JPH02266021A - Earth anchor and its executing method - Google Patents

Abstract

PURPOSE:To reduce building materials, by pressing an anchor body into the ground with rotation, fixing it by an extension juck after placing mortal in the external periphery and back-filling the cave of the pulled out anchor body. CONSTITUTION:Spiral ribs 7 are arranged on the external periphery of a steel pipe and an anchor body 1 provided with a cutter blade 8 at the front edge is pressed in the ground 21 with revolution and mortar 17 is poured to cure through a grout sheath 11 in the external periphery. Next, jacking tools 31, 32 are fitted at the head of the anchor body 1 to fix tensely the anchor body 1. After its execution, sand or the like is compressively stuffed in the hollow hole, while pulling out the anchor body 1 from the ground 21. In this way, even an anchor with optional sizes can be executed by a weak compressive force and also removing earth volume and mortar volume can be reduced without damage of the earth and also anchors can be removed without leaving foreign materials and cavities.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to slopes, slopes, cut surfaces, flat surfaces, and other structures,
The present invention relates to an earth anchor that forms a reaction force support anchor in the ground when attaching or towing and fixing structures, temporary objects, bars, and other members, etc., and a method for constructing the same.

[Conventional technology 1] Various techniques for installing earth anchors underground have been known for a long time, and when a bar with parts attached to the tip is driven into the ground and a force is applied in the pulling direction, the tip opens. There are known methods that significantly increase the pull-out resistance, and methods in which a poling hole is drilled and an earth anchor is inserted into the hole to secure it with grout.

Also, using a steel pipe as a core pipe, an earth anchor with a large-diameter head attached to the tip is driven into the ground, and at the same time, grout is injected into the core vibe, the inside and outside of the core vibe is hardened with grout material, and the core vibe is left in the ground. An earth anchor used as a reinforcing bar is disclosed in Japanese Unexamined Patent Publication No. 61-191721. Such earth anchors require a powerful device to drive, cause significant damage to the ground around the core vibrator, form a large cavity, require the injection of a large amount of grout, and have a relatively small pulling force. Also, it is not easy to insert a long vibrator.

Furthermore, conventional earth anchors have been inconvenient when they need to be removed after being temporarily used for temporary construction work.

When setting anchors on someone else's land or outside of a managed area, it is becoming increasingly difficult to obtain consent from land owners and managers. If the steel materials and cables that make up the anchor remain under roads, rivers, buildings, or on someone else's land, they may become an obstacle in future construction work, etc.
It may also become a problem of environmental pollution.

In the conventional removable earth anchor, as shown in FIG. An unpond layer 63 is provided to make it removable, and the tendon part 61 and the anchor part 62 are joined by mechanical joints 1 to 64, etc., and when removed, the mechanical joint 64 is released and the tendon part 61 is removed.
The mainstream is to remove the . In this case, there is a problem that the anchor part 62 still remains underground, and the removed tendon part 61 remains hollow.

[Problems to be Solved by the Invention] The present invention can be pushed into the ground with a small pushing force, can be made to have an arbitrary length, and can minimize disturbance of the ground around the outer periphery of the anchor. to stop excavation in a small area,
The present invention also aims to provide an earth anchor that has a high tensile strength with less materials and labor by press-fitting mortar into the earth anchor, and a construction method for fixing the earth anchor underground. An object of the present invention is to provide a method for constructing an earth anchor that allows the cavity to be backfilled with a material such as sand.

[Means for Solving the Problems] The present invention is an earth anchor made of a steel pipe provided with spiral ribs on its outer periphery. Hereinafter, this steel pipe will be referred to as an anchor body.

In addition, the method for constructing the earth anchor of the present invention involves rotating and press-fitting the anchor body into the ground, injecting mortar from the inner diameter of the sea lion body into the ground around the outer periphery to form an anchor fixing area in the ground, and applying this mortar to the ground. After curing, the earth anchor body is provided with a function of resisting pulling force, thereby being pulled toward the ground surface and anchored in the ground.

In addition, the earth anchor of the present invention can be removed, and in that case, the construction method is to fix the earth anchor in the ground and use it, then pull out the anchor body from the ground (tow it in the direction of Press sand or other filler into the tip of the anchor body through the hollow hole using sand conversion, etc., and repeat this pulling and press-fitting of the anchor body to ensure that the sand or other filler is densely filled into the area where the anchor body was pulled out. The feature is that the anchor body is removed from the ground.

[Operation 1] The earth anchor of the present invention belongs to the circumferential friction type anchor part. Structurally, the casing drill made of steel pipe serves as the tension member of the anchor body. Friction on the circumferential surface is provided by the adhesion of the injection mortar to the spiral protrusions (spiral ribs) provided on the outer periphery of the anchor body.5 The construction method belongs to the rotission drilling method. Also, based on the anchoring method, it can be classified as the nut anchoring method for steel pipes.

Its characteristics are as follows.

(1) Since the casing drill and the anchor body are integrated, the process of inserting the anchor body can be saved.

(2) Since the anchor body is formed with spiral ribs, the rotational compression speed can be significantly improved. In addition, sufficient adhesion with mortar can be expected.

(3) Spiral ribs facilitate rotary press-fitting, so no water supply is required.

(4) Since mortar injection only needs to be done once, it is possible to save labor in the secondary process.

In the method of the present invention, as shown in flowchart 1 to 1 in FIG. 5, after preparation including selection of a press-fitting machine, the anchor body is rotatably press-fitted into the ground, mortar is injected around the outer periphery of the anchor body for curing, and tension is applied. It is fixed by applying tensile force to the anchor body with jacks, and the final step is to apply anti-corrosion treatment to the head.

Next, removal of the earth anchor of the present invention will be explained.

The earth anchor of the present invention can be formed hollow with an open end. Therefore, instead of pulling out the earth anchor with a strong pulling force, sand is pressed in using the hollow part of the anchor body, and by repeating this pulling and press-fitting, a complete sand-filling part is formed in the place where the ground was pulled out, and the original Restored on the same ground as the geology,
Ass anchors can be removed.

[Example] Fig. 1 shows the structure of an earth anchor according to an example of the present invention.

The anchor body is made of a steel pipe 1, and includes a screw head portion 2, a straight portion 3, a drill portion 4, and a joint portion 5, and is provided with a mortar injection hole 6 and a cutter blade 8.

The drill part is provided with ribs 7. The material and specifications of the steel pipe I are preferably those scheduled for carbon steel pipes for pressure piping, taking into consideration strength, ductility, wall thickness, thread processing equipment, and weldability. The base standard is JISG3444 5TPG42
Schedule 80. In addition, the workability of penetrating mortar injection, required anchor strength, head bolts and nuts,
Considering the degree of utilization of the general-purpose auger machine, the base size was set to diameter α = φ], l 4.3, and wall thickness t = 8.6.

Drill part 4 is a φ9 mm round bar (spiral rib 7)
were welded together at a pitch of 1.20 mm until the length required for fixing the anchor body was obtained. The mortar injection holes 6 are provided with holes having an appropriate outer diameter at an appropriate pitch (circumferential direction, longitudinal direction) so that mortar can be passed from the inside of the anchor body tube to the outside of the tube. The base dimensions are: hole diameter 25mm, number of holes installed in the circumferential direction = 4, pitch in the length direction 300mm.

Further, the end portion on the head side has a threaded portion 2 necessary for introducing tension. Its standard length is 200 mm.

In order to improve workability, a threaded joint part 5 for joining the divided anchor bodies is appropriately provided on the straight drill part 4. Spiral ribs 7 are not provided at 1.50 mm on both sides of the joint line provided in the drill part 4. The head of the anchor body is the part that introduces tension into the anchor body.

The state in which this anchor body 1 is pushed into the ground 21 and fixed is the second state.
Shown in the figure. The screw portion 2 protrudes from the ground surface and is connected to a fixing plate 35,
It is fixed by a fixing nut 33. The straight part 3 and the drill part 4 are inserted into the ground 21.

FIG. 3 shows the grout sheath of the example.

The grout sheath 11 is used by being inserted into the anchor body when grouting mortar. The grout trace 11 is composed of a backer part 16, a straight part 15, and a coupler part 14.

The backer portion 16 includes a sleeve 12, which has front and rear end flanges 1, 2a inscribed in the inner diameter of the steel pipe 1. Mortar press-fitted from the ground surface passes through the grout hole 13, pressurizes and fills the space between the inner diameter of the anchor body 1 and the rib 12, and is injected around the outer wall from the injection hole provided in the anchor body. If the sheath is retracted without any damage, it is possible to perform maltunoline injection into the ground around the outer periphery of the anchor body with appropriate filling volume, pressure, and press-fitting performance.

The basic dimensions of the grout sheath 11 are as follows.

Outer diameter: Near 6.3mmφ Inner diameter: 52.9mm φ length
Size: 1000mm filling space 2,830
cc grout hole φ50-25 oval, 4 holes in circumferential direction,
The two rows and the straight section 15 are for feeding mortar under pressure to the backer section 16, and the material and dimensions are JTSG3452 (carbon steel pipe for piping). If a joint is provided, align it with the joint of the anchor body.

The coupler part 14 is a part that connects with a flexible tube for pouring mortar.

Next, a fourth example of the construction method of the earth anchor of the present invention will be described.
This will be explained according to the diagram.

(a) An earth anchor 1a equipped with a cutter blade 8 and a spiral rim 7 on its outer periphery is rotatably press-fitted into the underground 21 using a rotary press-fitting machine.

A hole drilling machine is used for the rotary press-in machine. The basic ability is N
For sand and gravel up to a value of 50:

Thrust ・1. 500kg torque:
2.000 kg・m Rotation speed: 21 ppm Stroke 1.5 m The target drilling machine is a TOP-10 (+-ne Bonong) valve.

The standard press-in speed is as follows for sandy material.

Sandy soil N value Pressing speed 10 1-l O min/m 203-10 min/m 30 3-10 min/m 40 5-15 min/m 5010-20 min/m [1]) Thrust when rotating press-fitting Rotate and press-fit without adjusting, and connect the anchor body and grout sheath according to the progress.

The next steel pipe 1b is connected to the steel pipe 1a at the joint part 5. The time required for fitting is based on 10 minutes/place.

(C) Spread mortar 17 into the ground from grout sheath 1).

The composition of the pouring mortar is as follows.

Semen h: 84
0 kg sand 84.0 kg Bobris No. 5]-+: 2. ] k
g water ・3〕3kg flow value
5 20 seconds ± 2 seconds 4 weeks Intensity 250 kg/crn'' or more -1 = (d) Retract the grout sheath without injecting the mortar.

The mortar shall be injected from the bottom of the anchor body in 1 m increments and successively proceed to the anchor head. The standard witnesses for each 1m test are as follows.

Injection pressure: 5 kg/c, injection time: 10 minutes The injected mortar is naturally cured until it solidifies and forms a load-bearing layer 18 that is integrated with the ground and ribs.

(e) Fixed @ plate on the head of the anchor body, 37! Fit the fixing nut 33 into the shirt king jig 31.3.
2 is attached and force 36 is applied in the direction of pulling out the anchor body by jacking. 1 and 37 are reaction forces. In this state, tighten the oak j-33 to fix the anchor body. Next,
Remove the shirt king jig 3132.

In this way, a strong earth anchor can be constructed.

Next, we will discuss the earth anchor removal process of the present invention in the sixth section.
This will be explained with reference to the figures.

(a) FIG. 6(a) shows the earth anchor of the present invention in use, and the anchor body (2) is fixed to the ground by a load-bearing layer 18 formed on its outer periphery by pouring mortar. This anchor body is hollow.

(b) After the earth anchor has been used, use a tensioning tool to slightly reduce the friction between the load-bearing layer and the ground, and then move the anchor body 1 into the ground 2 while rotating it with a polling machine.
Pull it out from 1. Or apply the pulling force with a strong jatsugi.
The anchor body 1 is pulled out to create a cavity 42.

(c) Instead of pulling out the anchor body 1, sand 43 is press-fitted using the hollow hole of the anchor body 1. The principle of driving sand compaction piles and its equipment will be applied to press in this sand. In this case, the key is to fill in the holes one by one instead of pulling them out. Figure 7 schematically shows the sand compaction method → sand pump 44 and sand 43
is pumped, and the anchor body l is rotated and pulled out, and then the hollow part 4 is
Step 2 is compacted and filled with sand.

(d) By repeatedly pulling out the anchor body 1 and press-fitting the sand 43, the cavity 42 created by pulling out the anchor body 1 can be completely and densely filled with sand, and the underground 21
The earth anchor can be removed without leaving any foreign objects or cavities.

[Effects of the Invention 1 The earth anchor and its construction method of the present invention have the following excellent effects.

■ You can freely select the diameter and length of the earth anchor according to the ground and desired anchor force.■ Penetration is easy, and the penetration and fixing are continuous processes, so there is no need for double work.

■ The penetration does not damage other mountains, and the amount of soil removed is small.

■ A large pulling force can be obtained by injecting a small amount of mortar.

■ Anchor construction speed is fast, construction period is short and construction cost is low.

■ As a removable earth anchor, it can be completely restored to its original condition before construction. Therefore, for example, as shown in FIG. 8, when it is necessary to drive an earth anchor l from a construction target area 51 to an adjacent area 52, it is easy to make adjustments with the adjacent land, and it is possible to leave the earth anchor underground. This prevents the occurrence of troubles and defects due to this, and also eliminates any problems caused by leaving cavities in the ground.

[Brief explanation of drawings]

Figure 1 is a side view of the earth anchor body of the present invention, Figure 2 is its underground construction diagram, Figure 3 is a side view of the grout system, and Figure 4 is a side view of the earth anchor body of the present invention.
The figure is a process diagram of the construction method, Figure 5 is a flow sheet of the construction method, Figure 6 is a process diagram of pulling out and removing the earth anchor, Figure 7 is an explanatory diagram of →)-nd conversion, and Figure 8 is an illustration of the construction method. FIG. 9 is an explanatory diagram for constructing an earth anchor in an adjacent area, and FIG. 9 is an explanatory diagram showing an example of a conventional removable earth anchor. 1...Anchor body (steel pipe) 3...Straight 5...-Joint part 7--Rib 11--Grou]・Shi 13--Graut hole 15--Straight part 2-・-Threaded portion 4・-・Drill portion 6・・-'t. IJE inlet hole 8 - Cutter blade 12 - Sleeve 14 - Coupler 16 - Backer part Application Kawasaki Steel Co., Ltd. Figure Figure

Claims (1)

[Claims] 1. An earth anchor made of a steel pipe with spiral ribs on its outer periphery. 2. The earth anchor according to claim 1 is rotatably press-fitted into the ground, mortar is injected from the inner diameter of the anchor body into the ground around the outer periphery to form an anchor fixing area, and after curing the mortar, the anchor body is subjected to a pulling force. A method for constructing an earth anchor, which is characterized by giving it a resistance function and fixing it in the ground. 3 After the earth anchor is fixed in the ground and put into service, the anchor body is towed in the pulling direction, and a filler such as sand is press-fitted into the tip of the anchor body from the hollow hole of the anchor body by sand compaction etc. By repeating towing and press-fitting, the area where the anchor body was pulled out is densely filled with filler such as sand.
3. The method of constructing an earth anchor according to claim 2, further comprising removing the anchor body from underground.