JPH06985B2 - Sand level gauge for compacted sand piles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sand gage for compaction sand piles, and more particularly to a sand gage for compaction sand piles that uses ultrasonic waves to measure the sand surface position.

Conventionally, for the purpose of improving the ground of soft ground, a so-called sand compaction construction method has been provided in which sand is embedded in the ground and the sand is piled by vibrating and impacting the sand to compact it.

In the sand compaction method, a hollow cylindrical sheath is usually buried in the ground, and a predetermined amount of sand is put into the sheath,
Raise the sheath slightly and apply vibration or impact with the tip of the sheath or a thrust rod housed in the sheath to compact it and form a part of sand pile, and repeat such a cycle in sequence. Had formed a sand pile of a predetermined length.

The strength of the formed sand pile is determined by compaction of sand, and it was confirmed by measuring the sand surface position after compaction to confirm that it was constructed with the set strength secured. .

As a sand level meter, for example, a metal electrode plate is hung in a sheath, a constant voltage is applied between the electrode plate and the sheath, and the sand resistance is changed by utilizing the resistance change between the electrode plate and the sheath. Means are provided for detecting the surface.

This sand surface meter measures the sand surface by detecting the change in electric resistance when air is present between the electrode plate and the sheath and when sand or sand containing water is present. There were the following drawbacks.

That is, an electric cord is connected to an electrode plate to which a weight or the like is fixed and suspended vertically in the sheath. It may come into contact with the sheath and cause a malfunction.

Further, there is also a drawback that the input sand adheres to the electrode plate and the measurement sensitivity is lowered.

As a means to avoid this problem, it is possible to remove the electrode plate at the time of throwing in sand and hang it in the sheath after compaction, but compaction is done many times with one sand pile, so handling is troublesome. There was a drawback that

The present invention has been made in view of the problems of the sand gage used in the sand compaction construction method described above, and the purpose of the present invention is to ensure sufficient mechanical strength even against the input of sand. , To provide a sand level gauge for compacted sand piles having high measurement accuracy.

In order to achieve this object, the present invention is a sand level meter used in a method of charging sand into a cylindrical casing embedded in soft ground and compacting the sand to form a sand pile, wherein the casing A case on the upper end side of which is provided with a space into which the sand can be introduced and fixed in the diametrical direction of the casing, and a vibration isolator interposed between the case and the casing. A plurality of ultrasonic sensors that are attached to the lower surface side of the case, oscillate ultrasonic waves on the sand surface in the casing, and receive reflected waves from the sand surface, and electrically with the ultrasonic sensor. And an electrical means for calculating a distance between the ultrasonic sensor and the sand surface based on a time difference between oscillation and vibration of the ultrasonic wave. Vertical of surface Line, characterized in that it is arranged to direct a point located in the axial lower end of the casing.

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

1 to 3 show an embodiment of a sand level gauge for compacted sand piles according to the present invention.

The sand level meter shown in the figure oscillates ultrasonic waves on a compacted sand surface, receives reflected ultrasonic waves from the sand surface, and converts the ultrasonic waves into electric signals. An electric circuit 20 that is electrically connected to the ultrasonic sensor 10 and drives it to oscillate at a predetermined frequency, and calculates the distance between the ultrasonic sensor 10 and the sand surface based on the time difference between the ultrasonic wave oscillation and the vibration reception. It is composed of and.

The ultrasonic sensor 10 is mounted near the upper end of a hollow cylindrical casing 30 that is embedded in soft ground, and a wing 32 that facilitates penetration of the casing 30 into the ground is mounted at the lower end of the casing 30. A chute 34 for supplying sand forming a sand pile to the casing 30 and a multivibro hammer 36 used for compaction of sand are attached to the upper end.

As shown in FIG. 2, each of the ultrasonic sensors 10 has a thin plate made of a magnetostrictive material such as an iron-nickel alloy, or a core 12a formed by sintering ferrite powder. A plurality of ultrasonic elements 12 formed by winding a wire 12b having a diameter are connected in parallel,
An elastic material (vibration isolation material) 1 such as rubber is used to surround these elements 12.
4 is covered. Multiple ultrasonic sensors 1
0 indicates that each oscillation and vibration receiving surface faces downward and the vertical axis of each oscillation and vibration receiving surface is the casing 30.
Are arranged linearly in the box-shaped case 16 at substantially equal intervals so as to point to the point A located at the lower end of the axis of the casing. In this embodiment, they are arranged symmetrically with respect to the axis of the casing 30. The vertical axis of the ultrasonic sensor 10 is arranged at an equal angle with respect to the axis of the casing 30.

The case 16 is fixed across the casing 30 so as to traverse the casing 30 through a vibration-proof rubber 18 in through-holes formed at opposite positions of the casing 30. The casing 30 defines a pair of space portions 19 having a substantially semicircular horizontal cross section, from which sand for forming sand piles can be introduced through the chute 34.

On the other hand, the electric circuit 20 is activated by a signal sent from the synchronous control circuit 21 as shown in FIG. 3, applies pulsed power to the ultrasonic sensor 10, and oscillates the electric power at a predetermined frequency. Pulse generating circuit 22, a receiving amplifier 23 that receives the reflected wave of the ultrasonic wave oscillated by the ultrasonic sensor 10 on the sand surface, converts it into an electric signal, and then amplifies it to a predetermined level, and this receiving amplifier 23. Analog recording device 24 for recording the output of the above as it is as it is, an AD converter 25 for converting the output of the receiving amplifier 23 into a digital amount, and a counter 26 for receiving the output of the AD converter 25, a counter It is composed of a digital recording device 27 for recording the output of 26 and a DC stable power supply 28.

In this electric circuit 20, for example, the analog recording device 2
If the time when the signal for oscillating the ultrasonic sensor 10 is transmitted is recorded in 4, the received signal of the reflected ultrasonic wave is received by the receiving amplifier 2
3 is input, the time from oscillation to vibration reception can be detected, and the distance from the ultrasonic sensor 10 to the sand surface can be calculated based on this.

When detecting this digitally, the distance to the sand surface can be calculated by activating the counter 26 with a signal for driving the ultrasonic sensor 10 and stopping it with the output of the reception amplifier 23.

By the way, the sand gage with the above-mentioned configuration calculates and measures the sand surface position using ultrasonic waves, so that the sand surface position can be precisely measured, and it is similar to a conventional sand surface gage with a pole plate suspended. There is no risk of disconnecting the connection part to
Since it is covered with the elastic material 14, the mechanical strength can be greatly improved.

Further, even if the ultrasonic sensor 10 is provided in the diameter direction of the casing 30, since the space portion 19 in which the sand can be thrown in can be secured in a sufficient area, this does not become an obstacle when throwing in the sand. Absent.

Furthermore, since the plurality of ultrasonic sensors 10 are arranged with the vertical axes of the respective oscillating surfaces or receiving surfaces oriented toward the point A located at the lower end of the axial line of the casing 30,
Most of the ultrasonic waves reflected by the sand surface can be efficiently captured by the vibration receiving surface of the ultrasonic sensor 10 arranged at a position symmetrical to this, and high measurement accuracy can be obtained.

This effect is remarkable when the tip portion of the casing 30 is vibrated to compact the sand, and the principle is as follows.
That is, when compacting sand using the tip of the casing 30 as a vibrating body, the vibration is large in the portion close to the inner wall of the casing 30 and small in the portion close to the axis, and the influence of the vibration received by the reflected wave on the sand surface is Paying attention to the smallness in the vicinity of the axis of the casing 30, the vertical axis of the ultrasonic sensor 10 is directed to the axis of the casing 30. The point A at which the vertical axes of the plurality of ultrasonic sensors 10 are oriented is set at the lower end, which is the lowest position of the sand surface in the casing 30, even if the sand surface becomes higher than this. The ultrasonic waves oscillated from the ultrasonic sensor 10 arranged on the outermost side are not reflected to the outside (inner wall of the casing 30) of the sensor 10 which is symmetrical to the ultrasonic sensor 10. This is because the reflected waves of ultrasonic waves can be reliably captured.

In the above embodiments, the magnetostrictive type ultrasonic sensor 10 is illustrated, but it is also possible to use an electrostrictive type vibrator using barium titanate, lead zirconate titanate or the like.

As described in the above examples, the sand grit for compaction sand piles according to the present invention can improve the measurement accuracy because it uses ultrasonic waves, and at the same time, cover the ultrasonic sensor with an elastic material. Therefore, the mechanical strength can be greatly improved without breaking the sand as it is thrown in or causing a malfunction.

[Brief description of drawings]

1 to 3 show an embodiment of a sand level gauge for compacted sand piles according to the present invention. FIG. 1 (a) is an overall view of a state in which a sensor is attached to a casing. (b) is an enlarged view of the sensor mounting portion, (c) is a sectional view taken along the line I-I of (b) in FIG. 2, (2) is a perspective view of the ultrasonic sensor, and (3) is a connection diagram of an electric circuit. . 10 ... Ultrasonic sensor 12 ... Ultrasonic element 12a ... Core 12b ... Wire 14 ... Elastic material 16 ... Case 18 ... Anti-vibration rubber 20 ... Electric circuit 21 ... Synchronous control circuit 22 ... Pulse transmission circuit 23 ...... Reception amplifier 24 …… Analog recording device 25 …… A / D converter 26 …… Counter 28 …… DC stable power supply 30 …… Casing 32 …… Wing 34 …… Shoot 36 …… Multi-vibro hammer

Claims (1)

[Claims] 1. A sand gage for use in a method of charging sand into a cylindrical casing buried in soft ground and compacting the sand to form a sand pile, which is located at the upper end side of the casing. A case fixed to the casing in a diametrical direction by providing a space into which the sand can be introduced, a vibration isolator interposed between the case and the casing, and a lower surface of the case Mounted on the side, while oscillating ultrasonic waves on the sand surface in the casing, a plurality of ultrasonic sensors for receiving reflected waves from the sand surface, electrically connected to the ultrasonic sensor, the ultrasonic wave Of the ultrasonic sensor and the electrical means for calculating the distance between the sand surface based on the time difference between the vibration receiving, the plurality of ultrasonic sensors, the vertical axis of each oscillation and the receiving surface is the Casing shaft Compaction sand pile sand level gauge, characterized in that it is arranged to direct a point located at the lower end.