JPS59173422A - Bedrock anchor - Google Patents

Abstract

PURPOSE:To hold sufficient bearing forces of anchors for long periods of time as well as enable the anchors to be deformed without causing breakage by attaching a flexible sheath packed with a plastic filler as a rust inhibitor to the intermediate section of the tensile steels of anchors. CONSTITUTION:An anchor cable 1 is covered with a flexible plastic sheath 3, e.g., polyethylene pipe, etc., in the upper and lower parts of the landslide face (s). A filler as a rust inhibitor 4 is injected into the sheath 3 to obtain a deformable and long-term rust-proof structure. The rust inhibitor 4 used includes plastic materials such as oily or paste rust inhibitors. Since no prestress is introduced into the anchor cable, administration after and during the construction work can be made easier, and anchors having long-term sufficient bearing forces can be formed without needs for special facilities and technology at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ground anchor used as a ground control work or earth retaining work.

[Background of the invention and prior art]

There are many types of earth retention works, but recently the trend of adopting the anchor method has been increasing year by year.

The reasons for this include that it is relatively easy to explain theoretically because steel is used as a tensile material, and that the hole diameter can be made smaller by using high-strength steel. This method is currently the most effective construction method in terms of the economic efficiency of earth retaining and earth bedding deterrent effects.

However, it is not entirely without problems. This means that construction management is somewhat more complicated than other construction methods. That is, when we talk about a normal anchor, we are currently referring to a breastrest ground anchor), and the inserted anchor couple has a free length section at the top and is fixed after being taut to give a grazing stress.

Therefore, it is necessary to manage tension, 610/Also,
As shown in the figure, in order for the anchor couple 1 to be anchored, a concrete plate or concrete beam 6 must be provided on the ground surface 7. Regarding these two points, there are no design problems or construction problems. In addition, the proportion of construction costs related to this item is relatively large. Therefore, how to deal with this problem has been the subject of many years of research.

This is the solution! The method we implemented as a solution was to simply insert the anchor cable into a drilled hole, inject grout, and install it in the garden without special processing as an anchor couple or placing a concrete plate on the ground surface. It is. In other words, as shown in FIG. 2, the constant length of the anchor called the sliding body part A ic a is set on the fixed ground B with the bell surface 8 on the ground as the border.
This is intended to eliminate the need for concrete plates and beams 2 to be installed on the ground surface by having the anchors share a fixed length with each other.

Jin's method is classified as a dead anchor, and it is not possible to introduce prestress force because it does not have a free length. Therefore, when a load is applied, the couple stretches to some extent, and this generates a tensile force on the couple, which acts as a reaction force and prevents the rock from sliding. This method has the disadvantage that the ground deforms as the couple stretches when a load is applied, but in cases where some deformation of the ground is allowed or where economic efficiency is important. has sufficient advantages to be adopted.

However, some deformation occurs, and although this may be acceptable in terms of deformation of the ground, the problem is near the landslide surface.

In other words, in reality, not only tensile force but also shear force acts on the anchor couple l, as shown in Figures 3 and 4.
As shown in the figure, local deformation occurs near the ground bell surface 8.

Therefore, the cement gract 2 injected to secure the anchor will be completely destroyed. If this anchor is used for a short period of time, there will be no major problem with its pull-out strength, but if this anchor is used for a long period of time,
The part where cement grout 2 is destroyed is originally a water-filled area, so the anchor coupe will soon rust after it is inserted, and it will not be able to demonstrate its strength in the long term. .

This locally destroyed part is within 1 m vertically in the case of hard rock, and t in the case of medium-hard rock, with the land surface 8 as the boundary.
sm~2. In the case of earth and sand, the range is generally about 2 m to 6 m. On the other hand, some tensile cracks naturally occur in the upper and lower parts, but they are tolerable, and there is no shear failure of the injected cement wood 2 in these parts.

Therefore, with regard to this section, it is necessary to devise a method that allows full deformation and does not cause destruction.

[Structure of the invention and examples]

This invention was developed against the background described above.
We considered a rock anchor with a structure shown in Figure 5, which is expected to have sufficient strength over the long term and can sufficiently follow shear and tensile deformation.

That is, as shown in Fig. 5 and Fig. 6, a total of 21 L to 6 wL above and below the ground bell surface 8, and 1 oa as necessary.
The anchor couple l is wrapped in a flexible or plastic 7-su 3 such as a polyethylene vibrator within a range of about t, and a rust preventive material 4 is injected into it as a filler to make it deformable and to prevent rust over a long period of time. It has a structure that can prevent this. Note that the rust preventive material 4 (corrosion preventive oil TFC) is a plastic material such as a paste-like rust preventive material. Further, for parts other than the tension part C in this intermediate section, steel or polyethylene 7-s 5 or the like may be used.

Since the steel material can stretch freely at the intermediate tension section C, the elongation lid will be somewhat larger than in the conventional method, but originally this type of material does not allow elongation when a load is applied. Since it is a method that does not require much consideration, there are basically no structural problems and it can be used satisfactorily. In addition, the results of model experiments indicate that the amount of elongation that can be considered with the anchor method, that is, the calculation of free length elongation, always shows a value of approximately 50- or less, and that the amount of elongation is not a problem. Ta.

〔Effect of the invention〕

In addition to the structure described above, the rock anchor of the present invention does not introduce prestress force to the anchor cable, so construction management and post-construction management are easy. In addition, since the area near the ground surface or the collapse surface of the ground is deformable and has a structure that does not break, it is possible to maintain sufficient strength over a long period of time. Furthermore, since no special equipment or technology is required, construction costs are also reduced.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views showing a conventional example, FIG. 5 is a cross-sectional view showing an embodiment of the present invention, and FIG. 6 is a cross-sectional view of a main part thereof. A: Sliding body part B: Fixed ground 8: Ground bell surface C: Tension part d: Destruction part 1 ...Anchor Couple 2...Graft 3...7-S 4...
... Rust preventive material 5 ... Irregular shape 7-S 6 ... Concrete plate or concrete beam 7
・・・・・・Fixing device Fig. 1 Fig. 2 Fig. 3 Fig. 4 Flash

Claims (3)

[Claims] (1) A flexible or plastic pipe-shaped 7-seat filled with a layered filler as a rust preventive material is installed in the intermediate section of the anchor tensile steel material located on the 9 sides of the landslide or on the ground failure surface. A rock anchor characterized in that the intermediate section is a deformable tensile part. (2) The tensile section shall be installed on the top and bottom of the multifaceted landslide or the ground collapse surface, each with a length of 1'IL or more and 5m or less.
A rock anchor according to claim 1. (3) The earth anchor according to claim 1 or 2, wherein the sheath is made of a polyethylene pipe.