Drilling method

Abstract

To provide an excavation method which dispenses with the alternate execution of excavation and stabilization countermeasure work for an excavated wall surface (slope) a plurality of times, and dispenses with the driving of a pile and a sheet pile requiring the introduction of a large-sized heavy machine.SOLUTION: An excavation method of the present invention is a method for excavating a slope (10), the method including reinforcing a region on a mountain side with respect to an excavation plan line (P), the region including an assumed collapse line (S) in a case where excavation is assumed to be performed along the excavation plan line (P), performing excavation along the excavation plan line (P) after the reinforcement, and not repeating excavation of a region on a valley side with respect to the excavation plan line (P) and stabilization countermeasure work for an excavated excavation surface continuously a plurality of times (reverse winding construction).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for excavating a slope of natural ground or an embankment, and more particularly to a technique for stabilizing the slope being excavated. [Background technology]

[0002] When excavating natural ground or embankments that would become unstable (prone to collapse) if the lower part of the slope were excavated, reverse winding construction is carried out, in which cutting is carried out sequentially while ensuring the stability of the excavation surface (reverse winding construction: see, for example, Patent Document 1). The reverse winding construction will be described with reference to Figs. In order to excavate the slope 10 shown in Fig. 16 along the excavation plan line P11 (virtual line), for example, as shown in Fig. 17, reinforcement earthwork (pouring of reinforcing material 11) is carried out in the uppermost region R11 of the slope 10 to be excavated, and only this uppermost region is excavated (first-stage excavation). Fig. 17 shows the state in which the region on the valley side (right side in Fig. 17) of the excavation plan line P11 in region R11 has been excavated. In Figs. 17 to 21, the region where excavation has been completed is comprehensively indicated by a thick solid arrow AC11, and is shown separately from the excavation plan line P11 shown as a virtual line. In the reverse winding construction, following the process shown in Figure 17, the uppermost continuous area R12 is excavated (Figure 18: second stage excavation), then the area R13 below that (Figure 19: third stage excavation), and the lowermost area R14 (see Figure 20: fourth stage excavation) are excavated, thereby completing excavation along the excavation plan line P11 (Figure 16) (Figure 21). To avoid complication of the illustration, FIGS. 16 to 21 show an example in which only the first to fourth stages of excavation are performed. However, in the reverse winding construction shown in Figures 16 to 21, excavation and stabilization work for the excavation wall (slope) (the work of placing reinforcement material 11 in Figures 17 to 21) must be repeated alternately multiple times (four times in the example of Figures 16 to 21) until the bottom of the planned excavation is reached over the entire area to be excavated. This makes the entire excavation work complicated, which poses the problem of prolonging the construction period.

[0003] Another conventional technique involves constructing a retaining wall in advance along the planned excavation line and then constructing earth retaining works such as burying piles extending vertically. However, when constructing an earth retaining wall, piles and sheet piles are driven in, which requires the use of large heavy machinery such as pile drivers, and a work platform must be set up as a scaffold for the heavy machinery to work on. This creates the problem of large-scale construction work. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-93919 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been proposed in consideration of the problems of the prior art described above, and aims to provide an excavation method that does not require alternating multiple excavation and stabilization measures for the excavation wall (slope), and can be carried out without driving piles or sheet piles, which require the introduction of large heavy machinery. [Means for solving the problem]

[0006] The excavation method of the present invention includes: A method for excavating a slope (10), comprising: a reinforcing step of reinforcing an area on the mountain side of the excavation plan line (P) that includes an expected collapse line (S) that would occur if excavation were performed along the excavation plan line (P); After the reinforcing step, a step of excavating along an excavation plan line (P) is included, A distinctive feature of this project is that excavation of the area on the valley side of the excavation plan line (P) and stabilization work on the excavated surface are not repeated multiple times in succession (reverse winding construction).

[0007] In the present invention, the reinforcing step includes: A step of placing a reinforcement material (1: first reinforcement material) for reinforcing the natural ground up to a position reaching the expected collapse line (S); It is preferable to include a step of placing a reinforcing material (2: second reinforcing material) for preventing hole-out in the region between adjacent reinforcing materials (1) for reinforcing the natural ground. Here, the positions at which the reinforcement material (1) for reinforcing the natural ground and the positions at which the reinforcement material (2) for preventing hollowing out are placed are determined in advance, It is preferable that the reinforcement material (1) for reinforcing the natural ground and the reinforcement material (2) for preventing hollowing out are cast in order from above the slope (10). Here, it is preferable that the longitudinal dimensions of the natural ground reinforcing material (1) and the reinforcing material (2) for preventing core loss are the same. However, the longitudinal dimensions of the ground reinforcement reinforcement material (1) and the penetration prevention reinforcement material (2) may be different. In this case, the longitudinal dimensions of each of the ground reinforcement reinforcement materials (1) and each of the penetration prevention reinforcement materials (2) may be different.

[0008] Alternatively, in the present invention, the reinforcing step includes: Drilling vertically extending boreholes (H) in the area to be reinforced; A step of inserting a ground improvement machine (M) having a function of injecting or injecting a ground improvement liquid (injection liquid or solidification material, etc.) into the borehole (H); It is preferable to have a step of spraying or injecting a soil improvement liquid into the area to be reinforced to improve the soil in the area including the expected collapse line (S). [Effects of the Invention]

[0009] According to the present invention having the above-mentioned configuration, a reinforcement step is included in which an area on the mountain side of the excavation plan line (P) that includes an expected collapse line (S) when excavation is assumed to be performed along the excavation plan line (P). Therefore, even when excavation is performed along the excavation plan line (P), the area including the expected collapse line (S) is reinforced, making it less likely that the expected collapse line (S) will occur, and the area on the mountain side will be less likely to collapse along the expected collapse line (S). In other words, by being reinforced, the area including the expected collapse line (S) acts like an integrated reinforced area as a pseudo-retaining wall. Therefore, in the area E that includes the expected collapse line (S) and is reinforced integrally, it is less likely that the area on the mountain side will collapse along the expected collapse line S. Therefore, even if excavation is performed along the excavation plan line (P), it is unlikely that the shear force (τ) will act along the expected collapse line (S) and cause the valley side area to collapse. And because the excavation plan line (P) is unlikely to collapse, it is possible to excavate the slope (10) area in one go along the excavation plan line (P) without having to alternately perform excavation and stabilization of the excavation surface multiple times as in reverse winding construction.

[0010] In the present invention, if the reinforcement material for reinforcing the ground (1: first reinforcement material) is cast in the reinforcement process so that it reaches the expected collapse line (S) (crosses the expected collapse line S), the expected collapse line (S) is less likely to occur even when excavating along the excavation plan line (P), and the area on the mountain side is less likely to collapse along the expected collapse line (S). When placing the ground reinforcement material (1), all that is required is to drill a borehole (H) horizontally or in a direction inclined from the horizontal, insert the ground reinforcement material (1), and then inject a hardening material (C: for example, grout material), so there is no need to introduce large heavy machinery such as a pile driver, and there is no need to set up a work platform. Therefore, large-scale construction work is not required.

[0011] In the present invention, a reinforcement material for preventing hole-holes (2: second reinforcement material) is cast in the area between the reinforcement materials for reinforcing the natural ground (1), thereby preventing the soil in the area between the reinforcement materials for reinforcing the natural ground (1) from collapsing (the occurrence of so-called "hole-holes"). If the soil in the area between the reinforcement materials for natural ground reinforcement (1) is prevented from collapsing (the so-called "holes" occurring), it is possible to prevent the collapse from progressing and the collapse of the area reinforced with the reinforcement materials for natural ground reinforcement (1) (E: Figure 3).

[0012] In the present invention, the reinforcement step can involve spraying or injecting a soil improvement liquid into the area to be reinforced to create a chemical injection area (EA1) by chemical injection, or spraying a solidification material to create a solidified underground body (EA2). By creating the chemical injection area (EA1) or spraying a solidification material to create a solidified underground body (EA2), the area including the expected collapse line (S) is integrated and reinforced, so even if excavation is performed along the excavation plan line (P), shear force (τ) acts along the expected collapse line (S) and the area on the valley side is less likely to collapse. Therefore, the slope (10) area can be excavated in one go along the excavation plan line (P) without having to alternately perform excavation and stabilization of the excavation surface multiple times as in reverse winding construction. Furthermore, the chemical grouting method or the underground solidification method does not require the introduction of large heavy machinery such as pile drivers, and there is no need to set up a work platform. Therefore, large-scale construction work is not required. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram showing an overview of a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram for explaining the mechanism of the first embodiment, and is an explanatory diagram showing the state in which a first reinforcing material has been cast. [Figure 3] FIG. 10 is an explanatory diagram showing the effect of casting the first reinforcing material. [Figure 4] FIG. 10 is an explanatory diagram showing a state in which the area between the cast first reinforcing materials collapses (is hollowed out). [Figure 5] FIG. 10 is an explanatory diagram showing the state in which a second reinforcing material has been poured to prevent hollowing out. [Figure 6] FIG. 2 is an explanatory view similar to FIG. 1, showing a first modified example of the first embodiment. [Figure 7] FIG. 10 is an explanatory view similar to FIG. 1, showing a second modified example of the first embodiment. [Figure 8] FIG. 4 is an explanatory diagram showing a borehole drilling step in the first embodiment. [Figure 9] FIG. 2 is an explanatory view showing a state in which a reinforcing member is inserted into a drilled hole in the first embodiment. [Figure 10] FIG. 2 is an explanatory diagram showing a state in which a hardening material is filled into a drilled hole into which a reinforcing member has been inserted in the first embodiment. [Figure 11] FIG. 2 is an explanatory diagram showing a state in which excavation has been carried out along an excavation plan line after a reinforcing member has been cast in the first embodiment. [Figure 12] FIG. 10 is a process diagram showing the state in which a borehole extending in the vertical direction has been drilled in the second embodiment of the present invention. [Figure 13] This is a process diagram showing the state in which a ground improvement machine that sprays or injects ground improvement liquid into an excavated borehole is inserted. [Figure 14] FIG. 8 is an explanatory diagram showing a process of improving the ground by injecting a chemical solution using the soil improvement machine of FIG. 7. [Figure 15] FIG. 8 is an explanatory diagram showing a process of rotating and raising the soil improvement machine shown in FIG. 7 while injecting a consolidation material, thereby performing underground consolidation and construction in a modified example of the second embodiment. [Figure 16] FIG. 1 is a diagram illustrating conventional reverse winding construction, showing the state before slope excavation. [Figure 17] FIG. 17 is an explanatory diagram showing the step following FIG. 16 of the reverse winding construction, showing the state in which the first stage of excavation has been completed. [Figure 18] FIG. 18 is an explanatory diagram showing the process following FIG. 17 of the reverse winding construction, showing the state in which the second stage of excavation has been carried out. [Figure 19] FIG. 19 is an explanatory diagram showing the process following FIG. 18 of the reverse winding construction, showing the state where the third stage of excavation has been completed. [Figure 20] FIG. 20 is an explanatory diagram showing the process following FIG. 19 of the reverse winding construction, showing the state where the fourth stage of excavation has been completed. [Figure 21] FIG. 10 is an explanatory diagram showing the state after excavation by reverse winding construction is completed. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will be described with reference to FIGS. First, the first embodiment will be described with reference to FIGS. In Fig. 1, the slope before excavation is indicated by the reference numeral 10, and the excavation plan line (virtual line) is indicated as a whole by the reference numeral P. The excavation plan line P illustrated in Fig. 1 includes a vertical line P1 on the top side, a first horizontal line P2 continuing from the vertical line P1, a diagonal line P3 continuing from the horizontal line P2, and a second horizontal line P4 below (on the foot side of the slope 10). Here, the illustrated embodiment is also applicable to the case of excavating along an excavation plan line that includes vertical lines, horizontal lines, and diagonal lines other than P1 to P4.

[0015] If excavation is carried out in the area on the valley side (to the right in Figure 1) of the vertical line P1 and the first horizontal line P2 of the excavation plan line P without constructing reverse winding construction or retaining walls and without pouring reinforcement materials, there is a risk that the area extending perpendicular to the plane of the paper in Figure 1, including the vertical line P1, will collapse. In contrast, in the first embodiment, as will be described later with reference to Figures 2 to 5, by casting first and second reinforcing members 1, 2, when excavating along an excavation plan line P, the excavation surface indicated by a vertical line P1 is prevented from collapsing. In Figure 1, a total of five first and second reinforcing members 1, 2 of the same length are shown in the vertical direction, but the number of members to be cast is not limited to five. Furthermore, a plurality of first and second reinforcing members 1, 2 are also cast in the direction perpendicular to the plane of Figure 1. In Figure 1, the reinforcement closest to the first horizontal line P2 (the lowest reinforcement) is the first reinforcement 1, but it could also be the second reinforcement 2. The vertical distance between the lowest reinforcement and the toe of the slope (the intersection of the vertical line P1 of the excavation plan line P and the first horizontal line P2 in Figure 1) is generally set to be the same as or shorter than the vertical distance between the reinforcements (vertical pouring intervals). This is because if the vertical distance between the lowest reinforcement and the toe of the slope is made longer (wider) than the vertical pouring intervals of the reinforcements, a so-called "hole" may occur. Generally, it is believed that a pouring interval of 0.5 m to 1.5 m will prevent "hole" from occurring.

[0016] Next, referring to Figures 2 to 5, we will explain the mechanism by which, in the first embodiment of Figure 1, even if the area on the valley side (right side in Figure 1) of the vertical line P1 and the first horizontal line P2 of the excavation planning line P is excavated, the area extending perpendicular to the plane of the paper in Figure 1, including the vertical line P1, does not collapse. For the sake of simplicity, the number of reinforcing materials shown in FIG. 1 is not the same as the number of reinforcing materials shown in FIGS. Figure 2 shows the state where excavation has been carried out along the excavation plan line P and the state where the first reinforcement material 1 has been cast. From the toe P0 of the slope (the intersection of the vertical line P1 and the first horizontal line P2), an assumed collapse line S is generated in a direction inclined by the active collapse angle θ with respect to the imaginary extension line P2E of the first horizontal line P2. Here, the active collapse angle θ is It is expressed by the formula θ=45°+(φ / 2), where the angle φ is a soil constant called the angle of internal friction, and differs depending on the soil type (geology).

[0017] If the first reinforcing material 1 is not cast, the shear force τ acts along the assumed collapse line S, causing the valley side area to collapse. In contrast, in Figure 2, if the first reinforcement material 1 is cast so that it reaches the expected collapse line S (crosses the expected collapse line S), the expected collapse line S is less likely to occur, and the area on the mountain side is less likely to collapse along the expected collapse line S. In other words, in Figure 3, the area E where the first reinforcement material 1 is cast acts like an integrated reinforced area as a pseudo-retaining wall. In the area E which includes the expected collapse line S and is reinforced as an integrated unit, the area on the mountain side is less likely to collapse along the expected collapse line S.

[0018] 2 and 3, there is a risk that relatively small soil masses m1 to m3 may fall off (collapse) from the area between the first reinforcement materials 1 on the vertical plane P1, causing a so-called "hole" (arrow M in Fig. 4). If a "hole" occurs, the collapse may progress, and the area E (Fig. 3) reinforced by the first reinforcement materials 1 may collapse. In order to prevent the region E (FIG. 3) reinforced with the first reinforcing material 1 from collapsing, in the first embodiment, second reinforcing material 2 is cast in the region between the first reinforcing material 1. Here, the first reinforcing material is cast in multiple locations in the vertical direction as shown in FIGS. 1 to 5, and is also cast in multiple locations in the direction perpendicular to the paper surface of FIGS. 1 to 5. Therefore, the second reinforcing material 2 is also cast in multiple locations not only in the vertical direction as shown in FIGS. 1 and 5, but also in the direction perpendicular to the paper surface of FIGS. 1 and 5. Here, the interval (casting interval) between the first and second reinforcing members 1, 2 is set to 0.5 m to 1.5 m, which is generally considered to prevent "holes" from occurring. Here, the positions at which the first reinforcing material 1 and the second reinforcing material 2 are cast are determined in advance, and the first reinforcing material 1 and the second reinforcing material 2 are cast in order, for example, from above the slope 10.

[0019] By casting the first and second reinforcing materials 1, 2, the collapse of the vertical line P1 is prevented, making it possible to carry out excavation along the excavation plan line P without performing reverse winding construction. Therefore, according to the first embodiment, it is possible to excavate the natural ground 10 all at once along the excavation plan line P including the vertical line P1, without having to divide the excavation into multiple areas and repeatedly perform excavation and stabilization of the excavated surface multiple times, as in the case of the back-to-back construction described with reference to Figures 16 to 21. In other words, in the first embodiment, it is not necessary to repeatedly perform excavation and stabilization measures for the excavated area multiple times, as in the case of the conventional back-to-back construction, and therefore it is possible to reduce construction costs and shorten the construction period. 3 to 5, the first and second reinforcing members 1 and 2 can be cast by drilling holes horizontally or in a direction inclined from the horizontal, inserting the first and second reinforcing members 1 and 2 into the holes, and then injecting the hardening material C (for example, grout material), eliminating the need for large heavy machinery such as a pile driver and the need to install a work platform. Therefore, there is no need for large-scale construction work.

[0020] In Figs. 1 to 5, the first and second reinforcing members 1 and 2 have the same length, and the same reinforcing member can be used. However, as in the first modified example shown in Figure 6, the length of the second reinforcing material 2, which prevents collapse (holes) in the area between the first reinforcing materials 1, may be shorter than the length of the first reinforcing material 1, which is poured so as to reach the expected collapse line S (spanning the expected collapse line S), making it less likely that the expected collapse line S will occur and preventing collapse along the expected collapse line S. As mentioned above, in order to prevent the core from being hollowed out, it is not necessary to pour the concrete so that it reaches the expected collapse line S (across the expected collapse line S). Alternatively, as in a second modified example shown in FIG. 7, the lengths of the plurality of first reinforcing members 1α, 1β, 1γ may be different, and the lengths of the plurality of second reinforcing members 2α, 2β may be different. Other configurations and effects of the modified examples of FIGS. 6 and 7 are the same as those of the first embodiment of FIGS. The reference numerals 1A and 2A in FIGS. 1, 6 and 7 will be described later with reference to FIGS.

[0021] In Figures 1, 6 and 7, the first and second reinforcing members 1 and 2 are cast at uniform intervals throughout the area extending in the vertical direction and in a direction perpendicular to the paper surface (in Figures 1, 6 and 7) (the area where the slope 10 at the construction site extends), thereby preventing the collapse of soil in the area extending in the vertical direction of the excavation surface P1 and in a direction perpendicular to the paper surface after excavation along the excavation plan line P is carried out. 1, 6, and 7, the first and second reinforcing members 1 and 2 are cast in a direction inclined downward from the horizontal. In order to reinforce the area including the expected collapse line S, it is desirable that the direction in which the reinforcing member 1 is cast is perpendicular to the expected collapse line S. However, even if the direction is not perpendicular to the expected collapse line S, there are no particular restrictions on the direction in which the reinforcing member 1 is cast, as long as the area on the mountain side of the expected collapse line S is reinforced to prevent collapse. There are no particular restrictions on the pouring direction of the second reinforcing material 2, as long as it does not interfere with the first reinforcing material 1 and can reliably prevent hollowing out. For example, the first reinforcing material 1 and the second reinforcing material 2 can be poured in parallel.

[0022] As will be described later with reference to Figures 8 to 10, when the first and second reinforcing members 1, 2 are cast, the insertion holes H are filled with hardening material C. However, if the hardening material C is grout, bleeding may occur, creating spaces above the insertion holes H where the grout is not filled (so-called "voids"). The direction in which the first and second reinforcing members 1, 2 are cast is preferably set so that such "voids" do not grow large. However, regardless of the direction in which the first and second reinforcing members 1, 2 are cast, it is possible to prevent the formation of such "voids" by, for example, pressurizing and injecting grout. However, the first and second reinforcing members 1 and 2 are not cast vertically because casting the first and second reinforcing members 1 and 2 vertically requires the use of large heavy machinery such as a pile driver, just as in the case of installing longitudinal reinforcement members that extend vertically.

[0023] Next, with reference to Figs. 8 to 10, a procedure for placing the first or second reinforcing member 1 or 2 in the illustrated embodiment will be described. In the process shown in Figure 8, insertion holes H for inserting the first or second reinforcing material 1, 2 are drilled into the slope 10 to be constructed. In Figures 8 to 10, arrow OG indicates the mountain side and arrow V indicates the valley side. The expected collapse line S is not shown in Figures 8 to 10. 8 to 10, when the first reinforcing member 1 and the second reinforcing member are the same length as in the first embodiment, the insertion holes H are drilled from the construction slope 10 to the mountain side of the expected collapse line S. The first reinforcing member 1 is cast so that it reaches the expected collapse line S (straddles the expected collapse line S), making it less likely that the expected collapse line S will occur and making it less likely that the area on the mountain side will collapse along the expected collapse line S.

[0024] After the insertion hole H has been drilled, the first or second reinforcing member 1 or 2 is inserted into the drilled insertion hole H as shown in FIG. 9 and 10, the vertical line P1 of the excavation plan line P is indicated by a dashed line. When excavating along the excavation plan line P, the entire area on the valley side of the vertical line P1 shown in Figures 1, 6, and 7 is excavated. Therefore, the reinforcement members 1 and 2 do not need to extend further into the valley than the vertical line P1. If they extend further into the valley than the vertical line P1, they may interfere with an excavation machine (not shown) during excavation and damage the excavation machine. This makes excavation of the area on the valley side of the excavation plan line P difficult. 9, the reinforcements 1 and 2 are pressed toward the mountain side using, for example, a push rod (not shown) so that the reinforcements 1 and 2 extend only toward the valley side of the vertical line P1. In this case, a mark or the like can be provided in the natural ground 10 at the position of the insertion hole H in order to determine the position where the reinforcement has been placed.

[0025] In the step shown in FIG. 10, the hardening material C is filled into the insertion hole H into which the reinforcing material has been inserted. Although not shown in Figure 10, a packer can be provided in the reinforcing member to prevent the filled hardening material C from flowing out of the insertion hole H. Alternatively, a hardening material C with high viscosity can be selected to prevent the hardening material C from flowing out of the drilled hole H without using a packer. In Figure 10, the areas 1A and 2A (see Figures 1, 6 and 7) on the valley side of the vertical line P1 of the insertion hole H are not filled with hardening material C. This is to make it easier to excavate along the excavation plan line P. However, it is also possible to fill the areas 1A and 2A on the valley side of the vertical line P1 of the insertion hole H with hardening material C. This is because, unlike the reinforcing material, even if the hardening material C is filled on the valley side of the vertical line P1, there is an extremely low possibility of damaging the excavation machine.

[0026] As described with reference to FIG. 9 , the reinforcing members 1 and 2 generally do not extend further down than the vertical line P1. However, although not shown, it is possible for the reinforcing members 1 and 2 to extend further up than the vertical line P1. In this case, the material (e.g., vinyl chloride) of the reinforcing members 1 and 2 extending in the regions 1A and 2A on the valley side of the vertical line P1 is set to be weaker than the material of the reinforcing members 1 and 2 extending in the region on the mountain side of the vertical line P1. Alternatively, the first and second reinforcing members 1 and 2 are configured to break at the vertical line P1. This configuration prevents the reinforcing members 1 and 2 from interfering with the excavation machine in the regions 1A and 2A on the valley side of the vertical line P1 and thus does not damage the excavation machine. This also facilitates excavation in the region on the valley side of the vertical line P1. Furthermore, the region on the mountain side of the vertical line P1 of the reinforcing members 1 and 2 is prevented from being caught in the excavated soil when the region on the valley side of the vertical line P1 is excavated.

[0027] Although not shown in Figures 8 to 10, it is also possible to form multiple protrusions intermittently in the longitudinal direction of the first and second reinforcing members 1, 2 to improve the adhesion strength between the first and second reinforcing members 1, 2 and the hardening material C. Alternatively, the diameter of a portion of the insertion hole H can be enlarged to improve the adhesion strength between the hardening material C filled in the insertion hole and the soil in the area including the assumed collapse line S. In addition, the hardening material C can be injected under pressure to penetrate into the ground in the area surrounding the insertion hole H, forming a penetration area, thereby improving the adhesion strength with the area including the expected collapse line S.

[0028] After the first and second reinforcing members 1 and 2 are cast to integrally reinforce the area including the expected collapse line S, excavation is carried out along the excavation plan line P, as shown in Figure 11. At this time, the area including the expected collapse line S has been reinforced by casting the reinforcing member 1 so as to straddle the expected collapse line S, so that when excavating along the excavation plan line P, the area on the mountain side is less likely to collapse along the expected collapse line S, and excavation can be carried out along the excavation plan line P in one go without having to repeat reinforcement and excavation as in reverse winding construction.

[0029] Next, a second embodiment of the present invention will be described with reference to FIGS. In the first embodiment shown in Figures 1 to 11, the area including the expected collapse line S is reinforced by a reinforcement method using reinforcing materials 1 and 2. In contrast, in the second embodiment shown in Figures 12 to 15, the area including the expected collapse line S is reinforced by carrying out ground improvement work. In Figure 12, a borehole H is drilled vertically from the top PT of the ground 10 to be excavated along the excavation plan line P. The borehole H is drilled at a location where the improved ground or underground solidified body shown in Figures 14 and 15 will include the expected collapse line S. Next, as shown in Figure 13, a soil improvement machine M is inserted into the excavated hole H. The soil improvement machine M has the function of injecting soil improvement liquid (injection chemical) or spraying soil improvement liquid (consolidation agent). The soil improvement machine M is connected via a rod 22 to soil improvement equipment (not shown in Figure 13) installed on the ground side. Here, examples of ground improvement methods in the second embodiment include a chemical injection method in which a chemical solution is injected into the soil around the borehole H to reinforce it, as shown in Figure 14, and a ground improvement method in which a solidified underground body is created using the soil around the borehole H, as shown in Figure 15.

[0030] 14, a soil improvement liquid D is injected from a soil improvement machine M into an area surrounding a borehole H that includes an expected collapse line S. Here, in order to prevent the soil improvement liquid D from leaking out of the borehole H to the ground, a packer 30 is provided directly above the soil improvement machine M, and when the soil improvement liquid D is injected, the packer 30 expands to seal the soil improvement liquid D. In FIG. 14, reference numeral 32 denotes a supply source of an expansion fluid (for example, high-pressure air) for expanding the packer 30, and reference numeral 34 denotes an injection machine for inserting and pulling up the packer 30 into the ground. By injecting soil improvement chemicals D from the soil improvement machine M, a multi-stage chemical injection area EA1 is created in the area surrounding the borehole H, encompassing the expected collapse line S, thereby integrating and reinforcing the area. After injecting soil improvement chemicals D from the soil improvement machine M to integrate and reinforce the area around the borehole H that includes the expected collapse line S, excavation is carried out along the excavation plan line P. At this time, since the area including the expected collapse line S has been reinforced by creating the chemical injection area EA1, even if excavation is carried out along the excavation plan line P, it is unlikely that the area on the mountain side will collapse along the expected collapse line S, and excavation can be carried out along the excavation plan line P in one go. Although not shown in FIG. 14, the liquid medicine injection area EA1 formed in multiple stages in the vertical direction is also formed in multiple stages in the direction perpendicular to the paper surface of FIG.

[0031] As shown in Figure 15, when using a ground improvement method to create an underground solidification body using the soil around a borehole H to integrate and reinforce the area including the expected collapse line S, a jet J containing a solidification material is sprayed from a ground improvement machine M inserted into the borehole H, and the ground improvement machine M is rotated, for example, as shown by the arrow MR, and raised from the bottom of the borehole H to the ground. As a result, the soil and the solidification material around the borehole H are mixed to create an underground solidification body EA2, and the area around the borehole H including the expected collapse line S is integrated and reinforced. Then, excavation can be carried out along the excavation plan line P in one go. In FIG. 15, a plurality of underground solidified bodies EA2 are also formed in the direction perpendicular to the paper surface of FIG.

[0032] It should be noted that the illustrated embodiments are merely examples and are not intended to limit the technical scope of the present invention. For example, although the illustrated embodiment excavates a normal natural slope, it is also possible to excavate an existing embankment in the same manner as the illustrated embodiment. [Explanation of symbols]

[0033] 1. First reinforcing member (ground reinforcement material) 2. Second reinforcing member (reinforcing member for preventing core breakage) 10...Slope (construction slope) S... Expected collapse line P···Drilling plan line P1: Vertical line in the uppermost area of ​​the drilling plan line M... Ground improvement machine

Claims

1. 1. A method for excavating a slope, comprising: a reinforcing step of reinforcing an area on the mountain side of the excavation plan line, the area including an estimated collapse line when excavation is performed along the excavation plan line; a step of excavating along an excavation plan line after the reinforcing step, An excavation method characterized in that excavation of an area on the valley side of an excavation plan line and stabilization measures for the excavated surface are not repeated multiple times in succession.

2. The reinforcing step includes: A step of placing a reinforcement material for reinforcing the natural ground up to a position where the reinforcement material reaches the expected collapse line; 2. The excavation method according to claim 1, further comprising the step of placing a reinforcement material for preventing a hole from being removed into a region between adjacent reinforcement materials for reinforcing the natural ground.

3. The positions at which the reinforcement material for natural ground reinforcement and the reinforcement material for preventing core hole are placed are determined in advance, 3. The excavation method according to claim 2, wherein the reinforcement material for reinforcing the natural ground and the reinforcement material for preventing hollowing out are driven into the slope in that order from above.

4. 4. The excavation method according to claim 2, wherein the longitudinal dimensions of the reinforcement material for reinforcing the natural ground and the reinforcement material for preventing the core from being pulled out are the same.

5. The excavation method according to claim 2 or 3, wherein the longitudinal dimensions of the reinforcement material for reinforcing the natural ground and the reinforcement material for preventing core removal are different.

6. 6. The excavation method according to claim 5, wherein the longitudinal dimension of each of said reinforcement materials for reinforcing the natural ground is different from the longitudinal dimension of each of said reinforcement materials for preventing the core from being pulled out.

7. The reinforcing step includes: Drilling vertically extending boreholes in the area to be reinforced; A step of inserting a soil improvement machine having a function of injecting or injecting soil improvement liquid into the borehole; 2. The excavation method according to claim 1, further comprising the step of spraying or injecting a soil improvement liquid into the area to be reinforced, thereby improving the soil in the area including the predicted collapse line.

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