JPS62288214A - Wall type bottom-expanded piling work - Google Patents

Abstract

PURPOSE:To integrally construct a wall type bottom-expanded pile with a sheathing wall by a method in which excavation is made for all cross section to a given depth to form the upper wall-type space of the wall type bottom- expanded pile and the wall type continuous wall, and given tapered faces are formed by a specific type bucket. CONSTITUTION:Excavation is made for all cross section to a given depth L1 while applying stabilizing treatment to the wall face by using a specific type bucket 100 to form the wall-type space for a wall type continuous wall and a wall type bottom-expanded pile 5. While opening the bucket 100 from the depth L1 to the depth L2 to the directions of a-a' in order, the pit wall is pressingly excavated to form a given tapered face 4. A reinforcing bar cage is set in the pit, and concrete is placed to complete the construction work. The continuous underground wall and the bottom-expanded pile can thus be constructed integrally or adjacently.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an expanded bottom pile construction method, and more specifically, to a wall type expanded bottom pile construction method used for earth retaining walls or cast-in-place piles. It is.

(Prior art) Expanded bottom piles for increasing the pile bearing capacity per pile are disclosed in Japanese Patent Application Laid-Open No. 59-185220 and Japanese Patent Publication No. 55-52.
It is disclosed in Publication No. 5.

In these disclosed expanded bottom piles, the foundation is constructed by using a special excavator to excavate the bottom of the hole wide in all directions in a conical or operisque shape.

(Problems to be Solved by the Invention) However, conventional expanded-bottom piles have had various problems as listed below.

■First, as shown in Fig. 6 (A) and (B), a conventional expanded bottom pile a is built close to the retaining wall, and an underground outer peripheral column d is connected to this expanded bottom pile via an underground beam C. When supporting with piles, the distance between the column core and the pile core from the retaining wall will differ due to the difference in diameter between the column d and the expanded-bottomed pile a. For this reason, an eccentricity e occurs between the underground peripheral column and the expanded bottom pile, and the upper load is not properly transmitted to the expanded bottom pile, and the structural problem is that bending stress and shearing stress due to the upper load are generated in the intermediate underground beam. There was a problem.

■Conventional expansion piles have expansion parts in all directions, such as when they are formed integrally with the foundation of an earth retaining wall. There was a problem in that only the expanded bottom part had to be separated, which was disadvantageous in terms of effective land use.

■The expanded bottom part of conventional expanded-bottom piles has a conical or operisk shape, and there was a structural problem in that the surrounding surface could not generate frictional force with the ground, leading to increased settlement.

■Conventional expanded-bottom piles had a structural problem in that the ratio of the cross-sectional area of the upper cylinder to the area of the expanded bottom was large, resulting in low horizontal rigidity.

■For conventional expanded bottom piles, the ratio of pile length to pile diameter is small,
Design guidelines (for example, according to the Tokyo guidelines, pile length/pile diameter ≦1
If it is 0, the pile bearing capacity will be reduced),
There was a structural problem in that the support strength had to be reduced.

■Conventional expanded-bottom piles have a large effective diameter, and when conforming to the design guideline of 2D or more between piles, there was a structural problem in that it was not possible to plan the proper arrangement of piles.

■Conventional expanded-bottom piles have a problem in construction because the expanded-bottom surface is wide, and the conical surface can easily collapse depending on the soil properties.

The present invention has been made in view of the above-mentioned conventional problems, and provides a wall-type expanded-bottom pile construction method that promotes effective land use, stabilizes structural design with an optimal cross section, and significantly improves construction accuracy. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, according to the wall-type expanded bottom pile construction method of the present invention, in the expanded bottom pile construction method of earth retaining walls or cast-in-place piles constructed close to the site boundary line, , using a means of excavating or widening excavation and removing earth between opposing sides, excavate the ground to a predetermined depth and remove the earth to form an upper hole, and then construct a wall that expands only in the predetermined opposing direction to the supporting ground. A trench is excavated and earth is removed to form an expanded bottom hole. Then, rigid material is built into the hole, and concrete is then poured to create a rectangular horizontal section and a nearly trapezoidal vertical section in the expanded bottom section. The wall-type bottom-expanding pile is constructed by forming the wall-type bottom-expanding pile in the shape of a wall, and the wall-type bottom-expanding pile is constructed close to the site boundary line integrally with the earth retaining wall or cast-in-place pile.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an underground structure constructed close to a site boundary line 13 using the construction method of the present invention.

In this underground structure, a wall-type bottom-expanding pile 1 having a tapered surface 4 in one direction from a to a is located close to a site boundary line 13 and has an earth retaining wall 10 (in this example, two continuous walls 10) with approximately the same thickness. It is built in one piece. Then, it is stably fixed to the supporting ground 14, and a sufficient ground reaction force is obtained from this supporting ground 14. Further, this wall-type bottom-expanding pile 1 is also used as a foundation for an underground outer peripheral column 12 that supports an upper structure (not shown). That is, the underground outer peripheral column 12 is fixed to the underground beam 11 in order to obtain a wider space, and is incorporated into a part of the type continuous wall 10 via the built-in part 6.

As a result, this underground structure has a rigid structure as a whole.

Next, a method of constructing a wall-type expanded bottom pile will be explained in relation to the continuous wall type 10 with reference to the same figure.

First, soil conditions 1! The most suitable excavator is selected according to the construction conditions. This excavator uses, for example, a specially shaped packet 100 disclosed in Japanese Utility Model Application No. 60-172891 by Akashi Suekan.

FIG. 4 is a side view without showing this specially shaped packet. This special shaped packet 100 has a triangular shape,
It has the characteristic that the maximum width in the open position is larger than the width in the closed position. Using this special-shaped packet 100, first, the entire section is excavated to a predetermined depth Ll while performing wall surface stabilization treatment to form a wall-shaped continuous wall 10 and a wall-shaped cavity in the upper part of the wall-type expanded bottom pile 5.

At this time, at the position of the wall-shaped bottom-expanding pile 1, further excavation is performed by a depth L2 to the point where the support layer is reached, thereby forming a rectangular parallelepiped 3 (indicated by diagonal lines) that becomes a part of the bottom-expanding portion 2.

Next, the specially shaped packet 100 is gradually opened in the a-a direction from depth Ll to depth L2 while pressing against the hole wall to scrape the hole wall, and then the scraped earth and sand are removed to form a predetermined tapered surface 4. Form. Once the predetermined continuous wall cavity and expanded bottom hole are formed, a reinforcing cage is erected and concrete is poured to complete the construction.

In this way, the earth retaining wall in which the type continuous wall and the wall type expansion pile are integrated can be constructed simultaneously and safely at a position closer to the site boundary line.

In addition, in the above-mentioned embodiment, the upper part 5 of the wall type expansion pile is connected to the earth retaining wall 1.
0, but as shown in FIG. 2, it may be constructed at the lower part of the earth retaining wall 10 and the earth retaining wall 10 may be supported at its upper end. In this case as well, the retaining wall 10 and the wall-type bottom expansion pile 1
is constructed integrally and simultaneously.

Further, the wall type bottom expanding pile may have a wall bottom having a multi-stage trapezoidal vertical cross section as shown in FIG.

Furthermore, in the first embodiment described above, an earth retaining wall in which a type continuous wall, a wall-type bottom expansion pile, and an underground peripheral column are integrated is illustrated, but according to this construction method, the structure shown in Figs. 5 (△) and (B) As shown, even when constructing the underground outer peripheral column 12a independently in the vicinity of the earth retaining wall 10a, it is of course possible to construct the underground outer peripheral column and the wall-type expansion pile 1a integrally and flush with each other.

(Effects of the Invention) As described above, according to the wall type expanded bottom pile using the wall type expanded bottom pile construction method of the present invention, since the expanded bottom portion is made the wall bottom, the underground continuous wall and the bottom expanded pile can be integrated or close to each other. In addition, if necessary, the vertical planes of the underground wall and the expansion pile can be made flush, so that the underground perimeter column built into the underground wall or the underground perimeter near the underground wall can be The pillars can be constructed closer to the property line, thus making effective use of the land.

Moreover, there are considerable advantages in terms of structural design, which will be explained below.

In other words, since the expanded bottom part is wall-shaped with parallel vertical surfaces,
On this vertical circumferential surface, a frictional force between the ground and the circumferential surface can be expected, and the pile supporting force is the sum of this circumferential surface frictional force and the tip supporting force, which acts on the safe side against subsidence.

In addition, the horizontal rigidity parallel to the longitudinal axis of the expanded bottom portion is greater than that of conventional conical expanded bottom piles, so if the desk arrangement is taken into account, it will work effectively against earthquakes.

In addition, since the ratio of the pile length to the pile diameter is large, it is unlikely to conflict with design guidelines, and is therefore advantageous in reducing the pile resistance.

Further, since the expanded bottom portion has a rectangular cross section, appropriate pile spacing can be maintained by arranging the desk along the short side direction.

Furthermore, as a construction advantage, since the groove is excavated in the shape of a wall in the widened bottom part, the arch action of the groove digging works on this widened side, preventing the hole wall from collapsing, improving construction accuracy. .

[Brief explanation of the drawing]

Fig. 1 is an overall perspective view of an underground structure constructed using the construction method according to the present invention, and Figs. 2 and 3 respectively show other embodiments of wall-type expanded bottom piles constructed in trenches according to the present invention. FIG. 4 is a side view showing an example of an excavator used in the present invention, FIG. 5 shows an underground structure constructed according to another embodiment of the present invention, and FIG. 5(A) is a plan view thereof. Figure, Figure 5 (B)
Figure 6 shows an underground structure using conventional expanded bottom piles, Figure 6 (A> is its plan view, Figure 6 (
B) is its vr-VI sectional view. 1.1a...Wall type bottom expansion pile 2...Bottom expansion part

Claims (1)

[Claims] (1) In the expanding bottom pile construction method for earth retaining walls or cast-in-place piles that are constructed close to the site boundary line, the ground is excavated to a predetermined depth and excavated between opposing sides by means of excavation or widening excavation and soil removal. Earth is removed to form an upper hole, and furthermore, a wall-shaped trench is excavated in the shape of a foot spreading only in a predetermined opposing direction to the supporting ground, and the earth is removed to form an enlarged bottom hole.Next, rigid material is built into the hole. After that, concrete is poured and the expanded bottom part is formed into a wall shape having a rectangular horizontal cross section and a substantially trapezoidal vertical cross section to construct a wall type expanded bottom pile, and the wall type expanded bottom pile is installed in the above-mentioned earth retaining wall or at the location. A wall-type expanded-bottom pile construction method that is characterized by being constructed in close proximity to the site boundary line together with driven piles.