JP7240667B2 - Reinforced soil structure and soil structure reinforcement method - Google Patents

Description

The present invention is a technology related to soil structures such as embankments, seawalls, and dikes in rivers, coasts, and reservoirs. The present invention relates to a soil structure reinforced with a "permeability improver" having a higher permeability coefficient than the soil structure itself, and a method therefor.

It has been pointed out that the construction infrastructure (hereinafter referred to as "construction infrastructure"), which was intensively developed during the high economic growth period, has already deteriorated considerably. In 2014, the “Proposals for full-scale implementation of measures to deal with aging roads (Social Infrastructure Development Council)” were compiled. It will lead to a fatal situation related to the equipment," he warned, strongly advocating the importance of maintenance of construction infrastructure. Against this background, the national government issued a ministerial ordinance to partially revise the Enforcement Regulations of the Road Act, and issued a regular ordinance indicating specific inspection methods for construction infrastructure, points to focus on major deformations, and photographs of judgment cases. We have established inspection guidelines.

Typical construction infrastructures include structures such as dams and bridges, as well as coastal embankments, river embankments, and seawalls. The total length of Japan's coastline is about 35,000 km, the sixth longest in the world. It is also an extremely important construction infrastructure.

Coastal levees are basically planned and constructed in accordance with the Coastal Law (Law No. 101 of May 12, 1956). This coastal law was enacted in 1956, triggered by Typhoon No. 13 in September 1953, which caused extensive damage mainly in Aichi Prefecture. In other words, a considerable amount of time has already passed since many coastal levees were built, and as of 2010, it is said that about 40% of the facilities have been in place for 50 years or more. Therefore, inspections for diagnosing the deterioration of coastal embankments are becoming more and more important.

Embankments and seawalls on rivers and coasts (hereinafter collectively referred to as "soil structures") are generally constructed by embankment. A right-angled cross section) is generally trapezoidal, and slopes are formed on the side of the embankment where the river and the sea are located (hereinafter referred to as the "front side") and on the land side of the embankment (hereinafter referred to as the "back side"). be.

Since the soil structure is an embankment, scouring occurs on the back side due to scouring and overflow water, especially near the toe of the slope (lower end of the slope) on the front side, piping that occurs on the back side of the soil structure, seepage water Phenomena such as deterioration of the strength of the embankment body (that is, the embankment body) (hereinafter referred to as “seepage failure”) are always a matter of concern. In addition, since many earthen structures have been completed for a considerable amount of time, many of them have already been scoured, piped, or seepage failure has progressed.

Depending on local conditions, soil structures may be built on soft layers such as permeable ground made of sand or sandy soil, or ground containing liquefaction layers. Due to the liquefaction of the foundation ground, there is a risk that the soil structure itself will also become unstable.

Reinforcement measures will be implemented for soil structures that have suffered severe scouring. Conventionally, as a method of reinforcing soil structures, the mainstream method was to form structures such as water-blocking soil improvement materials and steel sheet piles on the outside of the slope on both the front and back sides (that is, on the outside of the embankment). . However, in order to form this soil improvement body, a space for arranging relatively large-scale construction machines such as deep mixing treatment using a three-point pile driver is required, so considering the target length, considerable cost and There is also the problem that it requires a long construction period and cannot be easily commercialized.

Furthermore, in the conventional construction method of forming a ground improvement material with water cutoff properties on both the front and back sides, although the water cutoff performance is improved, the drainage function is significantly reduced. It is also possible to point out the problem that permeated water is stagnant in the water, and as a result, there is a risk of permeation failure. In particular, it is known that during an earthquake, seepage water within the levee body causes liquefaction of the levee body itself, and in this case deformation of the levee becomes prolonged.

Therefore, in Patent Document 1, by laying a shear reinforcement work made of porous concrete at the bottom of the slope on the back of the river so that it is integrated with the levee body, the infiltrated water in the levee body is drained from the back side of the river, and the strength of the levee body is reduced. We are proposing a technology to prevent

Japanese Patent Application Laid-Open No. 2006-200249

As mentioned above, the conventional technology for reinforcing soil structures has the problem that infiltrating water is retained in the cut-off wall due to the formation of a water-stopping ground improvement body on both the front and back sides. There is a problem that it cannot be easily commercialized because it requires Furthermore, since the ground improvement body is formed outside the levee body on both the front and back sides, the strength of the levee body itself does not increase, and there is also the problem that it is not possible to prevent settlement due to slipping or liquefaction inside the levee body during an earthquake. be. In Patent Document 1, by laying a shear reinforcement work made of porous concrete, the drainage function from the back side of the river is secured and the embankment body on the back side of the river is shear reinforced. It cannot be prevented, and since it does not reinforce the embankment on the front side of the river, it cannot be expected to have a reinforcing effect against earthquakes.

The object of the present invention is to solve the problems of the prior art, that is, to prevent scouring on the front and back sides, piping that occurs on the back side, and seepage failure of the levee body, and further An object of the present invention is to provide a soil structure capable of preventing subsidence due to slippage and liquefaction, and a method therefor. As a result, the groundwater in the cut-off wall can be quickly drained, and the reduction in strength of the embankment can be prevented.

The present invention constructs a "water stoppage improving body" with relatively low water permeability on the front side of the bank body and constructs a "water permeability improving body" with relatively high water permeability on the back side of the bank body. , scouring on the front and back sides, piping that occurs on the back side, and prevention of percolation failure of the embankment.

The reinforced soil structure of the present invention has a front side slope and a back side slope, and further includes a "main body" and a "water stop improving body" having lower water permeability than the main body, and water permeability than the main body. It is equipped with a "permeability improver" with high permeability. The water stop improving body is mainly made of cement material and is formed on a part of the front slope including the bottom of the slope, while the water permeability improving body is mainly made of cement material and is formed on the back slope including the bottom of the slope. formed in part of

In the reinforced soil structure of the present invention, the water cut-off improving body and the permeability improving body are also formed in a part of the ground outside the slope surface (that is, outside the bank body) beyond the toe of the slope. can also

The reinforced earthen structure of the present invention can also utilize a precast concrete water stop improving body or water permeability improving body.

The reinforced soil structure of the present invention can also be one in which the water stop improving bodies and the water permeability improving bodies are intermittently formed at intervals in the extension direction (the axial direction of the bank body).

The soil structure reinforcement method of the present invention is a method for reinforcing an existing soil structure having a front side slope and a back side slope, and is a method comprising a step of forming a water stop improving body and a step of forming a water permeability improving body. be. Among these, in the step of forming a water stop improving body, a "water stop improving body" having a lower water permeability than the soil structure (bank body) is formed on a part of the front slope surface including the toe of the soil structure. . On the other hand, in the water permeability improving body forming step, a water permeability improving body having a higher water permeability than the soil structure (bank body) is formed on a part of the back slope surface including the toe of the soil structure.

The soil structure reinforcement method of the present invention uses a mechanical agitation method, a high-pressure injection agitation method, or a chemical injection method to improve the ground of the soil structure with a cement-based solidification material, thereby forming a waterproof improved body. can also be

The soil structure reinforcement method of the present invention can also be used as a method of forming a water permeability improving body by forming a solidified body of underwater inseparable porous concrete.

The reinforced earth structure and earth structure reinforcement method of the present invention have the following effects.
(1) By forming a "water stop improving body" on a part of the front side of the slope including the toe of the bank, it is possible to prevent scouring on the front side, piping that occurs on the back side, and seepage failure of the bank. can be done.
(2) By forming a "permeability improver" on a part of the back side of the slope including the toe of the cut-off wall, it is possible to drain permeated water from inside the cut-off wall, thereby preventing scouring on the back side. It is possible to prevent the shear strength of the embankment from decreasing during an earthquake and avoid liquefaction damage.
(3) By forming a water stop improving body on the front side of the embankment and a water permeability improving body on the back side, a case where the improved body is formed only on either the front side or the back side, or a water stop improvement on both the front side and the back side It is possible to reduce the subsidence of the embankment during an earthquake, compared to a case with a body.

Cross-sectional view of general soil structures such as embankments and seawalls in rivers, coasts, etc. 1 is a cross-sectional view showing a reinforced soil structure of the present invention; FIG. FIG. 4 is a cross-sectional view showing the reinforced soil structure of the present invention when the water level of the river rises; FIG. 4 is a cross-sectional view showing a reinforced soil structure provided with a water-stopping improver and a water-permeability improver formed to protrude to the outside of the slope; (a) is a front view showing a reinforced earth structure with intermittently formed water stoppage improvers, and (b) is a front view showing a reinforced earth structure with a series of water stoppage improvers. figure. FIG. 2 is a construction flow diagram showing main steps of the soil structure reinforcement method of the present invention. A model diagram showing five cases analyzed. (a) is a graph showing the analysis results for each case, and (b) is a table showing the analysis results for each case.

An embodiment of a reinforced soil structure and a soil structure reinforcement method according to the present invention will be described with reference to the drawings.

1. Definitions Before describing examples of embodiments of the present invention, definitions of terms used herein will be given first.

(front side and back side)
FIG. 1 is a cross-sectional view of a general soil structure Dm such as an embankment or a seawall in a river, coast, or the like. A typical earthen structure Dm is an embankment constructed along a river or coast (in the depth direction of the paper surface in the figure) with a fairly long extension, and as shown in this figure, its cross-sectional shape is roughly trapezoidal. It is often done. The soil structure Dm is to block the inundation from the river and the sea. It separates. For the sake of convenience, the side of the embankment will be referred to as the "front side" and the side of the embankment will be referred to as the "back side."

(front side slope and back side slope)
As described above, since the cross-sectional shape of the soil structure Dm is generally trapezoidal, slope surfaces are formed on both side surfaces (left and right side surfaces in the figure). In order to distinguish between the left and right slopes, the slope formed on the front side of the soil structure Dm is here referred to as the "front slope Sf" for the sake of convenience, and the slope formed on the back side of the soil structure Dm. The surface will be referred to as "back side slope surface Sr". Similarly, the bottom of the seam (also referred to as the top of the seam) that is the lower end of the front seam Sf is referred to as the "front seam Tf", and the bottom of the seam that is the lower end of the back seam Sr is the "back seam". Tr”.

2. Reinforced Soil Structure Next, the reinforced earth structure of the present invention will be described in detail with reference to the drawings. The soil structure reinforcement method of the present invention is, so to speak, a method of constructing the reinforced soil structure of the present invention. A structure reinforcement method will be described. For the sake of convenience, a reinforced soil structure that functions as a river embankment will be described here, but the reinforced soil structure of the present invention is not limited to a river embankment, but can also function as a coastal embankment, a seawall, an erosion control dam, or a dam. It can also be used as a soil structure with

(overall structure)
FIG. 2 is a cross-sectional view of the reinforced earthen structure 100 of the present invention. As shown in this figure, a reinforced soil structure 100 includes a main body 110 located in the central part of the cross section, a water stop improving body 120 formed on the front side, and a water permeability improving body 130 formed on the back side. It is formed. It is preferable that the main body 110 is mainly formed of embankment material, and the water cut-off improver 120 and the permeability improver 130 are mainly formed of a cement-based material. Moreover, the water stopping improving body 120 is formed on a part of the front side slope surface Sf including the front side slope bottom Tf, and its water permeability is lower than that of the main body portion 110 (that is, the water stopping property is high). On the other hand, the water permeability improving body 130 is formed on a part of the back side slope surface Sr including the back side slope Tr, and has a higher water permeability than the main body portion 110 (that is, a higher drainage property).

As shown in FIG. 2, the body portion 110, the water blocking improver 120, and the water permeability improving body 130 each have an inclined surface. A series of front-side slopes Sf are formed by , and a series of back-side slopes Sr are formed by the inclined surface (back side) of the main body 110 and the sloped surface of the water permeability improver 130 . As a result, the reinforced soil structure 100 of the present invention has a cross-sectional view of is roughly trapezoidal.

The reinforced soil structure 100 of the present invention can be constructed as a new structure, or can be constructed by reinforcing an existing soil structure Dm. When constructing a new structure, the main body 110, the water blocking improver 120, and the water permeability improver 130 are installed and constructed so as to have the planned shape and dimensions. On the other hand, when reinforcing the existing soil structure Dm, the water stop improving body 120 is constructed on a part of the front side of the soil structure Dm, and the water permeability improving body is constructed on a part of the back side of the soil structure Dm. 130 is constructed, and the remaining portion of the soil structure Dm is used as the main body 110. As shown in FIG.

(Improved water stoppage)
As shown in FIG. 3, the water cut-off improving body 120 has a function of suppressing water permeating into the main body 110 when the water level of the river rises, and a function of suppressing water that permeates the main body 110 when the water level of the river rises. It has a function of preventing scouring (especially scouring near the toe of slope Tf on the front side) when it is in a state (the state of FIG. 2). Therefore, the water stopping improving body 120 is formed on a part of the front side slope surface Sf including the front side slope bottom Tf, and is formed so that its water permeability is lower than that of the main body portion 110 (that is, the water stopping property is higher). Moreover, the waterproof improving body 120 is preferably made mainly of a cement-based material so as to function as a reinforcing member in the event of an earthquake, that is, to have considerable strength (shear strength and bending strength).

The water stopping improving body 120 is designed so as to satisfy predetermined water permeability (water stopping) and strength, or considering workability. In particular, regarding water permeability and strength, it is necessary to design the reinforced soil structure 100 so that it does not undergo abnormal subsidence or deformation, or that the main body 110 does not liquefy even during heavy rains or earthquakes. desirable. Specifically, the river water level assumed during heavy rain and the load at the time of earthquake are given as conditions, and the water permeability and strength of the water cutoff improvement body 120 are designed based on the results obtained by numerical analysis (for example, FEM analysis). do it.

In forming the water cut-off improvement body 120, it can be formed by performing ground improvement on a part of the existing soil structure Dm (or the main body part 110). In this case, a part of the soil structure Dm (or main body 110) may be improved with a cement-based solidifying material by a mechanical agitation method, a high-pressure injection agitation method, or a chemical injection method. Alternatively, the water stopping improving body 120 can be designed as concrete, and the water stopping improving body 120 can be formed by placing a solidified body of cast-in-place concrete or a solidified body of precast concrete at a predetermined position.

(Permeability improver)
As shown in FIG. 3, the water permeability improving body 130 has a function of draining water that has penetrated into the main body 110 when the water level of the river rises, and a function of scouring (especially the back side slope Tr It has a function to prevent scouring in the vicinity. Therefore, the water permeability improving body 130 is formed on a part of the back slope surface Sr including the back slope bottom Tr, and is formed so that the water permeability thereof is higher than that of the main body portion 110 (that is, the drainage property is high). Moreover, the water permeability improving body 130 is preferably made mainly of a cement-based material so as to function as a reinforcing member in the event of an earthquake, that is, to have considerable strength (shear strength and bending strength). In order to allow the water drained from the water permeability improver 130 to flow to a predetermined position, a drainage ditch 140 shown in FIG.

The water permeability improving body 130 is designed so as to satisfy predetermined water permeability (drainability) and strength, or considering workability. In particular, regarding water permeability and strength, the reinforced soil structure 100 should be designed so as not to cause abnormal subsidence or deformation, or to prevent liquefaction damage to the main body 110 even during heavy rains or earthquakes. is desirable. Specifically, the river water level assumed during heavy rain and the load at the time of earthquake are given as conditions, and the permeability and strength of the permeability improving body 130 are designed based on the results obtained by numerical analysis (for example, FEM analysis). do it. In addition, as shown in FIG. 3, the water permeability improving body 130 is divided into a portion A located on the ground, a portion B located in the weak layer, and a portion C located in the support layer. The A part, the B part, and the C part can also be designed with materials having different physical properties (strength, water permeability, etc.). For example, in terms of slip stability, it is possible to design under the condition that the lower layer has higher strength, or to increase the piping resistance of the upper sand layer, the permeability improver 130 (B section in FIG. 3) located in the upper sand layer ) can also be designed under the condition that the hydraulic conductivity of ) is lower than that of the toe of the slope.

The permeability improving body 130 can be formed by installing a solidified body made of concrete. In this case, the solidified body can be installed with cast-in-place concrete, or the solidified body of precast concrete can be installed. However, since the water permeability improving body 130 is required to have appropriate water permeability (drainability), it is desirable to use a solidified body made of porous concrete (hereinafter referred to as "porous concrete"). Further, since the water permeability improving body 130 has a drainage function, it is preferable to use a solidified body made of concrete that is inseparable in water so that the cement component (mortar component) does not flow out during drainage.

When designing the mixture of porous concrete that is inseparable in water, the grain size of the aggregate should be selected to prevent clogging, that is, to secure an appropriate porosity, and to provide inseparability in water. In addition to adding an underwater non-separating material, it is preferable to add a high performance water reducing agent in consideration of workability.

(Formation range of improved body)
The reinforced soil structure 100 shown in FIGS. 2 and 3 is built on a weak layer (a permeable ground made of sand or sandy soil, a liquefaction layer, etc.) deposited on the support layer. Therefore, the water blocking improver 120 and the water permeability improver 130 shown in this figure are formed so as to penetrate the soft layer and further penetrate into the support layer. Of course, depending on the strength of the soft layer, the water stop improving body 120 and the water permeability improving body 130 can be formed so as to be embedded only in the soft layer without being embedded in the support layer, or they can be embedded in the support layer. The water stop improving body 120 and the water permeability improving body 130 can also be formed so as to be placed on the support layer without the coating.

Also, the water stop improving body 120 and the water permeability improving body 130 may be partially formed outside the front side slope Sf and the back side slope Sr. Specifically, as shown in FIG. 4, it is located beyond the front side slope Sf and the back side slope Sr, that is, on the river side of the front side slope Tf (left side in the figure), or on the opposite side of the river from the back side slope Tr. (Right side in the drawing), and a part of the water stop improving body 120 and the water permeability improving body 130 is formed under the ground (soft layer and support layer) in the overhanging range. A comparison of FIGS. 2 and 4 reveals that the water-blocking improving body 120 and the water-permeable improving body 130 shown in FIG. 4 are formed so as to be large only at the portions protruding from the front side slope Sf and the back side slope Sr. Therefore, although the construction period and cost for constructing the reinforced soil structure 100 increase, the scouring prevention function in the vicinity of the front side slope Tf and the rear side slope bottom Tr and the reinforcement function in the event of an earthquake are improved. Therefore, the water stop improving body 120 and the water permeability improving body 130 of the type shown in FIG. 4 may be appropriately designed according to the situation.

As already mentioned, a general earthen structure Dm is constructed with a considerably long extension along a river or coast. Similarly, the reinforced earthen structure 100 of the present invention is also better constructed in fairly long extensions (in the depth direction of the paper in FIGS. 2 and 4) along rivers and coasts. In this case, the water-blocking improver 120 and the water-permeable improver 130 are naturally formed with a considerable extension, but as shown in FIG. can also be formed. FIG. 5 is a front view showing the reinforced earthen structure 100 when the front slope Sf (back slope Sr) is viewed from the front. 4) water stop improving bodies 120 and water permeability improving bodies 130 are intermittently formed, and in FIG. is formed.

3. Earth Structure Reinforcement Method Next, the soil structure reinforcement method of the present invention will be described with reference to FIG. The soil structure reinforcement method of the present invention is a method of constructing the reinforced soil structure 100 described so far, so explanations overlapping with the contents described in the reinforced soil structure 100 are avoided. Only the contents specific to the soil structure reinforcement method of the present invention will be explained. That is, the contents not described here are the same as those described in "2. Reinforced soil structure" including the description of "1. Definition".

FIG. 6 is a construction flow diagram showing main steps of the soil structure reinforcement method of the present invention. First, preparatory work is carried out, such as surveying to indicate the positions for forming the water stoppage improving body 120 and the water permeability improving body 130, carrying in necessary equipment and arranging them at predetermined positions, and confirming the construction procedure for the day. .

When the preparations are complete, a water cut-off improving body 120 is formed on part of the front side of the existing soil structure Dm. Specifically, using a mechanical agitation method, a high-pressure injection agitation method, or a chemical injection method, ground improvement is performed on the soil structure Dm with a cement-based solidification material (Step 10), thereby forming the waterproof improvement body 120. do.

On the other hand, a permeability improver 130 is formed on part of the back side of the existing soil structure Dm. Specifically, the water permeability improver 130 is formed by placing a solidified body made of porous concrete that is inseparable in water at a predetermined position (Step 20). At this time, if the embankment material of the relevant portion of the soil structure Dm is to be removed to form the permeability improver 130, appropriate earth retaining work will be carried out according to the situation at the site, such as when the excavation height is above a predetermined height. It is better to use them together before carrying out the removal work. After forming the water permeability improver 130, the drain groove 140 shown in FIG. 2 can be installed along the extension direction of the water permeability improver 130.

Either the step of forming the water blocking improver 120 or the step of forming the water permeability improver 130 can be performed first, or both steps can be performed simultaneously (in parallel). . When the water stoppage improving body 120 and the water permeability improving body 130 are formed in the entire planned range, clean up is performed and the work is finished.

4. Results of Analysis The results of analysis performed by the inventors of the present application to confirm the effects of the present invention will be described below. FIG. 7 is a model diagram showing five cases in which the analysis was performed, and FIG. 8 is a result diagram showing the analysis results for each of these cases.

First, referring to FIG. 7, the five cases in which this analysis was performed will be described. FIG. 7(a) shows a case in which no countermeasures are taken for the existing soil structure Dm (hereinafter referred to as "case without countermeasures"), and FIG. 7(b) shows A case in which a water cut-off improving body 120 is formed on the front side (hereinafter referred to as “case of countermeasure 1”), FIG. Hereinafter referred to as "measure 2 case"), and FIG. 7(d) shows a case in which water cut-off improvement bodies 120 are formed on the front and back sides of the existing soil structure Dm (hereinafter referred to as "measure 3 case"). ), FIG. 7(e) shows a case of the present invention in which a water cut-off improving body 120 is formed on the front side of an existing soil structure Dm and a water permeability improving body 130 is formed on the back side (hereinafter referred to as "measure 4 case"). is. As shown in FIG. 7, the analysis is performed under the condition that the soft layer is a sand layer (liquefaction layer) and the support layer is a cohesive soil layer.

The river water level shown in the figure was given as a condition, and further 20 seconds of seismic motion was given, and the FEM analysis was performed for each of the five cases shown in FIG. As a result, as shown in Fig. 8(a), all 5 cases began to subside when seismic motion occurred, and all 5 cases showed maximum subsidence when the seismic motion ended. Looking at Fig. 8(b) showing the maximum amount of settlement, it can be seen that the case without countermeasures shows the largest amount of settlement (86 cm), and the case of countermeasure 4 shows the smallest amount of settlement (34 cm). Here, in cases where a large amount of subsidence is shown, it is presumed that liquefaction has occurred in the main body 110. On the other hand, in the present invention (case of measure 4), the amount of subsidence can be suppressed, that is, the foundation ground It is possible to reduce the subsidence damage of the embankment due to liquefaction.

Also, looking at the settlement reduction rate in FIG. 8B, the settlement reduction rate in the case of Measure 1 in which the water stop improving body 120 is formed on the front side is 15%, and the countermeasure in which the water permeability improving body 130 is formed on the back side The subsidence reduction rate in case 2 is 20%. In other words, it can be seen that the subsidence reduction rate (61%) of the case of Measure 4 is larger than the sum of both subsidence reduction rates (15+20=35%). That is, the present invention (case of measure 4) can expect an effect more than simply adding the effect of the case of measure 1 alone and the effect of the case of measure 2 alone. It can be understood that the water permeability improver 130 exhibits a greater effect by organically functioning with each other.

The reinforced soil structure and soil structure reinforcement method of the present invention are used for soil structures such as river embankments, coastal embankments, seawalls, sabo dams and dams where water remains on one side (front side). be able to. According to the present invention, it is possible to effectively reinforce coastal embankments and river embankments, that is, considering that it contributes to the extension of the life of construction infrastructure, the present invention is not only industrially applicable but also socially useful. It can be said that this is an invention that can be expected to make a significant contribution.

100 Reinforced Soil Structure 110 Body Part (of Reinforced Soil Structure) 120 Water Cutoff Improvement (of Reinforced Soil Structure) 130 Permeability Improvement (of Reinforced Soil Structure) 140 (Reinforcement Drainage ditch Dm Earthen structure Sf Front side slope Sr Back side slope Tf Front side slope bottom Tr Back side slope bottom Gp Gap

Claims (7)

In a soil structure built on a support layer and flooded on the front side ,
comprising a main body, a water stoppage improving body having lower water permeability than the main body, and a water permeability improving body having higher water permeability than the main body,
The water blocking improver is mainly made of a cement-based material and is formed on a part of the slope on the front side including the bottom of the slope,
The water permeability improving body is mainly made of a cement-based material and is formed on a part of the back side slope including the bottom of the slope,
The permeability improver is embedded in a support layer,
A reinforced soil structure characterized by: built on a soft layer deposited on a support layer,
The water permeability improving body has different shear strengths and/or bending strengths in the part located on the ground, the part located in the soft layer, and the part located in the support layer, and the shear strength and/or the bending strength increase in the lower layers. big,
A reinforced earth structure according to claim 1, characterized in that: built on a soft layer deposited on a support layer,
The water permeability improving body has different water permeability between the part located on the ground and the part located in the soft layer, and the water permeability of the part located in the soft layer is higher than the water permeability of the part located on the ground.
A reinforced earth structure according to claim 1, characterized in that: The water permeability improving body is made of precast concrete,
A reinforced soil structure according to any one of claims 1 to 3, characterized in that: A method for reinforcing an existing soil structure constructed on a support layer and flooded on the front side , comprising the steps of:
a step of forming a water stoppage improver having a lower water permeability than the soil structure on a portion of the front slope surface including the toe of the soil structure;
a water permeability improver forming step of forming a water permeability improver having higher water permeability than the soil structure on a part of the back slope surface including the toe of the soil structure.
In the water permeability improving body forming step, the water permeability improving body is formed so as to be embedded in the support layer.
A soil structure reinforcement method characterized by: The earthen structure is built on a soft layer deposited on a support layer,
Of the water permeability improving body, the portion located on the ground, the portion located in the weak layer, and the portion located in the support layer have different shear strengths and / or bending strengths, and the lower layers have shear strengths and bending strengths. / Or further comprising a step of designing so that the bending strength is increased,
In the water permeability improving body forming step, the water permeability improving body having higher shear strength and/or bending strength is formed in lower layers.
The method for reinforcing a reinforced soil structure according to claim 5, characterized in that: The earthen structure is built on a soft layer deposited on a support layer,
Of the water permeability improving body, the part located on the ground and the part located in the soft layer have different water permeability, and the part located in the soft layer is higher than the water permeability of the part located on the ground. Further comprising a step of designing to increase water permeability,
In the water permeability improving body forming step, the water permeability improving body is formed so that the water permeability of the portion located in the soft layer is higher than the water permeability of the portion located on the ground.
The method for reinforcing a reinforced soil structure according to claim 5, characterized in that:

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