JPH086337B2 - Foundation construction method and foundation pile - Google Patents

Description

TECHNICAL FIELD The present invention relates to the foundation of structures such as buildings and civil engineering structures, and more specifically, prevents liquefaction of aquifer sand ground and the like, and is soft. The present invention relates to a foundation construction method and its foundation piles that can remove the negative frictional force acting on the piles in a clay ground.

(Prior art) When constructing a structure such as a building or a civil engineering structure on a soft ground such as an aquifer sandy ground such as a landfill, consider the scale and shape of the structure, for example, In this way, the ground is improved and measures are taken to prevent liquefaction of the ground.

Ground improvement method by sandpack drain etc. Ground shape is restrained by sheet pile (steel sheet pile) etc. Ground improvement method by embankment and the above-mentioned method are combined and ground drainage method by gravel drain (crushed stone pile) etc. Installation method In addition, foundation piles are driven to support the structure, but in soft ground such as soft cohesive soil, the foundation piles are subjected to a negative frictional force that tends to pull in together with the subsidence due to consolidation due to consolidation. To work. Then, this negative frictional force causes an unexpected settlement of the foundation of the structure or causes a unequal settlement of the structure.

Therefore, measures have been taken in advance to apply a friction cutting material such as asphalt to a foundation pile used in a soft clay ground.

(Problems to be Solved by the Invention) However, the above-described conventional method has the following problems.

Construction equipment is required and construction time is long.

Construction costs increase.

Since the foundation piles are driven after the ground improvement, the previous ground improvement becomes uncertain.

Further, although measures have been taken to apply a friction cutting material in order to reduce the frictional force of the foundation pile, there is a problem that this application process is complicated.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to prevent liquefaction of aquifer sand ground or the like that occurs during an earthquake, and further to a foundation pile in a soft cohesive ground or the like. It is to provide a foundation construction method and a foundation pile that can remove the negative frictional force that acts and can shorten the construction period and the construction cost.

(Means for Solving the Problems) The structure of the present invention for achieving the above-mentioned object will be described with reference to FIGS. 1 to 6 corresponding to the embodiments.

The present invention is a foundation construction method for constructing a structure 1 on a soft ground 3, wherein a plurality of foundation piles 7 are pierced through the soft ground 3 on the soft ground 3 on which the structure 1 is constructed and firmly fixed. The foundation pile 7 has a drainage groove 17 formed along the longitudinal direction of the foundation pile 7 on the outer peripheral surface of the foundation pile 7 at least corresponding to the soft ground 3, and the drainage groove 17 of the foundation pile 7 is driven. A plurality of them are provided in the circumferential direction, and the outer peripheral surface of the foundation pile 7 is covered with a water permeable sheet 21 that allows only water to permeate from the soft ground 3 to the drain groove 17 side. The outer periphery is further covered with a low-friction sheet 23 having a small coefficient of friction and a large number of holes.
The pressure water of the soft ground 3 that passes through the low-friction sheet 23 and the water-permeable sheet 21 and rises up in the drainage groove 17 at a portion located below the foundation pile 7 on the lower side. To form a drainage permeable layer 9 that moves in the horizontal direction. The drainage permeable layer 9 and the ground surface G of the soft soil 3 are communicated with each other on the ground surface side of the soft soil 3. It is characterized by forming a drainage channel 11 for draining water to the ground.

Further, according to the present invention, the upper end surface of the foundation pile 7 is cap 27.
It is characterized by being covered with.

In addition, the present invention relates to the soft ground 3 from the bottom of the foundation of the structure 1.
A foundation pile 7 pierced through to the solid support ground 5 and having a length such that it is laid from the lower part of the foundation of the structure 1 through the soft ground 3 to the firm support ground 5 13
A drainage groove 17 extending along the longitudinal direction of the pile body 13 on at least the outer peripheral surface of the pile body 13 corresponding to the soft ground 3, and a plurality of drainage grooves 17 formed in the circumferential direction of the pile body 13; A water-permeable sheet 21 which covers the outer peripheral surface of the pile body 13 and allows only the water in the soft ground 3 to permeate into the drainage grooves 17, and the outer peripheral surface of the water-permeable sheet 21, which has a small friction coefficient and a large number of holes. And a low-friction sheet 23 having 25.

Further, according to the present invention, the upper end surface of the pile main body 7 is covered by the cap 27.
It is characterized by being covered with.

(Operation) According to the foundation construction method of the present invention, when the water pressure of the soft ground such as the aquifer sand ground 3 around the foundation pile increases during an earthquake,
Since the pressure water is pushed up in the drainage ditch 17 and discharged to the outside through the drainage permeable layer 9 and the drainage channel 11, it reduces the water pressure of the soft ground such as the aquifer sand ground 3 and prevents liquefaction. Can be stabilized.

Further, according to the foundation pile 7 of the present invention, when the water pressure of the soft ground such as the aquifer sand ground 3 around the foundation pile increases during the earthquake, the pressure water can be pushed up by the drainage groove 17, so that the aquifer sand It is possible to reduce the water pressure of soft ground such as the ground 3 to prevent liquefaction and stabilize the ground.

Also, if the outer peripheral surface of the foundation pile 7 is covered with a protective layer 15 that has a small coefficient of friction against the ground and that allows only water to pass from the ground to the drain groove 17, the drain groove 17 can be prevented from being clogged with sand and mud. The upward movement of the pressure water can be performed more smoothly. In addition, it is possible to remove the negative frictional force that acts on the foundation pile during an earthquake or consolidation in soft ground such as soft cohesive ground.

In addition, the upper end surface of the foundation pile 7 or the pile body 13 is capped with a cap 27.
By covering with, it is possible to prevent damage to the pile head and to prevent the base concrete from flowing into the hollow portion from the pile head when the foundation pile is finally hit.

(Examples) Examples of the method and the foundation pile according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of the structure and its basic portion, and FIG. 2 is an enlarged cross-sectional view of the same.

Reference numeral 1 is a structure, and the structure 1 is constructed on a foundation pile 7 that penetrates a soft aquifer sand ground 3 near the ground surface G and is driven up to a solid support ground 5.

Reference numeral 9 denotes a drainage permeable layer. The drainage permeable layer 9 is provided between the lower part of the structure 1 and the upper part of the foundation pile 7 so that water can move in the horizontal direction by crushed stone or the like.

Reference numeral 11 denotes a drainage drain, and a plurality of drainage drains 11 are formed outside the structure 1 between the drainage permeable layer 9 and the ground surface G.

The foundation pile 7 is a pile body 13 as shown in FIGS. 3 to 6.
And a protective layer 15 covering the outer periphery of the pile body 13.

The pile body 13 has an annular cross section and has a space 13A inside. The pile main body 13 is made of concrete in the embodiment, but may be made of steel pipe or the like.

Reference numeral 17 is a drainage groove formed on the outer peripheral surface of the pile body 13. A plurality of drainage grooves 17 are provided at intervals in the circumferential direction of the pile main body 13, and the drainage grooves 17 extend at least from a portion located in the aquifer sand ground 3 to a portion located in the drainage permeable layer 9 in the longitudinal direction of the foundation pile 7. It is formed extending along.

The protective layer 15 is a water-permeable sheet 21 that covers the outer periphery of the pile body 13.
And a low friction sheet 23 covering the outer periphery of the water permeable sheet 21.

The water-permeable sheet 21 allows water to permeate but prevents permeation of sand and mud. As the water-permeable sheet 21, for example, a non-corrosive polymer non-woven fabric or a natural fiber sheet is used.

The low-friction sheet 23 is formed by forming a large number of holes 25 for allowing water to permeate through a sheet material having a small friction coefficient. As the low-friction sheet 23, for example, a polymer sheet such as a polyethylene film or a vinyl chloride sheet is used.

Reference numeral 27 denotes a cap provided on the upper end of the anti-main body 13, and the cap 27 is for preventing damage to the drain groove 17 and the like when the foundation anti-earth 7 is set.

In the above configuration, when the water pressure of the aquifer sand ground 3 around the foundation pit 7 rises during an earthquake, the pressure water will cause the low friction sheet 23
And from the permeable sheet 21 to the drainage groove 17, it is pushed up and discharged through the drainage permeable layer 9 and drainage drain 11 to the outside, so that the water pressure of the aquifer sand ground 3 is lowered and the ground is prevented from liquefying. It can stabilize the ground.

Further, since the water-permeable sheet 21 can prevent clogging of the drainage groove 17 due to sand and mud, the pressure water can be moved upward more smoothly, and the low-friction sheet 23 allows the water-permeable sheet to move. 21 can be protected.

Further, the low-friction sheet 23 has good slipperiness and a small friction coefficient, so that it is possible to remove the negative frictional force acting on the foundation resistance 7 at the time of an earthquake or consolidation in a soft cohesive ground or the like.

Therefore, according to the present embodiment, the function of the gravel lane and the function of removing the frictional force can be exerted at the same time only by constructing the foundation pile, which is simply driving the foundation pit 7,
It is possible to prevent the liquefaction of the ground and the differential settlement of the structures that occur during an earthquake. In addition, mechanical equipment for ground improvement etc. is not required, so that it is possible to shorten the construction period and the construction cost. Further, even if the ground is improved, the foundation piles 7 are simply driven, so there is no fear of disturbing the formation.

In the example, the case where the outer periphery of the pile body 13 is covered with the protective layer 15 has been described, but it is possible to obtain the same effect even when the protective layer 15 is not used,
Further, the configuration of the drainage groove 17 is arbitrary, and in short, it is sufficient that the pressure water can move upward along the foundation pile 7.

(Effects of the Invention) As is clear from the above description, according to the foundation construction method and foundation pile of the present invention, it is possible to prevent liquefaction of soft ground such as aquifer sand ground that occurs during an earthquake, and further , It is possible to remove the negative frictional force that acts on the foundation pile in the soft ground such as soft cohesive ground, and to shorten the construction period and the construction cost.

Further, in the present invention, by covering the upper end surface of the foundation pile or the pile main body with a cap, when the foundation pile is finally hit, damage to the pile head is prevented and the foundation concrete from the pile head to the hollow part is Can be prevented from flowing in.

[Brief description of drawings]

FIG. 1 is a sectional view of a structure and a foundation portion, FIG. 2 is an enlarged sectional view of the same, and FIG. 3 is a front view of a foundation pile in which a water-permeable sheet and a low-friction sheet are partially broken, FIG. Is a plan view of the foundation pile, FIG. 5 is an enlarged front view of the foundation pile in a state in which the water-permeable sheet and the low-friction sheet are partially broken, and FIG. 6 is a sectional view taken along line VI-VI of FIG. In the figure, 1 is a structure, 3 is aquifer sand ground, 5 is a support ground,
7 is a foundation pile, 9 is a drainage permeable layer, 11 is a drainage drain, 13 is a pile body, 15 is a protective layer, 17 is a drainage groove, 21 is a water permeable sheet, 23
Is a low friction sheet.

Claims (4)

[Claims] 1. A foundation construction method for constructing a structure on soft ground, wherein a plurality of foundation piles are pierced through the soft ground to a solid support ground in the soft ground on which the structure is constructed. Installed, the foundation pile has a plurality of drainage grooves formed along the longitudinal direction of the foundation pile on the outer peripheral surface corresponding to at least the soft ground of the foundation pile in the circumferential direction of the foundation pile, and the foundation pile The outer peripheral surface of is covered with a water-permeable sheet that allows only water to permeate from the soft ground to the drain groove side, and the outer periphery of the water-permeable sheet further has a low friction coefficient and a large number of holes and low friction. It is configured to be covered with a sheet, and in the portion located above the foundation pile below the structure, when the earthquake occurs, the low friction sheet and the water permeable sheet are passed through to rise in the drainage ditch. The pressure water of the soft ground coming in is moved horizontally. To form a drainage permeable layer, on the ground surface side of the soft ground, to form a drainage channel for communicating the drainage permeable layer and the ground surface of the soft ground to drain the water of the drainage permeable layer to the ground The foundation construction method characterized by the following. 2. The foundation construction method according to claim 1, wherein an upper end surface of the foundation pile is covered with a cap. 3. A foundation pile that is driven from the lower part of the foundation of the structure to the solid support ground by penetrating the soft ground, and is driven from the lower part of the foundation of the structure to the solid support ground through the soft ground. A pile body having a length to be provided, and a drainage groove extending along the longitudinal direction of the pile body on at least the outer peripheral surface of the pile body corresponding to the soft ground, and a plurality of drain grooves formed in the circumferential direction of the pile body. And a water-permeable sheet that covers the outer peripheral surface of the pile main body and allows only the water in the soft ground to permeate into the drainage groove, and the outer peripheral surface of the water-permeable sheet that has a small friction coefficient and a large number of holes. A foundation pile characterized by having a low-friction sheet. 4. The foundation pile according to claim 3, wherein an upper end surface of the pile body is covered with a cap.