JP6238112B2 - Ground soundness evaluation method - Google Patents

Description

The present invention relates to a method of assessing the integrity of ground which multiple anchor is installed.

  The performance of the ground anchor varies depending on whether the design and construction are appropriately performed, and changes depending on subsequent factors such as earthquakes and precipitation that occur after construction. Therefore, a basic investigation test has been conducted so that the ground anchor exhibits the intended performance, and a quality confirmation test is conducted to confirm whether or not the ground anchor maintains the intended performance. Has been done. For example, a pull-out test and a long-term test exist as the basic survey test, and a multi-cycle confirmation test, a one-cycle confirmation test, a residual tension confirmation test, and the like exist as the quality confirmation test.

  In addition, as a residual tension confirmation test, there is a method in which a load meter is installed when a ground anchor is installed and the residual tension is confirmed using this load meter. It cannot be applied to existing ground anchors (existing anchors) that are not installed. Therefore, there is a lift-off test in which a tension jack or the like is installed when confirming the residual tension, and the residual tension is confirmed using the tension jack or the like. This lift-off test is a test in which a tensioning jack is installed in the ground anchor fixing tool and the tendon surplus length, and a load is loaded on the ground anchor using this tensioning jack, and the fixing tool starts to move away from the bearing plate. The load at the time is the residual tension. When this lift-off test is performed, it is possible to understand the behavior of the ground where the ground anchor is installed, to know the necessity of re-tensioning the ground anchor and whether the ground anchor is broken, etc. It is said that this is a serious test. The present applicant has also proposed a test method obtained by evolving this lift-off test (see Patent Document 1).

  However, when performing a lift-off test or an advanced version of this lift test, it is necessary to install a tension jack at the base end of the ground anchor, and various operations must be performed around the base end of the ground anchor. Occurs. In this regard, the ground on which the ground anchor is installed may be a steep slope or the like, and this operation is very troublesome and may be dangerous.

JP 2004-294235 A

The main object of the present invention is to provide is to provide a method for evaluating the integrity of the earth plate that Ru excellent work efficiency.

The present invention for solving this problem is as follows.
[ Reference invention]
A method for estimating the tension of an existing anchor,
The reference anchor is at least one of another existing anchor and a new anchor different from the existing anchor to be estimated,
A load of at least two stages is loaded on the reference anchor, and at each stage of the loading, the reference anchor is struck in the anchor axial direction to generate a reference elastic wave,
Obtain the dominant frequency of the reflected wave derived from this reference elastic wave,
Create a correlation formula between the dominant frequency and the load based on this dominant frequency and the load when hitting the reference anchor,
On the other hand, the estimated anchor wave is generated by hitting the existing anchor to be estimated in the anchor axis direction,
Obtain the dominant frequency of the reflected wave derived from this estimation elastic wave,
The load obtained by substituting this dominant frequency into the correlation equation is estimated as the tension of the existing anchor to be estimated.
A method for estimating the tension of an existing anchor.

[Invention of Claim 1 ]
A method for evaluating the soundness of a ground where a plurality of anchors are installed,
A part of the plurality of anchors is used as a reference anchor,
A test for confirming the residual tension on the reference anchor is performed, and the reference anchor is struck in the anchor axial direction in at least two stages with different loads in the test process for confirming the residual tension. Generate elastic waves,
Obtain the dominant frequency of the reflected wave derived from this reference elastic wave,
Create a correlation formula between the dominant frequency and the load based on this dominant frequency and the load when hitting the reference anchor,
On the other hand, the remaining anchor that has not been tested to confirm the residual tension is struck in the anchor axial direction to generate an estimation elastic wave,
Obtain the dominant frequency of the reflected wave derived from this estimation elastic wave,
The load obtained by substituting this dominant frequency into the correlation equation is estimated as the tension of the remaining anchor,
Perform a test to confirm the residual tension against an anchor whose estimated tension is outside the predetermined range.
A soil integrity evaluation method characterized by the above.

[Invention of Claim 2 ]
Assessing the soundness of the ground based on the ratio of anchors with the estimated tension within the predetermined range, the ratio of anchors with the residual tension within the predetermined range, and the ratio of anchors with the residual tension outside the predetermined range as basic information To
The ground soundness evaluation method according to claim 1 .

According to the present invention, a method for evaluating the health of the land board that Ru excellent work efficiency.

It is an installation example of an existing anchor. It is a process flow figure of the ground soundness evaluation method. It is a graph which shows the relationship between a dominant frequency and a load (experiment example). It is a graph which shows the relationship between a dominant frequency and a load (demonstration test 1). It is a graph which shows the relationship between a dominant frequency and a load (demonstration test 2).

  Next, the form for implementing this invention is demonstrated. In the following, a method for estimating the tension force of an existing anchor installed on the ground (load acting on the existing anchor) will be described first, and then a plurality of methods that apply this estimation method will be described. A method for evaluating the soundness of the ground where the existing anchor is installed will be described.

[Tension force estimation method]
The tension estimation method according to the present embodiment targets an existing anchor 10 already installed on the ground G as shown in (1) of FIG. The existing anchor 10 is mainly composed of an anchor head 11, a tension portion 12, and an anchor body 13.

  The anchor head 11 is a part that transmits the force received from the surface of the ground G to the pulling portion 12 as a pulling force. The anchor head 11 is mainly composed of, for example, a fixing tool 11A made of a nut, a wedge, or the like, and a bearing plate 11B. The pressure bearing plate 11B is a plate-like member interposed between the fixing tool 11A and a pedestal or ground G (not shown), and may be referred to as an anchor plate or the like.

  The tension portion 12 is a portion that transmits the tensile force from the anchor head 11 to the anchor body 13. The tension portion 12 is composed of a tendon 12A made of a PC steel wire, a PC steel strand, a PC steel rod, a continuous fiber reinforcing material, and the like.

  The anchor body 13 is a part that transmits the tensile force from the tensile portion 12 to the ground G by resistance such as frictional resistance and bearing resistance. The anchor body 12 is formed by forming a grout 13A around the tip of the tendon 12A.

  In estimating the tension of the existing anchor 10, a reference anchor (not shown) having the same or similar form as the existing anchor 10 is used. As this reference anchor, another existing anchor different from the existing anchor 10 to be estimated, for example, an existing anchor 30 installed on the ground around the existing anchor 10 as shown in FIG. Alternatively, a new anchor installed for the purpose of estimating the tension of the existing anchor 10 can be used. The reference anchor may be one, or may be a plurality of two or more, or an existing anchor and a new anchor may be used in combination.

  First, a reflected wave receiver is attached to the reference anchor. Here, the reflected wave is a response vibration wave of a reference elastic wave, which will be described later, and is derived from the reference elastic wave. Therefore, the mounting position of the receiver is a position where the reflected wave can be received, and is usually the base end face of the fixing tool or the base end face of the tendon. This is the case of the existing anchor 10 to be estimated, but FIG. 1 (1) shows an example in which the receiver 20 is attached to the base end face of a tendon 11A made of a PC steel rod.

  Next, at least two stages of loads are loaded on the reference anchor, and at each stage of the loading, the reference anchor is struck in the anchor axial direction. This striking can be performed using a striking device such as a hammer. The striking position is a portion where a reference elastic wave can be generated in the anchor axis direction, and is usually an anchor base end portion such as a base end surface of a fixing tool or a base end surface of a tendon. By this striking, a reference elastic wave is generated in the tendon 12A constituting the existing anchor 10.

  The loading of the load on the reference anchor may be performed so that the load applied to the reference anchor increases stepwise or continuously. When the load is continuously increased, the reference anchor is hit at an appropriate two or three or more time points. On the other hand, when the load is increased stepwise, for example, the load is loaded by the same method as the cycle confirmation test such as a one-cycle confirmation test, and two or more time points (stages) or three or more time points with different loads are applied. The reference anchor is hit at the time (stage).

  The cycle confirmation test is a test in which, for example, the initial load is set to 0.1 times the planned maximum load, the load is stepwise loaded up to the planned maximum load, and then unloaded to the initial load. , Loading and unloading will be repeated.

  When the reference elastic wave is generated as described above, a reflected wave derived from the reference elastic wave is generated and transmitted from the anchor body side to the anchor head side via the tendon. Therefore, in the present embodiment, this reflected wave is received by the receiver. The received signal received by this receiver is observed and recorded with an oscilloscope such as an oscilloscope, for example, and the dominant frequency (Hz) is obtained from this observation data using an electronic computer or the like (hereinafter referred to as hitting an anchor). The task of obtaining the dominant frequency (the frequency with the largest amplitude) is also called the “shock elastic wave test”.) The acquisition of the dominant frequency can be performed by frequency analysis such as FFT analysis.

  Next, based on the dominant frequency and the load when the reference anchor is struck, a correlation equation between the dominant frequency and the load, that is, a correlation equation using the dominant frequency and the load as variables is created. This correlation expression is expressed as, for example, “dominant frequency = α · load + β”. Note that “α” and “β” in this equation are values determined based on the dominant frequency and load.

On the other hand, in parallel with the work up to the creation of the above correlation formula, or before and after this work, the same work as the work for obtaining the above-mentioned dominant frequency, that is, the existing anchor for which the impact elastic wave test is to be estimated Repeat for 10.
That is, first, as shown in (1) of FIG. 1, a reflected wave receiver 20 is attached to the existing anchor 10 to be estimated. In this respect, the reflected wave is a response vibration wave of an estimation elastic wave to be described later, and is derived from the estimation elastic wave. However, the mounting position of the receiver 20 is the same as that of the reference anchor, and is the position where the reflected wave can be received, usually the base end face of the fixing tool 11A or the base end face of the tendon 12A as shown in the example.

  Next, the existing anchor 10 to be estimated is hit once in the anchor axis direction to generate an elastic wave for estimation. The method and position of hitting the existing anchor 10 are the same as in the case of the reference anchor.

  When the estimation elastic wave is generated in this way, a reflected wave derived from the estimation elastic wave is generated and transmitted from the anchor body 13 side to the anchor head 11 side via the tendon 12A. Therefore, the reflected wave is received by the receiver 20. The reception signal received by the receiver 20 is analyzed using an oscillograph, an electronic computer, or the like, as in the case of the reference anchor, and a dominant frequency (Hz) is acquired.

  Then, a load is calculated by substituting this dominant frequency into the above-described correlation equation, and this calculated value (load) is estimated as the tension of the existing anchor 10. According to this method, it is not necessary to load a load on the existing anchor 10 to be estimated, and it is not necessary to install a tension jack or the like. Therefore, it is not necessary to install a scaffold around the existing anchor 10, climbing exploration is possible, and work efficiency is greatly improved. In particular, when the number of existing anchors 10 to be estimated is large, or when the existing anchors 10 are present on a steep slope or the like, this work efficiency improvement effect is significant.

[Soundness evaluation method]
Next, the tension estimation method described above is applied. As shown in FIG. 1 (2), the soundness of the ground G such as a slope where a plurality of anchors (existing anchors) 10 are installed is measured. A method of evaluation will be described.

  In the soundness evaluation method of this embodiment, first, a part of the plurality of existing anchors 10 is selected as the reference anchor 30. The selection of the reference anchor 30 may be one of the plurality of existing anchors 10 or two or more. The selection of the reference anchor 30 can be performed in consideration of the state of the ground G, work efficiency, and the like.

Next, using the reference anchor (a part of anchors) 30, a correlation equation having the dominant frequency and the load as variables is created.
That is, as shown in FIG. 2, a reflected wave receiver is first attached to the reference anchor 30. The meaning of this reflected wave and the mounting position of the receiver are the same as in the tension estimation method described above, the reflected wave means the response vibration wave of the reference elastic wave, and the mounting position of the receiver is the reflected wave. The receivable position is usually the base end face of the fixing tool or the base end face of the tendon.

  Next, a test for confirming the residual tension force with respect to the reference anchor 30, for example, a lift-off test as in the illustrated example, is performed to obtain the residual tension force of the reference anchor 30.

  In addition, the reference anchor 30 is anchored in a plurality of stages of at least two stages or three or more stages in which the load applied to the reference anchor 30 is different during the lift-off test process, that is, from the start to the end of the lift-off test. Single shot in the axial direction. This striking generates a reference elastic wave. In this respect, the hitting method and position with respect to the reference anchor 30 are the same as those in the tension estimation method described above.

  Next, as in the tension estimation method described above, a reflected wave derived from the reference elastic wave is received by the receiver, and an oscillograph or an electronic computer is used from the received signal received by the receiver. To obtain the dominant frequency (Hz).

  Then, based on the dominant frequency and the load when the reference anchor 30 is struck, a correlation formula is created with the dominant frequency and the load as variables. This correlation expression is expressed as “excellent frequency = α · load + β”, for example, as in the tension estimation method described above.

On the other hand, a shock elastic wave test is performed on the remaining anchor 10 in parallel with the work up to the creation of the above correlation equation or before and after this work.
That is, first, a reflected wave receiver is attached to the remaining anchor 10. In this respect, the meaning of the reflected wave and the mounting position of the receiver are the same as those in the tension estimation method described above.

  Next, the remaining anchor 10 is hit once in the anchor axis direction. Due to this impact, an elastic wave for estimation is generated. In this respect, the method and position of hitting the remaining anchor 10 are the same as those in the tension estimation method described above.

  Next, in the same manner as in the tension estimation method described above, a reflected wave derived from the elastic wave for estimation is received by a receiver, and an oscillograph or an electronic computer is used from the received signal received by this receiver. To obtain the dominant frequency (Hz).

  Then, a load is calculated by substituting this dominant frequency into the above-described correlation equation, and this calculated value (load) is estimated as the tension of the remaining anchor 10.

  Next, the residual tension is confirmed with respect to the remaining anchor 10 where the estimated tension is outside the predetermined range, that is, the remaining anchor 10 where the estimated tension is below the predetermined range and the remaining anchor 10 where the estimated tension is above the predetermined range. A test, for example, a lift-off test is performed as in the illustrated example. This lift-off test can be performed in the same procedure as in the case of the reference anchor 30, and the residual tension of the remaining anchor 30 can be acquired by this lift-off test.

  Here, the predetermined range relating to the estimated tension is a range serving as a reference for determining whether or not to perform the lift-off test. That is, the method according to the present embodiment determines whether or not the lift-off test is performed by performing a shock elastic wave test on the remaining anchor 10, thereby significantly improving work efficiency. it can. Therefore, the predetermined range can be appropriately determined in consideration of the necessity of more surely grasping the performance of the remaining anchor 10, work efficiency, and the like. Anchor force "or the like.

  As described above, when the residual tension is acquired, it is confirmed whether or not the residual tension is within a predetermined range, and the soundness of the ground G is evaluated using the following ratios 1 to 5 as basic information. To do. The total anchor includes the reference anchor 30 in addition to the remaining anchor 10. In addition, the predetermined range related to the residual tension can be the same as that in the case of the estimated tension, but since the work efficiency does not matter in determining the predetermined range regarding the residual tension, a range different from the case of the estimated tension. It can also be.

(Ratio 1)
Number of remaining anchors 10 whose estimated tension is within a predetermined range / number of all anchors (Ratio 2)
Number of remaining anchors 10 in which residual tension is within a predetermined range / number of all anchors (ratio 3)
Number of remaining anchors 10 whose residual tension is outside the predetermined range / number of all anchors (ratio 4)
Number of reference anchors 30 with residual tension within a predetermined range / number of all anchors (rate 5)
Number of reference anchors 30 whose residual tension is outside the predetermined range / number of all anchors

  According to this method, since it is not necessary to install a scaffold around the remaining anchor 10 for obtaining the ratio 1, work efficiency is greatly improved. In general, the number of anchors (remaining) serving as the basis of the ratio 1 is the largest. Further, in evaluating the soundness of the ground G, basic information other than the ratios 1 to 5 such as the state of the ground G and the installation interval of the anchors 10 can be considered.

Next, an experimental example and an empirical test example that clarify that a correlation exists between the dominant frequency obtained by the shock elastic wave test and the tension force of the existing anchor will be described.
(Experimental example)
A one-cycle confirmation test and a shock elastic wave test were performed on the experimental anchors having physical properties and performance shown in Table 1. The load on the experimental anchor was increased stepwise to 50 kN, 75 kN, 100 kN, 150 kN, 200 kN, 250 kN, and 300 kN. In addition, an impact elastic wave test was performed at each stage of this load to obtain a dominant frequency. The relationship between the dominant frequency (Hz) and the load (tensile force, kN) obtained in this experimental example is shown in FIG. Further, the correlation formula and the determination coefficient are shown in Table 1.

(Verification test 1)
A one-cycle confirmation test and a shock elastic wave test were performed on the existing anchors having physical properties and performance shown in Table 1. The loads on the existing anchors were increased stepwise to 0 kN, 100 kN, 200 kN, 300 kN, 400 kN, and 500 kN. In addition, an impact elastic wave test was performed at each stage of this load to obtain a dominant frequency. FIG. 4 shows the relationship between the dominant frequency (Hz) and the load (tensile force, kN) obtained in this test example. Further, the correlation formula and the determination coefficient are shown in Table 1.

(Verification test 2)
A lift-off test and a shock elastic wave test were performed on the existing anchors having physical properties and performance shown in Table 1. The load on the existing anchors was increased step by step to 50 kN, 75 kN, 100 kN, 150 kN, 200 kN, 250 kN, and 300 kN. In addition, an impact elastic wave test was performed at each stage of this load to obtain a dominant frequency. FIG. 5 shows the relationship between the dominant frequency (Hz) and the load (tensile force, kN) obtained in this test example. Further, the correlation formula and the determination coefficient are shown in Table 1.

(Discussion)
As is clear from the above, there is a correlation between the dominant frequency obtained by the shock elastic wave test and the load loaded on the existing anchor. Therefore, it can be seen that the tension force of the existing anchor can be estimated by performing a shock elastic wave test on the existing anchor to obtain the dominant frequency and substituting this dominant frequency into the correlation equation.

  INDUSTRIAL APPLICABILITY The present invention can be applied as a method for estimating the tension force of an existing anchor installed on a ground such as a slope, and a method for evaluating the soundness of a ground on which a plurality of anchors are installed.

  DESCRIPTION OF SYMBOLS 10 ... Existing anchor, 11 ... Anchor head, 11A ... Fixing tool, 11B ... Bearing plate, 12 ... Tensile part, 12A ... Tendon, 13 ... Anchor body, 13A ... Grout, 20 ... Reflected wave receiver, 30 ... For reference Anchor, G ... ground.

Claims (2)

A method for evaluating the soundness of a ground where a plurality of anchors are installed,
A part of the plurality of anchors is used as a reference anchor,
A test for confirming the residual tension on the reference anchor is performed, and the reference anchor is struck in the anchor axial direction in at least two stages with different loads in the test process for confirming the residual tension. Generate elastic waves,
Obtain the dominant frequency of the reflected wave derived from this reference elastic wave,
Create a correlation formula between the dominant frequency and the load based on this dominant frequency and the load when hitting the reference anchor,
On the other hand, the remaining anchor that has not been tested to confirm the residual tension is struck in the anchor axial direction to generate an estimation elastic wave,
Obtain the dominant frequency of the reflected wave derived from this estimation elastic wave,
The load obtained by substituting this dominant frequency into the correlation equation is estimated as the tension of the remaining anchor,
Perform a test to confirm the residual tension against an anchor whose estimated tension is outside the predetermined range.
A soil integrity evaluation method characterized by the above. Assessing the soundness of the ground based on the ratio of anchors with the estimated tension within the predetermined range, the ratio of anchors with the residual tension within the predetermined range, and the ratio of anchors with the residual tension outside the predetermined range as basic information To
The ground soundness evaluation method according to claim 1 .

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