Gravel liquefaction countermeasure structure

Abstract

To provide a gravel liquefaction countermeasure structure capable of suppressing ejection of gravel.SOLUTION: A liquefaction countermeasure structure 10 comprises: a lower gravel layer portion 2 constructed by packing gravel material 22 into a bag body 21; a foundation 3 of a structure arranged above the lower gravel layer portion 2; an upper gravel layer portion 4 arranged adjacently to the foundation 3; and a filling layer 5 in which mortar is filled between the lower gravel layer portion 2 and the foundation 3. The filling layer 5 is not filled at the side of the lower gravel layer portion 2 facing the foundation 3 of the structure.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a structure for preventing liquefaction of gravel. [Background technology]

[0002] As a countermeasure against liquefaction damage to new or existing structures, a method has been proposed in the past in which highly permeable gravel material, such as No. 7 crushed stone, is laid near the ground surface to quickly dissipate the water pressure generated within the ground during liquefaction to the ground surface, thereby preventing sand boiling and foundation tilting (see Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6041118 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above construction method, if the foundation has a certain flat area, the amount of groundwater discharged during an earthquake becomes large, and the flow rate of the rising groundwater may cause gravel to erupt to the ground surface. The gravel laid under the foundation is pushed to the ground surface by the force of the water, and as a result, sand eruptions cannot be suppressed. If the area of ​​the foundation is large, the groundwater that rises to near the ground surface spreads horizontally under the foundation. Therefore, the larger the foundation, the greater the drainage flow rate. If the load on the foundation is large, the bearing capacity of the ground is lost during liquefaction, and the water pressure temporarily supports the load of the foundation, resulting in high water pressure. If the foundation is installed shallow, the weight of the soil cover is small, making it easier for gravel to erupt to the ground surface. In these cases, the phenomenon of gravel erupting to the ground surface is particularly likely to occur, so it is desirable to suppress the eruption of gravel in some way.

[0005] Therefore, the present invention has been made in consideration of the above circumstances, and provides a structure for preventing liquefaction of gravel that can suppress the eruption of gravel. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention employs the following means. In other words, the liquefaction prevention structure of the present invention comprises a lower gravel layer portion constructed by packing gravel into a bag, a foundation portion of a structure arranged above the lower gravel layer portion, an upper gravel layer portion arranged adjacent to the foundation portion, and a filling layer portion in which mortar is filled between the lower gravel layer portion and the foundation portion.

[0007] In a liquefaction prevention structure configured in this manner, even if upward groundwater flow occurs during an earthquake, the lower gravel layer and the filling layer can prevent gravel from erupting onto the ground surface from between the foundation of the structure and the lower gravel layer.

[0008] Furthermore, in the liquefaction countermeasure structure according to the present invention, the filled layer portion does not have to be filled on the side of the lower gravel layer portion facing the foundation portion of the structure.

[0009] In the liquefaction countermeasure structure constructed in this way, the filling layer is not filled on the side of the lower gravel layer facing the foundation of the structure, so there is no need to provide a large filling layer, which is easy to construct.

[0010] In addition, in the liquefaction countermeasure structure of the present invention, the lower gravel layer may be arranged extending from below the foundation of the structure to below the upper gravel layer.

[0011] In the liquefaction prevention structure constructed in this way, the lower gravel layer is disposed from below the foundation of the structure to below the upper gravel layer, thereby further suppressing the eruptions of gravel onto the ground surface. Effect of the Invention

[0012] According to the liquefaction prevention structure of the present invention, the eruption of gravel can be suppressed. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing a liquefaction prevention structure according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A liquefaction prevention structure according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a liquefaction-resistant structure according to one embodiment of the present invention. As shown in Figure 1, the liquefaction countermeasure structure 10 of this embodiment comprises a lower gravel layer portion 2, a foundation portion of the structure (hereinafter simply referred to as the "foundation portion") 3, an upper gravel layer portion 4, and a filled layer portion 5.

[0015] The lower gravel layer 2 has a plurality of gravel bags 20. The plurality of gravel bags 20 are arranged in a horizontal line and are stacked in the vertical direction. The lower gravel layer 2 has a drainage function with a larger hydraulic conductivity than the original ground G.

[0016] The gravel bag 20 has a water-permeable bag body 21 and gravel material 22 packed in a compressed state into the bag body 21. The gravel bag 20 is, for example, a sandbag.

[0017] The bag body 21 is made of, for example, a nonwoven fabric, a net, a basket, etc. The gravel material 22 is made of, for example, gravel, crushed stone, an artificial water-permeable material, etc.

[0018] The foundation portion 3 is made of, for example, concrete, etc. The upper gravel layer portion 4 is made of, for example, gravel material.

[0019] The foundation portion 3 and the upper gravel layer portion 4 are disposed above the lower gravel layer portion 2. The foundation portion 3 and the upper gravel layer portion 4 are disposed adjacent to each other. The upper gravel layer portion 4 is disposed on the outer periphery of the foundation portion 3. The upper gravel layer portion 4 is disposed, for example, in a ring shape on the outside of the foundation portion 3 in a plan view.

[0020] The lower gravel layer portion 2 is disposed from below the foundation portion 3 to below the upper gravel layer portion 4. In FIG. 1, the portion of the lower gravel layer portion 2 disposed below the upper gravel layer portion 4 (referred to as the "periphery of the gravel layer") 2B is higher than the portion of the lower gravel layer portion 2 disposed below the foundation portion 3 (referred to as the "directly below the gravel layer foundation") 2A, but the portion directly below the gravel layer foundation 2A and the peripheral portion of the gravel layer 2B may be at the same height, or the peripheral portion of the gravel layer 2B may be lower than the portion directly below the gravel layer foundation 2A. Furthermore, the lower gravel layer portion 2 may not be disposed below the upper gravel layer portion 4, but may be disposed only below the foundation portion 3.

[0021] The upper surface 2a of the portion directly below the gravel foundation 2A and the side surface 2b facing the center of the structure are covered with an impermeable sheet 24 such as a vinyl sheet. The portion of the sheet 24 that is placed above the portion directly below the gravel foundation 2A is referred to as the sheet upper portion 24a. The portions of the sheet 24 that are placed to the sides of the gravel layer outer periphery 2B are referred to as the sheet side portions 24b.

[0022] The filling layer 5 is disposed in the gap between the sheet 24 and the upper part of the lower gravel layer 2 in the foundation 3. The filling layer 5 is made of, for example, highly fluid non-shrink mortar. The filling layer 5 fills the gap between the sheet 24 and the upper part of the lower gravel layer 2 in the foundation 3 and hardens to close the gap. The filling layer 5 is not disposed on the side of the lower gravel layer 2 facing the foundation 3, that is, on the side of the sheet side portion 24b. The filling layer 5 is not disposed between the gravel layer outer periphery 2B and the upper gravel layer 4.

[0023] A water path is formed in the portion below the foundation portion 3 where the lower gravel layer portion 2 is not arranged.

[0024] In the liquefaction prevention structure 10 configured in this manner, even if upward groundwater flow occurs during an earthquake, the lower gravel layer 2 and the filling layer 5 can prevent gravel from erupting onto the ground surface from between the foundation portion 3 and the lower gravel layer 2.

[0025] Moreover, the filled layer portion 5 is not filled in the side of the lower gravel layer portion 2 facing the foundation portion 3. Therefore, it is not necessary to provide a large filled layer portion 5, and workability is good.

[0026] Moreover, the lower gravel layer 2 is disposed from below the foundation portion 3 to below the upper gravel layer 4. This makes it possible to further suppress the eruptions of gravel onto the ground surface.

[0027] Although one embodiment of the present invention has been described above, the technical scope of the present invention is not limited to the above embodiment, and it is possible to change the combination of components, add various modifications to each component, or delete components without departing from the spirit of the present invention. Some modifications are illustrated below, but these are not all inclusive, and other modifications are also possible. In addition, two or more of these modifications may be appropriately combined.

[0028] The "Sustainable Development Goals (SDGs)" are 17 international goals that were adopted at the United Nations Summit in September 2015. The liquefaction-resistant structure 10 according to this embodiment can contribute to the achievement of, for example, "11. Sustainable urban and human settlements" among the 17 SDGs. [Explanation of symbols]

[0029] 2 Lower gravel layer 3 Foundation of the structure 4 Upper gravel layer 5 Filled bed section 10 Liquefaction prevention structure 21 Bag body 22 Gravel material

Claims

1. A lower gravel layer portion formed by packing gravel material into a bag; A foundation portion of a structure disposed above the lower gravel layer; An upper gravel layer portion arranged adjacent to the foundation portion; A liquefaction prevention structure comprising a filled layer portion in which mortar is filled between the lower gravel layer portion and the foundation portion.

2. The liquefaction countermeasure structure according to claim 1 , wherein the filled layer portion is not filled on a side of the lower gravel layer portion facing the foundation of the structure.

3. The liquefaction prevention structure according to claim 1 or 2, wherein the lower gravel layer is disposed from below the foundation of the structure to below the upper gravel layer.

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