JP2005290870A - Substructure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new foundation structure capable of reliably preventing sewage penetration into a support tank and improving the overall seismic performance.
SOLUTION: A new footing 11 is attached to the heads 12b of a plurality of new piles 12 whose tips 12a are driven in order from the uppermost buried layer 5 to the waste layer 6, the impermeable layer 7 and the lowermost support layer 8. In the newly constructed pier 10 which is supported, a square cylindrical steel sheet pile wall 13 is provided in the ground at least above the impermeable layer 7 from the buried layer 5 around the new footing 11, and this square cylindrical steel sheet pile wall is provided. The ground of at least the upper part of the impermeable layer 7 in 13 was solidified and improved. Further, the cement-mixed soil 15 was filled from the lower surface 11a of the new footing 11 to a depth in a range effective for the horizontal resistance of the plurality of new piles 12 in the square cylindrical steel sheet pile wall 13.
[Selection] Figure 1

Description

  The present invention relates to a foundation structure such as a new foundation structure that also serves as a seismic reinforcement in a waste ground (in a final disposal site).

  As this kind of new foundation structure, there are those shown in FIGS.

  As shown in FIG. 7, a new footing (foundation) 2 of a new pier 1 as a new foundation structure is composed of a buried layer 5 at the tip to a waste layer 6, an impermeable layer 7 and a lowermost support layer. (Water-permeable layer) Supported by the heads of a plurality of new piles 3 driven to 8. The new pier 1 is constructed and constructed in the waste ground composed of the buried layer 5, the waste layer 6, the impermeable layer 7 and the support layer 8 in order from the upper layer by the following procedure.

That is, as shown in FIG. 8, a large-diameter, square cylindrical steel sheet pile 9 is buried in the ground of the buried soil layer 5 and the waste layer 6 around the new footing 2, and then fixed to the earth. As shown in FIG. 9, the ground of the buried layer 5 and the waste layer 6 in the steel sheet pile 9 is excavated. Then, as shown in FIG. 10, the high quality soil 4 is carried into the steel sheet pile 9, and the waste layer 6 in the steel sheet pile 9 is replaced with the high quality soil 4. Next, as shown in FIG. A plurality of new piles 3 are driven from the soil 4 to the support layer 8. Next, as shown in FIGS. 7 and 12, the footing 2 is created and constructed on a plurality of new piles 3 and then the excavated portion in the steel sheet pile 9 is backfilled with high quality soil 4 or the like, thereby establishing a new construction. The pier 1 is constructed.
JP 2002-188157 A JP 2000-238881 A

  In the conventional new pier 1, the ground of the waste layer 6 in the steel sheet pile 9 is excavated and completely replaced with the high quality soil 4, but the strength of the high quality soil 4 is sufficient for the seismic reinforcement of the new footing 2. It was difficult to get to. Further, the steel sheet pile 9 embedded in the ground around the new footing 2 is not completely water-stopping, and particularly when there is a leak from a joint portion (not shown) of the steel sheet pile 9, Since there is no water, sewage X permeates the entire foundation in the steel sheet pile 9. As a result, as shown by an arrow in FIG. 12, the sewage X penetrates to the support layer 8 through the water supply of the plurality of newly installed piles 3 penetrating the impermeable layer 7 and may contaminate the groundwater. .

  Therefore, the present invention has been made to solve the above-described problems, and provides a foundation structure that can reliably prevent sewage from penetrating into a support tank and can improve the overall seismic performance. The purpose is to do.

  According to a first aspect of the present invention, there is provided a foundation structure comprising a plurality of pile heads, the tips of which are driven in order from the uppermost buried layer to the waste layer and the lowermost support layer. An annular underground wall is provided at least in the ground below the waste layer from the buried soil layer around the ground, and at least the ground below the waste layer in the annular underground wall is solidified and improved. Features.

  According to a second aspect of the present invention, there is provided the foundation structure according to the first aspect, wherein the solidified filler is provided between the lower surface of the footing and a depth effective for the horizontal resistance of the plurality of piles in the annular underground wall. It is characterized by filling.

  As described above, according to the first aspect of the present invention, an annular underground wall is provided in the ground below the waste layer from the buried soil layer around the footing, and at least in the annular underground wall. Since the ground below the waste has been solidified and improved, the contaminated water that is going to flow to the support tank through the plurality of piles can be reliably blocked by the solidified portion of the ground below the waste layer. Thereby, sewage penetration into the support tank can be reliably prevented.

  According to the invention of claim 2, since the solidified filler is filled from the lower surface of the footing to the depth in a range effective for the horizontal resistance of the plurality of piles in the annular underground wall, The footing can be integrated with the solidified filler. Thereby, the seismic performance of the whole foundation structure can be enhanced, and damage to the foundation structure due to the earthquake can be reliably prevented.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a new foundation structure constructed and constructed on a waste ground according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a buried state of an underground wall, and FIG. 3 is a new pile driving state. FIG. 4 is a cross-sectional view showing a state of solidification material injection or stirring and mixing during ground improvement, FIG. 5 is a cross-sectional view showing a ground excavation state, and FIG. 6 is a cross-sectional view showing a filling state of the solidification filler. .

  As shown in FIG. 1, a new footing (foundation) 11 of a new road pier (new foundation structure) 10 for a road as a foundation structure is connected to a waste layer 6 from a buried soil layer 5 having a top end 12a. The permeable layer 7 and the lowermost support layer (permeable layer) 8 are supported by the heads 12b of a plurality of new piles (stakes) 12 driven into the bottom layer. In the ground above the buried layer 5, the waste layer 6 and the impermeable layer 7 around the new footing 11, a small-diameter, square-tube steel sheet pile wall (annular underground wall) 13 is impermeable. 7 or the depth effective in the horizontal resistance of the plurality of new piles 12 (for example, 1 / β to π / 2β), whichever is greater. In this embodiment, a case where the steel sheet pile wall 13 having a small diameter and a rectangular tube shape is embedded up to the upper part of the impermeable layer 7 is shown. And the whole solid of the upper part of the impermeable layer 7 in this square cylindrical steel sheet pile wall 13 is solidified and improved by injecting or stirring and mixing a predetermined solidifying material. This solidified portion is indicated by reference numeral 14.

  Further, cement mixed soil (solidified filler) from the lower surface 11a of the new footing 11 in the inner peripheral surface 13a of the square cylindrical steel sheet pile wall 13 to the depth in a range effective for the horizontal resistance of the plurality of new piles 12 15, the newly installed footing 11 and the square tubular steel sheet pile wall 13 are integrated and fixed. Accordingly, a part of the waste layer 6 is left (residual) between the solidified portion 14 and the cement-mixed soil 15 in the steel sheet pile wall 13 having a square cylindrical shape. This remaining waste is indicated by reference numeral 6 '.

  The range effective for the horizontal resistance of the plurality of new piles 12 is, for example, the characteristic length of the reciprocal (1 / β) of the characteristic value (β) in the case of a semi-infinite pile (Chang's method). .

  Next, the procedure for creating and constructing the newly constructed pier 10 will be described. First, as shown in FIG. 2, the buried layer 5 and the waste layer 6 corresponding to the periphery of the newly installed footing 11 and at least In the ground at the top of the impermeable layer 7, the steel sheet pile wall 13 having a small diameter and a rectangular tube is larger than the depth of the range effective for the horizontal resistance of the upper portion of the impermeable layer 7 or a plurality of newly installed piles 12. Buried in the direction. In this case, a square cylindrical steel sheet pile wall 13 is embedded up to the top of the impermeable layer 7.

  Next, as shown in FIG. 3, a plurality of new piles 12 are driven so that the tip 12 a reaches the support layer 8 from above the buried layer 5. Next, as shown in FIG. 4, a predetermined solidification material is injected or stirred and mixed by the high-pressure jet agitator 20 over the entire ground of the upper part of the water-impermeable layer 7 in the square cylindrical steel sheet pile wall 13. . This solidified portion is indicated by reference numeral 14.

  Next, as shown in FIG. 5, an effective range (for example, 1 / β for the horizontal resistance of a plurality of new piles 12 in the ground of the buried layer 5 and the waste layer 6 in the steel sheet pile wall 13 having a square cylindrical shape. Excavation to a depth of) (in this embodiment, a part of the waste layer 6 in the rectangular steel sheet pile wall 13 is left), and the waste in the waste layer 6 is appropriately treated. Next, the cement-mixed soil (solidified filler) 15 is filled into the square cylindrical steel sheet pile wall 13 to a depth within a range effective for the horizontal resistance of the plurality of new piles 12.

  And as shown in FIG. 1, the new footing 11 is constructed | assembled on the head 12b of the some new pile 12 from the internal peripheral surface 13a of the square cylindrical steel sheet pile wall 13, and from the upper surface 11b of this new footing 11 By cutting the upper end portion of the protruding steel sheet pile wall 13 and refilling the ground such as the buried soil layer 5 on the upper surface 11b of the new footing 11, the new pier 10 is completed.

  In this way, the square cylindrical steel sheet pile wall 13 is embedded from the buried soil layer 5 around the newly installed footing 11 to the ground above the impermeable layer 7, and the impervious water in the square cylindrical steel sheet pile wall 13 is embedded. Cement mixed soil between the lower surface 11a of the new footing 11 and the depth effective for the horizontal resistance of the plurality of new piles 12 in the square cylindrical steel sheet pile wall 13 while solidifying and improving the upper ground of the layer 7 15, a new footing 11, a square cylindrical steel sheet pile wall 13, a part of the waste waste 6 ′ of the waste layer 6, and a solidified improvement portion 14 are integrally fixed and fixed. Contaminated water from the waste layer 6 ′ and the waste layer 6 outside the steel sheet pile wall 13 that flows through the pile 12 to the impermeable layer 7 and the supporting tank (permeable layer) 8 is removed from the impermeable layer 7. It can be reliably blocked by the solidification improvement part 14 etc. of the upper ground That. Thereby, sewage penetration into the impermeable layer 7 and the support layer 8 can be reliably prevented.

  Further, the new footing 11 and the square cylindrical steel sheet pile wall 13 are integrally fixed through the solidification improved portion 14 and the cement mixed soil 15 to fix the strength of the cement mixed soil 15 and the solidified improved portion 14 and the square tube. The horizontal resistance (lateral resistance) of the plurality of newly installed piles 12 can be increased by the restraining effect of the steel sheet pile wall 13. Furthermore, adhesion resistance increases by the solidification improvement of the surrounding ground of the head 12b of the some new pile 12 in the square cylindrical steel sheet pile wall 13, and a vertical bearing force can be increased.

  Further, the ground around the square tubular steel sheet pile wall 13 improves the rigidity around the new footing 11, and the cement-mixed soil 15 portion and the solidified improvement portion 14 function as a basis. In addition, since the rigidity of the square tubular steel sheet pile wall 13 has an effect of suppressing deformation around the new footing 11, the horizontal displacement and rotation of the new footing 11 at the time of level 2 class seismic load action is suppressed, and the earthquake resistance Can be improved. By these, the proof stress of the new pier 10 can be improved, and the breakage of the new pier 10 due to a large earthquake can be surely prevented.

  Further, the new footing 11 and the steel sheet pile wall 13 are integrally fixed by aligning the outer peripheral surface 11 c of the new footing 11 with the inner peripheral surface 13 a of the square steel sheet pile wall 13, and on the upper surface 11 b of the new footing 11. Since it is only necessary to cut the upper end portion of the rectangular steel sheet pile wall 13, it is not necessary to remove the steel sheet pile wall 13, and accordingly, the steel sheet pile wall 13 can be reduced in size, cost, and construction period. And can be easily installed even in a narrow work site.

  In addition, according to the said embodiment, although the square cylindrical steel sheet pile wall was used as an annular underground wall, a cylindrical steel sheet pile wall may be sufficient, and a square cylindrical or cylindrical soil-cement wall is cyclic | annular. It may be used as an underground wall. When the underground wall is formed with a soil cement wall instead of the steel sheet pile wall, the optimum seismic reinforcement at the work site can be performed at a lower cost depending on the ground conditions and the situation of the new pier. Further, although cement mixed soil is used as the solidified filler, other materials such as cement slurry other than cement mixed soil may be used. Furthermore, although the description has been made on the newly installed underground piers on the ground, it is of course applicable to underwater piers (underwater new foundations) such as river crossings and existing foundations. Furthermore, although the case where a part of the waste layer is left in the steel sheet pile wall has been described, it is needless to say that the embodiment can be applied to the case where the entire waste layer in the steel sheet pile wall is deleted. . Furthermore, the ground outside the annular underground wall may be solidified and improved.

It is sectional drawing which shows the new foundation structure built and constructed in the waste ground of one Embodiment of this invention. It is sectional drawing which shows the underground wall embedding state of the said one Embodiment. It is sectional drawing which shows the new pile driving state of the said one Embodiment. It is sectional drawing which shows the state of solidification material injection | pouring or stirring mixing at the time of the ground improvement of the said one Embodiment. It is sectional drawing which shows the ground excavation state of the said one Embodiment. It is sectional drawing which shows the filling state of the solidification filler of the said one Embodiment. It is sectional drawing of the newly installed foundation structure of a prior art example. It is sectional drawing which shows the underground wall embedded state of the said prior art example. It is sectional drawing which shows the ground excavation state of the said prior art example. It is sectional drawing which shows the quality soil substitution state of the said prior art example. It is sectional drawing which shows the new pile driving state of the said prior art example. It is sectional drawing which shows the penetration | infiltration state of the contaminated water of the said prior art example.

Explanation of symbols

5 buried layer (top layer)
6 Waste layer 8 Support layer (lowermost layer)
10 New piers (foundation structures)
11 New footing (footing)
12 New piles
12a Tip 12b Head 13 Square tubular steel sheet pile wall (annular underground wall)
14 Solidification improvement part 15 Cement mixed soil (solidification filler)

Claims (2)

In the foundation structure in which the tip supports the footings on the heads of a plurality of piles driven in order from the uppermost buried layer to the waste layer and the lowermost support layer,
An annular underground wall is provided in the ground below the waste layer from the buried layer around the footing, and at least the ground below the waste layer in the annular underground wall is solidified and improved. Characteristic foundation structure. The foundation structure according to claim 1,
A foundation structure filled with a solidified filler from a lower surface of the footing to a depth in a range effective for horizontal resistance of the plurality of piles in the annular underground wall.

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