JPH0243846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for confirming the support layer of a pile when drilling a hole in the ground with an earth auger when driving a ready-made pile.

(Conventional structure and its problems) Traditionally, there are two methods for driving ready-made piles: the embedded pile method and the hollow pile method. This is a construction method in which the auger is pulled out while pouring foot hardening mortar and surrounding wall stabilizing liquid into the pile hole, and then solid ready-made piles are erected into the pile hole.

On the other hand, the latter is a construction method in which an auger is inserted into the hollow interior of a hollow ready-made pile, and the ready-made pile is inserted while drilling into the ground with the cutting bit facing the bottom end of the pile.

Therefore, in order to confirm the pile support layer in both of these construction methods, a soil profile map and a contour map of the surface depth of the support layer are created in advance based on the results of a boring survey, and the support layer is checked while referring to this contour map. When approaching the layer, the excavation speed is kept constant and the change in ampere meter attached to the auger motor is read to estimate when the support layer has been reached.

However, according to this method, as the excavation depth becomes deeper, the excavated soil adheres to the area around the auger and forms a cylindrical lump of soil.If the auger rotates in this state, the frictional resistance on the circumferential surface increases, and this resistance There was a problem that this added to the resistance of excavating the ground, making it unclear to confirm the supporting ground layer.

(Object of the Invention) The present invention eliminates the above-mentioned problems and provides a method for confirming the support layer of a ready-made pile, which allows the support layer of the pile to be accurately confirmed without being affected by the surrounding ground.

(Structure of the Invention) In order to achieve the above object, the method for confirming the support layer of ready-made piles of the present invention is based on the ground cutting resistance of the auger when drilling a hole in the ground for driving a ready-made pile with an auger. 5-10 caused by auger etc.
This is done by measuring the magnitude of vibration around Hz and comparing the change in the magnitude of vibration with a soil chart created in advance. Accurately confirm the supporting layer without being affected by vibrations caused by factors other than resistance, and by utilizing the fact that the stratum with a larger soil N value vibrates more strongly in this range, and that the gravel layer vibrates more strongly depending on the type of soil. This is the way to do it.

(Description of Embodiments) An embodiment of the present invention will be described with reference to the drawings. An auger leader 2 is vertically supported by a base machine 1 on the ground, and a drive device 4 for an auger 3 is arranged on the auger leader 2 so as to be vertically slidable. The auger 3 is rotated by the driving device 4, and the driving device 4 is lowered by operating a winch on the base machine 1, while a pile hole 6 is drilled in the ground 5 as is well known.

A vibration sensor 7 is fixedly attached to the drive device 4, and is electrically connected to a vibration measuring device 8 installed in the driver's seat of the base machine 1 and a display 9 for displaying vibration measurement results.

This sensor 7 senses vibrations caused by ground cutting resistance due to the rotation of the auger, and electrically captures the frequency and magnitude of the vibrations. Further, as shown in FIG. 2, the vibration measuring device 8 has electrical components connected to it in order to sequentially perform a pandobus filter 10, an amplification 11, a full-wave rectification 12, and a peak value fade-out 13, as well as a recorder 14. It is provided.

Note that the same effect can be obtained even if the sensor 7 is attached to the driver's seat.

Now, when the pile hole 6 is excavated by the auger 3, vibrations are generated at the tip of the auger due to ground cutting resistance, and the vibrations are transmitted to the sensor 7 and converted into an electric signal by the sensor 7. It is transmitted to the vibration measuring device 8.

In the vibration measuring device 8, only signals corresponding to frequencies around 5 to 10 Hz are passed through the pandobus filter 1.
0, perform amplification 11, full-wave rectification 12, and fade out the peak value 13, record the signal on the recorder 14 and display it on the display 9, and display this display on the driver's seat of the base machine 1. The driver etc. reads it.

On the other hand, as shown in Figure 4, the driver's seat is equipped with a soil log map 15 that has been recorded and displayed in advance through the Borin survey.
The rotational force of the auger 3 is kept constant in the vicinity of the estimated depth of the support layer, and the hole is drilled while checking the depth of the hole in the ground 5.

When the auger reaches the support layer, the cutting resistance increases, so the magnitude of the vibration generated in the auger in the vicinity of 5 to 10 Hz becomes large, and this is displayed on the display 9, and the driver cuts the auger tip into the support layer. This allows you to confirm that the part has arrived.

According to actual measurements, the vibrations generated when drilling into the ground become particularly large at frequencies around 5 to 10 Hz, while the vibrations caused by the base machine 1 and drive device 4
Since the vibration caused by cutting force becomes significantly large at frequencies of 40 to 250 Hz, it was found that by measuring only frequencies around 5 to 10 Hz, it was not affected by vibrations caused by factors other than cutting resistance. did.

Furthermore, as shown in Fig. 3, it was also found that in the frequency range of 5 to 10 Hz, the higher the N value of the soil, the more vibrations occur, and the more vibrations occur in gravel layers.

The support layer of piles is often a gravel layer, with an N value of 50
Since the above layers are selected, it is possible to determine the supporting layer by measuring the magnitude of vibration near the frequency of 5 to 10 Hz and checking the change in the magnitude of vibration corresponding to changes in the strata. It is possible.

FIG. 4 shows an actual example, and shows an output diagram 16 from the display device that displays the output of vibrations generated during drilling according to depth, in comparison with a soil columnar diagram 15 prepared in advance. It is expressed.

Note that this output diagram 16 is a diagram showing the output response based on the maximum vibration magnitude in the supporting layer when a test auger was drilled in the ground near where the soil columnar diagram 15 was created. From this figure, it can be seen that the output diagram 16 corresponds well to the change in the N value of the soil profile diagram 15.

(Effects of the Invention) As described above, according to the method of the present invention, when a hole for driving a ready-made pile is drilled in the ground with an auger, the auger etc. Since the support layer of ready-made piles is confirmed by measuring the magnitude of vibrations around 5 to 10 Hz, the vibrations generated at the tip of the auger are transmitted through the auger and measured by a vibration measuring device attached to the auger drive device. The information is transmitted without attenuation, and the support layer can be accurately confirmed even in deep pile holes without being affected by the surrounding ground.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and Fig. 1 is a simplified side view showing the state of drilling, Fig. 2 is a block diagram of a vibration measuring device, Fig. 3 is a table of soil quality and vibration level, and Fig. 3 is a diagram showing a vibration measuring device. Figure 4 is a comparison diagram between the soil columnar diagram and the output diagram. 1...Base machine, 3...Auger, 4...
... Drive device, 5 ... Ground, 6 ... Pile hole, 7 ... Vibration sensor, 8 ... Vibration measuring device, 9 ... Display device, 15 ...
...Soil log chart, 16...Output chart.

Claims (1)

[Claims] 1. When drilling holes in the ground for driving ready-made piles using an auger, measure the magnitude of vibrations around 5 to 10 Hz that occur in the auger due to the ground cutting resistance of the auger, and A method for confirming the bearing layer of ready-made piles, characterized by confirming the bearing layer by comparing changes in the magnitude of vibration with a soil profile diagram prepared in advance.