earth retaining wall

Abstract

This enables the easy construction of retaining walls. [Solution] A retaining wall 1 in which a predetermined horizontal direction is the longitudinal direction D1 in a horizontal cross-section, comprising: a first retaining member 2 having recesses 2a that are recessed from the inner surface outward and convex portions 2b that are projecting from the inner surface inward alternately 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, having recesses 3a that are recessed from the inner surface outward and convex portions 3b that are projecting from the inner surface inward alternately 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, wherein the relative positions of the first retaining member 2 and the second retaining member 3 in the longitudinal direction D1 are offset from the position where the recesses and convex portions face each other in the width direction D2, and the internal ground 4 has an unimproved portion 6.

Description

Technical Field

[0001] The present invention relates to a retaining wall.

Background Art

[0002] A retaining wall having a predetermined horizontal direction as the longitudinal direction in a horizontal cross-section, a first retaining material in which recesses recessed from the inner surface to the outside and protrusions protruding from the inner surface to the inside are continuously arranged alternately in the longitudinal direction, a second retaining material spaced apart from the first retaining material by a predetermined distance in the width direction orthogonal to the longitudinal direction, in which recesses recessed from the inner surface to the outside and protrusions protruding from the inner surface to the inside are continuously arranged alternately in the longitudinal direction, and an internal ground formed by improvement in the separated space between the first retaining material and the second retaining material is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is desirable that the retaining wall as described above is easy to construct.

[0005] Therefore, an object of the present invention is to realize easy construction of a retaining wall.

Means for Solving the Problems

[0006] One aspect of the present invention is as follows.

[0007] [1] A retaining wall having a predetermined horizontal direction as the longitudinal direction in a horizontal cross-section, comprising: 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 spaced a predetermined distance from the first retaining member in a width direction perpendicular to the longitudinal direction, 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; and an internal ground formed by improvement in the separated space between the first and second retaining members, wherein the relative positions of the first and second retaining members in the longitudinal direction are offset from the positions where the recesses and convex portions face each other in the width direction, and the internal ground has an unimproved portion.

[0008] [2] The retaining wall described in [1] is a self-supporting retaining wall.

[0009] [3] The retaining wall has an annular horizontal cross-sectional shape, as described in [1] or [2], and is a design method for a retaining wall. [Effects of the Invention]

[0010] According to the present invention, it is possible to easily construct retaining walls. [Brief explanation of the drawing]

[0011] [Figure 1] This is an explanatory diagram illustrating the rate of inadequacy when a stirring injection nozzle is placed between two opposing protrusions. [Figure 2] This is an explanatory diagram illustrating the rate of failure when a stirring injection nozzle is placed between two directly opposite recesses. [Figure 3] This is an explanatory diagram to illustrate the rate of inadequacy when the convex parts and concave parts are facing each other directly. [Figure 4] This is an explanatory diagram to illustrate the rate of inadequacy when the second retaining wall is shifted in the longitudinal direction by 1 / 8 of the pitch of the uneven shape from the arrangement shown in Figure 3. [Figure 5]It is an explanatory diagram for explaining the non-improvement rate in the arrangement where the second retaining material is shifted by 2 / 8 pitch of the uneven shape in the longitudinal direction from the arrangement shown in FIG. 3. [Figure 6] It is an explanatory diagram for explaining the non-improvement rate in the arrangement where the second retaining material is shifted by 3 / 8 pitch of the uneven shape in the longitudinal direction from the arrangement shown in FIG. 3. [Figure 7] It is an explanatory diagram for explaining the non-improvement rate in the arrangement where the second retaining material is shifted by 4 / 8 pitch of the uneven shape in the longitudinal direction from the arrangement shown in FIG. 3. [Figure 8] It is a flowchart showing the procedure of the retaining wall design method according to the first embodiment of the present invention. [Figure 9] FIG. 9(a) is a plan view in the vertical direction of the annular retaining wall, FIG. 9(b) is a cross-sectional view along the vertical direction of the retaining wall shown in FIG. 9(a), and FIG. 9(c) is an enlarged view of part A in FIG. 9(a). [[ID=I4]] [Figure 10] FIG. I0(a) is a perspective view of the annular retaining wall shown in FIG. 9, and FIG. I0(b) is an explanatory diagram for explaining the ring spring acting on the annular retaining wall shown in FIG. I0(a). [Figure 11] It is a flowchart showing the procedure of the retaining wall design method according to the second embodiment of the present invention. [Figure 12] It is an explanatory diagram showing the cross section of the model created as the first example (sandy soil ground equivalent to N = 10). [Figure 13] FIG. 13(a) shows a cross section along the width direction of the model (non-improvement rate = 50%) shown in FIG. 12, FIG. 13(b) is the ground reaction force 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 elements of the model of FIG. 13(a). [Figure 14] It is an explanatory diagram for explaining the positions focused on in FIGS. 13 and 15. [Figure 15]FIG. 15(a) shows the stress intensity of the improved body at the extraction position I shown in FIG. 14, FIG. 15(b) shows the stress intensity of the improved body at the extraction position II shown in FIG. 14, FIG. 15(c) shows the stress intensity of the improved body at the extraction position III shown in FIG. 14, FIG. 15(d) shows the stress intensity of the improved body at the extraction position IV shown in FIG. 14, and FIG. 15(e) shows the state of the joint element of the model. [Figure 16] It is an explanatory diagram showing a cross section of the model (the thinning plan of the improved body) created as the second embodiment. [Figure 17] It is an explanatory diagram for explaining the position focused on in FIG. 18. [Figure 18] FIG. 18(a) is a displacement distribution diagram obtained by the model of FIG. 16, FIG. 18(b) is a bending moment diagram obtained by the model of FIG. 16, and FIG. 18(c) shows the state of the joint element of the model. [Figure 19] It is an explanatory diagram for explaining the position focused on in FIG. 20. [Figure 20] FIG. 20(a) is a stress intensity distribution diagram of the steel sheet pile at the improved position obtained by the model of FIG. 16, and FIG. 20(b) is a stress intensity distribution diagram of the improved body at the improved position obtained by the model of FIG. 16.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be illustrated and described with reference to the drawings.

[0013] As shown in Figure 1, in the first embodiment of the present invention, the design method for the retaining wall 1 is a design method for the retaining wall 1 in which a predetermined horizontal direction is defined as the longitudinal direction D1 in the horizontal cross-section, and the retaining wall 1, as shown in Figure 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 first 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 longitudinal The design method for a retaining wall 1 comprises a second retaining wall 3 that are alternately arranged in direction D1, and an internal ground 4 formed by improvement by radially agitating and spraying an improved material using a stirring spray nozzle 5 positioned in a separated space between the first retaining wall 2 and the second retaining wall 3, and a non-improved section setting step S1 in which a non-improved section 6 including a part that is shaded when the improved material is agitated and sprayed, as shown in Figure 8, and a modeling analysis step S2 in which an analysis is performed by modeling the retaining wall 1 including the non-improved section 6.

[0014] In this embodiment, the first retaining wall 2 is composed of a plurality of steel sheet piles. However, the sheet piles are not limited to steel. The first retaining wall 2 is not limited to sheet piles, but may also be composed of a continuous column wall such as an SMW (Soil Mixing Wall). The recesses 2a of the first retaining wall 2 are arranged at a constant pitch in the longitudinal direction D1. The protrusions 2b of the first retaining wall 2 are arranged at a constant pitch in the longitudinal direction D1. The pitch of the recesses 2a and the pitch of the protrusions 2b of the first retaining wall 2 are equal, and in the example shown in Figure 1, it is 800 mm. However, the value of this pitch can be set as appropriate. Other dimensions can also be set as appropriate.

[0015] 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 column wall such as an SMW (Soil Mixing Wall). The recesses 3a of the second earth retaining material 3 are arranged at a constant pitch in the longitudinal direction D1. The protrusions 3b of the second earth retaining material 3 are arranged at a constant pitch in the longitudinal direction D1. The pitch of the recesses 3a and the pitch of the protrusions 3b of the second earth retaining material 3 are equal, and in the example shown in Figure 1, it is 800 mm. However, the value of this pitch can be set as appropriate. Other dimensions, such as a predetermined distance L, can also be set as appropriate.

[0016] The first retaining wall material 2 may be used as the retaining wall material on the natural ground side, and the second retaining wall material 3 may be used 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 may be used as the retaining wall material on the natural ground side.

[0017] 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.

[0018] In this embodiment, the internal ground 4 is composed of ground formed by ground improvement construction in which an improving material is radially agitated and sprayed by an agitation spray nozzle 5. The internal ground 4 is composed of an improved portion that is improved by the improving material and an unimproved portion 6 that is not improved by the improving material. As described above, the unimproved portion 6 includes a portion that is in shadow when the improving material is agitated and sprayed. In this application, the "in shadowed portion" means a portion that is in shadow (invisible) when viewed from the center of the agitation spray nozzle 5 in a horizontal cross-section. In other words, the "in shadowed portion" is a set of predetermined positions in a horizontal cross-section where, when a straight line is drawn radially from the center of the agitation spray nozzle 5 toward a predetermined position on the inner surface of the first retaining material 2, the straight line strikes another position on the inner surface of the first retaining material 2 before reaching the predetermined position.

[0019] As shown in Figure 8, the unimproved section setting step S1 includes a nozzle arrangement setting step S3, which sets the arrangement of the stirring injection nozzles 5 so that they are arranged in a line with spacing along the longitudinal direction D1 in the separation space, and a retaining material arrangement setting step S4, which adjusts the unimproved ratio, which is the ratio of the unimproved section 6 to the entire internal ground 4, by setting the relative arrangement of the first retaining material 2 and the second retaining material 3 to be shifted in the longitudinal direction D1. In this embodiment, the unimproved ratio is the ratio of the length of the unimproved section 6 in the longitudinal direction D1 to the entire internal ground 4. However, the unimproved ratio is not limited to this, and may be, for example, the ratio of the horizontal cross-sectional area of ​​the unimproved section 6 to the entire internal ground 4. The arrangement of the stirring injection nozzles 5 set in the nozzle arrangement setting step S3 is particularly preferred from the viewpoint of realizing construction that makes it easy to arrange the stirring injection nozzles 5 in a line with spacing along the longitudinal direction D1 in the separation space, but is not limited to this. In the retaining wall placement setting step S4, for example, as shown in Figure 8, the steps of setting the relative placement of the first retaining wall 2 and the second retaining wall 3 by shifting them in the longitudinal direction D1, and calculating the non-improvement rate are performed in this order.

[0020] As shown in Figures 1 and 2, the case where the stirring injection nozzle 5 is placed between opposing convex portions (resulting in a 17% failure rate) is preferable because it results in a lower failure rate than the case where the stirring injection nozzle 5 is placed between opposing concave portions (resulting in a 35% failure rate). Furthermore, as shown in Figures 3 to 7, the failure rate can be reduced by shifting the relative arrangement of the first retaining material 2 and the second retaining material 3 in the longitudinal direction D1 from an arrangement where the convex portions and concave portions face each other directly. In the example shown in Figures 3 to 7, the failure rate can be reduced from 17% to at least 13% (see Figure 4).

[0021] Therefore, in the nozzle placement setting step S3, it is preferable to set the placement of the stirring injection nozzle 5 so that in a horizontal cross-section, the stirring injection nozzle 5 is directly facing the protrusion of at least one of the first retaining wall material 2 and the second retaining wall material 3 in the width direction D2. Furthermore, in the retaining wall material placement setting step S4, it is preferable to set the relative placement of the first retaining wall material 2 and the second retaining wall material 3 by shifting them in the longitudinal direction D1 from an arrangement where the protrusions and recesses are directly facing each other.

[0022] As shown in Figure 8, the modeling analysis step S2 includes a cross-sectional modeling step S5 for modeling the horizontal cross-section of the retaining wall 1 including the unimproved section 6, a joint element condition setting step S6 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, and an FEM analysis step S7 for performing an elastoplastic analysis using the created elastoplastic FEM (Finite Element Method) model. In the modeling analysis step S2, for example, as shown in Figure 8, the cross-sectional modeling step S5, the joint element condition setting step S6, and the FEM analysis step S7 are performed in this order.

[0023] In the cross-sectional modeling step S5 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 12, 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.

[0024] Then, in the joint element condition setting step S6 of this embodiment, the joint elements (boundary surface elements) between the first retaining material 2 and the internal ground 4, and between the second retaining material 3 and the internal ground 4, are divided into improved and unimproved sections 6 in the horizontal cross-section, as shown in Figure 12, and vertical (peeling) characteristics and shear (sliding) characteristics are set for the improved and unimproved sections 6, respectively. For vertical (peeling) characteristics, for example, the stiffness modulus in the vertical direction and the tensile strength, which is the stress at which peeling occurs when tensile stress is generated, are set. For shear (sliding) characteristics, for example, the stiffness modulus in the shear direction and the allowable adhesion stress, which is the limit value at which sliding occurs, are set. For example, the allowable adhesion stress f = (1 / 3)C, where C is the cohesion of the internal ground 4.

[0025] As shown in Figure 8, the design method for the retaining wall 1 of this embodiment more specifically includes a soil condition setting step S8 in which soil conditions (such as N-value) are set, a retaining wall specification assumption step S9 in which the specifications of the first retaining material 2, the second retaining material 3, and the internal ground 4 are assumed, an unimproved section setting step S1, a modeling analysis step S2, and a displacement and stress confirmation step S10 in which the displacement and stress of the retaining wall 1 (composite retaining wall) are confirmed.

[0026] In this embodiment, the soil condition setting step S8, the retaining wall specification assumption step S9, the unimproved section setting step S1, the modeling analysis step S2, and the displacement / stress confirmation step S10 are performed in this order. In this embodiment, the modeling analysis step S2 has a repeating step S11 that returns to the retaining wall specification assumption step S9 if a problem is confirmed in the displacement / stress confirmation step S10, until it is confirmed that there is no problem in the displacement / stress confirmation step S10.

[0027] The construction method for the retaining wall 1 of this embodiment may include, in addition to the steps of the design method described above, an improvement step (not shown) in which an agitation and injection nozzle 5 is placed in a separated space and an improvement material is agitated and injected radially so that an unimproved section 6, which was set in the unimproved section setting step S1, is formed.

[0028] Therefore, according to the design method of the retaining wall 1 of this embodiment, it is not necessary to arrange the stirring and spray nozzles 5 in a complex and high density or to set the spray pressure in a complex manner to prevent the formation of unimproved sections 6 during construction, thus enabling easy construction of the retaining wall 1.

[0029] Furthermore, for the reasons mentioned above, a preferred retaining wall 1 that can be easily constructed is a retaining wall 1 in which a predetermined horizontal direction is the longitudinal direction D1 in the horizontal cross-section, and 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, wherein the relative positions of the first retaining member 2 and the second retaining member 3 in the longitudinal direction D1 are offset from the position in which the recesses and protrusions face each other in the width direction D2, and the internal ground 4 has an unimproved portion 6 (see Figures 4 to 7).

[0030] Furthermore, it is preferable that the aforementioned retaining wall 1 is a self-supporting retaining wall that does not require retaining wall shoring.

[0031] As shown in Figure 9, when the retaining wall 1 has an annular horizontal cross-sectional shape, as shown in Figure 10, in addition to the ground spring, a ring spring of the composite retaining wall acts on the retaining wall 1. Therefore, it is preferable to calculate and use this ring spring in the analysis. Specifically, as in the design method of the retaining wall 1 of the second embodiment shown in Figure 11, it is preferable to perform the joint element condition setting step S6 and the ring spring calculation step S12, which calculates the ring spring, between the cross-sectional modeling step S5 and the FEM analysis step S7. The spring constant K of the ring spring can be calculated, for example, by the following formula. K=(A·E m ) / R 2 K(kN / m 2 ): Spring constant of the ring spring in a composite retaining wall A(m 2): Effective cross-sectional area of ​​the ground improvement body E m (kN / m 2 ): Deformation coefficient of the ground improvement body R(m): Radius of the circular shaft at the improved body axis position.

[0032] The present invention is not limited to the embodiments described above, and can be modified in various ways without departing from its essence.

[0033] 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, and 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 third 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, 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 1 is modifiable as long as it includes a second retaining material 3 and an internal ground 4 formed by improvement, in which an improved material is radially mixed and sprayed by a stirring spray nozzle 5 positioned in a separated space between the first retaining material 2 and the second retaining material 3, and includes an unimproved section setting step S1 in which an unimproved section 6 including a part that is shaded when the improved material is mixed and sprayed, and a modeling analysis step S2 in which an analysis is performed by modeling the retaining wall 1 including the unimproved section 6. [Examples]

[0034] Figure 13(a) shows a cross-section along the width direction of the model shown in Figure 12 (unimproved rate = 50%) created as the first embodiment. Figure 13(b) is the ground reaction force diagram obtained by the model in Figure 13(a). Figure 13(c) is the displacement distribution diagram obtained by the model in Figure 13(a). Figure 13(d) is the bending moment diagram obtained by the model in Figure 13(a). Figure 13(e) shows the state of the joint elements of the model in Figure 13(a). The displacement confirmed in the displacement and stress confirmation step is shown in Figure 13(c). The bending moment, as stress confirmed in the displacement and stress confirmation step, is shown in Figure 13(d). It can be seen that there is almost no difference in ground reaction force, displacement, and bending moment depending on the extraction positions I to IV shown in Figure 14.

[0035] Figure 14 is an explanatory diagram to illustrate the locations that were the focus of attention in Figures 13 and 15.

[0036] Figure 15(a) shows the stress of the improved body at extraction position I shown in Figure 14, Figure 15(b) shows the stress of the improved body at extraction position II shown in Figure 14, Figure 15(c) shows the stress of the improved body at extraction position III shown in Figure 14, Figure 15(d) shows the stress of the improved body at extraction position IV shown in Figure 14, and Figure 15(e) shows the state of the joint elements of the model. It can be seen that stress tends to be transmitted to the improved body in areas where there are no unimproved parts (I and IV) at the peeling depth.

[0037] Based on the above results, it was confirmed that there were no problems with the displacement and stress in the first embodiment, and the structural feasibility was confirmed.

[0038] Figure 16 is an explanatory diagram showing a cross-section of a model created as a second embodiment, representing a thinning plan for the improved ground. For the internal ground 4, areas to be improved (indicated as "improved ground" in Figure 16) and areas not to be improved (indicated as "original ground" in Figure 16) were set up alternately along the longitudinal direction.

[0039] Figure 17 is an explanatory diagram to illustrate the location focused on in Figure 18.

[0040] Figure 18(a) shows the displacement distribution obtained by the model in Figure 16, Figure 18(b) shows the bending moment obtained by the model in Figure 16, and Figure 18(c) shows the state of the joint elements of the model. It can be seen that there is almost no difference in displacement and bending moment between the area where improvement is performed (indicated as "improved position" in Figure 18) and the area where improvement is not performed (indicated as "unimproved position" in Figure 18).

[0041] Figure 19 is an explanatory diagram to illustrate the location that was the focus of attention in Figure 20.

[0042] Figure 20(a) shows the stress distribution of the steel sheet pile at the improved location obtained by the model in Figure 16, and Figure 20(b) shows the stress distribution of the improved body at the improved location obtained by the model in Figure 16. It can be seen that stress tends to be transmitted from the unimproved location to the improved location at the peeling depth.

[0043] Based on these results, it was confirmed that there were no problems with the displacement and stress in the second embodiment, and the structural feasibility was confirmed. [Explanation of Symbols]

[0044] 1. Retaining wall 2. First retaining wall 2a Recess 2b Convex part 3. Second retaining wall 3a Recess 3b Convex part 4 Internal ground 5. Stirring and spray nozzle 6 Unimproved part D1 Longitudinal direction D2 width direction L specified distance S1 Step for setting unimproved parts S2 Modeling and Analysis Step S3 Nozzle placement setting step S4 Retaining wall placement setting step S5 Cross-sectional modeling step S6 Joint Element Condition Setting Step S7 FEM Analysis Step S8 Soil Condition Setting Step S9 Retaining wall specification (assumption step) S10 Displacement and stress confirmation step S11 Repeat Step S12 Ring spring calculation step

Claims

1. A retaining wall having a predetermined horizontal direction as the longitudinal direction in a horizontal cross-section, comprising: a first retaining member having alternating recesses that are recessed from the inner surface to the outer surface and convex portions that project from the inner surface to the inner surface in the longitudinal direction; a second retaining member spaced a predetermined distance from the first retaining member in a width direction perpendicular to the longitudinal direction, having alternating recesses that are recessed from the inner surface to the outer surface and convex portions that project from the inner surface to the inner surface in the longitudinal direction; and an internal ground formed by improvement in the separated space between the first and second retaining members, wherein the relative positions of the first and second retaining members in the longitudinal direction are offset from the positions where the recesses and convex portions face each other in the width direction, and the internal ground has an unimproved portion.

2. The retaining wall according to claim 1, wherein the retaining wall is a self-supporting retaining wall.

3. The retaining wall according to claim 1 or 2, wherein the retaining wall has an annular horizontal cross-sectional shape.

Images