ISO 18674-2:2016 地盤調査とテスト—フィールド計装による地盤モニタリング—パート2：線に沿った変位の測定：伸び計 | ページ 2

3.1

extensometer <geotechnical>

field instrument for monitoring changes of distance between two or more measuring points located along a measuring line

Note 1 to entry: Monitoring of such changes allows the determination of displacements of measuring points acting in the direction of the measuring line.

Note 2 to entry: At a measuring point, the movements of the medium (e.g. soil, rock, concrete and steel structures) being investigated are transferred to the measuring point by devices such as anchors, rings or bolts (see 5.1.6).

Note 3 to entry: In the ground, the measuring points are typically installed in boreholes. The measuring line then coincides with the axis of the borehole.

3.2

in-place extensometer

permanently installed extensometer, essentially consisting of anchor(s), connecting element(s) and at least one measuring head

Note 1 to entry: Each connecting element is affixed to an anchor and free to move along the measuring line.

Note 2 to entry: Measuring heads are commonly located at one end of the measuring line. When carrying out the measurements, they function as reference measuring points.

Note 3 to entry: For in-place extensometers in boreholes, see Reference [7].

Note 4 to entry: See Figure 1.

3.3

rod extensometer

in-place extensometer where the connecting element is a rod

Note 1 to entry: Common rod materials are steel or fibreglass.

Note 2 to entry: See Figure 1 a).

3.4

wire extensometer

in-place extensometer where the connecting element is a wire

Note 1 to entry: See Figure 1 b).

3.5

single extensometer

in-place extensometer with one anchor only

Note 1 to entry: See Figure 1 b).

3.6

multiple-point extensometer

in-place extensometer with more than one anchor

Note 1 to entry: Up to six anchor points are common in geo-engineering practice.

Note 2 to entry: See Figure 1 a).

3.7

chain extensometer

in-place extensometer formed of a series of single extensometer elements

Note 1 to entry: See Figure 1 c).

3.8

probe extensometer

extensometer where the connecting element is a moveable unit

Note 1 to entry: Probe extensometers can be developed as single-point probe extensometer (3.9) or double-point probe extensometer (3.10) .

Note 2 to entry: See Figure 2.

3.9

single-point probe extensometer

extensometer, essentially consisting of a measuring probe and a guiding tube with measuring marks and in which, at the measuring position, only one measuring mark interacts with the probe

Note 1 to entry: The connecting element is the unit consisting of a measuring cable and a probe. The measured value is the distance between the measuring mark and the reference mark at the head of the guiding tube.

Note 2 to entry: Because of its design, function and usual geotechnical application, the single-point probe extensometer is commonly designated as a “magnetic extensometer,” a “magnet settlement probe” or an “inductance probe.”

Note 3 to entry: See Figure 2 a).

3.10

double-point probe extensometer

extensometer, essentially consisting of a measuring probe and a guiding tube with measuring marks and in which, at the measuring position, two measuring marks interact with the probe

Note 1 to entry: The connecting element is the measuring probe. The measured value is the distance between the two measuring marks which are in interaction with the probe.

Note 2 to entry: Because of its design and function, the double-point probe extensometer is commonly designated as an “incremental extensometer” or a “sliding micrometer.”

Note 3 to entry: See Figure 2 b).

3.11

gauge length

L

nominal distance between the contact points of the double-point extensometer probe

Note 1 to entry:L is commonly 1,0 m.

Note 2 to entry:L is commonly verified in a calibration of the probe prior to the measurement.

3.12

tape extensometer

extensometer for distance measurements between two accessible measuring points by means of a measuring tape, essentially consisting of a device for tensioning of the tape with a reproducible pulling force, two end pieces for connecting the device to bolts (3.13) and of a read-out unit

Note 1 to entry: Traditionally, tape extensometers were used in tunnelling. By means of follow-up measurements, the change of the distances of two tunnel wall measuring points (in tunnelling, termed “convergence”) is determined. For this reason, tape extensometers are commonly designated as “convergence tapes.”

Note 2 to entry: See Figure 3.

3.13

convergence bolts

measuring bolts fitting to the type of tape extensometer used