Electrochemical reinforcement device and method for soft clay

Abstract

The application discloses a soft clay electrochemical reinforcement device and method, the device comprising a power supply, an anode, a cathode, and an intermediate grouting pipe; a cation exchange membrane is arranged in the area close to the cathode of the soil body to be reinforced, the cation exchange membrane only allows the migration of cations from the inside of the soil body to the direction of the cathode, and physically blocks the reverse diffusion of anions generated by the cathode electrolysis reaction to the direction of the soil body; the cation exchange membrane is wrapped on the outer surface of the cathode, or is arranged in the soil body around the cathode as an independent separation layer, forming an ion filtering interface completely surrounding the cathode. The method sets a selectively permeable cation exchange membrane at the interface between the cathode and the soil body, and combines the step grouting process of anode grouting first and then intermediate grouting pipe grouting, thereby significantly improving the unit energy consumption drainage capacity under the same voltage, and increasing the soil body settlement in the cathode area by nearly 4 times, thus solving the engineering problem of the traditional electro-osmosis "hard anode and soft cathode".

Description

Technical Field

[0001] This invention relates to a device and method for reinforcing soil for engineering foundations, and more particularly to a device and method for electrochemically reinforcing soft clay. Background Technology

[0002] With the rapid development of coastal economic zones and the advancement of urbanization, land resources are becoming increasingly scarce. Land reclamation and the use of dredged silt for land filling have become important means to address the contradiction between land supply and demand. However, these types of soft soil fills and widely distributed marine and lacustrine sedimentary soft clays typically have high natural water content (often greater than the liquid limit), large porosity, and extremely low permeability (k < 1×10⁻⁶). -7 Its low shear strength and high rheological properties, along with its low shear strength (cm / s), make it extremely unfavorable for engineering projects. If used directly as a foundation without treatment, it is highly likely to cause excessive settlement, uneven deformation, or even foundation instability, seriously threatening the safety of the project.

[0003] Currently, the main methods for treating soft soil foundations include physical reinforcement and chemical reinforcement. Chemical reinforcement includes electrochemical reinforcement, but existing electrochemical reinforcement methods still have the following unresolved issues:

[0004] (1) Cathode "softening" phenomenon: Under the existing anode grouting mode, modified ions such as calcium and potassium have difficulty migrating to areas far from the anode, especially near the cathode. Meanwhile, the OH- produced at the cathode... - However, ions accumulate in the cathode region, causing the soil in that area not only to fail to receive chemical reinforcement, but also to develop a dispersed structure due to the highly alkaline environment, resulting in extremely low strength and becoming a weak link in the foundation.

[0005] (2) Uneven reinforcement: Due to the limited migration speed of ions and the uneven distribution of soil resistance as the energizing time increases, the chemical slurry often remains near the anode, making it impossible to achieve uniform reinforcement across the entire field.

[0006] (3) Reduced drainage efficiency: Metal cations (such as Ca) that originate in the soil and migrate from the anodic region 2+ Mg 2+ Al 3+ (etc.) reacts with OH generated by cathode electrolysis - When they meet, a precipitation reaction occurs, forming non-conductive solid particles. These particles can clog the pore channels, leading to a decrease in drainage efficiency. Summary of the Invention

[0007] Purpose of the invention: This invention aims to provide an electrochemical reinforcement device for soft clay, which can effectively isolate the OH generated by the cathodic electrolysis reaction. - It diffuses in the reverse direction into the soil and achieves uniform distribution of the chemical grout in the soil, thereby improving the overall effect and uniformity of electrochemical reinforcement.

[0008] Another object of the present invention is to provide a method for electrochemically reinforcing soft clay using the above-described apparatus.

[0009] Technical solution: The electrochemical reinforcement device for soft clay of the present invention includes a power source, an anode connected to the positive terminal of the power source, a cathode connected to the negative terminal of the power source, and an intermediate grouting pipe located between the anode and the cathode; a cation exchange membrane is provided in the area of ​​the soil to be reinforced near the cathode, the cation exchange membrane only allows cations to migrate from the interior of the soil towards the cathode, and physically blocks the anions generated by the cathode electrolysis reaction from diffusing back towards the soil; the cation exchange membrane is wrapped around the outer surface of the cathode, or is set as an independent partition in the soil surrounding the cathode, forming an ion filtration interface that completely surrounds the cathode.

[0010] The cation exchange membrane has an ion exchange capacity of not less than 1.5 meq / g and is resistant to acid and alkali corrosion.

[0011] The anode and the intermediate grouting pipe are uniformly provided with grouting holes, with an opening rate ranging from 15% to 25%; a drainage hole is provided at the corresponding position at the bottom of the cathode; the drainage hole is connected to a drainage pipe.

[0012] For ease of testing, the drain hole is connected to an external drainage collection system, which includes a graduated cylinder and an electronic balance for real-time measurement and recording of changes in drainage volume; wherein the graduated cylinder has an accuracy of not less than 0.1 mL.

[0013] The intermediate grouting pipe is made of conductive metal or insulating polymer material. When conductive metal is used, the intermediate grouting pipe can be used as an auxiliary anode connected to the circuit to enhance the current intensity in the middle and later stages.

[0014] The method for electrochemically reinforcing soft clay using the above-described apparatus includes the following steps:

[0015] In the soft clay area to be reinforced, anodes, cathodes, and intermediate grouting pipes are arranged in a preset geometric array; a cation exchange membrane is installed between the cathode and the soil to be reinforced.

[0016] The first electrolyte solution is injected into the soil through the anode to start the first stage of grouting; the DC power supply is turned on and a constant or pulsed DC electric field is applied between the anode and the cathode to start the first stage of electro-osmosis drainage. The electric field force drives the cations and the first electrolyte solution at the anode to migrate towards the cathode, while the cation exchange membrane blocks the hydroxide ions generated by the cathode electrolysis reaction from entering the soil.

[0017] During the electroosmosis process, the current intensity and drainage volume are monitored in real time. When the current intensity is detected to decrease from the peak value, or when the energizing time reaches 40%-60% of the total design time, the second stage of grouting is initiated. A second electrolyte solution is injected into the middle of the soil through the intermediate grouting pipe. The fresh ion source injected into the middle activates the conductive channels in the deep soil, forming a secondary electroosmosis peak.

[0018] Maintain the DC electric field until the injected electrolyte solution covers the area near the cathode under the drive of the electric field and the drainage rate decreases to a preset threshold; stop the power supply, recover the reusable electrodes and grouting equipment, and carry out soil curing.

[0019] The first electrolyte solution is selected from potassium chloride solution and / or calcium chloride solution; the concentration of the first electrolyte solution is 2.0-5.0 mol / L.

[0020] The second electrolyte solution has the same chemical composition as the first electrolyte solution, and the volume ratio of the injected volume to the volume of the first electrolyte solution is 0.8:1-1.2:1.

[0021] The second stage of grouting is initiated 12-13 hours after power is applied, or when the current intensity drops to 70% of the initial peak value.

[0022] The applied DC voltage gradient is 0.8 -1.2 V / cm.

[0023] Between the first and second stages of grouting, a power outage interval of 2-12 hours is set according to the dissipation of pore water pressure.

[0024] Among these measures, reusable electrodes and grouting equipment are recycled before soil curing.

[0025] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0026] (1) The present invention introduces a cation exchange membrane around the cathode to convert the OH generated by the cathode electrolysis reaction into a cation exchange membrane. - Effectively isolated from the soil. Tests show that, under the same electrical conditions, the electroosmotic drainage rate using the method of this invention does not exhibit the rapid decline over time seen in traditional methods, but rather maintains a consistently high efficiency. Compared to the comparative example without a cation exchange membrane, this invention effectively prevents the exchange of cations and OH groups within the soil. -The reaction generates precipitation, which causes blockage of drainage channels and increased soil resistance. This invention successfully solves the key problems of "cathode blockage" and "reverse electroosmosis" that have long restricted the development of electroosmosis technology. (2) The "step-by-step grouting" method proposed in this invention, which involves grouting the anode first and then the intermediate grouting pipe, effectively solves the problem of "hard anode and soft cathode" caused by the limited range of action in traditional electroosmosis grouting technology. The highly active modified grout is directly transported to the middle area of ​​the soil through the intermediate grouting pipe, and the grout is fully covered to the cathode area by the electric field in the second half of the process. With the cation exchange membrane inhibiting the softening effect of the cathode, this invention successfully achieves uniform reinforcement of the soil from the anode to the cathode, which significantly improves the overall strength and stability. (3) This invention adopts intermittent step-by-step grouting technology, which replenishes the ion concentration of the solution in time during the electroosmosis process, effectively restoring and enhancing the driving force of electroosmosis. The test drainage rate curve shows a typical "double peak" characteristic, indicating that the electroosmotic flow is reactivated after grouting in the intermediate stage, and the drainage efficiency is significantly improved. Within the same energizing time, this invention can achieve the drainage of more pore water, thereby significantly shortening the time required for the foundation to reach the target degree of consolidation and significantly improving the efficiency of electrochemical reinforcement. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0028] Figure 2 This is a schematic diagram of the electrode arrangement and different test positions of the device of the present invention;

[0029] Figure 3 The cumulative drainage volume of Embodiment S5 and Comparative Examples S1, S2, and S3 of the present invention varies with the energizing time during the electroosmosis process.

[0030] Figure 4 The instantaneous drainage rate versus energizing time is shown in Embodiment S5 and Comparative Examples S1, S2, and S3 of the present invention.

[0031] Figure 5 The figures show the measured settlement curves of different locations of the reinforced soil after embodiment S5 and comparative examples S1, S2, and S3 of the present invention as a function of energization time, where (a) is measuring point 1#, (b) is measuring point 2#, (c) is measuring point 3#, (d) is measuring point 4#, and (e) is measuring point 5#.

[0032] Figure 6 The cumulative drainage volume during the electroosmosis process in Embodiment S5 and Comparative Examples S3 and S4 of the present invention varies with the energizing time.

[0033] Figure 7The figures are the measured settlement curves of soil at different locations after reinforcement and the change of energization time in Embodiment S5 and Comparative Examples S3 and S4 of the present invention, where (a) is measuring point 1#, (b) is measuring point 2#, (c) is measuring point 3#, (d) is measuring point 4#, and (e) is measuring point 5#.

[0034] Figure 8 The cumulative drainage volume during the electroosmosis process in Embodiment S5 and Comparative Examples S6 and S7 of the present invention varies with the energizing time.

[0035] Figure 9 The figures for Embodiment S5 and Comparative Examples S6 and S7 of the present invention are the measured settlement curves of soil at different locations after reinforcement as a function of energization time. Among them, (a) is measuring point 1#, (b) is measuring point 2#, (c) is measuring point 3#, (d) is measuring point 4#, and (e) is measuring point 5#.

[0036] Figure labels: 1 Model box, 2 Power supply, 3 Anode, 4 Cathode, 5 Intermediate grouting pipe, 6 Cation exchange membrane, 7 Data acquisition system, 8 Drain hole, 9 Drain pipe, 10 Dial gauge, 11 Voltage probe. Detailed Implementation

[0037] The present invention will now be described in further detail.

[0038] Example 1

[0039] like Figure 1 As shown, the present invention provides an electrochemical reinforcement device for soft clay, including a power source 2, an anode 3 as the positive electrode, a cathode 4 as the negative electrode, and an intermediate grouting pipe 5 located between the anode 3 and the cathode 4; a chemical solution is injected into the anode 3 and the intermediate grouting pipe 5 through external injection, and grouting is carried out in stages in different areas during the electroosmosis process; a cation exchange membrane 6 is set between the cathode 4 and the soil to be reinforced; the cation exchange membrane 6 only allows cations to migrate from the inside of the soil towards the cathode 4, and physically blocks the anions generated by the electrolytic reaction of the cathode 4 from diffusing in the opposite direction towards the soil; the cation exchange membrane 6 is wrapped around the outer surface of the tubular cathode 4, or is set as an independent partition in the soil around the cathode 4, forming an ion filtration interface that completely surrounds the cathode 4.

[0040] This embodiment also includes a model box 1, inside which the aforementioned cathode 4, anode 3, and intermediate grouting pipe 5 are all located. The model box 1 is made of high-transparency acrylic sheet, with internal dimensions of 400mm long × 300mm wide × 140mm high and a wall thickness of 10mm, which is sufficient to withstand the lateral pressure of the soil.

[0041] In this embodiment, the anode 3 is a 304 stainless steel pipe with an outer diameter of 10 mm and a wall thickness of 1 mm. Grouting holes with a diameter of 2 mm are evenly drilled in the pipe wall, with a hole spacing of 20 mm and arranged in a quincunx pattern. The opening rate ranges from 15% to 25%. A layer of 200 g / m² geotextile is wrapped around the outside of the pipe to prevent soil particles from clogging the grouting holes.

[0042] In this embodiment, the cathode 4 is made of the same material as the anode 3. A drainage hole 8 is provided at the bottom of the cathode 4, and the drainage hole 8 is connected to a drainage pipe 9. A cation exchange membrane 6 (CEM) is wrapped around the outside of the geotextile. In this embodiment, a sulfonated polystyrene-divinylbenzene copolymer cation exchange membrane 6 is selected. This membrane has excellent chemical stability and selective permeability, allowing only cations to pass through while strictly blocking anions, i.e., OH-. - For ease of testing, the bottom drain hole 8 of the cathode 4 in this embodiment is connected to an external drainage collection system. The drainage collection system includes a graduated cylinder (not shown in the figure) and an electronic balance (not shown in the figure) for real-time measurement and recording of changes in drainage volume; wherein, the accuracy of the graduated cylinder is not less than 0.1 mL.

[0043] The intermediate grouting pipe 5 is made of conductive metal or insulating polymer material. When conductive metal is used, the intermediate grouting pipe 5 can be used as an auxiliary anode connected to the circuit to enhance the current intensity in the middle and later stages. In this embodiment, the intermediate grouting pipe 5 has the same structural material as the anode 3 and is located at the geometric midpoint between the anode 3 and the cathode 4. Grouting holes are uniformly distributed on the surface of the intermediate grouting pipe 5, with an opening rate ranging from 15% to 25%.

[0044] The soil used in this experiment was taken from the dredged silt at a land reclamation project site. Its basic physical properties, determined through indoor geotechnical testing, are shown in Table 1 below:

[0045] Table 1 Basic physical properties of the soil used in the experiment

[0046]

[0047] Note: Chemical solution: Prepare an electrolyte solution with a concentration of 4.0 mol / L using pure potassium chloride (KCl).

[0048] Example 2

[0049] The soil sample was reinforced using the apparatus of Example 1 according to the following steps:

[0050] Step 1: Soil sample loading and electrode placement

[0051] The soil samples collected from the site were dried, crushed, and sieved through a 2mm sieve. Distilled water was added and stirred until the moisture content reached 42%. The samples were then left to stand for 24 hours to ensure even moisture distribution. Subsequently, the samples were filled into the mold box in layers, and air bubbles were eliminated by vibration. The dry density of the filling was controlled to be 1.21 g / cm³.

[0052] Anode 3, cathode 4, and intermediate grouting pipe 5 were vertically inserted into the soil, with the electrodes penetrating to a depth of 100mm and the distance between anode 3 and cathode 4 maintained at 350mm. Simultaneously, settlement observation points 1#-5#, voltage probe 11, and dial gauge 10 were set up at different locations. Figure 2 As shown, measuring point 1# is located at anode 3, measuring point 3 is located at the intermediate grouting pipe 5, measuring point 5# is located at cathode 4, measuring point 2# is located at the midpoint between measuring points 1# and 3#, and measuring point 4 is located at the midpoint between measuring points 3# and 5#. The distance between any two adjacent measuring points is equal. Voltage probe 11 and dial gauge 10 are respectively arranged at measuring points 1#-5#. Figure 2 The voltage probe marking at measuring point 3# is covered by a black dot. Each voltage probe 11 is connected to the data acquisition system 7 to automatically read voltage data; the dial indicator 10 is a general-purpose length measuring tool used to measure soil settlement, and the data is read manually.

[0053] Step 2: First stage: Anode 3 grouting and electroosmosis

[0054] Grouting: 70 mL of a 4.0 mol / L KCl solution is injected into the soil through anode 3. The solution seeps into the soil surrounding anode 3 by its own weight and the action of the electric current.

[0055] Power on: Connect DC regulated power supply 2, model RXN-605D, set the output voltage to 30V, corresponding to a potential gradient of 0.86 V / cm.

[0056] Process: Power is applied for 12.5 hours. During this period, current changes are recorded using voltage probe 11 and data acquisition system 7 to monitor current intensity in real time; an external drainage collection cylinder is connected to an electronic balance via drainage hole 8 to monitor drainage volume changes in real time. At this time, the high concentration of K in anode region 3... + Driven by an electric field, ions migrate toward cathode 4, displacing Na+ on the surface of soil particles. + Compression of the double electric layer; pore water follows K + Migration. At cathode 4, the CEM membrane intercepts the OH generated during electrolysis. - The discharged water is mainly pore water.

[0057] Step 3: Grouting of the intermediate grouting pipe in the second stage

[0058] Grouting: When the power is applied for 12.5 hours, stop the power supply and inject 70 mL of 4.0 mol / L KCl solution into the intermediate grouting pipe 5; alternatively, KCl solution can be injected into the intermediate grouting pipe 5 while it is energized.

[0059] Continue power supply: Maintain 30V voltage and continue power supply for 12.5 hours, for a total of 25 hours.

[0060] At this point, some of the ions injected in the first stage have been lost or diffused, and the current shows a decreasing trend; the fresh electrolyte solution injected in the middle rapidly reduces the resistance of the soil in the middle, and the electroosmotic flow accelerates again, forming a second peak in the drainage rate, such as Figure 3 As shown.

[0061] Step 4: Termination and Testing

[0062] After the power is turned on, disconnect power source 2 and let the soil stand for 24 hours to allow the pore pressure to dissipate. Then, take soil samples to determine the final moisture content.

[0063] Relevant tests and results analysis:

[0064] To verify the superiority of test number S5 of the present invention, six sets of comparative tests were set up, with conditions shown in Table 2 below:

[0065] Table 2 Six groups of comparative experiments

[0066]

[0067] (1) Analysis of drainage volume and drainage rate

[0068] Figure 3 The cumulative drainage volume of the four groups of tests (S1, S2, S3, and S5) as a function of energization time is shown.

[0069] 0-12.5h stage: During the initial energization, KCl solution was injected into both the anode 3 and the intermediate grouting pipe 5 in tests S1 and S3, resulting in a high ion concentration in the soil. Consequently, the drainage volume of tests S1 and S3 was significantly higher than that of tests S2 and S5. Furthermore, the drainage volume of test S3 was slightly greater than that of S1, and the drainage volume of test S5 was slightly greater than that of S2, indicating that the CEM film surrounding the cathode 4 had already hindered OH- ion exchange. - Its effect of spreading into the soil is not yet obvious.

[0070] 12.5-25h stage: At 12.5h, KCl solution was injected a second time into the intermediate grouting pipe 5 in tests S2 and S5, reactivating the electrochemical reaction within the soil. The drainage volume of test S2 exceeded that of S1 after 15h, and the drainage volume of test S5 exceeded that of S3 after 15h, indicating that the stepwise grouting method can effectively increase the total drainage volume of the soil sample. Furthermore, the drainage volume of test S5 was significantly greater than that of S2 after 15h, indicating that with increasing energizing time, the CEM film surrounding cathode 4 significantly hindered OH... - It diffuses into the soil, significantly increasing the total amount of drainage during the electroosmosis process.

[0071] End of power-on: After the power-on is completed, compared with comparative examples S1, S2 and S3, the cumulative drainage volume of S5 of the present invention is the largest.

[0072] Figure 4 The curves showing the instantaneous drainage rate versus energization time for four sets of tests (S1, S2, S3, and S5) are presented.

[0073] All four groups of experiments showed peak instantaneous drainage rates 2-3 hours after grouting. S2 and S5 both showed two peak instantaneous drainage rates after the second stage of step-by-step grouting. After the second stage of step-by-step grouting, the instantaneous drainage rate of S5 in this invention decreased the slowest, remaining at a higher level compared to comparative examples S1, S2, and S3. The drainage rate of comparative example S2 decreased significantly in the second stage, indicating that the OH generated by the electrolysis of cathode 4... - This would significantly reduce electroosmosis efficiency. However, in S5 of this invention, a CEM membrane is used to prevent the generation of OH radicals during electrolysis. - The grout diffuses into the soil, maximizing the effect of staged grouting.

[0074] (2) Settlement and Deformation Analysis

[0075] Figure 5 The four groups of experiments, S1, S2, S3, and S5, were demonstrated. Figure 2 The curves showing the change of measured soil settlement at five different measuring points with energization time are shown. Figure 5 In the diagram, (a) represents measuring point 1#, (b) represents measuring point 2#, (c) represents measuring point 3#, (d) represents measuring point 4#, and (e) represents measuring point 5#. (From...) Figure 5 It can be seen that as the energizing time increases, the final settlement at all five measuring points in Embodiment S5 of the present invention is the largest after the energizing is stopped. Specifically, for measuring points 1#, 2#, and 3#, due to their distance from cathode 4, they are less affected by the CEM film, and the final settlement of Embodiment S5 of the present invention is not significantly different from that of comparative examples S1, S2, and S3. For measuring points 4# and 5#, due to the influence of the CEM film, the final settlement of Embodiment S5 of the present invention is significantly higher than that of comparative examples S1, S2, and S3, indicating that Embodiment S5 of the present invention can solve the problem of "hard anode and soft cathode" that is difficult to deal with by traditional electrochemical reinforcement technology, and significantly improve the uniformity of soil reinforcement.

[0076] (3) Analysis of the influence of grouting method, i.e. grouting time interval, on electroosmosis effect.

[0077] Figure 6 The cumulative water displacement versus energization time curves for the three test groups S3, S4, and S5 are shown. Figure 7 The three sets of experiments, S3, S4, and S5, were demonstrated. Figure 2 The curves showing the variation of measured soil settlement at five different measuring points with energization time are shown. Figure 7Figure (a) shows measuring point 1#, (b) shows measuring point 2#, (c) shows measuring point 3#, (d) shows measuring point 4#, and (e) shows measuring point 5#. Comparing the three sets of tests S3, S4, and S5, it can be seen that after the power is turned off, the final settlement of the S5 test of this invention is the largest at all five measuring points. For measuring points 1#, 2#, and 3#, the time interval between grouting stages has a relatively small impact on the final settlement of the soil at different measuring points; for measuring points 4# and 5#, the time interval between grouting stages has a significant impact on the final settlement of the soil at different measuring points.

[0078] (4) Analysis of the influence of the placement of cation exchange membrane 6 on the electroosmosis effect

[0079] Figure 8 The cumulative water displacement versus energization time curves for the three test groups S5, S6, and S7 are shown. Figure 9 The three sets of experiments, S5, S6, and S7, were demonstrated. Figure 2 The curves showing the variation of measured soil settlement at five different measuring points with energization time are shown. Figure 9 Figure (a) shows measuring point 1#, (b) shows measuring point 2#, (c) shows measuring point 3#, (d) shows measuring point 4#, and (e) shows measuring point 5#. Comparing the three sets of tests S5, S6, and S7, it can be seen that after the power is turned off, the final settlement of the present invention S5 at all five measuring points is the largest.

[0080] Furthermore, wrapping the CEM membrane around the anode 3 significantly reduces the effect of electroosmosis, wrapping the CEM membrane around the intermediate grouting pipe 5 does not significantly improve the effect of electroosmosis, while wrapping the CEM membrane around the cathode 4 significantly improves the effect of electroosmosis.

[0081] Example 3

[0082] Application scenarios: Land reclamation foundation treatment in Binhai New Area, soft soil foundation reinforcement for highways, and silt reinforcement for deep foundation pits in subway stations.

[0083] Recommended parameters:

[0084] Electrode spacing: 0.8m - 1.2m.

[0085] Voltage: 30V - 60V DC, depending on safety regulations.

[0086] Grouting materials: For general soft soil, saturated KCl solution is recommended due to its high solubility (approximately 4.5 mol / L at room temperature), high electrical conductivity, and lack of precipitation that clogs the grouting pipe. For localized areas requiring extremely high strength, CaCl2 can be used, but it must be strictly used in conjunction with a CEM membrane.

[0087] Grouting timing: Current control method is adopted. That is, when the monitored current drops to 70% of the peak value, the intermediate pipe grouting is automatically triggered to achieve intelligent construction.

Claims

1. An electrochemical soft clay reinforcement device, characterized by, The device comprises a power supply (2), an anode (3) connected to the positive pole of the power supply (2), a cathode (4) connected to the negative pole of the power supply (2), and an intermediate grouting pipe (5) between the anode (3) and the cathode (4); a cation exchange membrane (6) is arranged in the area close to the cathode (4) of the soil body to be reinforced, the cation exchange membrane (6) only allows cations to migrate from the inside of the soil body to the direction of the cathode (4), and physically blocks the reverse diffusion of anions generated by the electrolytic reaction of the cathode (4) to the soil body; the cation exchange membrane (6) is wrapped on the outer surface of the cathode (4), or is arranged as an independent separation layer in the soil body around the cathode (4), forming an ion filtering interface completely surrounding the cathode (4); the material of the intermediate grouting pipe (5) is an electrically conductive metal or an insulating polymer material, when an electrically conductive metal material is used, the intermediate grouting pipe (5) is connected to the circuit as an auxiliary anode to enhance the current intensity in the middle and later stages.

2. The soft clay electrochemical reinforcement apparatus according to claim 1, wherein, The ion exchange capacity of the cation exchange membrane is not less than 1.5 meq / g, and it has acid and alkali corrosion resistance.

3. The soft clay electrochemical reinforcement apparatus according to claim 1, wherein, The anode (3) and the surface of the intermediate grouting pipe (5) are uniformly provided with grouting holes, and the opening rate is 15%-25%; the cathode (4) is provided with a drainage hole (8) at the corresponding position of the bottom.

4. A method for electrochemically reinforcing soft clay using the device of claim 1, characterized in that, The device comprises the following steps: In the soft clay area to be reinforced, the anode (3), the cathode (4), and the intermediate grouting pipe (5) are arranged according to the preset geometric array; the cation exchange membrane (6) is arranged in the soil body to be reinforced close to the cathode (4); injecting a first electrolyte solution into the interior of the soil body through the anode (3) to start the first stage grouting; connecting the direct current power supply (2) to apply a constant or pulsed direct current electric field between the anode (3) and the cathode (4) to start the first stage electro-osmotic drainage, and driving the cations at the anode (3) and the first electrolyte solution to migrate toward the cathode (4) direction by using the electric field force, while blocking the OH - generated by the cathode (4) electrolysis reaction through the cation exchange membrane The current intensity and the drainage amount are monitored in real time during the electro-osmosis process; when the current intensity starts to decay from the peak value, or the power-on time reaches 40%-60% of the total design time, the second stage grouting is started; the second electrolyte solution is injected into the middle of the soil body through the intermediate grouting pipe (5), and the fresh ion source injected in the middle is used to activate the conductive channel in the deep part of the soil body, forming a secondary electro-osmosis peak value; The direct current field is maintained until the electrolyte solution injected in the middle covers the area near the cathode (4) under the driving of the electric field, and the drainage rate decreases to the preset threshold value; the power supply is stopped, and the soil body is maintained.

5. The method of electrochemically consolidating soft clay according to claim 4, wherein, The first electrolyte solution is selected from potassium chloride solution and / or calcium chloride solution; the concentration of the first electrolyte solution is 2.0-5.0 mol / L.

6. The method of electrochemically consolidating soft clay according to claim 4, wherein, The chemical composition of the second electrolyte solution is the same as that of the first electrolyte solution, and the volume ratio of the second electrolyte solution to the first electrolyte solution is 0.8:1-1.2:

1.

7. The method of electrochemically consolidating soft clay according to claim 4, wherein, The starting time of the second stage grouting is between 12-13 hours of power-on, or when the current intensity decreases to 70% of the initial peak value.

8. The method of electrochemically consolidating soft clay according to claim 4, wherein, The applied direct current voltage gradient is 0.8-1.2 V / cm.

9. The method of electrochemically consolidating soft clay according to claim 4, wherein, Between the first stage grouting and the second stage grouting, an intermittent power-off period of 2-12 hours is set according to the dissipation of the pore water pressure.

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