A tunnel settlement control method for soft clay areas

Abstract

The invention discloses a tunnel settlement control method for soft clay areas, belonging to the technical field of tunnel settlement treatment. The control method uses nano-silica sol and sodium chloride slurry for double-liquid electrochemical grouting. A metal grouting pipe is inserted into the clay layer to be reinforced at the tunnel grouting hole, which also serves as an electrode. A direct current is passed and slurry is injected. Under the action of the electric field, the charged nano-silica sol and pore water will move with the action of the electric field. The nano-silica sol moves with the water body or fills the pores with the action of the electric field and forms a solid gel, thereby realizing the reinforcement and settlement control of the soft clay layer, and avoiding secondary settlement caused by the dissipation of pore water pressure after construction through construction measures such as reversing the electric field.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel settlement treatment, and in particular relates to a tunnel settlement treatment method for soft clay areas. Background Art

[0002] When a tunnel is built in a soft soil zone, its bearing capacity is weak. After the tunnel is put into operation, the tunnel is prone to settlement due to repeated load bearing. In order to solve this problem, some solutions have been proposed in the prior art, such as the Chinese patents "CN 103573274 B, a steel casing grouting reinforcement device for preventing the settlement of a soft soil foundation shield tunnel", "CN107060824B, a cement reinforcement device and method for preventing long-term settlement of a subway shield tunnel in soft soil", "CN 111287763B, a control method for preventing long-term settlement of a subway shield tunnel", etc., all of which form support columns after drilling and grouting at the bottom of the tunnel, and use the support columns inserted into the soil below the tunnel to prevent the tunnel from settling. When this technical solution is implemented, the soil at the bottom of the tunnel is still soft soil, and the support columns will continue to sink with the tunnel, so the anti-settlement effect is not good.

[0003] In order to solve the above technical problems, the existing technology uses grouting to treat soft soil. However, the traditional grouting method has the defects of poor injectability into soft clay layers and pressure grouting easily causing soil structure damage. At the same time, secondary settlement will occur as the pressure of pore water dissipates. Summary of the invention

[0004] The purpose of the embodiment of the present invention is to provide a method for controlling tunnel settlement in soft clay areas, which uses an electric field to accelerate the penetration of chemical slurry into low-permeability soft clay, causing little disturbance to the soil body and avoiding structural damage to the soft soil in the tunnel; nano-silica sol is used to replace pore water, and when the silica sol is gelled, it binds soft clay particles, which reinforces the soil body and controls settlement, while avoiding secondary settlement caused by the dissipation of pore water pressure after construction, thereby solving at least one technical problem involved in the background technology.

[0005] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0006] The embodiment of the present invention provides a method for controlling tunnel settlement in soft clay areas, comprising the following steps:

[0007] Step S1, setting a first grouting tube and a second grouting tube at the bottom of the tunnel to be reinforced clay layer, and connecting them to a DC power supply respectively, setting the first grouting tube as a cathode, and the second grouting tube as an anode, and setting the potential gradient between the cathode and the anode to 0.2~1v / cm;

[0008] Step S2, injecting nano-silica sol into the second grouting flower tube through a grouting pump, while turning on the DC power supply, disconnecting the DC power supply after the DC electric field acts for a certain period of time, and letting it stand so that the viscosity of the nano-silica sol begins to increase under the action of alkali metal ions in the clay particle diffusion layer, thereby preventing the nano-silica sol from continuing to migrate under the action of the electric field;

[0009] Step S3, injecting sodium chloride slurry into the second grouting flower tube through a grouting pump, turning on the DC power supply at the same time, disconnecting the DC power supply after the DC electric field acts for a certain period of time, and letting it stand;

[0010] Step S4, setting the second grouting flower tube as a cathode, setting the first grouting flower tube as an anode, and the potential gradient between the cathode and the anode is 0.2~1v / cm;

[0011] Step S5, injecting nano-silica sol into the first grouting flower tube through a grouting pump, while turning on the DC power supply, disconnecting the DC power supply after the DC electric field acts for a certain period of time, and letting it stand so that the viscosity of the nano-silica sol begins to increase under the action of alkali metal ions in the clay particle diffusion layer, thereby preventing the nano-silica sol from continuing to migrate under the action of the electric field;

[0012] Step S6, injecting sodium chloride slurry into the first grouting flower tube through a grouting pump, turning on the DC power supply at the same time, disconnecting the DC power supply after the DC electric field acts for a certain period of time, and letting it stand.

[0013] Optionally, the DC power supply is disconnected after the DC electric field is applied for 6 hours.

[0014] Optionally, in step S2 and step S5, the standing time is 2 hours.

[0015] Optionally, in step S3 and step S6, the standing time is 4 hours.

[0016] Optionally, in step S2 and step S5, the mass fraction of the nano-silica sol is 5-15%.

[0017] Optionally, in step S3 and step S6, the mass fraction of the sodium chloride slurry is 5-10%.

[0018] Optionally, the volume ratio of sodium chloride slurry to nano-silica sol is 1:5~1:8.

[0019] Optional, electrode DC power supply, maximum output voltage is 150V, maximum output current is 100A.

[0020] Optionally, the clay layer to be reinforced at the bottom of the tunnel is provided with two rows of the first grouting flower tubes arranged in parallel and spaced apart, and two rows of the second grouting flower tubes arranged in parallel and spaced apart and located between the two rows of the first grouting flower tubes.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention adopts nano silica sol, the initial viscosity of which is close to that of water. It not only has good permeability and durability, but also has harmless ingredients and is environmentally friendly, and will not pollute the environment;

[0023] 2. The present invention adopts cationic nano-silica sol material to allow it to enter the pores of soft clay without disturbance under the action of electric field, thus making up for the defects of poor injectability of traditional grouting method to soft clay formation and easy destruction of soil structure caused by pressure grouting;

[0024] 3. The present invention controls drainage through operations such as electrode reversal, increases the injection volume of slurry, and avoids formation settlement caused by drainage consolidation and dissipation of pore water pressure;

[0025] 4. The grouting amount of the present invention only needs to make up for the loss of pore water under the electric field to form a complete reinforcement body of the soil, which is less than the grouting amount required by the traditional pressure grouting method;

[0026] 5. Depending on the water content, strength and mineral composition of the stratum, the gel time and the strength after gelation can be controlled by adjusting the ratio of nano-silica sol to sodium chloride slurry (i.e. the volume ratio of sodium chloride slurry to nano-silica sol is 1:5~1:8). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0028] Figure 1 A schematic diagram of the structure of a clay stratum to be reinforced and a tunnel provided in an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of electrochemical grouting provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The terms "first", "second", etc. in the specification and claims of the present invention are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0032] See also Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a tunnel settlement control method for soft clay areas, comprising the following steps:

[0033] Step S1, setting a first grouting tube 2 and a second grouting tube 3 at the bottom of the tunnel 1 to be reinforced clay layer, and connecting them to a DC power supply respectively, setting the first grouting tube 2 as a cathode, and the second grouting tube 3 as an anode, and setting the potential gradient between the cathode and the anode to 0.2~1v / cm;

[0034] In this embodiment, the clay layer to be reinforced at the bottom of the tunnel 1 is provided with two rows of the first grouting flower tubes 2 arranged in parallel and spaced apart, and two rows of the second grouting flower tubes 3 arranged in parallel and spaced apart and located between the two rows of the first grouting flower tubes 2. Figure 2 As shown, it should be noted that the tunnel 1 is composed of pipe segments 4. Figure 2 R1 to R11 are the number of segment rings.

[0035] Step S2, injecting 5-15% nano-silica sol by mass into the second grouting flower tube 3 through a grouting pump, and turning on the DC power supply at the same time. After the DC electric field acts for 6 hours, the DC power supply is disconnected, and the mixture is left to stand for 2 hours so that the viscosity of the nano-silica sol begins to increase under the action of alkali metal ions in the clay particle diffusion layer, thereby preventing the nano-silica sol from continuing to migrate under the action of the electric field.

[0036] Step S3, injecting a sodium chloride slurry with a mass fraction of 5-10% into the second grouting flower tube 3 through a grouting pump, turning on the DC power supply at the same time, disconnecting the DC power supply after the DC electric field acts for 6 hours, and letting it stand for 4 hours;

[0037] Step S4, setting the second grouting flower tube 3 as a cathode, and the first grouting flower tube 2 as an anode, and the potential gradient between the cathode and the anode is 0.2~1v / cm;

[0038] Step S5, injecting 5-15% nano-silica sol by mass into the first grouting flower tube 2 through a grouting pump, and turning on the DC power supply at the same time. After the DC electric field acts for 6 hours, the DC power supply is disconnected, and the nano-silica sol is allowed to stand for 2 hours so that the viscosity of the nano-silica sol begins to increase under the action of alkali metal ions in the clay particle diffusion layer, thereby preventing the nano-silica sol from continuing to migrate under the action of the electric field.

[0039] Step S6, injecting sodium chloride slurry with a mass fraction of 5-10% into the first grouting flower tube 2 through a grouting pump, turning on the DC power supply at the same time, disconnecting the DC power supply after the DC electric field acts for 6 hours, and letting it stand for 4 hours.

[0040] It should be further explained that, in this embodiment, the volume ratio of sodium chloride slurry to nano-silica sol is 1:5-1:8; the potential gradient between the cathode and the anode is 0.5v / cm; the maximum output voltage of the DC power supply is 150V, and the maximum output current is 100A.

[0041] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0042] In addition, it should be noted that the scope of the methods and systems in the embodiments of the present invention is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

[0043] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for controlling tunnel settlement in soft clay areas, characterized in that: The steps include: Step S1, setting a first grouting tube and a second grouting tube at the bottom of the tunnel to be reinforced clay layer, and connecting them to a DC power supply respectively, setting the first grouting tube as a cathode, and the second grouting tube as an anode, and setting the potential gradient between the cathode and the anode to 0.2~1v / cm; Step S2, injecting 5-15% nano-silica sol by mass into the second grouting flower tube through a grouting pump, and turning on the DC power supply at the same time. After the DC electric field acts for a certain period of time, the DC power supply is disconnected, and the nano-silica sol is allowed to stand to allow the viscosity of the nano-silica sol to begin to increase under the action of alkali metal ions in the clay particle diffusion layer, thereby preventing the nano-silica sol from continuing to migrate under the action of the electric field. Step S3, injecting a sodium chloride slurry with a mass fraction of 5-10% into the second grouting flower tube through a grouting pump, wherein the volume ratio of the sodium chloride slurry to the nano-silica sol is 1:5-1:8; turning on the DC power supply at the same time, disconnecting the DC power supply after the DC electric field acts for a certain period of time, and letting it stand; Step S4, setting the second grouting flower tube as a cathode, setting the first grouting flower tube as an anode, and the potential gradient between the cathode and the anode is 0.2~1v / cm; Step S5, injecting 5-15% nano-silica sol by mass into the first grouting flower tube through a grouting pump, and turning on the DC power supply at the same time. After the DC electric field acts for a certain period of time, the DC power supply is disconnected, and the nano-silica sol is allowed to stand to allow the viscosity of the nano-silica sol to begin to increase under the action of alkali metal ions in the clay particle diffusion layer, thereby preventing the nano-silica sol from continuing to migrate under the action of the electric field. Step S6, injecting sodium chloride slurry with a mass fraction of 5-10% into the first grouting flower tube through a grouting pump, and the volume ratio of sodium chloride slurry to nano-silica sol is 1:5-1:8; at the same time, turning on the DC power supply, disconnecting the DC power supply after the DC electric field acts for a certain period of time, and letting it stand.

2. The tunnel settlement control method for soft clay areas according to claim 1, characterized in that: Disconnect the DC power supply after the DC electric field has been applied for 6 hours.

3. The tunnel settlement control method for soft clay areas according to claim 1, characterized in that: In step S2 and step S5, the standing time is 2 hours.

4. The tunnel settlement control method for soft clay areas according to claim 1, characterized in that: In step S3 and step S6, the standing time is 4 hours.

5. The tunnel settlement control method for soft clay areas according to claim 1, characterized in that: The maximum output voltage of the DC power supply is 150V, and the maximum output current is 100A.

6. The tunnel settlement control method for soft clay areas according to claim 1, characterized in that: The clay layer to be reinforced at the bottom of the tunnel is provided with two rows of the first grouting flower tubes arranged in parallel and spaced apart, and two rows of the second grouting flower tubes arranged in parallel and spaced apart and located between the two rows of the first grouting flower tubes.

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