A method for electroosmosis dehydration of sludge in geobag dams and a method for calculating the dehydration amount

Abstract

This invention provides a method for electro-osmotic dewatering of silt in geotextile ring-shaped dams and a method for calculating the dewatering volume, comprising: Step 1. Laying a drainage layer; Step 2. Filling conductive and non-conductive geotextile ring bags with fine sand; Step 3. Stacking conductive and non-conductive geotextile ring bags alternately and laying electrodes; Step 4. Injecting silt into the dam; Step 5. Performing electro-osmotic dewatering on the silt in the dam; Step 6. After achieving the expected dewatering effect, removing the geotextile ring bags and removing the dewatered silt. This invention uses a method of stacking ring-shaped geotextile ring bags to form a dam for electro-osmotic dewatering of silt, which requires less land, saves space, and fully utilizes the self-weight of the silt; the automated control power supply and the cyclic power supply method can rationally allocate power consumption; at the same time, the product formed after the silt is electro-osmotically consolidated can be bagged and used in other engineering constructions, greatly improving resource utilization efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering design, and in particular to a conductive annular tube bag dam sludge electroosmosis dehydration method and a dehydration amount calculation method thereof. Background Art

[0002] Rivers, lakes and reservoirs are the arteries of my country's social and economic development and important components of the ecosystem. Every year, hundreds of millions of cubic meters of high-water content silt are dredged from rivers, lakes and reservoirs. However, the current sludge treatment methods have shortcomings to varying degrees, such as lack of sludge storage space and insufficient treatment capacity. The ecological storage, low-carbon reduction and resource utilization of sludge are the key to promoting pollution reduction and carbon reduction in my country and synergistic efficiency improvement, and are an important issue facing river basin ecological protection.

[0003] At present, tailings dams are rarely used to store dredged sediment from rivers, lakes and reservoirs. On the one hand, tailings dams are costly and have many safety hazards. On the other hand, the construction of tailings dams requires the use of natural valleys or depressions as silt storage reservoirs. Therefore, when there are no valleys, depressions or lakes in the nearshore areas of rivers, lakes and reservoirs, some people use embankments to store sediment, but the safety hazards are greater. In recent years, there are many tube bag dams or embankment projects built at home and abroad using strip tube bags filled with silt or sand. They have the advantages of permeability, soil conservation, convenient construction and low cost. However, tube bag dams / embankments mainly rely on the friction between tube bag layers and between tube bags and foundations to maintain their own stability, and cannot give full play to the tensile strength of tube bag fabrics, making the design section of tube bag dams / embankments very large, resulting in waste of resources. Large-scale dredging of sediment not only occupies a large amount of land, but also has high environmental risks, so they should be quickly reduced and then used. The existing "dehydration and consolidation integration" technology at home and abroad usually requires the addition of flocculants, which is neither environmentally friendly nor costly. The vacuum preloading method commonly used in soft foundation reinforcement is slow or even ineffective for silt with extremely low hydraulic permeability coefficients.

[0004] Therefore, a new method for large-scale storage and rapid reduction of dredged sediment from rivers, lakes and reservoirs is needed, which can make full use of the tensile properties of the annular tube bag and the high efficiency and environmental protection characteristics of the electroosmotic dehydration technology. This conductive annular tube bag electroosmotic dehydration method for dam sludge should ensure the economic cost of the device, the stability and safety of normal operation. At the same time, it is also necessary to derive a theoretical calculation formula for the electroosmotic drainage per unit time applicable to this method to estimate the dehydration effect. Summary of the invention

[0005] The present invention provides a sludge dewatering method based on a conductive annular tube bag dam electroosmosis device, which can not only achieve rapid dehydration of sludge and effective removal of heavy metal ions, but also the sludge can be used as bagged soil for engineering after electroosmotic dehydration and solidification, which can greatly save the time and space occupied by the sludge. At the same time, the present invention also provides a calculation formula for the electroosmotic drainage per unit time corresponding to the electroosmotic method.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for electroosmotic dehydration of geotextile ring bag dam sludge, comprising the following steps:

[0008] Step 1. Lay an impermeable membrane on the foundation, set vertical pillars on the impermeable membrane, and then lay a drainage layer;

[0009] Step 2. Fill the conductive geotextile ring bag and the non-conductive geotextile ring bag with fine sand;

[0010] Step 3. Stack the conductive geotextile ring bags and the non-conductive geotextile ring bags in sequence, and arrange drainage boards between each layer of geotextile ring bags; insert a vacuum drainage pipe in the center of the dam formed by stacking annular tube bags, and arrange electrodes on the side walls, and arrange multiple plastic electrodes in a circular manner in the middle of the line connecting the inner side of the geotextile ring bag in the dam and the drainage pipe; the electrodes on the side walls of the drainage pipe and the conductive geotextile ring bags are connected to the cathode of the automatic control power supply; multiple plastic electrodes are arranged in a circular manner in the dam and connected to the anode of the automatic control power supply;

[0011] Step 4. Injecting silt into the dam;

[0012] Step 5. 1 to 3 hours after the injection of the sediment is completed, the automatic control power supply is turned on to perform electroosmotic dehydration on the sediment in the dam, and the power is turned off after a period of time;

[0013] Step 6. After achieving the desired dewatering effect, remove the geotube bag and remove the dewatered sludge.

[0014] Furthermore, the outer ring of the conductive geotextile ring bag is provided with a conductive plastic drainage board, the outer surface of the drainage board is woven with woven geotextile, and the outer ring of the non-conductive geotextile ring bag is provided with a non-conductive drainage board.

[0015] Furthermore, the electrodes are arranged on the side wall of the vacuum drainage pipe specifically by arranging a circle of conductive plastic at intervals on the vacuum drainage pipe.

[0016] Furthermore, the automatic control power supply increases the voltage during the electroosmosis process as the moisture content of the sediment decreases, with the voltage varying in the range of 20-60V, so as to maintain the stability of the electroosmotic dehydration effect.

[0017] Furthermore, in step 4, the dredged silt is injected into the top of the dam formed by the annular tube bag. The injection is stopped when the silt reaches the top of the dam. The silt gradually rises, causing its internal pressure to gradually increase. Part of the water contained in the silt is discharged, and the liquid level in the dam gradually decreases. At this time, the silt is repeatedly injected into the dam, and this is repeated 3-5 times.

[0018] Furthermore, when power is cut off in step 5, the plastic electrode is short-circuited with the conductive geotextile ring bag and the electrode on the side wall of the drainage pipe to discharge the charge, and the machine is controlled to beat the silt in the dam when power is cut off.

[0019] In another aspect, the present invention provides a method for calculating the amount of electroosmotic dehydration of sludge in annular bag-tube dam, comprising:

[0020] Step 1: Calculate the electrical energy density in the mud:

[0021] VIt

[0022] Among them, E f is the electric energy density in the mud, V is the power supply voltage, I is the current density in the mud, and t is the power-on time;

[0023] Step 2: Calculate the energy density of the mud:

[0024]

[0025] Among them, E s is the energy density of the mud, p c is the initial consolidation pressure of the mud, p is the stress function along the compression curve, C c is the mud compression index, e c is the porosity of the mud under the initial consolidation pressure, e0 is the initial porosity of the mud, C s is the mud rebound index;

[0026] Step 3: Calculate the distribution function of regional electroosmotic dehydration per unit time:

[0027]

[0028] in is the distribution function of regional electroosmotic dehydration per unit time, k qx is the mud electroosmotic coefficient; is the partial derivative; x is the direction vector along the line connecting the drain pipe side wall electrode and the plastic electrode;

[0029] Step 4, integrating the distribution function of regional electroosmotic dehydration per unit time: dividing the annular sludge into n equal parts, wherein the number of annular sludge equal parts is equal to the number of annularly arranged multiple plastic electrodes, taking the center of the dam as the center of the circle and the distance between the annularly arranged electrodes and the center of the dam as the radius, the fan-shaped area formed is the S1 area, taking the annularly arranged electrodes as the center of the circle and the distance between the annularly arranged electrodes and the inner circle of the dam as the radius, the fan-shaped area formed is the S2 area;

[0030] Discharge per unit time The calculation formula is expressed as:

[0031]

[0032] Among them, E f1 is the electric energy density in the mud in the S1 region, E s1 is the energy density of the mud in the S1 region, E f2 is the electric energy density in the mud in the S2 region, E s2 is the energy density in the mud in the S2 region, S1 is the area of ​​the S1 region, S2 is the area of ​​the S2 region, S1 is the electric field influence area formed by the plastic electrode and the vacuum drainage pipe, S2 is the electric field influence area formed by the plastic electrode and the annular tube bag, and d is the differential;

[0033] Step 5: Sum the dehydration amount per unit time obtained in each calculation time period to obtain the total dehydration amount:

[0034]

[0035] Where q represents the total dehydration amount and ∑ is the summation symbol.

[0036] Furthermore, the areas of the S1 region and the S2 region are respectively:

[0037]

[0038] Where r is the distance from the drain pipe to the inside of the annular pipe bag.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The above-mentioned conductive annular tube bag dam sludge electroosmotic dehydration method, on the one hand, adopts an electrode arrangement form of cathodes on both sides and multiple anodes in the center, which is conducive to the uniform distribution of electric energy in the sludge and greatly improves the electroosmotic dehydration speed. On the other hand, the interlayer arrangement of electrodes and the automatically controllable power supply can give full play to the drainage effect brought by the dead weight of water, and at the same time can timely adjust the power output power of the power supply according to the real-time state of the electric field distribution in the sludge to achieve the purpose of saving energy and improving energy utilization efficiency. At the same time, the electroosmotic dehydration amount calculation formula proposed in the present invention can quickly estimate the dehydration effect of the device under specific working conditions, so as to adjust and improve the construction plan in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 4 is a cross-sectional view of a geotextile ring bag according to an embodiment of the present invention.

[0043] Figure 2 Schematic diagram of an annular tube bag according to an embodiment of the present invention.

[0044] Figure 3 Schematic diagram of an overall device according to an embodiment of the present invention.

[0045] Figure 4 FIG. 4 is a diagram showing electrode distribution and calculation area division according to an embodiment of the present invention.

[0046] Figure 5 1 is a comparison chart of calculation results and test results according to an embodiment of the present invention.

[0047] Among them, 1-annular tube bag, 2-plastic electrode, 3-vacuum drainage pipe, 4-automatic control power supply, 5-electric field influence area S1 formed by the plastic electrode and the vacuum drainage pipe, 6-electric field influence area S2 formed by the plastic electrode and the annular tube bag. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1

[0050] This embodiment provides a method for electroosmotic dehydration of geobag dam sludge, comprising the following steps:

[0051] (1) Laying the drainage layer: Lay an impermeable membrane on a flat foundation, set vertical pillars on the impermeable membrane, and then lay the drainage layer.

[0052] The drainage layer is set to a rectangle with an area larger than the horizontal geotube bag. It is composed of graded particles with good permeability and hardness. Drainage pipes are arranged around the drainage layer to collect the escaped water and discharge it into the river or sewage treatment plant.

[0053] (2) Filling the annular geotube bag: Fill the conductive geotube bag and the non-conductive geotube bag with fine sand to make the filling degree of the geotube bag reach about 80%, forming a circular ring with an outer diameter of about 3m, an inner diameter of about 2m, and a height of about 0.4m. Figure 1 and Figure 2 .

[0054] (3) Combine geotubes and lay electrodes: refer to Figure 3 . Stack the filled conductive geo-ring bags and non-conductive geo-ring bags in the order of conductive, non-conductive, conductive, and non-conductive, and arrange a circle of drainage boards between each layer of geo-ring bags. Insert a vacuum drainage pipe in the center of the dam formed by the stacked annular tube bags and arrange electrodes at the corresponding positions above. n plastic electrodes are evenly arranged in the circular area formed by the point in the middle of the line connecting the inner side of the geo-ring bag and the drainage pipe. The electrodes on the side wall of the drainage pipe and the conductive geo-ring bag are connected to the cathode of the automatic control power supply; multiple plastic electrodes are arranged in a ring inside the dam and connected to the anode of the automatic control power supply.

[0055] The drainage boards between each layer of bags are inserted through the annular tube bags into the sludge inside the ring and fixed by the deadweight of the annular tube bags. The water generated by electroosmosis can flow out to the drainage layer through the drainage boards.

[0056] (4) Injecting silt: The dredged silt is injected into the top of the dam formed by the annular tube bag. When the silt reaches the top of the dam, the injection is stopped. The silt gradually rises, causing its internal pressure to gradually increase. Part of the water contained in the silt is discharged, and the liquid level in the dam gradually decreases. At this time, the silt is repeatedly injected into the dam, and this is repeated 3-5 times.

[0057] (5) Electro-osmotic dehydration: 1 to 3 hours after the last injection, turn on the power supply to perform electro-osmotic dehydration on the sediment in the dam. The power supply is turned on for 10 hours and then off for 10 hours. When the power is off, the positive and negative electrodes are short-circuited to discharge the charge. When the power is off, the machine can be controlled to beat the silt in the ring to accelerate dehydration and make the sediment more evenly distributed, making it easier to carry out subsequent electrical dehydration.

[0058] When performing electro-osmosis dehydration, it is necessary to repeatedly inject silt. When water flows out from the drainage board and the drainage layer, the liquid level will drop. At this time, the silt is repeatedly injected. Repeat the injection 3 to 5 times. There is no need to power on before the dam is full. When the last injection of silt is completed 1 to 3 hours later, start to turn on the power. The voltage adjustment range is 20 to 80V to keep the current in the silt at around 20A.

[0059] (6) Disassembly of geotube bags: The sludge in the ring is dehydrated, reduced in volume and solidified into a solid under the action of electroosmosis and natural gravity. After the expected dehydration effect is achieved, the power supply is disconnected and the ring-shaped geotube bags are pulled up one by one using machinery to separate them from the sludge solids.

[0060] (7) Removing solids and bagging: Use machinery to pack the dehydrated sludge into woven bags to form bagged soil, which is used in projects such as embankments, roadbeds or retaining walls.

[0061] Example 2

[0062] This embodiment provides a method for calculating the amount of electroosmotic dehydration of sludge in an annular bag-tube dam, comprising:

[0063] Step 1: Calculate the electrical energy density in the mud:

[0064] VIt

[0065] Among them, E f is the electric energy density in the mud, V is the power supply voltage, I is the current density in the mud, and t is the power-on time;

[0066] Step 2: Calculate the energy density of the mud:

[0067]

[0068] Among them, E s is the energy density of the mud, p c is the initial consolidation pressure of the mud, p is the stress function along the compression curve, C c is the mud compression index, e c is the porosity of the mud under the initial consolidation pressure, e0 is the initial porosity of the mud, C s is the mud rebound index;

[0069] Step 3: Calculate the distribution function of regional electroosmotic dehydration per unit time:

[0070]

[0071] in is the distribution function of regional electroosmotic dehydration per unit time, k qx is the mud electroosmotic coefficient; is the partial derivative; x is the direction vector along the line connecting the drain pipe side wall electrode and the plastic electrode;

[0072] Step 4: Integrate the distribution function of electroosmotic dehydration per unit time area: Figure 4 , which is the distribution of device electrodes and the calculation area division diagram, where 1 is the annular tube bag, 2 is the plastic electrode, 3 is the vacuum drainage pipe, 5 is the electric field influence area S1 formed by the plastic electrode and the drainage pipe, and 6 is the electric field influence area S2 formed by the plastic electrode and the annular tube bag.

[0073] The annular sludge is divided into n equal parts, where the number of annular sludge equals the number of annularly arranged plastic electrodes. The fan-shaped area formed by the center of the dam as the center and the distance between the annularly arranged electrodes and the center of the dam as the radius is the S1 area, and the fan-shaped area formed by the annularly arranged electrodes as the center and the distance between the annularly arranged electrodes and the inner circle of the dam as the radius is the S2 area.

[0074] Discharge per unit time The calculation formula is expressed as:

[0075]

[0076] Among them, E f1 is the electric energy density in the mud in the S1 region, E s1 is the energy density of the mud in the S1 region, E f2 is the electric energy density in the mud in the S2 region, E s2 is the energy density in the mud in the S2 region, S1 is the area of ​​the S1 region, S2 is the area of ​​the S2 region, S1 is the area of ​​the S1 region, S2 is the area of ​​the S2 region, S1 is the electric field influence area formed by the plastic electrode and the vacuum drainage pipe, S2 is the electric field influence area formed by the plastic electrode and the annular tube bag, and d is the differential;

[0077] Step 5: Sum the dehydration amount per unit time obtained in each calculation time period to obtain the total dehydration amount:

[0078]

[0079] Where q represents the total dehydration amount and ∑ is the summation symbol.

[0080] Furthermore, the areas of the S1 region and the S2 region are respectively:

[0081]

[0082] Where r is the distance from the drain pipe to the inside of the annular pipe bag.

[0083] Take the normally consolidated saturated soil with a moisture content of 60%, a wet density of 1.528g / cm3, a dry density of 0.981g / cm3, an electrical permeability coefficient of 4.857×10-6g / cm3, an initial porosity of 1.6, a compression coefficient of 0.1824, and an initial consolidation pressure of 30kpa as an example, and take the unit calculation time as 10h and the number of anode electrodes n as 3 for explanation.

[0084] See Figure 5 The calculation results obtained by this calculation method when the number of plastic electrodes is 3 are shown in the following table, and the results are highly consistent with the experimental results.

[0085]

[0086]

[0087] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0088] It should be understood that the above description of the preferred embodiment is relatively detailed, and it cannot be considered as limiting the scope of protection of the patent of the present invention. It is not necessary and impossible to list all the embodiments here. Under the enlightenment of the present invention, ordinary technicians in this field can also make substitutions or modifications without departing from the scope of protection of the claims of the present invention, which all fall within the scope of protection of the present invention. The scope of protection of the present invention shall be based on the attached claims.

Claims

1. A method for calculating the dehydration amount of geobag dam sludge electroosmosis dehydration, characterized in that: The dehydration amount is calculated based on the conductive annular tube bag dam sludge electroosmosis dehydration method, and the conductive annular tube bag dam sludge electroosmosis dehydration method includes: Step 1. Lay an impermeable membrane on the foundation, set vertical pillars on the impermeable membrane, and then lay a drainage layer; Step 2. Fill the conductive geotextile ring bag and the non-conductive geotextile ring bag with fine sand; Step 3. The conductive geotextile ring bags and the non-conductive geotextile ring bags are stacked in sequence, and interlayer drainage boards are arranged between each layer of geotextile ring bags; a vacuum drainage pipe is inserted into the center of the dam formed by stacking annular tube bags, and electrodes are arranged on the side walls, and multiple plastic electrodes are arranged in a circular manner in the middle of the line connecting the inner side of the geotextile ring bag in the dam and the drainage pipe; the electrodes on the side walls of the drainage pipe and the conductive geotextile ring bag are connected to the cathode of the automatic control power supply; and the multiple plastic electrodes arranged in a circular manner in the dam are connected to the anode of the automatic control power supply; Step 4. Injecting silt into the dam; Step 5. 1 to 3 hours after the injection of the sediment is completed, the automatic control power supply is turned on to perform electroosmotic dehydration on the sediment in the dam, and the power is turned off after a period of time; Step 6. After achieving the desired dewatering effect, remove the geotube bag and remove the dewatered sludge; The dehydration amount calculation method comprises: Step 1: Calculate the electrical energy density in the mud: in, is the electric energy density in the mud, V is the power supply voltage, I is the current density in the mud, and t is the power-on time; Step 2: Calculate the energy density of the mud: in, is the energy density of the mud, is the initial consolidation pressure of the mud, is the stress function along the compression curve, is the mud compression index, is the porosity ratio of the mud under the initial consolidation pressure, is the initial porosity of the mud, is the mud rebound index; Step 3: Calculate the distribution function of regional electroosmotic dehydration per unit time: in is the distribution function of electroosmotic dehydration per unit time area, is the mud electroosmotic coefficient; is the partial derivative; is the direction vector along the line connecting the drain pipe side wall electrode and the plastic electrode; Step 4: Integrate the electroosmotic dehydration distribution function: divide the annular sludge into n Block, where the number of annular sludge equals the number of annularly arranged multiple plastic electrodes, Dehydration per unit time The calculation formula is expressed as: in, is the electric energy density in the mud in the S1 region, is the energy density in the mud in the S1 region, is the electric energy density in the mud in the S2 region, is the energy density in the mud in the S2 region, is the area of ​​S1, is the area of ​​S2, S1 is the area affected by the electric field formed by the plastic electrode and the vacuum drain pipe, S2 is the area affected by the electric field formed by the plastic electrode and the annular tube bag, is the differential; Step 5: Sum the dehydration amount per unit time obtained in each calculation time period to obtain the total dehydration amount: in, Indicates the total dehydration amount, is the summation symbol.

2. The method for calculating the dehydration amount of geobag dam sludge electroosmosis dehydration according to claim 1 is characterized in that: The areas of the S1 region and the S2 region are: , in, r It is the distance from the vacuum drain pipe to the inside of the annular tube bag.

3. The method for calculating the dehydration amount of geobag dam sludge electroosmosis dehydration according to claim 1, characterized in that: The outer ring of the conductive geotextile ring bag is provided with a conductive plastic drainage board, and the outer surface of the drainage board is woven with woven geotextile. The outer ring of the non-conductive geotextile ring bag is provided with a non-conductive drainage board.

4. The method for calculating the dehydration amount of geobag dam sludge electroosmosis dehydration according to claim 1, characterized in that: The electrodes arranged on the side wall of the vacuum drain pipe are specifically: A circle of conductive plastic is arranged at a certain interval on the vacuum drainage pipe.

5. The method for calculating the dehydration amount of geobag dam sludge electroosmosis dehydration according to claim 1, characterized in that: The automatic control power supply increases the voltage in the electroosmotic process as the moisture content of the sediment decreases, and the voltage varies within a range of 20-60V to maintain the stability of the electroosmotic dehydration effect.

6. The method for calculating the dehydration amount of geobag dam sludge electroosmosis dehydration according to claim 1, characterized in that: In step 4, the dredged silt is injected into the top of the dam formed by the annular tube bag. The injection is stopped when the silt reaches the top of the dam. The silt gradually rises and its internal pressure gradually increases. Part of the water contained in the silt is discharged, and the liquid level in the dam gradually decreases. At this time, the silt is repeatedly injected into the dam, and this is repeated 3-5 times.

7. The method for calculating the dehydration amount of geobag dam sludge electroosmosis dehydration according to claim 1, characterized in that: When power is cut off in step 5, the plastic electrode is short-circuited with the conductive geotextile ring bag and the electrode on the side wall of the vacuum drainage pipe to discharge the charge, and the machine is controlled to beat the silt in the dam when power is cut off.

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