JP5990495B2 - Cast-in-place pile penetration detection device - Google Patents

Description

  The present invention relates to a support layer penetration detection device for a cast-in-place pile that detects that the cast-in-place pile has reached the support layer and has penetrated.

  In the cast-in-place pile of reinforced concrete, the hole drilled for construction must reach the support ground layer that supports the pile and penetrate, but excavated until the pile penetrates into the support layer intended by the designer (1) The excavation length is determined based on the ground survey results conducted in advance, and excavation is performed to that depth. (2) In the test construction pile, the excavated soil is confirmed as the support layer of the ground survey result, and in this construction, the soil at the planned depth is confirmed to be the same as the soil confirmed at the test pile, etc. Yes.

  However, the method cannot sufficiently cope with the design technique in which the support layer is set by the strength of the ground. A loading test is performed on the hole wall in the hole wall stabilizing liquid as necessary, and a method for confirming the strength is examined by this. However, the stability of the hole wall possessed by the action of the stabilizing liquid is confirmed. It is assumed that the ground will collapse during the measurement, and the pile will not be built.

  In order to keep the hole wall in a stable state during the measurement, it is required to perform measurement in the flow of the conventional construction process as a measurement method that does not give an impact to the hole wall ground.

  As a method for measuring the strength of the ground in a non-contact manner, there is a ground elastic wave velocity measuring method called PS logging that uses elastic wave velocity that can select hardness as an alternative characteristic value of strength and evaluate the hardness. .

  As this method, a downhole method for measuring the propagation speed of P-waves and S-waves oscillating from the ground surface using a boring hole having a diameter of about 10 to 15 cm, and an intra-hole vibration receiving method are in practical use.

  In the downhole method, the ground surface is vibrated in the horizontal and vertical directions, and the vibration is measured with a geophone in the borehole. The wave propagation time at each measurement depth is measured by moving the geophone position in the ground. This is a method of obtaining the wave velocity from the difference between the two.

  The in-hole vibration receiving method is a method in which elastic wave vibration is generated and received through water in the same boring hole. The in-hole excitation and reception method is a method that enables investigation at a large depth with a small excitation energy because the excitation and the receiving device are always at a constant distance.

  The PS logging measurement using the in-hole vibration receiving method can be conducted with a small vibration energy up to a large depth using a small boring hole with a diameter of about 10 to 15 cm as described above. In many cases, cast-in-place pile construction on a limited site site has a great merit in adopting an in-hole excitation receiving system with low excitation energy.

  However, in this method using a boring hole, a large-diameter hole having a diameter of several meters, such as a cast-in-place pile, cannot measure because vibration energy does not reach the hole wall ground.

On the other hand, the following patent document was previously proposed by the applicant. Suspension PS logging can be performed by using a half-pipe pseudo ground plate, and shear waves are measured using the same device after excavation at the planned depth. The numerical value of the support layer can be confirmed.
JP 2010-31576 A

  As shown in FIG. 8, this Patent Document 1 is provided with a reflector as a pseudo ground surface 5 in the vicinity of the measurement hole wall ground 2 along the measurement hole wall ground 2 of the hole of a large diameter cast-in-place pile. Then, a pseudo measurement region was formed, the vibration source 4 was installed near the center position of the reflector, and the geophones 6a and 6b were installed at the measurement position.

  In the figure, 1 is a large-diameter pile hole drilled for cast-in-place pile construction, 2 is the measurement hole wall ground of the pile hole 1, and 3 is the hole wall stabilizing liquid filled in the pile hole 1.

  In the figure, 7 is a filter tube, 8 is a weight, 9 is a driver, 10 is a head reducer connected to the driver 9, 11 is a suspension sonde, 12 is a pulley, 13 is a winch, and 14 is a measuring instrument.

  In order to detect whether the tip of the pile hole 1 has reached the support ground, if it oscillates from the vibration source 4, the elastic wave propagates through the measurement hole wall ground 2 and is received by the two geophones 6a and 6b below. The Based on the propagation times measured by the two geophones 6a and 6b, the hardness of the measurement hole wall ground 2 is determined, and it is determined whether the tip of the pile hole 1 has reached the support ground.

  When a field experiment was performed using the detection method [PS logging probe (PS logging device)] and the detection method at the tip of the cast-in-place pile in Patent Document 1, the detection device was mounted on the wall surface of the pile hole. 7 makes it possible to obtain the best waveform as shown in FIG. 7 and to easily identify the shear wave velocity. Unable to obtain a correct waveform.

  Since the oscillator (vibration source 4) and geophone attached to the PS logging probe (PS logging device) have the direction of the vibration wave and the direction of the vibration reception, it must be orthogonal to the hole wall of the pile. Diffusion and received vibration are reduced and the received waveform is not clear. However, it was difficult to control the probe orientation.

  The equipment can be lifted and lowered by attaching a pulley to a simple three-pronged column and passing a winch cable, which takes time to measure and can be measured only at night when the pile shaft excavation work is completed.

  The object of the present invention is to eliminate the inconvenience of the conventional example, and to make a PS logging probe (PS logging device) as close as possible to the hole wall of the pile while avoiding a bent hole wall in the middle. It is in providing the support layer penetration detection apparatus of this.

  In order to achieve the above object, the present invention according to claim 1 is a pseudo measurement region in which a reflector as a pseudo ground surface is installed in the vicinity of the measurement hole wall ground of the hole of the cast-in-place pile. In the PS logging device in which a vibration source is installed near the center position of the reflector and a geophone is installed at the measurement position, a suspension jig with a balance suspended by a wire cable is used. The gist is that the PS logging device is suspended and supported.

  According to the first aspect of the present invention, even if there is unevenness in the pile hole wall, it is possible to bring it close to the hole wall surface by using a balance for the suspension method of the PS logging device for suspension PS logging.

  The gist of the present invention described in claim 2 is that the hanging jig has a counterweight suspended on the other side of the balance.

  According to the second aspect of the present invention, the counterweight can serve as a weight for suspending the PS logging device downward and a balance material for supporting the PS logging device on the balance. .

  The gist of the present invention described in claim 3 is that the suspension jig is provided on a pulley that is slidably suspended by a parallel wire cable.

  According to the third aspect of the present invention, the direction of the probe can be controlled with respect to the hole wall by suspending the balance with two pulleys.

  The gist of the present invention described in claim 4 is that the PS logging device is suspended from the probe raising / lowering device by a wire cable.

  According to the present invention, the measurement time can be shortened by using the probe raising / lowering device.

  The gist of the present invention described in claim 5 is that the probe raising / lowering device is provided on a stand that is installed on a stand pipe of a pile and can rotate around a pile core.

  According to this invention of Claim 5, it can rotate on the standpipe of a pile and can measure a P wave S wave measurement in the hole wall position of the 360 degree circumference of a pile easily.

  As described above, the support layer penetration detection device for cast-in-place piles according to the present invention allows the PS logging probe to be as close to the hole wall of the pile as possible while avoiding the hole wall bent in the middle, and can be controlled accurately. It is possible to shorten the time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view showing a first embodiment of a cast-in-place pile support layer penetration detection apparatus according to the present invention, in which 20 is a pile hole, 21 is a hole wall, and 19 is a stand pipe.

  First, the suspension PS probe 16 will be described. This is the same as the suspension sonde 11 shown in FIG. 8, and is used for a ground elastic wave velocity measuring method called PS logging using elastic wave velocity. In addition, a reflection plate as a simulated ground surface is installed to form a pseudo measurement region, a vibration source (transmitter) is installed near the center position of the reflection plate, and a geophone is installed at the measurement position.

  Here, the pseudo measurement region includes both a region where a vibration source is installed in the vicinity of the center position of the reflector and a region including a measurement region where a geophone without a reflector is installed.

  In order to detect whether the tip of the pile hole 20 has reached the support ground, if it oscillates from a vibration source, an elastic wave propagates through the measurement hole wall ground and is received by two lower geophones. Based on the propagation time measured by these two geophones, the hardness of the measurement hole wall ground is determined to determine whether the tip of the pile hole 1 has reached the support ground. In the figure, 28 is a measurement data logger.

  The suspension PS probe 16 is suspended by a wire cable 22 from a drum winch 24 of a probe lifting / lowering device 17 movably provided on the device base 18.

  First, from the device stand 18, it is assumed that it can be installed at the center of the stand pipe 19 of the pile and can rotate (360 degrees) around the pile core. A derailment prevention pipe 32 is provided.

  Further, a leg 33 made of a square pipe projects from the end of the gantry body 30. The leg 33 is long enough not to be grounded when the gantry body 30 is placed on the stand pipe 19 via the roller casters 31. That's it.

  In this embodiment, the roller caster 31 is attached with a pin 36 inserted into a pin drop hole 35 provided in the gantry body 30.

  A grooved steel 29 as a linear winch guide rail is provided on the upper surface of the gantry body 30 in the length direction, and the probe raising / lowering device 17 can be moved by a wheel 34.

  As shown in FIGS. 2 and 3, the probe raising / lowering device 17 is a drum winch 24 for winding and feeding the wire cable 22, and includes a lifting wire drum 37, a lifting cable motor 38, an alignment winding device 39, an aligned winding reduction gear. 40, having a position fixing roller 41, and as a drum winch 42 for winding and unwinding the signal cable 23, a signal cable drum 43, a signal cable motor 44, an alignment winding device 45, a magnetic torque clutch 46, an alignment winding speed reduction A gear 47 and the like are included.

  In the figure, 48 is a suspension rope, 49 is a slip ring, 50 is a winch frame, 58 is a wire fixing hook, and 59 is a shaft.

  As shown in FIGS. 5 and 6, a sliding pulley 25 is interposed at the tip of the wire cable 22 suspended from the lifting wire drum 37, and the wire cable 22 is folded back from the pulley 25 to be parallel to the two wire cables. Suspend at 22.

  A link rod 51 as a balance 26 is pivotally attached to the pulley 25 by a link joint 52, and a tool support pipe 53 and a counterweight 27 are suspended and supported by the link joint 52 on the left and right sides of the balance 26.

  The suspension PS probe 16 is attached to the tool support pipe 53 with a U-shaped bolt 56 as a fixture.

  Further, the counterweight 27 is formed with a horizontally elongated hole 54 in the link rod 51, and the position of the counterweight 27 can be adjusted by allowing the link joint 52 to slide in the horizontally elongated hole 54. (Adjust so that the link rod 51 is horizontal.)

  In this way, the suspension PS probe 16 is suspended and supported using a pulley 25 that is suspended by two wire cables 22 and a suspension jig provided by a balance 26 provided on the pulley 25. In the figure, 57 indicates an armored cable.

  The wire cable 22 is lifted and lowered by the drum winch 24, and the signal cable 23 is also lifted and lowered by the drum winch 42, and is integrated as a PS probe lifting and lowering device.

  The device base 18 is provided with a grooved steel 29, which forms a track for the probe raising / lowering device 17 to move, and can easily approach the hole wall 21 of the pile. In addition, the roller base 31 is attached to the apparatus base 18 and can rotate on the stand pipe 19 of the pile, and the P wave S wave measurement can be easily performed at the hole wall position in the 360 ° direction of the entire circumference of the pile. Become.

  The suspension PS probe 16 can use the balance 26 to bring the suspension PS probe 16 closer to the hole wall 21 while the wire cable 22 suspended from the ground avoids the hole wall balance 26 bent in the middle.

  In addition, since the said balance jig has the directivity of a vibration wave in the oscillator and geophone attached to the suspension PS probe 16 and the direction of vibration reception, it is necessary to accurately maintain the orthogonal direction with respect to the hole wall. By adopting a method in which the device is suspended by two wire cables using a pulley 25 instead of one wire cable, the suspended suspension PS probe 16 does not rotate in the stable liquid of the pile, and the original It became possible to lower and lower while maintaining the direction.

  The wire cable 22 was raised and lowered by the drum winch 24, and the signal cable 23 was also raised and lowered by the drum winch, and was integrated as a PS probe raising and lowering device.

  The shear waveform obtained by the separation between the suspension PS probe 16 and the hole wall 21 of the pile becomes clear as shown in FIG. 7, and the time lag of the shear wave measured at the first receiving point and the second receiving point is easily interpreted. The effect of being able to approach the hole wall 21 by this balance is demonstrated.

It is a side view which shows Embodiment 1 of the support layer penetration detection apparatus of the cast-in-place pile of this invention. It is a top view of a probe raising / lowering device. It is a side view of a probe raising / lowering device. It is explanatory drawing of an apparatus stand. It is a front view of the hanging jig by a balance. It is a side view of the hanging jig by a balance. It is a graph which shows the difference in the waveform by separation from a hole wall. It is a side view which shows a prior art example.

DESCRIPTION OF SYMBOLS 1 ... Pile hole 2 ... Measurement hole wall ground 3 ... Hole wall stabilization liquid 4 ... Vibration source 5 ... Pseudo ground surface 6a, 6b ... Vibration receiving device 7 ... Filter tube 8 ... Weight 9 ... Driver 10 ... Head reducer 11 ... Suspension sonde DESCRIPTION OF SYMBOLS 12 ... Pulley 13 ... Winch 14 ... Measuring instrument 15 ... Indicator 15a, 15b ... Display part 16 ... Suspension PS probe 17 ... Probe raising / lowering device 18 ... Device mount 19 ... Stand pipe 20 ... Pile hole 21 ... Hole wall 22 ... Wire cable DESCRIPTION OF SYMBOLS 23 ... Signal cable 24 ... Drum winch 25 ... Pulley 26 ... Balance 27 ... Counterweight 28 ... Measurement data logger 29 ... Channel steel 30 ... Mount body 31 ... Roller caster 32 ... Derailment prevention pipe 33 ... Leg 34 ... Wheel 35 ... Pin drop hole 36 ... Pin 37 ... Drum for lifting wire 38 ... For lifting cable Motor 39 ... Aligned winding device 40 ... Aligned winding reduction gear 41 ... Position fixing roller 42 ... Drum winch 43 ... Signal cable drum 44 ... Signal cable motor 45 ... Aligned winding device 46 ... Magnetic torque clutch 47 ... Aligned winding reduction gear 48 ... Suspension rope 49 ... Slip ring 50 ... Winch frame 51 ... Link rod 52 ... Link joint 53 ... Link rod 54 ... Horizontal hole 56 ... U-bolt 57 ... Armored cable 58 ... Wire fixing hook 59 ... Shaft

Claims (5)

  A reflecting plate as a simulated ground surface is installed in the vicinity of the measurement hole wall ground of the hole of the cast-in-place pile to form a pseudo measurement area, and a vibration source is set near the center position of the reflecting plate. In the PS logging device with the geophone installed at the measurement position, the PS logging device is suspended and supported using a hanging jig with a balance suspended by a wire cable. Supporting layer penetration detector for cast-in-place piles.   2. The cast-in-place pile support layer penetration detection device according to claim 1, wherein the suspension jig has a counterweight suspended on the other side of the balance.   3. The cast-in-place pile support layer penetration detection device according to claim 1 or 2, wherein the suspension jig is provided on a pulley that is slidably suspended by parallel wire cables.   4. The cast-in-place pile support layer penetration detection device according to any one of claims 1 to 3, wherein the PS logging device is suspended from a probe raising / lowering device by a wire cable.   5. The cast-in-place pile support layer penetration detection device according to claim 1, wherein the probe raising / lowering device is installed on a stand that is installed on a stand pipe of the pile and can rotate around the pile core.

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