JPS6231124B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing cast-in-place concrete pile holes.

Currently, there are two methods for constructing pile holes that are drilled in advance when constructing cast-in-place concrete piles such as foundation piles: the Benoto method and the reverse circulation method (hereinafter referred to as the reverse method). Broadly classified.

Regarding the selection of each method, the reverse method is generally applied when the pile hole is large in diameter and deep, and the Benoto method is applied when the pile hole is relatively small in diameter and deep. However, recently, the Benoto method,
A combination construction method that takes advantage of the characteristics of each reverse construction method has been implemented, making possible construction techniques that cannot be obtained with conventional construction methods.

However, in this combined construction method, the Benoto method excavates the pile hole to the planned depth first, and the reverse method follows, and the Benoto pile hole that precedes and the reverse pile hole that follows do not have the same hole diameter. (Reverse pile holes have a small diameter) and the vertical accuracy of reverse pile holes constructed at large depths is significantly inferior to Benoto pile holes, so it is not possible to improve drilling accuracy. Therefore, the construction accuracy of the driven piles was also poor.

As a result of studies in view of the above-mentioned conventional circumstances, the present invention aims to provide a construction method that can improve the vertical accuracy of pile holes in the combination of Benoto and reverse construction methods, and its gist is as follows: Construct the casing at any desired depth of the planned excavation depth,
After excavating using the Benoto method, using an excavator equipped with a rotating rotating bit and a stabilizer, the stabilizer was pressed and fixed to the casing and the wall of the borehole formed during excavation using the reverse method. The point is that the excavation is carried out in predetermined depth units while repeating fixation and release of fixation using a vertically movable stabilizer while ensuring accuracy.

Hereinafter, the present invention will be described in detail with reference to a specific example shown in the drawings. FIG.
Pile holes will be constructed in the following order:

First, as shown in A, the base 1 is cast and formed on the ground G, and a suitable guiding machine (not shown) is installed.
After centering the pile hole at the planned drilling position, the casing 2 is erected while maintaining vertical accuracy and applying an appropriate penetration force.

As shown in the figure, the casing 2 is built by press-fitting short pieces coaxially to each other as shown in B. In parallel with the press-fitting, the casing 2 is inserted from the guide machine to the suspension wire 3 while operating the guide machine. The hole is drilled using the so-called Benoto method, which performs intermediate digging and soil removal using a bucket 4 suspended on the principle of a plumb bob.

Furthermore, the casing 2 is excavated up to an arbitrary desired depth L' within the planned excavation depth L (in the example shown, approximately the planned depth).
Up to 1/2) The construction accuracy and construction depth are set until the drilling accuracy of the subsequent reverse construction method can be ensured by the casing 2.

After completing the digging of the casing 2 in this way, as shown in C, a pedestal 5 is installed on the base 1, and the turntable 6 of the pedestal 5 supports the rotary shaft 7 made of a tube shaft. Further, as shown in FIG. 2, the excavator 8 is suspended within the casing 2 by a wire 16 from the guiding machine.

This excavator 8 is equipped with a wide-wing rotating bit 9 at the tip of a rotating shaft 7, and above it is equipped with a single or multiple stabilizers 10 and 11 (in the case of FIG. 1, two stabilizers rotate with respect to the rotating shaft 7). The lower stabilizer 10 is supported so as to be slidable in the axial direction, and a weight 12 is attached to the lower part of the lower stabilizer 10. , 11 guide plates 13 are driven by the jack 14 to extend in the radial direction and press against the inner wall surface of the casing 2. As a result, the vertical accuracy is maintained by the casing 2 which has been built with high precision in advance. is maintained, and in this state, while driving and rotating the rotary shaft 7 connected to a suction pump (not shown) by an appropriate drive source, the tip of the rotary shaft 7 or the expanded blade rotation bit is rotated. From the nozzle (not shown) drilled in 9 to the ground 15
Excavating the ground 15 by driving and rotating the expanding blade rotary bit 9 while supplying stabilizing liquid to the
Alternatively, the lower part of the casing 2 is excavated coaxially with the casing 2 by a so-called reverse construction method in which excavation is performed while applying an appropriate penetration force.

More specifically, as shown in FIG. 2 and FIG. Since the excavator 8 is set to be able to slide with an effective stroke l in the direction shown in FIG. Then, the guide plate 13 is pressed against the inner wall surface of the casing 2 to position and maintain the rotary shaft 7 at the axis of the casing 2. After that, the rotary shaft 7 is driven and rotated as described above and excavation is performed using the expanded blade rotary bit 9. After digging in this manner by the effective stroke l, the excavation is stopped for a moment.

Next, as shown in D, after pulling up the rotating shaft 7 by a length corresponding to the effective stroke l, the guide plate 13 is retreated to the position indicated by the two-dot chain line, and the excavator 8
is made free with respect to the casing 2 or the excavation hole a, and then the excavator 8 is lowered as shown in E, and the guide plate 13 is pushed outward and pressed against the inner wall surface of the casing 2 to fix the excavator 8. In this manner, the expanding blade rotary bit 9 is driven and rotated to dig again by the effective stroke l, and by repeating the above operations, the pile hole a is excavated in depth units of the effective stroke l.

Excavation of the lower part of the casing 2 is performed using the expanding blade rotation bit 9.
As a result, the inner diameter of the pile hole a is excavated to be equal to the outer diameter of the casing 2, as indicated by the dotted lines in each figure of FIG.

Furthermore, when the excavation of the pile hole a progresses and the position of the stabilizer 10 is removed from the lower end of the casing 2, a guide plate 14 is placed on the inner wall surface of the pile hole a excavated as described above using the casing 2 as the excavation reference. The excavator 8 is fixed by pressing .

Therefore, since the excavator 8 is fixed by the stabilizer 10 with the casing 2 and the inner wall surface of the excavation hole a being drilled using the casing 2 as a reference for excavation accuracy, the positioning of the expanding rotary bit 9 in the excavation direction is difficult. As will be described later, the vertical excavation accuracy of pile hole a is ensured, and after the casing is pulled out, the upper part of the pile hole by the Benoto method and the lower part of the pile hole by the reverse method are separated. The holes will be drilled to the same inner diameter.

In FIG. 2, 17 is a shock absorber, 18 is a hydraulic hose, 19 is a hydraulic hose reel, 20 is a cable, and 21 is a cable reel. Connected to a ground slope control device (not shown).

In the pile hole a drilled as described above, reinforcing bar cages 22 are erected via the G column 21 by crane operation in the order shown in D, E, H, G, and C in Figure 1. , After centering the steel frame 25,
Concrete 23 is placed and backfilled, a casing puller 24 is installed, and the casing 2 is pulled out, and the cast-in-place concrete pile b is constructed.

The excavator guide mechanism of the stabilizers 10 and 11 described above is constructed as follows.

In FIGS. 4A and 4B, the sliding pipe 26 that is slidably covered with the rotating shaft 7 of the excavator is made of a spline that is rotatable coaxially with the rotating shaft 7 and slidable in the axial direction. Related inner tube 26'
It consists of an outer tube 26'' which is connected to this via a bearing, and four guide tubes 27 are attached at 90 degree intervals to expand and contract outward from the outer tube 26'' in the radial direction. A guide rod 28 is installed inside, and a hydraulic jack 1 is installed between it and the outer tube 26''.
4 interposed between the tip of the guide rod 28 and
The guide plate 13 is fixedly attached to the tip of the jack 14. A roller 30 attached to the tip of a guide rod 50 protrudes slightly outward from a window 29 formed in the guide plate 13, as shown in FIG. The guide plate 13 is biased as a force, and the sliding movement of the guide plate 13 along the wall surface of the casing 2 or the excavation hole a is changed into rolling motion by rollers, thereby facilitating the vertical movement of the guide plate 13. It also prevents the rotary shaft 7 from rotating at the same time.

FIG. 6 shows another configuration example of the guide mechanisms 10, 11, which has almost the same configuration as that shown in FIG. A system is shown in which hydraulic jacks 14 are connected to boxes 33 and 34, respectively.

FIGS. 7A and 7B show still other configuration examples of the guide mechanisms 10 and 11, which have almost the same configuration as the embodiment shown in FIG. are arranged vertically and connected by a jack 35, and both the upper and lower sliding tubes 26,
Jacks 14 are arranged at right angles from 26 and have guide plates 13 fixed to the ends of the output shafts, respectively, projecting symmetrically, and when the jacks 14 and 35 are driven, the casing 2 or the inside of the excavation hole can be measured by inchworms. The rotary bit is moved (lowered) in this manner, and by moving it in this way, it is possible to continuously drill holes without stopping the rotating bit.

FIGS. 8A and 8B show details of the shock absorber 17 shown in FIG.
6, 37 and the lower substrate 3 hanging vertically from the upper substrate 36.
It consists of a compression spring 40 that surrounds a guide rod 39 fitted into a guide hole 38 of No. 7 and is interposed between both substrates 36 and 37. On the other hand, the upper substrate 36 is slidable and the lower substrate 37 is fixed, so that the seat plate 42 of the guide mechanism can prevent sudden shocks caused by lifting up the rotating shaft 7 or lowering the guide mechanisms 10 and 11.
Compression spring 40 due to abutting with upper substrate 36
The upper substrate 36 is provided with a projection 43, and the seat plate 42 of the guide mechanism 10, 11 facing this is provided with a limit switch 44. At the lowering limit of the guide mechanisms 10, 11, a limit switch 44 is operated by the protrusion 43, and the lowering limit can be detected on the ground.

45 in FIG. 7B shows an inclinometer. Further, when using the construction method of the present invention, the control of the rotary bit 9, that is, the inclination correction, is performed manually or automatically based on the inclinometer 45 as described below.

That is, manual correction is performed by connecting the inclinometer 45 installed in the excavator 8 and the depth detector installed in the guiding device that mounts the excavator to the calculation section via a multiplier in the middle. 45 and the depth detector, the data is always sent to the calculation section, and the calculation section converts it into the amount of deviation.The converted amount of deviation and depth are displayed on the display meter, and the data are sent via the amplifier. At the same time, the data is sent to the recorder and recorded, and the operator arbitrarily operates the jack 14 of the guide mechanism while viewing these data so that the amount of deviation falls within the set value. It is done.

In addition, for automatic correction, the correction setting position is stored in the calculation unit in advance, and the amplifier and control unit are connected to the calculation unit so that the guide mechanism is automatically driven when the set deviation amount is reached. A system is assembled from a panel, a hydraulic pump control section, and a jack drive section, which automatically performs corrections.

Therefore, vertical accuracy can always be accurately maintained.

As explained above, according to the pile hole construction method of the present invention, large diameter and deep pile holes, which were difficult to construct using conventional methods, are excavated at the vertical accuracy reference point using the casing in the combined Benoto and reverse construction method. It is possible to excavate with high vertical accuracy while positioning and fixing in the excavation direction using the machine guide mechanism, and excavation can be carried out to the same diameter as the casing outer diameter even to the planned depth. It is possible to improve the accuracy of construction, and it also has the effect of allowing large diameter and deep pile holes to be constructed without pollution.

In addition, in the present invention, it is possible to excavate the same hole diameter as the preceding vent in the subsequent reverse.
It is possible to lower the casing, which can also be advantageous on the basis of the stabilizer reaction force.

Further, as shown in FIG. 1C, it is advantageous to provide a plurality of stabilizers because the risk of the bit being affected by the vibration of the upper part of the rotating shaft 7 is drastically reduced.

[Brief explanation of the drawing]

Figures 1A to 1C are vertical cross-sectional views showing the pile hole and the pile construction order according to an embodiment of the pile hole construction method according to the present invention, and Figure 2 is a vertical cross-sectional view showing the ground equipment of the excavator guide. , Figures 3A to 3E are longitudinal sectional views showing the procedure of guiding the excavator, Figures 4A and 4B are a plan view and a half-sectional front view of the excavator guide mechanism, and Figure 5 is a guide roller of the excavator guide mechanism. 6 and 7A and 7B respectively show other configuration examples of the excavator guide mechanism. FIGS. 8A and 8B are a plan view and a front view showing a shock absorber in an excavator. Brief explanation of symbols, 2...Casing, 7...
Rotating shaft, 8...excavator, 9...blade rotation bit,
10/11... Stabilizer (guide mechanism),
13... Guide plate, 14... Jacket, 26... Sliding pipe, a... Pile hole.

Claims (1)

[Claims] 1 In the combination method of Benoto and reverse circulation, centering is performed in advance, the casing is built to any desired depth of the planned depth, and after excavation is carried out using the Benoto method, it is installed on the expanding blade rotary bit and the excavator. Reversing using an excavator equipped with a stabilizer that is operated based on the amount of deviation calculated by calculating the data sent from the inclinometer and the depth detector installed in the guide device that mounts the excavator. Using the circulation method, the stabilizer is pressed and fixed to the casing and to the wall of the excavation hole as the excavation progresses to ensure excavation accuracy, and the process of fixing the excavator, excavating, and removing the stabilizer is repeated for each predetermined depth unit. A construction method for cast-in-place concrete pile holes, which is characterized by excavating to a planned depth.