Design methods for retaining walls

Abstract

To provide an earth-retaining wall design method that can precisely assess feasibility of the structure easily.SOLUTION: An earth-retaining wall design method of this invention is for an earth-retaining wall 1 in which a designated horizontal direction is its longitudinal direction D1 as expressed in a horizontal section. The earth-retaining wall 1 comprises: a first earth-retaining material 2, which has concavity parts 2a recessing outwards from the inner face and convex parts 2b protruding inwards from the inner face, both alternately continuing along the longitudinal direction D1; a second earth-retaining material 3, which is separated from the first earth-retaining material 2 with a specific distance L in the width direction D2 perpendicular to the longitudinal direction D1, and which has concavity parts 3a recessing outwards from the inner face and convex parts 3b protruding inwards from the inner face, both alternately continuing along the longitudinal direction D1; and an internal ground 4 that is formed by improvement in the separation space between the first earth-retaining material 2 and the second earth-retaining material 3. The earth-retaining wall design method comprises: a study step of the elastoplasticity beam-spring model which studies the earth-retaining wall 1 with the elastoplasticity beam-spring model; a study step of the elastoplasticity FEM model which studies the earth-retaining wall 1 with the elastoplasticity FEM model; and a structure feasibility confirmation step which confirms feasibility of the structure of the earth-retaining wall 1 based on the study of the elastoplasticity beam-spring model and the study of the elastoplasticity FEM model.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for designing earth retaining walls. [Background technology]

[0002] A retaining wall is known in which a predetermined horizontal direction is the longitudinal direction in a horizontal cross-section, and comprises a first retaining member having recesses and protrusions that are continuous in the longitudinal direction, a second retaining member having recesses and protrusions that are continuous in the longitudinal direction and separated from the first retaining member by a predetermined distance in the width direction perpendicular to the longitudinal direction, and an internal ground formed by improvement in the separated space between the first and second retaining members (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-168550 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] There is a need for advantageous design methods for retaining walls as described above.

[0005] Therefore, the objective of the present invention is to provide a design method for retaining walls that makes it easy to accurately verify the structural feasibility. [Means for solving the problem]

[0006] One embodiment of the present invention is as follows:

[0007] [1] A method for designing a retaining wall in which a predetermined horizontal direction is the longitudinal direction of a horizontal cross-section, wherein the retaining wall comprises: a first retaining member having alternating recesses that are recessed from the inner surface to the outer surface and convex portions that are projecting from the inner surface to the inner surface in the longitudinal direction; a second retaining member having alternating recesses that are recessed from the inner surface to the outer surface and convex portions that are projecting from the inner surface to the inner surface in the longitudinal direction, separated from the first retaining member by a predetermined distance in a width direction perpendicular to the longitudinal direction; and an internal ground formed by improvement in the separated space between the first retaining member and the second retaining member, the method comprising: an elastoplastic beam spring model study step for examining the retaining wall with an elastoplastic beam spring model; an elastoplastic FEM model study step for examining the retaining wall with an elastoplastic FEM model; and a structural feasibility confirmation step for confirming the feasibility of the structure of the retaining wall based on the examination of the elastoplastic beam spring model and the examination of the elastoplastic FEM model.

[0008] [2] The method for designing an earth retaining wall according to [1], wherein the step of examining the elastoplastic beam spring model comprises a step of calculating composite cross-sectional quantities equivalent to the entirety of the first earth retaining material, the second earth retaining material, and the internal ground.

[0009] [3] The elastoplastic beam spring model study step comprises a soil condition setting step for setting soil conditions, a retaining wall specification assumption step for assuming the specifications of the first retaining material, the second retaining material, and the internal ground, a composite cross-sectional quantities calculation step, a beam spring analysis step for performing elastoplastic analysis with the created elastoplastic beam spring model, and a displacement and stress confirmation step for confirming the displacement and stress of the retaining wall, as described in [2].

[0010] [4] The elastoplastic FEM model study step further comprises a joint element condition setting step for setting conditions for joint elements between the first retaining member, the second retaining member, and the internal ground, as described in any one of items [1] to [3] for designing an earth retaining wall.

[0011] [5] The elastic-plastic FEM model study step includes a soil condition setting step for setting soil conditions, a retaining wall specification assumption step for assuming the specifications of each of the first retaining material, the second retaining material, and the internal ground, a cross-section modeling step for modeling the cross-section of the retaining wall, a joint element condition setting step, an FEM analysis step for performing elastic-plastic analysis with the created elastic-plastic FEM model, and a displacement amount / stress intensity confirmation step for confirming the displacement amount and stress intensity of the retaining wall, which is the design method of the retaining wall described in [4].

[0012] [6] The structural feasibility confirmation step includes a specification application step for applying the specifications of each of the first retaining material, the second retaining material, and the internal ground confirmed by one of the elastic-plastic beam spring model study step and the elastic-plastic FEM model study step for the purpose of assumption to the other of the elastic-plastic beam spring model study step and the elastic-plastic FEM model study step, which is the design method of the retaining wall described in any one of [1] to [5].[[ID=?]]

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a design method for a retaining wall that can easily and accurately confirm the feasibility of the structure.

Brief Description of the Drawings

[0014] [Figure 1] It is an external perspective view of an example of a retaining wall designed by the design method of the retaining wall according to an embodiment of the present invention. [Figure 2] FIG. 2(a) is a vertical cross-sectional view of the retaining wall shown in FIG. 1, FIG. 2(b) is an example of an elastic-plastic beam spring model of the retaining wall shown in FIG. 2(a), and FIG. 2(c) is an example of an elastic-plastic FEM model of the retaining wall shown in FIG. 2(a). [Figure 3] It is a flowchart showing the details of the elastic-plastic beam spring model study step. [Figure 4] It is a flowchart showing the details of the elastic-plastic FEM model study step. [Figure 5]It is a cross-sectional view showing an example when modeling the retaining wall shown in FIG. 1. [Figure 6] FIG. 6(a) shows a part of the FEM model shown in FIG. 2(c), and FIG. 6(b) shows an example of the condition setting of the joint element for the part shown in FIG. 6(a). [Figure 7] An example of the condition setting for the vertical (peeling) characteristics of the joint element shown in FIG. 6(b) is shown. [Figure 8] An example of the condition setting for the shear (sliding) characteristics of the joint element shown in FIG. 6(b) is shown. [Figure 9] FIG. 9(a) shows the model created as an example (sandy soil ground equivalent to N = 10), FIG. 9(b) is the ground reaction diagram obtained from the model of FIG. 9(a), FIG. 9(c) is the displacement distribution diagram obtained from the model of FIG. 9(a), FIG. 9(d) is the bending moment diagram obtained from the model of FIG. 9(a), and FIG. 9(e) shows the state of the joint element of the model of FIG. 9(a). [Figure 10] FIG. 10(a) is the stress distribution diagram in the depth direction of the steel sheet pile obtained from the model of FIG. 9(a), and FIG. 10(b) is the stress distribution diagram in the depth direction of the improvement body obtained from the model of FIG. 9(a). [Figure 11] It is the in-section stress distribution diagram at the maximum stress generation depth (-8.9 m) shown in FIG. 10(a). [Figure 12] It is the in-section stress distribution diagram at the peeling generation depth (-13.1 m) shown in FIG. 10(b). [Figure 13] FIG. 13(a) shows the model created as an example (cohesive soil ground equivalent to N = 2), FIG. 13(b) is the ground reaction diagram obtained from the model of FIG. 13(a), FIG. 13(c) is the displacement distribution diagram obtained from the model of FIG. 13(a), FIG. 13(d) is the bending moment diagram obtained from the model of FIG. 13(a), and FIG. 13(e) shows the state of the joint element of the model of FIG. 13(a). [Figure 14]Figure 14(a) shows the state of the joint elements of the model in Figure 13(a), Figure 14(b) is the stress distribution in the depth direction of the steel sheet pile obtained by the model in Figure 13(a), and Figure 14(c) is the stress distribution in the depth direction of the improved body obtained by the model in Figure 13(a). [Figure 15] Figure 14(b) shows the stress distribution within the cross-section at the maximum stress generation depth (-10.9m). [Figure 16] Figure 14(c) shows the stress distribution within the cross-section at the delamination initiation depth (-15.1m). [Modes for carrying out the invention]

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0016] In one embodiment of the present invention, the method for designing the retaining wall 1 is a method for designing the retaining wall 1 in which a predetermined horizontal direction is defined as the longitudinal direction D1 in a horizontal cross-section, and the retaining wall 1, as shown in Figures 1 to 2(a), comprises a first retaining member 2 in which recesses 2a that are recessed from the inner surface outward and protrusions 2b that are projecting from the inner surface inward are alternately continuous in the longitudinal direction D1, a second retaining member 3 separated from the first retaining member 2 by a predetermined distance L in the width direction D2 perpendicular to the longitudinal direction D1, and in which recesses 3a that are recessed from the inner surface outward and protrusions 3b that are projecting from the inner surface inward are alternately continuous in the longitudinal direction D1, and an internal ground 4 formed by improvement in the separated space between the first retaining member 2 and the second retaining member 3, and the method comprises an elastoplastic beam spring model study step in which the retaining wall 1 is examined using an elastoplastic beam spring model, and an elastoplastic FEM (Finite Element This is a design method for an earth retaining wall 1, comprising: a step of examining an elastoplastic FEM model using a finite element method (FEM) model; and a step of confirming the structural feasibility of the earth retaining wall 1 based on the examination of the elastoplastic beam spring model and the examination of the elastoplastic FEM model.

[0017] In this embodiment, the first earth retaining material 2 is composed of a plurality of steel sheet piles. However, the sheet piles are not limited to steel. The first earth retaining material 2 is not limited to sheet piles, but may also be composed of a continuous column wall such as an SMW (Soil Mixing Wall).

[0018] In this embodiment, the second earth retaining material 3 is composed of a plurality of steel sheet piles. However, the sheet piles are not limited to steel. The second earth retaining material 3 is not limited to sheet piles, but may also be composed of a continuous columnar wall such as an SMW (Soil Mixing Wall).

[0019] As shown in Figure 2(a), the first retaining wall material 2 may be used as the retaining wall material on the ground side and the second retaining wall material 3 as the retaining wall material on the excavation side, or conversely, the first retaining wall material 2 may be used as the retaining wall material on the excavation side and the second retaining wall material 3 as the retaining wall material on the ground side.

[0020] The horizontal cross-sectional shape of the retaining wall 1 is not particularly limited and may be, for example, I-shaped, arc-shaped, corrugated, or ring-shaped. In the case of a ring shape, the outside of the ring may face the ground and the inside may face the excavation side, or vice versa.

[0021] In this embodiment, the internal ground 4 is composed of ground formed by ground improvement work. The internal ground 4 is composed of an improved body which has been improved by an improving material injected into the ground by, for example, a high-pressure injection mixing method. The internal ground 4 may also be composed of the improved body and unimproved ground.

[0022] An example of an elastoplastic beam spring model for retaining wall 1 is shown in Figure 2(b), and an example of an elastoplastic FEM model for retaining wall 1 is shown in Figure 2(c).

[0023] As shown in Fig. 3, in this embodiment, the elastoplastic beam spring model study steps include a soil condition setting step S11 for setting soil conditions, a retaining wall specification assumption step S12 for assuming the specifications of each of the first retaining material 2, the second retaining material 3, and the internal ground 4, a composite cross-section quantity calculation step S13 for calculating the composite cross-section quantities equivalent to the whole of the first retaining material 2, the second retaining material 3, and the internal ground 4, a beam spring analysis step S14 for performing elastoplastic analysis with the created elastoplastic beam spring model, and a displacement amount / stress intensity confirmation step S15 for confirming the displacement amount and stress intensity of the retaining wall 1 (composite retaining wall).

[0024] In the composite cross-section quantity calculation step S13 of this embodiment, first, as shown in Fig. 5 for example, the retaining wall 1 is modeled by replacing each of the first retaining material 2, the second retaining material 3, and the internal ground 4 with a smooth plate shape. For example, when the retaining wall 1 has an I-shaped horizontal cross-section shape as described above, each of the first retaining material 2, the second retaining material 3, and the internal ground 4 is replaced with a smooth flat plate shape. Then, the composite cross-section quantities equivalent to the whole of the modeled first retaining material 2, the second retaining material 3, and the internal ground 4 are calculated.

[0025] As an example, when the internal ground 4 is sandy soil, when converting to steel sheet piles, the deformation coefficient E (kN / m 2 ) is 2.0×10 8 , the moment of inertia I (cm 4 ) of the heterogeneous material is 10,450,758, and the flexural rigidity (kN·m 2 ) E·I is 20,901,516. When converting to the internal ground 4, the deformation coefficient E (kN / m 2 ) is 1,200,000, the moment of inertia I (cm 4 ) of the heterogeneous material is 1,741,793,033, and the flexural rigidity (kN·m 2 ) E·I is 20,901,516. When the internal ground 4 is cohesive soil, when converting to steel sheet piles, the deformation coefficient E (kN / m 2 ) is 2.0×10 8 , the moment of inertia I (cm 4 ) of the heterogeneous material is 10,417,425, and the flexural rigidity (kN·m2 )E·I is 20,834,850, and when converted to internal ground level 4, the deformation coefficient E(kN / m 2 ) is 400,000, and the second moment of area I (cm) of dissimilar materials is 400,000. 4 The bending stiffness (kN·m) is 5,208,712,500. 2 )E·I is 20,834,850.

[0026] In this embodiment, the soil condition setting step S11, the retaining wall specification assumption step S12, the composite cross-sectional quantity calculation step S13, the beam spring analysis step S14, and the displacement and stress confirmation step S15 are performed in this order. In this embodiment, the elastoplastic beam spring model study step has a repeating step S16 in which, if a problem is confirmed in the displacement and stress confirmation step S15, the process returns to the retaining wall specification assumption step S12 until it is confirmed that there is no problem in the displacement and stress confirmation step S15.

[0027] As shown in Figure 4, in this embodiment, the elastoplastic FEM model study step includes a soil condition setting step S21 for setting soil conditions, a retaining wall specification assumption step S22 for assuming the specifications of the first retaining material 2, the second retaining material 3, and the internal ground 4, a cross-sectional modeling step S23 for modeling the cross-section of the retaining wall 1, a joint element condition setting step S24 for setting the conditions of the joint elements between each member of the first retaining material 2, the second retaining material 3, and the internal ground 4, an FEM analysis step S25 for performing elastoplastic analysis with the created elastoplastic FEM model, and a displacement and stress confirmation step S26 for confirming the displacement and stress of the retaining wall 1 (composite retaining wall).

[0028] In the cross-sectional modeling step S23 of this embodiment, the retaining wall 1 is modeled by replacing the first retaining member 2, the second retaining member 3, and the internal ground 4 with smooth plate shapes, as shown in Figure 5, for example. For example, if the retaining wall 1 has an I-shaped horizontal cross-section as described above, the first retaining member 2, the second retaining member 3, and the internal ground 4 are each replaced with smooth flat plate shapes.

[0029] Then, in the joint element condition setting step S24 of this embodiment, the vertical (separation) characteristics and shear (slip) characteristics of the joint elements (boundary surface joint elements) between the first earth retaining material 2 and the internal ground 4, and between the second earth retaining material 3 and the internal ground 4 are set, for example, as shown in Figures 6 to 8. For the vertical (separation) characteristics, for example, the rigidity modulus Kn in the vertical direction (corresponding to the slope in Figure 7) and the tensile strength σt, which is the stress at which separation occurs when tensile stress is generated, are set. For the shear (slip) characteristics, for example, the rigidity modulus Ks in the shear direction (corresponding to the slope in Figure 8) and the allowable adhesion stress f, which is the limit value at which slip occurs, are set. For example, f = (1 / 3)C, where C is the cohesion of the internal ground 4.

[0030] In this embodiment, the soil condition setting step S21, the retaining wall specification assumption step S22, the cross-sectional modeling step S23, the joint element condition setting step S24, the FEM analysis step S25, and the displacement and stress confirmation step S26 are performed in this order. In this embodiment, the elastoplastic FEM model study step has a repeating step S27 in which if a problem is found in the displacement and stress confirmation step S26, the process returns to the retaining wall specification assumption step S22 until it is confirmed that there is no problem in the displacement and stress confirmation step S26.

[0031] In this embodiment, the structural feasibility confirmation step includes a specification application step in which the specifications of the first retaining wall material 2, the second retaining wall material 3, and the internal ground 4, which were confirmed by either the elastoplastic beam spring model study step or the elastoplastic FEM model study step, are applied to the other of the elastoplastic beam spring model study step or the elastoplastic FEM model study step for assumption purposes. Through the specification application step, the specifications that were assumed in the retaining wall specification assumption step and confirmed to be without problems in the other of the elastoplastic beam spring model study step or the elastoplastic FEM model study step are determined in the structural feasibility confirmation step to be specifications that confirm the structural feasibility of the retaining wall 1.

[0032] According to the design method for the retaining wall 1 of this embodiment, which uses two models—an elastoplastic beam spring model and an elastoplastic FEM model—it is possible to easily and accurately verify the structural feasibility of the retaining wall 1.

[0033] The present invention is not limited to the embodiments described above, and can be modified in various ways without departing from its essence.

[0034] Therefore, the design method for the retaining wall 1 of the embodiment described above is a design method for the retaining wall 1 in which a predetermined horizontal direction is defined as the longitudinal direction D1 in a horizontal cross-section, wherein the retaining wall 1 comprises a first retaining member 2 in which recesses 2a that are recessed from the inner surface outward and protrusions 2b that are projecting from the inner surface inward are alternately continuous in the longitudinal direction D1, and a second retaining member 2 separated by a predetermined distance L in the width direction D2 perpendicular to the longitudinal direction D1, in which recesses 3a that are recessed from the inner surface outward and protrusions 3b that are projecting from the inner surface inward are alternately continuous in the longitudinal direction D1 The design method for a retaining wall is modifiable as long as it includes a retaining material 3 and an internal ground 4 formed by improvement in the separated space between the first retaining material 2 and the second retaining material 3, and comprises an elastoplastic beam spring model study step in which the retaining wall 1 is examined using an elastoplastic beam spring model, an elastoplastic FEM model study step in which the retaining wall 1 is examined using an elastoplastic FEM model, and a structural feasibility confirmation step in which the feasibility of the structure of the retaining wall 1 is confirmed from the examination of the elastoplastic beam spring model and the examination of the elastoplastic FEM model. [Examples]

[0035] Figure 9(a) shows a model created as an example (sandy soil ground equivalent to N=10), Figure 9(b) is the ground reaction force diagram obtained by the model in Figure 9(a), Figure 9(c) is the displacement distribution diagram obtained by the model in Figure 9(a), Figure 9(d) is the bending moment diagram obtained by the model in Figure 9(a), and Figure 9(e) shows the state of the joint elements of the model in Figure 9(a). Figure 9(c) shows the displacement confirmed in the displacement and stress confirmation step of the elastoplastic beam spring model study step and the displacement confirmed in the displacement and stress confirmation step of the elastoplastic FEM model study step. Figure 9(d) shows the bending moment as stress confirmed in the displacement and stress confirmation step of the elastoplastic beam spring model study step and the bending moment as stress confirmed in the displacement and stress confirmation step of the elastoplastic FEM model study step.

[0036] Figure 10(a) is a stress distribution diagram in the depth direction of the steel sheet pile obtained by the model in Figure 9(a), and Figure 10(b) is a stress distribution diagram in the depth direction of the improved body obtained by the model in Figure 9(a). The vertical stresses of the first and second earth retaining members, respectively, confirmed in the displacement and stress confirmation step of the elastoplastic FEM model study step, are shown in Figure 10(a). The vertical stresses of the internal ground confirmed in the displacement and stress confirmation step of the elastoplastic FEM model study step are shown in Figure 10(b).

[0037] Figure 11 is a cross-sectional stress distribution diagram at the maximum stress occurrence depth (-8.9m) shown in Figure 10(a). The cross-sectional stress distribution is almost linear, confirming that the cross-sectional stress at the maximum stress occurrence depth is not problematic.

[0038] Figure 12 is a cross-sectional stress distribution diagram at the delamination initiation depth (-13.1m) shown in Figure 10(b). The cross-sectional stress distribution is almost linear, confirming that the cross-sectional stress at the delamination initiation depth is not problematic.

[0039] As described above, the feasibility of the retaining wall structure was confirmed using two models—an elastoplastic beam spring model and an elastoplastic FEM model—in the case of sandy soil.

[0040] Similar to the case of sandy soil described above, the feasibility of the retaining wall structure was also confirmed for cohesive soil with an N value equivalent to 2, as shown in Figures 13 to 16. [Explanation of Symbols]

[0041] 1. Retaining wall 2. First retaining wall 2a Recess 2b Convex part 3. Second retaining wall 3a Recess 3b Convex part 4 Internal ground D1 Longitudinal direction D2 width direction L specified distance S11 Soil Condition Setting Step S12 Retaining wall specification (assumption step) S13 Step for calculating various quantities of composite section S14 Beam spring analysis step S15 Displacement and stress confirmation step S16 Repeat step S21 Soil Condition Setting Step S22 Retaining wall specification (assumption step) S23 Cross-sectional modeling step S24 Joint element condition setting step S25 FEM Analysis Step S26 Displacement and stress confirmation step S27 Repeat Step

Claims

1. A method for designing a retaining wall in which a predetermined horizontal direction is the longitudinal direction of a horizontal cross-section, wherein the retaining wall comprises: a first retaining member having alternating recesses that are recessed from the inner surface outward and convex portions that project from the inner surface inward in the longitudinal direction; a second retaining member having alternating recesses that are recessed from the inner surface outward and convex portions that project from the inner surface inward in the longitudinal direction, separated from the first retaining member by a predetermined distance in the width direction perpendicular to the longitudinal direction; and an internal ground formed by improvement in the separated space between the first retaining member and the second retaining member, the method comprising: an elastoplastic beam spring model study step for examining the retaining wall with an elastoplastic beam spring model; an elastoplastic FEM model study step for examining the retaining wall with an elastoplastic FEM model; and a structural feasibility confirmation step for confirming the feasibility of the structure of the retaining wall based on the examination of the elastoplastic beam spring model and the examination of the elastoplastic FEM model.

2. The method for designing an earth retaining wall according to claim 1, wherein the elastoplastic beam spring model study step includes a composite cross-sectional quantity calculation step for calculating composite cross-sectional quantities equivalent to the entirety of the first earth retaining material, the second earth retaining material, and the internal ground.

3. The method for designing an earth retaining wall according to claim 2, wherein the elastoplastic beam spring model study step comprises a soil condition setting step for setting soil conditions, an earth retaining wall specification assumption step for assuming the specifications of the first earth retaining material, the second earth retaining material, and the internal ground, a composite cross-sectional quantities calculation step, a beam spring analysis step for performing elastoplastic analysis with the created elastoplastic beam spring model, and a displacement and stress confirmation step for confirming the displacement and stress of the earth retaining wall.

4. The method for designing an earth retaining wall according to claim 1, wherein the elastoplastic FEM model study step includes a joint element condition setting step for setting conditions for joint elements between each member of the first earth retaining material, the second earth retaining material, and the internal ground.

5. The method for designing an earth retaining wall according to claim 4, wherein the elastoplastic FEM model study step comprises a soil condition setting step for setting soil conditions, an earth retaining wall specification assumption step for assuming the specifications of the first earth retaining material, the second earth retaining material, and the internal ground, a cross-sectional modeling step for modeling the cross-section of the earth retaining wall, a joint element condition setting step, an FEM analysis step for performing elastoplastic analysis with the created elastoplastic FEM model, and a displacement and stress confirmation step for confirming the displacement and stress of the earth retaining wall.

6. A method for designing an earth retaining wall according to any one of claims 1 to 5, wherein the structural feasibility confirmation step includes a specification application step in which the specifications of the first earth retaining material, the second earth retaining material, and the internal ground confirmed by either the elastoplastic beam spring model study step or the elastoplastic FEM model study step are applied for assumption to the other of the elastoplastic beam spring model study step or the elastoplastic FEM model study step.

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