A device for preparing different moisture content sand samples

Abstract

The present application relates to experimental equipment technical field, specifically, it is different to prepare equipment of sand sample of moisture content, including: compression rod device, sealing cylinder subassembly and pressurizing device, the sealing cavity of cylindrical is arranged in the sealing cylinder, the sealing membrane is arranged coaxially with the sealing cavity, and the annular surrounding pressure cavity is arranged between the inner peripheral wall of the sealing cavity, the outer peripheral wall of the sealing cylinder is provided with the surrounding pressure subassembly that communicates with the surrounding pressure cavity, and the surrounding pressure subassembly is used to pass into the pressure liquid in the surrounding pressure cavity, the compression rod device includes upper compression rod and lower compression rod, and the compression rod device further includes the water injection assembly that communicates with the sample cavity, the water injection assembly can inject liquid into the sample cavity, and the pressurizing device is used to push at least one of upper compression rod and lower compression rod to another close to each other, so as to solve the problem that the moisture content of sample decreases in the process of different moisture content sand sample and the process of transferring the sample prepared to the experimental equipment.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of experimental equipment, in particular to a device for preparing sand soil samples with different water contents. BACKGROUND

[0002] As a common geotechnical material, sand soil is widely present in various engineering sites and geotechnical structures. The sand soil will bear various static and dynamic loads, such as self-weight, upper structure load, construction load, seismic dynamic load and the like. In some special cases, the sand soil will bear strong dynamic loads such as explosion and impact under high strain rate loading conditions, such as strong compaction, when the sand soil constructed field works is attacked by a shell, and the like. The mechanical response characteristics of the sand soil under high strain rate loading conditions are quite different from those under static loading conditions and medium-low strain rate conditions, and need to be specially studied. On the other hand, the sand soil in different sites and environmental conditions has certain differences in physical and mechanical states such as water content and density state. The influence of the physical and mechanical states of the sand soil on the dynamic response characteristics of the sand soil under high-speed dynamic load conditions also needs to be studied. The sand soil in the actual engineering site is at different burial depths and is subjected to certain confining pressure, and the test on the dynamic characteristics of the sand soil needs to apply confining pressure to the sample in a proper manner to simulate the actual stress state.

[0003] The strain rate of the traditional hydraulic servo system on the quasi-static mechanical test is usually 1s -1 The following. To obtain a strain rate of 10 -2 ~ 10 - 4 s -1 , other loading means need to be used. However, it is difficult for most test machines to reach this strain rate range under precise control.

[0004] The split Hopkinson pressure bar (SHPB) is one of the effective experimental means for studying the dynamic compression performance of engineering materials under medium-high strain rate (10 -2 ~ 10 -4 s -1 ) conditions, and is an important part of impact dynamics experimental technology. Since Kolsky proposed the technology in 1949, the Hopkinson pressure bar device has been successfully applied to the dynamic mechanical property testing of various engineering materials such as metals, composite materials, polymers, rocks, concrete and foam materials, and is recognized as the most commonly used and effective experimental equipment for studying the mechanical properties of materials under pulse dynamic load. With the in-depth development of scientific research and engineering application, the mechanical properties of materials under complex dynamic load have become a problem that needs to be solved, and the corresponding testing technology demand is also getting higher and higher. In recent years, domestic and foreign scholars have carried out a lot of research on the dynamic mechanical properties of sand soil by using the split Hopkinson pressure bar.

[0005] Therefore, it is necessary to make different water content unsaturated sand soil samples and saturated sand soil samples for the split Hopkinson pressure bar test requirements, but it is found in actual operation that the existing sand soil sample making method has the following problems: (1) the sample is exposed to the air during the process of making different water content samples outside the sleeve and then transferring them into the sleeve, which causes the water content of the sample to decrease, thereby causing experimental errors; (2) the operation steps are complicated when making the sample. SUMMARY

[0006] To solve the problems of complex operation in the process of making different water content sand soil samples and the decrease of sample water content during the process of transferring the made sample to the experimental equipment, the present application provides a different water content sand soil sample preparation equipment, which comprises a compression rod device, a sealing cylinder assembly and a pressurizing device; the sealing cylinder assembly comprises a sealing cylinder and a sealing membrane, the sealing cylinder is vertically arranged in a cylindrical structure, a cylindrical sealing cavity is arranged in the sealing cylinder, a first through hole communicating with the sealing cavity is arranged at the upper end of the sealing cylinder, a second through hole communicating with the sealing cavity is arranged at the lower end of the sealing cylinder, the sealing membrane is cylindrical and arranged in the sealing cavity, a sample cavity for bearing the sand soil sample is arranged in the sealing membrane, the sealing membrane is coaxially arranged with the sealing cavity, and an annular confining pressure cavity is arranged between the sealing membrane and the inner circumferential wall of the sealing cavity, the outer circumferential wall of the sealing cylinder is provided with a confining pressure assembly communicating with the confining pressure cavity, and the confining pressure assembly is used for introducing pressure liquid into the confining pressure cavity; the compression rod device comprises an upper compression rod and a lower compression rod, the upper compression rod extends into the sample cavity through the first through hole and can abut against the upper end surface of the sand soil sample, the lower compression rod extends into the sample cavity through the second through hole and can support the lower end surface of the sand soil sample, the compression rod device further comprises a water injection assembly communicating with the sample cavity, the water injection assembly can inject liquid into the sample cavity, and the pressurizing device is used for pushing at least one of the upper compression rod and the lower compression rod to approach the other, so as to apply axial pressure to the sand soil sample.

[0007] In some embodiments, the sealing membrane comprises a cylindrical body part and a flange structure arranged at both ends of the body part, the flange structure comprises an extension part and a flange part, the extension part extends in the horizontal direction, and the flange part is arranged at the outer edge of the extension part and extends along the inner circumferential wall of the sealing cylinder.

[0008] In some embodiments, the pressurizing device comprises a fixed frame and a pressurizing assembly, the fixed frame comprises a base, a support column and an upper beam, the sealing cylinder assembly can be vertically fixed on the base in the vertical direction, the support column is fixed on the base, and the upper beam is arranged at the upper end of the support column and located at the upper side of the sealing cylinder assembly; the upper beam is provided with a threaded hole corresponding to the center axis of the sealing cylinder assembly, and the pressurizing assembly comprises a pressurizing screw rod, the pressurizing screw rod comprises a threaded portion, the threaded portion is provided with external threads matched with the threaded hole, and the bottom end of the pressurizing screw rod can pass through the threaded hole and abut on the top surface of the upper compression rod; the pressurizing screw rod can push the upper compression rod to move in the axial direction and compress the sand sample.

[0009] In some embodiments, the pressurizing device further comprises a clamping assembly, the clamping assembly comprises a driving part and two clamping arms respectively arranged corresponding to the two sides of the sealing cylinder, the clamping arm comprises a support arm extending in the horizontal direction and a clamping jaw arranged at the end of the support arm, and the clamping arm can be driven by the driving part to approach and clamp on the outer peripheral wall of the sealing cylinder.

[0010] In some embodiments, the water injection assembly comprises a water injection flow channel arranged on the upper compression rod and a drainage flow channel arranged in the lower compression rod, the inlet end of the water injection flow channel is arranged on the outer peripheral surface of the upper compression rod, the outlet end of the water injection flow channel is arranged on the end surface of the upper compression rod abutting on the sand sample, and the water injection flow channel is connected with the water injection device; the inlet end of the drainage flow channel is arranged on the lower side of the sand sample, and the outlet end of the drainage flow channel is arranged at the outer peripheral surface of the lower compression rod.

[0011] In some embodiments, the outlet end of the water injection flow channel is provided with a spraying structure, the spraying structure comprises a plurality of spraying openings extending in the radial direction of the upper compression rod, the plurality of spraying openings converge at the central position of the upper compression rod, the water injection flow channel is connected at the converging position of the plurality of spraying openings, and the diameter of the converging position is smaller than the diameter of the water injection flow channel; the width of the spraying opening gradually increases in the direction away from the converging position.

[0012] In some embodiments, the diameters of the water injection flow channel and the drainage flow channel are the same, and the diameter is:

[0013]

[0014] wherein d is the diameter of the water injection flow channel and the drainage flow channel, k1 is an adjustment coefficient, k1 is greater than or equal to 1.2 and less than or equal to 1.8, Q is the flow rate of the liquid flowing through the water injection flow channel, v is the water flow velocity in the water injection flow channel, t is the height of the upper compression rod or the lower compression rod, and D is the diameter of the upper compression rod or the lower compression rod; the distance z1 between the inlet end of the water injection flow channel and the bottom end of the upper compression rod is:

[0015]

[0016] wherein k2 and k3 are adjustment coefficients, k2 is greater than or equal to 0.4 and less than or equal to 0.6, k3 is greater than or equal to 0.2 and less than or equal to 0.5, Q is the flow rate of the liquid flowing through the water injection channel, v is the water flow velocity, U is the uniformity target, U is greater than or equal to 0 and less than or equal to 1, and H is the height of the sand sample; the distance z2 between the bottom end of the drainage channel and the top end of the lower compression rod is:

[0017]

[0018] wherein k4 and k5 are adjustment coefficients, k2 is greater than or equal to 0.4 and less than or equal to 0.6, k3 is greater than or equal to 0.2 and less than or equal to 0.5, Q is the flow rate of the liquid flowing through the water injection channel, v is the water flow velocity, U is the uniformity target, U is greater than or equal to 0 and less than or equal to 1, and H is the height of the sand sample; the distance r between the inlet end of the drainage channel and the central axis of the lower compression rod is:

[0019]

[0020] wherein k6 and k7 are adjustment coefficients, k6 is greater than or equal to 0.8 and less than or equal to 1.2, k7 is greater than or equal to 0.5 and less than or equal to 1, and D is the diameter of the lower compression rod.

[0021] In some embodiments, the width of the intersection is:

[0022]

[0023] wherein W min is the width of the intersection, d is the diameter of the water injection channel, k8 is an empirical adjustment coefficient, k8 = 0.7, and z2 is the total length of the drainage channel; the width of the spray nozzle is set to:

[0024]

[0025] wherein w(x) is the width value at a distance x from the center point of the intersection, W min is the width of the intersection, L is the distance from the end of the spray nozzle to the center point of the intersection, and k9 is a growth coefficient, dimensionless, typically greater than or equal to 0.5 and less than or equal to 1.

[0026] In some embodiments, the sealing cylinder assembly further comprises a support ring, which is annular in structure and is sleeved on the outside of the lower compression rod, the lower end surface of the support ring is arranged on the base, and the upper end surface of the support ring supports the lower end surface of the sealing cylinder; the support ring is provided with a connecting port, which is arranged corresponding to the outlet end of the drainage channel, and the connecting port is used for the drainage pipe to pass through and connect with the outlet end of the drainage channel.

[0027] In some embodiments, the pressurizing device further includes a positioning plate fixed to the pressurizing screw and a scale, the scale having graduations arranged in a vertical direction, and the positioning plate extending horizontally to the scale.

[0028] To address the issues of complex procedures in preparing sand samples with varying moisture contents and the resulting decrease in sample moisture content during transfer to experimental equipment, this invention offers the following advantages:

[0029] In the above technical solution, a sealed membrane is used to support a dry sand sample, and a predetermined amount of water is introduced into the sand sample using a water injection component in the upper compression rod device. Through methods such as static placement and vibration, the added water is evenly distributed in the sand sample, thus forming a sand sample with a predetermined moisture content within the sealed membrane. After the sand sample is prepared, pressurized liquid can be introduced into the confining pressure chamber. Simultaneously, at least one of the upper or lower compression rods is pushed to apply axial and circumferential pressure to the sand sample, placing it under the confining pressure environment required for the preliminary experiment. This operation is relatively simple and easy to implement. After the sand sample is prepared, the compression rod device and the sealed cylinder assembly can be transferred as a whole to the experimental equipment. During the transfer, the sample remains in a sealed, closed state, thus preventing a decrease in the sample's moisture content and effectively ensuring the accuracy of the experiment. Attached Figure Description

[0030] Figure 1 A schematic cross-sectional view of the combined compression rod assembly and sealing cylinder assembly according to one embodiment is shown.

[0031] Figure 2 A schematic diagram of the combined structure of the compression rod assembly and the sealing cylinder assembly according to one embodiment is shown.

[0032] Figure 3 A schematic diagram of the structure of a sealing membrane according to one embodiment is shown;

[0033] Figure 4 A schematic diagram of a device for preparing sand samples with different moisture contents according to one embodiment is shown.

[0034] Figure 5 A schematic diagram of the structure of a pressure screw according to one embodiment is shown;

[0035] Figure 6 It shows Figure 4 A schematic diagram of the structure of the BB section.

[0036] Reference numerals: 10-sealing cylinder assembly; 11-sealing cylinder; 111-upper end cover; 112-body cylinder; 113-lower end cover; 114-water inlet; 115-drainage outlet; 12-sealing membrane; 121-body part; 122-flange structure; 1221-extension part; 1222-flange part; 13-surrounding pressure cavity; 14-support ring; 20-compression rod device; 21-upper compression rod; 22-lower compression rod; 231-water injection flow channel; 232-drainage flow channel; 311-base; 312-support column; 313-upper cross beam; 32-pressurizing assembly; 321-pressurizing screw rod; 3211-threaded part; 3212-fixed part; 33-clamping assembly; 331-driving part; 332-clamping arm; 3321-support arm; 3322-clamping jaw; 34-positioning sheet; 35-ruler; 40-sand sample. DETAILED DESCRIPTION

[0037] The present disclosure will now be discussed with reference to several example embodiments. It should be appreciated that these embodiments are discussed only to better illustrate the present disclosure and thus enable its better utilization, and are not meant to limit the scope of the present disclosure in any way.

[0038] As used herein, the term "includes" and its variants are to be read as open-ended terms that mean "including, but not limited to." The term "based on" is to be construed as "based at least in part on." The terms "one embodiment" and "an embodiment" are to be read as "at least one embodiment." The term "another embodiment" is to be read as "at least one other embodiment." The terms "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," "longitudinal," and the like, shall mean the orientation or position as shown in the drawings. These terms are used primarily for better description rather than to limit the indicated device, element, or component must have a particular orientation or be constructed and operated in a particular orientation. Also, the aforementioned terms, in addition to their orientation or position meanings, can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain attachment or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present application can be understood according to the specific circumstances. In addition, the terms "mount," "set," "provided with," "connected," "linked" should be interpreted broadly. For example, it can be fixedly connected, detachably connected, or integrally configured; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances. In addition, the terms "first," "second," and the like are primarily used to distinguish different devices, elements or components (the specific types and configurations can be the same or different), and are not intended to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise stated, the meaning of "multiple" is two or more.

[0039] The present embodiment discloses a device for preparing different moisture content sand samples 40, such as Figures 1-6As shown, can include: compression rod device 20, sealing cylinder assembly 10 and pressurizing device; sealing cylinder assembly 10 includes sealing cylinder 11 and sealing film 12, sealing cylinder 11 is vertically arranged cylindrical structure, sealing cylinder 11 is provided with cylindrical sealing cavity, the upper end of sealing cylinder 11 is provided with first through hole communicated with the sealing cavity, the lower end of sealing cylinder 11 is provided with second through hole communicated with the sealing cavity, sealing film 12 is cylindrical and is arranged in the sealing cavity, sealing film 12 is provided with sample cavity for bearing sand sample 40, sealing film 12 is coaxially arranged with the sealing cavity, and the annular confining pressure cavity 13 is arranged between the inner peripheral wall of the sealing cavity, the outer peripheral wall of sealing cylinder 11 is provided with confining pressure assembly communicated with confining pressure cavity 13, confining pressure assembly is used for flowing into pressure liquid into confining pressure cavity 13; compression rod device 20 includes upper compression rod 21 and lower compression rod 22, upper compression rod 21 extends into sample cavity through first through hole and can abut on the upper end surface of sand sample 40, lower compression rod 22 extends into sample cavity through second through hole and can support the lower end surface of sand sample 40, compression rod device 20 further includes water injection assembly communicated with sample cavity, water injection assembly can inject liquid into sample cavity, pressurizing device is used for pushing at least one of upper compression rod 21 and lower compression rod 22 to be close to the other, to apply axial pressure to sand sample 40.

[0040] In the above technical scheme, the sealing film 12 is arranged to carry dry sand sample 40, and the water injection assembly of the compression rod device 20 is arranged to flow predetermined water into the sand sample 40, the added water is uniformly distributed in the sand sample 40 by standing, oscillation and the like, so that the sand sample 40 with a predetermined water content is formed in the sealing film 12, after the preparation of the sand sample 40, the pressure liquid can be flowed into the confining pressure cavity 13, and at least one of the upper compression rod 21 or the lower compression rod 22 is pushed to apply axial and circumferential pressure to the sand sample 40, so that the sand sample 40 is in the confining pressure environment of the preliminary experiment, the operation process is simple and easy to implement, after the preparation of the sand sample 40, the compression rod device 20 and the sealing cylinder assembly 10 can be transferred as a whole to the experimental equipment, and the sample is in a sealed closed state during the transfer process, so that the water content of the sample does not decrease due to the transfer, and the accuracy of the experiment is effectively ensured.

[0041] It should be noted that the sealing cylinder 11 can adopt a separate or multi-section structure, which can be disassembled to facilitate the installation and placement of the sealing film 12 and the sand sample 40; the sealing film 12 is made of elastic material with certain toughness and support, which can naturally maintain the shape of the sample cavity and the sand sample 40. Figure 3The shape of the sample chamber 10 is shown in the figure, and after the sand sample 40 and water are added to the sample chamber, the shape of the sample chamber 10 remains substantially unchanged. In addition, due to the elastic properties of the sample chamber 10, when pressure liquid is introduced into the confining chamber 13, the pressure of the pressure liquid can be transmitted to the sample chamber, so that the sand sample 40 can be subjected to the confining pressure generated by the pressure liquid in the confining chamber 13. The sealing membrane 12 is coaxially arranged with the sealing cylinder 11, so that the pressure in the confining chamber 13 can be evenly applied to the sealing membrane 12. In addition, for the preparation of unsaturated sand sample 40, the sealing membrane 12 can be made of a water-impermeable film, which can prevent the liquid introduced into the confining chamber 13 from flowing into the sample chamber, thereby changing the water content of the prepared sand sample 40. On the other hand, when preparing an unsaturated sand sample, the injected water can also be prevented from flowing out through the sealing membrane 12, thereby causing the water content of the prepared sample to deviate from the expected value. For the preparation of saturated sand sample 40, the sealing membrane 12 can be made of a water-permeable material, i.e., only water can pass through the material. When preparing the sand sample 40, a sufficient amount of water can be directly introduced to fully soak the dry sand sample 40, and the water can flow into the confining chamber 13 through the water-permeable sealing membrane 12. When the confining pressure is applied, pressure liquid can be introduced into the confining chamber 13 to adjust the pressure. Since the pressure in the confining chamber 13 is usually less than the axial pressure generated by the upper compression rod 21 and the lower compression rod 22 driven by the compression rod device 20, the upper compression rod 21 and the lower compression rod 22 will not be pushed, thereby affecting the application of the confining pressure. The compression rod device 20 can have various embodiments, as long as it can drive at least one of the upper compression rod 21 or the lower compression rod 22 to apply pressure to the sand sample 40. For example, only one of the upper compression rod 21 or the lower compression rod 22 can be driven, and the other can be fixed. Alternatively, both the upper compression rod 21 and the lower compression rod 22 can be driven to move closer to each other, thereby achieving the purpose of applying axial force.

[0042] In addition, the confining assembly includes a water inlet 114 and a water outlet 115 arranged on the side wall of the sealing cylinder 11. The water inlet 114 can be connected to a water pump capable of introducing pressure liquid, and the water outlet 115 can be connected to a drain pipe. By providing the water inlet 114 and the water outlet 115, liquid can be introduced into or drained from the confining chamber 13, thereby achieving the purpose of applying or removing confining pressure. This method is more convenient and does not require additional equipment or devices to be reinstalled, thereby simplifying the operation steps.

[0043] In order to facilitate the installation and positioning of the sealing membrane 12, the sealing cylinder 11 can be provided with a plurality of positioning grooves 111, and the sealing membrane 12 can be provided with a plurality of positioning protrusions 121 corresponding to the positioning grooves 111. When the sealing membrane 12 is installed in the sealing cylinder 11, the positioning protrusions 121 can be inserted into the positioning grooves 111, thereby achieving the purpose of positioning the sealing membrane 12. Figure 1 , Figure 3As shown, the sealing film 12 includes a cylindrical body part 121 and a flange structure 122 arranged at both ends of the body part 121, the flange structure 122 includes an extension part 1221 extending in the horizontal direction and a flange part 1222 arranged at the outer edge of the extension part 1221 and extending along the inner circumferential wall of the sealing cylinder 11. On the one hand, the sealing film 12 can be fixed at the center axis of the sealing cylinder 11 by the arranged flange structure 122, and on the other hand, the sealing cylinder 11 can adopt a multi-section split structure as shown, from top to bottom, an upper end cover 111, a body cylinder 112 and a lower end cover 113, and the parts can be connected by threads. There is a joint at the connection between the upper end cover 111 or the lower end cover 113 and the body cylinder 112. Even if a threaded connection is used, there is still a gap at this place, which has the risk of water leakage. By using the flange structure 122 formed by the integral extension part 1221 and the flange part 1222, the flange structure 122 covers the inside of the above-mentioned joint, so as to further prevent the occurrence of water leakage of the confining pressure cavity 13.

[0044] In some embodiments, as shown in Figure 4 、 Figure 5 The pressing device includes a fixing frame and a pressing assembly 32. The fixing frame includes a base 311, a support column 312 and an upper cross beam 313. The sealing cylinder assembly 10 can be vertically fixed on the base 311 in the vertical direction. The support column 312 is fixed on the base 311. The upper cross beam 313 is arranged at the upper end of the support column 312 and is located on the upper side of the sealing cylinder assembly 10. Threaded holes are arranged on the upper cross beam 313 corresponding to the center axis of the sealing cylinder assembly 10. The pressing assembly 32 includes a pressing screw 321. The pressing screw 321 includes a threaded part 3211 provided with external threads matched with the threaded holes. The bottom end of the pressing screw 321 can pass through the threaded holes and abut against the top surface of the upper compression rod 21. The pressing screw 321 can push the upper compression rod 21 to move in the axial direction and compress the sand sample 40.

[0045] In the above technical solution, the frame structure formed by the fixing frame supports the structural combination of the compression rod device 20 and the sealing cylinder assembly 10, and provides a basis for the arrangement of the pressing screw 321. The pressing screw 321 cooperates with the threaded holes through the threaded part 3211, so as to convert the rotating force into the axial pressure in the vertical direction and further drive the upper compression rod 21 to move in the axial direction. By rotating the pressing screw 321, the moving distance of the upper compression rod 21 can be accurately controlled, so as to accurately control the generated axial pressure.

[0046] The upper and lower ends of the sealing cylinder 11 can be provided with bolt holes arranged in the horizontal direction, one end of the bolt hole facing the outer circumferential surface of the upper compression rod 21 or the lower compression rod 22, and a locking bolt can pass through the bolt hole and abut against the outer circumferential surface of the upper compression rod 21 or the lower compression rod 22, so that the locking bolt can exert a greater pressure on the outer circumferential surface of the upper compression rod 21 or the lower compression rod 22, thereby increasing the friction between the end surface of the locking bolt and the outer circumferential surface of the upper compression rod 21 or the lower compression rod 22, and the relative position between the upper compression rod 21 and the lower compression rod 22 and the sealing cylinder 11 is locked by means of the friction, thereby achieving the purpose of fixing the compression rod device 20 and the sealing cylinder assembly 10 as a whole, which can facilitate the transfer of the compression rod device 20 and the sealing cylinder assembly 10 to the experimental equipment as a whole, and can also maintain the axial force exerted unchanged. In order to achieve better fixing effect, the locking bolt can be provided with a plurality of locking bolts.

[0047] Since the structure of the compression rod device 20 and the sealing cylinder assembly 10 is as shown in the figure, it has a structure with smaller diameters at the top and bottom and a larger diameter in the middle, and its stability is poor when placed, especially when the axial force is exerted on the compression rod device 20, the sealing cylinder assembly 10 lacks support and may be tilted or other problems. Therefore, as shown in Figure 4 、 Figure 6 The pressing device further comprises a clamping assembly 33, the clamping assembly 33 comprising a driving part 331 and two clamping arms 332 arranged on both sides of the sealing cylinder 11 respectively, the clamping arm 332 comprising a support arm 3321 extending in the horizontal direction and a clamping jaw 3322 arranged at the end of the support arm 3321, and the clamping arm 332 can be driven by the driving part 331 to approach and clamp on the outer circumferential wall of the sealing cylinder 11.

[0048] The clamping assembly 33 is arranged to clamp the sealing cylinder 11 from the side, and the two clamping arms 332 arranged on both sides can exert a more balanced force on the sealing cylinder 11, effectively providing support and preventing it from tilting. The driving part 331 can adopt various embodiments, such as a linear drive cylinder such as a hydraulic cylinder or a pneumatic cylinder, or a gear and rack driving structure, which can be driven to move by the driving force of an electric motor. In addition, a locking member can be provided to prevent the clamping assembly 33 from moving and causing clamping failure by locking the driving part 331. Alternatively, a fixing pin or other structure can be provided to directly mechanically connect the clamping arm 332 and the fixing frame, thereby achieving the purpose of fixing the clamping arm 332. Specifically, in order to facilitate the passage of the support arm 3321, a through hole is provided in the middle of the support part for the support arm 3321 to pass through.

[0049] The water injection assembly is used to inject water into the sand sample 40 to form a sample with a predetermined water content. It only needs to be able to communicate with the sample cavity containing the sand sample 40 and be able to inject liquid into it. As a specific implementation method, such as... Figure 1 As shown, the water injection assembly includes a water injection channel 231 disposed on the upper compression rod 21 and a drainage channel 232 disposed in the lower compression rod 22. The inlet end of the water injection channel 231 is disposed on the outer peripheral surface of the upper compression rod 21, and the outlet end of the water injection channel 231 is disposed on the end face of the upper compression rod 21 that abuts against the sand sample 40. The water injection channel 231 is connected to the water injection device. The inlet end of the drainage channel 232 is disposed on the lower side of the sand sample 40, and the outlet end of the drainage channel 232 is disposed on the outer peripheral surface of the lower compression rod 22.

[0050] In the above embodiment, by directly installing the water injection components inside the upper compression rod 21 and the lower compression rod 22, the number of parts can be reduced. Since the upper compression rod 21 and the lower compression rod 22 are in direct contact with the sand sample 40, the flow channel setup can also be simplified, eliminating the need for additional modifications to the components. To prevent water injected into the sand sample 40 from accidentally flowing out of the water injection channel 231 and the drainage channel 232, rubber plugs or valves can be installed at the inlet end of the water injection channel 231 and the outlet end of the drainage channel 232 to seal the flow channels.

[0051] In order to more evenly introduce water into the sand sample 40 and form a more uniform water distribution, a spray structure is provided at the outlet end of the water injection channel 231. The spray structure includes multiple spray nozzles extending radially along the upper compression rod 21. The multiple spray nozzles converge at the center of the upper compression rod 21. The water injection channel 231 is connected to the convergence point of the multiple spray nozzles. The diameter of the convergence point is smaller than the diameter of the water injection channel 231. As the spray nozzles extend away from the convergence point, the width of the spray nozzles is set to gradually widen. Since the diameter of the confluence is smaller than the diameter of the water injection channel 231, the water flowing into the water injection channel 231 cannot quickly flow directly into the sand sample 40 from the confluence. Therefore, under the pressure of the water, the water will first flow along the extension direction of the spray nozzle, and then flow into the sand sample 40 under the action of gravity. Furthermore, since the spray nozzle is designed to gradually widen in the direction away from the confluence, the setting of gradually widening from the narrow opening at the center to the far end can adapt to the need for pressure reduction; uniform flow control: by the relationship between the width and length, it is ensured that the flow rate of each spray nozzle is close to the same.

[0052] Specifically, the water injection channel 231 and the drainage channel 232 have the same diameter, which is:

[0053]

[0054] wherein d is the diameter of the water injection flow channel 231 and the drainage flow channel 232, k1 is an adjustment coefficient, k1 is greater than or equal to 1.2 and less than or equal to 1.8, Q is the flow rate of the liquid flowing in through the water injection flow channel 231, v is the water flow velocity, t is the height of the upper compression rod 21 or the lower compression rod 22, D is the diameter of the upper compression rod 21 or the lower compression rod 22; the distance z1 from the inlet end of the water injection flow channel 231 to the bottom end of the upper compression rod 21 is:

[0055]

[0056] wherein k2 and k3 are adjustment coefficients, k2 is greater than or equal to 0.4 and less than or equal to 0.6, k3 is greater than or equal to 0.2 and less than or equal to 0.5, Q is the flow rate of the liquid flowing in through the water injection flow channel 231, v is the water flow velocity, U is the uniformity target, U is greater than or equal to 0 and less than or equal to 1, H is the height of the sand sample 40; the distance z2 from the bottom end of the drainage flow channel 232 to the top end of the lower compression rod 22 is:

[0057]

[0058] wherein k4 and k5 are adjustment coefficients, k2 is greater than or equal to 0.4 and less than or equal to 0.6, k3 is greater than or equal to 0.2 and less than or equal to 0.5, Q is the flow rate of the liquid flowing in through the water injection flow channel 231, v is the water flow velocity, U is the uniformity target, U is greater than or equal to 0 and less than or equal to 1, H is the height of the sand sample 40; the distance r between the inlet end of the drainage flow channel 232 and the central axis of the lower compression rod 22 is:

[0059]

[0060] wherein k6 and k7 are adjustment coefficients, k6 is greater than or equal to 0.8 and less than or equal to 1.2, k7 is greater than or equal to 0.5 and less than or equal to 1, D is the diameter of the lower compression rod 22. It should be noted that, in the calculation of the water injection flow channel 231, t and D are the parameters related to the upper compression rod 21, and in the calculation of the drainage flow channel 232, t and D are the parameters related to the lower compression rod 22.

[0061] In addition, the width of the intersection is:

[0062]

[0063] wherein W min is the width of the intersection, d is the diameter of the water injection flow channel 231, k8 is an empirical adjustment coefficient, k8 = 0.7, z2 is the length of the drainage flow channel 232; the width of the spray nozzle is set to:

[0064]

[0065] where w(x) is the width value at a distance x from the center of the intersection, W min is the intersection width, L is the distance from the end of the spray nozzle to the center of the intersection, k9 is a growth coefficient, dimensionless, usually taking a value greater than or equal to 0.5 and less than or equal to 1, which is related to the flow demand and the size of the flow channel.

[0066] In order to ensure that the water flow uniformly fills the spray hole, therefore, the water inlet pressure must be greater than a certain minimum threshold to overcome the surface tension and viscosity effects of water to ensure that the jet can cover the entire spray hole.

[0067] The minimum water inlet pressure required to ensure uniform water flow distribution can be expressed as:

[0068]

[0069] where P in,min is the minimum water inlet pressure to ensure that the water flow uniformly fills the water outlet hole, P out is the ambient pressure outside the water outlet hole, usually atmospheric pressure, k 10 is a growth coefficient, dimensionless, recommended value range is 1.2~1.8, ρ is the density of water, Q is the total water inlet flow, w min is the intersection width, h is the height of the water inlet hole from the sample.

[0070] In the process of making the unsaturated sand sample 40, the mass of water required for different water content samples needs to be calculated first, and water of a specific mass is injected into the sand sample 40 through the water injection assembly, while the water in the sample needs to be distributed as evenly as possible. When injecting water, ensure that the device is placed vertically radially. Close the water injection channel 231 and the drainage channel 232 to close the sample and prevent water from overflowing. Then shake the device to mix the water and the sample as evenly as possible. After two days of standing, ensure that the water is evenly distributed in the sand sample 40. During the above process, the sand sample 40 needs to be closed for a long time, and it is difficult to fix the relative positions of the sealing cylinder 11, the upper compression rod 21 and the lower compression rod 22 by relying on the locking bolt alone, which is difficult to ensure the stability and reliability of the locking ability during long-term placement, therefore, as shown in Figure 4As shown, the sealing cylinder assembly 10 further comprises a support ring 14, which is annular in structure and is sleeved on the outside of the lower compression rod 22. The lower end surface of the support ring 14 is arranged on the base 311, and the upper end surface of the support ring 14 is supported on the lower end surface of the sealing cylinder 11. The support ring 14 is provided with a connecting port, which is arranged corresponding to the outlet end of the drainage channel 232, and is used for the drainage pipe to pass through and be connected with the outlet end of the drainage channel 232. The arrangement of the support ring 14 can provide strong support for the sand sample 40 when it is at rest, prevent the sealing cylinder 11 from relatively displacing with respect to the compression rod assembly and the like, and affect the preparation of the sample. Specifically, the outer peripheral surface of the support ring 14 can be a cylindrical surface or a circular truncated surface, which can be adjusted according to actual conditions and needs.

[0071] In order to facilitate the calculation of the moving distance of the upper compression rod 21, as shown, Figure 4 The pressing device further comprises a positioning sheet 34 fixed on the pressing screw rod 321 and a scale 35, the scale 35 is provided with scales arranged in the vertical direction, and the positioning sheet 34 extends to the scale 35 in the horizontal direction. The lower end of the pressing screw rod 321 can be provided with a fixing portion 3212 for fixing the positioning sheet 34, and the positioning sheet 34 can be installed on the fixing portion 3212. By means of the arrangement of the positioning sheet 34 and the scale 35, the moving distance of the upper compression rod 21 pushed can be measured more conveniently, thereby facilitating the calculation.

[0072] By means of the arrangement of the positioning sheet 34 and the scale 35, the moving distance of the upper compression rod 21 pushed can be measured more conveniently, and the actual length of the sample can be further calculated. The specific calculation method is as follows:

[0073] Wherein:

[0074] : the actual length of the sample; : the reading of the upper scale column; : the reading of the lower scale column; : the length of the first compression rod; : the length of the second compression rod.

[0075] Those skilled in the art can understand that the above-mentioned embodiments are specific cases for realizing the present disclosure, and in actual application, various changes can be made in form and details without departing from the scope of the present disclosure.

Claims

1. A device for preparing sand samples with different moisture contents, characterized in that, The equipment for preparing sand samples with different moisture contents includes: Compression rod device, sealing cylinder assembly and pressurization device; The sealing cylinder assembly includes a sealing cylinder and a sealing membrane. The sealing cylinder is a vertically arranged cylindrical structure with a cylindrical sealing cavity inside. A first through hole communicating with the sealing cavity is provided at the upper end of the sealing cylinder, and a second through hole communicating with the sealing cavity is provided at the lower end of the sealing cylinder. The sealing membrane is cylindrical and disposed inside the sealing cavity, with a sample cavity for holding the sand sample inside. The sealing membrane is coaxially arranged with the sealing cavity, and an annular confining pressure cavity is provided between the sealing membrane and the inner peripheral wall of the sealing cavity. A confining pressure assembly communicating with the confining pressure cavity is provided on the outer peripheral wall of the sealing cylinder, and the confining pressure assembly is used to introduce pressurized liquid into the confining pressure cavity. The compression rod device includes an upper compression rod and a lower compression rod. The upper compression rod extends into the sample cavity through the first through hole and can abut against the upper end face of the sand sample. The lower compression rod extends into the sample cavity through the second through hole and can support the lower end face of the sand sample. The compression rod device also includes a water injection assembly connected to the sample cavity. The water injection assembly can inject liquid into the sample cavity. The pressurizing device is used to push at least one of the upper compression rod and the lower compression rod closer to the other to apply axial pressure to the sand sample. The sealing film includes a cylindrical body and flange structures disposed at both ends of the body. The flange structure includes an extension and a flange. The extension extends in a horizontal direction, and the flange is disposed at the outer edge of the extension and extends to fit the inner circumferential wall of the sealing cylinder. After the sand sample is prepared, the compression rod device and the sealing cylinder assembly are transferred as a whole to the experimental equipment. During the transfer, the sand sample is in a sealed and closed state.

2. The equipment for preparing sand samples with different moisture contents according to claim 1, characterized in that, The pressurizing device includes a fixing frame and a pressurizing assembly. The fixing frame includes a base, a support column, and an upper crossbeam. The sealing cylinder assembly can be vertically fixed to the base in the vertical direction. The support column is fixed to the base. The upper crossbeam is disposed at the upper end of the support column and is located on the upper side of the sealing cylinder assembly. The upper crossbeam is provided with a threaded hole at the central axis of the sealing cylinder assembly. The pressurizing assembly includes a pressurizing screw, which includes a threaded portion. The threaded portion is provided with an external thread that matches the threaded hole. The bottom end of the pressurizing screw can pass through the threaded hole and abut against the top surface of the upper compression rod. The pressurizing screw can push the upper compression rod to move in the axial direction and compress the sand sample.

3. The equipment for preparing sand samples with different moisture contents according to claim 2, characterized in that, The pressurizing device further includes a clamping assembly, which includes a driving unit and two clamping arms respectively disposed on both sides of the sealing cylinder. The clamping arms include a support arm extending in a horizontal direction and a gripper disposed at the end of the support arm. The clamping arms can approach and clamp onto the outer peripheral wall of the sealing cylinder under the drive of the driving unit.

4. The equipment for preparing sand samples with different moisture contents according to claim 2, characterized in that, The water injection assembly includes a water injection channel disposed on the upper compression rod and a drainage channel disposed in the lower compression rod. The inlet end of the water injection channel is disposed on the outer peripheral surface of the upper compression rod, and the outlet end of the water injection channel is disposed on the end face of the upper compression rod that abuts against the sand sample. The water injection channel is connected to the water injection device. The inlet end of the drainage channel is located on the lower side of the sand sample, and the outlet end of the drainage channel is located on the outer circumferential surface of the lower compression rod.

5. The equipment for preparing sand samples with different moisture contents according to claim 4, characterized in that, The outlet end of the water injection channel is provided with a spray structure, which includes multiple spray nozzles extending radially along the upper compression rod. The multiple spray nozzles converge at the center of the upper compression rod. The water injection channel is connected to the convergence point of the multiple spray nozzles, and the diameter of the convergence point is smaller than the diameter of the water injection channel. As the spray nozzle extends away from the intersection, its width is set to gradually increase.

6. The equipment for preparing sand samples with different moisture contents according to claim 5, characterized in that, The water injection channel and the drainage channel have the same diameter, which is: ； Wherein, d is the diameter of the water injection channel and the drainage channel, k1 is the adjustment coefficient, k1 is greater than or equal to 1.2 and less than or equal to 1.8, Q is the flow rate of the liquid flowing into the water injection channel, v is the water flow velocity in the water injection pipe, t is the height of the upper or lower compression rod, and D is the diameter of the upper or lower compression rod. The distance z1 between the inlet end of the water injection channel and the bottom end of the upper compression rod is: ； Wherein, k2 and k3 are adjustment coefficients, k2 is greater than or equal to 0.4 and less than or equal to 0.6, k3 is greater than or equal to 0.2 and less than or equal to 0.5, Q is the flow rate of the liquid flowing into the water injection channel, v is the water flow velocity, U is the uniformity target, U is greater than or equal to 0 and less than or equal to 1, and H is the height of the sand sample. The distance z2 between the bottom end of the drainage channel and the top end of the lower compression rod is: ； Wherein, K4 and k5 are adjustment coefficients, k2 is greater than or equal to 0.4 and less than or equal to 0.6, k3 is greater than or equal to 0.2 and less than or equal to 0.5, Q is the flow rate of the liquid flowing into the water injection channel, v is the water flow velocity, U is the uniformity target, U is greater than or equal to 0 and less than or equal to 1, and H is the height of the sand sample. The distance r between the inlet end of the drainage channel and the central axis of the lower compression rod is: ； Wherein, k6 and k7 are adjustment coefficients, k6 is greater than or equal to 0.8 and less than or equal to 1.2, k7 is greater than or equal to 0.5 and less than or equal to 1, and D is the diameter of the lower compression rod.

7. The equipment for preparing sand samples with different moisture contents according to claim 6, characterized in that, The width of the intersection is: ； Among them, W min Z1 is the width of the intersection, d is the diameter of the water injection channel, k8 is an empirical adjustment coefficient, k8=0.7, and z2 is the length of the drainage channel. The width of the spray nozzle is set as follows: ； Where w(x) is the width value at a distance x from the center point of the intersection, W min L is the width of the intersection, L is the distance from the end of the spray nozzle to the center point of the intersection, and k9 is a growth coefficient, dimensionless, which is usually greater than or equal to 0.5 and less than or equal to 1.

8. The equipment for preparing sand samples with different moisture contents according to claim 4, characterized in that, The sealing cylinder assembly also includes a support ring, which is an annular structure and sleeved on the outside of the lower compression rod. The lower end face of the support ring is disposed on the base, and the upper end face of the support ring is supported on the lower end face of the sealing cylinder. The support ring is provided with a connection port, which is provided corresponding to the outlet end of the drainage channel. The connection port is used for the drainage pipe to pass through and connect to the outlet end of the drainage channel.

9. The equipment for preparing sand samples with different moisture contents according to claim 2, characterized in that, The pressurizing device also includes a positioning plate and a scale fixed on the pressurizing screw. The scale is provided with graduations arranged in the vertical direction, and the positioning plate extends to the scale in the horizontal direction.

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