JPH07138968A - Concrete block - Google Patents

Abstract

PURPOSE:To make it possible to construct a curved retaining wall of a revetment wall simply and quickly. CONSTITUTION:Two projections 26 are formed on the upper surface 24 of a block 22, and two recesses 30 are formed on the lower surface 28. The projections 26 of a downward block are stored in the recesses 30 of a blocked upward block, and both of them are put in an interlocking state. Even in the case axes are intersected in the horizontal direction between both up and down blocks, an interlocking state between the projections 26 and recesses 30 is maintained. Coupling bars as reinforcements are inserted into insertion holes 36, and in block bond for each step, blocks are successively fixed to form a block wall. Because both sides are formed in a circular shape, even in the case a curved block wall is formed, a face joint between both sides can be maintained in a fine state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stackable large-scale concrete block used for a retaining wall, a revetment wall or the like.

[0002]

2. Description of the Related Art Retaining walls for roads and seawalls for rivers are 1 m ³
It is constructed by stacking multiple large-sized concrete blocks. Generally, this kind of block wall is formed by stacking blocks while shifting the block rows of each stage by half blocks.

A conventional general concrete block is
The upper surface has an elongated protrusion extending in the left-right direction (transverse direction), and the lower surface has an elongated groove extending in the left-right direction. That is, the upper block is stacked over two lower blocks adjacent to each other, and at this time, the elongated groove portion of the upper block is fitted into the elongated protrusion of the lower block, whereby the upper block is Positioned.

In order to form a curved retaining wall or the like, it is necessary to fit between the blocks while slightly intersecting the virtual axis of the elongated protrusion with the virtual axis of the elongated protrusion. For this reason, in the conventional concrete block, the groove width of the elongated groove portion is often formed to be slightly larger than the groove width.

An example of a conventional block stacking method will be described with reference to FIG. 6 (A). First, after the first-stage block row is stacked, each rebar hole is provided with a length corresponding to the height of the block wall. The reinforcing bar 10 which it has is inserted. Next, while passing the upright reinforcing bar 10 through the reinforcing bar hole 12, the block 14 of the next stage
Lowering and stacking, backing material 16 on the back side of block 14
Etc., or mortar or the like is injected into the reinforcing bar hole 12 to fix the block 14. At that time, in order to prevent the block 14 from falling down to the back side, the block 14 itself is hung by a crane, and the support 20 is arranged between the block 14 and the natural ground 18. Then, such a process is repeated until the final block.

[0006]

However, when a curved retaining wall or revetment wall is formed using the above-mentioned conventional concrete block, the connection between blocks (connection between upper and lower blocks displaced by a half block) can be performed smoothly and It was difficult to do so reliably. That is, in the conventional art, as described above, the upper and lower elongated projections and the lower elongated groove are fitted to each other for vertical connection, but basically, in both fitted states, relative rotation can be freely performed. Since no special structure is adopted, it was difficult to apply a block wall with a particularly large degree of bending. Even if there is a certain amount of play in the width of the elongated groove, it takes skill to finish a curved block wall smoothly and beautifully. There has been a demand for a concrete block that can be formed into.

Further, in the above conventional block stacking method,
Since it was necessary to support the block stacking and to hang it up with a crane for a long time, it was complicated and reduced the work efficiency. Therefore, there has been a demand for a block stacking method that does not require support.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a concrete block capable of easily and quickly forming a curved retaining wall or a revetment wall.

Another object of the present invention is to provide a block stacking method that does not require support in block stacking at each stage.

[0010]

In order to achieve the above object, the invention according to claim 1 is a concrete block to be stacked in a block, wherein at least one convex shape provided on one of the upper surface or the lower surface. And at least one concave portion provided on the other surface of the upper surface or the lower surface and accommodating the convex portion, wherein the convex portion and the concave portion are relatively engaged with each other. It is characterized by having a shape capable of rotating.

According to a second aspect of the present invention, in a concrete block to be stacked in blocks, two convex portions provided on the upper surface side by side in the left-right direction and having a rotationally symmetrical shape,
Two concave portions that are provided on the lower surface side by side in the left-right direction and that have a hollow shape that extends in the left-right direction and that accommodates the convex portions;
It is characterized by having.

The invention according to claim 3 is characterized in that one side surface is formed into a cylindrical convex curved surface, and the other side surface is formed into a concave curved surface corresponding to the shape of the convex curved surface.

According to a fourth aspect of the present invention, an insertion hole is formed which vertically penetrates the convex portion and the concave portion.

The invention according to claim 5 has a connecting step of inserting a connecting rod having a length corresponding to the insertion hole into the insertion hole and connecting a lower end portion thereof to an upper end portion of the lower connection rod. The connecting step is performed for each block stack of each stage.

[0015]

According to the structure of the first aspect, since the convex portion and the concave portion are formed in a shape capable of relative rotation in the engaged state, basically with respect to the lower block. It is possible to tilt the upper block in the horizontal direction at an arbitrary angle. Then, even in such a tilted state, a reliable connection is secured between the upper and lower blocks. Therefore, in the case of forming a curved block wall, it is possible to easily and neatly finish the block wall without complicated work as in the conventional case.

According to the second aspect of the invention, the convex portion is formed in a rotationally symmetrical shape, and the concave portion is formed in a hollow shape that extends in the left-right direction to accommodate the convex portion. Therefore, as described above. The upper block can be connected to the lower block in the horizontal direction at an arbitrary angle, and the concave portion is provided with a certain amount of play, so that the upper wall or the lower wall of the block wall inclined while curving is curved. The generated distortion can be eliminated. That is, when forming a curved block wall, the path lengths are different between the upper side and the lower side, so that the distortion of the block wall due to such a difference in the path lengths can be prevented.

Here, the convex portion can be formed in, for example, a convex hemispherical shape, while the concave portion can be formed in a concave hemispherical shape extending in the left-right direction.

According to the third aspect of the present invention, since the both side surfaces are formed in the convex curved surface and the concave curved surface, it is possible to avoid the side surface collision between the blocks adjacent to each other when forming the curved block wall. Therefore, good surface bonding can be secured.

According to the structure of the fourth aspect, the insertion hole is formed, and the connecting rod as the divided reinforcing bar is inserted into the insertion hole.

According to the fifth aspect of the present invention, since the connecting step is performed every time the blocks are stacked in each stage, the stacked blocks can be fixed with a connecting rod, and a conventional support member is unnecessary. Becomes In addition, this can shorten the time for hanging with a crane.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram showing the overall construction of a concrete block according to the present invention. This block 22 is used for a retaining wall of a road or a revetment wall of a river, and is a so-called large-sized concrete block.

On the upper surface 24 of the block 22, two convex portions 26 are formed side by side in the left-right direction (X direction). The convex portion 26 has a bowl shape or a hemispherical shape. As will be described later, as the convex portion 26, for example, a conical shape or a disc shape can be adopted as long as it has a so-called rotationally symmetrical shape. Also,
Even if it is D-shaped when viewed from above, it may have a substantially rotationally symmetrical shape. The specific structure of the convex portion 26 will be described later with reference to FIG.

The lower surface 28 of the block 22 has the above-mentioned 2
Two concave portions 30 are formed immediately below the two convex portions 26. The concave portion 30 has a shape into which the convex portion 26 is fitted, and specifically has a hemispherical hollow shape extending in the left-right direction.

That is, in the state where the convex portion 26 and the concave portion 30 are engaged with each other, theoretically, the two can rotate relative to each other, which enables the connection between the bent blocks as described later.

A circular bolt accommodating hole 32 is formed in the convex portion 26 at a constant depth, and also in the concave portion 30, the bolt accommodating hole 34 is constant in depth from the bottom surface of the concave portion 30. Has been formed. An insertion hole 36 is formed which connects the bolt storage hole 32 and the bolt storage hole 34 to each other and spreads downward. Here, as will be described later, the insertion hole 36 is a through hole for inserting the connecting rod, and when a curved block wall is formed, the vertical axis is deviated between the upper block and the lower block. Correspondingly, the lower side of the insertion hole 36 is formed to be divergent.

The front surface 38 of the block 22 is shown as a flat surface in FIG. 1, but it is not limited to this, for example, a rough surface structure may be adopted, or it can be easily hung by a crane. A groove surface may be formed so as to be recessed inward.

Although the back surface 40 of the block 22 is a flat surface in this embodiment, it may be formed with a butt portion protruding in the back direction. Further, the entire surface and the rear surface may have the same shape.

In the present embodiment, the right side surface 41 of the block 22 is formed of a cylindrical curved surface having a curvature of a constant radius R (for example, 375 mm) centered on the vertical central axis of the right convex portion 26. ing. That is, the central portion projects in the shape of a convex cylinder.

On the other hand, the left side surface 42 of the block 22 is formed in a concave cylindrical surface shape. That is, it is formed in a concave arc shape with a curvature corresponding to that of the right side surface 41, in the present embodiment, the same curvature as that of the right side surface 41. By forming the two side surfaces with the same curvature in this way, the bondability of the side surfaces between adjacent blocks can be improved, as will be described later, regardless of the inter-block connection angle. When the both side surfaces are curved surfaces having the same curvature as described above, it is necessary to make the convex and concave polarities of the left and right surfaces of the odd-numbered block and the even-numbered block opposite to each other. It should be noted that in order to avoid providing such a type of block, it is conceivable that the curvature of the side surface on the concave surface side is made gentle, or the surfaces on both side surfaces can be tilted slightly rearward to allow play.

In the present embodiment, the upper surface 24 and the lower surface 28 are flat except for the convex portion 26 and the concave portion 30,
Surface bonding of the upper surface and the lower surface is performed between the upper and lower blocks. If necessary, a drainage groove can be provided on the side surface, for example.

In FIG. 1, in the present embodiment, the width (length) in the X direction is 1500 mm, and the distance between the central axes of the two convex portions 26 is 750 mm. And the right side surface 41
The center of curvature of is coincident with the center axis of the right convex portion 26, and its radius of curvature R is 375 mm. The radius of curvature R of the left side surface is also 375 mm. Height in Z direction is 666 mm
And the width in the Y direction is 350 mm.

Next, the convex portion 26 and the concave portion 3 will be described with reference to FIG.
The structure of 0 will be described in detail. 2A shows a top view of the convex portion 26, and FIG. 2B shows the convex portion 26.
A cross-sectional view of is shown. As described above, the convex portion 26
Is formed in a hemispherical shape as a whole, and a bolt insertion hole 32 is formed in the central portion thereof and is communicated with an insertion hole 36. The bolt insertion hole 32 is provided near the upper opening of the insertion hole 36.
Is formed with a shoulder portion 32A that forms the bottom surface of the joint, and a coupling bolt to be described later is arranged on the shoulder portion 32A. The convex portion 26 has an outer circle radius of 250 mm, and the upper opening of the bolt housing hole 32 has a radius of 100 mm. The radius of the circle on the lower side of the bolt storage hole 32 is 25 mm. The depth of the bolt storage hole 32 is 50 mm.

As shown in FIG. 2, by forming the convex portion 26 into a gentle bowl shape, it is possible to prevent the convex portion from being damaged due to collision of members during transportation of the block, and between the blocks. The connection can be smoothly performed.

FIG. 3A shows a sectional view of the concave portion 30, and FIG. 3B shows a plan view of the concave portion 30 as seen from the bottom side. As described above, the concave portion 30 has a shape in which a concave hemispherical recess is extended in the left-right direction, and specifically, the hemispherical concave groove is 40 mm in the left-right direction.
(T) A stretched shape is formed. A bolt accommodating hole 34 is formed in the center of the concave portion 30 and communicates with the lower opening of the insertion hole 36. Similar to the shoulder portion 32A described above, a shoulder portion 34A is formed on the bottom (upper surface) of the bolt storage hole 34. The radius of curvature of the outer circumference of the concave portion 30 is 250 mm.
And the radius of curvature of the circular opening of the bolt storage hole 34 is 10
It is 0 mm. The depth of the bolt storage hole 34 is 50 mm.
Is.

Thus, the convex portion 2 shown in FIGS. 2 and 3 is formed.
6 and the concave portion 30 are capable of relative rotation in a state where both are engaged. In addition, a reliable engagement state can be maintained at least within the maximum block connection angle. Since the concave portion 30 has a shape that is stretched to the left and right, even if the engagement positional relationship between the convex portion 26 and the concave portion 30 is slightly shifted to the left or right, the connection between the blocks will not be hindered. Therefore, it is possible to effectively eliminate the distortion between adjacent blocks that occurs above or below the block wall.

It should be noted that the numerical values described above are merely examples, and the present invention is not limited to these.

FIG. 4 shows the connecting state of the two connecting rods 44 made of metal. FIG. 4 shows the convex portion 26 and the concave portion 3
It is an enlarged view showing a joined state with 0, and a bolt storage hole 32.
A metal connecting bolt 46 is arranged in each of the wirings 34 and 34, and the two connecting rods 44 are firmly connected to each other by the connecting bolt 46. More specifically, after the blocks are stacked, the connecting rod 44 as a reinforcing bar is inserted into the insertion hole 36 from above, and the lower end of the connecting rod 44 is connected to the coupling bolt 46 already arranged in the lower block. It is screwed in. That is, a thread groove is formed on the inner surface of the connecting bolt 46 and both ends of the connecting rod 44, and the three members can be integrally connected in the vertical direction by the rotation of the connecting rod 44. The foot 46A on the lower end side of the coupling bolt 46 is disposed on the shoulder portion 32A described above. Note that the coupling bolt 46 may be divided into a cylindrical body and a ring-shaped pedestal (corresponding to the foot 46) and configured separately.

As described above, after the upper block is piled up, the connecting rod 44 is inserted and the lower end is fixed, the connecting bolt 46 is screwed to the upper end similarly to the structure shown in FIG. It is installed by including. Further, by firmly screwing in the connecting bolt 46, it is possible to give tension to the connecting rod 44. A concrete block stacking method will be described later.

FIG. 5 shows the upper end of the connecting rod 44. A cross groove 50 is formed on the end surface, and a cross-shaped metal fitting is inserted into the cross groove 50 and rotated to firmly screw the lower end of the connecting rod 44 into the coupling bolt 46. be able to.

It is desirable to provide at least one notch in the foot 46A of the connecting bolt 46, and by providing such notch, when mortar or the like is injected into the insertion hole 36, as will be described later, the mortar smoothly. Can be moved upwards. In this embodiment, although not shown, about two notches are formed.

The connecting rod 44 has a diameter of, for example, 22 mmφ, and its length is, for example, 6 depending on the height of the block 22.
The length is set to 66 mm or slightly shorter.

FIG. 6B shows the block stacking method of this embodiment.

Now, it is assumed that the lower block 52 is stacked and the connecting rod 43 and the connecting bolt 56 are respectively arranged. When the blocks 54 are stacked above the blocks 52, the blocks 54 are first stacked by a crane (not shown) and placed on the upper surface side of the blocks 52. In that case, face-to-face matching is performed so that the convex portion formed on the upper surface of the block 52 and the concave portion formed on the lower surface of the block 54 are firmly engaged with each other. Then, while the block 54 is being hung by the crane, the connecting rod 44 is inserted into the insertion hole, and the upper end side of the connecting rod 44 is rotated to screw and fix the lower end of the connecting rod 44 into the connecting bolt 56. . Then, a connecting bolt 58 is attached to the upper end of the connecting rod 44.
Is fixed by screwing in. At that time, by tightening the coupling bolt 58 with a constant load, it is possible to apply tension to the whole of the plurality of integrated connecting rods 44, and build up a strong block wall structure for each step. be able to.

After the connecting bolt 58 is provided, the crane is removed. After all the blocks are stacked horizontally,
The backing material 16 is put on the back side of the block 54. Then, in each stage, such a block stacking process is sequentially repeated.

Therefore, as in the conventional example shown in FIG. 6 (A), the support member 2 is hung while each block is suspended by a crane.
The complicated work of arranging 0s can be omitted, and the connection between the blocks can be strengthened in the block stacking of each stage, whereby sufficient work safety can be ensured. Conventionally, since the ground 18 has an uneven shape, the length of the support 20 of each block varies, and it takes an extremely long time to adjust the support length. However, according to the present embodiment, it is possible to significantly reduce the time of hanging by the crane, improve the work efficiency, and shorten the construction period. In addition, there is an advantage that masonry can be carried out simply and beautifully without the need for skilled workers.

FIG. 7 shows a block wall 60 using the concrete block 22 of this embodiment. After a plurality of rows of blocks are stacked, mortar injection is performed using the mortar injection hole formed in the base block 62, and the injected mortar rises in the clearance between the insertion hole of each block 22 and the connecting rod. Eventually, it will appear on the uppermost protrusion. After confirming this, the top end concrete 64 is provided.

FIG. 8 shows the curved block wall viewed from above. In (A), as a comparative example,
The case where the side surface of the block 23 is configured by a flat surface is shown. If the both side surfaces are simply flat surfaces as shown by the shaded portions in the figure, a collision occurs between the two blocks, which makes smooth and close surface joining difficult. Of course, since the concave portion 30 is formed by being stretched in the left-right direction, there is a certain amount of room, but the state shown in FIG. 8A is still feared.

Therefore, in the block 22 of this embodiment, as shown in FIG. 1, one side surface is formed into a cylindrical curved surface shape, and the other side surface is formed into a concave cylindrical curved surface surface.
Therefore, as shown in FIG. 8B, even when the left and right axis lines of the blocks 22 are intersected with each other, the joining can be smoothly performed on both side surfaces. That is, according to the block of the present embodiment, it is possible to always secure the joining between the side surfaces within a wide range of block connection angles. Of course, if necessary, for example, mortar or the like can be injected between the side surfaces.

As described above, the block 22 of this embodiment is
Since it has the convex portion 26 and the concave portion 30 and each side surface is formed into a cylindrical curved surface, it is possible to finish the block wall easily and without distortion when forming a curved block wall. In the past, the finished state of the curved block wall was apt to be influenced by the skill of the worker, but the block 22 of the present embodiment can always maintain a uniform finished state of the block wall. The joining state between the block side surfaces can be improved regardless of the degree of curve.

FIG. 9 shows a half-sized concrete block 66. Such a block 66 is used at the end of the block wall and is shown in FIG.
Similar to the block 22 shown in (1), the convex portion 26 is provided on the upper surface and the concave portion 30 is provided on the lower surface. However, in this block 66, one convex portion 26 and one concave portion 30 are formed. The side surface is formed into a curved surface like the block 22 shown in FIG. However, a block having a flat side on one side may be adopted if necessary.

FIG. 10 shows a state in which a curved block wall 60 is formed using the block 22 of this embodiment. The blocks 22 are stacked by being shifted in the left-right direction by half blocks in each stage, and the connecting rods described above are passed between the upper and lower blocks to realize a reinforced concrete wall structure. Then, the above-mentioned convex portion and concave portion are engaged between the upper and lower blocks, and even when a slight gap is provided between the lower blocks due to the above-mentioned play provided in the concave portion. It is possible to form a beautiful curved wall without causing unnecessary distortion as the entire block wall.

A top view of the curved block wall is shown in FIG. As in block 22 of this embodiment,
When the curvatures of both side surfaces are the same, it is necessary to alternately reverse the convex-concave polarities of the side surfaces of the even-numbered block (solid line) and the odd-numbered block (broken line). In addition, the protruding corner portion 1
00 is almost inconspicuous when the front surface is formed with a rough surface or the like, but if it is desired to improve the finished state of design, the corner portion 100 may be shaved off a little. The corners are inconspicuous.

By the way, if the radius of curvature of the side surface of the concave curved surface type is formed to be large, it is not always necessary to switch the convex and concave polarities in each step. Note that, as shown in FIG. 11, the horizontal axes of the blocks 22 labeled with A coincide with each other, and the same applies to the blocks 22 labeled with B.

The connecting rod 44 and the connecting bolt 4 described above are used.
Although it is configured separately from 6, the 44 and the coupling bolt 46 may of course be integrated. In that case, a coupling bolt 46 is provided on the upper end of the connecting rod 44. Also, FIG.
The cross groove 50 shown in FIG.
Other structures may be adopted as long as they can be reliably rotated.

As described above, according to the concrete block of the present embodiment, when a curved block wall is created, even if the axes intersect between the blocks stacked vertically, the convex portion and the The concave portion ensures the connection between the upper and lower blocks.
Therefore, the strength of the block wall can be improved and a sturdy block wall can be configured, as compared with the conventional case where the upper and lower blocks are engaged with each other by the elongated groove portion and the elongated protrusion portion. In addition, since a certain amount of play is formed in the concave portion, distortion due to the difference between the upper path length and the lower path length of the curved block wall is eliminated, making the curved block wall easy and beautiful. It is possible to raise.

Further, according to the block stacking method of the present embodiment, the working time using the crane can be extremely shortened and the upper and lower blocks can be connected very firmly. As a result, it is possible to improve the economical efficiency in constructing the block wall and ensure the integrity of the block wall itself. Therefore, it is possible to construct a block wall that is effective against strong stress such as landslide caused by an earthquake. In addition, by applying tension to the connecting rods and adopting a block structure of tension structure, it is possible to exclude performing tension work after all blocks have been stacked, and it is possible to reliably apply tension to each stage. it can. That is, after connecting the connecting rods, the connecting rods are integrated rods as connecting rods through the connecting bolts to form a sturdy block wall.

[0058]

As described above, according to the invention of claim 1, when a curved block wall is formed,
Even if the horizontal axis lines between the blocks intersect, the connection between the blocks can be strengthened. Further, at that time, the surfaces between the blocks can be surely aligned with each other. This makes it possible to construct a wall structure that is strong against pressure from the back surface.

Further, according to the second aspect of the present invention, since the concave portion has a hollow shape extending in the left-right direction, it is possible to effectively eliminate the distortion particularly in the case of forming a curved block wall.

Further, according to the third aspect of the present invention, even if the axis line between the two blocks is shifted in the horizontal direction, the surface joining state between the side surfaces is ensured satisfactorily. Can realize various structures.

According to the invention of claim 4, the connecting rod is inserted into the insertion hole to connect the connecting rods to each other as reinforcing bars, and the structure of the block wall is strengthened.

According to the fifth aspect of the present invention, since the connecting step is performed for each block stacking step, it is possible to eliminate the support member conventionally required and to use the heavy machine such as a crane for a long time. There is an effect that the block wall can be shortened and the block wall can be constructed more quickly and easily.

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall configuration of a concrete block according to the present invention.

FIG. 2 is a diagram showing a configuration of a convex portion.

FIG. 3 is a diagram showing a configuration of a concave portion.

FIG. 4 is a cross-sectional view showing the connection of connecting rods.

FIG. 5 is a perspective view showing an upper end of a connecting rod.

FIG. 6 is a diagram showing a conventional example of block stacking and this embodiment.

FIG. 7 is a cross-sectional view of a block-stacked block wall.

FIG. 8 is a top view of block walls stacked in blocks.

FIG. 9 is a diagram showing a half-sized concrete block.

FIG. 10 is a front view of a curved block wall.

FIG. 11 is a top view of a curved block wall.

[Explanation of reference numerals] 22 block 26 convex portion 30 concave portion 32, 34 bolt accommodating hole 36 insertion hole 40 right side surface 42 left side surface 44 connecting rod 46 connecting bolt

Claims (5)

[Claims] 1. In a concrete block to be stacked in blocks, at least one convex portion provided on one surface of an upper surface or a lower surface, and the convex portion provided on the other surface of an upper surface or a lower surface. A concrete block comprising: at least one concave portion to be housed; and the convex portion and the concave portion having a shape capable of relative rotation in an engaged state with each other. 2. In a concrete block to be stacked in blocks, two convex portions having a rotationally symmetrical shape are provided side by side on the upper surface, and two convex portions having a rotationally symmetrical shape are provided on the lower surface side by side. A concrete block, comprising: two recessed portions having a hollow shape that extends in the left-right direction for storage. 3. The concrete block according to claim 2, wherein one side surface is formed into a cylindrical convex curved surface and the other side surface is formed into a concave curved surface corresponding to the shape of the convex curved surface. And concrete blocks. 4. The concrete block according to claim 3, wherein an insertion hole that vertically penetrates the convex portion and the concave portion is formed. 5. The method of stacking the concrete blocks according to claim 4, wherein a connecting rod having a length corresponding to the insertion hole is inserted into the insertion hole, and a lower end portion of the connecting rod is an upper end of the lower connection rod. A block stacking method, characterized in that the block stacking method includes a connecting step of connecting the parts, and the connecting step is performed for each block stacking step.