JP2005213977A - Slope stabilizing technique - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slope stabilizing technique for securing the stabilization of a steep slope with greater retaining and supporting force than in a conventional technique. <P>SOLUTION: A precast PC beam member 10 with a flexible bag 13 attached over the total length of the back face is prepared long over the total height of a slope. A natural ground is cut to form an artificial slope 100. The PC beam member 10 is lined on the slope 100 with its longitudinal direction corresponding to the true inclination of the slope 100. Concrete or mortar is filled in the flexible bag 13 to put the back face of the PC beam member 10 in close contact with the slope 100 and fix it to the slope with a ground anchor 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a slope stabilization method, and more particularly to technical means for stabilizing a steep slope obtained by cutting a natural ground and cutting it relatively smoothly. In particular, the present invention relates to a technique for protecting slopes where vegetation is inappropriate, or slopes where long-term stability is considered uneasy only by vegetation.

  Conventionally, when a slope of a hard rock or soft rock is likely to collapse or peel off, the slope is protected by a frame work. There is a technology to form a grid-like frame on the slope using a cast-in-place concrete frame for the frame frame, or a frame block or pressure plate made of precast concrete such as a rod, rectangle or cross. (For example, refer to Patent Document 1).

  In addition, these method frames are often fixed to the slope with ground anchors or the like. Furthermore, there is a technique in which a flexible bag body is provided on the back surface of these pressure receiving plates, and concrete is placed in the bag body so that the pressure receiving plate and the slope surface are in close contact (for example, see Patent Documents 2 to 5). ).

However, these conventional slope protection technologies are constructed by arranging a large number of slope frame blocks on the slope, and by assembling each slope frame with fixing means such as a ground anchor on the slope. There was a problem of requiring construction of anchors and the like. On steep slopes, workability was poor and construction took a long time.
JP-A-9-88076 (page 2-3, FIG. 1) Japanese Patent Publication No. 4-77764 (page 2-4, Fig. 3) Japanese Patent Laid-Open No. 10-46588 (page 2-3, FIG. 4) JP 2000-80658 A (page 2-3, FIG. 4) Japanese Patent No. 3214809 (page 2-4, FIG. 2)

  In cliffs and weathered slopes, the slope of the natural slope may indicate the limit stable slope of the natural ground. Therefore, if such a part is cut with a steep slope from the natural ground, it naturally becomes an unstable slope, and long-term stability becomes a problem. In order to form a slope with a steeper slope than such a natural slope, a large deterrent and support force for maintaining the slope stably is required.

  The present invention provides a slope stabilization method that can be expected to have a greater deterring force and supporting force than conventional methods in order to ensure the stability of such a steep slope. With the goal.

  The present invention has been made to solve the above-described problems, and provides a slope stabilization method characterized by taking the following technical means. That is, the present invention prepares a long precast PC (pre-stressed concrete) beam member covering the entire height of the slope with a flexible bag attached to the entire length of the back surface, cuts the natural ground, and creates an artificial slope. The PC beam member is formed by aligning the longitudinal direction of the PC beam member with the true slope of the slope and arranging the PC beam members on the slope, and filling the flexible bag with concrete or mortar. The slope stabilization method is characterized in that the back surface of the steel plate is brought into close contact with the slope and the PC beam member is fixed to the slope with a ground anchor.

  The flexible bag is a bag made of a synthetic resin film, a rubber film or the like, or a bag made of a cloth grout jacket having water permeability, and is attached over the entire length of the back surface of the PC beam member. It is expanded by filling with concrete or mortar, and the PC beam member and the slope are brought into close contact with each other. The flexible bag having water permeability has an advantage of improving strength by promoting dehydration in concrete or mortar.

  Normally, if the PC beam members are arranged at an appropriate mutual interval, no other reinforcement is required, but if necessary, a horizontal member that connects the PC beam members to the side is provided depending on the ground conditions and other conditions. In addition, in the present invention, it is not limited to appropriately reinforce the exposed ground surface.

  The cross section of the PC beam member is U-shaped, the U-shaped open side faces the slope side, the bag body is positioned inside the U-shape, and the pretension type PC is placed in the bag body. If a tension material, a sheath, a pre-grout PC tension material or an unbonded PC tension material is disposed, concrete is placed in the bag body, and prestress is applied to the concrete, a stronger PC beam member is configured. This is preferable because the PC beam member can be brought into close contact with the back ground.

  In addition, as a slope to which the slope stabilization method of the present invention is applied, even if the slope of the slope is a slope that is steeper than a natural slope, stabilization according to the present invention can be achieved, It can also be suitably used for forming side surfaces of roads and the like that are provided.

  According to the present invention, there is an excellent effect that a steep slope can be stably maintained by using a continuous long precast PC beam member with high rigidity of the member.

  Further, according to the present invention, the slope that is expected to require a medium-scale deterrent by the ground anchor can be reasonably protected by the combined use of the ground anchor and the PC beam member structure, Very useful.

  Moreover, in this invention, the rigidity of a PC beam member can be improved, the mutual space | interval of a ground anchor can be taken widely, and it is excellent in terms of workability and economical efficiency.

  In addition, the technique of this invention can also be utilized for reinforcement of the masonry retaining wall which a deformation | transformation produced, and can repair and reinforce a retaining wall easily. Moreover, a leaning retaining wall having a high height can be formed by adjusting the size of the PC beam member.

  In the present invention, a PC beam member made of precast concrete is leaned on a slope, and after filling the gap between the PC beam member and the slope with concrete, a ground anchor is installed to fix the PC beam member to the slope, thereby stabilizing the slope. Plan. In the present invention, a horizontal member that connects the PC beam members to the side may be provided, and prestress may be introduced thereto. In this case, it is possible to widen the frame of the frame (PC beam member), and the economy. The advantages are great in terms of workability and workability. Further, it is possible to cope with a slope having a high slope height by connecting the PC beam members in the vertical direction. In addition, if the transverse member is made of cast-in-place concrete, it can be brought into close contact with the natural ground shape, and flexible support is possible.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 6 shows a part of a front view of an example of a conventional protective structure with a slope, in which a large number of cross-shaped concrete pressure receiving plates 31 are combined and a ground anchor fixing portion 23 is provided at the center of each pressure receiving plate 31. Is. The present invention is a slope protection technique that is completely different from such conventional techniques.

  FIG. 1 shows a slope stabilization method according to an embodiment of the present invention. The slope stabilization method of the present invention will be described with reference to FIG.

  First, the natural ground is cut to form the slope 100. At this time, in order to avoid the collapse of the slope 100 formed in the prior art, as shown in FIG. 5, when the slope 101 is formed by cutting the ground 110, a number of steps are formed above the slope 101. Steps 104, 102, 105, and 103 are formed so that the slope 101 does not collapse or collapse. In the present invention, since the slope is effectively protected, the slope 106 above the cut slope does not require stepping or the like. In addition, the surface of the slope 100 on which the PC beam member is stood is processed as flat as possible.

  Next, foundation concrete 11 is applied to the butt portion.

  The PC beam member 10 is installed on the slope 100 processed to be flat with the longitudinal direction of the PC beam member up and down along the inclination. The PC beam member 10 made of precast concrete has, for example, a U-shaped cross section like a corrugated beam member, and a flexible bag is attached to the back surface of the PC beam member 10. ing. The bag may be a film or may be a water-permeable cloth or other jacket. A cap concrete 12 is applied to the top end of the PC beam member 10.

  FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1. A PC beam member 10 having a U-shaped cross section is disposed on the slope 100, and the entire rear side surface along the longitudinal direction of the PC beam member 10. A flexible bag 13 is provided.

  Concrete 41 or mortar is filled into the bag 13 on the back surface of the PC beam member 10. Thereby, even if the slope 100 is uneven, the back surface of the PC beam member 10 and the slope 100 can be brought into close contact with each other. Further, by filling concrete 41 or mortar into the bag 13 on the back surface of the PC beam member 10, the resistance cross section of the PC beam member 10 is increased, and the adhesion between the PC beam member 10 and the slope 100 is improved. So you can expect great deterrence and support.

  After the PC beam member 10 is installed on the slope as shown in FIG. 1, a predetermined position of the PC beam member 10 is coupled to the ground anchor 20, and the ground anchor 20 is tensioned to fix the PC beam member 10 to the slope 100. To do. The cloud anchor 20 includes a fixing portion 21 fixed to the rock by concrete or the like in the underground hole, and includes a fixing body 22 on the ground surface, and is tension-fixed by a fixing member 23. In FIG. 1, the fixing body 22 is integrated with the PC beam member 10. The number of ground anchors 20 arranged on one PC beam member 10 is preferably as small as possible in consideration of economy and workability.

  If the distance between the ground anchors 20 is increased, it is necessary to increase the rigidity of the PC beam member 10 correspondingly. Therefore, in order to increase the bending rigidity of the PC beam member 10 and reduce the installation weight during construction, the PC beam member 10 has a corrugated or U-shaped beam member shape as shown in FIG. It is preferable.

  When the resistance of the precast PC beam member 10 is insufficient, as shown in FIGS. 3 and 4, the flexible cast body 13 provided in the recess on the back side of the PC beam member 10 having a U-shaped cross section is used. For example, a PC tension member 40 of a pretension type is arranged and tensioned, and then concrete 41 is placed. After the concrete is hardened, the tension of the PC tension member is released and prestress is introduced into the concrete 41. The proof stress of 10 can be increased. In place of the pre-tension type PC tension member 40, the sheath is disposed in the flexible bag 13, and after placing the concrete 41, the PC tension member 40 is inserted into the sheath. It is also possible to be tense and introduce prestress in a post-tension manner. Moreover, it is good also as using a pre-grout PC tendon and an unbond tendon.

  FIG. 4 shows a structure in which fixing members 14 and 15 provided with tension fixing portions 42 and 43 of PC tension members are formed at both ends of the PC beam member 10. Further, the ground anchor 20 and its tension fixing body 22 and fixing member 23 are also shown.

  The present invention can also be applied to installation or repair of a leaning retaining wall 50 as shown in FIGS. The leaning type retaining wall 50 is a gravity type retaining wall that is mainly used for a cut portion and cannot stand independently, and is a retaining wall of a type that resists earth pressure by its own weight while being supported by a natural ground or a backfiller 90. When such a leaning retaining wall 50 is newly installed, the PC beam member 10 and the ground anchor 20 are used to resist earth pressure. The concrete plate 91 is constructed so that the soil does not collapse between the PC beam members 10. The foundation concrete 11 is formed on the base portions of the PC beam member 10 and the concrete plate 91. The concrete plate 91 may be a precast plate or a cast-in-place concrete.

  The application range of the leaning retaining wall 50 is usually 3 to 8 m in height of the slope 100, but it can be applied by increasing the rigidity of the PC beam member 10 or adjusting the number and strength of the ground anchors 20. The range can be 8 m or more.

  When repairing a leaning retaining wall or other sloped structure that has been damaged by a disaster or the like, the PC beam members 10 are arranged at intervals of 2 to 3 m on the surface of an existing leaning type retaining wall or the like, and the back surface of the PC beam member 10 Concrete or mortar is filled in, the core is drilled, the ground anchor 20 is installed, and the PC beam member 10 and the ground anchor 20 newly installed against the earth pressure are resisted.

  Next, an embodiment (design example) of the present invention will be described with reference to FIGS.

The design conditions of the example are as follows. (Refer to FIGS. 9 to 11 for symbols)
Backside earth and sand internal friction angle φ = 30 °
Back soil adhesion C = 0
Unit volume weight of earth and sand γ = 18kN / m ³
Angles of ground collapse estimation lines θ = 50 ° and δ = 65 °
Next, earth load calculation calculation is performed.

Sliding clod area (A), the dimensions a = 10.3 m shown in FIG. 9, when b = 3.7m A = 1/2 × 3.7 × 10.3 = 19.06m 2
Sliding soil mass (W)
W = 19.06 x 18 = 343.0 kN / m
The sliding force along the estimated decay line is
W · sin θ = 343.0 × 0.766 = 262.7 kN / m
Estimated collapse line normal collapse force is
W · cos θ = 343.0 × 0.643 = 220.5 kN / m
It becomes. In the calculation of the ground anchor, if the inclination angle α, angle β, and angle ε of the ground anchor are determined as shown in FIG. 10 and the inclination angle α of the ground anchor is 20 degrees, β and ε are as follows.

β = α + θ = 20 ° + 50 ° = 70 °
ε = α + δ = 20 ° + 65 ° = 85 °
The target safety factor shown in equation (1) is Fs = 1.5,
tanφ = tan30 = 0.577
sin β = sin 70 = 0.940
cos β = cos 70 = 0.342
sinε = sin85 = 0.996
Is set, the tensile force T (see FIG. 10) of the ground anchor can be calculated as shown in Equation (2).

  When the ground anchors are arranged in two stages at intervals of 3.0 m in the horizontal direction, the tensile force Td and the horizontal component force P per ground anchor are as follows.

Td = 301.6 × 3/2 stage = 452.4 kN / line P = Td · sinε = 452.4 × 0.996 = 450.7 KN
The PC beam member 10 is considered as a beam on the elastic bearing 65 as shown in FIG. The vertical spring constant of the elastic bearing is a lateral ground reaction force coefficient (= 15000 kN / m ³ ) estimated from the assumed soil type (sand gravel with an N value of about 10). The cross-sectional force generated in the member when the tension T was applied to the rating points 62 and 63 at distances c = 3 m and d = 3 m from 64, respectively. As a result, it was found that using a member having a cross-sectional performance comparable to that of the prestressed concrete corrugated sheet pile JIS SW400B as the PC beam member.

It is sectional drawing of the slope which shows the Example of this invention. It is AA arrow sectional drawing of FIG. It is a cross-sectional view of the precast PC beam member of an Example. It is a longitudinal cross-sectional view of the precast PC beam member of an Example. It is a cross-sectional view which shows the slope cut of a prior art. It is a front view which shows the example of the slope restraining member of a prior art. It is a longitudinal cross-sectional view of a leaning type retaining wall. It is a front view of a leaning type retaining wall. It is explanatory drawing of an Example. It is explanatory drawing of an Example. It is explanatory drawing of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 PC beam member 11 Foundation concrete 12 Shade concrete 13 Bag body 14, 15 Fixing member 20 Ground anchor 21 Fixing part 22 Fixing body 23 Fixing member 40 PC tension material 41 Concrete 42, 43 Tension fixing part 50 Leaning type retaining wall 61, 62 Both ends 63, 64 Rating 65 Elastic bearing 90 Backfilling 91 Concrete plate 100, 101 Slope 102, 103, 104, 105 Step 106 Slope 110 Ground

Claims (3)

  Prepare a long precast PC beam member with a flexible bag attached to the entire length of the back surface over the entire height of the slope, cut a natural ground to form an artificial slope, and adjust the longitudinal direction of the beam member The PC beam members are arranged on the slope in accordance with the true slope of the slope, and the flexible bag body is filled with concrete or mortar, and the back surface of the PC beam member is brought into close contact with the slope. A slope stabilization method characterized by fixing beam members to slopes with ground anchors.   The cross section of the PC beam member is U-shaped, the U-shaped open side is arranged facing the slope side, the bag body is positioned inside the U-shape, and a pretension type is placed in the bag body. 2. Slope stability according to claim 1, wherein a PC tension material, a sheath, a pre-grout PC tension material, or an unbonded PC tension material is disposed, concrete is placed in the bag body, and prestress is applied to the concrete. Chemical method.   The slope stabilization method according to claim 1 or 2, wherein the slope of the slope is steeper than the natural slope.

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