JP3840971B2 - Ground anchor and method for fixing the ground anchor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground anchor that prevents a landslide by tensioning a tendon embedded in the ground by a fixing portion fixed to an outer end portion exposed on the ground surface and transmitting the reaction force to the ground by the fixing portion.
[0002]
[Prior art]
The ground anchor used to prevent landslides is a function that tightens a shallow ground where there is a risk of landslide due to the reaction force of tendon tension with one end fixed to the deep and hard ground and the other end exposed to the ground surface fixed to the anchorage. Have
[0003]
Even when the shallow ground expands and contracts due to frost heaving and thawing, it is interposed between the fixing unit and the pressure receiving plate described in, for example, Japanese Patent Application Laid-Open No. 2001-32273 so that a certain tension force acts on the tendon. In particular, a ground anchor structure has been proposed that can absorb an excessive force due to the above-described expansion by the elastic member.
[0004]
A characteristic required for such an elastic member is to have a later-described elastic force fluctuation dead zone region that gives a small change in elastic force to a large amount of deflection.
[0005]
[Problems to be solved by the invention]
However, in the elastic member having the above-described characteristics, particularly in a later-described elastic force fluctuation dead zone region, a large amount of bending is required to achieve a predetermined elastic force. The stroke must be long, and in order to fix the ground anchor, a jack with a long stroke was required at the construction site.
[0006]
Such a jack that can give a constant compressive force with a long stroke is expensive, and the construction for fixing the ground anchor is expensive. Although it is possible to resize and compress two types of large and small jacks that do not have a very long stroke, there is a problem that the work at the time of reordering is costly and time consuming.
[0007]
The present invention has been made in view of such problems, and an object of the present invention is to realize a ground anchor that can be fixed easily at low cost and a fixing method thereof.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the first invention is the first support plate and the ground surface, which are tensioned by a fixing tool fixed to the outer end exposed on the ground surface of the tendon embedded in the ground, and abut against the fixing tool. A ground anchor that prevents the landslide by transmitting the elastic force of the elastic member interposed between the second support plate and the ground via the tendon to the first support plate. A plurality of fixing jigs that fix one end and fix the other end to the second bearing plate, the fixing jig restricts the elastic member from extending from a predetermined distance and allows the elastic member to bend. It was set as the ground anchor characterized by doing.
[0009]
According to the first invention, before the ground anchor is fixed to the ground, the elastic member can be compressed and fixed to a predetermined separation distance in another place in advance.
[0010]
In the first invention, the fixing jig is fixed at a position corresponding to a separation distance in which the elastic member has a resilience of 50% to 90% (preferably 80%) of a predetermined resilience. A ground anchor having a certain feature is defined as the second invention.
[0011]
According to the second invention, in order to fix the ground anchor to the ground, the elastic member is further subjected to a compressive force that is a reaction force of the elastic force increased by 11% to 100%, and is bent. The separation distance can be shortened.
[0012]
In order to solve the above-mentioned problem, the third invention is characterized in that a tendon embedded in the ground is tensioned by a fixing tool fixed to an outer end portion exposed to the ground surface, and the first bearing plate contacting the fixing tool and the ground surface are provided. A ground anchor fixing method for preventing a landslide by transmitting an elastic force of an elastic member interposed between the second supporting plate and a ground to prevent the landslide from the ground. A plurality of fixing jigs having one end fixed to the support plate and the other end fixed to the second support plate restricts the elastic member from extending from a predetermined distance and allows the elastic member to bend. It was set as the fixing method of the ground anchor characterized by doing.
[0013]
According to the third invention, before the ground anchor is fixed to the ground, it is possible to compress and fix the elastic member to a predetermined separation distance in another place in advance.
[0014]
In the third invention, the fixing position of the fixing jig is a position corresponding to a separation distance in which the elastic member has a resilience of 50% to 90% (preferably 80%) of a predetermined resilience. A ground anchor fixing method characterized in that it is set as described above is a fourth invention.
[0015]
According to the fourth invention, in order to fix the ground anchor to the ground, a compression force which is a reaction force of the elastic force of 11% to 100% is further applied to the elastic member to bend it. It is possible to reduce the separation distance.
[0016]
According to a third or fourth aspect of the present invention, there is provided a ground anchor fixing method according to a fifth aspect, wherein the first bearing plate is pushed down toward the ground surface while receiving the drag of the elastic member by a jack. Invented.
[0017]
According to the fifth invention, in order to fix the ground anchor to the ground, a predetermined amount of compressive force is increased by a predetermined stroke through the first support plate without changing the jack. The elastic member can be provided.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
=== Outline of Ground Anchor ===
An example of using a ground anchor as one embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a side cross section of a ground anchor in the ground according to the present embodiment.
[0019]
For example, as a landslide countermeasure method such as a cut slope, a pressure receiving plate 11 made of concrete or the like is laid on a slope (ground surface) 21, and a plurality of ground anchors in the present embodiment are arranged at appropriate intervals on the ground surface 22 and 23. 31 is placed and the ground surface layer 22 is pressed against the ground deep portion 23 side through the pressure receiving plate 11 to prevent the ground surface layer 22 from collapsing. The above pressing method is as follows. A tendon 32 made of a linear member is inserted into the pressure receiving plate 11 and the grounds 22 and 23 substantially perpendicularly to the ground surface 21, and one end portion thereof is fixed to the ground deep portion 23 by the grout 24 and protrudes to the ground surface 21. The other end is fixed to the fixing tool 33a of the fixing unit 33 and fixed to the pressure receiving plate 11 via the first support plate 33b, the elastic member 34, and the second support plate 35, and tension is applied to the tendon 32. Thus, the compressive force as the reaction force is transmitted to the grounds 22 and 23 via the pressure receiving plate 11 to tighten the ground surface layer 22.
[0020]
In this embodiment, the tension of the tendon 32 is realized by a frictional force between the lower surface of the fixing nut 33c meshed with the tendon screw portion 32a and the upper surface of the fixing tool 33a, and the grout of the ground deep portion 23 from the lower surface of the fixing nut 33c. A separation distance 41 to the upper surface of 24 is maintained. Further, the above-described tension force is balanced with the elastic force of the elastic member 34, which will be described later, so that a later-described separation distance 42 is maintained.
[0021]
The elastic member 34 interposed between the first support plate 33b and the second support plate 35 has a function of avoiding an excessive tension force acting on the tendon 32 and applying a constant force as much as possible. In the present embodiment, as shown in FIG. 1, the elastic member 34 is formed by arranging six disc springs 34a in series. In this case, three sets of two sets each having a hole in the center and having a conical disc-shaped spring 34a arranged in two stages in different directions and fitted into the pipe portion 33d are arranged.
[0022]
The elastic member 34 can absorb the expansion and contraction of the ground surface layer 22. For example, when the ground surface layer 22 expands due to freezing, a tension force acts on the tendon 32. At the same time, the elastic member is compressed, so that the tension force is defined as a known force from the compression amount of the elastic member. As a result, the tendon 32 can be prevented from being broken.
[0023]
In addition, all the six disc springs 34a in the present embodiment are operated in the elastic force fluctuation dead zone region. Therefore, there is little change in the elastic force with respect to the amount of expansion and contraction expected for the elastic member 34, and the tension force of the tendon 32 can be kept approximately constant with respect to the freezing and thawing of the ground surface layer 22. .
[0024]
In addition, the ground anchor 31 in FIG. 1 represents the state which is functioning to clamp the ground surface layer 22, the fixing jig 36 which will be described later is not used, and the first nut 36b has a gap (not shown). 1 is not in contact with the pressure plate 33b.
[0025]
=== Configuration and Function of Fixed Jig ===
The configuration of the fixing jig 36 in the present embodiment will be described with reference to FIG. FIG. 2 shows details and arrangement of the fixing jig 36 according to an embodiment of the present invention. FIG. 2 shows the arrangement of the fixing jig 36 from above, and FIG. 2 shows a part of the fixing jig. FIG.
[0026]
The fixing jig 36 according to the present embodiment is provided with a total of four sets each including a rod screw 36a, a first nut 36b, a second nut 36c, a first washer 36d, and a second washer 36e.
[0027]
As shown in FIG. 2, the second bearing plate 35 is a disc, and a female screw having the same pitch as the rod screw 36a is cut so that the inner circumference having the same center as that of the second bearing plate 35 is divided into four equal parts. These can be set up with four bar screws. Then, the bar screw 36a is nut-fixed to the second bearing plate 35 by a friction force acting between the upper surface of the second bearing plate 35, both surfaces of the second washer, and the lower surface of the second nut 36c. .
[0028]
On the other hand, the first support plate 33b is also a disc and has the same center as the second support plate 35 described above. The first bearing plate 33b has four holes having a diameter larger than the diameter of the bar screw 36a at the same position as the bar screw 36a. A rod screw 36a is inserted into the hole, and the first support plate 33b is fixed to the fixing jig 36 by the elastic force of the first nut 36b, the first washer 36d, and the elastic member 34.
[0029]
That is, when the fixing jig 36 is functioning, the elastic force of the elastic member 34 pushes up the first support plate 33b, the upper surface of the first support plate 33b, both surfaces of the first washer 36d, and the first nut 36b. This balances with the frictional force that acts between the lower surfaces of the plates.
[0030]
By this fixing jig 36, the separation distance 42 of the elastic member 34 is defined and held as the distance from the lower surface of the first support plate 33 b to the upper surface of the second support plate 35. Furthermore, when the ground anchor 31 is fixed to the ground and the tension force is applied to the tendon 32, the separation distance 41 of the tendon 32 is defined as the distance from the lower surface of the fixing nut 33c to the upper surface of the grout 24 in the deep ground portion 23. And retained.
[0031]
The fixing jig 36 restricts the separation distance 42 from becoming longer and allows it to be shorter. Accordingly, the separation distance 42 is further reduced by a force greater than the elastic force of the elastic member 34, and the first nut 33b and the first washer 36d are again fastened and fixed to the first support plate 33b via the bar screw 36a. Is possible.
[0032]
=== Ground Anchor Fixing Method ===
The characteristic of the elastic member 34 which consists of the disk spring 34a in one Embodiment of this invention is demonstrated referring FIG. The graph of FIG. 3 represents the relationship between the amount of bending and the elastic force of the elastic member 34 of the present invention.
[0033]
Since the elastic member 34 in the present embodiment is constituted by a disc spring 34a, the elastic member 34 is a curve having a plateau as shown in the graph of FIG. 3, and this portion is called an elastic force fluctuation dead zone region.
[0034]
In the present embodiment, the tension force of the tendon 32 must be as constant as possible with respect to a change in the amount of bending of the elastic member 34 due to frost heaving and thawing of the ground surface layer 22. Therefore, in order for the ground anchor 31 of the present invention to function in the ground, it is necessary for the elastic member 34 to expand and contract within the elastic force fluctuation dead zone where the change in the elastic force is small with respect to the change in the deflection amount. is there.
[0035]
In this embodiment, the elastic force of the target elastic member 34 is q in the Z state of the graph of FIG. 3, and the amount of bending at this time is b. In addition, the state of the elastic force p corresponding to 80% of the elastic force q is Y, the amount of bending at this time is a, and the state where both the elastic force and the amount of bending are zero is X. Here, both a and b are the amount of deflection in the elastic force fluctuation dead zone region.
[0036]
The operation | work which bends the elastic member 34 from said X state to a Y state is shown in FIG. According to FIG. 4, it is a figure which shows the operation | movement which is making the elastic member 34 of the head part of the ground anchor 31 of this invention into the bending length (Y state) from natural length (X state). Such work does not need to be performed at the construction site where the ground anchor 31 is fixed, but can be performed at a predetermined work place equipped with a predetermined tool.
[0037]
Using a predetermined jack, the first support plate 33b is pressed against the second support plate 35, the elastic member 34 is bent from the X state to the Y state, and the loosened first nut 36b and first washer 36d are In this state, the first support plate 33b is tightened again. As is apparent from FIG. 4, the amount of bending of the elastic member 34 in this case is a.
[0038]
FIG. 5 shows that a tendon 32 housed in a sheath 37 is inserted into a drilling hole at a construction site and fixed with a grout 24 at a deep ground 23, and the head portion of a ground anchor 31 is disposed on the pressure receiving plate 1. The state which connected the end of the sheath 37 to the pipe part 33d is shown. The elastic member 34 here is in the Y state of FIG.
[0039]
The operation | work which bends the elastic member 34 from said Y state to Z state is shown in FIG. The fixing tool 33a through which the tendon 32 having one end as a tendon screw portion 32a passes is brought into contact with the first pressure plate 33b. The tendon 32 is pulled using a predetermined jack, and the elastic force q in the Z state of the elastic member 34 in FIG.
[0040]
On the other hand, by using the jack 50, the first support plate 33b is further pressed against the second support plate 35, the elastic member 34 is bent from the Y state to the Z state, and the loosened first nut 36b and first washer 36d are moved. In the Z state, the first support plate 33b is tightened again.
[0041]
Here, since the tension force of the tendon 32 and the elastic force of the elastic member 34 are both q, the fixing nut 33d is tightened with the tendon screw portion 32a and tightened against the upper surface of the fixing tool 33a. Thereby, the elastic force of the elastic member 34 and the tension force of the tendon 32 are balanced, and the tendon 32 is fixed with the target tension force q.
[0042]
As is apparent from FIGS. 3 and 6, the amount of deflection of the elastic member 34 from the Y state to the Z state is ba. Therefore, in order to give the tension q to the tendon 32 at the construction site, it is sufficient to use the jack 50 that pushes down the distance b-a by the force q.
[0043]
According to the present invention, if the elastic force p of the elastic member 34 set in the work place is made closer to the target q, the amount of deflection approaches a to b according to the graph of FIG. The stroke of the jack used at the construction site can be further shortened.
[0044]
【The invention's effect】
As described above, according to the first aspect of the present invention, before the ground anchor is fixed to the ground, it is possible to compress and fix the elastic member to a predetermined separation distance in another place in advance.
[Brief description of the drawings]
FIG. 1 is a diagram showing a side cross-section of a ground anchor that functions in the ground according to the present embodiment.
FIG. 2 is a diagram showing a case where the ground anchor fixing jig is viewed from above and a side surface.
FIG. 3 is a diagram showing the relationship between the amount of flexure of an elastic member of the ground anchor and the elastic force.
FIG. 4 is a view showing a step of bending an elastic member of the ground anchor from an X state to a Y state.
FIG. 5 is a view showing a state where an elastic member of the ground anchor is held in a Y state and a tendon is fixed.
FIG. 6 is a view showing a step of bending the elastic member of the ground anchor from the Y state to the Z state.
[Explanation of symbols]
22 Ground surface layer 23 Ground deep layer 24 Grout 31 Ground anchor 32 Tendon 33 Fixing part 33a Fixing tool 33b First support plate 33c Fixing nut 34 Elastic member 35 Second support plate 36 Fixing jigs 41 and 42 Separation distance 50 Jack

Claims (5)

The tendon embedded in the ground is tensioned by a fixing tool fixed to the outer end exposed on the ground surface, and is interposed between a first bearing plate that contacts the fixing tool and a second bearing plate on the ground surface. In the ground anchor that prevents the landslide by transmitting the elastic force of the elastic member to the ground via the tendon,
A plurality of fixing jigs for fixing one end to the first supporting plate and fixing the other end to the second supporting plate, the fixing jig restricts the elastic member from extending from a predetermined distance; And a ground anchor that allows bending. The ground anchor according to claim 1, wherein the fixing position of the fixing jig is a position corresponding to a separation distance in which the elastic member has a resilience of 50% to 90% of a predetermined resilience. . The tendon embedded in the ground is tensioned by a fixing tool fixed to the outer end exposed on the ground surface, and is interposed between a first bearing plate that contacts the fixing tool and a second bearing plate on the ground surface. In the anchoring method of the ground anchor for preventing the landslide by transmitting the elastic force of the elastic member to the ground via the tendon,
The elastic member is restricted from being extended from a predetermined separation distance and bent by a plurality of fixing jigs provided with one end fixed to the first support plate and the other end fixed to the second support plate. A ground anchor fixing method characterized by allowing the above. The fixing position of the fixing jig is set so that the elastic member is a position corresponding to a separation distance in which the elastic member has an elastic force of 50% to 90% of a predetermined elastic force. The fixing method of the ground anchor as described. 5. The ground anchor fixing method according to claim 3, wherein the first support plate is pushed down toward the ground surface by a jack while receiving a drag force of the elastic member.

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