Reinforced soil structure and method for reinforcing soil structure

Abstract

To provide an earth structure capable of reinforcing while enabling water discharge from a rear side sloped face and suppressing water immersion from a top end face, and to provide a construction method of the same.SOLUTION: A reinforced earth structure has a main body portion formed of a front side sloped face, a rear side sloped face, and a top end face, and comprises a top end water cut-off improvement body and a sloped face water permeable improvement body. The top end water cut-off improvement body exhibits a water permeability lower than the main body portion, and is formed at an upper part of the top end face so as to cover the top end face. The sloped face water permeable improvement body contains a cement-based material as the main constituent, exhibits a water permeability higher than the main body portion, and is formed on a front face of the rear side sloped face so as to cover the rear side sloped face.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a technology for earth structures such as dikes, flood control dikes, and embankments in rivers, coasts, reservoirs, etc. More specifically, it relates to an earth structure reinforced by a "waterstop improvement body" having a lower permeability coefficient than the earth structure body and a "permeability improvement body" having a higher permeability coefficient than the earth structure body, and a construction method thereof.

Background Art

[0002] It has been pointed out that the construction infrastructure (hereinafter referred to as "construction infrastructure") intensively developed during the period of high economic growth has already advanced considerably in aging. In 2014, a "Proposal on the Full Implementation of Measures against Road Aging (Council for the Development of Social Infrastructure)" was compiled, sounding the alarm by citing the example of the Sasago Tunnel in 2012 that "in the near future, it will lead to a fatal situation related to human life and social facilities such as the collapse of bridges," and strongly advocating the importance of the maintenance and management of construction infrastructure. Under such circumstances, the state has promulgated an ordinance amending part of the Enforcement Regulations of the Road Act, and has formulated a regular inspection guide showing specific inspection methods for construction infrastructure, key points for noticing main changes, and judgment case photos.

[0003] Typical construction infrastructure includes structures such as dams and bridges, as well as coastal dikes, river dikes, flood control dikes, etc. The total length of the coastline of our country is about 35,000 km, which is the sixth longest in the world. Naturally, coastal dikes have been constructed in necessary places such as coastal protection areas, and its function is extremely important construction infrastructure not only in terms of its function but also in terms of its huge extension.

[0004] Coastal levees are basically planned and constructed in accordance with the Coastal Act (Act No. 101 of May 12, 1956). This Coastal Act was enacted in 1956, triggered by Typhoon No. 13 in September 1953, which caused severe damage mainly in Aichi Prefecture. That is, a considerable period of time has passed since many coastal levees were constructed, and it is said that approximately 40% of the facilities had passed 50 years or more as of 2010. Therefore, inspections for diagnosing the deterioration of coastal levees are becoming increasingly important.

[0005] Dikes, flood control dikes, etc. (hereinafter collectively referred to as "earth structures") in rivers, coasts, etc. are generally constructed by embankment filling. The cross-sectional shape (the shape when looking at the cross-section perpendicular to the levee body extension direction) is generally trapezoidal, and slope surfaces are formed on the outer side of the levee (hereinafter referred to as the "front side") and the inner side of the levee (hereinafter referred to as the "back side") facing the river or the sea, respectively. A flat surface (hereinafter referred to as the "top end surface") is formed at the upper part (the position corresponding to the upper base in the trapezoid).

[0006] Since earth structures are embankment bodies, phenomena such as scouring near the lower end of the front slope surface (so-called slope toe), scouring occurring on the back side of the earth structure due to overflow water, piping occurring on the back side of the earth structure, and strength deterioration of the embankment body (i.e., the levee body) due to seepage water (hereinafter referred to as "seepage failure") are always a concern. Moreover, since many earth structures have been completed for a considerable number of years, it can be easily predicted that scouring, piping, and seepage failure have already progressed in some cases.

[0007] Also, depending on the local situation, earth structures may be constructed on soft layers such as permeable ground composed of sand or sandy soil, or ground containing a liquefaction layer. In this case, there is even a risk that the earth structure itself may become unstable due to liquefaction of the foundation ground during an earthquake.

[0008] Generally, when significant scouring or the like occurs in an earth structure, reinforcement measures are implemented. Conventionally, as a construction method for reinforcing an earth structure, a method of forming a structure such as a water-stop ground improvement body or a steel sheet pile on the outer side of the mortar surface (that is, the outer side of the embankment body) on both the front side and the back side has been the mainstream. However, in order to form this ground improvement body, a relatively large-scale construction machine such as a three-point pile driver used for deep mixing treatment is required, which not only incurs considerable costs (such as material losses), but also requires a considerable amount of space for arranging the construction machine. Considering the extension of the target earth structure, it also requires a considerable amount of construction cost and construction period, so there is also a problem that it cannot be easily commercialized.

[0009] Furthermore, in the conventional construction method of forming a water-stop ground improvement body on both the front side and the back side, although the water-stop performance is improved, the drainage function is significantly reduced. Therefore, once seawater or river water penetrates into the embankment body, the infiltrated water will stagnate in the embankment body, and as a result, there is also a problem that there is a risk of occurrence of seepage failure. In particular, during an earthquake, the infiltrated water in the embankment body is a factor, and liquefaction of the embankment body itself occurs. In this case, it is known that the deformation of the levee will be prolonged.

[0010] Therefore, in Patent Document 1, a technique is proposed in which a "water-stop improvement body" mainly composed of a cement-based material is formed on a part of the front mortar surface, and a "permeability improvement body" mainly composed of the same cement-based material is formed on a part of the back mortar surface.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] The invention disclosed in Patent Document 1 can prevent surface erosion, piping occurring on the back side, and seepage failure of the embankment body by forming a "waterproofing improvement body" on a part of the surface plastering surface. Moreover, by forming a "water permeability improvement body" on a part of the back plastering surface, the infiltrated water in the embankment body can be drained. As a result, back side erosion can be prevented, the reduction of the shear strength of the embankment body during an earthquake can be prevented, and liquefaction damage can be avoided. In addition, by forming a waterproofing improvement body on the front side and a water permeability improvement body on the back side, the effect of reducing the settlement of the embankment body during an earthquake can also be obtained.

[0013] On the other hand, the invention of Patent Document 1 is not very suitable for preventing water intrusion from the top end surface. For example, in the case of a considerable heavy rain, the river water level may exceed the embankment height (the height of the top end surface) and overtop. In this case, the embankment fill may be eroded by the overtopping water invading from the unreinforced top end surface. As a result, large-scale damage may occur to a series of embankment bodies.

[0014] The problem of the present invention is to solve the problems of the prior art, that is, to provide an earth structure that can reinforce while enabling drainage from the back plastering surface and suppress water intrusion from the top end surface, and a construction method thereof.

Means for Solving the Problem

[0015] The present invention focuses on the fact that by constructing a "waterproofing improvement body" with relatively low water permeability on the top end surface of the embankment body and a "water permeability improvement body" with relatively high water permeability on the back plastering surface of the embankment body, water intrusion and erosion into the embankment body can be suppressed, and moreover, erosion of the embankment fill due to rainfall or overtopping water can be suppressed. It is an invention made based on an unprecedented idea.

[0016] The reinforced soil structure of the present invention is a soil structure having a "main body part" formed by a front slope surface, a rear slope surface, and a top end surface, and is provided with a "top end water stop improvement body" and a "slope surface water permeability improvement body". Among these, the top end water stop improvement body exhibits lower water permeability than the main body part and is formed on the upper part of the top end surface so as to cover the top end surface. On the other hand, the slope surface water permeability improvement body is mainly composed of a cement-based material, exhibits higher water permeability than the main body part, and is formed on the surface of the rear slope so as to cover the rear slope surface.

[0017] The reinforced soil structure of the present invention can further be provided with a "front side water stop improvement body" and a "rear side water permeability improvement body". This front side water stop improvement body is mainly composed of a cement-based material, exhibits lower water permeability than the main body part, and is formed at the toe of the front slope surface. Also, the rear side water permeability improvement body is mainly composed of a cement-based material, exhibits higher water permeability than the main body part, and is formed at the toe of the rear slope surface.

[0018] The reinforced soil structure of the present invention can also be such that the top end water stop improvement body has a protrusion. In this case, when the top end water stop 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 part.

[0019] The method for reinforcing a soil structure of the present invention is a method for reinforcing an existing soil structure, and is a method provided with a top end water stop improvement body forming step and a slope surface water permeability improvement body forming step. Among these, in the top end water stop improvement body forming step, a top end water stop 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 surface water permeability improvement body forming step, a slope surface water permeability improvement body is formed on the surface of the rear slope so as to cover the rear slope surface.

[0020] The method for reinforcing a soil structure of the present invention can further be a method provided with a front side water stop improvement body forming step and a rear side water permeability improvement body forming step. In this front side water stop improvement body forming step, a front side water stop improvement body is formed at the toe of the front slope surface, and in the rear side water permeability improvement body forming step, a front side water stop improvement body is formed at the toe of the rear slope surface.

Advantages of the Invention

[0021] The reinforced earth structure and the earth structure reinforcement method of the present invention have the following effects. (1) Since the top surface of the embankment fill is covered by the top surface waterstop improvement body, it is possible to suppress the intrusion and erosion of rainwater and overflow water into the embankment. (2) Since the back slope is covered by the slope surface water permeability improvement body, it is possible to suppress the erosion of the embankment fill by rainwater and overflow water, and by smoothly draining the water in the embankment, it is possible to suppress the decrease in the stability of the embankment fill.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0023] Examples of embodiments of the reinforced earth structure and the earth structure reinforcement method of the present invention will be described based on the drawings.

[0024] 1. Definition In describing examples of embodiments of the present invention, first, definitions of terms used here will be shown. Regarding the terms defined so far, they will also be repeatedly defined here for the sake of safety.

[0025] (Front side and back side) FIG. 1 is a cross-sectional view of a general soil structure Dm such as a levee or a seawall in a river or a coast. The general soil structure Dm is an embankment constructed along a river or a coast (in the depth direction of the paper in the figure) with a considerably long extension, and as shown in this figure, its cross-sectional shape is generally trapezoidal. The soil structure Dm blocks inundation from a river or the sea. In other words, it separates the outside of the embankment side (left side in the figure) where there is a river or the sea from the opposite inside of the embankment side (right side in the figure). For convenience, here the outside of the embankment side is referred to as the "front side", and the inside of the embankment side is referred to as the "back side".

[0026] (Top end face and slope face) As described above, since the cross-sectional shape of the soil structure Dm is generally trapezoidal, a flat surface is formed at the upper part (the position corresponding to the upper base of the trapezoid), and slope faces are formed on both of its side faces (left and right side faces in the figure). For convenience, here the upper flat surface is referred to as the "top end face St", and in order to distinguish between the two left and right slope faces, the slope face formed on the front side of the soil structure Dm is referred to as the "front side slope face Sf", and the slope face formed on the back side of the soil structure Dm is referred to as the "back side slope face Sr". Similarly, the slope bottom (also called the slope tip) at the lower end of the front side slope face Sf is referred to as the "front side slope bottom Tf", and the slope bottom at the lower end of the back side slope face Sr is referred to as the "back side slope bottom Tr".

[0027] 2. Reinforced soil structure Next, the "reinforced soil 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 for constructing the reinforced soil structure of the present invention. Therefore, first, the reinforced soil structure of the present invention will be described, and then the soil structure reinforcement method of the present invention will be described. For convenience, here it will be described as a reinforced soil structure that functions as a river embankment. However, the reinforced soil structure of the present invention can be used not only as a river embankment but also as a soil structure having functions such as a coastal embankment, a flood control embankment, or a sand control dam or weir embankment.

[0028] (Overall structure) Figure 2 is a cross-sectional view showing the "reinforced soil structure 100" of the present invention. As shown in this figure, the reinforced soil structure 100 includes a "main body part 130" located at the central part of the cross-section, a "top water-stopping improvement body 110" formed on the top end surface St, and a "slope surface water permeability improvement body 120" formed on the back slope surface Sr. The main body part 130 is mainly formed of embankment material, and the slope surface water permeability improvement body 120 is preferably mainly formed of a cement-based material. Further, the top water-stopping improvement body 110 is formed so as to cover the top end surface St and exhibits lower water permeability (for example, permeability coefficient) than the main body part 130 (that is, higher water-stopping property). On the other hand, the slope surface water permeability improvement body 120 is formed so as to cover the back slope surface Sr and exhibits higher water permeability (for example, permeability coefficient) than the main body part 130 (that is, higher drainage property). Note that the top water-stopping improvement body 110 and the slope surface water permeability improvement body 120 can be formed so as to completely cover the top end surface St and the back slope surface Sr, or can be formed so as to cover generally (for example, at a predetermined ratio or more such as 80% or more).

[0029] Further, the reinforced soil structure 100 of the present invention can also include a "front side water-stopping improvement body 150", a "back side water-permeable improvement body 160", and a "siding water-stopping improvement body 170" as shown in FIG. 3. As shown in this figure, the front side water-stopping improvement body 150 is formed mainly of a cement-based material on a part of the front side siding surface Sf including the front side siding edge Tf, and exhibits lower water permeability than the main body part 130 (that is, higher water-stopping property). The back side water-permeable improvement body 160 is formed mainly of a cement-based material on a part of the back side siding surface Sr including the back side siding edge Tr, and exhibits higher water permeability than the main body part 130 (that is, higher drainage property). The siding water-stopping improvement body 170 is formed mainly of a cement-based material so as to cover the front side siding surface Sf, and exhibits lower water permeability than the main body part 130 (that is, higher water-stopping property).

[0030] As shown in FIG. 3, the main body part 130, the front side water-stopping improvement body 150, and the back side water-permeable improvement body 160 each have an inclined surface, and a series of inclined surfaces are formed by the front side inclined surface (siding water-stopping improvement body 170) of the main body part 130 and the inclined surface of the front side water-stopping improvement body 150, and a series of inclined surfaces are formed by the back side inclined surface (siding water-permeable improvement body 120) of the main body part 130 and the inclined surface of the back side water-permeable improvement body 160. As a result, the cross-sectional view of the reinforced soil structure 100 of the present invention is generally trapezoidal by the main body part 130 (siding water-stopping improvement body 170 and siding water-permeable improvement body 120), a part of the front side water-stopping improvement body 150 (above-ground part), and a part of the back side water-permeable improvement body 160 (above-ground part).

[0031] 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 as a new structure, after constructing the main body part 130 so as to have a planned shape and dimensions, the top-end water-stopping improvement body 110 and the siding water-permeable improvement body 120 are constructed. On the other hand, when reinforcing an existing soil structure Dm, the top-end water-stopping improvement body 110 is constructed on the upper part of the top end surface St of the soil structure Dm, and the siding water-permeable improvement body 120 is constructed on the surface of the back side siding surface Sr of the soil structure Dm, and it is preferable to use the existing soil structure Dm as the main body part 130.

[0032] As described above, in the reinforced earth structure 100 of the present invention, the top surface St is reinforced by the top surface water-stopping improvement body 110, and the back slope surface Sr is reinforced by the slope surface water-permeability improvement body 120. Therefore, for example, when the river water level rises beyond the embankment height as shown in FIG. 4 due to heavy rain and even if it overflows (overtops) the embankment body, the top surface water-stopping improvement body 110 suppresses the intrusion into the main body portion 130 from the top surface St and also suppresses the erosion of the top surface St, and the slope surface water-permeability improvement body 120 suppresses the erosion of the back slope surface Sr. Moreover, even if the main body portion 130 is flooded, the water in the main body portion 130 is smoothly drained by the drainage effect of the slope surface water-permeability improvement body 120. As a result, it is possible to suppress the decrease in the stability of the embankment fill due to the rise in the water level in the embankment body (main body portion 130).

[0033] Hereinafter, each main element constituting the reinforced earth structure 100 of the present invention will be described in detail.

[0034] (Top surface water-stopping improvement body) The top surface water-stopping improvement body 110 has a function of suppressing the water that intrudes into the main body portion 130 when the river water level rises as shown in FIG. 4. Therefore, the top surface water-stopping improvement body 110 is formed above the top surface St and covers the top surface St, and is supposed to have a lower water permeability than the main body portion 130 (that is, a higher water-stopping property). For this top surface water-stopping improvement body 110, various materials showing a lower water permeability than the main body portion 130 can be used, and it can be formed, for example, by a cement-based material, an asphalt-based material, or other resin-based materials. Also, when it is formed mainly of a cement-based material, a precast product of the top surface water-stopping improvement body 110 can be used, and of course, the top surface water-stopping improvement body 110 can also be formed by in-situ concrete. Alternatively, by using a mechanical agitation method, a high-pressure jet agitation method, or a chemical solution injection method, the top surface water-stopping improvement body 110 can also be formed by improving a part near the top surface St of the main body portion 130 with a cement-based solidifying material. In the case of laying a road on the top surface St, an asphalt pavement body or a concrete pavement body may be utilized as the top surface water-stopping improvement body 110.

[0035] Also, the top-end waterstop improvement body 110 can be provided with protrusions 114 as shown in FIG. 5. FIG. 5(a) is a cross-sectional view schematically showing the top-end waterstop improvement body 110 provided with the protrusions 114, and FIG. 5(b) is a cross-sectional view schematically showing the soil structure 100 in which the top-end waterstop improvement body 110 having the protrusions 114 is installed. The top-end waterstop improvement body 110 shown in FIG. 5 is generally an isosceles trapezoid composed of a substantially parallel (including parallel) upper surface 111, a lower surface 112, and a side surface 113. In this case, the inclination angle of the side surface 113 may be adjusted according to the inclination angle of the front-side slope surface Sf and the inclination angle of the back-side slope surface Sr. Further, a plurality of spike-shaped protrusions 114 are provided on the lower surface 112. Although five protrusions 114 are shown in FIG. 5(a), since the top-end waterstop improvement body 110 is continuous in the extension direction of the main body portion 130 (the depth direction in the drawing), a row (in this case, five) of protrusions 114 is also provided at regular intervals in the extension direction of the main body portion 130. The top-end waterstop improvement body 110 having the protrusions 114 is installed such that the protrusions 114 penetrate from the top-end surface St into the main body portion 130 as shown in FIG. 5(b). When the protrusions 114 are inserted into the main body portion 130, a so-called spike effect is generated, and thereby the top-end waterstop improvement body 110 is more firmly fixed to the top-end surface St.

[0036] (Slope surface water permeability improvement body) The slope surface water permeability improvement body 120 has a function of suppressing the erosion of the back-side slope surface Sr and smoothly draining the water that has entered the main body portion 130 when the water level of the river rises and overflows as shown in FIG. 4. For this purpose, the slope surface water permeability improvement body 120 is formed on the surface of the back-side slope surface Sr and covers the back-side slope surface Sr, and is made to have higher water permeability (that is, higher drainage property) than the main body portion 130. Further, in order to flow the water drained from the slope surface water permeability improvement body 120 to a predetermined position, a drainage groove 140 shown in FIGS. 2 and 3 can also be installed along the extension direction of the main body portion 130.

[0037] The surface permeability improver 120 is formed mainly of a cementitious material. For example, the surface permeability improver 120 of a precast product can be used, and of course, the surface permeability improver 120 can also be formed by in-situ concrete. However, since the surface permeability improver 120 requires appropriate water permeability (drainage), it is desirable to make it of porous concrete (hereinafter referred to as "porous concrete"). Further, since the surface permeability improver 120 has a drainage function, it is advisable to use non-segregating concrete in water so that the cement content (mortar content) does not flow out during construction or during drainage in the initial stage of construction. When designing the mix of non-segregating porous concrete, the aggregate particle size should be selected to prevent clogging, that is, to ensure an appropriate porosity, and a non-segregating material in water should be added to provide non-segregating property in water, and a high-performance water reducer should be added in consideration of workability.

[0038] (Waterstop improvement body on the front side) As shown in Fig. 4, the waterstop improvement body 150 on the front side has a function of suppressing the water that enters the main body 130 when the water level of the river rises, and a function of preventing scouring (especially scouring near the front surface toe Tf) when the water level of the river changes from a high water level state to a low water level state. Therefore, the waterstop improvement body 150 on the front side is formed on a part of the front surface Sf including the front surface toe Tf, and is formed so that its water permeability is lower than that of the main body 130 (that is, the waterstop property is higher). Further, it is advisable to form the waterstop improvement body 150 on the front side mainly of a cementitious material so that it also functions as a reinforcing member during an earthquake, that is, it has a considerable strength (shear strength and bending strength).

[0039] The surface-side waterstop improvement body 150 is designed while further considering constructability so as to satisfy predetermined water permeability (waterstop property) and strength. Particularly regarding water permeability and strength, it is desirable to design so that the reinforced soil structure 100 does not undergo abnormal settlement or deformation even during heavy rain or an earthquake, or so that liquefaction of the main body 130 does not occur. Specifically, assuming the river water level expected during heavy rain and the earthquake load as given conditions, it is advisable to design the water permeability and strength of the surface-side waterstop improvement body 150 based on the results obtained by numerical analysis (for example, FEM analysis).

[0040] When forming the surface-side waterstop improvement body 150, it can be formed by performing ground improvement on a part of the existing soil structure Dm (or the main body 130). In this case, it is advisable to improve a part of the soil structure Dm (or the main body 130) with a cement-based solidifying material by using a mechanical agitation method, a high-pressure jet agitation method, or a chemical solution injection method. Alternatively, the surface-side waterstop improvement body 150 can be designed to be made of concrete, and the surface-side waterstop improvement body 150 can also be formed by installing a solidified body by in-situ concrete or a solidified body of precast concrete at a predetermined position.

[0041] (Back-side water permeability improvement body) As shown in FIG. 4, the back-side water permeability improvement body 160 has a function of draining the water that has entered the main body 130 to the outside when the water level of the river rises, and a function of preventing scouring near the back-side crest Tr due to overflow water. Therefore, the back-side water permeability improvement body 160 is formed on a part of the back-side crest surface Sr including the back-side crest Tr, and is formed so that its water permeability is higher than that of the main body 130 (that is, its drainage property is high). Also, so that it functions as a reinforcing member during an earthquake, that is, so that it has a considerable strength (shearing strength and bending strength), the back-side water permeability improvement body 160 is preferably formed mainly of a cement-based material.

[0042] The backside water permeability improvement body 160 is designed while further considering workability so as to satisfy predetermined water permeability (drainage property) and strength. Particularly regarding water permeability and strength, it is desirable to design so that the reinforced soil structure 100 does not undergo abnormal settlement or deformation even during heavy rain or an earthquake, or so that liquefaction damage to the main body part 130 does not occur. Specifically, assuming the river water level expected during heavy rain and the seismic load as given conditions, it is advisable to design the water permeability and strength of the backside water permeability improvement body 160 based on the results obtained by numerical analysis (for example, FEM analysis). Further, as shown in FIG. 3, the backside water permeability improvement body 160 is divided into part A located on the ground, part B located in the soft layer, and part C located in the support layer, and according to the target stability performance, part A, part B, and part C can also be designed with materials having different physical properties (such as strength and water permeability). For example, it can be designed under the condition that the strength increases as the lower layer is stronger in terms of slip stability, or it can also be designed under the condition that the permeability coefficient of the backside water permeability improvement body 160 (part B in FIG. 3) located in the sand layer is made lower than that of the trailing end part (part A in FIG. 3) in order to increase the piping resistance of the upper sand layer (soft layer).

[0043] The backside water permeability improvement body 160 can be formed by installing a solidified body made of concrete. In this case, the solidified body can be installed by in-situ concrete, or a solidified body of precast concrete can also be installed. However, since the backside water permeability improvement body 160 requires appropriate water permeability (drainage property), it is desirable to use a solidified body made of porous concrete. Further, since the backside water permeability improvement body 160 has a drainage function, it is advisable to use a solidified body made of concrete with water non-separability so that the cement component (mortar component) does not flow out during construction or during drainage in the initial stage of construction. When performing the mix design of concrete with water non-separability, in order to prevent clogging, that is, to ensure an appropriate porosity, the particle size of the aggregate is selected, a water non-separating material is added to have water non-separability, and a high-performance water reducing agent is added in consideration of workability for mixing.

[0044] The main body 130 shown in Fig. 3 is constructed on a soft layer (such as a permeable ground composed of sand or sandy soil, or a liquefied layer) deposited on a support layer. Therefore, the front-side water-stopping improvement body 150 and the back-side water-permeable improvement body 160 shown in this figure are formed so as to penetrate the soft layer and further take root in the support layer. Of course, depending on the strength of the soft layer, the front-side water-stopping improvement body 150 or the back-side water-permeable improvement body 160 can also be formed so as to take root only in the soft layer without taking root in the support layer, or the front-side water-stopping improvement body 150 or the back-side water-permeable improvement body 160 can be formed so as to be placed on the support layer without taking root in the support layer.

[0045] Also, a part of the front-side water-stopping improvement body 150 and the back-side water-permeable improvement body 160 can be formed outside the front-side slope surface Sf and the back-side slope surface Sr. Specifically, as shown in Fig. 6, it extends beyond the front-side slope surface Sf and the back-side slope surface Sr, that is, to the river side (left side in the figure) from the front-side slope toe Tf or to the opposite side of the river (right side in the figure) from the back-side slope toe Tr, and a part of the front-side water-stopping improvement body 150 and the back-side water-permeable improvement body 160 is also formed under the ground (soft layer and support layer) in the extended range, so it is in the form of a footing. Comparing Fig. 3 and Fig. 6, the front-side water-stopping improvement body 150 and the back-side water-permeable improvement body 160 shown in Fig. 6 are formed larger only in the part protruding from the front-side slope surface Sf and the back-side slope surface Sr. Therefore, although the construction period and cost for constructing the reinforced soil structure 100 increase, the anti-erosion prevention function near the front-side slope toe Tf and the back-side slope toe Tr and the reinforcement function during an earthquake are improved. Therefore, the front-side water-stopping improvement body 150 and the back-side water-permeable improvement body 160 in the form shown in Fig. 6 should be appropriately designed according to the situation.

[0046] (Slope surface water-stopping improvement body) The calking surface water-stopping improvement body 170 has a function of suppressing the erosion of the front calking surface Sf when the water level of the river rises as shown in FIG. 4. For this purpose, the calking surface water-stopping improvement body 170 is formed on the surface of the front calking surface Sf and covers the front calking surface Sf, and is shown to have a lower water permeability (that is, higher water-stopping property) than the main body 130. This calking surface water-stopping improvement body 170 is formed mainly of a cement-based material. For example, a calking surface water-stopping improvement body 170 of a precast product can be used, and of course, the calking surface water-stopping improvement body 170 can also be formed by in-situ concrete. Alternatively, by using a mechanical agitation method, a high-pressure jet agitation method, or a chemical solution injection method, the calking surface water-stopping improvement body 170 can be formed by improving a part of the main body 130 near the front calking surface Sf with a cement-based solidifying material.

[0047] 3. Soil structure reinforcement method Next, the soil structure reinforcement method of the present invention will be described with reference to FIG. 7. The soil structure reinforcement method of the present invention is a method of constructing the reinforced soil structure 100 described so far. Therefore, descriptions overlapping with those described for the reinforced soil structure 100 will be avoided, and only the content specific to the soil structure reinforcement method of the present invention will be described. That is, the content not described here is the same as that described in "2. Reinforced soil structure" including the description of "1. Definition".

[0048] FIG. 7 is a construction flow chart showing the main steps of the soil structure reinforcement method of the present invention. As shown in this figure, first, preparatory work such as surveying to indicate the positions for forming the top water-stopping improvement body 110 and the calking surface water-permeability improvement body 120, carrying in necessary equipment and arranging it at predetermined positions, and confirming the construction procedure for that day is performed (Step 10 in FIG. 7).

[0049] When preparations are complete, a top-end waterstop improvement body 110 is formed above the top end surface St of the existing earth structure Dm (Step 20 in FIG. 7). Specifically, a precast top-end waterstop improvement body 110 is installed, the top-end waterstop improvement body 110 is formed by in-situ concrete, a part of the main body 130 near the top end surface St is improved with a cement-based solidifying material, or the top-end waterstop improvement body 110 is formed by laying an asphalt pavement body or a concrete pavement body. When the protrusion 114 is provided on the top-end waterstop improvement body 110, the top-end waterstop improvement body 110 is formed so that the protrusion 114 penetrates from the top end surface St into the main body 130.

[0050] On the other hand, a slope surface water permeability improvement body 120 is formed on the surface of the back slope surface Sr of the existing earth structure Dm (Step 30 in FIG. 7). Specifically, a precast product of the slope surface water permeability improvement body 120 made of water-non-separable porous concrete can be installed, or the slope surface water permeability improvement body 120 can be formed by placing water-non-separable porous concrete in-situ. Also, after the slope surface water permeability improvement body 120 is formed, the drainage ditch 140 can be installed along the extension direction of the slope surface water permeability improvement body 120.

[0051] The process of forming the top-end waterstop improvement body 110 and the process of forming the slope surface water permeability improvement body 120 can be carried out with either one of the processes preceding or both processes carried out simultaneously (in parallel). Also, when constructing the front-side waterstop improvement body 150 or the back-side water permeability improvement body 160, it is advisable to construct the front-side waterstop improvement body 150 or the back-side water permeability improvement body 160 prior to the top-end waterstop improvement body 110 and the slope surface water permeability improvement body 120. Hereinafter, in the case of reinforcing the existing earth structure Dm, the procedure for constructing the front-side waterstop improvement body 150 and the back-side water permeability improvement body 160 will be described.

[0052] The front-side water-stopping improvement body 150 is formed on the front side of the existing soil structure Dm. Specifically, by using a mechanical agitation method, a high-pressure jet agitation method, or a chemical solution injection method to perform ground improvement on a part of the existing soil structure Dm with a cement-based solidifying material, the front-side water-stopping improvement body 150 is formed on the front side of the soil structure Dm. On the other hand, the back-side water-permeability improvement body 160 is formed on the back side of the existing soil structure Dm. Specifically, the back-side water-permeability improvement body 160 is formed by installing a solidified body made of water-insoluble porous concrete on the back side of the soil structure Dm. At this time, when partially removing the embankment material of the soil structure Dm to form the back-side water-permeability improvement body 160, it is advisable to appropriately use an earth retaining work in accordance with the site conditions such as the excavation height being equal to or higher than a predetermined height, and then perform the removal work.

[0053] After forming the top-edge water-stopping improvement body 110 and the slope surface water-permeability improvement body 120 within all the planned ranges, and forming the planned front-side water-stopping improvement body 150, back-side water-permeability improvement body 160, and slope surface water-stopping improvement body 170, perform the cleanup and end the work.

Industrial Applicability

[0054] The reinforced soil structure and the soil structure reinforcement method of the present application can be used for various soil structures where water accumulates on one side (front side), such as river levees, coastal levees, flood control dikes, or sand control dams and weirs. According to the present application, river levees and coastal levees can be effectively reinforced. That is, considering that it contributes to the extended lifespan of construction infrastructure, it can be said that the present application is not only industrially applicable but also an invention that can be expected to make a great social contribution.

Explanation of Reference Numerals

[0055] 100 Reinforced soil structure of the present application 110 Top-edge water-stopping improvement body (of the reinforced soil structure) 120 Slope surface water-permeability improvement body (of the reinforced soil structure) 130 Main body part (of the reinforced soil structure) 140 Drainage ditch (of the reinforced soil structure) 150 (Reinforced soil structure) front side water-stopping improvement body 160 (Reinforced soil structure) back side water-permeability improvement body 170 (Reinforced soil structure) slope surface water-stopping improvement body Dm Soil structure Sf Front side slope surface Sr Back side slope surface St Top end surface Tf Front side slope bottom Tr Back side slope bottom

Claims

1. In an earth structure having a main body formed by a front-facing plaster surface, a back-facing plaster surface, and a top surface, it is provided with a top waterproofing improvement body having lower water permeability than the main body, and a plaster surface water permeability improvement body having higher water permeability than the main body, the top waterproofing improvement body is formed at the upper part so as to cover the top surface, the plaster surface water permeability improvement body is mainly composed of a cement-based material and is formed on the surface so as to cover the back-facing plaster surface, only the plaster surface water permeability improvement body is formed on the back-facing plaster surface, A reinforced earth structure, characterized in that.

2. A front-side waterproofing improvement body having lower water permeability than the main body, further provided with a back-side water permeability improvement body having higher water permeability than the main body, the front-side waterproofing improvement body is mainly composed of a cement-based material and is formed at the edge of the front-facing plaster surface, the back-side water permeability improvement body is mainly composed of a cement-based material and is formed at the edge of the back-facing plaster surface, The reinforced earth structure according to claim 1, characterized in that.

3. The top waterproofing improvement body has a protrusion penetrating from the top surface into the interior of the main body, The reinforced earth structure according to claim 1 or claim 2, characterized in that.

4. In a method for reinforcing an earth structure having a main body formed by a front-facing plaster surface, a back-facing plaster surface, and a top surface, a top waterproofing improvement body forming step of forming, at the upper part of the top surface of the earth structure, a top waterproofing improvement body having lower water permeability than the earth structure so as to cover the top surface; a plaster surface water permeability improvement body forming step of forming, on the surface of the back-facing plaster surface of the earth structure, a plaster surface water permeability improvement body having higher water permeability than the earth structure so as to cover the back-facing plaster surface, In the plaster surface water permeability improvement body forming step, only the plaster surface water permeability improvement body is formed on the back-facing plaster surface, A method for reinforcing an earth structure, characterized in that.

5. In the top waterproofing improvement body forming step, the top waterproofing improvement body having a protrusion is used, and the top waterproofing improvement body is installed so that the protrusion penetrates from the top surface into the main body. The method for reinforcing an earth structure according to claim 4, characterized in that.

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