JP6899057B2 - Foundation block of concrete block for retaining wall - Google Patents

Description

The present invention relates to a foundation block of a large concrete block related to the construction of a civil engineering structure such as a retaining wall.

Civil engineering structure construction using ordinary concrete masonry blocks (holding length of about 35 cm to 50 cm) is carried out by the "experience-based design method" for the ground with a relatively stable back surface. In recent years, precast products have been widely used in civil engineering work in order to ensure a certain level of quality while saving labor and shortening the construction period. As for the block retaining wall, the construction of a large concrete block for checking the stability is frequently performed based on the "stability calculation of the leaning type retaining wall".

Among various concrete blocks, the large concrete block for building a retaining wall that has self-supporting structure has a front slope of 3 to 5 minutes (height: width 1: 0.3 to 1: 0.5). Is the main. Construction of the retaining wall using such a block is performed by the following steps shown in FIG.
(1) For the block installation foundation, dig the floor, level the foundation, and crush the foundation if necessary.
(2) A concrete foundation (FIG. 7 (1)) having a width required for block installation and a required thickness is placed on the ground leveling in (1).
(3) After the concrete foundation is hardened, the front and rear parts of the concrete are backfilled, the first stage block is placed, and the joint reinforcing bars provided at predetermined intervals in the foundation concrete are included in the block inclusion space. Fill the filling concrete up to the casting line in the middle of the height of the block shown in (1).
(4) After laying a backfill material such as crushed stone on the back surface of the block, the second-stage block is placed, and the filling concrete is filled up to the casting line in the same manner as described above.
By repeating the above work, the block product of the required height is formed and the structure is constructed. Further, FIG. 7 (2) shows a case where a conventional foundation block is used instead of the foundation concrete. When the foundation block is used, as shown in the figure, the foundation block and the main body block are provided with a slip-preventing convex portion and a slip-preventing concave portion.

In such a conventional construction method, when the foundation concrete is used, it is necessary to provide a joint reinforcing bar on the joint surface between the foundation structure and the concrete block as described above in order to ensure the integrity of the structure. This joint reinforcing bar is arranged in the filled concrete portion of the block installed above when the foundation concrete is placed. However, if the joint reinforcing bars are placed at a thickness of 20 cm to 40 cm of the foundation concrete, the fixing length of the reinforcing bars (about 40 cm under certain conditions) specified in the concrete standard specification (JSCE, 2012, p333) cannot be secured. , The integrity of the concrete foundation and the concrete block has become an issue. In addition, when the foundation block is used as the foundation, the structure is such that the foundation block and the main body block can be fitted with unevenness that secures frictional resistance, but the block foundation is only placed on the ground. The issue of frictional resistance between the ground and the structure remains.

As a foundation block for the retaining wall, the block is provided with through holes in the vertical direction, and the concrete placed in the through holes provides unevenness between the foundation blocks on the left and right sides while ensuring friction with the foundation ground. Therefore, an invention for integrating the left and right blocks has been proposed (Japanese Patent Laid-Open No. 2012-202202), but the frictional resistance between the foundation ground and the foundation block cannot be said to be sufficient.

Japanese Unexamined Patent Publication No. 2012-202202

"Road earthwork retaining wall construction guideline" Japan Road Association July 2012

Regarding the construction of the foundation of a large concrete block for construction of civil engineering structures, when the foundation concrete is placed at the site and the main body block is installed, there is a problem with the integrity of the foundation concrete and the main body block, so the foundation block is used. When installing the main body block, there is a problem that the frictional resistance between the foundation ground and the foundation block is insufficient.

It is a foundation block that forms the foundation of a retaining wall that is constructed by connecting self-supporting concrete blocks in the horizontal or vertical direction and filling the enclosed space with concrete. Equipped with a connecting material that connects the materials
The upper surfaces of the front surface material and the rear surface material have horizontal planes of the same height, and the lower surfaces have the same flat surface.
A foundation block having a penetrating portion between the foundation block installation surface and the lower surface of the connecting material so that the filled concrete to be cast can pass under the connecting material.

The foundation block, wherein the same plane formed by the lower surfaces of the front surface material and the rear surface material is an inclined surface in which the lower surface of the front surface material is at a high position.

The foundation block, the foundation block having a penetrating portion between the foundation block installation surface and the lower surface of the rear surface material so that the filled concrete to be cast can pass under the rear surface material.

The foundation block, the foundation block having a penetrating portion between the foundation block installation surface and the lower surface of the front surface material so that the filled concrete to be cast can pass under the front surface material.

The stability of concrete structures such as retaining walls is examined by three factors: "overturn", "sliding", and "ground bearing capacity". The foundation block of the present invention is intended to improve sliding, which is a weak point of precast concrete products. When using precast concrete products for the construction of the foundation, the frictional resistance is lower than that of cast-in-place concrete. Regarding the foundation block of the present invention, the contact surface between the foundation block and the installation ground surface (foundation block installation surface) is almost only the flat surface portion of the front surface material and the rear surface material, and the other surfaces of the bottom surface of the foundation block are all one surface. Covered with cast-in-place concrete with one-piece filled concrete. Therefore, in this foundation block, it is possible to obtain the same frictional resistance as cast-in-place concrete while using a precast concrete product, which contributes to the stability of "sliding".
It is also an effective means of ensuring stability regarding "sliding" even when installed on a sloping ground surface. In addition, when backfilling concrete is placed at the same time as filling concrete by providing penetrations below the rear surface material and below the front surface material, the contact surface of the cast-in-place concrete should be expanded. It is effective when more stability is required.

FIG. 1 is an explanatory diagram regarding the structure of a horizontal plane type foundation block. (Example 1) FIG. 2 is an explanatory diagram relating to the installation of a horizontal surface type foundation block. (Example 1) FIG. 3 is an explanatory diagram regarding the structure of the main body block. (Examples 1 and 2) FIG. 4 is an explanatory view regarding the structure of the inclined surface type foundation block. (Example 2) FIG. 5 is an explanatory view regarding installation of an inclined surface type foundation block. (Example 2) FIG. 6 is an explanatory view of a back-penetrating type and a front-penetrating type foundation block. (Examples 3 and 4) FIG. 7 is an explanatory diagram relating to the construction of a conventional foundation portion.

Generally, regarding the construction of the retaining wall 6, the space side of the retaining wall is referred to as "front" of the retaining wall, and the ground side is referred to as "rear" or "back". In the present invention, regarding the portion of the block used for constructing a civil engineering structure such as a retaining wall, a member installed on the space side is referred to as a front member 2 and a member installed on the ground side is referred to as a rear surface member 3. Further, a member that connects the front surface material and the rear surface material is referred to as a connecting material 4. The self-supporting concrete block of the present invention is a block that can be installed on a flat mounting surface without falling, and is a block that does not need to be installed while being balanced like a masonry block. The foundation concrete block 1 (hereinafter, also referred to as a foundation block) in the present invention means a concrete block for installing the lowermost block when stacking the concrete blocks. With respect to the foundation block, the concrete block is also referred to as a main body concrete block 5 or a main body block. Regarding the gradient, the rise from the horizontal is said to be 0.1 to 0.9 in the horizontal direction, while 1.0 in the vertical direction is called a 1 to 9 minute gradient.

Regarding the foundation block 1 in the present invention, the main body block 5 mounted on the upper surface is a self-standing block, and the mounting surface is a horizontal plane except for the convex portion 11 which is fitted with the concave portion 58 of the upper block and serves as a slip stopper. To form. In the following embodiment, it is shown that the lower surface of the front surface member 51 and the lower surface of the rear surface member 52, which are the horizontal planes of the main body block, are placed on the mounting surface of the foundation block. Retaining wall construction using large blocks is generally used for gradients of about 3 to 5 minutes, but in the following, a 5-minute gradient will be shown as an example. In addition, the main body block is about 1 m in length and width x 1.5 to 2.0 m (excluding the 1/2 adjustment block) when viewed from the front, and is reserved (front surface of front member 51 and rear surface of rear surface member 52). It is a so-called large concrete block with an interval of about 0.65 m to 2.0 m. The foundation blocks have a shape that conforms to those main body blocks. Equipment such as cranes is indispensable for the installation of blocks, and anchors and rings for hanging metal fittings are also installed for foundation blocks, but they are omitted.

FIG. 1 shows a structural diagram of the foundation block 1 installed on the horizontal foundation ground 63. From the plan view of FIG. 1 (1), the front view of (2), and the rear view of (5), the upper surfaces of the front member 2, the rear surface member 3, and the two connecting members 4 except for the slip-preventing convex portion 11. It shows that they form the same horizontal plane. The hollow portion in the center sandwiched between the two connecting members forms one space through the connecting member penetrating portion 43 below the connecting member from the bottom view and (4) side view of FIGS. 1 (3) and mainly the front surface. It is shown that only the lower surface of the material and the rear surface material is in contact with the foundation ground. The penetrating portion below the connecting material has a height through which the coarse aggregate of ready-mixed concrete (diameter 20 mm to 40 mm) passes, and is inserted from the hollow portion or the space portion between the left and right continuous foundation blocks. The filled concrete 56 spreads over the foundation block inclusion space 12, and after hardening, becomes an integral concrete block in contact with the foundation base, and the frictional strength between the structure and the ground can be obtained in the same manner as the cast-in-place concrete.

The resistance to sliding used to check the stability of the retaining wall 6 regarding "sliding" is the frictional force and adhesive force acting on the structure and the foundation ground 63 on the lower surface of the structure, and the foundation ground is rock or gravel soil. In the case of, it is said that only the frictional force acts without considering the adhesive force (Non-Patent Document 1p70). The frictional force is obtained by multiplying the vertical load acting on the contact surface by the tangent of the friction angle φ (hereinafter, tanφ is also referred to as the friction coefficient μ) (p69, p64, p113), and the friction angle is In the case of cast-in-place concrete retaining wall, it is φ, whereas in the case of precast concrete retaining wall, it is 2/3 × φ (p69). However, in the first embodiment of the present invention, in the bottom view shown in FIG. 1 (3), the area ratio of the filled concrete to the contact surface of the entire foundation structure with the foundation ground is about 67%. Assuming that the reduction rate of the friction angle due to the use of precast is 2/3 of the above, and if the reduction rate can be corrected by the area ratio, it becomes (2/3 × 0.33 + 1 × 0.67), and the reduction rate of the friction angle is 0. It becomes .89, and the numerical value of the improvement effect is estimated. It should be noted that this is to expand the contact area when the foundation block 1 in the conventional invention described in "0005" is provided with a through hole in the vertical direction and the friction with the foundation ground is secured by the concrete placed in the through hole. It is not such an improvement. Rather than partially providing a contact surface, it is a filling of ready-mixed concrete that is sufficiently compacted and has a single contact surface on the foundation ground. It cannot be taken into consideration by the contact area ratio. Regarding the integrity of the filling concrete 56, as described in the following "0019", the filling concrete is cast at the same time as the filling concrete of the main body block 5, and the I-shaped main body block and the foundation block 1 shown in FIG. 3 are placed. Even in the space, each contact surface is only the front surface material 2 and the rear surface material 3, and the filling concrete filled in the inclusion space between the main body block and the foundation block is cast as an integral body that encloses the connecting member 4. ..

FIG. 2 shows the structure and construction procedure of the retaining wall 6 including the installation of the foundation block 1 and the main body block 5 shown in FIG. The structure consists of four main blocks stacked on the foundation block, and the front surface 61 of the retaining wall becomes a mountain retaining wall with a 5-minute gradient. The front view from the front of the retaining wall is shown in FIG. 2 (2). FIG. 2 (1) is a cross-sectional view taken along the line AA. A simple structural diagram of the main body block is shown in FIG. The I-shaped main body block is composed of one connecting member 53 that connects the front surface member 51 and the rear surface member 52 of the main body block. Regarding the vertical connection of the foundation block and the main body block, the front surface material 2 and the rear surface material 3 of the foundation block are in contact with the front surface material and the rear surface material of the main body block in a horizontal plane. However, on the horizontal plane, four convex portions 11 of the foundation block and four concave portions 58 of the main body block that fit the convex portions are installed in consideration of lateral slip resistance and workability of the foundation block and the main body block. The foundation block inclusion space 12 and the main body block inclusion space 55 are integrated inclusion spaces except for the front material and the rear surface material, and all the inclusion spaces are continuous filling concrete. Regarding the connectivity between the main body blocks, the space of the block inclusion and the inclusion space of the left and right continuous blocks are passed through the through holes in the upper and lower parts and the central portion of the connecting material 53 of the front material 51 and the rear surface material 52 of the main body block. Are integrated, and for the vertically connected blocks, the space is an integral inclusion space except for the upper and lower surfaces of the front surface material and the rear surface material of the main body block.
Further, in this example, as shown in FIG. 2 (2), the front view is a so-called staggered arrangement in which the foundation block and the main body block and between the main body blocks are alternately installed. This is effective in further strengthening the unity between blocks. This is feasible because the slip-prevention recesses and protrusions are arranged at a position 1/4 of the width of the block from the side surface of the block. Further, in order to ensure the straightness of the fastening formwork 68 installation surface on the side side of the retaining wall, a 1/2 adjustment block 54 is provided on the foundation block and the main body block.

The construction procedure is shown below based on FIG. 2 (1).
(1) Cut the original ground as shown in a and b.
(2) Excavate the floor where the foundation block 1 is installed.
(3) The lower floor excavation surface 66 is leveled, and if necessary, foundation crushed stone and leveling concrete 63 are performed.
(4) Install the foundation block 1. The front surface 23 and the rear surface 34 of the foundation block are backfilled.
(5) The main body block 5 of the first stage is installed.
(6) The backfilling 67 up to the backfilling line and the backfilling crushed stone or the chestnut stone 57 are charged and compacted.
(7) Filling concrete 56 of the foundation block and the main body block is put up to the line h shown in FIG. 2 (1) and compacted.
(8) The work of (5) to (6) is repeated until the uppermost stage is constructed, and the top concrete 69 is placed.
In addition, in FIG. 6 and the above-mentioned work, the drainage from the back of the retaining wall to the front is omitted.

In the above procedure, the backfilling 67 after the foundation block 1 is installed takes into consideration the stability when the main body block 5 is placed, and the same applies to the backfilling before the filling concrete 56 is placed and the backfilling material 57 is put in. Is. Regarding the filled concrete, the input line of the main body block of the first stage is cast at the same time for the purpose of establishing the integrity of the foundation block and the foundation ground, and the integrity of the foundation block and the main body block, and after hardening, it is placed. As described above, it becomes one continuous concrete block, and the foundation block and the main body block can be integrated. It should be noted that placing filled concrete from the input line in the middle of the main body block to the next input line connected to the same input line compensates for the weakness of the structure of the contact surface between the upper and lower main body blocks. Because.

FIG. 4 shows a structural diagram of the foundation block 1 installed on the inclined foundation ground 63. The shapes of the upper surfaces of the plan view of FIG. 4 (1), the front view of (2), and the rear view of (5) are the same as those of FIG. The same horizontal plane is formed except for the slip stopper convex portion 11. From the side view of FIG. 4 (4) and the cross-sectional view of FIG. 4 (6), the anteroposterior angle (inclination angle 14) of the foundation ground is about 11.3 °, which has an effect of enhancing safety regarding sliding.

The effects on the stability of sliding when the bottom surface of the foundation block 1 is an inclined surface are shown below. Assuming that the vertical load acting on the bottom surface of the foundation block is Q _v and the horizontal load is Q _h , the safety factor of sliding when the bottom surface is horizontal is
Obtained by μ × Q _v / Q _h ,
When the bottom surface is an inclined surface and the inclination angle 14 is θ, it becomes μ × (Q _v × cos θ + Q _h × sin θ) / (Q _h × cos θ −Q _v × sin θ).
Therefore, as compared with the case where the bottom surface is horizontal, Q _h × sin θ / cos θ is added _{for resistance to sliding, and Q v} × sin θ / cos θ is reduced for sliding power, so that the effect can be clearly understood. However, providing an inclined surface on the bottom surface causes the sliding surface related to earth pressure from the back surface of the structure to recede, which increases instability with respect to overturning. Therefore, in this example, it is opposite to the retaining wall. We use -11.3 °, which is a gradient of 50% in the direction (ratio of aspect ratio is 1: 5), but consider the gradient according to the ground condition, the height of the retaining wall, and the ground condition on the back. Is desirable.

FIG. 5 shows the construction state of the retaining wall 6 using the foundation block 1 installed on the sloped ground having the inclination angle 14 of θ. As shown in FIG. 5, it is used when an embankment portion (between the original ground 64 and the rear surface 62 of the retaining wall) is provided on the back surface of the roadside retaining wall or the like. This is because, in the embankment portion, a large sliding force acts on the bottom surface of the foundation block as compared with the retaining wall shown in FIG. 2, and the sliding of the structure is often unstable. When a foundation block is used in the case of having an embankment portion, as shown in FIG. 5, it is desirable that the foundation ground 63 has sufficient strength in soil or rock foundation.

6 (1), (2), (3), (7) show a structural diagram of a foundation block 1 installed on a horizontal foundation ground with a penetration portion below the front surface material 2 and the rear surface material 3. .. FIG. 6 (1) The penetrating portion 25 shown below the front material in the front view secures a height on the foundation ground that allows the filled concrete 56 to pass through, similarly to the connecting material penetrating portion 43. In this example, the rear surface material penetrating portion 35 is also provided as shown in the rear view of FIG. 6 (2). Filled concrete 56 can be cast into the front material penetrating portion at the same time as the backfill portion on the front surface of the foundation block, and an increase in resistance to sliding due to an increase in the cast-in-place concrete surface on the lower surface of the foundation block can be expected. Further, when the concrete of the backfill portion of the front surface 23 and the retaining wall can be expected to be integrated, the toe of the retaining wall, which is the fulcrum of the overturning moment related to the examination of the safety of overturning, may be forward to enhance the safety. .. As for the penetration part below the back surface material, the backfill concrete of the backfilling part of the foundation block is also filled with concrete at the same time, so that the resistance to sliding due to the increase of the cast-in-place concrete surface on the lower surface of the foundation block can be expected to increase. In this example, a penetrating portion is provided in both the front surface material and the rear surface material, but either one of the penetrating portions has an effect. Regarding the construction procedure, regarding (4), (5), (6), and (7) of the above "0020", after installing the foundation block of (4), continue to install the main block of (5), and then continue ( The filling concrete of 7) and the backfilling of (4) will be performed at the same time. Therefore, it is desirable to decide whether or not to adopt it in consideration of the safety in construction and the ground bearing capacity at the contact surface between the foundation block and the foundation ground.

In the foundation block 1 installed on the inclined foundation ground in FIGS. 6 (4), (5), (6), and (8), the front material 2 and the rear surface material 3 are provided with the front material penetrating portion 25 and the rear surface material 35. The structural diagram of the thing is shown.

1 Foundation block, 11 Anti-slip convex part, 12 Foundation block inclusion space, 13 1/2 Adjustment foundation block, 14 Tilt angle (θ)
2 Front material, 21 Front material top surface, 22 Front material bottom surface, 23 Front material front surface, 24 Front material rear surface, 25 Front material penetration 3 Rear surface material, 31 Rear surface material top surface, 32 Rear surface material bottom surface, 33 Rear surface material front surface, 34 Rear surface Material rear surface, 35 Rear surface material penetration part 4 Connecting material, 41 Connecting material upper surface, 42 Connecting material bottom surface, 43 Connecting material penetrating part 5 Main body block, 51 Main body block front material, 52 Main body block rear surface material, 53 Main body block connecting material, 54 1/2 adjustment main body block, 55 main body block inclusion space, 56 filled concrete, 57 backfill material, 58 slip prevention uneven part
6 Retaining wall, 61 Retaining wall front, 62 Retaining wall rear surface, 63 Foundation ground, foundation crushed stone or leveled concrete, 64 original ground, 65 cut slope surface, 66 floor excavation surface, 67 backfill, 68 retaining mold, 69 Top concrete, 70 Foundation concrete, 71 Retaining wall, 72 Foundation bedrock line

Claims (3)

A concrete retaining wall constructed by connecting large self-supporting concrete blocks in the horizontal or vertical direction and filling the space contained in the concrete block with concrete without arranging backfill concrete on the back side of the concrete block. And
The foundation block installed on the foundation of the retaining wall is
It is equipped with a front and rear surface materials that face each other and a connecting material that connects the two materials.
The upper surfaces of the front surface material and the rear surface material have horizontal planes of the same height, and the lower surfaces have the same flat surface.
Between the installation surface of the foundation block and the lower surface of the connecting material, there is a penetrating portion through which the filled concrete to be cast can pass under the connecting material .
A concrete retaining wall provided with a foundation block having a penetration portion between the foundation block installation surface and the lower surface of the rear surface material so that the filled concrete to be cast can pass under the rear surface material . A concrete retaining wall constructed by connecting large self-supporting concrete blocks in the horizontal or vertical direction and filling the space contained in the concrete block with concrete without arranging backfill concrete on the back side of the concrete block. And
The foundation block installed on the foundation of the retaining wall is
It is equipped with a front and rear surface materials that face each other and a connecting material that connects the two materials.
The upper surfaces of the front surface material and the rear surface material have horizontal planes of the same height, and the lower surfaces have the same flat surface.
Between the installation surface of the foundation block and the lower surface of the connecting material, there is a penetrating portion through which the filled concrete to be cast can pass under the connecting material .
A concrete retaining wall having a foundation block having a penetration portion between the foundation block installation surface and the lower surface of the front surface material so that the filled concrete to be cast can pass under the front surface material . A concrete retaining wall provided with a foundation block according to claim 1 or 2, wherein the same flat surface of the front surface material and the lower surface of the rear surface material is an inclined surface in which the lower surface of the front surface material is at a high position.

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