Methods for reinforcing existing embankments

Abstract

We offer a reinforcement method for existing embankments that is cost-effective, allows for shorter construction periods, and keeps temporary construction costs low. [Solution] The present invention relates to a method for reinforcing an existing embankment (EE) in which an existing embankment (EE) is constructed on an inclined base (OG: natural ground), a flat surface (FS) is created at its top, and a building is constructed on the flat surface (FS), wherein a reinforcing material (1) is driven into the area directly below the top, with its lower end reaching the base (OG: natural ground) and in a horizontal direction or inclined with respect to the horizontal direction.

Description

Technical Field

[0001] The present invention relates to a technique for reinforcing an existing embankment constructed on an inclined foundation (natural ground).

Background Art

[0002] When reinforcing an existing embankment EE constructed on an inclined foundation OG (natural ground) such as a single embankment, a single cut-and-fill embankment, or a valley-fill embankment, conventionally, in order to ensure the safety of the entire existing embankment, for example, as shown in FIG. 20, ground anchors 21 are driven across the entire surface of the existing embankment EE. Alternatively, as shown in FIG. 21, restraining piles 22 are constructed from the middle to the lower part of the existing embankment EE, and ground anchors 21, ground reinforcement geotextiles 23, and gabions 24 are constructed on the entire slope surface. In FIGS. 20 and 21, the symbol SS (dashed line) indicates the slip surface, and the symbol FS indicates the flat surface at the top of the existing embankment EE. As shown in FIGS. 20 and 21, ground reinforcement geotextiles and ground anchors fix the tension members to the surface of the existing embankment EE and extend from the surface of the existing embankment EE deep into the ground. For the restraining piles, they are also installed extending from the surface of the existing embankment EE deep into the ground, thereby ensuring the safety of the entire existing embankment and suppressing the occurrence of sliding or collapse in the existing embankment EE.

[0003] [[ID=第十九]] However, for example, the conventional technologies shown in FIGS. 20 and 21 have the problems that the countermeasures for preventing the sliding of the entire existing embankment are large-scale, costly, and have a long construction period. In addition, since countermeasures are taken for the entire surface of the existing embankment, there is also a problem that temporary scaffolds and the like become large-scale and the temporary costs become enormous.

[0004] As another conventional technology, a ground reinforcement geotextile for excavating an existing embankment in a steep slope has been proposed (see Patent Document 1). However, such a conventional technology does not intend to solve the problems of high cost, long construction period, and enormous temporary costs for taking countermeasures against the sliding of the entire existing embankment.

Prior Art Documents

[0005] [Patent Document 1] Patent No. 2653731 [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention was proposed in view of the problems of the conventional technology described above, and aims to provide a reinforcement structure for existing embankments that is inexpensive, allows for shorter construction periods, and keeps temporary construction costs low, as well as a reinforcement method for implementing it. [Means for solving the problem]

[0007] As a result of various studies, the inventor It is important to note that when roads, railways, houses, and other structures are built on existing embankments (EE) constructed on sloping bedrock (OG), the majority are built on the flat top surface (FS), and not across the entire existing embankment (EE). We found that if the area above the existing embankment (EE) is stable, the entire existing embankment (EE) will be stable.

[0008] This invention was created based on the aforementioned findings, and the reinforcement structure for existing embankments (EE) of this invention is In a reinforcement structure for an existing embankment (EE) constructed on a sloping base (OG: natural ground), where a flat surface (FS) is created at its top and a building is constructed on the flat surface (FS), The method is characterized by installing a reinforcing material (1) having tensile strength in the area directly below the top, so as to extend in a horizontal direction or in a direction inclined with respect to the horizontal direction. Here, it is preferable that the excavated hole (H) in the area from the slope-side end (1EV: valley-side end) of the reinforcing material (1) to the embankment surface is filled with backfill material. In that case, it is preferable that a low-strength tensile member is installed in the area from the slope-side end (1EV) of the reinforcing material (1) to the embankment surface where the backfill material is filled. The backfill material filled in the area from the slope-side end (1EV) of the reinforcing material (1) to the embankment surface needs to have a strength similar to that of the existing embankment (EE), and low-strength materials (hardening material C1) such as cement milk, fluidized soil, or cement bentonite can be used. In the present invention, the reinforcing material (1) is preferably inserted into a borehole (H) drilled in an existing embankment (EE), and the gap between the borehole (H) and the reinforcing material (1) is filled with a hardening agent (C) to integrate the ground around the borehole (H) with the reinforcing material (1). The hardening agent (C) is not particularly limited as long as it has adhesion to the reinforcing material (1), such as cement milk, and possesses a certain degree of strength. A material with excellent filling properties is preferred. In the present invention, if the reinforcing material (1) is a steel material that has frictional resistance with the ground, such as when the reinforcing material (1) has an uneven structure perpendicular to the axial direction (for example, a structure with large screw threads), the hardening material (C) may be omitted. Furthermore, in the present invention, if deformation due to the closure of the drilled hole on the embankment surface side from the slope-side end (1EV) of the reinforcing material (1) is permitted, then the region (HE) of the excavated hole (1) on the embankment surface side from the slope-side end (1EV) of the reinforcing material (1) can be configured so that no filler material is filled in.

[0009] Here, the aforementioned structures include, for example, roads (highways), railways, houses, etc. Furthermore, the reinforcing material (1) can be made of a material with high tensile strength, such as deformed reinforcing bars or FRP. Here, the pitch (spacing), length, and number of reinforcing members (1) are calculated, with the spacing (pitch) being, for example, 0.5m to 1.5m. The same applies to both vertical and horizontal spacing. Furthermore, the spacing of the reinforcing members (1) does not necessarily have to be constant. For example, it is possible to cast the reinforcing members (1) in a dense state by making the spacing (pitch) smaller in the lower area, and in a sparse state by making the spacing (pitch) larger in the upper area.

[0010] In the present invention, the reinforcing material (1) includes material that is cast so as to straddle (penetrate) the assumed slip surface of the existing embankment (EE) (cast beyond the assumed slip surface). In cases where the expected slip surface cannot be determined, the reinforcing material (1) includes those that are driven in so as to reach the bedrock (ground) layer. Furthermore, the vertical arrangement of the tops of the multiple reinforcing members (1) has a steeper gradient (angle θ) than the gradient of the existing embankment EE, for example, between 0° and 45°.

[0011] In the excavated hole (H), it is preferable that the area on the surface side of the existing embankment (EE) is filled with a low-strength material (hardening material C1: infill material: for example, cement grout, fluidized soil, cement bentonite, etc.) having a strength similar to that of the existing embankment (EE). Alternatively, in the area of ​​the excavation hole (H) on the surface side of the existing embankment (EE) from the head of the reinforcing member (1), a low-strength tensile material such as a polyvinyl chloride pipe may be installed as a reinforcing material, and a hardening agent may be filled into the gap between the excavation hole and the low-strength reinforcing material. When using a low-strength tensile material, it is necessary to use a reinforcing material with high tensile strength for the deep side of the reinforcing material (1) and a reinforcing material with low tensile strength for the shallow side, thereby differentiating the placement of the reinforcing materials according to depth. The high-tensile strength reinforcing material in the deep area and the low-tensile strength reinforcing material in the shallow area may be connected. In the present invention, it is preferable to install a reinforcing material (2: a reinforcing material with a shorter longitudinal dimension) in the region between adjacent reinforcing materials (1) (in the vertical direction in Figure 1 and in the direction perpendicular to the plane of the paper in Figure 1) in the horizontal direction or in the direction inclined from the horizontal direction to prevent the material from falling out. The angle at which the reinforcing material (2) for preventing internal collapse is inclined from the horizontal is determined by design (strength calculation), but it is possible to set it to an angle that is advantageous in calculations or in terms of mechanism. Generally, the direction in which the reinforcing material (2) for preventing internal collapse is cast (angle with respect to the horizontal plane) is the same as the direction in which the reinforcing material (1) is cast (angle with respect to the horizontal plane).

[0012] The present invention provides a method for reinforcing existing embankments (EE). In a method for reinforcing an existing embankment (EE) constructed on a sloping base (OG: natural ground), in which a flat surface (FS) is created at the top of the embankment (EE) and a structure is built on the flat surface (FS), The method is characterized by installing a reinforcing member (1) in the area directly below the top, so as to extend horizontally or in a direction inclined with respect to the horizontal. In the present invention, the reinforcing material (1) is inserted into a borehole (H) drilled in an existing embankment (EE), and it is preferable to fill the gap between the borehole (H) and the reinforcing material (1) with a hardening agent (C) to integrate the reinforcing material (1) with the ground surrounding the borehole (H). However, depending on the type of reinforcing material (1), the hardening agent (C) may be omitted. Furthermore, the method for reinforcing existing embankments (EE) according to the present invention is: A method for constructing a reinforcing structure according to any one of claims 1 to 4, In installing the reinforcing material (1), the process involves drilling holes in the area directly below the top of the existing embankment from the surface of the embankment to install the reinforcing material (1) in a horizontal direction or in an inclined direction relative to the horizontal direction, The process involves installing a reinforcing material (1) in the drilled borehole (H) so as to reach (straddle) the expected slip surface (SS), The process involves filling the area around the reinforcing material with a hardening agent (C), The method is characterized by having a step of filling the area from the slope-side end (1EV) of the reinforcing material (1) to the embankment surface side with a filler material. Furthermore, in the method for constructing the reinforcement structure according to claim 4, it is preferable to attach a packer (1P) to the head of the reinforcing material (1), perform packer injection, and then pressure inject the hardening material (C) around the reinforcing material (1). [Effects of the Invention]

[0013] According to the present invention having the above-described configuration, a reinforcing material (1) whose lower end reaches the assumed sliding surface (SS) or the base (OG: natural ground) and extends in a horizontal direction or a direction inclined with respect to the horizontal direction is placed in the region directly below the flat surface (FS) at the top of the existing embankment. Therefore, only the region directly below the flat surface (FS) at the top of the existing embankment (the region directly below the region where the construction part is constructed) is prevented from collapsing (or falling) due to sliding. In other words, according to the present invention, although the overall collapse (or slip) of the existing embankment (EE) cannot be prevented, the collapse (slip) of the region directly below the flat surface (FS) at the top of the existing embankment (the region directly below the region where the construction part is constructed) is prevented, and the safety of the structures (roads, railways, and other various structures) at the top of the existing embankment (EE) is ensured.

[0014] Then, since it is only necessary to place the reinforcing material (1) extending horizontally only in the region directly below the flat surface (FS) at the top of the existing embankment, compared with the case of taking anti-slip measures for the entire existing slope (EE), the measures are much smaller in scale, the cost is reduced, and the construction period is shortened. Also, compared with the case of taking measures for the entire surface of the existing embankment (EE), the temporary scaffolding and the like are also smaller in scale, and the temporary cost becomes much smaller. Furthermore, the operation of placing the reinforcing material (1) extending horizontally only in the region directly below the flat surface (FS) at the top of the existing embankment may be carried out on the slope near the top of the existing embankment (EE). Therefore, even when there are already roads, railways, and other structures on the flat surface (FS), it can be easily constructed. Also, the temporary scaffolding can be provided as little as possible, and only the minimum necessary construction can be carried out (for example, only the region of about one slope level of the slope is reinforced).

[0015] Furthermore, in the present invention, in the region between the adjacent reinforcing members (1) (the vertical direction in FIG. 1 and the direction perpendicular to the plane of FIG. 1), if the anti-collapse reinforcing member (2) is placed horizontally or in a direction inclined from the horizontal direction in such a manner that the lower end does not reach the assumed sliding surface (SS) or the base (OG: natural ground), it is possible to prevent a part of the existing embankment (EE) in the region between the reinforcing members (1) (the vertical direction in FIG. 1 and the direction perpendicular to the plane of FIG. 1) from collapsing (so-called "collapse in the middle").

Brief Description of the Drawings

[0016] [Figure 1] It is an explanatory diagram showing the first embodiment of the present invention. [Figure 2] It is an explanatory diagram showing the operation and effect of the first embodiment. [Figure 3] It is an explanatory diagram showing the second embodiment of the present invention. [Figure 4] It is an explanatory diagram showing the third embodiment of the present invention. [Figure 5] It is an explanatory diagram showing the fourth embodiment of the present invention. [Figure 6] It is an explanatory diagram showing the fifth embodiment of the present invention. [Figure 7] In the embodiment of the present invention, it is an explanatory diagram showing a state where a hole is drilled for placing a horizontal reinforcing member. [Figure 8] It is an explanatory diagram showing a state where a horizontal reinforcing member provided with a packer is inserted. [Figure 9] It is an explanatory diagram showing a state where the packer is inflated. [Figure 10] It is an explanatory diagram showing a state where a curing material is injected. [Figure 11] It is an explanatory diagram showing a state where the region on the valley side of the horizontal reinforcing member is removed. [Figure 12] It is an explanatory diagram showing a state where the region on the valley side of the packer is filled. [Figure 13] It is an explanatory diagram showing a state where a reinforcing member with low tensile strength is installed and filled in the region on the valley side of the packer. [Figure 14]This is an explanatory diagram showing the state after drilling in the first modified example. [Figure 15] This is an explanatory diagram showing the state after the hardening agent has been injected in the first modified example. [Figure 16] This is an explanatory diagram showing the state after the hardening agent has been injected in the second modified example. [Figure 17] This is an explanatory diagram showing the state in which a horizontal reinforcing material is inserted into the drilled insertion hole in the third modified example and a hardening material is injected. [Figure 18] This diagram shows a modified example of the third modification, illustrating the state in which the hardening agent has been pressure-injected into the insertion hole. [Figure 19] This is an explanatory diagram of the fourth modified example. [Figure 20] This is an explanatory diagram showing an example of conventional technology. [Figure 21] This is an explanatory diagram of a conventional technology that differs from Figure 20. [Figure 22] This is an explanatory diagram showing the state in which a reinforcing material is inserted in the fifth modified example. [Figure 23] The fifth modified example is an explanatory diagram showing the state in which, after inserting the reinforcing material, the nut is rotated and screwed only onto the reinforcing material on the valley side. [Figure 24] The fifth modified example is an explanatory diagram showing the state in which, after inserting the reinforcing material, the nut is rotated and screwed only onto the reinforcing material on the threaded side. [Figure 25] This is an explanatory diagram of the sixth modified example. [Figure 26] This is an explanatory diagram showing the state in which a reinforcing material is inserted using a push-in member in the sixth modified example. [Figure 27] This is an explanatory diagram showing the state in which the pushing member is withdrawn from the excavated hole in the sixth modified example. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described below with reference to the attached drawings. In Figure 1, an existing embankment (EE) is constructed on a sloping bedrock (OG), and a flat surface (FS) is created at the top of the existing embankment (EE). Roads (highways), railways, or houses and other various structures are built on the flat surface (FS). In Figure 1, multiple reinforcing members 1 (horizontal reinforcing members) are installed in the area directly below the flat surface FS at the top of the embankment where the structure will be built (area indicated by symbol EE-1). The lower ends of the reinforcing members 1 reach the assumed slip surface (SS) or the bedrock OG (natural ground) and extend in a horizontal direction or in a direction inclined with respect to the horizontal direction. The spacing P (pitch dimension) between adjacent reinforcing members 1 in the vertical direction is, for example, 0.5m to 1.5m. Reinforcement material 1 can be made of materials with high tensile strength, such as deformed reinforcing bars or FRP. Reinforcement material 1, made of reinforcing bars, etc., is inserted into the excavated hole (horizontal hole) as described later with reference to Figures 7 to 19, and a hardening material (such as a fluid hardening material like grout) C is filled around it. This fixes the reinforcing material 1 to the natural ground OG and / or the existing embankment EE.

[0018] In Figure 1, with the exception of the uppermost reinforcing member 1, the tip of the reinforcing member 1 on the mountain side (ground OG side) reaches the assumed slip surface SS (the assumed slip surface of the existing embankment EE in the case where no collapse countermeasures have been taken), and with the exception of the uppermost reinforcing member 1, the reinforcing members 1 are driven so as to straddle (or penetrate) the assumed slip surface SS. Here, if an assumed slip surface cannot be assumed, the reinforcing member (1) can be driven so as to reach the base (ground) layer. In Figure 1, the embankment portion directly below the flat surface FS at the top of the embankment is indicated by the symbol EE-1, and the embankment portion further towards the valley is indicated by the symbol EE-2. Although not explicitly shown in Figure 1, reinforcing material 1 is inserted into a borehole H (see Figures 7-19), which is not explicitly shown in Figure 1. Hardening material C (see Figures 10-19) is filled into the area deeper underground (mountain side in Figure 1) than the slope-side end 1EV (valley-side end) of reinforcing material 1. As will be described later, high-strength grout material is used. Furthermore, although not explicitly shown in Figure 1, the area from the valley-side end 1EV of the reinforcing material 1 to the embankment surface is filled with a filler material (a low-strength filler material: for example, a low-strength hardening agent C1).

[0019] Figure 1 shows multiple reinforcing members 1 (seven in Figure 1) in the vertical direction. Although not shown in the illustration, multiple reinforcing members 1 are also installed in the direction perpendicular to the plane of the paper in Figure 1. The spacing P (pitch dimension) between adjacent reinforcing members 1 in the direction perpendicular to the plane of the paper is, for example, 0.5m to 1.5m. Whether or not reinforcing material 1 reaches the base OG, the number of reinforcing material 1 installed in the vertical direction in Figure 1, the number of reinforcing material 1 installed in the direction perpendicular to the plane of Figure 1, the distance (spacing, pitch) between adjacent reinforcing material 1 in the vertical direction in Figure 1, and the distance (spacing, pitch) between adjacent reinforcing material 1 in the direction perpendicular to the plane of Figure 1 are determined and calculated according to the conditions of the construction site so as to prevent the collapse of the embankment portion EE-1 directly below the flat surface FS at the top of the embankment, and the design is made so as to prevent the collapse of the embankment portion EE-1 directly below the flat surface FS at the top of the embankment. In Figure 1, the valley side (right side in Figure 1) of the reinforcing material 1, region 1A, is shown with a dashed line because, as will be explained later, in region 1A, the reinforcing material 1 has been removed or its strength has been reduced to make it more prone to fracture.

[0020] The reinforcing material 1, installed in the area directly below the flat surface FS at the top of the embankment, prevents only the area EE-1 directly below the flat surface FS at the top of the embankment from sliding and collapsing. In other words, in the illustrated embodiment, the existing embankment EE-2 in the area on the valley side (to the right in Figure 1) from the area where the reinforcing material 1 is installed (area EE-1 directly below the flat surface FS at the top of the embankment) is not considered in terms of whether or not it will slide and collapse, and the intention is not to ensure the stability of the entire existing embankment EE. In the illustrated embodiment, the intention is only to ensure the stability of the existing embankment top, or of structures (roads, railways, houses, etc.) built on the flat surface FS at the top of the existing embankment. In the illustrated embodiment, when reinforcing an existing embankment EE, since roads (highways), railways, houses, and other structures are mostly built on the flat surface FS at the top, the design prevents the flat surface FS from collapsing due to sliding, thereby ensuring the safety of structures (roads, railways, and various other structures) on the flat surface FS. In Figure 1, the imaginary line V1E connecting the valley-side ends 1EV of the cast-in reinforcement members 1 is inclined at an angle θ (e.g., 0° to 45°) with respect to the vertical line LV. Although not explicitly stated, the gradient (angle θ) of the vertical arrangement of the tops of the reinforcement members is steeper than the gradient of the existing embankment EE, for example, between 0° and 45°.

[0021] The effects of the first embodiment will be explained with reference to Figure 2. As described above with reference to Figure 1, in the first embodiment, in the region EE-1 (Figure 1) directly below the flat surface FS at the top of the existing embankment EE, the reinforcing material 1 is installed so as to straddle the assumed slip surface SS (Figure 1) (or reach the base OG). Therefore, although the collapse of the existing embankment EE may occur along the assumed slip surface SS3 (Figure 2), collapse along the assumed slip surface SS1 (Figure 2) is prevented. As a result, collapse and erosion are prevented only in the region directly below the flat surface FS at the top of the existing embankment EE. In Figure 2, the existing embankment EE after collapse is shown by a solid line, and the existing embankment EE before collapse is shown by a dotted line. In the embodiment shown in Figure 1, there is a reinforcing material 1 that is driven across the assumed slip surface SS (Figure 1), and in the existing embankment EE where the reinforcing material 1 is driven across (or penetrates) the assumed slip surface SS (Figure 1), the assumed slip surface becomes indicated by symbol SS3 (Figure 2), and collapse along the assumed slip surface SS1 (Figure 2: assumed slip surface SS in Figure 1) that would occur if no reinforcement measures were taken does not occur. In Figure 2, the collapsed soil of the collapsed existing embankment is indicated by symbol EE-A, but the flat surface FS does not collapse. Therefore, no damage occurs to structures (roads, railways, and various other structures) not shown on the top flat surface FS of the existing embankment EE, and the safety of structures on the flat surface FS is ensured.

[0022] In the first embodiment, construction is only required in the area EE-1 (Figure 1) directly below the flat surface FS at the top of the existing embankment EE. Therefore, unlike the conventional technology, there is no need to implement slip prevention measures over the entire area of ​​the existing embankment EE. Compared to the reinforcement measures implemented in the conventional technology, the reinforcement work in the first embodiment is on a much smaller scale, resulting in reduced costs and a shorter construction period. In addition, the temporary scaffolding and other equipment are also on a smaller scale, resulting in significantly lower temporary construction costs. Furthermore, since construction can be carried out near the flat surface FS at the top of the existing embankment EE, it can be easily performed even if roads, railways, or other structures already exist on the flat surface FS. Furthermore, temporary scaffolding can be minimized, and only the bare minimum necessary can be constructed (for example, reinforcing only an area of ​​about one level of slope). Here, in the event of a collapse along the assumed slip surface SS3 in Figure 2, the area on the valley side of the valley end 1EV (see Figure 1) of the reinforcing material 1 in the excavated hole H drilled for the placement of the reinforcing material 1 will not affect area EE-1 (the underground area). (Even if a collapse occurs along the assumed slip surface SS3, the reinforcing material 1 will not be carried away by the collapsed soil EE-A.) Therefore, the area on the valley side of the valley end 1EV of the reinforcing material 1 in the excavated hole H is filled with a low-strength material such as cement grout, fluidized soil, or cement bentonite as a backfill material (hardening agent C1). This backfill material has a strength similar to that of the existing embankment (EE). Then, in the area on the valley side of the valley end 1EV of the reinforcing material 1, a material with low tensile strength such as polyvinyl chloride is installed as a reinforcing material. In this case as well, the area between the low-tensile strength reinforcing material and the excavated hole is filled with a low-strength material as a backfill material (for example, a low-strength hardening agent C1).

[0023] In the first embodiment shown in Figures 1 and 2, the imaginary line V1E connecting the valley-side ends 1EV of the multiple reinforced members 1 that have been cast is inclined with respect to the vertical line VL. Furthermore, the vertical gradient of the tops of the multiple reinforced members 1 (angle θ: the angle of inclination of the imaginary line V1E with respect to the vertical line VL) is steeper than the gradient of the existing embankment EE, for example, set to 0° to 45°. However, as shown in the second embodiment in Figure 3, the reinforcing members 1 may be cast in such a way that the valley-side ends 1EV of the multiple reinforcing members 1 are located on the same vertical line. The other configurations and effects in the second embodiment shown in Figure 3 are the same as those in the embodiments shown in Figures 1 and 2.

[0024] In the first and second embodiments shown in Figures 1 to 3, the mountain-side (ground OG-side) ends 1EG of the multiple cast reinforcing members 1 are arranged on the same vertical line. In contrast, as shown in the third embodiment in Figure 4, the multiple cast reinforcing members 1 may be cast such that the mountain-side ends 1EG of the multiple cast reinforcing members 1 (or imaginary lines connecting them, not shown) are inclined with respect to the vertical. In the third embodiment shown in Figure 4, the mountain-side ends 1EG of the multiple cast reinforcing members 1 are also cast in such a way that the imaginary line (not shown) connecting them is inclined with respect to the vertical. In Figures 1 and 3, there are many reinforcing members 1 placed across the assumed slip surface SS, but in Figure 4, there are fewer reinforcing members 1 cast across the assumed slip surface SS. The number of reinforcing members 1 cast across the assumed slip surface SS is also determined by strength calculations. The other configurations and effects in the third embodiment shown in Figure 4 are the same as those in the embodiments shown in Figures 1 to 3.

[0025] In the first to third embodiments shown in Figures 1 to 4, the longitudinal dimensions of the multiple reinforcing members 1 to be cast are approximately equal. However, as shown in the fourth embodiment shown in Figure 5, in addition to the reinforcing members 1, reinforcing members 1α with clearly longer longitudinal dimensions may also be cast. In Figure 5, reinforcing material 1α reaches the ground OG, but whether or not reinforcing material 1 or 1α reaches the ground OG is determined by strength calculations. The other configurations and effects in the fourth embodiment shown in Figure 5 are the same as those in the embodiments shown in Figures 1 to 4.

[0026] In the fifth embodiment shown in Figure 6, reinforcing members 2, which are shorter in the longitudinal direction than the reinforcing members 1 and do not reach the assumed slip surface SS, are installed in the region between the reinforcing members 1 to prevent internal collapse. Although not shown in the figure, the spacing between the internal collapse prevention reinforcing members 2 is, for example, 0.5m to 1.5m between adjacent reinforcing members 1 or between internal collapse prevention reinforcing members 2. Reinforcement material 2, installed to prevent collapse, is designed to prevent the embankment in the area between reinforcement materials 1 from collapsing (a so-called "collapse"). Although not shown in the illustration, in the direction perpendicular to the plane of the paper in Figure 1, the reinforcing material 2 for preventing internal collapse is also installed in the area between the reinforcing materials 1. The spacing (pitch dimension) between adjacent reinforcing materials 2 for preventing internal collapse in the direction perpendicular to the plane of the paper is, for example, 0.5m to 1.5m, which is the spacing between adjacent reinforcing materials 1 or the pitch between other reinforcing materials 2 for preventing internal collapse.

[0027] Both the collapse (hollowing out) of the embankment EE in the region between adjacent reinforcing members 1 in the vertical direction of Figure 6, and the collapse (hollowing out) of the embankment EE in the region between adjacent reinforcing members 1 in the direction perpendicular to the plane of the paper in Figure 1, are prevented by installing reinforcing members 2 to prevent hollowing out. Reinforcement material 2 can also be constructed of reinforcing steel, similar to reinforcement material 1. And, like reinforcement material 1, it can be fixed to the natural ground OG and / or existing embankment EE, as will be described later with reference to Figures 7 to 19. The other configurations and effects in the fifth embodiment shown in Figure 6 are the same as those in the embodiments shown in Figures 1 to 5.

[0028] Next, the procedure for pouring the reinforcing material 1 will be explained with reference to Figures 7 to 13. As shown in Figure 7, the first step involves drilling an insertion hole H into which the reinforcing material 1 will be inserted. In Figures 7 to 13, arrow OG indicates the base OG side, and arrow V indicates the valley side. In the process shown in Figure 7, drilling for the reinforcing material 1 is carried out from the valley-side surface of the existing embankment EE (Figures 1 and 2) to a predetermined depth. The predetermined depth is, for example, a depth to which the reinforcing material 1 is positioned across the assumed slip surface SS (see Figures 1 to 6). In the next step shown in Figure 8, the reinforcing material 1 is inserted into the drilled insertion hole H. In the illustrated embodiment, a reinforcing material with a packer 1P attached is used as the reinforcing material 1.

[0029] In the process shown in Figure 9, packer expansion fluid is pressurized and injected into packer 1P. This injection causes packer 1P to expand, and the outer surface of packer 1P presses against the inner wall of the insertion hole H. The process then proceeds to the process shown in Figure 10. In the process shown in Figure 10, the hardening agent C is injected into the region of the insertion hole H deeper than packer 1P (the region on the side of arrow OG from packer 1P in Figure 10: the region on the substrate OG side in Figures 1 and 2). It is preferable to inject the hardening agent C under pressure. The hardening material C is filled into the area EE-1 (Figure 1) directly below the flat surface FS (see Figure 1) at the top, or into the area on the deeper underground side (arrow OG side in Figure 10: mountain side in Figure 1) from the valley-side end 1EV of the reinforcing material 1 in Figures 1 to 5, and a high-strength grout material is used. Then, in the process shown in Figure 11, the area of ​​the reinforcing material 1 on the front side of packer 1P (the side indicated by arrow V in Figure 11; the valley side in Figures 1 and 2) is removed (deleted).

[0030] In Figures 7 to 13, packer 1P is positioned on the valley side (arrow V side) of the reinforcing material 1, rather than at the position where it straddles the assumed slip surface SS. In the process shown in Figure 11, the area of ​​the reinforcing material 1 on the front side (valley side) of packer 1P is removed. Then, in the process shown in Figure 12, the area within the insertion hole H on the front side of packer 1P (towards arrow V in Figure 12) (the area of ​​the reinforcing material 1 from which the aforementioned area was removed) is filled with a backfill material. A low-strength material C1 can be used as the backfill material. For example, cement bentonite can be used as the low-strength material C1. Cement bentonite has the same strength as the embankment material of the existing embankment EE. Alternatively, as shown in Figure 13, a material with low tensile strength may be installed in the area of ​​the insertion hole H on the front side (arrow V side) of the packer 1P (the area of ​​the reinforcing material 1 after removing the aforementioned area) where the filler material is packed. The tensile strength of the area 1A on the valley side of the packer 1P in the reinforcing material 1 is reduced so that the area 1A on the valley side of the packer 1P in the reinforcing material 1 is more prone to fracture. For example, the area 1A on the valley side of the packer 1P in the reinforcing material 1 can be made of a material with low tensile strength, such as a PVC pipe.

[0031] As described above, a packer 1P is placed at a predetermined position near the valley-side end of the reinforcing member 1, and in the process shown in Figure 11, the area on the side of arrow V from packer 1P is removed (deleted). Alternatively, as shown in Figure 13, the strength of the material in area 1A on the side of arrow V from packer 1P is reduced to make it more prone to fracture. Even if the area of ​​the existing embankment EE on the valley side of the top flat surface FS (i.e., the area where the area on the arrow V side of the packer 1P of the reinforcing material 1 has been removed) were to collapse, the low-strength portion (1A) would fracture and be carried away by the collapsing soil on the valley side, but the reinforcing material 1 installed directly below the flat surface FS on which the building is constructed would not be carried away by the collapsing soil, and the existing embankment EE-1 (Figure 1) directly below the building would not be affected by the collapse, thus ensuring the stability of the building on the top flat surface FS of the existing embankment EE.

[0032] Although not shown in the diagram, reinforcing material 1 can be installed without the need for packers. For example, when using a highly viscous hardening agent, the agent is less likely to leak out of the insertion hole H, so the hardening agent (injection agent) can be filled into the insertion hole H (excavation hole) without using a packer.

[0033] In the illustrated embodiment, the adhesion strength between the reinforcing material 1, the hardening material C (filler), and the base OG (ground) can be improved. Referring to Figures 14 to 19, a modified example that improves the adhesion strength between the reinforcing material 1, the hardening material C (filling material), and the natural ground OG or existing embankment EE will be described. In the first modified example shown in Figures 14 and 15, as shown in Figure 14, an insertion hole H1 is drilled in which only a portion of the insertion hole H1 is enlarged in the longitudinal direction (a portion of the insertion hole H1 is enlarged). On the side of the insertion hole H1 that is deeper underground than the valley-side end 1EV of the reinforcing material 1 (Figure 1) (arrow OG side in Figure 14: mountain side in Figure 1), there are multiple enlarged portions H1A (portions with a large inner diameter of the circular hollow cross-section) arranged at roughly equal intervals in the longitudinal direction. Here, the enlarged portions H1A may or may not be at equal intervals in the longitudinal direction of the insertion hole H1. When drilling the insertion hole H1, drilling is carried out from the valley-side slope of the existing embankment EE (Figures 1 and 2) to a predetermined depth. In Figures 14 to 19, arrow OG indicates the base OG side, and arrow V indicates the valley side. In the process shown in Figure 15, reinforcing material 1 is inserted into the drilled insertion hole H1, and then hardening material C is injected into the insertion hole H1.

[0034] According to the first modified example in Figures 14 and 15, the insertion hole H1 has an enlarged diameter portion H1A, which improves the adhesion strength with the base OG or existing embankment EE. Therefore, even if an external force in the direction of arrow V (for example, a force that tries to pull collapsing soil) is applied, the enlarged diameter portion H1A can resist the external force. Note that in Figures 15 to 19, the valley side of reinforcing member 1 (the side indicated by arrow V in Figure 15, etc.: the valley side of packer 1P) is omitted from the diagram.

[0035] In the second modified example shown in Figure 16, the diameter of the insertion hole H is the same, but a hardening agent C corresponding to the seepage characteristics of the drilled ground is injected under pressure into the hole. As a result, the adhesion strength between the natural ground OG or existing embankment EE and the hardening agent C is improved, so that the reinforcing material 1 and the hardening agent C can resist external forces in the direction of arrow V. Here, if the hardening agent C is a grout material, it is selected according to the characteristics (seepage characteristics) of the ground in the surrounding area. For example, depending on whether the drilled ground is gravel, sand, or cohesive soil, a material with different characteristics (seepage characteristics) is used for the grout material. If the ground to be drilled is gravel, a material with high viscosity and low seepage is used for the grout material, and if the ground to be drilled is cohesive soil, a material with extremely low viscosity and high seepage is used for the grout material. In Figure 16, the region where the hardening agent C has penetrated the area surrounding the insertion hole H (penetration region) is indicated by the symbol PE.

[0036] In the third modified example shown in Figure 17, a reinforcing material 1 with multiple packers 1P is inserted into the insertion hole H, and a hardening agent C is pressurized and injected into the packers 1P to cause them to expand. Then, the hardening agent C is injected into the insertion hole H. In Figure 17, when the hardening agent C is pressure-injected into the packers 1P arranged in multiple locations on the reinforcing material 1, the packers 1P expand as shown in Figure 17, increasing the pull-out resistance (adhesion) of the reinforcing material 1. Therefore, in the third modified example in Figure 17, it is not necessary to pressure-inject the hardening agent into the region between the packers 1P in the insertion hole H.

[0037] On the other hand, in Figure 18, which is a modified version of Figure 17, the hardening agent C is also pressure-injected into the area between the packers 1P, thereby exhibiting the combined functions and performance of Figures 16 and 17. That is, in Figure 18, as in Figure 17, the pull-out resistance of the reinforcing material 1 increases as multiple packers 1P expand. At the same time, in Figure 18, the hardening agent C pressure-injected into the area where packers 1P are not placed in the longitudinal direction of the insertion hole H penetrates into the ground OG or existing embankment EE in the area surrounding the insertion hole H, forming a permeation area PE. Due to the increase in pull-out resistance caused by the expansion of multiple packers 1P and the formation of multiple permeation areas PE intermittently in the longitudinal direction of the insertion hole H, the adhesion strength with the ground OG or existing embankment EE is improved, so that the reinforcing material 1 and the hardening agent C can withstand the tensile force even when an external force in the direction of arrow V is applied.

[0038] In the fourth modified example shown in Figure 19, multiple protrusions 1B are formed intermittently along the longitudinal direction of the reinforcing material 1. By installing the protrusions 1B on the reinforcing material 1, the adhesion strength between the reinforcing material 1 and the hardening material C (filler, such as grout) is improved. Therefore, even if a tensile force acts on the reinforcing material 1 in the direction of arrow V, the multiple protrusions 1B can resist this tensile force. The other configurations and effects of the first to fourth modifications are the same as those of the embodiments described above.

[0039] Referring to Figure 13, in the modified example described above, the reinforcement material in the area of ​​the insertion hole H on the front side of packer 1P (the side of arrow V in Figure 13: the valley side) (the area of ​​reinforcement material 1 after removing the aforementioned area) is made of a material 1A (such as PVC pipe) with low tensile strength. This configuration makes the area 1A on the valley side of packer 1P in reinforcement material 1 more prone to fracture, thereby preventing the mountain-side reinforcement material 1 from being carried along by the collapsed soil EE-A (Figure 2) even if a collapse occurs along the assumed slip surface SS3 (Figure 2). However, even if reinforcement material 1 and 1A are made of the same material in the mountain-side (opposite side of arrow V) and valley-side (arrow V side) areas of reinforcement material 1, it is possible to prevent the mountain-side reinforcement material 1 from being carried along by the collapsed soil EE-A (Figure 2). In the fifth modified example shown in Figure 22, threads are formed on the valley end (the side of arrow V in Figure 22) of the crest end (opposite to arrow V in Figure 22) of the crest end (the side of arrow V in Figure 22) and on the crest end of the valley end reinforcing member 1A, and a nut N connects the valley end 1E of the crest end reinforcing member 1 and the crest end 1AE of the valley end reinforcing member 1A. Reinforcing members 1 and 1A are made of the same material (a material with high tensile strength: such as deformed reinforcing bars or FRP). When inserting reinforcing members 1 and 1A into the insertion hole H (inserting in the opposite direction to arrow V in Figure 22), as shown in Figure 22, both the valley end 1E of the crest end reinforcing member 1 and the crest end 1AE of the valley end reinforcing member 1A can be screwed into the nut N (reinforcing members 1 and 1A are connected via the nut N). Next, the nut N is rotated using a known mechanism so that it is screwed onto the valley-side reinforcing member 1A only, as shown in Figure 23, or so that it is screwed onto the crest-side reinforcing member 1 only, as shown in Figure 24. As a result, the crest-side reinforcing member 1 is not connected to the valley-side reinforcing member 1A. In the state shown in Figures 23 and 24, even if area EE-A (Figure 22: collapsed soil) collapses, the mountain-side reinforcement member 1 is not connected to the valley-side reinforcement member 1A, thus preventing the mountain-side reinforcement member 1 from being carried away by the collapsed soil EE-A.

[0040] In Figure 22, if nut N is made of a low-strength material (e.g., polyvinyl chloride), even if region EE-A (Figure 2) collapses in the state shown in Figure 22, nut N will easily break, releasing its screw connection with reinforcing member 1 or reinforcing member 1A. Therefore, reinforcing member 1 on the mountain side will not be carried away by the collapsed soil and debris EE-A.

[0041] In the embodiment described above, the area from the valley-side end 1EV (Figure 1) of the reinforcing material 1 to the embankment surface is filled with backfill material. However, as shown in the sixth modified example in Figures 25 to 27, it is also possible not to fill the area from the valley-side end 1EV (Figure 1) of the reinforcing material 1 to the embankment surface with backfill material. As shown in Figure 25, in the sixth modified example, the reinforcing material 1 is inserted into the area on the ground side (left side in Figure 25) of the imaginary line V1E connecting the valley-side ends 1EV of the reinforcing material 1 within the insertion hole H, and the hardening material C is filled around it. However, no filling material is filled into the area HE on the embankment surface side (right side in Figure 25) of the imaginary line V1E connecting the valley-side ends 1EV of the reinforcing material 1 within the insertion hole H. Even in this state, the reinforcing material 1 in the area on the ground side of the imaginary line V1E connecting the valley-side ends 1EV of the reinforcing material 1 prevents the existing embankment EE-1 (Figure 1) directly beneath the building from being affected by the collapse, and the stability of the building on the flat surface FS (Figure 1) at the top of the existing embankment EE is ensured. Furthermore, even if a collapse occurs along the assumed slip surface SS3, since no filling material is filled into the area HE on the embankment surface side within the insertion hole H, it is prevented from being pulled out by the collapsed soil EE-A (Figure 2).

[0042] In carrying out the sixth modification, first, as shown in Figure 26, insert the reinforcing member 1 into the insertion hole H using the pushing member AP (move it in the direction of arrow β1 in Figure 26). Once the reinforcing member 1 has moved toward the ground side (to the left in Figure 26) of the imaginary line V1E connecting the valley-side ends 1EV of the reinforcing member 1, pull out the pushing member AP in the direction of arrow β2 as shown in Figure 27, and fill with hardening material C. The hardening material C is not filled into the area HE. According to the sixth modified example in Figures 25 to 27, even if the ground EE collapses, the reinforcement material 1 (Figure 25) in the area on the ground side of the imaginary line V1E connecting the valley-side ends 1EV of the reinforcement material 1 will not be affected by the collapse, and the stability of the structure on the flat surface FS (Figure 1) at the top of the existing embankment EE will be ensured. Furthermore, even if a collapse occurs along the assumed slip surface SS3, the area HE on the embankment surface side within the insertion hole H is not filled with backfill material, so the reinforcement material 1 will not be pulled out by the collapsed soil EE-A (Figure 2).

[0043] The illustrated embodiments are for illustrative purposes only and are not intended to limit the technical scope of the present invention. [Explanation of symbols]

[0044] 1. Reinforcement material 2. Reinforcement material to prevent the center from falling out. EE... Existing embankment FS...Flat surface OG... Foundation (earth) VL... End virtual line

Claims

1. In a reinforcement structure for an existing embankment constructed on a sloping base, where a flat surface is created at the top of the embankment and a building is constructed on the flat surface, A reinforcement structure for an existing embankment, characterized in that reinforcing material is driven into the area directly below the top of the embankment in a horizontal direction or in a direction inclined with respect to the horizontal direction.

2. The reinforcement structure for an existing embankment according to claim 1, wherein a filler material is filled in the area from the slope-side end of the reinforcing material to the embankment surface side.

3. The reinforcement structure for an existing embankment according to claim 1, wherein no filler material is filled in the area from the slope-side end of the reinforcing material to the embankment surface side.

4. The reinforcing structure according to claim 2, wherein a low-strength tensile member is installed in the area where the infill material is filled from the slope-side end of the reinforcing material to the embankment surface side.

5. The reinforcement structure for an existing embankment according to claim 1, wherein a reinforcing material for preventing erosion is installed in the region between adjacent reinforcing materials in a horizontal direction or in a direction inclined from the horizontal direction.

6. A method for constructing a reinforcing structure according to any one of claims 1 to 5, In installing the above-mentioned reinforcing material, the process involves drilling holes in the area directly below the top of the existing embankment, either horizontally or inclined to the horizontal, to install the reinforcing material. The process involves installing reinforcing material in the drilled hole so that it reaches the expected sliding surface, A method for constructing a reinforcement structure for existing embankments, characterized by having a step of filling the area around the reinforcing material with a hardening agent.

7. The method according to claim 6, further comprising the step of filling the area from the slope-side end of the reinforcing material to the embankment surface side with a filler material.

8. The construction method according to claim 6, wherein a packer is attached to the head of the reinforcing material, packer injection is performed, and then a hardening agent is pressure-injected around the reinforcing material.

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