Three-dimensional test device and method for determining collapsing deformation of shield tunnel in loess stratum

Abstract

The invention provides a three-dimensional test device and method for determining loess stratum shield tunnel collapsing deformation. The three-dimensional test device comprises a loading frame, a geotechnical model box, a left jack, a left spring loading plate, a right jack, a right spring loading plate, a pressure sensor, an upper middle jack, an upper side jack, a longitudinal partition plate, a top loading plate, a water injection pipe and an inclined partition plate. According to the three-dimensional test device and the test method, the loading sequence and the loading value of the jacks at different parts are adjusted, and the longitudinal partition plate, the inclined partition plate and the water injection pipe are mounted at different angles, so that the three-dimensional stress and deformation characteristics of the shield tunnel under the loess stratum collapsing condition and the stress condition of the tunnel collapsing foundation can be simulated. The research on mechanical and deformation behavior characteristics of the shield tunnel under loess stratum collapse is beneficial to optimization of a foundation collapse calculation method and engineering treatment measures, and has important guiding significance for construction and operation of the shield tunnel in the loess area.

Description

Technical Field

[0001] The invention relates to the technical field of shield tunnels, and in particular to a three-dimensional test device and method for determining the collapse deformation of a shield tunnel in a loess stratum. Background Art

[0002] Waterlogging and collapsing is one of the most typical engineering geological characteristics of loess strata. Under the background of the national new urbanization strategy, cities in central and western my country, represented by Xi'an, Lanzhou and Taiyuan, have ushered in a great development of rail transit. Subway lines will inevitably pass through collapsible loess strata, and the number of loess shield tunnels has gradually increased. Due to the special engineering properties of loess, on the one hand, waterlogging and wetting will soften and significantly deform the surrounding rock, thereby changing the interaction between the surrounding rock and the lining, resulting in increased surrounding rock pressure; on the other hand, the collapse deformation of the shield tunnel foundation will significantly increase the additional stress inside the lining structure, resulting in longitudinal uneven settlement, joint leakage, misalignment and other diseases.

[0003] There is currently no specific specification for the impact of waterlogging and collapsing in loess strata on shield tunnel structures and their treatment. The current "Building Standards for Collapsible Loess Areas" (GB50025-2018) is usually used for reference in design and construction. However, this specification is mainly for surface buildings, and there are significant differences between it and shield tunnels in terms of base pressure characteristics and the ability to adapt to uneven structural deformation. Direct application of this specification has the problem of overly strict requirements for foundation collapsing control and excessively high treatment costs. In addition, as a prefabricated and assembled underground tubular structure, a key mechanical feature of shield tunnels is the presence of longitudinal stress between segment rings, the maximum value of which can reach about 30% of the jack thrust during construction. This longitudinal stress plays an important role in improving the overall stiffness of shield tunnels and improving the bending, shear and torsion resistance of the structure. When stratum collapse occurs, shield tunnels show typical three-dimensional deformation characteristics under longitudinal load. Existing studies that study shield collapse using two-dimensional models are unscientific and cannot reasonably reveal the three-dimensional stress deformation characteristics of shield tunnels under stratum collapse conditions and their related interactions with the stratum, nor can they provide good guidance for related research and engineering practice. Related research requires the support of a three-dimensional test device and test method for collapse deformation of loess stratum shield tunnels. Summary of the invention

[0004] In order to study the stress deformation characteristics of shield tunnels under stratum collapse conditions and the related interaction relationship with the stratum, the present invention provides a three-dimensional test device and method for determining the collapse deformation of shield tunnels in loess strata, specifically including: Loading rack; The geotechnical model box is installed on the loading frame, and includes a model shield tunnel, a water injection pipe, two longitudinal partition plates, two oblique partition plates and a top loading plate; the top loading plate is located at the top of the geotechnical model box; the cross section of the model shield tunnel is located at the horizontal center of the geotechnical model box; The oblique partition plate is used to achieve different similar scales C n The two oblique partition plates are located in the area surrounded by the two longitudinal partition plates and the geotechnical model box, the bottom ends of the two oblique partition plates are connected to the middle of the waist of the model shield tunnel, and extend obliquely upward, and the top ends thereof are detachably connected to the top of the geotechnical model box; The water injection pipe is used to meet the requirement of complete wetting of the shield tunnel foundation soil in the area surrounded by the two longitudinal partition plates in the lower stratum wetting condition, and the water injection pipe includes multiple water injection pipe branches.

[0005] As a further illustration of the present invention, the loading frame includes a loading frame top longitudinal rod, two loading frame bottom longitudinal rods, four loading frame vertical rods, six loading frame side cross rods and four loading frame bottom cross rods. The length of the loading frame side cross rods is less than the cross-sectional width of the geotechnical model box. The two loading frame bottom longitudinal rods and the one loading frame top longitudinal rod are parallel to each other, the six loading frame side cross rods and the four loading frame bottom cross rods are parallel to each other, and the one loading frame top longitudinal rod, the two loading frame bottom longitudinal rods and the four loading frame vertical rods, the six loading frame side cross rods and the four loading frame bottom cross rods are installed perpendicularly to each other.

[0006] As a further illustration of the present invention, two upper side jacks and one upper middle jack are connected between the top of the geotechnical model box and the loading frame, a left spring loading plate, a pressure sensor and a left jack are sequentially connected between the left side of the geotechnical model box and the loading frame; a right spring loading plate, a pressure sensor and a right jack are sequentially connected between the right side of the geotechnical model box and the loading frame; The left spring-loaded plate and the right spring-loaded plate both include a spring-loaded plate connecting piece, a spring-loaded plate upper plate, a spring-loaded plate force transmission rod, a connecting spring and a spring-loaded plate lower plate; the spring-loaded plate connecting piece is a circular steel plate with a thickness of 1.5 cm, the spring-loaded plate upper plate and the spring-loaded plate lower plate are circular steel plates of the same size with a thickness of 1.5 cm, the inner diameter of the circular steel plate is 1 cm smaller than the inner diameter of the model shield tunnel, and the outer diameter of the circular steel plate is 1 cm larger than the outer diameter of the model shield tunnel.

[0007] As a further explanation of the present invention, there are n connecting springs between the upper plate of the spring loading plate and the lower plate of the spring loading plate, and they are evenly distributed at 360° / n, the total length of the connecting springs is less than 5 cm, the deformation of the connecting springs under the maximum thrust of the left jack or the right jack is less than 80% of the limit deformation, and the compression stiffness k of a single connecting spring is calculated as follows: (1); (2); in, k is the compression stiffness of a single connecting spring, n is the number of connecting springs, F is the thrust of the left jack or the right jack, △ l is the compression deformation of the spring when the thrust is F, l max is the limiting compaction deformation of a single spring.

[0008] As a further explanation of the present invention, the top loading plate is divided into blocks, and the longitudinal block length corresponds to the position of the two longitudinal partition plates; the longitudinal spacing d1 of the longitudinal partition plates is calculated as d1=D1 / C n ; Where D1 is the longitudinal collapse range of the actual shield tunnel, C n For similar scale.

[0009] As a further illustration of the present invention, the distance between the two ends of the two oblique partition plates (15) and the two ends of the two longitudinal partition plates (9) is ≤5 cm; in the process of the oblique partition plates (15) extending obliquely upward to the top of the geotechnical model box (2), the angle between the oblique partition plates (15) and the horizontal axis is α Calculate as follows: (3); in, f is the internal friction angle of the soil in the model box; When the oblique partition plate extends to the top of the geotechnical model box, the opening width of the oblique partition plate is greater than the width of the top loading plate and is less than or equal to the width of the geotechnical model box.

[0010] As a further illustration of the present invention, a plurality of displacement test points are arranged along the longitudinal direction on the inner wall of the model shield tunnel, and a plurality of strain gauges are pasted on the inner wall of the model shield tunnel in the form of strain rosettes; a plurality of miniature soil pressure boxes are arranged around the outside of the model shield tunnel to detect the stratum stress around the shield tunnel under different wetting conditions.

[0011] The present invention also provides a method used in the above test device, which specifically comprises the following steps: Step 1: Determine the shield tunnel collapse test conditions; Step 2: Determine the stiffness and quantity of the loading plate spring; Step 3: Determine the installation angle of the oblique partition plate; Step 4: Determine the similar scale and size of the model shield tunnel; Step 5: Determine the longitudinal stress of the shield tunnel in the test condition; Step 6: Determine the installation position of the longitudinal partition plate; Step 7: Install the longitudinal partition plate and adjust the water injection pipe branches to make them evenly distributed in the area to be wetted; Step 8: Fill the soil, install the model shield tunnel, and lay out displacement test points and pressure sensors; Step 9: Adjust the jacks on both sides and the top to complete the preparation work for the shield collapse test; Step 10: Loading through water injection pipes and upper jacks to achieve wetting collapse of the shield tunnel foundation and upper strata of the shield tunnel respectively; Step 11: Read the data and complete the corresponding working condition test.

[0012] As a further illustration of the present invention, the longitudinal stress of the shield tunnel in step 5 is achieved by adjusting the loading conditions, loading values, and filling sequence of the left jack, the right jack, the upper middle jack, and the upper side jack, and the filling sequence in the geotechnical model box. The longitudinal stress of the shield tunnel is calculated as follows: (4); (5); (6); Where N is the longitudinal axial force of the model shield tunnel under different wet collapse conditions of the test device; F0 is the jack thrust in the actual shield tunnel construction; C n The ratio of the actual shield tunnel radius (outer diameter) R to the model shield tunnel radius (outer diameter) r is C n =R / r; β 1 is the attenuation coefficient of the shield starting section; m1 is the number of segments corresponding to the end of the shield starting section; m is the number of segments at the location where the actual interval tunnel collapses; l g is the shield segment ring width; β 2 is the attenuation coefficient of the shield receiving section; m2 is the number of segments corresponding to the shield receiving section; m0 is the total number of segments in the actual interval shield tunnel; P is the creep coefficient considering the weakening of the annular joint; The loading values ​​of the upper middle jack and the upper side jack are calculated as follows: (7); in, N z is the loading value of the upper jack; s sat is the earth pressure on the shield tunnel when the upper stratum actually collapses; Cn The ratio of the actual shield tunnel radius R to the model shield tunnel radius r is C n =R / r; c is the weight of the soil above the shield tunnel in the geotechnical model box; h is the buried depth of the model shield tunnel; A1 is the projected area of ​​the soil surrounded by two longitudinal partition plates in the geotechnical model box; G1 is the weight at the middle position of the top loading plate; s 0 is the actual soil pressure on the shield tunnel in the initial state of the upper stratum; A2 is the projected area of ​​the soil on both sides of the A1 area; G2 is the weight on both sides of the top loading plate.

[0013] As a further explanation of the present invention, the wetting of the shield tunnel foundation in step ten is achieved through the water injection pipe pre-buried in the bottom of the shield tunnel, the wetting of the upper stratum of the shield tunnel is achieved through the loading of the inclined partition plate and the upper middle jack, and the simultaneous wetting of the shield tunnel foundation and upper stratum is achieved jointly by the water injection pipe, the inclined partition plate and the loading of the upper middle jack.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: 1. The present invention has the ability to load the longitudinal axis of the shield tunnel, breaking through the constraints of the traditional two-dimensional plane strain model box test scheme of the tunnel, and can truly reflect the three-dimensional stress state of the shield tunnel, especially the changes in the longitudinal axial force at different parts of the actual interval shield tunnel; 2. The present invention reduces the difficulty of soil matching in geotechnical model tests under different similar scales by setting oblique partitions and longitudinal partitions and cooperating with the top middle jack, and can realize the test conditions of foundation collapse, upper stratum collapse, and simultaneous collapse of foundation and upper stratum.

[0015] 3. The three-dimensional test device of the present invention has a clear structure and is easy to install. The overall structure consists of a loading frame, a geotechnical model box, a partition plate, a load plate and other structures. The changes in the axial force of the shield tunnel and the stratum stress are mainly achieved through the loading jack, and the operation is relatively simple.

[0016] 4. The three-dimensional test device of the present invention can easily obtain test data by installing micro earth pressure cells, strain gauges, displacement measuring points and other components at relevant positions; 5. The three-dimensional test device of the present invention can be reused and can simulate multiple times the relevant tests on the wetting collapse of the loess shield tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the three-dimensional test device for the collapse deformation of a loess shield tunnel provided by the present invention.

[0018] Figure 2It is a schematic cross-sectional view of a three-dimensional test device for collapse deformation of a loess shield tunnel provided by the present invention.

[0019] Figure 3 It is a schematic diagram of the loading frame provided by the present invention.

[0020] Figure 4 Schematic diagram of the longitudinal spring loading plate provided by the present invention.

[0021] Figure 5 It is a flow chart of the test method provided by the present invention.

[0022] Reference numerals: 1—loading frame, 101—loading frame vertical rod, 102—loading frame top longitudinal rod, 103—loading frame side crossbar, 104—loading frame bottom crossbar, 105—loading frame bottom longitudinal rod, 2—geotechnical model box, 3—left jack, 4—left spring loading plate, 401—spring loading plate connector, 402—spring loading plate upper plate, 403—loading plate bolt hole, 404—spring loading plate force transmission rod, 405—spring loading plate lower plate, 406—connecting spring, 5—right jack, 6—right spring loading plate, 7—pressure sensor, 8—upper middle jack, 801—upper side jack, 9—longitudinal partition plate, 10—model shield tunnel, 11—displacement test point, 12—micro earth pressure box, 13—top loading plate, 14—water injection pipe, 15—oblique partition plate, 16—strain gauge, 17—water injection pipe branch. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0027] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The technical solution of the present invention will be explained below in conjunction with specific embodiments.

[0030] like Figure 1-4 As shown, a three-dimensional test device for the collapse deformation of a shield tunnel in a loess stratum is provided, comprising a loading frame 1, a loading frame vertical rod 101, a loading frame top longitudinal rod 102, a loading frame side cross rod 103, a loading frame bottom cross rod 104, a loading frame bottom longitudinal rod 105, a geotechnical model box 2, a left jack 3, a left spring loading plate 4, a spring loading plate connecting piece 401, a spring loading plate upper plate 402, a loading plate bolt hole 403, a spring loading plate force transmission rod 404, a spring loading plate lower plate 405, a connecting spring 406, a right jack 5, a right spring loading plate 6, an upper middle jack 8, an upper side jack 801, a longitudinal partition plate 9, a top loading plate 13, a water injection pipe 14, an oblique partition plate 15, and a water injection pipe branch 17.

[0031] In the present invention, the longitudinal bars, cross bars and vertical bars of the loading frame are perpendicular to each other, and the installation error rate does not exceed 1%; the top longitudinal bar of the loading frame does not deflect by more than 1 / 500 under a total thrust of 300kN from the upper middle and side jacks; the length of the side cross bars of the loading frame should be greater than the cross-sectional width w of the model box, and the side cross bars do not deflect by more than 1 / 500 under a thrust of 5kN from the left and right jacks, respectively.

[0032] Two upper side jacks 801 and an upper middle jack 8 are connected between the top of the geotechnical model box 2 and the loading frame 1; a left spring loading plate 4, a pressure sensor 7 and a left jack 3 are connected in sequence between the left side of the geotechnical model box 2 and the loading frame 1; a right spring loading plate 6, a pressure sensor 7 and a right jack 5 are connected in sequence between the right side of the geotechnical model box 2 and the loading frame 1.

[0033] The left spring-loaded plate 4 and the right spring-loaded plate 6 both include a spring-loaded plate connector 401, a spring-loaded plate upper plate 402, a spring-loaded plate force transmission rod 404, a connecting spring 406 and a spring-loaded plate lower plate 405. The spring-loaded plate upper plate 402 and the spring-loaded plate lower plate 405 are circular steel plates of the same size, with a plurality of connecting springs 406 connected therebetween. The spring-loaded plate connector 401 is circular and has a thickness of 1.5 cm.

[0034] In the present invention, the diameter of the spring loading plate is the same as that of the pressure sensor, and it reserves 4 bolt holes with a diameter of 6 mm. The bolt holes penetrate the loading plate connector and are evenly distributed at 90° to each other, corresponding to the bolt vacancies on the pressure sensor; the upper and lower plates of the spring loading plate are circular steel plates of the same size, with a thickness of 1.5 cm, an inner diameter less than 1 cm smaller than the inner diameter of the model shield tunnel, and an outer diameter greater than 1 cm larger than the outer diameter of the model tunnel; the number of connecting springs 406 between the upper and lower plates of the spring loading plate is n, which are evenly distributed at 360° / n, and the deformation of the connecting spring 406 under the maximum thrust of the left or right jack should be less than 80% of the limit deformation, the total length of the connecting spring 406 is less than 5 cm, and the compression stiffness of a single connecting spring 406 is k Calculate according to the following formula: (1); (2); in, k is the compaction stiffness of a single connecting spring, n is the number of connecting springs, F is the thrust of the left or right jack, △ l is the compression deformation of the spring when the thrust is F, l max is the limiting compaction deformation of a single spring.

[0035] In the present invention, the connecting piece, the upper plate and the lower plate of the spring loading plate are concentric circles with overlapping axes after assembly, and the center distance error is within 2 mm.

[0036] The top loading plate 13 is divided into blocks, and the longitudinal length of the blocks corresponds to the position of the two longitudinal partition plates 9; the longitudinal spacing d1 of the longitudinal partition plates 9 is calculated as d1=D1 / C n ; Where D1 is the longitudinal collapse range of the actual shield tunnel, C n For similar ratios; In the present invention, the longitudinal partition plate 9 and the oblique partition plate 15 are mainly composed of PVC board material. The connection parts of the longitudinal partition plate 9, the oblique partition plate 15 and the geotechnical model box 2 and the model shield tunnel 10 should be sealed. The longitudinal spacing d1 of the two longitudinal partition plates 9 can be adjusted according to the test conditions. If the actual longitudinal shrinkage range of the shield tunnel is D1, then d1=D1 / C n The main purpose of the oblique partition plate 15 is to cooperate with the upper jack 8 and the top loading plate 13 to achieve different similar scales C n The model shield tunnel 10 below is used to test the stratum stress under the upper part of the wetting condition, avoiding the problems of soil matching and water infiltration.

[0037] The distance between the two ends of the two oblique partitions 15 and the two ends of the two longitudinal partitions 9 is ≤5 cm; The oblique partition plate 15 is arranged from the middle of the waist of the model shield tunnel 10, and extends obliquely upward to the top of the geotechnical model box 2, with an angle of α Calculate according to the following formula: (3); in, α is the angle between the oblique partition plate and the horizontal line; f is the internal friction angle of the soil in the model box.

[0038] When the oblique partition plate 15 extends to the top of the geotechnical model box 2, its opening width w2 should satisfy: ; Among them, w is the width of the geotechnical model box, w1 is the width of the top loading plate, and w2 is the opening width of the diagonal partition plate.

[0039] The top loading plate 13 should have a certain bending rigidity, and the deflection under the thrust of 1150 kN of a single upper middle jack 8 and an upper side jack 80 should not exceed 1 / 100.

[0040] In the present invention, the water injection pipe 14 is composed of a plurality of branch pipes, which should meet the requirement that all the shield tunnel foundation soil in the area surrounded by the two longitudinal partition plates 9 in the lower stratum wetting condition is completely wetting; in addition, the water injection pipe 14 should be laid synchronously when filling the model box according to the designed wetting condition; the cross section of the model shield tunnel 10 should be located in the middle of the horizontal position of the geotechnical model box 2, that is, the distance d2=d3 from the outside of the model shield tunnel 10 to the two sides of the geotechnical model box 2; the maximum value of the radius (outer diameter) r of the model shield tunnel 10 should meet 2r≤d2 or 2r≤d3.

[0041] A plurality of displacement test points 11 are also arranged on the inner wall of the model shield tunnel 10 along the longitudinal direction, and a plurality of strain gauges 16 are pasted on the inner wall of the model shield tunnel 10 in the form of strain gauges; a plurality of micro earth pressure cells 12 are arranged around the outside of the model shield tunnel 10 to detect the stratum stress around the shield tunnel under different collapsible working conditions; In the present invention, a micro earth pressure box 12 is buried in the stratum near the model shield tunnel 10; the displacement test points 11 are longitudinally installed on the inner wall of the model shield tunnel 10, and the heights of the test points are different. The gap intervals through the spring loading plate can be measured by a level to grasp the longitudinal deflection of the shield tunnel under different wetting conditions; the strain gauge 16 is longitudinally pasted on the inner wall of the model shield tunnel 10 in the form of a strain rosette to measure the stress of the shield tunnel segment under different wetting conditions.

[0042] Before the collapse test, the model shield tunnel 10 needs to be loaded to a suitable longitudinal stress state according to different test conditions. The specific stress N is determined according to the following formula: (4); (5); (6); in, N is the longitudinal axial force of the model shield tunnel under different wet collapse conditions of the test device; F0 is the jack thrust in the actual shield tunnel construction; C n The ratio of the actual shield tunnel radius (outer diameter) R to the model shield tunnel radius (outer diameter) r is C n =R / r; β 1 is the attenuation coefficient of the shield starting section; m1 is the number of segments corresponding to the end of the shield starting section; m is the number of segments at the location where the actual interval tunnel collapses; l g is the shield segment ring width; β 2 is the attenuation coefficient of the shield receiving section; m2 is the number of segments corresponding to the shield receiving section; m0 is the total number of segments in the actual interval shield tunnel; P is the creep coefficient considering the weakening of the annular joint.

[0043] The specific longitudinal stress N of the shield tunnel is achieved by adjusting the loading smoothness, loading value and filling sequence of the left jack 3, the right jack 6, the upper middle jack 8 and the upper side jack 801, and the filling sequence in the model box; The longitudinal stress of the model shield tunnel is applied when the model shield tunnel 10 is installed. It is first loaded to the target value, then overloaded by 10%, and then unloaded to 0 to eliminate the installation gap of the shield tunnel 10; then the left jack 3 and the right jack 6 are loaded to the target value again; before the wetting test, the longitudinal starting section and the longitudinal receiving section will unload the corresponding left or right jacks from the target value by 50% to achieve the stress effect of gradually increasing or decreasing the longitudinal stress between the rings.

[0044] The shield tunnel foundation is flooded through the water injection pipe 14 pre-buried at the bottom, the upper strata of the shield tunnel are flooded through the inclined partition plate 15 and the upper middle jack 8 loading, and the shield tunnel foundation and upper strata are flooded simultaneously through the water injection pipe 14, the inclined partition plate 15 and the upper middle jack 8 loading.

[0045] Upper middle jack 8, upper side jack 801 loading value N z Related to the actual formation stress after collapse, the loading value N z Calculate according to the following formula: (7); N z is the loading value of the upper jack, and the calculation methods of the middle jack and the side jack are different; s sat C is the earth pressure on the shield tunnel when the upper stratum actually collapses, calculated according to the saturated density of the original stratum; n The ratio of the actual shield tunnel radius (outer diameter) R to the model shield tunnel radius (outer diameter) r is C n =R / r; c is the weight of the soil above the shield tunnel in the model box; h is the buried depth of the model shield tunnel; A1 is the projected area of ​​the soil surrounded by two longitudinal partition plates in the geotechnical model box; G1 is the weight of the top loading plate (middle position); s 0 It is the soil pressure on the shield tunnel in the actual initial state of the upper stratum, calculated according to the natural weight of the original stratum; A2 is the projected area of ​​the soil on both sides of the A1 area; G2 is the weight of the top loading plate (on both sides).

[0046] The three-dimensional test method for determining the collapse deformation of a shield tunnel in loess strata provided by the present invention is described below through specific embodiments. Example 1

[0047] This test device is used to simulate the collapse deformation of a 3km long shield tunnel in loess stratum. The shield tunnel radius (outer diameter) is R=3.0 m, the segment thickness is 35 cm, and the ring width is l g =1.5m, a total of 2000 rings. During construction, the thrust of the shield machine jack is 15000 kN. The tunnel is buried 20m deep, and the average weight of the loess layer in its natural state is 17.5 kN / m 3 The saturated weight after immersion is 20 kN / m 3 . Attenuation coefficient of the shield starting section in the embodiment β 1 takes 0.05, the attenuation coefficient of the receiving section β 2 is taken as 0.03. The width of the geotechnical model box is 2m, the longitudinal length is 5m, and the soil density in the model box is γ=18 kN / m 3 , the internal friction angle is 18°.

[0048] Specifically, the operation steps are explained by taking two working conditions: the upper stratum and foundation are simultaneously subsided within 25 m around the 30th ring of the shield starting section, and the upper stratum is subsided within 30 m around the 1500th ring of the shield middle section. Working condition 1: Upper strata and foundation collapse within 25m around the 30th ring of the shield starting section

[0049] Step 1: Determine the stiffness and quantity of the loading leaf springs The left spring loading plate 4 and the right spring loading plate 6 mainly play the role of transmitting and distributing the thrust of the jack, and can also buffer the sudden change of the pressure of the jack cylinder. The connecting springs used are the same, and the spring stiffness k is calculated according to the following formula (1) (2) k is the compaction stiffness of a single connecting spring, n is the number of connecting springs, F is the thrust of the left or right jack, △ l is the compression deformation of the spring when the thrust F is applied, △ l max is the limit compaction deformation of a single spring.

[0050] Formula (1) is a theoretical formula for calculating the compression stiffness of the spring. For this test device, since the spring loading plate is self-assembled, the compression stiffness of finished steel springs on the market varies. In order to simplify the assembly process of the test equipment, according to the principle of parallel stiffness, the total spring compression stiffness can be adjusted by adjusting the number n to meet the requirements. At the same time, in order to select a spring with appropriate deformation and leave a certain amount of margin, the spring model to be used is preliminarily selected in combination with formula (2).

[0051] For example: the maximum thrust of the left jack required in the test plan is 5kN, the compression stiffness of the purchased spring is 0.05kN / mm, and the ultimate compression is 2cm. Then the number of springs is at least 7 and at most 16. In order to facilitate installation and ensure the deformation when the pressure is relatively small, 8 springs can be used.

[0052] Step 2: Determine the installation angle of the diagonal partition.

[0053] More specifically, the angle of the oblique partition plate 15 when arranged starts from the middle of the waist of the model shield tunnel and extends obliquely upward, with an angle of α Calculate according to the following formula: (3) α is the angle between the oblique partition plate and the horizontal line; f is the internal friction angle of the soil in the model box.

[0054] For example, if the internal friction angle of the actual soil layer in the geotechnical model box is 18°, then the angle between the oblique partition plate and the horizontal line is α Set to 54°.

[0055] Step 3: Determine the similarity scale and size of the model shield tunnel.

[0056] Specifically, the width of the geotechnical model box is 2m, and the distance from the outside of the shield tunnel to the two sides of the model box is d2=d3, and the radius (outer diameter) of the model shield tunnel is r The maximum value should satisfy 2 r ≤d2 or 2 r ≤d3 calculation, the maximum radius (outer diameter) of the model shield tunnel is 0.33m. For the convenience of calculation, the radius of the model tunnel is 0.3m, that is, the similarity scale C n =10.

[0057] Step 4: Determine the longitudinal stress of the shield tunnel under the test conditions.

[0058] Specifically, the model shield tunnel segment needs to be loaded to a suitable longitudinal stress state according to different test conditions before the collapse test, and the specific stress N is determined according to the following formula: (4) (5) (6) N is the longitudinal axial force of the model shield tunnel under different wet collapse conditions of the test device; F0 is the jack thrust in the actual shield tunnel construction; C n The ratio of the actual shield tunnel radius (outer diameter) R to the model shield tunnel radius (outer diameter) r is C n =R / r;β 1 is the attenuation coefficient of the shield starting section; m1 is the number of segments corresponding to the end of the shield starting section; m is the number of segments at the location where the actual interval tunnel collapses; l g is the shield segment ring width; β 2 is the attenuation coefficient of the shield receiving section; m2 is the number of segments corresponding to the shield receiving section; m0 is the total number of segments in the actual interval shield tunnel; P is the creep coefficient considering the weakening of the annular joint.

[0059] Specifically, the shield starting section attenuation coefficient in the embodiment β 1 is taken as 0.05, then m1=47 rings can be calculated from formula (5), that is, the 1st to 47th rings are the starting section of the shield. If the location where the formation collapse occurs (the mth ring segment) is near the 30th ring, it can be seen from formula (4) that the corresponding model shield tunnel jack thrust is 1.21 kN.

[0060] Step 5: Determine the installation position of the longitudinal partition.

[0061] The longitudinal spacing d1 between the two longitudinal partitions can be adjusted according to the test conditions. If the actual longitudinal collapse range of the shield tunnel is 25m, then d1=2.5m.

[0062] Step 6: Determine the loading values ​​of the upper center and side jacks.

[0063] Specifically, the upper middle and side jack loading values ​​N z It is related to the actual formation stress after collapse and is calculated according to the following formula: (7) N z is the loading value of the upper jack, and the calculation methods of the middle jack and the side jack are different; s sat C is the earth pressure on the shield tunnel when the upper stratum actually collapses, calculated according to the saturated density of the original stratum; n The ratio of the actual shield tunnel radius (outer diameter) R to the model shield tunnel radius (outer diameter) r is C n =R / r; γ is the weight of the soil above the shield tunnel in the model box; h is the buried depth of the model shield tunnel; A1 is the projected area of ​​the soil surrounded by two longitudinal partition plates in the geotechnical model box; G1 is the weight of the top loading plate (middle position); s 0 is the soil pressure on the shield tunnel in the initial state of the actual upper stratum, calculated according to the natural weight of the original stratum; A2 is the projected area of ​​the soil on both sides of the A1 area; G2 is the weight of the top loading plate (on both sides).

[0064] Specifically, in the embodiment, the shield tunnel is buried at a depth of 20m, and the average weight of the loess layer in its natural state is 17.5 kN / m 3 The saturated weight after immersion is 20 kN / m 3 , it can be seen s sat =20*20=400kPa, s 0=17.5*20=350kPa. If the soil density in the geotechnical model box is γ=18 kN / m 3 , burial depth h = 1.0m, according to the projection area, A1 = 5m 2 , A2=2.5m 2 , correspondingly G1=0.4kN, G2=0.2kN, then from formula (7) we can know that the thrust of the middle jack is 109.6kN, and the thrust of the side jack is 42.3kN.

[0065] Step 7: Install two longitudinal partitions in the geotechnical model box with a spacing of 2.5m, and adjust the water injection pipe branches to make them evenly distributed in the simulated collapsible area; Step 8: Fill the geotechnical model box with soil at a density of γ=18 kN / m 3 , the internal friction angle is controlled at 18°, filled to the shield tunnel foundation position, and the micro earth pressure box in the lower layer is laid; Step 9: Install the model shield segment, the radius of the model segment is 0.3m, and install displacement measurement points and strain gauges inside it; Step 10: Load the left and right sides according to the calculated values. Load the left and right jacks to 1.21 kN respectively, then overload by 10%, and then unload to 0 to eliminate the shield tunnel installation gap; then load the left and right jacks to 1.21 kN again; Step 11: Fill the model tunnel halfway, then lay out the oblique partition board with an installation angle of 54° as determined by calculation, continue filling the shield tunnel to the top, and install the top micro earth pressure cell; Step 12: Fill the soil to the top of the model box and install the top loading plate; Step 13: Load the upper part according to the calculated value. The upper middle jack and the upper side jack are first loaded to 42.3 kN, and then the left jack is unloaded by 50% to 0.605 kN to simulate the ring-by-ring growth state of the longitudinal stress in the starting section of the shield. At this time, the preliminary work of the immersion test is completed, and the data of the micro earth pressure cell, strain gauge, and displacement measurement point are recorded. Step 14: The lower water injection pipe begins to inject water, and the upper middle jack is further loaded to 109.6kN to simulate the simultaneous collapse of the upper stratum and the shield tunnel foundation. The data of the micro-earth pressure box, strain gauge, and displacement measurement point are recorded at this time, the test is completed, and relevant data analysis is performed. The data of the micro-earth pressure box reflects the stress changes of the shield tunnel foundation before and after the collapse, and the data of the strain gauge and displacement measurement point reflect the stress and deformation of the shield tunnel before and after the collapse. Working condition 2: Upper stratum collapse occurred 30m near the 1500 ring in the middle section of the shield

[0066] Step 1 to Step 3: Same as Condition 1.

[0067] Step 4: Determine the longitudinal stress of the shield tunnel under the test conditions.

[0068] Specifically, the model shield tunnel segment needs to be loaded to a suitable longitudinal stress state according to different test conditions before the collapse test, and the specific stress N is determined according to the following formula: (4) (5) (6) N is the longitudinal axial force of the model shield tunnel under different wet collapse conditions of the test device; F0 is the jack thrust in the actual shield tunnel construction; C n The ratio of the actual shield tunnel radius (outer diameter) R to the model shield tunnel radius (outer diameter) r is C n =R / r; β 1 is the attenuation coefficient of the shield starting section; m1 is the number of segments corresponding to the end of the shield starting section; m is the number of segments at the location where the actual interval tunnel collapses; l g is the shield segment ring width; β 2 is the attenuation coefficient of the shield receiving section; m2 is the number of segments corresponding to the shield receiving section; m0 is the total number of segments in the actual interval shield tunnel; P is the creep coefficient considering the weakening of the annular joint.

[0069] Specifically, the shield starting section attenuation coefficient in the embodiment β 1 takes 0.05, the attenuation coefficient of the receiving section β 2 is taken as 0.03, then m1=47 rings can be calculated by formula (5), and m2=1922 rings can be calculated by formula (6), that is, the 48th to 1921st rings are the middle section. If the location where the formation collapse occurs (the mth ring segment) is near the 1500th ring, it can be seen from formula (4) that the corresponding model shield tunnel jack thrust is 1.35 kN.

[0070] Step 5: Determine the installation position of the longitudinal partition.

[0071] The longitudinal spacing d1 between the two longitudinal partitions can be adjusted according to the test conditions. If the actual longitudinal wetting range of the shield tunnel is 30m, then d1=3m.

[0072] Step 6: Determine the loading values ​​of the upper center and side jacks.

[0073] Specifically, the upper middle and side jack loading values ​​N z It is related to the actual formation stress after collapse and is calculated according to the following formula: (7) N z is the loading value of the upper jack, and the calculation methods of the middle jack and the side jack are different; s sat C is the earth pressure on the shield tunnel when the upper stratum actually collapses, calculated according to the saturated density of the original stratum; n The ratio of the actual shield tunnel radius (outer diameter) R to the model shield tunnel radius (outer diameter) r is C n =R / r; γ is the weight of the soil above the shield tunnel in the model box; h is the buried depth of the model shield tunnel; A1 is the projected area of ​​the soil surrounded by two longitudinal partition plates in the geotechnical model box; G1 is the weight of the top loading plate (middle position); s 0 is the soil pressure on the shield tunnel in the initial state of the actual upper stratum, calculated according to the natural weight of the original stratum; A2 is the projected area of ​​the soil on both sides of the A1 area; G2 is the weight of the top loading plate (on both sides).

[0074] Specifically, in the embodiment, the shield tunnel is buried at a depth of 20m, and the average weight of the loess layer in its natural state is 17.5 kN / m 3 The saturated weight after immersion is 20 kN / m 3 , it can be seen s sat =20*20=400kPa, s 0=17.5*20=350kPa. If the soil density in the geotechnical model box is γ=18 kN / m 3 , burial depth h = 1.0m, according to the projection area, A1 = 6m 2 , A2=2m 2 , correspondingly G1=0.48kN, G2=0.16kN, then from formula (7) we can know that the thrust of the middle jack is 131.52kN, and the thrust of the side jack is 33.84kN.

[0075] Step 7: Install two longitudinal partitions in the geotechnical model box with a spacing of 3.0m, and adjust the water injection pipe branches to make them evenly distributed in the simulated collapsible area; Step 8: Fill the geotechnical model box with soil at a density of γ=18 kN / m 3 , the internal friction angle is controlled at 18°, filled to the shield tunnel foundation position, and the micro earth pressure box in the lower layer is laid; Step 9: Install the model shield segment, the radius of the model segment is 0.3m, and install displacement measurement points and strain gauges inside it; Step 10: Load the left and right sides according to the calculated values. Load the left and right jacks to 1.35 kN respectively, then overload by 10%, and then unload to 0 to eliminate the shield tunnel installation gap; then load the left and right jacks to 1.35 kN again; Step 11: Fill the model tunnel halfway, then lay out the oblique partition board with an installation angle of 54° as determined by calculation, continue filling the shield tunnel to the top, and install the top micro earth pressure cell; Step 12: Fill the soil to the top of the model box and install the top loading plate; Step 13: Load the upper part according to the calculated value. The upper middle jack and the upper side jack are both loaded to 33.84 kN. The preliminary work of the immersion test is completed. The data of the micro earth pressure cell, strain gauge, and displacement measurement point are recorded at this time. Step 14: Start injecting water into the lower water injection pipe to simulate the collapse of the shield tunnel foundation, record the data of the micro earth pressure box, strain gauge, and displacement measurement point at this time, complete the test, and conduct relevant data analysis. The data of the micro earth pressure box reflects the stress changes of the shield tunnel foundation before and after collapse, and the data of the strain gauge and displacement measurement point reflect the stress and deformation of the shield tunnel before and after collapse. Simulation of other working conditions

[0076] Specifically, if you want to simulate the ring-by-ring attenuation state of the longitudinal stress in the receiving section of the shield, after the upper middle jack and the upper side jack complete the initial state loading, the right jack can be unloaded by 50%; if you only simulate the subsidence of the shield tunnel foundation, only water is injected through the water injection pipe, and the loading value of the upper middle jack does not increase. Through the above operations, relevant test simulations under combined conditions such as different parts of the interval shield tunnel (shield starting section, middle section, shield receiving section), different subsidence conditions (upper stratum subsidence, foundation subsidence and simultaneous subsidence), and different longitudinal subsidence ranges can be realized respectively.

[0077] The above embodiments are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions and substitutions made by those skilled in the art based on the technical features of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata, characterized in that: Include Loading frame (1); A geotechnical model box (2) is installed on the loading frame (1), comprising a model shield tunnel (10), a water injection pipe (14), two longitudinal partition plates (9), two oblique partition plates (15) and a top loading plate (13); the top loading plate (13) is located at the top of the geotechnical model box (2); and the cross section of the model shield tunnel (10) is located at the horizontal center of the geotechnical model box (2); The longitudinal partition plates (9) are used to limit the longitudinal collapse range of the model shield tunnel (10), and the top ends and bottom ends of the two longitudinal partition plates (9) are respectively vertically and detachably connected to the top and bottom of the geotechnical model box (2); The oblique partition plate (15) is used to realize different similar scales. C n The two oblique partition plates (15) are located in the area enclosed by the two longitudinal partition plates (9) and the geotechnical model box (2), the bottom ends of the two oblique partition plates (15) are connected to the middle of the waist of the model shield tunnel (10), and extend obliquely upwards, and the top ends thereof are detachably connected to the top of the geotechnical model box (2); The water injection pipe (14) is used to ensure that the shield tunnel foundation soil in the area surrounded by the two longitudinal partition plates (9) is completely submerged in the lower stratum subsidence condition, and the water injection pipe (14) comprises a plurality of water injection pipe branches (17).

2. A three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata according to claim 1, characterized in that: The loading frame (1) comprises a loading frame top longitudinal rod (102), two loading frame bottom longitudinal rods (105), four loading frame vertical rods (101), six loading frame side cross rods (103) and four loading frame bottom cross rods (104); the length of the loading frame side cross rods is less than the cross-sectional width of the geotechnical model box; the two loading frame bottom longitudinal rods (105) and the one loading frame top longitudinal rod (102) are parallel to each other; the six loading frame side cross rods (103) and the four loading frame bottom cross rods (104) are parallel to each other; and the one loading frame top longitudinal rod (102), the two loading frame bottom longitudinal rods (105) and the four loading frame vertical rods (101) and the six loading frame side cross rods (103) and the four loading frame bottom cross rods (104) are installed perpendicularly to each other.

3. A three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata according to claim 1, characterized in that: Two upper side jacks (801) and an upper middle jack (8) are connected between the top of the geotechnical model box (2) and the loading frame (1); a left spring loading plate (4), a pressure sensor (7) and a left jack (3) are connected in sequence between the left side of the geotechnical model box (2) and the loading frame (1); and a right spring loading plate (6), a pressure sensor (7) and a right jack (5) are connected in sequence between the right side of the geotechnical model box (2) and the loading frame (1); The left spring loading plate (4) and the right spring loading plate (6) both comprise a spring loading plate connecting piece (401), a spring loading plate upper plate (402), a spring loading plate force transmission rod (404), a connecting spring (406) and a spring loading plate lower plate (405); the spring loading plate connecting piece (401) is a circular steel plate with a thickness of 1.5 cm, the spring loading plate upper plate (402) and the spring loading plate lower plate (405) are circular steel plates with the same size and a thickness of 1.5 cm, the inner diameter of the circular steel plate is 1 cm smaller than the inner diameter of the model shield tunnel (10), and the outer diameter of the circular steel plate is 1 cm larger than the outer diameter of the model shield tunnel (10).

4. A three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata according to claim 3, characterized in that: There are n connecting springs (406) between the upper plate (402) of the spring loading plate and the lower plate (405) of the spring loading plate, and they are evenly distributed at 360° / n. The total length of the connecting springs (406) is less than 5 cm. The deformation of the connecting springs (406) under the maximum thrust of the left jack (3) or the right jack (5) is less than 80% of the limit deformation. The compression stiffness k of a single connecting spring (406) is calculated as follows: （1）； （2）； in, k is the compression stiffness of a single connecting spring, n is the number of connecting springs, F is the thrust of the left jack or the right jack, △ l is the compression deformation of the spring when the thrust is F, l max is the limiting compaction deformation of a single spring.

5. A three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata according to claim 1, characterized in that: The top loading plate (13) is of a block type, and its longitudinal block length corresponds to the position of the two longitudinal partition plates (9); the longitudinal spacing d1 of the longitudinal partition plates (9) is calculated as d1=D1 / C n ; Among them, D1 is the longitudinal collapse range of the actual shield tunnel, C n For similar scale.

6. A three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata according to claim 1, characterized in that: The distance between the two ends of the two oblique partition plates (15) and the two ends of the two longitudinal partition plates (9) is ≤5 cm; in the process of the oblique partition plates (15) extending obliquely upward to the top of the geotechnical model box (2), the angle between the oblique partition plates (15) and the horizontal axis is α Calculate as follows: （3）； in, φ is the internal friction angle of the soil in the model box; When the oblique partition plate (15) extends to the top of the geotechnical model box (2), the opening width of the oblique partition plate (15) is greater than the width of the top loading plate (13) and less than or equal to the width of the geotechnical model box (2).

7. A three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata according to claim 1, characterized in that: A plurality of displacement test points (11) are also arranged on the inner wall of the model shield tunnel (10) along the longitudinal direction, and a plurality of strain gauges (16) are pasted on the inner wall of the model shield tunnel (10) in the form of strain gauge flowers; a plurality of micro earth pressure boxes (12) are arranged around the outside of the model shield tunnel (10) for detecting the stratum stress around the shield tunnel under different collapsible working conditions.

8. A method for a three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata as claimed in any one of claims 1 to 7, characterized in that: The test method comprises the following steps: Step 1: Determine the shield tunnel collapse test conditions; Step 2: Determine the stiffness and quantity of the loading plate spring; Step 3: Determine the installation angle of the oblique partition plate; Step 4: Determine the similar scale and size of the model shield tunnel; Step 5: Determine the longitudinal stress of the shield tunnel in the test condition; Step 6: Determine the installation position of the longitudinal partition plate; Step 7: Install the longitudinal partition plate and adjust the water injection pipe branches to make them evenly distributed in the area to be wetted; Step 8: Fill the soil, install the model shield tunnel, and lay out displacement test points and pressure sensors; Step 9: Adjust the jacks on both sides and the top to complete the preparation work for the shield collapse test; Step 10: Loading through water injection pipes and upper jacks to achieve wetting collapse of the shield tunnel foundation and upper strata of the shield tunnel respectively; Step 11: Read the data and complete the corresponding working condition test.

9. A method for a three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata according to claim 8, characterized in that: The longitudinal stress of the shield tunnel in step 5 is achieved by adjusting the loading conditions and loading values ​​of the left jack (3), the right jack (6), the upper middle jack (8), and the upper side jack (801) as well as the filling sequence in the geotechnical model box (2). The longitudinal stress of the shield tunnel is calculated according to the following formula: （4）； （5）； （6）； in, N is the longitudinal axial force of the model shield tunnel of the test device under different collapsible conditions; F 0 is the jack thrust in actual shield tunnel construction; C n The ratio of the actual shield tunnel radius R to the model shield tunnel radius r is C n =R / r; β 1 is the attenuation coefficient of the starting section of the shield; m 1 is the number of segment rings corresponding to the end of the shield starting section; m is the number of segment rings at the location where the actual interval tunnel collapses; l g is the shield segment ring width; β 2 is the attenuation coefficient of the receiving section of the shield; m 2 is the number of segment rings corresponding to the receiving section of the shield machine; m 0 is the total number of segment rings in the actual interval shield tunnel; Ψ is the creep coefficient considering the weakening of the annular joint; The loading values ​​of the upper middle jack (8) and the upper side jack (801) are calculated as follows: （7）； in, N z is the loading value of the upper jack; σ sat is the earth pressure on the shield tunnel when the upper stratum actually collapses; C n The ratio of the actual shield tunnel radius R to the model shield tunnel radius r is C n =R / r; γ is the weight of the soil above the shield tunnel in the geotechnical model box; h is the buried depth of the model shield tunnel; A1 is the projected area of ​​the soil surrounded by two longitudinal partition plates in the geotechnical model box; G1 is the weight at the middle position of the top loading plate; σ 0 is the actual soil pressure on the shield tunnel in the initial state of the upper stratum; A2 is the projected area of ​​the soil on both sides of the A1 area; G2 is the weight on both sides of the top loading plate.

10. The method of a three-dimensional test device for determining the collapse deformation of a shield tunnel in loess strata according to claim 8, characterized in that: In step 10, the collapse of the foundation of the shield tunnel is achieved through the water injection pipe (14) pre-buried at the bottom of the shield tunnel, the collapse of the upper strata of the shield tunnel is achieved through the loading of the oblique partition plate (15) and the upper middle jack (8), and the simultaneous collapse of the foundation and upper strata of the shield tunnel is achieved through the loading of the water injection pipe (14), the oblique partition plate (15) and the upper middle jack (8).

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