A Radial Displacement Measuring Device for Small Aperture Tunnel Model Test

Abstract

The invention relates to a radial displacement measuring device for a small aperture tunnel model test, and belongs to the technical field of geotechnical engineering measurement. The device is composed of a magnetic base, a radial displacement meter, and a static strain gauge. A measuring head stretches into the inner wall of the small aperture tunnel and makes contact measurement of a target measuring point to obtain radial absolute displacement by calibrating a relation between the strain of an elastic measuring head end part of a cantilever structure and a displacement of the measuring head. Measurement of the target measuring point at any circumferential position on the inner wall of the tunnel can be achieved through the free rotation of a small diameter cylindrical base. Measurementof radial displacement of the small aperture tunnel in a predetermined diameter range can be accommodated through the adoption of the detachable elastic measuring head with different sizes and the rotation of the elastic measuring head around a U-shaped groove of the cylindrical base. The radial displacement measuring device for the small aperture tunnel model test is simple in structure, is easyand convenient to operate, can directly obtain the absolute displacement of the measuring point, and can be conveniently applied to measurement of radial displacement of small aperture tunnels in anindoor model test.

Description

technical field [0001] The invention relates to a radial displacement measuring device for a small-diameter tunnel model test, belonging to the technical field of geotechnical engineering measurement. Background technique [0002] In order to respond to the great demand for energy, transportation and underground resources generated by the rapid development of the national economy, the construction of underground engineering continues to develop in depth. Accompanying it is the construction of a large number of deep-buried long tunnels (underground chambers, tunnels, roadways). Super long tunnel. Under high ground stress and other deep conditions, the mechanical properties and engineering response of the surrounding rock structure of underground tunnels present new discipline phenomena and laws. The traditional underground engineering theory system faces huge challenges when solving deep underground engineering problems. Therefore, it is imperative to systematically study t...

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Problems solved by technology

[0006] (1) Shanxi Architecture (2017, Vol. 43, No. 4) "GeoPIV Image Processing Technology and Its Application in Geotechnical Tests" article uses the non-contact measurement method based on the principle of particle image velocimetry for edge The measurement of the displacement of the slope model test; but because the tunnel model is prone to peeling off from the surface layer and the inner side during the loading test, this non-contact surface measurement method based on the digital image correlation method can only measure the surface displacement. When applied to a small aperture There will be a large deviation in the displacement measurement inside the tunnel, resulting in distortion of the measurement results

[0007] (2) The Chinese patent authorization announcement number is CN102607396B, the announcement date is 2015.04.15, and the invention name is "a radial displacement sensor". This patent discloses a passive magnetoelectric radial displacement sensor; but the device is only for Measures radial displacement of rotating parts, not suitable for static load tests of tunnel models

[0008] (3) The Chinese patent application publication number is CN108981535A, the publication date is December 11, 2018, and the title of the invention is "contact displacement measurement method and its measurement device". The measuring device to the output end of the outer displacement; however, due to the structure and size of the device itself is too large, it is not suitable for the radial displacement measurement of small-diameter tunnels, and it is difficult to adapt to the measurement requirements of small holes with different aperture ranges

[0009] (4) The Chinese patent authorization announcement number is CN102721399B, the announcement date is 2015.01.28, and the invention name is "wall-attached wellbore radial displacement micrometer and its measurement method". This patent discloses a displacement sensor through a herringbone A device fixed on the inner wall of the wellbore for radial displacement measurement; however, due to the large size of the fixing device, the device cannot perform contact measurement on the inner wall of a small-diameter tunnel, and it is also not suitable for situations where the internal deformation of the small hole is too large

[0010] (5) The Chinese patent authorization announcement number is CN104501682B, the announcement date is 2017.11.21, and the title of the invention is "device and method for measuring bolt hole misalignment". A device for measuring the radial displacement of a tubular body; however, in addition to its inappropriate size, the device can only obtain the relative displacement of the hole wall, and cannot obtain the absolute displacement of a specific measurement point on the hole wall

Since the hole size of the tunnel model produced by the new technology represented by 3D printing is smaller than that of the traditional sample preparation model, its diameter scale is usually at the centimeter level. Most of the current radial displacement measurement devices are difficult to measure the small size of the indoor model test due to their own size. The radial displacement of the aperture tunnel can be effectively measured, while the non-contact surface measurement based on the principle of digital image correlation method has limitations such as measurement distortion when monitoring the internal deformation of the small hole

[0011] It can be seen that the radial displacement measurement inside the small hole used in the model test is not yet mature, and there is also a lack of measuring devices that can have good adaptability to the small hole displacement measurement within a certain aperture range and can obtain large deformation of a single small hole. radial displacement

In addition, traditional mechanical methods such as extensometers or extensometers can only obtain the relative radial displacement of the tunnel wall, but cannot obtain the absolute displacement of a specific feature point in a small-diameter tunnel.

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