MEASURING DEVICE AND METHOD

Description

[0001] The invention relates firstly to a measuring device comprising two rock anchors and a linear potentiometer mounted between the rock anchors with an extension element, which measures a change in length in a straight connecting line between the rock anchors. The invention further relates to a measuring method to be carried out using such a measuring device.

[0002] Such measuring devices and methods are used to detect small rock displacements over long periods of time. The extension element bridges a distance between the reference points that exceeds the length of the linear potentiometer. The measuring device can thus be used for measurements over distances from 30 cm to 3 m. Conventional measuring devices feature aluminum extension elements, whose length changes under the influence of temperature are laboriously calculated or must be distinguished from the actual rock movement using a sufficiently long series of measurement data.

[0003] Furthermore, CN209727633U describes a measuring device for measuring a change in length of a concrete component. Task

[0004] The invention is based on the object of making the measuring device less sensitive to temperature influences. Solution

[0005] Based on the known measuring device, the invention proposes that the extension element be made of a carbon composite. In the measuring device according to the invention, the extension element combines high mechanical stability and rigidity with negligible thermal expansion in the temperature range between -30 and +50 °C, which is relevant for rock movements: Carbon composite, for example, has a thermal expansion coefficient 240 times lower than that of aluminum.

[0006] The measuring device according to the invention has standardized pins, in particular Leica pins, on the rock anchors, as well as two adapters for the pins connected to the linear potentiometer. In such a measuring device, the rock anchors can be attached to the reference points for the measurement in the rock independently of the linear potentiometer. The linear potentiometer can then be attached and easily removed from the rock anchors without compromising the reproducibility of the measurement. The measurement can thus also be easily verified or calibrated using other measuring systems (e.g., laser reflectors, mechanical measuring instruments, or theodolites).

[0007] Preferably, such a measuring device according to the invention has internal threads in the rock anchors, with the pins being screwed into the internal threads. The pins remain screwed onto the rock anchors and are not removed thereafter.

[0008] The measuring device according to the invention has a ball joint between each linear potentiometer and the rock anchors. The articulated connection between the linear potentiometer and the rock anchors prevents transverse stresses in the linear potentiometer and the resulting impairment of the measurement due to shifts of the reference points that are not in the connecting line.

[0009] A measuring device according to the invention preferably has a communication element to which the linear potentiometer transmits the length change via a wired connection, and which sends a message about the length change via a radio connection. Such a communication element is known from the applicant's program under the product name Aartelink. Based on the known measuring method, the invention proposes that the extension element be made of a carbon composite. The measuring method according to the invention can be implemented in particular with a measuring device according to the invention and is equally characterized by the aforementioned advantages thereof.

[0010] In a method according to the invention, the rock anchors are preferably glued into the rock at the reference points. The use of glued rock anchors is widespread and proven in practice. Example

[0011] The invention is explained below using an exemplary embodiment. Fig. 1 shows a measuring device according to the invention and Fig. 2 shows an application of the measuring device.

[0012] The Figure 1 The measuring device 1 according to the invention shown consists of two rock anchors 2, a linear potentiometer 3 with an extension element 4 and two adapters 6 attached to it via a ball joint 5, as well as a communication element 7.

[0013] Internally threaded sleeves V-IG M 8 A4 from MKT Weilerbach / DE are used as rock anchors 2, into each of which a pin 8 - here: a Leica pin - is screwed.

[0014] Linear potentiometer 3 is a precision linear potentiometer model LZW-IP from WayCon GmbH, Taufkirchen / Germany, with a measuring range of 50 mm. Extension element 4 is a carbon composite rod with a diameter of 20 mm. The prefabricated extension element 4 is glued at both ends with 3D-printed carbon threaded bushings (not shown) in such a way that the glue galvanically isolates the ends from each other.

[0015] The adapters 6 are steel sleeves with a length of 95 mm and a diameter of 35 mm and can be fixed to the pins 8 with a clamping screw 9. The joint points of the ball joints 5 according to DIN 648 in size M8 are located on the longitudinal axis 10 of the pins 8 and have a distance 11 of 60 mm from their heads and form the measuring points of the measuring device 1.

[0016] Communication element 7 is a universal sensor, model name Aartelink, designed by the applicant as a data logger with a battery and remote communication device. Communication element 7 is connected to linear potentiometer 3 via an M12 connector with IP68 protection and a four-pin cable 12 with rodent protection.

[0017] To apply the measuring device 1 according to the invention and to carry out the method according to the invention on a rock crevice 13, the rock anchors 2 are glued into bores 14 in the opposite rock 15 and the pins 8 are screwed into the rock anchors 2 and the communication element 7 is anchored in a third bore (not shown).

[0018] The appropriately pre-assembled extension element 4 is connected to the linear potentiometer 3. The linear potentiometer 3 is then placed on the pins 8 with the adapters 6, secured with the clamping screws 9, and connected to the communication element 7 via the cable 12.

[0019] The communication element 7 detects voltage changes at the linear potentiometer 3, calculates a change in length between the rock anchors 2, compares this with internally stored, adjustable threshold values, and, if these are exceeded, communicates the measured values ​​via a short-range radio connection to a downstream gateway and from there via a wired or wireless mobile connection to the AarteLink application server. To monitor the functionality of the measuring device 1, a "sign of life" is sent hourly to the downstream gateway, which also contains the temperature measured in the communication element at that time. On the application server, the current distance 16 between the reference points 17 is calculated and displayed from a previously known value and the change in length. The gateway and the application server are not shown. The battery of the communication element 7 has a service life of ten years.

[0020] In the figures are 1Measuring device 2Rock anchor 3Linear potentiometer 4Extension element 5Ball joint 6Adapter 7Communication element 8Pin 9Clamping screw 10Longitudinal axis 11Distance 12Cable 13Rock crevice 14Borehole 15Rock 16Distance 17Measuring point

Claims

1. A measuring device (1) with two rock anchors (2) and a linear potentiometer (3) mounted with an extension element (4) between the rock anchors (2), which measures a change in length in a straight connecting line between the rock anchors (2), wherein the extension element (4) consists of a carbon composite, characterised by standardised pins (8) on the rock anchors (2) and two adapters (6) for the pins, wherein the adapters are each connected via a ball joint (5) to the linear potentiometer (3).

2. The measuring device (1) according to the preceding claim, characterised by internal threads in the rock anchors (2), wherein the pins (8) are screwed into the internal threads.

3. The measuring device (1) according to any one of the preceding claims, characterised by a communication element (7), to which the linear potentiometer (3) transmits the change in length by wire, and which sends a message about the change in length by means of a radio link.

4. A method of measurement, wherein a rock anchor (2) is attached at each of two reference points (17) and a linear potentiometer (3) attached with an extension element (4) between the rock anchors (2) measures a change in length in a straight connecting line between the rock anchors (2), wherein the extension element (4) consists of a carbon composite, characterised in that standardised pins are on the rock anchors (2) and that two adapters (6) for the pins (8) are each connected via a ball joint (5) to the linear potentiometer (3).

5. The method of measurement according to the preceding claim, characterised in that the rock anchors (2) are glued into rock at the reference points (17).