A ct scanning device for large geotechnical direct shear test and a test method thereof

Abstract

The application provides a CT scanning device for large-scale rock-soil body direct shear test and a test method thereof, and relates to the technical field of rock-soil mechanics, comprising: a box body, which comprises a groove body, a top plate and a bottom plate, the upper and lower ends of the groove body are open, the upper end of the groove body is provided with an upper insertion groove horizontally penetrating through one side surface thereof, the middle part of the groove body is provided with two middle insertion grooves horizontally penetrating through opposite two side surfaces thereof, the lower end of the groove body is provided with a lower insertion groove horizontally penetrating through one side surface thereof, the top plate is detachably inserted into the upper insertion groove, and the bottom plate is detachably inserted into the lower insertion groove; and a load-bearing cloth strip, which passes through the two middle insertion grooves. The application has the beneficial effects that: the reloading process after the CT scanning is completed in the test process can be avoided, so that the test steps are simplified, the consistency between the CT scanning result and the real microstructure of the soil sample at the shear surface in the actual shearing process is ensured, and the influence of the microstructure of the soil sample on the shear strength index of the shear surface can be more accurately studied.

Description

Technical Field

[0001] This invention relates to the field of geotechnical mechanics, and in particular to a CT scanning device and its testing method for direct shear tests on large-scale soil and rock masses. Background Technology

[0002] The shear strength of soil and rock reflects their inherent mechanical properties, and its magnitude is typically determined by the shear strength index. For coarse-grained soils or fractured rock masses, due to their larger particle size or fractures, conventional small-scale direct shear tests are not suitable; large-scale direct shear tests must be used to determine their shear strength index. The commonly used equipment for large-scale direct shear tests is a large direct shear apparatus, which consists of two interconnected shear chambers, with the lower chamber fixed to a base. During the test, a soil sample is filled into the shear chamber and a certain vertical pressure is applied. After the pressure stabilizes, a horizontal thrust is applied to the lower shear chamber, causing a certain horizontal displacement. This results in shearing of the soil sample at the interface between the upper and lower shear chambers, thus yielding the corresponding shear strength index.

[0003] Currently, when studying the influence of the microstructure of coarse-grained soils or fractured rock masses on their shear strength, CT scanning technology is often combined with direct shear tests. This involves using CT scanning to obtain the soil's microstructure and comparing it with the shear strength indices obtained from direct shear tests, thus investigating the impact of the microstructure at the shear surface on the shear strength. Conventional small direct shear apparatuses can be directly placed inside a CT scanner to observe changes in the microstructure of soil and rock before, during, and after shearing. However, large direct shear apparatuses cannot be directly placed inside a CT scanner. Existing experimental methods typically involve first performing a CT scan on the soil sample, and then reloading the sample into the shear chamber for shearing. During the reloading process, the soil's microstructure is inevitably disrupted, causing a discrepancy between the actual microstructure at the shear surface and the CT scan results, introducing errors into subsequent experimental analysis.

[0004] In summary, there is an urgent need for a CT scanning device and testing method for direct shear tests on large-scale soil and rock masses to solve the problems existing in the current technology. Summary of the Invention

[0005] In view of this, in order to solve the problem that large direct shear apparatus cannot be directly put into CT scanners, and that the microstructure is disrupted when soil samples are refilled into the shear box after CT scanning for shearing, embodiments of the present invention provide a CT scanning device and test method for direct shear tests on large rock and soil masses.

[0006] Embodiments of the present invention provide a CT scanning device for direct shear tests on large-scale soil and rock masses, comprising:

[0007] The box body includes a groove, a top plate, and a bottom plate. The groove has openings at both the top and bottom ends. The upper end of the groove has an upper slot that extends horizontally through one side, the middle part has two middle slots that extend horizontally through opposite sides, and the lower end has a lower slot that extends horizontally through one side. The top plate can be detachably inserted into the upper slot to open or close the upper end of the groove, and the bottom plate can be detachably inserted into the lower slot to open or close the lower end of the groove.

[0008] The load-bearing cloth strip passes through the two slots, with the middle part of the load-bearing cloth strip adhering to the surface of the base plate, and the two ends bent to adhere to the two sides of the groove and extend out of the two sides of the groove. When the box is placed in the CT scanner for scanning, the soil and rock sample contained in the box is supported on the load-bearing cloth strip. After the box is scanned, the load-bearing cloth strip can be lifted and the base plate can be pulled out so that the soil and rock sample can be placed into the shear box of the direct shearing instrument.

[0009] Furthermore, the number of the central slots is set to four, arranged in pairs opposite each other, and the number of the load-bearing cloth strips is two. Each load-bearing cloth strip passes through the two central slots arranged opposite each other, and the two load-bearing cloth strips are arranged crosswise.

[0010] Furthermore, each of the load-bearing strips has tapered ends that pass through the central slot.

[0011] Furthermore, the slot is a rectangular slot with a width greater than or equal to the width of the fabric end.

[0012] Furthermore, the shape of the overlapping portion of the two load-bearing strips is the same as the cross-sectional shape of the inner wall of the groove.

[0013] Furthermore, the groove is a cuboid.

[0014] Furthermore, the groove includes a front plate, a rear plate opposite to the front plate, a left plate, and a right plate opposite to the left plate, and the upper slot and the lower slot are both disposed through the upper ends of the front plate.

[0015] Furthermore,

[0016] Both the upper slot and the lower slot are arranged around the left plate, the rear plate, and the right plate.

[0017] Furthermore, embodiments of the present invention also provide a test method for a CT scanning device used in direct shear tests of large-scale soil and rock masses, using the aforementioned CT scanning device for direct shear tests of large-scale soil and rock masses, and including the following steps:

[0018] S1. Pass the load-bearing cloth strip through the two central slots on the groove body, so that the two ends of the load-bearing cloth strip extend out of the two central slots;

[0019] S2. Insert the base plate into the lower slot;

[0020] S3. Pull the top plate out from the upper slot, and put the soil sample into the trough from the upper port of the trough. Press the soil sample down on the load-bearing strip so that the load-bearing strip is in contact with the bottom plate and the side of the trough.

[0021] S4. After the soil and rock sample is filled, insert the top plate back into the upper slot and place the box in the CT scanner for scanning.

[0022] S5. After scanning is complete, lift both ends of the load-bearing cloth strip, pull the bottom plate out of the lower slot, place the box in the shear box of the direct shear tester, then lift the box and remove it from the shear box to perform a direct shear test on the soil and rock sample.

[0023] Furthermore, in step S5, when the two ends of the load-bearing cloth strip are lifted, the load-bearing cloth strip does not move relative to the groove.

[0024] The beneficial effects of the technical solutions provided by the embodiments of the present invention are as follows:

[0025] 1. The present invention relates to a CT scanning device and its testing method for direct shear tests on large-scale soil and rock masses. Soil and rock samples are loaded into a box and supported by a load-bearing cloth strip. During CT scanning, the box is directly placed inside the CT scanner for scanning. After the CT scan, the bottom plate is removed, the load-bearing cloth strip is lifted, and the lower port of the groove is sealed by the load-bearing cloth strip. The box is then moved into the shearing box of the direct shear apparatus, and then removed. This allows the soil and rock samples to be placed into the shearing box for shear testing, avoiding the need for reloading the samples after the CT scan. This simplifies the testing process and ensures consistency between the CT scan results and the actual microstructure of the soil sample at the shear surface during the actual shearing process. Furthermore, it enables a more accurate study of the influence of the soil sample's microstructure on its shear strength index.

[0026] 2. The CT scanning device for direct shear tests of large-scale soil and rock masses provided by this invention has a simple structure and is easy to operate. With the cooperation of a large shear tester and a CT scanner, the shear strength index of coarse-grained soil with different microstructures can be obtained through the CT scanning device and test method for direct shear tests of large-scale soil and rock masses provided by this invention. It is especially suitable for the study of coarse-grained soil or relatively broken rock masses with large particle size or cracks, and thus provides micromechanical parameter support for numerical simulation of actual engineering. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the housing of a CT scanning device for direct shear testing of large-scale soil and rock masses according to the present invention;

[0028] Figure 2 This is a schematic diagram of a load-bearing cloth strip for a CT scanning device used in direct shear tests of large-scale soil and rock masses according to the present invention;

[0029] Figure 3 This is a schematic diagram of the tank.

[0030] Figure 4 This is a schematic diagram of the left panel, right panel, or back panel;

[0031] Figure 5 This is a schematic diagram of the front panel;

[0032] Figure 6 This is a schematic diagram of the top or bottom plate;

[0033] Figure 7 This is a flowchart of a test method for a CT scanning device used in direct shear tests of large-scale soil and rock masses, according to the present invention.

[0034] In the diagram: 1. Box body; 2. Load-bearing strip; 3. Groove; 4. Top plate; 5. Bottom plate; 6. Upper slot; 7. Lower slot; 8. Middle slot; 9. Front plate; 10. Rear plate; 11. Left plate; 12. Right plate; 13. Fabric end. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0036] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0037] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0038] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures. Also, it should be understood that, for ease of description, the dimensions of the various parts shown in the figures are not drawn to actual scale.

[0039] It should be noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Please refer to Figure 1 and 2 The present invention provides a CT scanning device for direct shear testing of large soil and rock masses, including a housing 1 and a load-bearing cloth strip 2, which is mainly suitable for testing soil and rock samples made of coarse-grained soil or relatively broken rock masses with large particle size or cracks.

[0041] like Figure 1 As shown, the box body 1 mainly includes a groove 3, a top plate 4, and a bottom plate 5. The groove 3 has openings at both the top and bottom ends. The upper end of the groove 3 is provided with an upper slot 6 that horizontally penetrates one side of it, the middle part is provided with two middle slots 8 that horizontally penetrate the two opposite sides of it, and the lower end is provided with a lower slot 7 that horizontally penetrates one side of it. The top plate 4 can be detachably inserted into the upper slot 6 to open or block the upper end of the groove 3, and the bottom plate 5 can be detachably inserted into the lower slot 7 to open or block the lower end of the groove 3.

[0042] The trough 3 is used to hold soil and rock samples. The shape and size of the trough 3 can be flexibly set according to the shape and size of the shear box of the direct shear apparatus used in the actual shear test. For example, in this embodiment, the shear box of the large direct shear apparatus is 200mm×200mm×200mm, and the shape of the trough 3 is a cuboid with an internal space of 190mm×190mm×190mm.

[0043] More specifically, such as Figure 3-6 As shown, the groove 3 includes a front plate 9, a rear plate 10 opposite to the front plate 9, a left plate 11, and a right plate 12 opposite to the left plate 11. The upper slot 6 and the lower slot 7 both penetrate the upper ends of the front plate 9. The top plate 4, the bottom plate 5, the front plate 9, the rear plate 10, the left plate 11, and the right plate 12 are all acrylic sheets, and are bonded together with adhesive. The upper slot 6 and the lower slot 7 both penetrate the front plate 9 and surround the left plate 11, the rear plate 10, and the right plate 12. The top plate 4, when inserted into the upper slot 6, can seal the upper end of the groove 3, and the bottom plate 5, when inserted into the lower slot 7, can seal the lower end of the groove 3.

[0044] The load-bearing fabric strip 2 passes through both of the central slots 8, with its middle portion fitting against the surface of the base plate 5, and its two ends bent to fit against the two sides of the groove 3 and extend beyond the two sides of the groove 3. Specifically, the central slots 8 are horizontally arranged on opposite sides of the groove 3, such as on the front plate 9 and the rear plate 10, and are located at the same level. The load-bearing fabric strip 2 passes through both of the central slots 8 simultaneously, and its middle portion is supported on the base plate 5, sealing the lower end of the groove 3.

[0045] In some embodiments, the number of the central slots 8 is set to four, arranged in pairs opposite each other, and the number of load-bearing cloth strips 2 is two. Each load-bearing cloth strip 2 passes through the two oppositely arranged central slots 8, and the two load-bearing cloth strips 2 are arranged crosswise. For example, central slots 8 are provided on the front plate 9, the rear plate 10, the left plate 11, and the right plate 12. One load-bearing cloth strip 2 passes through the two central slots 8 on the front plate 9 and the rear plate 10, and the other load-bearing cloth strip 2 passes through the two central slots 8 on the left plate 11 and the right plate 12. Thus, the two load-bearing cloth strips 2 are arranged perpendicularly and crosswise to seal the lower end of the groove 3. In order to achieve a better sealing effect, the shape of the overlapping part of the two load-bearing cloth strips 2 is the same as the cross-sectional shape of the inner wall of the groove 3.

[0046] In some embodiments, each load-bearing fabric strip 2 has tapered ends 13 at both ends. The load-bearing fabric strip 2 is a rectangular strip, and the fabric ends 13 are rectangular. The fabric ends 13 extend through the central slots 8, and the middle portion of the load-bearing fabric strip 2 is confined within the groove 3 and located between the central slots 8. The width of the central slot 8 is less than the width of the side of the groove 3 in which it is located, and the central slot 8 is a rectangular groove with a width greater than or equal to the width of the fabric ends 13. Thus, the fabric ends 13 can pass through the central slots 8 and move along the central slots 8.

[0047] When the CT scanning device used for direct shear tests of large soil and rock masses scans the soil and rock samples, the soil and rock samples contained in the box 1 are supported on the load-bearing cloth strip 2, and the box 1 is placed in the CT scanner for scanning. After scanning, the load-bearing cloth strip 2 is lifted, the bottom plate 5 is pulled out to put the soil and rock samples into the shear box of the direct shear instrument, and then the box is removed, leaving the load-bearing cloth strip 2 and the soil and rock samples in the shear box, thus realizing the shear test.

[0048] In addition, such as Figure 7As shown, embodiments of the present invention also provide a test method for a CT scanning device used in direct shear tests of large-scale soil and rock masses, using the aforementioned CT scanning device for direct shear tests of large-scale soil and rock masses, and including the following steps:

[0049] S1. Pass the load-bearing cloth strip 2 through the two central slots 8 on the groove 3, so that the two ends of the load-bearing cloth strip 2 extend out of the two central slots 8. In this embodiment, the two load-bearing cloth strips 2 are passed through the four central slots 8 in a cross manner, so that the cloth ends 13 of each load-bearing cloth strip 2 extend out of the groove 3 for subsequent lifting.

[0050] S2. Insert the base plate 5 into the lower slot 7 to close the lower port of the slot 3.

[0051] S3. Pull the top plate 4 out from the upper slot 6, open the upper port of the trough 3, and put the soil sample into the trough 3 through the upper port of the trough 3. The soil sample presses down on the load-bearing strip 2 so that the load-bearing strip 2 is in contact with the bottom plate 5 and the side of the trough 3. The ends 13 of each load-bearing strip 2 move along the middle slot 8 and are still in the state of extending out of the trough 3.

[0052] S4. After the soil and rock sample is filled, insert the top plate 4 back into the upper slot 6, close the upper port of the slot 3, place the box 1 in the CT scanner for scanning, obtain the microstructure of the soil and rock sample, import the real microstructure of the soil and rock sample obtained by scanning into the numerical simulation software, and establish the numerical model of the soil and rock sample.

[0053] S5. After scanning, lift both ends of the load-bearing cloth strip 2, pull the bottom plate 5 out of the lower slot 7, place the box 1 into the shearing box of the direct shear tester, then lift the box 1 and remove it from the shearing box to perform a direct shear test on the soil and rock sample. When lifting the load-bearing cloth strip 2, lift both ends of the load-bearing cloth strip 2 simultaneously to prevent the load-bearing cloth strip 2 from moving relative to the slot 3, thus avoiding damage to the true microstructure of the soil and rock sample.

[0054] Thus, the shear strength parameters of soil samples at the shear plane were determined through direct shear tests. The micromechanical parameters of the soil obtained from large-scale direct shear tests were compared with the parameters of a numerical model of the soil established based on CT scan results to investigate the influence of the microstructure of the soil samples on their shear strength parameters and other mechanical parameters.

[0055] In this document, the directional terms such as front, back, top, and bottom are defined based on the position of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on different methods of use and placement; the use of these directional terms should not limit the scope of protection claimed in this application.

[0056] Where there is no conflict, the embodiments and features described above can be combined with each other. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements 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 CT scanning device for direct shear tests on large-scale soil and rock masses, characterized in that, include: The box body includes a groove, a top plate, and a bottom plate. The groove has openings at both the top and bottom ends. The upper end of the groove has an upper slot that extends horizontally through one side, the middle part has two middle slots that extend horizontally through opposite sides, and the lower end has a lower slot that extends horizontally through one side. The top plate can be detachably inserted into the upper slot to open or close the upper end of the groove, and the bottom plate can be detachably inserted into the lower slot to open or close the lower end of the groove. The load-bearing cloth strip passes through the two slots and extends out of the two sides of the trough. When the soil sample is loaded into the trough, the load-bearing cloth strip is pressed down so that the middle part of the load-bearing cloth strip is in contact with the surface of the bottom plate and the two ends are bent to be in contact with the two sides of the trough. When the box is placed in the CT scanner for scanning, the soil sample contained in the box is supported on the load-bearing cloth strip. After the box is scanned, the load-bearing cloth strip can be lifted and the bottom plate can be pulled out so that the soil sample can be placed into the shear box of the direct shearing instrument.

2. The CT scanning device for direct shear tests of large-scale soil and rock masses as described in claim 1, characterized in that: The number of the middle slots is set to four, arranged in pairs opposite each other. The number of the load-bearing cloth strips is two, and each load-bearing cloth strip passes through the two oppositely arranged middle slots, with the two load-bearing cloth strips arranged crosswise.

3. A CT scanning device for direct shear testing of large-scale soil and rock masses as described in claim 1 or 2, characterized in that: Each of the load-bearing strips has tapered ends that pass through the central slot.

4. The CT scanning device for direct shear testing of large-scale soil and rock masses as described in claim 3, characterized in that: The slot is a rectangular slot with a width greater than or equal to the width of the fabric end.

5. A CT scanning device for direct shear testing of large-scale soil and rock masses as described in claim 2, characterized in that: The shape of the overlapping portion of the two load-bearing strips is the same as the cross-sectional shape of the inner wall of the trough.

6. The CT scanning device for direct shear testing of large-scale soil and rock masses as described in claim 1, characterized in that: The groove is a cuboid.

7. A CT scanning device for direct shear testing of large-scale soil and rock masses as described in claim 6, characterized in that: The groove includes a front plate, a rear plate and a left plate disposed opposite to the front plate, and a right plate disposed opposite to the left plate. The upper slot and the lower slot are both disposed through the upper ends of the front plate.

8. A CT scanning device for direct shear testing of large-scale soil and rock masses as described in claim 7, characterized in that: Both the upper slot and the lower slot are arranged around the left plate, the rear plate, and the right plate.

9. A test method for a CT scanning device used in direct shear tests of large-scale soil and rock masses, characterized in that: Using a CT scanning device for direct shear tests of large-scale soil and rock masses as described in any one of claims 1-8, and comprising the following steps: S1. Pass the load-bearing cloth strip through the two central slots on the groove body, so that the two ends of the load-bearing cloth strip extend out of the two central slots; S2. Insert the base plate into the lower slot; S3. Pull the top plate out from the upper slot, and put the soil sample into the trough from the upper port of the trough. Press the soil sample down on the load-bearing strip so that the load-bearing strip is in contact with the bottom plate and the side of the trough. S4. After the soil and rock sample is filled, insert the top plate back into the upper slot and place the box in the CT scanner for scanning. S5. After scanning is complete, lift both ends of the load-bearing cloth strip, pull the bottom plate out of the lower slot, place the box in the shear box of the direct shear tester, then lift the box and remove it from the shear box to perform a direct shear test on the soil and rock sample.

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