This patent application claims benefit under 35 U.S.C. 119(e), 120, 121, or 365(c), and is a National Stage entry from International Application No. PCT/KR2012/008765, filed 24 Oct. 2012, which claims priority to Korean Patent Application No. 10-2011-0118731, filed Nov. 15, 2011, entire contents of which are incorporated herein by reference.
The present invention relates to a mesh foundation construction method using hollow blocks. More particularly, the invention relates to a mesh foundation construction method using hollow blocks with which a ground that does not provide a supporting force sufficient to hold an upper structure can be reinforced to support an upper structure without forming a deep foundation, such as piles, etc.
When constructing a structure such as a building over a ground surface, a foundation may be formed to transfer the weight of the structure, and loads applied on the structure, to the ground in a stable manner, as well as to prevent intolerable levels of defects such as subsidence, inclination, movement, deformation, vibration, etc.
The types of a foundation can be divided largely into a direct foundation (or shallow foundation), which may be applied when the ground is capable of sufficiently supporting the loads of a structure, and which may involve directly transferring the loads from the foundation slab to the ground, and a deep foundation, which may be applied when the ground does not provide a sufficient supporting force or when there is a risk of excessive subsidence, and which may involve transferring the loads of the structure to deeper ground levels by using piles, piers, caissons, etc.
Also known in the art is the top-base foundation (also called the “top-pile foundation”), used on a ground that does not provide a sufficient supporting force, where the ground is reinforced with concrete blocks having the shape of a top and filler gravel, and a direct foundation is formed on the reinforced ground without forming support piles.
Applying a deep foundation according to the related art on a ground that does not provide a sufficient supporting force may entail the problem of increased costs, as piles, piers, etc., have to be placed up to the deeper ground levels.
Also, the top-base foundation described above may involve a complicated process, due to the critical processes of installing the top-shaped concrete blocks, welding the connector rebars, compacting the filler gravel, and the like, and may hence entail increased construction costs.
The present invention provides a mesh foundation construction method using hollow blocks with which a ground that does not provide a supporting force sufficient to hold an upper structure can be reinforced to support an upper structure without forming a deep foundation, such as piles, etc.
Also, the invention provides a mesh foundation construction method using hollow blocks which can reinforce a ground by using hollow blocks having a simplified shape to induce an increase in the supporting force and a reduction in the amount of subsidence.
An aspect of the present invention provides a method of constructing a mesh foundation using hollow blocks that includes: leveling an upper part of a ground selected for reinforcing; arranging a multiple number of hollow blocks adjacent to one another in a mesh form such that one side touches the upper part of the ground, where a hollow block includes an enclosed sidewall that defines a hollow part, which penetrates from said one side to the other side; and filling the hollow parts with a filler, which includes one or more of gravel and sandy soil.
The method can further include, after the filling: forming a concrete foundation by casting unhardened concrete over the hollow blocks filled with the filler and curing the concrete.
The method can further include, before the forming of the concrete foundation: covering an upper part of the hollow blocks to prevent moisture of the unhardened concrete from entering the hollow parts of the hollow blocks.
The leveling operation can include flattening an upper surface by spreading and compacting a base material that includes one or more of gravel and sandy soil.
The base material can be formed to a depth greater than ½ of a length of the longest possible line segment connecting two points on an outer perimeter of the horizontal cross section of the hollow block.
The hollow block can be formed such that a cross section formed by the sidewall is shaped as a circle.
In the arranging operation, a multiple number of the hollow blocks can be arranged in a mesh form with a particular distance in-between, with the distance being smaller than or equal to a thickness of the sidewall.
In the arranging operation, a multiple number of the hollow blocks can be arranged such that the outer perimeters of the sidewalls touch one another.
A multiple number of hollow blocks can be integrated as a unit block set.
The hollow block can be formed such that a cross section formed by the sidewall is shaped as a regular hexagon, and multiple hollow blocks can share the sidewall to be integrated as a unit block set having a honeycomb shape.
The proportion of a distance D2 between intersection points of an imaginary line segment passing through a center of a horizontal cross section of the hollow block and an outer perimeter of the horizontal cross section to a distance D1 between intersection points of an imaginary line segment passing through a center of a horizontal cross section of the hollow block and an inner perimeter of the horizontal cross section can be from 0.32 to 0.98.
The proportion of the distance D2 between intersection points between an imaginary line segment passing through a center of a horizontal cross section of the hollow block and an outer perimeter of the horizontal cross section to a height H of the hollow block can be from 0.15 to 1.1.
After the filling with the filler, the method can include repeatedly performing the operations of: flattening an upper surface by again spreading and compacting a base material including one or more of gravel and sandy soil over the hollow blocks filled with the filler; arranging the hollow blocks adjacent to one another in a mesh form again over the flattened base material; and filling the hollow parts and spaces formed by the hollow blocks with a filler including one or more of gravel and sandy soil.
According to certain embodiments of the present invention, a ground that does not provide a supporting force sufficient to hold an upper structure can be reinforced to support an upper structure without forming a deep foundation, such as piles, etc.
Also, a ground can be reinforced by using hollow blocks having a simplified shape to induce an increase in the supporting force and a reduction in the amount of subsidence.
As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present invention are encompassed in the present invention. In the description of the present invention, certain detailed explanations of the related art are omitted when it is deemed that they may unnecessarily obscure the essence of the present invention. Certain embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
A mesh foundation construction method according to certain embodiments of the present invention will be described below in more detail. In describing the appended drawings, identical or corresponding elements will be represented by the same reference numerals, and redundant descriptions will be omitted.
A mesh foundation construction method using hollow blocks according to this embodiment may include the operations of leveling an upper part of the ground 12 selected for reinforcing; arranging the hollow blocks 16 adjacent to one another in a mesh form such that one side touches the upper part of the ground 12, where a hollow block 16 includes an enclosed sidewall 18 that defines a hollow part 20 which penetrates from said one side to the other side; and filling the hollow parts 20 with a filler 22 that includes one or more of gravel and sandy soil. Thus, a ground 12 that otherwise does not provide a supporting force sufficient to hold an upper structure can be reinforced to support an upper structure, without having to form a deep foundation such as piles, etc., in the ground 12.
Considering a mesh foundation construction method using hollow blocks according to the present embodiment, the upper part of the ground 12 for which reinforcement is desired may first be leveled (S100), as illustrated in
In the case of sandy soil ground where the ground 12 has adequate strength, the leveling work can be performed on the original ground 12, and in the case of weak ground 12 or cohesive soil ground 12 where the ground 12 has low strength, the upper surface can be flattened by leveling the upper part of the ground 12 to be flat and even, and afterwards spreading and compacting a base material 14 including one or more of gravel and sandy soil over the leveled ground 12.
According to the load of the upper structure that is to be constructed, the original ground 12 can be leveled, or the base material 14 can be spread and compacted over the leveled ground 12 to improve the upper part of the ground 12 to a more adequate ground 12.
The base material 14 can include gravel having good particle size distribution with particles of various sizes distributed evenly, sandy soil which provides adequate ground strength, or a mixture of gravel and sandy soil. The selection of the base material 14 can be determined according to the load of the upper structure that is to be constructed.
An upper structure refers to a structure such as a building, bridge pillar, culvert, drainage conduit, underground parking lot, retaining wall, etc., that is constructed or placed over a foundation reinforced according to the present embodiment.
Then, the hollow blocks 16, each of which has an enclosed sidewall 18 that defines a hollow part 20 penetrating from one side to the other side, may be arranged adjacent to one another in a mesh form such that one side of the hollow blocks touch the upper part of the ground 12 (S200), as illustrated in
The hollow block 16 may be a tube-shaped block having an enclosed sidewall 18 that defines the hollow part 20, which forms a penetration along the up/down direction, and the hollow blocks 16 may be arranged adjacent to one another in a mesh form such that one side of the hollow block 16 touches the top of the leveled ground 12. The multiple hollow blocks 16 can be arranged separated from one another by a particular distance or can be arranged such that their outer perimeters are in contact.
In this embodiment, a hollow block 16 may be used, of which the cross section formed by the sidewall 18 is shaped as a regular hexagon, as illustrated in
Then, the hollow parts 20 may be filled with a filler 22 that includes one or more of gravel and sandy soil (S300), as illustrated in
Similar to the base material 14, the filler 22 can include gravel having good particle size distribution with particles of various sizes distributed evenly, sandy soil which provides adequate ground strength, or a mixture of gravel and sandy soil. The selection of the filler 22 can be determined according to the load of the upper structure that is to be constructed, as in the case of selecting the base material 14. During the filling operation, compaction can be applied so that the filler 22 may be filled well in the hollow parts 20 and in spaces formed by the multiple hollow blocks 16.
In this embodiment, the multiple hexagonal hollow blocks 16 may be arranged in a mesh form with one sidewall 18 touching another in the shape of a honeycomb so that there may be no space formed between the hollow blocks 16. Thus, the filler 22 may be filled only in the hollow parts 20 of the hollow blocks 16.
Then, a concrete foundation 26 may be formed by casting unhardened concrete over the hollow blocks 16 filled with the filler 22 and curing the concrete (S400), as illustrated in
In cases where the upper structure is a culvert or a box structure, it may also be possible to place the upper structure directly over the hollow blocks 16 filled with the filler 22, without forming the concrete foundation 26.
During the process of casting unhardened concrete and curing the concrete to form the concrete foundation 26, the moisture from the unhardened concrete can seep into the hollow parts 20 to alter the properties of the filler 22 and the base material 14, and thus in order to prevent this, a cover 24, etc., can be used to cover an upper part of the hollow blocks 16.
The following will consider the behavior of the ground 12 beneath the hollow blocks 16 when a surcharge load 30 is applied over the hollow blocks 16, for the case of multiple hollow blocks 16 that are arranged adjacently in a mesh form over the leveled ground 12 with the hollow parts 20 of the hollow blocks 16 filled in with a filler 22.
In order to measure the increase in the supporting force and the reduction in subsidence resulting from the hollow parts 20 of the hollow blocks 16, a comparative test was performed by fabricating a circular contrast block 28 having the same area as the area formed by the outlines of the hollow blocks 16, applying surcharge loads 30 in a stepwise manner, and measuring the amount of subsidence.
That is, a test setup was prepared by forming in a soil tank a base material 14 of gravel having good particle size distribution with particles of various sizes distributed evenly, arranging seven hexagonal hollow blocks 16 in a mesh form shaped as a honeycomb such that one sidewall 18 touches another as illustrated in drawing (a) of
) represents the amount of subsidence according to applied load for the hollow blocks 16, while the contrast-block line marked by squares (□) represents the amount of subsidence according to applied load for the contrast block 28.
Referring to
The results of decreased subsidence and increased supporting force provided by the hollow blocks 16 compared to the contrast block 28, as indicated above, may be due to an arching phenomenon occurring in the soil beneath the hollow blocks.
When a portion of the ground 12 is made to deform, a shear resistance may be created at the interface between the portion being deformed and the stable portions of the ground 12. Since the shear resistance hinders the deformation of the portion where a break is to occur, the soil pressure may be decreased at the portion being broken, while the soil pressure may be increased at the adjacent portions. The phenomenon of pressure transfer, whereby the soil pressure of the portion where a break is to occur is transferred to the soil of adjacent portions, is referred to as an arching phenomenon.
The arching phenomenon is more pronounced in sand compared to silt or clay, and is more pronounced in dense sand compared to loose sand. For example, when a small hole is bored into soil that is not viscous, such as sand, the upper part remains stable in the shape of an arch.
Thus, when a surcharge load 30 is applied to the test setup, a redistribution of soil pressure may occur in an arch form for the two points beneath a sidewall 18 and the other opposing sidewall 18 of a hollow block 16, so that the soil pressure may be increased, and the surcharge load 30 can be supported with a smaller supporting force. Also, a friction resistance may be created between the sidewalls 18 of the hollow part 20 and the filler which, together with the increase in soil pressure caused by the arching phenomenon, can reduce the transfer of the surcharge load 30 to the ground 12.
The redistribution of soil pressure due to the arching phenomenon may increase the elastic coefficient of the soil below the hollow blocks 16, and such increase in elastic coefficient and increase in supporting force may suppress the subsidence of the hollow blocks 16.
As the arching phenomenon is more pronounced in dense sand and gravel, it may be advantageous to use gravel having good particle size distribution with particles of various sizes distributed evenly, sandy soil which provides adequate strength of the ground 12, or a mixture of gravel and sandy soil, as the base material 14 and filler 22.
In this embodiment, hollow blocks 16 that are shaped as regular hexagons may be arranged in a mesh form such that one sidewall 18 of the hollow block 16 touches another, so that the two sidewalls 18 touching each other may form one support point for an arch.
In cases where the multiple hollow blocks 16 are arranged in a mesh form with a particular distance in-between, the distance can be made smaller than or equal to the thickness of the sidewall 18. This is because the regions beneath two adjacent sidewalls 18 and the region between the portions beneath the two sidewalls 18 can form one support point of an arch if the distance between the two adjacent sidewalls 18 are smaller than or equal to the thickness of a sidewall 18.
The arching effect that occurs beneath the hollow block 16 may be affected by the distance between the opposing sidewalls 18, the thickness of the sidewall 18, and the height (H) of the hollow block 16.
According to research performed by the inventors, a significant increase in supporting force and decrease in subsidence caused by the arching effect were observed when the proportion of the distance D2 between the intersection points of an imaginary line segment (L) that passes through the center (G) of a horizontal cross section of the hollow block 16 and the outer perimeter of the horizontal cross section to the distance D1 between the intersection points of an imaginary line segment (L) that passes through the center (G) of the horizontal cross section of the hollow block and the inner perimeter of the horizontal cross section is from 0.32 to 0.98.
Also, a significant increase in supporting force and decrease in subsidence caused by the arching effect were observed when the proportion of the distance D2 between the intersection points of the line segment (L) passing through the center (G) of the horizontal cross section of the hollow block 16 and the outer perimeter of the horizontal cross section to the height H of the hollow block 16 is 1.1.
Since the sidewall 18 of the hollow block 16 becomes a support point of an arch, it may be needed for the hollow block 16 to have a certain level of strength. Thus, the hollow block 16 can be fabricated from concrete, steel, high-strength plastic, etc.
Although this embodiment presents a hollow block 16 of which the cross section formed by the sidewall 18 has the shape of a regular hexagon, other polygonal or circular shapes in which an enclosed sidewall 18 defines a hollow part 20 that penetrates from one side to the other side such that the arching effect is achieved are also possible for the hollow block 16. That is, the hollow block 16 can be used with various shapes, such as a triangle, quadrilateral, pentagon, circle, oval, etc., for the shape of the cross section formed by the enclosed sidewall 18.
When forming the base material 14 on the upper part of the ground 12, the thickness of the base material 14 may be formed greater than ½ of the length of the longest line segment from among the possible line segments connecting two arbitrary points on the outer perimeter of the horizontal cross section of the hollow block 16, in order that a semicircular arch can be formed with a sidewall 18 and its opposing sidewall 18 of the hollow block 16 serving as the support points. For example, in the case of a hollow block 16 shaped as a regular hexagon as in the present embodiment, the thickness of the base material 14 can be made greater than ½ of the distance between two opposing vertices, and in the case of a circular hollow block 16, the thickness of the base material 14 can be made greater than ½ of the outer diameter of the circular hollow block 16. Also, in the case of a polygonal hollow block 16, the base material 14 can be made to a depth greater than ½ of the longest side of the outer perimeter of the polygonal hollow block 16.
To facilitate the fabrication and placement of the hollow blocks 16, it is possible to integrate a multiple number of hollow blocks 16 into a unit block set.
Drawing (a) of
Drawing (b) of
This variation may involve implementing multiple layers of the lower foundation according to an embodiment of the invention described above, when the load caused by the upper structure is large or when the ground 12 is very soft.
That is, after the operation of filling the filler 22 according to an embodiment of the invention described above, the base material 14 including one or more of gravel and sandy soil may again be spread and compacted over the hollow blocks 16 filled with the filler 22, to flatten the upper surface. Then, the operations of arranging the hollow blocks 16 again adjacent to one another in a mesh form over the flattened base material 14 and filling the hollow parts 20 and spaces formed by multiple hollow blocks 16 with a filler 22 that includes one or more of gravel and sandy soil can be performed repeatedly, to implement the lower foundation according to an embodiment of the invention in multiple layers.
While the spirit of the present invention has been described in detail with reference to particular embodiments, the embodiments are for illustrative purposes only and do not limit the invention. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the invention.
Many embodiments other than those set forth above can be found in the appended claims.
Number | Date | Country | Kind |
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10-2011-0118731 | Nov 2011 | KR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/KR2012/008765 | 10/24/2012 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2013/073781 | 5/23/2013 | WO | A |
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Entry |
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International Search Report for PCT/KR2012/008765. |
Number | Date | Country | |
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20140311084 A1 | Oct 2014 | US |