WO2021212255A1

WO2021212255A1 - Pneumatic fracturing technology-based "mobile electrode" electro-osmotic drainage consolidation treatment method and device

Info

Publication number: WO2021212255A1
Application number: PCT/CN2020/085523
Authority: WO
Inventors: 周建; 甘淇匀; 魏利闯
Original assignee: 浙江大学
Priority date: 2020-04-20
Filing date: 2020-04-20
Publication date: 2021-10-28

Abstract

Disclosed are a pneumatic fracturing technology-based "mobile electrode" electro-osmotic drainage consolidation treatment method and an electro-osmotic consolidation device. The treatment method comprises the steps of electro-osmotic construction and pneumatic fracturing. The pneumatic fracturing process comprises: injecting gas and a modifier having conductivity into an electrode tube having holes, and spraying the gas from the holes to enable a soil body around an electrode to generate cracks, wherein the cracks are filled with water having conductivity, and the modifier fills the soil body along the cracks to enable the soil body around the cracks to be consolidated and conductive. The method of the present invention can produce a "mobile electrode" construction effect in the soil body, thereby achieving the effects of improving osmotic coefficient, accelerating soil body consolidation speed and deepening the treatment depth of the soil body, and solving the problems of non-uniformity and high energy consumption of an electro-osmotic dehydration method.

Description

Electro-osmosis drainage consolidation treatment method and device for "electrode movement" based on air pressure splitting technology

Technical field

The present invention relates to the technical field of geotechnical engineering, in particular to a new construction method based on electroosmosis combined with air pressure splitting technology to produce the effect of "electrode movement".

Background technique

The electroosmosis method applies a direct current to the electrode inserted into the soil to accelerate the drainage and consolidation of the soil to increase its strength. Its drainage efficiency has nothing to do with the size of the soil particles. It is considered to deal with high water content and low permeability. The promising method for the development of sexual fine-grained soil has attracted wide attention. Scholars at home and abroad have been trying to use it in various soft soil projects. Although there are many successful examples, it has not been widely promoted and applied. The main reasons include two aspects: uneven treatment effect and relatively low energy consumption. Big.

The uneven treatment effect is reflected in the field test and the indoor test. Field observation data show that the increase in anode strength is significantly greater than that of the cathode. This is due to the migration of water from the anode to the cathode, which causes the cathode to have a larger water content and lower strength, but it still increases compared to before treatment. It was also observed through field tests that the settlement value was the smallest at both ends and the middle was the largest, and the final settlement was bowl-shaped, showing the unevenness of the electroosmosis treatment foundation more obviously. The electroosmosis laboratory experiment also found that the soil water content reduction value after different electrode materials showed obvious unevenness. On the whole, the soil moisture content at the cathode was much higher than that at the anode, and the soil at the anode was due to the decrease in water content It will "dry and crack", resulting in a sharp increase in electrical resistance, but the water at the cathode cannot be effectively discharged. This is caused by the accumulation of charges/cations in the soil at the cathode.

The large energy consumption of electroosmosis is reflected in the fact that the electrode and the soil are often separated in the later stage of electroosmosis, which causes the resistance to increase and the current heating effect to increase, which causes the temperature of the soil to rise and consumes a lot of electricity. Power consumption has been reported from several degrees to tens of degrees. There are two main reasons for the large energy consumption of electroosmosis: one is that the utilization rate of electric energy is not high when the electricity is turned on, the effective contact between the electrode and the soil becomes poor, and the power supply continues to supply power for a long time when the electroosmosis efficiency is low; Passivation occurs after the metal electrode is corroded, the interface resistance increases, and a large amount of electric energy is consumed at the interface. The emergence of EKG electrodes has solved the problem of electrode corrosion and passivation, but the low utilization rate of electric energy has not been solved.

technical problem

The existing electroosmotic drainage treatment and consolidation treatment methods have three problems: uneven effects, charge accumulation and large energy consumption.

Technical solutions

The purpose of the present invention is to address the shortcomings of the prior art, that is, to solve the three problems of uneven treatment effect, charge accumulation and large energy consumption, and provide an electroosmosis based on the "electrode movement" of gas pressure splitting technology. New construction method for drainage consolidation. The technical scheme of the present invention is:

An electroosmotic drainage consolidation treatment method based on "electrode movement" of air pressure splitting technology, including electroosmosis construction and air pressure splitting steps; wherein the air pressure splitting process is as follows: inject gas and modifier into the electrode tube with holes , Causing cracks in the soil around the electrode, and the cracks are filled with conductive water and modifiers. The modifier is filled into the soil along the cracks to solidify the soil around the cracks and conduct electricity. A small hole is opened on the tubular electrode. After a period of time of electroosmosis reinforcement, the modifier and gas are sprayed out of the small hole. Under the action of air pressure splitting, the soil produces directional cracks. The cracks are filled with conductive water and conductive. The flexible modifier fills the soil along the expanding cracks, solidifying and conducting the soil around the cracks, just like a growing dendritic small electrode. The electric potential applied at the electrode position can be smoothly "moved" to The end of the crack greatly shortens the distance between the anode and the anode electrode, and strengthens the contact between the soil and the electrode to ensure the continuity of the electric field. At the same time, after the soil around the crack is solidified, the crack forms a stable drainage channel, and the drainage effect is greatly increased. .

Further, the modifier includes a curing agent and a flocculant with conductive properties.

Based on the "moving electrode" effect, the gas injection pressure, gas injection volume, suitable modifiers are selected, and the dehydration range and effect can be flexibly adjusted to effectively improve the unevenness of the electroosmosis method in the treatment of soft soil. From the above research results of air pressure splitting and modifiers, it can be seen that the "moving electrode" electroosmosis method based on air pressure splitting provides innovative ideas for solving the long-term problem of electroosmosis in uneven treatment, charge accumulation and large energy consumption.

Further, the perforated electrode tube is composed of an inner sleeve and an outer sleeve coaxially sleeved. The inner sleeve and the outer sleeve are provided with holes, and the holes on the inner sleeve pass through the holes. It is connected with the holes of the outer casing, and the number of holes on the inner casing is less than that of the outer casing. The material of the outer sleeve is conductive material.

Further, the modifier and the gas are mixed to form an aerosol and then passed into the electrode tube with holes. Preferably, the aerosol is sprayed to create fissures in the soil. The air-jet hole spacing, distribution shape, air-jet pressure, air-jet volume, air-jet interval and other air pressure splitting parameters of the above-mentioned perforated electrode tube, depending on the specific situation.

Furthermore, during the electroosmosis process, implement intermittent energization, intermittent air pressure splitting and/or electrode reversal according to the actual drainage conditions. The intermittent time and splitting position depend on the dehydration of the soil. Split alternately.

The present invention also provides an electroosmotic consolidation device of the above method, comprising a box body, a perforated electrode tube placed in the box, an external power source for providing a stable power source for the perforated electrode tube, a water pumping device, and a gas pressure source And provide modifier injection source of modifier. The water pumping device, the air pressure source and the modifier injection source are all connected to the perforated electrode tube through a pipeline. Among them, the connected pipes can be multiple or combined into one, which can be used as a gas guide pipe and a drainage pipe at the same time, which can be used for high-pressure gas transmission by air pressure splitting, and can also be used for pumping water; in this case, the perforated electrode tube is also conductive , The function of air conduction and drainage, the hole on the electrode tube is used as a jet hole and also as a drainage hole.

Further, the air pressure source is connected to the modifier injection source and then connected to the perforated electrode tube.

Further, it also includes a stack preloading device or a vacuum preloading device.

The present invention also provides a method for sludge dewatering or soft foundation treatment for on-site construction of "electrode movement" based on air pressure splitting technology, which includes the following steps:

(1) Site leveling: level the site to be treated with soft soil, and at the same time excavate drainage ditches around the site to facilitate timely drainage of site water. The site is best formed with a certain drainage slope.

(2) Drilling electrode tubes with holes: According to the design requirements, evenly select drainage distribution points in the site, and then drill the electrode tubes with holes to the design depth at each distribution point.

(3) Arrange the electroosmosis device: connect the external power supply and the pumping device with the holed electrode tube, arrange the wire line and the drain line of the holed electrode tube; then connect the air pressure source, the modifier injection source and the holed electrode tube .

(4) First turn on the air pressure source and the modifier injection source to perform air pressure splitting to create cracks in the soil around the electrode. The cracks are filled with conductive water and modifier. After the soil around the cracks is solidified, connect to the outside. Power, turn on the pumping device for electroosmosis drainage consolidation work.

Further, in step (4), stacking preloading or vacuum preloading is jointly implemented on site, a sand cushion is covered on the silt soil during stacking preloading, and a vacuum sealing film is covered on the silt soil during vacuum preloading.

In order to optimize the above technical solutions, the measures taken also include:

The above-mentioned air pressure source is an air compressor.

The above-mentioned modifiers have good electrical conductivity, such as polyacrylamide (PAM) solutions, including cationic polyacrylamide (CPAM), anionic polyacrylamide (APAM), non-ionic polyacrylamide, etc.

Preferably, the outer wall and bottom of the perforated electrode tube are wrapped with a non-conductive geotextile filter layer. The perforated electrode tube has high hardness and can maintain a stable structure and good sealing performance under a large cleavage pressure.

Beneficial effect

1. The "moving electrode" electroosmosis method comprehensively uses the fissure channel formed by the air pressure splitting method to inject a conductive modifier, so that the originally fixed electrode changes from a "fixed tree trunk type" to a "gradually growing tree type";

2. The distance between the electrodes has changed from "unchanged" to "gradually reduced", and the drainage of the soil has also changed from "microcapillary channels" to "cristal and crisscross tributaries", and the drainage performance is greatly improved.

3. By means of the flow filling of the modifier, the potential loss in the soil and the electrode and the cracks in the soil is reduced, and the electric field distribution is more uniform; in addition, the later strength of the modifier can be used to effectively control the cracks. Drainage and late strength.

4. Due to the continuous movement of the "new cathode", cations can continuously accumulate to the "new cathode", thereby avoiding the "charge accumulation" caused by the "electrode fixation" to a certain extent, and also avoiding the accumulation of cations near the "cathode" And the phenomenon that the water content "does not drop but rises", promotes the even drainage of the soil.

5. This method turns the design parameters that were difficult to adjust in the electroosmosis method into flexible and controllable, and enhances the operability of adjusting the construction period and strengthening effect.

Description of the drawings

1 is a schematic diagram of the electroosmotic drainage consolidation treatment method of "electrode movement" caused by cleavage fissures of the present invention; where a is a layout diagram of a perforated electrode tube, b is a schematic diagram of air pressure cleavage, and c is a schematic diagram of electrode movement.

Figure 2 is a diagram of the electroosmotic consolidation device of the present invention; in the figure, 1 is the box, 2 is the external power source, 3 is the air pressure source, 4 is the pipe, 5 is the electrode hole, 6 is the soil, 7 is the anode, and 8 Is the cathode, 9 is the modifier injection source, 10 is the pumping device, 11 is the cleavage fissure, and 12 is the mixture of pore water and modifier;

Figure 3 is a flow chart of ready-made construction silt drainage or soft soil treatment.

Embodiments of the present invention

The present invention provides an electroosmotic drainage consolidation treatment method based on the "electrode movement" of air pressure splitting technology. The method includes the steps of electroosmosis construction and air pressure splitting; wherein the air pressure splitting process is as follows: Inject gas and modifier into the electrode tube. As shown in Figure 1, the gas is sprayed from the hole of the electrode tube with holes to create cracks in the soil around the electrode. At this time, the cracks are filled with water, and the soil around the cracks is changed. The sexing agent is mixed to form the modifier treatment layer. The water in the fissures contains inorganic salts, which can introduce an electric potential into the modifier treatment layer. After the steam injection is stopped, the soil around the crack remains stable under the action of the injected flocculant and curing agent, and a stable drainage channel can be formed. And the flocculant (PAM) dissociates the negatively charged functional groups and H ⁺ in the aqueous solution, so that the modifier treatment layer has good conductivity. The good conductivity of the modifier treatment layer ensures that the electric potential can be transferred to the soil. Therefore, it can be ensured that the cleavage crack can also play the role of electric conduction. The conductivity of the water and the modifier in the cracks is much higher than that of the sludge, especially when the interfacial resistance between the electrode and the silt severely limits the effective potential transfer, and the water in the cracks and the modifier treatment layer itself act as A good conductive layer is obviously better than sludge, thereby improving the contact performance with the electrode, which can greatly reduce the "interface resistance" and increase the utilization rate of electric energy. As the electrode potential is transferred to the end of the fissure with higher efficiency, on the one hand, the contact area between the "electrode" and the silt is greatly expanded, and on the other hand, a higher effective potential can be applied to the soil outside the end of the fissure. To the effect of "electrode movement". With the gradual progress of electroosmosis dehydration, the water content of the soil decreases, especially the resistivity of the anode area will increase sharply, and the split fissures will gradually shrink. At this time, the modifier has been fully mixed with the soil around the fissures. In the later stage of infiltration, it can still ensure that the soil has good electrical conductivity. The combination of gas injection and intermittent energization is performed alternately, so that new conductive paths can be opened in the soil at any time, and the simultaneous injection of modifiers will correspondingly improve the conductivity of the cleavage zone and reduce the generation of Joule heat. , Improve energy utilization.

In the above method, the function of the gas is to generate cracks in the soil around the electrode and at the same time transport the modifier to the cracks. The gas can be any gas that does not react with the modifier, such as air, nitrogen, oxygen, argon, and the like. In addition, in order to uniformly transport the modifier to the fissures, the modifier can be mixed with air to form an aerosol and then passed into the perforated electrode tube.

The modifier includes a curing agent and a flocculant with conductive properties, and the flocculant and the curing agent are used to flocculate and solidify the soil around the cracks, maintain stability for a certain period of time, and make the cracks become a stable drainage channel. Among them, the conductivity and permeability of the modifier is the key to the success of the "moving electrode" electroosmosis method. According to the organic matter content, chemical composition and physical characteristics of the dredged sludge/sludge, the modifier (including flocculant and solidification The type, concentration, and ratio of the agent) are improved, and the appropriate modifier type is determined through comparison and selection. Preferably, under normal circumstances, the flocculant can be polyacrylamide (PAM), including cationic polyacrylamide (CPAM), anionic polyacrylamide (APAM), non-ionic polyacrylamide, etc., and the curing agent can be commonly used The soil curing agent, such as calcium chloride solution, ionic curing agent, etc., is preferably a liquid ionic soil curing agent.

The holed electrode tube is a generally conductive tubular electrode, and the surface of the electrode is provided with a number of through holes, which are shaped like EKG electrodes. The number, arrangement and size of the through holes can be optimized according to the electroosmosis drainage effect.

Preferably, the perforated electrode tube is composed of an inner sleeve and an outer sleeve coaxially sleeved. The surfaces of the inner sleeve and the outer sleeve are provided with holes, and the holes on the inner sleeve pass through the holes. It is connected with the holes of the outer casing, and the number of holes on the inner casing is less than that of the outer casing. The material of the outer sleeve is conductive material. The holes on the inner casing are used for gas injection to perform air pressure splitting of the soil. After the completion, the holes of the outer casing and the inner casing are used for drainage at the same time, which can ensure a better splitting effect and drainage at the same time The effect is to avoid the problems that the holes are too dense, the splitting effect is not good, and the holes are too sparse and not conducive to drainage.

It should be pointed out that there is no absolute sequence relationship between the electroosmosis construction and the air pressure fracturing step and then the implementation process. The air pressure fracturing can be carried out first and then the electroosmosis construction can be carried out, or the air pressure fracturing can be carried out before the electroosmosis construction.

The present invention also provides an electroosmotic consolidation device based on the above method. As shown in Figure 2, it includes a box body 1, a perforated electrode tube placed in the box, an external power source for providing a stable power source for the perforated electrode tube, and water pumping. Device 10, gas pressure source 3 and modifier injection source 9 for modifier. Among them, the water pumping device 10, the air pressure source 3 and the modifier injection source 9 are all connected to a perforated electrode tube. As shown in Figure 2, the electrode tube with holes includes an anode 7 and a cathode 8. The anode 7 and the cathode 8 are evenly distributed in the box 1, and a pipe 4 is arranged above the electrode tube with holes. The pipeline 4 is connected to the external power source 2, the pumping device 10, the air pressure source 3 and the modifier injection source 9. When working, fill the box 1 with silt or soft soil, and pass the air pressure source 3 and the modifier according to the above method. The injection source 9 injects gas and modifier into the perforated electrode tube. At this time, the pipe 4 is used as a gas guide tube, and the electrode hole 5 is used as a jet hole. The treatment layer of the sex agent improves the contact performance with the electrode plate and improves the energy utilization rate at the same time. After the cracks are generated, stop gas injection, start electroosmotic consolidation, turn on the external power supply 2 and the pumping device 10. At this time, the pipe 4 is used as a drain pipe, and the electrode hole 5 is used as a drain hole. Under the action of the voltage and the pumping device 10, the water is The drain hole enters the drain pipe and finally discharges.

The device can also be combined with a stacking preloading device or a vacuum preloading device. The stacking preloading device is any device or object that can provide a load on the soil to be processed, such as preloading soil. The vacuum preloading device is any device that can provide vacuum to the box, such as a vacuum pump. At this time, the box 1 should be a closed box, and the vacuum pump is connected to the box 1.

In addition, the flow of the sludge dewatering or soft foundation treatment method for on-site construction based on the pneumatic fracturing technology "electrode movement" is shown in Figure 3, which specifically includes the following steps:

(2) Drilling electrode tubes with holes: According to the design requirements, evenly select the drainage body distribution points in the site, and then at each distribution point, punch the electrode tubes with holes to the design depth.

(3) Arrange the electroosmosis device: connect the external power source 2, the pumping device 10 and the electrode tube with holes, arrange the wire line and the drain line of the electrode tube with holes; then connect the air pressure source 3, the modifier injection source 9 and the belt Hole electrode tube connection.

(4) As shown in Figure 2, first, perform air pressure splitting. Add modifier to the splitting gas to artificially extend the electrode to produce the effect of "electrode movement". After the soil around the crack is solidified, connect the external The power supply 2 turns on the pumping device 10 to perform electroosmotic drainage consolidation work. Electrode reversal, intermittent energization, and stepwise pressurization techniques, which are commonly used methods to reduce energy consumption and improve the effect of electroosmotic reinforcement, can also be applied in the "moving electrode" method. Preferably, during the electroosmosis process, construction methods such as intermittent energization, electrode reversal, and intermittent air pressure splitting are implemented according to actual drainage conditions, and the intermittent time and splitting position depend on the dehydration of the soil.

(5) Until the drainage consolidation is completed, the construction ends.

In the above method and device, the air pressure source 3 is a device capable of stably supplying gas, such as an air compressor, a gas cylinder, and the like. The modifier injection source 9 is a device for stably supplying modifier, such as a sprayer. Or connect the air pressure source 3 to the atomization device, and the modifier and the gas are mixed in the atomization device to form an aerosol and then pass into the electrode tube with holes. The water pumping device 10 can be a water pump or the like.

The invention can also be implemented in conjunction with other construction methods, such as stack preloading or vacuum preloading. When combined with other construction methods, the modified split fissure area can still maintain high permeability, can act as a drainage layer and reduce the attenuation coefficient of vacuum preload, improve the transmission performance of vacuum pressure, and accelerate the dewatering of sludge.

In the above method and device, the conductivity and permeability of the modifier is the key to the success of the "moving electrode" electroosmosis method. According to the organic matter content, chemical composition and physical characteristics of the dredged sludge/sludge, the modifier (including The type, concentration and ratio of flocculant and curing agent are improved, and the appropriate modifier type is determined through comparison and selection. The effects of modifiers on the microscopic pore structure are studied in the laboratory, and the effects of different modifiers on the number and distribution of large and medium pores, soil conductivity and permeability of the soil are studied, which is the mixing of modifiers. Provide guidance on the amount of input, and then provide guidance in large-scale construction.

The expansion, morphology and stability of the fissure are the important basis for the success of the "moving electrode" electroosmosis method. It is also possible to determine the development, morphology and expansion range of the cracks, the stability of the cracks and the closing time by modifying the air pressure splitting parameters such as the spacing, distribution shape, jet pressure, jet volume, and jet interval of different jet holes.

The conventional electroosmosis method adopts a plum blossom arrangement to have a better effect. Taking into account the comprehensive effects of air pressure splitting and other comprehensive effects, it is possible to change the layout of different electrodes and adopt rectangular, triangular, hexagonal and other perforated electrode tube layouts. . As a preferred solution, when the silt soft soil is drained and reinforced in a laboratory or outdoor field, the installation of the holed electrode tube and the lead can be arranged in a rectangular or plum blossom shape, and the holes on the adjacent holed electrode tubes are staggered, as shown in the figure 2 shown.

The above are only specific embodiments of the present invention. It should be pointed out that any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be covered by the protection scope of the present invention. within.

Claims

An electroosmotic drainage consolidation treatment method based on the "electrode movement" of air pressure splitting technology is characterized in that the method includes the steps of electroosmosis construction and air pressure splitting; wherein the air pressure splitting process is as follows: Inject gas and a conductive modifier into the hole. The gas is sprayed from the hole to create cracks in the soil around the electrode. The cracks are filled with conductive water. The modifier fills the soil along the cracks to make the cracks. The surrounding soil solidifies and conducts electricity.
The method according to claim 1, wherein the modifier comprises a curing agent and a flocculant with conductive properties.
The method according to claim 1, wherein the electrode tube with holes is composed of an inner sleeve and an outer sleeve coaxially sleeved, and the inner sleeve and the outer sleeve are provided with holes on their surfaces. , The holes on the inner sleeve are connected with the holes of the outer sleeve through the channels, and the number of holes on the inner sleeve is less than the outer sleeve; the outer sleeve is made of conductive material.
The method according to claim 1, wherein the modifier is mixed with the gas to form an aerosol and then passed into the perforated electrode tube.
The method according to claim 1, characterized in that, during the electroosmosis process, intermittent electroosmosis, intermittent gas pressure splitting and/or electrode inversion methods are implemented.
An electroosmotic consolidation device based on the method of claim 1, characterized in that it comprises a box (1), a perforated electrode tube placed in the box, and an external power source (2) that provides a stable power source for the perforated electrode tube. ), a water pumping device (10), a gas pressure source (3) and a modifier injection source (9) that provides a modifier; the water pumping device (10), a gas pressure source and a modifier injection source (9) All are connected to the electrode tube with holes through the pipeline.
The electroosmotic consolidation device according to claim 6, characterized in that the gas pressure source (3) is connected to the modifier injection source (9) and then connected to the electrode tube with holes.
The electroosmotic consolidation device according to claim 6, characterized in that it further comprises a stack preloading device or a vacuum preloading device.
A method for on-site construction of sludge dewatering or soft foundation treatment based on the "electrode movement" of the air pressure splitting technology is characterized in that it comprises the following steps:

(1) Site leveling: level the site to be treated with soft soil, and at the same time excavate drainage ditches around the site to facilitate timely drainage of site water. The site is best formed with a certain drainage slope;

(2) Drilling electrode tubes with holes: according to the design requirements, select drainage distribution points uniformly in the site, and then drill the electrode tubes with holes to the design depth at each distribution point;

(3) Arrange the electroosmosis device: connect the external power source (2) and the pumping device (10) with the electrode tube with holes, arrange the wire lines and the drainage and exhaust pipes connected with the electrode tube with holes; then connect the air pressure source ( 3) The modifier injection source (9) is connected to the perforated electrode tube through drainage and exhaust pipes;

(4) First turn on the air pressure source (3) and the modifier injection source (9) to perform air pressure splitting to create cracks in the soil around the electrode. The cracks are filled with conductive water and modifier, and the soil around the cracks After curing, turn on the external power supply (2) and turn on the pumping device (10) to perform electroosmotic drainage consolidation work.
The method according to claim 9, characterized in that, in step (4), stacking preloading or vacuum preloading is jointly implemented on site, and a sand cushion is covered on the silt soil during stacking preloading, and during vacuum preloading Cover the silt soil with a vacuum sealing film.