Equipment for preparing sandy soil samples with different water contents

Abstract

The invention relates to the technical field of experimental equipment, in particular to equipment for preparing sandy soil samples with different water contents, which comprises a compression rod device, a sealing cylinder assembly and a pressurizing device, a cylindrical sealing cavity is formed in the sealing barrel, the sealing film and the sealing cavity are coaxially arranged, an annular confining pressure cavity is formed between the sealing film and the inner circumferential wall of the sealing cavity, a confining pressure assembly communicated with the confining pressure cavity is arranged on the outer circumferential wall of the sealing barrel, 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 compression rod device further comprises a water injection assembly communicated 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 be close to the other one. Therefore, the problems that the operation is complicated in the process of sand samples with different water contents and the water contents of the samples are reduced in the process of transferring the manufactured samples to experimental equipment are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of experimental equipment, and more particularly to an equipment for preparing sand samples with different water contents. Background Art

[0002] As a common geotechnical material, sand widely exists in various engineering sites and geotechnical structures. It will be subjected to various static and dynamic loads, such as self-weight, upper building structure load, construction load, seismic dynamic load, etc. In some special cases, sand will be subjected to strong dynamic loads such as explosion and impact, and is under high strain rate loading conditions, such as dynamic compaction, when field fortifications built with sand are attacked by artillery shells. The mechanical response characteristics of sand under high strain rate loading conditions are significantly different from those under static loading conditions and medium and low strain rate conditions, and special research needs to be carried out. On the other hand, the physical and mechanical states of sand in different sites and environmental conditions, such as water content and density state, will have certain differences. The influence of the physical and mechanical state of sand on its dynamic response characteristics under high-speed dynamic load conditions also needs to be studied. The sand in the actual engineering site is at different burial depths and is subjected to a certain confining pressure. For the test of the dynamic characteristics of sand, the confining pressure must be applied to the sample in an appropriate way to simulate the actual stress state.

[0003] The strain rate of the quasi-static mechanical test on the traditional hydraulic servo system is usually below 1 s -1 . To obtain a strain rate of 10 -2 ~10 - 4 s -1 , other loading means need to be adopted. However, it is difficult for most testing machines to achieve 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 and high strain rates (10 -2 ~10 -4 s -1 ), and is an important part of the impact dynamics experimental technology. Since Kolsky proposed this technology in 1949, the Hopkinson pressure bar device has been successfully applied to the dynamic mechanical property tests of various engineering materials such as metals, composite materials, polymers, rocks, concretes, and foam materials, and is recognized as the most commonly used and effective test equipment for studying the mechanical properties of materials under impulsive dynamic loads. With the in-depth development of scientific research and engineering applications, the mechanical characteristics of materials under complex dynamic loads have become urgent problems to be solved, and the corresponding test technology requirements are also getting higher and higher. In recent years, domestic and foreign scholars have conducted many studies on the dynamic mechanical characteristics of sand using the Split Hopkinson Pressure Bar.

[0005] Therefore, it is necessary to prepare unsaturated sand specimens and saturated sand specimens with different water contents for the split Hopkinson pressure bar test. However, in actual operation, it is found that the existing methods for preparing sand specimens have the following problems: (1) When preparing specimens with different water contents outside the sleeve and then transferring them into the sleeve, the water content of the specimens will decrease because the specimens are exposed to the air during the transfer process, resulting in experimental errors. (2) The operation steps are cumbersome when preparing specimens. Summary of the Invention

[0006] To solve the problems of complex operation in the process of preparing sand specimens with different water contents and the decrease in the water content of the specimens during the transfer of the prepared specimens to the experimental equipment, the present invention provides a device for preparing sand specimens with different water contents, including: a compression rod device, a sealing cylinder assembly, and a pressurizing device; the sealing cylinder assembly includes a sealing cylinder and a sealing film. The sealing cylinder is a vertically arranged cylindrical structure, and a cylindrical sealing cavity is provided inside the sealing cylinder. 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 film is cylindrical and is arranged inside the sealing cavity. A sample cavity for carrying the sand specimen is provided inside the sealing film. The sealing film is coaxially arranged with the sealing cavity, and an annular confining pressure cavity is provided between the sealing film 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 pressure 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 specimen, and the lower compression rod extends into the sample cavity through the second through hole and can support the lower end face of the sand specimen. The compression rod device further includes a water injection assembly communicating with the sample cavity, and 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 an axial pressure to the sand specimen.

[0007] In some embodiments, the sealing film includes a cylindrical body portion and flanging structures provided at both ends of the body portion. The flanging structures include extending portions and flanging portions. The extending portions extend in the horizontal direction, and the flanging portions are provided at the outer edges of the extending portions and extend along the inner peripheral wall of the sealing cylinder.

[0008] In some embodiments, 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 and fixedly mounted on the base. The support column is fixed on the base, and the upper crossbeam is disposed at the upper end of the support column and is located above the sealing cylinder assembly. A threaded hole is provided at the center axis of the upper crossbeam corresponding to the sealing cylinder assembly. The pressurizing assembly includes a pressurizing screw rod. The pressurizing screw rod includes a threaded portion provided with an external thread matching the threaded hole. The bottom end of the pressurizing screw rod can pass through the threaded hole and abut against the top surface of the upper compression rod. The pressurizing screw rod can push the upper compression rod to move axially and press the sand sample tightly.

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

[0010] In some embodiments, the water injection assembly includes a water injection flow channel provided in the upper compression rod and a drainage flow channel provided in the lower compression rod. The inlet end of the water injection flow channel is disposed on the outer peripheral surface of the upper compression rod, and the outlet end of the water injection flow channel is disposed on the end surface of the upper compression rod abutting against the sand sample. The water injection flow channel is connected to the water injection device. The inlet end of the drainage flow channel is disposed below the sand sample, and the outlet end of the drainage flow channel is disposed at the outer peripheral surface of the lower compression rod.

[0011] In some embodiments, a spraying structure is provided at the outlet end of the water injection flow channel. The spraying structure includes a plurality of spraying ports extending in the radial direction of the upper compression rod. The plurality of spraying ports converge at the central position of the upper compression rod. The water injection flow channel is connected to the convergence of the plurality of spraying ports. The diameter of the convergence is smaller than the diameter of the water injection flow channel. In the process of the spraying port extending away from the convergence, the width of the spraying port is set to gradually become wider.

[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 into 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, D is the diameter of the upper compression rod or the lower compression rod; the distance z1 from the inlet end of the water injection flow channel to the bottom end of the upper compression rod is:

[0015]

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

[0017]

[0018] Among them, K4 and k5 are adjustment coefficients, where k2 ranges from greater than or equal to 0.4 to less than or equal to 0.6, k3 ranges from greater than or equal to 0.2 to less than or equal to 0.5, Q is the flow rate of the liquid flowing into the injection water channel, v is the water flow velocity, U is the uniformity target, where U ranges from greater than or equal to 0 to 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] Among them, k6 and k7 are adjustment coefficients, where k6 ranges from greater than or equal to 0.8 to less than or equal to 1.2, k7 ranges from greater than or equal to 0.5 to 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] Among them, W min is the width of the intersection, d is the diameter of the injection water 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] Among them, w(x) is the width value at a distance x from the center point of the intersection, and 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, usually ranging from greater than or equal to 0.5 to less than or equal to 1.

[0026] In some embodiments, the seal cylinder assembly further includes a support ring. The support ring is an annular structure and is sleeved outside the lower compression rod. The lower end surface of the support ring is disposed on the base, and the upper end surface of the support ring supports the lower end surface of the seal cylinder; the support ring is provided with a connection port, the connection port is correspondingly disposed at the outlet end of the drainage channel, and the connection port is used for the drain pipe to pass through and be connected to the outlet end of the drainage channel.

[0027] In some embodiments, the pressurizing device further includes a positioning piece fixed on the pressurizing screw and a scale. The scale is provided with graduations arranged in the vertical direction, and the positioning piece extends horizontally to the scale.

[0028] To solve the problems of complex operation during the process of different water content sand specimens and the decrease in the water content of the specimens during the transfer of the fabricated specimens to the experimental equipment, the present invention has the following advantages:

[0029] In the above technical solution, the set sealing film is used to carry the dry sand specimen, and the water injection component provided in the upper compression rod device is used to introduce a predetermined amount of water into the sand specimen. By means of standing, shaking, etc., the added water is evenly distributed in the sand specimen, so as to form a sand specimen with a predetermined water content in the sealing film. After the production of the sand specimen is completed, pressure liquid can be introduced into the confining pressure chamber, and at the same time, at least one of the upper compression rod or the lower compression rod is pushed to apply axial and circumferential pressures to the sand specimen, so that the sand specimen is in the confining pressure environment for preliminary experiments. This operation process is relatively simple and easy to implement. After the production of the sand specimen is completed, the compression rod device and the sealing cylinder assembly can be transferred to the experimental equipment as a whole. During the transfer process, the specimen is in a sealed state, so the water content of the specimen will not decrease due to the transfer, effectively ensuring the accuracy of the experiment. Description of the Drawings

[0030] Figure 1 Shows a schematic cross-sectional structure diagram of the combination of the compression rod assembly and the sealing cylinder assembly of an embodiment;

[0031] Figure 2 Shows a schematic structure diagram of the combination of the compression rod assembly and the sealing cylinder assembly of an embodiment;

[0032] Figure 3 Shows a schematic structure diagram of the sealing film of an embodiment;

[0033] Figure 4 Shows a schematic structure diagram of the preparation equipment for sand specimens with different water contents of an embodiment;

[0034] Figure 5 Shows a schematic structure diagram of the pressurizing screw of an embodiment;

[0035] Figure 6 Shows Figure 4 The schematic cross-sectional structure diagram of the B-B section in.

[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 - drain outlet; 12 - sealing film; 121 - body portion; 122 - flanging structure; 1221 - extension portion; 1222 - flanging portion; 13 - confining pressure chamber; 14 - support ring; 20 - compression rod device; 21 - upper compression rod; 22 - lower compression rod; 231 - water injection channel; 232 - drainage channel; 30 - pressurizing device; 31 - fixing frame; 311 - base; 312 - support column; 313 - upper cross beam; 32 - pressurizing assembly; 321 - pressurizing screw; 3211 - threaded portion; 3212 - fixing portion; 33 - clamping assembly; 331 - driving portion; 332 - clamping arm; 3321 - support arm; 3322 - jaw; 34 - positioning piece; 35 - scale; 40 - sand sample. Detailed implementation manners

[0037] The present disclosure will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are described only to enable those of ordinary skill in the art to better understand and thus implement the present disclosure, rather than implying any limitation on the scope of the present disclosure.

[0038] As used herein, the term "comprising" and its variants are to be construed as open-ended terms meaning "including but not limited to". The term "based on" is to be construed as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be construed as "at least one embodiment". The term "another embodiment" is to be construed as "at least one other embodiment". The terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation, or be constructed and operated in a specific orientation. Also, in addition to being used to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship 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 specific circumstances. In addition, the terms "mounted", "arranged", "provided with", "connected", "coupled" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral structure; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, or there may be 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 specific circumstances. In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, the meaning of "a plurality of" is two or more.

[0039] This embodiment discloses a preparation device for sandy soil specimens 40 with different water contents, such as Figures 1-6As shown in the figure, it may include: a compression rod device 20, a sealing cylinder 11 assembly 10, and a pressurizing device 30; the sealing cylinder 11 assembly 10 includes a sealing cylinder 11 and a sealing film 12. The sealing cylinder 11 is a vertically arranged cylindrical structure. A cylindrical sealing cavity is provided inside the sealing cylinder 11. A first through hole communicating with the sealing cavity is provided at the upper end of the sealing cylinder 11, and a second through hole communicating with the sealing cavity is provided at the lower end of the sealing cylinder 11. The sealing film 12 is cylindrical and is arranged inside the sealing cavity. A sample cavity for carrying the sandy soil sample 40 is provided inside the sealing film 12. The sealing film 12 is coaxially arranged with the sealing cavity, and an annular confining pressure cavity 13 is provided between the sealing film 12 and the inner peripheral wall of the sealing cavity. A confining pressure assembly communicating with the confining pressure cavity 13 is provided on the outer peripheral wall of the sealing cylinder 11. The confining pressure assembly is used to introduce pressure liquid into the confining pressure cavity 13; the compression rod device 20 includes an upper compression rod 21 and a lower compression rod 22. The upper compression rod 21 extends into the sample cavity through the first through hole and can abut against the upper end surface of the sandy soil sample 40. The lower compression rod 22 extends into the sample cavity through the second through hole and can support the lower end surface of the sandy soil sample 40. The compression rod device 20 further includes a water injection assembly communicating with the sample cavity. The water injection assembly can inject liquid into the sample cavity. The pressurizing device 30 is used to push at least one of the upper compression rod 21 and the lower compression rod 22 closer to the other to apply axial pressure to the sandy soil sample 40.

[0040] In the above technical solution, the set sealing film 12 is used to carry the dry sandy soil sample 40, and the water injection assembly provided in the upper compression rod 21 device 20 is used to introduce a predetermined amount of water into the sandy soil sample 40. By means of standing, shaking, etc., the added water is evenly distributed in the sandy soil sample 40, so as to form a sandy soil sample 40 with a predetermined moisture content in the sealing film 12. After the production of the sandy soil sample 40 is completed, pressure liquid can be introduced into the confining pressure cavity 13. At the same time, by pushing at least one of the upper compression rod 21 or the lower compression rod 22 to apply axial and circumferential pressures to the sandy soil sample 40, so that the sandy soil sample 40 is in the confining pressure environment for preliminary experiments. This operation process is relatively simple and easy to implement. After the production of the sandy soil sample 40 is completed, the compression rod device 20 and the sealing cylinder 11 assembly 10 can be transferred to the experimental equipment as a whole. During the transfer process, the sample is in a sealed state, so the moisture content of the sample will not decrease due to the transfer, effectively ensuring the accuracy of the experiment.

[0041] Among them, it should be noted that the sealing cylinder 11 can adopt a split or multi-segment structure, and these structures can be disassembled to facilitate the installation and placement of the sealing film 12 and the sandy soil sample 40; the sealing film 12 is made of an elastic material with a certain toughness and support, and can naturally maintain Figure 3The shown shape state, and at the same time, after adding the sand sample 40 and water into its internal sample cavity, it can still maintain the shape basically unchanged. In addition, due to its elastic characteristics, when pressure liquid is introduced into the confining pressure cavity 13, it can transfer the pressure of the pressure liquid to the internal sample cavity, so that the sand sample 40 can be subjected to the confining pressure generated by the pressure liquid in the confining pressure cavity 13. The sealing film 12 and the sealing cylinder 11 are coaxially arranged, so that the pressure in the confining pressure cavity 13 can be applied to the sealing film 12 more evenly. In addition, when making an unsaturated sand sample 40, the sealing film 12 can be selected as a non-permeable thin film. On the one hand, it can prevent the liquid introduced into the confining pressure cavity 13 from flowing into it, resulting in a change in the water content of the made sand sample 40. On the other hand, when making an unsaturated sand sample, it can also prevent the injected water from flowing out through the sealing film 12, thus causing the water content of the made sample to deviate from the expected value. When making a saturated sand sample 40, the sealing film 12 can be made of a material that can permeate water, that is, only water can permeate through the material. When making the sand sample 40, sufficient water can be directly introduced to fully soak the dry sand sample 40, and the water can flow into the confining pressure cavity 13 through the water-permeable sealing film 12. When applying the confining pressure, pressure liquid can be introduced into the confining pressure cavity 13 again to adjust the pressure. Since generally the pressure in the confining pressure cavity 13 is less than the axial pressure generated by the compression rod device 20 pushing the upper compression rod 21 and the lower compression rod 22, it will not push the upper compression rod 21 and the lower compression rod 22 and thus affect the application of the confining pressure. The compression rod device 20 can have various implementation manners, 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 is fixedly arranged, or the upper compression rod 21 and the lower compression rod 22 can be driven to approach each other at the same time, so as to achieve the purpose of applying the axial force.

[0042] In addition, the confining pressure assembly includes a water inlet 114 and a drain outlet 115 provided on the side wall of the sealing cylinder 11. The water inlet 114 can be connected to a water inlet pump capable of introducing pressure liquid, and the drain outlet 115 can be connected to a drain pipe. By setting the water inlet 114 and the drain outlet 115, liquid can be introduced into or discharged from the confining pressure cavity 13 to achieve the purpose of applying or removing the confining pressure. This method is more convenient and no additional equipment or device needs to be reinstalled, simplifying the operation steps.

[0043] For the convenience of installing and positioning the sealing film 12, such as Figure 1 、 Figure 3As shown, the sealing film 12 includes a cylindrical body portion 121 and flanging structures 122 provided at both ends of the body portion 121. The flanging structure 122 includes an extension portion 1221 and a flanging portion 1222. The extension portion 1221 extends in the horizontal direction. The flanging portion 1222 is provided at the outer edge of the extension portion 1221 and extends along the inner peripheral wall of the sealing cylinder 11. On the one hand, the set flanging structure 122 can fix the sealing film 12 at the central axis of the sealing cylinder 11. On the other hand, the sealing cylinder 11 can adopt the multi-section split structure as shown in the figure, which is successively an upper end cover 111, a body cylinder 112, and a lower end cover 113 from top to bottom. Each part can be connected by threads. There is a seam at the connection between the upper end cover 111 or the lower end cover 113 and the body cylinder 112. Even with threaded connection, there are indeed gaps at this place, posing a risk of water leakage. However, with the flanging structure 122 formed by the integral extension portion 1221 and flanging portion 1222, the flanging structure 122 covers the inside of the above-mentioned seam, thereby further preventing the occurrence of water leakage in the confining pressure chamber 13.

[0044] In some embodiments, as Figure 4 、 Figure 5 shown, the pressurizing device 30 includes a fixing frame 31 and a pressurizing assembly 32. The fixing frame 31 includes a base 311, support columns 312, and an upper cross beam 313. The sealing cylinder 11 assembly 10 can be vertically and fixedly mounted on the base 311. The support columns 312 are fixed on the base 311. The upper cross beam 313 is provided at the upper ends of the support columns 312, and the upper cross beam 313 is located above the sealing cylinder 11 assembly 10. A threaded hole is provided at the position corresponding to the central axis of the sealing cylinder 11 assembly 10 on the upper cross beam 313. The pressurizing assembly 32 includes a pressurizing screw 321. The pressurizing screw 321 includes a threaded portion 3211. The threaded portion 3211 is provided with an external thread that matches the threaded hole. The bottom end of the pressurizing screw 321 can pass through the threaded hole and abut against the top surface of the upper compression rod 21. The pressurizing screw 321 can push the upper compression rod 21 to move in the axial direction and press the sand sample 40.

[0045] In the above technical solution, the frame structure formed by the fixing frame 31 supports the structural combination formed by the compression rod device 20 and the sealing cylinder 11 assembly 10, and at the same time provides a basis for the setting of the pressurizing screw 321. The pressurizing screw 321 uses the threaded portion 3211 to cooperate with the threaded hole, thereby converting the rotational force into an axial pressure in the vertical direction and further driving the upper compression rod 21 to move in the axial direction. At the same time, by rotating the pressurizing screw 321, the moving distance of the upper compression rod 21 can be more accurately driven, so as to accurately control the generated axial pressure.

[0046] Both the upper and lower ends of the sealing cylinder 11 can be provided with bolt holes arranged horizontally. One end of the bolt hole faces the outer peripheral surface of the upper compression rod 21 or the lower compression rod 22. The locking bolt can pass through the above bolt hole and abut against the outer peripheral surface of the upper compression rod 21 or the lower compression rod 22. With the additional friction generated by the thread, the locking bolt can apply a large pressure on the outer peripheral surface of the upper compression rod 21 or the lower compression rod 22, thereby increasing the friction between the end face of the locking bolt and the outer peripheral surface of the upper compression rod 21 or the lower compression rod 22. With the help of this friction, the relative positions between the upper compression rod 21, the lower compression rod 22 and the sealing cylinder 11 are locked, and further the purpose of fixing the compression rod device 20 and the sealing cylinder 11 assembly 10 as a whole is achieved. On the one hand, this can facilitate transferring it as a whole to the experimental equipment. On the other hand, it can also keep the applied axial force unchanged. To achieve a better fixing effect, multiple locking bolts can be provided.

[0047] Since the structure composed of the compression rod device 20 and the sealing cylinder 11 assembly 10 is as shown in the figure, presenting a structural form with a smaller diameter at the upper and lower parts and a larger diameter in the middle. When placed, its structural stability is poor. Especially when an axial force is applied to the compression rod device 20, the sealing cylinder 11 assembly 10 lacks support and may tip over or have other problems. Therefore, as Figure 4 、 Figure 6 shown, the pressurizing device 30 further includes a clamping assembly 33. The clamping assembly 33 includes a driving part 331 and two clamping arms 332 respectively arranged corresponding to the two sides of the sealing cylinder 11. The clamping arm 332 includes a support arm 3321 extending in the horizontal direction and a clamping jaw 3322 arranged at the end of the support arm 3321. The clamping arm 332 can be driven by the driving part 331 to approach and clamp on the outer peripheral wall of the sealing cylinder 11.

[0048] By using the provided clamping assembly 33 to clamp the sealing cylinder 11 from the side, the two clamping arms 332 arranged correspondingly can apply a relatively balanced force to the sealing cylinder 11, effectively providing support for it and preventing it from tipping over. The driving part 331 can adopt various implementation manners. For example, a linear driving cylinder such as a hydraulic cylinder or a pneumatic cylinder can be adopted, or a driving structure such as a gear and rack can also be adopted, and the driving force generated by the motor is used to drive it to move. In addition, a locking component can be provided to lock the driving part 331 to prevent the clamping assembly 33 from displacing and causing clamping failure. Or, the clamping arm 332 can also be directly mechanically connected to the fixed frame 31 through structures such as fixing pins, so as to achieve the purpose of fixing the clamping arm 332. Specifically, for the convenience of the support arm 3321 to pass through, a through hole through which the support arm 3321 passes is provided in the middle of the support part.

[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 where the sand sample 40 is located and be able to inject liquid inward. As a specific implementation, such as Figure 1 shown, the water injection assembly includes a water injection flow channel 231 provided on the upper compression rod 21 and a drainage flow channel 232 provided in the lower compression rod 22. The inlet end of the water injection flow channel 231 is provided on the outer peripheral surface of the upper compression rod 21, and the outlet end of the water injection flow channel 231 is provided on the end surface of the upper compression rod 21 that abuts against the sand sample 40. The water injection flow channel 231 is connected to the water injection device; the inlet end of the drainage flow channel 232 is provided on the lower side of the sand sample 40, and the outlet end of the drainage flow channel 232 is provided at the outer peripheral surface of the lower compression rod 22.

[0050] In the above implementation, by directly arranging the water injection assembly in 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, therefore, the setting of the flow channel can also be simplified, and there is no need to make additional modifications to the components for the setting of the flow channel. To prevent the water injected into the sand sample 40 from accidentally flowing out from the water injection flow channel 231 and the drainage flow channel 232, rubber plugs or valves and other structures can be provided at the inlet end of the water injection flow channel 231 and the outlet end of the drainage flow channel 232 to block the flow channel.

[0051] In order to be able to introduce water flow into the sand sample 40 more evenly so that it can form a relatively uniform water distribution state, a spraying structure is provided at the outlet end of the water injection flow channel 231. The spraying structure includes a plurality of spraying ports extending along the radial direction of the upper compression rod 21. The plurality of spraying ports converge at the central position of the upper compression rod 21. The water injection flow channel 231 is connected to the convergence of the plurality of spraying ports. The diameter of the convergence is smaller than the diameter of the water injection flow channel 231; during the process of the spraying port extending away from the convergence, the width of the spraying port is set to gradually become wider. Since the diameter of the convergence is smaller than the diameter of the water injection flow channel 231, the water flow introduced into the water injection flow channel 231 cannot quickly flow directly into the sand sample 40 from the convergence. Then, under the pressure of the water pressure, the water flow will first flow along the extending direction of the spraying port and further flow into the sand sample 40 under the action of gravity. Further, since the spraying port is set to gradually become wider during the process of extending away from the convergence, the setting method of gradually widening from the narrow port at the central position to the distal end can meet the requirement of pressure reduction; uniform flow control: by the relationship between the width and the length, ensure that the flow rates of each spraying port are close to the same.

[0052] Specifically, the diameters of the water injection flow channel 231 and the drainage flow channel 232 are the same, and their diameter is:

[0053]

[0054] Wherein, d is the diameter of the water injection channel 231 and the drainage 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 into through the water injection channel 231, v is the water flow velocity in the water injection channel, 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 channel 231 to the bottom end of the upper compression rod 21 is:

[0055]

[0056] Wherein, k2 and k3 are adjustment coefficients, k2 ranges from greater than or equal to 0.4 to less than or equal to 0.6, k3 ranges from greater than or equal to 0.2 to less than or equal to 0.5, Q is the flow rate of the liquid flowing into through the water injection channel 231, v is the water flow velocity, U is the uniformity target, U ranges from greater than or equal to 0 to 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 channel 232 to the top end of the lower compression rod 22 is:

[0057]

[0058] Wherein, K4 and k5 are adjustment coefficients, k2 ranges from greater than or equal to 0.4 to less than or equal to 0.6, k3 ranges from greater than or equal to 0.2 to less than or equal to 0.5, Q is the flow rate of the liquid flowing into through the water injection channel 231, v is the water flow velocity, U is the uniformity target, U ranges from greater than or equal to 0 to 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 channel 232 and the central axis of the lower compression rod 22 is:

[0059]

[0060] Wherein, k6 and k7 are adjustment coefficients, k6 ranges from greater than or equal to 0.8 to less than or equal to 1.2, k7 ranges from greater than or equal to 0.5 to less than or equal to 1, D is the diameter of the lower compression rod 22. It should be noted that when calculating the water injection channel 231, the values of t and D are the relevant parameters of the upper compression rod 21, and when calculating the drainage channel 232, the values of t and D are the relevant parameters of 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 channel 231, k8 is an empirical adjustment coefficient, k8 = 0.7, z2 is the length of the drainage 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 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, k9 is the growth coefficient, dimensionless, usually taking a value greater than or equal to 0.5 and less than or equal to 1, and its value is related to the flow demand and the channel size.

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

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

[0068]

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

[0070] During the production of the unsaturated sand specimen 40, it is necessary to first calculate the mass of water required for specimens with different water contents, inject a specific mass of water into the sand specimen 40 through the water injection assembly, and at the same time, make the water in the specimen as evenly distributed as possible. When injecting water, ensure that the device is placed radially vertically. Close the water injection flow channel 231 and the drainage flow channel 232, so as to seal the specimen and make it difficult for water to overflow. Then shake the device to make the water and the specimen mix as evenly as possible. After standing for two days, ensure that the water is evenly distributed in the sand specimen 40. During the above process, it is necessary to keep the sand specimen 40 closed for a long time, and it is relatively difficult to rely only on the locking bolts to fix the relative positions of the sealing cylinder 11, the upper compression rod 21, and the lower compression rod 22, and it is difficult to ensure the stability and reliability of its locking ability during long-term placement. Therefore, as Figure 4As shown, the sealing cylinder 11 assembly 10 further includes a support ring 14. The support ring 14 is of an annular structure and is sleeved outside the lower compression rod 22. The lower end face of the support ring 14 is disposed on the base 311, and the upper end face of the support ring 14 supports the lower end face of the sealing cylinder 11. The support ring 14 is provided with a connection port, which is disposed corresponding to the outlet end of the drainage channel 232. The connection port is for a drain pipe to pass through and be connected to the outlet end of the drainage channel 232. The setting of the support ring 14 can provide strong support for the static sand sample 40, preventing the sealing cylinder 11 from having relative displacement with respect to the compression rod assembly, etc., and affecting the preparation of the sample. Specifically, the outer peripheral surface of the support ring 14 can be a cylindrical surface or a conical surface, which can be adjusted according to actual situations and needs.

[0071] To facilitate calculating the moving distance of the upper compression rod 21, as Figure 4 shown, the pressurizing device 30 further includes a positioning piece 34 fixed on the pressurizing screw 321 and a scale 35. The scale 35 is provided with graduations arranged in the vertical direction, and the positioning piece 34 extends horizontally to the scale 35. A fixing portion 3212 for fixing the positioning piece 34 can be provided at the lower end of the pressurizing screw 321. The positioning piece 34 can be installed on the fixing portion 3212. By means of the setting of the positioning piece 34 and the scale 35, it is relatively convenient to measure the moving distance by which the upper compression rod 21 is pushed, thus facilitating the calculation.

[0072] By means of the setting of the positioning piece 34 and the scale 35, it is relatively convenient to measure the moving distance by which the upper compression rod 21 is pushed, and further calculate the actual length of the sample. The specific calculation method is as follows:

[0073] L 试样 =(R 上 -R 下 )-(L 第一压缩杆 +L 第二压缩杆 ) Where:

[0074] L 试样 : The actual length of the sample; R 上 : The reading of the upper scale column; R 下 : The reading of the lower scale column; L 第一压缩杆 : The length of the first compression rod; L 第二压缩杆 : The length of the second compression rod.

[0075] Those of ordinary skill in the art can understand that the above embodiments are specific cases for implementing the present disclosure, and in actual applications, 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 comprises: A compression rod device, a sealing cylinder assembly, and a pressurizing device; The sealing cylinder assembly includes a sealing cylinder and a sealing membrane. The sealing cylinder is a vertically arranged 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 carrying a sand 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 peripheral wall of the sealing cavity. A confining pressure assembly communicating with the confining pressure cavity is arranged on the outer peripheral wall of the sealing cylinder. The confining pressure assembly is used to introduce pressure 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 surface of the sand sample, the lower compression rod extends into the sample cavity through the second through hole and can be supported on the lower end surface 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, and 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.

2. The equipment for preparing sand samples with different moisture contents according to claim 1, characterized in that: The sealing film includes a cylindrical main body and a flange structure arranged at both ends of the main body, the flange structure includes an extension part and a flange part, the extension part extends in a horizontal direction, the flange part is arranged at the outer edge of the extension part, and is extended to fit the inner circumferential wall of the sealing cylinder.

3. The equipment for preparing sand samples with different moisture contents according to claim 1, characterized in that: The pressurizing device comprises a fixing frame and a pressurizing assembly, the fixing frame comprises a base, a support column and an upper crossbeam, the sealing cylinder assembly can be vertically fixed on the base in a vertical direction, the support column is fixed on the base, the upper crossbeam is arranged at the upper end of the support column, and the upper crossbeam is located on the upper side of the sealing cylinder assembly; The upper cross beam is provided with a threaded hole corresponding to the central axis of the sealing cylinder assembly. The pressurizing assembly includes a pressurizing screw, and the pressurizing screw includes a threaded portion. The threaded portion is provided with an external thread matching 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.

4. The equipment for preparing sand samples with different moisture contents according to claim 3 is characterized in that: The pressurizing device also includes a clamping assembly, which includes a driving unit and two clamping arms respectively arranged corresponding to objects on both sides of the sealing tube, the clamping arm includes a supporting arm extending in a horizontal direction and a clamping claw arranged at the end of the supporting arm, and the clamping arm can approach and clamp the outer peripheral wall of the sealing tube under the drive of the driving unit.

5. The equipment for preparing sand samples with different moisture contents according to claim 3 is characterized in that: The water injection assembly includes a water injection channel arranged on the upper compression rod and a drainage channel arranged in the lower compression rod, the inlet end of the water injection channel is arranged on the outer peripheral surface of the upper compression rod, the outlet end of the water injection channel is arranged on the end surface of the upper compression rod abutting against the sand sample, and the water injection channel is connected to the water injection device; The inlet end of the drainage channel is arranged at the lower side of the sand sample, and the outlet end of the drainage channel is arranged at the outer peripheral surface of the lower compression rod.

6. The equipment for preparing sand samples with different moisture contents according to claim 5, characterized in that: The outlet end of the water injection flow channel is provided with a spray structure, the spray structure includes a plurality of spray ports extending in the radial direction of the upper compression rod, the plurality of spray ports intersect at the center of the upper compression rod, the water injection flow channel is connected to the intersection of the plurality of spray ports, and the diameter of the intersection is smaller than the diameter of the water injection flow channel; The width of the spray port is configured to gradually widen as the spray port extends in a direction away from the intersection.

7. The equipment for preparing sand samples with different moisture contents according to claim 6, 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 through the water injection channel, v is the water flow velocity in the water injection pipe, 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 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 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: 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: Among them, 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.

8. The equipment for preparing sand samples with different moisture contents according to claim 7, characterized in that: The width of the intersection is: Among them, W min is the width of the intersection, d is the diameter of the water injection channel, k8 is the empirical adjustment coefficient, k8=0.7, z2 is the length of the drainage channel; The width of the spray port is set to: 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 port to the center point of the intersection, k9 is the growth coefficient, which is dimensionless and usually takes a value greater than or equal to 0.5 and less than or equal to 1.

9. The equipment for preparing sand samples with different moisture contents according to claim 5, characterized in that: The sealing cylinder assembly further comprises a support ring, which is an annular structure and sleeved on the outer side 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 is supported on the lower end surface of the sealing cylinder; The support ring is provided with a connection port, and the connection port is provided corresponding to the outlet end of the drainage channel. The connection port is used for a drainage pipe to pass through and be connected to the outlet end of the drainage channel.

10. The equipment for preparing sand samples with different moisture contents according to claim 3, characterized in that: The pressurizing device further comprises a positioning piece and a scale fixed on the pressurizing screw, the scale is provided with scales arranged along the vertical direction, and the positioning piece extends to the scale along the horizontal direction.

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