Earth retaining structure, earth retaining structure analysis program, and earth retaining structure construction method

Abstract

To provide an earth retaining structure appropriately evaluating an acting earth pressure, a program analyzing the structure, and a method for constructing the earth retaining structure.SOLUTION: An earth retaining structure constructed by ground improvement comprises a bottom slab and an earth retaining wall. The bottom slab is a substantially horizontal (including horizontal) slab body formed in a ground. The earth retaining wall is a substantially vertical (including vertical) wall body formed underground. A lower end of the earth retaining wall is rigidly joined to the bottom slab. When a ground mounted on the bottom slab is excavated, the bottom slab is pushed upward, and a force pushing to a rear side by the earth retaining wall is applied to the ground.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to technology related to earth retaining structures, and more specifically to an earth retaining structure that can efficiently and rationally retain earth by properly understanding the behavior of the earth retaining structure after excavation, a program for analyzing the structure, and a method for constructing the earth retaining structure. [Background technology]

[0002] Japan has suffered devastating damage from a series of disasters, including the Ise Bay Typhoon in 1959, the Great Hanshin-Awaji Earthquake in 1995, and the Great East Japan Earthquake in 2011. However, lessons learned from these disasters have led to the implementation of various measures, including disaster prevention and mitigation measures, as well as evacuation methods. Furthermore, the Fundamental Plan for National Resilience was approved by the Cabinet in 2014, with the aim of building a safe and secure nation, region, and economy that is both strong and resilient.

[0003] Against this background, more efficient and rational methods are being sought for various types of construction in order to promote efficient countermeasures. Earth retaining construction methods are one example of this, and although design methods have already been generalized based on the extensive experience accumulated to date, more efficient and rational methods are desired from the perspectives of improving workability and safety and shortening construction periods. In particular, earth retaining construction methods using cut and shoring require considerable construction effort and time, so an effective alternative method is desired in cases where a rapid response is required, such as in the event of a disaster.

[0004] Therefore, in recent years, a self-supporting earth retaining structure using a ground improvement body has been applied, which allows for the practical application of an earth retaining method that does not require earth retaining supports. For example, Patent Document 1 proposes a technology in which a columnar improved body is constructed by discharging a cement-based solidification material from a part of the mixing blades of a mixing and mixing device, and also a so-called preloading technology is proposed in which a load is applied from above the improved body. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 10-292364 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, freestanding earth retaining construction methods using ground improvement bodies have adopted not only a structure consisting of only an earth retaining wall, as in Patent Document 1, but also a structure consisting of a base slab and an earth retaining wall. In conventional designs, not only in structures consisting of only an earth retaining wall, but also in structures consisting of a base slab and an earth retaining wall, the earth pressure (mainly active earth pressure) acting on the earth retaining wall after excavation of the ground was considered only from the side (ground side). However, when the ground above the base slab (hereinafter referred to as the "overlying ground") is excavated, not only does earth pressure act on the earth retaining wall, but it also has a structural impact on the base slab. Specifically, as the overlying ground is removed, the base slab changes from a loaded state to an excavated state.

[0007] The inventors of the present invention realized that this "rebound" effect, which occurs when the load changes from a loaded state to an excavated state, also affects the behavior of the earth-retaining wall. Specifically, when the soil above the base slab is excavated, the load (the weight of the overlying soil) that had been applied is released, resulting in a vertically upward load acting on the base slab. Furthermore, if the earth-retaining wall and base slab are rigidly connected (a connection that transmits bending moments), the wall will tend to collapse toward its rear (the ground). Because the rear-facing slope of the earth-retaining wall provides the ground with a force that resists earth pressure, the earth pressure applied in conventional designs is actually reduced by the resistance provided by the earth-retaining wall. In other words, when it comes to a structure consisting of a base slab and earth-retaining wall, the conventional design concept, which only considered lateral earth pressure, resulted in excessively large structural dimensions (shape, strength, etc.).

[0008] The object of the present invention is to solve the problems associated with conventional technology, namely, to provide a retaining structure that appropriately evaluates the acting earth pressure, a program for analyzing the structure, and a method for constructing the retaining structure. [Means for solving the problem]

[0009] The present invention was made with a focus on the realization of an efficient and rational earth retaining structure by calculating external forces (mainly earth pressure) that take into account the behavior of the retaining wall due to the rebound of the base slab, and is an invention based on an unprecedented idea.

[0010] The earth retaining structure of the present invention is constructed by ground improvement and comprises a base slab and an earth retaining wall. The base slab is a generally horizontal (including horizontal) slab formed in the ground, while the earth retaining wall is a generally vertical (including vertical) wall formed underground. The lower end of the earth retaining wall is rigidly connected to the base slab. When the ground above the base slab is excavated, the base slab is pushed upward, and the earth is subjected to a force pushing it backward by the earth retaining wall.

[0011] The earth retaining structure analysis program of the present invention is a program that causes a computer to execute functions for analyzing the behavior of the earth retaining structure of the present invention, and has functions for causing the computer to execute a specification setting process, a model setting process, and a structural analysis process. The specification setting process is a process for setting base slab specifications (including the base slab's shape and physical properties) and earth retaining wall specifications (including the earth retaining wall's shape and physical properties). The model setting process is a process for setting a structural model including the ground and earth retaining structure (base slab specifications and earth retaining wall specifications). The structural analysis process is a process for calculating stress and displacement of the earth retaining wall by performing stress and deformation analysis on a structural model from the initial state (a state in which the base slab is loaded with the soil on top) to the excavation state (a state in which the soil on top is unloaded). The structural analysis process calculates the stress and displacement of the earth retaining wall based on the "backside earth pressure" acting on the earth retaining wall from its back side in the excavation state, which is the force exerted by the earth retaining wall pushing the ground toward its back side.

[0012] The earth retaining structure analysis program of the present invention can also cause a computer to execute processing assuming an excavation state in which the overlying ground is gradually unloaded. In this case, the structural analysis processing is a process of determining the stress and displacement of the earth retaining wall in each excavation state by performing stress and deformation analysis on a structural model in multiple stages of excavation in which the overlying ground is gradually unloaded.

[0013] The retaining wall structure analysis program of the present invention can also cause a computer to execute processing assuming a model including preload material. In this case, the model setting process is a process of setting a structural model including the preload material when the preload material to be placed on the overlying ground is input. The structural analysis process is a process of performing stress and deformation analysis on the structural model in an excavated state after the overlying ground and preload material are unloaded from the initial state in which the overlying ground and preload material are loaded.

[0014] The earth retaining structure construction method of the present invention is a method for constructing an earth retaining structure of the present invention, and includes a structural specification design process, a base slab formation process, an earth retaining wall formation process, and an excavation process. In the structural specification design process, the earth retaining wall specifications (including the shape and physical properties of the earth retaining wall) are determined. In the base slab formation process, the base slab is formed by ground improvement. In the earth retaining wall formation process, the earth retaining wall is formed by ground improvement based on the earth retaining wall specifications determined in the structural specification design process. In the excavation process, the ground above the base slab is excavated. The structural specification design process also includes a specification setting process, a model setting process, and a specification determination process. In the specification setting process, the base slab specifications (including the shape and physical properties of the base slab) and the earth retaining wall specifications are provisionally set. In the model setting process, a structural model including the ground and the earth retaining structure (the base slab specifications and the earth retaining wall specifications) is set. In the specification determination process, stress and deformation analysis is performed on a structural model from the initial state (a state in which the base slab is loaded with the soil above it) to the excavated state (a state in which the soil above it is unloaded) to determine the stress and displacement of the retaining wall, and then the specifications of the retaining wall are determined.In the specification determination process, the stress and displacement of the retaining wall are determined based on the "backside earth pressure" that acts on the retaining wall from the back side in the excavated state, which is the force that pushes the ground toward the back side of the retaining wall.

[0015] The retaining structure construction method of the present invention can also be a method that further includes a preloading step. In this preloading step, preload material is placed on the overlying ground before the base slab formation step and the retaining wall formation step. In this case, the model setting step temporarily sets the preload material and sets a structural model including the preload material. In the specification determination step, stress and deformation analysis is performed on the structural model in an excavated state in which the overlying ground and preload material are removed from the initial state in which the overlying ground and preload material are loaded, and the preload material is determined after calculating the stress and displacement of the retaining wall. In the preloading step, the amount of preload material determined in the specification determination step is placed.

[0016] The method for constructing an earth retaining structure of the present invention can also be a method for constructing an earth retaining structure of the present invention in which the earth retaining walls are configured to include a left retaining wall and a right retaining wall. In this case, in the earth retaining wall formation step, the left retaining wall is formed so as to be rigidly joined to the left end of the base slab, and the right retaining wall is formed so as to be rigidly joined to the right end of the base slab. [Effects of the Invention]

[0017] The retaining wall structure, the retaining wall structure analysis program, and the retaining wall structure construction method of the present invention have the following advantages. (1) Conventionally, designs have been made taking into account wall deformation caused only by lateral earth pressure, which has led to the tendency to plan earth retaining structures with excessive specifications (wall thickness, strength, etc.). In contrast, the present invention utilizes "rebound reaction force" to design taking into account wall stress and deformation, making it possible to plan earth retaining structures with appropriate specifications. (2) When the rebound effect due to the unloading of the overlying soil is insufficient, the desired rebound effect can be achieved by placing preloading material. In other words, the preloading effect can be flexibly adjusted according to the dimensions and shape of the bottom slab or the excavation depth. (3) Because it is possible to construct an earth retaining structure without using cut and shoring, it can be used in cases where a rapid response is required, such as in the event of a disaster, and it can also reduce the time and cost required for construction. Furthermore, it is possible to secure sufficient working space, which improves workability and safety. [Brief explanation of the drawings]

[0018] [Figure 1] (a) is a cross-sectional view showing the double-wall structure before the overlying ground is excavated, and (b) is a cross-sectional view showing the double-wall structure after the overlying ground is excavated and the structure is constructed. [Figure 2] A top view showing a schematic diagram of the retaining structure that supports the earth pressure from behind in four directions. [Figure 3] (a) is a cross-sectional view showing a schematic diagram of the single-wall type before the overlying ground is excavated, and (b) is a cross-sectional view showing a schematic diagram of the single-wall type after the structure has been constructed after the overlying ground is excavated. [Figure 4] (a) is a cross-sectional view showing a schematic diagram of a double-wall type earth retaining structure that has been deformed due to excavation of the overlying ground, and (b) is a cross-sectional view showing a schematic diagram of a single-wall type earth retaining structure that has been deformed due to excavation of the overlying ground. [Figure 5] A model diagram that shows the relationship between the "reaction force due to rebound," the "backside earth pressure" that was previously considered the design load, and the "reaction force acting backside earth pressure" that takes into account the reaction force due to rebound in an excavation state. [Figure 6] 1 is a flowchart showing the main processing flow of the retaining wall structure analysis program of the present invention. [Figure 7] 1 is a flow chart showing the main steps of the method for constructing an earth retaining structure of the present invention. [Figure 8] FIG. 2 is a step diagram showing the main steps of the method for constructing an earth retaining structure according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] An example of an earth retaining structure, an earth retaining structure analysis program, and an earth retaining structure construction method according to the present invention will be described with reference to the drawings.

[0020] 1. Earth retaining structure First, the earth retaining structure of the present invention will be described in detail with reference to the drawings. Note that the earth retaining structure analysis program of the present invention is a program for analyzing the earth retaining structure of the present invention, and the earth retaining structure construction method of the present invention is a method for constructing the earth retaining structure of the present invention. Therefore, the earth retaining structure of the present invention will be described first, and then the earth retaining structure analysis program and earth retaining structure construction method of the present invention will be described.

[0021] FIG. 1 is a cross-sectional view (cut along a vertical plane) showing a schematic diagram of an earth retaining structure 100 of the present invention. (a) shows the state before the overlying ground UG is excavated (hereinafter referred to as the "initial state"), and (b) shows the state after the overlying ground UG has been excavated (hereinafter referred to as the "excavated state") and a structure ST has been constructed. As shown in this figure, the earth retaining structure 100 of the present invention is composed of a generally vertical (including vertical) earth retaining wall 110 and a generally horizontal (including horizontal) base slab 120. However, the earth retaining wall 110 and the base slab 120 are rigidly connected (a connection that transmits bending moments). Furthermore, as shown in FIG. 1(a), the earth retaining structure 100 is initially constructed within the ground. That is, the earth retaining wall 110 and the base slab 120 are constructed within the ground, and the "overlying ground UG" remains above the base slab 120. As already mentioned, the "overlying ground UG" refers to the ground above the base slab 120, and is the ground that will ultimately be excavated and removed as shown in FIG. 1(b).

[0022] It is advisable to use ground improvement techniques when forming the retaining wall 110 and the base slab 120 in the ground. Ground improvement is a technique for forming an improved body in the ground by stirring and mixing a cement-based solidification material or improvement material (hereinafter collectively referred to as "additives") with in-situ soil, and this improved body becomes the retaining wall 110 and the base slab 120. As long as the retaining wall 110 and the base slab 120 can be formed, various conventional methods such as mechanical stirring and high-pressure jetting can be used for ground improvement, and for example, the "WILL Method (registered trademark)" can be used.

[0023] The WILL method forms an improved soil by mixing and stirring a slurry-like solidification or improvement material (i.e., additives) with in-situ soil. Specifically, a rod attached to a base machine (such as a backhoe) is inserted into the ground, and additives are injected through a mixing blade attached to the end of the rod. The additives and in-situ soil are then mixed and stirred to form an improved soil. For example, to form the base slab 120, the rod is used to drill a hole in the ground to the planned depth, and the in-situ soil is stirred and mixed while injecting additives. The additives are injected and mixed in the planned amount to achieve the planned thickness and range (i.e., shape) of the base slab 120. It is not necessary to inject additives while drilling the overlying soil UG; instead, a lean additive can be injected and mixed. Similarly, to form the retaining wall 110, additives are injected and the in-situ soil is stirred and mixed in the planned amount so that the retaining wall 110 has the planned thickness and range (i.e., shape).

[0024] In the retaining structure 100 shown in FIG. 1, a retaining wall 110 (hereinafter, specifically referred to as the "left retaining wall 110L") is rigidly connected to the left end of the base slab 120, and a retaining wall 110 (hereinafter, specifically referred to as the "right retaining wall 110R") is rigidly connected to the right end of the base slab 120. For convenience, the retaining structure 100 in which the retaining walls 110 are rigidly connected to the left and right ends of the base slab 120 will be referred to as the "double-wall retaining structure 100." In the case of the double-wall retaining structure 100, when the overlying ground UG is excavated, the earth pressure acting on the retaining wall 110 from the excavation side (hereinafter, referred to as the "front earth pressure") decreases as the excavation progresses. As a result, the earth pressure acting on the left retaining wall 110L from the back side (the left side in the figure) (hereinafter, simply referred to as the "back earth pressure") becomes dominant, and similarly, the back earth pressure acting on the right retaining wall 110R becomes dominant. The backside earth pressure is supported by the left retaining wall 110L, the right retaining wall 110R, and the base slab 120 rigidly connected to them, allowing the structure ST to be constructed stably inside (excavation side) the double-wall retaining structure 100.

[0025] The double-wall type earth retaining structure 100 shown in FIG. 1 has a structure in which a left retaining wall 110L and a right retaining wall 110R are rigidly connected to a base slab 120, and is structured to support backside earth pressure acting in two directions within the same vertical plane. The double-wall type earth retaining structure 100 is not limited to a structure that supports backside earth pressure in two directions (left and right on the page in FIG. 1), but can also be structured to support backside earth pressure in four directions (left and right, up and down on the page in FIG. 2), as shown in FIG. 2. FIG. 2 is a plan view, viewed from above, that schematically shows an earth retaining structure 100 that supports backside earth pressure in four directions. In this case, if the base slab 120 is rectangular in plan view, the retaining walls 110 are rigidly connected to all sides that make up the rectangle. In this case, adjacent retaining walls 110 can also be rigidly connected to each other, or the retaining walls 110 can be structured not to be rigidly connected to each other.

[0026] The earth retaining structure 100 of the present invention is not limited to a double-wall type earth retaining structure 100. It can also be a structure in which the earth retaining wall 110 is rigidly connected only to one end of the base slab 120, as shown in FIG. 3. For convenience, this type of earth retaining structure 100 in which the earth retaining wall 110 is rigidly connected only to one end of the base slab 120 will be referred to as a "single-wall type earth retaining structure 100." FIG. 3 is a cross-sectional view (cut along a vertical plane) schematically illustrating the single-wall type earth retaining structure 100. (a) shows the initial state before the overlying ground UG is excavated, and (b) shows the excavated state after the overlying ground UG has been excavated and the structure ST has been constructed. While FIG. 3 shows two single-wall type earth retaining structures 100, one on each side, it is of course preferable to place the single-wall type earth retaining structure 100 in one location when retaining earth on only one side. When retaining earth in four directions as shown in FIG. 2, it is advisable to place individual wall-type retaining structures 100 in four locations.

[0027] In the case of the single-wall type earth retaining structure 100 shown in Figure 3, when the overlying ground UG is excavated, the front earth pressure acting on the earth retaining wall 110 decreases as a result of the excavation, and as a result, the back earth pressure acting on the earth retaining wall 110 becomes dominant. The back earth pressure is then supported by the earth retaining wall 110 and the base slab 120 rigidly connected to it, allowing the structure ST to be stably constructed inside (the excavation side) of the single-wall type earth retaining structure 100. Note that the back earth pressure acts on the earth retaining wall 110 even before excavation (i.e., in the initial state), and the back earth pressure continues to act after excavation (i.e., in the excavation state), and the wall is designed to prevent displacement in this state.

[0028] 4A and 4B are cross-sectional views schematically illustrating the retaining structure 100 deformed due to the excavation of the overlying ground UG, where (a) shows the case of a double-wall type retaining structure 100 and (b) shows the case of a single-wall type retaining structure 100. When the retaining structure 100 of the present invention is constructed, the overlying ground UG is placed on the base slab 120, i.e., the base slab 120 and the ground below it (hereinafter referred to as the "supporting ground") are loaded with the weight of the overlying ground UG (hereinafter simply referred to as the "surcharge load"). On the other hand, when the overlying ground UG is excavated, in other words, when the overlying ground UG is removed from the base slab 120, the base slab 120 and the supporting ground are released from the previous overlying load. Then, as a result of the removal of the surcharge load from above, a so-called rebound state is created in which a vertically upward force (hereinafter referred to as "rebound force") acts on the supporting ground to push up the base slab 120.

[0029] For example, in the case of the double-wall type earth retaining structure 100 shown in Figure 4(a), the rebound force causes the base slab 120 to have an upward convex shape, and the base slab 120 is deformed so that it is pulled inward (towards the excavation). In addition, as the base slab 120 is deformed by the rebound force, the retaining walls 110 rigidly joined to the base slab 120 are deformed so that they tilt toward their rear faces. Specifically, the left retaining wall 110L is deformed so that it tilts to the left in the figure, and the right retaining wall 110R is deformed so that it tilts to the right in the figure.

[0030] In the case of the single-wall type earth retaining structure 100 shown in Figure 4(b), the rebound force causes the base slab 120 to rotate upward, displacing the base slab 120 so that it is moved inward (towards the excavation side). In addition, as the base slab 120 rotates due to the rebound force, the retaining wall 110 rigidly joined to the base slab 120 rotates so that it tilts toward its rear. Specifically, the retaining wall 110 on the left side of the figure tilts so that it rotates counterclockwise, and the retaining wall 110 on the right side of the figure tilts so that it rotates clockwise.

[0031] When the retaining wall 110 tilts toward its rear side in this way, the wall 110 presses against the ground behind it (hereinafter simply referred to as the "rear ground"), causing the ground to displace toward the rear side. For example, if an appropriate spring constant can be set for the rear ground, it is possible to calculate the force acting on the rear ground based on the amount of displacement and the spring constant, i.e., the force with which the retaining wall 110 presses against the rear ground (hereinafter referred to as the "rebound reaction force"). In any case, a rebound reaction force caused by the tilt of the retaining wall 110 acts on the rear ground.

[0032] As shown in Figure 5, this rebound reaction force acts in a direction opposite to the earth pressure (active earth pressure and static earth pressure) exerted by the back ground on the retaining wall 110. Figure 5 is a model diagram that schematically illustrates the relationship between the "rebound reaction force," the "back ground earth pressure" that was previously used as a design load, and the back ground earth pressure that takes into account the rebound reaction force during excavation. For convenience, the back ground earth pressure that takes into account the rebound reaction force generated during excavation will be referred to as the "reaction back ground earth pressure." Traditionally, when performing so-called structural design to consider the displacement and strength of a retaining wall, the back ground earth pressure was calculated based on the excavation height, soil specifications (unit weight, internal friction angle, or cohesion), groundwater level, and other conditions. However, in the case of the retaining wall 110 of the present invention, as shown in Figure 5, the "rebound reaction force" actually acts. Therefore, it is reasonable to perform structural design using the reaction back ground earth pressure that takes into account this rebound reaction force, i.e., it is reasonable to perform structural design so that the back ground earth pressure and the rebound reaction force are balanced. In this way, the retaining wall 110 of the present invention can be structurally designed using the reaction force acting on the backside earth pressure, taking into account the reaction force due to rebound, and as a result, economical retaining work can be realized by avoiding over-design.

[0033] 2. Earth retaining structure analysis program Next, the earth retaining structure analysis program of the present invention will be described in detail with reference to the drawings. Note that the earth retaining structure analysis program of the present invention is a program for analyzing the earth retaining structure 100 described so far, and therefore, we will avoid overlapping explanations with those described for the earth retaining structure 100 and will only explain the content unique to the earth retaining structure analysis program of the present invention. In other words, content not described here is the same as that described in "1. Earth Retaining Structure."

[0034] The earth retaining structure analysis program of the present invention is a program for analyzing the earth retaining structure 100 of the present invention, and has the function of causing a computer to execute specification setting processing, model setting processing, earth pressure calculation processing, and structural analysis processing. Here, the computer is equipped with a processor such as a CPU, memory such as ROM and RAM, input means such as a mouse and keyboard, and a display, and can be a personal computer (PC), a tablet PC such as an iPad (registered trademark), or a mobile terminal including a smartphone.

[0035] The main processing flow of the earth retaining structure analysis program of the present invention will be explained below with reference to Figure 6. Figure 6 is a flow chart showing the main processing flow of the earth retaining structure analysis program of the present invention, with the central column showing the processing to be performed, the left column showing information necessary for that processing, and the right column showing information resulting from that processing.

[0036] First, the operator performs input operations to set the specifications for forming the retaining wall 110 (hereinafter, specifically referred to as "retaining wall specifications") and the specifications for forming the base slab 120 (hereinafter, specifically referred to as "base slab specifications") (Step 201 in Figure 6). However, the base slab specifications and retaining wall specifications set here are only provisional values, and will be finally determined after structural analysis of the retaining wall 110 and base slab 120 is performed and verified. The retaining wall specifications include the shape of the retaining wall 110 (dimensions such as thickness, height, and width) and the physical properties of the retaining wall 110 (density, strength, elastic modulus, etc.), and can also include the type and amount of additive (e.g., amount injected per unit). Similarly, the base plate specifications include the shape of the base plate 120 (dimensions such as thickness, width, and depth) and the physical properties of the base plate 120 (density, strength, elastic modulus, etc.), and can also include the type and amount of additive (such as the amount injected per unit).

[0037] Once the slab specifications and retaining wall specifications have been set, a model for numerical analysis (hereinafter referred to as the "structural model") is set based on the ground and the retaining structure 100 formed within the ground (Step 202 in Figure 6). The retaining structure 100 that constitutes the structural model is naturally configured based on the slab specifications and retaining wall specifications that have been set in advance. The operator also performs input operations to set each element of the ground, i.e., the shape of the ground surface, the shape of each layer (including layer thickness), and the ground parameters of each layer. Examples of ground parameters include unit volume weight, deformation coefficient, cohesion, internal friction angle, initial void ratio, compression index, expansion index, and dilatancy coefficient.

[0038] As described above, when the initial state (the state before the overlying ground UG is excavated) is changed to the excavated state (the state after the overlying ground UG is excavated), a rebound force acts to push up the base slab 120, causing the retaining wall 110 to tilt, resulting in a rebound reaction force on the back ground. The greater the surcharge load from the overlying ground UG, the greater the rebound force and the rebound reaction force, thereby reducing the difference between the back earth pressure and the rebound reaction force. Therefore, if the excavation height (i.e., the thickness of the overlying load) is small, the rebound reaction force also decreases, and it may be that sufficient resistance to the back earth pressure is not obtained. In such cases, it is recommended to place a heavy object (hereinafter referred to as a "preload material") above the overlying ground UG, i.e., to set a preload. Specifically, the operator inputs the amount of preload material to be placed, the unit weight, and the placement shape (area and layer thickness), etc., and then creates a structural model including the preload material. Examples of preload materials include embankment materials, concrete, and steel weights.

[0039] Once the structural model is set, a numerical analysis is performed in the initial state using the structural model (Step 203 in FIG. 6). This numerical analysis is an analysis that can determine the stress distribution and deformation of the ground (hereinafter referred to as "stress deformation analysis"), and various conventional analytical methods can be used, such as the finite element method (FEM) and analysis methods using models that use spring constants. Note that the stress deformation analysis in the initial state can be performed only in the state where the retaining structure 100 is formed in the ground (hereinafter referred to as the "initial state after formation"), or it can be performed in the state before the retaining structure 100 is formed in the ground (hereinafter referred to as the "initial state before formation") and in the initial state after formation. Of course, when the structural model is set up including a preload material, both the initial state before formation and the initial state after formation are analyzed using the structural model including the preload material.

[0040] After a stress and strain analysis is performed on the structural model in its initial state, a stress and strain analysis is then performed on the structural model in its excavated state (Step 204 in Figure 6). Of course, the stress and strain analyses for the initial state and the excavated state are performed using the same analysis method (for example, FEM). Note that the stress and strain analysis for the excavated state can be performed for only the final excavated state as the excavated state, or it can be performed for each excavated state by setting stages of excavation (for example, GL-2.5m, GL-4.0m, GL-6.0m, etc.). Of course, when the structural model is set up including a preload material, the analysis is performed using the structural model in its excavated state with the preload material removed along with the overlying ground UG.

[0041] By performing a stress deformation analysis on a structural model in the initial state and then performing a stress deformation analysis on a structural model in the excavated state (for example, analysis using a model using spring constants), the stress intensity (stress distribution) and displacement amount (displacement distribution) of the ground and earth retaining structure 100 in the excavated state can be obtained, i.e., the backside earth pressure (earth pressure distribution) acting on the earth retaining wall 110 can be determined. Of course, if a structural model is set up with stepwise excavation states, the backside earth pressure in each excavation state can be determined.

[0042] On the other hand, when performing analysis using FEM, if a stress / deformation analysis is performed on a structural model in an excavated state, the stress and displacement of the retaining wall 110 and the base slab 120, which are based on the reaction force acting on the backside earth pressure, can be obtained. In this case, if a structural model of a stepwise excavation state is set, the stress and displacement can be obtained for each excavation state. Specifically, based on the set base slab specifications and retaining wall specifications, the displacement (displacement distribution) and stress (stress distribution) of the retaining wall 110 are calculated, and the displacement (displacement distribution) and stress (stress distribution) of the base slab 120 are also calculated.

[0043] Once the stress levels and displacement amounts of the retaining wall 110 and the base slab 120 have been obtained, the results (i.e., the stress levels and displacement amounts) are verified (Step 205 in Figure 6). At this time, if a structural model for various excavation states has been set up, it is advisable to verify the results for each excavation state. Specifically, the stress levels and displacement amounts of the retaining wall 110 and the base slab 120 are compared with predetermined allowable values ​​(or allowable ranges), and the suitability of the retaining structure 100 based on the set base slab specifications and retaining wall specifications is determined. If the stress levels and displacement amounts are below the allowable values ​​(or within the allowable ranges) (Yes in Step 205 in Figure 6), the base slab specifications and retaining wall specifications are finalized (Step 206 in Figure 6). On the other hand, if the stress level or displacement is above the allowable value (or outside the allowable range) (No in Step 205 in Figure 6), the base slab specifications or retaining wall specifications are changed, or various values ​​related to the preload material (such as the loading amount or unit volume weight) are changed, and the series of processes (Steps 201 to 205 in Figure 6) are repeated.

[0044] 3. Earth retaining structure construction method Next, the earth retaining structure construction method of the present invention will be described in detail with reference to the drawings. Note that the earth retaining structure construction method of the present invention is a method for constructing the earth retaining structure 100 described up to this point, and therefore, we will avoid overlapping explanations with those explained in the earth retaining structure 100 and the earth retaining structure analysis program, and will only explain content unique to the earth retaining structure construction method of the present invention. In other words, content not described here is the same as that explained in "1. Earth Retaining Structure" and "2. Earth Retaining Structure Analysis Program."

[0045] Figure 7 is a flow chart showing the main steps of the earth retaining structure construction method of the present invention, and Figure 8 is a step diagram showing the main steps of the earth retaining structure construction method of the present invention. As shown in this figure, the earth retaining structure construction method of the present invention can be broadly divided into "structural specification design," which designs the specifications of the earth retaining structure 100 (particularly the base slab specifications and earth retaining wall specifications), and "construction," which actually builds the earth retaining structure 100. Of these, the structural specification design can be carried out using the earth retaining structure analysis program of the present invention.

[0046] In the structural specification design, the slab specifications and the retaining wall specifications are first set (Step 311 in FIG. 7), and then the structural model is set (Step 312 in FIG. 7). As mentioned above, a structural model including a preload material can be set at this time. After the structural model is set, stress and deformation analysis is performed on the structural model in the initial state and on the structural model in the excavated state to calculate the stress and displacement of the retaining wall 110 and the slab 120, which are based on the backside earth pressure acting as a reaction force (Step 313 in FIG. 7). The stress and displacement are then compared with allowable values ​​(or allowable ranges) to determine the suitability of the retaining structure 100 based on the set slab specifications and retaining wall specifications. Finally, the final specifications of the retaining structure 100 (particularly the slab specifications and the retaining wall specifications) are determined (Step 314 in FIG. 7).

[0047] In the actual construction, the retaining structure 100 is constructed based on the specifications determined in the structural specification design. If a preload material is specified in the structural specification design, the preload material PL is first placed on the top surface of the overlying ground UG as shown in FIG. 8(a) (Step 321 in FIG. 7). Then, using a ground improvement technique such as the WILL method, the base slab 120 is formed in the ground as shown in FIG. 8(b) (Step 322 in FIG. 7), and the retaining wall 110 is formed in the ground as shown in FIG. 8(c) (Step 323 in FIG. 7). The retaining wall 110 can be formed first after the base slab 120, or after the base slab 120, or the retaining wall 110 and base slab 120 can be formed simultaneously. After the retaining wall 110 and base slab 120 are formed and a predetermined curing period has elapsed, the overlying ground UG within the retaining structure 100 is excavated as shown in FIG. 8(d) (Step 324 in FIG. 7). When applying a mechanical mixing type ground improvement method such as the WILL method, the upper part of the base slab 120 (i.e., the excavated part) can be treated without adding solidification material or with a lean mixture. It is also possible to use a high-pressure jet mixing method or a chemical injection method to replace only the base slab 120 with improved soil. [Industrial Applicability]

[0048] The earth retaining structure, earth retaining structure analysis program, and earth retaining structure construction method of the present invention can be used in various situations where earth retaining is required, such as earth retaining work when constructing underground structures, earth retaining work when constructing foundations for retaining walls and bridge abutments, earth retaining work when excavating the bottom of a slope, etc. The present invention realizes efficient and rational earth retaining work, which in turn contributes to the "national resilience" promoted by the government. Considering this, the present invention can be said to be an invention that is not only applicable industrially but is also expected to make a significant contribution to society. [Explanation of symbols]

[0049] 100 Earth retaining structure of the present invention 110 Earth retaining wall (of earth retaining structure) 110L Left retaining wall (of earth retaining structure) 110R Right retaining wall (of earth retaining structure) 120 (Earth retaining structure) base plate PL preload material ST structure UG overlaying ground

Claims

1. An earth retaining structure constructed by ground improvement, a horizontal or approximately horizontal base slab formed in the ground; a vertical or nearly vertical retaining wall formed underground; The lower end of the earth retaining wall is rigidly connected to the bottom slab, When the ground above the base plate is excavated, the base plate is pushed upward, and a force is applied to the ground by the retaining wall, pushing it toward its back side. An earth retaining structure characterized by:

2. A program that causes a computer to execute a function of analyzing a retaining structure constructed by ground improvement, The retaining structure has a horizontal or approximately horizontal base plate formed in the ground and a vertical or approximately vertical retaining wall formed underground, and the lower end of the retaining wall is rigidly connected to the base plate, a specification setting process for setting base slab specifications including the shape and physical properties of the base slab and retaining wall specifications including the shape and physical properties of the retaining wall; a model setting process for setting a structural model including the ground and the retaining structure based on the base slab specifications and the retaining wall specifications; a structural analysis process for determining the stress and / or displacement of the retaining wall by performing a stress deformation analysis on the structural model in a state where the overlying ground of the base slab is unloaded from an initial state where the overlying ground is loaded, In the structural analysis process, the stress and / or displacement of the retaining wall is calculated based on the backside earth pressure acting on the retaining wall from the backside in the excavation state, the backside earth pressure being a force acting on the retaining wall to push the ground toward its backside. A retaining wall structure analysis program characterized by:

3. The structural analysis process performs stress and deformation analysis on the structural model in the excavation state in multiple stages in which the overlying ground is unloaded in stages, thereby determining the stress and / or displacement of the retaining wall in each of the excavation states.

3. The retaining wall structure analysis program according to claim 2.

4. In the structural analysis process, when a preload material to be placed on the upper ground is input, the structural model including the preload material is set, The structural analysis process performs a stress and deformation analysis on the structural model in the excavated state after the overlying ground and the preload material are unloaded from the initial state in which the overlying ground and the preload material are loaded.

4. The retaining wall structure analysis program according to claim 2 or 3.

5. A method for constructing an earth retaining structure having a horizontal or nearly horizontal base slab formed in the ground and a vertical or nearly vertical earth retaining wall formed underground, with the lower end of the earth retaining wall rigidly connected to the base slab, a structural specification design process for determining the specifications of the earth retaining wall, including the shape and physical properties of the earth retaining wall; a base slab forming step of forming the base slab by ground improvement; a retaining wall formation step of forming the retaining wall based on the retaining wall specifications determined in the structural specification design step by ground improvement; and an excavation step of excavating the ground above the bottom slab, The structural specification design process includes: a parameter setting step of provisionally setting the bottom slab parameters including the shape and physical properties of the bottom slab and the parameters of the retaining wall; a model setting process for setting a structural model including the ground and the retaining structure based on the base slab specifications and the retaining wall specifications; and a specification determination step of determining the specifications of the earth retaining wall by performing a stress and deformation analysis on the structural model in a state where the overlying ground of the base slab is unloaded from an initial state where the overlying ground is loaded, thereby determining the stress and / or displacement of the earth retaining wall, In the parameter determination step, the stress and / or displacement of the retaining wall is calculated based on the backside earth pressure acting on the retaining wall from the backside in the excavation state, the backside earth pressure being a force acting on the retaining wall to push the ground toward its backside. A method for constructing an earth retaining structure.

6. Further provided is a preloading step of placing a preload material on the upper ground before the base slab forming step and the retaining wall forming step, In the model setting step, the preload material is temporarily set, and the structural model including the preload material is set; In the specification determination step, a stress deformation analysis is performed on the structural model in the excavated state in which the overlying ground and the preload material are unloaded from the initial state in which the overlying ground and the preload material are loaded, and the preload material is determined after determining the stress and / or displacement of the retaining wall; In the preloading step, the amount of the preload material determined in the specification determining step is placed. The method for constructing an earth retaining structure according to claim 5.

7. The retaining wall is configured to include a left retaining wall and a right retaining wall, In the earth retaining wall forming step, the left earth retaining wall is formed so as to be rigidly joined at the left end of the bottom slab, and the right earth retaining wall is formed so as to be rigidly joined at the right end of the bottom slab. The retaining structure according to claim 5 or 6.

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