A composite thawing method for frozen soil in tunnel boring machines

Abstract

A composite thawing method for frozen soil in tunnel boring machines (TBMs) includes the following steps: S1, driving sheet piles into the frozen soil location to break up the frozen soil; S2, extracting the sheet piles after construction; S3, applying high-pressure jet grouting with salt-cement slurry to the frozen soil location, using the high-pressure jet grouting to cut and thaw the frozen soil. This invention employs a composite thawing method combining sheet pile breaking and high-pressure jet grouting with salt-cement slurry. During construction, the frozen soil is first mechanically broken up using sheet piles, and then cut and thawed again using salt-cement slurry. Compared to traditional natural thawing or mud circulation thawing methods, this method effectively improves thawing efficiency, shortens the construction period, avoids the problem of soil voids in front of the cutterhead caused by mud circulation thawing methods, improves safety, and has the advantage of low construction cost.

Description

Technical Field

[0001] This invention relates to the field of tunnel boring machine (TBM) construction technology, and in particular to a composite thawing method for frozen soil in TBMs. Background Technology

[0002] In the frozen-opening construction of tunnel boring machines (TBMs), there are currently two main technical approaches for thawing frozen soil: 1. Slurry TBMs use in-cell slurry circulation thawing technology; 2. Earth pressure TBMs rely on natural thawing technology. Both methods have significant technical limitations in practical applications.

[0003] The mud circulation thawing technology can continuously provide heat to achieve relatively rapid thawing, but its process inevitably brings out a large amount of slag in front of the cutterhead, which in turn leads to cavities in front of the cutterhead. This kind of ground disturbance is prone to ground subsidence accidents.

[0004] While natural thawing avoids the risk of ground disturbance and is relatively safe, it takes a long time, which can easily cause construction delays and significantly affect the economic efficiency of the project.

[0005] Current thawing methods cannot solve the technical problem of balancing thawing efficiency and construction safety. Therefore, there is an urgent need to develop a new thawing technology that can simultaneously meet the requirements of construction safety and efficiency. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a composite thawing method for frozen soil in tunnel boring machines. This method combines sheet pile crushing with high-pressure jet grouting of salt cement, enabling safe and efficient thawing of frozen soil.

[0007] To achieve the above objectives, the present invention provides a composite thawing method for frozen soil in tunnel boring machines, comprising the following steps:

[0008] S1. Drive sheet piles into the frozen soil to break up the frozen soil.

[0009] S2. After the sheet pile construction is completed, the sheet piles are pulled out.

[0010] S3. High-pressure jet grouting of salt-cement slurry is performed at the location of frozen soil using a high-pressure jet grouting device. The high-pressure jet grouting of salt-cement slurry is used to cut and thaw the frozen soil.

[0011] As a further improvement of the present invention, in step S1, the steel sheet pile is driven downward into the frozen soil from a position directly above the cutterhead of the tunnel boring machine, with a horizontal net distance of 0.4m to 0.6m from the front of the cutterhead and a vertical distance of 0.1m to 0.3m from the cutterhead.

[0012] As a further improvement of the present invention, in step S1, the steel sheet piles are constructed using continuous non-overlapping construction.

[0013] As a further improvement of the present invention, the sheet piles are made of sheet piles with a width of 0.4 to 0.6 m.

[0014] As a further improvement of the present invention, in step S3, the high-pressure rotary jetting pressure of the high-pressure rotary jetting device is 25-35 MPa.

[0015] As a further improvement of the present invention, in step S3, the high-pressure jet grouting equipment is a high-pressure jet grouting pile machine, and the salt cement slurry is jetted at high pressure using the high-pressure jet grouting pile machine, specifically, the high-pressure nozzle is jetted at 180° toward the cutterhead of the tunnel boring machine.

[0016] As a further improvement of the present invention, in step S3, the high-pressure jet grouting equipment performs high-pressure jet grouting through high-pressure jet grouting holes. The horizontal net distance between the high-pressure jet grouting holes and the front of the shield machine cutterhead is 0.4m to 0.6m, the high-pressure jet grouting diameter is 1.4 to 1.6m, and the jet grouting overlap range is 0.3m to 0.5m.

[0017] As a further improvement of the present invention, the ratio of brine to mud in the salt-cement slurry is: calcium chloride: bentonite: water = 50kg: 30kg: 920kg per 1T of salt-cement slurry. In actual operation, the ratio of calcium chloride to bentonite needs to be adjusted according to temperature and soil permeability.

[0018] As a further improvement to the present invention, the following steps are also included:

[0019] S4. Repeat the high-pressure jet grouting construction to ensure that the frozen soil around the cutterhead of the tunnel boring machine is completely constructed.

[0020] S5. Test rotation of the cutter head.

[0021] As a further improvement of the present invention, in step S1, the horizontal clearance between the sheet pile and the front of the shield machine cutterhead is 0.4m, and the vertical distance is 0.2m; the sheet pile is 0.5m wide; in step S3, the high-pressure jet grouting pressure of the high-pressure jet grouting equipment is 30MPa; the high-pressure jet grouting equipment performs high-pressure jet grouting through high-pressure jet grouting holes, the horizontal clearance between the high-pressure jet grouting holes and the front of the shield machine cutterhead is 0.5m, the high-pressure jet grouting diameter is 1.5m, and the jet grouting overlap range is 0.4m.

[0022] The beneficial effects of this invention are as follows:

[0023] I. Improved Thawing Efficiency. This invention employs a composite thawing method combining sheet pile crushing with high-pressure jet grouting of saline-cement slurry. During construction, the frozen soil is first mechanically crushed using sheet piles, and then the frozen soil is further cut and thawed using saline-cement slurry. This is similar to breaking ice blocks before thawing them. Compared to traditional natural thawing or mud circulation thawing methods, this method effectively improves thawing efficiency and shortens the construction period.

[0024] II. Enhanced Safety. The combination of sheet piles breaking up frozen soil and high-pressure jet grouting with salt cement slurry avoids the problem of soil voids in front of the cutterhead caused by mud circulation thawing methods. Furthermore, the high-pressure jet grouting with salt cement slurry can form high-pressure jet piles to reinforce the strata, further preventing subsidence accidents while thawing the frozen soil.

[0025] Third, low construction cost. Steel sheet piles and high-pressure jet grouting equipment are commonly used equipment in civil construction, requiring no investment in specialized equipment. The equipment costs are low and the operation is simple. In addition, the main material, salt cement grout, has a low cost, thereby reducing the overall cost and making it highly practical. Attached Figure Description

[0026] Figure 1 This is a top view schematic diagram of the construction structure of the present invention;

[0027] Figure 2 This is a side view of the construction structure of the present invention;

[0028] Marking descriptions: 1. Tunnel boring machine cutterhead; 2. Sheet pile; 3. High-pressure jet grouting pile; 4. Frozen soil. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0030] A composite thawing method for frozen soil in tunnel boring machines includes the following steps:

[0031] S1. First, measure and mark the top area of ​​the tunnel boring machine cutterhead 1 to be opened at the ground surface, and mark the construction point of steel sheet pile 2 within this area. The construction point is located directly above the cutterhead 1. To ensure that the steel sheet pile 2 will not damage the cutterhead equipment, the horizontal clearance between the construction point of steel sheet pile 2 and the front of the cutterhead 1 is 0.4m to 0.6m, and the vertical distance is 0.1m to 0.3m. Install and debug the steel sheet pile 2 equipment at the construction point, using steel sheet piles 2 with a width of 0.4m to 0.6m. Using the marked point as the base point, drive the steel sheet pile 2 downward into the frozen soil 4 using the steel sheet pile 2 equipment. The construction adopts continuous non-overlapping construction, breaking up the frozen soil 4 by driving the steel sheet pile 2 into the frozen soil 4. High-pressure jet grouting equipment is brought in simultaneously during the construction of steel sheet pile 2.

[0032] S2. After the steel sheet pile 2 is completed, pull out the steel sheet pile 2 and remove the steel sheet pile 2 equipment to make way for the high-pressure jet grouting construction.

[0033] S3. Prepare salt-cement slurry on site. The ratio of salt water to slurry is: calcium chloride: bentonite: water = 50kg:30kg:920kg per ton of salt-cement slurry. In actual operation, the specific gravity of calcium chloride and bentonite needs to be adjusted according to temperature and soil permeability. High-pressure jet grouting of salt-cement slurry is performed at location 4 of the frozen soil using a high-pressure jet grouting machine. The high-pressure jet grouting slurry cuts and thaws the frozen soil 4, forming high-pressure jet grouting piles 3. The high-pressure jet grouting pressure is 25-35MPa. The high-pressure jet grouting machine is a high-pressure jet grouting pile machine. The salt-cement slurry is applied using a high-pressure swirl jetting machine, specifically by swirl-jetting the high-pressure nozzle 180° towards the tunnel boring machine cutterhead. The high-pressure jet grouting equipment performs high-pressure jet grouting through high-pressure jet grouting holes. The horizontal clearance between the high-pressure jet grouting holes and the front of the shield machine cutterhead 1 is 0.4m to 0.6m, the diameter of the high-pressure jet grouting is 1.4m to 1.6m, and the overlap range of the jet grouting is 0.3m to 0.5m to ensure sufficient jet grouting.

[0034] S4. Repeat the high-pressure jet grouting construction to ensure that the frozen soil around the cutterhead 1 of the tunnel boring machine is completely constructed.

[0035] S5. Observe the changes in ground monitoring data. After the construction is completed, slowly test rotate the shield machine cutterhead 1.

[0036] In this embodiment, in step S1, the horizontal clearance between the sheet pile 2 and the front of the shield machine cutterhead 1 is preferably 0.4m, and the vertical distance is preferably 0.2m; the width of the sheet pile 2 is preferably 0.5m; in step S3, the high-pressure jet grouting pressure of the high-pressure jet grouting equipment is preferably 30MPa; the horizontal clearance between the high-pressure jet grouting hole and the front of the shield machine cutterhead 1 is preferably 0.5m, the high-pressure jet grouting diameter is preferably 1.5m, and the jet grouting overlap range is preferably 0.4m.

[0037] The construction structure of the above method is as follows Figure 1 , 2 As shown in the figure, both sheet pile 2 and high-pressure jet grouting pile 3 are displayed to indicate their positions. However, in actual construction, sheet pile 2 is removed first, and then high-pressure jet grouting of salt cement slurry is carried out to form high-pressure jet grouting pile 3.

[0038] The above method combines the advantages of sheet piles 2, mud slurry, and brine. First, sheet piles 2 are used to break up the frozen soil above the tunnel boring machine cutterhead 1, disrupting its integrity. Then, high-pressure jet grouting with brine further breaks up the smaller pieces of frozen soil, creating even smaller fragments and improving thawing efficiency. Simultaneously, the properties of brine are utilized to thaw the frozen soil. This method enables rapid thawing of the frozen soil, avoids the problem of soil voids in front of the tunnel boring machine cutterhead 1, and prevents subsidence accidents.

[0039] The above-described embodiments are merely illustrative of the present invention. Any equivalent embodiments made by those skilled in the art, without departing from the scope of the technical features disclosed in the present invention, using partial modifications or alterations to the technical content disclosed in the present invention, shall still fall within the scope of the technical features of the present invention.

Claims

1. A composite thawing method for frozen soil in tunnel boring machines, characterized in that... Includes the following steps: S1. Drive sheet piles into the frozen soil to break up the frozen soil. S2. After the sheet pile construction is completed, the sheet piles are pulled out. S3. High-pressure jet grouting of salt-cement slurry is carried out at the location of frozen soil using a high-pressure jet grouting device. The high-pressure jet grouting of salt-cement slurry is used to cut and thaw the frozen soil. S4. Repeat the high-pressure jet grouting construction to ensure that the frozen soil around the cutterhead of the tunnel boring machine is completely constructed. S5. Test rotation of the cutter head; In step S1, the sheet piles are driven downwards into the frozen soil from directly above the cutterhead of the tunnel boring machine (TBM), with a horizontal clearance of 0.4m to 0.6m from the front of the TBM cutterhead and a vertical distance of 0.1m to 0.3m from the TBM cutterhead. In step S3, the high-pressure jet grouting equipment performs high-pressure jet grouting through high-pressure jet grouting holes. The horizontal net distance between the high-pressure jet grouting holes and the front of the shield machine cutterhead is 0.4m to 0.6m, the high-pressure jet grouting diameter is 1.4m to 1.6m, and the jet grouting overlap range is 0.3m to 0.5m. In the salt-cement slurry, the ratio of brine to slurry is: calcium chloride: bentonite: water = 50kg: 30kg: 920kg per 1T of salt-cement slurry.

2. The method for composite thawing of frozen soil in a tunnel boring machine according to claim 1, characterized in that: In step S1, the sheet piles are constructed using continuous, non-overlapping construction.

3. The method for composite thawing of frozen soil in a tunnel boring machine according to claim 1, characterized in that: The sheet piles used are 0.4 to 0.6 m wide.

4. The method for composite thawing of frozen soil in a tunnel boring machine according to claim 1, characterized in that: In step S3, the high-pressure rotary jetting pressure of the high-pressure rotary jetting equipment is 25-35 MPa.

5. The method for composite thawing of frozen soil in a tunnel boring machine according to claim 1, characterized in that: In step S3, the high-pressure jet grouting equipment is a high-pressure jet grouting pile machine. The saline-cement grout is jetted at high pressure using the high-pressure jet grouting pile machine, specifically with the high-pressure nozzle facing 180 degrees towards the cutterhead of the tunnel boring machine. o Spray.

6. The method for composite thawing of frozen soil in a tunnel boring machine according to claim 1, characterized in that: In step S1, the horizontal clearance between the sheet pile and the front of the tunnel boring machine cutterhead is 0.4m, and the vertical distance is 0.2m; the sheet pile is 0.5m wide. In step S3, the high-pressure jet grouting equipment has a high-pressure jet grouting pressure of 30MPa; the high-pressure jet grouting equipment performs high-pressure jet grouting through high-pressure jet grouting holes, the horizontal clearance between the high-pressure jet grouting holes and the front of the tunnel boring machine cutterhead is 0.5m, the high-pressure jet grouting diameter is 1.5m, and the jet grouting overlap range is 0.4m.

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