JPH0343408B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention provides a ground anchor for preventing a high-rise building or a tower-like building _A1 as shown in FIG. 10 from falling during an earthquake or a storm.
B ₁ , or as ground anchor B ₂ to prevent floating by groundwater when building A ₂ with a deep underground part is constructed in a place where the groundwater level W is relatively high as shown in Figure 11. As shown in Figure 12, this article relates to a method of constructing a ground anchor that can be effectively used as a ground anchor _B3 to prevent uneven earth pressure or sliding in a building _A3 built on a slope, etc. This paper relates to a construction method for a permanent ground anchor that has been improved so that it can be expected to have a service life of more than 100 years for permanent installation.

Conventional technology Conventionally, as shown in Figure 10, for high-rise buildings _A1 that require measures to prevent them from falling during earthquakes or strong winds,
Even if it was not necessary, this problem was dealt with by adding a deeper underground structure (a) underground.

Furthermore, as shown in Figure 11, building _A2 , which requires measures to prevent surfacing due to groundwater, has been dealt with by increasing the weight of the building frame.

Furthermore, as shown in Figure 12, building _A3 , which requires countermeasures against uneven earth pressure and sliding, was dealt with by scraping away the ground on the mountain side and constructing a retaining wall c.

This is because, until now, there has been no permanent ground anchor or construction method that is sufficiently reliable in terms of quality and service life.

BACKGROUND ART Conventionally, a wide variety of so-called temporary ground anchors and their construction methods, which support retaining walls such as sheet piles and are removed after use, are known and are currently in use.

For example, FIG. 13 shows the main parts of a temporary ground anchor described in Japanese Patent Publication No. 57-13686.

In the figure, e is a tensile steel material, and a bearing plate f is attached to its tip, and a load-bearing body g made of reinforced mortar or the like is brought into contact with the pull-out side of the bearing plate f. It is fixed in the ground by injection material h.

The construction method for this temporary ground anchor is as follows: First, a load-bearing member g is wrapped around and fixed to the tip of a tensile steel member e.
, attach a pressure plate f to the part beyond that, insert these assemblies into the fixing hole, simultaneously inflate the inserted packer k to seal the fixing hole, and pour the injection material h into it. is injected under pressure.

Problems to be Solved by the Present Invention () Although the purpose is to prevent falls during earthquakes and storms, it is necessary to purposely attach an unnecessary underground structure a as shown in Figure 10, or to prevent floating. However, as shown in Figure 11, it is necessary to increase the weight of the building frame A ₂ , or to remove the retaining wall by scraping the ground as shown in Figure 12, even though it is a countermeasure against uneven earth pressure and sliding.
Countermeasures such as building a new one are too short-sighted and useless, and are also wasteful and uneconomical solutions.

() Despite the fact that temporary ground anchors and their construction methods have been known and there are many examples, the reason why it has not been possible to create a permanent ground anchor that can be used as a countermeasure for the above () is the following: This is because no reliable anchor structure or construction method for rust prevention was found.

For example, even in the case of the temporary ground anchor shown in Fig. 13, the attachment means j between the tensile steel e and the bearing plate f are left exposed, and once this is corroded and damaged, its useful life as a ground anchor is over. .

Additionally, anti-rust coated PC steel stranded wire is usually used for tensile steel e, but if the sheath is damaged or damaged due to an accident during construction or due to deterioration over time during use, the PC steel Since the stranded wire begins to corrode, it is impossible to expect a long service life of 10 or 20 years in any case, and it is impossible to expect quality and reliability as a permanent ground anchor for permanent installation. I didn't get it.

Means for Solving the Problems As a means for solving the problems of the prior art described above, a construction method for a permanent ground anchor according to the present invention is as shown in preferred embodiments in FIGS. 1 to 9 of the drawings. (a) First, a fixing hole 14 of a predetermined depth is drilled in the ground using a casing pipe 16 and a drilling machine, and the water from the hole is replaced with cement milk 5.

(b) On the other hand, on the ground, a bearing plate 2 is attached to the tip of the tensile steel material 1 made of unbonded PC steel strands, and the mounting portion is protected by a tip cap 9 containing antirust oil 10. Furthermore, a tubular load-bearing body 3 is welded watertightly all the way around the outer periphery of the tensile steel material 1 on the pull-out side of the bearing plate 2, and the tensile steel material 1 is also connected to the pull-out side of the load-bearing plate 2 in a water-tight manner. The tubular free length sheath 4 is properly assembled by welding the entire circumference in a watertight manner so as to surround the outer periphery of the sheath 4.

(c) The assembly S assembled as described above is suspended by a crane or the like, and inserted into the center of the fixing hole 14 and installed.

(d) After that, connect the cement milk injection hose 17 to the upper end of the casing pipe 16, and while pulling out the casing pipe 16, pressurize and fill the outer periphery of the load-bearing body 3 with the injection material 5 over at least the length range of the load-bearing body 3. do.

(E) Thereafter, a frame 6 of a building, etc. is constructed, and a prestress of a predetermined amount is introduced into the tensile steel 1 by the controlled setting method of the strong hold construction method, and the upper end of the tensile steel 1 is placed on the frame 6. It is fixed by the head bearing pressure plate 12 and the wedge 19.

Function The installation of the tensile steel material 1 and the bearing pressure plate 2, the rust-proof protection of the attachment part with the tip cap 9, and the assembly of joining the load-bearing body 3 and the free length sheath 4 to the bearing pressure plate 2 are all performed respectively. Since the work is carried out completely on the ground, quality control can be completely controlled and assembly and construction can be carried out with extremely high reliability.

Moreover, with such a complete assembly, the fixing hole 14 can be completely protected from the outer periphery of the tensile steel material 1.
Since it is inserted and installed inside, at least tensile steel material 1
There is never any chance of contact or contact with ground water or cement milk5.

Therefore, the double and heavy rust prevention treatment for the tensile steel material 1 is completely effective. Therefore, sufficient quality and reliability can be ensured as a permanent ground anchor.

Further, since the injection material 5 is pressurized and filled by drawing out the casing pipe 16, there is no need for any equipment such as a packing car, and the construction is easy.

Embodiment Next, a preferred embodiment of the present invention shown in FIGS. 1 to 9 of the drawings will be described.

First, FIGS. 1 to 4 show important process diagrams of the construction method according to the present invention.

That is, FIG. 1 shows the process of drilling a fixing hole 14 for anchor construction in the target ground 15 and inserting the anchor element assembly S assembled on the ground by suspending it with a crane or the like.

The hole is drilled using a rotary percution installed on the ground and a casing pipe (drill pipe) 16 with a tip bit, so that the covering thickness of the injection material 5 is increased.
Dig a fixing hole 14 with a diameter of about φ130 so that it is 20 mm or more. The drilling depth is said to be the anchor design length plus approximately 30 cm of extra drilling length.

Immediately after the fixing hole 14 is excavated, an injection hose that reaches the bottom of the hole is inserted, cement milk 5 as an injection material is injected, and the cutting water is replaced with the cement milk 5.

Prior to assembling each anchor element on the ground, the cast steel load bearing body 3, tip bearing plate 2, and free length sheath 4 are processed in advance at a factory, and the load bearing body 3 and tip bearing plate 2 are welded all around to make them watertight. Welded joints as well as unbonded PC steel strands 1
Processing is performed to attach a crimp grip 13 to the tip of each.

Then, at the site, first insert the PC steel strands 1 one by one into the load-bearing body 3 from the tip bearing plate 2 side as shown in FIG.

Next, the tip cap 9 filled with Procoat oil 10 as a rust preventive oil is attached to the pull-out side of the pressure plate 2 in a watertight manner so as to cover the outer periphery of the crimp grip 13 (FIG. 6).

Next, the free length sheath 4 is attached to the PC steel stranded wire 1.
Through this, the free length sheath 4 and the load-bearing body 3 are welded together in a watertight manner by welding the entire circumference (FIG. 7).

The total length of the free length sheath 4 is about 10 meters, but the assembly method requires a unit length of 3 meters.
Sequentially add approximately 300 gas pipes to form the desired length.

In addition, in order to prevent the PCC steel stranded wire 1 from bending when lifted by a crane when inserted into the fixing hole 14, the outer periphery of the load-bearing body 3 and the free length sheath 4 are protected with, for example, a channel. It is preferable to tie and reinforce with wire.

After inserting the anchor element assembly S assembled as described above into the fixing hole 14, immediately connect the cement milk injection hose 17 to the upper end of the casing pipe 16, and pour the cement milk 5 while pulling up the casing pipe 16. Perform pressure filling (Figure 2).

Furthermore, in order to prevent the protrusion of the PC steel stranded wire 1 from soaking in the cement milk, a dedicated protective tube 18 with approximately the same diameter as the free length sheath 4 and an upper end cap is attached to the upper end of the free length sheath 4. Join to protect the inside.

To fill the cement milk 5 under pressure, first, the casing pipe 16 is pulled up by approximately 1/2 of the total length of the load-bearing body 3 to perform the first stage of pressurized filling, and then the casing pipe 16 is pulled up the remaining 1/2 of the length to perform the first stage of pressure filling. Perform two-stage pressurized filling. In this way, the cement milk 5 covering at least the entire length of the outer circumference of the load-bearing body 3 is densely filled, and is configured to penetrate strongly into the ground 15 and reliably absorb the reaction force.

Thereafter, the casing pipe 16 is completely withdrawn. Adjust the insertion length for PC steel stranded wire 1,
It is fixed on a stand set on the ground, and the injection material 5 is cured.

After this curing, a frame 6 of a building or the like is constructed on the ground, jacks 20 are installed to introduce prestress, and the upper ends of the PC steel strands 1 are fixed to the frame 6.

For this purpose, a jack 20 shown in FIG. 8 is used, and the control setting method of the so-called strong hold construction method is used. That is, the head bearing plate 12, the anchor head 18, and the temporary bearing plate 2 are mounted on the frame 6.
1 and set the jack 20 on it. Then, use the wedge 19 in the jack 20 to PC
Grasp the upper end of wire 1 with steel strands and tension each steel strand 1 at the same time, for example, in the 100 ton class (or
We will introduce a pre-tress sized to accommodate the design load of 200 ton class (possibly 200 ton class).

Subsequently, the fixing wedge 19 is pushed forward with the index plate 23, and the PC steel stranded wire 1 is forcibly fixed while being held in the tensioned state.

Therefore, the problem of loosening of the PC steel stranded wire 1 does not occur at all, and the pretress of the set size can be reliably and tightly introduced.

After that, the PC steel stranded wire 1 fixed on the frame 6
The upper end of the protrusion is treated with a head cap 25 to prevent rust (Fig. 4).

As for the details of its structure, as shown in FIG. 9 in its completed state, a head cap 25 filled with grease 24, which is an anti-rust oil, is mounted on the head bearing pressure plate 12 in an oil-tight manner.

Note that, as shown in FIG. 9, the free length sheath 4 has a length that reaches the anchor opening of the building frame 6. The upper end of the sheath 4 is connected to the head sheath 7 installed in the anchor opening by a damper 8.
They are fitted together so that they can slide freely through them. The damper 8 and the head sheath 7 are attached to predetermined positions before concrete placement of the frame 6.

Therefore, due to the free sliding of the free length sheath 4 and the head sheath 7, the subsidence of the ground accompanying the construction of the upper structure of the frame 6 can be completely absorbed, without causing any trouble to the anchor structure. Further, due to the sealing properties of the damper 8, the rust prevention treatment of the PC steel wire 1 can be completely achieved.

In addition, if re-tensioning of wire 1 from PC steel is required, a method of determining the re-tensioning load each time, or a method of long-term observation by attaching a load cell, strain gauge, etc. is adopted.

Effects of the present invention As described above in detail in conjunction with the embodiments, according to the construction method for the permanent ground anchor according to the present invention, the main structure of the underground part of the anchor is completely assembled on the ground in advance. , the quality can be completely controlled, and construction can be performed with sufficiently high reliability for permanent installation.

Moreover, the tensile steel material 1 and the tip bearing plate 2 are completely protected by the tip cap 9, the anti-rust oil 10 filled therein, the load-bearing body 3, and the free length sheath 4, and the fixing hole 1
Since the work is carried out in such a way that it never comes into contact with the cement milk 5 in 4 or underground water, the double and triple anti-corrosion treatments for the tensile steel 1 can be fully utilized. Therefore, reliability as a permanent ground anchor can be ensured and its useful life can be maintained.

[Brief explanation of drawings]

Figures 1 to 4 are important process diagrams of the anchor construction method according to the present invention, Figures 5 to 7 are explanatory diagrams showing the procedure for assembling the anchor, and Figure 8 is a detailed diagram of tension fixing by jacking. , Fig. 9 is an overall diagram conceptually showing a permanent ground anchor constructed by the method of this invention, Figs. 10 to 12 are explanatory diagrams of the use of the ground anchor of this invention, and Fig. 13 is a conventional temporary It is a detailed diagram of the main parts of the ground anchor.

Claims (1)

[Claims] 1. (a) Drilling a fixing hole 14 to a predetermined depth in the ground using a casing pipe 16 and a drilling machine, and replacing the drilling water with cement milk 5; (b) On the ground, a bearing plate 2 is attached to the tip of the tensile steel material 1, and the mounting part is protected by a tip cap 9 containing antirust oil 10, and the bearing plate 2 is
A tubular load-bearing body 3 is joined to the drawing side of the load-bearing body 3 so as to surround the outer periphery of the tensile steel material 1, and a tubular free length sheath is further arranged to surround the outer periphery of the tensile steel material 1 on the drawing-out side of the load-bearing body 3. (c) suspending the assembly S using a crane or the like, and inserting and installing it into the center of the fixing hole 14; (d) connecting the cement milk injection hose to the casing pipe 16; 17 and the same casing pipe 16
(e) constructing a frame 6, and then filling the outer periphery of the load-bearing body 3 with cement milk 5 over at least the length range of the load-bearing body 3;
A method of constructing a permanent ground anchor, comprising the steps of: introducing a prestress of a predetermined magnitude into the tensile steel member 1 and fixing the upper end of the tensile steel member 1 on the frame 6;