Shield tunnel butt joint section frozen soil reinforcement monitoring and evaluating method

Abstract

The invention discloses a shield tunnel butt joint section frozen soil reinforcement monitoring and evaluating method, and relates to the technical field of shield construction, the method comprises the following steps: respectively constructing a freezing hole, a temperature measuring hole and a pressure relief hole, and respectively installing a freezing pipe and a temperature measuring pipe in the freezing hole and the temperature measuring hole; collecting a soil body in the opening process of the freezing hole in the outermost side of each shield tunneling machine, and transferring the soil body to a laboratory curing room for an experiment to obtain a strength index of the soil body; monitoring the temperature data of each temperature sensor in real time, and calculating the development condition of the shield and frozen soil interface based on the temperature data; and according to the strength index, the development condition of the shield and frozen soil interface and the temperature data, the excavation condition of the butt joint section soil body is evaluated, and according to the evaluation result and the monitoring and early warning judgment basis, the excavation operation of the butt joint section soil body is executed. According to the method, the development state of the freezing interface can be effectively judged before the soil body of the butt joint section of the two shield tunneling machines is excavated, and real-time monitoring and early warning in the freezing wall forming process are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shield construction, in particular to a method for monitoring and evaluating frozen soil body reinforcement of a shield tunnel butt joint section. BACKGROUND

[0002] With the rapid development of economy and engineering technology, the application of underwater large-diameter shield tunnels is increasingly widespread, and the construction scale presents a trend of "larger diameter and longer length". In the current planning of cross-sea tunnel construction projects, the tunnel length has broken through 30 kilometers. In order to shorten the construction period, such long-distance underwater shield tunnels generally adopt a construction scheme of two shield machines excavating towards each other and connecting through. Due to the limitation of the cutter head structure of the shield machine, when the underwater shield machines are connected towards each other, the soil body around the connection needs to be treated by cold freezing reinforcement to ensure the safe excavation of the soil body in the cutter head area of the butt joint section and the smooth development of subsequent connection construction.

[0003] However, the core technical difficulty of underwater shield machine connection construction is to accurately determine whether the frozen reinforced soil body meets the excavation construction requirements. If the freezing reinforcement effect does not meet the technical standards, it is easy to cause leakage and sand leakage at the connection, and in severe cases, it may cause tunnel flooding accidents, which not only brings major hidden dangers to the personal safety of construction personnel, but also significantly increases the difficulty and risk of excavation construction of the butt joint section. Therefore, real-time monitoring of the development state of the shield-soil frozen body at the connection and real-time monitoring and risk warning of the freezing reinforcement effect are the key prerequisites for ensuring the safety of underwater shield connection construction.

[0004] In the prior art, the monitoring method of shield peripheral soil body freezing reinforcement is mostly applied to the construction scene of small-diameter shield connecting passages. However, compared with small shield connecting passages, the area and volume of the frozen body of the underwater large-diameter shield tunnel butt joint section are significantly increased. This makes it difficult for the existing monitoring method to meet the safety technical requirements of the opposite shield machine connection construction in terms of monitoring range, accuracy and real-time performance, and it is difficult to accurately evaluate the reinforcement effect of the large-volume frozen body and to achieve effective risk warning.

[0005] At present, no effective solution has been proposed for the problems in the related art. SUMMARY

[0006] In view of the problems in the related art, the present application proposes a method for monitoring and evaluating frozen soil body reinforcement of a shield tunnel butt joint section to overcome the above technical problems existing in the prior art.

[0007] To this end, the specific technical solutions adopted by the present application are as follows:

[0008] A method for monitoring and evaluating frozen soil body reinforcement of a shield tunnel butt joint section, the method comprising:

[0009] constructing a freezing hole, a temperature measuring hole and a pressure relief hole on each shield machine shield respectively, and installing a freezing pipe and a temperature measuring pipe in the freezing hole and the temperature measuring hole respectively;

[0010] collecting soil in the process of opening the outermost freezing hole of each shield machine, and moving the soil to a laboratory curing room for experiment to obtain the strength index of the soil;

[0011] laying temperature sensors to monitor the temperature data of each temperature sensor in real time, and calculating the development of the interface between the shield and the frozen soil based on the temperature data;

[0012] According to the strength index, the development of the interface between the shield and the frozen soil, and the temperature data, the excavation conditions of the soil of the docking section are evaluated, and the excavation operation of the soil of the docking section is performed according to the evaluation results and the monitoring and early warning judgment basis.

[0013] Further, before constructing a freezing hole, a temperature measuring hole and a pressure relief hole on each shield machine shield respectively, and installing a freezing pipe and a temperature measuring pipe in the freezing hole and the temperature measuring hole respectively, the method further comprises:

[0014] According to the pre-defined design requirements, the size and thickness of the steel plate for reinforcing the shield machine shield are determined, and the reinforcing position of the steel plate is determined in combination with the preset construction range of the freezing pipe and the temperature measuring pipe;

[0015] According to the size, thickness and reinforcing position of the steel plate, the shield machine shield is welded and reinforced with the steel plate.

[0016] Further, the soil in the process of opening the outermost freezing hole of each shield machine is collected, and the soil is moved to a laboratory curing room for experiment to obtain the strength index of the soil, which comprises:

[0017] Selecting the outermost freezing hole of each shield machine, collecting the complete soil in the process of opening the selected freezing hole for storage, and moving the stored soil to an experimental curing room for storage;

[0018] The stored soil is taken out from the experimental curing room, parallel freezing experiments are carried out on the soil according to the preset temperature stages, and the average value of the experimental results is calculated to obtain the strength index of the soil.

[0019] Further, the strength index includes: compressive strength index, bending strength index and tensile strength index.

[0020] Further, the temperature sensors are laid in the temperature measuring pipe within the freezing range and the inner wall of the shield machine shield, and the temperature sensors are laid according to the laying rules.

[0021] Further, the laying rules include:

[0022] Temperature sensors are installed at preset intervals along the depth direction of the shield tunnel;

[0023] Temperature sensors are installed at preset angle intervals along the circumferential direction of the shield tunnel.

[0024] Furthermore, the expression for calculating the development of the interface between the tunnel boring machine and the permafrost is as follows:

[0025] ;

[0026] In the formula, L imn t represents the thickness of the frozen wall at position m and time n for the i-th freezing tube; i0 Indicates the temperature of the freezing brine in the i-th freezing tube; l ijm t represents the vertical distance from position m of the i-th freezing tube to the j-th temperature measuring tube; jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature sensing tube; r i This represents the inner diameter of the i-th freezing tube.

[0027] Furthermore, the expression for the excavation conditions is:

[0028] ;

[0029] In the formula, D ij K1 represents the distance from the i-th freezing tube to the j-th freezing tube; L represents the safety factor; imn The thickness of the frozen wall at position m and time n represents the thickness of the frozen wall at position m of the i-th freezing tube; T1 represents the design average temperature of the frozen wall; K2 represents the safety factor; t jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature measuring tube; M represents the total number of temperature sensors arranged inside the temperature measuring tube; K3 represents the safety factor; T ij This represents the temperature measured by the temperature sensor at position j on the inner side of the i-th shield; N represents the total number of temperature sensors arranged on the inner side of the shield.

[0030] Furthermore, the criteria for monitoring and early warning determination include:

[0031] The computer collects temperature data at preset time intervals and calculates the strength index of the frozen wall based on the temperature data;

[0032] The calculated strength index is tested. If the strength index does not meet the stability standard at the same time, an alarm is triggered, the excavation operation is suspended, and the frozen wall is reinforced with freezing measures until the strength index meets the excavation conditions at the same time, and construction is resumed.

[0033] Furthermore, the expression for the stability criterion is:

[0034] ;

[0035] In the formula, t m This indicates the temperature measured by the temperature sensor at position m; t jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature measuring tube; M represents the total number of temperature sensors arranged inside the temperature measuring tube; α1 represents the required compressive strength of the frozen wall; K4 represents the safety factor; α im Indicates the i-th soil layer at t m The compressive strength value at temperature; β1 represents the required flexural strength of the frozen wall as designed; β im Indicates the i-th soil layer at t m Flexural strength at temperature; γ1 represents the design requirement for the tensile strength of the frozen wall; γ im Indicates the i-th soil layer at t m Tensile strength at temperature; T ij This represents the temperature measured by the temperature sensor at position j on the inner side of the i-th shield; N represents the total number of temperature sensors arranged on the inner side of the shield.

[0036] The beneficial effects of this invention are as follows:

[0037] This invention can effectively determine the development status of the frozen interface before the excavation of the soil in the docking section between two tunnel boring machines, and realize real-time monitoring and early warning of the frozen wall formation process. The method is technically reliable, easy to implement, and has controllable risks, which significantly reduces the construction risks of the soil excavation in the docking section. It has good operability and scalability, and is applicable to various frozen soil reinforcement projects, with significant engineering application value. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. 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 effort.

[0039] Figure 1 This is a flowchart of a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to an embodiment of the present invention;

[0040] Figure 2 This is a flowchart illustrating the implementation of a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to an embodiment of the present invention.

[0041] Figure 3 This is a schematic diagram of the underwater docking soil layer freezing monitoring in a shield tunnel docking section freezing monitoring and evaluation method according to an embodiment of the present invention.

[0042] Figure 4This is a schematic diagram of the cross-section of the soil freezing monitoring point of the tunnel boring machine in a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to an embodiment of the present invention.

[0043] Figure 5 This is a schematic diagram of the arrangement of underwater temperature measuring holes for shield tunnel docking in a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to an embodiment of the present invention.

[0044] Figure 6 This is a schematic diagram of the longitudinal arrangement of temperature measuring holes in a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to an embodiment of the present invention.

[0045] Figure 7 This is a schematic diagram of the whole-process shield shell inner surface temperature monitoring arrangement in a shield tunnel docking section frozen soil reinforcement monitoring and evaluation method according to an embodiment of the present invention;

[0046] Figure 8 This is a schematic diagram of the development of frozen soil boundary in a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to an embodiment of the present invention.

[0047] Figure 9 This is a schematic diagram of the temperature contour lines at the shield-frozen soil interface in a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to an embodiment of the present invention. Detailed Implementation

[0048] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention.

[0049] According to an embodiment of the present invention, a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel is provided.

[0050] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 1 As shown, the method for monitoring and evaluating the reinforcement of frozen soil in the shield tunnel docking section according to an embodiment of the present invention includes:

[0051] On the shield shell of each tunnel boring machine that arrives at the docking target position, freezing holes, temperature measuring holes and pressure relief holes are constructed respectively, and freezing pipes and temperature measuring pipes are installed in the freezing holes and temperature measuring holes respectively.

[0052] In this optional embodiment, freezing holes, temperature measuring holes, and pressure relief holes are constructed on the shield shell of each tunnel boring machine upon reaching the docking target position, and the following steps are taken before installing freezing pipes and temperature measuring pipes in the freezing holes and temperature measuring holes respectively:

[0053] Based on the predefined design requirements, determine the size and thickness of the steel plate used for reinforcing the shield shell of the tunnel boring machine, and determine the reinforcement location of the steel plate in conjunction with the pre-defined construction range of the freezing pipe and the temperature measuring pipe.

[0054] Based on the size, thickness, and reinforcement location of the steel plates, welded steel plates are used to reinforce the shield shell of the tunnel boring machine.

[0055] It should be noted that before installing freezing pipes and temperature measuring pipes on the shield shells of the tunnel boring machines, the shield shells need to be reinforced with welded steel plates. The size and thickness of the reinforcing steel plates need to be determined according to the design. The location of the steel plate reinforcement should avoid the construction range of the freezing pipes and temperature measuring pipes to avoid affecting the construction of the freezing pipes and temperature measuring pipes.

[0056] Soil samples were collected during the opening process of the outermost freezing hole of each tunnel boring machine, and the soil was transferred to the laboratory curing room for testing to obtain the soil strength index.

[0057] In this optional embodiment, soil samples are collected during the opening process of the outermost freezing hole of each tunnel boring machine, and the soil is transferred to a laboratory curing room for testing. The strength indicators of the soil are obtained, including:

[0058] Select the outermost freezing hole of each tunnel boring machine, collect the complete soil during the opening process of the selected freezing hole, seal it, and transfer the sealed soil to the experimental curing room for storage.

[0059] The stored soil was taken out of the experimental curing room and subjected to parallel freezing tests at preset temperature levels. The strength index of the soil was obtained by calculating the average value of the experimental results.

[0060] In this optional embodiment, the strength indicators include: compressive strength, flexural strength, and tensile strength.

[0061] It should be noted that during the opening of the freezing pipe, a complete soil sample was taken out and sealed in accordance with the requirements of the national geotechnical testing regulations. The soil sample was placed in the laboratory curing room and taken out before the test. Three sets of parallel freezing tests were conducted on each soil layer at 0℃, -5℃, -10℃, -15℃, and -20℃. The average value of the three test results was taken to measure the compressive strength, flexural strength, and tensile strength of the soil layer.

[0062] (1) The compressive strength, flexural strength, and tensile strength of the i-th soil layer measured in the indoor test at 0℃, -5℃, -10℃, -15℃, and -20℃ are as follows:

[0063] ;

[0064] In the formula, α inα represents the average compressive strength of the i-th soil layer at 0℃, -5℃, -10℃, -15℃, and -20℃; ijn This represents the test value of the compressive strength of the i-th soil layer measured in the j-th group of tests at 0℃, -5℃, -10℃, -15℃, and -20℃; β in β represents the average flexural strength of the i-th soil layer at 0℃, -5℃, -10℃, -15℃, and -20℃; ijn γ represents the test value of the flexural strength of the i-th soil layer measured in the j-th group of tests at 0℃, -5℃, -10℃, -15℃, and -20℃; in γ represents the average tensile strength of the i-th soil layer at 0℃, -5℃, -10℃, -15℃, and -20℃; ijn This represents the test value of the tensile strength of the i-th soil layer measured in the j-th group of tests at 0℃, -5℃, -10℃, -15℃, and -20℃.

[0065] (2) Any temperature range of -20℃ to 0℃ in the i-th soil layer. m The compressive strength, flexural strength, and tensile strength at a given temperature can be calculated using the following formula:

[0066] ;

[0067] In the formula, α im Indicates the i-th soil layer at t m Compressive strength at temperature; α i,n-1 This indicates that the i-th soil layer is in any t n-1 Compressive strength at temperature; α in β represents the average compressive strength of the i-th soil layer at 0℃, -5℃, -10℃, -15℃, and -20℃; im Indicates the i-th soil layer at t m Flexural strength at temperature; β i,n-1 This indicates that the i-th soil layer is in any t n-1 Flexural strength at temperature; β in γ represents the average flexural strength of the i-th soil layer at 0℃, -5℃, -10℃, -15℃, and -20℃; im Indicates the i-th soil layer at t m Tensile strength at temperature; γ i,n-1 This indicates that the i-th soil layer is in any t n-1 Tensile strength at temperature; γ in t represents the average tensile strength of the i-th soil layer at 0℃, -5℃, -10℃, -15℃, and -20℃; n t n-1 They represent t respectively n ≤t m ≤t n-1 , t n=1,2,3,4,5These are equal to 0℃, -5℃, -10℃, -15℃, and -20℃ respectively.

[0068] Temperature sensors are deployed to monitor the temperature data of each sensor in real time, and the development of the interface between the tunnel boring machine and the frozen soil is calculated based on the temperature data.

[0069] In this optional embodiment, temperature sensors are installed on the temperature measuring tubes within the freezing range and on the inner wall of the shield shell of the tunnel boring machine, and the temperature sensors are installed according to the installation rules.

[0070] In this optional embodiment, the deployment rules include:

[0071] Temperature sensors are installed at preset intervals along the depth direction of the shield tunnel;

[0072] Temperature sensors are installed at preset angle intervals along the circumferential direction of the shield tunnel.

[0073] It should be further explained that temperature sensors are installed inside the temperature measuring tube. One temperature monitoring sensor is installed every 2 meters along the tunnel depth direction, and arranged at 60° intervals circumferentially. Within the excavation influence range of the two tunnel boring machines, one sensor is installed every 2 meters along the tunnel depth direction on the inner side of the shield shell, also arranged at 60° intervals circumferentially. The temperature sensors have a range of -35℃ to 35℃ and an accuracy requirement of 0.05℃. In addition, the insulation material is a 30mm thick, self-adhesive aluminum foil insulation material with heat insulation, frost resistance, and fire resistance. The material consists of aluminum foil, nitrile rubber, insulation cotton, and a protective film. The insulation coefficient is not less than 60%. Other functions include low-temperature resistance, frost resistance, and fire resistance.

[0074] In this optional embodiment, the expression for calculating the development of the interface between the tunnel boring machine and the permafrost is:

[0075] ;

[0076] In the formula, L imn t represents the thickness of the frozen wall at position m and time n for the i-th freezing tube; i0 Indicates the temperature of the freezing brine in the i-th freezing tube; l ijm t represents the vertical distance from position m of the i-th freezing tube to the j-th temperature measuring tube; jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature sensing tube; r i This represents the inner diameter of the i-th freezing tube.

[0077] It should be further explained that the freezing pipe circulates brine and begins freezing. The area affected by the freezing pipe inside the shield is wrapped with insulating cotton, and the data from each temperature sensor is recorded and monitored. Specifically, the freezing pipe and temperature measuring pipe are constructed according to the freezing design by the first and second tunnel boring machines. During the construction process, it is necessary to prevent water and soil from leaking from the outside of the shield into the tunnel. At the same time, soil samples are taken out during the opening of the freezing pipe. Temperature sensors are installed on the temperature measuring pipe and inside the shield. After the temperature sensors are installed inside the shield, a layer of insulating cotton is pasted on. During the construction process, a layer of insulating cotton is immediately pasted on the part of the inner soil that is exposed to the shield to prevent the new shield from providing a large amount of heat exchange between the inside and outside.

[0078] Based on the strength indicators, the development of the interface between the tunnel boring machine and the frozen soil, and temperature data, the excavation conditions of the connecting section soil are assessed. Based on the assessment results and the monitoring and early warning judgment criteria, the excavation operation of the connecting section soil is carried out.

[0079] In this optional embodiment, the expression for the excavation conditions is:

[0080] ;

[0081] In the formula, D ij This represents the distance from the i-th freezing tube to the j-th freezing tube; K1 represents the safety factor, typically taken as 1.2~1.5; L imn T1 represents the thickness of the frozen wall at position m and time n for the i-th freezing pipe; T2 represents the design average temperature of the frozen wall; K2 represents the safety factor, typically taken as 1.2~1.5; t jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature measuring tube; M represents the total number of temperature sensors arranged inside the temperature measuring tube; K3 represents the safety factor, typically taken as 1.2~1.5; T ij This represents the temperature measured by the temperature sensor at position j on the inner side of the i-th shield; N represents the total number of temperature sensors arranged on the inner side of the shield.

[0082] It should be noted that after debugging the freezing equipment according to the procedure, freezing begins. Every 5 minutes, the temperature of the brine in all freezing tubes, the temperature of the freezing holes, and the temperature inside the shield are automatically collected and recorded as t. i0 t jp T ij r was calculated according to the frozen design drawings. i l ijm The computer can calculate the development of the frozen wall thickness every 5 minutes. If the following formula is met at the same time, it means that the frozen soil outside the shield meets the excavation requirements.

[0083] In this optional embodiment, the criteria for monitoring and early warning determination include:

[0084] The computer collects temperature data at preset time intervals and calculates the strength index of the frozen wall based on the temperature data;

[0085] The calculated strength index is tested. If the strength index does not meet the stability standard at the same time, an alarm is triggered, the excavation operation is suspended, and the frozen wall is reinforced with freezing measures until the strength index meets the excavation conditions at the same time, and construction is resumed.

[0086] In this optional embodiment, the expression for the stability criterion is:

[0087] ;

[0088] In the formula, t m This indicates the temperature measured by the temperature sensor at position m; t jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature measuring tube; M represents the total number of temperature sensors arranged inside the temperature measuring tube; α1 represents the required compressive strength of the frozen wall according to the design; K4 represents the safety factor, typically taken as 0.1~0.33; α im Indicates the i-th soil layer at t m The compressive strength value at temperature; β1 represents the required flexural strength of the frozen wall as designed; β im Indicates the i-th soil layer at t m Flexural strength at temperature; γ1 represents the design requirement for the tensile strength of the frozen wall; γ im Indicates the i-th soil layer at t m Tensile strength at temperature; T ij This represents the temperature measured by the temperature sensor at position j on the inner side of the i-th shield; N represents the total number of temperature sensors arranged on the inner side of the shield.

[0089] It should be added that during the excavation process, the computer automatically calculates the stability of the frozen wall every 5 minutes based on temperature monitoring data. If it finds that the stability standard is not met simultaneously, an alarm is triggered, excavation is stopped, and after the frozen wall is frozen again and the excavation conditions are met, construction is restarted.

[0090] like Figure 2 As shown, a method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel specifically includes:

[0091] Step 1: After the two tunnel boring machines arrive at the designated docking position, the front shield of the tunnel boring machine is reinforced with welded steel according to the design to ensure the safety of the freezing holes, temperature measuring holes and pressure relief holes drilled outward on the tunnel shell;

[0092] Step 2: According to the design, construct freezing holes, temperature measuring holes, and pressure relief holes on the shield shells of the two tunnel boring machines. Install freezing pipes and temperature measuring pipes in the freezing holes and temperature measuring holes respectively. Select the outermost freezing hole of each tunnel boring machine. Take out a complete soil sample during the hole opening process, seal it, and move it to the indoor laboratory. Indoor tests are conducted to measure the compressive strength, flexural strength, and tensile strength of each soil layer.

[0093] Step 3: Arrange temperature monitoring sensors within the freezing area and on the inner wall of the shield according to the design;

[0094] Step 4: Circulate brine inside the freezing tube to begin freezing. Wrap the area affected by the freezing tube inside the shield with insulating cotton and record and monitor the data from each temperature sensor.

[0095] Step 5: Calculate the development of the shield-permafrost interface based on sensor monitoring data;

[0096] Step Six: Assess whether excavation conditions are met based on the development of the shield-frozen soil interface and the shield shell temperature;

[0097] Step 7: During the excavation of the shield shell soil, propose real-time monitoring and early warning judgment criteria to guide the excavation of the connecting section soil.

[0098] In a specific embodiment, such as Figure 3 As shown, 100 is the lead tunnel boring machine (TBM); 200 is the follow-up TBM; 3 is the shield shell reinforcement steel plate; 411 is the freezing pipe of the lead TBM; 412 is the temperature measuring pipe of the lead TBM; 421 is the freezing pipe of the follow-up TBM; 422 is the temperature measuring pipe of the follow-up TBM; 5 is the temperature sensor inside the temperature measuring pipe; 6 is the shield shell temperature sensor; 7 is the shield shell insulation cotton; 8 is the soil inside the mud chamber and cutterhead; 9 is the range of the frozen and reinforced soil.

[0099] like Figure 4 As shown, 100 is the pilot tunnel boring machine; 411 is the freezing pipe of the pilot tunnel boring machine; 412 is the temperature measuring pipe of the pilot tunnel boring machine; 5 is the temperature sensor inside the temperature measuring pipe; 6 is the shield shell temperature sensor; and 7 is the shield shell insulation cotton.

[0100] like Figure 5 As shown, the Yangtze River Tunnel uses two 16m diameter tunnel boring machines (TBMs) for underwater docking in the river. Eight temperature measurement holes are arranged on each side of the advancing and retreating TBMs. The minimum distance between adjacent temperature measurement holes on the outer edge of the circumference is 6.28m from the hole opening position. All 16 temperature measurement holes are arranged on the outer side of the designed frozen soil curtain, making it impossible to determine the extent of frozen soil development inward. The interface between the frozen soil curtain and the outer surface of the shield shell is an important channel to ensure the freezing effect, and it is also a weak channel connecting the inside of the shield shell with the external groundwater during the freezing process. In the water-rich environment of the Yangtze River bed, the complexity of groundwater flow velocity and direction conditions may create weak freezing zones, and the limited number of temperature measurement holes cannot fully monitor the freezing risk.

[0101] like Figure 6 As shown, 16 external temperature measuring holes are arranged in the freezing design. Temperature measuring holes C1~C8 and C9~C16 are the outer temperature measuring holes of the design. The measuring points are arranged such that there is no less than one measuring point in every 2m of the measuring hole. For the section near the middle and bottom of the measuring hole, the measuring points are arranged at intervals of 1m. The position near the opening of the measuring hole is densified, with 4 measuring points arranged within 500mm of the opening, at distances of 0mm, 100mm, 300mm and 500mm from the opening.

[0102] like Figure 7 As shown, eight temperature measuring cables are arranged along the circumference of the shield on the inner surface of the shield shell, covering the boundary control points of the frozen soil area on both sides and the boundary point of the interface between the two shields; eight temperature sensors are initially arranged in each cable to monitor the temperature of the inner surface of the shield shell. Under the condition of applying insulation to the inner surface of the shield shell, the temperature measuring cables are placed inside the insulation board.

[0103] like Figure 8 As shown, temperature monitoring of the frozen soil curtain was carried out using temperature measuring holes C1~C8 and C9~C16, and the development of the shield-frozen soil interface was calculated.

[0104] like Figure 9 As shown, during the excavation process, the computer automatically calculates the stability of the frozen wall every 5 minutes based on temperature monitoring data, generating a contour map of the development temperature at the shield-frozen soil interface.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel, characterized in that, The method includes: On the shield shell of each tunnel boring machine that has reached the docking target position, freezing holes, temperature measuring holes and pressure relief holes are constructed respectively, and freezing pipes and temperature measuring pipes are installed in the freezing holes and temperature measuring holes respectively. Soil samples were collected during the opening of the outermost freezing hole of each tunnel boring machine, and the soil was transferred to the laboratory curing room for testing to obtain the soil strength index. Temperature sensors are deployed to monitor the temperature data of each sensor in real time, and the development of the interface between the tunnel boring machine and the frozen soil is calculated based on the temperature data. Based on the strength indicators, the development of the interface between the tunnel boring machine and the frozen soil, and temperature data, the excavation conditions of the connecting section soil are assessed. Based on the assessment results and the monitoring and early warning judgment criteria, the excavation operation of the connecting section soil is carried out.

2. The method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 1, characterized in that, Before constructing freezing holes, temperature measuring holes, and pressure relief holes on the shield shell of each tunnel boring machine upon reaching the docking target position, and before installing freezing pipes and temperature measuring pipes in the freezing holes and temperature measuring holes respectively, the following steps are included: Based on the predefined design requirements, determine the size and thickness of the steel plate used for reinforcing the shield shell of the tunnel boring machine, and determine the reinforcement location of the steel plate in conjunction with the pre-defined construction range of the freezing pipe and the temperature measuring pipe. Based on the size, thickness, and reinforcement location of the steel plates, welded steel plates are used to reinforce the shield shell of the tunnel boring machine.

3. The method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 1, characterized in that, The soil samples collected during the opening of the outermost freezing hole of each tunnel boring machine were then transferred to a laboratory curing room for testing. The resulting soil strength indicators included: Select the outermost freezing hole of each tunnel boring machine, collect the complete soil during the opening process of the selected freezing hole, seal it, and transfer the sealed soil to the experimental curing room for storage. The stored soil was taken out of the experimental curing room and subjected to parallel freezing tests at preset temperature levels. The strength index of the soil was obtained by calculating the average value of the experimental results.

4. The method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 3, characterized in that, The strength indicators include: compressive strength, flexural strength, and tensile strength.

5. The method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 1, characterized in that, The temperature sensors are installed on the temperature measuring tubes within the freezing range and on the inner wall of the shield shell of the tunnel boring machine, and the temperature sensors are installed according to the installation rules.

6. The method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 5, characterized in that, The deployment rules include: Temperature sensors are installed at preset intervals along the depth direction of the shield tunnel; Temperature sensors are installed at preset angle intervals along the circumferential direction of the shield tunnel.

7. The method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 1, characterized in that, The expression for calculating the development of the interface between the tunnel boring machine and the permafrost is as follows: ； In the formula, L imn t represents the thickness of the frozen wall at position m and time n for the i-th freezing tube; i0 Indicates the temperature of the freezing brine in the i-th freezing tube; l ijm t represents the vertical distance from position m of the i-th freezing tube to the j-th temperature measuring tube; jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature sensing tube; r i This represents the inner diameter of the i-th freezing tube.

8. The method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 1, characterized in that, The expression for the excavation conditions is: ； In the formula, D ij K1 represents the distance from the i-th freezing tube to the j-th freezing tube; L represents the safety factor; imn The thickness of the frozen wall at position m and time n represents the thickness of the frozen wall at position m of the i-th freezing tube; T1 represents the design average temperature of the frozen wall; K2 represents the safety factor. t jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature measuring tube; M represents the total number of temperature sensors arranged inside the temperature measuring tube; K3 represents the safety factor; T ij This represents the temperature measured by the temperature sensor at position j on the inner side of the i-th shield; N represents the total number of temperature sensors arranged on the inner side of the shield.

9. A method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 8, characterized in that, The monitoring and early warning determination criteria include: The computer collects temperature data at preset time intervals and calculates the strength index of the frozen wall based on the temperature data; The calculated strength index is tested. If the strength index does not meet the stability standard at the same time, an alarm is triggered, the excavation operation is suspended, and the frozen wall is reinforced with freezing measures until the strength index meets the excavation conditions at the same time, and construction is resumed.

10. A method for monitoring and evaluating the reinforcement of frozen soil in the docking section of a shield tunnel according to claim 9, characterized in that, The expression for the stability criterion is: ； In the formula, t m This indicates the temperature measured by the temperature sensor at position m; t jp This represents the temperature measured by the temperature sensor at position p inside the j-th temperature measuring tube; M represents the total number of temperature sensors arranged inside the temperature measuring tube; α1 represents the required compressive strength of the frozen wall; K4 represents the safety factor; α im Indicates the i-th soil layer at t m Compressive strength at temperature; β 1 indicates the required flexural strength of the frozen wall as per design specifications; β im Indicates the i-th soil layer at t m Flexural strength at temperature; γ1 represents the design requirement for the tensile strength of the frozen wall; γ im Indicates the i-th soil layer at t m Tensile strength at temperature; T ij This represents the temperature measured by the temperature sensor at position j on the inner side of the i-th shield; N represents the total number of temperature sensors arranged on the inner side of the shield.

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