Lightweight embankment structure and its construction method

Abstract

This solves the construction and construction management challenges associated with conventional lightweight embankment structures. [Solution] A lightweight embankment structure 1 comprising a foundation block 3 constructed in front of the sloping ground 2a, a retaining wall 4 consisting of multiple PC panels 4a constructed above the foundation block 3, and a lightweight embankment layer 5 constructed in the area enclosed by the sloping ground 2a and the retaining wall 4, and comprising unbonded PC steel rods 4d embedded in the PC panels 4a, unbonded PC steel rods 3a embedded in the foundation block 3, and anchor reinforcement bars 7 fastened to ground reinforcement bolts 6 driven into the sloping ground 2a.

Description

Technical Field

[0001] The present invention relates to the structure of a lightweight embankment structure and a method for constructing a lightweight embankment structure.

Background Art

[0002] Conventionally, in this technical field, a lightweight embankment structure disclosed in Japanese Patent No. 5113342 has been widely known. This lightweight embankment structure includes a sloping natural ground in which shear prevention bolts are driven at predetermined intervals on a slope, a horizontal natural ground extending horizontally from the lowermost end of the sloping natural ground, a foundation block fixed to the horizontal natural ground with small-diameter anchors, a retaining wall composed of PC boards (precast concrete panels) laminated above the foundation block, and a lightweight embankment layer laminated in a recess surrounded by the retaining wall, the sloping natural ground, and the horizontal natural ground. Two bearing plates are installed at intervals on the head of the shear prevention bolt. One bearing plate is tightly fixed to the sloping natural ground to stabilize the sloping natural ground, and the other bearing plate is embedded in the lightweight embankment to integrate the sloping natural ground and the lightweight embankment. Also, PC steel bars for applying a tensile force are inserted into through holes provided in the retaining wall in the height direction of the retaining wall and are tightly connected to the lower PC board.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the conventional lightweight embankment structure configured as described above sufficiently ensures structural safety, some problems can be pointed out in terms of construction or construction management. (1) The through-holes in the PC plate are filled with grout after tension is applied to the inserted PC steel rods, but the filling process is time-consuming and labor-intensive, and checking the amount of grout required a high level of skill. (2) Since the shear prevention bolts are installed with their heads protruding 50 cm or more from the ground, they become obstacles during subsequent construction work such as retaining wall construction or embankment construction. [Means for solving the problem]

[0005] To address the aforementioned problems, a first aspect of the present invention provides a lightweight embankment structure comprising a foundation block constructed in the natural ground, a retaining wall constructed above the foundation block, and a lightweight embankment layer constructed in a section enclosed by the natural ground and the retaining wall, wherein the retaining wall is composed of a plurality of PC panels connected in the vertical direction, the PC panels are equipped with embedded unbonded PC steel rods and connecting fittings, the foundation block is equipped with embedded unbonded PC steel rods, and ground reinforcement bolts are driven into the natural ground, with anchors connected to the tip side of the ground reinforcement bolts.

[0006] A second aspect of the present invention is a method for constructing a lightweight embankment structure, comprising the steps of: constructing the foundation block in the ground; driving the ground reinforcement bolts into the ground; installing a PC slab above the foundation block; fastening the unbonded PC steel rods embedded in the foundation block and the connecting fittings embedded in the PC slab to introduce prestress and connect the foundation block and the PC slab; connecting the anchors to the tip side of the ground reinforcement bolts; constructing a lightweight embankment layer in the area surrounded by the ground and the PC slab; installing a new PC slab above the PC slab; fastening the unbonded PC steel rods embedded in the PC slab and the connecting fittings embedded in the new PC slab to introduce prestress and connect the PC slab and the new PC slab; and constructing a lightweight embankment layer in the area surrounded by the ground and the new PC slab. [Effects of the Invention]

[0007] The present invention, through the means for solving the aforementioned problems, is expected to have the following effects. (1) By eliminating through-holes in the PC panels and adopting unbonded PC steel bars, grout filling work after fastening is unnecessary, reducing the time and labor required for filling work and eliminating the need for skilled work required to check the amount of filling. In addition, the watertightness of the PC panels is ensured by eliminating through-holes. (2) By eliminating the shear prevention bolts that have two bearing plates installed on the head and adopting ground reinforcement bolts that connect to the anchor reinforcement, the protrusion of the bolt heads is eliminated, thus ensuring workability in other processes. [Brief explanation of the drawing]

[0008] [Figure 1] Diagram showing the structure of a lightweight embankment structure. [Figure 2] Diagram showing the structure of a PC panel. [Figure 3] Diagram showing the structure of the connecting fittings [Figure 4] Diagram showing the structure of the foundation block when the retaining wall is a straight wall. [Figure 5] Diagram showing the structure of the foundation block when the retaining wall is a sloped wall. [Figure 6] Diagram showing a structure to prevent the foundation blocks from lifting. [Figure 7] Diagram showing a conventional structure to prevent the foundation blocks from lifting. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the lightweight embankment structure and its construction method according to the present invention will be described based on the drawings.

[0010] [Structure of lightweight embankment structures] The structure of the lightweight embankment structure 1 will be explained with reference to Figures 1 to 3. The lightweight embankment structure 1 consists of the natural ground 2, a foundation block 3, a retaining wall 4, and a lightweight embankment layer 5 constructed in the area enclosed by the natural ground 2 and the retaining wall 4.

[0011] The natural ground 2 consists of a sloped natural ground 2a, which is shaped like a slope, and a horizontal natural ground 2b, which is shaped like a horizontal surface. Multiple ground reinforcement bolts 6 are driven into the sloped natural ground 2a at intervals, and L-shaped anchor bars 7 are connected to the tips of the ground reinforcement bolts 6. The foundation block 3 is constructed on the horizontal natural ground 2b.

[0012] The ground reinforcement bolts 6 prevent the slope ground 2a from sliding and collapsing. After the ground reinforcement bolts 6 are inserted into the boreholes 8 in the slope ground 2a, grout 9 is injected into the gap between the bolts and the boreholes 8. Furthermore, the heads are anchored by a square washer 10 and a coupler 11 attached to the part that protrudes from the slope ground 2a. The anchor reinforcement bars 7 are fastened to the ground reinforcement bolts 6 by being screwed into the coupler 11. Since the anchor reinforcement bars 7 are embedded in the lightweight embankment layer 5 after the completion of the lightweight embankment structure 1, the ground reinforcement bolts 6 fastened to the anchor reinforcement bars 7 work together to firmly integrate the slope ground 2a and the lightweight embankment layer 5. In addition to the ground reinforcement bolts 6, other anchoring members such as rock bolts and permanent anchors can also be used.

[0013] The foundation block 3 is the foundation member of the retaining wall 4 and is constructed from cast-in-place concrete or precast concrete. The foundation block 3 has tapered anchoring holes 15 that decrease in diameter towards the bottom and are continuous with anchor holes 12 drilled into the horizontal ground 2b. Small-diameter anchors 13 are inserted into the anchoring holes 15 and anchor holes 12 and fixed to the horizontal ground 2b by anchor grout 14. In addition, an unbonded PC steel bar 3a, which is unbonded in the middle section sandwiched between the threaded sections at both ends, is embedded in the foundation block 3. The threaded section at the upper end protrudes from the top surface of the foundation block 3, and the threaded section at the lower end embedded in the foundation block 3 is secured to an anchor plate 3b with a nut.

[0014] The retaining wall 4 is constructed by stacking a plurality of PC boards 4a in the vertical direction. The PC board 4a is a precast concrete plate-like body presenting a horizontally long rectangular shape when viewed from the front, with a standard specification of 1000 mm in length, 2000 mm in width, and 160 mm or 225 mm in depth. As shown in FIGS. 2 and 3, a connecting fitting 4c composed of metal plates on four sides, top, bottom, left, and right is embedded in a working hole 4b opening to the ground side of the PC board 4a. An unbonded PC steel bar 4d is embedded inside the PC board 4a. The unbonded PC steel bar 4d has screw threads processed at both upper and lower ends, and the intermediate part sandwiched between the screw parts at both ends is unbonded. The screw part on the upper end side of the unbonded PC steel bar 4d protrudes from the upper surface of the PC board 4a, and the screw part on the lower end side is fastened with a nut 4f to the upper surface connecting hole 4e of the connecting fitting 4c. When connecting the upper PC board 4a and the lower PC board 4a, the screw part on the upper end side of the PC steel bar 4d on the lower stage is fastened with a nut 4f to the lower surface connecting hole 4g of the connecting fitting 4c on the upper stage.

[0015] The lightweight embankment layer 5 is constructed by placing lightweight embankment materials every time the PC boards 4a are connected upward.

[0016] 〔Construction method of embankment structure〕 The construction method of the lightweight embankment structure 1 will be described. First, holes 8 are drilled at appropriate intervals on the entire surface of the sloping ground 2a, the ground reinforcement bolts 6 are inserted, and grout 9 is filled. After confirming the strength of the grout 9, the angle washer 10 and the coupler 11 are installed to tighten the head of the ground reinforcement bolt 6 to stabilize the sloping ground 2a.

[0017] Next, the foundation block 3 is fixed. Anchor holes 12 are drilled in the horizontal ground 2b, after filling with anchor grout 14, the small-diameter anchor 13 is pressed in. The foundation block 3 is installed so that the upper end of the small-diameter anchor 13 protruding from the horizontal ground 2b is inserted into the fixing hole 15, and the fixing hole 15 is filled with anchor grout 14 to fix the foundation block 3 to the horizontal ground 2b.

[0018] Next, install the PC board 4a. Fasten the threaded portion of the unbonded PC steel bar 3a protruding from the upper surface of the foundation block 3 to the lower surface connection hole 4g of the connecting fitting 4c of the first-stage PC board 4a with a nut 4f. In this way, the foundation block 3 and the first-stage PC board 4a are firmly connected. For the installation of the second-stage PC board 4a, install the second-stage PC board 4a so that the upper-end side threaded portion of the unbonded PC steel bar 4d of the first stage passes through the lower surface connection hole 4g of the connecting fitting 4c of the second stage, and fasten the upper-end side threaded portion with a nut 4f. In this way, the first-stage PC board 4a and the second-stage PC board 4a are firmly connected. For the subsequent third stage and onwards, install them step by step while fastening the unbonded PC steel bar 4d and the connecting fitting 4c.

[0019] Next, construct the lightweight backfill layer 5. The lightweight backfill layer 5 is constructed step by step each time a PC board 4a is installed in one stage. The first-stage lightweight backfill layer 5 is constructed by placing lightweight backfill material in the section surrounded by the first-stage PC board 4a, the slope natural ground 2a, and the foundation block 3. The second-stage lightweight backfill layer 5 is constructed by placing lightweight backfill material in the section surrounded by the second-stage PC board 4a, the slope natural ground 2a, and the first-stage lightweight backfill layer 5. The lightweight backfill layer 5 for the third stage and onwards is also constructed in the same way by placing lightweight backfill material in the section surrounded by the newly installed PC board 4a, the slope natural ground 2a, and the lower-stage lightweight backfill layer 5 constructed previously. Since the lightweight backfill material solidifies in a state including the anchor bars 7 tightly connected to the slope natural ground 2a via the ground reinforcement bolts 6, the lightweight backfill layer 5 and the slope natural ground 2a are firmly joined via the anchor bars 7.

[0020] Through the above construction work, a lightweight retaining structure 1 in which the retaining wall 4 composed of a plurality of PC boards 4a, the slope natural ground 2a, and the lightweight backfill layer 5 are firmly joined is constructed.

[0021] Regarding the form of the retaining wall 4, in addition to the straight-wall type with a vertical wall surface as described above, there is an inclined-wall type with a wall surface inclined towards the natural ground side. As shown in FIGS. 4 and 5, the difference between the straight-wall type and the inclined-wall type lies in that the shape of the top end of the foundation block 3 is a horizontal plane for one and an inclined plane for the other, but the structure of the PC board 4a and other structures are the same.

[0022] Finally, referring to Figures 6 and 7, the function and effect of the tapered shape of the anchoring holes 15 in the foundation block 3 will be explained. As described above, the lightweight embankment structure 1 is a structure in which the retaining wall 4, the slope ground 2a, and the lightweight embankment layer 5 are firmly connected. However, since the retaining wall 4 is a cantilever structure with the foundation block 3 as the fixed end, it is unavoidable that an outward bending moment acts on the retaining wall 4 when the lightweight embankment material is poured and hardened. As a result, the foundation block 3, which is tightly connected to the retaining wall 4, will experience uplift, attempting to separate from the horizontal ground 2b. To prevent this uplift of the foundation block 3, conventionally, as shown in Figure 7, anchor holes 101 and insertion holes 105 were provided on the uplift side of the foundation block 100, a small-diameter anchor 102 was inserted, and after filling with anchor grout 106, it was anchored using a square washer 103 and a nut 104.

[0023] On the other hand, as shown in Figure 6, the foundation block 3 of the present invention is anchored by inserting a small-diameter anchor 13 into a tapered anchoring hole 15 that is continuous with the anchor drilling hole 12, and filling the anchor drilling hole 12 and the anchoring hole 15 with anchor grout 14. In conventional designs, the shape of the through hole 105 is cylindrical without a taper, so simply filling it with anchor grout 106 does not provide sufficient resistance between the through hole 105 and the anchor grout 106, requiring a square washer 103 and a nut 104 to suppress uplift. However, by making the anchoring hole 15 tapered, the anchor grout 14 injected into the anchoring hole 15 is filled in a tapered shape, creating a force where the tapered anchor grout 14 pushes downwards, preventing the foundation block 3 from uplifting. This makes it possible to effectively prevent the foundation block 3 from uplifting without using a square washer and a nut. [Explanation of Symbols]

[0024] 1. Lightweight embankment structure 2. Natural terrain 2a Sloping ground 2b Horizontal ground 3. Foundation Blocks 3a Unbonded PC steel bar 3b Anchor plate 4. Retaining wall 4a PC board 4b working hole 4c Connecting fittings 4D Unbonded PC Steel Bar 4e Top connection hole 4f nut 4g Bottom connection hole 5. Lightweight embankment layer 6. Ground reinforcement bolts 7 Anchor reinforcing bars 8. Drilling 9 Grout 10 Square Washer 11 Couplers 12 Anchor drilling 13 Small diameter anchors 14 Anchor Grout 15 Fixing holes 100 base blocks 101 Anchor drilling 102 Small Diameter Anchors 103 Square Washer 104 Nut 105 Through hole 106 Anchor Grout

Claims

1. Foundation blocks constructed in the natural ground, A retaining wall constructed above the aforementioned foundation block, The area enclosed by the aforementioned natural ground and the aforementioned retaining wall comprises a lightweight embankment layer, The retaining wall is composed of a plurality of PC panels connected in the vertical direction, and the PC panels are equipped with embedded unbonded PC steel bars and connectors. The foundation block is equipped with embedded unbonded PC steel bars. Reinforcement bolts are driven into the ground, and anchors are connected to the tips of the reinforcement bolts. Lightweight embankment structure.

2. The aforementioned foundation block is provided with tapered anchoring holes. A lightweight embankment structure according to claim 1.

3. The aforementioned foundation block is equipped with an anchor for fixing it to the ground, The anchor is inserted through an anchor bore drilled in the ground and a fixing hole continuous with the anchor bore drilled. A lightweight embankment structure according to claim 2.

4. A method for constructing a lightweight embankment structure according to claim 1, The process of constructing the foundation block on the aforementioned ground, The process of driving the ground reinforcement bolts into the ground, The process of installing a PC panel on top of the aforementioned foundation block, The process involves fastening the unbonded PC steel bar embedded in the foundation block and the connecting fitting embedded in the PC plate to introduce prestress, and connecting the foundation block and the PC plate. The process of connecting the anchor to the tip side of the ground reinforcement bolt, The process of constructing a lightweight embankment layer in the area enclosed by the aforementioned natural ground and the aforementioned PC slab, The process of installing a new PC board on top of the aforementioned PC board, The process involves fastening the unbonded PC steel bar embedded in the PC plate and the connector embedded in the new PC plate to introduce prestress, and connecting the PC plate and the new PC plate, The process includes constructing a lightweight embankment layer in the area enclosed by the aforementioned natural ground and the new PC slab, Method for constructing lightweight embankment structures.

5. A method for constructing a lightweight embankment structure according to claim 1, In the step preceding the process of constructing a lightweight embankment layer in the area surrounded by the natural ground and the PC panels, the anchor is connected to the tip side of the natural ground reinforcement bolt. Method for constructing lightweight embankment structures.

6. A method for constructing a lightweight embankment structure according to claim 3, The process of inserting the anchor through the anchoring hole and the anchor drilling hole, The process includes filling the gap between the anchoring hole and the anchor drilling hole with grout, Method for constructing lightweight embankment structures.

Images