JPH0530933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a ground anchor body equipped with a bag-shaped anchoring portion and its anchoring structure.

[Prior Art] Ground anchors are used for a number of purposes, such as retaining mountains in construction work, preventing landslides, stabilizing slopes, and reinforcing various structures. There are two types of ground anchors: rock anchors that are anchored to bedrock, and soil anchors that are anchored in sediments such as gravel and clay.
It consists of an anchor head.

The structure of a conventional anchor body fixing section is shown in FIG. As shown in FIG. 8, an anchor hole 30 in the ground
A tensile material 31 such as a PC steel wire or a PC steel rod is inserted inside, and cement paste (water-cement ratio of about 50%), which will become the anchor grout 32, is injected under low pressure to fill the anchor hole 30, and the cement paste solidify. After the cement paste hardens, a tensile force is applied to the anchor head, and the force is applied to the hole wall 33 of the anchor hole 30 through the anchor grout 32.
It is transmitted to the rock or soil of the earth and obtains the anchor strength. 3
4 is a spacer that holds the grout covering of the tensile material 31, and 35 is an injection hose for injecting cement paste.

[Problems with Prior Art] Conventional ground anchors with such a structure have the following problems.

If cracks occur in the surrounding ground of the anchor body anchorage part of the anchor hole, and the width of this crack is large, the cement paste injected into the anchor body anchorage part will flow away from the cracks, and the anchorage layer will deteriorate. It cannot take root even in strong rock.

Since the amount of cement paste injected into the anchor body fixing part is not constant depending on the hardness and softness of the ground and the condition of cracks, quantitative production control of cement paste cannot be performed sufficiently.

Spacers are attached to the tension members at predetermined pitches to maintain grout coverage over the tension members, but the work of installing these spacers is troublesome.

When tensile force is applied to the tension material, tension cracks occur in the anchor grout due to the difference in elastic range between the tension material and the anchor grout.
There is a risk that the function of the anchor will be adversely affected in the future due to infiltration of groundwater, etc.

An anchor inclination angle in the range of -10° to +10° with respect to the horizontal plane is considered to be unfavorable as a casting angle because it is susceptible to the occurrence of anchor grout breathing.

[Means for Solving the Problems] The present invention aims to solve the above problems. That is, in the first invention, a tensile member; a bag made of high-tensile cloth attached to surround the anchor fixing portion of the tensile member; and a bag in which cement paste is injected into the bag. a body injection tube; a tubular covering covering the tensioning material from the tensioning side end of the tensioning material surrounded by the bag body toward the insertion side end; This is a ground anchor body equipped with a bag-shaped anchoring part characterized in that the tension side end is closed, the insertion side end is open, and the tensioning part of the tensioning member is covered with a waterproof material.

In the second invention, a tensile member; a bag made of high-tensile cloth attached to surround the anchor fixing portion of the tensile member; and bag injection for injecting cement paste into the bag. a tube; a tubular covering covering the tensile material from the tension side end of the part of the tension material surrounded by the bag toward the insertion end; and the tension side of the covering. A bag-shaped fixing device characterized in that the end and the insertion side end are closed, the covering body is provided with a covering injection pipe for injecting cement paste, and further, the tensioning part of the tensioning material is covered with a waterproof material. Ground anchor body with parts.

In the third invention, the ground anchor body according to the first invention is inserted into an anchor hole provided in the ground, and the bag body of the ground anchor body is filled with grout. This is the anchoring structure for the ground anchor body.

In the fourth invention, the ground anchor body according to the second invention is inserted into an anchor hole provided in the ground, and the bag body of the ground anchor body is filled with grout. This is the anchoring structure for the ground anchor body.

In the fifth invention, the ground anchor body according to the first invention is inserted into an anchor hole provided in the ground, and the bag body and the anchor hole of the ground anchor body are filled with grout. This is the anchoring structure of the grind anchor body.

In the sixth invention, the ground anchor body according to the first invention is inserted into an anchor hole provided in the ground, and the bag body and the anchor hole of the ground anchor body are filled with grout. This is the anchoring structure of the ground anchor body.

Examples of the high tensile strength fabric used for the bag body include Kevlar (registered trademark DuPont), Technora (registered trademark Teijin Ltd.), which are aramid fibers with high tensile strength. This aramid fiber has high tensile strength and is suitable as a material for the bag of the present invention. Although one bag is usually provided between the head of the anchor body fixing section and the inserted tip, if the anchor body fixation length is long, a plurality of bags can be installed.

Hereinafter, in the present invention, the grout (cement paste or solidified product thereof) that is injected into the bag and becomes the anchor body will be referred to as backed grout. Also,
The grout (cement paste or its solidified product) that is interposed between the soil consolidation around the anchor, the hole wall, and the bag body and has the role of transmitting the shear stress of the ground to the anchor is called around grout.

The injection pressure for backed grout varies depending on the intended use of the crown anchor. For example, if a crack occurs in the ground around the anchorage part of the anchor hole, and the cement paste injected into the anchorage part flows away from the crack, the pressure is low enough to close the crack ( It is sufficient to inject at around 5Kg/ ^cm2 ).

However, for example, when anchoring in soil, the cross-sectional area of the anchor anchoring part is expanded by expanding the bag and the friction surface area with the hole wall is increased, and the bearing pressure resistance of the head of the anchor anchoring part is If the amount is also increased, high-pressure injection (approximately 5 to 50 kg/cm ² ) is performed.

A around grout is usually injected into the anchor hole, but if the anchor function is performed only by the packed grout, the around grout is not necessary. Although the bag made of high-tensile cloth has good water permeability and air permeability, the cement paste clogs between the fibers for a while and is difficult to penetrate, so high-pressure injection is possible. In this way, the bag body has good water permeability and air permeability, so if a tension crack occurs in the cross-sectional direction of the tensile material in the packed grout, water, gas, etc. in the ground will pass through the tension crack. There is a risk that it will invade the inside of the dog grout and corrode the tensile material, and the long-term strength of the anchor cannot be guaranteed. Mechanically, it is thought that this tension crack occurs from the end of the tensile portion of the tension member covered with the bag, and gradually moves toward the end of the insertion side.

Therefore, it is necessary to cover the tensile member with a covering member having an inner diameter larger than the outer diameter of the tensile member, such as a convex-concave tubular covering member, from the side end of the tensioning part to the insertion side end, or over the entire length of the tensile member surrounded by the bag. It's on. As a result, even if a tension crack occurs in the packed grout, it will be blocked by the coating, so there is no risk of corrosion of the tension member.

Further, even if a tension crack occurs in the tension part, there is no risk of corrosion of the tension member because the tension part is covered with a waterproof material.

[Examples] The present invention will be described in more detail with reference to embodiments shown in the drawings.

Figure 1 is an explanatory diagram showing the schematic structure of the first embodiment of the ground anchor, and Figure 2 is A-A in Figure 1.
Vertical sectional view, Figure 3 is a BB sectional view of Figure 1, Figure 4
The figure is a sectional view taken along the line CC in FIG.

A tensile steel material 1 is inserted into an anchor hole 10 drilled underground E. The tensile steel member 1, except for the anchor body fixing portion 13, is covered with a synthetic resin covering member 1a to prevent corrosion by water or gas even if a tension crack occurs. A cladding tube 15 having an uneven structure made of synthetic resin and having an inner diameter larger than the outer diameter of the tensile steel material 1 is attached to the anchor body fixing section 13 . Cladding tube 1
A sealing portion 15a is provided on the tensioning portion side of 5, and an opening portion 15b is provided on the insertion side end. Cladding tube 15
The length is approximately 2/3 or the entire length of the anchor body fixing portion 13.

In the anchor body fixing part 13 of the tensile steel material 1, a bag body 2 made of Technora (registered trademark Teijin Ltd.) is formed into a cylindrical shape with a required diameter (slightly larger than the anchor hole), and one end thereof is attached to the tip of the tensile steel material 1. 3, and then the cylindrical body is turned over, and the opening of the other end 4 is closed so that there is some room on the head side of the tensile steel material 1, and the tube is tightly fixed to the tensile steel material 1. Other end 4
is located slightly closer to the tensile part than the part covered with the synthetic resin 1a.

An injection port 5 for cement paste (packed grout) is provided on the anchor head side of the bag body 2, and an injection hose 6 for injecting cement paste into the bag body 2 is tightly connected to the injection port 5. ing.

On the other hand, cement paste is injected into the anchor hole 10 to form the around grout 7. Inside the bag body 2, there is a around grout 7.
Cement paste similar to the above is injected (5 to 50 kg/
cm ² ) to form packed grout 8,
By this injection, the bag body 2 is infiltrated, and the around grout 7 and packed grout 8 are integrated through the bag body 2. The bag body 2 is swollen outwardly by the injected cement paste, and is solidified while prestressing the hole wall 9 with the same force as the injection pressure.

FIG. 5 is a vertical cross-sectional view showing the schematic structure of the second embodiment of the ground anchor, and FIG.
It is a D sectional view.

In this embodiment, instead of the tensile steel material in the first embodiment, a plurality of recesses 2 are provided on the outer periphery along the longitudinal direction.
A spacer 20 is used which has a hollow part 26 in which a steel material 24 is mounted in each recess 22, and an injection pipe 28 is inserted into the spacer 20. The anchor body fixing part 13 is made of a cladding tube 15 having irregularities made of synthetic resin and having an inner diameter larger than the spacer 20 to which the steel material 24 is attached.
is attached. A sealing part 15a is provided on the tension side of the cladding tube 15, and a sealing part 15a is provided on the insertion side end.
c is provided. The length of the cladding tube 15 extends over the entire length of the anchor body fixing section 13.

A cement paste discharge port 21 is formed in a portion of the spacer 20 where the cladding tube 15 is layered. An air vent gap (not shown) is provided between the sealing portion 15a and the spacer 20 to allow internal air to escape when cement paste is injected into the cladding tube 15. The opening of the other end 4 of the bag body 2 is closed and tightly fixed to a spacer 20 to which a steel material 24 is attached. Note that parts that are the same as or equivalent to those in the first embodiment are denoted by the same reference numerals.

The construction method according to this embodiment is generally the same as that of a conventional ground anchor, and is constructed in approximately the following order.

(1) The tensile material 1 is processed at an on-site processing yard or at a factory before being inserted into the anchor hole 10.
The entire anchor body fixing part 13 of the tensile material 1 is attached to the bag body 2.
The cylindrical cloth is then wrapped in the tension member 1 at the head portion of the anchor body fixing portion 13 and the tip end on the insertion side, and the cylindrical cloth is processed into a bag shape. Incidentally, an injection hose 6 for injecting cement paste into the bag body 2 is tied to the head side of the anchor body fixing part 13 in a similar manner.

(2) Casing pipe (not shown) (diameter 50mm
After completing the drilling work of the anchor hole (above), the cement paste which will become the around grout 7 is replaced and injected into the casing pipe at low pressure. Thereafter, the tensile material 1 processed as described above is inserted into the casing pipe to a predetermined depth.
After the insertion is completed, pull out the casing pipe, and then insert the pack trout 8 into the bag body 2 from the injection hose 6.
Inject 5 to 50 kg/cm ² of cement paste (the same as that injected into the casing pipe). If the structure is such that cement paste is injected into the cladding tube 15, the cement paste is injected into the cladding tube 15 at the same time. Through this injection step, the bag body 2 is infiltrated with the around grout 7 and the pack grout 8 and becomes integrated. The bag body 2 expands outwardly by the injected cement paste, and solidifies while applying pressure to the hole wall 9 with the same force as the injection pressure.

Therefore, the packed grout 8 becomes a high-strength anchor anchor body, and the around grout 7 is integrated with the packed grout 8 and serves to adhere to the anchor hole wall 9 (soil or rock).

Note that because packed grout is injected under high pressure, a dehydration effect occurs, and the unit amount of water in the grout decreases, resulting in higher strength than the grout before injection. Moreover, since the bag body 2 has a high tensile strength, it acts as a stiffening material similar to reinforcing bars in a concrete structure. In addition, water and air inside the bag body 2 are injected into the packed grout 8 and are expelled from the bag body 2 without resistance, but the grout clogs between the fibers and oozes inside the bag body 2. will be put on hold.

FIG. 7 is an explanatory diagram showing the state in which the anchor body is used on a rock having a crack in the anchorage part. If a crack 11 occurs in the hole wall 9 of the anchor body fixing portion 13 of the anchor hole 10, the bag body 2 expands due to the injection of packed grout, and a part of the crack 11 enters the key. A portion 12 is formed. Further, the key portion 12 closes the crack 11, thereby preventing the around grout 7 from flowing out, and the anchor can be fixed.

[Effect of the invention] The present invention has the following effects.

(1) With normal ground anchors, no matter how strong the anchorage layer is, if the width of the crack is large, the cement paste injected into the anchorage part of the anchor body will wash away from the crack.
It cannot be established. However, the ground anchor according to the present invention can be freely anchored in rocks with many cracks, and when the cracks are large, the key effect contributes to the anchor strength.

(2) When backed grout is injected and fixed under high pressure, it has higher strength than conventional anchor grout.

(3) In conventional ground anchors, the difference in elastic range between the tensile material and the grout causes tensile cracks, but according to the present invention, since the back grout has high strength, the adhesive force with the tensile material is reduced. The higher the grout strength, the wider its elastic range will be. Moreover, since the high tensile strength cloth has a much higher tensile strength than grout, it acts as a stiffener (like reinforcing bars in concrete) and can control the occurrence of tension cracks.

In addition, even if a tension crack occurs in the packed grout in the cross-sectional direction of the tensile material, the coating covers the appropriate position from the tension side end to the insertion side end, so water and gas will not be covered. It is blocked by the body, and there is no risk of corrosion of the tensile material, and the long-term strength of the anchor can be guaranteed. Further, even if a tension crack occurs in the tension part, since the tension part is covered with a waterproof material, there is no risk of corrosion of the tension member.

(4) When injecting packed grout at high pressure, the frictional resistance between the anchor body anchorage part and the rock or soil will be greater than that of conventional ground anchors. In particular, when anchored to rock, packed grout hardens while applying prestress to the rock that is the wall of the anchor hole, resulting in greater frictional resistance than conventional anchor grout and rock.

(5) When it settles on soil, the soil around the anchorage can be compacted and removed by injecting packed grout into the bag at high pressure. Therefore, it is possible to reliably create an anchor body with a predetermined diameter. Further, the cross-sectional area and therefore the frictional area of the created anchor body fixing portion become larger than the cross-sectional area of the anchor hole, and both the frictional force and the bearing force increase. Therefore, it is possible to create a ground anchor that has the same anchor hole diameter as a conventional anchor but has a greater ability.

(6) In conventional ground anchors, spacers are attached to the tensile material at predetermined pitches to maintain grout coverage over the tensile material. However, according to the present invention, when the packed grout is injected into the bag, the bag expands and acts as a spacer, so the tensile material is inevitably centered at the anchor hole, so no spacer is required.

(7) Conventionally, the amount of cement paste was required to be several times or tens of times the anchor hole capacity depending on the hardness and softness of the ground and the state of cracks. Moreover, the amount was not constant. However, according to the present invention, the amount of cement paste is limited to the capacity of the casing pipe and the capacity of the bag, and no larger amount of cement paste is required. Therefore, the amount of cement paste can be easily controlled regardless of the ground condition.

(8) Due to the effects of cement paste breathing, etc., the anchor installation angle may vary from -10° to +10° from the horizontal.
The above range was considered to be unfavorable, but since the high-pressure injection of packed grout promotes dehydration within the packed grout, the influence of breathing is extremely reduced, so it can also be applied to the above range, expanding the ground anchor driving angle. .

[Brief explanation of the drawing]

FIG. 1 is a structural diagram showing the structure of the first embodiment of the present invention, FIG. 2 is a vertical cross-sectional view taken along line A-A in FIG. 1, FIG. 3 is a cross-sectional view taken along line B-B in FIG. The figure is C- in Figure 1.
C sectional view, FIG. 5 is a vertical sectional view showing the schematic structure of the second embodiment of the ground anchor, and FIG.
FIG. 7 is an explanatory view showing a state in which the anchor is used in an anchor hole having a crack, and FIG. 8 is an explanatory view showing the structure of a conventional anchor body fixing portion. E: underground, 1: tensile steel, 2: bag, 7: around grout, 8: packed grout, 10:
Anchor hole, 13: anchor body fixing part, 15: covering body, 15a, 15c: sealing part, 15b: opening part.

Claims (1)

[Scope of Claims] 1. A tension member; A bag made of high-tensile cloth attached to surround the anchor fixing portion of the tension member; A bag injection pipe for injecting cement paste into the bag; ; a tubular covering covering the tensioning material from the tensioning side end of the part of the tensioning material surrounded by the bag toward the insertion side end; and the tensioning side end of the covering is A ground anchor body equipped with a bag-shaped anchoring part, characterized in that the insertion side end is closed, the insertion side end is open, and the tensioning part of the tensioning member is covered with a waterproof material. 2. A tensile material; A bag made of high-tensile cloth attached to surround the anchor body fixing portion of the tensile material; A bag injection pipe for injecting cement paste into the bag; A bag of the tensile material a tubular covering covering the tensile material from the tension side end to the insertion side end of the area surrounded by the body; the tension side end and the insertion side end of the covering are closed; The covering body is provided with a covering injection pipe for injecting cement paste, and the tensioning part of the tensioning material is further provided with a bag-shaped fixing part characterized in that it is covered with a waterproof material. Ground anchor body. 3. A bag-shaped anchoring part, characterized in that the ground anchor body according to claim 1 is inserted into an anchor hole provided in the ground, and the bag body of the ground anchor body is filled with grout. Anchoring structure for ground anchor body. 4. A bag-shaped bag, characterized in that the ground anchor body according to claim 2 is inserted into an anchor hole provided in the ground, and grout is filled in the bag body and the covering body of the ground anchor body. An anchoring structure for a ground anchor body with an anchoring part. 5. A bag characterized in that the ground anchor body according to claim 1 is inserted into an anchor hole provided in the ground, and grout is filled in the bag body and the anchor hole of the ground anchor body. An anchoring structure for a ground anchor body with a shaped anchoring part. 6. The ground anchor body according to claim 2 is inserted into an anchor hole provided in the ground, and grout is filled in the bag and covering body of the ground anchor body, and the anchor hole is further filled with grout. An anchoring structure for a ground anchor body including a bag-shaped anchoring portion filled with grout.