JP2559265B2 - Judgment method of ground properties - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for determining a ground property used for inspecting a ground property improved by a grout and for determining a loose state of a surrounding ground due to tunnel excavation. It is a thing.

[Conventional technology]

At civil engineering work sites, etc., the ground at the construction site is often improved with grout such as cement milk or mortar prior to the construction. A decision is made. A conventional example of this determination method is shown in FIG. This is the first vertical hole 2 in the ground 1.
And the second standing hole 3 is excavated, and in the first standing hole 2,
An oscillator 4 to be crimped is provided on the inner peripheral surface of the first standing hole 2, and a receiver 5 is provided on the other second standing hole 3. Then, the rod 6 inserted from the ground to the oscillator 4 is struck in the up-down direction, and an elastic wave including a displacement of a vertical component (hereinafter referred to as an elastic wave) from the oscillator 4 to the inner peripheral surface of the first standing hole 2 and the ground. , SV wave) 7 is generated and propagated. On the other hand, this SV wave 7 is transmitted to the receiver 5 through the inner peripheral surface of the second standing hole 3. Then, the ground property is analyzed by the vibration analyzer (not shown) from the time from the oscillation of the elastic wave to the reception, that is, how the elastic wave is transmitted to the ground 1, and the measurement test is performed by the first standing hole 2 and It is repeatedly performed at a plurality of locations in the second standing hole 3 to comprehensively determine the property in the depth direction of the ground.

[Problems to be Solved by the Invention]

However, in such a conventional ground property determination method, since the SV wave 7 is used as an elastic wave propagating to the ground 1, the SV wave 7 is incident near the boundary between the high rigidity layer and the low rigidity layer of the ground 1. A part of the reflected vertical elastic wave is received by the receiver 5 as the P wave 8, which increases the disturbance of the waveform of the elastic wave to be originally received, and improves the measurement accuracy of the elastic wave velocity, that is, the ground property. There was a problem of lowering it.

The present invention has been made by paying attention to such a conventional problem, and a shear wave propagating horizontally in the ground is emitted from the shear wave oscillator crimped to the first vertical hole, and this is transmitted to the second By receiving with the receiver installed in the vertical hole, P
An object of the present invention is to obtain a method for determining a ground property that enables highly accurate detection of elastic waves and measurement of elastic wave velocity without generation of waves and interference.

[Means for solving the problem]

Then, in order to achieve such an object, the method for determining the ground property according to the present invention provides the first standing hole and the second standing hole in the ground, and receives the impact torque,
The shear wave generated by the shear wave oscillator crimped in the first standing hole is received by the receiver provided in the second standing hole, and the shear wave is received between the first standing hole and the second standing hole. The elastic wave velocity of the ground is measured.

[Action]

The shear wave generator according to the present invention instantaneously applies a horizontal torsional force to the inner peripheral surface (inner peripheral wall) of the first vertical hole and the surrounding ground by applying a horizontal impact torque from the outside. Propagated to. This propagating elastic wave is an oscillating wave that is displaced in the horizontal direction, and therefore is less likely to be incident on or reflected in a layer having different rigidity in the depth direction.
Does not generate waves. Therefore, the shear wave is not disturbed by the P wave, and the measurement accuracy of the ground property can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
In FIG. 1, 1 is the ground, 2 is the first standing hole, and 3 is the second
These are the same as those shown in FIG.
Reference numeral 11 denotes a shear wave oscillator according to the present invention, which is crimped to the first standing hole 2. Reference numeral 12 is a receiver for elastic waves as shear waves 13, which is provided in the second standing hole 3.

The shear wave oscillator 11 is configured as shown in FIG. 2 as a whole, and has a rod 14 inserted into the first standing hole 2 and an upper portion of the rod 14 (in the first standing hole 2). ) And a pair of packers 15 and 16 attached to the lower part, and a strut cell part 17 installed in the outer circumference of the rod 14 between these packers 15 and 16 in a circumferentially and vertically divided manner. , An air hose 18 for supplying compressed air to the packers 15 and 16, and a hydraulic hose 19 for supplying hydraulic pressure to a hydraulic cylinder (not shown) for driving the strut cell portion 17 through a passage (not shown) in the rod 14. And above rod
An impact receiving arm 20 fixed as shown in FIG. 3 in a direction orthogonal to the upper end of 14 and a rod above the impact receiving arm 20.
Horizontal impact load arm rotatably mounted on 14
21 and a weight suspended from both ends of this impact load arm 21.
22 and. The packers 15 and 16 are provided to divide a part of the first vertical hole 2 from the other as a water-free region, and the compressed air is sent through the air hose 18 to expand the compressed air. 11 The installation space for the main body is secured. In addition, the tension cell part 17 is a hydraulic hose.
By sending hydraulic pressure into the hydraulic cylinder through 19, it projects in the outer diameter direction and presses the inner peripheral surface (inner peripheral wall) of the first standing hole 2 from the inside, and the rod 14 and the first standing hole 2 It enables an integral connection with the inner wall.

 Next, the operation will be described.

First, the rod 14 having the packers 15 and 16 and the tension cell portion 17 attached thereto is used as a first excavation in the first ground in the ground 1.
It is inserted in the vertical hole 2 of the, and the tension cell portion 17 is aligned with the impact application site on the ground 1. Next, by sending compressed air to the packers 15 and 16 and enlarging them,
Isolate the impacted part from other parts and drain water from this part. Further, subsequently, the hydraulic cylinder (not shown)
A hydraulic pressure is sent to each of the tension cell parts 17 so as to project in the outer diameter direction, and the tension cell parts 17 are stretched to the inner peripheral wall of the first standing hole 2 so that the rod 14 and the inner peripheral wall of the standing hole 2 are rigidly connected to each other.

On the other hand, before and after the work of inserting the rod 14 into the first standing hole 2, the impact receiving arm 20 is fixed to the upper end of the rod 14 and is above the impact receiving arm 20. An impact load arm 21 having a weight 22 at both ends is rotatably attached to the.

Next, in such a state, the impact load arm 21 is externally rotated at a predetermined constant speed. Then, the weight 22 also rotates and rotates up to a maximum of about 180 °, and the weight 22 collides with the impact receiving arm 20. That is,
This shear wave oscillator generates a shear wave (hereinafter referred to as SH wave) due to the impact torque applied by this collision, and the shear wave (hereinafter referred to as SH wave) is generated through the rod 14 and the strut cell portion 17 to the first standing hole 2
Is propagated to the inner wall of. Then, this SH wave is transmitted to the ground as a force to twist the ground around the inner peripheral wall in the horizontal direction, and finally received by the receiver fixed to the inner circumference of the second standing hole 3, and the reception result is shown in the figure. Not transmitted to ground vibration analyzer. This vibration analysis device analyzes the propagation velocity and the like from the received shear waveform which is an elastic wave, measures the properties of the ground, and prints out or displays it on a display as necessary. In this case,
The SH wave does not generate the P wave even when incident and reflected on different layers of the ground 1, and therefore the measurement result by the SH wave becomes extremely reliable. Therefore, the measurement of the ground property using this shear wave is particularly suitable and effective for the saturated ground greatly affected by the P wave.

In addition, in practice, a large number of shear wave application sites in the first standing hole 2 are set in the depth direction, and the shear waves are received at a plurality of positions in the second standing hole 2 corresponding thereto. By comprehensively analyzing the plurality of received data, the property of the ground in the predetermined depth area can be obtained as three-dimensional data, and the property determination can be performed with higher accuracy. In this case, the above-mentioned measurement can be carried out while a plurality of shear wave oscillators 11 and receivers 12 are individually arranged side by side or one of them is moved.

Further, when the measurement work is completed, the compressed air in the packers 15 and 16 is evacuated, the hydraulic pressure of the hydraulic cylinder is evacuated, and the tension cell portion 17 is retracted.
It can be easily removed from the first standing hole 2 and can be carried to the next working position for reuse.

Therefore, for example, it is possible to quickly and accurately determine whether or not the ground has been improved by injecting grout into the ground and whether or not the ground property is improved by the grout of the tunnel ground.

〔The invention's effect〕

As described in detail above, according to the present invention, a shear wave is provided in which the first standing hole and the second standing hole are provided in the ground and is pressed into the first standing hole by receiving an impact torque. The shear wave generated by the oscillator is received by the receiver provided in the second vertical hole, and the first vertical hole and the second vertical hole are received.
Since the elastic wave velocity of the ground between the vertical holes is measured, the propagation velocity of the elastic wave, which is a shear wave, can be measured with high accuracy without any obstacle due to the P wave. The effect that the measurement can be accurately performed is obtained.

[Brief description of drawings]

FIG. 1 is a principle view showing a shear wave generation system for carrying out the method for determining the ground property according to the present invention, FIG. 2 is a front view of a shear wave oscillator used in the present invention, and FIG. FIG. 4 is a perspective view showing the configuration, and FIG. 4 is a principle diagram showing an elastic wave generation system for carrying out a conventional method for determining the ground property. 1 ... Ground, 2 ... First standing hole, 3 ... Second standing hole, 11
…… Shear wave oscillator, 12 …… Receiver, 13 …… Shear wave.

Claims (2)

(57) [Claims] 1. A first standing hole and a second standing hole are provided in the ground, and a shear wave oscillator generated by receiving a shock torque by a shear wave oscillator crimped in the first standing hole generates A method for determining a ground property, which is received by a receiver provided in the second standing hole and measures an elastic wave velocity of the ground between the first standing hole and the second standing hole. 2. The method for determining the ground property according to claim 1, wherein the shear wave oscillator instantaneously propagates a torsional force to the ground around the first upright hole by impact torque.