JP7699500B2 - Reinforced earth structure and method for reinforcing earth structure - Google Patents

Description

This invention relates to technology related to earth structures such as levees, seawalls, and embankments in rivers, coasts, and reservoirs, and more specifically to an earth structure reinforced with a "water-stopping improvement body" that has a lower hydraulic conductivity than the earth structure itself and a "permeable improvement body" that has a higher hydraulic conductivity than the earth structure itself, and a method for constructing the same.

It has been pointed out that the construction infrastructure (hereafter referred to as "construction infrastructure"), which was developed intensively during the period of high economic growth, is already showing signs of considerable deterioration. In 2014, the "Recommendations for Full-Scale Implementation of Measures to Counter Aging Roads (Council for Social Capital Development)" was compiled, which, citing the example of the Sasago Tunnel in 2012, sounded a warning that "in the near future, this will lead to fatal incidents involving human lives and social facilities, such as the collapse of bridges," and strongly advocated the importance of maintaining and managing construction infrastructure. Against this background, the national government issued a ministerial ordinance amending part of the Road Act Enforcement Regulations, and has formulated regular inspection guidelines that show specific construction infrastructure inspection methods, areas to look for in major abnormalities, and photographs of case studies.

Representative examples of construction infrastructure include structures such as dams and bridges, as well as coastal levees, river levees, and seawalls. Japan's total coastline is approximately 35,000 km long, making it the sixth longest in the world, and coastal levees are naturally constructed in necessary locations such as coastal conservation areas. Not only do they function well, but they are also extremely important construction infrastructure due to their enormous length.

Coastal levees are basically planned and constructed in accordance with the Coast Act (Act No. 101 of May 12, 1956). This Coast Act was enacted in 1956, prompted by Typhoon No. 13 in September 1953, which caused devastating damage mainly in Aichi Prefecture. This means that many coastal levees have been in use for a considerable amount of time since they were constructed, and as of 2010, it is said that approximately 40% of the facilities were in use for more than 50 years. For this reason, inspections to diagnose the deterioration of coastal levees are becoming increasingly important.

Embankments and tide barriers on rivers and coasts (hereafter collectively referred to as "earth structures") are generally constructed by filling the soil, and their cross-sectional shape (the shape when viewed from a cross section perpendicular to the extension direction of the embankment) is roughly trapezoidal, with slopes formed on both the side outside the embankment where the river or sea is (hereafter referred to as the "front side") and the side inside the embankment (hereafter referred to as the "back side"), and a flat surface (hereafter referred to as the "top surface") is formed on the top (the position corresponding to the upper base of the trapezoid).

Because the earth structure is an embankment, there are always concerns about phenomena such as scouring, particularly near the bottom end of the front slope (the so-called toe of the slope), scouring on the back side of the earth structure due to overflow water, piping on the back side of the earth structure, and deterioration of the strength of the embankment body (i.e., the embankment) due to seepage water (hereafter referred to as "seepage failure"). Moreover, since many earth structures have been completed a considerable amount of time ago, it is easy to predict that scouring, piping, and seepage failure have already progressed in some places.

Depending on the local conditions, earth structures may be built on soft layers, such as permeable ground made of sand or sandy soil, or ground containing a liquefaction layer. In such cases, there is even a risk that the earth structure itself may become unstable due to liquefaction of the foundation ground during an earthquake.

Normally, when severe scouring occurs in an earth structure, reinforcement measures are implemented. Conventionally, the mainstream method for reinforcing earth structures has been to form structures such as water-stopping ground improvement bodies or steel sheet piles on the outside of the slope (i.e. the outside of the embankment) on both the front and back sides. However, forming these ground improvement bodies requires relatively large construction machinery, such as a three-point pile driver used in deep mixing treatment, which requires considerable costs (rentals, etc.) and a considerable amount of space to place the construction machinery. Considering the length of the target earth structure, considerable construction costs and construction time are required, making it difficult to commercialize.

Furthermore, in the conventional method of forming water-stopping ground improvement bodies on both the front and back sides, although water-stopping properties are improved, drainage functions are significantly reduced. Therefore, once seawater or river water has penetrated into the embankment, the seeping water will remain inside the embankment, which may result in seepage failure. In particular, it is known that in earthquakes, the seeping water inside the embankment can cause liquefaction of the embankment itself, which can lead to long-term deformation of the embankment.

Therefore, Patent Document 1 proposes a technology to form a "water-stopping improvement body" mainly made of cement-based materials on a portion of the front slope, and a "water-permeability improvement body" mainly made of cement-based materials on a portion of the back slope.

JP 2020-133311 A

The invention disclosed in Patent Document 1 can prevent scouring on the front side, piping on the back side, and seepage destruction of the embankment by forming a "water-stopping improvement body" on part of the front slope, and can drain seepage water from within the embankment by forming a "permeability improvement body" on part of the back slope, thereby preventing scouring on the back side, preventing a decrease in the shear strength of the embankment during an earthquake, and avoiding liquefaction damage. In addition, by forming a water-stopping improvement body on the front side and a permeability improvement body on the back side, it is also possible to reduce the settlement of the embankment during an earthquake.

On the other hand, the invention in Patent Document 1 is not very suitable for preventing water from entering through the top surface. For example, in the event of a heavy rain, the river water level may exceed the levee height (height of the top surface) and overflow. In this case, the overflowing water may seep in through the unreinforced top surface and erode the embankment, which may result in large-scale damage to the entire levee.

The objective of the present invention is to solve the problems of the conventional technology, that is, to provide an earth structure and a method for constructing the same that can reinforce the underside slope while allowing drainage from the underside slope and prevent water from seeping in from the top surface.

The present invention was developed based on an unprecedented idea that prevents water infiltration and erosion into the embankment and also prevents erosion of the embankment fill caused by rainfall and overflow by constructing a "water-stopping improvement body" with relatively low water permeability on the top surface of the embankment and a "water-permeability improvement body" with relatively high water permeability on the underside slope of the embankment.

The reinforced earth structure of the present invention is an earth structure having a "main body" formed by a front slope, a back slope, and a top surface, and is equipped with a "top water-stopping improvement body" and a "slope permeability improvement body." Of these, the top water-stopping improvement body has lower permeability than the main body, and is formed on the upper part of the top surface so as to cover it. On the other hand, the slope permeability improvement body is mainly made of cement-based material, has higher permeability than the main body, and is formed on the surface of the back slope so as to cover it.

The reinforced earth structure of the present invention can further comprise a "front-side water-stopping improved body" and a "rear-side water-permeability improved body." The front-side water-stopping improved body is mainly made of cement-based material, has lower water permeability than the main body, and is formed at the bottom of the front slope. The rear-side water-permeability improved body is also mainly made of cement-based material, has higher water permeability than the main body, and is formed at the bottom of the rear slope.

The reinforced earth structure of the present invention can also have a top end waterproofing improvement body with a protrusion. In this case, when the top end waterproofing improvement body is formed on the upper part of the top end surface, this protrusion penetrates from the top end surface into the inside of the main body.

The earth structure reinforcement method of the present invention is a method for reinforcing an existing earth structure, and is a method that includes a top end water-stopping improvement body forming process and a slope permeability improvement body forming process. In the top end water-stopping improvement body forming process, a top end water-stopping improvement body is formed on the upper part of the top end surface so as to cover the top end surface, and in the slope permeability improvement body forming process, a slope permeability improvement body is formed on the surface of the back side slope so as to cover the back side slope.

The earth structure reinforcement method of the present invention can also be a method further comprising a front-side water-stopping improvement body forming process and a back-side water-permeability improvement body forming process. In this front-side water-stopping improvement body forming process, a front-side water-stopping improvement body is formed at the bottom of the front-side slope, and in the back-side water-permeability improvement body forming process, a front-side water-stopping improvement body is formed at the bottom of the back-side slope.

The reinforced earth structure and the method for reinforcing an earth structure according to the present invention have the following advantages.
(1) Since the top surface of the embankment fill is covered with the water-stopping improvement body, it is possible to prevent water infiltration and erosion into the embankment caused by rainfall and overflow water.
(2) Since the underside of the slope is covered with the slope permeability improvement material, it is possible to suppress the erosion of the embankment due to rainfall and overflow water, and by smoothly draining the water from within the embankment, it is possible to suppress a decrease in the stability of the embankment.

Cross-sectional view of typical earth structures such as levees and seawalls on rivers, coasts, etc. 1 is a cross-sectional view showing a reinforced earth structure according to the present invention. A cross-sectional view showing a reinforced soil structure of the present invention, which includes a front-side water-stopping improvement body, a back-side water-permeability improvement body, and a slope water-stopping improvement body. FIG. 2 is a cross-sectional view showing the reinforced earth structure of the present invention when the water level of the river rises. (a) is a cross-sectional view showing a schematic diagram of a top-end water-stopping improvement body having a protrusion, and (b) is a cross-sectional view showing a schematic diagram of an earth structure in which a top-end water-stopping improvement body having a protrusion is installed. A cross-sectional view showing a reinforced soil structure having a front-side water-stopping improvement body and a back-side water-permeability improvement body formed by protruding outward from the slope. 1 is a construction flow diagram showing the main steps of the earth structure reinforcement method of the present invention.

The following describes an example of an embodiment of the reinforced earth structure and the earth structure reinforcement method of the present invention with reference to the drawings.

1. Definitions In describing the embodiments of the present invention, the definitions of the terms used herein are provided first. Note that the terms defined up to this point will also be defined here again for completeness.

(Front and back)
Fig. 1 is a cross-sectional view of a typical earth structure Dm such as a levee or seawall on a river or coast. A typical earth structure Dm is an embankment constructed with a fairly long extension along a river or coast (in the depth direction of the paper in the figure), and as shown in this figure, its cross-sectional shape is often roughly trapezoidal. The earth structure Dm blocks flooding from the river or sea, in other words, it separates the side outside the embankment where the river or sea is located (left side in the figure) from the opposite side inside the embankment (right side in the figure). For convenience, the side outside the embankment will be referred to as the "front side" and the side inside the embankment will be referred to as the "back side".

(Top surface and slope surface)
As described above, the cross-sectional shape of the earth structure Dm is generally trapezoidal, so that a flat surface is formed on the top (the position corresponding to the upper base of the trapezoid) and slopes are formed on both sides (the left and right sides in the figure). For convenience, the flat surface on the top is referred to as the "top surface St", and in order to distinguish between the two slopes on the left and right, the slope formed on the front side of the earth structure Dm is referred to as the "front slope Sf" and the slope formed on the back side of the earth structure Dm is referred to as the "back slope Sr". Similarly, the bottom of the front slope Sf (also called the tip) at the bottom of the front slope Sf is referred to as the "front slope Tf", and the bottom of the back slope Sr is referred to as the "back slope Tr".

2. Reinforced earth structure Next, the "reinforced earth structure" of the present invention will be described in detail with reference to the drawings. The earth structure reinforcing method of the present invention is, so to speak, a method for constructing the reinforced earth structure of the present invention, so the reinforced earth structure of the present invention will be described first, and then the earth structure reinforcing method of the present invention will be described. For convenience, the reinforced earth structure will be described here as functioning as a river embankment, but the reinforced earth structure of the present invention can be used not only as a river embankment, but also as an earth structure having functions such as a coastal embankment, a tide barrier, or a sand-control dam or a dam.

(Overall composition)
FIG. 2 is a cross-sectional view showing the "reinforced earth structure 100" of the present invention. As shown in this figure, the reinforced earth structure 100 includes a "main body 130" located at the center of the cross section, a "top end water-stopping improvement body 110" formed on the top end surface St, and a "slope permeability improvement body 120" formed on the back side slope surface Sr. The main body 130 is preferably formed mainly of a banking material, and the slope permeability improvement body 120 is preferably formed mainly of a cement-based material. The top end water-stopping improvement body 110 is formed to cover the top end surface St, and exhibits lower water permeability (e.g., permeability coefficient) than the main body 130 (i.e., high water stoppage). On the other hand, the slope permeability improvement body 120 is formed to cover the back side slope surface Sr, and exhibits higher water permeability (e.g., permeability coefficient) than the main body 130 (i.e., high drainage). In addition, the top end water-stopping improvement body 110 and the slope permeability improvement body 120 can be formed so as to completely cover the top end surface St and the back side slope Sr, or they can be formed so as to cover them roughly (for example, at least a predetermined percentage, such as more than 80%).

The reinforced earth structure 100 of the present invention can also include a "front side water stoppage improvement body 150", a "rear side water permeability improvement body 160", and a "slope surface water stoppage improvement body 170" as shown in FIG. 3. As shown in this figure, the front side water stoppage improvement body 150 is formed mainly of a cement-based material on a part of the front side slope Sf including the front side slope bottom Tf, and has lower water permeability than the main body 130 (i.e., high water stoppage). The rear side water permeability improvement body 160 is formed mainly of a cement-based material on a part of the rear side slope Sr including the rear side slope bottom Tr, and has higher water permeability than the main body 130 (i.e., high drainage). The slope surface water stoppage improvement body 170 is formed mainly of a cement-based material to cover the front side slope Sf, and has lower water permeability than the main body 130 (i.e., high water stoppage).

As shown in FIG. 3, the main body 130, the front water stop improvement body 150, and the back water permeability improvement body 160 each have an inclined surface, and a series of inclined surfaces are formed by the front inclined surface of the main body 130 (slope water stop improvement body 170) and the inclined surface of the front water stop improvement body 150, and a series of inclined surfaces are formed by the inclined surface of the back side of the main body 130 (slope water permeability improvement body 120) and the inclined surface of the back water permeability improvement body 160. As a result, the reinforced earth structure 100 of the present invention has a generally trapezoidal cross-sectional shape due to the main body 130 (slope water stop improvement body 170 and slope water permeability improvement body 120), a part of the front water stop improvement body 150 (above ground portion), and a part of the back water permeability improvement body 160 (above ground portion).

The reinforced earth structure 100 of the present invention can be constructed as a new structure, or can be constructed by reinforcing an existing earth structure Dm. When constructing a new structure, the main body 130 is constructed to have the planned shape and dimensions, and then the top end water-stopping improvement body 110 and the slope permeability improvement body 120 are constructed. On the other hand, when reinforcing an existing earth structure Dm, the top end water-stopping improvement body 110 is constructed on the top of the top surface St of the earth structure Dm, and the slope permeability improvement body 120 is constructed on the surface of the back slope Sr of the earth structure Dm, and the existing earth structure Dm is used as the main body 130.

As described above, the top surface St of the reinforced earth structure 100 of the present invention is reinforced by the top surface water-stopping improvement body 110, and the backside slope Sr is reinforced by the slope permeability improvement body 120. Therefore, even if the water level of the river rises to exceed the levee height due to heavy rain as shown in Figure 4 and further exceeds the levee body (overflows), the top surface water-stopping improvement body 110 suppresses infiltration from the top surface St into the main body 130 and suppresses erosion of the top surface St, and the slope permeability improvement body 120 suppresses erosion of the backside slope Sr. Moreover, even if the main body 130 is flooded, the drainage effect of the slope permeability improvement body 120 allows the water in the main body 130 to be smoothly drained, and as a result, it is possible to suppress the deterioration of the stability of the embankment embankment due to the rise in the water level in the embankment (main body 130).

Below, we will explain in detail each of the main elements that make up the reinforced earth structure 100 of the present invention.

(Top water-repellent improved body)
The top end water-stopping improved body 110 has a function of suppressing water from infiltrating into the main body 130 when the water level of the river rises, as shown in FIG. 4. Therefore, the top end water-stopping improved body 110 is formed on the top end surface St, and is formed so as to cover the top end surface St, and is made to have lower water permeability (i.e., higher water-stopping ability) than the main body 130. This top end water-stopping improved body 110 can be formed using various materials that have lower water permeability than the main body 130, such as cement-based materials, asphalt-based materials, and other resin-based materials. In addition, when the top end water-stopping improved body 110 is formed mainly from cement-based materials, it is possible to use a precast top end water-stopping improved body 110, and of course it is also possible to form the top end water-stopping improved body 110 using cast-in-place concrete. Alternatively, the top end water-stopping improved body 110 can be formed by improving a part of the main body 130 near the top end surface St with a cement-based solidification material by using a mechanical mixing method, a high-pressure jet mixing method, or a chemical injection method. In addition, in the case of laying a road on the top surface St, it is a good idea to use asphalt pavement or concrete pavement as the top water-stopping improvement body 110.

The top end water-stopping improvement body 110 can also be provided with a protrusion 114 as shown in FIG. 5. FIG. 5(a) is a cross-sectional view showing a top end water-stopping improvement body 110 equipped with a protrusion 114, and FIG. 5(b) is a cross-sectional view showing an earth structure 100 on which a top end water-stopping improvement body 110 equipped with a protrusion 114 is installed. The top end water-stopping improvement body 110 shown in FIG. 5 is a roughly isosceles trapezoid consisting of an upper surface 111, a lower surface 112, and a side surface 113 that are approximately parallel (including parallel). In this case, the inclination angle of the side surface 113 should be adjusted to the inclination angle of the front side slope Sf and the inclination angle of the back side slope Sr. In addition, a plurality of spike-shaped protrusions 114 are provided on the lower surface 112. In FIG. 5(a), five protrusions 114 are shown, but since the top end water-stopping improver 110 is continuous in the extension direction of the main body 130 (in the drawing, the depth direction of the page), a row (five in this case) of protrusions 114 is also provided at regular intervals in the extension direction of the main body 130. The top end water-stopping improver 110 having protrusions 114 is installed so that the protrusions 114 penetrate into the main body 130 from the top end surface St, as shown in FIG. 5(b). The protrusions 114 are inserted into the main body 130, creating a kind of spike effect, which allows the top end water-stopping improver 110 to be more firmly fixed to the top end surface St.

(Slope permeability improvement body)
The slope permeability improver 120 has the function of suppressing the erosion of the rear slope Sr and smoothly draining the water that has infiltrated into the main body 130 when the water level of the river rises and overflows as shown in Fig. 4. For this purpose, the slope permeability improver 120 is formed on the surface of the rear slope Sr so as to cover the rear slope Sr, and is made to exhibit higher permeability (i.e., higher drainage) than the main body 130. In addition, a drainage ditch 140 shown in Fig. 2 and Fig. 3 can be installed along the extension direction of the main body 130 to allow the water drained from the slope permeability improver 120 to flow to a specified position.

The slope permeability improver 120 is mainly made of cement-based materials. For example, a precast product slope permeability improver 120 can be used, and of course the slope permeability improver 120 can be made of cast-in-place concrete. However, since the slope permeability improver 120 requires appropriate permeability (drainage), it is preferable to use porous concrete (hereinafter referred to as "porous concrete"). In addition, since the slope permeability improver 120 has a drainage function, it is recommended to use concrete that does not separate underwater so that the cement (mortar) does not flow out during construction or when draining at the beginning of construction. When designing the mix for porous concrete that does not separate underwater, it is recommended to select the particle size of the aggregate to prevent clogging, that is, to ensure an appropriate porosity, add an underwater non-separating material to provide underwater non-separation, and add a high-performance water reducing agent to take workability into consideration.

(Front side water stop property improved body)
The front-side water-stopping improved body 150 has a function of suppressing water from entering the main body 130 when the water level of the river rises as shown in Fig. 4, and a function of preventing scouring (particularly scouring near the front-side slope toe Tf) when the water level of the river drops from a high water level. Therefore, the front-side water-stopping improved body 150 is formed on a part of the front-side slope Sf including the front-side slope toe Tf, and is formed so that its water permeability is lower (i.e., water-stopping is higher) than that of the main body 130. In addition, the front-side water-stopping improved body 150 is preferably formed mainly of a cement-based material so that it can also function as a reinforcing member during an earthquake, i.e., so that it has considerable strength (shear strength and bending strength).

The front-side water-stopping improvement body 150 is designed to meet the required water permeability (water stoppage) and strength, while also taking into consideration ease of construction. In particular, with regard to water permeability and strength, it is desirable to design it so that the reinforced earth structure 100 does not experience abnormal settlement or deformation, or so that liquefaction of the main body 130 does not occur, even during heavy rain or earthquakes. Specifically, it is advisable to design the water permeability and strength of the front-side water-stopping improvement body 150 based on the results obtained by numerical analysis (e.g. FEM analysis) using the expected river water level during heavy rain and earthquake load as given conditions.

The surface water-stopping improvement body 150 can be formed by carrying out ground improvement work on a part of the existing earth structure Dm (or the main body 130). In this case, it is advisable to improve a part of the earth structure Dm (or the main body 130) with a cement-based solidification material by using a mechanical mixing method, a high-pressure jet mixing method, or a chemical injection method. Alternatively, the surface water-stopping improvement body 150 can be designed to be made of concrete, and the surface water-stopping improvement body 150 can be formed by installing a cast-in-place concrete solidification body or a precast concrete solidification body in a specified position.

(Backside water permeability improver)
The back-side permeability improver 160 has the function of draining water that has infiltrated into the main body 130 to the outside when the river water level rises, as shown in Fig. 4, and the function of preventing scouring near the back-side slope toe Tr due to overflow water. For this reason, the back-side permeability improver 160 is formed on a part of the back-side slope Sr including the back-side slope toe Tr, and is formed so that its permeability is higher than that of the main body 130 (i.e., its drainage is higher). In addition, the back-side permeability improver 160 is preferably formed mainly of a cement-based material so that it can also function as a reinforcing member during an earthquake, i.e., so that it has considerable strength (shear strength and bending strength).

The backside permeability improvement body 160 is designed to meet the required permeability (drainage) and strength, and also with consideration given to workability. In particular, it is desirable to design the permeability and strength so that the reinforced earth structure 100 does not experience abnormal subsidence or deformation, or so that the main body 130 does not experience liquefaction damage, even during heavy rain or earthquakes. Specifically, the permeability and strength of the backside permeability improvement body 160 can be designed based on the results obtained by numerical analysis (e.g. FEM analysis) under the given conditions of the expected river water level during heavy rain and the load during earthquakes. In addition, as shown in Figure 3, the backside permeability improvement body 160 can be divided into part A located on the ground, part B located in the soft layer, and part C located in the support layer, and parts A, B, and C can be designed with materials with different physical properties (strength, permeability, etc.) according to the target stability performance. For example, it can be designed so that the lower layers have greater strength in terms of slippage stability, or it can be designed so that the permeability coefficient of the back permeability improver 160 (part B in Figure 3) located in the sand layer is lower than that of the bottom of the glue line (part A in Figure 3) in order to increase the piping resistance of the upper sand layer (weak layer).

The backside permeability improvement body 160 can be formed by installing a concrete solidification body. In this case, the solidification body can be installed using cast-in-place concrete or a precast concrete solidification body, but since the backside permeability improvement body 160 requires appropriate permeability (drainage), it is desirable to use a porous concrete solidification body. In addition, since the backside permeability improvement body 160 has a drainage function, it is preferable to use a concrete solidification body that does not separate underwater so that the cement content (mortar content) does not flow out during construction or when draining at the beginning of construction. When designing the mix for the porous concrete that does not separate underwater, it is recommended to select the particle size of the aggregate to prevent clogging, that is, to ensure an appropriate porosity, add an underwater non-separating material to provide underwater non-separation, and add a high-performance water reducing agent to take workability into consideration.

The main body 130 shown in FIG. 3 is constructed on a soft layer (such as a permeable ground made of sand or sandy soil, or a liquefied layer) deposited on the support layer, so the front water stop improvement body 150 and the back water permeability improvement body 160 shown in this figure are formed to penetrate the soft layer and further root into the support layer. Of course, depending on the strength of the soft layer, the front water stop improvement body 150 and the back water permeability improvement body 160 can be formed to root only in the soft layer without rooting in the support layer, or the front water stop improvement body 150 and the back water permeability improvement body 160 can be formed to be placed on the support layer without rooting in the support layer.

The front-side water-stopping improved body 150 and the back-side water-permeability improved body 160 can also be formed partly outside the front-side slope Sf and the back-side slope Sr. Specifically, as shown in FIG. 6, the front-side water-stopping improved body 150 and the back-side water-permeability improved body 160 can be formed partly beyond the front-side slope Sf and the back-side slope Sr, that is, beyond the front-side slope bottom Tf toward the river side (left side in the figure), or beyond the back-side slope bottom Tr toward the opposite side of the river (right side in the figure), and part of the front-side water-stopping improved body 150 and the back-side water-permeability improved body 160 can be formed under the ground (weak layer and supporting layer) in the protruding range, so to speak, in a footing type. Comparing FIG. 3 and FIG. 6, the front-side water-stopping improved body 150 and the back-side water-permeability improved body 160 shown in FIG. 6 are formed larger only in the parts protruding from the front-side slope Sf and the back-side slope Sr. Therefore, although the construction period and cost required for constructing the reinforced earth structure 100 will increase, the scouring prevention function near the front side bottom end Tf and the back side bottom end Tr, and the reinforcement function during earthquakes will be improved. Therefore, the front side water-stopping improvement body 150 and the back side water-permeability improvement body 160 of the type shown in Figure 6 should be designed appropriately depending on the situation.

(Slope surface water-stopping improvement body)
The slope water-stopping improver 170 has a function of suppressing the erosion of the front slope Sf when the water level of the river rises as shown in Fig. 4. For this purpose, the slope water-stopping improver 170 is formed on the surface of the front slope Sf, and is formed so as to cover the front slope Sf, and exhibits lower water permeability (i.e., higher water-stopping ability) than the main body 130. The slope water-stopping improver 170 is formed mainly of cement-based materials, and for example, a precast slope water-stopping improver 170 can be used, or the slope water-stopping improver 170 can be formed by cast-in-place concrete. Alternatively, the slope water-stopping improver 170 can be formed by improving a part of the main body 130 near the front slope Sf with a cement-based solidification material by using a mechanical mixing method, a high-pressure jet mixing method, or a chemical injection method.

3. Earth structure reinforcing method Next, the earth structure reinforcing method of the present invention will be described with reference to Fig. 7. The earth structure reinforcing method of the present invention is, so to speak, a method for constructing the reinforced earth structure 100 described so far, and therefore, we will avoid any overlapping description with the description of the reinforced earth structure 100, and will only describe the contents unique to the earth structure reinforcing method of the present invention. In other words, the contents not described here are the same as those described in "2. Reinforced earth structure", including the explanation in "1. Definition".

Figure 7 is a construction flow diagram showing the main steps of the earth structure reinforcement method of the present invention. As shown in this figure, first, preparatory work is carried out, such as surveying the positions for forming the top-end water-stopping improvement body 110 and the slope permeability improvement body 120, bringing in the necessary equipment and placing it in the designated positions, and confirming the construction procedure for that day (Step 10 in Figure 7).

When preparations are complete, the top end water-stopping improvement body 110 is formed above the top end surface St of the existing earth structure Dm (Step 20 in Figure 7). Specifically, the top end water-stopping improvement body 110 is formed by installing a precast top end water-stopping improvement body 110, forming the top end water-stopping improvement body 110 with cast-in-place concrete, improving a part of the main body 130 near the top end surface St with a cement-based solidification material, or laying an asphalt pavement or concrete pavement. When the top end water-stopping improvement body 110 has a protrusion 114, the top end water-stopping improvement body 110 is formed so that the protrusion 114 penetrates from the top end surface St into the main body 130.

On the other hand, a slope permeability improver 120 is formed on the surface of the rear slope Sr of the existing earth structure Dm (Step 30 in FIG. 7). Specifically, the slope permeability improver 120 can be a precast product using porous concrete that does not separate underwater, or the slope permeability improver 120 can be formed by casting in place porous concrete that does not separate underwater. Also, after the slope permeability improver 120 is formed, a drainage ditch 140 can be installed along the extension direction of the slope permeability improver 120.

The process of forming the top end water-stopping improvement body 110 and the process of forming the slope surface water-permeability improvement body 120 can be carried out in advance, or both processes can be carried out simultaneously (in parallel). In addition, when constructing the front side water-stopping improvement body 150 and the back side water-permeability improvement body 160, it is recommended to construct the front side water-stopping improvement body 150 and the back side water-permeability improvement body 160 prior to the top end water-stopping improvement body 110 and the slope surface water-permeability improvement body 120. The procedure for constructing the front side water-stopping improvement body 150 and the back side water-permeability improvement body 160 in the case of reinforcing an existing earth structure Dm will be described below.

The front water-stopping improvement body 150 is formed on the front side of the existing earth structure Dm. Specifically, the front water-stopping improvement body 150 is formed on the front side of the earth structure Dm by performing ground improvement with a cement-based solidification material on a part of the existing earth structure Dm using a mechanical mixing method, a high-pressure jet mixing method, or a chemical injection method. On the other hand, the back permeability improvement body 160 is formed on the back side of the existing earth structure Dm. Specifically, the back permeability improvement body 160 is formed by installing a submersible non-separable porous concrete solidification body on the back side of the earth structure Dm. At this time, when the fill material of the earth structure Dm is partially removed to form the back permeability improvement body 160, it is recommended to use a retaining wall as appropriate depending on the site conditions, such as when the excavation height is greater than a specified height, before carrying out the removal work.

After forming all the planned areas of the top edge water-stopping improvement body 110 and the slope water-permeability improvement body 120, and forming the planned front side water-stopping improvement body 150, back side water-permeability improvement body 160, and slope water-stopping improvement body 170, the work is finished with cleanup.

The reinforced earth structure and earth structure reinforcing method of the present invention can be used for various earth structures where water remains on one side (front side), such as river levees, coastal levees, tide embankments, erosion control dams and dams. The present invention can effectively reinforce river levees and coastal levees, which contributes to extending the lifespan of construction infrastructure. Considering this, the present invention can be said to be an invention that can be expected to not only be used industrially, but also to make a significant contribution to society.

100 Reinforced earth structure of the present invention 110 Top end water-stopping improved body (of reinforced earth structure) 120 Slope surface water-permeability improved body (of reinforced earth structure) 130 Main body (of reinforced earth structure) 140 Drainage ditch (of reinforced earth structure) 150 Front side water-stopping improved body (of reinforced earth structure) 160 Back side water-permeability improved body (of reinforced earth structure) 170 Slope surface water-stopping improved body (of reinforced earth structure) Dm Earth structure Sf Front side slope Sr Back side slope St Top surface Tf Front side slope bottom Tr Back side slope bottom

Claims (5)

An earth structure having a main body formed by a front slope, a back slope, and a top surface,
The method comprises: a top end water-stopping improvement body having a lower water permeability than the main body portion; and a slope water-permeability improvement body having a higher water permeability than the main body portion;
The top end waterproofing improver is formed on the upper part so as to cover the top end surface,
The slope permeability improver is mainly made of a cement-based material and is formed on the surface so as to cover the rear slope,
Only the slope water permeability improver is formed on the back slope.
A reinforced earth structure. A surface side water-stopping improved body having a lower water permeability than the main body portion;
A back-side water permeability improver having a higher water permeability than the main body portion,
The front-side water-stopping improvement body is mainly made of a cement-based material and is formed at the bottom of the front-side slope,
The backside water permeability improver is mainly made of a cement-based material and is formed at the bottom of the backside slope.
2. The reinforced earth structure according to claim 1. The top end waterproofing improver has a protrusion that penetrates into the inside of the main body from the top end surface,
3. A reinforced earth structure according to claim 1 or 2. A method for reinforcing an earth structure having a main body formed by a front slope, a back slope, and a top surface, comprising:
A top end water-stopping improvement body forming process for forming a top end water-stopping improvement body having lower water permeability than the soil structure so as to cover the top end surface of the soil structure;
and a slope permeability improver forming step for forming a slope permeability improver having higher permeability than the soil structure on the surface of the rear slope of the soil structure so as to cover the rear slope,
In the slope water permeability improver forming step, only the slope water permeability improver is formed on the back slope.
A method for reinforcing an earth structure comprising the steps of: In the top end water-stopping improvement body forming process, the top end water-stopping improvement body having a protrusion is used, and the top end water-stopping improvement body is installed so that the protrusion penetrates into the main body from the top end surface.
5. The method for reinforcing an earth structure according to claim 4.

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