because of sinking by about 10 mm by vibration. This is consistent with the fact that the osmotic flow rate decreased to about 2/3 after vibration.

<Specific embodiment>
(Inner depth of wall (sheet pile))
In the present invention, the underground steel wall body 14 (the sheet pile 13) is embedded in such a depth that it does not reach the support layer 9 and does not collapse even during an earthquake or overflow. A method for determining the penetration depth will be described below. Specific numerical values in the following description are those in the above experimental example.

  First, assuming a time of overflow, assume a state in which the embankment 1 on the inside of the embankment has disappeared from the state of the embankment 1 in FIG. 7 (a) as shown in FIG. 7 (b). In this state, as shown in FIGS. 8 (a) and 8 (b), the main earth pressure and the water pressure act on the underground steel wall body 14 from the embankment layer and the liquefied layer 8 on the outside of the bank, and the inside of the bank It is considered that passive earth pressure acts from the liquefied layer. Assuming the soil conditions in Table 2, when the penetration depth in the liquefied layer 8 is 220 mm (that is, the lower end of the sheet pile is 30 mm above the support layer), the horizontal force between the two is substantially balanced.

  As shown in the experimental example, even if the depth of the underground steel wall 14 does not reach the support layer 9, if the depth of the underground wall 14 is not reached the support layer 9, The collapse of the medium steel wall body 14 (the sheet pile 13) does not occur. The above-mentioned penetration depth is based on an experimental example. However, in actual construction, ground survey is conducted, and the main earth pressure and water pressure from the embankment layer and liquefaction layer 8 outside the bank are measured. It is possible to determine the depth of penetration that balances the horizontal force due to the horizontal force of the passive earth pressure from the liquefied layer 8 inside the bank.

  In this embankment reinforcement structure, the underground steel wall body 14 does not collapse during an earthquake or water overflow even if the underground steel wall body 14 is not embedded up to the support layer 9, and the embankment is underground. It is held by the steel wall 14. Therefore, even if an earthquake occurs at the time of flooding, the river becomes high after the earthquake, or the river overflows, the embankment 1 is prevented from being broken, and the underground steel wall body 14 is It is possible to prevent the water from flowing into the bank at a stretch.

Moreover, the underground steel wall body 14 can be shortened by not putting the underground steel wall body 14 up to the support layer 9. Further, in a state where the liquefied layer 8 exists between the lower end of the underground steel wall body 14 and the support layer 9, the liquefied layer 8 exhibits a seismic isolation effect during an earthquake.
Therefore, while the length of the sheet pile 13 used for the underground steel wall body 14 can be shortened, a cross section can be reduced and the steel material cost required for the underground steel wall body 14 can be reduced.

  As described above, in the state where the liquefied layer 8 exists between the underground steel wall body 14 and the support layer 9, it becomes possible to flow permeated water (groundwater) into the liquefied layer 8, Even if the steel wall body 14 is not made water permeable, the flow of ground water can be secured, and in order to make the underground steel wall body 14 water permeable, a through hole is provided in the sheet pile 13. This is not necessary, and the cost can be reduced.

  In addition, since the underground steel wall body 14 has a structure in which adjacent sheet piles 13 are joined by joints, there is a possibility that the respective sheet piles 13 may move up and down relative to each other when the ground liquefies during an earthquake. Therefore, by fixing the heads of the adjacent sheet piles 13 by welding or the like, the adjacent sheet piles 13 do not sink separately, and each sheet pile 13 sinks uniformly. Thereby, for example, when the top end 6 of the embankment 1 is used as a road for a vehicle for restoration work, an emergency vehicle, or the like after an earthquake, it can be used as a road relatively easily.

  FIG. 9 shows another embodiment of the underground steel wall body 14. As described above, the underground steel wall body 14a in FIG. 9 has a depth shallower than that of the support layer 9, and is deeply embedded to such a depth that the underground steel wall body 14 does not collapse at the time of an earthquake or water overflow. The first regions 14b and the second regions 14c rooted up to the support layer 9 are formed alternately as in the prior art. Furthermore, it is preferable that the upper end portion of the sheet pile 13 or the vicinity of the upper end portion is fixed to each other by welding or the like.

If it does in this way, the underground steel wall body 14a is supported by the 2nd area | region 14c rooted to the support layer 9, and the underground steel which has the 1st area | region 14b not rooted in the support layer 9 will be mentioned. The sinking of the wall-making body 14 can be suppressed.
The pitch (the length of the first region 14b) for providing the second region 14c in the extending direction of the embankment and the length of the second region 14c may be determined according to the degree of subsidence to be suppressed and the examination conditions. Needless to say, the smaller the second region 14c is, the more secure the flow is. Therefore, each 1st field is made longer than each 2nd field, for example, as a standard, long sheet pile 13a which constitutes 2nd field 14c every 10-20m of 1st field 14b along the extension direction of embankment 1 It is considered appropriate to provide one to several sheets.

The position in the width direction of the embankment 1 of the underground steel wall body 14 is arranged at a position where the earth pressure applied to both sides of the underground steel wall body 14 is balanced as a position in the width direction of the embankment. Is preferred.
When the underground steel wall bodies 14 are arranged in a row, in many embankments 1 that are generally symmetric in the width direction, the left and right sides of the underground steel wall bodies 14 are normally disposed if arranged at the center in the width direction of the embankment 1. Thus, the earth pressure generated in the sheet pile 13 can be balanced. The underground steel wall body 14 may be provided near the shoulder 5 of the embankment 1, but the earth pressure of the embankment 1 acts from one side of the underground steel wall body 14 and the opposite side is the underground steel wall body. Since the earth pressure from the side which supports 14 cannot be expected, the necessary cross section of the sheet pile 13 becomes large and the necessary cost may increase so that the horizontal displacement of the sheet pile 13 does not occur at the time of an earthquake.

  However, when roads are laid on the top 6 of the embankment 1 and it is necessary to take countermeasures without obstructing traffic, the underground steel wall 14 is near the shoulder 5 of the embankment 1 It is possible to take measures without blocking the road traffic on the top 6.

  The underground steel wall bodies 14 may be in two or more rows. For example, as shown in the modified example of FIG. 10, a total of two rows of underground steel wall bodies 14 may be provided near both shoulders 5. Good. Each underground steel wall body 14 is rooted in the liquefied layer 8 above the support layer 9 without being rooted to the support layer 9 similarly to the above-mentioned underground steel wall body 14. . Moreover, the underground steel wall body 14 is embedded to the depth which the liquefied layer 8 does not collapse as mentioned above. Reference numeral 20 denotes a connecting member such as a tie rod, which connects two rows of underground steel wall bodies 14 and is arranged at predetermined intervals along the length direction of the underground steel wall bodies 14. .

  Moreover, in the reinforcement structure of the embankment 1, in addition to the underground steel wall body 14 provided in the range of the substantially top end 6 of the embankment 1, further embankment is carried out like the modification shown in FIG. 11 and FIG. It is preferable to arrange the underground steel wall body 21 at the left and right nose butt 2 portions of 1 or the nose butt 2 portion of the embankment 1 outside embankment.

  By disposing the underground steel wall body 21 in the portion of the hoop 2 of the embankment 1, the settlement of the embankment 1 at the time of an earthquake can be suppressed, and the subsurface steel wall body 21 is the hull of the embankment 1 outside the bank. If it is arranged in the portion 2, it also serves as a measure against base water leakage of the embankment 1. In some existing dikes, underground steel walls are already provided on the embankment of the embankment from the viewpoint of measures for base water leakage and embankment settlement during an earthquake. If there is such an existing levee, an effective and rational dyke disaster countermeasure can be achieved by placing the above-mentioned underground steel wall in the range of the top.

  In addition, it is preferable to take measures against drainage such as installing a drain material 15 on the bottom edge 2 corresponding to the inside of the bank in order to prevent osmotic damage.

  The sheet pile 13 used in the present invention is a hat-shaped steel sheet pile, a U-shaped steel sheet pile, a Z-shaped steel sheet pile, a linear steel sheet pile, a steel pipe sheet pile, or a combined steel sheet pile obtained by stiffening a steel sheet pile with an H-shaped steel or the like. Can be used.

1 Embankment 2 Method bottom 6 Top edge 8 Liquefaction layer 9 Support layer 12 Compaction layer (support layer)
13 sheet pile (steel sheet pile and / or steel pipe sheet pile)
14, 14a Underground steel wall body 14b First region 14c Second region

Claims (7)

Within the range of the approximate top edge of the continuous embankment, underground steel wall bodies made of steel sheet piles and / or steel pipe sheet piles are provided in one or more rows along the continuous direction of the embankment,
Reinforcement of embankment characterized in that the underground steel wall body has a depth shallower than the support layer and is deeply embedded so that the underground steel wall body does not collapse during an earthquake or a flood. Construction. The underground steel wall body is provided in a row along the continuous direction of the embankment,
When the underground steel wall body is assumed to have no embankment on one side partitioned by the underground steel wall body, earth pressure and water pressure acting from both sides of the underground steel wall body, respectively. 2. The embankment reinforcing structure according to claim 1, wherein the embedding structure has a depth equal to or less than a depth at which the horizontal force is balanced, and is embedded to a position above the support layer. Within the range of the approximate top edge of the continuous embankment, underground steel wall bodies made of steel sheet piles and / or steel pipe sheet piles are provided in one or more rows along the continuous direction of the embankment,
The underground steel wall has a depth that is shallower than the support layer and is deeply embedded to a depth at which the underground steel wall does not collapse during an earthquake or a flood, and the support layer And second regions that are rooted in are alternately formed,
The length of the extending direction of the embankment of each 1st area | region is longer than the length of the extending direction of the embankment of each 2nd area | region, The reinforcement structure of the embankment characterized by the above-mentioned. The underground steel wall body is provided in a row along the continuous direction of the embankment,
The first region of the underground steel wall body acts from both sides of the underground steel wall body, assuming that there is no embankment on one side partitioned by the underground steel wall body. 4. The embankment reinforcing structure according to claim 3, wherein the structure is embedded to a position below a depth at which horizontal forces due to earth pressure and water pressure are balanced and to a position above the support layer.   The said underground steel wall body is arrange | positioned in the position where the earth pressure concerning both sides of this underground steel wall body equilibrates as a position of the width direction of embankment at normal time. 5. The embankment reinforcement structure according to any one of 4 above.   6. The embankment reinforcing structure according to claim 1, wherein upper ends of the steel sheet piles and / or the steel pipe sheet piles adjacent to each other are fixed to each other.   The embankment reinforcing structure according to any one of claims 1 to 6, wherein an underground steel wall is provided on at least one of the embankment of the embankment.

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