JP4336828B2 - Substructure - Google Patents

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. 6, the new footing (foundation) 2 of the 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. In addition, the code | symbol S in FIG. 6 shows a groundwater level.

  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 according to the following procedure.

That is, as shown in FIG. 7, a square cylindrical steel sheet pile 9 having a diameter larger than the ground surface of the buried layer 5 is buried in the ground of the buried layer 5 and the waste layer 6 around the new footing 2. Next, as shown in FIG. 8, a plurality of pile retaining works P are provided in the steel sheet pile 9 to completely pump the ground water in the steel sheet pile 9, and then the buried layer 5 and the disposal The ground of the layer 6 is completely excavated. And as shown in FIG. 9, the quality soil 4 is carried in in the steel sheet pile 9, and the waste layer 6 in this steel sheet pile 9 is replaced with the 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. 6 and 11, 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 and the steel sheet pile. The new pier 1 is constructed by cutting the upper end of 9.
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 the arrows in FIG. 11, the sewage X penetrates to the support layer 8 through the water supply of the plurality of newly installed piles 3 penetrating the water-impermeable layer 7 and may contaminate the groundwater. .

  Furthermore, since the excavation of the ground of the buried layer 5 and the waste layer 6 in the steel sheet pile 9 is a dry construction, as shown in FIG. The cost was increased accordingly.

  Therefore, the present invention has been made to solve the above-described problems, and can reliably prevent sewage from penetrating into the supporting tank and can improve the overall seismic performance. The purpose is to provide.

  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 a waste of the waste layer in the annular underground wall is completely excavated into a space. It is characterized by being filled with a solidified filler.

  According to a second aspect of the present invention, there is provided the foundation structure according to the first aspect, wherein the solidification filling is performed from a lower surface of the footing to a depth within a range effective for horizontal resistance of the plurality of piles in the annular underground wall. It is characterized by filling the material.

  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 solidified filler is filled in the space where the waste is completely excavated, even if there is leakage of contaminated water from the joint part of the underground wall, the solidified part of the solidified filler can be surely stopped. It is possible to prevent the diffusion of contaminated water that is about to flow through the piles to the support tank. 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 an underground wall embedded state, and FIG. 3 shows an excavation state of the ground FIG. 4 is a cross-sectional view showing a state in which the solidified filler is filled, and FIG. 5 is a cross-sectional view showing a new pile driving state.

  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) or more, 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. Moreover, the code | symbol S in the figure has shown the groundwater level. The waste 6 'of the waste layer 6 in the square cylindrical steel sheet pile wall 13 is completely excavated, and the new footing 11 in the inner peripheral surface 13a of the square cylindrical steel sheet pile wall 13 is removed. Cement mixed soil (solidified filler) 14 is filled from the lower surface 11a to a depth in a range effective for the horizontal resistance of the plurality of new piles 12. In this embodiment, a cement mixed soil 14 is filled in a space formed between the lower surface 11a of the newly installed footing 11 in the inner peripheral surface 13a of the square cylindrical steel sheet pile wall 13 and the excavation bottom, and the newly installed footing. 11 and a square cylindrical steel sheet pile wall 13 and cement mixed soil 14 are integrated and fixed.

  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 above the impermeable layer 7, a steel sheet pile wall 13 having a diameter smaller than the ground surface of the buried layer 5 is effective for the horizontal resistance of the pile 12 newly formed above the impermeable layer 7. It is buried up to the larger one of the depths of the appropriate range plus the length of digging. In this case, a state in which the square cylindrical steel sheet pile wall 13 is embedded up to the upper part of the impermeable layer 7 is shown.

  Next, as shown in FIG. 3, the ground resistance of the buried layer 5 and the waste layer 6 in the square cylindrical steel sheet pile wall 13 is the lower end of the waste layer 6 or the horizontal resistance of the plurality of new piles 12. And excavating to a depth within the effective range (for example, 1 / β), and appropriately treating the waste 6 ′ of the waste layer 6. Next, as shown in FIG. 4, cement mixed soil (solidified filler) 14 is used in a square cylindrical steel sheet pile wall 13 to a depth effective for the horizontal resistance of a plurality of new piles 12 using a tremy pipe 20. Then, fill underwater from the bottom of the drilling. At that time, simultaneously with the filling of the cement-mixed soil 14, water (contaminated water) W in the steel sheet pile wall 13 in the shape of a square cylinder is pumped up by the pump 21 and appropriately processed.

  Next, as shown in FIG. 5, a plurality of new piles 12 are driven so that the tip 12 a reaches the support layer 8 from the cement mixed soil 14. 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 steel sheet pile wall 13, and after that, in the steel sheet pile wall 13 The excavated portion is backfilled with high quality soil 4 and the like, and the upper end portion of the steel sheet pile wall 13 protruding from the upper surface 11b of the new footing 11 is cut, whereby the new pier 10 is completed.

  In this manner, a square cylindrical steel sheet pile wall 13 is embedded from the buried soil layer 5 around the new footing 11 to the ground above the impermeable layer 7, and the square cylindrical steel sheet pile is formed from the lower surface 11 a of the new footing 11. Mixing cement into the depth of the effective range for the horizontal resistance of the plurality of new piles 12 in the wall 13 (in this embodiment, in the space formed by completely excavating the waste 6 'in the steel sheet pile wall 13) The soil 14 is filled and the new footing 11, the square cylindrical steel sheet pile wall 13 and the cement-mixed soil 14 are integrated and fixed, so that the impermeable layer 7 and the supporting tank ( The contaminated water from the waste layer 6 outside the steel sheet pile wall 13 that is about to flow to the water-permeable layer 8 can be reliably blocked by the solidified portion of the cement-mixed soil 14 or the like. Thereby, sewage penetration into the impermeable layer 7 and the support layer 8 can be reliably prevented.

  Further, the newly installed footing 11 and the square cylindrical steel sheet pile wall 13 are integrated and fixed via the cement mixed soil 14, so that the strength of the cement mixed soil 14 and the restraining effect by the square cylindrical steel sheet pile wall 13 are obtained. The horizontal resistance (lateral resistance) of the plurality of new piles 12 can be increased. Furthermore, adhesion resistance increases by solidification of the cement-mixed soil 14 around the heads 12b of the plurality of new piles 12 in the square cylindrical steel sheet pile wall 13, and the vertical bearing force can be increased.

  Further, the ground around the square cylindrical steel sheet pile wall 13 improves the rigidity around the new footing 11 and the cement-mixed soil 14 functions as a foundation. Moreover, since the rigidity of the square steel sheet pile wall 13 has the effect of suppressing deformation around the new footing 11, the horizontal displacement and rotation of the new footing 11 during the action of level 2 class seismic load is suppressed, and it is earthquake resistant. 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 11c of the new footing 11 with the inner peripheral surface 13a of the square steel sheet pile wall 13, and on the upper surface 11b 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, thereby reducing the size and cost of the steel sheet pile wall 13 and shortening the construction period. In addition to being able to plan, it can be easily constructed even in a narrow work site.

  Further, the filling of the cement-mixed soil 14 can be performed underwater, and the conventional large-scale mountain retaining work P is not necessary, and the mountain retaining structure P can be simplified. Cost reduction can be achieved.

  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 for the work site can be performed at a lower cost depending on the ground conditions and the situation of the new underwater 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. In addition, the explanation has been made on the newly installed underground piers and existing foundations on the ground, but it is of course applicable to underwater piers (new underwater foundations) such as river crossings. Furthermore, although the case where all the waste layers in the steel sheet pile wall were excavated and deleted was explained, the entire area of the ground above the impermeable layer 7 in the steel sheet pile wall 13 was excavated and formed by this excavation. Of course, the space may be filled with a solidified filler. 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 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 which shows the new pile driving state 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 6 'Waste 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 Cement mixed soil (solidified 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 waste of the waste layer in the annular underground wall is completely excavated in the space. A foundation structure that is filled with a solidified filler. The foundation structure according to claim 1,
A foundation structure filled with the 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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