Vacuum-vertical shaft-electroosmosis combined dehydration test device for waste mud

Abstract

The invention discloses a vacuum-vertical shaft-electroosmosis combined dehydration test device for waste mud, and belongs to the technical field of geotechnical tests. The device is composed of a modular model cylinder, a direct-current power supply system, a measuring system, a vacuum pump and a vertical vacuum drainage body. The model cylinder is formed by connecting a top cylinder, a middle cylinder and a bottom cylinder through bolts and stacking sealing rings, the height can be flexibly adjusted, and good air tightness is kept. And the cylinder side is provided with a standard quick-plug interface, so that a vacuum meter and a pore pressure sensor can be conveniently connected. An anode electrode plate and a cathode electrode plate which are connected with a direct-current power supply are respectively arranged on the top surface and the bottom surface of the slurry, and the vertical vacuum drainage body penetrates through the bottom horizontal drainage layer and is fixed on the positioning frame to form a vacuum-vertical shaft combined drainage channel. The device effectively overcomes the problems of vacuum pressure transmission attenuation, overlong drainage path, non-uniform electroosmosis dehydration and the like through the coupling effect of vacuum, the vertical shaft and electroosmosis, can realize accurate research on different depth dehydration mechanisms of slurry, and has the advantages of rapid dehydration, simplicity and convenience in operation, environmental protection and high efficiency.

Description

[0001] The application belongs to the field of geotechnical experiments and researches, and particularly relates to a waste mud vacuum-shaft-electro-osmosis combined dewatering test device. BACKGROUND

[0002] A large amount of waste mud with high water content and low permeability is generated in pile foundation construction, underground continuous wall slotting and shield tunneling and other engineering activities. If the waste mud is not properly disposed, not only land resources will be occupied, but also serious environmental pollution will be caused. At present, the waste mud is mainly treated by natural airing, mechanical dewatering or chemical solidification, but there are problems of low dewatering efficiency, high energy consumption, large cost or secondary pollution.

[0003] Vacuum preloading method and electro-osmosis method are effective methods for treating soft clay or silt soil, but still face challenges in treating waste mud with extremely high water content. When the vacuum preloading method is used alone, the vacuum pressure is significantly attenuated in the mud, and the effective influencing depth is limited. When the electro-osmosis method is used alone, electrode corrosion, uneven dewatering and edge effect and other phenomena are prone to occur, which affects the overall dewatering effect. In addition, the existing test devices are mostly single-function or fixed size, and it is difficult to flexibly simulate the dewatering process of mud at different depths, and it is also impossible to effectively couple multiple dewatering technologies to study the synergistic mechanism thereof.

[0004] Therefore, it is urgent to develop a test device capable of coupling multiple dewatering mechanisms, highly adjustable, and accurate in measurement, to deeply study the efficient dewatering law and mechanism of waste mud, and to provide theoretical basis and test support for developing economic and environmentally friendly mud treatment technology. SUMMARY

[0005] The application aims to solve the deficiencies and problems in the prior art, and provides a waste mud vacuum-shaft-electro-osmosis combined dewatering test device, which can flexibly adjust the model height under the premise of maintaining good air tightness, integrate a multi-parameter monitoring system, ensure the effective transmission of vacuum pressure and the improvement of drainage efficiency, and thus provide a reliable experimental platform for the dewatering mechanism research of waste mud.

[0006] This invention provides a vacuum-shaft-electroosmosis combined dewatering test device for waste mud. The device mainly includes a model cylinder, a DC power supply system, a vacuum pump, a vertical vacuum drainage body, and a measurement system. The model cylinder adopts a modular assembly structure, consisting of a top cylinder, at least one middle cylinder module, and a bottom cylinder, sealed and stacked together with bolts and sealing rings to form a height-adjustable sealed test space. The side wall of the cylinder is equipped with a standard quick-connect interface for connecting a vacuum gauge and a pore pressure sensor. Inside the bottom cylinder, from bottom to top, a drainage pad, a horizontal annular vacuum drainage pipe, geotextile, a sand pad, filter cloth, and a cathode electrode are laid sequentially. The horizontal annular vacuum drainage pipe has through holes in its wall and is connected to an external vacuum pipeline via a drainage valve. The DC power supply system includes a 0-30V adjustable regulated DC power supply, an anode electrode, and a cathode electrode. The positive terminal of the DC power supply is connected to the anode electrode arranged on the top surface of the mud, and the negative terminal is connected to the cathode electrode buried in the bottom drainage layer, to form a uniform electroosmotic field during the test. The measurement system includes a vacuum gauge, a pore pressure sensor, a stress-strain integrated tester, a water collection bottle, and an electronic scale, which are used to simultaneously monitor key parameters such as the vacuum degree inside the mud, top surface settlement, pore water pressure, and drainage volume.

[0007] Preferably, the model cylinder is made of plexiglass, and the side wall of the cylinder is attached with precise scale strips for real-time observation of changes in mud height; the mud sample is placed inside the cylinder, and its top surface settlement is automatically monitored and recorded by a computer data acquisition system.

[0008] Preferably, the wire connecting the DC power supply to the cathode is led out through an opening in the side wall of the bottom cylinder and sealed with waterproof silicone; the wire connecting the anode is led out through an opening in the top cover and is also sealed with waterproof silicone.

[0009] Preferably, the bottom cylinder is provided with the following components from bottom to top: a drainage pad, a horizontal annular vacuum drainage pipe with through holes, geotextile, a sand pad, a filter cloth, and a cathode electrode plate. The sand pad is 40mm thick standard quartz sand, and the filter cloth is 100-200 mesh.

[0010] Preferably, the vertical vacuum drainage body is a hollow PVC pipe with holes, the pipe wall has through holes, and it is wrapped with a layer of geotextile filter cloth.

[0011] Preferably, the positioning frame is a plate-shaped or frame-type structure with multiple positioning holes. During installation, it is supported on a horizontal drainage pad. Each positioning hole is used to insert and fix the vertical vacuum drainage body to ensure that it maintains the set verticality and spacing during the test.

[0012] Preferably, the horizontal vacuum drain pipe is an annular loop formed by connecting multiple perforated PVC short pipes with elbow joints, and the pipe wall is evenly perforated to efficiently transmit vacuum negative pressure and collect and discharge the seeping pore water.

[0013] Preferably, the vacuum pump is an adjustable vacuum type, and the target negative pressure value can be flexibly set according to the test requirements.

[0014] Preferably, the water collection bottle is made of transparent material and is used in conjunction with an electronic scale with an accuracy of 0.1g to achieve gas-water separation, vacuum stabilization, and real-time monitoring of drainage volume. Pore pressure sensors are deployed at different depths to reveal the pressure transmission characteristics under vacuum-shaft-electroosmosis conditions.

[0015] Compared with existing technologies, this invention significantly improves the efficiency and scientific research value of waste mud dewatering experiments through multiple structural and methodological innovations. Specifically, the modular combination structure consisting of a top cylinder, middle cylinder, and bottom cylinder allows for flexible adjustment of the model height according to experimental needs, greatly expanding the adaptability of the device to mud conditions at different depths. Rubber sealing rings and sealing materials are installed at the connections of each cylinder, effectively ensuring the airtight stability of the system under long-term negative pressure conditions, fundamentally avoiding interference from vacuum leakage on the experimental results. The coordinated arrangement of the horizontal annular vacuum drain pipe and electrode plates significantly shortens the drainage path and enhances the efficiency of vacuum pressure transmission in the mud. Experimental data shows that the dewatering efficiency is optimal when vertical drain bodies are arranged around the mud, followed by those in the center; both methods significantly outperform the conventional method without vertical drain bodies. In addition, this device integrates three functional modules: vacuum preloading, vertical well drainage, and electroosmosis. By removing the vertical drainage body or turning off the vacuum pump, it can easily carry out single-method or combination experiments of any two methods. It provides a fully functional and flexible experimental platform for systematically studying the independent effects and synergistic effects of different dehydration mechanisms, and has important theoretical research value and engineering application prospects. Attached Figure Description

[0016] Figure 1 A schematic diagram of the structure of the present invention.

[0017] Figure 2 A schematic diagram of a ring-shaped vacuum drainage pipe laid horizontally in the lower cylinder.

[0018] Figure 3 Enlarged view of the bottom of the lower cylinder.

[0019] Figure 4 Schematic diagram of the slotted opening of the vertical vacuum drainage body positioning frame.

[0020] Figure 5 Schematic diagram of the electrode sheet.

[0021] The diagram shows the following labels: 1-Drainage cushion layer; 2-Horizontal annular vacuum drainage pipe; 3-Geotextile; 4-Sand cushion layer; 5-Filter cloth; 6-Pumping valve; 7-Bottom cylinder; 8-Annular rubber ring; 9-Middle cylinder; 10-Pore pressure sensor quick-connect interface; 11-Pore pressure sensor; 12-Vacuum gauge quick-connect interface; 13-Bolt; 14-Vacuum gauge; 15-Vertical vacuum drainage body; 16-Top cylinder; 17-Electronic scale; 18-Water collection bottle; 19-Vacuum pump; 20-6mm inner diameter PU air tube; 21-Data transmission line; 22-Stress-strain comprehensive tester; 23-Computer; 23b-Electronic camera. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0023] Example 1

[0024] The specific implementation method of a waste mud vacuum-shaft-electroosmosis combined dewatering test device is as follows:

[0025] 1. Device Assembly

[0026] Determine the number of middle cylinder modules based on the required mud depth for the experiment. Place the bottom cylinder on a horizontal base, install the sealing ring, and then stack the middle cylinder modules and top cylinder in sequence, securing them together with high-strength bolts to ensure the airtightness of the model cylinder. Check the integrity of the standard quick-connect interfaces on the side walls of the cylinder.

[0027] 2. Drainage system and electrode arrangement

[0028] The bottom cylinder is arranged from bottom to top as follows: (i) a crushed stone drainage pad layer with a thickness of approximately 30 mm and a particle size of 20–50 mm; (ii) a horizontal annular vacuum drainage pipe formed by splicing perforated PVC short pipes with elbows; (iii) a layer of geotextile; (iv) a standard quartz sand pad layer with a thickness of approximately 40 mm; (v) a 100–200 mesh filter cloth; (vi) a cathode electrode plate (stainless steel mesh); (vii) a vertical vacuum drainage body wrapped with geotextile filter cloth, fixed to the center of the cylinder by a positioning frame, with its lower end inserted into the drainage layer and its upper end connected to the vacuum system. The anode electrode plate (stainless steel plate) is placed on the top surface of the mud, forming an electric field with the cathode electrode plate.

[0029] 3. Sample preparation and loading

[0030] Slowly inject a uniform slurry with a water content of approximately 150% into the mold cylinder, filling it to the predetermined height, avoiding the formation of air bubbles, and then smooth the surface.

[0031] 4. Measurement and Control System

[0032] The device is equipped with a digital vacuum gauge (range -100 to 0 kPa), a pore water pressure sensor (range 0 to 200 kPa), a displacement sensor (for monitoring sedimentation), a water collection bottle, and an electronic scale (accuracy 0.1 g). A DC power supply (DPS-305 type, adjustable output 0 to 30V) is used to power the cathode and anode electrodes. The cathode wire is led out through an opening in the side wall of the cylinder, and waterproof silicone is used to seal the contact points to prevent leakage.

[0033] 5. Test conditions and data acquisition

[0034] This device can support vacuum dewatering alone, electroosmotic dewatering alone, combined vacuum-electroosmotic dewatering, and combined shaft-electroosmotic dewatering. During the experiment, vacuum degree-time curves, pore water pressure dissipation curves, settling-time curves, and drainage-time curves can be collected to analyze the mud dewatering efficiency and consolidation performance.

[0035] Example 2: Standalone vacuum dehydration condition

[0036] Based on Example 1, the vacuum pump was turned on to maintain a negative pressure of -80 kPa in the system, and the DC power supply was turned off. The consolidation characteristics of the mud under vacuum alone were evaluated by collecting the changes in vacuum degree, pore water pressure, and sedimentation over time through the measurement system.

[0037] Example 3: Electroosmotic Dehydration Operation Only

[0038] Based on Example 2, a 15V DC power supply was used, and the vacuum pump was turned off. Changes in pore water pressure, sedimentation, and drainage volume over time were monitored to analyze the mud dewatering performance under electroosmosis alone.

[0039] Example 4

[0040] Based on Example 1, this example employs a combined vacuum-electroosmosis dewatering process. A vacuum pump generates a negative pressure of -80 kPa, while a DC power supply applies a 15V voltage to the anode and cathode electrodes. A measurement system simultaneously collects curves for vacuum level, pore water pressure, sedimentation, and drainage volume to compare the dewatering efficiency differences between the combined and individual dewatering conditions.

[0041] Example 5

[0042] Based on Example 1, this example employs a combined vertical well-electroosmosis dewatering process. The vertical vacuum drainage body and the top anode electrode plate operate simultaneously, with a 15V DC power supply output. A vacuum pump acts on the vertical drainage body to create negative pressure. Settlement, pore water pressure, and drainage volume data are collected through a measurement system to analyze the dewatering effect of the combined vertical well drainage and electroosmosis.

[0043] Example 6

[0044] Based on Example 1, this example adjusts the parameters of the drainage cushion layer and sand cushion layer, specifically including: setting the thickness of the crushed stone drainage cushion layer to 20-40 mm and maintaining the particle size at 20-50 mm; adjusting the thickness of the quartz sand cushion layer to 30-50 mm; and using 100-200 mesh filter cloth. Simultaneously, the DC power supply output voltage is adjustable within the range of 5-30V. By collecting data on settlement, pore water pressure, and drainage volume under different parameter combinations, the system analyzes the optimization effect of each parameter on mud dewatering efficiency and settlement control, providing a basis for parameter selection in practical engineering.

[0045] Example 7

[0046] Based on Example 1, this example uses a mud moisture content of approximately 120% and conducts experiments under different working conditions (vacuum alone, electroosmosis alone, and combined working conditions) to collect data on the changes in sedimentation, pore water pressure, and drainage over time, in order to analyze the consolidation characteristics of low moisture content mud under different working conditions.

[0047] Example 8

[0048] Based on Example 1, this example uses a mud moisture content of approximately 180%. By comparing the changes in settling rate and drainage volume of mud with different moisture contents under the same working conditions, the influence of mud moisture content on dewatering efficiency and consolidation performance is evaluated.

[0049] Example 9

[0050] Based on Example 1, this example changes the DC power supply output voltage to 5-30V and compares the mud electroosmosis dewatering effect under different voltages (5, 10, 15, 20, 25, 30V).

[0051] Example 10

[0052] Based on Example 1, this example adjusts the vacuum pump output negative pressure to -50kPa, -80kPa, and -100kPa, and conducts individual vacuum and combined working condition tests to evaluate the effects of different vacuum intensities on mud consolidation rate and drainage efficiency.

[0053] Example 11

[0054] Based on Example 1, this example adjusts the number and diameter of the vertical vacuum drainage bodies (1 to 3) and analyzes the influence of the arrangement of the vertical drainage bodies on the mud dewatering efficiency and consolidation uniformity.

[0055] Example 12

[0056] Based on Example 1, this example changes the cathode electrode material (stainless steel mesh or graphite sheet) for comparative experiments to analyze the effects of different cathode materials on electroosmotic dewatering efficiency and mud consolidation rate.

[0057] Example 13

[0058] Based on Example 1, this example focuses on the effect of the anode electrode size on the electroosmotic dehydration effect. This is achieved by changing the area of ​​the anode electrode (200–400 cm²). 2 The uniformity of the electroosmotic field distribution, dewatering efficiency, and mud consolidation rate under electrode sheets of different sizes (1–3 mm) were systematically tested. Other parameters were kept consistent throughout the experiment. By comparing the drainage-time curves and the final settling volume, the influence of anode size changes on electroosmotic dewatering performance was evaluated, providing experimental basis for electrode optimization design.

[0059] Example 14

[0060] Based on Example 1, this example changes the filter cloth material and pore size (polyester or polypropylene, pore size 50-200 mesh) and analyzes the influence of filter cloth parameters on the uniformity of mud drainage and consolidation effect.

[0061] Example 15

[0062] Based on Example 1, this example changes the composition of mud particles (30%, 50%, and 70% fine particles) to analyze the effect of mud particle composition on dewatering efficiency under different working conditions.

[0063] Example 16

[0064] Based on Example 1, this example adjusts the layout combination of vertical vacuum drainage body and horizontal drainage pipe (such as single vertical shaft + multiple ring horizontal pipe, double vertical shaft + single ring horizontal pipe) and analyzes the influence of drainage layout on dewatering efficiency and consolidation uniformity.

[0065] Example 17

[0066] Based on Example 1, this example combines mud moisture content, voltage, vacuum strength, electrode arrangement, filter cloth combination and number of vertical drainage bodies to conduct multiple combination tests, analyze the sedimentation, pore water pressure and drainage data under different combinations, and optimize the dewatering conditions.

[0067] Example 18

[0068] Based on Example 1, this example uses high water content mud (approximately 160%), power supply voltage 25V, vacuum -100kPa, 3 vertical drainage bodies, and a combination of double-ring horizontal drainage pipes to analyze the mud consolidation rate and drainage efficiency.

[0069] Example 19

[0070] Based on Example 1, this example uses a combination of low vacuum intensity (-50kPa), power supply voltage of 10V, and single vertical shaft and single ring horizontal drainage pipe to analyze the changes in mud consolidation performance and drainage efficiency under low-intensity combined dewatering conditions.

[0071] Example 20

[0072] Based on Example 1, this example uses a combination of 100-mesh polyester upper filter cloth and 150-mesh polypropylene lower filter cloth to analyze the optimization effect of the filter cloth combination on the uniformity of mud drainage and the consolidation effect.

[0073] Example 21

[0074] Based on Example 1, this example uses a segmented cathode electrode arrangement (each segment having an area of ​​100 cm²). 2 The effect of segmented arrangement (with a spacing of 5 mm) on improving the uniformity of electroosmotic field distribution and dewatering efficiency was analyzed.

[0075] Example 22

[0076] Based on Example 1, this example comprehensively adjusts the mud moisture content, power supply voltage, vacuum intensity, electrode arrangement, filter cloth combination, and number of vertical drainage bodies to form the optimal combination working conditions, and analyzes the conditions for achieving rapid mud consolidation and maximizing drainage efficiency.

[0077] It should be understood that the above embodiments are merely typical implementations listed to clearly illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. For those skilled in the art, various modifications, substitutions, or improvements made to the form and details of the technical solutions described in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the claims.

Claims

1. A waste mud vacuum-shaft-electroosmosis combined dewatering test device, characterized in that: The system includes a model cylinder, a DC power supply system, a measurement system, a vacuum pump, and a vertical vacuum drainage system. The model cylinder adopts a modular assembly structure, consisting of a top cylinder, at least one middle cylinder module, and a bottom cylinder, which are sealed and stacked together with bolts and sealing rings to form a height-adjustable sealed test space. The cylinder sidewalls are equipped with standard quick-connect interfaces for connecting vacuum gauges and pore pressure sensors. The bottom cylinder's interior is laid with, from bottom to top, a drainage pad, a horizontal annular vacuum drainage pipe, geotextile, a sand pad, filter cloth, and cathode electrode plates. The DC power supply system includes a DC power supply, an anode electrode plate, and a cathode electrode plate. The anode electrode plate is positioned on the top surface of the mud, and the cathode electrode plate... The electrode plates are embedded in the bottom drainage layer. The positive and negative terminals of the DC power supply are connected to the anode and cathode electrode plates, respectively, to form an electroosmotic field during the experiment. The horizontal annular vacuum drainage pipe has uniformly distributed through holes in its wall and is connected to the external vacuum pipeline through a drainage valve. The bottom of the vertical vacuum drainage body extends to the horizontal vacuum drainage layer, forming a combined vacuum-shaft drainage channel. The measurement system includes a vacuum gauge, a pore pressure sensor, a stress-strain integrated tester, a water collection bottle, an electronic scale, a computer, and an electronic camera, used to monitor the changes in the vacuum degree inside the mud, the top surface settlement, the pore water pressure, and the drainage volume in real time.

2. The apparatus as described in claim 1, characterized in that: The model cylinder is made of plexiglass. The top and bottom end faces of the middle cylinder module are provided with grooves and bolt holes for installing sealing rings and achieving airtight connection. The sealing rings are made of silicone or nitrile rubber.

3. The apparatus as described in claim 1, characterized in that: The DC power supply is a DPS-305 type, a regulated DC power supply with an adjustable output voltage range of 0 to 30V.

4. The apparatus as described in claim 3, characterized in that: The DC power supply is connected to the negative electrode plate on the lower side of the mud by a wire, which is led out of the barrel through a hole in the side wall of the bottom cylinder. Waterproof silicone is used to seal the contact point between the wire and the barrel wall to prevent leakage from affecting the test results.

5. The apparatus as described in claim 3, characterized in that: The DC power supply is connected to the wires of the anode electrode plates on the upper side of the mud. The wires are left inside the drum and led out of the drum through an opening in the top cover of the top drum. Waterproof silicone is used to seal the contact point between the wires and the top cover of the top drum.

6. The apparatus as claimed in claim 1, characterized in that: The vertical vacuum drainage body is covered with geotextile filter cloth and fixed by an plexiglass positioning frame. The positioning frame is a circular frame structure with through holes for positioning the drainage body.

7. The apparatus as claimed in claim 1, characterized in that: The vacuum pump is an adjustable vacuum pressure pump, connected to the water collection bottle via pipeline, used to provide negative pressure and achieve gas-water separation. The vacuum gauge is a digital or pointer type vacuum gauge, and the pore pressure sensor is a miniature pore water pressure sensor. Both are installed and sealed via quick-connect interfaces. The pore pressure sensors are placed at different depths to reveal pressure transmission characteristics.

8. The apparatus as claimed in claim 1, characterized in that: The water collection bottle is made of transparent material and has two quick-connect connectors on the top. It is connected to the vacuum pump and the model cylinder respectively through PU air tubes, and the bottom is placed on an electronic scale to achieve real-time weighing.

9. The apparatus as claimed in claim 1, characterized in that: The sand cushion layer uses standard quartz sand with a particle size of 0.5-1mm and a thickness of 40mm.

10. The apparatus as claimed in claim 1, characterized in that: The computer is equipped with data acquisition and processing software, which is used to display, record and output the curves of change of vacuum degree, pore water pressure and dewatering quality over time in real time, and an electronic camera is used to monitor the surface image of the mud.

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