A method of coring a structural concrete core for a construction project

Abstract

This invention provides a method for core sampling of concrete in building structures, comprising: probing a predetermined area of ​​the building structure to determine the centerlines of each vertical and horizontal reinforcing bar in the predetermined area; probing the vertical and horizontal reinforcing bars with determined centerlines again to determine the boundaries of each vertical and horizontal reinforcing bar; determining the horizontal boundary line spacing between two adjacent horizontal reinforcing bars and the vertical boundary line spacing between two adjacent vertical reinforcing bars; determining the core drilling area based on the horizontal boundary line spacing between the horizontal reinforcing bars and the vertical boundary line spacing between the vertical reinforcing bars; installing and fixing a core drilling machine in the core drilling area and starting core drilling; stopping core drilling when the drilling depth of the core drilling machine reaches a predetermined length threshold and removing the core sample. This method effectively avoids reinforcing bars, reduces damage to the reinforcing bars, and also reduces the loss length of the core sample.

Description

Technical Field

[0001] This application relates to the field of building engineering structural technology, and in particular to a method for core sampling of concrete core samples in building engineering structures. Background Technology

[0002] Currently, core drilling is an effective method for testing and estimating the strength of concrete materials in both new and existing concrete structures. However, in existing technologies, the core samples often contain reinforcing bars, especially in densely spaced structures. The core-taking process is not mature enough, leading to problems such as the inability to extract core samples even after changing multiple sampling locations, breakage of reinforcing bars, excessively long core samples (wasting time and damaging the structure), or insufficient length (not meeting the acceptable core sample length requirements), causing irreparable damage to the main structure and affecting its lifespan and safety. Summary of the Invention

[0003] In view of this, the present invention provides a method for core sampling of concrete in building engineering structures, which can effectively avoid reinforcing bars, reduce damage to reinforcing bars, and reduce the loss length of core samples, thereby reducing unnecessary drilling depth, improving drilling efficiency, and reducing damage to the structure.

[0004] The technical solution of this invention is implemented as follows:

[0005] A method for core sampling of concrete in building structures, the method comprising:

[0006] The pre-defined area of ​​the building structure is probed to determine the centerline of each vertical and horizontal reinforcing bar in the pre-defined area;

[0007] The vertical and horizontal reinforcing bars with the centerline already determined are probed again to determine the boundaries of each vertical and horizontal reinforcing bar;

[0008] Determine the horizontal boundary line spacing between two adjacent horizontal reinforcing bars, and determine the vertical boundary line spacing between two adjacent vertical reinforcing bars;

[0009] The core drilling area is determined based on the spacing between the horizontal boundary lines of the horizontal reinforcing bars and the spacing between the vertical boundary lines of the vertical reinforcing bars.

[0010] Install and secure the core drilling machine in the core drilling area, and begin core drilling in the core drilling area;

[0011] When the drilling depth of the core drill reaches the preset length threshold, the core drilling is stopped and the core sample is removed.

[0012] Preferably, the method further includes:

[0013] After core drilling is stopped and before sampling, an initial crack is pre-set at the root of the core sample.

[0014] Preferably, the length threshold is the sum of the finishing layer thickness, carbonization depth, required core sample length, and loss length.

[0015] Preferably, the loss length is determined by the following method:

[0016] Based on the core sample diameter and core length, a finite element geometric model of the core sample is established, and the parameters of each model in the model are determined.

[0017] An initial crack is set at a preset location in the core sample of the model;

[0018] The maximum circumferential stress propagation criterion is used to determine the direction of crack initiation at the crack tip.

[0019] Pre-set the stress damage value for newly generated crack segments;

[0020] Predetermine the crack propagation area;

[0021] A preset load is continuously applied to the end of the core sample in the model, and the extended finite element method is used to calculate crack propagation until the core sample in the model fractures.

[0022] The loss length at which the core sample breaks is taken as the loss length corresponding to the current core sample diameter and core length.

[0023] Preferably, initial cracks are set at the ends, middle or root of the core sample in the model.

[0024] Preferably, a rebar scanner is used to determine the centerline of each vertical and horizontal rebar in the preset area, as well as the boundary of each vertical and horizontal rebar.

[0025] Preferably, if the horizontal boundary line spacing between two horizontal reinforcing bars on one side of a region is greater than or equal to a preset threshold, and the vertical boundary line spacing between two vertical reinforcing bars on the other side of the region is also greater than or equal to a preset threshold, then the region is designated as a core drilling region.

[0026] Preferably, the preset threshold is the sum of the diameter of the required core sample and twice the thickness of the drill barrel wall.

[0027] Preferably, during core drilling, the drill bit feed rate is controlled within a preset speed range, and the flow rate of cooling water used to cool the drill bit and remove concrete debris is controlled within a preset flow rate range.

[0028] Preferably, the flow rate range is 3 to 5 liters per minute.

[0029] As can be seen above, in the core sampling method for concrete structures in this invention, the centerlines of each vertical and horizontal reinforcing bar in the predetermined area are first determined, then the boundaries of each vertical and horizontal reinforcing bar are determined, and then the drilling area is determined based on the horizontal boundary line spacing between two adjacent horizontal reinforcing bars and the vertical boundary line spacing between two adjacent vertical reinforcing bars. This ensures that in the determined drilling area, the horizontal boundary line spacing between two horizontal reinforcing bars on both sides and the vertical boundary line spacing between two vertical reinforcing bars on the other two sides are both greater than the diameter of the core sample plus the wall thickness of the drill barrel on both sides of the core drilling machine. Therefore, there is no reinforcing steel in this drilling area. Thus, when drilling in this drilling area, the reinforcing steel can be effectively avoided, reducing damage to the reinforcing steel and ensuring that the obtained core sample does not contain reinforcing steel. Furthermore, the core drilling machine can drill smoothly in the drilling area, improving drilling efficiency and construction efficiency.

[0030] In addition, the technical solution of the present invention can effectively control the drilling depth of the core drilling machine, reduce the loss length of the core sample, thereby reducing unnecessary core drilling depth and ensuring that the length of the final obtained core sample meets the corresponding requirements, effectively saving unnecessary core sampling time, while also reducing damage to the structure and reducing the cost of transporting the core sample. Attached Figure Description

[0031] Figure 1 This is a schematic flowchart of the method for core sampling of concrete core samples in building structures according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the positioning process for detecting vertical reinforcing bars 1 using a rebar scanner in an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the positioning process for detecting vertical reinforcing bars 2 using a rebar scanner in an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of the positioning process of the horizontal rebar 1 detected by the rebar scanner in an embodiment of the present invention.

[0035] Figure 5 This is a schematic diagram of the process for locating the boundary of horizontal reinforcing bars 2 using a rebar scanner in an embodiment of the present invention.

[0036] Figure 6 This is a schematic diagram of the process for detecting the boundary positioning of vertical reinforcing bars 1 using a rebar scanner in an embodiment of the present invention.

[0037] Figure 7 This is a schematic diagram of the process for detecting the boundary positioning of vertical reinforcing bars 2 using a rebar scanner in an embodiment of the present invention.

[0038] Figure 8 This is a schematic diagram of the process for locating the boundary of horizontal reinforcing bar 1 using a rebar scanner in an embodiment of the present invention.

[0039] Figure 9 This is a schematic diagram of the process for locating the boundary of horizontal reinforcing bars 2 using a rebar scanner in an embodiment of the present invention.

[0040] Figure 10 This is a schematic diagram of the final concrete core positioning in an embodiment of the present invention.

[0041] Figure 11 This is a schematic diagram of the drilling depth in an embodiment of the present invention.

[0042] Figure 12 This is a schematic diagram of the process for determining the loss length in an embodiment of the present invention.

[0043] Figure 13 This is a schematic diagram of the loss length in an embodiment of the present invention, where the core diameter is 100 mm and the core length is 250 mm.

[0044] Figure 14 This is a schematic diagram of the loss length in an embodiment of the present invention, where the core diameter is 100 mm and the core length is 200 mm.

[0045] Figure 15 This is a schematic diagram of the loss length in an embodiment of the present invention, where the core diameter is 100 mm and the core length is 150 mm.

[0046] Figure 16 This is a schematic diagram of the loss length in an embodiment of the present invention, where the core diameter is 75 mm and the core length is 120 mm.

[0047] Figure 17 This is a schematic diagram of the loss length in an embodiment of the present invention, where the core diameter is 75 mm and the core length is 150 mm.

[0048] Figure 18 This is a schematic diagram of the loss length in an embodiment of the present invention, where the core diameter is 75 mm and the core length is 200 mm.

[0049] Figure 19 This is a schematic diagram of the loss length in an embodiment of the present invention, where the core diameter is 100 mm and the core length is 200 mm. Detailed Implementation

[0050] To make the technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Figure 1This is a schematic flowchart of the method for core sampling of concrete core samples in building structures according to an embodiment of the present invention.

[0052] like Figure 1 As shown, the method for core sampling of concrete core samples in building structures according to embodiments of the present invention includes:

[0053] Step 101: Detect the preset area of ​​the building structure and determine the center lines of each vertical and horizontal steel bar in the preset area.

[0054] In the technical solution of this invention, before core drilling, it is necessary to first determine a suitable area for core drilling. Therefore, in this step, some areas that may be suitable for core drilling can be pre-determined on the building structure to be cored as preset areas. Then, preliminary detection is carried out in these preset areas to determine the centerline of each vertical and horizontal reinforcing bar present in the preset areas, thereby determining the specific location of each vertical and horizontal reinforcing bar. This detection process can be called coarse positioning of the concrete area.

[0055] In the technical solution of the present invention, various specific implementation methods can be used to perform the above-mentioned coarse positioning of the concrete area.

[0056] For example, as an illustration, in a specific embodiment of the present invention, a rebar scanner can be used to determine the centerlines (i.e., rebar centerlines) of each vertical and horizontal rebar in the preset area, such as... Figures 2-5 As shown.

[0057] Additionally, as an example, in a specific embodiment of the present invention, when using a rebar scanner, the eight-line positioning method can be applied to determine the center lines of each vertical and horizontal rebar in the preset area.

[0058] For example, the position of each vertical and horizontal steel bar (i.e., the centerline of each vertical and horizontal steel bar) can be determined based on the minimum thickness of the concrete cover.

[0059] Step 102: Probe the vertical and horizontal reinforcing bars with the center line already determined again to determine the boundaries of each vertical and horizontal reinforcing bar.

[0060] In the technical solution of this invention, after determining the center lines of each vertical and horizontal reinforcing bar, the boundaries of each vertical and horizontal reinforcing bar can be further determined. This detection process can be referred to as precise positioning of the concrete area.

[0061] For example, as an illustration, in a specific embodiment of the present invention, a rebar scanner can be used to determine the boundaries (i.e., rebar edge lines) of each vertical and horizontal rebar in the preset area, such as... Figures 6-9As shown.

[0062] Additionally, as an example, in a specific embodiment of the present invention, when using a rebar scanner, the boundaries of each vertical and horizontal rebar can be determined based on the presence or absence of the scanner's sensor beeping sound.

[0063] Step 103: Determine the horizontal boundary line spacing between two adjacent horizontal reinforcing bars, and determine the vertical boundary line spacing between two adjacent vertical reinforcing bars.

[0064] In the technical solution of the present invention, after determining the boundaries of each vertical and horizontal steel bar in the preset area, the horizontal boundary line spacing d1 between two adjacent horizontal steel bars and the vertical boundary line spacing d2 between two adjacent vertical steel bars can be determined according to the above boundaries.

[0065] Step 104: Determine the core drilling area based on the horizontal boundary line spacing between horizontal reinforcing bars and the vertical boundary line spacing between vertical reinforcing bars.

[0066] In the technical solution of this invention, after determining the horizontal boundary line spacing between any two adjacent horizontal reinforcing bars and the vertical boundary line spacing between any two adjacent vertical reinforcing bars in the preset area, the core drilling area (i.e., the concrete core sampling location) can be determined based on the aforementioned horizontal and vertical boundary line spacing. For example, as... Figure 10 As shown.

[0067] For example, as an example, in a specific embodiment of the present invention, if the horizontal boundary line spacing between two horizontal reinforcing bars on one side of a region is greater than or equal to a preset threshold, and the vertical boundary line spacing between two vertical reinforcing bars on the other side of the region is also greater than or equal to a preset threshold, then the region can be designated as a core drilling region.

[0068] The preset threshold can be the sum of the required core sample diameter and twice the drill barrel wall thickness, i.e.:

[0069] Preset threshold = diameter of required core sample + 2 × wall thickness of drill barrel.

[0070] Therefore, by using the above method, a suitable core drilling area can be determined based on the spacing between the horizontal boundary lines of the horizontal reinforcing bars and the spacing between the vertical boundary lines of the vertical reinforcing bars.

[0071] Step 105: Install and secure the core drilling machine in the core drilling area, and begin core drilling in the core drilling area.

[0072] In the technical solution of the present invention, after determining a suitable core drilling area, a core drilling machine can be installed and fixed on the determined core drilling area, and then the core drilling machine can be used to start core drilling on the core drilling area.

[0073] Additionally, as an example, in a specific embodiment of the present invention, when core drilling is performed, the drill bit feed speed can be controlled within a preset speed range, and the flow rate of cooling water used to cool the drill bit and remove concrete debris can also be controlled within a preset flow rate range.

[0074] For example, as an example, in a specific embodiment of the present invention, the flow rate range can be 3 to 5 liters per minute (L / min).

[0075] Step 106: When the drilling depth of the core drill reaches the preset length threshold, stop drilling and remove the core sample.

[0076] In the technical solution of the present invention, a length threshold is also preset. Therefore, when the drilling depth of the core drill reaches the preset length threshold, the core drilling is stopped and the core sample is taken out, so that the length of the obtained core sample is neither too long nor too short, which meets the requirements for core taking.

[0077] In the technical solution of the present invention, various specific implementation methods can be used to pre-set the above-mentioned length threshold.

[0078] For example, as an example, in a specific embodiment of the present invention, the length threshold may be:

[0079] D = a + b + c + Δ

[0080] Where D is the length threshold, a is the thickness of the finishing layer (e.g., the thickness of the plaster layer), b is the carbonization depth, c is the required core sample length (i.e., the core sample length), and Δ is the loss length, such as... Figure 11 As shown.

[0081] In the above formula, the values ​​of a, b, and c are usually known or can be directly measured. Therefore, by determining the value of the loss length Δ, the value of the corresponding length threshold can be determined.

[0082] In practical applications, the extracted core samples may have oblique cross-sections with varying slopes (e.g., fracture surfaces caused by vibration during drilling or core sample breakage). Therefore, when sampling the extracted core samples, it is usually necessary to laterally cut the oblique cross-section portion of the core sample (i.e., cut parallel to the circumferential plane), and then use the core sample after removing the oblique cross-section as the final sample. Therefore, in the technical solution of this application, the aforementioned length threshold includes a corresponding loss length, Δ, which is the difference between the longest core sample length (i.e., the highest point of the cross-section) obtained from the core drilling machine and the shortest core sample length after sampling. The purpose of setting the aforementioned loss length is mainly to ensure that the shortest core sample length obtained from the core drilling machine (i.e., the length of the core sample after removing the oblique cross-section) also meets the required core sample length, thereby ensuring that the final obtained core sample length meets the corresponding requirements.

[0083] By following steps 101 to 106 above, the core sampling of concrete for building structures can be completed.

[0084] Furthermore, in the technical solution of the present invention, various specific implementation methods can be used to determine the above-mentioned loss length.

[0085] For example, as an example, such as Figure 12 As shown, in a specific embodiment of the present invention, the loss length can be determined by the following method:

[0086] Step 21: Based on the core sample diameter and core length, establish a finite element geometric model of the core sample and determine the various model parameters in the model.

[0087] In the technical solution of this application, the diameter and core length of the core sample can be predetermined as needed, and a finite element geometric model of the core sample can be established based on the core sample diameter and core length, and the various model parameters (e.g., material property parameters of concrete) in the model can be determined. By using the finite element geometric model of the core sample, corresponding simulation calculations can be performed on the core sample in subsequent processing.

[0088] For example, as an example, in a specific embodiment of the present invention, the core diameter may be 100 mm or 75 mm, or other desired values.

[0089] For example, as an example, in a specific embodiment of the present invention, the core length can be 250 mm, 200 mm, 150 mm or 120 mm, or other desired values.

[0090] Furthermore, in the technical solution of this application, various finite element analysis software can be used to establish the aforementioned finite element geometric model.

[0091] For example, as an example, in a specific embodiment of the present invention, ANSYS or ABAQUS can be used to build the above-described finite element geometric model.

[0092] Step 22: Set initial cracks at preset positions on the core sample in the model.

[0093] In the technical solution of this application, in order to simulate and calculate the fracture surface that may appear on the core sample, an initial crack can be set at one or more preset positions of the core sample in the model, so as to facilitate subsequent crack propagation simulation calculation.

[0094] In addition, in the technical solution of this application, the specific location of the initial crack can be determined in advance according to the actual application situation, so as to simulate the fracture surface that may appear in various parts of the core sample.

[0095] For example, as an example, in a specific embodiment of the present invention, corresponding initial cracks can be set at the ends (i.e., end portions), middle and / or root of the core sample in the model, so that different fracture surface conditions can be simulated and calculated in subsequent processing.

[0096] Step 23: Use the maximum circumferential stress propagation criterion to determine the direction of crack initiation at the crack tip.

[0097] In the technical solution of this application, in order to better simulate the occurrence of cracks on the core sample, the maximum circumferential stress propagation criterion can be used to determine the direction of cracking at the crack tip, so that the direction of the maximum circumferential stress at the crack tip can be taken as the direction of cracking at the crack tip.

[0098] The maximum circumferential stress propagation criterion is a stress concentration criterion that can be used to assess the extent and intensity of stress concentration in a structure. Therefore, by using the aforementioned maximum circumferential stress propagation criterion, the direction of crack initiation at the crack tip (e.g., the direction of maximum stress in the structure) can be simulated relatively accurately, allowing the crack on the simulated core sample to propagate in various possible directions (e.g., vertically downward, inclined downward, or even laterally), thereby accurately simulating the crack propagation process on a real core sample.

[0099] Step 24: Preset the stress damage value of the newly generated crack segment.

[0100] In the technical solution of this application, the stress damage value of the newly generated crack segment can be preset to determine the distance when the crack interface (i.e., the surface located on both sides of the crack) separates when the crack is generated in the subsequent simulation calculation process. Thus, the convergence of the subsequent simulation calculation can be controlled by determining the magnitude of this distance.

[0101] For example, as an example, in a specific embodiment of the present invention, the stress damage value may be 0.01 mm or other suitable values.

[0102] Step 25: Predetermine the crack propagation area.

[0103] In the technical solution of this application, the crack propagation area can be pre-determined in the model, and areas where the crack is obviously impossible to propagate to or other areas that do not meet the requirements can be excluded, thereby greatly reducing the amount of computation in the subsequent simulation calculation process.

[0104] Step 26: Simulate the continuous application of a preset load to the end of the core sample in the model, and use the extended finite element method to calculate crack propagation until the core sample in the model fractures.

[0105] In the technical solution of this application, after setting an initial crack and configuring the corresponding parameters, a preset load (the magnitude of which can be predetermined according to the needs of the actual application) can be continuously applied to the end of the core sample in the model. Simultaneously, the extended finite element method (XFEM) is used to calculate crack propagation to simulate the extension of the crack. During the simulation, the initial crack will begin to propagate and grow larger; when the crack extends to a certain extent, the core sample in the model will fracture.

[0106] Step 27: Use the loss length at the time of core sample fracture as the loss length corresponding to the current core sample diameter and core length.

[0107] In the technical solution of this application, when the core sample in the model fractures, it indicates that the crack has expanded to its maximum extent (i.e., the extent to which the core sample in the model can fracture). At this time, the loss length (i.e., the length of the part that needs to be cut off from the core sample) can be determined based on the crack propagation calculation results. Therefore, the loss length at this time can be used as the loss length corresponding to the current core sample diameter and core drilling length.

[0108] Therefore, by using steps 21 to 27 above, you only need to set the corresponding core sample diameter and core drill length in step 21 to obtain the loss length corresponding to core samples with different core sample diameters and different core drill lengths.

[0109] For example, as an illustration, in a specific embodiment of the present invention, for a drill core with a diameter of 100 mm, when the initial crack is located at the end of the core sample, and the drill core lengths are 250 mm, 200 mm, and 150 mm, the loss lengths obtained by the above method are basically the same, all approximately 78 mm. Figures 13-15As shown.

[0110] For example, as an illustration, in a specific embodiment of the present invention, for a core sample with a diameter of 75 mm, when the initial crack is located at the end of the core sample, and the core lengths are 120 mm, 150 mm, and 200 mm, the loss length obtained by the above method is also basically the same, approximately 55 mm. Figures 16-18 As shown.

[0111] For example, in a specific embodiment of the present invention, for a drill core with a diameter of 100 mm, when the drill core length is 200 mm and the initial crack is located at the root of the core sample, the loss length obtained by the above method is approximately 10 mm. Figure 19 As shown.

[0112] Furthermore, as can be seen from the above specific embodiments, when the initial crack is set at the root of the core sample, the corresponding loss length is minimal, much smaller than the loss length when the initial crack is set at the end of the core sample.

[0113] Therefore, as an example, in a specific embodiment of the present invention, after core drilling is stopped, a corresponding initial crack can be pre-set at the root of the core sample, thereby effectively reducing the length loss, effectively saving unnecessary core sampling time, reducing damage to the structure, and reducing the cost of transporting the core sample.

[0114] In summary, in the technical solution of this invention, the centerlines of each vertical and horizontal reinforcing bar in the preset area are first determined, then the boundaries of each vertical and horizontal reinforcing bar are determined, and then the core drilling area is determined based on the horizontal boundary line spacing between two adjacent horizontal reinforcing bars and the vertical boundary line spacing between two adjacent vertical reinforcing bars. This ensures that in the determined core drilling area, the horizontal boundary line spacing between two horizontal reinforcing bars on both sides and the vertical boundary line spacing between two vertical reinforcing bars on the other two sides are both greater than the diameter of the core sample plus the wall thickness of the drill barrel on both sides of the core drilling machine. Therefore, there are no stressed reinforcing bars in this core drilling area. Thus, when using a core drilling machine to drill in this core drilling area, reinforcing bars can be effectively avoided, reducing damage to the reinforcing bars and ensuring that the obtained core sample does not contain reinforcing bars. Furthermore, the core drilling machine can drill smoothly in the core drilling area, improving drilling efficiency and construction efficiency.

[0115] In addition, the technical solution of the present invention can effectively control the drilling depth of the core drill, ensuring that the length of the core sample obtained meets the corresponding requirements, effectively saving unnecessary core sampling time, reducing damage to the structure, and reducing the cost of transporting the core sample.

[0116] Therefore, the above-mentioned method for core sampling of concrete structures in building engineering according to the present invention is a core sampling method that is accurate in positioning, efficient, and minimizes damage to the main structure. Using the above-mentioned method of the present invention, effective core samples can be obtained from each drilled component. Moreover, this method can ensure the core sample length, reduce damage to the main structure, improve construction efficiency, and save core sampling time and sampling costs.

[0117] In addition, corresponding initial cracks can be pre-formed at the root of the core sample before sampling, which can effectively reduce the loss length, save unnecessary core sampling time, reduce damage to the structure, and reduce the cost of transporting the core sample.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for core sampling of concrete core samples in building engineering structures, characterized in that, The method includes: The pre-defined area of ​​the building structure is probed to determine the centerline of each vertical and horizontal reinforcing bar in the pre-defined area; The vertical and horizontal reinforcing bars with the centerline already determined are probed again to determine the boundaries of each vertical and horizontal reinforcing bar; Determine the horizontal boundary line spacing between two adjacent horizontal reinforcing bars, and determine the vertical boundary line spacing between two adjacent vertical reinforcing bars; The core drilling area is determined based on the spacing between the horizontal boundary lines of the horizontal reinforcing bars and the spacing between the vertical boundary lines of the vertical reinforcing bars. Install and secure the core drilling machine in the core drilling area, and begin core drilling in the core drilling area; When the drilling depth of the core drill reaches the preset length threshold, the core drilling is stopped and the core sample is removed. The length threshold is the sum of the finishing layer thickness, carbonization depth, required core sample length, and loss length. The loss length is determined using the following method: Based on the core sample diameter and core length, a finite element geometric model of the core sample is established, and the parameters of each model in the model are determined. An initial crack is set at a preset location in the core sample of the model; The maximum circumferential stress propagation criterion is used to determine the direction of crack initiation at the crack tip. Pre-set the stress damage value for newly generated crack segments; Predetermine the crack propagation area; A preset load is continuously applied to the end of the core sample in the model, and the extended finite element method is used to calculate crack propagation until the core sample in the model fractures. The loss length at which the core sample breaks is taken as the loss length corresponding to the current core sample diameter and core length.

2. The method according to claim 1, characterized in that, The method further includes: After stopping core drilling, an initial crack is pre-set at the root of the core sample.

3. The method according to claim 1, characterized in that: Initial cracks are set at the ends, middle or root of the core sample in the model.

4. The method according to claim 1, characterized in that: Use a rebar scanner to determine the centerline of each vertical and horizontal rebar in the preset area, as well as the boundaries of each vertical and horizontal rebar.

5. The method according to claim 1, characterized in that: If the horizontal boundary line spacing between two horizontal reinforcing bars on one side of a region is greater than or equal to a preset threshold, and the vertical boundary line spacing between two vertical reinforcing bars on the other side of the region is also greater than or equal to a preset threshold, then that region is designated as a core drilling region.

6. The method according to claim 5, characterized in that: The preset threshold is the sum of the diameter of the required core sample and twice the thickness of the drill barrel wall.

7. The method according to claim 1, characterized in that: When core drilling, the drill bit feed speed is controlled within a preset speed range, and the flow rate of cooling water used to cool the drill bit and remove concrete debris is controlled within a preset flow rate range.

8. The method according to claim 7, characterized in that: The flow rate range is 3 to 5 liters per minute.

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