CT scanning device for direct shear test of large rock-soil body and test method of CT scanning device

Abstract

The invention provides a CT scanning device for a direct shear test of a large rock-soil body and a test method of the CT scanning device, and relates to the technical field of rock-soil mechanics, and the CT scanning device comprises a box body which comprises a groove body, a top plate and a bottom plate, an upper slot horizontally penetrating through one side face is formed in an upper port of the groove body, two middle slots horizontally penetrating through the two opposite side faces of the groove body are formed in the middle of the groove body, a lower slot horizontally penetrating through one side face is formed in a lower port of the groove body, the top plate is detachably inserted into the upper slot, and the bottom plate is detachably inserted into the lower slot. And the bearing cloth strip penetrates through the two middle slots. The method has the beneficial effects that a sample reloading process after CT scanning in a test process can be avoided, so that test steps are simplified, and the consistency between a CT scanning result and a real microstructure of a soil sample at a shearing surface in an actual shearing process is ensured; further, the influence of the microstructure of the soil sample on the shear strength index of the shear surface can be more accurately researched.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical mechanics, and in particular to a CT scanning device for large geotechnical body direct shear test and a test method thereof. BACKGROUND

[0002] The shear strength of a geotechnical body reflects its own mechanical properties, and the shear strength is usually determined by the shear strength index of the geotechnical body. For coarse-grained soil or broken rock mass, because the particle size or fissure is large, the conventional small-scale direct shear test cannot be used, and the shear strength index must be determined by large-scale direct shear test. The commonly used equipment for large-scale direct shear test is a large-scale direct shear apparatus, which is composed of upper and lower shear boxes. The upper and lower shear boxes are interconnected, and the lower shear box is fixed with the base. During the test, the soil sample is filled into the shear box and a certain vertical pressure is applied. After the pressure is stable, a horizontal thrust is applied to the lower shear box to produce a certain horizontal displacement, so that the soil sample is sheared at the interface between the upper and lower shear boxes, and the corresponding shear strength index is obtained.

[0003] Currently, when studying the influence of the microstructure of coarse-grained soil or broken rock mass on its shear strength index, CT scanning technology and direct shear test are often combined. That is, the microstructure of the soil body is obtained by CT scanning technology, and it is corresponded with the shear strength index obtained by direct shear test, so as to study the influence of the microstructure of the soil shear surface on the shear strength index. The conventional small-scale direct shear apparatus can be directly placed in the CT scanner to observe the microstructure changes of the geotechnical body before and after shearing and during shearing, but the large-scale direct shear apparatus cannot be directly placed in the CT scanner. The existing test method usually first performs CT scanning on the soil sample to be tested, and then re-fills the soil sample into the shear box for shearing. In the process of re-filling the soil sample, the microstructure of the soil sample will inevitably be disturbed, resulting in a difference between the true microstructure of the soil sample at the shear surface and the CT scanning result, and bringing errors to the subsequent test analysis.

[0004] In view of the above, there is an urgent need for a CT scanning device and test method for large geotechnical body direct shear test to solve the problems existing in the prior art. SUMMARY

[0005] Therefore, in order to solve the problem that the large-scale direct shear apparatus cannot be directly placed in the CT scanner, and the microstructure is disturbed when the soil sample after CT scanning is re-filled into the shear box for shearing, the embodiments of the present application provide a CT scanning device and test method for large geotechnical body direct shear test.

[0006] The embodiments of the present application provide a CT scanning device for large geotechnical body direct shear test, comprising: The box body 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 slot horizontally penetrating one side face, the middle part is provided with two middle insertion slots horizontally penetrating opposite two side faces, the lower end is provided with a lower insertion slot horizontally penetrating one side face, the top plate is detachably inserted into the upper insertion slot to open or block the upper end of the groove body, and the bottom plate is detachably inserted into the lower insertion slot to open or block the lower end of the groove body. And a load-bearing cloth strip is arranged through the two middle insertion slots, the middle part of the load-bearing cloth strip is attached to the surface of the bottom plate, the two ends of the load-bearing cloth strip are bent to be attached to the two side faces of the groove body and extend out of the two side faces of the groove body, and when the box body is placed in a CT scanner for scanning, the rock-soil sample contained in the box body is supported on the load-bearing cloth strip, and after the box body is scanned, the load-bearing cloth strip can be pulled out, and the bottom plate is pulled out to place the rock-soil sample into a shear box of a direct shear instrument.

[0007] Further, the number of the middle insertion slots is four, and the two are arranged opposite to each other, and the number of the load-bearing cloth strips is two, each of the load-bearing cloth strips is arranged through the two middle insertion slots arranged opposite to each other, and the two load-bearing cloth strips are arranged crosswise.

[0008] Further, the two ends of each of the load-bearing cloth strips are provided with cloth heads with reduced width, and the cloth heads are arranged through the middle insertion slots.

[0009] Further, the middle insertion slots are rectangular slots with a width greater than or equal to the width of the cloth head.

[0010] Further, the cross-sectional shape of the overlapping part of the two load-bearing cloth strips is the same as the cross-sectional shape of the inner wall of the groove body.

[0011] Further, the groove body is a cuboid.

[0012] Further, the groove body comprises a front plate, a rear plate arranged opposite to the front plate, a left plate, and a right plate arranged opposite to the left plate, and the upper insertion slot and the lower insertion slot are arranged through the upper ends of the front plate.

[0013] Further, The upper insertion slot and the lower insertion slot are arranged around the left plate, the rear plate and the right plate.

[0014] In addition, the embodiment of the application also provides a test method of a CT scanning device for large rock-soil direct shear test, which uses the CT scanning device for large rock-soil direct shear test and comprises the following steps: S1, the load-bearing cloth strip is arranged through the two middle insertion slots on the groove body, and the two ends of the load-bearing cloth strip extend out of the two middle insertion slots; S2, the bottom plate is inserted into the lower insertion slot; S3, pull out the top plate from the upper slot, load the geotechnical sample into the groove body from the upper end of the groove body, and press the geotechnical sample down the load-bearing cloth, so that the load-bearing cloth is attached to the bottom plate and the side of the groove body; S4, after the geotechnical sample is filled, the top plate is inserted back into the upper slot, and the box body is placed in the CT scanner for scanning; S5, after scanning, pull the two ends of the load-bearing cloth, pull out the bottom plate from the lower slot, place the box body in the shear box of the direct shear instrument, then lift and remove the box body from the shear box, and perform a direct shear test on the geotechnical sample.

[0015] Further, when pulling the two ends of the load-bearing cloth in step S5, the load-bearing cloth does not move relative to the groove body.

[0016] The technical scheme provided by the embodiment of the present application has the following beneficial effects: 1. The CT scanning device and test method for large-scale geotechnical direct shear test of the present application, the geotechnical sample is loaded in the box body and supported on the load-bearing cloth, the box body is directly placed in the CT scanner for scanning during CT scanning, after CT scanning, the bottom plate is pulled out, the load-bearing cloth is pulled, the lower end of the groove body is blocked by the load-bearing cloth, the box body is moved to the shear box of the direct shear instrument, and then the box body is removed, so that the geotechnical sample can be placed in the shear box for shear test, the re-sampling process after CT scanning in the test process can be avoided, the test steps are simplified, the consistency between the CT scanning result and the actual shear process of the soil sample at the shear surface 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.

[0017] 2. The CT scanning device for large-scale geotechnical direct shear test of the present application has the advantages of simple structure and convenient operation, the shear strength index of coarse-grained soil with different microstructures can be obtained by the CT scanning device and test method for large-scale geotechnical direct shear test provided by the present application under the cooperation of the large-scale shear instrument and the CT scanner, which is especially suitable for the study of coarse-grained soil with large particle size or large cracks or broken rock mass, and further provides support for the meso-mechanical parameters of the numerical simulation of actual engineering. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic view of the box body of the CT scanning device for large-scale geotechnical direct shear test of the present application; Figure 2 is a schematic view of the load-bearing cloth of the CT scanning device for large-scale geotechnical direct shear test of the present application; Figure 3 is a schematic view of the groove body; Figure 4 is a schematic view of a left plate, a right plate or a back plate; Figure 5 is a schematic view of a front plate; Figure 6 is a schematic view of a top plate or a bottom plate; Figure 7 is a flow chart of a test method of a CT scanning device for large-scale rock-soil body direct shear test according to the present application.

[0019] In the figure: 1, box body; 2, bearing cloth strip; 3, groove body; 4, top plate; 5, bottom plate; 6, upper slot; 7, lower slot; 8, middle slot; 9, front plate; 10, back plate; 11, left plate; 12, right plate; 13, cloth head. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the present application clearer, the following will further describe the embodiments of the present application with reference to the drawings. The following introduces a relatively preferred one of the multiple possible embodiments of the present application, which is intended to provide a basic understanding of the present application, but is not intended to confirm the key or decisive elements of the present application or limit the scope of protection.

[0021] In all examples shown and discussed herein, any specific values should be interpreted as merely illustrative and not as a limitation. Thus, other examples of example embodiments can have different values.

[0022] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as part of the specification, where appropriate.

[0023] It should be noted that like reference numerals and letters refer to like items in the several views of the drawings, and as such, no further discussion on the same will be "repeated" in the several views of the drawings. It will be understood that the dimensions of the various parts shown in the attached drawings are not necessarily to scale.

[0024] It should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting" should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] Reference should be made to Figure 1 and 2The 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.

[0026] 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.

[0027] 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.

[0028] More specifically, such as Figures 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.

[0029] 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.

[0030] In some embodiments, the number of the middle slots 8 is set to four, and two of them are arranged oppositely, and the number of the load-bearing cloth strips 2 is two, each of the load-bearing cloth strips 2 passes through two oppositely arranged middle slots 8, and the two load-bearing cloth strips 2 are arranged crossly. As shown in the front plate 9, the rear plate 10, the left plate 11 and the right plate 12 of the present embodiment, one of the load-bearing cloth strips 2 passes through two middle slots 8 on the front plate 9 and the rear plate 10, and the other load-bearing cloth strip 2 passes through two middle slots 8 on the left plate 11 and the right plate 12, so that the two load-bearing cloth strips 2 are arranged crossly and vertically, and the lower end of the groove body 3 is blocked. In order to make the two load-bearing cloth strips 2 have better blocking effect, the shape of the cross section of the inner wall of the groove body 3 is the same as the shape of the cross section of the crossly overlapped part of the two load-bearing cloth strips 2.

[0031] In some embodiments, the two ends of each of the load-bearing cloth strips 2 are provided with cloth heads 13 with reduced width, the load-bearing cloth strips 2 are rectangular cloth strips, the cloth heads 13 are rectangular cloth heads 13, the cloth heads 13 pass through the middle slots 8, and the middle part of the load-bearing cloth strips 2 is limited to the groove body 3 and located between the middle slots 8. The width of the middle slot 8 is smaller than the width of the side of the groove body 3 in which the middle slot 8 is arranged, and the middle slot 8 is a rectangular slot with a width greater than or equal to the width of the cloth head 13. In this way, the cloth head 13 can pass through the middle slot 8 and move along the middle slot 8.

[0032] When the CT scanning device for large-scale rock-soil direct shear test scans the rock-soil sample, the rock-soil sample in the box body 1 is supported on the load-bearing cloth strip 2, and the box body 1 is placed in the CT scanner for scanning. After scanning, the load-bearing cloth strip 2 is pulled, the bottom plate 5 is pulled out, the rock-soil sample is placed in the shear box of the direct shear instrument, the contract is removed, and the load-bearing cloth strip 2 and the rock-soil sample are retained in the shear box, so that the shear test can be realized.

[0033] In addition, as shown in the front plate 9, the rear plate 10, the left plate 11 and the right plate 12 of the present embodiment, one of the load-bearing cloth strips 2 passes through two middle slots 8 on the front plate 9 and the rear plate 10, and the other load-bearing cloth strip 2 passes through two middle slots 8 on the left plate 11 and the right plate 12, so that the two load-bearing cloth strips 2 are arranged crossly and vertically, and the lower end of the groove body 3 is blocked. In order to make the two load-bearing cloth strips 2 have better blocking effect, the shape of the cross section of the inner wall of the groove body 3 is the same as the shape of the cross section of the crossly overlapped part of the two load-bearing cloth strips 2. Figure 7 The present embodiment further provides a test method of the CT scanning device for large-scale rock-soil direct shear test, which uses the CT scanning device for large-scale rock-soil direct shear test and comprises the following steps: S1, the load-bearing cloth strip 2 passes through two middle slots 8 on the groove body 3, and the two ends of the load-bearing cloth strip 2 extend out of the two middle slots 8. As in the present embodiment, the two load-bearing cloth strips 2 pass through four middle slots 8 crossly, so that the cloth heads 13 at the two ends of each load-bearing cloth strip 2 extend out of the groove body 3 and are used for subsequent pulling.

[0034] S2, the bottom plate 5 is inserted into the lower slot 7, so that the lower end of the groove body 3 is closed.

[0035] S3, the top plate 4 is pulled out of the upper slot 6, the upper port of the slot body 3 is opened, the geotechnical sample is loaded into the slot body 3 from the upper port of the slot body 3, the geotechnical sample presses the load-bearing cloth 2, the load-bearing cloth 2 is attached to the bottom plate 5 and the side of the slot body 3, and the cloth head 13 at both ends of each load-bearing cloth 2 moves along the middle slot 8 and is still in the state of extending out of the slot body 3.

[0036] S4, after the geotechnical sample is filled, the top plate 4 is inserted into the upper slot 6, the upper port of the slot body 3 is closed, the box body 1 is placed in the CT scanner for scanning, the microstructure of the geotechnical sample is obtained, and the real microstructure of the geotechnical sample obtained by scanning is introduced into the numerical simulation software to establish a numerical model of the geotechnical sample.

[0037] S5, after scanning, the load-bearing cloth 2 at both ends is pulled, the bottom plate 5 is pulled out of the lower slot 7, the box body 1 is placed in the shear box of the direct shear instrument, the box body 1 is lifted and moved out of the shear box, and the direct shear test is performed on the geotechnical sample. When the load-bearing cloth 2 is pulled, the load-bearing cloth 2 at both ends is pulled at the same time, so that the load-bearing cloth 2 does not move relative to the slot body 3, and the real microstructure of the geotechnical sample is avoided to be damaged.

[0038] In this way, the shear strength index of the geotechnical sample at the shear surface is determined by the direct shear test. The soil micro-mechanical parameters obtained by the large-scale direct shear test are compared with the soil numerical model parameters established based on the CT scanning results, and the influence of the microstructure of the geotechnical sample on the shear strength index and other mechanical parameters is studied.

[0039] In this article, the front, back, up, down and other orientation words are defined according to the position of the parts in the drawing and the position of the parts relative to each other in the drawing, just to express the technical scheme clearly and conveniently. It should be understood that they are relative concepts, which can be changed accordingly according to different ways of use and placement, and the use of the orientation words should not limit the scope of the application.

[0040] In the case of no conflict, the above-mentioned embodiments and features in the embodiments can be combined with each other. The above-mentioned only the preferred embodiments of the present application, and not to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application, should be included in the protection scope of the present application.

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, 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.

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 central slots is set to four, arranged in pairs opposite each other. The number of load-bearing cloth strips is two, and each load-bearing cloth strip passes through the two central slots arranged opposite each other, 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 cloth strip so that the load-bearing cloth 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.

10. The test method of a CT scanning device for direct shear testing of large-scale soil and rock masses as described in claim 9, characterized in that: In step S5, when the two ends of the load-bearing strip are lifted, the load-bearing strip does not move relative to the groove.

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