A method for in-situ shearing test of structural plane

Abstract

The application provides a structural plane in-situ shearing test method, selects a structural plane test piece test point in-situ, tests a plurality of test points in stages, respectively draws stress deformation curves, obtains shearing strength characteristic values, applies Coulomb strength fitting, and obtains in-situ shearing mechanical parameter values. The shearing creep test is carried out in-situ, the sampling difficulty of the structural plane in the indoor test is avoided, the structural plane original state is maintained to the maximum extent in the in-situ sampling, the test principle is simple and convenient to implement; the test method considers the weak property of the structural plane in the vertical load, and the stable pressure load system is adopted to ensure the implementation of the creep load, the data collection interval is reasonably set, and the test result reliability is ensured.

Description

Technical Field

[0001] This invention relates to the field of structural surface field testing technology, and in particular to a method for on-site shear testing of structural surfaces. Background Technology

[0002] Geological conditions and soil properties determine many aspects of hydropower projects, including site selection, design, construction, and operation, and are key factors for the safety and stability of such large-scale geotechnical engineering projects. In addition to fault structures such as faults and fissures, the geological structures of many hydropower station hub areas in Southwest my country also include unique large structural planes such as inter-layer and intra-layer fault zones. Deep deformation of these structural planes affects the overall safety of the project.

[0003] The mechanical properties of structural surfaces are crucial for engineering design and safe operation. In addition to indoor testing, on-site testing is also required to obtain the mechanical properties of structural surfaces at the macroscopic level. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for on-site shear testing of structural surfaces, which can solve the problem of needing to test structural surfaces on-site to obtain the mechanical properties at a macroscopic scale.

[0005] Therefore, the present invention adopts the following technical solution: A method for in-situ shear testing of structural surfaces, comprising the following steps: 1. Determine the structural surface located on site, and select several test points on the structural surface. Establish a structural test specimen at each test point, plan the normal stress at each test point, and conduct graded tests on the normal stress at different test points. 2. Install a normal jack and a tangential jack at the structural test piece at the first test point. The normal jack is used to apply normal stress to the structural test piece, and the tangential jack is used to apply shear stress to the structural test piece. 3. Set the normal stress of the normal jack and test the first test point. During this period, keep the normal stress constant and continuously increase the shear stress applied by the tangential jack until the structural test piece at the first test point fails in shear. During this process, the vertical deformation and horizontal deformation at that point when the shear stress changes should be recorded. IV. Based on the data recorded in step three, plot the stress-deformation curves, including the curves showing the relationship between shear stress and vertical deformation, and the curves showing the relationship between shear stress and horizontal deformation. V. Based on the stress-deformation curve, determine the characteristic value of shear strength at the first test point, including the proportional limit, yield limit, peak strength, and residual strength characteristic value. 6. Repeat steps two through five for the remaining test points in sequence to ensure that the normal stress at each test point is different, thereby obtaining the corresponding shear strength characteristic values ​​under multiple normal stress conditions; VII. Based on the normal stress and corresponding peak shear strength of multiple test points, plot each point on a coordinate graph, and apply the Coulomb strength criterion to fit each point. The intercept of the fitted curve on the vertical axis is the cohesion, and the angle between the curve and the horizontal axis is the friction angle. In this way, the in-situ shear mechanical parameters of the structural surface are obtained.

[0006] Based on the above technical solutions, the present invention may also employ the following further technical solutions, or combine these further technical solutions: In step two, as the shear stress increases, it is necessary to ensure that the normal stress remains constant.

[0007] The maximum normal stress should not expel the filling material from the structural test piece.

[0008] Compared with the prior art, the present invention has the following advantages and beneficial effects: it adopts on-site in-situ shear creep test, which avoids the sampling problem of structural surface during indoor test, and the on-site sample preparation maintains the original state of the structural surface to the greatest extent. The test principle is simple and easy to implement. The test normal load takes into account the weak nature of the structural surface, and the use of a pressure-stabilized load system ensures the implementation of creep load. The data acquisition interval is reasonably set, which is scientific and effective and ensures the reliability of the test results. Attached Figure Description

[0009] Figure 1 This is a schematic diagram illustrating the experimental principle of the present invention.

[0010] Figure 2 This is a diagram illustrating the characteristics of shear failure in this invention.

[0011] Figure 3 This is a schematic diagram of the shearing parameters of the present invention. Detailed Implementation

[0012] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote elements with the same or similar functions throughout. However, it should be understood that the drawings are for illustrative purposes only and should not be construed as limiting the present invention. To better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size. It is understandable for those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present invention.

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0014] This invention provides a method for in-situ shear testing of structural surfaces, comprising the following steps: 1. Determine the structural surface located on site, and select several test points on the structural surface. Establish a structural test specimen 1 at each test point, plan the normal stress at each test point, and conduct graded tests on the normal stress at different test points. 2. Install a normal jack 2 and a tangential jack 3 at the structural test piece 1 at the first test point. The normal jack 2 is used to apply normal stress to the structural test piece 1, and the tangential jack 3 is used to apply shear stress to the structural test piece 1. 3. Set the normal stress of the normal jack 2 and test the first test point. During this period, keep the normal stress constant and continuously increase the shear stress applied by the tangential jack 3 until the structural test piece 1 at the first test point fails in shear. During this process, the vertical deformation and horizontal deformation at the point when the shear stress changes should be recorded. IV. Based on the data recorded in step three, plot the stress-deformation curves, including the curves showing the relationship between shear stress and vertical deformation, and the curves showing the relationship between shear stress and horizontal deformation. V. Based on the stress-deformation curve, determine the characteristic value of shear strength at the first test point, including the proportional limit, yield limit, peak strength, and residual strength characteristic value. 6. Repeat steps two through five for the remaining test points in sequence to ensure that the normal stress at each test point is different, thereby obtaining the corresponding shear strength characteristic values ​​under multiple normal stress conditions; VII. Based on the normal stress and corresponding peak shear strength of multiple test points, plot each point on the coordinate graph, and apply the Coulomb strength criterion to fit each point. The intercept of the fitted curve on the vertical axis is the cohesion, and the angle between the curve and the horizontal axis is the friction angle. In this way, the in-situ shear mechanical parameter values ​​of structural surface 1 are obtained.

[0015] In step two, as the shear stress increases, it is necessary to ensure that the normal stress remains constant.

[0016] The maximum normal stress should not expel the filling material from structural test piece 1.

[0017] One embodiment of the present invention is as follows: During the site survey of a hydropower station, shear field tests were required on typical structural surfaces within the plant area. First, the exposed areas of the structural surfaces were selected, and shear equipment was transported to these locations. Then, the testing equipment was installed at the selected structural specimen locations. Five measuring points were selected on the same structural surface for testing, with different normal stress settings at each point: 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, and 1 MPa.

[0018] Set the normal stress and test the first measuring point. Keep the normal stress constant and continuously increase the shear stress until shear failure occurs.

[0019] Record the vertical and horizontal deformations at the measuring point, plot the curves showing the relationship between shear stress and vertical and horizontal deformations, and obtain the shear strength value at the measuring point under a normal stress of 0.2 MPa.

[0020] The same steps were performed on the other four measuring points to obtain the corresponding shear strength values ​​under normal stress.

[0021] Set the coordinates for normal stress (x-axis) and peak shear strength (y-axis). Combine the normal stress and corresponding peak shear strength values ​​at five measuring points and plot each point on the coordinate graph. All five points are on the shear failure curve, and the Coulomb strength criterion is applied to fit the curve to the shear failure curve. The intercept of the fitted line on the y-axis is the cohesion *c*, and the angle between the curve and the x-axis is the friction angle. This is used to obtain the in-situ shear mechanical parameters of the structure.

[0022] Based on the description and accompanying drawings of this invention, those skilled in the art can readily manufacture or use the on-site shear test method for structural surfaces according to this invention, and can achieve the positive effects described in this invention.

[0023] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. The terms "installed," "set," "equipped with," "connected," "linked," and "sleeve" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral construction; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two mechanisms, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] In the description of this invention, it should be understood that the terms "one end," "the other end," "outer side," "inner side," "horizontal," "end," "length," "outer end," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the mechanism or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. The terms "first" and "second" are also used only for the sake of brevity in description and do not indicate or imply relative importance.

[0025] Furthermore, in practicing the claims of this invention, those skilled in the art can understand and influence variations to the disclosed embodiments through a study of the drawings, the disclosure, and the appended claims. Additionally, in the claims and description, words such as "comprising" and "containing" do not exclude other elements or steps, and non-plural nouns do not exclude their plural forms.

[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes and modifications made in accordance with the present invention are covered by the scope of the claims of the present invention, and will not be listed here.

Claims

1. A method for in-situ shear testing of structural surfaces, characterized in that, Includes the following steps:

1. Determine the structural surface located on site, and select several test points on the structural surface. Establish a structural test specimen (1) at each test point, plan the normal stress at each test point, and conduct graded tests of normal stress at different test points.

2. Install a normal jack (2) and a tangential jack (3) at the structural test piece (1) of the first test point. The normal jack (2) is used to apply normal stress to the structural test piece (1), and the tangential jack (3) is used to apply shear stress to the structural test piece (1).

3. Set the normal stress of the normal jack (2) and test the first test point. During this period, keep the normal stress constant and continuously increase the shear stress applied by the tangential jack (3) until the structural test piece (1) at the first test point is sheared. During this process, the vertical deformation and horizontal deformation at the point when the shear stress changes should be recorded. IV. Based on the data recorded in step three, plot the stress-deformation curves, including the curves showing the relationship between shear stress and vertical deformation, and the curves showing the relationship between shear stress and horizontal deformation. V. Based on the stress-deformation curve, determine the characteristic value of shear strength at the first test point, including the proportional limit, yield limit, peak strength, and residual strength characteristic value.

6. Repeat steps two through five for the remaining test points in sequence to ensure that the normal stress at each test point is different, thereby obtaining the corresponding shear strength characteristic values ​​under multiple normal stress conditions; VII. Based on the normal stress and corresponding peak shear strength of multiple test points, plot each point on a coordinate graph, and apply the Coulomb strength criterion to fit each point. The intercept of the fitted curve on the vertical axis is the cohesion, and the angle between the curve and the horizontal axis is the friction angle. In this way, the in-situ shear mechanical parameters of the structural surface are obtained.

2. The method for in-situ shear testing of structural surfaces as described in claim 1, characterized in that, In step two, as the shear stress increases, it is necessary to ensure that the normal stress remains constant.

3. The method for in-situ shear testing of structural surfaces as described in claim 1, characterized in that, The maximum normal stress should not expel the filling material of the structural test piece (1).

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