JP5468165B1 - Sand sand control method - Google Patents

Abstract

[Problem] To provide a sand-sand-suppressing method that is highly effective in suppressing sand-sand caused by liquefaction of sandy ground during an earthquake, displacement of the ground surface caused by sand-sand, and suppression of uneven settlement of works and buildings.
Synthetic pile construction is performed by pouring cement milk into a steel pipe pile 4 for composite pile construction having wings 42 on the peripheral surface so that the tip reaches the ground below the ground to be liquefied. The composite pile 1 in which the peripheral surface of the steel pipe pile 4 is covered with the solidified body 12 in which the cement and the ground of the peripheral surface are mixed is formed, and the pile head 11 which is the head of the composite pile 1 is permeable to water. And a box-shaped box part 3 that covers the outside with a sheet-like sheet part 2 that shields the permeation of earth and sand and that has a hollow inside and that has an opening 32 connected to the cavity on the upper surface, the lower surface, and the side surface. The box part 3 is installed so as to be located between the ground surface or the foundation of the work / building and the upper end of the groundwater level.
[Selection] Figure 1

Description

  The present invention relates to a sand-sand-suppressing construction method, which is a construction method for suppressing sand-sand generated due to liquefaction of sandy ground during an earthquake.

  The damage to the work, buildings, and the ground surface due to the vibration during the earthquake is mainly divided into the following two types. The first is damage caused by deformation, movement, or destruction caused by earthquakes caused by earthquakes directly to the work or building through the ground or ground surface, causing the work or building to vibrate vertically or horizontally. is there. Secondly, the liquefaction phenomenon occurs in loose sandy ground saturated with groundwater near the ground surface due to earthquake vibrations, resulting in damage to the work, buildings, and the ground surface. is there.

  Conventionally, various countermeasures have been taken for the first damage, but there are not many countermeasures for the second damage, that is, the liquefaction damage caused by sand sand, because the idea of sand sand itself is not well known.

  As a measure to prevent sand blowing, when building a building using the floating foundation method, a floor slab made of reinforced concrete with one end tightly connected to the building was installed between the edge of the building and the site boundary line. Floor slabs shall be provided with a hanging wall at the end of the site boundary line. In addition, floor slabs made of reinforced concrete shall support drainage side grooves at the end of the site boundary line. There is a sandblast prevention structure whose main point is to improve the ground between the wires (for example, see Patent Document 1).

  In addition, after laying a water-permeable layer, which is a layer having good water permeability and having a water-conducting material, laid horizontally above the groundwater level surface, earth and sand are buried in the upper part of the water-permeable layer, and a lower end is formed on the water-permeable layer. There is also a sand-sand-prevention mat construction method in which a plurality of pressure relief pipes that extend in the vertical direction and reach the surface of the landfill are provided (for example, see Patent Document 2).

JP 09-003923 A Japanese Patent Laid-Open No. 08-302661

  In the methods for preventing sand blowing of Patent Document 1, Patent Document 1 and Patent Document 2, since the movement of the floor slab and the mat itself due to vibration during an earthquake cannot be prevented, there is a problem in that the effect of preventing sand blowing during an earthquake is reduced. is there.

  Therefore, the present invention provides a sand-sand-suppressing construction method that is highly effective in suppressing sand-sand caused by liquefaction of sandy ground during an earthquake, displacement of the ground surface accompanying sand-sand, and suppression of uneven settlement of work and buildings. The purpose is to do.

  In the first aspect of the present invention, the steel pipe pile for forming a synthetic pile having wings on the peripheral surface is poured into the mortar while pouring the mortar into the ground lower than the ground to be liquefied. A synthetic pile is formed in which the peripheral surface of the steel pipe pile for composite pile construction is covered with a solidified body that is a mixture of mortar and the ground of the peripheral surface. A box-shaped box part that covers the outside with a sheet-like sheet part that shields the infiltration of earth and sand and that has a cavity inside and that has an opening connected to the cavity on the upper surface, the lower surface, and the side surface; Provided is a sand-sand-suppressing method characterized in that the box portion is installed so as to be positioned between the ground surface or the foundation of a work / building and the upper end of a groundwater level.

  According to the sand buff suppression method of the present invention, there are high effects of suppressing sand clogging caused by liquefaction of sandy ground during an earthquake, displacement of the ground surface associated with sand buffing, and suppression of uneven settlement of works and buildings.

It is explanatory drawing of the sand sand suppression construction method of Example 1 of this invention. It is explanatory drawing 1 explaining the difference of the case where it does not give with the case where the sandblast suppression construction method of Example 1 of this invention is given. It is explanatory drawing 2 explaining the difference between the case where it does not give with the case where the sandblast suppression construction method of Example 1 of this invention is given. It is explanatory drawing 3 explaining the difference between the case where it does not give with the case where the sandblast suppression construction method of Example 1 of this invention is given. It is explanatory drawing 4 explaining the difference between the case where it does not give with the case where the sandblast suppression construction method of Example 1 of this invention is given. It is explanatory drawing 5 explaining the difference between the case where it does not give with the case where the sandblast suppression construction method of Example 1 of this invention is given. It is the plane schematic which shows the usage example of the sand buff suppression construction method of Example 1 of this invention. It is a plane enlarged view which shows the usage example of the sand sand suppression construction method of Example 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the cross-sectional schematic 1 which shows the usage example of the sand buff suppression construction method of Example 1 of this invention. It is the cross-sectional schematic 2 which shows the usage example of the sand buff suppression construction method of Example 1 of this invention.

(Liquefaction phenomenon)
The liquefaction phenomenon at the time of an earthquake is likely to occur on the ground with loose sandy soil saturated with groundwater or on the ground where artificial soil is buried. Here, the sandy ground is the ground where the proportion of sand particles is large among the soil particles that make up the ground, but it depends on the particle size of the sand particles, the type of mineral, the time of deposition and the process of deposition. Not all of the sandy ground below the groundwater level will be liquefied at the time of an earthquake. Sandy ground that tends to liquefy during an earthquake is often found in “alluvial ground” that is saturated with groundwater (below the groundwater level) and consists of Holocene sediments that are the latest geological period.

  The process of liquefaction during an earthquake is as follows. When an earthquake occurs, in the sandy ground with a loose degree of saturation that is below the groundwater level near the ground surface, stress is generated by the vibration of the sand particles due to the earthquake vibration, and the groundwater existing around the sand particles is generated. Local volume compression occurs and excessive pore water pressure is generated. When excessive pore water pressure is generated in the groundwater around the sand particles, the apparent adhesive force between the sand particles is lost, and this ground (sand particles + groundwater) loses its properties as a normal solid. Become. This phenomenon is called a liquefaction phenomenon.

(Damage during liquefaction and damage from sand buff)
When liquefaction occurs, “sand particles + groundwater”, which has a pressure close to that of liquid when liquefied, tries to go to the “surface” where the pressure is low to release the excess pore water pressure of groundwater. Movement occurs. “Sand particles + groundwater” travels through lower pressure areas, causing cracks and cracks to reach the ground surface caused by earthquakes, and in some cases, ground on the sides of piles and structures buried in the ground from the ground surface Since the air gap is large and the air gap is large, it moves from the point where liquefaction occurs using the part where the pressure is low as a route, and releases the pressure to the ground surface. The phenomenon that “sand particles + groundwater” liquefied under this pressure moves through the ground and is released to the ground surface is called sand sand.

  When sandblast occurs and liquefied “sand particles + groundwater” is released to the ground, “sand particles + (old) groundwater” accumulates on the ground surface. Thereafter, when the groundwater discharged to the ground surface is dispersed or evaporated, the volume is reduced by the amount of the groundwater, and the ground surface may sink or sink. In addition, the volume shrinkage due to the change in the gap ratio between the sand particles due to tightening by vibration appears slightly compared to the volume reduction of the groundwater.

  Since land subsidence and depression are uneven and local, existing works and buildings will be subsidized, causing serious damage.

  One form of the sand buff suppression method of the present invention is to first pour mortar into the steel pipe pile for composite pile construction having wings, while driving so that the tip reaches the lower ground than the ground to be liquefied. The synthetic pile which made the state which covered the circumference of the steel pipe pile for synthetic pile construction with the solidified body which mixed the ground of the mortar and the circumference is formed. And the pile head which is the head of the synthetic pile is covered with the sheet-like sheet portion which has water permeability and shields the infiltration of earth and sand, and the inside is a cavity, and the cavity is connected to the upper surface, the lower surface and the side surface. The box-shaped box part which has an opening part is provided integrally, and it installs so that the said box part may be located between the ground surface or the foundation of a structure and a building, and a groundwater level upper end.

  Hereinafter, although one Embodiment of the sand buff suppression construction method of this invention is described concretely using an Example, this invention is not limited to these.

{Construction method}
FIG. 1 is an explanatory diagram of a sand blowing suppression method according to Embodiment 1 of the present invention. In the sand blowing suppression method according to the first embodiment of the present invention, the synthetic pile-forming steel pipe pile 4 having the wings 42 on the peripheral surface is placed inside such that the tip reaches the lower ground than the ground to be liquefied. The pile which is the head of the composite pile 1 is formed by pouring the mortar into the composite pile 1 in which the peripheral surface of the steel pipe pile 4 for composite pile formation is covered with the solidified body 12 mixed with the ground of the mortar and the peripheral surface. The head 11 has a box-like shape having a water-permeable and sheet-like sheet portion 2 that shields the permeation of earth and sand and has an opening 32 connected to the cavity on the upper surface, the lower surface, and the side surface. The box part 3 is provided so as to be integrated, and the box part 3 is installed so as to be located between the ground surface or the foundation of the work / building and the upper end of the groundwater level. For example, when installing when building a building, a box part 3 integrated with a synthetic pile 1 and covered with a sheet part 2 is installed at the corner of the foundation of the building, and the synthetic pile is attached to the box part 3 on the side surface. It is desirable that one or more other box portions 3 (each covered with the sheet portion 2) to which 1 is not connected are connected and installed to integrate the whole.

  In this embodiment, the composite pile building steel pipe pile 4 has a steel pipe portion provided with a bottom lid at the tip, and has a bottom wing on the side surface of the tip portion of the steel pipe portion, and is erected on the bottom wing and parallel to the direction of excavation. A plurality of agitating blades provided, having discharge holes for discharging mortar at a plurality of locations on the side surface of the tip of the steel pipe part, and a bottom expansion wing spirally protruding outward from the steel pipe part. The blade has a stirring hole penetrating the front and back surfaces, and the discharge hole is provided at a position following the stirring blade when the steel pipe portion is rotationally press-fitted and below the bottom expanded blade. It is a steel pipe pile that allows a small lump to pass through and discharges mortar from the discharge hole and mixes and stirs it with soil by means of a widening blade and a stirring blade. Because of this configuration, when rotating press-fitted, it was mixed with the ground repair liquid discharged from the ground repair liquid discharge hole to the soil small lump that passed through the stirring hole of the stirring blade, and adhered to the soil small lump. The mortar can be used as an adhesive to connect the small blocks and restore the original ground strength. The steel pipe pile 4 for composite pile construction of the present embodiment is a steel pipe pile that is relatively easy to construct, and the pile peripheral surface is covered with a repair ground constructed by mixing mortar and peripheral ground. Yes. In addition, even if it is not this structure, if it is a steel pipe pile for synthetic pile construction which has a wing | blade, it will not be limited.

  In this embodiment, the blade 42 is a steel pile pile 4 for composite pile formation in the present embodiment. The bottom wing on the side surface of the tip portion of the steel pipe portion, and a plurality of stirring blades that are erected on the bottom wing and provided in parallel in the excavation direction. Although there are two types, both are collectively referred to as “wings” in the present application. The wing may be both a bottom wing and a stirring wing, or only a bottom wing.

  In the present embodiment, the composite pile building steel pipe pile 4 connects the upper end, that is, the pile head 11 with the box portion 3, and the lower end is driven to the lower ground than the ground that may be liquefied.

  In this embodiment, the steel pipe pile 4 for composite pile construction is, for example, an AQ pile in which the diameter is 165.2 mm, the bottom wing is 340 mm, the thickness is 5.0 mm, and the length of the STK400 that is a hollow cylindrical portion is 6.28 m. (AQ pile association) may be used, but is not limited to this.

  In this embodiment, the composite pile 1 is composed of cement and sand while the stirring blades of the steel pipe pile 4 for composite pile formation press the soil around the steel pipe part in the same direction as the rotation direction of the steel pipe part preceding the discharge hole. The mortar which is a mixture of water and water is discharged from the discharge hole, and the steel pipe pile 4 for synthetic pile formation is rotationally pressed to a predetermined depth, and stirred and mixed by the stirring blade having the stirring hole and the bottom expanding blade. The ground is built as a solidified body in a mixed state with the surrounding ground, and at the same time, piles are buried in the ground at the same time, and the steel pipe pile for composite pile construction and the ground of the surrounding solidified body are combined and formed.

  The synthetic pile 1 is a pile having a solidified body 12 in which cement and a ground of the peripheral surface are mixed on the peripheral surface of the pile. With such a configuration, the adhesion between the pile and the peripheral ground is improved, and therefore, the path between the side of the pile and the peripheral ground becomes a path of “sand particles + groundwater” that has been liquefied during an earthquake, preventing further inducing sand. be able to.

  In the present embodiment, the box portion 3 has a hollow inside and has an opening 32 connected to the hollow on the upper surface, the lower surface, and the side surface. Among them, the opening ratio on the side and bottom is approximately 20% or more, and the material has the necessary strength as a part of the foundation. Made of concrete, metal, resin, which is durable against aging, and does not require great strength In this case, the wood should be preserved. The box part 3 is made into the shape close | similar to the cube whose one side is about 0.5-1.0 m in consideration of workability and transportability. The box portion 3 may be used in the longitudinal direction under the foundation as needed, such as the shape of the foundation, or may be used in several layers. The box unit 3 may be a plastic underground storage and penetration tank used in an underground infiltration facility, a perforated concrete iron slab, or the like. For example, the box part 3 is made of recycled polypropylene / polyethylene, and is a rectangular AE-1 and AE1-K (Akita Ecobrush Co., Ltd.) having a square with a length and width of 0.54 m and a height of 0.52 m. However, the present invention is not limited to this.

  In the present embodiment, the sheet portion 2 is a sheet-like material that has water permeability and shields the penetration of earth and sand (fine sand mixed with gravel), but more specifically, has high durability and 1 × 10 ^ −1 cm. It is a sheet made of cloth-like synthetic fibers and synthetic resin nonwoven fabrics or long fibers having good water permeability of at least / s and high sandproof effect. The sheet portion 2 is also suitable as a water-permeable civil engineering sheet. For example, the sheet portion 2 may be TT-150 (manufactured by Tokyo Ink Co., Ltd.) having a thickness of 1.5 mm, but is not limited thereto.

{Mechanism of sandblast suppression}
The following is a description of the mechanism that suppresses the damage caused by sand liquefaction during the earthquake in this method.

  FIG. 2 is explanatory drawing 1 explaining the difference between the case where it does not give with the case where the sandblast suppression construction method of Example 1 of this invention is given. (1) The box part 3 is covered with the sheet part 2 between the ground surface or the foundation of the workpiece / building and the upper end of the groundwater level, and the synthetic pile 1 is installed and connected. Here, in the normal state, the box portion 3 is located above the groundwater level surface, and the surrounding soil is blocked by the sheet portion 2, so the inside of the box portion 3 is hollow. The synthetic pile 1 is driven to the ground lower than the ground to be liquefied as an earth anchor, and the pile head 11 is integrated with one box portion 3. Since the synthetic pile 1 is driven to the ground lower than the ground to be liquefied, the movement of the box portion 3 and the seat portion 2 when the ground is shaken by an earthquake can be prevented.

  FIG. 3 is an explanatory view 2 for explaining the difference between the case where the sand blowing suppression method of Example 1 of the present invention is applied and the case where it is not applied. (2) When liquefaction occurs, “sand particles + groundwater”, which is a fluid having excess pore water pressure, moves in the ground toward the ground surface in order to reduce the pressure.

  FIG. 4 is an explanatory view 3 for explaining the difference between the case where the sand blowing suppression method of Example 1 of the present invention is applied and the case where it is not applied. FIG. 5 is an explanatory view 4 for explaining the difference between the case where the sand blowing suppression method of Example 1 of the present invention is applied and the case where it is not applied. (3) When the sand sand suppression method of Example 1 of the present invention is applied, since the pressure in the box part 3 is small, “sand particles + groundwater” will go into the box part 3. At that time, since it passes through the sheet portion 2, “sand particles” in “sand particles + groundwater” are blocked by the sheet portion 2 and do not enter the box portion 3, and only the excess pore water (groundwater) is contained in the box portion 3. It penetrates into the inside and lowers the pore water pressure in “sand particles + groundwater” to converge liquefaction. In other words, once the liquefied “sand particles + ground water” reaches the box portion 3, the liquefaction is converged to prevent the sand surface from reaching the ground surface (sand sand), and displacement of the ground surface is suppressed. On the other hand, in the case where the sand sand suppression method of Example 1 of the present invention is not applied, sand sand is generated, the total volume of sand and water moved by the sand sand is reduced, and the foundation of the building sinks unevenly. In addition, in FIGS. 4-6, the synthetic | combination pile 1 is shown as "anchor."

  FIG. 6 is explanatory drawing 5 explaining the difference between the case where it does not give with the case where the sandblast suppression construction method of Example 1 of this invention is given. (4) When the shaking of the earthquake converges and the pore water pressure of the liquefied layer converges to a normal pressure, the groundwater accumulated in the box part 3 also drops to the depth of the conventional groundwater level due to the action of gravity. On the other hand, in the case where the sand blowing suppression method according to the first embodiment of the present invention is not applied, when the water is dispersed or evaporated from the sand deposited on the surface of the earth, and the subsidence on the ground surface is compensated, only the volume of water evaporated is The surface sinks and the foundation of the building sinks unevenly.

{Example of use}
This construction method is applied to the foundations of structures and buildings to be built on the ground that may be liquefied in the event of an earthquake, thereby suppressing damage caused by sand sand when the ground is liquefied. This method will be laid so as to cover the entire base of the work / building and the entire area where it is not desired to cause unevenness of the ground surface due to sand.

  FIG. 7 is a schematic plan view showing an example of use of the sand sand suppression method according to Example 1 of the present invention. That is, FIG. 7 is a sketch of the construction method of the first embodiment. Install the box part 3 covered with the seat part 2 in the quantity required to fill the entire area under the foundation of the work or building or the part where you do not want to cause unevenness of the ground surface by the sand buffing. Some of the box parts 3 are installed with the synthetic piles 1 integrated as lower parts as earth anchors.

  FIG. 8 is an enlarged plan view showing a usage example of the sand buff suppression method of Example 1 of the present invention. The synthetic pile 1 is connected and integrated under the box portion 3 at the corner portion, and the other box portion 3 is installed at the side surface. The synthetic pile 1 has a mortar filling portion 43 filled with mortar, and an anchor rust stopper 31 is provided in the box portion 3 for rust prevention of the synthetic pile 1. The whole box part 3 connected is surrounded by a side plate 6.

FIG. 9 is a schematic cross-sectional view 1 illustrating an example of use of the sand buff suppression method of Example 1 of the present invention. FIG. 9 is a schematic cross-sectional view of a place where the synthetic pile 1 is connected and integrated under the box portion 3. The pile head 11 is placed in the box part 3 and the synthetic pile 1 and the box part 3 are integrated and installed. Moreover, FIG. 10 is the cross-sectional schematic 2 which shows the usage example of the sand sand suppression construction method of Example 1 of this invention. FIG. 10 is a schematic cross-sectional view of a place where the synthetic pile 1 is not connected to the bottom of the box portion 3.
The box part 3 and the sheet part 2 are located under the foundation of the work or building or under a part where the surface of the ground is not to be generated due to sandblast, and between the ground surface and the upper end of the groundwater level. By installing it with the surface covered with the sheet portion 2, it suppresses sand blowing caused by liquefaction during the earthquake of the ground beneath the foundation.
The synthetic pile 1 is driven as a ground anchor to the ground below the ground that may be liquefied, and the pile head 11 is integrated with one of the box portions 3. The composite pile 1 functions to prevent the movement of the box portion 3 and the seat portion 2 due to vibration during an earthquake.
Here, in piles that do not have a solidified body in which cement and peripheral ground are mixed on the periphery of the pile, the peripheral ground is often disturbed by construction, and there is a gap between the side of the pile and the peripheral ground. It is likely to become a passage for “sand particles + groundwater” that has been liquefied during an earthquake, and may cause more sand blowing when liquefaction occurs. On the other hand, the composite pile 1 is a construction method that does not disturb the post-construction pile surface and the pile from the pre-construction ground due to the solidified material such as cement and peripheral ground mixed on the peripheral surface of the composite pile construction steel pipe pile 4 It has become a pile with.

{effect}
According to the present embodiment, the effect of suppressing the sand that is generated by the liquefaction of the sandy ground during an earthquake, the displacement of the ground surface accompanying the sand and the uneven settlement of the work and the building is high. The combination of the ground and steel pipe piles can generate bearing capacity and prevent movement due to vibration during an earthquake, so it is possible to effectively suppress the unsettled settlement caused by sand sand.

DESCRIPTION OF SYMBOLS 1 Composite pile 11 Pile head 12 Solidified body 2 Sheet | seat part 3 Box part 31 Anchor rust prevention 32 Opening part 4 Steel pipe pile for synthetic | combination pile construction 42 Wing | blade 43 Mortar filling part 6 Side plate

Claims (1)

The steel pipe pile for composite pile formation having wings on the peripheral surface is poured so that the tip reaches the ground lower than the ground to be liquefied, and the mortar is poured into the peripheral surface of the steel pipe pile for composite pile formation Is formed with a synthetic pile covered with a solidified body mixed with mortar and ground surface, and the pile head, which is the head of the synthetic pile, has permeability and shields the infiltration of earth and sand. A box-shaped box part covering the outside with a sheet-like sheet part and having an inside with a cavity and having an opening connected to the cavity on the upper surface, the lower surface and the side surface is provided integrally. A sand-sand suppression method that is installed between the foundation of the building and the top of the groundwater level.