JPH066807B2 - Grand anchor construction method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a civil engineering for connecting a structure to a ground and a basic structure of a building, and particularly to a ground anchor construction method for increasing pull-out resistance to the ground. Regarding

[Conventional technology]

A ground anchor is a columnar structure with pull-out resistance that is installed on the ground.It is composed of an anchor body, a tension part, and an anchor head. Depending on the force transmission method of the anchor body, the grout type anchor construction method and mechanical Can be roughly divided into anchor construction methods. The former is transmitted by bearing pressure of the anchor body against the ground, and the latter is transmitted by friction between the peripheral surface of the anchor body and the ground. FIG. 5 is a diagram showing a conventional grout anchor construction method, and FIG. 6 is a diagram showing a conventional mechanical anchor construction method. In the figure, 1 is a boring machine, 2 and 7 are tensile members, 3 is a grout injection device, and 4 and 6
Is an anchor body, 5 is a pedestal, 8 is a hydraulic piston, and 9 is a fixing device.

The grout type anchor construction method is as shown in Fig. 5 (a)
Drilling the ground with the drilling machine 1 (b) Pulling material 2 into the hole
After the insertion of (c), the grout injecting device 3 injects grout such as mortar and cement paste, and at the same time, the compressor is pressed to expand the drilled portion to form the anchor body 4, and finally (ni ) It is a system in which prestress is applied to the tension member 2 and the pedestal 5 is tensioned and fixed. In this method, the anchor body supports (resists) the force transmitted from the tension portion (tensile member) by the frictional force between the peripheral surface of the anchor body and the ground.

In addition, the mechanical anchor construction method, as shown in FIG.
(B) Anchor body 6 is created on the ground and tensile member 7
, The end of the hydraulic piston 8 is engaged with the anchor body 6, and the anchor body 6 is pushed to a predetermined depth by the piston 8, and then the engagement between the hydraulic piston 8 and the anchor body is released, Pull out only the piston 8, (b)
Fix the ground side end of the tension member 7 to the fixing device 9, and (c)
This is a method in which the tension jack 7 is pulled by extending the hydraulic jack of the fixing device 9 and the anchor body 6 is rotated 90 degrees to set it in a predetermined state. The anchor body 6 is generally made of a steel material and is pushed in a state of being erected horizontally, so that the apparent cross section from the side is made small, and the connection with the tension member 7 is rotatably formed. . Similar to this method, as shown in (d), the bearing surface of the anchor body opens like an umbrella by pulling out the tension material, and as shown in (e), the blade is opened and the anchor body Some are screwed. In these mechanical anchors, the anchor body supports (resists) the force transmitted from the pulling portion (pulling material) by the bearing pressure between the anchor body and the soil on the upper surface of the anchor body. However, when the anchor body is a screw, the anchor body supports (resists) the force transmitted from the tension portion (tensile member) by the frictional force between the peripheral surface of the anchor body and the ground.

[Problems to be solved by the invention]

In general, the ultimate pull-out force of an anchor (the force necessary for breaking when breaking occurs) is determined by the ground strength and the strength of the anchor material (tensile member and anchor body). However,
All of the above-mentioned conventional ground anchor construction methods have a problem that the ultimate pull-out force is small on the ground with small original ground strength, and it cannot be used, for example, to prevent the rocking of the floating foundation and is practically difficult to adopt. Have

In particular, the grout type anchor construction method has a problem that it causes stress relief of the original ground and weakens the original ground strength because it involves drilling. If the tension material is located in the center of the anchor body, the tension material and the anchor body will be strongly connected, but if the drill hole is deformed or collapsed due to the influence of groundwater or stress in the ground, the tension material Since the material is located unevenly in the peripheral part of the anchor body, the connection between the tension material and the anchor body is weakened, and in this state, that is, the shape of the anchor support part cannot be confirmed, there is a problem that it lacks reliability. There is. Furthermore, the construction speed is 1 per
It also has a drawback that it takes time.

In addition, the mechanical anchor construction method has a problem that since the hydraulic piston is pushed into the ground, the ground is disturbed and only the original ground strength (strength before anchor installation) can be expected even in the best installation. As for the strength of the anchor material, the strength of the joint is determined by the strength of the joint, because the strength of the strength of the joint between the tension member and the anchor body tends to be smaller than the strength of the tension member and the anchor body. It has the problem that only a small supporting capacity can be expected. Furthermore, since the processing of the anchor body and the structure of the joint part between the anchor body and the tension member become complicated, and the anchor body is required to have a shape that is easy to push in and difficult to pull out, the shape and strength of the tension member and the anchor body are required. Will be very limited and special. Therefore, at present, the frequency of use of mechanical anchors is extremely low.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide an anchor that can have sufficient strength even in alluvial sandy ground that was not suitable as an anchoring layer for the anchor.

[Means for solving problems]

Therefore, in the present invention, attention is paid to the outer pipe penetration device used in the sand compaction method, which is one of the ground improvement methods. As shown in FIG. 4, a trolley has a crawler crane 10 and a guide mast 11, and a lifting jig 12 is provided from the upper end of the guide mast 11.
The vibrator 13 and the outer pipe 14 are suspended via the, and a tip shoe 15 that can be opened and closed is attached to the tip of the outer pipe 14. The construction method of soil improvement using this outer pipe penetration device is to insert sand into the outer pipe 14 while inserting the outer pipe 14 into the ground while vibrating the outer pipe 14 by the vibration exciter 13. After raising and lowering while vibrating, the tip shoe 15 is opened and closed to discharge the sand into the ground, and again while vibrating, the outer pipe 14 is moved up and down to press the sand into the ground and finally the outer pipe. 14 is pulled out to make a compacted sand column.

The ground anchor construction method according to the present invention eliminates the conventional problems by adopting the above-mentioned outer pipe penetrating device. In the state where the tip of the outer pipe is closed, the outer pipe is vibrated in the ground. After inserting it, put the tension material and the filling material into the outer tube, re-penetrate it to the specified position while vibrating the outer tube again, and then open the tip of the outer tube and pull out while vibrating the outer tube. The present invention is characterized in that after the ground and the filler in the peripheral portion of the pipe are compacted, a prestress is applied to the tensile member to fix it.

[Action]

By inserting the outer pipe into the ground while vibrating the outer pipe with the tip closed, the ground density around the outer pipe is increased and the strength is increased. In addition, after the filler is put into the outer pipe, the ground and the filler around the outer pipe are compacted by performing an extracting work while vibrating the outer pipe.

〔Example〕

Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the ground anchor construction method of the present invention, and FIG.
The figure shows each embodiment of the anchor material, and FIG. 3 shows the ground improvement effect after the anchor is installed. In the figure, 14 is an outer tube, 15 is a tip shoe, 16 is a tension material, and 17 is a filler.

The construction method will be described with reference to FIG. 1. First, (a) by the outer pipe penetrating device shown in FIG.
In the closed state, the outer pipe 14 is inserted into the sandy ground while vibrating. At this time, the density of the raw ground (sandy ground) around the outer pipe 14 increases and the strength increases. Next, (b) after inserting the outer tube to a certain position, the tension member 16
Then, the filling material 17 is put into the outer pipe 14, and the filling material is compacted while vibrating the outer pipe 14 and penetrated to a predetermined position. At this time, the filling material 17 in the outer tube has little variation in quality due to the mixing effect. As the filler 17, an origin generation site (sand) or a poorly mixed mortar (mixture of origin generation soil and cement) is used, but other materials may be used as long as a predetermined strength can be obtained. Various materials such as steel rods, stranded steel wires, and new materials such as FRP can be considered as the tensile material. (C) After the outer pipe 14 is penetrated to a predetermined position, the tip shoe 15 is opened and the outer pipe 14 is pulled out while vibrating to compact the ground and the filling material 17 around the outer pipe 14, Finally, prestressing is applied to the tension material to fix it and the anchor construction is completed.

The improvement effect of the ground by installing the anchor will be described. FIG. 3 shows the relationship between the depth and the N value (the number of hits in the standard penetration test) before and after the anchor is installed for each of several measurement points around the anchor.
According to this, the N value can be compacted to an average of 20 or more by installing the anchor according to the present invention in which the N value in the original ground is about 5 on both the peripheral portion and the inside of the outer pipe. As a result, the pullout resistance of the anchor can be increased to 1.8 kg / cm ² or more on the sand ground, and sufficient strength can be provided.

The present invention is not limited to the above embodiment,
Of course, various modifications are possible. . For example, in the above embodiment, the tension member is inserted as it is as the anchor material, but as shown in FIG. 2, the anchor body 18 made of mortar may be fixed to the tip of the tension member 16 (a). (B) A large number of ribs 19 may be attached to the tension member 16 or (c) grass-root type ribs 20 may be attached. In these cases, the pullout resistance can be further increased.

In the above embodiment, the outer tube is inserted into the ground while vibrating the outer tube in a state where the tip of the outer tube is closed.
After inserting sand into the outer tube during the insertion, open the tip shoe, then move the outer tube upward, close the tip shoe, and insert it into the ground while oscillating the outer tube again. You may employ the method of compacting the sand discharged | emitted.

〔The invention's effect〕

As is apparent from the above description, the present invention has the following effects.

By installing anchors, the N value of the ground around the outer pipe and the filling material inside the outer pipe can be increased to 20 or more even on the ground where the N value of the original ground is about 5, and it has been used as a anchor anchoring layer up to now. Sufficient strength can be given to alluvial sandy soil that was not suitable.

Particularly when a mixed material such as mortar is used as the filler, it is possible to perform sufficient mixing by vibration and reduce variations in the quality of the anchor body.

Since the anchor material is assembled on the ground, the designer's intention can be sufficiently reflected in the shape and quality of the anchor fixing portion.

Since the filler can use the soil generated in the original area, the cost required for the filler can be reduced.

The outer pipe penetrating device that has been conventionally used in the sand compaction method can be used as it is as a vibrating device and a sand feeding device.

The construction time is about the same as the sand compaction construction method (about 15 minutes per cycle) and about 1/4 of the conventional grout type anchor construction method, so it is extremely effective in reducing construction costs and shortening the construction period. .

Vibration and noise during construction are also about the sand compaction method.

[Brief description of drawings]

FIG. 1 is a diagram showing one embodiment of the ground anchor construction method of the present invention, FIG. 2 is a diagram showing each embodiment of anchor material, and FIG.
Figure shows the ground improvement effect after anchor installation, Figure 4 shows the outer pipe penetration device, Figure 5 shows the conventional grout anchor method, and Figure 6 shows the conventional mechanical anchor method. Is. 14 ... Outer tube, 15 ... Tip shoe, 16 ... Tensile material, 17
... filling material, 18 ... anchor body, 19, 20 ... rib.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-53-73810 (JP, A) JP-A-53-73809 (JP, A) JP-A-51-148916 (JP, A)

Claims (1)

[Claims] 1. An outer tube is inserted into the ground while vibrating the outer tube in a state where the tip of the outer tube is closed. Then, a tension material and a filling material are put into the outer tube, and the outer tube is vibrated to a predetermined position. After the penetration, the tip of the outer tube is opened and the outer tube is pulled out while vibrating to compact the ground and the filling material around the outer tube, and then prestressing the tension material to fix it. The characteristic ground anchor construction method.