JP3100904B2 - Foundation construction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a foundation constructed on a support base for stably supporting a structure.

[0002]

2. Description of the Related Art In constructing various structures, a direct foundation method is adopted when a support base can be found in a relatively shallow place where excavation is possible. Generally, a basic method is adopted.

[0003]

However, if the pile foundation method is adopted when the support base is inclined, the pile lengths become uneven, and particularly, the structure to be constructed is large in weight and large in plan. And if the support base is rock,
When an earthquake occurs, the entire structure behaves like a twist, which causes a problem in design.

[0004] In view of this, a stratum having a poor supporting capacity on the support base is removed, and an inexpensive material having sufficient strength to support the structure, for example, wrapping concrete in which cracks and the like are made of coarse aggregate is replaced. It is conceivable to adopt a direct foundation method. Conventionally, the direct foundation method using lap concrete has been frequently used when the support base is relatively shallow, but when the amount of excavated soil to be replaced with lap concrete is small, construction is easy, and It is also advantageous in terms of cost.

However, when the support base is inclined, the excavation work is performed in a state where the excavation bottom surface is inclined. Therefore, the earth pressure acting on the retaining wall becomes uneven earth pressure, and the construction is troublesome. . In addition, if it is large on a plane, it will be difficult to adopt a normal girder method, so a tieback anchor method will be used instead of this girder to make the retaining wall self-supporting. Is difficult to construct on soil with loose earth and sand and abundant groundwater, and the cost tends to be high.

[0006]

SUMMARY OF THE INVENTION In order to solve such a problem and simplify the construction and reduce the construction cost, in the present invention, from one side of the construction area of the structure to be supported to the other. In a method of constructing a foundation for stably supporting the structure at a predetermined ground height with respect to a support base inclined downward, a strut is applied to a stratum on the support base at the other end where the depth is substantially maximum. Preliminary excavation in a belt-like shape, a cement-based solidification material is poured into the pre-excited trench, a wall is constructed, and the wall is used as a retaining wall, and subsequent excavation is performed without retaining the remaining stratum on the support base. Then, the remaining cement-based solidified material is cast into the subsequent excavated portion integrally with the wall body. As the cement-based solidifying material, there is a material that solidifies to a required strength capable of suitably supporting the structure according to the weight of the structure, for example, wrap concrete, soil cement, poorly mixed mortar, and the like.

[0007] In particular, the wall blocks the underground water flowing from the other side of the stratum on the support base toward one side, that is, from flowing into the subsequent excavation portion from the opposite side of the subsequent excavation portion with the wall interposed therebetween. It is preferable.

[0008] In addition to this, it is preferable that a pier in the excavation of the preceding excavation trench is supported by a cutting beam.

[0009] Further, it is preferable that the wall has a protruding portion protruding toward one side.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below based on embodiments shown in the accompanying drawings.

FIG. 1 shows a foundation concrete constructed based on the foundation construction method according to the present invention. The foundation concrete 1 is provided on a support surface 2 inclined downward from the right side to the left side in the figure, and in order to stably support the structure 3 at a predetermined ground height, a construction surface of the structure 3 and a support base. After excavating and removing the soft stratum between the entire area and the lap, concrete was poured and the supporting base 2 was removed.
It is constructed at a predetermined height in a state in which it is in close contact with.

The support base 2 is located above the construction surface of the structure 3 on the right side in the figure, and is horizontally flat so as to be continuous with the finished surface of the foundation concrete 1.
The support base 2 is cut so that the structure 3 can be constructed at a predetermined ground height by the raised portion of the base concrete 1 and the cut part 4 of the support base 2.

The support base 2 is curved like a valley, and as shown in FIG. 2, a boundary line 5 between a portion where the foundation concrete 1 is constructed and the cut portion 4 is curved in a substantially U-shape. The depth gradually increases from the boundary line 5 toward the outer edge of the root cutting plane 6, and the depth becomes maximum at the outer peripheral edge of the root cutting plane 6.

When excavating the stratum on the support base 2, a root cutting plane 6 is formed by a dividing line 7 shown by a broken line in FIG.
Is divided into two sections. That is, the preceding excavation groove 8 divided into a band shape with a predetermined width along the outer edge of the root cutting plane 6 where the excavation depth is the largest is constructed prior to the subsequent excavation portion 9.

The preceding excavation groove 8 has an F-shape in plan view as a whole, and has a portion 8a extending over the entire length of one side of the outer periphery of the square root cutting plane 6 and a portion along the adjacent edge. And a portion 8b extending from the portion 8a to the cut portion 4 and a portion 8c extending substantially at a right angle from a substantially middle position of the portion 8a.

First, as shown in FIG. 3A, a sheet pile 11 is driven along a root cutting plane corresponding to the preceding excavation groove 8, and a cutting beam 12 is erected between the sheet piles 11 facing each other. The preceding excavation groove 8 is excavated while providing the support. Then, as shown in FIG. 3 (b), lapping concrete is poured into the preceding excavation groove 8 to construct a concrete wall 13 having a F-shape in plan view which forms a part of an outer peripheral portion of the foundation concrete 1. Is done.

Next, a subsequent excavation portion 9 extending from the concrete wall 13 to the cut portion 4 is excavated. As shown in FIG. 3B, the vertical cross section of the subsequent excavation portion 9 forms a substantially right triangle having the support base 2 inclined downward from the cut portion 4 toward the concrete wall 13 as an oblique side. Then, since the concrete wall 13 functions as a gravity-type retaining wall having high stability, the subsequent excavated portion 9 is excavated without particularly applying the retaining. At this time, the concrete wall 13 can obtain a large reaction force against the earth pressure acting on the portion 8a by the projecting portion constructed on the portion 8c of the preceding excavation groove 8.

When the support base 2 corresponding to the subsequent excavation portion 9 is exposed in this way, finally, the lapping concrete is cast into the subsequent excavation portion 9 integrally with the concrete wall 13 of the preceding excavation groove 8 to form the foundation concrete 1. Is completed.

In the above excavation step, since a high water level groundwater zone exists in the upper layer of the support base 2, when excavating the preceding excavation groove 8, a steel sheet pile having water-blocking properties is used, or A water impermeable wall is appropriately provided outside the root cutting plane 6.

On the other hand, in the excavation of the subsequent excavation portion 9,
The concrete wall 13 is in close contact with the water-impermeable support base 2 and also functions as a water-blocking wall having a high water-blocking property, thereby preventing groundwater from flowing into the excavation recess of the subsequent excavation portion 9 from the outside. Therefore, work can be performed efficiently without bothering with groundwater treatment.

In the present embodiment, the preceding excavation groove 8 has an F-shaped planar shape as a whole.
The present invention is not limited to such a form, and is appropriately divided into an optimal plane shape according to the shape of the structure 3, the ground, and the condition of groundwater.

In the present embodiment, the support base 2
Is partially located above the construction surface of the structure 3, and the support base 2
However, it is not always necessary to use the cut, and the support base 2 is located in the vicinity of the ground surface and can be similarly constructed as long as the excavation depth does not need the mountain retaining. .

Further, in this embodiment, the case where the construction method according to the present invention is particularly effective, that is, the case where a large amount of groundwater exists, has been described. However, the present invention has no groundwater or can be ignored in a small amount. In this case, it can be applied substantially in the same manner.

[0024]

As described above, according to the present invention, an inexpensive layer having sufficient strength to support a structure by excavating and removing a stratum having a poor supporting force on a supporting base inclined downward from one side to the other side. Since it is replaced with a cement-based solidifying material such as laple concrete, sufficient supporting force can be ensured and construction can be performed at low cost. Then, when casting the cement-based solidified material, first, the other end where the depth is substantially maximum is excavated in a strip shape to construct a wall. Excavation, and the mountain retaining is largely omitted. At this time, since the wall functions as a large-capacity gravity-type retaining wall having high stability, there is an extremely large effect in performing construction safely, reliably, and economically. This is particularly effective in the construction of large structures.

In addition, in the case where a groundwater zone exists above the support base, the groundwater is prevented from flowing into the subsequent excavation portion by the wall, so that groundwater treatment in the excavation process of the subsequent excavation portion is greatly reduced. You. In other words, a large-volume wall body is superior in water-blocking and less likely to be broken compared to a mountain retaining plate made of steel sheet pile or the like in the conventional method, and moreover, it is easy to inject grout into the inflow of groundwater. Since it can be easily dealt with by processing, it has a very large effect in performing work safely, reliably and economically. This is particularly effective for large-scale constructions where the groundwater flow is large and a large excavation pit may be submerged when collapsed, making it difficult to respond.

Further, in the preceding excavation groove which is excavated while being grounded, if the preceding excavation groove is set to have such a dimension width that a cutting beam can be easily erected, and the girder is supported by the cutting beam, the cost can be reduced. In addition, since it is possible to securely support the mountain retaining, there is a great effect in reducing the construction cost.

Further, when the wall is provided with the protruding portion, the supporting force of the wall can be increased without increasing the width of the preceding excavation groove. For this reason, it is possible to prevent the span of the cutting beam from becoming longer during the excavation of the preceding excavation groove, which is effective in reducing the construction cost.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a foundation concrete constructed based on a foundation construction method according to the present invention.

FIG. 2 is a plan view showing the entire view of the construction area.

FIG. 3 is a longitudinal sectional view similar to FIG. 1, which comprises (a) and (b), and shows a step-by-step construction state of a foundation concrete.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Foundation concrete 2 Support base 3 Structure 4 Cut part 5 Boundary line 6 Root cutting plane 7 Dividing line 8 Prior excavation groove 9 Subsequent excavation part 11 Sheet pile 12 Cut beam 13 Concrete wall

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-74269 (JP, A) JP-A-8-277520 (JP, A) JP-A 5-118025 (JP, A) JP-A-5-180520 140955 (JP, A) Special Table 63-501435 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) E02D 27/00-27/52 E02D 3/00 101 E02D 3/12 E02D 31/02

Claims (4)

(57) [Claims] 1. A method for constructing a foundation for stably supporting a structure at a predetermined ground height on a support base inclined downward from one side of the construction area of the structure to be supported toward the other, comprising: Is preliminarily excavated in a band shape while applying a mountain retaining to the stratum on the support base at the other end that is substantially the maximum, and a cement-based solidified material is poured into the preceding excavation groove to construct a wall body,
Subsequent excavation of the wall body as a retaining wall without retaining the remaining stratum on the support base, and casting the remaining cement-based solidified material integrally with the wall body in the subsequent excavated portion. The construction method of the foundation. 2. The method according to claim 1, wherein groundwater flowing from one side to the other in the stratum on the support base is blocked by the wall. 3. A pier in the excavation of the preceding excavation trench is supported by a cutting beam.
Alternatively, the method for constructing a foundation according to claim 2. 4. The method according to claim 1, wherein the wall is provided with a protruding portion protruding toward one side.