Large-scale underground shield docking model test platform and test method

Abstract

The present invention relates to the technical field of shield tunnel engineering. Provided are a large-scale underground shield docking model test platform and a test method therefor. The large-scale underground shield docking model test platform comprises a test soil trough, a partition wall, a shield docking model and a freezing system, wherein the test soil trough is of an underground foundation pit structure, and the partition wall is provided in the test soil trough; the partition wall divides the test soil trough into a soil-filling area and a non-soil-filling area, and the partition wall is configured to prevent soil and water in the soil-filling area from entering the non-soil-filling area; the shield docking model is arranged in the soil-filling area, and the shield docking model is a reduced-scale test model; the freezing system is arranged on the shield docking model, and the freezing system comprises a refrigeration system, a cold liquid circulation system and a freezing pipe; and the freezing pipe is arranged on the shield docking model, and is connected to the refrigeration system by means of the cold liquid circulation system, and the refrigeration system is arranged on a laminated plate in the non-soil-filling area of the test soil trough. In the test platform designed in the present invention, underground shield docking grouting and freezing reinforcement tests can be performed, thereby providing a new and reliable solution for research into shield docking construction technology.

Description

A large-scale shield underground docking model test platform and test method Technical Field

[0001] The invention relates to the technical field of shield tunnel engineering, in particular to a large-scale shield underground docking model test platform and a test method. Background Art

[0002] With socioeconomic development, the length of shield tunnels constructed in my country is also increasing. However, long-distance shield tunneling can present numerous problems, such as cutterhead wear, shield tail seal failure, main bearing seal failure, and wear and tear of slurry pipelines, which can seriously impact the construction progress and safety of shield tunnels. The use of shield underground docking technology can effectively reduce the length of a single shield tunneling run, improve the safety of shield projects, and significantly shorten the construction period. This technology is particularly suitable for shield tunneling projects crossing rivers, lakes, and seas, where vertical shaft excavation is difficult.

[0003] Shield tunneling in-ground jointing construction requires sufficient reinforcement of the soil at the jointing section to maintain the stability of the surrounding strata. Freezing is often used as the primary reinforcement method in water-rich, weak strata. Currently, there are few examples of shield tunneling in-ground jointing in China and abroad, and the construction technology is immature. Systematic and in-depth research is needed on shield tunneling in-ground jointing. In particular, the impact of frost heave loads on the stability of the shield structure during freeze reinforcement, the effect of frost heave and thaw settlement on the longitudinal deformation of the shield and segment lining along the tunnel, and the opening and misalignment of segment joints remain unexplored. Compared to theoretical research and numerical simulations, research results obtained through physical model testing are more realistic and reliable, especially those from prototype or large-scale tests, which offer greater guidance.

[0004] Currently, few model tests have been conducted on shield tunneling in-ground. Shi Rongjian et al. (2016) conducted a model test on shield tunneling in-ground frozen reinforcement in soft soil, using a shield tunneling frozen reinforcement project in Shanghai as a prototype. They investigated the distribution characteristics of the ground freezing temperature field and the frost heave effect of the strata. However, the boundary conditions in this model test differed significantly from those in actual projects, making the development of the frozen wall difficult to simulate actual working conditions. Furthermore, this test made it difficult to study the deformation of the cross and longitudinal sections of the shield tunnel under the effects of frost heave and thaw settlement. Patent number CN103235110A discloses a freezing reinforcement simulation test method suitable for shield tunneling in the ground, but this scheme still has the following shortcomings: (1) In this scheme, the model tunnel needs to be buried in the test box, and the freezing system needs to be pre-installed before the tunnel is buried in the soil. After the tunnel is buried in the soil, personnel can no longer enter the tunnel, so it is impossible to debug and operate the freezing system, and it is impossible to carry out pre-grouting reinforcement before freezing. It is impossible to study the coupling effect of grouting and freezing reinforcement, and therefore it is impossible to make reliable suggestions for the optimization and selection of the ground layer reinforcement scheme in the shield tunneling. (2) In this scheme, the horizontal and vertical boundary conditions of the model tunnel are quite different from the actual situation, making it difficult to effectively simulate the stress and deformation of the cross section of the model tunnel caused by frost heave and thaw settlement, and thus it is difficult to accurately judge whether the stress safety and deformation of the shield structure exceed the limit during the docking construction; (3) In this scheme, the segment lining behind the shield tail is not considered, and it is impossible to explore the relative displacement between the shield body and the segment lining caused by the frost heave and thaw settlement process, and it is impossible to explore the deformation of the segment lining along the longitudinal direction and the opening and misalignment of the segment joints. Therefore, it is impossible to accurately judge the waterproof safety of the segment lining joints of the shield tunnel during the docking construction.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to address the above-mentioned problems existing in the prior art, overcome the shortcomings of the prior art, and design a large-scale shield underground docking model test platform. The test platform can meet the needs of test personnel to enter the shield docking model to debug and operate various test systems, and can effectively simulate the shield underground docking grouting reinforcement, freezing reinforcement, frozen body melting and other processes. Through the test platform and test method, shield underground docking grouting and freezing reinforcement tests can be carried out, and the deformation characteristics of the shield body and segment lining tunnel cross section, longitudinal deformation characteristics, segment joint opening and misalignment, shield body stress and stability characteristics, grouting and freezing coupling reinforcement effect, grouting diffusion and other problems can be accurately explored. It provides a reliable solution for the research of shield docking construction technology and can provide reliable suggestions for the optimization and selection of stratum reinforcement schemes.

[0007] A large shield underground docking model test platform, including a test soil trough, a partition wall, a shield docking model and a freezing system.

[0008] The test soil trough is an underground foundation pit structure. A partition wall is provided in the test soil trough. The partition wall separates the test soil trough into a fill area and a non-fill area. The partition wall is used to prevent soil and water in the fill area from entering the non-fill area. A shield docking model is provided in the fill area. The shield docking model is a scaled test model.

[0009] The shield docking model is provided with a freezing system, which includes a refrigeration system, a cold liquid circulation system and a freezing pipe. The freezing pipe is arranged on the shield docking model, and the freezing pipe is connected to the refrigeration system through the cold liquid circulation system. The refrigeration system is placed on the non-fill area layer plate of the test soil trough.

[0010] The internal length L of the test soil trough satisfies: L=L1+t w +L2

[0011] Where L1 is the inner length of the fill area, t w is the thickness of the partition wall, L2 is the internal length of the non-fill area of ​​the test soil trench;

[0012] The internal width W and depth H of the test soil trough are the same, satisfying the following formula: W = H = D m +2l′ fmax +2B

[0013] Among them, D m is the outer diameter of the shield of the shield docking model, l′ fmax is the longest projected length of the freezing pipe in the radial direction of the shield, and B is the distance from the outermost end of the freezing pipe to the inside of the test soil trough.

[0014] Furthermore, the shield docking model is composed of a model tunnel 1 and a model tunnel 2 arranged longitudinally. The interiors of the model tunnel 1 and the model tunnel 2 are kept connected to facilitate personnel to enter the interior of the shield docking model from the non-fill area. The model tunnel 1 is composed of a first model shield body and a first model segment lining. The model tunnel 2 is composed of a second model shield body and a second model segment lining. The model tunnel 1 is perpendicular to the side wall of the soil trough, and the model tunnel 2 is perpendicular to the partition wall. The outer diameters of the first model shield body and the second model shield body are the same, and the outer diameters and inner diameters of the first model segment lining and the second model segment lining are the same.

[0015] A circular portal is reserved on the partition wall as a passage for personnel to enter the shield docking model from the non-fill area. The inner size of the circular portal is the same as the inner size of the second model shield body. Part of the second model segment lining is placed inside the circular portal on the partition wall. A second sealing brush and a sealing rubber plate are arranged between the circular portal and the second model segment lining to prevent soil and water in the fill area from entering the shield docking model or the non-fill area.

[0016] Furthermore, a first oil cylinder group is provided on the side wall of the soil trough perpendicular to the first model segment lining, which is telescopic along the axis of the first model segment lining. The first oil cylinder group is arranged in a circular direction, with one end fixed to the side wall of the soil trough and the other end acting on the end face of the first model segment lining to provide annular pre-tightening force for the first model segment lining.

[0017] A second cylinder group is arranged in the circular hole in the partition wall, which is telescopic along the axis of the second model segment lining. The second cylinder group is arranged in a circular direction, with one end fixed in the partition wall and the other end acting on the end face of the second model segment lining to provide annular pre-tightening force for the second model segment lining. The second cylinder group is sufficient to provide annular joint pre-tightening force for the second model segment lining.

[0018] Furthermore, the inner length L of the test soil trough satisfies: L = L s1 +L t1 -L′ t1 +L c1 +L s2 +L t2 -L′ t2 -L″ t2 +Δ+t w +L2

[0019] Where, L s1 is the length of the shield of the first model; L t1 is the length of the first model segment lining, L′ t1 is the length of the first model segment lining contained in the first model shield, L c1 is the length of the first cylinder group; L s2 is the length of the second model shield, L t2 is the length of the second model segment lining, L′ t2 is the length of the second model segment lining contained in the second model shield, L″ t2 is the length of the second model segment lining inside the partition wall, and Δ is the butt joint gap between the two model tunnels.

[0020] Furthermore, a half sleeve is preset on the side wall of the soil trough. The half sleeve is cylindrical and one end is fixed to the side wall of the soil trough. The inner dimension of the half sleeve is the same as the inner dimension of the first model shield body. A first sealing brush and a sealing rubber plate are arranged between the half sleeve and the first model segment lining to prevent soil and water in the fill area from entering the interior of the shield docking model.

[0021] Furthermore, model tunnel 1 and model tunnel 2 are provided with ring beams at the butt ends to simulate the front shield part of the actual shield body. The inner contour dimensions of the ring beam are the same as the inner dimensions of the lining of the first model segment, and the inner contour dimensions of the ring beam are the same as the inner dimensions of the lining of the second model segment. A temporary support structure is installed between the butt end ring beam of the first model shield body and the butt section ring beam of the second model shield body to ensure that soil and water in the fill area are prevented from entering the interior of model tunnel 1 or model tunnel 2, and without increasing the connection stiffness of the butt section between the first model shield body and the second model shield body.

[0022] Preferably, the device further comprises a sensor, wherein the sensor comprises a surface strain gauge, a thermometer, an embedded strain gauge, an earth pressure gauge, an array displacement gauge and a crack gauge.

[0023] The surface strain gauges are arranged on the inner and outer surfaces of the first and second model shields, and are arranged circumferentially and longitudinally to monitor the stress of the shields; the thermometers are arranged in the stratum to monitor the development of the frozen body; the embedded strain gauges are buried inside the first and second model segment linings, and are arranged circumferentially and longitudinally; the earth pressure gauges arranged on the outer surfaces of the first and second model shields are used to monitor the frost heave loads during the freezing process, and the earth pressure gauges arranged on the side walls of the soil trench are used to monitor the impact of the frost heave loads on the test boundaries; array displacement gauges are arranged on the inner surfaces of the first and second model shields, the first and second model segment linings, the circumferentially arranged array displacement gauges measure the cross-sectional deformation of the shield joint model, and the longitudinally arranged array displacement gauges measure the longitudinal deformation of the shield joint model; the joint gauges are arranged in the annular joints between the first and second model segment linings to monitor changes in the opening amount of the annular joints between the first and second model segment linings.

[0024] Furthermore, the length of the half sleeve is sufficient to cover the first cylinder group and the half-width model segment lining, and meet the requirements of waterproof sealing measures, specifically satisfying the following formula:

[0025] Length of half sleeve l hs Satisfy: l hs ≥l c1 +0.5w s +Δl ws

[0026] Where, l c1 is the maximum length of the first cylinder group, w s is the width of the lining ring of the single-ring model, Δl ws The length for setting waterproof sealing measures.

[0027] Furthermore, the preload force of the inter-ring joint of the first model segment lining provided by the first cylinder group satisfies the following formula:

[0028] Where p is the preload stress of the inter-ring joint of the first model segment lining, F is the resultant force of water and soil pressure in front of the prototype shield cutterhead, S is the contact area of ​​the prototype lining ring joint, c σ is the stress similarity ratio of the model test.

[0029] The inter-ring preload force provided by the second cylinder group is the same as that of the first cylinder group.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The purpose of the present invention is to address the above-mentioned problems existing in the prior art, overcome the shortcomings of the prior art, and design a large-scale shield underground docking model test platform. The test platform can meet the needs of test personnel to enter the shield docking model to debug and operate various test systems, and can effectively simulate the shield underground docking grouting reinforcement, freezing reinforcement, frozen body melting and other processes. Through the test platform and test method, shield underground docking grouting and freezing reinforcement tests can be carried out, and the deformation characteristics of the shield body and segment lining tunnel cross section, longitudinal deformation characteristics, segment joint opening and misalignment, shield body stress and stability characteristics, grouting and freezing coupling reinforcement effect, grouting diffusion and other problems can be accurately explored. It provides a reliable solution for the research of shield docking construction technology and can provide reliable suggestions for the optimization and selection of stratum reinforcement schemes.

[0032] 1. During the test process, the present invention allows personnel to enter the shield docking model to carry out debugging of the freezing system, grouting or installation of freezing system pipelines, and parameter adjustment during the test, thereby enabling testing of more working conditions. The test soil trough is divided into a fill area and a non-fill area by a partition wall. The shield docking model is buried in the fill area. One end of the shield docking model passes through a hole reserved on the partition wall, so that the internal space of the shield docking model is connected to the non-fill area. Then, test personnel can enter the interior of the shield docking model from the non-fill area through the hole reserved on the partition wall. In addition, waterproof components such as sealing brushes and sealing rubber plates are set at the connection between the shield docking model and the hole door, which is ingenious and practical.

[0033] 2. The present invention is designed with respect to the width and depth of the test soil trench, which can meet the requirements of the cross-sectional boundary conditions of the shield docking model test, thereby being able to more accurately study the stress and deformation characteristics of the shield cross-section, and thus accurately evaluate the safety and deformation limit of the shield structure during the shield docking process.

[0034] 3. The present invention takes into account the arrangement of at least 7 rings of model lining behind the shield tail in the shield docking model, and simulates the longitudinal preload of the model segment lining ring. This can more accurately judge the longitudinal deformation characteristics of the model tunnel and the opening and staggering characteristics of the joints during the shield docking process, and then judge the waterproof safety of the joints, thereby providing a reference for the design of the segment lining structure reinforcement plan.

[0035] 4. The present invention can effectively study the diffusion mechanism of grouting reinforcement, the effect of grouting reinforcement, and the coupling effect of grouting and freezing reinforcement, and provide a reference basis for the design of similar engineering reinforcement schemes. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a front view of the test platform;

[0037] Figure 2 is a cross-sectional side view of the test platform;

[0038] Figure 3 is a top view of the test platform;

[0039] FIG4 is a schematic diagram of the structure of the connection between the first model segment lining and the side wall of the test soil trench;

[0040] Figure 5 is a schematic diagram of the structure of the connection between the segment lining and the partition wall of the second model.

[0041] In the figure: 1-test soil trough, 2-partition wall, 3-shield docking model, 4-freezing system, 5-sensor, 6-data acquisition system, 11-soil trough side wall, 12-soil trough bottom plate, 13-fill area, 14-non-fill area, 15-layer plate, 16-staircase, 31-first model shield, 32-first model segment lining, 33-second model shield, 34-second model segment lining, 35-first cylinder group, 36-half sleeve, 37-first sealing brush, 38-second cylinder group, 39-second sealing brush, 41-refrigeration system, 42-cold liquid circulation system, 43-freezing pipe. DETAILED DESCRIPTION

[0042] The following is a further detailed description of a large-scale shield underground docking model test platform of the present invention in conjunction with the accompanying drawings and specific implementation methods.

[0043] The present invention designs a large-scale shield underground docking model test platform, as shown in Figures 1 to 5, a large-scale shield underground docking model test platform, including a test soil trough 1, a partition wall 2, a shield docking model 3, a freezing system 4, a sensor 5 and a data acquisition system 6.

[0044] The test soil trough 1 is an underground foundation pit structure with the top flush with the ground surface. The soil trough sidewalls 11 and the soil trough bottom plate 12 of the test soil trough 1 are both reinforced concrete structures. In this example, the soil trough sidewalls 11 are 1200 mm thick and the soil trough bottom plate 12 is 1500 mm thick.

[0045] A partition wall 2 is provided in the test soil trough 1. The partition wall 2 is a reinforced concrete structure, which divides the test soil trough 1 into a fill area 13 and a non-fill area 14. The partition wall 2 is rigidly connected to the soil trough side wall 11 and the soil trough bottom plate 12. The partition wall 2 can prevent soil and water in the fill area 13 from entering the non-fill area 14.

[0046] The shield joint model 3 is a scaled test model consisting of a longitudinally arranged model tunnel 1 and a model tunnel 2, located within the fill area 13 of the test soil trench 1. Model tunnel 1 consists of a first model shield 31 and a first model segment lining 32, while model tunnel 2 consists of a second model shield 33 and a second model segment lining 34. Model tunnel 1 is perpendicular to the soil trench sidewall 11, while model tunnel 2 is perpendicular to the partition wall 2. The scale ratio of this test is 1:7, meaning that the model shield outer diameter, model shield inner diameter, model shield length, gap between the two model shields, model segment lining outer diameter, and model segment lining ring width all have a similarity ratio of 1:7 to the prototype. In this example, the outer diameter of the prototype shield is 15.97m, and the outer diameters of the first model shield 31 and the second model shield 33 are the same, which is 2.28m; the outer diameter of the prototype segment lining is 15.5m, and the outer and inner diameters of the first model segment lining 32 and the second model segment lining 34 are the same, which is 2.21m and 2.02m respectively. This test platform allows personnel to stand in the model tunnel to perform test operations.

[0047] A first oil cylinder group 35 is provided on the side wall 11 of the test soil trough perpendicular to the first model segment lining 32, which can be extended and retracted along the axis of the first model segment lining 32. The first oil cylinder group 35 is arranged in a circular direction, with one end fixed to the side wall 11 of the soil trough and the other end acting on the end face of the first model segment lining 32 to provide annular preload for the first model segment lining 32. The first oil cylinder group 35 should be able to provide annular joint preload for the first model segment lining 32, and the preload p satisfies the following formula:

[0048] Where p is the preload stress between the model segment lining rings, F is the resultant water and soil pressure in front of the prototype shield cutterhead, S is the contact area of ​​the prototype lining ring joint, and c is the contact area of ​​the prototype lining ring joint. σ is the stress similarity ratio of the model test. In this example, the preload force of the annular joint of the first model segment lining is not less than 3MPa.

[0049] A half sleeve 36 is preset on the soil trough side wall 11 perpendicular to the first model segment lining 32. The half sleeve 36 is cylindrical, and one end is fixed to the soil trough side wall 11. The inner size of the half sleeve 36 is the same as the inner size of the first model shield body 31. A first sealing brush 37 and a sealing rubber plate are set between the half sleeve 36 and the first model segment lining 32 to prevent the soil and water in the fill area 13 from entering the interior of the shield docking model 3. The length of the half sleeve 36 must meet the requirements of covering the first cylinder group 35 and the half-ring width model segment lining, and waterproof sealing measures can be set. The length of the half sleeve is l hs Satisfy the formula: l hs ≥l c1 +0.5w s +Δl ws

[0050] Where, l c1 is the maximum length of the first cylinder group 35, w s is the width of the lining ring of the single-ring model, Δl ws The length for setting waterproof sealing measures.

[0051] In this example, the extended length of the first cylinder group 35 is 300 mm, the width of one ring of the first model segment lining 32 is 286 mm, the length of the half sleeve 36 is 586 mm, and the inner diameter of the half sleeve 36 is 2.24 m.

[0052] A circular portal is reserved in the partition wall 2 as a passage for personnel to enter the interior of the shield docking model 3 from the non-fill area 14. The inner dimensions of the circular portal are the same as those of the second model shield body 33. A portion of the second model segment lining 34 is placed inside the circular portal on the partition wall 2. A second sealing brush 39 and a sealing rubber sheet are installed between the circular portal and the second model segment lining 34 to prevent soil and water in the fill area 13 from entering the interior of the shield docking model 3 or the non-fill area 14.

[0053] A second cylinder group 38 that extends and contracts along the axis of the second model segment lining 34 is set in the circular hole in the partition wall 2. The second cylinder group 38 is arranged in a ring direction, one end is fixed in the partition wall 2, and the other end acts on the end face of the second model segment lining 34 to provide annular pre-tightening force for the second model segment lining 34. The second cylinder group 38 should be able to provide annular joint pre-tightening force for the second model segment lining 34. The pre-tightening force calculation formula is the same as that of the first model segment lining 32.

[0054] The interiors of model tunnel 1 and model tunnel 2 are kept connected, which facilitates personnel to enter the shield docking model 3 from the non-fill area 14 to carry out equipment installation, data collection, freezing control and other operations.

[0055] Model tunnels 1 and 2 are equipped with ring beams at their butt joints, simulating the front shield portion of an actual shield. This portion has higher rigidity, and the inner dimensions of the ring beam are identical to those of the model segment lining. A temporary support structure is installed between the butt joint ring beam of the first model shield 31 and the butt joint ring beam of the second model shield 33. This temporary support structure is designed to prevent soil from the fill area 13 from entering the interior of model tunnel 1 or model tunnel 2, while also ensuring that the rigidity of the butt joint between the first and second model shields 31 and 33 is not increased.

[0056] Six temporary support structures are set up inside the model tunnel 1 and the model tunnel 2, which mainly serve as safety reserves. During the test phase, the temporary support structures do not provide support force and do not affect the rigidity of the model tunnel. They mainly provide support when the model tunnel becomes unstable and damaged, so as to avoid excessive deformation of the tunnel that threatens the safety of test personnel and equipment.

[0057] One of the core functions of this test is the freezing test. The core system of the freezing test is the freezing system 4, which includes a refrigeration system 41, a cold liquid circulation system 42 and a freezing pipe 43. The freezing system 4 can realize freezing of different rows of the freezing pipes 43 at different temperatures and different times. The freezing pipes 43 arranged on the first model shield body 31 and the second model shield body 33 are connected to the refrigeration system 41 through the cold liquid circulation system 42. The refrigeration system 41 is placed on the layer 15 of the non-fill area 14.

[0058] The steel shells of the first and second shield models 31, 33 contain holes for the freezing pipes 43 to pass through. The number, location, and angle of these holes should be tailored to the project's specific needs. After the shield docking model 3 is buried in the soil, all freezing pipes 43 are inserted into the soil through the holes in the first and second shield models 31, 33. The gaps between the freezing pipes 43 and the holes in the first and second shield models 31, 33 are sealed by welding.

[0059] The test platform includes the function of grouting test. The grouting test can use the freezing pipe 43. The pipeline is replaced according to the test progress. The grouting method can be sleeve valve pipe grouting, drill rod retreat grouting or hole grouting.

[0060] The sensors 5 include surface strain gauges, which are arranged on the inner and outer surfaces of the first model shield 31 and the second model shield 33, and are arranged in the circumferential and longitudinal directions to monitor the stress of the shield; thermometers, which are arranged in the stratum to monitor the development of the frozen body; embedded strain gauges, which are buried in the first model segment lining 32 and the second model segment lining 34, and are arranged in the circumferential and longitudinal directions; soil pressure gauges, some of which are fixed on the outer surfaces of the first model shield 31 and the second model shield 33 to monitor the frost heave load during the freezing process, and some of which are fixed on the soil On the side wall 11 of the trough, the influence of the frost heave load on the test boundary is monitored; array displacement meters are set on the inner surfaces of the first model shield 31, the second model shield 33, the first model segment lining 32 and the second model segment lining 34. The circumferentially arranged array displacement meters measure the cross-sectional deformation of the shield docking model 3, and the longitudinally arranged array displacement meters measure the longitudinal deformation of the shield docking model 3; joint meters are set at the annular joints between the first model segment lining 32 and the second model segment lining to monitor the changes in the joint opening amount between the first model segment lining 32 and the second model segment lining 34.

[0061] The data acquisition system 6 is located outside the test soil trough 1 and has the functions of real-time data acquisition, display and storage.

[0062] The data lines for the surface strain gauges and earth pressure gauges installed on the exterior of the shield joint model 3 are routed to the sidewalls 11 of the earth trench in the fill area 13 and extend upward to connect to the surface-mounted data acquisition system 6. The data lines for the surface strain gauges, array displacement gauges, and crack gauges installed inside the shield joint model 3, as well as the embedded strain gauges embedded within the first and second model segment linings 32, 34, are routed along the interior surface of the shield joint model 3, pass through the inner portal of the partition wall 2, extend upward along the partition wall 2, and connect to the surface-mounted data acquisition system 6.

[0063] The calculation formula of the internal length L of the test soil trough 1 is: L=L1+t w +L2=L s1 +L t1 -L′ t1 +L c1 +L s2 +L t2 -L′ t2 -L″ t2 +Δ+t w +L2

[0064] The required length of the model soil trench can be calculated using this formula, providing a reference for the construction of the model soil trench.

[0065] Where L1 is the inner length of the fill area 13; t wis the thickness of the partition wall 2, which is 1.0m; L2 is the internal length of the non-fill area 14 of the test soil trench; L s1 is the length of the shield body 31 of the first model, which is 2.14 m according to the similarity ratio of 1:7; L t1 is the length of the first model segment lining 32, is the width of the 9-ring model lining, and the width of the single-ring model lining ring is calculated based on the similarity ratio of 1:7, which is 0.286m. Therefore, L t1 2.574m; L' t1 is the length of the first model segment lining 32 contained in the first model shield 31, is the width of the 1-ring model lining, which is 0.286m; c1 L is the length of the first oil cylinder group 35, which is 0.3m; s2 is the length of the shield body 33 of the second model, which is also converted according to the similarity ratio of 1:7 and is 2.14m; t2 is the length of the second model segment lining 34, is the width of the 10-ring model lining, which is 2.86m; L′ t2 L″ is the length of the second model segment lining 34 contained in the second model shield 33, and is the width of the 1-ring model lining, which is 0.286m; t2 is the length of the second model segment lining 34 inside the partition wall 2, is the width of the two-ring model lining, which is 0.572m; Δ is the butt gap between the two model tunnels, which is 0.116m; L2 is the internal length of the non-fill area 14, which is 2.5m to meet the requirements of equipment lifting, personnel passage, and test operations. In summary, the internal length of the model soil trench is approximately 12.5m.

[0066] The internal width W and depth H of the model soil trench 1 are determined by the following formula: W = H = D m +2l′ fmax +2B

[0067] The required width and depth of the model soil trench can be calculated by this formula, providing a reference for the construction of the model soil trench.

[0068] Where D m is the outer diameter of the model shield, which is 2.28 m according to the similarity ratio of 1:7; l′ fmax is the longest radial projection of freezing tube 43 on the model shield, calculated based on the similarity ratio to be 0.937 m. B is the distance from the outermost end of freezing tube 43 to the interior of test soil trench 1. This was determined based on considerations of boundary effects, cost, and difficulty, ultimately set at 2.42 m. This is greater than twice the outer extension of freezing tube 43, and therefore greater than twice the thickness of the model freezing wall. The internal width and height of test soil trench 1 were both determined to be 9 m.

[0069] Two sets of ladders can be installed on the sidewalls 11 of the soil trough in the fill area 13 to facilitate access to the fill area 13, installation of the shield docking model 3, and placement of the sensors 5. Water supply and drainage systems must be installed within the fill area 13. A deck 15 should be installed within the non-fill area 14 of the test soil trough 1. The top surface of the deck 15 should be lower than the reserved portal in the partition wall 2, allowing easy access to the shield docking model 3 through the portal. The deck 2 should be able to support test equipment and personnel, such as the refrigeration system. A pedestrian staircase 16 should be installed in the non-fill area 14 to facilitate access to the deck 15 and then through the portal into the shield docking model 3 to conduct test-related operations. A ventilation system should be installed within the non-fill area 14 and the shield docking model 3. The test platform should be equipped with safety and emergency facilities: a fence should be installed around the test soil trough 1, and the test platform should be equipped with safety ropes, lifebuoys, liquid nitrogen freezing equipment, cement mortar and injection equipment, polyurethane and injection equipment, etc.

[0070] The present invention also provides a large-scale shield underground docking model test method, which performs the following steps based on the above-mentioned test platform:

[0071] S1: Build the test platform, including constructing the test soil trough 1, building the partition wall 2 and reserving the tunnel door, installing the water supply and drainage system, ventilation system, data acquisition system 6, safety and emergency facilities, ladders in the fill area 13, pedestrian stairs 16 and deck 15 in the non-fill area 14;

[0072] S2: Produce a shield docking model 3, including a first model shield body 31, a second model shield body 33, a first model segment lining 32, a second model segment lining 34, a first cylinder group 35, a half sleeve 36 and a first sealing brush 37, a second cylinder group 38 and a second sealing brush 39;

[0073] S3: grouting system, freezing system 4, sensor 5 components and data lines, and test soil used in the preliminary test;

[0074] S4: Install the first cylinder group 35, the half sleeve 36 and the first sealing brush 37, the second cylinder group 38, and the second sealing brush 39;

[0075] S5: Lay the fill soil at the bottom of the shield tunnel in layers, compact it in layers, and bury the sensor 5 at the designed position. The overall fill soil height is slightly higher than the bottom of the shield docking model 3.

[0076] S6: Install the shield joint model 3, including the first model shield body 31, the second model shield body 33, the first model segment lining 32, the second model segment lining 34, the model tunnel internal temporary support structure, and the joint section temporary support structure;

[0077] S7: Waterproofing the model tunnel. The waterproofing treatment locations include: the model joint section, the connection between the first model shield 31 and the first model segment lining 32, the connection between the second model shield 33 and the second model segment lining 34, the connection between the first model segment lining 32 and the side wall half sleeve 36, and the connection between the second model segment lining 34 and the partition wall 2 portal.

[0078] S8: Install the internal and external sensors 5 of the shield docking model 3, and introduce the sensors 5 into the data acquisition system 6;

[0079] S9: Fill the soil layer by layer to the designed height, compact the soil layer by layer and bury the sensor 5 at the designed position;

[0080] S10: inject water into the soil of the filling area, and during the water injection process, check whether there is water leakage in the half sleeve 36, the shield docking model 3, the partition wall 2 door, etc.;

[0081] S11: Carry out grouting reinforcement, freeze reinforcement, freeze-thaw and thaw-sink grouting tests according to the test plan, monitor the response of the shield docking model 3 and the soil during the test, record the test process, and store the test data;

[0082] S12: After the test, drain the water from the fill area, excavate the test soil layer by layer, check and record the diffusion of the grouting slurry, and collect soil samples to carry out mechanical parameter tests of the reinforced soil;

[0083] S13: Save test data and image data;

[0084] S14: Arrange test equipment and tools, and clean the test platform in preparation for the next test.

[0085] Furthermore, in S7, the data lines of the strain gauges and earth pressure gauges installed on the external surface of the shield docking model 3 are led to the side wall 11 of the soil trough in the fill area, and extend upward to be connected to the data acquisition system 6 set up on the surface; the data lines of the strain gauges, array displacement meters, crack meters and embedded strain gauges installed on the internal surface of the shield docking model 3 and buried in the lining of the model pipe segment are laid along the inner surface of the model tunnel, pass through the portal of the partition wall 2 and extend upward along the partition wall 2 to be connected to the data acquisition system 6 set up on the surface.

[0086] Furthermore, the grouting reinforcement scheme in S10 can be designed with different grouting processes, grouting materials, grouting sequences, grouting pressures, and grouting volumes; the freezing reinforcement scheme in S10 can set different cold liquid temperatures in different freezing pipelines, and can design different freezing pressure relief schemes, freezing pipe lengths, etc.; the freeze-thaw and melt-sinking grouting in S10 can be designed with different melt-sinking grouting schemes, including melt-sinking grouting processes, grouting volumes, grouting timing, etc.; after the grouting test phase is completed, personnel enter the shield docking model, remove the grouting test system, and install the freezing test system.

[0087] Furthermore, in S11, the mechanical parameter tests that can be carried out on the grouting reinforced soil may include: direct shear test; permeability test; thermodynamic test of specific heat capacity and thermal conductivity; sampling for laboratory frozen soil test, including uniaxial compressive strength test, shear strength test, and flexural strength test.

[0088] The present invention has been described in detail through the above preferred embodiments. However, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention is defined by the appended claims.

Claims

1. A large-scale shield underground docking model test platform, characterized by: It includes a test soil trench (1), a partition wall (2), a shield connection model (3) and a freezing system (4). The test soil trough (1) is an underground foundation pit structure. A partition wall (2) is provided in the test soil trough (1). The partition wall (2) divides the test soil trough (1) into a fill area (13) and a non-fill area (14). The partition wall (2) is used to prevent soil and water in the fill area (13) from entering the non-fill area (14). A shield docking model (3) is provided in the fill area (13). The shield docking model (3) is a scaled test model. The shield connection model (3) is provided with a freezing system (4), the freezing system (4) comprising a refrigeration system (41), a cold liquid circulation system (42) and a freezing pipe (43). The freezing pipe (43) is arranged on the shield connection model (3), the freezing pipe (43) is connected to the refrigeration system (41) through the cold liquid circulation system (42), and the refrigeration system (41) is placed on the non-filling area layer plate (15) of the test soil trough (1). The internal length L of the test soil trough (1) satisfies: L=L1+t w +L2 Where L1 is the inner length of the fill area (13), t w is the thickness of the partition wall (2), L2 is the internal length of the non-filled area (14) of the test soil trench; The internal width W and depth H of the test soil trough (1) are the same, satisfying the following formula: W=H=D m +2l′ fmax +2B Among them, D m is the outer diameter of the shield body of the shield docking model (3), l' fmax is the longest projection length of the freezing pipe (43) in the radial direction of the shield, B is the distance from the outermost end of the freezing pipe (43) to the inside of the test soil trough (1), The shield connection model (3) is composed of a model tunnel 1 and a model tunnel 2 arranged in a longitudinal direction. The interiors of the model tunnel 1 and the model tunnel 2 are kept in communication, so that personnel can conveniently enter the interior of the shield connection model (3) from the non-filling area (14). The model tunnel 1 is composed of a first model shield body (31) and a first model segment lining (32). The model tunnel 2 is composed of a second model shield body (33) and a second model segment lining (34). The model tunnel 1 is perpendicular to the side wall of the soil trench (11), and the model tunnel 2 is perpendicular to the partition wall (2). The first model shield body (31) and the second model shield body (33) have the same outer diameter, and the first model segment lining (32) and the second model segment lining (34) have the same outer diameter and inner diameter. A circular door is reserved on the partition wall (2) as a passage for personnel to enter the shield connection model (3) from the non-filled area (14). The inner size of the circular door is the same as the inner size of the second model shield body (33). Part of the second model segment lining (34) is placed inside the circular door on the partition wall (2). A second sealing brush (39) and a sealing rubber plate are arranged between the circular door and the second model segment lining (34) to prevent soil and water in the fill area (13) from entering the shield connection model (3) or the non-filled area (14). A first oil cylinder group (35) is arranged on the soil trough side wall (11) perpendicular to the first model segment lining (32) and is telescopic along the axis direction of the first model segment lining (32). The first oil cylinder group (35) is arranged in a ring direction, one end of which is fixed on the soil trough side wall (11) and the other end of which acts on the end face of the first model segment lining (32) to provide annular pre-tightening force for the first model segment lining (32). A second oil cylinder group (38) is arranged in the circular hole in the partition wall (2) and is telescopic along the axis direction of the second model segment lining (34). The second oil cylinder group (38) is arranged in a ring direction, one end of which is fixed in the partition wall (2) and the other end acts on the end surface of the second model segment lining (34) to provide an inter-annular pre-tightening force for the second model segment lining (34). The second oil cylinder group (38) is sufficient to provide an inter-annular joint pre-tightening force for the second model segment lining (34). The internal length L of the test soil trough (1) satisfies: L=L s1 +L t1 -L' t1 +L c1 +L s2 +L t2 -L' t2 -L" t2 +Δ+t w +L2 Where, L s1 L is the length of the first model shield (31); t1 is the length of the first model segment lining (32), L' t1 is the length of the first model segment lining (32) contained in the first model shield (31), L c1 L is the length of the first cylinder group (35); s2 is the length of the second model shield (33), L t2 is the length of the second model segment lining (34), L' t2 is the length of the second model segment lining (34) contained inside the second model shield (33), L" t2 is the length of the second model segment lining (34) inside the partition wall (2), Δ is the butt joint gap between the two model tunnels, A half sleeve (36) is preset on the soil trough side wall (11). The half sleeve (36) is cylindrical, one end of which is fixed on the soil trough side wall (11). The inner dimension of the half sleeve (36) is the same as the inner dimension of the first model shield body (31). A first sealing brush (37) and a sealing rubber plate are arranged between the half sleeve (36) and the first model segment lining (32) to prevent soil and water in the fill area (13) from entering the interior of the shield docking model (3). The pre-tightening force of the inter-annular joint of the first model segment lining (32) provided by the first oil cylinder group (35) satisfies the following formula: Where p is the preload stress of the inter-ring joint of the first model segment lining (32), F is the resultant force of water and soil pressure in front of the prototype shield cutterhead, S is the contact area of ​​the prototype lining ring joint, and c σ is the stress similarity ratio of the model test, The inter-ring preload force provided by the second cylinder group (38) is the same as that provided by the first cylinder group.

2. A large-scale shield underground docking model test platform according to claim 1, characterized in that: The model tunnel 1 and the model tunnel 2 are provided with ring beams at the butt ends to simulate the front shield part of the actual shield body. The inner contour size of the ring beam is the same as the inner dimension of the first model segment lining (32), and the inner contour size of the ring beam is the same as the inner dimension of the second model segment lining (34). A temporary support structure is installed between the butt end ring beam of the first model shield body (31) and the butt section ring beam of the second model shield body (33) to ensure that soil and water in the fill area (13) are prevented from entering the interior of the model tunnel 1 or the model tunnel 2, and the connection stiffness of the butt section between the first model shield body (31) and the second model shield body (33) is not increased.

3. A large-scale shield underground docking model test platform according to claim 2, characterized in that: It also includes a sensor (5), wherein the sensor (5) includes a surface strain gauge, a thermometer, an embedded strain gauge, an earth pressure gauge, an array displacement gauge and a crack gauge. The surface strain gauges are arranged on the inner and outer surfaces of the first model shield (31) and the second model shield (33), and are arranged in the circumferential and longitudinal directions to monitor the stress of the shields; the thermometers are arranged in the stratum to monitor the development of the frozen bodies; the embedded strain gauges are buried inside the first model segment lining (32) and the second model segment lining (34), and are arranged in the circumferential and longitudinal directions; the soil pressure gauges arranged on the outer surfaces of the first model shield (31) and the second model shield (33) are used to monitor the frost heave load during the freezing process, and the soil pressure gauges arranged on the side walls (11) of the soil trench are used to monitor the The influence of frost heave load on the test boundary is measured; array displacement meters are arranged on the inner surfaces of the first model shield body (31), the second model shield body (33), the first model segment lining (32) and the second model segment lining (34); the array displacement meters arranged in the circumferential direction measure the cross-sectional deformation of the shield butt joint model (3), and the array displacement meters arranged in the longitudinal direction measure the deformation of the shield butt joint model (3) in the longitudinal direction; the joint meter is arranged in the inter-circumferential joint between the first model segment lining (32) and the second model segment lining (34) to monitor the change in the opening amount of the inter-circumferential joint between the first model segment lining (32) and the second model segment lining (34).

4. A large-scale shield underground docking model test platform according to claim 3, characterized in that: The length of the half sleeve (36) is sufficient to cover the first cylinder group (35) and the half-ring width of the model segment lining, and meet the requirements of waterproof sealing measures, specifically satisfying the following formula: Length l of half sleeve (36) hs satisfy: l hs ≥l c1 +0.5w s +Δl ws In the formula, l c1 is the maximum length of the first cylinder group (35), w s is the width of the lining ring of the single-ring model, Δl ws The length for setting waterproof sealing measures.

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