Slope stabilization ground anchor method

Abstract

To provide a construction method for stabilizing a slope without using a pressure plate.SOLUTION: An installation position of tensioning and anchoring anchors 3 is determined. The amount of rebar required to maintain the strength necessary to stabilize a slope 1 using a flat block body 30 is calculated. Multiple rebars are prepared to match this determination. Multiple rebar frame fixing anchors 5 are installed on the slope. The prepared multiple rebars are connected and fixed to each other to assemble a reinforcing rebar frame 10. This reinforcing rebar frame is connected and fixed to the rebar frame fixing anchors. A hole retaining pipe is connected and fixed at a prescribed position on the reinforcing rebar frame. Mortar is sprayed to fill and surround the reinforcing rebar frame. A flat block body is formed on the slope. Boring is performed to form anchor holes. The tensioning and anchoring anchors are inserted into the anchor holes. Grout material is injected to fix the anchors. The anchors are tensioned. Initial tension is applied so that the required residual tensile force is obtained. The anchors are fixed in position while maintaining the tension.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a construction method for stabilizing inclined surfaces (including cut slopes) such as mountain slopes and river embankments.

Background Art

[0002] As a method for reinforcing and stabilizing inclined surfaces (slopes) such as mountain slopes and river embankments, a ground anchor method or a steel bar insertion method is known in which a tension member (anchor or bolt) inserted into a drilled anchor hole is grouted, and a pressure receiving plate is pressed against the slope with this tension member.

[0003] For example, Japanese Patent No. 5907443 (Patent Document 1) discloses a method for installing a pressure receiving plate using an unevenness adjustment frame for pressure receiving plate construction. The method disclosed in this Patent Document 1 generally consists of the following steps.

[0004] a) Assemble the unevenness adjustment frame for pressure receiving plate construction at a factory away from the construction site. The weight per unit of the unevenness adjustment frame is relatively light, and it can be installed manually without the need for a special crane device for lifting.

[0005] b) Transport the assembled unevenness adjustment frame for pressure receiving plate construction to the construction site.

[0006] c) Drill a plurality of auxiliary anchor holes in the slope at the construction site, and insert and fix auxiliary anchors into these auxiliary anchor holes.

[0007] d) Connect the fixed auxiliary anchors and the unevenness adjustment frame for pressure receiving plate construction with a binding member or the like.

[0008] e) Install an insertion / extraction pipe at the anchor hole drilling position inside the unevenness adjustment frame for pressure receiving plate construction.

[0009] f) Place mortar or concrete inside the unevenness adjustment frame using a pumping pump, and finish the surface with a trowel to form an unevenness adjustment spraying pedestal.

[0010] g) Drill a hole to a predetermined depth with a dedicated machine through the insertion / extraction pipe, and insert an anchor material such as PC steel wire.

[0011] h) After going through the curing period of cement hardening for several days, lift the secondary product pressure plate (made of steel or precast, etc.) transported to the construction site with a crane or the like and install it on the upper surface of the unevenness adjustment spraying pedestal, and tension and fix the anchor material with a dedicated jack, thereby fixing the pressure plate corresponding to the anchor load on the unevenness adjustment spraying pedestal. Thus, all the construction up to the installation of the pressure plate is completed.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0013] In the ground anchor work or steel bar insertion work as disclosed in Patent Document 1, an unevenness adjustment frame is installed on the slope surface, mortar or concrete is placed to form an unevenness adjustment spraying pedestal, and after going through the curing period of several days, the secondary product pressure plate (hereinafter referred to as the pressure plate) is lifted with a crane or the like and installed and fixed at a predetermined position on the unevenness adjustment spraying pedestal.

[0014] The pressure plate is a factory-made product, requires a bearing capacity corresponding to the anchor load, and the manufacturing process depends on the factory production capacity. Also, it weighs several hundred kilograms, and it is impossible to manually lift such a heavy pressure plate with a crane or the like and install it at a predetermined position on the unevenness adjustment spraying pedestal on the inclined slope surface, resulting in high product prices.

[0015] Also, before installing the pressure plate, it is necessary to have a curing period of several days for the unevenness adjustment spraying pedestal, so the overall construction period is relatively long.

[0016] The unevenness adjustment frame disclosed in Patent Document 1 is for firmly fixing and holding mortar or concrete for forming an unevenness adjustment spraying pedestal, and the frame itself does not act to strengthen the slope structure. It is the pressure receiving plate that presses on the upper surface of the unevenness adjustment spraying pedestal while fixing the anchor material in a tensioned state that strengthens the slope structure.

[0017] An object of the present invention is to provide a construction method for stabilizing a slope without using a pressure receiving plate.

Means for Solving the Problems

[0018] The slope stabilization construction method according to the present invention is a construction method for stabilizing inclined surfaces such as mountain slopes and river embankments, and includes the following steps.

[0019] a) A step of determining the placement positions of the tensioning and fixing anchors on the slope.

[0020] b) A step of calculating the amount of steel bars that can maintain the strength required to stabilize the slope from the plate thickness and the grounding area of the flat steel bar structure of the reinforcing steel bar frame and the mortar that fills and surrounds this reinforcing steel bar frame.

[0021] c) A step of determining the diameter, length, and number of the steel bars to be used so that the amount exceeds the required amount of steel bars calculated based on the strength calculation, and preparing a plurality of steel bars to match the determination.

[0022] d) A step of previously driving a plurality of anchor bars for fixing the steel bar frame on the slope in a predetermined positional relationship to assemble the reinforcing steel bar frame at a position surrounding the placement position of the tensioning and fixing anchor.

[0023] e) A step of connecting and fixing the plurality of prepared steel bars to each other at a predetermined positional relationship and arrangement interval to assemble the reinforcing steel bar frame, and connecting and fixing this reinforcing steel bar frame to the anchor bar for fixing the steel bar frame.

[0024] f) Select an appropriate hole retaining pipe according to the hole diameter for drilling for the tensioning and fixing anchor, and connect and fix this hole retaining pipe to a predetermined position of the reinforcing steel bar frame.

[0025] g) Spray mortar so as to fill and surround the reinforcing steel bar frame to produce a flat plate-shaped steel bar structure (flat block body) on the slope surface.

[0026] h) Perform boring through the hole retaining pipe to form an anchor hole for receiving the tensioning and fixing anchor.

[0027] i) Insert the tensioning and fixing anchor into the anchor hole, and inject grout material to fix the tensioning and fixing anchor.

[0028] j) Use a tensioning jack to pull the tensioning and fixing anchor, introduce an initial tension force so as to obtain a required residual tension force, and fix the position of the tensioning and fixing anchor while maintaining the tension force.

[0029] In the description according to the embodiment of the present invention, as a term expressing mortar or concrete, the term "mortar" is uniformly used. Therefore, even if it is expressed as "mortar", it also includes using concrete instead of mortar. Further, for the fixing anchor, it also includes a steel bar anchor.

[0030] In a preferred embodiment of the present invention, after the step of fixedly connecting the reinforcing steel bar frame to the anchor for fixing the steel bar frame, and before the step of spraying mortar to produce a flat plate-shaped steel bar structure (flat block body) on the slope surface, a step of installing a formwork for the frame surrounding the periphery of the reinforcing steel bar frame (which may not be required when the beam height is 15 cm or less) is provided.

[0031] Preferably, after the step of fixing the tensioning and fixing anchor to the anchor hole and before pulling the tensioning and fixing anchor, a step of installing a head plate for supporting the exposed tensioning and fixing anchor is provided. Further, the step of fixing the position of the tensioning and fixing anchor includes driving a wedge while maintaining the tension of the tensioning and fixing anchor, and firmly fixing the head of the tensioning and fixing anchor and the head plate.

[0032] More preferably, after firmly fixing the head of the tensioning and fixing anchor and the head plate, the portion of the anchor material protruding from the head plate is cut, and then a step of attaching a head protection cap to the head plate so as to cover the cut head of the tensioning and fixing anchor is provided.

[0033] In a preferred embodiment, the reinforcing steel bar frame (it is also possible to install only the lower steel bar frame) includes a lower steel bar frame including a plurality of vertical steel bars and a plurality of horizontal steel bars intersecting vertically and horizontally at a relatively low height position, an upper steel bar frame including a plurality of vertical steel bars and a plurality of horizontal steel bars intersecting vertically and horizontally above the lower steel bar frame, and a connecting member connecting the lower steel bar frame and the upper steel bar frame. The completed structure thus collectively referred to is hereinafter referred to as a "flat block body".

Advantages of the Invention

[0034] According to the slope stabilization method of the present invention, the flat block body composed of the reinforcing steel bar frame and the mortar filling and surrounding the reinforcing steel bar frame is provided so as to ensure the amount of steel bars, plate thickness, and contact ground area necessary to maintain strength, so it can cope with a wide range of anchor loads. In addition, by continuously spraying the uneven adjustment part and the main body part with mortar without using a pressure plate, the working efficiency is greatly improved by forming a flat block body capable of realizing a structure for stabilizing the slope. Further, since a crane or the like is not required, it can cope with various site conditions and can be made inexpensive.

Brief Description of the Drawings

[0035]

Figure 1

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Mode for Carrying Out the Invention

[0036] The slope stabilizing construction method according to the present invention is a construction method for obtaining a structure for stabilizing a slope without using a pressure plate. An embodiment of the construction method according to the present invention will be described below with reference to the drawings.

[0037] [1. Determination of the Placement Position of the Tension and Fixing Anchor] First, refer to FIG. 1. After appropriately shaping the slope and performing lathing work or the like, the measurement of the placement position of the tension and fixing anchor is carried out to determine the placement position. At that time, the height dimension from the position of the head plate 4 attached to the top end portion of the anchor 3 to the surface of the slope 1 is recorded and left.

[0038] In Fig. 1, the hole-retaining pipe 2 to be placed later, the tensioning and fixing anchor 3 cast into the slope 1 through the hole-retaining pipe 2, and the head plate 4 attached to the head of the tensioning and fixing anchor are shown by phantom lines.

[0039] [2. Calculation of the required amount of steel bars] Calculate the amount of steel bars that can maintain the strength required to stabilize the slope with a flat steel structure (flat block body) composed of a reinforcing steel frame to be assembled later and mortar that fills and surrounds this reinforcing steel frame. The calculation of this amount of steel bars will be described again later.

[0040] [3. Determination of the steel bars to be used and the number] Based on the strength calculation, determine the length, diameter, shape, and number of the steel bars to be used so that they exceed the required amount of steel bars calculated, and prepare a plurality of steel bars to match the determination.

[0041] [4. Prior placement of the anchors for fixing the reinforcing steel frame] As shown in Fig. 2, in order to assemble the reinforcing steel frame 10 at a position surrounding the placement position of the tensioning and fixing anchor 3, a plurality of anchors 5 for fixing the steel frame are placed in advance on the slope 1 in a predetermined positional relationship.

[0042] [5. Assembly of the reinforcing steel frame] In the recessed part of the slope 1, it is necessary to provide a leveling adjustment part 20 that fills the recessed part with mortar (or concrete). When assembling the reinforcing steel frame 10 with the prepared plurality of steel bars, consider the leveling adjustment part 20 as shown in the figure to determine the height of the reinforcing steel frame 10. As shown in Fig. 2, assemble the steel frame 10 by fixing and connecting the prepared plurality of steel bars to each other at a predetermined position and arrangement interval, and connect and fix this steel frame 10 to the anchor 5 for fixing the steel frame using a binding member or the like.

[0043] The reinforcing steel frame 10 includes an upper frame 11 and a lower frame 12, and its specific structure will be described later.

[0044] [6. Installation of the hole-retaining pipe] As shown in Fig. 3, select an appropriate hole-retaining pipe 2 according to the hole diameter for drilling for the insertion and fixation of the tensioning and fixing anchor 3, and install this hole-retaining pipe 2 at a predetermined position on the reinforcing steel bar frame 10. The hole-retaining pipe 2 serves as a protective pipe for the anchor material 3 to be inserted later. When installing the hole-retaining pipe 2, pay attention to the orientation during tensioning, arrange and fix the reinforcing steel bar 16 at the position where the sag of the head of the anchor material 3 is corrected, and fix the hole-retaining pipe 6 to the reinforcing steel bar frame 10. Fig. 11 shows the state where the hole-retaining pipe 2 is fixed to the reinforcing steel bar frame 10 using the reinforcing steel bar 16.

[0045] [7. Installation of formwork for frame (made of wire mesh)] As shown in Fig. 4, surround the periphery of the reinforcing steel bar frame 10 attached to the anchor 5 for fixing the steel bar frame, ensure a predetermined cover, and install the formwork 17. Drive additional fixing anchors 13 on the surface where the height of the uneven adjustment part 20 provided in the recess of the slope increases, newly add reinforcing steel bars 14, install a dedicated repair wire mesh 15, and tie and fix them.

[0046] [8. Spraying work for formwork] The mortar used for the spraying work of the formwork is prepared to meet the required performance such as strength based on past experience and test mixes. As shown in Fig. 5, spray the prepared mortar densely into the formwork 17. During spraying, fill from below so that the formwork 17 does not deform, and continuously spray upwards until a predetermined height is reached.

[0047] When the height of the uneven adjustment part 20 is large, switch to spraying in stages. Specifically, as the primary spraying, fill only the uneven adjustment part 20 with mortar and perform the base treatment. The finishing of the spraying surface is mainly based on troweling work.

[0048] After that, as the secondary spraying, perform the main body spraying to fill the reinforcing steel bar frame 10.

[0049] [9. Head surface adjustment] When the angle between the upper surface of the flat block body 30 of mortar that fills and surrounds the reinforcing steel frame 10 and the anchor material 3 is not orthogonal, as shown in Fig. 6, adjustment of the head surface with respect to the anchor direction is performed. The adjuster is a steel pedestal 31, which is installed on the upper surface of the flat block body 30. The upper surface of the adjuster 31 and the anchor material 3 are in an orthogonal relationship.

[0050] The reason for using the adjuster 31 is to suppress the enlargement of the uneven adjustment part 20.

[0051] [10. Drilling] Drilling is carried out through the hole protection pipe 2 to form a hole for inserting and fixing the anchor material 3.

[0052] [11. Fixing of Anchor Material] As shown in Fig. 7, the anchor material 3 is inserted into the hole for fixing the anchor material, and grout material is injected to fix the anchor material 3.

[0053] [12. Tension Fixing Work] The tension fixing work is carried out after confirming that the mortar has reached a predetermined strength according to the age of the material, etc. A head plate 4 surrounding the head of the exposed anchor material 3 is installed, and the anchor material 3 is pulled using a tension jack 32 to introduce an initial tension so that a required residual tensile force can be obtained.

[0054] Then, wedges are driven in while maintaining the tension to firmly fix the head of the anchor material 3 and the head plate 4.

[0055] [13. Installation of Head Protection Cap] The part of the anchor material 3 that protrudes significantly from the head plate 4 is cut, and then a head protection cap 33 is attached to the head plate 4 so as to cover the cut head of the anchor material 3.

[0056] The above completes the entire process. Different from the prior art, since a pressure plate weighing several hundred kilograms is not required, the applicable range at the site is improved and the cost is reduced.

[0057] This will be described in more detail. The flat block body 30, which consists of the reinforcing steel frame 10 and the mortar (or concrete) that fills and surrounds the reinforcing steel frame 10, is provided to ensure the amount of steel bars, plate thickness, and contact area with the ground necessary to maintain strength. Therefore, the use of a heavy pressure plate can be omitted.

[0058] By continuously spraying mortar at the construction site without using a pressure plate, a flat block body capable of realizing a structure for stabilizing a slope can become a universal independent plate by corresponding to a wide range of anchor loads and site conditions.

[0059] [An example of strength calculation of the flat block body] Figs. 9 and 10 show the shape and dimensions of the flat block body.

[0060] a) Calculation conditions The conditions for strength calculation are, for example, as follows.

[0061] External force (design anchor force): Td = 400 kN / bar for each tension and fixing anchor Allowable bearing capacity: qa = 300 kN / m 2 Vertical dimension L1 of the flat block body 30: 1.50 m Horizontal dimension L2 of the flat block body 30: 1.50 m Width u of the head plate 2: 280 mm Virtual beam width (beam height h × beam width b): 500 mm × 1080 mm Beam cross-section (effective height d): 400 mm Allowable stress (concrete) Design standard strength: σck = 18.0 N / mm 2 Allowable compressive stress: σca = 7.0 N / mm 2 Allowable shear stress: τca = 0.400 N / mm 2 Allowable punching shear stress: τpa = 0.800 N / mm 2 Allowable adhesion stress: τoa = 1.40 N / mm 2 Allowable tensile stress (reinforcing bar): σ sa = 196.0 N / mm 2 b) Calculation results The calculation results under the above conditions are as follows.

[0062] Maximum bending moment: 38.76 kN·m Maximum shear force: 127.08 kN c) Conditions of the reinforcing bars An example of the conditions of the main reinforcing bars that satisfy the above conditions and calculation results is, for example, as follows.

[0063] Diameter of the main reinforcing bars to be used: 22 mm Shape of the reinforcing bar frame: Place frames with reinforcing bars arranged vertically and horizontally above and below.

[0064] Amount and number of vertical reinforcing bars in the upper frame: 1548.4 mm 2 and 4 or more Amount and number of horizontal reinforcing bars in the upper frame: 1548.4 mm 2 and 4 or more Amount and number of vertical reinforcing bars in the lower frame: 1548.4 mm 2 and 4 or more Amount and number of horizontal reinforcing bars in the lower frame: 1548.4 mm 2 and 4 or more [An example of the structure of the reinforcing bar frame] Figs. 11 and 12 show an example of the structure of the reinforcing bar frame 10. In the illustrated embodiment, the reinforcing bar frame 10 includes a lower reinforcing bar frame including a plurality of vertical reinforcing bars 41a and a plurality of horizontal reinforcing bars 42a intersecting vertically and horizontally at a relatively low height position, an upper reinforcing bar frame including a plurality of vertical reinforcing bars 41b and a plurality of horizontal reinforcing bars 42b intersecting vertically and horizontally at an upper position of the lower reinforcing bar frame, and a connecting member connecting the lower reinforcing bar frame and the upper reinforcing bar frame. In order to exceed the amount of reinforcing bars required for strength, the number of the lower vertical reinforcing bars 41a, the lower horizontal reinforcing bars 42a, the upper vertical reinforcing bars 41b, and the upper horizontal reinforcing bars 42b is 8 each, and the diameter of each reinforcing bar is 19 mm.

[0065] As shown in Fig. 12, the lower reinforcing bars 41a and 42a are each bent upward at both ends, and the upper reinforcing bars 41b and 42b are each bent downward at both ends. Both ends of the reinforcing bars of the upper and lower frames are connected and fixed with a connecting member. Also, the intersecting portions of the vertical reinforcing bars 41a, 41b and the horizontal reinforcing bars 42a, 42b are connected and fixed with a connecting member.

[0066] With the above structure, the amount of reinforcing bars exceeds the amount required to maintain the necessary strength, and it becomes possible to stabilize the slope with the flat block body without using a pressure plate.

[0067] Note that as a high-quality optional finish, by spraying a polyurethane resin on the flat block body, the service life of the structure can be significantly increased. Also, when a landscape color is required, such as within a national park, a coloring agent may be added to the sprayed mortar. Further, when long-term durability against salt damage and freeze-thaw is required, a reinforcing material (for example, vinylon fiber) may be included in the mortar.

[0068] In the illustrated embodiment, the reinforcing bar frame has a structure including a lower reinforcing bar frame and an upper reinforcing bar frame. However, for example, only the lower reinforcing bar frame or only the upper reinforcing bar frame may be installed alone. In that case, in order to obtain an appropriate amount of reinforcing bars, each vertical reinforcing bar and each horizontal reinforcing bar may be each composed of two pairs of reinforcing bars extending in parallel.

[0069] As described above, an embodiment of the present invention has been illustratively described with reference to the drawings. However, within the scope of this invention or within an equivalent scope, various modifications and changes can be made to the illustrated and described embodiment.

Industrial Applicability

[0070] The present invention can be advantageously used as a method for efficiently and inexpensively stabilizing a slope.

Explanation of Reference Numerals

[0071] 1 Normal plane, 2 Hole retaining pipe, 3 Anchor for tension and fixing, 4 Head plate, 5 Anchor for fixing the reinforcing bar frame, 10 Reinforcing bar frame, 11 Upper frame, 12 Lower frame, 13 Fixing anchor, 14 Reinforcing bar, 15 Repair wire mesh, 16 Reinforcing bar, 17 Formwork, 20 Uneven adjustment part, 30 Flat block body, 31 Steel pedestal (adjusting fitting), 32 Tension jack, 33 Head protection cap, 41a Lower vertical reinforcing bar, 42a Lower horizontal reinforcing bar, 41b Upper vertical reinforcing bar, 42b Upper horizontal reinforcing bar.

Claims

1. A slope stabilization method for stabilizing slopes such as mountain slopes and river embankments, comprising: a step of determining the placement positions of tension and fixing anchors on the slope; a step of calculating the amount of reinforcing bars capable of maintaining the strength required to stabilize the slope with a flat block body composed of a reinforcing bar frame and mortar that fills and surrounds the reinforcing bar frame; a step of determining the diameter, length, and number of reinforcing bars to be used so that the amount of reinforcing bars exceeds the required amount calculated based on the strength calculation, and preparing a plurality of reinforcing bars to match the determination; a step of previously driving a plurality of anchor fixing anchors for reinforcing bars onto the slope in a predetermined positional relationship to assemble a reinforcing bar frame at a position surrounding the placement position of the tension and fixing anchors; a step of assembling a reinforcing bar frame by connecting and fixing a plurality of prepared reinforcing bars to each other in a predetermined positional relationship and arrangement interval, and connecting and fixing this reinforcing bar frame to the anchor fixing anchors for reinforcing bars; a step of selecting an appropriate hole retaining pipe according to the hole diameter drilled for the tension and fixing anchor, and connecting and fixing this hole retaining pipe to a predetermined position of the reinforcing bar frame; a step of spraying mortar so as to fill and surround the reinforcing bar frame to produce a flat block body on the slope; a step of performing boring through the hole retaining pipe to form an anchor hole for receiving the tension and fixing anchor; a step of inserting the tension and fixing anchor into the anchor hole and injecting a grout material to fix the tension and fixing anchor; a step of pulling the tension and fixing anchor using a tension jack, introducing an initial tension so that a required residual tension is obtained, and fixing the position of the tension and fixing anchor while maintaining the tension. A slope stabilization method.

2. The slope stabilization method according to claim 1, further comprising a step of installing a formwork surrounding the periphery of the reinforcing bar frame after the step of fixedly connecting the reinforcing bar frame to the anchor fixing anchors for reinforcing bars and before the step of spraying mortar to produce a flat block body on the slope.

3. After the step of fixing the tension and fixing anchor to the anchor hole and before pulling the tension and fixing anchor, a step of installing a head plate surrounding the exposed tension and fixing anchor is provided, The step of fixing the position of the tension and fixing anchor includes driving a wedge while maintaining the tension of the tension and fixing anchor to firmly fix the head of the tension and fixing anchor and the head plate. The slope stabilization method according to claim 1.

4. After firmly fixing the head of the tension / fixing anchor and the head plate, cutting the portion of the anchor material protruding from the head plate, and then attaching a head protection cap to the head plate so as to cover the cut head of the tension / fixing anchor. The slope stabilization method according to claim 3, comprising the steps of:

5. The reinforcing steel bar frame includes a lower steel bar frame including a plurality of vertical steel bars and a plurality of horizontal steel bars intersecting vertically and horizontally at a relatively low height position, an upper steel bar frame including a plurality of vertical steel bars and a plurality of horizontal steel bars intersecting vertically and horizontally above the lower steel bar frame, and a connecting member connecting the lower steel bar frame and the upper steel bar frame. The slope stabilization method according to claim 1, comprising the steps of:

6. The slope stabilization method according to claim 1, further comprising the step of spraying a polyurethane resin on the flat block body.

7. The slope stabilization method according to claim 1, wherein a coloring agent or reinforcing fiber is contained in the mortar constituting the flat block body.

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