CN111560944A

CN111560944A - Method and device for 'electrode moving' electroosmosis drainage consolidation treatment based on air pressure splitting technology

Info

Publication number: CN111560944A
Application number: CN202010311938.0A
Authority: CN
Inventors: 甘淇匀; 魏利闯; 周建
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2020-04-20
Filing date: 2020-04-20
Publication date: 2020-08-21

Abstract

The invention discloses an 'electrode moving' electroosmosis drainage consolidation processing method and an electroosmosis consolidation device based on an air pressure splitting technology, wherein the method comprises the steps of electroosmosis construction and air pressure splitting; wherein, the air pressure splitting process is as follows: injecting gas and a modifier with conductivity into the electrode tube with holes, wherein the gas is sprayed from the holes to generate cracks in soil around the electrodes, the cracks are filled with water with conductivity, and the modifier is filled into the soil along the cracks to solidify and conduct the soil around the cracks. The method can produce the construction effect of a 'moving electrode' in the soil body, thereby achieving the effects of improving the permeability coefficient, accelerating the consolidation speed of the soil body and deepening the treatment depth of the soil body and solving the problems of uneven dehydration and high energy consumption of an electroosmosis method.

Description

Method and device for 'electrode moving' electroosmosis drainage consolidation treatment based on air pressure splitting technology

Technical Field

The invention relates to the technical field of geotechnical engineering, in particular to a new construction method for generating an 'electrode moving' effect based on an electroosmosis and air pressure splitting technology.

Background

The electroosmosis method applies direct current to electrodes inserted into soil to accelerate drainage consolidation of the soil and improve the strength, has drainage efficiency unrelated to the size of soil particles, is considered to be a method with development prospect for treating fine-grained soil with high water content and low permeability, and receives wide attention. Scholars at home and abroad continuously try to apply the soft soil to various soft soil projects, although the successful examples are not lacked, the soft soil projects are not widely popularized and applied, and the main reasons of the soft soil projects comprise two aspects: uneven treatment effect and larger energy consumption.

The uneven treatment effect is reflected in field test and indoor test. In situ observations show that the strength of the anode increases significantly more than the cathode due to water migration from the anode to the cathode, resulting in a cathode with a higher water content and lower strength, but still increased compared to before the treatment. The field test also observes that the settlement value is minimum at two ends and maximum in the middle, the final settlement is bowl-shaped, and the nonuniformity of the electroosmosis treatment foundation is obviously shown. The electroosmosis indoor test also finds that the water content reduction value of the soil body treated by different electrode materials shows obvious nonuniformity, the water content of the soil body at the cathode is far higher than that of the soil body at the anode, the resistance of the soil body at the anode is increased greatly due to the fact that the water content of the soil body is reduced and the soil body at the anode can be cracked, and water at the cathode cannot be effectively discharged, which is caused by the fact that charges/cations are accumulated in the soil body at the cathode.

Electroosmosis energy consumption is almost the current, the phenomenon that an electrode is separated from a soil body at the later stage of electroosmosis often occurs, so that resistance is increased, current heat effect is enhanced, the temperature of the soil body is increased, a large amount of electric energy is consumed, and the electricity consumption of treating the soil body per cubic meter by an electroosmosis method is reported from several degrees to dozens of degrees. The reason why electroosmosis consumes a large amount of energy is mainly two-fold: firstly, the electric energy utilization rate is not high when the power is on, the effective contact between the electrode and the soil body is poor, and the power supply continuously supplies power for a long time under the condition of low electroosmosis efficiency; secondly, after the metal electrode is corroded, passivation is generated, the interface resistance is increased, and a large amount of electric energy is consumed at the interface. The EKG electrode solves the problem of electrode corrosion passivation, but the problem of low electric energy utilization rate is not solved well.

Disclosure of Invention

The invention aims to provide a novel electroosmotic drainage consolidation method based on 'electrode movement' of an air pressure splitting technology, aiming at the defects of the prior art, namely three problems of uneven treatment effect, charge accumulation and large energy consumption.

The technical scheme of the invention is as follows:

an 'electrode moving' electroosmosis drainage consolidation processing method based on air pressure splitting technology comprises the steps of electroosmosis construction and air pressure splitting; wherein, the air pressure splitting process is as follows: gas and modifier are injected into the electrode tube with holes, so that cracks are generated in soil around the electrodes, and the cracks are filled with water and modifier with conductive performance. The modifier is filled into the soil body along the crack, so that the soil body around the crack is solidified and is conductive. The tubular electrode is provided with small holes, the modifier and gas are sprayed out of the small holes after electroosmosis reinforcement is carried out for a period of time, soil bodies generate directional cracks under the action of air pressure splitting, the cracks are filled with water with conductive performance, meanwhile, the modifier with the conductivity is filled into the soil bodies along the cracks which are continuously expanded, the soil bodies around the cracks are solidified and conducted, the electric potential applied to the positions of the electrodes can smoothly move to the ends of the cracks just like dendritic small electrodes which are continuously grown, the distance between a positive electrode and a negative electrode is greatly shortened, the contact between the soil and the electrodes is enhanced, the continuity of an electric field is ensured, meanwhile, after the soil bodies around the cracks are solidified, the cracks form stable drainage channels, and the drainage effect is greatly increased.

Further, the modifier comprises a curing agent and a flocculating agent with conductive properties.

Based on the effect of a 'moving electrode', the gas injection pressure and the gas injection quantity are changed, a proper modifier is selected, the dehydration range and the dehydration effect are flexibly adjusted, and the problem of non-uniformity of soft soil treatment by an electroosmosis method is effectively solved. As can be seen from the research results of the air pressure splitting and the modifier, the 'moving electrode' electroosmosis method based on the air pressure splitting provides an innovative idea for solving the problems of uneven treatment, charge accumulation and high energy consumption which are puzzled by electroosmosis for a long time.

Further, the modifier is mixed with gas to form aerosol, and then the aerosol is introduced into the electrode tube with holes. Preferably, the aerosol is swirled to create fissures in the soil. The gas pressure splitting parameters such as the gas injection hole spacing, the distribution shape, the gas injection pressure, the gas injection amount, the gas injection interval and the like of the electrode tube with the hole are determined according to specific conditions.

Furthermore, in the electroosmosis process, working methods such as intermittent electrification, intermittent air pressure splitting and/or electrode inversion are implemented according to the actual drainage condition, and the intermittent time and the splitting position are determined according to the soil body dehydration condition, so that electroosmosis drainage and air pressure splitting are alternately performed.

The invention also provides an electroosmosis consolidation device of the method, which comprises a box body, the electrode tube with holes, an external power supply, a water pumping device, a gas pressure source and a modifier injection source, wherein the electrode tube with holes is arranged in the box body, the external power supply is used for providing a stable power supply for the electrode tube with holes, the gas pressure source is used for providing gas, and the modifier injection source is used for providing a modifier. The water pumping device, the air pressure source and the modifier injection source are all connected with the electrode tube with the hole through pipelines. The connecting pipelines can be a plurality of pipelines or a pipeline which can be combined into a whole and can be used as an air duct and a water drainage pipe at the same time, and the connecting pipelines can be used for transmitting high-pressure gas of air pressure splitting and can also be used for pumping water by a water pump; at the moment, the electrode tube with the hole has the functions of conducting electricity, guiding air and draining water, and the hole on the electrode tube is used as an air injection hole and a drain hole.

Furthermore, the air pressure source is communicated with the modifier injection source and then is connected with the electrode tube with the hole.

Further, the device also comprises a preloading device or a vacuum preloading device.

The invention also provides a sludge dewatering or soft foundation treatment method for the field construction of 'electrode movement' based on the air pressure splitting technology, which is characterized by comprising the following steps of:

(1) leveling the field: the method comprises the steps of leveling a to-be-treated soft soil body field, and digging drainage ditches around the field to conveniently drain water of the field in time, wherein the field is optimally formed with a certain drainage gradient.

(2) Drilling a perforated electrode tube: uniformly distributing and selecting drainage distribution points in the field according to design requirements, and then punching the electrode pipes with holes to the designed depth at each distribution point.

(3) Arranging an electroosmotic device: connecting an external power supply and a water pumping device with the electrode pipe with the hole, and arranging a lead line and a drainage pipeline of the electrode pipe with the hole; then the air pressure source and the modifier injection source are connected with the electrode tube with the hole.

(4) Firstly, opening an air pressure source and a modifier injection source to carry out air pressure splitting to generate cracks in soil around an electrode, filling the cracks with water and a modifier with conductive performance, connecting an external power supply after the soil around the cracks is solidified, and opening a water pumping device to carry out electroosmosis drainage consolidation work.

Further, in the step (4), in-situ preloading or vacuum preloading is jointly performed, a sand cushion layer is covered on silt soil during preloading, and a vacuum sealing film is covered on the silt soil during vacuum preloading.

In order to optimize the technical scheme, the adopted measures further comprise:

the air pressure source is an air compressor.

The modifier has good conductivity, such as Polyacrylamide (PAM) solution, including Cationic Polyacrylamide (CPAM), Anionic Polyacrylamide (APAM), nonionic polyacrylamide, etc.

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

The invention has the advantages that:

1, the electroosmosis method of the 'movable electrode' comprehensively utilizes a crack channel formed by an air pressure splitting method, and injects a conductive modifier to change an originally fixed electrode from a 'fixed tree type' into a 'gradually growing tree type';

2. the space between the electrodes is changed from 'invariable' to 'gradually reduced', the drainage of the soil body is also changed from 'micro capillary channels' to 'criss-cross tributaries', and the drainage performance is greatly improved.

3. By means of the flowing filling of the modifier, the potential loss among the soil body, the electrode and the soil body cracks is reduced, and the electric field distribution is more uniform; in addition, the water drainage and later strength of the crack can be effectively controlled by utilizing the growth characteristic of later strength of the modifier along with time.

4. Because the new cathode continuously moves, cations can be continuously gathered to the new cathode, thereby avoiding the charge accumulation caused by the fixation of the electrode to a certain extent, also avoiding the phenomena of cation gathering and water content 'non-decreasing and non-increasing' near the cathode and promoting the uniform drainage of the soil body.

5. The method changes the originally difficult-to-adjust design parameters in the electroosmosis method into flexible and controllable, and enhances the operability of the adjusting period and the reinforcing effect.

Drawings

FIG. 1 is a schematic diagram of an electroosmotic drainage consolidation process of the present invention in which splitting a fracture causes "electrode migration"; wherein, a is an arrangement diagram of the electrode tube with holes, b is a schematic diagram of air pressure splitting, and c is a schematic diagram of electrode movement.

FIG. 2 is a diagram of an electroosmotic consolidation apparatus according to the present invention; in the figure, 1 is a box body, 2 is an external power supply, 3 is an air pressure source, 4 is a pipeline, 5 is an electrode hole, 6 is a soil body, 7 is an anode, 8 is a cathode, 9 is a modifier injection source, 10 is a water pumping device, 11 is a splitting crack, and 12 is a mixture of pore water and a modifier;

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

Detailed Description

The invention provides an electroosmosis drainage consolidation processing method of 'electrode movement' based on air pressure splitting technology, which comprises the steps of electroosmosis construction and air pressure splitting; wherein, the air pressure splitting process is as follows: injecting gas and modifier into the electrode tube with holes, as shown in figure 1, injecting the gas from the holes of the electrode tube with holes to generate cracks in soil around the electrode, filling water into the cracks, and mixing the soil around the cracks with the modifier to form a modifier treatment layer. The water in the fissures contains inorganic salts that can introduce an electrical potential into the modifier treatment layer. After the steam injection is stopped, the soil around the cracks is kept stable under the action of the injected flocculating agent and curing agent, and a stable drainage channel can be formed. And the flocculant (PAM) dissociates negatively charged functional groups and H in the aqueous solution⁺The modifier treatment layer has good conductivity, and the good conductivity of the modifier treatment layer ensures that the potential can be transmitted to the soil body, so that the cleavage fracture can be ensured to play a role in conducting. The conductivity of the water and the modifier in the cracks is far higher than that of the sludge, particularly when the effective potential transmission is severely limited by the interface resistance between the electrode and the sludge, and the water and the modifier treatment layer in the cracks are taken as good conductive layers and are obviously superior to the sludge, so that the contact performance with the electrode is improved, the interface resistance can be greatly reduced,the utilization rate of electric energy is improved. With the electrode potential being transmitted to the crack tail end with higher efficiency, on one hand, the contact area of the 'electrode' and the sludge is greatly expanded, and on the other hand, higher effective potential can be applied to soil outside the crack tail end, so that the 'electrode moving' effect is achieved. Along with the gradual progress of electroosmosis dehydration, the water content of the soil body is reduced, especially the resistivity of the anode region is increased rapidly, the splitting crack is also shrunk gradually, and at the moment, the modifier is fully mixed with the soil body around the crack, so that the soil body can still be ensured to have good conductivity in the later stage of electroosmosis. The gas injection splitting and intermittent electrification are combined and carried out alternately, so that a new conductive path can be guaranteed to be opened up in the soil body at any time, the conductivity of a splitting fracture area can be correspondingly improved by synchronously injecting the modifier, the generation of joule heat is reduced, and the energy utilization rate is improved.

In the method, the gas acts to cause fissures in the soil surrounding the electrodes and to deliver the modifier to the fissures. The gas may 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 deliver the modifier to the cracks, the modifier can be mixed with air to form aerosol and then the aerosol is introduced into the perforated electrode tube.

The modifier comprises a curing agent and a flocculating agent with conductive performance, and the flocculating agent and the curing agent are used for flocculating and solidifying soil around the cracks, maintaining stability for a certain time and enabling the cracks to become stable drainage channels. The conductivity and permeability of the modifier are the key points for the success of the 'moving electrode' electroosmosis method, the category, concentration and proportion of the modifier (including flocculating agent and curing agent) are improved according to the organic matter content, chemical components and physical characteristics of the dredged sludge/sludge, and the proper type of the modifier is determined by comparison and selection. Preferably, the flocculating agent is Polyacrylamide (PAM), including Cationic Polyacrylamide (CPAM), Anionic Polyacrylamide (APAM), nonionic polyacrylamide, etc., and the curing agent is commonly used soil curing agent, such as calcium chloride solution, ionic curing agent, etc., preferably liquid ionic soil curing agent.

The electrode tube with the holes is a common tubular electrode with conductive performance, and the surface of the electrode is provided with a plurality of through holes, which are shaped like an EKG electrode. The number, arrangement and size of the through holes can be optimized according to the electroosmotic drainage effect.

It should be noted that there is no absolute precedence relationship between the electroosmosis construction and the air pressure splitting step, and the air pressure splitting may be performed first and then the electroosmosis construction, or the air pressure splitting may be performed and then the electroosmosis construction.

The invention also provides an electroosmosis consolidation device based on the method, which comprises a box body 1, a perforated electrode pipe arranged in the box body, an external power supply 2 for providing stable power supply for the perforated electrode pipe, a water pumping device 10, a gas pressure source 3 for providing gas and a modifier injection source 9 for providing modifier, as shown in figure 2. Wherein, the water pump 10, the air pressure source 3 and the modifier injection source 9 are all connected with the electrode tube with holes. As shown in figure 2, the perforated electrode pipe comprises an anode 7 and a cathode 8, the anode 7 and the cathode 8 are uniformly distributed in the box body 1, and a pipeline 4 is arranged above the perforated electrode pipe. The pipeline 4 is connected with an external power supply 2, a water pumping device 10, an air pressure source 3 and a modifier injection source 9; when the device works, sludge or soft soil is filled into the box body 1, gas and a modifier are injected into the electrode tube with the hole through the gas pressure source 3 and the modifier injection source 9 according to the method, at the moment, the pipeline 4 is used as a gas guide pipe, the electrode hole 5 is used as a gas jet hole, the gas and the modifier are subjected to gas pressure splitting through the gas jet hole, a conductive crack and a modifier treatment layer are generated, the contact performance with an electrode plate is improved, and the energy utilization rate is improved. After the crack is generated, gas injection is stopped, electroosmosis consolidation is started, the external power supply 2 and the water pumping device 10 are started, the pipeline 4 is used as a water drainage pipe, the electrode hole 5 is used as a water drainage hole, and water enters the water drainage pipe from the water drainage hole and is finally drained out under the action of voltage and the water pumping device 10.

The device can also be combined with a preloading device or a vacuum preloading device, wherein the preloading device is any device or object capable of providing load on the soil body to be treated, such as prestressed soil. The vacuum preloading device is any device capable of providing vacuum for the box body, such as a vacuum pump, at the moment, the box body 1 is a closed box body, and the vacuum pump is connected with the box body 1.

In addition, the flow of the sludge dewatering or soft foundation treatment method based on the field construction of the 'electrode movement' of the air pressure splitting technology is shown in fig. 3, and the method specifically comprises the following steps:

(2) Drilling a perforated electrode tube: and uniformly distributing and selecting distribution point positions of the drainage body in the field according to design requirements, and then punching the electrode pipe with the holes to the designed depth at each distribution point position.

(3) Arranging an electroosmotic device: connecting an external power supply 2 and a water pumping device 10 with the perforated electrode pipe, and arranging a lead line and a drainage pipeline of the perforated electrode pipe; then the air pressure source 3 and the modifier injection source 9 are connected with the perforated electrode pipe.

(4) As shown in figure 2, firstly, the gas pressure splitting is carried out, modifier is added into the splitting gas, the electrode is artificially extended to generate the effect of 'electrode movement', after the soil body around the crack is solidified, an external power supply 2 is connected, and the water pumping device 10 is opened to carry out the electroosmosis drainage consolidation work. The common methods of electrode inversion, intermittent energization and step-by-step pressurization, which reduce energy consumption and improve electroosmosis reinforcement effect, can also be applied to the 'moving electrode' method. Preferably, in the electroosmosis process, working methods such as intermittent electrification, electrode inversion and intermittent air pressure splitting are carried out according to the actual drainage condition, and the intermittent time and the splitting position are determined according to the soil body dehydration condition.

(5) And finishing construction until the drainage consolidation is finished.

In the method and the device, the air pressure source 3 is a device capable of stably providing air, such as an air compressor, an air bottle and the like. The modifier injection source 9 is a device for stably supplying a modifier, such as a sprayer or the like. Or the air pressure source 3 is connected with an atomizing device, and the modifier and the gas are mixed in the atomizing device to form aerosol and then are introduced into the perforated electrode tube.

The invention can also be simultaneously implemented by combining other construction methods, such as preloading or vacuum preloading and the like. When the modified splitting fracture zone is used in combination with other construction methods, the modified splitting fracture zone can still maintain high permeability, can serve as a drainage layer, reduces the vacuum preloading attenuation coefficient, improves the transmission performance of vacuum pressure, and accelerates sludge dewatering.

In the method and the device, the conductivity and the permeability of the modifier are the key points for the success of the electroosmosis method of the 'moving electrode', the category, the concentration and the proportion of the modifier (comprising the flocculating agent and the curing agent) are improved according to the organic matter content, the chemical components and the physical characteristics of the dredged sludge/sludge, and the proper type of the modifier is determined by comparison and selection. The effect of the modifier on the micro-pore structure is researched in a laboratory, the influence of the doping amount of different modifiers on the large and medium pore numbers and distribution of the soil body, the conductivity and the permeability of the soil body is researched, and guidance is provided for the doping amount of the modifier, so that guidance is provided for large-area construction.

The expansion, morphology and stability of the crevice are important bases for the success of "moving electrode" electroosmosis. And the crack development, form and expansion range, the crack stability, the crack closing time and the like can be determined by modifying air pressure splitting parameters such as different air jet hole intervals, distribution shapes, air jet pressure, air jet quantity, air jet intervals and the like.

The electrode arrangement form of the conventional electroosmosis method has a good quincunx arrangement effect, and the comprehensive effects such as the air pressure splitting influence range are considered, so that the plane arrangement forms of different electrodes can be changed, and the arrangement of electrode tubes with holes such as a rectangle, a triangle and a hexagon is adopted. Preferably, when the soft silt soil is drained and reinforced in a laboratory or an outdoor place, the electrode tubes with holes and the conducting wires can be arranged in a rectangular or quincunx shape, and the holes on the adjacent electrode tubes with holes are staggered, as shown in fig. 2.

The above description is only an embodiment of the present invention, and it should be noted that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention.

Claims

1. An electroosmosis drainage consolidation processing method of 'electrode movement' based on air pressure splitting technology is characterized by comprising the steps of electroosmosis construction and air pressure splitting; wherein, the air pressure splitting process is as follows: injecting gas and a modifier with conductivity into the electrode tube with holes, wherein the gas is sprayed from the holes to generate cracks in soil around the electrodes, the cracks are filled with water with conductivity, and the modifier is filled into the soil along the cracks to solidify and conduct the soil around the cracks.

2. The method of claim 1, wherein the modifying agent comprises a curing agent having electrically conductive properties and a flocculating agent.

3. The method of claim 1, wherein the modifier is mixed with the gas to form an aerosol and introduced into the perforated electrode tube.

4. The method of claim 1, wherein the electroosmosis process is performed by intermittent electroosmosis, intermittent air pressure splitting, and/or electrode inversion.

5. An electroosmotic consolidation apparatus according to the method of claim 1, comprising a housing (1), a perforated electrode tube disposed in the housing, an external power source (2) for supplying a stable power to the perforated electrode tube, a water pumping means (10), a gas pressure source (3) for supplying gas, and a modifier injection source (9) for supplying a modifier. The water pumping device (10), the air pressure source and the modifier injection source (9) are connected with the electrode tube with the hole through pipelines.

6. An electroosmotic consolidation apparatus according to claim 5, wherein the pneumatic pressure source (3) is connected to the perforated electrode tube after communicating with the modifier injection source (9).

7. An electroosmotic consolidation apparatus according to claim 5, further comprising a preloading device or a vacuum preloading device.

8. An 'electrode moving' field construction sludge dewatering or soft foundation treatment method based on an air pressure splitting technology is characterized by comprising the following steps:

(3) Arranging an electroosmotic device: an external power supply (2) and a water pumping device (10) are connected with the electrode tube with the hole, and a lead line, a drainage pipeline and an exhaust pipeline which are connected with the electrode tube with the hole are arranged; then the air pressure source (3) and the modifier injection source (9) are connected with the electrode tube with the hole through a drainage pipeline and an exhaust pipeline.

(4) Firstly, an air pressure source (3) and a modifier injection source (9) are opened to carry out air pressure splitting to generate cracks in soil around an electrode, the cracks are filled with water and modifiers with conductive performance, an external power source (2) is connected after the soil around the cracks is solidified, and a water pumping device (10) is opened to carry out electroosmosis drainage consolidation work.

9. The method as claimed in claim 8, wherein in the step (4), the preloading is performed in situ in combination with the vacuum preloading in which a sand cushion is coated on the silt and the vacuum preloading in which a vacuum sealing film is coated on the silt.