A device and method for transient permeation testing of time-varying slurries in a dispersion

Abstract

This invention discloses a transient permeability testing device and method for time-varying viscosity slurry in bulk materials. The slurry conveying unit transports the slurry to the permeability testing unit. The lower part of the permeability testing unit is connected to the slurry conveying unit. Pressure sensors are installed at the top and bottom of the permeability testing unit, and perforated mesh plates for covering are installed at the upper and lower parts of the permeability testing unit. The first telescopic cylinder of the air pressure measuring unit has a double-layer structure, and the upper part of the second telescopic cylinder is fitted into the gap of the double-layer structure of the first telescopic cylinder, enabling the second telescopic cylinder to move up and down relative to the first telescopic cylinder in the central axis direction, so that the upper part of the pressure plate, the first telescopic cylinder, and the second telescopic cylinder form a sealed air-filled cavity. This invention utilizes the air pressure measuring unit to set the air pressure value, thereby stabilizing the slurry during the test. The pressure value inside the air pressure pipe can be flexibly set through the air delivery pipe, and a wide range of measurable grouting pressures can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering testing technology, specifically relating to a transient permeability test device and method for time-varying viscosity slurry in granular materials. Background Technology

[0002] In the application of quick-setting grouts, the proportions of various additives (such as quick-setting agents) are crucial for adjusting the main properties of the grout. Grouts with different proportions exhibit varying permeability in different types of fragmented media. Furthermore, the grouting pressure needs to be adjusted for different engineering conditions. Therefore, adjusting the permeability parameters and operating pressure of the quick-setting grout in different regions and situations is critical to its effectiveness. If the grout and pressure used during construction do not match the actual conditions, it will severely affect the grouting effect, leading to insufficient grout quality or grout loss, causing serious construction problems and directly impacting the safety of people's lives and property during disaster relief. Conversely, excessive grouting volume or pressure may result in grout waste and even affect structural safety, causing secondary damage. However, because grouting points are often underground, the projects are concealed, and quick-setting grouts exhibit time-varying viscosity, it is difficult to study their permeability performance under different pressure conditions. Therefore, the testing method for the permeability performance of quick-setting grouts under different pressures is a widely concerned and urgently needed problem in engineering construction.

[0003] Currently, methods for testing permeability can be broadly categorized into two types: testing the permeability coefficient of water flow under different soil conditions and testing grout under permeation grouting conditions. Chinese Patent Publication No. CN209069798U proposes a soil permeability testing instrument capable of simultaneously mounting multiple soil samples. By connecting two different sample media vertically, it can simultaneously measure the permeability coefficient of two sample media. Furthermore, by incorporating a flow meter, level sensor, and external receiver, it achieves automatic data acquisition, analysis, and calculation, reducing errors from manual monitoring and improving test accuracy. Although this method can accurately and efficiently perform monitoring and calculations, it still has several drawbacks. First, the quick-setting grout will solidify rapidly after use, and may solidify inside the experimental pipe during testing. Second, the permeation process simulated by this device is a low-pressure permeation process. If a high-pressure grouting test is conducted inside the experimental pipe, it may damage the testing instrument and result in inaccurate monitoring results. Finally, the flow of the grout cannot be monitored inside the experimental pipe. Uneven grout permeation will lead to large pores in the permeation path within the experimental body, resulting in the compression and destruction of the debris and poor grouting effect. Therefore, this device is not suitable for measuring and calculating the permeation parameters of quick-setting grout in different soil types.

[0004] Furthermore, Chinese patent documents CN108036985A and CN114324110A propose methods for testing the permeability coefficient of soil reinforced with grout. Both methods involve injecting grout into the soil using an instrument, allowing it to solidify, and then conducting a permeability test on the reinforced soil after a certain curing time. The permeability coefficient of the grout-reinforced soil is determined by the amount of water that seeps in over a specific time. While these tests measure the permeability coefficient of soil reinforced with grout, the preparation of the test materials is time-consuming, and fundamentally, they do not test the permeability coefficient of the grout itself. Due to the characteristics of the instruments used, they are not suitable for grouting tests under high pressure environments and cannot collect grout under significant impact.

[0005] Chinese patent document CN109781603B proposes a nuclear magnetic resonance (NMR) simulation experimental system and method for synchronous grouting permeation and diffusion in ultra-deep strata shield tunneling. It obtains grout seepage information based on NMR imaging, but this method does not measure the grout permeability coefficient. Chinese patent document CN111006952A proposes a method for precisely controlling the grouting environment of an experimental device using air pressure loading to conduct grouting seepage experiments under high pressure. This device can collect ultrafine cement grout and inject it into rock samples and construct a high-pressure experimental chamber using air pressure. It can also clean the experimental pipes with high-pressure water to prevent siltation, and the grouting process can be observed through a transparent glass cover. However, this experimental method and device only construct a high-pressure grouting environment but do not study high-pressure grouting. Furthermore, although permeation was observed through the experimental device, the permeability parameters of the grout were not accurately calculated.

[0006] The above-mentioned solutions have the following technical problems: (1) Existing measuring instruments (such as Darcy permeability testers) are all in a low-speed state, which cannot be used to measure high-speed, high-permeability (i.e., high-pressure grouting). The water head pressure measured by the Darcy permeability tester is in a steady state or the pressure gradually decreases, which cannot be used to measure the pressure at any time, and cannot measure the permeability performance under various grouting pressures. (2) Existing instruments fail to pay attention to the uniformity of seepage liquid in seepage tests. The preparation of transparent soil samples is too complicated, and the uniformity of grout in the soil cannot be guaranteed. (3) Existing methods for measuring the grouting effect require curing the grout-reinforced soil for a certain period of time before measuring its permeability coefficient. Direct testing of its permeability parameters cannot be carried out. (4) The high-pressure grouting environment is more dangerous than permeable grouting, and the grout collection is more complicated. Existing permeability testers cannot test and measure grouting under different pressures, and cannot guarantee the safety and stability of the test. (5) Existing measuring instruments mostly use flow meters to measure liquid flow rate and velocity, but existing flow meters cannot accurately measure time-varying viscosity slurries, and may even cause damage to the instruments. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a transient permeation test device and method for time-varying viscosity slurry in bulk materials, which solves the above-mentioned technical problems existing in the prior art.

[0008] The objective of this invention can be achieved through the following technical solutions: A transient permeability testing device for time-varying viscosity slurry in a bulk material includes a slurry conveying unit, a permeability testing unit, and a pressure velocity measuring unit. The slurry conveying unit is used for conveying the slurry and delivering it to the permeation test unit. The permeation test section has a sleeve structure that runs through the top and bottom, and the lower part is connected to the slurry conveying section. Pressure sensors are installed at the top and bottom of the permeation test section to monitor the pressure of the slurry when it is delivered to the permeation test section and when it leaves the permeation test section. At the same time, perforated mesh plates for covering are installed at the top and bottom of the permeation test section. The air pressure speed measuring unit includes a first telescopic cylinder and a second telescopic cylinder. The first telescopic cylinder has a double-layer structure. The upper part of the second telescopic cylinder is fitted into the gap of the double-layer structure of the first telescopic cylinder, and the second telescopic cylinder moves up and down relative to the first telescopic cylinder in the direction of the central axis. The lower part of the second telescopic cylinder is sealed by a pressure plate, so that the upper part of the pressure plate, the first telescopic cylinder, and the second telescopic cylinder form a sealed air chamber. The air is inflated and deflated in the air chamber through the air pressure pipe set at the top.

[0009] Furthermore, the slurry conveying section is a cone-shaped uniform grouting assembly that is wider at the top and narrower at the bottom, with the tip of the cone-shaped uniform grouting assembly located at the bottom as the feed inlet for conveying the slurry.

[0010] Furthermore, a slurry pump is installed at the feed inlet of the uniform grouting assembly.

[0011] Furthermore, the mesh size of the porous mesh plate is smaller than the minimum particle size of the test fragments in the grout.

[0012] Furthermore, an outwardly extending baffle is provided on the lower edge of the air pressure measuring unit, and a downwardly extending lug is provided on the outer edge of the baffle, so that the baffle as a whole covers the outer periphery of the slurry outlet of the permeation test unit below.

[0013] Furthermore, a first support column is provided at the lower part where the permeation test section is located; a second support column is provided at the top where the air pressure measuring section is located, so that the upper opening of the permeation test section is concentrically set with the pressure plate at the lower part where the air pressure measuring section is located.

[0014] Furthermore, the pressure sensing element located on the inner wall of the pressure sensing element is configured as an optical fiber pressure measuring ring.

[0015] Furthermore, the outer wall of the first telescopic cylinder of the permeation test section is made transparent and has annular scale markings, so that the movement state of the upper part of the second telescopic cylinder can be observed through the outer wall of the first telescopic cylinder.

[0016] The method for the transient permeation test device for time-varying viscosity slurry in the aforementioned bulk material includes the following steps: S1. First, the permeation test unit is fixedly erected. Then, the air pressure velocity measuring unit is erected on the upper part of the permeation test unit and fixed as a whole. The external pumping slurry machine is connected to the inlet of the slurry conveying unit to carry out slurry conveying operation. At the same time, after being conveyed by the pumping slurry machine, the pressure values ​​of the conveyed slurry and the slurry output monitored by the pressure sensors at the bottom and top of the permeation test unit are fed back to the control center. S2. Inflate the inflation chamber of the air pressure measuring unit to reach the preset pressure specified in the test; S3. The slurry injected into the permeation test section is detected by the pressure sensor to change the slurry pressure and feedback. At the same time, it generates an upward impact force on the pressure plate of the air pressure velocity measuring section located at the top of the permeation test section, and simultaneously drives the second telescopic cylinder of the air pressure velocity measuring section to move upward a distance.

[0017] The beneficial effects of this invention are: 1. This invention utilizes a pneumatic speed measuring unit to set the pneumatic pressure value, thereby stabilizing the grout in tests with high grouting pressure. The pressure value inside the pneumatic pipe can be flexibly set through the air delivery pipe, enabling grout permeability tests under different grouting pressure environments. It can measure high-speed, high-permeability grouts, has a wide measurement range, and simultaneously ensures the safety of the test to meet the test requirements.

[0018] 2. This device adopts a uniform grouting assembly with a cone shape that is wider at the top and narrower at the bottom for the grout delivery section, in order to prevent uneven grouting in the test tube due to excessive pressure.

[0019] 3. This device collects the pressure data of the inlet and outlet slurry in the permeation test section and measures the volume data of the outlet slurry. It can be directly monitored and recorded through the control center. The outlet velocity and flow rate of the slurry can be directly determined through calculation. This avoids the limitations of using a flow meter on the properties of the slurry, improves the accuracy of the test and saves a lot of repeated tests.

[0020] 4. This device is composed of three interconnected parts: a slurry delivery section, a permeation test section, and a pressure velocity measurement section. It can meet the testing needs under various environments and ensure the safety and stability of the test under various pressure conditions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0022] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 This is a schematic diagram of the overall structure connecting the slurry delivery unit and the permeation test unit according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the porous mesh structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the air pressure velocity measuring unit according to an embodiment of the present invention; Figure 5 This is a schematic cross-sectional view of the structure before grouting in an embodiment of the present invention; Figure 6 This is an embodiment of the present invention. Figure 5 Schematic diagram of a partial structural cross-section at point A; Figure 7 This is a schematic diagram of the cross-sectional structure after grouting in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Against the backdrop of my country's rapid economic development, the construction of underground space has entered a new stage, with space development and utilization venturing into deeper strata. However, this has also brought engineering hazards, such as water inrushes, posing a significant threat to the safety of construction projects. Rapid-setting grout, as a new type of grout material in recent years, has advantages such as fast setting speed, low-temperature resistance, and high early compressive strength, and has become a commonly used material for sealing, preventing leaks, and reinforcing in various emergency rescue and disaster relief operations.

[0025] Therefore, this application proposes the following solutions to address the problems existing in the prior art, such as... Figure 1 , Figure 5 As shown, an embodiment of the present invention provides a transient permeation test device for time-varying viscosity slurry in a bulk material, comprising a slurry conveying unit 1, a permeation test unit 2, and a pressure velocity measuring unit 3.

[0026] like Figure 2As shown, the grout conveying section 1 is used to convey the grout and deliver it to the permeability test section 2. The grout conveying section 1 is a cone-shaped uniform grouting assembly 11 that is wider at the top and narrower at the bottom. The tip of the cone-shaped uniform grouting assembly 11 is located at the bottom as the feed inlet for conveying the grout. This is to prevent the grout from being injected unevenly into the permeability test section 2 due to excessive pressure (to avoid the grout from concentrating and creating a large seepage channel during high-pressure grouting).

[0027] A grout pump 12 is installed at the inlet of the uniform grouting assembly 11, which delivers the grout to the permeation test section 2. Taking into full account the time-varying viscosity characteristics of the grout, the vertical length of the permeation test device is shortened, making it suitable for grouts whose viscosity changes significantly over time.

[0028] like Figure 2 , Figure 3 As shown, the permeation test section 2 has a sleeve structure that runs through the top and bottom, and the lower slurry delivery section 1 is connected to it. Inside the permeation test section 2, there is a pressure sensor (the pressure sensor surrounding the inner wall of the permeation test section is set in the form of a fiber optic pressure measuring ring. The distribution of this fiber optic pressure measuring ring 22 can simultaneously monitor the grouting pressure and slurry seepage time during the grouting test). The fiber optic pressure measuring ring 22 is connected to an external data processor, which makes the data monitoring more accurate.

[0029] This allows us to obtain the uniformity of slurry penetration within the test tube during the permeation test. Simultaneously, porous mesh plates 201 are installed above and below the permeation test section 2, with the mesh aperture of the porous mesh plates 201 being smaller than the minimum particle size of the test fragments. This prevents the test fragments from being carried out of the tube due to slurry seepage (the porous mesh plate aperture is smaller than the minimum particle size of the test fragments).

[0030] The lower part of the permeation test section 2 is provided with a first support column 210 to support the whole.

[0031] like Figure 4 As shown, the barometric pressure measuring unit 3 has a sleeve structure that extends vertically, including a first telescopic cylinder 31 and a second telescopic cylinder 32. The first telescopic cylinder 31 has a double-layer structure, and the upper part of the second telescopic cylinder 32 is fitted into the gap of the double-layer structure of the first telescopic cylinder 31. This arrangement allows the second telescopic cylinder 32 to move up and down relative to the first telescopic cylinder 31 in the direction of the central axis. At this time, the outer wall of the first telescopic cylinder 31 is set to a transparent structure and is provided with annular scale markings, so that the movement state of the upper part of the second telescopic cylinder 32 can be observed through the outer wall of the first telescopic cylinder 31, and the overall movement volume change can be recorded.

[0032] The lower part of the second telescopic cylinder 32 is sealed by the pressure plate 321, so that the upper part of the pressure plate 321, the first telescopic cylinder 31 and the second telescopic cylinder 32 form a sealed air chamber 301. The air pressure pipe 33 set at the top is used to inflate and deflate the air in the air chamber 301 in order to control the pressure value in the area where the air chamber 301 is located.

[0033] A baffle plate 34 extending outward is provided at the lower edge of the air pressure measuring unit 3, and an ear extending downward is provided at the outer edge of the baffle plate 34, so that the baffle plate 34 as a whole covers the outer periphery of the grout outlet of the permeability test unit 2 below. A first support column 210 is provided at the lower part of the permeability test unit 2; a second support column 310 extending downward is provided at the top of the air pressure measuring unit 3, so that the upper opening of the permeability test unit 2 is concentric with the pressure plate 321 at the lower part of the air pressure measuring unit 3, so that the permeability test unit 2 is aligned with the pressure plate 321 at the lower part of the air pressure measuring unit 3 during grouting.

[0034] like Figure 5 , Figure 7 As shown, the method for transient permeation testing of time-varying viscosity slurry in bulk materials includes the following steps: S1. When the permeation test is carried out, the permeation test unit 2 is first fixedly erected. Then, the air pressure measuring unit 3 is erected on the upper part of the permeation test unit 2 and fixed as a whole. The external pumping slurry machine 12 is connected to the inlet of the slurry conveying unit 1 to carry out the slurry conveying operation. At the same time, after the slurry is conveyed by the pumping slurry machine 12, the pressure P1 of the conveyed slurry and the pressure P2 of the discharged slurry monitored by the pressure sensors at the bottom and top of the permeation test unit 2 are fed back to the control center. The slurry mass m is calculated based on the density ρ of the injected slurry.

[0035] S2. Inflate the inflation chamber 301 of the air pressure measuring unit 3 to reach the preset pressure p1 specified under test conditions.

[0036] S3. The slurry injected into the permeation test section 2 is detected by the pressure sensor to change the slurry pressure in the flow state and feedback is given. At the same time, it generates an upward impact force on the pressure plate 321 of the air pressure measuring section 3 located at the top of the permeation test section 2, and simultaneously drives the second telescopic cylinder 32 of the air pressure measuring section 3 to move upward a distance h1-h2, forming a volume change V.

[0037] During the test, the change in gas volume V (i.e., the volume of the compressed part) in the inflation chamber 301 is recorded. In this application, V is measured by observation (observation is only used as an auxiliary measurement tool; this application uses a more accurate numerical control method to calculate the volume data). Alternatively, the change in volume in the inflation chamber 301 can be directly measured by numerical control. At the same time, the instantaneous velocity v of the slurry impacting the pressure plate 321 is calculated based on the above data.

[0038] The real-time slurry outlet velocity can be calculated based on the law of conservation of energy. The calculation formula is as follows: (1) (2) (3) In the formula, E k There are two ways to express the kinetic energy of the slurry, namely, formula (1) = formula (3); m is the mass of the injected grout; v is the instantaneous velocity of the slurry outlet (i.e., the instantaneous velocity of the impact plate 321). ρ is the density of the slurry; V is the volume of the injected grout; E p This refers to the gravitational potential energy of the slurry when it impacts the baffle.

[0039] E 板 Work done by the impact plate to push the rear plate up by gravity (4) In the formula, E 压 The energy required to fill the air in the air-filled cavity 301; p1 and V1 are the original air pressure and volume inside the barometric velocity measuring unit 3; p2 and V2 are the air pressure and volume inside the air pressure measuring unit 3 after the slurry impact.

[0040] (5) (6) In the formula, It is the quality of the impact pressure plate; This is the original length of the barometric velocity measuring unit; The length of the barometric velocity measuring unit after it has been retracted; This is the gravitational acceleration at the Earth's surface.

[0041] Please refer to Table 1 below for details: Table 1 ; at this time, The weight is 50g.

[0042] According to the above formulas (1)-(5), the instantaneous velocity at the grout infiltration outlet can be calculated at any time as the grouting pressure is adjusted; the initial and final pressure values ​​of the test grout are obtained from the pressure sensors installed on the upper and lower sides of the test section, and the transient seepage performance of medium-speed coagulation grout of different granules is obtained according to the instantaneous velocity of the grout, the grout seepage flow rate and the collection amount within a certain time.

[0043] The experiment fully considers the time-varying viscosity of the grout and can simulate the high grouting pressure in actual engineering. A pressure sensor is installed in the pressure pipe to realize the automatic acquisition and analysis of test data, which improves the accuracy of the data and saves the time required for the experiment.

[0044] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A transient permeability testing device for time-varying viscosity slurry in a bulk material, comprising a slurry conveying unit (1) and a permeability testing unit. (2) A barometric velocity measuring unit (3), characterized in that, The slurry conveying section (1) is used for conveying slurry and delivering it to the permeation test section (2). The permeation test section (2) has a sleeve structure that runs through the top and bottom, and the lower part is connected to the slurry conveying section (1). Pressure sensors are provided at the top and bottom of the permeation test section (2). The pressure sensors monitor the pressure of the slurry when it is delivered to the permeation test section (2) and when it leaves the permeation test section (2). At the same time, the upper and lower parts of the permeation test section (2) are respectively provided with perforated mesh plates (201) for covering. The air pressure speed measuring unit (3) includes a first telescopic cylinder (31) and a second telescopic cylinder (32). The first telescopic cylinder (31) has a double-layer structure. The upper part of the second telescopic cylinder (32) is fitted into the gap of the double-layer structure of the first telescopic cylinder (31) and realizes that the second telescopic cylinder (32) moves up and down relative to the first telescopic cylinder (31) in the direction of the central axis. The lower part of the second telescopic cylinder (32) is sealed by a pressure plate (321), so that the upper part of the pressure plate (321) forms a sealed air chamber (301) with the first telescopic cylinder (31) and the second telescopic cylinder (32). The air is filled and released in the air chamber (301) through the air pressure pipe (33) set at the top. The lower part of the permeation test section (2) is provided with a first support column (210); the top of the air pressure measuring section (3) extends downward and is provided with a second support column (310), so that the upper opening of the permeation test section (2) is concentrically arranged with the pressure plate (321) at the lower part of the air pressure measuring section (3). The grout conveying unit (1) is a uniform grouting assembly (11) that is cone-shaped with a wider top and a narrower bottom. The tip of the uniform grouting assembly (11) is located at the bottom as a feed inlet for conveying grout. A grout pump (12) is provided at the feed inlet of the uniform grouting assembly (11).

2. The transient permeation test apparatus for time-varying viscosity slurry in bulk materials according to claim 1, characterized in that, The mesh size of the porous mesh plate (201) is smaller than the minimum particle size of the test fragments in the grout.

3. The transient permeation test apparatus for time-varying viscosity slurry in bulk materials according to claim 1, characterized in that, The lower edge of the air pressure measuring unit (3) is provided with an outwardly extending baffle plate (34), and the outer edge of the baffle plate (34) is provided with a downwardly extending ear, so that the baffle plate (34) as a whole covers the outer periphery of the slurry outlet of the permeation test unit (2) below.

4. The transient permeation test apparatus for time-varying viscosity slurry in bulk materials according to claim 1, characterized in that, The pressure sensing element on the inner wall of the permeation test section (2) is set as an optical fiber pressure measuring ring.

5. The transient permeation test apparatus for time-varying viscosity slurry in bulk materials according to claim 4, characterized in that, The outer wall of the first telescopic cylinder (31) of the air pressure measuring unit (3) is set to a transparent structure and is provided with annular scale markings, so that the movement state of the upper part of the second telescopic cylinder (32) can be observed through the outer wall of the first telescopic cylinder (31).

6. The method of using the transient permeability testing apparatus for time-varying viscosity slurry in bulk materials according to any one of claims 1-5, characterized in that, Includes the following steps: S1. First, fix the permeation test section (2). Then, install the air pressure measuring section (3) on the upper part of the permeation test section (2) and fix it as a whole. Connect the external pump slurry machine (12) to the feed port of the slurry conveying section (1) to carry out slurry conveying operation. At the same time, after conveying through the pump slurry machine (12), the pressure of the conveyed slurry and the pressure of the discharged slurry monitored by the pressure sensor at the bottom and top of the permeation test section (2) are fed back to the control center. S2. Inflate the air chamber (301) of the air pressure measuring unit (3) to reach the preset pressure specified in the test; S3. The slurry injected into the permeation test section (2) is detected by the pressure sensor to change the slurry pressure in the flow state and feedback is given. At the same time, it generates an upward impact force on the pressure plate (321) of the air pressure measuring section (3) located above the permeation test section (2) and simultaneously drives the second telescopic cylinder (32) of the air pressure measuring section (3) to move upward a distance.

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