WO2020192279A1

WO2020192279A1 - Electro-osmosis strengthening method used for reinforcing soft clay foundations

Info

Publication number: WO2020192279A1
Application number: PCT/CN2020/074456
Authority: WO
Inventors: 孙召花; 周威; 包华; 石智玮; 姚言飞; 周文博; 谢仁杰; 阮晨成
Original assignee: 南通大学
Priority date: 2019-10-13
Filing date: 2020-02-06
Publication date: 2020-10-01
Also published as: LU101745B1; CN110670574A; CN110670574B

Abstract

Disclosed is an electro-osmosis strengthening method used for reinforcing soft clay foundations, comprising the following steps: inserting electrodes in the vertical and horizontal directions into a soft clay foundation; forming a horizontal electric field by means of the vertical electrodes and forming a vertical electric field by means of the horizontal electrodes; transporting water in soil body to a cathode area in a shallow layer of the soil body and discharging the water using vacuumization; performing spraying and humidification when the vertical anodes are powered. With the present invention, the water accumulated at the cathode can be effectively discharged from the soil body, thereby extending the electrode service life, solving the problem of uneven soil body reinforcement due to regular electro-osmosis methods and the problem of server anode corrosion. The operation is simple, the efficiency is high, and the cost is low.

Description

Strengthening electroosmosis method and system for strengthening soft clay foundation

Technical field

The invention belongs to the field of geotechnical engineering, and specifically relates to an enhanced electroosmosis method for strengthening soft clay foundations.

Background technique

When the cathode and anode electrodes are inserted into the soil and the DC power supply is connected, under the action of the electric field force of the power supply, the electrons on the negative pole of the power supply migrate to the cathode through the wire, while the electrons on the anode migrate to the positive pole of the power supply through the wire, in order to maintain the For the flow of electrons in the anode electrode, the cathode must continuously lose electrons, and the anode must continuously obtain electrons. Since electrons cannot directly enter the aqueous solution in the soil from the cathode to the anode, a reduction reaction that consumes electrons occurs at the interface of the cathode and the aqueous solution, and an oxidation reaction that generates electrons occurs at the interface between the anode and the aqueous solution. At the same time, the negative and positive electrodes are respectively charged with negative and positive charges, so that there is an electric field in the soil between the two electrodes. Therefore, the anions and cations in the aqueous solution move to the anode and the cathode respectively, thereby forming an electric current in the aqueous solution. Among them, some fine soil particles with negative charges on the surface also move to the anode. This phenomenon is called electrophoresis. Since most of the soil particles with negative charges on the surface have a relatively stable structure and will not move during the electroosmosis process, the number of movable anions in the aqueous solution is far less than the number of cations. At the same time, the ions in the aqueous solution generally exist in the form of hydrated ions. The water molecules are bound in the solvation layer around the ions and cannot move independently, but can only move together with the ions. Therefore, the relatively excessive hydrated cations in the aqueous solution are moving towards The movement of the cathode forms electroosmosis.

technical problem

Scholars from various countries have carried out many studies on the electroosmosis method based on indoor tests, field tests, engineering applications and calculation theory, and reported its application in various soil types, including organic soil, peat soil, oily sludge, industrial tailings , Dredging silt, dredging silt, waste mud, ocean bottom mud, polluted soil, urban sludge, etc. However, the following problems restrict the popularization and application of electroosmosis:

(1) The transmission efficiency of electric potential decreases. As the water in the soil near the anode migrates toward the cathode, the water content of the soil near the anode gradually decreases, the resistance gradually increases, and the anode is affected by corrosion, resulting in a significant potential drop. Only 75% of the rated voltage is valid.

(2) Reinforce the unevenness of the soil. After the completion of the project, it is found that the shear strength of the soil in the anode area has increased significantly, followed by the shear strength of the soil in the middle of the cathode and anode, while the shear strength of the soil at the cathode is still low. This is related to the fact that the water in the soil near the cathode cannot be effectively discharged from the soil surface, and the soil moisture content is still high.

There is an urgent need to provide an enhanced electroosmosis method for strengthening soft clay foundations to solve the above-mentioned problems in the prior art.

Technical solutions

An enhanced electroosmosis system for strengthening soft clay foundations, including:

The vertical drainage assembly includes a plurality of sets of vertical cathodes and vertical anodes arranged in the foundation, a first DC power source electrically connected to the vertical cathodes and the vertical anodes, one end extending to the vertical cathode, and the other A drainage pipe connected to a vacuum jet pump at one end; a horizontal electric field is formed between the vertical anode and the vertical cathode, and water is concentrated toward the vertical cathode under working conditions;

Horizontal drainage assembly, two or more horizontal electrodes arranged along the length of the vertical cathode, and a second DC power source electrically connected to the horizontal electrodes, and the horizontal electrode on the upper layer is connected to the cathode of the second DC power source; A vertical upward electric field is formed between the electrodes. In the working state, water is concentrated in the vertical direction toward the top of the cathode.

In a further embodiment, in the horizontal section, the horizontal electrodes are evenly arranged between the vertical cathodes.

In a further embodiment, a sand cushion is laid on the vertical cathode, the drainage pipe is buried in the sand cushion, and the water inlet end of the drainage pipe is provided with a sealing cover.

In a further embodiment, the sealing cover is made of PVC.

In a further embodiment, the vertical anode is a tube body, and the tube body is provided with a plurality of through holes.

In a further embodiment, the vertical anode is in communication with a spray system, and the inner and outer surfaces of the vertical anode are kept moist through spray humidification.

An enhanced electroosmosis method for strengthening soft clay foundations, using the enhanced electroosmosis system described in any one of the above; the method includes the following steps:

Step 1. Drill vertical anodes and vertical cathodes into the soft clay foundation, and set horizontal electrodes between the vertical cathodes; lay out the first DC power supply, the second DC power supply and wires; lay out the drainage system;

Step 2. Start the vertical drainage assembly and the horizontal drainage assembly to treat the soft clay foundation, so that the water moves from the vertical anode to the vertical cathode, and then moves from the bottom to the top of the vertical cathode, and is discharged through the drainage system;

Step 3. Repeat step 2 until the strength of the soil reaches the design requirements, and the components of the drainage system are recovered.

In a further embodiment, in the step 2, the working process of the vertical drainage assembly includes: connecting the vertical anode to the positive pole of the first DC power supply, and the vertical cathode to the negative pole of the first DC power supply, and turning on The first direct current power supply uses the spray head to move up and down inside the vertical anode during the power-on process to spray and humidify the inner wall of the vertical anode.

In a further embodiment, in the step 2, the working process of the horizontal drainage assembly includes:

Connect the bottommost horizontal electrode to the positive pole of the second DC power supply, and connect the adjacent horizontal electrode to the negative pole of the second DC power supply. After a period of time, stop the power supply, and then connect the second horizontal electrode from the bottom to the second DC The positive pole of the power supply, the third horizontal electrode is connected to the negative pole of the second DC power supply, and the energization is performed for a period of time until the horizontal electrode on the surface of the soil is the cathode, and water collects within a depth of about 0.5 m below the surface of the soil.

An enhanced electroosmosis method for strengthening soft clay foundations, including the following steps:

Step 1. According to the designed spacing and layout form, manually or mechanically drive electrodes into the soft clay foundation, and drive several horizontal electrodes horizontally between the vertical cathode electrodes. The electrodes are connected to the lead before being driven. Connect, waterproof the joints;

Step 2. Lay a sand cushion on the surface of the soil directly above the horizontal electrode. A section of drainage filter pipe is buried in the sand cushion. The other end of the drainage filter pipe is connected to the drainage hole of the sealing cover, and the sealing cover is pressed into the soil. Body, using a drain pipe to connect the drain hole of the sealing cover with the vacuum jet pump;

Step 3. Connect the vertical anode to the positive pole of the first DC power supply, and connect the vertical cathode to the negative pole of the first DC power supply, turn on the first DC power supply, and use the nozzle to move up and down inside the vertical anode during power-on Spray humidification on the inner wall of the vertical anode;

Step 4. Connect the bottommost horizontal electrode to the positive pole of the second DC power supply, and connect its adjacent horizontal electrode to the negative pole of the second DC power supply. After a period of time, stop energizing, and then count the second horizontal electrode from bottom to top. Connect the positive pole of the second DC power supply, and connect the third horizontal electrode to the negative pole of the second DC power supply. Power on for a period of time and proceed in sequence until the horizontal electrode on the surface of the soil is the cathode, and water converges within a predetermined depth below the surface of the soil;

Step 5: Turn on the vacuum jet pump to drain the water collected in the shallow soil;

Step 6, repeat steps 3~5 until the strength of the soil reaches the design requirements, and recover the electrode and sealing cover.

Beneficial effect

The invention realizes the uniform reinforcement of the soft clay through the combined action of the horizontal electric field, the vertical electric field and the vacuum in the soft clay foundation, and protects the anode by spraying and humidifying the anode, prolongs the effective treatment time of electroosmosis, and solves the problem of existing electric The infiltration method has short effective treatment time, uneven soil reinforcement, serious potential drop at the anode, etc., which improves the drainage and consolidation rate of soft clay and improves the reinforcement effect of the electroosmosis method; in addition, the invention is simple to operate, and can be fast and efficient The realization of soft clay reinforcement.

Description of the drawings

Fig. 1 is a schematic diagram of the operation of the enhanced electroosmosis method for strengthening soft clay foundations of the present invention.

Figure 2 is a schematic cross-sectional view of the electrode arrangement of the present invention.

Figure 3 is a schematic plan view of the electrode arrangement of the present invention.

Figure 4 is a schematic diagram of the drainage of the present invention.

Figure 5 is a schematic diagram of the horizontal electrode placement tube of the present invention.

The reference signs in the figure are: soft clay 1, vertical anode 2, vertical cathode 3, horizontal electrode 4, wire 5, direct current power supply 6, nozzle 7, water pipe 8, water tank 9, sand cushion 10, sealing cover 11 , Drainage pipe 12, Vacuum jet pump 13, Drainage hole 14, Electrode placement pipe 15, Guide part 16, Insulating sleeve 17.

The best mode of the invention

As shown in Figure 1, the enhanced electroosmosis system used to reinforce soft clay foundations mainly includes vertical drainage components and horizontal drainage components. They are used to form a horizontal electric field and a vertical electric field respectively, so that water is concentrated and discharged in a fixed direction.

The processing method for strengthening soft clay foundation of the present invention mainly includes the following steps:

Step 1: According to the designed spacing and layout, use manual or mechanical methods to vertically drive electrodes into the soft clay foundation, drive several electrodes horizontally between the vertical cathode electrodes, and connect the electrodes to the wires before drilling. Waterproof the joints;

Step 2: Lay a sand cushion on the surface of the soil directly above the horizontal electrode, and bury a section of drainage filter pipe in the sand cushion. The other end of the drainage filter pipe is connected to the drainage hole of the sealing cover, and the sealing cover is pressed into the soil. , Use a drain pipe to connect the drain hole of the sealing cover with the vacuum jet pump;

Step 3: Connect the vertical anode to the positive pole of the DC power supply, and connect the vertical cathode to the negative pole of the DC power supply. Turn on the DC power supply. During power-on, use the nozzle to move up and down inside the vertical anode to spray and humidify the inner wall of the vertical anode;

Step 4: Connect the bottom horizontal electrode to the positive pole of the DC power supply, and connect the adjacent horizontal electrode to the negative pole of the DC power supply. After a period of time, stop the power supply, and then connect the second horizontal electrode from the bottom to the top of the DC power supply. , The third horizontal electrode is connected to the negative electrode of the DC power supply, and the power is turned on for a period of time, and then proceed in sequence until the horizontal electrode on the surface of the soil is the cathode, and water converges within a depth of about 0.5m below the surface of the soil;

Step 6: Repeat steps S3~S5 until the strength of the soil meets the design requirements, and recover the electrode and sealing cover.

It should be noted that in step 1, the vertical electrodes can be arranged in a rectangular or quincunx pattern, and the distance between the same- and opposite-sex electrodes is 1~1.5m. The setting position of the horizontal electrode is located in the middle of the two vertical cathodes, the length of the horizontal electrode is 1m, and the vertical spacing of the horizontal electrode in the soil is 1m. The vertical and horizontal electrode setting depth can be determined according to the difficulty of laying the soft clay. For soft clay foundations that are difficult for machinery to enter, woven cloth can be laid on the site, and the electrodes can be manually laid 3~4m deep and shallow with the help of foam boards. After the soil has been processed, it meets the requirements that the machine can enter the site, and then conduct a second treatment in the same way.

In step 2, the sealing cover is made of PVC material, and the shape is similar to an uncovered cube box. The length and width of the top cover are 0.8~1m, the height of the box is 0.5~0.8m, and the thickness is 0.5~1cm, with the sealing cover facing down When driven into the soil, there is a 5~10cm drainage hole on the top cover of the sealing cover.

In step 3, the vertical anode is a tube body, the tube body is filled with small holes, and the vertical anode tube is sprayed and humidified by a high-pressure nozzle to keep the inner and outer surfaces of the anode moist.

In step 4, when the soil moisture content is higher than 80%, the energization time of adjacent horizontal electrodes in one cycle is 0.5~1h. When the soil moisture content is lower than 80%, the adjacent horizontal electrodes are in one cycle. The power-on time in the medium is extended to 2~4h.

Embodiments of the invention

In a further embodiment, the horizontal drainage assembly in the above-mentioned drainage system further includes a horizontal electrode placement tube 15, and more than two rows of through holes are arranged along the length of the horizontal electrode placement tube, and each group of through holes is symmetrically arranged. The horizontal electrodes and wires are installed at predetermined positions through the L-shaped guide tube to form a multilayer horizontal electrode layout. The wires on the same horizontal plane are connected to the same pole of the DC power supply.

In a further embodiment, in step 1 of the enhanced electroosmosis method, when the horizontal electrode is installed, the L-shaped guide tube extends to a certain through hole, the end of the guide tube is connected to the through hole, and the electrode with a lead The L-shaped guide tube extends to the through hole and moves outward along the through hole for a predetermined distance. Take the L-shaped guide tube out of the other end of the wire and repeat the above steps until all the horizontal electrodes are installed.

In step 4, when performing vertical drainage, connect the horizontal electrode on the same horizontal plane to the same pole of the DC power source, and connect the horizontal electrode on the other horizontal plane to the other pole of the DC power source to form an electric field distribution with the cathode on the top and the anode on the bottom. The water is concentrated near the top of the cathode.

The distance between horizontal electrodes on the same horizontal plane can be adjusted by the length of the insulating sleeve.

Industrial applicability

The enhanced electroosmosis method for strengthening soft clay foundation provided by the present invention has the following advantages: First, in the soft clay foundation, through the combined action of horizontal electric field, vertical electric field and vacuum, the uniform reinforcement of soft clay is realized, and through The spray humidification treatment of the anode protects the anode and prolongs the effective treatment time of electroosmosis. It solves the problems of short effective treatment time of the existing electroosmosis method, uneven soil reinforcement, serious potential drop at the anode, etc., and improves the drainage and consolidation of soft clay Speed, reduce energy consumption, and improve the reinforcement effect of electroosmosis. Second, the present invention is easy to operate, fast and efficient, shortens the construction period, and saves cost.

The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solution of the present invention. These equivalent transformations All belong to the protection scope of the present invention.

Claims

An enhanced electroosmosis system for strengthening soft clay foundations, which is characterized by comprising:

The vertical drainage assembly includes a plurality of sets of vertical cathodes and vertical anodes arranged in the foundation, a first DC power source electrically connected to the vertical cathodes and the vertical anodes, one end extending to the vertical cathode, and the other A drainage pipe connected to a vacuum jet pump at one end; a horizontal electric field is formed between the vertical anode and the vertical cathode, and water is concentrated toward the vertical cathode under working conditions;

Horizontal drainage assembly, two or more horizontal electrodes arranged along the length of the vertical cathode, and a second DC power source electrically connected to the horizontal electrodes, and the horizontal electrode on the upper layer is connected to the cathode of the second DC power source; A vertical upward electric field is formed between the electrodes. In the working state, water is concentrated in the vertical direction toward the top of the cathode.
The enhanced electroosmosis system for strengthening soft clay foundations according to claim 1, wherein in a horizontal section, the horizontal electrodes are evenly arranged between the vertical cathodes.
The enhanced electroosmosis system for strengthening soft clay foundations according to claim 1, wherein a sand cushion is laid at the vertical cathode, the drainage pipe is buried in the sand cushion, and the drainage pipe The water inlet end is provided with a sealing cover.
The enhanced electroosmosis system for strengthening soft clay foundations according to claim 3, wherein the sealing cover is made of PVC.
The enhanced electroosmosis system for strengthening soft clay foundations according to claim 1, wherein the vertical anode is a tube body with a number of through holes provided on the tube body.
The enhanced electroosmosis system for strengthening soft clay foundations according to claim 5, wherein the vertical anode is in communication with a spray system, and the inner and outer surfaces of the vertical anode are kept wet by spray humidification.
An enhanced electroosmosis method for strengthening soft clay foundations, characterized in that the enhanced electroosmosis system according to any one of claims 1 to 6 is adopted; the method includes the following steps:

Step 1. Drill vertical anodes and vertical cathodes into the soft clay foundation, and set horizontal electrodes between the vertical cathodes; lay out the first DC power supply, the second DC power supply and wires; lay out the drainage system;

Step 2. Start the vertical drainage assembly and the horizontal drainage assembly to treat the soft clay foundation, so that the water moves from the vertical anode to the vertical cathode, and then moves from the bottom to the top of the vertical cathode, and is discharged through the drainage system;

Step 3. Repeat step 2 until the strength of the soil reaches the design requirements, and the components of the drainage system are recovered.
The strengthened electroosmosis method for strengthening soft clay foundations according to claim 7, wherein:

In said step 2, the working process of the vertical drainage assembly includes: connecting the vertical anode to the positive pole of the first DC power supply, and the vertical cathode to the negative pole of the first DC power supply, turning on the first DC power supply, and energizing During the process, the nozzle is used to move up and down inside the vertical anode to spray and humidify the inner wall of the vertical anode.
The strengthened electroosmosis method for strengthening soft clay foundations according to claim 7, wherein:

In the step 2, the working process of the horizontal drainage assembly includes:

Connect the bottommost horizontal electrode to the positive pole of the second DC power supply, and connect the adjacent horizontal electrode to the negative pole of the second DC power supply. After a period of time, stop the power supply, and then connect the second horizontal electrode from the bottom to the second DC The positive pole of the power supply, the third horizontal electrode is connected to the negative pole of the second DC power supply, and the energization is performed for a period of time until the horizontal electrode on the surface of the soil is the cathode, and water collects within a depth of about 0.5 m below the surface of the soil.
An enhanced electroosmosis method for strengthening soft clay foundation, which is characterized in that it comprises the following steps:

Step 1. According to the designed spacing and layout form, manually or mechanically drive electrodes into the soft clay foundation, and drive several horizontal electrodes horizontally between the vertical cathode electrodes. The electrodes are connected to the lead before being driven. Connect, waterproof the joints;

Step 2. Lay a sand cushion on the surface of the soil directly above the horizontal electrode. A section of drainage filter pipe is buried in the sand cushion. The other end of the drainage filter pipe is connected to the drainage hole of the sealing cover, and the sealing cover is pressed into the soil. Body, using a drain pipe to connect the drain hole of the sealing cover with the vacuum jet pump;

Step 3. Connect the vertical anode to the positive pole of the first DC power supply, and connect the vertical cathode to the negative pole of the first DC power supply, turn on the first DC power supply, and use the nozzle to move up and down inside the vertical anode during power-on Spray humidification on the inner wall of the vertical anode;

Step 4. Connect the bottommost horizontal electrode to the positive pole of the second DC power supply, and connect its adjacent horizontal electrode to the negative pole of the second DC power supply. After a period of time, stop energizing, and then count the second horizontal electrode from bottom to top. Connect the positive pole of the second DC power supply, and connect the third horizontal electrode to the negative pole of the second DC power supply. Power on for a period of time and proceed in sequence until the horizontal electrode on the surface of the soil is the cathode, and water converges within a predetermined depth below the surface of the soil;

Step 5: Turn on the vacuum jet pump to drain the water collected in the shallow soil;

Step 6, repeat steps 3~5 until the strength of the soil reaches the design requirements, and recover the electrode and sealing cover.