Fine micro-grouting thaw collapse control method after MJS method and freezing method combined reinforcement

Abstract

The invention discloses a fine micro-grouting thaw collapse control method after combined reinforcement of an MJS method and a freezing method. In order to meet the requirement of strictly controlling post-construction thaw collapse of a newly-built metro station passing through an existing metro operation station, micron CT and mercury injection tests are combined, the pore volume of a soil body is calculated after normalization, and the grouting amount is accurately determined. Grouting holes are reserved in the coverage range of the freezing curtain, fine grouting is conducted on the bottom plate, the side wall and the top plate according to the unfreezing sequence, and three-dimensional digital model grouting simulation is conducted through Autodesk revit software. The fine micro-grouting thaw collapse control method after MJS method and freezing method combined reinforcement has the following advantages that a high-precision three-dimensional model is constructed to represent the microstructure of MJS soil, and therefore the grouting amount is accurately determined; the problem of thaw collapse after freezing construction of the underneath pass project is effectively controlled while normal work of the existing project is guaranteed through fine micro-grouting, and economic benefits are improved; the three-dimensional digital model can carry out technical disclosure on grouting and unfreezing synchronous collaborative construction management.

Description

Technical Field

[0001] The invention belongs to the technical field of melting-sinking grouting construction, and relates to a fine micro-grouting melting-sinking control method after combined reinforcement by an MJS method and a freezing method, and specifically to a fine melting-sinking micro-grouting method after combined reinforcement by an MJS method and a freezing method in the construction of a new subway line passing under an existing subway line. Background Art

[0002] In recent years, my country has vigorously developed the construction of underground space, and the planning of urban underground railways has also been accelerated. There are many lines in the urban underground subway line network that intersect with each other. The construction of the subway line under the subway line will affect the normal use of the existing subway line. The reinforcement methods for the soil layer of the underpass section include grouting method, horizontal freezing method, pipe shed and small pipe grouting combined reinforcement and other methods. Compared with these traditional reinforcement methods, the combined reinforcement of MJS method and freezing method has better reinforcement effect, and can better control the frost heave and thaw settlement caused by the freezing method and the groundwater seepage problems, ensuring the normal operation of the existing subway line while also better controlling the deformation of the soil layer under the subway line construction.

[0003] After the reinforcement and excavation of existing tunnels, the natural thawing method was selected to strictly control the melting settlement. However, due to the long natural thawing time, the later grouting could not be guaranteed, and the frozen soil melted and caused settlement, resulting in excessive surface settlement, which had a great impact on the existing tunnels and even brought major safety problems.

[0004] In order to solve the thawing settlement problem of the ground after the construction of the MJS method and the freezing method in the underpass project, it is necessary to study a thawing settlement grouting method that will not affect the existing subway line and can reduce the deformation of the soil layer during the construction of the underpass subway line. Therefore, fine micro-grouting can be carried out on the frozen soil after MJS reinforcement to control the thawing settlement.

[0005] BIM technology is a huge database model that covers the entire life cycle of a building, and the model contains a large amount of construction information. Using BIM technology, scientific and meticulous management can be carried out on the construction operation, renovation, demolition and other stages. In various design and construction companies, the application of BIM is becoming more and more extensive and mature. Autodesk Revit and Navisworks, as two important basic BIM software among various BIM software, will give full play to their role in promoting. At the same time, switching editing can be achieved between Revit software and Navisworks software, which increases the convenience of editing and reviewing. Summary of the invention

[0006] To overcome the deficiencies of the existing technologies, the MJS method and the freezing method are jointly used to reinforce the subway line underpass. The MJS cement soil and the freezing curtain act together to control the problems of frost heaving, thaw settlement, and groundwater seepage caused by the freezing method. Frost heaving and thaw settlement will occur during the freezing and thawing processes. To address the adverse effects caused by thaw settlement, the present invention provides a fine micro-injection thaw settlement control method after the joint reinforcement of the MJS method and the freezing method.

[0007] A fine micro-injection thaw settlement control method after the joint reinforcement of the MJS method and the freezing method. In this method, grouting holes are reserved and grouting pipes are buried within the scope covered by the freezing curtain after the soil is reinforced by the MJS method and the freezing method, and fine thaw settlement micro-injection is performed on the reinforced body based on the natural thawing sequence. The BIM technology means are used to optimize the synchronous grouting and thawing processes, realizing information-based collaborative management under the simultaneous progress of the two processes. At the same time, construction simulation is carried out with a three-dimensional model and animation to form a visual disclosure, which is more conducive to on-site construction guidance compared with the plane disclosure.

[0008] A fine micro-injection thaw settlement control method after the joint reinforcement of the MJS method and the freezing method. The specific steps of the method are as follows:

[0009] S1: For a newly built station, the diaphragm wall is first used as the retaining structure and also serves as the water-stop curtain. The MJS method is used for the construction of the reinforced body in the excavation section of the mined tunnel. Subsequently, the horizontal freezing method is used for reinforcement construction and temperature measuring holes are set. According to the horizontal freezing reinforcement temperature measuring design scheme, the positions of the temperature measuring holes and the measuring points are determined. The freezing temperature measuring holes and the thawing temperature measuring holes are "used for two purposes with one hole". The reinforced body is divided into five areas, and temperature measuring holes are set at each position far from the freezing area. Temperature measuring points are arranged at intervals of "from near to far" in each temperature measuring hole.

[0010] S2: After the frozen wall is formed and meets the design thickness requirements, the diaphragm wall is chiseled and the soil in the excavation section is excavated and constructed. After the construction is completed, natural thawing is carried out. During the natural thawing process, actual measurements are taken with an automatic electronic temperature measuring system, and the thawing sequence and thawing range are determined through numerical simulation. The upper part, both sides, and the lower part of the freezing curtain are thawed first, and the junction between the middle and the lower part of the left and right lines is thawed last; the farther away from the diaphragm wall interface, the slower the temperature rises; finally, thawing within the entire scope of the freezing curtain is achieved. At the same time, a settlement monitoring system is set up to monitor the surface settlement throughout the process. When the settlement value reaches 3 mm / day, grouting starts.

[0011] S3: During excavation, samples are taken to analyze the changes in the microscopic pore structure and deformation mechanism of MJS soil under freeze-thaw conditions. The samples are scanned by micro-CT to achieve three-dimensional visualization of the pore structure inside the specimens, and the microscopic structure of MJS soil is characterized. The mercury intrusion test is used to analyze pore parameters such as the pore size, pore volume distribution, and total porosity of pores smaller than the image resolution of the specimens. The mercury intrusion test data is mapped to the range of micro-CT scanning for normalization, converting the dimensional expression into a dimensionless expression, facilitating the comparison and weighting of different-order data obtained from the two tests, and further calculating the pore volume within the reinforcement range to accurately determine the total grouting volume.

[0012] S4: According to the shape of the reinforcement area, equidistant layout is adopted, and grouting holes are reserved during excavation. The preset grouting holes are divided into a bottom plate part, a side wall part, and a top plate part. According to the temperature field and deformation monitoring, the timing of starting grouting, continuing grouting, and stopping grouting in each area of the station is accurately determined. When the temperature monitoring shows that local thawing has occurred or the displacement has changed significantly, thaw settlement grouting construction is started, and according to the thickness of the frozen wall and the layout of the freezing pipes, grouting is carried out in groups in different areas in small amounts and multiple times to achieve fine and micro grouting in groups in different areas. The grouting volume of each hole in each area is refined according to the designed grouting volume, and the grouting pressure is adjusted according to the changes in the surface settlement and uplift rate to make the deformation tend to be stable. The multi-control indicators of grouting time (not less than 150 days), total grouting volume, and surface settlement rate (less than 0.5 mm / 15 d for two consecutive times) are used as the stop grouting standard.

[0013] S5: During thaw settlement grouting, the grouting sequence is determined as the bottom plate first, then the side wall, and finally the top plate. After the combined reinforcement of the MJS method and the freezing method, the layout density of the grouting holes is reduced to 1 / 2 - 1 / 3 of that of the conventional channel, and the density of the embedded grouting holes inside the structure is reduced to 5 m 2 ~10 m 2 per hole. The grouting holes at the top plate, bottom plate, left and right side walls are divided into three columns of grouting hole units, and each unit contains 11 grouting holes.

[0014] S6: According to the construction drawings, three-dimensional animations are used for the synchronous collaborative construction management of grouting and thawing, and technical disclosure is carried out.

[0015] Preferably, in S1, the opening position error of the temperature measurement hole ≤ 100 mm, the deviation ≤ 150 mm; the drilling depth is not less than the designed value and not more than 0.5 m of the designed value.

[0016] Preferably, in S2, the time required for the complete thawing of the naturally thawed frozen soil area is about 120 days, and the thawing range is the entire frozen curtain. Thawing starts at the top plate first, followed by the bottom plate, then the two side walls and the middle vertical wall thaw, and finally the thawing at the intersection of the middle vertical wall and the bottom plate is completed.

[0017] Preferably, in S3, a combination of micro-CT test and mercury intrusion experiment is adopted to overcome the deficiency that micro-CT cannot identify micro-pores, while nano-CT can identify micro-pores but due to the too small sampling size, the results of heterogeneous soil bodies vary greatly. The micro-CT scan uses the Nano Voxel-3502E high-resolution X-ray 3D imaging detection system. The main technical indicators of the instrument are as follows:

[0018] Preferably, in S4, the frozen soil is divided into the bottom plate part, side wall part, and top plate part. Grouting holes are reserved at the top as grouting observation holes, and grouting can be stopped until slurry overflows. Re-grouting is carried out at intervals of 8 - 24 hours, and re-grouting 2 - 3 times is sufficient to stop the filling grouting. When the ground settlement is greater than 0.5 mm / d or the cumulative ground settlement is greater than 3 mm, thaw settlement compensation grouting should be carried out; when the ground heave reaches 3 mm, grouting should be suspended. When carrying out filling grouting, the strength of the lining concrete should reach more than 60% of the design strength. A single-fluid cement slurry with a ratio of 1∶0.8 - 1 is used. Before injecting the cement slurry, clear water should be injected first to check whether the gap behind the lining between each grouting hole is unobstructed.

[0019] Preferably, in S4, the multi-control indicators of grouting time, total grouting volume, and ground surface settlement rate are used as the grouting stop standard, which can effectively control the thaw settlement displacement value and displacement rate of the ground surface, and improve the efficiency and quality of grouting construction. Grouting at the bottom and sides is carried out first. The gap between the support and the frozen soil curtain: Using the pre-buried grouting pipes, in the order from bottom to top. When continuous backflow occurs in the grouting holes of the upper layer, grouting of the lower layer can be stopped until the top plate is grouted; The gap between the support layer and the structural layer of the top plate: Grouting is carried out in the order from the middle to both ends, and the upper gap is filled with grouting using the pre-buried grouting pipes.

[0020] Preferably, in S5, the grouting holes should evenly cover the entire range of the frozen soil curtain. When constructing the temporary support, a certain number of grouting pipes are pre-buried to a depth behind the support. The specific position of each grouting hole should be arranged according to the design drawing. The grouting holes are divided into the first row of grouting hole units, the second row of grouting hole units, the third row of grouting hole units, the fourth row of grouting hole units, the fifth row of grouting hole units, the sixth row of grouting hole units, the seventh row of grouting hole units, the eighth row of grouting hole units, the ninth row of grouting hole units, the tenth row of grouting hole units, and the eleventh row of grouting hole units according to the layout position. Each row of grouting hole units contains 11 grouting holes. There are 132 grouting holes in each of the left and right line channels, with a total of 264 grouting holes.

[0021] Preferably, in S5, before grouting, all the valves of the grouting pipes to be grouted and their adjacent grouting pipes are opened. During the grouting process, when continuous slurry comes out from the adjacent hole, the valve of the adjacent hole is closed. After quantitative pressure injection, grouting of this hole can be stopped, and the valve is closed, and then grouting of the adjacent hole is carried out. When blockage occurs due to the consolidation of slurry flowing through the grouting pipe, a lengthened impact drill bit is needed to unblock the pipe.

[0022] Preferably, in S6, first, create grouting holes in Autodesk revit, set corresponding parameters, define different types of grouting holes, including parameters such as diameter, depth, and position, and use formulas and instance parameters to control the size and shape of the grouting holes, so that the single-hole grouting model can be adjusted according to different lengths at any time. Finally, automatically calculate the grouting volume of the sub-grouting holes during the grouting process through the Autodesk revit schedule, import the grouting volume of each item into the Excel table, and assist project technicians in analyzing the spatial distribution of the holes with large grouting volume losses. In addition, the Naviswork software can be used to produce construction simulation animations to optimize the construction schedule and synchronize the construction procedures during thawing grouting. Description of the Drawings

[0023] Figure 1 is the sectional view of the grouting hole layout;

[0024] Figure 2 is the position map of the measuring points of the temperature measuring holes;

[0025] Figure 3 is Figure 1 the top view of the sectional grouting holes of

[0026] Description of the reference numerals: 1 is the solidified body in area A, 2 is the solidified body in area B, 3 is the solidified body in area C, 4 is the solidified body in area D, 5 is the solidified body in area E, 6 is the T1 temperature measuring hole, 7 is the T2 temperature measuring hole, 8 is the T3 temperature measuring hole, 9 is the T4 temperature measuring hole, 10 is the T5 temperature measuring hole, 11 is the T6 temperature measuring hole, 12 is the T7 temperature measuring hole, 13 is the diaphragm wall, 14 is the T3-1 temperature measuring point, 15 is the T3-2 temperature measuring point, 16 is the T3-3 temperature measuring point, 17 is the T3-4 temperature measuring point, 18 is the bottom slab part, 19 is the side wall part, 20 is the top slab part, 21 is the first row of grouting holes, 22 is the second row of grouting holes, 23 is the third row of grouting holes, 24 is the fourth row of grouting holes, 25 is the fifth row of grouting holes, 26 is the sixth row of grouting holes, 27 is the seventh row of grouting holes, 28 is the eighth row of grouting holes, 29 is the ninth row of grouting holes, 30 is the tenth row of grouting holes, 31 is the eleventh row of grouting holes, 32 is the twelfth row of grouting holes. Detailed Embodiments

[0027] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, the modifications and substitutions made to the methods, steps, or conditions of the present invention all belong to the scope of the present invention. If not specifically specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0028] Line 7 of a certain city is arranged along the north-south direction and crosses with Line 10. At the intersection, Line 7 passes under Line 10, while the existing Line 10 is arranged in an east-west direction. The east side of the station is Shazhou East River, the southeast side is a driving school, the southwest side is a hospital, the northeast side is a high-rise office building, and the northwest side is an open space. The strata from top to bottom are: ①-1 plain fill, ②-2b silty silty clay, ②-3b silty silty clay, ②-3d silty sand mixed with silty soil, ②-4d medium-dense silty fine sand.

[0029] The project has the following difficulties:

[0030] Line 7 is located in a pressurized water-rich sand layer, and the MJS method and freezing method are used to reinforce it. The volume of the soil expands during the freezing process, and the volume decreases during the later melting process, causing the existing Line 10 above to sink. Therefore, it is necessary to strictly control the thawing settlement, and the natural thawing method and the first filling grouting and then the follow-up grouting are used to reinforce the thawing settlement soil. Control the uneven settlement of the ground.

[0031] The method comprises the following steps:

[0032] 1. The temperature measuring hole pipe is the same as the freezing pipe, with a size of Φ108×8mm and a total length of 272.5m. The temperature measuring hole opening position error is not greater than 100mm, and the deviation is not greater than 150mm; the drilling depth is not less than the design value, and not greater than the design value by 0.5m. Before drilling the temperature measuring hole, the temperature measuring hole should be piped according to the actual length, and the amount of soil and water loss during construction shall not be greater than the volume of the temperature measuring hole.

[0033] 2. The top plate begins to thaw first, followed by the bottom plate, then the vertical walls on both sides and the middle vertical wall, and finally the junction of the middle vertical wall and the bottom plate is completely thawed.

[0034] 3. Overall construction process of thaw-sinking grouting: filling grouting (3-5 days after the completion of the structure) → cutting and sealing the frozen pipes → thaw-sinking grouting (starting 7 days after the completion of the structure) → grouting in sections and groups using the preset grouting holes → until all the frozen soil melts and the ground settlement is stable.

[0035] 4. Grouting equipment: Grouting equipment uses one single-liquid pump and one double-liquid pump. The single-liquid slurry pump model is SYB50 / 45-II, and the double-liquid slurry pump model is KBY50 / 70. The grouting flow range is about 0L~70L / min, and a mixer should be equipped when injecting double-liquid slurry to mix the slurry evenly before it enters the formation.

[0036] 5. Grouting: The grouting holes should evenly cover the entire frozen soil curtain. When applying temporary support, a certain amount of Grouting pipe, the depth of the grouting pipe is behind the wooden backboard. Since the reinforcement of this project is artificially frozen on the basis of MJS, the density of grouting holes can be appropriately reduced to 1 / 2 to 1 / 3 of the conventional channel, and the density of the pre-buried grouting holes inside the structure is about 5m 2~10m 2 / piece.

[0037] 6. Filling grouting process and requirements:

[0038] (1) Grouting location: Filling grouting mainly fills the gaps between the wooden back panels and the frozen soil curtain, as well as the gaps between the support layer and the structural layer at the top of the arch.

[0039] (2) Grouting timing: Complete filling grouting 3 - 5 days after stopping freezing.

[0040] (3) Grouting pressure: Inject single - liquid cement slurry for filling. The grouting pressure is 1.5 - 2 times the hydrostatic pressure.

[0041] (4) Grouting flow rate: Control the grouting flow rate at about 15 L / min.

[0042] (5) Grouting sequence: Give priority to grouting at the bottom and sides. For the gap between the wooden back panel and the frozen soil curtain: Use the pre - embedded grouting pipes and carry out grouting in the order from bottom to top. When continuous backflow occurs from the grouting holes in the upper layer, stop grouting the lower layer until the top plate is grouted. For the gap between the support layer and the structural layer of the top plate: Grout in the order from the middle to both ends and use the pre - embedded grouting pipes to fill the upper gap.

[0043] (6) Conditions for stopping grouting: Reserve the grouting holes at the top as grouting observation holes. Stop grouting until grout overflows. Re - grout after an interval of 8 - 24 hours or more, and stop filling grouting after re - grouting 2 - 3 times.

[0044] 7. After the freezing is completed, the orifice pipes and freezing pipes on the diaphragm wall should be cut off. All freezing holes should be dried with compressed air to remove the brine inside the pipes, and then compacted and filled with mortar with a strength not less than M10 or concrete with a strength above C20. The filling length is not less than 1500 mm. Weld a 10 - mm steel plate to connect the remaining orifice pipes and freezing pipes. Symmetrically drive 2 M12 expansion bolts at the empty positions inside the holes; implant steel bars on the completed cut - and - cover working shaft structure and construct a 400 - mm - thick freezing hole plugging wall.

[0045] 8. Thaw settlement grouting process and requirements:

[0046] (1) Grouting principle and grouting time: The natural thaw settlement compensation grouting should follow the principles of small quantity, multiple points, multiple times, and uniformity to control the formation loss rate. It should also adjust the grouting volume and grouting time interval in a timely manner according to the monitoring of the structure, ground, pipelines, and the settlement of buildings and the thawing temperature field to ensure the settlement stability. The grouting scope is the entire frozen area. Grouting frequency: At least once every 3 days in the first month, at least once every 2 days in the second month, and at least once every 4 days in the third month. The actual grouting frequency and the grouting volume each time should also be determined with reference to the ground and tunnel settlement tracking monitoring. When the formation settlement is greater than 0.5 mm / d or the cumulative formation settlement is greater than 3 mm, thaw settlement compensation grouting should be carried out; when the formation heave reaches 3 mm, the grouting should be suspended.

[0047] (2) Grouting slurry: The thaw settlement compensation grouting slurry is mainly single-fluid cement slurry and supplemented by cement-sodium silicate double-fluid slurry. During the stage when the frozen wall has not melted (partially melted), cement slurry is used for grouting. After all melting, cement slurry is the main component, supplemented by double-fluid slurry. The volume ratio of cement slurry to sodium silicate solution is 1:1, in which the water-cement ratio of the cement slurry is 1:1, and the sodium silicate solution uses B35 - B40 sodium silicate and is diluted with 1 - 2 times the volume of water.

[0048] (3) Conditions for stopping grouting: When the frozen wall has completely melted, and the measured relative settlement of the formation compared with the non-frozen area around it is not greater than 0.5 mm every half month for one month, and it is judged that the formation is stable according to the settlement deformation of the stations on Line 10 during operation, and the total grouting volume reaches the designed grouting volume, the thaw settlement compensation grouting can be stopped.

[0049] 9. Import the structural model that needs to be grouted in Autodesk Revit, and select to define and label the grouting treatment area. Add the grouting material properties that affect the simulation and analysis of the grouting process, including the composition, proportion, and performance parameters of the grout. Then create a grouting hole family in Autodesk Revit, define different types of grouting holes, including parameters such as diameter, depth, and position, and use formulas and instance parameters to control the size and shape of the grouting holes. Draw the position and shape of the grouting holes, determine the grouting hole type, quickly create the grouting holes, and import them into the structural model. Edit the properties such as the material, mark, and color of the grouting holes through the property panel. In the 3D view, select the cutting plane and determine the cutting range to deduct the space occupied by the grouting holes in the model to form a real hole effect. Automatically calculate the grouting consumption of the sub-grouting holes during the grouting process through the Autodesk Revit schedule, import the grouting consumption of each item into the Excel table to assist project technicians in analyzing the spatial distribution of the holes with large grouting volume losses. Use the Animator module in Navisworks software to create a construction simulation progress diagram. Select the animation corresponding to the task name through "Animation" under the Timeliner extended list, associate the calculation model with the construction sequence and progress plan, and make the construction content accurate to each grouting hole per day to achieve the informatization management of the daily construction content and construction area.

Claims

1. A fine micro-grouting settlement control method after combined reinforcement by MJS method and freezing method, characterized in that, in the method, grouting holes are reserved and grouting pipes are buried within the scope covered by the freezing curtain after the soil is reinforced by the MJS method and the freezing method, and the grouting process is highly combined with the melting law of frozen soil to carry out fine settlement micro-grouting on the reinforced body. The specific steps of the method are as follows: S1: For a newly built station, the diaphragm wall is first used as the retaining structure and also serves as the water-stop curtain. The MJS method is used for the construction of the reinforced body in the excavation section of the mined tunnel. Subsequently, the horizontal freezing method is used for reinforcement construction and temperature measurement holes are set. According to the horizontal freezing reinforcement temperature measurement design scheme, the positions of the temperature measurement holes and measurement points are determined, and the freezing temperature measurement holes and thawing temperature measurement holes are "used for two purposes". The reinforced body is divided into five regions, and temperature measurement holes are set at each position far from the freezing zone. Each temperature measurement hole is arranged with temperature measurement points at intervals of "from near to far". S2: After the frozen wall is formed and reaches the design thickness requirement, the diaphragm wall is chiseled and the soil in the excavation section is excavated and constructed. After the construction is completed, natural thawing is carried out. During the natural thawing process, it is measured by an automatic electronic temperature measurement system, and the thawing sequence and thawing range are determined through numerical simulation. The upper part, both sides and the lower part of the freezing curtain are thawed first, and the junction between the middle and the lower part of the left and right lines is thawed last; the farther away from the interface of the diaphragm wall, the slower the temperature rises; finally, the thawing within the entire freezing curtain range is realized. At the same time, a settlement monitoring system is set to monitor the surface settlement throughout the process. When the settlement value reaches 3 mm / day, grouting starts. S3: Samples are taken during excavation to analyze the change of the microscopic pore structure and deformation mechanism of MJS soil under freeze-thaw conditions. The samples are scanned by micron CT to realize the three-dimensional visualization of the pore structure inside the specimens and characterize the microscopic structure of MJS soil. The mercury intrusion test is used to analyze the pore size, pore volume distribution, total porosity and other pore parameters of the pores smaller than the image resolution of the samples. The mercury intrusion test data is mapped to the range of micron CT scanning for normalization processing to make the dimensional expression become dimensionless, so that the data of different orders of magnitude obtained from the two tests can be compared and weighted, and further calculate the pore volume within the reinforcement range, so as to accurately determine the total grouting volume. S4: According to the shape of the reinforcement area, the grouting holes are arranged at equal distances. The grouting holes are reserved while excavating. The preset grouting holes are divided into the bottom plate part, the side wall part and the top plate part. According to the temperature field and deformation monitoring, the timing of starting grouting, continuing grouting and stopping grouting in each area of the station is accurately determined. When the temperature monitoring shows that local thawing has occurred or the displacement has changed significantly, the settlement grouting construction starts, and according to the thickness of the frozen wall and the arrangement of the freezing pipes, grouting is carried out in groups in small amounts and multiple times in different areas to achieve fine micro-grouting in groups in different areas. The grouting volume of each hole in each area is refined according to the designed grouting volume, and the grouting pressure is adjusted according to the change of the surface settlement and uplift rate to make the deformation tend to be stable. The multi-control indexes of grouting time (not less than 150 d), total grouting volume and surface settlement rate (less than 0.5 mm / 15 d for two consecutive times) are used as the stopping grouting standard. S5: During thaw settlement grouting, determine the grouting sequence as the floor first, then the side walls, and finally the roof. After the combined reinforcement of the MJS method and the freezing method, the layout density of grouting holes is reduced to 1 / 2 to 1 / 3 of that in the conventional passage, and the density of pre-embedded grouting holes inside the structure is reduced to 5m 2 ~10m 2 apart. Divide the grouting holes in the roof, floor, and left and right side walls into three columns of grouting hole units, and each unit contains 11 grouting holes. S6: According to the construction drawings, use 3D animation to conduct technical disclosure on the synchronous collaborative construction management of grouting and thawing.

2. A fine micro grouting settlement control method after combined reinforcement by MJS method and freezing method according to claim 1, characterized in that, In S1, the solidified body between the existing station floor slab and the new station roof slab is divided into area A (1), the solidified body on the left side of the left line is divided into area B (2), the solidified body between the left and right lines is divided into area C (3), the solidified body on the right side of the right line is divided into area D (4), and the lower part of the new station floor slab is divided into area E (5). Temperature measuring holes are set in each solidified body area. The T1 temperature measuring hole (6) is set in area B, the T2 temperature measuring hole (7) is set in area D, the T3 temperature measuring hole (8) is set in area C, the T4 temperature measuring hole (9) and the T5 temperature measuring hole (10) are set in area A, and the T6 temperature measuring hole (11) and the T7 temperature measuring hole (12) are set in area E. Taking the T3 temperature measuring hole as an example, four temperature measuring points are set in each temperature measuring hole, and the temperature measuring points are arranged at intervals from the diaphragm wall (13): the T3-1 temperature measuring point (14), the T3-2 temperature measuring point (15), the T3-3 temperature measuring point (16), and the T3-4 temperature measuring point (17).

3. A fine micro grouting settlement control method after combined reinforcement by MJS method and freezing method according to claim 1, characterized in that, In S2, the thawing sequence is that the freezing curtain in area A melts first, followed by the freezing curtains in areas B, the upper part of area C, area D, and area E, and finally the freezing curtain in the lower part of area C melts. The thawing range is the entire freezing curtain. The temperature of the T3-1 temperature measuring point near the diaphragm wall interface rises the fastest; the farther the T3-2 temperature measuring point, the T3-3 temperature measuring point, and the T3-4 temperature measuring point are from the diaphragm wall interface, the slower the temperature rises.

4. A fine micro grouting settlement control method after combined reinforcement by MJS method and freezing method according to claim 1, characterized in that, In S3, use an X-ray beam to scan a certain thickness layer of an object. After processing the micron CT scan image with Image-Pro Plus software, conduct three-dimensional reconstruction and visualization processing on the binary image of the soil micron CT to establish a clear and intuitive three-dimensional pore map of the internal pore structure morphology. Use mercury intrusion experiments for combined analysis. By applying a certain pressure, fill the mercury liquid into the pores of the sample, take the mercury intrusion volume as a function of the external pressure, and obtain the pore volume in the evacuated sample under the action of the external pressure. Subsequently, establish a scale-normalized volume pore model. Crop some micron CT images with a fixed volume pore size (V). After segmentation, the scale of the target pore volume in the image remains unchanged. For smaller mercury intrusion pore volumes (V1 < V), use bilinear interpolation amplification to make their sizes larger. For larger micron CT pore volumes (V2 > V), use equidistant sampling to reduce them, and the pore volumes with equal scales (V3 = V) remain unchanged. After scaling, the pore volumes of the same size are relatively consistent. Before processing, the pore scale distribution shows bipolar aggregation. After scale normalization, the target scale pore volume is more concentrated, and the pore volume can be superimposed and calculated at one scale to determine the size of the grouting volume.

5. A fine micro-grouting thaw settlement control method after combined reinforcement by the MJS method and the freezing method according to claim 1, characterized in that, in S4, the frozen soil is divided into regions according to the location: the bottom plate part (18), corresponding to each hole of the bottom plate of the grouting hole; the side wall part (19), corresponding to the left (right) side wall holes of the grouting hole; the top plate part (20), corresponding to each hole of the top plate of the grouting hole.

6. A fine micro-grouting thaw settlement control method after combined reinforcement by the MJS method and the freezing method according to claim 1, characterized in that, in S5, the grouting sequence is first the bottom plate, then the side wall, and then the top plate; when grouting the bottom plate, according to the principle of spreading from the middle to both sides, grouting is carried out from the middle of the freezing curtain to both sides, and the grouting range is the entire freezing curtain, which is carried out in 3 to 4 times according to the thawing situation.

7. A fine micro-grouting thaw settlement control method after combined reinforcement by the MJS method and the freezing method according to claim 1, characterized in that, In S5, after artificial freezing is carried out on the basis that the solidifying agent is MJS, the arrangement density of grouting holes is 1 / 2 to 1 / 3 of that of the conventional channel, and the density of the embedded grouting holes inside the structure is 5m 2 ~10m 2 each. The grouting holes are arranged on the top plate, bottom plate, left wall and right wall at intervals of 2.0m to 2.5m. Each side is divided into 3 columns of grouting hole units, namely the first column of grouting hole unit (21), the second column of grouting hole unit (22), the third column of grouting hole unit (23), the fourth column of grouting hole unit (24), the fifth column of grouting hole unit (25), the sixth column of grouting hole unit (26), the seventh column of grouting hole unit (27), the eighth column of grouting hole unit (28), the ninth column of grouting hole unit (29), the tenth column of grouting hole unit (30), the eleventh column of grouting hole unit (31), and the twelfth column of grouting hole unit (32). Each column of grouting hole unit contains 11 grouting holes.

8. A fine micro-grouting thaw settlement control method after combined reinforcement by the MJS method and the freezing method according to claim 1, characterized in that, in S6, BIM technology is used for the collaborative construction management of calculating the grouting volume of the sub-grouting holes in the three-dimensional digital model and synchronizing grouting and thawing: the calculation model uses Autodesk revit software, different types of grouting holes are drawn in the three-dimensional digital model, and divided into n regions, and the region matrix is expressed as: A n = [A 1 A 2 … A n-1 A n ​ There are m columns of grouting holes in each region, and there are k sub-grouting holes corresponding to each column of grouting holes. The number of grouting holes in each region is the same, and the number of sub-grouting holes is also the same. The grouting hole matrix is expressed as: A three-dimensional grouting model with automatic deduction of the overlapping part is formed, and through parameter setting (Q = V three-dimensional model volume × η × β, where η is the formation porosity and β is the slurry loss coefficient). Using Navisworks software, the three-dimensional model exported from Autodesk revit software is reviewed, and a three-dimensional construction animation is made, including view point animation, script animation and advanced animation, for visual disclosure of the construction sequence of grouting and thawing on each partition. Then, using the Animator module in Navisworks software to make a construction simulation process diagram, select the animation corresponding to the task name through "Animation" in the Timeliner extended list, associate the calculation model with the construction sequence and progress plan, and the construction content is accurate to each grouting hole every day, realizing the informatization management of the construction content and construction area on the same day.

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