JP7426964B2 - How to design a transverse cross section of a tunnel box - Google Patents

Description

The present invention relates to a method for designing a transverse cross section of a tunnel box.

In the propulsion method and the shield method, multiple propulsion boxes are connected via ring joints (the end of one propulsion box is inserted into the end of the other propulsion box, or the end of the other propulsion box is connected by bolts, etc.). Alternatively, by connecting multiple shield boxes to each other via ring joints (bolted joints, etc.), tunnel boxes such as propulsion boxes and shield boxes can be built underground. Construction. Hereinafter, in this specification, the propulsion box and the shield box will be collectively referred to as a tunnel box, and the propulsion box group and the shield box group will be collectively referred to as a tunnel box group.
There are various vertical alignments of tunnel box groups, such as straight lines, circular lines, curved lines with multiple curvatures, and mixed straight and curved lines. In a tunnel box group having a section (curvilinear shape), a jack thrust acts from an adjacent tunnel box, and a ground reaction force acts on the tunnel box due to this jack thrust.
Regarding the above-mentioned tunnel box group with the curved section, in the design of the transverse cross section of the conventional tunnel box, a uniformly distributed load that balances the normal component of the arc of the curved section of the jack thrust is applied to the ground reaction. A method of calculating the cross-sectional force when the ground reaction force caused by the jack thrust is applied is applied by uniformly loading a beam that simulates the bottom plate that makes up the cross-direction beam model of the tunnel box. has been done. However, with this method of applying a uniformly distributed load to the beam model as a ground reaction force, the jack thrust is not applied to the position where the jack thrust actually acts on the ring joint surface of the tunnel box. Therefore, it is difficult to say that the cross-sectional force has been calculated with high accuracy.

Here, in Patent Document 1, when constructing a tunnel in soft ground using the shield construction method or the propulsion construction method, there is a method for determining whether or not to install a reaction wall at a sharply curved part of the tunnel. A method for determining necessity has been proposed. Specifically, this method determines whether or not it is necessary to install a reaction wall by comparing the ground reaction force of the tunnel lining calculated through structural analysis simulating a sharp curve with the strength of the original ground. This is a method of determining whether or not it is necessary to increase the axial rigidity of the tunnel to reduce the ground reaction force when it is determined that the reaction force is greater than the original ground strength, making it unnecessary to install a reaction wall.

Japanese Patent Application Publication No. 2002-194989

According to the method for determining the necessity of installing a reaction wall described in Patent Document 1, it is possible to provide a method for determining the necessity of installing a reaction wall corresponding to the actual situation. However, as mentioned above, in the cross-direction design of tunnel boxes constituting a tunnel box group having at least a curved section, the jack thrust is applied to the position where the jack thrust actually acts on the ring joint surface of the tunnel box. This does not solve the problem of not being able to calculate the cross-sectional force with high accuracy based on the fact that no load is applied.

The present invention provides a method for designing a transverse section of a tunnel box, which can realize highly accurate calculation of section force in the transverse direction design of a tunnel box constituting a group of tunnel boxes having at least a curved section. The purpose is to

In order to achieve the above object, one aspect of the method for designing a cross section of a tunnel box according to the present invention is as follows:
While receiving the jack thrust from the propulsion jack of the propulsion device or the excavator, the transverse cross section of the tunnel box, which is formed by a plurality of tunnel boxes and has at least a curved section, is perpendicular to the longitudinal direction of the tunnel box group. A design method,
A first normal load, which is a normal component of the jack thrust in the curve section, or a second ground reaction force, which is a ground reaction force received from the ground in the normal direction as a reaction force to the jack thrust in the curve section. A step of calculating at least one of the normal direction load;
Step B of creating a beam model of the cross section of the tunnel box, and attaching a ground spring to the beam model of the cross section to create a cross section beam model;
C step of calculating a first cross-sectional force caused by the jack thrust by applying the first normal direction load or the second normal direction load to the transverse beam model. It is characterized by

According to this aspect, the first normal load is the normal component of the jack thrust in the curve section, or the ground reaction force received from the ground in the normal direction as a reaction force of the jack thrust in the curve section. By calculating at least one of the second normal direction load and applying the first normal direction load or the second normal direction load to the transverse beam model, the first cross-sectional force caused by the jack thrust is calculated. By calculating, it is possible to appropriately reflect the normal load caused by the jack thrust acting on the ring joint surface of the tunnel box, and it is possible to calculate the cross-sectional force with high accuracy. In this specification, the first normal direction load and the second normal direction load applied to the transverse beam model are collectively referred to as a normal direction load.
Here, in step C, the method of applying the normal load to the transverse beam model is to apply it as a concentrated load to the ring joint position, or to apply it as a distributed load around the entire circumference of the transverse beam model. etc.

Further, in another aspect of the method for designing a cross section of a tunnel box according to the present invention,
The method for calculating the first normal direction load is as follows:
The required jack thrust is calculated by adding the tip resistance force acting on the cutter head of the tunneling machine and the circumferential surface resistance force applied to the circumferential surface of the tunnel box group, and when the curved section is within the vertical plane. calculates the necessary jack thrust by further adding the dead weight resistance of the tunnel box group and the excavator,
Calculating the jack thrust acting on each tunnel box constituting the tunnel box group based on the required jack thrust,
The first normal direction load is calculated based on the jack thrust and the bending angle of the tunnel box in the longitudinal direction.

According to this aspect, after calculating the required jack thrust (total jack thrust) necessary to propel the tunnel box group, the jack thrust acting on each tunnel box constituting the tunnel box group is calculated. By calculating the first normal load based on the jack thrust and the bending angle in the longitudinal direction of the tunnel box, it is possible to efficiently calculate the normal load acting on the tunnel box.
Here, as a method of calculating the first normal direction load, the method of adding the tip resistance force and the peripheral surface resistance force is based on the guidelines such as "Guidelines and explanations of sewerage propulsion method - 2010 edition - Japan Sewage Works Association", etc. This is based on the thrust calculation formula described in this guideline, and in the case of curved sections in the vertical plane, the addition of the self-weight resistance of the tunnel box group and the excavation machine is a modification of the thrust calculation formula described in this guideline. It is something. The required jack thrust, which is obtained by adding the tip resistance force, peripheral surface resistance force, and self-weight resistance force as necessary, is multiplied by a predetermined safety factor, for example, to increase the required jack thrust force, and the required jack thrust after the addition is calculated. The jack thrust acting on each tunnel box may be calculated based on the thrust.

Further, in another aspect of the method for designing a cross section of a tunnel box according to the present invention,
The method for calculating the second normal direction load is as follows:
In a computer, a curve-containing beam model having equivalent stiffness or a curve-containing beam model formed by connecting beam models of adjacent tunnel boxes with a rotation spring is created for the tunnel box group, and the curve-containing A ground spring is attached to the beam model to create a longitudinal beam model.
The method is characterized in that the jack thrust is applied to the longitudinal beam model, and the second normal load, which is a ground reaction force generated on the longitudinal beam model, is calculated.

According to this aspect, a jack thrust is applied to a longitudinal beam model formed by a curve-containing beam model and a ground spring, and the second normal direction load, which is a ground reaction force, is calculated. The normal load acting on the box can be calculated with high accuracy.
Here, in the case where the curved section has a single circular longitudinal alignment, the tunnel box group is a longitudinal beam model at each construction stage, for example, at the 10R stage in which 10 tunnel boxes 1 ring (1R) are advanced. , longitudinal beam models at various construction stages, such as a longitudinal beam model at the 20R stage, a circular longitudinal beam model propagated all around, etc., were created, and each time the longitudinal direction of the tunnel box was Section forces are calculated. Here, each tunnel box that makes up the tunnel box group will have a different section force calculated depending on the location, but at the design stage, the specifications of the tunnel box are determined based on the most severe section force. be done.
In addition, the jack thrust includes the jack thrust by the main push jack of the main push device in the propulsion method, the jack thrust by the middle push jack of the intermediate push device in addition to the main push jack, and the jack thrust by the propulsion jack equipped on the excavator in both the propulsion method and the shield method. Examples include jack thrust due to For example, in a propulsion method that uses an excavator equipped with a propulsion jack, the jack thrust from the main push jack is loaded on one end of the longitudinal beam model (starting shaft position), and the jack thrust from the main push jack is loaded on the other end of the longitudinal beam model (excavator position). ) is loaded with jack thrust by the propulsion jack provided in the excavator, and if an intermediate push device is present in the tunnel box group, the jack thrust by the intermediate push jack is loaded at that position.
Furthermore, there are various mounting forms for the ground spring, such as a form in which the ground spring is attached to each tunnel box, and a form in which it is attached to each 10R. Furthermore, it is desirable that the soil properties be appropriately reflected in the soil springs for each location (each soil layer), and the N value, internal friction angle of the soil, adhesion force (viscosity), etc. for each soil layer are evaluated and the soil It is better to have a spring set.

Further, in another aspect of the method for designing a cross section of a tunnel box according to the present invention,
In the step C,
By dividing the first normal load or the second normal load calculated in step A by the number of ring joints provided on the ring joint surface that is the transverse cross section, Find the concentrated load per joint and apply it to each ring joint position.
Alternatively, a distributed load is calculated by dividing the first normal direction load or the second normal direction load calculated in step A by the circumference of the ring joint surface that is the transverse cross section, The method is characterized in that the distributed load is applied to the ring joint surface.

According to this aspect, by loading a suitable load of a concentrated load based on a normal direction load or a distributed load on a transverse direction beam model according to the arrangement of the ring joint on the ring joint surface, the tunnel box is The position of action of the jack thrust on the ring joint surface of the body can be appropriately reflected, making it possible to calculate the cross-sectional force with high accuracy.
For example, if a plurality of ring joint positions are relatively uneven on the ring joint surface, it is preferable to apply a concentrated load per ring joint to each ring joint position in the transverse beam model. By applying a normal load (concentrated load) per ring joint to each ring joint position, the actual phenomenon in which jack thrust acts from each ring joint position can be reproduced as faithfully as possible. It becomes possible to calculate the cross-sectional force with even higher accuracy.
On the other hand, when a plurality of ring joint positions are relatively uniform on the ring joint surface, it is preferable to apply a distributed load to the entire circumference (entire area) of the transverse beam model.

Further, in another aspect of the method for designing a cross section of a tunnel box according to the present invention,
When the second normal direction load is used in the C step, the C step is characterized in that the maximum ground reaction force is extracted and used from among the plurality of calculated ground reaction forces.

According to this aspect, when using the second normal direction load in the C process, by extracting the maximum ground reaction force from among the plurality of calculated ground reaction forces and loading it on the transverse direction beam model, The transverse section of the tunnel box can be designed based on the safest design.

Further, another aspect of the method for designing a cross section of a tunnel box according to the present invention is as follows:
A step D of calculating a second cross-sectional force caused by the earth pressure or earth water pressure by applying earth pressure or earth water pressure to the beam model of the transverse cross section;
Calculate a superimposed cross-sectional force by superimposing the first cross-sectional force and the second cross-sectional force calculated in the C step and the D step, and check the cross-sectional force of the transverse cross section based on the superimposed cross-sectional force. The method is characterized by further comprising a step E of performing.

According to this aspect, the first cross-sectional force is calculated when a normal load due to the jack thrust acts on the transverse beam model, and the ground spring is calculated from the beam model of the transverse cross section (the ground spring is Calculate the second section force when earth pressure or earth water pressure acts on the removed beam model), and check the section force of the transverse section based on the superimposed section force obtained by superimposing both section forces. This makes it possible to calculate the cross-sectional force with even higher accuracy. In addition, process C and process D should be performed simultaneously, in other words, the cross-sectional force should be calculated by simultaneously applying the normal load caused by the jack thrust and the earth pressure or earth water pressure to the transverse beam model. This calculation method is also included in this aspect.

According to the method for designing a cross section of a tunnel box according to the present invention, it is possible to calculate a cross-sectional force with high accuracy in designing a cross section of a tunnel box constituting a group of tunnel boxes having at least a curved section.

It is a flow chart which shows an example of the design method of the transverse direction cross section of the tunnel box concerning an embodiment. FIG. 2 is a schematic diagram showing a state in which a group of tunnel boxes having a single circular vertical line is being propelled in a vertical plane by a propulsion method. FIG. 2 is a schematic diagram showing a state in which the excavator creates an over-excavation section and propels the tunnel box group while filling the over-excavation section with slipping material in a curved section. It is a schematic diagram explaining the calculation method of the first normal direction load. It is a schematic diagram explaining the calculation method of the second normal direction load, Comprising: It is a figure explaining an example of a longitudinal direction beam model. It is a schematic diagram explaining the external force which acts on one tunnel box in the process of propulsion. FIG. 2 is a front view showing an example of a cross section of a tunnel box. FIG. 6 is a schematic diagram illustrating an example of a transverse beam model and explaining a state in which a normal load due to a jack thrust is applied at each ring joint position on a ring joint surface. It is a schematic diagram which shows an example of the beam model of a transverse direction cross section, and explains the state where earth water pressure is loaded.

Hereinafter, a method for designing a transverse cross section of a tunnel box according to an embodiment will be described with reference to the accompanying drawings. Note that in this specification and the drawings, substantially the same constituent elements may be given the same reference numerals to omit redundant explanation.

[Design method of transverse cross section of tunnel box according to embodiment]
An example of a method for designing a transverse cross section of a tunnel box according to an embodiment will be described with reference to FIGS. 1 to 9. Here, FIG. 1 is a flowchart illustrating an example of a method for designing a transverse cross section of a tunnel box according to an embodiment. Furthermore, Fig. 2 is a schematic diagram showing a state in which a group of tunnel boxes having a single-circle longitudinal alignment is propelled in a vertical plane by the propulsion method, and Fig. 3 shows a state in which an excavator is used in a curved section. It is a schematic diagram which shows the state which a tunnel box group is propelled while creating the excavation part and filling the remaining excavation part with lubricating material. Further, FIG. 4 is a schematic diagram illustrating the method for calculating the first normal direction load, and FIG. 5 is a schematic diagram illustrating the method for calculating the second normal direction load, in which It is a figure explaining an example. Further, FIG. 6 is a schematic diagram illustrating an external force acting on one tunnel box during the propulsion process, and FIG. 7 is a front view showing an example of a transverse cross section of the tunnel box. Furthermore, FIG. 8 is a schematic diagram showing an example of a transverse beam model and illustrating a state in which a normal load due to jack thrust is applied at each ring joint position on the ring joint surface, and FIG. , is a schematic diagram showing an example of a beam model in a cross section in the transverse direction and explaining a state in which soil water pressure is applied.

In the illustrated example of the method for designing a cross section of a tunnel box, the vertical alignment of the tunnel box group to be designed is a single circle in the vertical plane, and the entire section is a curved section. In addition to the illustrated example, the vertical alignment of the tunnel box group that makes up the tunnel body can be of various types, such as a vertical alignment with multiple curvatures in the vertical or horizontal plane, or a vertical alignment with a mixture of curved sections and straight sections. A group of linear tunnel boxes can be a design target.

As shown in FIG. 1, the method for designing a tunnel box in the transverse direction according to the embodiment includes steps A to E.

The A process mainly includes a process of setting input conditions and a process of calculating a first normal direction load or a second normal direction load. The first normal load is the normal component of the jack thrust in the curved section, and the second normal load is the normal component of the ground that is received from the ground in the normal direction as a reaction force to the jack thrust in the curved section. It is a reaction force. Both normal loads are loads resulting from the normal component of the jack thrust acting on the tunnel box, so they are referred to as normal loads.

As explained in detail below, the method for calculating the first normal direction load is to use the thrust calculation formula described in the publicly known guidelines, use a modified thrust calculation formula that is a modified version of this thrust calculation formula, and also use a curve The first normal load is calculated based on the bending angle of each tunnel box in the longitudinal direction in the section. On the other hand, the method for calculating the load in the second normal direction is to create a longitudinal beam model (analytical model) in a computer and perform an analysis to load the jack thrust on the beam model. Calculate the load (ground reaction force).

On the other hand, the B process includes a process of creating a transverse beam model (analytical model). Step C includes a step of performing a first analysis in the transverse direction to calculate the first section force based on the first normal direction load or the second normal direction load using the created transverse direction beam model. , D process includes a step of performing a second transverse analysis to calculate a second section force based on soil water pressure using a beam model obtained by removing the ground spring from the transverse beam model.

Finally, step E includes a step of performing stress level verification based on the cross-sectional force obtained by superimposing the first cross-sectional force and the second cross-sectional force.

In setting the input conditions in step A, set the specifications of the tunnel box, and determine the vertical alignment of the tunnel box group (in the case of a single circle, its diameter, and in the case of multiple curvatures, each curvature and its alignment, etc.). Set up and model the soil layer that the tunnel box group passes through. When modeling soil layers, we calculate the properties of each soil layer (sandy layer, clay layer, gravel layer, etc.), N value, unit volume weight of the ground, internal friction angle, and Set physical properties such as adhesion force.

The example shown in FIG. 2 is an example in which a tunnel box group 20 (circumferential tunnel) having a single-circular vertical line shape with a radius r is constructed using the propulsion method in a vertical plane. As shown in Figure 2, when connecting and widening the main line tunnel HT (e.g. main line shield tunnel) that has already been constructed underground in underground G with the lamp tunnel RT (e.g. lamp shield tunnel) located on the side thereof, , a vertical shaft T will be constructed using the ramp tunnel RT and extending vertically below it. Note that this vertical shaft may extend diagonally downward instead of vertically.

A starting pedestal R is installed below the shaft T built to a predetermined depth, and a starting pedestal 30 equipped with a starting pedestal jack is installed on the starting pedestal R. The excavator 10 and the tunnel box 21 are suspended from the lamp tunnel RT at any time, the excavator 10 is made to dig underground, and a plurality of tunnel boxes 21 are sequentially arranged behind it, and by the jack thrust of the main push jack 30. , propels a tunnel box group 20 formed by the excavator 10 and a plurality of tunnel boxes 21.

The illustrated example of the excavator 10 includes a front body 11 and a rear body 12, and a propulsion jack (not shown) between the two (a jack that not only propels the excavator itself but also controls the direction of the excavator). There is. The front view shape of the excavator 10 is, for example, a horizontally long rectangle, and a plurality of cutter heads 13 are disposed on the front surface thereof, for example. Each cutter head 13 has a built-in copy cutter that can be moved in and out from the side. When creating an over-excavation area, the copy cutter protrudes outward from each cutter head 13 and rotates as the cutter head 13 rotates. A copy cutter that rotates accordingly creates an over-dig area. At this time, the size of the overcut portion can be adjusted as desired by adjusting the overhang length of the copy cutter.

As described above, the tunnel box 21 connected to the rear of the excavator 10, which has a rectangular shape when viewed from the front, is made of a steel shell having the same shape as the excavator 10 when viewed from the front, as shown in FIG.

Returning to FIG. 2, face pressure S acts on the cutter head 13 of the excavator 10 from the front. In addition, since the propulsion is in a vertical plane as shown in the illustrated example, an axial component force W1 of its own weight acts on the excavator 10, and an axial component force W2 of its own weight acts on each tunnel box 21. do.

A peripheral surface resistance force F1 with respect to the surrounding ground G acts on the tunnel box group 20 being propelled, and furthermore, a frictional resistance force F2 due to a ground reaction force Q due to curved construction acts on the tunnel box group 20. Here, since the front excavator 10 and the tunnel box group 20 are propelled by the jack thrust P1 acting from the main push jack 30 in the shaft T, the acting jack increases as you move forward of the tunnel box group 20. Thrust forces P2, P3, and P4 gradually become smaller. Since the ground reaction force Q associated with curved construction is a reaction force caused by this jack thrust P, as shown in FIG. It has a tendency to gradually become smaller.

In this way, in the propulsion method that follows the curved line in the vertical plane in the illustrated example, the face pressure S acting on the excavator 10, the axial component force W1 of its own weight acting on the excavator 10, and the axial component force W1 acting on each tunnel box 21. The excavation is carried out by a jack thrust P that is greater than the sum of the axial component force W2 of its own weight, the circumferential surface resistance force F1 between it and the surrounding ground G, and the frictional resistance force F2 caused by the ground reaction force Q associated with curved construction. Propulsion of the aircraft 10 and the tunnel box group 20 is realized. For example, in construction in a horizontal plane, the axial component force W1 of the self-weight acting on the excavator 10 and the axial component force W2 of the self-weight acting on each tunnel box 21 are used to calculate the jack thrust of the main push jack 30. becomes unnecessary.

If the jack thrust of the main push jack 30 is insufficient, one or more intermediate push jacks are disposed between the tunnel box groups 20 to compensate for the insufficient jack thrust.

When setting the jack thrust of the main push jack 30 and the jack thrust of the main push jack 30 and an intermediate push jack provided as necessary, the necessary jack thrust changes from time to time during the process of propulsion of the tunnel box group 20. The necessary jack thrust is set according to each stage, such as the stage when the number of tunnel box groups 20 reaches 10 (10R), the stage until 20R, the final stage when the excavator 10 reaches the shaft T, etc.

As shown in FIG. 3, the copy cutter 14 protrudes from the side of the cutter head 13 (here, for ease of explanation, the figure is shown as having only one cutter head 13), and the copy cutter 14 protrudes from the side of the cutter head During the process in which the excavator 10 excavates in the excavation direction along the planned vertical alignment L1 while rotating, an over-excavation part 25 with a predetermined width t1 is created on the side of the excavator 10 and the following tunnel box group 20. Then, the over-digging portion 25 is filled with slipping material 28 from the excavator 10. A rectangular frame-shaped over-digging section 25 having a width t1 is created around the excavator 10 which is rectangular in front view. In the illustrated example, the width t1 of the extra digging portion 25 is set according to the radius r of the single circle, etc.

FIG. 3 shows a state in which the excavator 10 is excavating along the planned vertical alignment L1 and the tunnel box group 20 is being propelled. There is a line L2, and on the outside in the radial direction there is an outer line L3 of the extra digging portion 25. That is, FIG. 3 shows a state in which the excavator 10 is not meandering. Further, the width t1 is the design surplus amount under the input conditions.

Here, a method for calculating the first normal direction load in step A will be explained. Based on the thrust force calculation formula described in "Guidelines and Explanations of Sewer Propulsion Methods - 2010 Edition - Japan Sewage Works Association" (hereinafter referred to as the "Sewerage Guidelines"), the required jack thrust can be expressed by the following formula (X) .

In addition, in propulsion construction in a vertical plane as shown in the example, it is necessary to take into account the self-weight resistance of the excavator 10 and the tunnel box group 20, so the required jack thrust in this case is calculated using the above formula (X ) can be expressed by the following formula (Y) with modification.

Furthermore, in propulsion construction with a curved section as shown in the illustrated example, the required jack thrust can be expressed by the following equation (Z). In addition, since formula (Z) is the formula for calculating the required jack thrust during propulsion construction with a curved section in the horizontal plane, as stated in the sewerage guidelines, in more detail, the self-weight resistance force of the above formula (Y) It is necessary to add (take into consideration), but here we will introduce the formula described in the sewerage guidelines.

As shown in FIG. 4, by calculating the jack thrust acting on each tunnel box from the required jack thrust (for example, F1), and calculating the normal component force T1 of this jack thrust by F1 × sin α, The first normal load acting on the tunnel box can be determined.

Next, a method for calculating the second normal direction load in step A will be explained. As shown in FIG. 5, the tunnel box group 20 is modeled into a curve-containing beam model BM1 having equivalent rigidity in a computer. In this modeling, although not shown, a curved beam model may be created by connecting beam models of adjacent tunnel boxes 21 with rotating springs.

A longitudinal beam model M1 is created by attaching a ground spring JM1 to the curve-containing beam model BM1. The ground spring JM1 may be attached to each tunnel box position in the curve-containing beam model BM1, or may be attached at every 10R, for example.

The ground spring JM1 has a normal ground spring JMa in the normal direction of the circumferential tunnel with a radius r, and a tangential ground spring JMb in the tangential direction, and both ground springs are simulated by, for example, a connector element. Also, although not shown, one end BM1' (or its vicinity) of the curved beam model BM1 to which the jack thrust P from the main jack is loaded, and the other end BM1' of the curved beam model BM1 that has reached the shaft. Attach a restraining spring to each (or its vicinity).

In the computer, a curve-containing beam model BM1 is created for each construction stage, and ground springs JM1 having a normal direction ground spring JMa and a tangential direction ground spring JMb are attached to multiple positions of the curve-containing beam model BM1. A longitudinal beam model M1 (analytical model) is created.

As shown in FIG. 5, the tunnel box group 20 is constructed by performing a longitudinal analysis on the longitudinal beam model M1 in which a jack thrust by a propulsion jack such as the main pusher jack 30 is set and loaded. The cross-sectional force in the longitudinal direction of each tunnel box 21 and the ground reaction force Q in the longitudinal direction of the tunnel box group 20 are calculated. This cross-sectional force includes bending moment, shear force, and axial force (compressive force and tensile force in the longitudinal direction). In the model illustrated in which all sections are curved sections, the calculated ground reaction force Q gradually changes in the longitudinal direction, as shown in FIG.

For example, in the initial stage, as explained with reference to FIG. 2, the jack thrust of the main push jack 30 is processed into a jack thrust capable of propelling the excavator 10 and the tunnel box group 20, and longitudinal direction analysis is performed. However, if the axial force at the position of the leading excavator 10 among the axial forces included in the cross-sectional force in the longitudinal direction is a compressive force equivalent to or more than the face pressure S, it is determined that the set jack thrust is large. Then, the longitudinal direction analysis is repeated while changing the jack thrust until the compression force equivalent to the face pressure S is achieved, and the required jack thrust is set.

On the other hand, if the longitudinal analysis results show that the axial force at the position of the excavator 10 is smaller than the compressive force equivalent to the face pressure S, it is determined that the set jack thrust is insufficient, and the jack thrust is increased. The required jack thrust force is set by repeating the longitudinal analysis described above until the axial force becomes a compressive force equivalent to the face pressure S.

By longitudinal analysis, calculate the ground reaction force Q acting on the tunnel box group, identify the maximum ground reaction force Qmax among the calculated ground reaction forces Q, and calculate this ground reaction force Qmax using the second method. It is preferable to use a linear load.

Here, as shown in FIG. 6, focusing on one tunnel box 21n (the n-th tunnel box from the excavator 10 side) constituting the tunnel box group 20, the force in the axial direction (longitudinal direction) is The balance of the force in the direction perpendicular to the axis is established.

The balance of forces in the axial direction is (Load transmitted to adjacent steel shells Pn) = (Axial component of load (jack thrust) transmitted from adjacent steel shells Pn-1v) - (Surface resistance force F1n) - (Frictional resistance force F2n due to ground reaction force) - (axial component W2v of steel shell weight).

On the other hand, the balance of forces in the direction perpendicular to the axis is (ground reaction force Q (suppressing outward deformation)) = (component force in the direction perpendicular to the axis Pn - 1h of the load transmitted from the adjacent steel shell (jack thrust)) Become.

As described above, setting the input conditions and calculating the first normal direction load or the second normal direction load become the A process.

Next, a transverse beam model (analytical model) is created. In this example, a tunnel box 21 having a horizontally long rectangular cross-sectional shape shown in FIG. 7 is modeled. Here, FIG. 7 shows the front view shape of the tunnel box 21 and shows the ring joint surface 22. Rigidity is provided by two internal partition walls, and the ring joint surface 22 is shown in a front view. A plurality of ring joints 23 are provided. This ring joint 23 is constituted by, for example, a ring joint bolt or the like, and the jack thrust is transmitted between the other adjacent tunnel box body via the plurality of ring joints 23.

The tunnel box 21 having the shape of the transverse cross section shown in FIG. 7 is modeled as a transverse beam model M2 shown in FIG. 8. Here, the transverse beam model M2 is created by attaching a ground spring JM2 to a beam model BM2 whose transverse cross section follows the linear line of the cross section of the tunnel box 21. Although the ground spring JM2 in the illustrated example includes only a straight spring, the ground spring JM2 may include both a straight spring and a shear spring perpendicular to the straight spring (the above is Step B).

Next, a first transverse analysis is performed in which a normal load (a first normal load or a second normal load) is applied to the transverse beam model M2. This first analysis in the transverse direction is based on the maximum ground reaction force Qmax (second normal direction load) calculated and identified (extracted) in the longitudinal analysis in process A, and the calculated required jack thrust. A first normal load determined by the jack thrust acting on the tunnel box and the bending angle is applied to the transverse beam model M2.

Figure 8 shows the transverse beam model M2, and also shows the jack thrust calculated from the second normal load, which is the ground reaction force, at each ring joint position (dot position in the beam model) set on the ring joint surface. This shows a state in which a normal component force of .

That is, by dividing the maximum ground reaction force Qmax by the number of ring joints 23 provided on the ring joint surface that is the transverse cross section, the concentrated load, which is the normal component of the jack thrust per ring joint, can be calculated. v is determined, and a concentrated load v, which is the normal component of the jack thrust per ring joint, is applied to each ring joint position.

Alternatively, the distributed load may be calculated by dividing the normal load by the circumference of the ring joint surface shown in FIG. 7, and the distributed load may be applied to the entire ring joint surface. . In particular, since the ring joint positions in the illustrated example are relatively evenly arranged, highly accurate analysis results can be obtained even with a method in which a distributed load is determined and the load is applied to the entire ring joint surface.

In this way, the normal load calculated in the longitudinal direction analysis is divided by the number of ring joints 23 to find the concentrated load v, which is the normal component of the jack thrust per ring joint, and the concentrated load v is determined at each ring joint position. By applying a load to the ring joint, it is possible to simulate as faithfully as possible the state in which the jack thrust is actually acting on each ring joint position, and it is possible to calculate the cross-sectional force (first cross-sectional force) in the transverse cross section with high accuracy. becomes possible. Further, by using the maximum ground reaction force Qmax as the second normal direction load, a safer design can be realized.

Through the first analysis in the transverse direction, the ground reaction force that can actually occur is output to the ground spring JM2, which increases the reaction force under the side walls and bulkheads as shown in Figure 8 (hereinafter referred to as C process).

Next, as shown in Fig. 9, a second transversal analysis is performed in which soil water pressure is applied to the transverse beam model M2', which consists of only the beam model BM2 in the transverse cross section (without the ground spring JM2). implement. In this second transverse analysis, the cross-sectional force in the transverse cross section (the 2 section force) (hereinafter, step D).

Next, superimpose the first section force calculated in step C and the second section force calculated in step D to calculate the superimposed section force, and use this superimposed section force to A force check (stress degree check) is carried out (the above is Step E). Note that the C step and the D step may be performed simultaneously. Specifically, in the beam model BM2 of the transverse cross section, a concentrated load v, which is the normal component of the jack thrust per ring joint, is applied to each ring joint position, and at the same time, the ceiling vertical earth water pressure U1 is The cross-sectional force may be calculated by loading the bottom plate vertical earth water pressure U3 and the left and right earth water pressures U2.

By checking the stress level, we identified the specifications (strength, bearing capacity) of the tunnel box originally set, the bearing capacity of the ground, and the necessary jack thrust, and determined whether the tunnel box did not have enough bearing capacity or the ground did not have enough bearing capacity. If so, return to the input condition settings, change the specifications of the tunnel box (including changing the cross section of the tunnel box), review the vertical alignment, consider soil improvement to improve soil bearing capacity, etc. We re-created the analytical models such as the directional beam model and the transverse beam model, re-performed the longitudinal analysis, the first analysis in the transverse direction, the second analysis in the transverse direction, etc., and checked the stress level again. Specifications that satisfy the bearing capacity of both the structure and the ground are determined, and a construction plan is created.

According to the illustrated cross-sectional design method of a tunnel box, in the cross-sectional design of the tunnel box 21 constituting the tunnel box group 20 having at least a curved section, the ring joint surface 22 of the tunnel box 21 is By appropriately reflecting the action position of the jack thrust and loading the jack thrust at each action position, it is possible to calculate the cross-sectional force with high accuracy, realizing a rational design of the transverse cross-section of the tunnel box. can.

It should be noted that other embodiments may be adopted in which other components are combined with the configurations listed in the above embodiments, and the present invention is not limited to the configurations shown here. In this regard, changes can be made without departing from the spirit of the present invention, and can be appropriately determined depending on the application form.

10: Excavation machine 11: Front shell 12: Rear shell 13: Cutter head 20: Tunnel box group 21: Tunnel box 22: Ring joint surface 23: Ring joint 25: Excavation section 28: Sliding material 30: Main push device (Original push jack)
G: Ground (underground)
P: Jack thrust S: Face pressure (tip resistance force)
W1: Axial component force of the excavator's own weight W2: Axial component force of the weight of the tunnel box group F1: Frictional force on the circumferential surface F2: Frictional resistance force due to ground reaction force in the curve section Q: Ground reaction force Qmax: Maximum ground reaction force Force v: Ground reaction force per ring joint U1: Ceiling vertical soil water pressure U2: Earth water pressure U3: Bottom vertical soil water pressure M1: Vertical beam model M2, M2': Transverse beam model BM1: Curved beam model BM2: Transverse direction Cross-sectional beam model JM1, JM2: Ground spring JMa: Normal ground spring JMb: Tangential ground spring

Claims (6)

While receiving the jack thrust from the propulsion jack of the propulsion device or the excavator, the transverse cross section of the tunnel box, which is formed by a plurality of tunnel boxes and has at least a curved section, is perpendicular to the longitudinal direction of the tunnel box group. A design method,
A first normal load, which is a normal component of the jack thrust in the curve section, or a second ground reaction force, which is a ground reaction force received from the ground in the normal direction as a reaction force to the jack thrust in the curve section. A step of calculating at least one of the normal direction load;
Step B of creating a beam model of the cross section of the tunnel box, and attaching a ground spring to the beam model of the cross section to create a cross section beam model;
C step of calculating a first cross-sectional force caused by the jack thrust by applying the first normal direction load or the second normal direction load to the transverse beam model. A method for designing a transverse cross section of a tunnel box, characterized by: The method for calculating the first normal direction load is as follows:
The required jack thrust is calculated by adding the tip resistance force acting on the cutter head of the tunneling machine and the circumferential surface resistance force applied to the circumferential surface of the tunnel box group, and when the curved section is within the vertical plane. calculates the necessary jack thrust by further adding the dead weight resistance of the tunnel box group and the excavator,
Calculating the jack thrust acting on each tunnel box constituting the tunnel box group based on the required jack thrust,
2. The method for designing a transverse cross section of a tunnel box according to claim 1, wherein the first normal load is calculated based on the jack thrust and the bending angle in the longitudinal direction of the tunnel box. . The method for calculating the second normal direction load is as follows:
In a computer, a curve-containing beam model having equivalent stiffness or a curve-containing beam model formed by connecting beam models of adjacent tunnel boxes with a rotation spring is created for the tunnel box group, and the curve-containing A ground spring is attached to the beam model to create a longitudinal beam model.
The tunnel according to claim 1, wherein the jack thrust is applied to the longitudinal beam model, and the second normal load, which is a ground reaction force generated on the longitudinal beam model, is calculated. How to design the transverse section of a box. In the step C,
By dividing the first normal load or the second normal load calculated in step A by the number of ring joints provided on the ring joint surface that is the transverse cross section, Find the concentrated load per joint and apply it to each ring joint position.
Alternatively, a distributed load is calculated by dividing the first normal direction load or the second normal direction load calculated in step A by the circumference of the ring joint surface that is the transverse cross section, 4. The method for designing a transverse cross section of a tunnel box according to claim 1, wherein the distributed load is applied to the ring joint surface. When the second normal direction load is used in the C step, the maximum ground reaction force is extracted and used from among the plurality of calculated ground reaction forces in the C step. 5. A method for designing a transverse cross section of a tunnel box according to any one of 1 to 4. A step D of calculating a second cross-sectional force caused by the earth pressure or earth water pressure by applying earth pressure or earth water pressure to the beam model of the transverse cross section;
Calculate a superimposed cross-sectional force by superimposing the first cross-sectional force and the second cross-sectional force calculated in the C step and the D step, and check the cross-sectional force of the transverse cross section based on the superimposed cross-sectional force. 6. The method for designing a transverse cross section of a tunnel box according to claim 1, further comprising a step E of performing the following steps.

Images