Setting system for managed earth pressure

Abstract

Provided is a setting system for a managed earth pressure of a shield excavator, which sets the managed earth pressure not via assumptions or estimations, but by directly measuring the relationship between face displacement and mud pressure in a chamber. The same is a setting system for a managed earth pressure in, as a shield excavator, an earth-pressure shield 1. This setting system for a managed earth pressure comprises: a pressure gauge 22 for measuring the mud pressure in a chamber 16; an earth removal apparatus 17 as a mud pressure changing means for changing the mud pressure in the chamber 16; displacement measurement means 6, 7 for measuring the displacement of a face F; an analysis unit 41 that analyzes a deformation characteristic of the ground on the basis of the measured mud pressure and the measured displacement of the face; and a setting unit 42 for setting the managed earth pressure on the basis of the analyzed deformation characteristic.

Description

Controlled earth pressure setting system

[0001] The present invention relates to a system for controlling and setting mud pressure in a chamber used in a shield tunneling machine.

[0002] Traditionally, managing the mud pressure inside the chamber of an earth pressure shield has been essential for maintaining the stability of the face while allowing the shield to excavate without causing deformation or subsidence of the surrounding ground, and proper management can suppress displacement of the surrounding ground.

[0003] In earth pressure shield tunneling, the controlled earth pressure of the chamber is set within the following range: (passive earth pressure + water pressure) > chamber earth pressure (controlled earth pressure) > (active earth pressure + water pressure). While maintaining the chamber earth pressure within this range theoretically ensures face stability, high chamber earth pressure increases cutter torque and jack thrust, resulting in construction inefficiencies. Therefore, it is desirable to set the controlled earth pressure as low as possible within a range that ensures face stability. Therefore, the lower limit is typically set to (active earth pressure + water pressure) plus a value, and the upper limit is typically set to the lower limit (active earth pressure + water pressure + α) plus a value that takes construction fluctuations into account, or to (static earth pressure + water pressure). Note that passive earth pressure, active earth pressure, and static earth pressure refer to the effective earth pressure transmitted between soil particles and do not include pore water pressure. On the other hand, the mud pressure in the chamber refers to the total soil pressure considering the soil particles and pore water in the chamber as a whole, and includes pore water pressure.

[0004] Conventional methods for managing the mud pressure inside the chamber of an earth pressure shield include methods 1) and 2) shown below. 1) A method in which active earth pressure, passive earth pressure, and static earth pressure are calculated using an earth pressure calculation formula based on the soil constants (φ, C, γ, etc.) of the target ground estimated by a prior soil survey, the groundwater level, and the overburden load, and upper and lower limits of the mud pressure inside the chamber are set based on these values ​​(see, for example, Patent Document 1). 2) A method in which the managed earth pressure is set based on the mud pressure inside the chamber when the shield is stopped, which is measured (see, for example, Non-Patent Document 1).

[0005] JP 2012-233372 A, "Guidelines for safe and secure construction of shield tunnels," Shield Tunnel Construction Technology Review Committee, December 2021, p. 19

[0006] - Issues with management method 1): Preliminary soil surveys are usually conducted by boring, and are often conducted at intervals of about 200 m along the length of the line. Therefore, if the soil conditions change between survey points, it may not be possible to calculate the appropriate management earth pressure. Furthermore, because the calculation formula for earth pressure is theoretical and based only on a simplified two-dimensional balance of forces, it does not necessarily accurately calculate the earth pressure on the shield face ground in an actual three-dimensional state.

[0007] - Issues with management method 2): The mud pressure measured when the shield is stopped is thought to reflect the earth pressure acting on the face relatively accurately if the shield itself does not move and the cutter head does not have a face plate. However, if these conditions are not maintained, the mud pressure measured when the shield is stopped does not necessarily represent the static earth pressure of the ground or the active earth pressure plus water pressure.

[0008] Therefore, the present invention aims to provide a system for setting the controlled earth pressure of a shield tunneling machine, which sets the controlled earth pressure by directly measuring the relationship between the mud pressure in the chamber and the displacement near the face, rather than setting the controlled earth pressure based on assumptions or estimates.

[0009] In order to achieve the above-mentioned object, the controlled earth pressure setting system for a shield tunneling machine of the present invention comprises a pressure gauge that measures the mud pressure in a chamber, a mud pressure changing means that changes the mud pressure in the chamber, a displacement measuring means that measures the displacement of the face, an analysis unit that analyzes the deformation characteristics of the ground based on the measured mud pressure and the measured displacement of the face, and a setting unit that sets the controlled earth pressure based on the analyzed deformation characteristics.

[0010] In this way, the controlled earth pressure setting system for a shield tunneling machine of the present invention comprises a pressure gauge that measures mud pressure in the chamber, mud pressure changing means that changes the mud pressure in the chamber, displacement measuring means that measures the displacement of the tunneling face, an analysis unit that analyzes the deformation characteristics of the ground based on the measured mud pressure and the measured displacement of the tunneling face, and a setting unit that sets the controlled earth pressure based on the analyzed deformation characteristics.With this configuration, the controlled earth pressure can be set by directly measuring the relationship between the mud pressure in the chamber and the displacement of the tunneling face, rather than setting the controlled earth pressure based on assumptions or estimates.

[0011] 1 is a cross-sectional view illustrating the internal structure of a shield tunneling machine. 2 is a cross-sectional view illustrating the configuration of the detection jig and measurement sensor. 3 is an explanatory diagram of a face displacement measurement method using on-machine measurement. (a) is an explanatory diagram during excavation, (b) is an explanatory diagram of inserting the detection jig, and (c) is an explanatory diagram during displacement measurement. 4 is an explanatory diagram of a face displacement measurement method using pre-installation. (a) is a cross-sectional view, and (b) is a longitudinal sectional view. 5 is a flowchart illustrating the procedure for the controlled earth pressure setting system. 6 is a graph showing the relationship between mud pressure and horizontal displacement in a depressurization test. 7 is an explanatory diagram illustrating the concept of an FEM model.

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the components described in the following embodiments are merely examples and are not intended to limit the technical scope of the present invention to those. Note that, although the following description will be given using an earth pressure shield 1 as an example, the present invention can also be applied to other types of shield tunneling machines.

[0013] (Configuration of shield tunneling machine) Figure 1 is a longitudinal side view showing an embodiment of the present invention. As shown in Figure 1, the earth pressure shield 1 as a shield tunneling machine of this embodiment comprises a skin plate (shield main body cylinder) 2, a partition wall 3, a cutter head 5, a cutter rotation shaft 10, a cutter drive unit 12, a chamber 16, an earth removal device 17, a shield propulsion jack 18, mud-making material supply piping 21, a pressure gauge 22, a water pressure gauge 23, and a control unit 40 including an analysis unit 41 and a setting unit 42 arranged inside an operation chamber or the like.

[0014] The cutter head 5 has cutter spokes 51, a plurality of cutter bits 52 provided on the front surface of the cutter spokes 51, a fishtail bit 53 provided in the center of the front surface of the cutter spokes 51, and a plurality of stirring blades 54 provided on the back surface of the cutter spokes 51. The cutter head 5 is integrally attached to the cutter rotation shaft 10.

[0015] The cutter rotation shaft 10 is rotatably supported by a bearing 11 provided in the partition wall 3 and a bearing provided at the rear of a gear box 13 (described later). The cutter rotation shaft 10 is connected to a cutter drive unit 12. The cutter drive unit 12 has a gear box 13 installed on the rear side of the partition wall 3, a rotary drive source 14 connected to the gear box 13, and a reduction gear (disposed in the gear box 13; not shown) interposed between the output shaft of the rotary drive source 14 and the cutter rotation shaft 10.

[0016] The chamber 16 is formed by a space surrounded by the hood portion 2a of the skin plate 2, the partition wall 3, and the working face F. A screw conveyor, for example, is used as the earth removal device 17. The mud intake port of the earth removal device 17 is opened and installed so as to face the chamber 16. In this embodiment, the earth removal device 17 also functions as a mud pressure changing means.

[0017] Furthermore, an erector 15 for assembling the segments 90 is installed in the tail portion 2b of the skin plate 2. Furthermore, a plurality of shield propulsion jacks 18 are installed at required intervals in the circumferential direction inside the skin plate 2. In addition, a tail seal 19 is provided at the rear end of the skin plate 2.

[0018] The earth pressure shield 1 as a shield tunneling machine of this embodiment is further equipped with displacement measurement means 6, 7 that measure the displacement of the tunnel face or the area around the tunnel face. First, the on-board displacement measurement means 6 that measures the displacement of the tunnel face from inside the machine will be described using Figures 2 and 3, and then the pre-installed displacement measurement means 7, in which an instrument is installed in advance from the ground, will be described using Figure 4.

[0019] As shown in Figure 2, the on-board displacement measuring means 6 is composed of a rod-shaped detecting jig 61 that is long enough to penetrate the bulkhead 3 and allow its tip 61a to reach the working face F, a hydraulic chuck 63 that grips and releases the detecting jig 61, thereby moving and releasing the detecting jig 61 as the jacks 62, 62 extend and retract, a detecting unit 64 that is attached integrally to the end of the detecting jig 61, a guide 65 that supports the sliding movement of the detecting unit 64, a displacement sensor 66 that measures the displacement of the detecting jig 61 by measuring the distance from the detecting unit 64, a water stop device 67 for the detecting jig 61, and water stop valves 68, 68.

[0020] Therefore, when the detecting jig 61 is gripped by the hydraulic chuck 63, the detecting jig 61 retreats when the jacks 62, 62 extend, and advances when the jack 62 retracts. When the hydraulic chuck 63 is released, the detecting jig 61 is free. Therefore, in the released state (the detecting jig 61 can move freely), if the tip 61a of the detecting jig 61 is in contact with the face F, the detecting jig 61 moves (in the tunnel longitudinal direction) in accordance with the displacement of the face F. As will be described later, in the present invention, the face F protrudes slightly by reducing the mud pressure in the chamber 16, so the detecting jig 61 moves in the tunnel longitudinal direction toward the tunnel portal.

[0021] Next, using Figure 2 and Figures 3(a)-(c), the operating procedure of the displacement measuring means 6 having the detection jig 61 and displacement sensor 66 in the depressurization test of this embodiment will be explained. 1. During shield tunneling, the detection jig 61 is retracted to the partition wall 3 position (Figure 3(a)). 2. After the shield stops, the detection jig 61 is gripped by the hydraulic chuck 63 and slid to a position where the tip 61a contacts the face F (see Figure 3(b)). The jack 62 is retracted. 3. Once the tip 61a of the detection jig 61 is pressed against the face F, the hydraulic chuck 63 is released. 4. The soil removal means is operated at a slow speed, and the mud pressure in the chamber 16 is gradually reduced. 5. When the face F is displaced due to the reduced pressure, the displacement pushes the detection jig 61 into the shield (see Figure 3(c)). 6. The detection jig 61 is fitted with a measuring device (detection unit 64, displacement sensor 66) within the shield. The displacement amount is measured by the displacement sensor 66 via the detection unit 64. 7. The measurement value is sent from the displacement sensor 66 to the PC. At the same time, the pressure gauge 22 installed on the partition wall 3 measures the mud pressure in the chamber 16. 8. Using the above procedure, the relationship between the mud pressure in the chamber 16 and the displacement amount of the face F is determined. 9. The depressurization test is stopped when all or part of the transition region (including the yield point) in the face displacement has become clear. 10. For example, the soil removal means is reversed to return the mud and increase the mud pressure in the chamber 16 to its initial state. 11. The detection jig 61 is gripped by the hydraulic chuck 63, and the jack 62 is operated to pull back the detection jig 61 to the partition wall 3 position (Figure 3(a)). The jack 62 is extended.

[0022] Of the components of the on-board displacement measurement means 6 described above, the component for measuring displacement can also be replaced with pre-installed multi-stage inclinometers (or layer-by-layer settlement meters) 71-74, 75-78 that are installed in advance from the ground. That is, the pre-installed displacement measurement means 7 is configured by installing a plurality of multi-stage inclinometers 71-74, 75-78 at a predetermined depth from the ground surface, as shown in Figure 4. The installation locations preferably include, for example, in addition to the vicinity of the face at the planned tunnel excavation position, directly above it and positions shifted to the left and right (and directly above them).

[0023] In other words, it is possible to measure ground displacement by installing multi-stage inclinometers 71-74 and layer-by-layer settlement meters in advance from the ground in the cross section where the shield is scheduled to pass, temporarily halting shield excavation just before the measuring device, and conducting a decompression test. These multi-stage inclinometers 71-74 are preferably buried at predetermined intervals in the area where the shield is scheduled to pass. In this case, it is preferable to bury them at intervals narrower than the conventional boring interval (200 (m)).

[0024] In addition, the earth pressure shield 1 further includes a control unit 40. The control unit 40 is, for example, a general-purpose personal computer having a memory, a CPU, an SSD, etc. The control unit 40 sets the controlled earth pressure of the earth pressure shield 1 and controls the excavation. That is, during excavation, the earth pressure is changed by discharging mud using the shield propulsion jack 18 while the earth discharge device 17 (screw conveyor) as an earth pressure changing means is used. At the same time, the earth pressure is measured using the pressure gauge 22. Furthermore, the water pressure is measured using the water pressure gauge 23. Of course, the functions of the analysis unit 41 and the setting unit 42, which will be described later, can be executed by a control unit (computing device; personal computer) separate from the control unit 40 that controls the excavation of the earth pressure shield 1. In this sense, the control unit can also be referred to as a "computing unit."

[0025] The control unit 40 of this embodiment further functions as an analysis unit 41 that analyzes the deformation characteristics of the ground based on the measured mud pressure and the measured displacement of the excavation face (for example, horizontal displacement), and as a setting unit 42 that sets the controlled earth pressure based on the analyzed deformation characteristics. The control unit 40 is input with the mud pressure value from the pressure gauge 22, the water pressure value from the water pressure gauge 23, and the input value (displacement) from the displacement sensor 66 via a communication cable 43, and is also connected to input means such as a keyboard and a mouse. Furthermore, the control unit 40 is connected to a monitor or a separate PC for excavation management as output means. The functions of the analysis unit 41 and setting unit 42 will be explained in the control flow described next.

[0026] The control earth pressure setting system S of the present invention is made up of the pressure gauge 22, the earth removal device 17 as the mud pressure changing means, the displacement measuring means 6 (7), and the control unit 40 including the analysis unit 41 and the setting unit 42. In addition, a water pressure gauge 23 is provided.

[0027] (Operation) Next, the flow of the controlled earth pressure setting system S of this embodiment will be described with reference to Figures 5 to 7. As shown in Figure 5, the flow of the controlled earth pressure setting system S is realized by executing the following steps S1 to S14.

[0028] Processing of initial values ​​(step S1) First, an initial value of the controlled earth pressure is set (step S2) based on the initial calculated earth pressure set by a boring test or the like (step S1). Then, the shield excavates according to this initial value of the controlled earth pressure (step S3). That is, in the initial stage after the shield starts excavating (before the decompression test is conducted), the controlled earth pressure is set based on the theoretical earth pressure calculated from the soil constants obtained from the preliminary soil survey. Alternatively, the mechanical constants of the ground obtained from the preliminary soil survey are given to the 3D-FEM model, and the controlled earth pressure is set from the relationship between the earth pressure and ground displacement.

[0029] Depressurization Test (Steps S4 to S8) Next, while the shield machine is stopped, the mud pressure in the chamber is reduced (Step S4). That is, when excavation is stopped, such as when assembling the segments 90, the screw conveyor is rotated at a slow speed to gradually discharge the mud from the chamber 16 and reduce the pressure. During depressurization, the mud pressure is measured using the pressure gauge 22. At the same time, the water pressure is measured using the water pressure gauge 23. Furthermore, during depressurization, the displacement of the face F is directly measured using the displacement measuring devices 6 and 7 (Step S5). The deformation characteristics are determined based on the measured mud pressure and face displacement (e.g., horizontal displacement) (Step S6). That is, the mud pressure-face displacement relationship is plotted on a graph to determine the deformation characteristics. Once the deformation characteristics are determined, the mechanical constants of the ground are analyzed by back analysis (Step S7) (Step S8).

[0030] 3D-FEM model analysis (steps S9 to S12) Then, using the mechanical constants of the ground analyzed by the depressurization test, a 3D-FEM analysis is performed as shown in Fig. 7 (step S9). Then, this 3D-FEM model analysis predicts the impact on the surrounding ground and adjacent structures (step S10).

[0031] That is, once the deformation characteristics of the target ground are clarified by the depressurization test, the mechanical constants of the ground are calculated (Step S8) by back analysis of a ground model based on the in-situ boundary conditions such as the ground structure assumed from boring surveys and the measured water pressure (Step S7). Using the mechanical constants of the ground calculated in this way, a 3D-FEM analysis is performed (Step S9) as shown in Fig. 7.

[0032] As a result of the analysis, the presence or absence of harmful effects is determined by determining whether the amount of ground surface subsidence, etc. is below the allowable displacement amount (step S11). If harmful effects are found ("Yes" in step S11), the controlled earth pressure is changed (step S12) and the analysis is redone (steps S9 to S11). On the other hand, if harmless ("No" in step S11), the process returns to step S2, where the controlled earth pressure setting system S is executed at the next position and time.

[0033] Here, mechanical constants include, for example, Young's modulus, Poisson's ratio, angle of internal friction, and cohesion. A rational simulation of behavior can be performed by employing an FEM model based on the ground characteristics obtained based on this on-site behavior. Such a rational simulation based on on-site behavior makes it possible to predict ground surface subsidence and its impact on adjacent structures in advance and more accurately, minimizing the impact on the surrounding area or setting controlled earth pressures that correspond to regulatory values ​​for ground displacement, etc.

[0034] Analysis and Settings (Steps S13-S14) Once the ground deformation characteristics are understood, the yield point earth pressure is calculated by analysis from a mud pressure-displacement graph, as shown in Figure 6 (Step S13). That is, the analysis unit 41 of the control unit 40 determines the point where the gradient suddenly increases, regards this point as the yield point, and calculates the active earth pressure. For example, an approximate line can be calculated using the least squares method from multiple plots in the elastic region, and an approximate line can be calculated using the least squares method from multiple plots in the plastic region, and the intersection of these lines can be determined as the yield point. Alternatively, the appearance of consecutive plots that significantly deviate from the moving average can indicate that the transition region has been reached. If a 3D-FEM model analysis is required due to the presence of nearby buildings, etc. (Step S14, "Required"), the impact on the surrounding ground and adjacent structures is predicted using the 3D-FEM analysis (Step S10). If 3D-FEM model analysis is not required ("Not required" in step S14), the controlled earth pressure is reset based on the active earth pressure (step S2). Specifically, since it is necessary to ensure that the controlled earth pressure in the chamber 16 during excavation does not fall below the active earth pressure plus water pressure, the calculated active earth pressure plus water pressure is added with a plus alpha (0 to 20 kN / m ２ ) is set as the lower limit of the controlled earth pressure. On the other hand, the upper limit of the controlled earth pressure may be theoretically calculated using C and φ calculated back from the active earth pressure (yield point earth pressure), or may be set as a value that further takes into account the range of construction fluctuations in the above lower limit. On the other hand, if a 3D-FEM model analysis is required ("Required" in step S14), the 3D-FEM model analysis is performed (step S9).

[0035] In this way, the observed digital values ​​(observed values) are compared with the digital values ​​(analytical values) obtained from analysis using the model ground, and the model is constantly corrected to create a model ground that is consistent with changes in the ground as the shield face advances (the so-called "digital twin").

[0036] (Effects) Next, the effects achieved by the controlled earth pressure setting system S of this embodiment will be listed and explained.

[0037] (1) As described above, the controlled earth pressure setting system S of this embodiment is a controlled earth pressure setting system S for an earth pressure shield 1 as a shield tunneling machine, and includes a pressure gauge 22 that measures mud pressure in the chamber 16, an earth removal device 17 as mud pressure changing means that changes the mud pressure in the chamber 16, displacement measuring means 6, 7 that measure the displacement of the face F, an analysis unit 41 that analyzes the deformation characteristics of the ground based on the measured mud pressure and the measured displacement of the face, and a setting unit 42 that sets the controlled earth pressure based on the analyzed deformation characteristics. Because of this configuration, the controlled earth pressure setting system S can set the controlled earth pressure by directly measuring the relationship between the mud pressure in the chamber and the displacement of the face, rather than setting the controlled earth pressure based on assumptions or estimates.

[0038] (2) Furthermore, when the shield machine is stopped, the mud discharge device 17, which serves as a mud pressure changing means, discharges a small amount of mud, thereby reducing the mud pressure inside the chamber 16, and the active earth pressure can be found from the deformation of the ground by the analysis unit 41. Therefore, when the shield machine is stopped from excavating - for example, when the segments are being assembled - the pressure inside the chamber 16 is slightly reduced, causing the face F to move slightly towards the chamber 16, and the active earth pressure can be directly found by analyzing the yield point from the transition region in the graph showing the relationship between mud pressure and face displacement.

[0039] (3) Furthermore, by rotating the earth removal device (screw conveyor) 17, which serves as an earth pressure changing means, the mud pressure in the chamber 16 is reduced, and the analysis unit 41 determines the active earth pressure by analyzing the yield point of the ground based on the measured mud pressure and the measured displacement of the face F. Therefore, the active earth pressure can be directly determined by an extremely simple method while utilizing existing machinery and equipment.

[0040] (4) The displacement measurement means 6 also includes an exploration tool 61 that penetrates the partition wall 3 to reach the working face F, and a displacement sensor 66 that measures the displacement of the exploration tool 61 on the minehead side of the partition wall 3. Therefore, the displacement of the working face F can be measured directly from inside the machine using the exploration tool 61 and the displacement sensor 66. Therefore, the displacement sensor 66 itself is less likely to get dirty or break down. Note that the displacement measurement means 6 may be configured so as not to penetrate the partition wall 3, by installing the exploration tool, displacement sensor, etc. in the chamber 16 in front of the partition wall.

[0041] (5) Furthermore, as the displacement measurement means 7, a multi-stage inclinometer and / or layer-specific settlement meter 71-78 are installed in advance in the ground where excavation is planned, so that displacement over a wide area can be directly measured not only around the working face F but also to measurement points near the ground surface.

[0042] (6) In addition, the analysis unit 41 estimates the mechanical constants of the ground by inverse analysis based on the analyzed deformation characteristics of the ground, updates the FEM model using the estimated mechanical constants of the ground, and uses the updated FEM model to predict the impact on the surrounding ground and / or structures. Therefore, although not completely in real time, by updating the FEM model at intervals that are close to real time and much shorter than conventional methods, the characteristics of the ground can be made much closer to the actual characteristics. As a result, predictions and impact assessments using the FEM model can be achieved with extremely high accuracy.

[0043] Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes that do not deviate from the gist of the present invention are included in the present invention.

[0044] For example, in the embodiment, an example has been described in which the detection jig 61 penetrates the bulkhead 3 and reaches the working face F, but this is not limited to this, and the detection jig 61 does not have to penetrate the bulkhead 3 as long as it is configured to be able to move forward and backward within the chamber 16. Also, in the embodiment, the water pressure gauge 23 is attached to the bulkhead 3, but this is not limited to this, and it may be attached to, for example, the skin plate 2, the cutter head 5, etc.

[0045] In addition, in the embodiment, the control flow is divided into steps depending on whether 3D-FEM model analysis is required or not, but this is not limited to this, and it is of course possible to configure the control flow so that 3D-FEM model analysis is always performed.

[0046] 1: Earth pressure shield 2: Skin plate 2a: Hood section 2b: Tail section 3: Bulkhead 5: Cutter head 6: Displacement measuring means 7: Displacement measuring means 10: Cutter rotating shaft 11: Bearing 12: Cutter drive section 13: Gearbox 14: Rotation drive source 15: Erector 16: Chamber 17: Soil removal device 18: Shield propulsion jack 19: Tail seal 21: Mud supply pipe 22: Pressure gauge 23: Water pressure gauge 40: Control section 41: Analysis section 42: Setting section 43: Communication cable 51: Cutter spoke 52: Cutter bit 53: Fishtail bit 54: Mixing blade 61: Inspection jig 61a: Tip 62: Jack 63 : Hydraulic chuck 64 : Detector 65 : Guide 66 : Displacement sensor 67 : Water stop device 68 : Valve 71-78 : Multi-stage inclinometer (or layer-by-layer settlement meter) 90 : Segment S : Control earth pressure setting system F : Face

Claims

1. A controlled earth pressure setting system for a shield tunneling machine comprising: a pressure gauge which measures the mud pressure in a chamber; a mud pressure changing means which changes the mud pressure in the chamber; a displacement measuring means which measures the displacement of the face towards the tunnel entrance in the longitudinal direction of the tunnel; an analysis unit which determines the yield point earth pressure from a mud pressure-displacement graph based on the mud pressure during the decompression process measured when excavation is stopped and the displacement of the face measured corresponding to that process; and a setting unit which sets the controlled earth pressure based on the determined yield point earth pressure.

2. A controlled earth pressure setting system for a shield tunneling machine comprising: a pressure gauge which measures the mud pressure in a chamber; a mud pressure changing means which changes the mud pressure in the chamber; a displacement measuring means which measures the displacement of the face; an analysis unit which analyzes the deformation characteristics of the ground based on the measured mud pressure and the measured displacement of the face; and a setting unit which sets the controlled earth pressure based on the analyzed deformation characteristics, wherein when the shield tunneling machine is stopped, the mud pressure changing means reduces the mud pressure in the chamber, so that the analysis unit can determine the active earth pressure from the deformation of the ground.

3. A system for setting controlled earth pressure as described in claim 2, wherein the mud pressure in the chamber is reduced by rotating a screw conveyor as the mud pressure changing means, and the analysis unit determines the active earth pressure by analyzing the yield point of the ground based on the measured mud pressure and the measured displacement of the face.

4. A system for setting controlled earth pressure as described in any one of claims 1 to 3, comprising, as the displacement measuring means, an exploration tool that reaches the face, and a displacement sensor that measures the displacement of the exploration tool.

5. A system for setting controlled earth pressure as described in any one of claims 1 to 3, in which a multi-stage inclinometer and / or a layer-by-layer settlement meter are installed in advance in the ground where excavation is planned as the displacement measuring means.

6. A system for setting controlled earth pressure as described in claim 4, wherein the analysis unit estimates the mechanical constants of the ground by inverse analysis based on the analyzed deformation characteristics of the ground, updates the FEM model using the mechanical constants of the ground, and predicts the impact on the surrounding ground and / or structures using the updated FEM model.

7. A system for setting controlled earth pressure as described in claim 5, wherein the analysis unit estimates the mechanical constants of the ground by inverse analysis based on the analyzed deformation characteristics of the ground, updates the FEM model using the mechanical constants of the ground, and predicts the impact on the surrounding ground and / or structures using the updated FEM model.

Images