JP2002275907A - Stabilization construction method for slope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stabilization construction method for a slope having a large profit on the sides of workability and profitability by improving the applicability of a micro pile construction method to the stabilization of the slope. SOLUTION: The first micro piles 12 are driven at each step 4 and 5 in a vertical pile shape with the object of the small steps 4 and 5 on its midway to a cut slope and slopes 6 and 7 in sections just above these small steps and the second micro piles 12 to each slope 6 and 7 in an inclined shaft shape respectively. The first micro piles 11 are driven in a row at regular pitches on each small step 4 and 5 and the second micro piles 12 in a row at regular pitches along each small step 4 and 5 respectively, and the pile head sections of the micro piles 11 and 12 are rigidly coupled mutually by footing beams 13 among each row and in each row and coupled piles are manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilization method for stabilizing a slope, particularly a cut slope.

[0002]

2. Description of the Related Art As a method of stabilizing a slope, a reinforcing bar is inserted into a hole drilled in the ground, a hardening material grout is injected, and the reinforcing bar is fixed to the ground. After drilling holes, insert an anchor into the casing, pull out the casing, and then inject a hardening material grout into the hole to fix the anchor to the ground, cast a steel pipe, ground anchor method Deterrent pile construction methods for deterrent piles have been conventionally used.

[0003]

However, according to the above-mentioned reinforcing bar reinforced earth method, in addition to using a reinforcing bar having a small diameter (approximately D20 to 30), both the drilling diameter and the drilling length are considerably small (drilling diameter: 40). 6060 mm, drilling length: about 5 m), the thickness of the grout fixing layer is also small, and the strength against pulling, bending, shearing, etc. cannot be expected so much, and it is limited to small-scale slope stabilization measures. Was. In addition, according to the above-mentioned ground anchor method, a large rigid frame or cross block is required as a pressure receiving plate to apply a large prestress to the anchor, and a large number of man-hours and time are required for placing them. And the construction becomes troublesome. Further, although the anchor thus cast has a sufficient strength against tension, it has a low strength against bending and shear, and there is also a problem that a deterrent effect against landslide cannot be expected. On the other hand, according to the above-mentioned deterrent pile method, although the deterrent effect against landslides is sufficient by using large-diameter steel pipes, the burden of material costs due to the use of large-diameter steel pipes is large, and large-scale construction machinery is also required. There have been many problems in terms of economic efficiency when applied to stabilization of small to medium scale slopes such as cut slopes such as roads.

A micropile for fixing a steel pipe to the ground by inserting a steel pipe having a diameter of 100 to 300 mm into a hole drilled in the ground and then injecting hardening material grout into a space around the steel pipe under pressure. A construction method is conventionally known. According to this micropile method, the construction is simple and the strong steel pipe and the thick grout fixing layer are integrated to exhibit a large supporting force, so if this is applied to the slope stabilization method, It is expected that the above-mentioned problems of the conventional method can be solved. However, this micropile generally has insufficient bending strength (horizontal supporting force) as compared with tensile strength, and if it is simply cast on a slope, it may not be possible to obtain a sufficient deterrent effect against landslides. In order to eliminate this anxiety, a large number of micropiles must be cast on the slope at a small pitch (about 1 m), and the precious advantage (economical efficiency) of the micropile method described above is lost. Will be.

The present invention has been made in view of the above technical background, and an object of the present invention is to improve the applicability of the micropile method for stabilizing slopes, thereby improving workability and economic efficiency. It is an object of the present invention to provide a method for stabilizing a large slope, which is advantageous.

[0006]

In order to achieve the above object, the present invention is to provide a vertical pile of micro piles in a row on a middle step of a cut slope, and a part just above the small step. Micro piles are laid in a row in a slant pile shape with respect to the slope, and thereafter, the pile heads of the micro piles between each row and in each row are rigidly connected by a foundation beam. In the slope stabilization method performed in this way,
The vertical pile-shaped micropile and the inclined pile-shaped micropile form a group pile, exhibiting a large strength against tension, bending, shearing, etc., and a sufficient landslide suppression effect. Also, since the micro piles are cast in two rows in the middle of the slope, the number of micro piles can be significantly reduced, and the small steps in the cut slope can be used efficiently. Micro pile can be cast. in this case,
By arranging the vertical pile-shaped micropile and the inclined pile-shaped micropile mutually in a staggered manner, even if the pitch of the micropile in each row is set to be large, the effect of suppressing landslides is substantially reduced. It is not reduced, and the number of micro piles to be cast can be further reduced.

According to the present invention, prior to placing a micropile, an improved pillar is formed in the ground by a high-pressure jet stirring method,
The micropile may be cast in the improved pillar. In this case, in addition to the large-diameter improvement column and the micropile integrally exhibiting a large supporting force, the improvement column greatly contributes to the stabilization of the ground,
It can be sufficiently stabilized even for soil containing collapsible soil.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a state of a slope stabilized according to the first embodiment of the present invention. The stabilization method according to the first embodiment is intended for a cut slope 3 formed by excavating an existing ground 2 to construct a road (planned road) 1. The earth slope 3 includes three slopes 6, 7, 8 divided by two small steps 4, 5 here.

In the first embodiment, with respect to the two small steps 4 and 5 and the slopes 6 and 7 immediately above these small steps, a direction substantially perpendicular to each of the small steps 4 and 5 is set. The first micropile 11 is formed (in a vertical pile shape), and the second micropile 12 is formed in a substantially vertical direction with respect to each of the slopes 6 and 7 (in a slanted pile shape). I have. The first micropile 11 is cast in a row at a predetermined pitch on each of the small steps 4 and 5, while the second micropile 12 is cast in a row at a predetermined pitch along each of the small steps 4 and 5. . Also, the first and second micro piles 11,
Numeral 12 is sufficiently deeper than the slip surfaces A and B behind the cut slope 2. That is, the vertical pile-shaped first micropile 11 and the inclined pile-shaped second micropile 12 are arranged in two rows in the middle of the cut slope 3 so as to reach the slip planes A and B behind. Has been cast. Thus, the pile heads of the first and second micropiles 11 and 12 are rigidly connected to each other by the foundation beams 13 between each row and within each row. The foundation beam 13 is, for example, cast in place from reinforced concrete. The first and second micro piles 11 and 12 are configured as a pile by the foundation beam 13. Here, since the slip surface C with respect to the upper slope 6 is considerably shallow, a general-purpose reinforcing-bar-reinforced earth method for driving a plurality of reinforcing bars 14 is applied to the slope 6 here.

The cut slope 3 of the road 1 is usually
Is formed by stepwise excavating the ground 2 adjacent to the bottom from the upper side to the lower side. In this case, the boundary of each step is generally set on a plane including the small steps 4 and 5 as shown in FIG. 1. Therefore, here, the ground 2 is divided into three regions I, II and III. Will be excavated.

Therefore, in the present embodiment, the construction is performed stepwise in accordance with the excavation of the ground 2 described above. Specifically, first, when excavation of the upper region I from the upper side of the ground 2 to the upper small step 4 is completed, the small step 4
The construction machine is loaded on the excavation bottom including the vertical pile 4 and the vertical micro pile 11 and the inclined micro pile 12 are arranged in a row on the small step 4 and the slope 6 immediately above the small step 4. The pile heads of the micropiles 11 and 12 are rigidly connected to each other by the foundation beam 13 to complete the assembled pile. Next, excavation of the middle region II from the upper small step 4 to the lower small step 5 is carried out, the construction machine is again put on the excavated bottom surface, and the small step 5 and the slope 7 immediately above the small step 5 are described above. A vertical pile-shaped first micropile 11 and a slanted pile-shaped second micropile 12 are placed in a row, and the micropile 11,
Twelve pile heads are rigidly connected to each other by the foundation beam 13 to complete the assembled pile. After that, excavation of the lower section III from the lower step 5 to the planned road 1 is performed, and the cut slope 3 is reinforced by the piles and has sufficient deterrent effect against landslide.
Is completed.

Here, the first micropile 1 having a vertical pile shape is used.
As shown in FIG. 2, it is desirable that the 1 and the slant pile-shaped second micropile 12 are arranged in a zigzag manner. In this case, the pitch P1 of the first micropile 11 and the pitch P2 of the second micropile 12 are, for example, 1 to 1.
The distance S between the row of the first micropile 11 and the row of the second micropile 12 is about 2 m, for example, 0.5 to 1 m.
Set to about. When a micropile is used as a deterrent pile, it is usually necessary to set the pitch at about 1 m. However, when the piles are arranged in a staggered manner as described above, the micropiles 11 and 12 in each row are increased as described above. (1-2
m) Even if it is set, a sufficient deterrent effect can be exerted, and the number of micropiles 11 and 12 to be cast can be further reduced.

The construction procedure for placing the micropiles 11, 12 will be specifically described. First, as shown in FIGS. 3A and 4, a plurality of check valves 20 are provided on the pipe wall. A steel pipe 21 having the following formula is prepared.
A drilling rod 25 having a drilling tool 24 at the tip thereof, in which an eccentric enlarged bit 22 and a down-the-hole hammer 23 are connected, is inserted. Then, the steel pipe 21 and the drilling rod 25 are integrally supported by a construction machine (a drilling machine) (not shown), and while the drilling rod 25 is rotated using the steel pipe 21 as a casing, the slope 6, The steel pipe (casing) 21 is penetrated into the ground by making a hole so as to be substantially perpendicular to 7 (or the small steps 4 and 5). The down-the-hole hammer 23 has a function of applying an impact load to the eccentric enlarged bit 22 by activating the hammer portion by air pressure. By using the down-the-hole hammer 23 and the eccentric enlarged bit 22 together, the ground is smaller than the steel pipe 21. The large-diameter hole 26 is efficiently drilled. At this time, the excavated shear generated by the drilling is discharged to the outside through a flow hole (not shown) penetrating the eccentric enlarged bit 22 through an annular passage 27 between the casing 21 and the drilling rod 25. . The steel pipe 21 has an outer diameter of about 200 to 300 mm as an example. The drilling is performed to a predetermined depth while adding the steel pipe 21, and after the drilling is completed, the drilling rod 2 is formed.
5 is pulled out of the steel pipe 21 together with the drilling tool 24, leaving only the steel pipe 21 in the hole 26.

Next, as shown in FIGS. 3B and 4, an injector 30 is inserted into the steel pipe 21. The injector 30 is called a single packer, and includes one swelling body 31 swelling by air pressure and a discharge nozzle 32. The swelling body 31 extends from a compressed air source on the ground. An air hose 33 is connected to the discharge nozzle 32 and a grout pipe 34 extending from a grout supply source on the ground. The injecting machine 30 first inserts the steel pipe 21 to the deepest position, and sends compressed air to the swelling body 31 through the air hose 33 at that position to swell the steel.
Fix its position with respect to 1. Then grout tube 3
4, grout cement milk to the discharge nozzle 32,
A grout of hardening material such as cement mortar is pumped. Then, the hardened material grout is discharged from the discharge nozzle 32 and injected under pressure from the front end opening of the steel pipe 21 into the ground in front, and a part of the grout also goes outside the front end of the steel pipe 21, Of the swollen body 31 in the front area. Then, when the internal pressure increases due to the fill-up into the steel pipe 21, the check valve 20 is opened and the hardening material grout is radiated radially around the steel pipe 21, and is injected under pressure into the ground around the steel pipe 21. The discharge pressure of the hardening material grout from the discharge nozzle 32 is, for example, 1 to 2 MPa (10 to 20 kgf / c
m ² ) is set to a considerably high pressure, so that the hardening material grout penetrates into the ground, and especially the ground is made up of cobble-mixed gravel, talus sedimentary layers, or easily collapsed rock If it penetrates well into these.

In this manner, a thick grout layer 35 containing earth and sand is formed in the front region and the peripheral region of the steel pipe 21, and the grout layer 35 is used to connect the injector 30 to the arrangement pitch of the check valves 20. By repeatedly discharging the hardening material grout while pulling up at a pitch corresponding to the above, the material gradually expands upward as shown in FIG. When the grout layer 35 expands to the vicinity of the small steps 4 and 5 or the slopes 6 and 7, the discharge of the hardening material grout from the injector 30 is stopped, and at the same time, the air hose 33 connected to the swelling body 31.
Is switched to the atmosphere side to reduce the diameter of the swollen body 31,
From the injection machine 30. The grout layer 35 is hardened after a predetermined time elapses, is transformed into a fixing layer 36 as shown in FIG. 4, and the micropiles 11, 12 in which the steel pipe 21 and the fixing layer 36 are integrated (FIG. 1). Is installed. It should be noted that a double packer having a pair of swelling bodies may be used as the injecting machine 30 instead of the single packer described above. However, in this case, since the inside of the steel pipe 21 becomes hollow, it is desirable to insert a reinforcing core material such as a reinforcing steel bar, an H-section steel, a small-diameter steel pipe or the like into the steel pipe 21.

FIG. 5 shows a slope reinforcing method according to a second embodiment of the present invention. The feature of the second embodiment is that, prior to the first and second micropiles 11 and 12, the high pressure is applied to the ground under the small steps 4 and 5 or the slopes 6 and 7. The point is that an improved column 40 is formed by the injection stirring method, and the micropiles 11 and 12 are cast into the improved column 40.

In order to form the improved pillar 40 by the high-pressure jet stirring method, as shown in FIGS.
After drilling by using a steel pipe (here, it is not necessary to have the check valve 20) 21 and a drilling rod 25, as shown in FIG. 5, in a hole 26 formed by the drilling, An injection rod (single pipe or double pipe) 42 having an injection nozzle 41 at the tip is inserted. Then, the injection rod 42 is rotated and lowered, and when the injection nozzle 41 at the tip thereof reaches a predetermined depth, an ultra-high pressure (30 to 40 M
(Approximately Pa) of water (compressed air may be used in some cases), and ultra high-pressure water is jetted from the jet nozzle 41 in the horizontal direction. The ground is cut and agitated (pre-cutting) over a wide area by the jet of the ultra-high pressure water, and a large-diameter cutting and stirring layer 43 is formed in the ground. The cutting and stirring layer 43 responds to the rotation and lowering of the injection rod 42. To expand downwards.
The surplus slime generated at this time is discharged to the ground through a space around the injection rod 42.

After the pre-cutting to a position slightly deeper than the setting depth of the micropiles 11, 12, the ultrahigh-pressure water is grouted (cement milk: water / cement ratio W / C = about 60 to 70). Switching, injection nozzle 4
While injecting grout of 1 to ultra high pressure (about 40 MPa) in the horizontal direction (in some cases, compressed air is also used), the injection rod 42 is rotated and raised as shown in FIG. By the high pressure injection of the grout, the cutting stirring layer 4
The earth and sand in 3 is stirred and mixed with the grout to change into a grout mixed layer 44, and this grout mixed layer 44 is
2 expands upwards according to the rotation and ascent. At this time,
Excess slime is guided and discharged to the ground. At this stage, since the injection of water is stopped, the degree of the guided discharge is small, and wasteful consumption of grout is suppressed. When the formation of the grout mixed layer 44 reaches the upper limit of the planned improvement area in this way, the supply of grout to the injection rod 42 is stopped, and the injection rod 42 is pulled out from the ground and cured as it is. By this curing, the grout mixed layer 44 is hardened, and the large-diameter improved pillar 40 described above is formed in the ground as shown in FIG.

Next, as shown in FIG. 5, the vertical hole 46 is excavated in the improved pillar 40 formed as described above, for example, using an earth auger 45. The excavation of the vertical hole 46 is performed to the vicinity of the bottom surface of the improved column 40, and after the excavation is completed, the earth auger 45 is pulled out from the improved column 40. Then, FIG.
As shown in FIG.
0, and further, the injector 30 is inserted into the steel pipe 21, and the hardened material grout is passed around the steel pipe 21 through the check valve 20 as shown in FIG. 4 and FIG. The steel pipe 21 and the fixing layer 3 are injected under pressure.
Micro piles 11 and 12 in which 6 are integrated are cast. As the steel pipe 21, as shown in FIG. 5, a knotted steel pipe having a large number of nodes 47 in the axial direction may be used.
2, the supporting force is further improved.

[0020]

As described above, according to the slope stabilization method according to the present invention, the pile heads of the vertical pile-shaped micropile and the inclined pile-shaped micropile are rigidly connected to each other. As a result, it exerts great strength against tension, bending, shearing, etc., and the deterrent effect against landslide is also sufficient,
The applicability of the micropile method to the stabilization of the slope is significantly improved. In addition, since the micro piles are cast in two rows in the middle of the slope, the number of micro piles can be minimized, and the micro piles can be efficiently used by using the small steps in the middle of the cut slope. Since the pile can be cast, the good workability and economic efficiency of the micropile method can be fully utilized, and the utility value of the present invention is generally large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a state of a slope stabilized according to a first embodiment of the present invention.

FIG. 2 is a plan view schematically showing a driving state of the micropile driving in the first embodiment.

FIG. 3 is a cross-sectional view showing a drilling step and a grout injection step in micropile driving.

FIG. 4 is a sectional view sequentially showing a micropile placing step in the first embodiment.

FIG. 5 is a sectional view sequentially showing an improved column forming step and a micropile placing step in the second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Road 2 Ground 3 Cut slope 4, 5 Small step 6, 7, 8 Slope 11 1st micropile (vertical pile-shaped micropile) 12 2nd micropile (sloped pile-shaped micropile) 13 Foundation beam 43 Improved pillar

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) E02D 7/00 E02D 7/00 AZ 7/24 7/24 (72) Inventor Takeo Miki Osaka-shi, Osaka 4-1-1 Koraibashi, Chuo-ku, Toyo Construction Co., Ltd. (72) Inventor Nozomi 4-1-1 Koraibashi, Chuo-ku, Osaka, Osaka Toyo Construction Co., Ltd. (72) Inventor Kazuya Goda Osaka, Osaka 4-1-1, Komyo-bashi, Chuo-ku Toyo Construction Co., Ltd. (72) Tetsuo Matsuda 2-15-6 Otsuka, Bunkyo-ku, Tokyo F-term in the Foundation Advanced Construction Technology Center 2D041 AA02 AA03 BA20 DA12 DA13 DB02 EB09 EC02 FA03 FA05 FA15 2D044 DB11 EA01 2D050 AA06 CA02 CB03 CB16 CB42

Claims (3)

[Claims] 1. A micropile is laid in a row in the form of a vertical pile on a small step in the middle of a cut slope, and a micropile is laid in a row on a slope immediately above the small step in a slanted pile. A stabilizing method for slopes, wherein the pile heads of the micropiles are rigidly connected to each other between the rows and in the rows by foundation beams. 2. The slope stabilizing method according to claim 1, wherein the vertical pile-shaped micropile and the inclined pile-shaped micropile are arranged in a zigzag manner. 3. The method according to claim 1, wherein prior to placing the micropile, an improved pillar is formed in the ground by a high-pressure jet stirring method, and the micropile is placed in the improved pillar. 2. The method for stabilizing a slope according to 2.