Winter continuous construction method for deep and long tunnel in high and cold region

Abstract

The invention discloses a winter continuous construction method for a deep and long tunnel in an alpine region. The method comprises the following steps that S1, tunnel site frozen soil information and meteorological information are collected; s2, primary support sprayed concrete and secondary support molded concrete are tested, and the optimal mixing ratio is determined; s3, a wind field-temperature field of the tunnel portal is simulated through Ansys-Fluent; s4, a fluid-solid coupling model is established through Fluent and Workbench; s5, simulating the stress field model of the hole in the construction stage through Ansys-Workbench; s6, tunnel portal temperature and wind speed monitoring is carried out, and actually measured portal temperature field and wind field information is obtained; s7, simulating a hole thermal insulation facility; s8, anti-freezing measures are taken for site construction of sprayed concrete; s9, acquiring surrounding rock characteristics, stratum physical and mechanical parameters, rock mass integrity and surrounding rock basic quality indexes through tunnel geological exploration data and design data; compared with the prior art, the method has the advantages that the winter construction quality can be effectively controlled, the winter construction progress is guaranteed, and the construction quality and safety of the unfavorable geological zone tunnel are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of continuous construction of tunnels in winter, and in particular to a continuous construction method of deep and long tunnels in high-altitude cold areas in winter. Background Art

[0002] The climate in high-altitude cold regions is complex, characterized by low temperatures, large temperature swings, and long winters. To shorten construction periods and maximize the return on investment, tunnel construction in these regions is often unavoidable under negative temperatures. Winter temperatures significantly impact the quality of concrete construction. When temperatures drop below freezing, the water in the concrete begins to freeze and expand, damaging the internal structure and causing concrete frost damage.

[0003] Deep and long tunnels in high-altitude and cold regions often have very complex surrounding rock conditions. Improper construction control often leads to numerous quality and safety issues. Over-excavation and under-excavation are typical construction quality issues. Excessive over-excavation increases the amount of rock removed during tunnel excavation, prolongs the initial support period, increases construction costs, and impacts the construction progress. Over-excavation and under-excavation can also cause local stress concentrations, posing safety hazards. Of particular concern is the complex geological conditions of deep and long tunnels, which result in diverse and fluid safety risk sources for tunnel construction. These different risk sources are also prone to coupling, leading to unpredictable construction disasters and risks. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above defects and provide a method for continuous construction of deep and long tunnels in high-altitude cold areas in winter, which can effectively control the quality of winter construction, ensure the progress of winter construction, and ensure the construction quality and safety of tunnels in poor geological zones.

[0005] To solve the above technical problems, the present invention provides a technical solution: a method for continuous winter construction of a deep and long tunnel in a high-altitude cold region, comprising the following steps:

[0006] S1. Obtain the annual average temperature, extreme maximum temperature, extreme minimum temperature, standard frozen depth, and maximum frozen depth of the tunnel entrance and exit based on tunnel geological survey data and design data;

[0007] S2. Testing of primary support shotcrete and secondary support cast-in-place concrete and determination of the optimal mix ratio;

[0008] S3. Use Ansys-Fluent to simulate the wind field and temperature field at the tunnel entrance;

[0009] S4. Establish a fluid-structure interaction model using Fluent and Workbench;

[0010] S5. Use Ansys-Workbench to simulate the stress field model of the opening during the construction phase;

[0011] S6. Tunnel entrance temperature and wind speed monitoring to obtain measured entrance temperature and wind field information;

[0012] S7, simulated cave insulation facilities;

[0013] S8. Anti-freeze measures for shotcrete construction on site;

[0014] S9. Obtain surrounding rock characteristics, stratum physical and mechanical parameters, rock mass integrity, basic surrounding rock quality indicators, and surrounding rock drilling and blasting construction methods through tunnel geological survey and design data. Predict over-excavation and under-excavation control sections and sections with high construction safety risks through surrounding rock stability assessment.

[0015] S10. Control of over-excavation and under-excavation in drilling and blasting construction;

[0016] S11. Construction safety control of high-risk sections;

[0017] As an improvement, step S2 includes the following specific contents:

[0018] 1) Four groups of concrete mix proportions were determined based on previous experience in similar projects;

[0019] 2) Select admixtures;

[0020] 3) Experimental instruments: forced concrete mixer SH-03, cement concrete vibrating table SH-11, slump tester SH-14, cement concrete permeameter;

[0021] 4) According to different concrete mix ratio schemes, concrete test blocks of 150 mm × 150 mm × 150 mm were prepared and cured for 28 days. The concrete mixtures used in the experiments were mixed using a forced concrete mixer SH-03.

[0022] 5) Strength test: Place the test block in the press and input the acceleration load. When the specimen approaches failure and begins to deform rapidly, stop adjusting the throttle of the testing machine until the specimen fails. Record the ultimate failure load of the test block and calculate the compressive strength (MPa) of the concrete test block according to the formula (T0553-1) of the "Test Procedure for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020);

[0023] 6) Slump test and slump loss over time test: Using a slump tester SH-14, slump tests and slump loss over time tests were conducted on the mixtures prepared with various mix ratios in accordance with the "Standard for Test Methods for Properties of Ordinary Concrete Mixtures" (GB / T 50080-2016) (Chapter 4), and the slump loss over time values ​​were measured;

[0024] 7) Water-resistance test: Use specimens aged between 28 and 90 days. After drying, apply a layer of melted sealing material. Immediately press the specimens into a test mold preheated in an oven or electric furnace using a screw press. After the test mold cools, place it in a permeameter for testing. During the permeameter test, the water pressure starts at 0.1 MPa and increases by 0.1 MPa every 8 hours. After 8 hours, the specimen is water-proof. The water-resistance grade is calculated in accordance with (T0568-1) of the "Testing Procedures for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020).

[0025] 8) Antifreeze test: First, soak the prepared and cured test blocks, and then conduct freeze-thaw tests. Each freeze-thaw cycle should be completed in 2 to 5 hours. Usually, the transverse fundamental frequency of the specimen is tested and weighed every 25 freeze-thaw cycles. The test interval can also be determined according to the frost resistance of the specimen. The experiment can be stopped when one of the following two situations is reached: a. The relative dynamic elastic modulus of the specimen drops below 60%; b. The mass loss rate of the specimen reaches 5%;

[0026] 9) Analyze the mix ratios that meet the requirements in the strength test, conduct slump tests in order of compressive strength from high to low, and select the mix ratio with the least slump loss over time. If the mix ratio still meets the impermeability test and meets the concrete design requirements, then the mix ratio is the optimal mix ratio.

[0027] As an improvement, step S3 includes the following specific contents:

[0028] 1) Establish a tunnel model: Use CAD to import the model into SCDM and create a 3D geometry. The tunnel cross-sectional dimensions of the model adopt the tunnel's design dimensions, and the tunnel's inner contour design adopts a single-center circle cross-section. SCDM (pre-processing module) in ANSYS sets the surrounding rock properties, tunnel depth, tunnel curvature radius, and the thickness of the ground rock layer above and below the tunnel to establish a large-scale wind field model that wraps the tunnel model.

[0029] 2) Based on the modeling, the Realizable k-ε two-equation model was selected to establish the turbulence model. The established geometric model was imported into the Fluent solver for meshing, boundary conditions, wind speed, temperature and other parameter settings.

[0030] The transport equation of turbulent kinetic energy k is:

[0031]

[0032] The transport equation for the turbulent kinetic energy dissipation rate ε is:

[0033]

[0034] 3) After importing into Fluent, structured grids are preferred for dividing the three-dimensional tunnel model.

[0035] 4) Tunnel inlet boundary: The boundary of the tunnel inlet adopts the velocity inlet (inlet) in Fluent. Tunnel outlet boundary: The boundary of the tunnel outlet is set as the free outlet boundary (outflow). Wall boundary: In addition to the above-mentioned tunnel inlet boundary and tunnel outlet boundary that define the model boundary, the rest are defined as wall boundary conditions. The wall boundary temperature is set to constant temperature and no slip.

[0036] 5) Parameter setting: set the inlet wind speed, outlet return flow parameters, and turbulence equation.

[0037] 6) Select the Simple algorithm as the calculation method for numerical simulation.

[0038] Based on the collection of frozen soil information and meteorological information at the tunnel site and the setting of different excavation depths of the tunnel face for winter construction, the tunnel entrance and wind field conditions under different working conditions were recorded.

[0039] 7) Calculate the results of the Fluent model to obtain the wind field distribution cloud map such as wind track and wind direction at the tunnel entrance when the wind speed changes.

[0040] As an improvement, step S4 includes the following specific contents:

[0041] 1) Import the Fluent fluid analysis project created by the Fluid Flow (Fluent) module into the established ANSYS workbench. When coupling the temperature field and stress field, it is necessary to convert the SOLID 65 into a three-dimensional SOLID45 unit with an equivalent structure.

[0042] 2) In the Fluent project view, right-click on Mesh and select Edit to enter the meshing interface. First remove the solid part and keep only the fluid geometry. Use ICEM CFD for meshing and select MultiZone in the Method option.

[0043] 3) Update the mesh in meshing, close SCDM and automatically return to the model interface, select update to update.

[0044] 4) Based on the collected permafrost information and meteorological information of the tunnel site, the winter construction temperature conditions of the tunnel site are set to record the atmospheric temperature, mountain temperature, ground temperature and initial temperature of the tunnel entrance under different working conditions.

[0045] 5) Calculate the model: Close the mesh window and return to the Fluent project window. Right-click Setup, select Edit, and use the Ke turbulence model to perform the calculation. This calculation will reveal the temperature distribution at the tunnel entrance as wind speed and temperature change.

[0046] 6) Import fluid and temperature loads: Insert fluid load and temperature load, connect Imported load in the Static Structural section, and select pressure to set the properties.

[0047] 7) Set solid constraints: Set the bottom surface of the constraint to fixed. After setting, perform fluid-solid coupling calculation to obtain the stress calculation results of the fluid load diagram.

[0048] 8) View the temperature contour of the coupled flow-thermal-solid model: After calculating the results, right-click Equivalent Plastic Strain in the Solution interface and select Evaluate All Results. After setting the settings, right-click in the model interface and select Show All Bodies to view the entire model. This will show the temperature distribution contour caused by the parameter changes after coupling temperature and wind speed.

[0049] As an improvement, step S5 includes the following specific contents:

[0050] 1) Convert SOLID45 into SOLID 65 elements that can simulate the cracking, crushing, plastic deformation and creep of concrete materials;

[0051] 2) Import the pre-processing module in S3 into the Engineering Data of the Steady-state Thermal module in the workbench to edit the material properties;

[0052] 3) Edit materials and import them into the software’s comprehensive material library to change material properties;

[0053] 4) Use the built-in function SPANANGLE CENTER in Model to generate the grid;

[0054] 5) Add various thermodynamic parameters (thermal conductivity, specific heat, density, and convective heat transfer coefficient) to the additional model.

[0055] The law of heat conduction is:

[0056]

[0057] As the fluid temperature increases:

[0058] q=h(t w -t f )

[0059] When the fluid temperature drops

[0060] q=h(t w -t f )

[0061] In the formula, tw and tf are the wall temperature and fluid temperature respectively, h is the surface heat transfer coefficient, also known as the convection heat transfer coefficient, with the unit of W / (m2.K);

[0062] 6) The tunnel exit is a pressure exit boundary wall set as a convection heat transfer boundary, and the surrounding rock is a fixed temperature boundary, and the thermal load and wind pressure load in the fluid are introduced.

[0063] 7) Add the bulk density, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and linear expansion coefficient of surrounding rock and concrete;

[0064] 8) After calculating the results, right-click Equivalent Plastic Strain in the Solution interface and select Evaluate All Results. After setting the settings, right-click in the model interface and select Show All Bodies to view the entire model. View the concrete stress contour caused by the parameter changes after the temperature and wind speed coupling and determine the cracking of the lining structure.

[0065] As an improvement, step S6 includes the following specific contents:

[0066] 1) Based on the structural characteristics, environmental complexity, and project feasibility, wind speed, temperature, and stress monitoring points are determined. The principle for arranging monitoring points is to arrange them in the winter construction section of the tunnel. As the construction face advances, the number of monitoring sections is continuously increased.

[0067] 2) Seven monitoring sections were set up in the winter construction section of the tunnel entrance, at 10m, 15m, 20m, 25m, 30m, 35m, and 40m from the tunnel entrance, with measuring points located at the arch crown, arch waist, arch foot, and inverted arch positions to monitor temperature, wind speed, wind pressure, wind direction, and other data;

[0068] 3) Measuring points are set up at the arch crown, arch waist, arch foot and inverted arch of the tunnel portal lining surface to measure lining stress, wind speed and temperature. Temperature measuring holes with a depth of 1.5m are arranged at the arch crown, arch waist, arch foot and arch bottom facing the surrounding rock for measurement and control. The distances between each temperature sensor in the temperature measuring hole and the inner surface of the lining structure are 0m, 0.3m, 0.8m and 1.5m respectively.

[0069] 4) Monitor the ambient temperature of the surrounding rock, permafrost temperature, and earth temperature. Place temperature measuring holes at the top of the tunnel at 30m, 35m, and 40m from the tunnel entrance, from the top of the mountain toward the tunnel. Since the thickness of the surrounding rock at the entrance is thin, oblique drilling is chosen. Earth temperature measuring points are arranged at 25m in the tunnel section with surrounding rock, 10m in the tunnel section without surrounding rock, and 25m from the outside of the tunnel entrance. The distances between the temperature sensor in each temperature measuring hole and the surface of the lining structure are 0m, 0.3m, 0.8m, and 1.5m, respectively.

[0070] 5) By collecting data from temperature, wind speed and direction, and stress sensors, temperature, stress, and wind speed change curves at different locations of the arch crown, arch waist, arch foot, and invert monitoring holes are drawn, and the temperature and stress change patterns at different depths of the arch crown, arch waist, arch foot, and invert are analyzed.

[0071] 6) Input the actual monitoring data into the finite element model to simulate the on-site wind field and temperature field conditions, and obtain the finite element model tunnel internal temperature and lining stress data and trends. Compare them with the actual monitored tunnel internal temperature, stress data and trends to verify the model fitting accuracy and determine whether insulation treatment is needed, thereby assisting in guiding actual construction.

[0072] As an improvement, step S7 includes the following specific contents:

[0073] 1) Determine whether insulation is required. If not, additional insulation facilities need to be installed.

[0074] 2) Use ANSYS Fluent to simulate air source heat pump heating equipment, hot air cannons, and insulation sheds. Given the known outside temperature, set the initial temperature of the insulation measures, and add boundary conditions and insulation material properties.

[0075] 3) Re-divide the mesh according to the Fluent meshing steps and import the wall mesh divided by ANSYS ICEM into ANSYS Fluent.

[0076] 4) After checking that the mesh is read in correctly, set the solver parameters, open the energy equation, define the physical properties of the insulation shed materials, and set the regional conditions and boundary conditions.

[0077] 5) Analysis of simulation results shows that the tunnel is qualified if it meets the concrete stress requirements of clauses (5.2.3) and (5.2.6) and the safety factor requirements of clause (9.2.4) in the Code for Design of Highway Tunnels (JTG 3370.1-2018).

[0078] As an improvement, step S8 includes the following specific contents:

[0079] 1) Set construction anti-freezing measures based on the simulation results in S7 and actual engineering experience;

[0080] 2) Air source heat pump heating equipment, hot air guns and insulation sheds are installed at the tunnel entrance. Shotcrete construction is carried out in the insulation shed, and concrete trucks are driven into the tunnel to ensure that the concrete construction temperature inside the tunnel is above 5°C;

[0081] 3) The concrete mixing station adopts a heat preservation shed for heat preservation, and the heat preservation shed adopts sandwich heat preservation color steel plate;

[0082] 4) The concrete pump is installed in the greenhouse, and a steam pipe is laid on one side of the concrete delivery pipe, which is wrapped with a 5cm thick quilt for insulation;

[0083] 5) Set up a high-pressure air station near the cave entrance to shorten the length of the air duct outside the cave for easier insulation. Wrap the air duct outside the cave and about 100m into the cave with insulation materials;

[0084] 6) A water storage tank is set up in the greenhouse at the cave entrance, and water is transported outside by water truck to ensure water supply for construction.

[0085] As an improvement, step S10 includes the following specific contents:

[0086] 1) Analyze the tunnel drilling and blasting construction methods corresponding to different geological and surrounding rock conditions and predict the key control sections of over-excavation and under-excavation.

[0087] 2) Ansys / Ls-Dyna mainly includes the Lagrange algorithm, Euler algorithm, ALE algorithm and the fluid-solid coupling algorithm that combines the first two. The Lagrange method and multi-material fluid-solid coupling method are used in blasting analysis.

[0088] 3) Model building

[0089] ① Apply the rock, joint, air, explosive and other material models in the Ansys / Ls-Dyna material library to simulate the effects of stress waves and explosive gas on rocks during blasting.

[0090] ② Establish a model based on the actual project. The upper boundary of the model is to the ground surface, the lower boundary is selected as 3 to 5 times the height of the tunnel hole, and the left and right boundaries should be more than 3 to 5 times the distance from the wall of the adjacent tunnel hole to establish a two-dimensional basic model of the tunnel.

[0091] ③ Establish a model coordinate system, stretch the two-dimensional tunnel model along the coordinate system, and establish a complete three-dimensional tunnel model.

[0092] 4) The grid division adopts the sweeping grid division method. The grid division is dense around the blast hole, and the farther away from the blast hole, the sparser the grid division.

[0093] 5) Set boundary conditions:

[0094] ① The model does not consider the reflection of stress waves at the boundary, and non-reflecting boundaries are used on all sides;

[0095] ② When calculating the initial self-weight stress and excavation effect, the left and right boundaries are boundaries constrained by horizontal displacement, the bottom boundary is a boundary constrained by vertical displacement, and the upper boundary is a free deformation boundary.

[0096] 6) Tunnel blasting simulation

[0097] ①Simulate the blasting design plan, and only set a row of holes around the perimeter during the simulation;

[0098] ② A blasting stress field is formed between the blast holes in the peripheral holes, and the model equivalent stress cloud map and blasting forming contour line at each time are recorded.

[0099] 7) Predict the over-excavation and under-excavation values, adjust and revise the blasting design plan to ensure the minimum over-excavation and under-excavation, establish a systematic construction management system, strengthen personnel training, strictly design in accordance with specifications, ensure the accuracy of the excavation contour line, and strictly control the charge amount and drilling quality.

[0100] As an improvement, step S11 includes the following specific contents:

[0101] 1) Control section selection

[0102] Analyze the tunnel drilling and blasting construction methods corresponding to different geological and surrounding rock conditions: predict high-risk sections for construction safety, generally selected as V-level surrounding rock, faults and other unfavorable geological zones.

[0103] 2) Establishment of high-risk section model

[0104] ① Determine the tunnel cross-section size based on the design data and import the tunnel cross-section into Midas / GTS through CAD.

[0105] ② Establish structural material characteristics based on actual tunnel material parameters;

[0106] ③ Establish formation material characteristics based on actual geological material parameters;

[0107] ④ Build a tunnel model based on the actual project. The upper boundary of the model is at the ground surface, the lower boundary is 3 to 5 times the height of the tunnel, and the left and right boundaries should be at least 3 to 5 times the distance from the adjacent tunnel walls. Build a 2D tunnel model. Build a 3D model by stretching the 2D model.

[0108] ⑤ For the fault part, the corresponding entity is made at the corresponding position through the embedding function. The connection between the fault and the mountain is achieved by Boolean operation.

[0109] 3) Grid division

[0110] ① Grid division is performed for different structures. When grid division is performed for surrounding rock fault areas, small grid division is selected to make the model calculation more accurate;

[0111] ② Use Boolean operations to connect different structural parts.

[0112] 4) Apply load

[0113] Add the self-weight load through the static slope analysis - self-weight, and keep the direction consistent with when the model was first created.

[0114] 5) Add constraints to the model through static slope analysis - boundary - constraint. The left and right boundaries are boundaries constrained by horizontal displacement, the bottom boundary is a boundary constrained by vertical displacement, and the upper boundary is a free deformation boundary.

[0115] 6) Construction process

[0116] ① The effect of the timing of support structure construction is simulated by the load release factor (LDF). LDF = 0.0, which means that support is immediately applied after tunnel excavation.

[0117] ② During calculation, the load release coefficient should be determined based on actual tunnel engineering monitoring and measurement results and previous construction experience. It should be approximately determined as the ratio of the deformation value at the tunnel control measurement point in the current excavation step to the total deformation value at that measurement point. In the absence of measured deformation data, the load release coefficient can be determined by engineering analogy using measured results from similar tunnels.

[0118] ③ By adding the construction process to the construction stage management, each stage will be excavated in the order of "excavation - primary support - secondary lining".

[0119] 7) After building the stratigraphic model, analyze the working conditions. Use "Analyze > Create" to create excavation conditions. This condition can be used to predict surrounding rock stress and structural deformation during construction, and to determine whether the construction method meets safety requirements. By modifying model construction parameters, such as the drilling and blasting method and excavation footage, the most unfavorable surrounding rock conditions can be estimated during construction.

[0120] 8) During the construction of high-risk sections, the model parameters are adjusted based on the results of advanced geological forecasts and construction monitoring to predict the construction safety of the tunnel surrounding rock under actual construction conditions. Based on the safety prediction results, actual construction parameters such as different drilling and blasting methods, construction excavation footage, and initial support types and stiffness are adjusted.

[0121] The advantages of the present invention compared with the prior art are:

[0122] 1. The present invention focuses on the construction quality control and construction safety control of tunnels in cold regions. In the process of traditional antifreeze and insulation measures for winter construction, air source heat pump heating equipment is added to improve the temperature level of tunnel entrance during winter construction, reduce winter construction energy consumption, and reduce environmental pollution.

[0123] 2. The combined use of test data, actual monitoring data, and theoretical simulation data as construction guidance provides a strong reference for the winter construction process of deep and long tunnels in high-altitude cold regions, with significant guiding significance:

[0124] First, based on the laboratory test results, the "Test Code for Cement and Cement Concrete in Highway Engineering" (JTG 3420-2020), the "Standard for Test Methods for Performance of Ordinary Concrete Mixtures" (GB / T 50080-2016) and design requirements, the most suitable mix ratio of primary support shotcrete + secondary support cast-in-place concrete for cold-region projects is selected.

[0125] Secondly, before construction, a three-factor fluid-solid coupling model for temperature, wind speed, and stress was established using Ansys Fluent and Ansys Workbench. This model determined the concrete stress state during winter construction at the tunnel entrance, converted the units, and calculated concrete cracking. Based on the cracking patterns calculated by the model, a monitoring plan for tunnel temperature and lining stress was determined. Monitoring instruments were installed according to the monitoring plan to collect data on mountain temperature, ground temperature, tunnel wind speed and direction, lining temperature, and lining stress. Based on the monitoring data from the winter construction section of the tunnel entrance, Ansys was used to simulate the actual wind, temperature, and stress fields to determine whether the initial support shotcrete for winter tunnel construction met design requirements. Additional insulation measures for the tunnel entrance were also simulated, and the model served as a guide for implementing the actual insulation measures during construction.

[0126] Finally, blasting plans for key control sections were simulated using Ansys / Ls-Dyna to predict over-break and under-break, allowing adjustments to be made to the blasting design to ensure minimal over-break and under-break.

[0127] Midas / GTS is used to simulate the construction process of high-risk sections, predict construction risks, and adjust actual construction parameters for different drilling and blasting methods to ensure construction safety.

[0128] 3. Establish a joint construction simulation system using Ansys-Fluent, Ansys Workbench, Ansys / Ls-Dyna, and Midas / GTS to guide winter construction and construction in soft surrounding rock of deep and long tunnels in high-altitude cold regions, improve tunnel construction quality, predict construction risk points, and promptly adopt construction control measures to ensure construction safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0129] Figure 1 This is a flow chart of the present invention

[0130] Figure 2 It is a diagram of a large-scale wind field model of the tunnel model wrapped in the present invention.

[0131] Figure 3 This is a wind farm establishment diagram of the present invention.

[0132] Figure 4 It is a wind path diagram without a windshield of the present invention.

[0133] Figure 5 This is the temperature distribution diagram without a windshield of the present invention.

[0134] Figure 6 It is a cross-sectional layout diagram of the present invention.

[0135] Figure 7 It is the measuring point arrangement diagram of the present invention.

[0136] Figure 8 This is a diagram of the arrangement of measuring points outside the cave of the present invention.

[0137] Figure 9 It is a drawing of establishing a heat preservation shed according to the present invention.

[0138] Figure 10 It is a diagram showing the windshield of the present invention.

[0139] Figure 11 The present invention has a wind path diagram of a windshield.

[0140] Figure 12 The present invention has a temperature distribution diagram of the windshield.

[0141] Figure 13 This is a simulation diagram of the high-risk section (fault fracture zone) of the tunnel of the present invention.

[0142] Figure 14 This is a displacement comparison diagram of the high-risk section of the tunnel under different construction parameters of the present invention. DETAILED DESCRIPTION

[0143] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0144] A method for continuous winter construction of a deep and long tunnel in a high-altitude cold region comprises the following steps:

[0145] S1. Obtain the annual average temperature, extreme maximum temperature, extreme minimum temperature, standard frozen depth, and maximum frozen depth of the tunnel entrance and exit based on tunnel geological survey data and design data;

[0146] S2. Testing of primary support shotcrete and secondary support cast-in-place concrete and determination of the optimal mix ratio;

[0147] 1) Four groups of concrete mix proportions were determined based on previous experience in similar projects;

[0148] 2) Select admixtures;

[0149] 3) Experimental instruments: forced concrete mixer SH-03, cement concrete vibrating table SH-11, slump tester SH-14, cement concrete permeameter;

[0150] 4) According to different concrete mix ratio schemes, concrete test blocks of 150 mm × 150 mm × 150 mm were prepared and cured for 28 days. The concrete mixtures used in the experiments were mixed using a forced concrete mixer SH-03.

[0151] 5) Strength test: Place the test block in the press and input the acceleration load. When the specimen approaches failure and begins to deform rapidly, stop adjusting the throttle of the testing machine until the specimen fails. Record the ultimate failure load of the test block and calculate the compressive strength (MPa) of the concrete test block according to the formula (T0553-1) of the "Test Procedure for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020);

[0152] 6) Slump test and slump loss over time test: Using a slump tester SH-14, slump tests and slump loss over time tests were conducted on the mixtures prepared with various mix ratios in accordance with the "Standard for Test Methods for Properties of Ordinary Concrete Mixtures" (GB / T 50080-2016) (Chapter 4), and the slump loss over time values ​​were measured;

[0153] 7) Water-resistance test: Use specimens aged 28-90 days. After drying, apply a layer of melted sealing material. Then, immediately press the specimen into a test mold preheated in an oven or electric furnace using a screw press. After the test mold cools, place it in a permeameter for testing. During the permeameter test, the water pressure starts at 0.1 MPa and increases by 0.1 MPa every 8 hours. After 8 hours, the specimen is water-proof. The water-resistance grade is calculated according to (T0568-1) of the "Testing Procedures for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020).

[0154] 8) Frost resistance test: First, soak the prepared and cured test blocks, and then conduct freeze-thaw tests. Each freeze-thaw cycle should be completed in 2 to 5 hours. Usually, the specimen is tested for transverse fundamental frequency and weighed every 25 freeze-thaw cycles. The test interval can also be determined based on the frost resistance of the specimen. The experiment can be stopped when one of the following two situations is reached: a. The relative dynamic elastic modulus of the specimen drops below 60%; b. The mass loss rate of the specimen reaches 5%;

[0155] 9) Analyze the mix ratios that meet the requirements in the strength test, conduct slump tests in order of compressive strength from high to low, and select the mix ratio with the least slump loss over time. If the mix ratio still meets the impermeability test and meets the concrete design requirements, then the mix ratio is the optimal mix ratio.

[0156] S3. Use Ansys-Fluent to simulate the wind field and temperature field at the tunnel entrance;

[0157] 1) Establish a tunnel model: Use CAD to import the model into SCDM and establish 3D geometry. The tunnel cross-section size of the model adopts the tunnel design size, and the tunnel inner contour design adopts a single center circle cross-section. SCDM (pre-processing module) in ANSYS sets the surrounding rock properties, tunnel depth, tunnel curvature radius, thickness of the ground rock layer above the tunnel, and thickness of the rock layer below the tunnel. Establish a large wind field model that wraps the tunnel model, such as Figure 2 shown.

[0158] 2) Based on the modeling, the Realizable k-ε two-equation model was selected to establish the turbulence model. The established geometric model was imported into the Fluent solver for meshing, boundary conditions, wind speed, temperature and other parameter settings.

[0159] The transport equation of turbulent kinetic energy k is:

[0160]

[0161] The transport equation for the turbulent kinetic energy dissipation rate ε is:

[0162]

[0163] 3) After importing into Fluent, structured grids are preferred for dividing the three-dimensional tunnel model.

[0164] 4) Tunnel inlet boundary: The boundary of the tunnel inlet adopts the velocity inlet (inlet) in Fluent. Tunnel outlet boundary: The boundary of the tunnel outlet is set as the free outlet boundary (outflow). Wall boundary: In addition to the above-mentioned tunnel inlet boundary and tunnel outlet boundary that define the model boundary, the rest are defined as wall boundary conditions. The wall boundary temperature is set to constant temperature and no slip.

[0165] 5) Parameter setting: set the inlet wind speed, outlet return flow parameters, and turbulence equation.

[0166] 6) Select the Simple algorithm as the calculation method for numerical simulation.

[0167] Based on the collection of frozen soil information and meteorological information at the tunnel site and the setting of different excavation depths of the tunnel face for winter construction, the tunnel entrance and wind field conditions under different working conditions were recorded.

[0168] 7) Calculate the results of the Fluent model to obtain the wind field distribution cloud map of the wind track and wind direction at the tunnel entrance when the wind speed changes, such as Figure 3 、 4 shown.

[0169] S4. Establish a fluid-structure coupling model using Fluent and Workbench;

[0170] 1) Import the Fluent fluid analysis project created by the Fluid Flow (Fluent) module into the established ANSYS workbench. When coupling the temperature field and stress field, it is necessary to convert the SOLID 65 into a three-dimensional SOLID45 unit with an equivalent structure.

[0171] 2) In the Fluent project view, right-click on Mesh and select Edit to enter the meshing interface. First remove the solid part and keep only the fluid geometry. Use ICEM CFD for meshing and select MultiZone in the Method option.

[0172] 3) Update the mesh in meshing, close SCDM and automatically return to the model interface, select update to update.

[0173] 4) Based on the collected permafrost information and meteorological information of the tunnel site, the winter construction temperature conditions of the tunnel site are set to record the atmospheric temperature, mountain temperature, ground temperature and initial temperature of the tunnel entrance under different working conditions.

[0174] 5) Calculate the model: Close the mesh window and return to the Fluent project window. Right-click Setup, select Edit, and use the Ke turbulence model to perform the calculation. This calculation will reveal the temperature distribution at the tunnel entrance as wind speed and temperature change.

[0175] 6) Import fluid and temperature loads: Insert fluid load and temperature load, connect Imported load in the Static Structural section, and select pressure to set the properties.

[0176] 7) Set solid constraints: Set the bottom surface of the constraint to fixed. After setting, perform fluid-solid coupling calculation to obtain the stress calculation results of the fluid load diagram.

[0177] 8) View the temperature cloud map of the fluid-thermal-solid coupling model: After calculating the results, right-click Equivalent Plastic Strain in the Solution interface and select Evaluate All Results. After setting, right-click in the model interface and select Show All Bodies to view the entire model and view the temperature distribution cloud map caused by the parameter changes after the temperature and wind speed are coupled, such as Figure 5 shown.

[0178] S5. Use Ansys-Workbench to simulate the stress field model of the opening during the construction phase;

[0179] 1) Convert SOLID45 into SOLID 65 elements that can simulate the cracking, crushing, plastic deformation and creep of concrete materials;

[0180] 2) Import the pre-processing module in S3 into the Engineering Data of the Steady-state Thermal module in the workbench to edit the material properties;

[0181] 3) Edit materials and import them into the software’s comprehensive material library to change material properties;

[0182] 4) Use the built-in function SPANANGLE CENTER in Model to generate the grid;

[0183] 5) Add various thermodynamic parameters (thermal conductivity, specific heat, density, and convective heat transfer coefficient) to the additional model.

[0184] The law of heat conduction is:

[0185]

[0186] As the fluid temperature increases:

[0187] q=h(t w -t f )

[0188] When the fluid temperature drops

[0189] q=h(t w -t f )

[0190] In the formula, tw and tf are the wall temperature and fluid temperature respectively, h is the surface heat transfer coefficient, also known as the convection heat transfer coefficient, with the unit of W / (m2.K);

[0191] 6) The tunnel exit is a pressure exit boundary wall set as a convection heat transfer boundary, and the surrounding rock is a fixed temperature boundary, and the thermal load and wind pressure load in the fluid are introduced.

[0192] 7) Add the bulk density, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and linear expansion coefficient of surrounding rock and concrete;

[0193] 8) After calculating the results, right-click Equivalent Plastic Strain in the Solution interface and select Evaluate All Results. After setting the settings, right-click in the model interface and select Show All Bodies to view the entire model. View the concrete stress contour caused by the parameter changes after the temperature and wind speed coupling and determine the cracking of the lining structure.

[0194] S6. Tunnel entrance temperature and wind speed monitoring to obtain measured entrance temperature and wind field information;

[0195] 1) Based on the structural characteristics, environmental complexity, project feasibility, and the key finite element calculation results of S3, S4, and S5, wind speed, temperature, and stress monitoring points are formulated. The principle of arranging monitoring points is to arrange them in the winter construction section of the tunnel. As the construction face advances, the monitoring section is continuously increased.

[0196] 2) Seven monitoring sections are set up in the winter construction section of the tunnel entrance, which are 10m, 15m, 20m, 25m, 30m, 35m and 40m away from the tunnel entrance respectively. The section measuring points are arranged at the arch top, arch waist, arch foot and inverted arch position respectively to monitor temperature, wind speed, wind pressure, wind direction and other data, such as Figure 6 shown.

[0197] 3) Set measuring points at the top, waist, foot and invert of the tunnel lining surface to measure lining stress, wind speed and temperature. Also, set 1.5m deep temperature measuring holes at the top, waist, foot and bottom of the tunnel towards the surrounding rock for measurement and control. Figure 7 As shown, the distances between each temperature sensor in the temperature measuring hole and the inner surface of the lining structure are 0m, 0.3m, 0.8m, and 1.5m respectively;

[0198] 4) Monitor the ambient temperature of the surrounding rock, frozen soil and earth temperature. Place temperature measuring holes at the top of the tunnel at 30m, 35m and 40m from the tunnel entrance, from the top of the mountain toward the tunnel. Since the thickness of the surrounding rock at the tunnel entrance is thin, oblique drilling is selected. Place earth temperature measuring points at 25m in the tunnel section with surrounding rock, 10m in the tunnel section without surrounding rock and 25m from the outside of the tunnel entrance. The distances between the temperature sensor in each temperature measuring hole and the surface of the lining structure are 0m, 0.3m, 0.8m and 1.5m respectively. Figure 8 shown.

[0199] 5) By collecting data from temperature, wind speed and direction, and stress sensors, temperature, stress, and wind speed change curves at different locations of the arch crown, arch waist, arch foot, and invert monitoring holes are drawn, and the temperature and stress change patterns at different depths of the arch crown, arch waist, arch foot, and invert are analyzed.

[0200] 6) Input the actual monitoring data into the finite element model to simulate the on-site wind field and temperature field conditions, and obtain the finite element model tunnel internal temperature and lining stress data and trends. Compare them with the actual monitored tunnel internal temperature, stress data and trends to verify the model fitting accuracy and determine whether insulation treatment is needed, thereby assisting in guiding actual construction.

[0201] S7, simulated cave insulation facilities;

[0202] 1) Use S6 to determine whether the concrete in the winter construction section meets the concrete stress requirements of clauses (5.2.3) and (5.2.6) and the safety factor requirements of clauses (9.2.4) in the "Code for Design of Highway Tunnels" (JTG 3370.1-2018). If not, additional insulation facilities, including insulation layers, windbreaks, etc., are required. Figure 9 、 10 shown.

[0203] 2) Use ANSYS Fluent to simulate air source heat pump heating equipment, hot air cannons, and insulation sheds. Given the known outside temperature, set the initial temperature of the insulation measures, and add boundary conditions and insulation material properties.

[0204] 3) Re-divide the mesh according to the Fluent meshing steps and import the wall mesh divided by ANSYS ICEM into ANSYS Fluent.

[0205] 4) After checking that the mesh is read in correctly, set the solver parameters, open the energy equation, define the physical properties of the insulation shed materials, and set the regional conditions and boundary conditions.

[0206] 5) Analysis of simulation results shows that the tunnel is qualified if it meets the concrete stress requirements of clauses (5.2.3) and (5.2.6) and the safety factor requirements of clauses (9.2.4) in the Code for Design of Highway Tunnels (JTG 3370.1-2018). Figure 11 、 12 shown.

[0207] S8. Anti-freeze measures for shotcrete construction on site;

[0208] 1) Set construction anti-freezing measures based on the simulation results in S7 and actual engineering experience;

[0209] 2) Air source heat pump heating equipment, hot air guns and insulation sheds are installed at the tunnel entrance. Shotcrete construction is carried out in the insulation shed, and concrete trucks are driven into the tunnel to ensure that the concrete construction temperature inside the tunnel is above 5°C;

[0210] 3) The concrete mixing station adopts a heat preservation shed for heat preservation, and the heat preservation shed adopts sandwich heat preservation color steel plate;

[0211] 4) The concrete pump is installed in the greenhouse, and a steam pipe is laid on one side of the concrete delivery pipe, which is wrapped with a 5cm thick quilt for insulation;

[0212] 5) Set up a high-pressure air station near the cave entrance to shorten the length of the air duct outside the cave for easier insulation. Wrap the air duct outside the cave and about 100m into the cave with insulation materials;

[0213] 6) A water storage tank is set up in the greenhouse at the cave entrance, and water is transported outside by water truck to ensure water supply for construction.

[0214] S9. Obtain surrounding rock characteristics, stratum physical and mechanical parameters, rock mass integrity, basic surrounding rock quality indicators, and surrounding rock drilling and blasting construction methods through tunnel geological survey and design data. Predict over-excavation and under-excavation control sections and sections with high construction safety risks through surrounding rock stability assessment.

[0215] S10. Control of over-excavation and under-excavation in drilling and blasting construction;

[0216] 1) Analyze the tunnel drilling and blasting construction methods corresponding to different geological and surrounding rock conditions and predict the key control sections of over-excavation and under-excavation.

[0217] 2) Ansys / Ls-Dyna mainly includes the Lagrange algorithm, Euler algorithm, ALE algorithm and the fluid-solid coupling algorithm that combines the first two. The Lagrange method and multi-material fluid-solid coupling method are used in blasting analysis.

[0218] 3) Model building

[0219] ① Apply the rock, joint, air, explosive and other material models in the Ansys / Ls-Dyna material library to simulate the effects of stress waves and explosive gas on rocks during blasting.

[0220] ② Establish a model based on the actual project. The upper boundary of the model is to the ground surface, the lower boundary is selected as 3 to 5 times the height of the tunnel hole, and the left and right boundaries should be more than 3 to 5 times the distance from the wall of the adjacent tunnel hole to establish a two-dimensional basic model of the tunnel.

[0221] ③ Establish a model coordinate system, stretch the two-dimensional tunnel model along the coordinate system, and establish a complete three-dimensional tunnel model.

[0222] 4) The grid division adopts the sweeping grid division method. The grid division is dense around the blast hole, and the farther away from the blast hole, the sparser the grid division.

[0223] 5) Set boundary conditions:

[0224] ① The model does not consider the reflection of stress waves at the boundary, and non-reflecting boundaries are used on all sides;

[0225] ② When calculating the initial self-weight stress and excavation effect, the left and right boundaries are boundaries constrained by horizontal displacement, the bottom boundary is a boundary constrained by vertical displacement, and the upper boundary is a free deformation boundary.

[0226] 6) Tunnel blasting simulation

[0227] ①Simulate the blasting design plan, and only set a row of holes around the perimeter during the simulation;

[0228] ② A blasting stress field is formed between the blast holes in the peripheral holes, and the model equivalent stress cloud map and blasting forming contour line at each time are recorded.

[0229] 7) Predict the over-excavation and under-excavation values, adjust and revise the blasting design plan to ensure the minimum over-excavation and under-excavation, establish a systematic construction management system, strengthen personnel training, strictly design in accordance with specifications, ensure the accuracy of the excavation contour line, and strictly control the charge amount and drilling quality.

[0230] S11. Safety control of high-risk section construction, such as Figure 13 As shown;

[0231] 1) Control section selection

[0232] Analyze the tunnel drilling and blasting construction methods corresponding to different geological and surrounding rock conditions: predict high-risk sections for construction safety, generally selected as V-level surrounding rock, faults and other unfavorable geological zones.

[0233] 2) Establishment of high-risk section model

[0234] ① Determine the tunnel cross-section size based on the design data and import the tunnel cross-section into Midas / GTS through CAD.

[0235] ② Establish structural material characteristics based on actual tunnel material parameters;

[0236] ③ Establish formation material characteristics based on actual geological material parameters;

[0237] ④ Build a tunnel model based on the actual project. The upper boundary of the model is at the ground surface, the lower boundary is 3 to 5 times the height of the tunnel, and the left and right boundaries should be at least 3 to 5 times the distance from the adjacent tunnel walls. Build a 2D tunnel model. Build a 3D model by stretching the 2D model.

[0238] ⑤ For the fault part, the corresponding entity is made at the corresponding position through the embedding function. The connection between the fault and the mountain is achieved by Boolean operation.

[0239] 3) Grid division

[0240] ① Grid division is performed for different structures. When grid division is performed for surrounding rock fault areas, small grid division is selected to make the model calculation more accurate;

[0241] ② Use Boolean operations to connect different structural parts.

[0242] 4) Apply load

[0243] Add the self-weight load through the static slope analysis - self-weight, and keep the direction consistent with when the model was first created.

[0244] 5) Add constraints to the model through static slope analysis - boundary - constraint. The left and right boundaries are boundaries constrained by horizontal displacement, the bottom boundary is a boundary constrained by vertical displacement, and the upper boundary is a free deformation boundary.

[0245] 6) Construction process

[0246] ① The effect of the timing of support structure construction is simulated by the load release factor (LDF). LDF = 0.0, which means that support is immediately applied after tunnel excavation.

[0247] ② During calculation, the load release coefficient should be determined based on actual tunnel engineering monitoring and measurement results and previous construction experience. It should be approximately determined as the ratio of the deformation value at the tunnel control measurement point in the current excavation step to the total deformation value at that measurement point. In the absence of measured deformation data, the load release coefficient can be determined by engineering analogy using measured results from similar tunnels.

[0248] ③ By adding the construction process to the construction stage management, each stage will be excavated in the order of "excavation - primary support - secondary lining".

[0249] 7) After building the stratigraphic model, analyze the working conditions. Use "Analyze > Create" to create excavation conditions. This condition can be used to predict surrounding rock stress and structural deformation during construction, and to determine whether the construction method meets safety requirements. By modifying model construction parameters, such as the drilling and blasting method and excavation footage, the most unfavorable surrounding rock conditions can be estimated during construction.

[0250] 8) During the construction of high-risk sections, the model parameters are adjusted according to the results of advanced geological prediction and construction monitoring to predict the construction safety of the tunnel surrounding rock under actual construction conditions. According to the safety prediction results, the actual construction parameters such as different drilling and blasting excavation methods, construction excavation footage size, and initial support form and support stiffness are adjusted. Figure 14 shown.

[0251] In specific use, the finite element construction joint simulation system is used, combined with indoor test results and on-site monitoring results, to predict the construction process. The construction process is adjusted based on the prediction results, saving inappropriate construction settings, reducing construction costs, and improving construction quality.

[0252] In the winter construction section of the tunnel entrance, full use is made of the low-level energy in the atmospheric environment to improve the construction environment, effectively increase the construction temperature, reduce construction pollution, and make winter construction efficient, energy-saving, and environmentally friendly.

[0253] During the construction of tunnel surrounding rock, the drilling and blasting design plan is rationally optimized to reduce the over-excavation and under-excavation value of smooth blasting, saving the construction cost of secondary excavation and secondary spraying.

[0254] During the construction stage of weak surrounding rock, the construction risks of the surrounding rock should be reasonably predicted to ensure smooth excavation of the surrounding rock and reduce the safety cost of surrounding rock construction.

[0255] Through the finite element construction joint simulation system, combined with indoor test results and on-site monitoring results, the construction process is predicted and adjusted based on the prediction results, thus saving inappropriate construction settings, reducing construction costs and improving construction quality.

[0256] In the winter construction section of the tunnel entrance, full use is made of the low-level energy in the atmospheric environment to improve the construction environment, effectively increase the construction temperature, reduce construction pollution, and make winter construction efficient, energy-saving, and environmentally friendly.

[0257] During the construction of tunnel surrounding rock, the drilling and blasting design plan is rationally optimized to reduce the over-excavation and under-excavation value of smooth blasting, saving the construction cost of secondary excavation and secondary spraying.

[0258] During the construction stage of weak surrounding rock, the construction risks of the surrounding rock should be reasonably predicted to ensure smooth excavation of the surrounding rock and reduce the safety cost of surrounding rock construction.

[0259] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0260] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0261] The present invention and its implementation methods are described above. This description is not restrictive. In short, if ordinary technicians in this field are inspired by it and do not depart from the purpose of the invention, they can creatively design structures and embodiments similar to the technical solution, which should fall within the scope of protection of the present invention.

Claims

1. A method for continuous construction of deep and long tunnels in high-cold areas in winter, characterized in that: The following steps are involved: S1. Obtain the annual average temperature, extreme maximum temperature, extreme minimum temperature, standard frozen depth and maximum frozen depth of the tunnel entrance and exit through tunnel geological survey data and design data; S2. Test of initial support shotcrete and secondary support cast-in-place concrete and determination of the optimal mix ratio; S3, simulate the wind field and temperature field at the tunnel entrance through Ansys-Fluent; S4. Establish a fluid-structure interaction model through Fluent and Workbench; S5. Use Ansys-Workbench to simulate the stress field model of the opening during the construction phase; S6, monitoring the temperature and wind speed at the tunnel entrance to obtain the measured temperature field and wind field information at the tunnel entrance; S7, simulated cave insulation facilities; S8. Antifreeze measures for on-site construction of shotcrete; S9. Obtain surrounding rock characteristics, formation physical and mechanical parameters, rock mass integrity, basic surrounding rock quality indicators, and surrounding rock drilling and blasting construction methods through tunnel geological survey data and design data. Predict over-excavation and under-excavation key control sections and construction safety high-risk sections through surrounding rock stability evaluation. S10. Control of over-excavation and under-excavation in drilling and blasting construction; S11. Safety control of construction in high-risk sections.

2. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 1 is characterized in that: Step S2 includes the following specific contents: 1) Four groups of concrete mix proportions were determined based on previous experience in similar projects; 2) Select admixtures; 3) Experimental instruments: forced concrete mixer SH-03, cement concrete compaction table SH-11, slump tester SH-14, cement concrete permeameter; 4) According to different concrete mix ratio schemes, concrete test blocks of 150 mm × 150 mm × 150 mm were prepared and cured for 28 days. The forced concrete mixer SH-03 was used to mix the concrete to prepare the mixture for the experiment; 5) Strength test: Place the test block in the press and input the acceleration load. When the test piece is close to failure and begins to deform rapidly, stop adjusting the throttle of the test machine until the test piece fails. Record the ultimate failure load of the test block and calculate the compressive strength (MPa) of the concrete test block according to the formula (T0553-1) of the "Test Code for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020); 6) Slump test and slump loss over time test: Use SH-14 slump tester to conduct slump test and slump loss over time test on the mixtures made with each mix ratio according to the Standard for Test Methods for Performance of Ordinary Concrete Mixtures (GB / T 50080-2016) (Chapter 4), and determine the slump loss over time value; 7) Anti-seepage test: Use the test specimens aged between 28d and 90d, apply a layer of melted sealing material after drying, and then immediately press them into the test mold preheated in an oven or electric furnace on a screw press. After the test mold cools down, put it into the permeameter for testing. During the permeameter test, the water pressure starts from 0.1MPa and increases by 0.1MPa every 8h. After 8h, the test specimen is water-free. The anti-seepage grade is calculated according to (T0568-1) of the "Test Procedures for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020); 8) Antifreeze test: First, soak the prepared and cured test blocks, and then conduct freeze-thaw test. Each freeze-thaw cycle should be completed within 2 to 5 hours. Usually, the transverse fundamental frequency of the specimen is tested and weighed every 25 freeze-thaw cycles. The test interval can also be determined according to the frost resistance of the specimen. The experiment can be stopped when one of the following two conditions is reached: a. The relative dynamic elastic modulus of the specimen drops below 60%; b. The mass loss rate of the specimen reaches 5%; 9) Analyze the mix ratios that meet the requirements in the strength test, conduct slump tests in order of compressive strength from high to low, and select the mix ratio with the least slump loss over time. If the mix ratio still meets the impermeability test and meets the concrete design requirements, then the mix ratio is the optimal mix ratio.

3. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 1 is characterized in that: Step S3 includes the following specific contents: 1) Establish a tunnel model: Use CAD to import the model into SCDM and establish 3D geometric figures. The tunnel cross-sectional dimensions of the model adopt the design dimensions of the tunnel, and the tunnel inner contour design adopts a single-center circle section. The SCDM (pre-processing module) in ANSYS sets the surrounding rock properties, tunnel depth, tunnel curvature radius, ground rock thickness above the tunnel, and rock thickness below the tunnel to establish a large wind field model that wraps the tunnel model. 2) Based on the modeling, the Realizable k-ε two-equation model is selected to establish the turbulence model. The established geometric model is imported into the fluent solver for meshing, boundary conditions, wind speed, temperature and other parameter settings. The transport equation of turbulent kinetic energy k is: The transport equation for the turbulent kinetic energy dissipation rate ε is: 3) After importing into Fluent, structured grids are used to divide the three-dimensional model of the tunnel. 4) Tunnel inlet boundary: The boundary of the tunnel inlet adopts the velocity inlet (inlet) in Fluent; Tunnel outlet boundary: The boundary of the tunnel outlet is set as the free outlet boundary (outflow); Wall boundary: In addition to the above-mentioned tunnel inlet boundary and tunnel outlet boundary to define the model boundary, the rest are defined as wall boundary conditions, and the wall boundary temperature is set to constant temperature and no slip. 5) Parameter setting: set the inlet wind speed, outlet return flow parameters, and turbulence equation. 6) Select Simple algorithm as the calculation method for numerical simulation. Based on the collection of frozen soil information and meteorological information at the tunnel site and the setting of different excavation depths of the tunnel face for winter construction, the tunnel entrance and wind field conditions under different working conditions were recorded. 7) Calculate the results of the Fluent model to obtain the wind field distribution cloud map such as wind track and wind direction at the tunnel entrance when the wind speed changes.

4. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 1, characterized in that: Step S4 includes the following specific contents: 1) Import the Fluent fluid analysis project created by the Fluid Flow (Fluent) module into the established ANSYS workbench. When coupling the temperature field and stress field, it is necessary to convert the SOLID 65 into a three-dimensional SOLID45 unit of equivalent structure. 2) In the Fluent project view, right-click on Mesh and select Edit to enter the meshing interface. First remove the solid part and keep only the fluid geometry. Use ICEM CFD for meshing and select MultiZone in the Method option. 3) Update the mesh in meshing, close SCDM and automatically return to the model interface, and select update to update. 4) Based on the collected frozen soil information and meteorological information of the tunnel site, the winter construction temperature conditions of the tunnel site are set to record the atmospheric temperature, mountain temperature, ground temperature and initial temperature of the tunnel entrance under different conditions. 5) Calculation model: Close mesh and return to the Fluent project window, right-click setup, select edit, and use the Ke turbulence model to perform the calculation. After calculation, the temperature distribution of the temperature field at the tunnel entrance section can be obtained when the wind speed and wind temperature change. 6) Import fluid and temperature loads: Insert fluid load and temperature load, connect Imported load in Static Structural block, and select pressure to set properties. 7) Set solid constraints: Set the bottom surface of the constraint to fixed. After setting, perform fluid-solid coupling calculation to obtain the stress calculation results of the fluid load diagram. 8) View the temperature cloud map of the fluid-thermal-solid coupling model: After calculating the results, right-click Equivalent Plastic Strain in the Solution interface and select Evaluate All Results. After setting, right-click in the model interface and select Show ALL Bodies to view all models and view the temperature distribution cloud map caused by the parameter changes after the temperature and wind speed are coupled.

5. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 3 is characterized in that: Step S5 includes the following specific contents: 1) Convert SOLID45 into SOLID65 unit which can simulate the cracking, crushing, plastic deformation and creep of concrete materials; 2) Import the pre-processing module in S3 into the Engineering Data of the Steady-state Thermal module in the workbench to edit the material properties; 3) Edit materials and import materials into the software's comprehensive material library to change material properties; 4) Use the built-in function SPANANGLE CENTER in Model to generate a grid; 5) Add various thermodynamic parameters (thermal conductivity, specific heat, density, and convection heat transfer coefficient) to the additional model. The law of heat conduction is: As the fluid temperature increases: q=h(t w -t f ) When the fluid temperature drops q=h(t w -t f ) In the formula, tw and tf are the wall temperature and fluid temperature respectively, h is the surface heat transfer coefficient, also known as the convection heat transfer coefficient, and the unit is W / (m2.K); 6) The tunnel exit is a pressure exit, and the boundary wall is set as a convection heat exchange boundary. The surrounding rock is a fixed temperature boundary, and the thermal load and wind pressure load in the fluid are introduced. 7) Add the bulk density, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and linear expansion coefficient of surrounding rock and concrete; 8) After calculating the results, right-click Equivalent Plastic Strain in the Solution interface and select Evaluate All Results. After setting, right-click in the model interface and select Show All Bodies to view all models, view the concrete stress cloud map caused by the parameter changes after the coupling of temperature and wind speed, and judge the cracking of the lining structure.

6. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 1, characterized in that: Step S6 includes the following specific contents: 1) According to the structural characteristics, environmental complexity and project feasibility, the wind speed, temperature and stress monitoring points are arranged in the winter construction section of the tunnel. With the advancement of the construction face, the monitoring section is continuously increased. 2) Seven monitoring sections are set up in the winter construction section of the tunnel entrance, which are 10m, 15m, 20m, 25m, 30m, 35m and 40m away from the tunnel entrance respectively. The section measuring points are arranged at the arch top, arch waist, arch foot and invert arch position respectively to monitor temperature, wind speed, wind pressure, wind direction and other data; 3) Measuring points are set at the top, waist, foot and invert of the tunnel entrance lining surface to measure lining stress, wind speed and temperature. Temperature measuring holes with a depth of 1.5m are arranged at the top, waist, foot and bottom of the tunnel towards the surrounding rock for measurement and control. The distances between each temperature sensor in the temperature measuring hole and the inner surface of the lining structure are 0m, 0.3m, 0.8m and 1.5m respectively. 4) Monitor the ambient temperature of the surrounding rock, frozen soil and ground temperature. Place temperature measuring holes at 30m, 35m and 40m from the top of the tunnel to the tunnel. Since the surrounding rock thickness at the tunnel entrance is thin, diagonal drilling is selected. Earth temperature measuring points were arranged at 25m in the tunnel section with surrounding rock, 10m in the tunnel section without surrounding rock, and 25m outside the tunnel entrance. The distances between the temperature sensor in each measuring hole and the surface of the lining structure were 0m, 0.3m, 0.8m, and 1.5m, respectively. 5) By collecting data from temperature, wind speed and direction, and stress sensors, the temperature, stress, and wind speed change curves at different locations of the monitoring holes of the arch crown, arch waist, arch foot, and invert are drawn, and the temperature and stress change laws at different depths of the arch crown, arch waist, arch foot, and invert are analyzed. 6) Input the actual monitoring data into the finite element model to simulate the on-site wind field and temperature field conditions, obtain the finite element model tunnel internal temperature and lining stress data and trends, and compare them with the actual monitored tunnel internal temperature, stress data and trends to verify the model's fitting accuracy and determine whether insulation treatment is needed, thereby assisting in guiding actual construction.

7. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 1, characterized in that: Step S7 includes the following specific contents: 1) Determine whether insulation is required. If not, additional insulation facilities need to be set up. 2) Use ANSYS Fluent to simulate air source heat pump heating equipment, hot air cannons and insulation sheds. Under the condition of known outside temperature, set the initial temperature of the insulation measures, add boundary conditions and insulation material properties. 3) Re-divide the mesh according to the Fluent meshing steps and import the wall mesh divided by ANSYS ICEM into ANSYS Fluent. 4) After checking that the grid is read in correctly, set the solver parameters, open the energy equation, define the physical properties of the insulation shed materials, and set the regional conditions and boundary conditions. 5) Analysis of simulation results shows that the tunnel is qualified if it meets the concrete stress requirements of clause (5.2.3) and clause (5.2.6) and the safety factor requirements of clause (9.2.4) in the Code for Design of Highway Tunnels (JTG 3370.1-2018).

8. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 1, characterized in that: Step S8 includes the following specific contents: 1) Set construction antifreeze measures according to the simulation results in S7 and actual engineering experience; 2) Air source heat pump heating equipment, hot air guns and insulation sheds are installed at the tunnel entrance. The shotcrete construction is carried out in the insulation shed. The concrete transport truck is driven into the tunnel to ensure that the concrete construction temperature in the tunnel is above 5°C; 3) The concrete mixing station uses a heat preservation shed for heat preservation, and the heat preservation shed uses sandwich heat preservation color steel plate; 4) The concrete delivery pump is set in the greenhouse, a steam pipe is laid on one side of the concrete delivery pipe, and it is wrapped with a 5cm thick quilt for insulation; 5) Set up a high-pressure wind station near the cave entrance to shorten the length of the air duct outside the cave for easy insulation. Wrap the air duct outside the cave and about 100m into the cave with insulation materials; 6) A water storage tank is set up in the greenhouse at the cave entrance, and water is transported outside by water truck to ensure water supply for construction.

9. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 1, characterized in that: Step S10 includes the following specific contents: 1) Analyze the tunnel drilling and blasting construction methods corresponding to different geological and surrounding rock conditions and predict the key control sections of over-excavation and under-excavation. 2) Ansys / Ls-Dyna mainly includes Lagrange algorithm, Euler algorithm, ALE algorithm and fluid-solid coupling algorithm combining the first two. Lagrange method and multi-material fluid-solid coupling method are used in blasting analysis. 3) Model building ① Use the rock, joint, air, explosive and other material models in the Ansys / Ls-Dyna material library to simulate the effects of stress waves and explosive gas on rocks during blasting. ② Establish the model according to the actual project. The upper boundary of the model is to the ground surface, the lower boundary is selected as 3 to 5 times the height of the tunnel rough hole, and the left and right boundaries should be more than 3 to 5 times the distance from the wall of the adjacent tunnel rough hole to establish a two-dimensional basic model of the tunnel. ③ Establish a model coordinate system, stretch the two-dimensional tunnel model along the coordinate system, and establish a complete three-dimensional tunnel model. 4) The grid division adopts the sweeping grid division method. The grid division is dense around the blast hole, and the farther away from the blast hole, the sparser the grid division. 5) Set boundary conditions: ① The model does not consider the reflection of stress waves at the boundary, and non-reflecting boundaries are used on all sides; ② When calculating the initial self-weight stress and excavation effect, the left and right boundaries are boundaries constrained by horizontal displacement, the bottom boundary is a boundary constrained by vertical displacement, and the upper boundary is a free deformation boundary. 6) Tunnel blasting simulation ①Simulation of blasting design, only one row of holes is set around the perimeter during simulation; ② A blasting stress field is formed between the blast holes in the surrounding holes, and the model equivalent stress cloud diagram and blasting forming contour line at each time are recorded. 7) Predict the over-excavation and under-excavation values, adjust and correct the blasting design plan, ensure the minimum over-excavation and under-excavation, establish a systematic construction management system, strengthen personnel training, strictly design in accordance with specifications, ensure the accuracy of the excavation contour line, and strictly control the charge amount and drilling quality.

10. The method for continuous construction of deep and long tunnels in high-cold areas in winter according to claim 1, characterized in that: Step S11 includes the following specific contents: 1) Control section selection Analyze the tunnel drilling and blasting construction methods corresponding to different geological and surrounding rock conditions: predict the high-risk sections for construction safety, which are generally selected as V-level surrounding rock, faults and other adverse geological zones. 2) Establishment of high-risk section model ① Determine the tunnel section size based on the design data and import the tunnel section into Midas / GTS through CAD. ② Establish structural material characteristics based on actual tunnel material parameters; ③ Establish formation material characteristics based on actual geological material parameters; ④ According to the actual project, the tunnel model is established. The upper boundary of the model is to the ground surface, the lower boundary is selected as 3 to 5 times the height of the tunnel rough hole, and the left and right boundaries should be more than 3 to 5 times the distance from the wall of the adjacent tunnel rough hole. The two-dimensional model of the tunnel is established. The 3D model is established by stretching the two-dimensional model. ⑤ For the fault part, the corresponding entity is made at the corresponding position through the embedding function. The connection between the fault and the mountain is made by Boolean operation. 3) Grid division ① Grid division is performed for different structures. When grid division is performed for surrounding rock faults, small grid division is selected to make the model calculation more accurate; ② Use Boolean operations to connect different structural parts. 4) Apply load Add the self-weight load through static slope analysis - self-weight, and keep the direction consistent with when the model was first created. 5) Add constraints to the model through static slope analysis - boundary - constraint. The left and right boundaries are boundaries constrained by horizontal displacement, the bottom boundary is a boundary constrained by vertical displacement, and the upper boundary is a free deformation boundary. 6) Construction process ① The effect of the timing of the support structure construction is simulated by the load release factor (LDF). LDF = 0.0, which means that the support is provided immediately after the tunnel is excavated. ②When calculating, the load release coefficient should be determined in combination with the actual monitoring and measurement results of the tunnel engineering and previous construction experience, and it should be approximately determined as the ratio of the deformation value of the tunnel control measuring point in this excavation step to the total deformation value of the measuring point. In the absence of measured deformation data, it can be determined by the engineering analogy method using the measured results of similar tunnels. ③ By adding the construction process in the construction stage management, each stage is excavated in the order of "excavation - primary support - secondary lining". 7) After building the stratigraphic structure model, it is necessary to analyze the working conditions and create excavation working conditions by "Analysis-New". The working conditions are used to predict the surrounding rock stress and structural deformation during the construction process, and to predict whether the construction method meets the construction safety requirements. And by changing the model construction parameters: such as drilling and blasting excavation method, construction excavation footage, etc., the most unfavorable surrounding rock conditions during the construction process are estimated. 8) During the construction of high-risk sections, the model parameters are adjusted according to the results of advanced geological prediction and construction monitoring to predict the construction safety of the tunnel surrounding rock under actual construction conditions. According to the safety prediction results, the actual construction parameters such as different drilling and blasting methods, construction excavation footage, and initial support forms and support stiffness are adjusted.

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