Methods for Performance Testing and Evaluation of Downhole Thin-Layer Sprayed Support Layer

Abstract

This invention discloses a method for testing and evaluating the performance of downhole thin-layer sprayed support. The method includes: preparing sprayed layer samples and metal mesh samples with different spraying materials in a laboratory environment; testing and comparing the mechanical properties of different sprayed layer samples and the mechanical properties of the metal mesh samples to select a sprayed layer sample with comparable mechanical properties to the metal mesh sample and designate it as a qualified sprayed layer sample; cutting a standard sample from the qualified sprayed layer sample and testing it; spraying a qualified spraying material onto the surface of a section of the roadway to form a construction sprayed layer; taking samples at the corresponding locations of the construction sprayed layer to obtain construction samples and testing their mechanical properties in a laboratory environment; comparing the mechanical properties of the construction samples and the standard samples; if the difference in mechanical properties between the construction samples and the standard samples is less than 20%, the sprayed layer is qualified; if the difference exceeds 20%, the sprayed layer is unqualified. This invention effectively evaluates the support effect of downhole sprayed layers and characterizes the quality of the sprayed layer throughout the entire roadway.

Description

Technical Field

[0001] This invention belongs to the field of tunnel support technology, and particularly relates to a method for testing and evaluating the performance of underground thin-layer sprayed support. Background Technology

[0002] Temporary support in coal mine roadways is a temporary support method used after excavation is completed to prevent the collapse of coal and rock mass, supporting the roof and sides to allow construction to continue. Temporary support has always been a challenge in coal mine roadway excavation. Related technologies include metal probe beams, single hydraulic props, and metal canopies mounted on the tunneling machine. Most of these temporary supports require manual transport to the excavation face and erection, resulting in slow construction speed and high labor intensity. Furthermore, coal mine roadways typically require the laying of metal mesh in conjunction with rock bolts to support the surrounding rock. Laying and connecting the metal mesh requires manual labor, resulting in low automation.

[0003] Thin-layer spraying is an important means of solving temporary support and replacing metal mesh. Through automated spraying equipment, liquid high-performance thin-layer spraying material is sprayed onto the surface of coal and rock. The liquid thin-layer spraying material reacts rapidly to form a thin-layer spraying layer with excellent mechanical properties, realizing the function of temporary support and replacing metal mesh, and preventing broken coal pieces and rocks from falling.

[0004] However, thin-layer shotcrete support needs to be constructed in a high-dust, high-humidity environment. The surface of the coal and rock mass is uneven, and there is moisture and coal dust adhering to the surface. The mixing ratio and working conditions of the construction equipment will all affect the mechanical properties of the shotcrete layer. The thin-layer shotcrete material, which forms a shotcrete layer with excellent mechanical properties from liquid thin-layer shotcrete material, will be affected by the above factors. Therefore, how to test the mechanical properties of the thin-layer shotcrete layer during on-site construction is the key to ensuring the effectiveness of thin-layer shotcrete support. Summary of the Invention

[0005] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0006] In related technologies, CN114812901A describes a method and device for measuring the stress of a thermally sprayed coating, which uses strain gauges attached to the bottom of the sprayed layer to measure the stress on the sprayed layer. CN108680446A describes a method for predicting the maximum hardness of a thermally sprayed coating, which uses a microhardness tester and a nanoindentation tester to test the performance of the sprayed layer in the laboratory. CN111707609B describes a testing device and method for testing the tangential bond strength of a thin sprayed liner. CN105424510A describes a test device for testing the strength of a powder-coated coating, which is designed for laboratory testing of bond strength and sprayed layer strength. The above-mentioned test devices can test the mechanical properties of the sprayed layer in the laboratory. However, due to the influence of the downhole construction environment, the thickness and mechanical properties of the sprayed layer may change compared to the laboratory sprayed layer, requiring monitoring and evaluation of the performance of the downhole sprayed layer.

[0007] CN108593434A describes a device for testing the initial strength of shotcrete and its usage method; CN214201025U describes an in-situ testing device for the shear strength of the concrete-rock-shotcrete interface; and CN1321881A describes a method for measuring the bonding strength of a coating and the sample used for measurement. These methods design in-situ testing methods for various in-situ strengths of concrete and shotcrete, but they are not standard experiments and cannot intuitively evaluate the feasibility of using shotcrete quality for support.

[0008] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for testing and evaluating the performance of downhole thin-layer sprayed support. This method involves downhole feature point arrangement and sampling, and testing with large-size, standard samples on the surface. The method compares and evaluates whether the mechanical properties of the downhole support layer meet the performance indicators for roadway and other support scenarios, thereby achieving a safety evaluation that ensures the safety of the supported surrounding rock through thin-layer sprayed support.

[0009] The method for testing and evaluating the performance of downhole thin-layer sprayed support in this invention includes:

[0010] Multiple spray layer samples and metal mesh samples of the same size as the spray layer samples were prepared in a laboratory environment, with different spraying materials for the multiple spray layer samples.

[0011] The mechanical properties of different sprayed layer samples and the mechanical properties of the metal mesh sample are tested and compared respectively, so as to select a sprayed layer sample with mechanical properties equivalent to the metal mesh sample, and the sprayed layer sample is recorded as a qualified sprayed layer sample. The material of the qualified sprayed layer sample is a qualified spraying material.

[0012] A standard sample is cut from the qualified sprayed sample, and the standard sample is tested to obtain the mechanical properties of the standard sample.

[0013] A qualified spraying material is sprayed onto the surface of one section of the tunnel to form a construction spray layer.

[0014] Samples were taken at locations corresponding to the sprayed layer to obtain construction specimens, and the mechanical properties of the construction specimens were tested in a laboratory environment.

[0015] Comparing the mechanical properties of the construction sample and the standard sample, if the difference between the mechanical properties of the construction sample and the standard sample is less than 20%, the spray layer is qualified, and the next section of the tunnel is sprayed; if the difference between the mechanical properties of the construction sample and the standard sample exceeds 20%, the spray layer is unqualified, and the spraying construction is stopped.

[0016] The method for testing and evaluating the performance of downhole thin-layer sprayed support in this invention compares the mechanical properties of different sprayed layer samples and the mechanical properties of the metal mesh sample in a laboratory environment to select qualified spraying materials. By comparing the mechanical properties of construction samples and standard samples, the mechanical properties of the sprayed layer that plays a supporting role in the well can be intuitively evaluated to see if they meet the performance indicators of roadway and other support scenarios, effectively characterizing the quality of the sprayed layer of the entire roadway.

[0017] In some embodiments, the construction specimen is obtained by sampling at a characteristic location, which is at least one of a weak point in the sprayed layer, an uneven working surface, and a location with severe water seepage on the working surface.

[0018] In some embodiments, the tunnel includes a roof and two sidewalls, and the weak point of the sprayed layer is at least one of the middle position of the roof, the two sides of the roof, and the shoulder angle position of the two sidewalls.

[0019] In some embodiments, if the relevant mechanical properties of the construction specimen and the standard specimen differ by more than 20%, the method further includes:

[0020] Samples are taken from other locations corresponding to the sprayed layer of the test sample to obtain a control sample. The mechanical properties of the control sample are tested in a laboratory environment. The mechanical properties of the control sample and the construction sample are compared. If the difference between the mechanical properties of the control sample and the construction sample is less than 20%, the sprayed layer at the characteristic location is unqualified, and the spraying construction is stopped. If the difference between the mechanical properties of the control sample and the construction sample exceeds 20%, the spraying tools are repaired.

[0021] In some embodiments, the remaining locations are located on the same longitudinal section of the roadway or coal / rock as the feature locations.

[0022] In some embodiments, the distance between characteristic positions of two adjacent segments of the tunnel in the excavation direction is 40m-60m.

[0023] In some embodiments, the method for detecting and evaluating the performance of downhole thin-layer sprayed support layers according to the present invention further includes:

[0024] Before applying qualified coating material to the surface of one section of the roadway, at least one hard plate and at least one film are laid on the coal and rock surface at the characteristic location.

[0025] Taking samples at locations corresponding to the sprayed layer to obtain the construction specimen includes:

[0026] The hard plate at the characteristic location, a portion of the coal and rock connected to the hard plate, and a portion of the construction spray layer are cut to obtain a first sample, which is used to conduct tensile and tear resistance tests.

[0027] The thin film at the characteristic location, the portion of coal and rock connected to the thin film, and the portion of the construction spray layer are cut to obtain a second sample, which is used for tests such as bending and flexural strength.

[0028] In some embodiments, the rigid plate is at least one of glass plate, steel plate, alloy plate, and brick, and the film is at least one of plastic film and adhesive film.

[0029] In some embodiments, preparing various sprayed layer samples in a laboratory environment includes:

[0030] A portion of coal or rock is cut off as a model or a model similar to coal or rock is made according to the principle of similarity. A spraying material is then sprayed onto the first surface of the model to cover the first surface with the spraying material.

[0031] In some embodiments, the area of ​​the first surface is greater than one square meter. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the downhole thin-layer sprayed support performance testing and evaluation method according to an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of some feature positions in an embodiment of the present invention, wherein the elliptical positions are feature positions. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] The following describes, in conjunction with the appendix, the method for testing and evaluating the performance of downhole thin-layer sprayed support sprayed layer according to an embodiment of the present invention.

[0036] The method for testing and evaluating the performance of downhole thin-layer sprayed support in this invention includes:

[0037] In a laboratory environment, various sprayed layer specimens and metal mesh specimens of the same size as the sprayed layer specimens were prepared, with different spraying materials used for each type of specimen. Specifically, a spraying material was sprayed onto one surface of a coal and rock model to create a sprayed layer, thus completing the preparation of one sprayed layer specimen. Similarly, different spraying materials were sprayed onto different coal and rock models to create multiple sprayed layers, thereby completing the preparation of various sprayed layer specimens. A metal mesh was then laid on another coal and rock model to complete the preparation of a metal mesh specimen.

[0038] The mechanical properties of different sprayed layer samples and metal mesh samples were tested and compared separately to select sprayed layer samples with mechanical properties comparable to those of the metal mesh samples. These selected samples were designated as qualified sprayed layer samples, and the material of the qualified sprayed layer samples was considered a qualified spraying material. Specifically, a performance testing bench was used to compare the load-bearing capacity of sprayed layer samples and metal mesh samples prepared under laboratory conditions. When the performance of the sprayed layer reached that of the metal mesh, it was proven that the performance of the sprayed material could be used as a substitute for metal mesh support material.

[0039] Standard samples are cut from qualified sprayed sample samples and tested to obtain the mechanical properties of the standard samples, such as bending resistance, tensile strength, adhesion, and tear resistance.

[0040] A qualified spraying material is sprayed onto the surface of one section of the tunnel to form a construction spray layer.

[0041] Samples were taken at the locations corresponding to the sprayed layer to obtain construction specimens, and the mechanical properties of the construction specimens were tested in a laboratory environment.

[0042] Compare the mechanical properties of the construction test sample and the standard test sample. If the difference between the mechanical properties of the construction test sample and the standard test sample is less than 20%, the spray layer is qualified and the next section of the tunnel can be sprayed. If the difference between the mechanical properties of the construction test sample and the standard test sample is more than 20%, the spray layer is unqualified and the spraying construction is stopped.

[0043] The method for testing and evaluating the performance of downhole thin-layer sprayed support in this invention compares the mechanical properties of different sprayed layer samples and metal mesh samples in a laboratory environment to select qualified spraying materials. By comparing the mechanical properties of construction samples and standard samples, the mechanical properties of the sprayed layer that plays a supporting role in the well can be intuitively evaluated to see if they meet the performance indicators of roadway and other support scenarios, effectively characterizing the quality of the sprayed layer of the entire roadway.

[0044] In some embodiments, samples are taken at characteristic locations to obtain construction specimens, wherein the characteristic locations are at least one of the following: a weak point in the sprayed layer, an uneven working surface, and a location with severe water seepage on the working surface.

[0045] It should be noted that the working face is the surface of the roadway or the coal and rock surface. Since the characteristic location is a weak point in the sprayed layer, an uneven working face, or a location with severe water seepage, the mechanical properties of the construction samples taken at the characteristic location are lower than those at other locations. When the construction samples taken at the characteristic location are qualified, the mechanical properties of the sprayed layer in other locations are very likely to be qualified as well. Conversely, if the mechanical properties of the sprayed layer in other locations are qualified, the characteristic location may fail to meet the mechanical properties due to the weak sprayed layer, which could lead to an accident.

[0046] Furthermore, the roadway includes a roof and two sidewalls. The weak points of the shotcrete layer are at least one of the middle of the roof, the two sides of the roof, and the shoulder corners of the two sidewalls. Due to the trajectory of the shotcrete gun and the stress characteristics of the coal and rock, the shotcrete layer at these locations is relatively weak compared to other locations.

[0047] In some embodiments, if the relevant mechanical properties of the construction specimen and the standard specimen differ by more than 20%, the method further includes:

[0048] Samples were taken from the remaining locations corresponding to the sprayed layer of the test sample to obtain control samples. The mechanical properties of the control samples were tested in a laboratory environment. The mechanical properties of the control samples and the construction samples were compared. If the difference between the mechanical properties of the control samples and the construction samples was less than 20%, the sprayed layer at the characteristic location was unqualified and the spraying construction was stopped. If the difference between the mechanical properties of the control samples and the construction samples exceeded 20%, the spraying tools were repaired.

[0049] Understandably, by taking samples from other locations and testing the control samples, we can rule out the possibility that the spraying layer is unqualified due to damage to the spraying tools (such as spray guns and pumps), and we can also comprehensively evaluate the effect of the spraying layer support of the entire tunnel.

[0050] Furthermore, the remaining locations are located on the same longitudinal section of the roadway or coal / rock as the characteristic locations.

[0051] In some embodiments, the distance between the characteristic positions of two adjacent sections of the roadway in the excavation direction is 40m-60m. This avoids increasing the workload of workers due to excessively close intervals, while also preventing the accuracy of detection from being affected by excessively large intervals.

[0052] Optionally, the roadway includes a first section and a second section arranged adjacent to each other in the tunneling direction. The second section is sprayed after the first section is sprayed. The distance between the characteristic positions of the first section and the second section is 40m-60m.

[0053] In some embodiments, the method for detecting and evaluating the performance of downhole thin-layer sprayed support layers according to the present invention further includes:

[0054] Before applying qualified coating material to the surface of one section of the roadway, at least one hard plate and at least one film are laid on the coal and rock surface at the characteristic location.

[0055] Taking samples at locations corresponding to the sprayed layer during construction to obtain construction specimens includes:

[0056] The first sample is obtained by cutting out the hard plate at the characteristic location, the part of coal and rock connected to the hard plate, and part of the construction spray layer. The first sample is used to conduct tensile and tear resistance tests.

[0057] The second sample is obtained by cutting out the film at the characteristic location and the part of coal and rock connected to the film and part of the construction spray layer. The second sample is used for tests such as bending resistance and flexural resistance.

[0058] It should be noted that rigid plates and thin films facilitate the cutting of construction samples at characteristic locations, and also facilitate the reference of trimming dimensions when trimming the corners of the first and second samples. The first and second samples are independent of each other and different mechanical properties are tested separately, avoiding the reduction of mechanical properties of the samples after testing, which would interfere with subsequent experiments.

[0059] Furthermore, the rigid plate is at least one of glass plate, steel plate, alloy plate, glass plate, and brick, and the film is at least one of plastic film and adhesive film.

[0060] In some embodiments, preparing multiple spray layer samples in a laboratory environment includes:

[0061] A portion of coal or rock is cut off as a model or a model similar to coal or rock is made according to the principle of similarity. A spraying material is then applied to the first surface of the model to cover it with the spraying material.

[0062] In some embodiments, the area of ​​the first surface is greater than one square meter, which facilitates the cutting of standard samples on the one hand, and on the other hand, facilitates the cutting of standard samples at different positions of the same sprayed sample, thereby reducing the impact of random errors on the mechanical property testing of the standard sample.

[0063] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" 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 simplifying the description, and do not indicate or imply that the device 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.

[0064] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0065] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0066] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0067] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0068] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for testing and evaluating the performance of downhole thin-layer sprayed support, characterized in that, include: In a laboratory environment, various spray layer samples and metal mesh samples of the same size as the spray layer samples were prepared, with different spraying materials for the various spray layer samples; The mechanical properties of different sprayed layer samples and the mechanical properties of the metal mesh sample are tested and compared respectively, so as to select a sprayed layer sample with mechanical properties equivalent to the metal mesh sample, and the sprayed layer sample is recorded as a qualified sprayed layer sample. The material of the qualified sprayed layer sample is a qualified spraying material. A standard sample is cut from the qualified sprayed layer sample, and the standard sample is tested to obtain the mechanical properties of the standard sample. Apply qualified spraying material to the surface of one section of the tunnel to form a construction spray layer; Samples were taken at locations corresponding to the sprayed layer to obtain construction specimens, and the mechanical properties of the construction specimens were tested in a laboratory environment. If the mechanical properties of the construction sample and the standard sample differ by less than 20%, the spraying layer is qualified, and the next section of the tunnel can be sprayed. If the mechanical properties of the construction sample and the standard sample differ by more than 20%, the sprayed layer is unqualified, and the spraying process should be stopped.

2. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to claim 1, characterized in that, The construction specimen is obtained by sampling at a characteristic location, which is at least one of the following: a weak point in the sprayed layer, an uneven working surface, and a location with severe water seepage on the working surface.

3. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to claim 2, characterized in that, The tunnel includes a roof and two sidewalls, and the weak point of the sprayed layer is at least one of the middle position of the roof, the two sides of the roof, and the shoulder angle of the two sidewalls.

4. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to claim 2, characterized in that, If the relevant mechanical properties of the construction specimen and the standard specimen differ by more than 20%, the method further includes: Samples were taken from the remaining locations corresponding to the sprayed layer of the sample to obtain a control sample, and the mechanical properties of the control sample were tested in a laboratory environment. If the mechanical properties of the control sample and the construction sample differ by less than 20%, the spray layer at the characteristic location is unqualified, and the spraying process is stopped; if the mechanical properties of the control sample and the construction sample differ by more than 20%, the spraying tools are inspected and repaired.

5. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to claim 4, characterized in that, The remaining locations are located on the same longitudinal section of the roadway or coal / rock as the characteristic locations.

6. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to any one of claims 2-5, characterized in that, The distance between the characteristic positions of two adjacent sections of the tunnel in the excavation direction is 40m-60m.

7. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to any one of claims 2-5, characterized in that, Also includes: Before applying qualified coating material to the surface of one section of the roadway, at least one hard plate and at least one film are laid on the coal and rock surface at the characteristic location. Taking samples at locations corresponding to the sprayed layer to obtain the construction specimen includes: The hard plate at the characteristic location, a portion of the coal and rock connected to the hard plate, and a portion of the construction spray layer are cut to obtain a first sample, which is used for tensile and tear resistance tests. The thin film at the characteristic location, the portion of coal and rock connected to the thin film, and the portion of the construction spray layer are cut to obtain a second sample, which is used for bending and flexural strength tests.

8. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to claim 7, characterized in that, The rigid plate is at least one of glass plate, steel plate, alloy plate, glass plate, and brick, and the film is at least one of plastic film and adhesive film.

9. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to any one of claims 1-5, characterized in that, The preparation of various sprayed layer samples under laboratory conditions includes: A portion of coal or rock is cut off as a model or a model similar to coal or rock is made according to the principle of similarity. A spraying material is then sprayed onto the first surface of the model to cover the first surface with the spraying material.

10. The method for testing and evaluating the performance of downhole thin-layer sprayed support according to claim 9, characterized in that, The area of ​​the first surface is greater than one square meter.

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