JP2022174912A - Design method for transversal cross section of tunnel box body - Google Patents

Abstract

To provide a design method for a transversal cross section of a tunnel box body forming a tunnel box body group having at least a curved segment, capable of realizing calculation of sectional force with high accuracy.SOLUTION: Provided is a design method for a transversal cross section of a tunnel box body forming a tunnel box body group 20 having at least a curved segment. The method has: a step A for calculating any one of a first normal directional load being a normal directional component of jack thrust in the curved segment, or a second normal directional load being ground reaction received in the normal direction from the ground as reaction of the jack thrust in the curved segment; a step B for forming a transversal beam model M2 of a tunnel box body 21; and a step C for calculating a first sectional force caused by the jack thrust by loading the first normal directional load or the second normal directional load to the transversal beam model M2.SELECTED DRAWING: Figure 8

Description

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

In the jacking method and the shield method, a plurality of jacking boxes are connected via a ring joint (a form in which the end of one jacking box is inserted into the end of the other jacking box, or a form that is bolted, etc.). or by connecting a plurality of shield boxes to each other via ring joints (bolt joints, etc.), tunnel box groups such as propulsion box groups and shield box groups can be placed underground. to construct. Hereinafter, in this specification, the promotion box and the shield box are collectively referred to as the tunnel box, and the promotion box group and the shield box group are collectively referred to as the tunnel box group.
There are various vertical alignments in the tunnel box group, such as straight alignments, circular alignments, curved alignments with multiple curvatures, and alignments that mix straight lines and curves. In a tunnel box group having a section (curved line), 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 tunnel box group including the above-mentioned curved section, in the design of the transverse cross section of the conventional tunnel box, among the jack thrust, the ground reaction load that balances the normal direction component force of the arc of the curved section is applied. As for the force, a method of calculating the cross-sectional force when the ground reaction force caused by the jack thrust acts by uniformly loading the beam that simulates the bottom slab that constitutes the beam model of the tunnel box in the transverse direction is applied. It is However, in the method in which a uniform, uniformly distributed load acts on the beam model as a ground reaction force, the jack thrust is not loaded at 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 is calculated with high accuracy.

Here, in Patent Document 1, when constructing a tunnel in soft ground in the shield construction method or the jacking method, it is determined whether or not to install a reaction wall at a sharply curved portion of the tunnel. Necessity determination methods have been proposed. Specifically, it is a method to judge whether or not to install a reaction wall by comparing the ground reaction force of the tunnel lining calculated by structural analysis simulating a sharp curve with the strength of the original ground. This is a method for judging the necessity of increasing the axial rigidity of a tunnel to eliminate the need to install a reaction wall in order to reduce the ground reaction force when it is judged that the reaction force is greater than the original ground strength.

JP-A-2002-194989

According to the method for determining whether or not to install a reaction wall described in Patent Document 1, it is possible to provide a method for determining whether or not to install a reaction wall corresponding to the actual situation. However, as described above, in the design of the transverse direction of the tunnel box constituting the tunnel box group having at least curved sections, the jack thrust is applied at the position where the jack thrust actually acts on the ring joint surface of the tunnel box. It does not solve the problem that a highly accurate cross-sectional force cannot be calculated based on the fact that no load is applied.

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

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

According to this aspect, the first normal direction load, which is the normal direction component of the jack thrust in the curved section, or the ground reaction force received from the ground in the normal direction as the reaction force of the jack thrust in the curved section, 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 section force caused by the jack thrust is calculated. By calculating, it is possible to appropriately reflect the normal direction 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 load and the second normal load applied to the transverse beam model are collectively referred to as normal load.
Here, the method of loading the normal direction load on the transverse beam model in the C process is a method of applying a concentrated load to the ring joint position or a method of applying a distributed load to the entire circumference of the transverse beam model. etc.

In another aspect of the method for designing the transverse cross section of the tunnel box according to the present invention,
The method for calculating the first normal direction load is
When the necessary jack thrust is calculated by adding the tip resistance acting on the cutter head of the excavator and the peripheral surface resistance force received by the peripheral surface of the tunnel box group, and the curved section is in the vertical plane calculates the required 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 from the jack thrust and the bending angle of the tunnel box in the vertical direction.

According to this aspect, following the calculation of the required jack thrust (total jack thrust) required 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 direction load based on the jack thrust force and the bending angle of the tunnel box in the longitudinal direction, the normal direction load acting on the tunnel box can be efficiently calculated.
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, for example, in the guidelines such as "Guidelines and explanations of the sewerage promotion method - 2010 edition - Japan Sewage Works Association" It 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 excavator is a modification of the thrust calculation formula described in this guideline. It is. For the required jack thrust obtained by adding the tip resistance, the peripheral surface resistance, and, if necessary, the self-weight resistance, the required jack thrust is multiplied by, for example, a predetermined safety factor to increase the required jack thrust, and the required jack after the addition You may calculate the jack thrust which acts on each tunnel box based on a thrust.

In another aspect of the method for designing the transverse cross section of the tunnel box according to the present invention,
The method for calculating the second normal direction load is
In a computer, a curve-containing beam model having equivalent rigidity or a curve-containing beam model formed by connecting the beam models of the adjacent tunnel boxes with a rotating spring is created for the tunnel box group, and the curve-containing beam model is created. A ground spring is attached to the beam model to make it a longitudinal direction beam model,
The jack thrust force is applied to the longitudinal beam model, and the second normal direction load, which is ground reaction force generated in the longitudinal beam model, is calculated.

According to this aspect, the longitudinal direction beam model formed by the curve containing beam model and the ground spring is loaded with the jack thrust, and the second normal direction load, which is the ground reaction force, is calculated, thereby the tunnel The normal direction load acting on the box can be calculated with high accuracy.
Here, the tunnel box group is a longitudinal direction beam model at the 10R stage in which, for example, 10 tunnel box 1 rings (1R) are propelled at each construction stage when the curved section has a single circular vertical alignment. , longitudinal direction beam model at the 20R stage, circular longitudinal direction beam model that was propelled all around, etc., longitudinal direction beam models at various construction stages were created. Section forces are calculated. Here, each tunnel box that constitutes the tunnel box group has a different section force calculated for each 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 is the jack thrust due to the main pushing jack of the main pushing device in the jacking method, the jack thrust due to the medium pushing jack of the main pushing device in addition to the main pushing jack, and the jack thrust provided by the excavator in both the jacking method and the shield method. The jack thrust due to For example, in a jacking method using an excavator equipped with a jack, the jack thrust is applied to one end (starting shaft position) of the longitudinal beam model, and the other end of the longitudinal beam model (excavator position) is loaded with the jack thrust. ) is loaded with the jack thrust by the propulsion jack provided in the excavator, and when the intermediate pushing device is interposed in the tunnel box group, the jack thrust by the intermediate pushing jack is loaded at that position.
Furthermore, ground springs are installed in various forms, such as a form in which the ground spring is installed in each tunnel box, a form in which the ground spring is installed in every 10R, and the like. Furthermore, it is desirable that the ground properties are appropriately reflected in the ground spring for each location (soil layer). A spring is preferably set.

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

According to this aspect, depending on the manner in which the ring joints are arranged on the ring joint surface, a suitable load, either a concentrated load or a distributed load based on the normal direction load, is applied to the transverse beam model, and the tunnel box is It is possible to appropriately reflect the acting position of the jack thrust on the ring joint surface of the body, and it is possible to calculate the cross-sectional force with high accuracy.
For example, if the ring joint locations are relatively uneven in the ring joint plane, a concentrated load per ring joint may be applied to each ring joint location in the transverse beam model. By applying a normal load (concentrated load) per ring joint position to each ring joint position, it is possible to reproduce as faithfully as possible the actual phenomenon of the jack thrust acting from each ring joint position. It is possible to calculate the cross-sectional force with even higher accuracy.
On the other hand, when a plurality of ring joint positions are relatively even on the ring joint surface, it is preferable to apply the distributed load to the entire circumference (entire area) of the transverse beam model.

In another aspect of the method for designing the transverse cross section of the tunnel box according to the present invention,
When the second normal direction load is used in the step C, the step C is characterized by extracting and using the maximum ground reaction force among the plurality of calculated ground reaction forces.

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

Another aspect of the method for designing the transverse cross section of a tunnel box according to the present invention is
D step of calculating a second cross-sectional force caused by earth pressure or earth and water pressure by applying earth pressure or earth and water pressure to the beam model of the cross section in the transverse direction;
Calculate the 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 in the transverse direction based on the superimposed cross-sectional force and an E step of performing the above.

According to this aspect, the first cross-sectional force is calculated when the normal direction load caused by the jack thrust is applied to the transverse beam model, and the beam model of the transverse cross section (the ground spring is Calculate the second cross-sectional force when earth pressure or earth-water pressure acts on the removed beam model), and check the cross-sectional force in the transverse direction based on the superimposed cross-sectional force obtained by superimposing both cross-sectional forces. Therefore, it is possible to calculate the cross-sectional force with higher accuracy. It should be noted that C process and D process are carried out at the same time, in other words, the cross-sectional force is calculated by simultaneously applying the normal direction 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 the cross section of a tunnel box according to the present invention, it is possible to calculate the cross-sectional force with high accuracy in the design of the cross direction of tunnel boxes that constitute a group of tunnel boxes having at least curved sections.

It is a flow chart which shows an example of a design method of a cross section of a tunnel box concerning an embodiment. It is a schematic diagram which shows the state which is propelling the tunnel box group which has a vertical line of a single circle in a vertical plane by a jacking method. FIG. 4 is a schematic diagram showing a state in which a tunneling machine creates an overcut portion in a curved section, and the tunnel box group is propelled while filling the overcut portion with a lubricant. It is a schematic diagram explaining the calculation method of a 1st normal direction load. FIG. 4 is a schematic diagram for explaining a method of calculating a second normal direction load, and is a diagram for 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. It is a front view which shows an example of the transverse direction cross section of a tunnel box. While showing an example of a transverse direction beam model, it is a schematic diagram explaining the state which loads the normal direction load by a jack thrust in each ring joint position of a ring joint surface. While showing an example of the beam model of the cross section in the transverse direction, it is a schematic diagram explaining the state which loads the earth and water pressure.

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. In the present specification and drawings, substantially the same constituent elements may be given the same reference numerals to omit redundant description.

[Method for designing transverse cross section of tunnel box according to embodiment]
An example of a method for designing a transverse section of a tunnel box according to an embodiment will be described with reference to FIGS. 1 to 9. FIG. Here, FIG. 1 is a flowchart which shows an example of the design method of the transverse direction cross section of the tunnel box which concerns on embodiment. Fig. 2 is a schematic diagram showing a state in which a group of tunnel boxes having a single circular vertical alignment in the vertical plane is propelled by the jacking method. FIG. 4 is a schematic diagram showing a state in which a group of tunnel bodies is propelled while creating an excavated portion and filling the overdrilled portion with a lubricant. Further, FIG. 4 is a schematic diagram for explaining the calculation method of the first normal direction load, and FIG. 5 is a schematic diagram for explaining the calculation method of the second normal direction load. It is a figure explaining an example. Moreover, FIG. 6 is a schematic diagram explaining the external force which acts on one tunnel box in the process of propulsion, and FIG. 7 is a front view which shows an example of the cross-section of a tunnel box. Furthermore, FIG. 8 shows an example of a transverse beam model, and is a schematic diagram illustrating a state in which a normal direction load due to jack thrust is applied at each ring joint position on the ring joint surface, and FIG. FIG. 10 is a schematic diagram illustrating an example of a cross-sectional beam model in the transverse direction and explaining a state in which earth and water pressure is applied;

In the method of designing the cross section of the tunnel box in the illustrated example, the longitudinal 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 constitutes the body has various vertical alignments, such as vertical alignments with multiple curvatures in the vertical or horizontal plane, vertical alignments in which curved sections and straight sections are mixed. A group of linear tunnel bodies can be designed.

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

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

As will be explained in detail below, the method for calculating the first normal direction load uses a thrust calculation formula described in a known guideline or a modified thrust calculation formula that is a modification of this thrust calculation formula. Based on the vertical bending angle of each tunnel box in the section, the first normal direction load is calculated. On the other hand, the method of calculating the load in the second normal direction is to create a longitudinal direction beam model (analysis model) in a computer, and perform an analysis in which the jack thrust is applied to the beam model. Calculate the load (soil reaction force).

On the other hand, the B process comprises a process of creating a transverse beam model (analysis model). Process C includes a step of performing a first transverse direction analysis using the created transverse beam model to calculate a first section force based on a first normal load or a second normal load. , D includes a step of performing a transverse second analysis for calculating a second sectional force based on earth and water pressure, using a beam model from which ground springs are removed from the transverse beam model.

Finally, step E comprises a step of performing a stress degree check 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 the A process, the specifications of the tunnel box are set, and the longitudinal alignment of the tunnel box group (in the case of a single circle, its diameter, and if it has multiple curvatures, each curvature and its alignment, etc.) Model the soil layer through which the tunnel box group passes. In the modeling of soil layers, based on the ground survey results, the properties (sandy layer, clay layer, gravel layer, etc.), N value, unit weight of the ground, internal friction angle, and Set physical properties such as adhesion force.

The example shown in FIG. 2 is an example of constructing a tunnel box group 20 (circumferential tunnel) having a single circular longitudinal line with a radius r in the vertical plane by the jacking method. As shown in FIG. 2, when the main tunnel HT (for example, the main shield tunnel) that has already been constructed in the underground G and the ramp tunnel RT (for example, the ramp shield tunnel) on the side thereof are connected underground and widened. , using the ramp tunnel RT, construct a shaft T extending vertically below it. Note that the vertical shaft may extend obliquely downward instead of vertically.

A starting pedestal R is installed below a pit T formed to a predetermined depth, and a starting pedestal device 30 equipped with a priming jack is installed on the starting pedestal R. An excavator 10 and a tunnel box 21 are suspended from the ramp tunnel RT at any time, the excavator 10 is excavated into the ground, and a plurality of tunnel boxes 21 are sequentially arranged behind it, and jack thrust by a main pushing jack 30 is used. , a tunnel box group 20 formed by the excavator 10 and a plurality of tunnel boxes 21 are propelled.

The excavator 10 of the illustrated example includes a front body 11 and a rear body 12, and a not-shown propulsion jack (a jack for controlling the direction of the excavator in addition to propelling the excavator itself) between the two. there is The shape of the excavator 10 when viewed from the front is, for example, a horizontally long rectangle, and a plurality of cutter heads 13, for example, are arranged on the front surface thereof. Each cutter head 13 has a built-in copy cutter that can be freely moved in and out from the side thereof. A copy cutter that rotates accordingly creates the overcut portion. 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 is rectangular in front view, is composed of a steel shell having the same shape as the excavator 10 in front view, as shown in FIG.

Returning to FIG. 2, the face pressure S acts on the cutter head 13 of the excavator 10 from the front. In addition, as shown in the figure, since the vehicle is propelled in a vertical plane, 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.

The tunnel box group 20 to be propelled is subjected to a peripheral surface resistance force F1 with respect to the surrounding ground G, and further, a frictional resistance force F2 caused by the ground reaction force Q associated with curved construction. Here, since the excavator 10 and the tunnel box group 20 in front are propelled by the jack thrust P1 acting from the main pushing jack 30 in the vertical shaft T, the jack that acts as it goes forward of the tunnel box group 20 Thrusts P2, P3, and P4 gradually decrease. Since the ground reaction force Q associated with curved construction is a reaction force resulting from this jack thrust P, as shown in FIG. It has a tendency to gradually decrease over time.

As described above, in the jacking method along the curved line in the vertical plane of 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 respective tunnel bodies 21 Axial component force W2 of its own weight, peripheral surface resistance force F1 between itself and the surrounding ground G, and frictional resistance force F2 caused by ground reaction force Q due to curved construction work. Propulsion of the machine 10 and the tunnel box group 20 is realized. For example, in construction in a horizontal plane, the axial component force W1 of its own weight acting on the excavator 10 and the axial component force W2 of its own weight acting on each tunnel box 21 are used to calculate the jack thrust of the main pushing jack 30. becomes unnecessary when

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

In setting the jack thrust of the main push jack 30 and the jack thrust of the main push jack 30 and the intermediate push jack provided as necessary, the required jack thrust changes from time to time in the process of propelling the tunnel box group 20, The required jack thrust is set according to each stage, such as the stage up to 10 (10R) tunnel box groups 20, the stage up to 20R, the final stage when the excavator 10 reaches the shaft T, and the like.

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

FIG. 3 shows a state in which the excavator 10 is excavating along the planned vertical line L1, and the tunnel box group 20 is being propelled. There is L2, and there is an outer line L3 of the overcut portion 25 on the radially outer side. That is, FIG. 3 shows a state in which the excavator 10 is not meandering. Also, the width t1 is the designed overcut amount under the input conditions.

Here, a method for calculating the first normal direction load in the A process will be described. Based on the thrust calculation formula described in "Guidelines and explanations for sewerage jacking methods - 2010 edition - Japan Sewage Works Association" (hereinafter referred to as sewerage guidelines), the required jack thrust can be expressed by the following formula (X). .

In addition, as in the illustrated example, in the promotion work in the vertical plane, it is necessary to consider the self-weight resistance of the excavator 10 and the tunnel box group 20, so the required jack thrust in this case is given by the above formula (X ) can be represented by the following formula (Y), which is a modified version of

Furthermore, in jacking construction with a curved section as in the illustrated example, the required jack thrust can be expressed by the following equation (Z). In addition, since the formula (Z) is a required jack thrust calculation formula at the time of propulsion construction with a curved section in the horizontal plane, described in the sewage guidelines, more specifically, the dead weight resistance of the above formula (Y) should be added (considered), but here we introduce the formula described in the Sewerage Guideline.

As shown in FIG. 4, the jack thrust acting on each tunnel box is calculated from the required jack thrust (for example, F1), and the normal direction component force T1 of this jack thrust is calculated by F1×sinα. The first normal direction load acting on the tunnel body can be obtained.

Next, a method for calculating the second normal direction load in the A process will be described. As shown in FIG. 5, in a computer, the tunnel box group 20 is modeled as a curve containing beam model BM1 having equivalent stiffness. In this modeling, although illustration is omitted, a curve containing beam model may be created by connecting beam models of the adjacent tunnel box 21 with a rotating spring.

A longitudinal direction beam model M1 is created by attaching ground springs 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, for example, every 10R.

The ground spring JM1 comprises a normal ground spring JMa in the direction normal to the circumferential tunnel of radius r and a tangential ground spring JMb in the tangential direction, both ground springs being simulated, for example, by connector elements. Also, although illustration is omitted, one end BM1′ (or its vicinity) of the curve-containing beam model BM1 to which the jack thrust P from the main pushing jack is loaded, and the other end BM1″ of the curve-containing beam model BM1 that has reached the shaft. (or in the vicinity thereof) are each fitted with a restraining spring.

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

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

For example, the jack thrust of the main pushing jack 30, as described with reference to FIG. Then, if the axial force at the position of the excavator 10 located at the forefront among the axial forces included in the cross-sectional force in the longitudinal direction is a compressive force equal to or greater 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 compressive force corresponding to the face pressure S is reached, and the required jack thrust is set.

On the other hand, if the longitudinal direction analysis shows that the axial force at the position of the excavator 10 is smaller than the compressive force corresponding 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 is set by repeating the above-described longitudinal analysis until the axial force becomes the compressive force corresponding to the face pressure S.

Calculate the ground reaction force Q acting on the tunnel box group by longitudinal direction analysis, identify the maximum ground reaction force Qmax among the calculated ground reaction forces Q, and apply this ground reaction force Qmax to the second method A linear load is preferred.

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) and the balance of forces in the direction perpendicular to the axis are established.

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

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

As described above, the setting of the input conditions and the calculation of the first normal direction load or the calculation of the second normal direction load are the A process.

Next, create a transverse beam model (analysis model). In this example, a model of the tunnel box 21 shown in FIG. 7 whose cross section in the transverse direction has a laterally long rectangular shape is modeled. Here, FIG. 7 shows the front view shape of the tunnel box 21 and shows the ring joint surface 22, which is stiffened by two internal partition walls, and along the linear cross section in the transverse direction. A plurality of ring joints 23 are provided. This ring joint 23 is composed of, for example, a ring joint bolt or the like, and the jack thrust is transmitted to the other adjacent tunnel box via a plurality of ring joints 23 .

The tunnel box 21 having the transverse cross-sectional shape shown in FIG. 7 is modeled as a transverse beam model M2 shown in FIG. Here, the transverse beam model M2 is created by attaching ground springs JM2 to the transverse cross section beam model BM2 along the line of the transverse cross section of the tunnel box 21 . The ground spring JM2 in the illustrated example includes only a straight spring, but the ground spring JM2 may include both a straight spring and a shear spring orthogonal thereto (the above is step B).

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

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

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

In addition, a distributed load may be calculated by dividing the normal direction 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 positions of the ring joints in the illustrated example are arranged relatively evenly, highly accurate analysis results can be obtained even by the method of determining the distributed load and applying it to the entire ring joint surface.

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

According to the first analysis in the transverse direction, the ground reaction force that can actually occur is output to the ground spring JM2, where the reaction force increases under the side walls and partition walls as shown in FIG. process).

Next, as shown in FIG. 9, a second analysis in the transverse direction is performed in which earth and water pressure is applied to the transverse beam model M2' consisting only of the beam model BM2 of the transverse cross section (without the ground spring JM2). implement. In this transverse direction second analysis, by loading the ceiling vertical earth and water pressure U1, the bottom floor vertical earth and water pressure U3, and the left and right earth and water pressure U2 on the transverse direction beam model M2', the sectional force in the transverse direction cross section (the second Two-section force) is calculated (above, D process).

Next, the first section force calculated in the C process and the second section force calculated in the D process are superimposed to calculate the superimposed section force, and using this superimposed section force, the section of the cross section in the transverse direction A force check (stress check) is carried out (above, step E). In addition, you may implement C process and D process simultaneously. Specifically, in the beam model BM2 of the cross section in the transverse direction, a concentrated load v, which is the normal direction component force of the jack thrust per ring joint, is applied to each ring joint position. , the bottom base vertical soil water pressure U3, and the left and right soil water pressure U2 may be loaded to calculate the cross-sectional force.

By checking the stress level, we identified the initially set tunnel box specifications (strength, yield strength), ground bearing capacity, and required jack thrust, and determined that the tunnel box had insufficient bearing capacity and that the ground had insufficient bearing capacity. If so, return to the setting of the input conditions, change the specifications of the tunnel box (including changing the cross section of the tunnel box in the transverse direction), review the vertical alignment, and consider ground improvement to improve soil bearing capacity. Re-create analysis models such as directional beam models and transverse beam models, perform longitudinal direction analysis, transverse direction first analysis, transverse direction second analysis, etc., re-check the stress level, A construction plan is created after determining the specifications that satisfy the bearing strength of both the body and the ground.

According to the illustrated method for designing the cross section of the tunnel box, in the design of the transverse direction 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 Appropriately reflecting the working position of the jack thrust and applying the jack thrust to each working position enables highly accurate calculation of cross-sectional force, realizing a rational cross-sectional design of the tunnel box. can.

It should be noted that other embodiments may be possible in which other components are combined with the configurations described in the above embodiments, and the present invention is not limited to the configurations shown here. Regarding this point, it is possible to change without departing from the gist of the present invention, and it can be determined appropriately according to the application form.

10: Excavator 11: Front body 12: Rear body 13: Cutter head 20: Tunnel box group 21: Tunnel box 22: Ring joint surface 23: Ring joint 25: Overcut part 28: Lubricant 30: Base pushing device (Original push jack)
G: Ground (underground)
P: Jack thrust S: Face pressure (tip resistance)
W1: Axial force component of the weight of the excavator itself W2: Axial force component of the weight of the tunnel box group F1: Surface friction force F2: Frictional resistance force due to ground reaction force in curved sections Q: Ground reaction force Qmax: Maximum ground reaction force Force v: Ground reaction force per ring joint U1: Ceiling vertical earth water pressure U2: Earth water pressure U3: Bottom floor vertical earth water pressure M1: Beam model in longitudinal direction M2, M2': Beam model in transverse direction BM1: Beam model containing curve BM2: In transverse direction Beam model of cross section JM1, JM2: ground spring JMa: ground spring in normal direction JMb: ground spring in tangential direction

Claims (6)

A cross section of a tunnel box formed by a plurality of tunnel boxes and having at least a curved section perpendicular to the longitudinal direction of the tunnel box group while receiving the jack thrust from the propulsion jack of the propulsion device or the excavator. A design method,
The first normal direction load, which is the normal direction component of the jack thrust in the curved section, or the ground reaction force received from the ground in the normal direction as the reaction force of the jack thrust in the curved section, the second A step of calculating at least one of the normal load;
B step of creating a beam model of the transverse cross section of the tunnel box, and attaching a ground spring to the beam model of the transverse cross section to obtain a transverse beam model;
C step of calculating a first cross-sectional force caused by the jack thrust by applying the first normal load or the second normal load to the transverse beam model. A method for designing a transverse section of a tunnel box, characterized by: The method for calculating the first normal direction load is
When the necessary jack thrust is calculated by adding the tip resistance acting on the cutter head of the excavator and the peripheral surface resistance force received by the peripheral surface of the tunnel box group, and the curved section is in the vertical plane calculates the required 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 section of a tunnel box according to claim 1, wherein the first normal direction load is calculated from the jack thrust and the bending angle of the tunnel box in the longitudinal direction. . The method for calculating the second normal direction load is
In a computer, a curve-containing beam model having equivalent rigidity or a curve-containing beam model formed by connecting the beam models of the adjacent tunnel boxes with a rotating spring is created for the tunnel box group, and the curve-containing beam model is created. A ground spring is attached to the beam model to make it a longitudinal direction beam model,
2. The tunnel according to claim 1, wherein said longitudinal beam model is loaded with said jack thrust, and said second normal direction load, which is a ground reaction force generated in said longitudinal beam model, is calculated. How to design the transverse section of the box. In the C step,
Ring Find the concentrated load per joint and apply it to each ring joint position,
Alternatively, calculating the distributed load by dividing the first normal direction load or the second normal direction load calculated in the step A by the circumference of the ring joint surface, which is the cross section in the transverse direction, 4. The method for designing a transverse cross section of a tunnel box according to any one of claims 1 to 3, wherein the distributed load is applied to the ring joint surface. When the second normal direction load is used in the step C, the step C extracts and uses the maximum ground reaction force among the plurality of calculated ground reaction forces. 5. A method for designing a transverse cross section of a tunnel box according to any one of 1 to 4. D step of calculating a second cross-sectional force caused by earth pressure or earth and water pressure by applying earth pressure or earth and water pressure to the beam model of the cross section in the transverse direction;
Calculate the 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 in the transverse direction based on the superimposed cross-sectional force 6. The method for designing a transverse cross section of a tunnel body according to any one of claims 1 to 5, further comprising a step E of performing

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