Gland assembly, modular permeation apparatus, permeation testing system, and permeation testing method

Abstract

This invention relates to a capping assembly, a modular permeameter, a permeameter testing system, and a permeameter testing method. The capping assembly includes a cap plate and a permeable plate. The cap plate has a gas distribution chamber and an interface, the interface being connected to the gas distribution chamber. One end of the permeable plate is located at one end of the cap plate, and the permeable plate has multiple permeable holes that communicate with the gas distribution chamber. The other end of the permeable plate is used to abut the sample. The capping assembly of this invention has a simple structure, good compatibility with permeameters in related technologies, and improves the efficiency and accuracy of permeameter testing without changing the original permeameter structure, while effectively protecting the core sealing components.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing equipment technology, specifically to a pressure cap assembly, a modular permeameter, a permeability testing system, and a permeability testing method. Background Technology

[0002] The permeability coefficient is a core parameter characterizing the ability of porous media (such as soil, rock, and filter media) to allow fluid to pass through. In permeability coefficient testing, the sample is first saturated with water, and then the seepage flow rate is measured and calculated to obtain the permeability coefficient. The TST-55 permeameter is one of the commonly used instruments for measuring permeability coefficients in geotechnical testing. However, permeameters face three major technical challenges: sample sidewall leakage, low saturation efficiency in fine-grained soils, and disturbance of sand samples. Summary of the Invention

[0003] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0004] The TST-55 permeameter is one of the most commonly used instruments for measuring permeability coefficients in geotechnical testing in my country. It boasts a simple design, low cost, and intuitive operation. However, with the development of geotechnical engineering technology and the increasing demands for testing accuracy, the inherent shortcomings of this instrument in practical applications have become increasingly apparent. 1. Sidewall leakage problem (systematic error source) Ring sampling techniques cannot guarantee ideal contact between the sample and the inner wall of the ring, especially in structural soils or fractured soils, where micron-sized gaps can create dominant seepage channels. Studies have shown that this sidewall leakage can overestimate test results for low-permeability clays by 1-2 orders of magnitude. Although the current "Standard for Geotechnical Testing Methods" (GB / T 50123) recommends using high-viscosity media such as petroleum jelly for sealing, this method has significant shortcomings.

[0005] 2. Technical bottlenecks (affecting the foundation of testing) For permeability coefficient k < 10 -6 For fine-grained soils with a density of cm / s, the traditional hydraulic saturation method is extremely inefficient, often requiring hundreds of hours to reach a high degree of saturation. Prolonged saturation can lead to time-related changes in soil structure, such as secondary consolidation. For sandy soils, top-down hydraulic saturation easily generates seepage forces, causing fine particle migration and altering the sample gradation.

[0006] 3. Instrument maintenance and reliability issues During long-term use, the flat sealing ring of the standard top cover is easily worn or embedded by fine particles carried in the water, leading to seal failure.

[0007] The present invention aims to at least partially solve one of the technical problems in the related art.

[0008] Therefore, embodiments of the present invention propose a capping assembly including a capping plate and a permeable plate. The capping plate is provided with an air distribution chamber and an interface, the interface and the air distribution chamber being connected. One end of the permeable plate is located at one end of the capping plate, and the permeable plate is provided with a plurality of permeable holes, the permeable holes being connected to the air distribution chamber. The other end of the permeable plate is used to abut against the sample inside the ring cutter of the permeameter.

[0009] Therefore, the capping assembly of this invention has a simple structure, good compatibility with permeameters in related technologies, and improves the efficiency and accuracy of permeameter testing without changing the original permeameter structure, while effectively protecting the core sealing components.

[0010] In some embodiments, the cap assembly includes a dynamic sealing ring sleeved on the permeable plate, the dynamic sealing ring being axially opposite to the cap plate, the dynamic sealing ring being adjacent to or abutting one end of the cap plate, and the outer diameter of the dynamic sealing ring being interference-fitted with the inner diameter of the ring cutter.

[0011] In some embodiments, the dynamic sealing ring is lip-shaped.

[0012] In some embodiments, the lip angle of the dynamic sealing ring is α, and the range of α is 30°-60°.

[0013] In some embodiments, the air distribution chamber is open at one end of the cover plate, and the permeable plate is threadedly connected to the cover plate; and / or, one end of the permeable plate is nested within the cover plate, the pressure cap assembly includes a sealing ring, and an mounting annular groove is provided on one of the inner wall of the cover plate or the circumferential surface of the permeable plate, the sealing ring being disposed in the mounting annular groove and abutting against the other of the inner wall of the cover plate and the circumferential surface of the permeable plate.

[0014] In some embodiments, the pore size of the permeable pores ranges from 10 to 30 μm, and the pore size of the permeable pores is smaller than the particle size of the sample; and / or, a plurality of the permeable pores are uniformly arranged; and / or, the porosity of the permeable plate is ≥40%; and / or, the surface roughness Ra of the other end of the permeable plate is ≤0.6 μm.

[0015] The modular permeameter of this invention includes a body and the aforementioned capping assembly. The body includes a base and an upper permeable assembly. The permeameter has a saturation operating state and a test operating state. In the saturation operating state, the base of the permeameter is connected to the capping assembly, and in the test operating state, the base of the permeameter is connected to the upper permeable assembly.

[0016] The penetration testing system of this invention includes a vacuum pumping device and the modular penetration analyzer, wherein the vacuum pumping device is connected to the interface of the capping assembly.

[0017] The penetration testing method of this invention, using the aforementioned penetration testing system, includes the following steps: S1, System Assembly: The ring cutter of the base obtains the sample, the base with the sample and the gland assembly are assembled to form the permeameter in saturation working state, the pressure rod of the base is tightened, and the vacuum equipment and the interface are connected; S2, Vacuum Saturation: Connect the water inlet of the base to a degassing water source, and then start the vacuum pumping device to perform vacuuming. Degassing water enters the base from the water inlet under the pressure difference drive, permeates and saturates the sample. After the sample is saturated, turn off the vacuum pumping device. S3: Mode conversion: Disconnect the inlet from the airless water source, disconnect the interface from the vacuum equipment, remove the cap assembly, and then assemble the upper permeable assembly with the base to form the permeameter in the test operation state, and tighten the pressure rod. S4: Standard permeability test: Connect the inlet to the variable head pipeline, inject de-aired water, conduct a variable head permeability test, record the water drop process, and calculate the permeability coefficient.

[0018] In some embodiments, in step S2, the permeameter assembled in S1 is placed into a saturation container, and deaerated water is injected into the saturation container to connect the inlet with the deaerated water. The water level covers the cap assembly. In step S3, the permeameter in saturation operation is removed from the container, and the connection between the inlet and the deaerated water source is disconnected.

[0019] In some embodiments, during the vacuuming process in step S2, the first stage is preliminary venting: the vacuum level of the vacuuming device is raised to -50 kPa and then maintained for 30 minutes; the second stage is enhanced venting, raising the vacuum level to -80 kPa and then maintaining it for 60 minutes; the third stage is final saturation: the vacuum level is raised and stabilized between -95 kPa and -98 kPa and maintained for 90 minutes; after the vacuuming device is turned off, it is left to stand for 10 minutes to observe whether the vacuum level is stable. If it is stable, it indicates that the system is well sealed and step S4 can be continued; if it is unstable, it indicates that the system has failed to seal and the operation should be restarted from S1. Attached Figure Description

[0020] Figure 1 This is an exploded structural diagram of a permeameter in related technologies, and also an exploded structural diagram of a permeameter in the test operation state of an embodiment of the present invention; Figure 2This is a schematic diagram of the structure of the capping assembly according to an embodiment of the present invention; Figure 3 This is a partial cross-sectional view of the dynamic sealing ring according to an embodiment of the present invention; Figure 4 This is a flowchart of the penetration testing method according to an embodiment of the present invention.

[0021] Figure label: 100. Capping assembly; 1. Cover plate; 11. Interface; 2. Permeable board, 21. Permeable holes; 3. Dynamic sealing pressure ring; 4. Sealing ring; 200, base; 2001, base; 20011, inlet; 2002, first permeable stone; 2003, fixing rod; 2004, ring cutter; 2005, sleeve; 2006, pad; 2007, pressure rod; 300. Upper permeable component; 3001. Upper cover; 3002. Second permeable stone; 3003. O-ring; 1000, Permeameter. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] The capping assembly, modular permeameter, permeameter, and permeameter testing system and method of the present invention are described in detail below with reference to the accompanying drawings.

[0024] The permeation testing system of this invention includes a vacuum pumping device and a modular permeameter 1000.

[0025] like Figure 1 and Figure 2 As shown, the modular permeameter 1000 of this embodiment of the invention includes a body and a capping assembly 100. The body includes a base 200 and an upper permeable assembly 300.

[0026] like Figure 2 As shown, the capping assembly 100 of this embodiment includes a cover plate 1 and a permeable plate 2. The cover plate 1 is provided with an air distribution chamber and an interface 11. The interface 11 is connected to the air distribution chamber. One end of the permeable plate 2 is located at one end of the cover plate 1. The permeable plate 2 is provided with a plurality of permeable holes 21. The permeable holes 21 are connected to the air distribution chamber. The other end of the permeable plate 2 is used to abut against the sample inside the ring cutter. The pore size of the permeable holes 21 is smaller than the particle size of the sample.

[0027] The permeameter 1000 has a saturation operating state and a test operating state. In the saturation operating state, the base 200 of the permeameter 1000 is connected to the gland assembly 100 (not shown in the figure). In the test operating state, the base 200 of the permeameter 1000 is connected to the upper permeable assembly 300 (e.g., ...). Figure 1 (As shown). That is, the upper permeable component 300 and the cap component 100 can be interchangeably connected to the base 200. When the cap component 100 is connected to the base 200, the permeameter 1000 is in a saturated operating state. In this state, the upper permeable component 300 is not connected to the base 200. When the upper permeable component 300 is connected to the base 200, the permeameter 1000 is in a test operating state. In this state, the cap component 100 is not connected to the base 200.

[0028] The vacuum pump is connected to the interface 11 of the gland assembly 100.

[0029] Among them, such as Figure 1 As shown, the base 200 includes a base 2001, a first permeable stone 2002, a fixing rod 2003, a ring cutter 2004, a sleeve 2005, a pad 2006, and a pressure rod 2007. The base 2001 has a water inlet 20011. The first permeable stone 2002 is located inside the base 2001. Fixing rods 2003 are provided on both sides of the base 2001. The ring cutter 2004 is detachably nested within the sleeve 2005. 4. Used for cutting geotechnical samples, the ring cutter 2004 with the sample is placed inside the sleeve 2005, the sleeve 2005 is placed on the base 2001, the ring cutter 2004 is located on the first permeable stone 2002, the pad 2006 is detachably installed on the fixing rod 2003, the pressure rod 2007 is provided with external threads, the pad 2006 is provided with internal threads, and the pressure rod 2007 can be moved downward or upward by rotating the pressure rod 2007.

[0030] like Figure 1 As shown, the upper permeable component 300 includes an upper cover 3001, a second permeable stone 3002, and an O-ring 3003. The second permeable stone 3002 is used to abut against the sample. The O-ring 3003 is sleeved on the second permeable stone 3002 and the ring cutter 2004. The upper cover 3001 is located between the pressure rod 2007 and the second permeable stone 3002. The upper cover 3001 is used to abut against the pressure rod 2007 and bear the pressure of the pressure rod 2007.

[0031] like Figure 4 As shown, the penetration testing method of this invention, using the penetration testing system of this invention, includes the following steps: S1, System Assembly: The ring cutter 2004 of the base 200 acquires the sample. The base 200 with the sample and the gland assembly 100 are assembled to form a permeameter 1000 in saturated operating state. The pressure rod 2007 of the base 200 is tightened, and the vacuum equipment and interface 11 are connected. The acquisition of the sample by the ring cutter 2004 and the assembly of the base 200 are existing technologies.

[0032] S2, Vacuum Saturation: Connect the water inlet 20011 of the base 200 to a gas-free water source, and then start the vacuum pumping equipment to perform vacuuming. Under the pressure difference drive, the gas-free water enters the base 200 from the water inlet 20011 of the base 200, permeates and saturates the sample. After the sample is saturated, turn off the vacuum pumping equipment. S3: Mode conversion: Disconnect the inlet 20011 from the airless water source, disconnect the interface 11 from the vacuum equipment, remove the pressure cap assembly 100, and then assemble the upper permeable assembly 300 and the base 200 to form the permeameter 1000 in the test operation state, and tighten the pressure rod 2007. S4: Standard Permeability Test: Connect the inlet 20011 to the variable head pipeline, inject de-aired water, conduct a variable head permeability test, record the water drop process, and calculate the permeability coefficient.

[0033] In this embodiment of the invention, the cover plate 1 of the capping assembly 100 is provided with an air distribution chamber and an interface 11. The interface 11 can be connected to a vacuuming device. The air distribution chamber is connected to the water permeable holes 21 of the water permeable plate 2. Thus, when the vacuuming device is turned on, a negative pressure is formed in the air distribution chamber. The negative pressure of the air distribution chamber can act on the other end of the water permeable plate 2 through the water permeable plate 2. At the same time, the capping assembly 100 can replace the upper water permeable assembly 300 and cooperate with the base 200 to form a permeameter 1000 in a saturated working state. Thus, when vacuuming in the saturated working state (that is, in step S2), the negative pressure acts on the sample, so that the upper end of the sample is in a negative pressure state and the lower end of the sample is in a normal pressure state or close to normal pressure state. The airless water in the inlet 20011 enters the base 200 under the drive of the pressure difference and gradually permeates upward into the sample, making the sample water saturated.

[0034] The permeation testing method of this invention employs a saturated working state permeameter 1000 formed by the cap assembly 100 and the base 200. A pressure difference generated by vacuuming rapidly saturates the sample, significantly shortening the saturation time and increasing the saturation degree compared to permeameters in related technologies. Furthermore, the cap assembly 100 and the upper permeable assembly 300 are interchangeable as a functional add-on module. This module is low-cost, highly compatible with permeameters in related technologies, and requires minimal modification to the overall permeation testing process, without affecting the user's basic operating habits. Simultaneously, the saturation stage and the permeation test stage are functionally separated, avoiding the possibility of impurities contaminating the sealing ring 4 of the upper cap during the saturation stage, as is possible in related technologies. This extends the service life of the entire machine, improves its reliability, and facilitates cleaning and maintenance.

[0035] Therefore, the capping assembly 100 of this embodiment has a simple structure, good compatibility with permeameters in related technologies, and improves the efficiency and accuracy of permeameter testing without changing the original permeameter structure, while effectively protecting the core sealing components.

[0036] like Figure 2 As shown, in the saturated operating state of the permeameter 1000, the upper end surface of the cover plate 1 is the pressure bearing surface, which abuts against the lower end of the pressure rod 2007. That is, during the process of tightening the pressure rod 2007 of the base 200, the lower end of the pressure rod 2007 moves downward, causing the cover plate 1 and the permeable plate 2 to move downward, gradually pressing the sample.

[0037] Optionally, the cover plate 1 is made of 304 stainless steel or 316 stainless steel and is precision machined to provide good corrosion resistance and structural strength.

[0038] Specifically, interface 11 can use M10. 1. Quick-change female threaded interface 11.

[0039] Optionally, the permeable plate 2 is prepared from 316L stainless steel powder through molding and vacuum sintering processes. The permeable plate 2 has a compressive strength ≥25 MPa, exhibiting high strength and rigidity, thus capable of withstanding axial pressure and achieving effective sealing and force transmission between the cover plate 1 and the sample. The permeability of the metal-sintered permeable plate 2 is better than that of ceramic permeable stones in related technologies.

[0040] The pore size of the permeable pore 21 ranges from 10 to 30 μm, which is smaller than the particle size of the sample. This prevents sample particles from leaking out through the permeable pore 21 during the vacuum saturation stage, ensuring the accuracy of the permeability coefficient test.

[0041] For example, the pore size of the permeable pore 21 is 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm or 30μm.

[0042] The multiple permeable holes 21 on the permeable plate 2 are evenly distributed, thus ensuring that the negative pressure is evenly distributed at the upper end of the sample, so that the negative pressure acts evenly and quickly on the entire sample, which is beneficial to improving the saturation efficiency of the sample.

[0043] In some embodiments, the porosity of the permeable plate 2 is ≥40%. The high porosity of the permeable plate 2 increases the area of ​​negative pressure acting on the upper end of the sample, thereby improving the saturation efficiency of the sample and enhancing the efficiency of the permeation test.

[0044] For example, the porosity of the permeable plate 2 is 45%, 50%, 55%, 60%, or 65%.

[0045] The surface roughness Ra of the other end of the permeable plate 2 is ≤0.6μm. The surface of the other end of the permeable plate 2 is the end face that abuts the sample. Its roughness is small, which can reduce the embedding and disturbance to the sample surface, which is conducive to ensuring the accuracy of the permeation test, and also facilitates cleaning.

[0046] Specifically, the end face of the other end of the permeable plate 2 is mirror polished.

[0047] In some embodiments, the air distribution chamber is open at one end (lower end) of the cover plate 1, and the permeable plate 2 is threadedly connected to the cover plate 1. Specifically, the lower end of the cover plate 1 is provided with an internal thread, and the upper end of the permeable plate 2 is provided with an external thread. The external thread and the internal thread are engaged to connect the cover plate 1 and the permeable plate 2.

[0048] The permeable plate 2 and the cover plate 1 are connected by threads, which not only makes it easy to disassemble and replace the permeable plate 2, thus adapting to the saturation operation of samples with different particle sizes, but also the threaded connection has good sealing performance, ensuring that the vacuum equipment exerts negative pressure on the sample through the air distribution chamber and the air vent, thereby improving the saturation efficiency of the sample.

[0049] In other embodiments, the air distribution chamber is open at one end (lower end) of the cover plate 1, and the other end (upper end) of the permeable plate 2 is nested inside the cover plate 1. The capping assembly 100 includes a sealing ring 4. An mounting annular groove is provided on either the inner wall of the cover plate 1 or the circumferential surface of the permeable plate 2. The sealing ring 4 is disposed within the mounting annular groove and abuts against the other of the inner wall of the cover plate 1 and the circumferential surface of the permeable plate 2. For example, the inner wall of the cover plate 1 has a mounting annular groove, and the sealing ring 4 is disposed within the mounting annular groove and abuts against the circumferential surface of the dehydration plate; or, the circumferential surface of the permeable plate 2 has a mounting annular groove, and the sealing ring 4 is disposed within the mounting annular groove and abuts against the inner wall of the cover plate 1. The sealing ring 4 seals the permeable plate 2 and the cover plate 1, ensuring the airtightness between the air distribution chamber and the permeable hole 21, and ensuring the negative pressure effect of the vacuum equipment on the sample through the air distribution chamber and the permeable hole, thereby improving the saturation efficiency of the sample.

[0050] In some other embodiments, the air distribution chamber is open at one end (lower end) of the cover plate 1, the permeable plate 2 is threadedly connected to the cover plate 1, the pressure cap assembly 100 includes a sealing ring 4, and an installation ring groove is provided on one of the inner wall of the cover plate 1 or the peripheral surface of the permeable plate 2. The sealing ring 4 is disposed in the installation ring groove and abuts against the other of the inner wall of the cover plate 1 and the peripheral surface of the permeable plate 2.

[0051] In some embodiments, the other end (lower end) of the permeable plate 2 is fitted into the ring cutter 2004 of the permeameter 1000. That is, the diameter of the permeable plate 2 matches the inner diameter of the ring cutter 2004, and the dimensional tolerance zone of the permeable plate 2 and the ring cutter 2004 is a clearance fit, thus the permeable plate 2 corresponds to the sample inside the ring cutter 2004. When the permeameter 1000 is in saturated operation, the sample inside the ring cutter 2004 is in close contact with the permeable plate 2, thereby forming a seal on the upper surface of the sample, preventing sample particle leakage, and further ensuring the accuracy of the sample permeation test.

[0052] Specifically, the thickness of the permeable board 2 is 3-5mm. For example, the thickness of the permeable board 2 is 3mm, 3.5mm, 4mm, 4.5mm, or 5mm.

[0053] In some embodiments, the cap assembly 100 includes a dynamic sealing ring 3, which is sleeved on the permeable plate 2. The dynamic sealing ring 3 is axially opposite to the cap plate 1 and is adjacent to or abuts one end of the cap plate 1. The outer diameter of the dynamic sealing ring 3 is interference-fitted with the inner diameter of the ring cutter 2004. The dynamic sealing ring 3 has a certain degree of elasticity and variability. In the unused state (without external force), the inner diameter of the dynamic sealing ring 3 is interference-fitted with the diameter of the permeable plate 2. The inner diameter of the dynamic sealing ring 3 is smaller than the diameter of the permeable plate 2, which allows the elasticity of the dynamic sealing ring 3 to be installed on the permeable plate 2. The dynamic sealing ring 3 can be sleeved on the permeable plate 2 without external force. The outer diameter of the dynamic sealing ring 3 is interference-fitted with the inner diameter of the ring cutter 2004. The outer diameter of the dynamic sealing ring 3 is larger than the inner diameter of the ring cutter 2004, thus enabling the dynamic sealing ring 3 to be installed on the permeable plate 2 in step S. In step S1, when the pressure rod 2007 of the base 200 is tightened, the pressure rod 2007 pushes the cover plate 1 and the permeable plate 2 downward. Due to the resistance of the ring cutter 2004, the dynamic sealing ring 3 moves relative to the cover plate 1, causing the upper end face of the dynamic sealing ring 3 to be subjected to the axial clamping force of the cover plate 1. The clamping force causes the dynamic sealing ring 3 to undergo radial outward expansion deformation, and under the action of the clamping force, the dynamic sealing ring 3 is forcefully "squeezed" into the possible micro-gap between the side wall of the sample and the inner wall of the ring cutter 2004, achieving adaptive, gapless active sealing. Furthermore, in step S3, when switching modes, the dynamic sealing ring 3 remains between the inner wall of the ring cutter 2004 and the side wall of the sample, and continues to maintain the seal in the permeation test in step S4.

[0054] Therefore, the active radial pressure provided by the dynamic sealing ring 3 in this embodiment of the invention can effectively eliminate micron-level sidewall gaps, prevent sample leakage from the source, ensure that water flows strictly through the soil, and measure the true permeability coefficient.

[0055] Furthermore, such as Figure 2 and Figure 3 As shown, the dynamic sealing ring 3 is lip-shaped. The contact lip of the lip-shaped sealing ring is a locally protruding elastic protrusion. Through the locally elastic protrusion, the contact pressure at the sealing interface is enhanced, ensuring the sealing performance.

[0056] like Figure 3 As shown, the lip angle of the dynamic sealing ring 3 is α, and the range of α is 30°-60°. For example, the lip angle is 30°, 35°, 40°, 45°, 50°, 55°, or 60°.

[0057] In this embodiment, the lip angle is 45°. The upper end face of the dynamic sealing ring 3 is subjected to an axial pressing force Fz from the cover plate 1. Due to its 45° lip angle, according to the principle of mechanical decomposition, a radially outward expanding force Fr will be generated, Fr ≈ Fz. tan(45°) = Fz.

[0058] Specifically, the dynamic sealing ring 3 is made of fluororubber (FKM) with a Shore hardness of A60, which has good elasticity, aging resistance and media resistance.

[0059] Specifically, when performing a penetration test using the penetration testing system of this embodiment, in the system assembly step S1, when tightening the pressure rod 2007, stop tightening after feeling obvious resistance. The axial clamping force Fz corresponding to the obvious resistance is approximately 300-500N. Through torque estimation, the dynamic sealing ring 3 has generated approximately 15% axial compressive strain, the lip structure has deformed, and a radial seal has been established.

[0060] In some embodiments, when performing a permeation test using the permeation testing system of this invention, in step S2, the permeameter 1000 assembled in S1 is placed into a saturation container, and degassed water is injected into the saturation container to connect the inlet 20011 with the degassed water. The water level covers the gland assembly 100, and the system enters underwater vacuum saturation. The degassed water can be boiled and cooled degassed distilled water.

[0061] The operation of placing the saturated permeameter 1000 into the saturation container and injecting degassing water into the container is simple. The saturation container has a simple structure, which helps to reduce the cost of permeameter testing.

[0062] Specifically, transparent acrylic containers were chosen as saturation containers to facilitate observation of the contents.

[0063] During vacuuming in step S2, a phased, stepped vacuuming process is employed. The first phase is preliminary venting: the vacuum level of the vacuuming equipment is raised to -50 kPa and maintained for 30 minutes. The second phase is enhanced venting: the vacuum level is increased to -80 kPa and maintained for 60 minutes. The third phase is final saturation: the vacuum level is increased and stabilized between -95 kPa and -98 kPa, and maintained for 90 minutes. After shutting down the vacuuming equipment, allow it to stand for 10 minutes and observe whether the vacuum level is stable. If stable, the system is well-sealed, and step S4 can proceed. If unstable, the system seal has failed, and the operation must restart from S1.

[0064] In step S3, the permeameter 1000 in saturated operating state is removed from the container, and the connection between the inlet 20011 and the airless water source is disconnected. During removal, the permeameter 1000 is kept vertical to avoid disturbing the sample. After removal, the surface of the permeameter 1000 is wiped dry.

[0065] For a certain undisturbed clay sample, a permeability test was conducted using the relevant technique of applying Vaseline followed by constant head saturation. The saturation time was approximately 168 hours (7 days), the saturation degree was approximately 93%, and the measured permeability coefficient k1 = 2.1. 10 -8 The permeability test data exhibits significant dispersion due to the speed of cm / s. Using the permeability testing method of this invention, the total saturation time is approximately 3 hours, the estimated saturation level is greater than 99%, and the measured permeability coefficient k2 = 7.3. 10 -9 cm / s. k2=7.3 10 -9 The smaller and more stable values ​​indicate that the sidewall short-circuit flow is effectively suppressed. The testing efficiency is improved by more than 50 times, and the results better reflect the true permeability of the soil.

[0066] The modular permeameter 1000 of this invention is also applicable to easily disturbed cohesive soils.

[0067] The applicability of the permeameter 1000 in saturated operating state according to this invention to loose sandy soil is verified as follows: (1) Sample loading: Load the dried standard sand (d 50 =0.2mm) Carefully insert the ring cutter 2004 to the predetermined density using the rain method.

[0068] (2) Pre-immersion: Assemble the cap assembly 100 and the base 200 to form the permeameter 1000 in saturated working state. First, do not tighten the cap assembly 100. Gently place the cap assembly 100 on the sand sample. Then slowly immerse the entire device into the saturated container, allowing the water to naturally wet the sand sample from bottom to top. This process can avoid water flow impact.

[0069] (3) Vacuum saturation: After the sand sample is completely submerged, gently tighten the pressure rod 2007 underwater to press the pressure cap assembly 100 against the sand sample. Then perform vacuum saturation according to step S2 in the above-mentioned permeability test method. This process can avoid the floating of fine particles and stratification.

[0070] After the vacuum saturation test, the dried sample was subjected to particle analysis. Compared with the initial batch before loading, the loss rate of fine particles (d<0.075mm) was less than 0.5%, which is much lower than that of the TST-55 permeameter 1000 saturation method used in related technologies (more than 5%). This effectively maintained the original gradation structure of the sample and protected the authenticity of the sample.

[0071] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0072] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0073] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0074] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0075] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0076] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A capping assembly (100), characterized in that, include Cover plate (1), the cover plate (1) is provided with an air distribution chamber and an interface (11), the interface (11) and the air distribution chamber are connected; and A permeable plate (2) is provided at one end of the cover plate (1). The permeable plate (2) has multiple permeable holes (21) that are connected to the air distribution chamber. The other end of the permeable plate (2) is used to abut against the sample inside the ring cutter of the permeameter.

2. The capping assembly (100) according to claim 1, characterized in that, Includes a dynamic sealing ring (3), which is sleeved on the permeable plate (2). The dynamic sealing ring (3) is opposite to the cover plate (1) in its axial direction. The dynamic sealing ring (3) is adjacent to or abuts one end of the cover plate (1). The outer diameter of the dynamic sealing ring (3) is interference-fitted with the inner diameter of the ring cutter (2004).

3. The capping assembly (100) according to claim 2, characterized in that, The dynamic sealing ring (3) is lip-shaped.

4. The capping assembly (100) according to claim 3, characterized in that, The lip angle of the dynamic sealing ring (3) is α, and the range of α is 30°-60°.

5. The capping assembly (100) according to claim 1, characterized in that, The air distribution chamber is open at one end of the cover plate (1), and the permeable plate (2) is threadedly connected to the cover plate (1); and / or, one end of the permeable plate (2) is nested inside the cover plate (1), the pressure cap assembly (100) includes a sealing ring (4), and an installation ring groove is provided on one of the inner wall of the cover plate (1) or the circumferential surface of the permeable plate (2), and the sealing ring (4) is provided in the installation ring groove and abuts against the other of the inner wall of the cover plate (1) and the circumferential surface of the permeable plate (2).

6. The capping assembly (100) according to claim 1, characterized in that, The pore size of the permeable hole (21) is in the range of 10-30 μm, and the pore size of the permeable hole (21) is smaller than the particle size of the sample; and / or, a plurality of the permeable holes (21) are evenly arranged; and / or, the porosity of the permeable plate (2) is ≥40%; and / or, the surface roughness Ra of the other end of the permeable plate (2) is ≤0.6 μm.

7. A modular permeameter (1000), characterized in that, The device includes a body and a capping assembly (100) as described in any one of claims 1 to 6. The body includes a base (200) and an upper permeable assembly (300). The permeameter (1000) has a saturated operating state and a test operating state. The base (200) of the permeameter (1000) in the saturated operating state is connected to the capping assembly (100), and the base (200) of the permeameter (1000) in the test operating state is connected to the upper permeable assembly (300).

8. A penetration testing system, characterized in that, It includes a vacuum pumping device and a modular permeameter (1000) as described in claim 7, wherein the vacuum pumping device is connected to the interface (11) of the capping assembly (100).

9. A penetration testing method, characterized in that, The penetration testing system according to claim 8 includes the following steps: S1, System assembly: The ring cutter (2004) of the base (200) obtains the sample, and the base (200) with the sample and the gland assembly (100) are assembled to form the permeameter (1000) in saturated working state. The pressure rod (2007) of the base (200) is tightened, and the vacuum equipment and the interface (11) are connected. S2, Vacuum Saturation: Connect the water inlet (20011) of the base (200) to a gas-free water source, and then start the vacuum pumping device to perform vacuuming. Under the pressure difference drive, the gas-free water enters the base (200) from the water inlet (20011) of the base (200), permeates and saturates the sample. After the sample is saturated, turn off the vacuum pumping device. S3: Mode conversion: Disconnect the inlet (20011) from the airless water source, disconnect the interface (11) from the vacuum equipment, remove the cap assembly (100), and then assemble the upper permeable assembly (300) and the base (200) to form the permeameter (1000) in the test operation state, and tighten the pressure rod (2007). S4: Standard permeability test: Connect the inlet (20011) to the variable head pipeline, inject de-aired water, conduct a variable head permeability test, record the water drop process, and calculate the permeability coefficient.

10. The penetration testing method according to claim 9, characterized in that, In step S2, the permeameter (1000) assembled in S1 is placed into a saturation container, and deaerated water is injected into the saturation container to connect the inlet (20011) with the deaerated water. The water level covers the cap assembly (100). In step S3, the permeameter (1000) in its saturated operating state is removed from the container, and the connection between the inlet (20011) and the deaerated water source is disconnected; and / or, During the vacuuming process in step S2, the first stage of preliminary venting involves controlling the vacuum level of the vacuuming equipment to rise to -50 kPa and then maintaining it for 30 minutes. The second stage involves enhanced venting, raising the vacuum level to -80 kPa and maintaining it for 60 minutes. The third stage is final saturation: the vacuum level is raised and stabilized between -95 kPa and -98 kPa for 90 minutes. After turning off the vacuum equipment, let it stand for 10 minutes and observe whether the vacuum level is stable. If it is stable, it indicates that the system is well sealed and step S4 can be continued. If it is unstable, it indicates that the system has failed to seal and the operation should be restarted from S1.

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