Shear box and apparatus for hollow torsion triaxial instrument interface ring shear test

Abstract

The present invention provides a shear box and device for an interface ring shear test of a hollow torsion triaxial instrument. The shear box comprises: a base and a soil sample box arranged on the base. The base is used to connect to the base of the hollow torsion triaxial instrument. The soil sample box comprises an inner tube and an outer tube. An annular cavity for accommodating a soil sample is formed between the inner tube and the outer tube. The upper ends of the tube walls of the inner tube and the outer tube are both provided with elastic seals. The bottom of the soil sample box is provided with a protruding structure for fixing the soil sample. The shear box of the present invention can be directly installed on the base of an existing hollow torsion triaxial instrument, replacing the conventional base used for hollow torsion shear tests of pure soil samples. The interface ring shear test can be realized by utilizing the loading system of the hollow torsion triaxial instrument itself. The interface shear test means can be expanded without making complex modifications to the original test instrument. The shear box has a simple principle, is easy to process, and is easy to realize.

Description

Technical Field

[0001] The present invention relates to the technical field of soil-structure interface shear testing, in particular to a shear box and a device for a hollow torsion triaxial instrument interface ring shear test. Background Art

[0002] The study of the mechanical properties of the soil-structure interface has always attracted widespread attention in the field of geotechnical engineering. Various test methods are used, mainly involving direct shear test, simple shear test, ring shear test, etc. The existing interface ring shear tester is mainly developed by modifying the Bromhead ring shear tester. The shear box is a whole, and the soil sample is installed inside. By applying vertical load and torque to the loading plate on the top of the sample, the loading plate and the soil sample are sheared, and the failure occurs near the interface. The loading plate can be installed with different types of structures, and its material and roughness can be controlled to simulate actual engineering structures. The ring shear test has the following advantages: (1) convenient sample preparation and simple operation; (2) large shear displacement, which can more accurately measure the residual strength of the contact surface; (3) the contact area does not change during the shear process, and the interface stress is more uniform.

[0003] The hollow torsion triaxial apparatus is the primary instrument for studying the mechanical properties of soils subjected to rotation of the principal stress axis. This type of apparatus can apply axial force, torque, and internal and external pressure to hollow cylindrical specimens to continuously rotate the principal stress axis. Many hollow torsion triaxial apparatuses can not only achieve monotonic torsion but also apply cyclic loads with waveforms such as sine, cosine, and custom waveforms according to stress or strain control modes. The loading frequency can be set, and important parameters such as normal stress, shear stress, strain, and volume deformation can be measured simultaneously. The upper specimen cap and loading device of the hollow torsion triaxial apparatus specimen are similar in principle to the loading plate and loading device of the ring shear test, and both can apply torque to the upper part of the specimen. Therefore, by replacing the original soil sample and lower base of the hollow torsion triaxial apparatus with a specially designed shear box, the ring shear test function can be realized by using the original loading device of the instrument without the need for complex modifications to the instrument.

[0004] According to preliminary research, there are currently no related inventions or research. Therefore, a shear box is designed that can realize the interface ring shear test function of the hollow torsional triaxial instrument. This is of great significance for expanding the test functions of existing instruments and enriching the research methods of interface shear tests. Summary of the Invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a shear box and a device for hollow torsion triaxial instrument interface ring shear test.

[0006] According to one aspect of the present invention, a shear box for an interface ring shear test of a hollow torsion triaxial apparatus is provided, comprising: a base and a soil sample box arranged on the base, the base being used to connect to the base of the hollow torsion triaxial apparatus, the soil sample box comprising an inner cylinder and an outer cylinder, an annular cavity for accommodating a soil sample is formed between the inner cylinder and the outer cylinder; elastic seals are provided at the upper ends of the cylinder walls of the inner cylinder and the outer cylinder, and a protruding structure for fixing the soil sample is provided at the bottom of the soil sample box.

[0007] Furthermore, the width of the inner cylinder elastic seal on the inner cylinder is the same as the thickness of the cylinder wall of the inner cylinder, and the width of the outer cylinder elastic seal on the outer cylinder is the same as the thickness of the cylinder wall of the outer cylinder; the height of the inner cylinder elastic seal and the outer cylinder elastic seal is 2-5mm.

[0008] Furthermore, the diameters of the inner cylinder and the outer cylinder are determined according to the sample size of the hollow torsion triaxial apparatus.

[0009] Furthermore, the shear box is made of stainless steel or brass.

[0010] Furthermore, the wall thickness of the inner tube and the outer tube is not less than 2 mm.

[0011] Furthermore, the height of the annular cavity inside the soil sample box is at least 20 mm.

[0012] Furthermore, the height of the base is determined according to the length of the loading rod of the hollow torsion triaxial apparatus, and the height of the base is set to enable the loading rod to apply a load to the soil sample in the shear box.

[0013] Furthermore, the base and the soil sample box are connected by bolt anchoring.

[0014] Furthermore, the shear box also calibrates and corrects the friction force of the hollow torsion triaxial apparatus itself before use.

[0015] According to another aspect of the present invention, an interface ring shear test device is provided, which includes a hollow torsion triaxial apparatus and the above-mentioned shear box for the interface ring shear test of the hollow torsion triaxial apparatus, wherein the shear box is located on the base of the hollow torsion triaxial apparatus, and a loading plate for simulating a structure is provided above the shear box, and a specimen cap for applying torque to the specimen in the shear box is provided above the loading plate.

[0016] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0017] The shear box of the present invention, used for the interface ring shear test of a hollow torsion triaxial apparatus, can be directly installed on the base of an existing hollow torsion triaxial apparatus, replacing the conventional base used for hollow torsion shear tests of pure soil specimens. The interface ring shear test can be performed using the hollow torsion triaxial apparatus's own loading system. This invention adds interface shear functionality to the instrument without requiring complex modifications to the existing test apparatus, expanding the range of interface shear testing methods. The shear box has a simple principle, is easy to manufacture, and is readily implemented.

[0018] 2. The present invention is applicable and economical. It has the structure of a hollow torsion triaxial instrument and can realize the test function of an expensive interface ring shear instrument through a relatively low-cost shear box. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0020] Figure 1 Schematic diagram of the structure of a shear box used for the hollow torsion triaxial apparatus interface ring shear test in an embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the assembly of a shear box for a hollow torsion triaxial apparatus interface ring shear test in an embodiment of the present invention;

[0022] Figure 3 Schematic diagram of the structure of the interface ring shear test device in an embodiment of the present invention;

[0023] In the figure: 1 is a soil sample box, 11 is an outer cylinder, 12 is an inner cylinder, 13 is an elastic seal, 14 is a raised structure, 2 is a base, 3 is a pedestal, 4 is a soil sample, 5 is a loading plate, and 6 is a sample cap. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the spirit of the present invention. These all fall within the scope of protection of the present invention. In the description of the embodiments of the present invention, it should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0025] The embodiment of the present invention provides a shear box for the hollow torsion triaxial instrument interface ring shear test, referring to Figure 1-3 , including: a base 2 and a soil sample box 1 arranged on the base 2, the base 2 is used to connect with the base 3 of the hollow torsion triaxial instrument, the soil sample box 1 includes an inner tube 12 and an outer tube 11, and an annular cavity for accommodating a soil sample 4 (or test specimen) is formed between the inner tube 12 and the outer tube 11; the upper ends of the inner tube 12 and the outer tube 11 are provided with elastic seals 13, and the bottom of the soil sample box 1 is provided with a raised structure 14 for fixing the soil sample 4. For example, the raised structure 14 formed by a raised steel sheet at the bottom of the soil sample box 1 can prevent the loading plate 5 and the soil sample 4 from rotating as a whole when the roughness of the loading plate 5 is high, and damage does not occur at the interface position. The shear box for the interface ring shear test of the hollow torsion triaxial apparatus in the embodiment of the present invention can be directly installed on the base of the existing hollow torsion triaxial apparatus, replacing the conventional base used for the hollow torsion shear test of pure soil samples. The interface ring shear test can be realized by using the hollow torsion triaxial apparatus's own loading system. Specifically, the original torsion and vertical loading system of the hollow triaxial apparatus is used to apply torsion and normal pressure to the loading plate 5 on the sample cap 6, thereby realizing the annular shear test function between the soil sample and the loading plate interface.

[0026] The function of the elastic seal 13 is to prevent the soil sample 4 from overflowing and to prevent the loading plate 5 of the upper simulated structure from squeezing the rigid shear box to make the interface stress uneven. In some preferred embodiments, the width of the inner cylinder elastic seal on the inner cylinder 12 is the same as the wall thickness of the inner cylinder 12, and the width of the outer cylinder elastic seal on the outer cylinder 11 is the same as the wall thickness of the outer cylinder 11; the height of the inner cylinder elastic seal and the outer cylinder elastic seal are the same, both of which are 2-5mm, which can not only prevent the soil sample from overflowing, but also avoid the phenomenon of increased friction between the elastic seal 13 and the sample cap 6 due to the elastic seal 13 being too high; the elastic seal 13 can be made of rubber material or polyurethane. In some other embodiments, the elastic seal 13 can also be made of other materials, as long as it can achieve the same function as in the embodiment of the present invention. The diameters of inner cylinder 12 and outer cylinder 11 are determined based on the specimen size of the hollow torsion triaxial apparatus. Specifically, the outer diameter of the shear box inner cylinder 12 and the inner diameter of the outer cylinder 11 are determined based on the cross-sectional dimensions of the hollow torsion triaxial specimen. For example, if the cross-sectional dimensions of the hollow torsion triaxial specimen are 60mm inner diameter and 100mm outer diameter, the outer diameter of the shear box inner cylinder is 60mm, and the inner diameter of the outer cylinder is 100mm. Based on this, the dimensions of the inner and outer cylinders can be determined based on their thickness. The annular cavity within the soil sample box 1, i.e., the height of the inner and outer cylinders, is at least 20mm, which is the height of the soil sample 4 within the shear box. This ensures that the soil sample 4 has a certain thickness, reduces the influence of the bottom rigid boundary on the stress distribution at the upper interface, and makes the stress distribution at the soil-structure interface more uniform.

[0027] To ensure the rigidity of the soil sample tube, in some preferred embodiments, the shear box is made of stainless steel or brass, and the wall thickness of the inner tube 12 and the outer tube 11 is not less than 2 mm. More preferably, for ease of processing, the wall thickness of the inner tube 12 and the outer tube 11 are the same.

[0028] As a preferred embodiment, the height of the soil sample space filled inside the soil sample box 1, that is, the height of the annular cavity is 20 mm, the inner diameter of the soil sample 4 is 60 mm, and the outer diameter is 100 mm. The material of the soil sample box 1 is stainless steel, and the wall thickness of the inner tube 12 and the outer tube 11 of the soil sample box is 2 mm. The outer diameter of the inner tube is 60 mm and the inner diameter is 56 mm. The outer diameter of the outer tube is 104 mm and the inner diameter is 100 mm.

[0029] The base 2 can be installed on the base of a general hollow torsion triaxial apparatus, replacing the conventional base used for hollow torsion shear tests of pure soil samples. The main function of the base 2 is to increase the height of the shear box to avoid the insufficient length of the loading rod of the hollow torsion apparatus, which makes it impossible to apply a load to the soil sample 4 in the shear box. In some preferred embodiments, the height of the base 2 is determined according to the length of the loading rod of the hollow torsion triaxial apparatus, and the height of the base 2 is set to enable the loading rod to apply a load to the soil sample 4 in the shear box. The original sample sizes of different hollow torsion triaxial apparatuses are different, and the required height of the base 2 is also different. For example, the original sample size is 100 mm in outer diameter, 60 mm in inner diameter, and 100 mm in height, and the height of the base 2 is 60 mm.

[0030] In order to achieve a stable connection between the base 2 and the soil sample box 1, in some preferred embodiments, the base 2 and the soil sample box 1 are connected by bolt anchoring.

[0031] There is friction between the loading plate 5 of the simulated structure and the inner wall of the soil sample box 1 or the elastic seal 13. In some preferred embodiments, the shear box also calibrates and corrects the friction of the hollow torsion triaxial apparatus before use. The method for calibrating and correcting the friction of the apparatus itself is as follows:

[0032] After the shear box is installed, a rubber block of the same size as the soil sample is placed in the shear box. The top of the rubber block is covered with a Teflon film and coated with lubricant.

[0033] The loading plate 5 used to simulate the structure above the soil sample uses the lowest roughness loading plate 5 and is also coated with Teflon film and lubricant. The lowest roughness refers to the loading plate 5 surface being ground and polished to a roughness of less than 0.1 micron. At this point, it is considered that the interface has basically no bearing capacity, and the interface friction is entirely caused by the friction of the instrument itself.

[0034] The treated interface is subjected to shear tests under different normal stresses. For example, the normal stress can include five stress levels: 50kPa, 100kPa, 150kPa, 200kPa and 300kPa. The interface friction force under different stress levels is obtained and calibrated. The calibration result, i.e., the friction force of the instrument itself, is used to correct subsequent tests.

[0035] The embodiment of the present invention also provides an interface ring shear test device, continue to refer to Figure 3 The apparatus comprises a hollow torsion triaxial apparatus and a shear box for performing the interface ring shear test on the hollow torsion triaxial apparatus, as described in the above embodiment. The shear box is located on the base 3 of the hollow torsion triaxial apparatus and is connected to the base 3 by bolt anchoring. A loading plate 5 for simulating a structure is located above the shear box. A specimen cap 6 for applying torque to the specimen within the shear box is located above the loading plate 5. The interface ring shear test can be performed using the hollow torsion triaxial apparatus's own loading system.

[0036] The shear box and device for the hollow torsion triaxial instrument interface ring shear test in the embodiments of the present invention can add instrument interface shear functionality without complex modifications to the original test instrument, expanding the interface shear testing capabilities. The shear box has a simple principle, is easy to manufacture, and is easy to implement. The present invention is both applicable and economical. By utilizing the structure of a hollow torsion triaxial instrument, the shear box can achieve the testing functions of a more expensive interface ring shear instrument using a relatively low-cost shear box.

[0037] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various modifications or variations within the scope of the claims without affecting the essence of the present invention. The above preferred features may be used in any combination as long as they do not conflict with each other.

Claims

1. A shear box for hollow torsion triaxial instrument interface ring shear test, characterized in that: include: A base and a soil sample box provided on the base, wherein the base is used to connect to the base of the hollow torsion triaxial instrument, and the soil sample box includes an inner cylinder and an outer cylinder, wherein an annular cavity for accommodating the soil sample is formed between the inner cylinder and the outer cylinder; The upper ends of the inner and outer cylinders are provided with elastic seals, and the bottom of the soil sample box is provided with a protruding structure for fixing the soil sample; The elastic seal of the inner tube and the elastic seal of the outer tube are the same height, both of which are 2-5 mm; the outer diameter of the inner tube and the inner diameter of the outer tube of the shear box are determined according to the cross-sectional dimensions of the hollow torsional triaxial specimen, and the wall thickness of the inner tube and the outer tube is not less than 2 mm; the height of the annular cavity inside the soil sample box is at least 20 mm.

2. The shear box for the hollow torsion triaxial apparatus interface ring shear test according to claim 1, characterized in that: The width of the inner cylinder elastic seal on the inner cylinder is the same as the thickness of the cylinder wall of the inner cylinder, and the width of the outer cylinder elastic seal on the outer cylinder is the same as the thickness of the cylinder wall of the outer cylinder.

3. The shear box for the hollow torsion triaxial apparatus interface ring shear test according to claim 1, characterized in that: The shear box is made of stainless steel or brass.

4. The shear box for the hollow torsion triaxial apparatus interface ring shear test according to claim 1, characterized in that: The height of the base is determined according to the length of the loading rod of the hollow torsion triaxial apparatus, and the height of the base is set to enable the loading rod to apply a load to the soil sample in the shear box.

5. The shear box for the hollow torsion triaxial apparatus interface ring shear test according to claim 1, characterized in that: The base and the soil sample box are connected by bolt anchoring.

6. The shear box for the hollow torsion triaxial apparatus interface ring shear test according to claim 1, characterized in that: The shear box also calibrates and corrects the friction force of the hollow torsion triaxial apparatus itself before use.

7. An interface ring shear test device, characterized in that: It comprises a hollow torsion triaxial apparatus and a shear box for the interface ring shear test of the hollow torsion triaxial apparatus as described in any one of claims 1 to 6, wherein the shear box is located on the base of the hollow torsion triaxial apparatus, a loading plate for simulating a structure is provided above the shear box, and a specimen cap for applying torque to the specimen in the shear box is provided above the loading plate.

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