JP2016069971A - Construction method of retaining wall by mortar spraying - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for constructing a retaining wall by spraying such as mortar.SOLUTION: A construction method of a retaining wall by mortar spraying is composed of a lock bolt driving process of reinforcing a natural ground surface layer, a reinforcement installing process of fixing a reinforcement grid in the longitudinal-lateral direction via an anchor plate to a lock bolt head part, a spraying process of spraying mortar mixed with synthetic resin short fiber from above this reinforcement grid and a coating process of coating a silane-siloxane-based permeable water absorption preventive agent on a surface of the sprayed mortar.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for constructing a retaining wall by spraying mortar or concrete. In the following specification and claims, “mortar” is used to mean concrete.

The construction method to construct the retaining wall by spraying mortar has not been established yet.
Instead, for example, as shown in Patent Document 1, a lock bolt is placed on the slope, a reinforcing bar assembly is constructed by attaching reinforcing bars vertically and horizontally to the lock bolt, and a mesh body is attached to the reinforcing bar assembly. A construction method in which concrete is placed between the net and the slope is known.
In that case, concrete or mortar is not sprayed, but is a construction method in which a retaining wall is formed by filling physical properties that do not flow out from the mesh of the mesh body between the mesh body and the slope from the opening on the side of the shoulder.

Japanese Patent Application Laid-Open No. 2004-251072.

The reason for adopting the method of pouring from the opening of the shoulder opening instead of spraying concrete or mortar is described in the column [0016] of the effect of Patent Document 1 as follows.
In other words, when building a mortar spray wall by spraying on a steep rocky slope or a weathered slope, there is a great risk that the mortar wall will collapse due to surface slippage, landslide, etc. On slopes with many irregularities or overhanging slopes, it is difficult to spray mortar on the slopes, so the construction method of spraying mortar on concrete could not be adopted in the construction of retaining walls.

In this way, the limitations when attempting to construct a retaining wall by spraying concrete or mortar are summarized as follows.
<1> Spraying mortar is an operation called spraying, so thick spraying is impossible, and sagging or peeling occurs.
<2> If this is the case, it is only necessary to wait for curing and blow twice, but if you blow twice, rebound particles on the surface of the first spray layer will be sandwiched between the two layers. It causes peeling and strength reduction. Therefore, it is not suitable for retaining walls that require a certain amount of thickness.
<3> Since it is exposed to wind and rain immediately after construction, a good curing period cannot be maintained, and as a result, strength reduction and cracks are likely to occur.
<4> Low resistance to surface layer collapse and landslide.
<5> The hydration reaction is inhibited by spring water from the slope surface layer, and internal voids and cracks are generated.
<6> Due to the above problems, it has been considered that mortar spraying work cannot be adopted as a construction method for constructing a retaining wall, apart from a weathering prevention and erosion prevention method on the rock surface.

The construction method of the retaining wall by spraying mortar according to claim 1 of the present invention that solves the above-described problems includes a lock bolt placing step that reinforces the ground surface layer, and a vertical and horizontal direction through the anchor plate on the lock bolt head. Reinforcing bar installation process to fix the reinforcing bar grid in the direction, spraying process of spraying mortar mixed with synthetic resin short fiber from above the reinforcing bar grid, and silane / siloxane based permeable water absorption inhibitor on the surface of the sprayed mortar It is characterized by the construction method of the retaining wall by spraying mortar consisting of the coating process of coating.
According to the second aspect of the present invention, in the above process, the anchor plate fixed to the head of the lock bolt has a substantially U-shaped cross section, and a notch, a bent portion, or a protrusion is provided at an end of the anchor plate. It is characterized by the construction method of retaining walls by mortar spraying, which is provided and the reinforcing bars are fixed by the notches, bent portions or protrusions.
According to the invention of claim 3, in the above process, after the synthetic resin short fiber mixed mortar is sprayed, the sprayed surface is washed and cleaned with high-pressure washing water, and then a silane / siloxane based permeable water absorption inhibitor is applied. Retaining wall construction method by mortar spraying.
According to a fourth aspect of the present invention, in the above step, before the rock bolt placing step for reinforcing the natural ground surface layer, a step of draining water from the natural ground, and an adhesive wire mesh is stretched over the entire construction surface. It is characterized by a method of constructing a retaining wall by spraying mortar, which includes a process, or a process of spraying mortar or polymer cement mortar.
Further, the invention according to claim 5 is characterized in that, in the above step, before the mortar spraying step, the separating wire mesh is fixed by an anchor bolt attached with a sheath tube or a spacer having a desired length, and the separating wire mesh is grounded. Construction method of retaining wall by spraying mortar, with the process of fixing at a certain distance from the mountain.
Further, in the invention described in claim 6, in the above process, the synthetic resin short fiber material sprayed in the spraying process has a length of 20 to 50 mm and a thickness of 0.5 to 2 mm, and the surface thereof is uneven processing or a protrusion. The construction method of the retaining wall by the mortar spraying which is a synthetic resin short fiber material provided with is characterized by.
Further, the invention according to claim 7 is the retaining wall by mortar spraying provided with a step of installing a water permeable pipe or a water permeable mat on the slope before the rock bolt placing step for reinforcing the natural ground surface layer in the above step. It is characterized by the construction method.

Since the construction method of the retaining wall by mortar spraying according to the present invention is as described above, the following effects can be obtained.
<1> Since the number of steps in all the steps is small and the construction is simple, the construction period can be greatly shortened, and since the construction can be performed only by the slope work, the process management can be performed smoothly. For this reason, the cut ground can be stabilized quickly.
<2> The head of the rock bolt placed in the natural ground is connected to the embedded anchor plate by reinforcing bars arranged vertically and horizontally. Therefore, the whole ground can be reinforced continuously and integrally to counter surface collapse and landslide. Further, the short fiber mixed mortar resists the earth pressure between the rock bolts and anchors, and can prevent the hollowing out.
<3> Even if it is a natural ground where the geology and the rock quality are not constant, a more stable reinforcement effect can be obtained by continuously reinforcing it.
<4> Since the process is simple and excellent in workability, it is possible to construct a stable retaining wall work at a lower cost than conventional leaning retaining wall works and building block works.
<5> If a method of applying a silane / siloxane penetrable water-absorbing agent as a concrete protective material to the surface of the sprayed retaining wall is adopted, water and water vapor are prevented from entering, and alkali-aggregate reaction is suppressed. In addition, the life can be extended. Furthermore, the application of a silane / siloxane penetrable water-absorbing inhibitor can also suppress drastic drying shrinkage due to wind and suppress the generation of cracks.
<6> After installing the drainage on the back side, if a construction method that stretches a close-contact wire mesh over the entire construction surface is adopted, accidents during construction due to falling rocks of unstable stones and gravel will be prevented, and safe work will be promoted. be able to.
<7> By adopting a method of spraying mortar or polymer cement mortar at a stretched wire mesh with a length of about 1 to 3 cm, it is possible to seal ground that is heavily weathered or eroded easily in a short period of time, making it safer and more The mountain can be stabilized. In particular, when polymer cement mortar is sprayed, the adhesion is increased, it is in close contact with the natural ground, and the sealing performance is high, so it is highly effective.
<8> If anchor bolts with sheath pipes or spacers are used prior to spraying synthetic resin short fiber mortar, steep slope by spraying short fiber mixed mortar with fixing wire mesh fixed near the spray surface Even on the slopes, dripping and peeling can be prevented, and a desired thickness can be sprayed at once, and a more stable spray retaining wall can be constructed.
If a method of mixing <9> synthetic resin short fibers in 0.5 VOL% to 2.0 VOL% mortar is adopted, a more stable spray retaining wall with high toughness can be constructed. In particular, short fibers with irregularities and protrusions on the surface of the short fibers have a high binding force, which can further increase the usage limit of the spray retaining wall, and further improve the ultimate limit by the reinforcing bars connected with the lock bolts. A spray retaining wall can be constructed.
<10> Mortar with high toughness with relatively thin thickness of about 30 cm or less by mixing synthetic resin short fibers in mortar, improving the bending strength of mortar, and building a mortar wall with high toughness A wall can be constructed and drooping and cracking can be greatly suppressed.
If a <11> back surface drainage is carried out, cracks and voids due to spring water on the slope surface can be suppressed and the surface spring water can be discharged out of the retaining wall.
<12> Spray a single layer with a thickness of up to about 30 cm, and spray a mesh of 5 cm or more that can be sprayed from the surface in order to suppress the occurrence of peeling and strength reduction by a predetermined distance from the slope. It is installed and fixed with anchor bolts to which sheath pipes are attached, and when the mesh body is installed by bending the shoulder portion, the side surface and / or the joint portion of the mesh body on the slope side with a width of 25 to 30 cm and approximately 90 °, It is possible to construct a retaining wall with a thickness of up to about 30 cm by blowing further while suppressing the above.
<13> On a slope with extremely fast weathering, a more stable retaining wall can be constructed by spraying a thin layer of mortar or polymer cement mortar prior to the construction of the retaining wall.

Explanatory drawing of the construction state of the construction method of the retaining wall by the mortar spraying of this invention. Sectional drawing of the retaining wall by mortar spraying. Explanatory drawing of the rebar lattice before mortar spraying. The perspective view of an anchor plate. Explanatory drawing of the state which attached the reinforcing bar to the anchor plate. Explanatory drawing of the strength test apparatus of the test piece of a short fiber mixed mortar. The figure which shows a test result.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a method for constructing a retaining wall by spraying mortar according to the present invention will be described in detail with reference to the drawings.

<1> Overall process.
The main steps of the construction method of retaining walls by spraying according to the present invention are 1) a step of discharging spring water from the natural ground, 2) a step of placing a rock bolt that reinforces the natural ground surface layer, and 3) the head of the rock bolt. The process of forming a reinforcing bar lattice by fixing the reinforcing bar to the part 4) The step of spraying a mortar mixed with synthetic resin short fibers on the upper surface of the reinforcing bar lattice 5) The silane / siloxane penetrable water absorption inhibitor on the surface of the sprayed mortar It is comprised by the process of apply | coating. Each step will be described below.

<2> A step of discharging spring water.
The surface of the retaining wall to be constructed is cleaned to remove root stocks, floats, and earth and sand that hinder the attachment of mortar, and a permeable mat 60 is laid in a substantially horizontal direction in the vicinity of the upper boundary point to be constructed.
The water permeable mat 60 is connected to the water permeable mat 60 in the vertical direction toward the lower portion of the slope, for example, with a pitch of 1.5 m, and fixed with anchor bolts or the like.
Further, the lower and end portions of the water-permeable mat 60 installed in the vertical direction are connected to the PVC pipe and discharged at the lower portion of the retaining wall.

<3> Step of laying a close-contact wire mesh.
After installation of the above-mentioned back surface drainage, it is also possible to stretch a close-contact wire mesh 70 that is fixed to the entire construction surface with anchor bolts or the like.
In particular, in the case of rock slopes that are heavily weathered, expansible slopes, and slopes that are easily eroded, for example, a galvanized wire mesh with a diamond wire mesh diameter of 2.0 mm and a mesh size of 50 × 50 is used to have a diameter of 16 mm × 400 mm. And it fixes to a natural ground using the anchor bolt of diameter 9mm x 200mm.
When mortar is sprayed on the adhesion wire mesh 70 at a thickness of about 2 cm, the slope that is likely to be cut and eroded or the rock face that is heavily weathered will be sealed immediately after cutting, and weathering and erosion will occur. Stability can be secured without receiving.
Moreover, since the adhesion | attachment metal mesh 70 is still exposed, when the short fiber mixing mortar 10 is sprayed in the below-mentioned process, the attachment becomes easy.

<4> A step of placing a lock bolt.
Subsequently, the rock bolt 40 which reinforces the natural ground surface layer is driven on the slope.
For this purpose, the drilling positions are evenly allocated at a pitch of 1.5 m, for example, and drilled to a predetermined length.
After the drilling is finished, cement milk is injected, and the lock bolt 40 or deformed reinforcing bar is inserted and fixed.
For example, D19 × 3000 mm rock bolts 40 and deformed reinforcing bars are cast at a pitch of 1.5 m evenly in the X and Y directions of the slope, and cement milk is injected and fixed.
The anchor plate 20 is attached to the head of the fixed lock bolt 40.
For example, a method of attaching an embedded anchor plate 20 having a thickness of 9 mm, 160 × 160, and a height of 90 mm and having a substantially U-shaped cross section and fixing with a nut can be adopted. For details of the structure of the anchor plate 20 It will be described later.

<5> A step of forming a reinforcing bar lattice.
The anchor plate 20 fixed to the exposed end of the lock bolt 40 is formed with a wedge-shaped notch and a bent portion.
For example, when the deformed reinforcing bar D10 is fixed to the portion, a reinforcing bar lattice arranged in the XY direction can be formed along the slope and at a certain distance from the slope.

<6> A laying process of the isolation wire mesh.
Next, the isolation wire mesh 50 is laid at a position away from the slope by a certain distance, that is, in a state of floating from the slope.
For example, the isolation wire mesh 50 is a welded wire mesh having a diameter of 2.6 mm and a size of 100 × 100.
In order to keep a certain distance from the slope, the steel pipe 51 is used for installation.
As the sheath steel pipe 51, for example, a sheath steel pipe 51 having an outer diameter of 34 mm and a length of 150 mm is used, and anchor bolts 52 are driven through the sheath steel pipe 51 in a natural ground.
The anchor bolt 52 is provided, for example, with a substantially L-shaped hook on the head of φ16 × 400 mm.
As a result, the isolation wire mesh 50 can be laid over the entire surface at a position about 150 mm away from the natural ground.

<7> Mortar spraying step.
A mortar or concrete mixed with synthetic resin short fibers is sprayed on the top of the finished reinforcing bar lattice.
In that case, for example, a synthetic resin short fiber material having a length of 20 to 50 mm and a thickness of 0.5 to 2 mm, and a synthetic resin short fiber material having a concavo-convex process / or projections may be employed. it can.
When spraying the short fiber-containing mortar 10, a polypropylene short fiber material having a diameter of 0.7 mm and a length of 30 mm, which has been embossed on the surface, is charged at a rate of 1 VOL% from the upper charging port of the mortar agitator manufactured at the plant. After sufficiently kneading, spray with a mortar / concrete sprayer until the thickness reaches 100 mm to 200 mm.

<8> A step of applying a water absorption inhibitor.
Although the construction of the retaining wall is completed by the above-described process in which the mortar is sprayed, the silane / siloxane-based permeable water absorption inhibitor 80 can be applied to the surface of the sprayed mortar.
At that time, as a preliminary treatment, for example, the rebound on the surface of the mortar spraying is cleaned with high-pressure washing water having a water amount of 120 L / min and a discharge pressure of 8 MPa or more.
Then, after confirming the drying of the sprayed surface layer of about 30 mm, the silane / siloxane-based water-absorbing agent 80 is applied at a rate of, for example, 200 g per square meter using an airless gun.

<9> Loading experiment.
As described above, the construction method of the present invention constructs a retaining wall by spraying mortar mixed with short fibers.
In order to confirm the practicality of this construction method, a test piece T was prepared and a loading experiment was performed.
The specifications of the experimental apparatus 90 are as shown in FIG.
The material of the test piece T is 1: 4 mortar, the mixed polypropylene short fiber is 3 cm long and 0.7 mm thick, and the mixing amount is 1.0% VOL of the mortar.
The dimensions of the test piece T are 1.5 m × 1.5 m and the thickness is 7 cm.
The load is sand thrown into the load tank 91 and is 3,270 kg.

<10> Results of the experiment.
Immediately after the load of 3,270 kg was applied, the initial elastic strain deflection of the test piece T was 635 μm, and the subsequent change is as shown in FIG. 7. A crack occurred on the surface after 200 days.
The deflection at that time is 4800 μm, the gap width is 0.8 to 1.2 mm and the depth is 6 to 10 mm near the center of the crack, and the gap width is 0.2 to 0.4 mm and the depth is about 4 to 5 mm in other portions. Met.
After that, cracks increased slightly, but even after 1 year from the occurrence, the crack interval width did not increase, and peeling and peeling did not occur.

<11> Summary of experiment.
It is estimated that the following functions can be achieved when the short fiber mixed mortar 10 of the present invention is sprayed for retaining wall construction according to the result of the experiment.
1) Cracks are generated, but peeling and peeling do not occur, and the shape of the retaining wall at the time of spraying is maintained by the tensile stress of the fiber.
2) Brittle collapse does not occur in the retaining wall.
3) The tensile resistance of polypropylene short fibers is greater than the tensile resistance of mortar, and the bending toughness functions to maintain the shape of the retaining wall.
4) The short fiber mixed mortar 10 sufficiently functions as a retaining wall that receives tensile stress.

<12> Structure of the anchor plate.
Next, details of an embodiment of the anchor plate 20 that holds the vertical and horizontal reinforcing bars 30 in the present invention will be described with reference to FIGS.

<13> Basic configuration.
The anchor plate 20 of the present invention is a steel member, and is composed of a substrate 21, a reinforcing bar gripping part 22 formed in a part thereof, and a reinforcing bar receiving groove 23 formed in another part.
The anchor plate 20 itself cannot determine the directions such as “up and down”, “left and right”, “vertical”, and “horizontal”. However, for convenience of explanation along the drawings, the specification and claims are as shown in the drawings. It will be referred to as such on the assumption that the anchor plate 20 is viewed in plan.
In this case, the term “vertical” does not mean a mathematical verticality, but a vertical meaning.

<14> Substrate.
The anchor plate 20 of the present invention is a member formed by folding up and down a substantially rectangular steel plate into a strip shape.
Thus, if it is the structure where the upper and lower edges of a steel plate are folded up substantially at right angles and the reinforcing bar holding part 22 and the reinforcing bar receiving groove 23 are positioned, it can be economically manufactured especially when this is formed at one time by press working. .
If it demonstrates in order of a manufacturing process, if the upper and lower edges of a rectangular board will be folded up at right angles to a strip | belt shape, a flat plate-shaped member can be formed by side view.
The flat portion that hits the flat plate-like bottom plate in a side view is the substrate 21.
A reinforcing bar gripping part 22 and a reinforcing bar receiving groove 23, which will be described later, are located in a band-like part folded up at the upper and lower edges of the substrate 21.
However, the manufacturing process is not limited to pressing, and both the reinforcing bar gripping portion 22 and the reinforcing bar receiving groove 23 can be manufactured by, for example, welding a U-shaped pipe around the substrate 21.
A through-hole 24 for penetrating the lock bolt 40 in the orthogonal direction is opened at substantially the center of the substrate 21.

<15> A reinforcing bar gripping part.
At both ends of the edge folded up and down of the substrate 21, cuts opened outward are formed as the reinforcing bar gripping portions 22.
The notch of the reinforcing bar gripping portion 22 is a bottomed slit having a width and a depth capable of accommodating the vertical reinforcing bar 31 therein.
With this reinforcing bar gripping part 22, it is possible to grip a vertical reinforcing bar 31 positioned vertically on the left and right of the substrate 21.
By making the cut into a wedge shape, the vertical reinforcing bar 31 can be temporarily fixed to the reinforcing bar holding portion 22 if the vertical reinforcing bar 31 is lightly driven into the wedge during construction.

<16> Reinforcing bar receiving groove.
Reinforcing bar receiving grooves 23 are formed on the upper side of the edge folded on the substrate 21 and on the lower side of the edge folded on the lower side of the substrate 21.
The reinforcing bar receiving groove 23 can be configured by a plate body that protrudes horizontally in a side view from the folded edge, that is, in parallel with the substrate 21 in a bowl shape.
The horizontal reinforcing bar 32 cannot be gripped only by projecting outward, but the anchor plate 20 is directly or indirectly attached to the slope as will be described later. The horizontal rebar 32 can be accommodated to maintain the position.
Since the horizontal reinforcing bar 32 cannot be maintained in the lower reinforcing bar receiving groove 23, the worker binds and fixes it with a binding wire.
The lower reinforcing bar receiving groove 23 can also be formed by folding the edge upward.
In this case, since the lower reinforcing bar receiving groove 23 is formed above the edge, the horizontal reinforcing bar 32 can be placed and maintained without using a binding wire or the like.

DESCRIPTION OF SYMBOLS 10 Short fiber mixed mortar 20 Anchor plate 21 Substrate 22 Reinforcing bar gripping part 23 Reinforcing bar receiving groove 24 Through hole 30 Reinforcing bar 31 Vertical reinforcing bar 32 Horizontal reinforcing bar 40 Rock bolt 50 Isolation wire net 51 Sheath steel pipe 52 Anchor bolt 60 Water permeability mat 70 Adhesion wire net 80 Siloxane-based penetrable water absorption inhibitor 90 Experimental device 91 Load tank 92 Mounting base 93 Deflection measuring device T Test piece

Claims (7)

Rock bolt placement process to reinforce the ground surface,
A reinforcing bar mounting step for fixing the reinforcing bar lattice in the vertical and horizontal directions via the anchor plate to the lock bolt head;
A spraying process of spraying a short fiber mixed mortar mixed with synthetic resin short fibers from above the reinforcing bar lattice,
It consists of a coating process in which a silane / siloxane based permeable water absorption inhibitor is applied to the surface of the sprayed short fiber mixed mortar.
Retaining wall construction method by mortar spraying. The process of claim 1,
The anchor plate fixed to the head of the lock bolt is
It has a substantially U-shaped cross section and is provided with a notch, a bent part, or a protrusion at its end,
The construction method of the retaining wall by the mortar spraying of Claim 1 which fixes a reinforcing bar by this notch part, a bending part, or a processus | protrusion. The process of claim 1,
After spraying the short fiber mixed mortar,
Wash and clean the spray surface with high-pressure washing water,
Then apply a silane-siloxane based permeable water absorption inhibitor,
The construction method of the retaining wall by the mortar spraying of Claim 1. The process of claim 1,
Before the rock bolting process to reinforce the ground surface,
Draining water from natural ground,
It was equipped with a process of stretching a tight wire mesh over the entire construction surface, or a process of spraying mortar or polymer cement mortar.
The construction method of the retaining wall by the mortar spraying of Claim 1. The process of claim 1,
Before the mortar spraying process,
A step of fixing the isolation wire mesh at a position apart from the natural ground by fixing the isolation wire mesh with anchor bolts having a desired length of sheath or pipe or spacer,
The construction method of the retaining wall by the mortar spraying of Claim 1. The process of claim 1,
The synthetic resin short fiber material to be sprayed in the spraying step is a synthetic resin short fiber material having a length of 20 to 50 mm and a thickness of 0.5 to 2 mm, and having a concavo-convex process or a protrusion on the surface thereof.
The construction method of the retaining wall by the mortar spraying of Claim 1. The process of claim 1,
Before the rock bolting process to reinforce the ground surface,
It was equipped with a process of installing a permeable pipe or permeable mat on the slope.
The construction method of the retaining wall by the mortar spraying of Claim 1.

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