Anchor structure and method for forming an anchor structure

Abstract

To provide an anchor structure that is driven into the ground and connected to a supported object to support a load, and that can suppress an increase in the amount of displacement of the anchor due to a decrease in the resistance of the ground caused by excavation and backfilling. [Solution] The anchor structure 1 comprises a main anchor 11 that is driven into the ground, connected to an object to be held, and to which a load is applied, and a sub-anchor 12 that is driven into the ground adjacent to the main anchor 11 on the side of the direction in which the main anchor 11 is displaced when the load is applied, and is configured so that when the main anchor 11 is displaced by the load, the sub-anchor 12 that receives the load from the main anchor 11 generates resistance force while displacing in a direction having a directional component perpendicular to the displacement direction of the main anchor 11.

Description

[Technical Field]

[0001] The present invention relates to an anchor structure that is driven into the ground and connected to an object to be held to hold a load, and a method for forming the same. [Background technology]

[0002] Anchors driven into the ground have traditionally been used to hold structures (such as safety fences and safety nets) on slopes. Anchors are basically "piles," but anchors equipped with earth pressure plates or bearing plates (wing-shaped reinforcing parts) are used to improve bearing capacity in soft ground, for example. Patent Document 1 discloses a technique relating to an anchor having such a wing-shaped reinforcing portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Publication No. 57-075033 Summary of the Invention [Problem to be solved by the invention]

[0004] Anchors equipped with earth pressure plates and bearing plates (wing-shaped reinforcing parts) as shown in Patent Document 1 are able to suppress the amount of displacement of the anchor and demonstrate resistance strength even in soft ground, as the pressure-receiving surface formed by the earth pressure plates and bearing plates resists earth pressure. However, because of the presence of earth pressure plates and bearing plates (the protruding parts of the "pile"), driving them can be difficult when there are obstacles such as tree roots, stones, or rocks in the ground. This is because if the earth pressure plate or bearing plate hits an obstacle underground, it is difficult to drive it in by striking it. Naturally sloping ground often contains obstacles such as tree roots, stones, or rocks. As a result, the area where the earth pressure plate or bearing plate will be installed (an area of ​​a certain size that can accommodate the "wing-shaped" part) must be excavated in advance, anchors must be installed, and the area must then be backfilled. This excavation and backfilling process reduces work efficiency (especially on slopes where heavy machinery cannot be brought in). In addition, because it is difficult to use compaction equipment on slopes and slope heads, compaction of the backfilled area using compaction equipment may not be possible, which tends to reduce the earth pressure in the backfilled area where the earth pressure plate or bearing plate will be installed. As a result, the displacement of the anchor tends to be somewhat large, or it is difficult to achieve uniform strength.

[0005] In view of the above, an object of the present invention is to provide an anchor structure that is driven into the ground and connected to a held object to hold a load, and that can reduce an increase in the amount of displacement of the anchor or variations in bearing strength due to a decrease in the resistance of the ground caused by excavation and backfilling. [Means for solving the problem]

[0006] (Configuration 1) An anchor structure comprising: a main anchor that is driven into the ground and connected to a held object to which a load is applied; and a sub-anchor that is driven into the ground on the side of the direction in which the main anchor is displaced when the load is applied; and the sub-anchor that receives the load directly or indirectly from the main anchor is configured so that when the main anchor is displaced by the load, it generates resistance force while displacing in a direction having a directional component perpendicular to the displacement direction of the main anchor.

[0007] (Configuration 2) 2. The anchor structure according to configuration 1, wherein the main anchor and the sub-anchor are pipe anchors, and the center of the sub-anchor is disposed offset with respect to the center of the main anchor from a displacement direction in which the main anchor is displaced when the load is applied to the main anchor, thereby causing the sub-anchor that receives a load directly or indirectly from the main anchor to be displaced in a direction having a directional component perpendicular to the displacement direction.

[0008] (Configuration 3) 3. The anchor structure according to configuration 1 or 2, comprising two sub-anchors, the two sub-anchors being aligned in a direction substantially perpendicular to the displacement direction and being disposed on the displacement direction side of the main anchor, and configured so that a triangle is formed by the centers of the main anchor and the two sub-anchors.

[0009] (Configuration 4) 4. The anchor structure according to configuration 3, wherein the two sub-anchors are arranged at a distance smaller than the diameter of the main anchor and are driven in substantially parallel to the main anchor.

[0010] (Configuration 5) The anchor structure according to configuration 3, wherein the two sub-anchors are arranged at a distance smaller than the diameter of the main anchor, and are driven so that the distance on the anchor tip side is smaller than the distance on the anchor head side.

[0011] (Configuration 6) 6. The anchor structure of any one of Aspects 1 to 5, wherein the diameter of the sub-anchor is larger than the diameter of the main anchor.

[0012] (Configuration 7) 7. The anchor structure according to any one of configurations 1 to 6, further comprising a second sub-anchor that is a pipe anchor that is driven into the ground on the displacement direction side of the sub-anchor, and the second sub-anchor is disposed with its center offset from the sub-anchor in the displacement direction.

[0013] (Configuration 8) 8. The anchor structure according to any one of configurations 1 to 7, wherein the driving length of the sub-anchor is shorter than the driving length of the main anchor.

[0014] (Configuration 9) 9. The anchor structure according to any one of configurations 1 to 8, wherein the length of the sub-anchor is 30 cm or more and 70% or less of the length of the main anchor.

[0015] (Configuration 10) 10. The anchor structure according to any one of configurations 1 to 9, wherein the length of the main anchor projecting above ground is longer than the length of the sub-anchor projecting above ground.

[0016] (Configuration 11) 11. The anchor structure according to any one of configurations 1 to 10, having two sub-anchors and including a stopper member that prevents the main anchor from passing between the two sub-anchors.

[0017] (Configuration 12) 12. The anchor structure according to claim 11, wherein the stopper member is a member that allows the heads of the two sub-anchors to move in a direction perpendicular to the displacement direction of the main anchor and regulates the distance between the two sub-anchors so that it does not exceed the diameter of the main anchor.

[0018] (Configuration 13) 13. A method for forming an anchor structure according to any one of configurations 1 to 12, comprising: a step of driving the main anchor into the ground in a state in which the main anchor is attached to a drill bit of a boring machine, as the drill bit excavates with the main anchor; and a step of driving the sub-anchor into the ground in a state in which the sub-anchor is attached to the drill bit of a boring machine, as the drill bit excavates with the sub-anchor.

[0019] (Configuration 14) 14. The method for forming an anchor structure according to claim 13, wherein a guide member is used to maintain a positional relationship between the main anchor and the sub-anchor in the step of driving the sub-anchor into the ground.

[0020] (Configuration 15) 15. The method for forming an anchor structure according to Configuration 14, wherein the guide member is attached to a head of the driven main anchor, or is a member that is fixed to the ground and holds the position of the sub-anchor attached to the drill bit of the boring machine while inserting it therethrough. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide an anchor structure that is driven into the ground and connected to a held object to hold a load, and that can prevent an increase in the amount of displacement of the anchor due to a decrease in resistance caused by excavation and backfilling, or reduce variations in bearing strength. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing an anchor structure according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating a state in which a load is applied to the anchor structure of the first embodiment. [Figure 3] Diagram showing the boring machine used to drive pipe anchors [Figure 4] 1 is an explanatory diagram of the formation of an anchor structure according to the first embodiment; [Figure 5] FIG. 10 is a diagram showing another example of a guide member used when forming an anchor structure; [Figure 6] FIG. 10 is an explanatory diagram of an anchor structure according to a second embodiment. [Figure 7] FIG. 10 is an explanatory diagram showing another example of the stopper member; [Figure 8] FIG. 10 is an explanatory diagram showing another example of the stopper member; [Figure 9] FIG. 10 is an explanatory diagram showing another example of the stopper member; [Figure 10] FIG. 10 shows another example of an anchor structure. [Figure 11] FIG. 10 shows another example of an anchor structure. [Figure 12] FIG. 10 shows another example of an anchor structure. [Figure 13] FIG. 10 shows another example of an anchor structure. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are merely examples of how the present invention can be realized, and are not intended to limit the scope of the present invention.

[0024] <Embodiment 1> Fig. 1 shows an anchor structure 1 according to a first embodiment of the present invention, with Fig. 1(a) being a view from below a slope (a view showing the anchor structure driven into the ground) and Fig. 2(b) being a top view. Fig. 2 also shows the same anchor structure 1, and is an explanatory diagram showing a state in which the anchor has been displaced due to a load being applied, with Fig. 1(a) being a view from below a slope and Fig. 2(b) being a top view. The anchor structure 1 of the first embodiment is installed on a slope or the like to hold an object to be held (for example, a protective fence or a protective net), A main anchor 11 that is driven into the ground and connected to a supported object to which a load is applied; and a sub-anchor 12 that is driven into the ground adjacent to the main anchor 11 on the slope lower side of the main anchor 11 (the front side of the page in FIG. 1(a) and the lower side in FIG. 1(b)). Note that in this application, "adjacent" is not limited to a state of contact, but also includes a state of being nearby without contact.

[0025] The main anchor 11 is a pipe anchor made of a circular steel pipe having a diameter of 114.3 mm and a length of 1000 mm to 5000 mm, although not limited to this. The main anchor 11 is connected to an object to be held (not shown) and holds the object. The connection to the object may be indirect, for example, via a connecting member such as a wire rope, or the object may be directly connected to the main anchor 11 (for example, a support pole that is the object to be held is erected inside the main anchor (sheath pipe method)). When connecting via a wire rope, it is advisable to eye the end of the wire rope and hook it onto the head of the main anchor 11 (and to provide a retaining member such as a pin bolt). For ease of connection, it is preferable that the head of the main anchor 11 protrudes from the ground surface GL (note that, depending on the connection method, such as the above-mentioned sheath pipe method, the head does not necessarily have to protrude above the ground surface). A shoe S, which is a ring-shaped member, is fixed (welded) to the inside of the tip (lower end) of the main anchor 11. The shoe S is used when drilling is performed using a boring machine while simultaneously driving the main anchor 11, and is not necessary when this construction method is not used (for example, in the case of a construction method in which an anchor is inserted into a hole after drilling, or in the case of a construction method in which the anchor is driven in by hammering, etc.) (the shoe S is not an essential component of the present invention).

[0026] The sub-anchor 12 is a pipe anchor made of a circular steel pipe having a diameter of 114.3 mm and a length of 300 mm, which is 70% of the length of the main anchor 11, although it is not limited to this (therefore, the installation length of the sub-anchor 12 is shorter than the installation length of the main anchor 11). The sub-anchor 12 is driven adjacent to the main anchor 11 on the side in the direction in which the main anchor 11 will be displaced when a load is applied to the main anchor 11. "The direction in which the main anchor 11 will be displaced when a load is applied to the main anchor 11" basically means the direction toward the bottom of the slope (the downward side in Figure 1(b)) when the main anchor is used to hold an object to be held on sloping ground, as in this embodiment. Note that "the direction in which the main anchor will be displaced when a load is applied to the main anchor" in this invention is not limited to the direction toward the bottom of the slope, but means the direction in which the main anchor 11 is displaced when a load is applied to the main anchor 11 in relation to the object to be held (hereinafter simply referred to as "displacement direction"). The anchor structure 1 of this embodiment has two sub-anchors 12, which are arranged side by side in a direction (left and right direction in FIG. 1(b)) that is approximately perpendicular to the displacement direction of the main anchor 11 and are disposed on the displacement direction side (lower side in FIG. 1(b)) of the main anchor 11, and are configured so that a triangle (approximately an equilateral triangle in this embodiment) is formed by the centers of the main anchor 11 and the two sub-anchors 12. In addition, two sub-anchors 12 are arranged at a distance smaller than the diameter of the main anchor 11 (in this embodiment, they are arranged so that they are in contact with each other with almost no distance between them), and are driven in approximately parallel to the main anchor 11. The sub-anchor 12 of this embodiment is driven so that it is almost entirely buried in the ground (with its head barely protruding above the ground surface). A shoe S, which is a ring-shaped member, is fixed (welded) to the inside of the tip (lower end) of the sub-anchor 12. Like the main anchor 11, it is used when drilling and driving are performed simultaneously using a boring machine, and is not necessary when this construction method is not used (for example, when the method involves inserting the anchor into the hole after drilling, or when the method involves driving the anchor in by hammering, etc.).

[0027] The sub-anchor 12 is disposed so that its center is offset from the displacement direction of the center of the main anchor 11. The main anchor 11 and sub-anchor 12, which are made of circular steel pipes, have a circular outer diameter in cross section. Therefore, due to the offset arrangement described above, the normal direction of the point where the main anchor 11 and sub-anchor 12 contact each other (load transfer surface) is a direction that has a component in the direction (left-right direction in FIG. 1(b)) that is perpendicular to the displacement direction (bottom side in FIG. 1(b)), as can be seen from FIG. 1(b) . As a result, as shown in FIG. 2, when the main anchor 11 is displaced by a load, the sub-anchor 12 that receives the load from the main anchor 11 (either by direct contact with the main anchor 11 and receiving the load, or by indirectly receiving the load via soil or other members such as a stopper member or buffer material described later) generates a resistance force while being displaced in a direction having a directional component perpendicular to the displacement direction. Therefore, in the anchor structure 1 of this embodiment, when a load is applied to the main anchor 11 and the main anchor 11 attempts to displace, the sub-anchors 12 move in a manner such that they are pushed apart in the left-right direction, and the resulting resistance reduces the amount of displacement of the main anchor 11. Furthermore, "displacement in a direction having a directional component perpendicular to the displacement direction" means that when the anchor structure 1 is viewed along the displacement direction, the projected area of ​​the anchor structure 1 increases, as can be seen from the change from Figure 1(a) to Figure 2(a). Therefore, in the anchor structure 1 of this embodiment, when a load is applied to the main anchor 11 and the main anchor 11 attempts to displace, the projected area of ​​the anchor structure 1 gradually increases, which acts to gradually increase the resistance force of the entire anchor structure 1 (resistance force against displacement in the displacement direction), thereby achieving an even higher resistance force (reduction in the amount of displacement), thereby achieving an extremely excellent operational effect.

[0028] Next, a method for forming the anchor structure 1 will be described. FIG. 3 shows a boring machine 100 used to drive a pipe anchor (in a state in which the main anchor 11 is set to be driven), where FIG. 3(a) is a side view and FIG. 3(b) is an enlarged view of the vicinity of the drill bit. The boring machine 100 itself has been used conventionally, and is based on a concept similar to that disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-32169 and Japanese Patent Application Laid-Open No. 2009-68229, etc. Therefore, only an outline will be described here, and a detailed description will be omitted. As shown in FIG. 3(a), the boring machine 100 includes a stand 101, a drill bit driving unit (motor) 102, a winch 106, and the like. The drill bit driving unit 102 is configured to slide (up and down in the drawing) on ​​a stand 101, and can be lifted up and down by a winch 106. An air hammer 104 and a drill bit 103 are attached to the drill bit driving unit 102 via a boring rod 105, causing the drill bit 103 to rotate and generate an impact by striking, thereby generating a drilling force. Although not shown, other devices such as a hydraulic unit that supplies pressure oil to the drill bit driving unit 102, which is a hydraulic motor, and a compressor that supplies air to the air hammer 104 are also used. As shown in Figure 3(b), when driving the main anchor 11 (or sub-anchor 12), which is a pipe anchor, the drill bit 103 and air hammer 104 (and boring rod 105) are inserted into the pipe anchor to be embedded, and the bit head 1031 protrudes from the bottom end of the pipe anchor. In this state, the rotation of the bit head 1031 and the impact given by the air hammer 104 excavate downward in the drawing, thereby embedding the pipe anchor. The bit head 1031 is configured to be able to contract / expand its diameter, and when it is inserted into the inside of the pipe anchor, it contracts so that its outer dimensions become smaller than the inner diameter of the pipe anchor, and then expands at a position protruding from the lower end of the pipe anchor, resulting in the state shown in Figure 3(b). As described above, the shoe S, which is a ring-shaped member, is attached to the inside of the lower end of the pipe anchor, and the upper end of the shoe S forms a step inside the pipe anchor that abuts against the flange 1032 of the drill bit 103. With this configuration, the pipe anchor is driven into the ground together with the drill bit 103, which rotates and applies impact while drilling downward in the drawing.

[0029] FIG. 4 is an explanatory diagram relating to the formation of the anchor structure 1 of the first embodiment (driving the main anchor 11 and the sub-anchor 12). First, as can be understood from the explanation based on Fig. 3, with the main anchor 11 attached to the drill bit 103 of the boring machine 100, the main anchor 11 is driven into the ground as drilling is performed with the drill bit 103. Because drilling is performed with a drill bit, it is possible to drill holes (and drive anchors) even if there are tree roots, stones, rocks, etc. in the ground. The main anchor 11 is driven so that its head protrudes above the ground surface.

[0030] Next, the sub-anchors 12 are cast. When driving the sub-anchor 12, a guide member 200 is used to maintain the positional relationship between the main anchor 11 and the sub-anchor 12. The guide member 200 is a member that is attached to the head of the driven main anchor 11, and that maintains its position while inserting the sub-anchor 12 attached to the drill bit 103 of the boring machine 100. In this embodiment, in the positional relationship between the main anchor 11 and the sub-anchor 12 shown in Fig. 1(b), a guide member 200 is used that has a side wall portion 201 (see Fig. 4(a-1)) that is configured to surround them, and a tubular portion 202 through which one of the sub-anchors 12 fixed to the side wall portion 201 is inserted.

[0031] As shown in Figure 4(a), the guide member 200 is installed on the head of the main anchor 11, and the boring machine 100 is positioned with respect to the cylindrical portion 202 of the guide member 200 (Figure 4(b)). Then, as shown in Figure 4(c), with the sub-anchor 12 attached to the drill bit 103 of the boring machine 100, the sub-anchor 12 is driven into the ground as drilling is performed with the drill bit 103. At this time, the sub-anchor 12 is inserted through the cylindrical portion 202 of the guide member 200, and its position is maintained. Next, the remaining sub-anchors 12 are driven in the same manner. The driving is performed so that the sub-anchors 12 are placed in the remaining space within the side wall portion 201 of the guide member 200. As a result, the anchor structure 1 having the positional relationship shown in Figure 1 is formed. Similar to the driving of the main anchor 11 described above, the sub-anchor can be driven even if there are tree roots, stones, rocks, etc. in the ground. The sub-anchor 12 in this embodiment may be driven so that its head is also buried.

[0032] Here, guide member 200 is used as an example of a guide member, which is a jig used when driving in an anchor, but the shape of the guide member is not limited to this, and a guide member of any shape that functions as a guide member as described above can be used. FIG. 5 shows another example of such a guide member. 5(a) to (c) are diagrams showing the guide member 300, with FIG. 5(a) being a top view, FIG. 5(b) being a side view, and FIG. 5(c) being a front view (viewed from the lower side of the inclined surface). The guide member 300 has a plate portion 301 in which a hole H1 through which the main anchor 11 is inserted and a hole H2 through which the sub-anchor 12 is inserted are formed, and guide ribs 302 erected on the plate portion 301 around the holes H1 and H2. In addition, a plurality of holes H3 are formed around the periphery of the plate portion 301 for inserting and fixing pin members (or anchor members) for fixing to the ground (from the perspective of ease of viewing the drawings, only some of the members are given reference numerals; some other members are also given reference numerals only in some cases). The guide member 300 may be used from the time the main anchor 11 is driven, or, similar to the method of using the guide member 200 described above, it may be attached to the head of the main anchor 11 after the main anchor 11 has been driven and then used to drive the sub-anchor 12. When the guide member 300 is in use, multiple pin members (or anchor members) are driven into the ground through holes H3, thereby fixing the guide member 300 to the ground. The main anchor 11 passed through hole H1 and the sub-anchor 12 passed through hole H2 are supported by the guide rib 302. Therefore, the guide member 300 can more stably guide the driving of the main anchor 11 and sub-anchor 12. As can be seen from the drawing, the guide member 300 is used when driving the sub-anchors 12 adjacent to each other. 5(d) to (f) show a guide member 300' used when driving sub-anchors 12 with gaps between them. The guide member 300' is conceptually similar to the guide member 300, except that there are gaps between the holes H2 through which the sub-anchors 12 are inserted, and the position of the guide rib 302 differs accordingly.

[0033] As described above, according to the anchor structure 1 of this embodiment, casting can be performed using a boring machine (casting while drilling holes), which eliminates the need to excavate a predetermined area and then backfill when installing the anchor structure. This improves work efficiency and reduces the increase in anchor displacement or variation in bearing capacity due to a decrease in the ground resistance caused by excavation and backfilling. This is not limited to the above-mentioned method of "drilling holes and driving anchors simultaneously," but can also have the same effect in methods such as drilling holes and then driving anchors into the ground where the hole walls are stable, or in methods of driving anchors by hammering. Furthermore, even in cases where, for example, a hole slightly larger than the anchor is drilled and the anchor is erected due to the selected anchor shape or ground conditions, and the gap between the hole and the anchor is filled with excavated soil, sand, grout, or the like, the concept of the anchor structure of this embodiment can "reduce the increase in anchor displacement due to a decrease in ground resistance caused by excavation and filling, or reduce variations in bearing capacity." As described above, the anchor structure of this embodiment has the excellent effect of increasing the projected area of ​​the anchor structure when a load is applied to the main anchor and the main anchor attempts to displace, thereby increasing the resistance of the entire anchor structure (resistance to displacement in the direction of displacement). Therefore, it is possible to increase the projected area of ​​the anchor structure beyond the "filling range." Therefore, even if filling is performed, it is possible to "reduce the increase in anchor displacement due to a decrease in ground resistance caused by excavation and filling."

[0034] <Embodiment 2> 6A and 6B are explanatory diagrams of the anchor structure of the second embodiment, in which FIG. 6A is a top view showing the state when it is first installed, and FIG. 6B is a diagram explaining the state when displacement occurs due to a load. The anchor structure of this embodiment is the anchor structure 1 of embodiment 1 provided with a stopper member 13. The same components as those in embodiment 1 are given the same reference numerals, and the description here will be simplified or omitted. The main anchor 11 and sub-anchor 12 are basically the same as in embodiment 1, but differ from embodiment 1 in that the sub-anchor 12 is driven in so that its head protrudes above the ground surface in order to fit the stopper member 13. In this embodiment, for the convenience of connecting the object to be held (not shown in particular) to the main anchor 11, the head of the main anchor 11 is configured to protrude higher than the sub-anchor 12 (the length of the main anchor protruding above ground is longer than the length of the sub-anchor protruding above ground), but depending on the method of connecting the object to be held, it is not necessarily necessary to make the head of the main anchor 11 higher than the sub-anchor 12.

[0035] The stopper member 13 is intended to "prevent the main anchor from passing between the two sub-anchors" and is "a member that allows the heads of the two sub-anchors to move in a direction perpendicular to the displacement direction of the main anchor, and regulates the distance between the two sub-anchors so that it does not exceed the diameter of the main anchor." The stopper member 13 of this embodiment is an annular member that surrounds the heads of the main anchor 11 and the two sub-anchors 12, and is configured so that its inner dimension in the width direction (the direction perpendicular to the displacement direction) (more precisely, the inner dimension in the direction perpendicular to the displacement direction at the position where the sub-anchor 12 is arranged) is larger than the sum of two diameters of the sub-anchors 12 and smaller than the sum of the diameter of the main anchor 11 and two diameters of the sub-anchors 12. With this configuration, the two sub-anchors 12 are movable in the direction perpendicular to the displacement direction, and the distance between the two sub-anchors is regulated so that it does not exceed the diameter of the main anchor.

[0036] As can be seen from FIG. 6(b), when the main anchor 11 tries to be displaced by the load, the same action as that described in the first embodiment occurs. If the displacement of the main anchor 11 continues further, in the anchor structure of embodiment 1, the distance between the two sub-anchors 12 may become larger than the diameter of the main anchor 11, and the main anchor 11 may pass through between the two sub-anchors 12. If it gets to that point, the sub-anchors 12 will no longer generate resistance (the effect of increasing the projected area of ​​the anchor structure will not be obtained). In contrast to this, in this embodiment, the stopper member 13 keeps the distance between the two sub-anchors 12 less than the diameter of the main anchor 11, preventing the main anchor from passing between the two sub-anchors, thereby maintaining the excellent effect described in embodiment 1, that is, "the projected area of ​​the anchor structure is increased, thereby increasing the resistance force of the entire anchor structure (resistance force against displacement in the displacement direction)."

[0037] As described above, according to this embodiment, the provision of the stopper member makes it possible to maintain the excellent effect of "increasing the projected area of ​​the anchor structure and increasing the resistance force of the entire anchor structure (resistance force against displacement in the displacement direction)," which is preferable. In addition, an anti-detachment engagement portion (a member that engages between the stopper member and the main anchor and / or sub-anchor to restrict the stopper member from moving upward) may be provided as appropriate to prevent the stopper member from detaching.

[0038] In this embodiment, an annular rice ball-shaped member (a member that fits into the main anchor and sub-anchor) as shown in FIG. 6 is used as an example of the stopper member, but the stopper member of the present invention is not limited to this, and any mechanism that functions as the stopper member described above may be used. 7 to 9 show other examples of the stopper member. The stopper member 13-1, shown in Fig. 7(a) in its initial installed state and in Fig. 7(b) in its displaced state, is an annular member that fits into the two sub-anchors 12 and has an internal shape that guides the movement of the sub-anchors 12 along a relative trajectory with respect to the main anchor 11 as the main anchor 11 and sub-anchor 12 are displaced as described in embodiment 1. The stopper member 13-1 prevents the main anchor from passing between the two sub-anchors. Stopper member 13-2, shown in a top view in Figure 7(c) and a view from below the slope in Figure 7(d), comprises a plate portion 31-21, a guide rib 13-22, and a fall-prevention engaging portion 13-23. Similar to stopper member 13-1, it serves the purpose of guiding the trajectory of the sub-anchor 12, and the plate portion 31-21 and guide rib 13-22 provide greater strength. The fall-prevention engaging portion 13-23 is a bolt attached to the sub-anchor 12, which prevents stopper member 13-2 from coming off. The stopper member 13-3, shown in its initial installed state in Figure 8(a) and its displaced state in Figure 8(b), is made up of a bolt and nut inserted into an elongated hole formed in the sub-anchor 12, and a washer 13-31, the enlarged views of which are shown in Figures 8(c) and (d). The sub-anchor 12 has an elongated hole formed therein through which the shank of the bolt is inserted and which allows the bolt to move horizontally, but through which the washer 13-31 (if the washer 13-31 is not used, the bolt head or nut (or washer if a washer is used)) cannot pass. The bolt and nut attached to the elongated hole and the washer 13-31 prevent the main anchor from passing between the two sub-anchors. Washer 13-31 is a component that has a tapered shape when viewed from above (Figure 8(c)) and has a hole through which the bolt is inserted, and is a component that reduces undesirable stress at the contact point between the head of the bolt or the nut and the inner surface of the anchor. The hole H formed in the sub-anchor 12 is an insertion hole for placing a bolt inside the sub-anchor 12 when the stopper member 13-3 is installed. The stopper member 13-4 shown in Figures 8(e) to (h) is composed of a connecting plate with an elongated hole, and a bolt and nut that joins the sub-anchor 12 to the connecting plate. The elongated hole formed in the connecting plate is an elongated hole through which the shank of the bolt attached to the sub-anchor 12 is inserted and which allows the bolt to move horizontally, but does not allow the head of the bolt or nut (or the washer, if used) to pass through. This configuration prevents "the main anchor from passing between the two sub-anchors." The stopper member 13-5 shown in Figures 9(a) to (d) has a winding plate 13-51 formed by bending a flat bar so as to wrap around the heads of the main anchor 11 and two sub-anchors 12, a stopper bolt 13-52 that attaches the sub-anchor 12 and winding plate 13-51 via an insertion hole formed in the winding plate 13-51, and a connecting bolt 13-53 that connects both end portions of the winding plate 13-51 so that the end portion can slide (be widened) via an elongated hole formed at the end portion of the winding plate 13-51. Both ends of the hoist plate 13-51 are slidably connected by connecting bolts 13-53 inserted into elongated holes formed at the ends of the hoist plate 13-51, and therefore the hoist plate 13-51, which is wound around the heads of the main anchor 11 and the two sub-anchors 12, can be widened. As shown in Figures 9(c) and (d), the widening caused by the elongated holes is configured so that "the main anchor does not pass between the two sub-anchors," while allowing the two sub-anchors to move in a direction perpendicular to the displacement direction. The pin bolt PB attached to the main anchor 11 is a member that prevents the wire rope (used to connect the object to be held) that is hung on the head of the anchor 11 from coming loose, but at the same time, it also functions as a member that prevents the hoist plate 13-51 from coming loose from the main anchor 11. Any of the above stopper members allows the sub-anchor 12 to move a certain amount in a direction perpendicular to the displacement direction, and therefore the effect described in embodiment 1, that is, "the projected area of ​​the anchor structure increases, and the resistance force of the entire anchor structure (resistance force against displacement in the displacement direction) is increased," can be obtained, and the main anchor is prevented from passing between the two sub-anchors, so that the same effect as described in embodiment 2 can be obtained. Note that, as shown in Figures 7 and 8, in cases where the stopper member attached to the sub-anchor itself is configured to abut against the main anchor, thereby preventing the main anchor from passing between two sub-anchors, it is not necessarily necessary to restrict the distance between the two sub-anchors so as not to exceed the diameter of the main anchor. 6 to 9 show examples having a space through which the sub-anchor can move, or an elongated hole through which a component (bolt) connected to the sub-anchor can move, but the stopper member of the present invention is not limited to those having such pre-formed spaces for component movement. For example, the stopper member may be a component having a predetermined elasticity and wound around the outer periphery of the main anchor and sub-anchor (as shown in FIG. 9(a)), and may allow the sub-anchor to move a certain amount in a direction perpendicular to the displacement direction by extending the stopper member by a predetermined amount. It is not limited to elastic deformation, and may also be a component that allows the sub-anchor to move a certain amount in a direction perpendicular to the displacement direction while plastically deforming (the stopper member may be any member that does not break until it reaches the required yield strength).

[0039] In the example shown in Embodiment 2 and Figures 6 to 9, the stopper member is located above the ground surface, but the present invention is not limited to this, and the stopper member may be located underground. The stopper member is not a large component in height, and therefore can be attached below the ground surface by simply excavating the ground surface slightly, and with such slight excavation, the "reduction in ground resistance due to excavation and backfilling" does not pose a problem. Therefore, it is not essential that the head of the sub-anchor protrudes above the ground surface.

[0040] In each embodiment, the sub-anchor is driven approximately parallel to the main anchor (parallel in the longitudinal direction of the anchor), but the present invention is not limited to this, and the sub-anchors may be driven at an angle to each other. An example of such a structure is shown in Figure 10. Figure 10(a) shows the initial state when installed, and Figure 10(b) is a diagram illustrating the state after displacement due to load. The anchor structure in Figure 10 differs from that in embodiment 1 only in the driving direction (angle) of the sub-anchor 12, and the main anchor 11 itself and the sub-anchor 12 themselves are the same as those in embodiment 1. In the anchor structure of FIG. 10, the sub-anchors 12 are "arranged at intervals smaller than the diameter of the main anchor, and are driven in so that the intervals on the anchor tip side are smaller than the intervals on the anchor head side." In most natural soil conditions, the soil is soft near the surface and often becomes harder as you go deeper into the ground. In the anchor structure of Fig. 10, the part where the sub-anchor 12 assists (contacts) the main anchor 11 in bearing capacity is underground, and when an external force from the main anchor 11 is transmitted to the sub-anchor 12, the part that is installed in the hard soil exerts bearing capacity, reinforcing the bearing capacity of the main anchor 11 (note that the anchor structure 1 of Embodiment 1 also has this effect because the sub-anchor 12 and main anchor 11 come into contact underground). In each embodiment, an example is given in which there are almost no gaps between the sub-anchors during the installation stage, but gaps may also be provided between the sub-anchors during the installation stage. However, the gaps must be less than the diameter of the main anchor. In principle, smaller gaps are preferable, and it is often preferable to have virtually no gaps, as in each embodiment (however, if the soil quality (particularly soft ground) means that there is almost no impact from consolidation due to displacement, it may be that resistance with a wider width from the start is more effective (greater bearing capacity can be obtained)).

[0041] In each embodiment, an example is given in which there are two sub-anchors, but the present invention is not limited to this, and three or more sub-anchors may be provided for one main anchor, or conversely, one sub-anchor may be provided for one main anchor. FIG. 11 shows an example in which three or more sub-anchors are provided for one main anchor. Each anchor structure in Fig. 11 has a second sub-anchor 14 driven into the ground adjacent to the sub-anchor 12 on the displacement direction side of the sub-anchor 12 of the anchor structure 1 of Embodiment 1. Each second sub-anchor 14 is a pipe anchor with the same specifications as the sub-anchor 12. In the anchor structure of Figure 11(a) (the left side of the figure shows the initial installation state, and the right side is an explanatory diagram of the displaced state), one second sub-anchor 14 is positioned so as to be in contact with two sub-anchors 12 (in a position that is a mirror image of the main anchor 11). In the anchor structure of Figure 11(b), the two second sub-anchors 14 are arranged so as to contact each of the two sub-anchors 12 at a position that is an extension of the normal direction of the point where the main anchor 11 and sub-anchors 12 contact each other as shown in Figure 1(b). The anchor structure of FIG. 11(c) is provided with both the second sub-anchor 14 of FIG. 11(a) and the second sub-anchor 14 of FIG. 11(b). Each anchor structure in Figure 11 is "equipped with a second sub-anchor, which is a pipe anchor that is driven into the ground on the displacement direction side of the sub-anchor, and the second sub-anchor is positioned with its center offset from the displacement direction (displacement direction of the main anchor) relative to the sub-anchor." Note that, although the example given here is one in which the sub-anchor and second sub-anchor are pipe anchors with the same specifications, the sub-anchor and second sub-anchor may be anchors with different specifications (for example, different lengths or diameters). Of course, a stopper member may also be provided for the second sub-anchor. For the second sub-anchor, a third sub-anchor, a fourth sub-anchor, and so on may be further provided based on the same concept as above.

[0042] FIG. 12 shows an example in which one sub-anchor is provided for one main anchor. The anchor structure in Fig. 12 is similar to the anchor structure 1 of Embodiment 1 in that one of the two sub-anchors 12 has been removed. Fig. 12(a) is a diagram showing the initial state after installation, and Fig. 12(b) is a diagram illustrating the state after displacement due to a load. As can be seen from FIG. 12(b), the same effect as that explained in the first embodiment (although the effect is smaller, the same effect) can be obtained. Note that, here, an example is taken in which one of the sub-anchors 12 of the anchor structure 1 of embodiment 1 has been deleted (the sub-anchor 12 is positioned diagonally relative to the main anchor 11 in FIG. 12(a)), but even if the main anchor 11 and the sub-anchor 12 are arranged vertically in FIG. 12(a), it is possible to obtain substantially the same effect as that described in embodiment 1. Considering the installation accuracy of the anchors that are driven into the ground and the processing accuracy of the steel pipes, even when the sub-anchors 12 are arranged vertically relative to the main anchor 11, slight misalignment will occur, and such slight misalignment will result in the displacement directions of the main anchor 11 and the sub-anchor 12 being different, as in Figure 12(b). Above all, in a natural environment, the load direction itself is unlikely to be constant (misalignment will occur), and also, due to factors such as uneven earth pressure on natural slopes (the presence of foreign objects such as stones or rocks in the ground), even when the sub-anchors 12 are arranged vertically relative to the main anchor 11, a misalignment will actually occur in the displacement directions of the two, and therefore, as in Figure 12(b), the displacement directions of the main anchor 11 and the sub-anchor 12 will be different. In other words, even if the main anchor and sub-anchor are aligned in a direction along the expected load direction, as long as the main anchor and sub-anchor are not fixed to each other, it can still fall under the category of "a sub-anchor that receives a load directly or indirectly from the main anchor is configured to generate resistance while displacing in a direction having a directional component perpendicular to the displacement direction of the main anchor."

[0043] In the embodiment, the length of the sub-anchor 12 is 300 mm to half the length of the main anchor 11, but the present invention is not limited to this. For example, the sub-anchor may have a length similar to that of the main anchor. However, while the displacement of the main anchor is greatest at a point close to the ground surface, the tip of the main anchor generally does not experience much displacement. Therefore, with regard to the above-described effects, there is no significant improvement even if the sub-anchor is driven deeper than necessary. Considering the above-described effects and cost-effectiveness, including work efficiency, it is sufficient for the sub-anchor to be driven to a length of 300 mm or more, and it is preferable for the sub-anchor to be 70% or less of the length of the main anchor 11 (or half or less of the length of the main anchor 11). Furthermore, in the embodiment, the main anchor 11 and the sub-anchor 12 are formed from similar circular steel pipes, but the present invention is not limited to this. For example, the diameter of the sub-anchor may be made larger than the diameter of the main anchor, thereby increasing the bearing capacity (if a long main anchor is made thick, there is a risk that the casting work will become difficult, but if the sub-anchor is relatively short, even if the diameter is made thicker, the impact on the casting work will be relatively small).

[0044] Furthermore, in each embodiment, the main anchor and sub-anchor are circular steel pipes as an example, but the present invention is not limited to this, and any member that can be used as a "pile" can be used. FIG. 13 shows an example of such a structure, where FIG. 13(a) shows a structure in which the main anchor 11-1 and sub-anchor 12-1 are made of square steel pipes, and FIG. 13(b) shows a structure in which the main anchor 11-2 and sub-anchor 12-2 are made of H-shaped steel. Furthermore, the main anchor and sub-anchor do not have to be made from the same material; for example, as shown in Figure 13(c), the main anchor and sub-anchor may be made from different materials, such as by making the main anchor from a circular steel pipe and the sub-anchor from an H-shaped steel. As can be seen from each diagram in Figure 13, when a load is applied to the main anchors (11, 11-1, 11-2) and the main anchors (11, 11-1, 11-2) attempt to displace in the displacement direction (downward in this example), the normal direction of the points (load transfer surfaces) where the main anchors (11, 11-1, 11-2) and sub-anchors (12-1, 12-2) contact each other becomes a direction that has a component perpendicular to the displacement direction. Therefore, the sub-anchors (12-1, 12-2) are pushed apart in the left and right directions, and the same effect as that described in the embodiment can be obtained.

[0045] In the embodiment, the anchor structure is shown as being cast in order to hold an object to be held (for example, a protective fence or a protective net) on sloping ground, but the present invention is not limited to this and can be cast in any ground and used to hold any object to be held. [Explanation of symbols]

[0046] 1. Anchor structure 11...Main anchor 12...Sub-anchor 13...Stopper member 14...Second sub-anchor 100...boring machine 103...Drill bit 200...Guide member

Claims

1. a main anchor that is driven into the ground and connected to the object to be held; a sub-anchor that is driven into the ground on the side of the main anchor in the direction of a load having a directional component along the ground surface that is received from the object to be held, An anchor structure in which the normal to a load transfer plane that directly or indirectly transfers the load from the main anchor to the sub-anchor is in a direction having a component perpendicular to the direction of the load received from the held object, and the sub-anchor is configured to be movable relative to the main anchor in a direction having a component perpendicular to the direction of the load received from the held object, so that when the main anchor is displaced by the load received from the held object, the sub-anchor that has received the load directly or indirectly from the main anchor displaces in a direction having a component perpendicular to the displacement direction of the main anchor, thereby increasing the projected area of ​​the anchor structure that includes the main anchor and the sub-anchor as viewed along the displacement direction of the main anchor, and generating resistance force.

2. 2. The anchor structure according to claim 1, wherein the main anchor and the sub-anchor are pipe anchors, and the center of the sub-anchor is disposed offset with respect to the center of the main anchor from a displacement direction in which the main anchor is displaced when a load from the object to be held is applied to the main anchor, thereby configuring the sub-anchor that receives a load directly or indirectly from the main anchor to be displaced in a direction having a directional component perpendicular to the displacement direction.

3. 3. The anchor structure according to claim 2, comprising two sub-anchors, the two sub-anchors being aligned in a direction substantially perpendicular to the displacement direction and being disposed on the displacement direction side of the main anchor, and configured so that a triangle is formed by the centers of the main anchor and the two sub-anchors.

4. The anchor structure according to claim 3 , wherein the two sub-anchors are disposed at an interval smaller than the diameter of the main anchor and are driven in substantially parallel to the main anchor.

5. 4. The anchor structure according to claim 3, wherein the two sub-anchors are arranged at a distance smaller than the diameter of the main anchor, and are driven so that the distance on the anchor tip side is smaller than the distance on the anchor head side.

6. The anchor structure of claim 2 , wherein the diameter of the sub-anchor is greater than the diameter of the main anchor.

7. 3. The anchor structure according to claim 2, further comprising a second sub-anchor that is a pipe anchor that is driven into the ground on the displacement direction side of the sub-anchor, and the second sub-anchor is disposed with a center offset from the sub-anchor in the displacement direction.

8. 8. The anchor structure according to claim 1, wherein the driving length of the sub-anchor is shorter than the driving length of the main anchor.

9. 9. The anchor structure according to claim 8, wherein the length of the sub-anchor is 300 mm or more and 70% or less of the length of the main anchor.

10. 8. The anchor structure according to claim 1, wherein a length of the main anchor projecting from the ground is longer than a length of the sub-anchor projecting from the ground.

11. 8. The anchor structure according to claim 1, further comprising two sub-anchors, and a stopper member that prevents the main anchor from passing between the two sub-anchors.

12. 12. The anchor structure according to claim 11, wherein the stopper member is a member that restricts the heads of the two sub-anchors to be movable relative to the main anchor in a direction having a directional component perpendicular to the direction of the load received from the held object, and that restricts the spacing between the two sub-anchors so that it does not exceed the diameter of the main anchor.

13. A method for forming an anchor structure according to any one of claims 1 to 7, comprising: a step of driving the main anchor into the ground while drilling with the drill bit in a state where the main anchor is attached to a drill bit of a boring machine; a step of driving the sub-anchor into the ground in conjunction with drilling by the drill bit in a state in which the sub-anchor is attached to a drill bit of a boring machine; A method for forming an anchor structure, comprising:

14. 14. The method for forming an anchor structure according to claim 13, wherein a guide member is used to maintain a positional relationship between the main anchor and the sub-anchor in the step of driving the sub-anchor into the ground.

15. 15. The method for forming an anchor structure according to claim 14, wherein the guide member is attached to a head of the driven main anchor or fixed to the ground, and is a member that holds the position of the main anchor while allowing the sub-anchor attached to the drill bit of the boring machine to pass through.

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