Internal strain testing device and method for rock hollow cylinder

Abstract

The invention discloses an internal strain testing device for a rock hollow cylinder, and relates to the technical field of rock mass mechanical test equipment. The device comprises an internal strain testing device, the internal strain testing device is located in a sample, and the internal strain testing device comprises an LVDT shell, a conversion cone shell and a base shell; one end of each compression probe contacts with the inner wall of the sample, the other end of each compression probe radially penetrates through the conversion cone shell to contact with the lower end of the conversion cone, the contact position of each compression probe and the conversion cone is an inclined platform, and each compression probe is internally provided with a semi-compression spring. The internal strain testing device for converting the radial displacement in the rock into the vertical displacement is designed, and the measurement precision of the strain of the inner ring of the sample is high.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mechanics test equipment, and more specifically, it is an internal strain test device for a rock hollow cylinder. The present invention also relates to a method for using such an internal strain test device for a rock hollow cylinder. Background Art

[0002] The triaxial rock experiment is an important method in rock mechanics research. Its test results can more comprehensively reflect the mechanical properties of rock and soil under the initial in-situ stress conditions, which is of great significance for engineering design. With the continuous increase of deep rock mass projects in China, there have emerged complex engineering geological problems such as active faults, high in-situ stress, high geothermal temperature, and underground natural gas storage. Therefore, carrying out indoor mechanical experiment research under different environments is an important scientific issue in the current field of rock mechanics.

[0003] At present, the triaxial compression tests mainly include uniaxial, conventional triaxial, true triaxial, dynamic impact, and rheological tests, and they cannot well simulate complex geological environments in the laboratory. For example, the test device of the Chinese patent "A Rock Hollow Cylinder Torsional Shear Apparatus for Improving Torque Application Accuracy" (Application No.: 201611029623.7) uses conventional strain gauges when measuring the internal ring strain of the hollow cylinder, resulting in poor measurement accuracy.

[0004] Therefore, it is necessary to develop an internal strain test device for a rock hollow cylinder and its use method. Summary of the Invention

[0005] The first object of the present invention is to overcome the deficiencies of the above background art and provide an internal strain test device for a rock hollow cylinder.

[0006] The second object of the present invention is to provide a method for using such an internal strain test device for a rock hollow cylinder.

[0007] To achieve the above first object, the technical solution of the present invention is: an internal strain test device for a rock hollow cylinder, characterized in that: it includes an internal strain test device, the internal strain test device is located inside the sample, and the internal strain test device successively includes an LVDT housing, a conversion cone housing, and a base housing from top to bottom; the upper end of the LVDT is outside the LVDT housing and the lower end is inside the LVDT housing; the upper end of the conversion cone is inside the LVDT housing and contacts the lower end of the LVDT, and the lower end is inside the conversion cone housing; the upper end of the base is inside the base housing;

[0008] One end of a plurality of compression probes contacts the inner wall of the sample, and the other end radially passes through the conversion cone housing and contacts the lower end of the conversion cone. The contact part between the compression probe and the conversion cone is an inclined platform, and a semi-compression spring is arranged inside the compression probe.

[0009] In the above technical solution, the inclination angle of the inclined platform is 45°; a combined fixing gasket is provided between the LVDT housing and the conversion cone housing.

[0010] To achieve the above second object, the technical solution of the present invention is: a method for using an internal strain testing device for a rock hollow cylinder, characterized by comprising the following steps:

[0011] Step 1: Place the internal strain testing device inside the specimen and fix it;

[0012] Step 2: Compress the probe head to press against the inner wall of the specimen for elongation or contraction;

[0013] When the semi-compressed spring contracts, the tip of the conversion cone moves upward on the inclined platform to raise the conversion cone, driving the LVDT to rise;

[0014] When the semi-compressed spring elongates, the tip of the conversion cone moves downward on the inclined platform to lower the conversion cone, driving the LVDT to descend;

[0015] The inclined platform is made at 45°, and the height of the rise or fall of the conversion cone is the displacement generated in the horizontal direction of the specimen.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1) Since the internal space size of the specimen is limited and a radial displacement sensor cannot be placed, while the vertical space is sufficient, the present invention designs an internal strain testing device that converts the internal radial displacement of the rock into a vertical displacement, and the measurement accuracy of the internal ring strain of the specimen is high. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of the present invention.

[0019] Figure 2 It is a schematic structural diagram of the internal strain testing device.

[0020] Figure 3 It is a cross-section of the internal strain testing device Figure 1 .

[0021] Figure 4 It is a cross-section of the internal strain testing device Figure 2 .

[0022] Among them, A - sample, B - rock hollow cylinder torsional shear apparatus, 100 - internal strain testing device, 110 - LVDT housing, 111 - LVDT, 120 - conversion cone housing, 121 - conversion cone, 130 - base housing, 131 - base, 140 - compression probe, 141 - inclined platform, 142 - semi-compressed spring, 150 - combined fixing gasket. Specific Embodiments

[0023] The implementation of the present invention will be described in detail below with reference to the accompanying drawings. However, they do not constitute a limitation to the present invention and are only for illustration purposes. Meanwhile, the advantages of the present invention will become clearer and easier to understand through the description.

[0024] Referring to the accompanying drawings, it can be seen that the internal strain testing device for a rock hollow cylinder is characterized in that it includes an internal strain testing device 100. The internal strain testing device 100 is located inside the sample A and successively includes an LVDT housing 110, a conversion cone housing 120, and a base housing 130 from top to bottom. The upper end of the LVDT 111 is located outside the LVDT housing 110, and the lower end is located inside the LVDT housing 110. The upper end of the conversion cone 121 is located inside the LVDT housing 110 and contacts the lower end of the LVDT 111, and the lower end is located inside the conversion cone housing 120. The upper end of the base 131 is located inside the base housing 130. The base 131 is fixed to the sample A with bolts.

[0025] One end of a plurality of compression probes 140 contacts the inner wall of the sample A, and the other end radially penetrates the conversion cone housing 120 and contacts the lower end of the conversion cone 121. The contact portion between the compression probe 140 and the conversion cone 121 is an inclined platform 141, and a semi-compression spring 142 is arranged inside the compression probe 140.

[0026] The inclination angle of the inclined platform 141 is 45°. A combined fixing gasket 150 is arranged between the LVDT housing 110 and the conversion cone housing 120.

[0027] The tip of the LVDT 411 probe contacts the upper end of the conversion cone 421. The conversion cone housing 420 and the combined fixing gasket 450 play a role in fixing and guiding the conversion cone 421, and the conversion cone 421 receives the probe of the LVDT 411.

[0028] The compression probe 440 penetrates the conversion cone housing 420 such that the tip at the lower end of the conversion cone 421 is on the inclined platform 441 at the upper end of the compression probe 440. There are three compression probes 440.

[0029] The usage method of the internal strain testing device for a rock hollow cylinder is characterized by including the following steps:

[0030] Step 1: Place the internal strain testing device 100 inside the specimen A and fix it.

[0031] Step 2: The compression probe 140 abuts against the inner wall of the specimen A to elongate or contract.

[0032] When the semi-compression spring 142 contracts, the tip of the conversion cone 121 moves upward to the inclined platform 141, causing the conversion cone 121 to rise and driving the LVDT 111 to rise.

[0033] When the semi-compressed spring 142 elongates, the tip of the conversion cone 121 moves towards the lower end of the inclined platform 141, causing the conversion cone 121 to descend and driving the LVDT 111 to descend.

[0034] The inclined platform 141 is made at 45°, and the height by which the conversion cone 121 rises or falls is the displacement generated in the transverse direction of the specimen A.

[0035] The specimen A is located inside the rock hollow cylinder torsional shear apparatus B.

[0036] Other parts not described belong to the prior art.

Claims

1. Internal strain testing device for a rock hollow cylinder, characterized in that: It includes an internal strain testing device (100) which is located inside the sample (A). The internal strain testing device (100) successively includes an LVDT housing (110), a conversion cone housing (120), and a base housing (130) from top to bottom; the upper end of the LVDT (111) is outside the LVDT housing (110), and the lower end is inside the LVDT housing (110); the upper end of the conversion cone (121) is inside the LVDT housing (110) and contacts the lower end of the LVDT (111), and the lower end is inside the conversion cone housing (120); the upper end of the base (131) is inside the base housing (130). One end of a plurality of compression probes (140) contacts the inner wall of the sample (A), and the other end radially penetrates the conversion cone housing (120) and contacts the lower end of the conversion cone (121). The contact part between the compression probe (140) and the conversion cone (121) is an inclined platform (141), and a semi-compression spring (142) is arranged inside the compression probe (140).

2. The internal strain testing device for the rock hollow cylinder according to claim 1, characterized in that: The inclination angle of the inclined platform (141) is 45°; a combined fixing gasket (150) is arranged between the LVDT housing (110) and the conversion cone housing (120).

3. Method for using the internal strain testing device of the rock hollow cylinder, characterized in that, It includes the following steps: Step 1: Place the internal strain testing device (100) inside the specimen (A) and fix it. Step 2: The compression probe (140) presses against the inner wall of the specimen (A) to elongate or contract. When the semi-compression spring (142) contracts, the tip of the conversion cone (121) moves upward towards the upper end of the inclined platform (141) to raise the conversion cone (121), driving the LVDT (111) to rise. When the semi-compression spring (142) elongates, the tip of the conversion cone (121) moves downward towards the lower end of the inclined platform (141) to lower the conversion cone (121), driving the LVDT (111) to descend. The inclined platform (141) is made at 45°, and the height of the rise or fall of the conversion cone (121) is the displacement generated in the transverse direction of the specimen (A).

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