Ground evaluation method and method for determining specification of lattice-like improvement body

Abstract

To reflect a parameter indicating characteristics of a ground, and evaluate the ground while suppressing increase in calculation loads.SOLUTION: A method for evaluating a ground 100 includes: a first evaluation step (S121) of setting specification of a lattice-like improvement body 1 surrounding an in-lattice ground 81 including a region where liquefaction is assumed; a second evaluation step (122) of defining a ground dynamic model 100M including a model component stimulating the lattice-like improvement body 1 and a model component stimulating the in-lattice ground 81; a third evaluation step (123) of obtaining an equivalent repeated shear stress degree (τd) generated in the in-lattice ground 81, using the ground dynamic model 100M; and a fourth evaluation step (S13) of obtaining a liquefaction safety ratio (FL value) evaluating whether or not liquefaction of the in-lattice ground 81 is generated using the equivalent repeated shear stress degree (τd).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating ground and a method for determining the specifications of a grid-like improvement body. [Background technology]

[0002] Regarding ground liquefaction, methods are being considered to predict whether or not liquefaction will occur, and methods such as ground improvement to prevent liquefaction when liquefaction is predicted are also being considered.

[0003] For example, one method for predicting whether liquefaction will occur is the so-called F L There is an evaluation using F values. L The value is the resistance to liquefaction (τ L ) is the equivalent repeated shear stress (τ d ) is the value divided by F L If the value is 1 or less, it is assessed that liquefaction may occur. In other words, the resistance value (τ L ) to obtain the equivalent repeated shear stress (τ d ) is large, it is assessed that liquefaction may occur. L If the value is greater than 1, it is assessed that there is no possibility of liquefaction occurring. In other words, the resistance value (τ L ) to obtain the equivalent repeated shear stress (τ d ) is small, it is assessed that there is no possibility of liquefaction occurring.

[0004] When there is a possibility of liquefaction, measures to prevent liquefaction are implemented in the ground. Several principles and methods have been proposed as measures to prevent liquefaction. Representative methods have been established based on the combination of the principles and methods. For example, grid-like improvement employs the principle of improving (solidifying) the ground and achieves this improvement through a solidification method.

[0005] Although several evaluation methods have been proposed for assessing liquefaction in response to grid-like improvement using deep mixing treatment methods, no established evaluation method exists at present. L We propose a simple evaluation method using values. In these evaluation methods, the shear stiffness reduction rate of a certain ground (G / G0-γ curve) is used to perform an analysis using parameters such as the depth of the liquefied layer and grid spacing. Then, by statistically processing the analysis results, we obtain a specification calculation formula for the grid-type improvement body required for liquefaction countermeasures.

[0006] For example, Patent Document 1 discloses L This paper provides a simple method for calculating grid spacing based on a simplified liquefaction assessment method using values. The calculation method in Patent Document 1 simply calculates the appropriate grid spacing by taking into account the rigidity of the improved body in a grid-like improved ground for liquefaction prevention and the thickness of the liquefaction layer.

[0007] Furthermore, Patent Document 2 provides a method for easily evaluating liquefaction strength and deformation. The calculation method in Patent Document 2 targets partially improved ground such as buttress-shaped, lattice-shaped, or columnar improved ground. In the calculation method in Patent Document 2, first, the partially improved ground is constructed as an assembly of unit periodic structures. Next, the rigidity of the unit periodic structures is calculated based on mathematical homogenization theory. The rigidity of these unit periodic structures is assumed to be the equivalent rigidity of the entire partially improved ground. Then, the deformation of the partially improved ground is predicted in advance using the external forces acting on the partially improved ground after construction and this equivalent rigidity.

[0008] Furthermore, Non-Patent Document 1 recommends an improvement rate of 50% as a liquefaction countermeasure for grid-type improvement. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 4605856 [Patent Document 2] Patent No. 5190655 [Patent Document 3] Patent No. 5758837 [Patent Document 4] Patent No. 5088619 [Non-patent literature]

[0010] [Non-Patent Document 1] Architectural Institute of Japan, "Draft Guidelines for Ground Improvement Design for Building Foundations," 1st ed., Japan, Architectural Institute of Japan, November 2006, pp. 100-113. [Non-patent document 2] The Building Center of Japan and Better Living, and the Architectural Institute of Japan, "Design and Quality Control Guidelines for Improved Ground for Buildings," 1st Edition, Japan, The Building Center of Japan and Better Living, November 30, 2018, pp. 114-127. [Non-patent document 3] Architectural Institute of Japan, "Guidelines for Architectural Foundation Design," 3rd Edition, Japan, Architectural Institute of Japan, November 2019, pp. 49-55. Summary of the Invention [Problem to be solved by the invention]

[0011] There are a variety of parameters that indicate the characteristics of the ground that is the target of liquefaction assessment. Simple calculation methods such as those in Patent Document 1 impose preconditions for the calculation, and if the preconditions are not met, the calculation cannot be carried out in the first place. In other words, the parameters that can be reflected in the liquefaction assessment are limited.

[0012] Because simplified calculation methods are subject to various assumptions, it is possible to use more versatile analytical methods that do not require such assumptions. For example, applying advanced analysis such as the finite element method is highly versatile because it is not affected by the assumptions that are imposed on simplified calculation methods. However, such advanced analysis requires a large amount of computational resources and time. As a result, determining the optimal specifications for the improved structure requires a great deal of effort and time.

[0013] Therefore, the present invention provides a method for evaluating ground and a method for determining the specifications of a lattice-shaped improvement body that can reflect parameters that indicate the characteristics of the ground while suppressing an increase in calculation load. [Means for solving the problem]

[0014] One aspect of the present invention is a method for evaluating the equivalent repeated shear stress (τ) generated in the inter-lattice ground using a first evaluation step of setting specifications for a lattice-shaped improvement body surrounding the inter-lattice ground including an area where liquefaction is expected; a second evaluation step of defining a geomechanical model including model components simulating the lattice-shaped improvement body and model components simulating the inter-lattice ground; and d ) or equivalent cyclic shear strain (γ), and the equivalent cyclic shear stress intensity (τ d ) to evaluate whether liquefaction of the ground within the grid will occur or not. L value), or obtain the horizontal displacement (D i and a fourth evaluation step of obtaining a ground surface roughness (a surface roughness of the ground).

[0015] This method prepares a geomechanical model that includes a model component that simulates the grid-like improvement body, which is the target of evaluation, and a model component that simulates the ground within the grid. Then, using this geomechanical model, a liquefaction safety factor (F) is calculated to evaluate whether or not liquefaction will occur in the ground within the grid, which is the target of evaluation. L value) or horizontal displacement occurring in the ground within the grid (D i According to the geomechanical model, the parameters of the ground properties are calculated as the liquefaction safety factor (F L value) or horizontal displacement (D i ) can be more easily reflected in the calculation results. Furthermore, the geomechanical model makes it possible to suppress an increase in the calculation load. Therefore, this method makes it possible to evaluate the ground while reflecting parameters that indicate the characteristics of the ground and suppressing an increase in the calculation load.

[0016] One form of the ground evaluation method may be [2] "The ground evaluation method described in [1] above, wherein in the second evaluation step, the ground mechanical model is defined by shear spring elements constituting model components that simulate the lattice-shaped improvement body, and shear spring elements and axial spring elements that simulate the ground within the lattice." According to this method, the geomechanical model is constructed by multiple shear spring elements. The geomechanical model constructed by shear spring elements can calculate the equivalent cyclic shear stress (τ d ) or equivalent cyclic shear strain (γ), the computational load can be reduced.

[0017] In one embodiment of the ground evaluation method, [3] "the third evaluation step is to calculate a first shear stress (τ s1 ) and a step of obtaining a second shear stress intensity (τ s2 ) and obtaining the first shear stress intensity (τ s1 ) to the second shear stress (τ s2 and adding a value of (a) to (b) of the ground surface area. This method makes it possible to easily incorporate the load acting on the lattice-shaped improvement body due to the ground outside the lattice-shaped improvement body into the calculation for ground evaluation, thereby enabling the evaluation of the ground to take into account the load when the outside of the lattice-shaped improvement body liquefies.

[0018] One form of the ground evaluation method may be [4] "The ground evaluation method described in [1] above, wherein in the second evaluation step, the ground is defined by shear spring elements constituting a model component simulating the lattice-shaped improvement body, shear spring elements and axial spring elements constituting a model component simulating the intra-lattice ground, and shear spring elements and axial spring elements constituting a model component simulating the extra-lattice ground existing outside the lattice-shaped improvement body." The model components simulating the grid-like improved body are constructed with shear spring elements, the model components simulating the in-grid ground are constructed with shear spring elements and axial spring elements, and the model components simulating the out-grid ground are constructed with shear spring elements and axial spring elements. This also allows the liquefaction safety factor (F L value) or horizontal displacement (D i ) can be calculated more accurately.

[0019] In one embodiment of the ground evaluation method, [5] "the third evaluation step is to calculate a first shear stress (τ s1 ) and a step of obtaining a second shear stress intensity (τ s2 ) and obtaining the first shear stress intensity (τ s1 ) to the second shear stress (τ s2 The method for evaluating ground according to the above item [4] may also include a step of adding a value of (a) to (b). This method also makes it possible to easily incorporate the load acting on the lattice improvement structure due to the extra-lattice ground existing outside the lattice improvement structure into calculations for ground evaluation. As a result, it is possible to perform ground evaluation that takes into account the shear stress intensity obtained using a geomechanics model that includes model components simulating the extra-lattice ground existing outside the lattice improvement structure and the shear stress intensity resulting from liquefied extra-lattice ground.

[0020] One form of the ground evaluation method may be [6] "a non-liquefaction layer exists below the lattice-shaped improvement body and the intra-lattice ground, and in the second evaluation step, the ground mechanics model is defined by shear spring elements constituting a model component simulating the lattice-shaped improvement body, shear spring elements and axial spring elements constituting a model component simulating the intra-lattice ground, and shear spring elements and axial spring elements constituting a model component simulating the non-liquefaction layer." The geomechanics model consists of shear spring elements for the model components simulating the grid-like improvement body, shear spring elements and axial spring elements for the model components simulating the ground within the grid, and shear spring elements and axial spring elements for the non-liquefaction layer.By using this geomechanics model in calculations for ground evaluation, it is possible to evaluate the ground while taking into account the effects of the non-liquefaction layer.

[0021] One form of the ground evaluation method may be [7] "a non-liquefaction layer exists below the lattice-shaped improvement body and the intra-lattice ground, and in the second evaluation step, the ground mechanical model is defined by shear spring elements constituting model components that simulate the lattice-shaped improvement body shallower than the non-liquefaction layer, shear spring elements and axial spring elements that simulate the intra-lattice ground shallower than the non-liquefaction layer, and shear spring elements and axial spring elements that simulate the extra-lattice ground that exists outside the lattice-shaped improvement body." The geomechanical model includes model components that simulate the grid-like improvement body and the ground within the grid that exist in the shallower part than the non-liquefiable layer. As a result, it is possible to evaluate the ground without taking into account the influence of the non-liquefiable layer.

[0022] One form of the ground evaluation method may be [8] "The ground evaluation method described in [1] above, wherein the lattice-shaped improvement body is composed of a boundary improvement body surrounding the intra-lattice ground and an intra-lattice improvement body provided in the intra-lattice ground surrounded by the boundary improvement body." This method makes it possible to evaluate ground that has a lattice-like improvement body that is composed of a boundary improvement body that surrounds the intra-lattice ground and an intra-lattice improvement body that is provided in the intra-lattice ground surrounded by the boundary improvement body.

[0023] One form of the ground evaluation method may be [9] "The ground evaluation method described in [1] above, wherein the lattice-shaped improvement body is composed only of a boundary improvement body surrounding the ground within the lattice." This method makes it possible to evaluate ground that has a lattice-shaped improvement body that consists only of boundary improvement bodies that surround the ground within the lattice.

[0024] One form of the ground evaluation method may be

[10] "the ground evaluation method described in [1] above, wherein the lattice-shaped improvement body is composed of a boundary improvement body surrounding the intra-lattice ground and an intra-lattice improvement body provided in the intra-lattice ground surrounded by the boundary improvement body, and the intra-lattice improvement body includes an in-plane improvement body whose long side of the cross section is aligned with the direction of the external force and an out-of-plane improvement body whose short side of the cross section is aligned with the direction of the external force." This method makes it possible to evaluate ground that has a lattice-like improvement body that is composed of a boundary improvement body that surrounds the intra-lattice ground and an intra-lattice improvement body that is provided in the intra-lattice ground surrounded by the boundary improvement body.

[0025] Another aspect of the present invention is

[11] "a first determination step of setting specifications for a grid-like improvement body surrounding the grid-like ground including the area where liquefaction is expected, a second determination step of setting a geomechanical model including a model component simulating the grid-like improvement body and a model component simulating the grid-like ground, and a second determination step of setting a geomechanical model including a model component simulating the grid-like improvement body and a model component simulating the grid-like ground using the geomechanical model. d ) or equivalent cyclic shear strain (γ), and a third determination step of obtaining the equivalent cyclic shear stress (τ d ) to evaluate whether liquefaction of the ground within the grid will occur or not. L value), or obtain the equivalent repeated shear stress (τ d ) to calculate the horizontal displacement (D i ) and a fourth determination step of obtaining the liquefaction safety factor (F L value) and the horizontal displacement (D i and a fifth determination step of evaluating the liquefaction of the ground within the grid using at least one of the above methods, wherein the second, third, fourth and fifth determination steps are repeated while changing the specifications of the grid-shaped improved body in the first determination step until the result of the evaluation of the liquefaction of the ground within the grid satisfies a predetermined condition in the fifth determination step.

[0026] According to this method, the ground within the grid, which is the target for evaluating the possibility of liquefaction, is simulated as a geomechanical model. This geomechanical model is then used to calculate the liquefaction safety factor (F L value) or horizontal displacement occurring in the ground within the grid (D i ), the equivalent cyclic shear stress (τ d ) or equivalent cyclic shear strain (γ). The geomechanical model makes it easier to reflect parameters that are ground characteristics. Furthermore, the geomechanical model makes it possible to suppress an increase in the calculation load. Therefore, this method makes it possible to obtain the liquefaction safety factor (F L value) or horizontal displacement (D i The specifications of the grid-like improvement body can be determined based on the results of the ground evaluation based on the above.

[0027] Another method for determining the specifications of the grid-like improved body is

[12] "The shear stress intensity (τ s ) further comprises a sixth determination step of determining whether the grid-like improvement body is an acceptable value, and in the third determination step, the equivalent repeated shear stress intensity (τ d ) and the shear stress intensity (τ s ) and further obtained, and in the fifth determination step, the result of the evaluation regarding the liquefaction of the ground in the grid satisfies the predetermined conditions, and in the sixth determination step, the shear stress intensity (τ s ) may be a method for determining specifications of a lattice-shaped improved body as a liquefaction countermeasure as described in

[11] above, wherein the second determination step, the third determination step, the fourth determination step, the fifth determination step, and the sixth determination step are repeated while changing the specifications of the lattice-shaped improved body in the first determination step until a determination result is obtained that the lattice-shaped improved body has an acceptable value. According to this method, the liquefaction safety factor (F L value) or horizontal displacement (D iIn addition to the evaluation results of the ground based on the shear stress intensity (τ s ) can be taken into account when determining the specifications for the grid-shaped improved structure. As a result, it is possible to determine the specifications for the grid-shaped improved structure that can continue to maintain its liquefaction suppression function even when earthquake motion is input. [Effects of the Invention]

[0028] According to the present invention, there is provided a method for evaluating ground and a method for determining the specifications of a lattice-shaped improvement body that can suppress an increase in calculation load while reflecting parameters that indicate the characteristics of the ground. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a perspective cross-sectional view showing a ground to be evaluated by the ground evaluation method of the first embodiment. [Figure 2] FIG. 2 is a flowchart of the ground evaluation method according to the first embodiment. [Figure 3] Figure 3 shows an analytical element model that simulates the cross section of the ground shown in Figure 1 using multiple analytical elements. [Figure 4] Figure 4 shows a geomechanical model that simulates the analytical element model of the ground shown in Figure 3 using multiple spring elements. [Figure 5] Figure 5(a) is a graph showing the relationship between the shear stiffness reduction rate of the boundary improvement body and shear strain. Figure 5(b) is a graph showing the relationship between the shear stiffness reduction rate of the ground within the grid and shear strain. Figure 5(c) is a graph showing the relationship between the shear stiffness reduction rate of the non-liquefiable layer and shear strain. [Figure 6] FIG. 6 is a schematic plan view for explaining the modeling of the shear rigidity of the boundary improvement body. [Figure 7] FIG. 7 is a flowchart of a method for determining the specifications of a grid-like improved body according to the second embodiment. [Figure 8] FIG. 8 is a flowchart of a method for determining the specifications of a grid-like improved body according to the third embodiment. [Figure 9]FIG. 9 is a flowchart of the ground evaluation method according to the fourth embodiment. [Figure 10] FIG. 10 is a graph showing the relationship between the corrected N value and the cyclic shear stress ratio. [Figure 11] FIG. 11 is a flowchart of a method for determining the specifications of a grid-like improved body according to the fifth embodiment. [Figure 12] FIG. 12 is a flowchart of a method for determining the specifications of a grid-like improved body according to the sixth embodiment. [Figure 13] FIG. 13 shows an example of a geomechanical model employed in the ground evaluation method of the first modification. [Figure 14] FIG. 14 is a flowchart of the ground evaluation method of the first modification. [Figure 15] FIG. 15 is a flowchart of the ground evaluation method of the second modification. [Figure 16] FIG. 16 shows an example of a geomechanical model employed in the ground evaluation method of the third modification. [Figure 17] FIG. 17 shows another modification of the modeling of the ground. [Figure 18] Figure 18(a) shows yet another modified example of modeling the ground, and Figure 18(b) shows yet another modified example of modeling the ground. [Figure 19] FIG. 19 shows yet another modification regarding the modeling of the ground. [Figure 20] FIG. 20 shows an example of a modified example of a plan view of improved ground in which improvement bodies are provided on the ground. [Figure 21] FIG. 21 is an illustration of a geomechanical model corresponding to FIG. DETAILED DESCRIPTION OF THE INVENTION

[0030] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0031] FIG. 1 shows ground 100 provided with a lattice-shaped improvement body 1. The ground 100 includes a liquefaction layer 8 on the ground surface 100a side, which is expected to liquefy, and a non-liquefaction layer 9 located below the liquefaction layer 8, which is not expected to liquefy. The lattice-shaped improvement body 1 is provided in the liquefaction layer 8. A portion of the liquefaction layer 8 surrounded by the lattice-shaped improvement body 1 is referred to as the intra-lattice ground 81. In the example shown in FIG. 1, the intra-lattice ground 81 includes a liquefaction region 81a, which is a portion of the liquefaction layer 8, and an intra-lattice improvement body 12. The liquefaction region 81a is separated by the intra-lattice improvement body 12, which has relatively high shear rigidity.

[0032] The evaluation method for the ground 100 obtains an index for evaluating the occurrence of liquefaction of the ground 81 within the grid. An example of this index is the liquefaction safety factor (F L value) and maximum horizontal displacement (D cy In the first embodiment, the liquefaction safety factor (F L In the evaluation method for the ground 100 of the fourth embodiment described later, the maximum horizontal displacement (D cy ) will be adopted.

[0033] <Lattice-like improved body 1> First, we will explain the lattice-shaped improved body 1. As shown in Figure 1, the lattice-shaped improved body 1 is a frame-shaped member that includes a boundary improved body 11 and an intra-lattice improved body 12. The lattice-shaped improved body 1 is formed by a solidification method in which the original ground and a cement-based solidification material are stirred and mixed, and then solidified.

[0034] The boundary improvement body 11 surrounds the intra-lattice ground 81. In other words, the inside of the boundary improvement body 11 is the intra-lattice ground 81, and the outside of the boundary improvement body 11 is the extra-lattice ground 82 (extra-lattice liquefaction area). The upper end surface of the boundary improvement body 11 may be exposed to the ground surface 100a. The lower end surface of the boundary improvement body 11 may reach the non-liquefaction layer 9.

[0035] The intra-lattice improvement body 12 is provided in the area surrounded by the boundary improvement body 11. The intra-lattice improvement body 12 is provided additionally. The intra-lattice improvement body 12 further divides the area surrounded by the boundary improvement body 11 into several smaller areas. For example, the intra-lattice improvement body 12 may extend from the first boundary improvement body 11 to the second boundary improvement body 11. The upper end surface of the intra-lattice improvement body 12 may be exposed to the ground surface 100a. The lower end surface of the intra-lattice improvement body 12 does not have to reach the non-liquefaction layer 9. Note that if liquefaction can be suppressed by the boundary improvement body 11 alone, the intra-lattice improvement body 12 may be omitted.

[0036] <First embodiment: Liquefaction safety factor (F L Ground evaluation method using the (value) The method for evaluating the ground 100 will be described in detail below. FIG. 2 is a flowchart showing the main steps of the method for evaluating the ground 100. The method for evaluating the ground 100 according to the first embodiment uses a geomechanics model 100M (see FIG. 4) based on the flowchart shown in FIG. 2 to calculate the safety factor of liquefaction (F L value).

[0037] First, a ground survey is carried out (S10). Specifically, in step S10, the ground properties of the liquefaction layer 8 on which the lattice-shaped improvement body 1 is to be provided are measured and obtained. Also, in step S10, the ground properties of the non-liquefaction layer 9 may be obtained. For example, in step S10, the ground properties may include the stratum classification, unit volume weight, shear velocity, N value, Poisson's ratio, and the relationship between shear stiffness reduction rate and shear strain (G / G0-γ). Some of these properties may be obtained by using properties described in literature such as Non-Patent Documents 1, 2, and 3, without being obtained by measurement.

[0038] Next, the liquefaction resistance (τ L ) is calculated (S11). Specifically, the liquefaction resistance (τ L ) can be obtained using the N value, the fine particle content, etc. For example, the content described in the Architectural Institute of Japan's "Guidelines for Designing Foundation Structures in Buildings," 3rd Edition, which is non-patent document 3, may be applied.

[0039] Next, the equivalent repeated shear stress intensity (τ d ) is obtained (S12). In the method of the first embodiment, a geomechanical model 100M (see FIG. 4) is used, in which the evaluation object including the intra-grid ground 81 is expressed as an aggregate of multiple spring elements. According to the geomechanical model 100M expressed by spring elements, the displacement and strain occurring in each spring element can be obtained by simple iterative calculations.

[0040] Furthermore, the relationship between the shear stiffness reduction rate and shear strain (G / G0-γ), which is an important parameter in assessing liquefaction, is introduced as a parameter of the spring element. Therefore, according to step S12 of the first embodiment, it is possible to suppress an increase in the calculation load while reflecting the parameters that indicate the characteristics of the ground 100.

[0041] First, the specifications of the lattice-shaped improved body 1 are set (S121). The specifications of the lattice-shaped improved body 1 include the spacing of the improved bodies that make up the lattice-shaped improved body 1, the rigidity of the improved bodies, and the depth of the improved bodies.

[0042] Next, the physical properties of the intra-lattice ground 81, the extra-lattice ground 82, and the lattice-shaped improved body 1 are set, and the geomechanics model 100M is also set (S122). The parameters to be set are the relationship between the stiffness reduction rate and shear strain (G / G0-γ) corresponding to the intra-lattice ground 81, and the relationship between the shear stiffness reduction rate and shear strain (G / G0-γ) corresponding to the lattice-shaped improved body 1. Furthermore, in step S122, the unit volume weight of the improved body (γ t ), shear rate (V S ), and Poisson's ratio (ν) may be set. Based on the setting of these relationships, a geomechanical model 100M is set in which specific numerical values ​​are defined.

[0043] Here, the geomechanics model 100M set in step S122 will be described in detail. First, the ground 100 shown in FIG. 1 is simulated by an analytical element model 100E, in which the cross section of the ground 100 is divided into multiple elements, as shown in FIG. 3. In the example shown in FIG. 3, the analytical elements are divided into analytical elements with the width of the boundary improvement body 11 and the width of the intra-lattice improvement body 12 as the smallest unit. The analytical element model 100E includes a liquefied layer region 8E that simulates the liquefied layer 8 and a non-liquefied layer region 9E that simulates the non-liquefied layer 9. Furthermore, the liquefied layer region 8E includes a boundary improvement body region 11E that simulates the boundary improvement body 11, an intra-lattice improvement body region 12E that simulates the intra-lattice improvement body 12, a liquefied region 81E that simulates the liquefied region 81a of the intra-lattice ground 81, and an extra-lattice ground region 82E that simulates the extra-lattice ground 82. Each of these regions is simulated by multiple analysis elements. Specifically, the boundary improvement region 11E is composed of multiple boundary improvement analysis elements 11C. Similarly, the intra-lattice improvement region 12E is composed of multiple intra-lattice improvement analysis elements 12C. The liquefaction region 81E is composed of multiple liquefaction region analysis elements 81C. The extra-lattice ground region 82E is composed of multiple extra-lattice ground analysis elements 82C. The non-liquefaction layer region 9E is composed of multiple non-liquefaction layer analysis elements 9C.

[0044] Next, the analytical element model 100E shown in Fig. 3 is converted into a geomechanics model 100M simulated by a plurality of spring elements SE shown in Fig. 4. The geomechanics model 100M shown in Fig. 4 is a model of the left half of the analytical element model 100E shown in Fig. 3. The geomechanics model 100M includes a liquefaction layer model 8M and a non-liquefaction layer model 9M. Furthermore, the liquefaction layer model 8M includes a boundary improvement body model 11M, an intra-lattice improvement body model 12M, an intra-lattice ground model 81M, and an extra-lattice ground model 82M.

[0045] In the geomechanics model 100M, one analytical element shown in Fig. 3 may be replaced with one spring element SE. For example, one analytical element constituting the boundary improvement body model 11M is replaced with one spring element SE. Similarly, in the intra-grid improvement body model 12M, one analytical element is replaced with one spring element SE.

[0046] In the lattice-shaped improvement body 1, the boundary improvement body 11 reaches the non-liquefaction layer 9, but the intra-lattice improvement body 12 does not reach the non-liquefaction layer 9. The geomechanics model 100M can also simulate this difference. The fact that the boundary improvement body model 11M reaches the non-liquefaction layer model 9M can be simulated by connecting in series the spring element SE (11S1) that simulates the analysis element 11C located at the bottom of the boundary improvement body model 11M to the spring element SE (9S1) that simulates the analysis element 9C located at the top of the non-liquefaction layer model 9M. On the other hand, the fact that the intra-lattice improvement body 12 does not reach the non-liquefaction layer 9 can be simulated by connecting in series the spring element SE (12S1) simulating the analytical element 12C located at the bottom of the intra-lattice improvement body model 12M to the spring element SE (9S1) simulating the analytical element 9C located at the top of the non-liquefaction layer model 9M via spring elements SE (81S1) simulating several analytical elements 81C of the intra-lattice ground model 81M.

[0047] In the geomechanics model 100M, multiple analytical elements shown in Figure 3 may be replaced with a single spring element SE. For example, several analytical elements 81C arranged horizontally that make up the intra-lattice ground model 81M are replaced with one or more spring elements SE. Note that, since it is necessary to obtain the distribution of displacement and shear strain in the depth direction, the analytical elements 81C arranged in the depth direction that make up the intra-lattice ground model 81M are each replaced with a spring element SE. The analytical elements 82C and 9C that make up the extra-lattice ground model 82M and the non-liquefaction layer model 9M are also replaced with spring elements SE using a similar concept. The geomechanics model 100M will be described in more detail below.

[0048] The geomechanical model 100M includes a boundary improvement body model 11M, an intra-grid improvement body model 12M, an intra-grid ground model 81M, an extra-grid ground model 82M, and a non-liquefaction layer model 9M. In this case, the geomechanical model 100M calculates the shear stiffness (K S11 , K. S12 , K. S81 , K. S82 , K. S9 ) can be expressed as a shear stiffness matrix defined by (see equation (1)).

number

[0049] Furthermore, the soil mechanics model 100M uses the axial stiffness (K N81 , K. N82 ) (see equation (2)). The boundary improvement body model 11M and the intra-lattice improvement body model 12M, which simulate the lattice improvement body 1, are simulated only by shear spring elements 11S1 and 12S1. In other words, the axial stiffness matrix of the geomechanical model 100M does not include the axial stiffness spring element that simulates the boundary improvement body 11 and the axial stiffness spring element that simulates the intra-lattice improvement body 12.

number

[0050] The relationship between the shear stiffness reduction rate and shear strain can be introduced into the characteristics of shear spring elements 81S1, 82S1, 11S1, and 12S1. For example, the characteristics shown in graph G51 in Figure 5(a) may be given to the shear spring elements 11S1 and 12S1 of the lattice-shaped improved body 1. The characteristics shown in graph G52 in Figure 5(b) may be given to the shear spring element 81S1 of the intra-lattice ground model 81M. The characteristics shown in graph G53 in Figure 5(c) may be given to the shear spring element 9S1 of the non-liquefaction layer model 9M. The stiffness reduction rate may also be calculated from the value of the equivalent cyclic shear strain based on graphs G51 to G53. The shear strain and equivalent cyclic shear strain can be obtained using the following equations (3) and (4).

number

number

[0051] <Shear stiffness of boundary improvement body 11 (K S11 )> Shear stiffness (K) for shear spring element 11S1 of boundary refinement model 11M S11 ) may be obtained by taking into consideration the shear cross-sectional area and height of the shear spring element 11S1 in addition to the shear modulus of the boundary improvement body 11. For example, it may be obtained by the following formula (5):

number

[0052] The shear cross-sectional area borne by the shear spring element 11S1 of the boundary improvement body model 11M may be obtained by taking into consideration the sum of the shear cross-sectional areas of the inner and outer walls of the plane. For example, the equivalent shear cross-sectional area (A2') of the boundary improvement body 11 can be obtained by the following equation (6).

number

[0053] <Shear stiffness of the lattice improvement body 12 (K S12 )> For example, the shear stiffness (K S12 ) may be obtained by the following equation (7):

number

[0054] <Shear stiffness of the ground in the grid (K S81 )> Shear stiffness of the grid soil model 81M Shear stiffness of the spring element 81S1 (K S81 ) may be obtained by taking into account the shear modulus of the ground 81 in the grid and the cross-sectional area and height of the shear spring element 81S1. For example, the shear stiffness (K S81 ) may be obtained by the following formula (8):

number

[0055] <Shear stiffness of the outer grid ground 82 (K S82 )> For example, the shear stiffness (K S82 ) may be obtained by the following equation (9):

number

[0056] <Shear stiffness of non-liquefiable layer 9 (K S9 )> For example, the shear stiffness (K S9 ) may be obtained by the following equation (10):

number

[0057] <Axial stiffness of the ground in the grid (K N81 )> Axial stiffness of the grid soil model 81M Axial stiffness (K N81 ) may be obtained by dividing the deformation coefficient of the ground 81 within the grid by the cross-sectional area, length, etc. of the ground 81 within the grid, taking into account the shape of the ground 81 within the grid, and by dividing the deformation coefficient of the boundary improvement body 11 by the cross-sectional area, length, etc. of the boundary improvement body 11, taking into account the shape of the boundary improvement body 11. For example, the axial stiffness (K N81 ) may be obtained by the following formula (11):

number

[0058] <Axial stiffness of the outer grid ground 82 (K N82 )> For example, the axial stiffness (K N82 ) may be obtained by the following equation (12):

number

[0059] <Axial stiffness of non-liquefiable layer 9 (K N9 )> For example, the axial stiffness (K N9 ) may be obtained by the following equation (13):

number

[0060] Using this geomechanical model 100M, the equivalent cyclic shear stress (τ d ) is obtained (S123a). The equivalent cyclic shear stress (τ d ) may be calculated using the following formula (14):

number

[0061] Using this geomechanical model 100M, the shear stress intensity (τ s ) is obtained (S123a). Shear stress (τ s ) may be calculated using the following formula (15).

number

[0062] Next, using this geomechanical model 100M, the equivalent cyclic shear stress intensity (τ d ) is obtained (S123a). Shear stress (τ d ) is a so-called iterative calculation. Specifically, the iterative calculation is performed until the relationship between the shear stiffness reduction rate and the shear strain satisfies the convergence condition. The seismic external force applied to the geomechanical model 100M may be determined by any definition. For example, it may be applied using the shear force distribution form obtained by the equation shown in Non-Patent Document 3 (Equation (16) below). In this calculation, the seismic external force may be applied as a static load. In other words, the analysis of the first embodiment may be a static analysis that obtains a solution by assuming that the seismic external force acts statically without changing over time. By using a static analysis, the calculation load can be reduced.

number

[0063] The obtained shear stress (τ d , τ s If the convergence condition is satisfied (S124: YES), the shear stress intensity (τ d , τ s ) using the liquefaction safety factor (F LThe process proceeds to a process (S13) for obtaining the value of .times. ...

[0064] In step S12, the calculations of steps S122, S123a, and S124 are repeated until the convergence judgment in step S124 is satisfied. As a result, when the lattice-shaped improved body 1 having the specifications set in step S121 is installed in the liquefaction layer 8, the equivalent repeated shear stress intensity (τ d ) is obtained.

[0065] Next, the liquefaction safety factor (F L Specifically, the liquefaction resistance value (τ L ) is the equivalent cyclic shear stress in the grid (τ d ) and divide by (F L value = τ L / τ d As a result, the liquefaction safety factor (F L value).

[0066] <Effects of the First Embodiment> The evaluation method for the ground 100 according to the first embodiment includes a first evaluation step (S121) of setting specifications for the lattice-shaped improved body 1 surrounding the lattice-shaped ground 81 including the area where liquefaction is expected, a second evaluation step (S122) of defining a geomechanical model 100M including model components simulating the lattice-shaped improved body 1 and the lattice-shaped ground 81, and calculating the equivalent repeated shear stress (τ d ) and the third evaluation step (S123a) to obtain the equivalent cyclic shear stress (τ d ) to evaluate whether liquefaction of the ground 81 in the grid will occur or not. L and a fourth evaluation step (S13) of obtaining a value of the

[0067] This method prepares a geomechanics model 100M including a model component that simulates the lattice-shaped improved body 1, which is the object of evaluation, and a model component that simulates the intra-lattice ground 81. Then, using this geomechanics model 100M, a liquefaction safety factor (F L According to the geomechanical model 100M, the parameters of the ground characteristics are used to obtain the liquefaction safety factor (F L This makes it easier to reflect the parameters that indicate the characteristics of the ground 100 in the calculation results of the parameter (value). Furthermore, the geomechanical model 100M makes it possible to suppress an increase in the calculation load. Therefore, this method makes it possible to evaluate the ground 100 while reflecting the parameters that indicate the characteristics of the ground 100 and suppressing an increase in the calculation load.

[0068] A non-liquefaction layer 9 exists below the lattice-shaped improved body 1 and the intra-lattice ground 81. In the second evaluation step (S122), a geomechanics model 100M is defined by shear spring elements constituting the model components simulating the lattice-shaped improved body 1, shear spring elements and axial spring elements constituting the model components simulating the intra-lattice ground 81, and shear spring elements and axial spring elements constituting the model components simulating the non-liquefaction layer 9. In the geomechanics model 100M, the model components simulating the lattice-shaped improved body 1 are configured with shear spring elements, the model components simulating the intra-lattice ground 81 are configured with shear spring elements and axial spring elements, and the non-liquefaction layer 9 is configured with shear spring elements and axial spring elements. By using the geomechanics model 100M in calculations for evaluating the ground 100, it is possible to evaluate the ground 100 while taking into account the influence of the non-liquefaction layer 9.

[0069] The lattice-shaped improvement body 1 is composed of a boundary improvement body 11 that surrounds the lattice-internal ground 81, and an intra-lattice improvement body 12 that is provided in the lattice-internal ground 81 surrounded by the boundary improvement body 11. According to this method, it is possible to evaluate ground 100 provided with a lattice-shaped improvement body 1 composed of a boundary improvement body 11 surrounding the intra-lattice ground 81 and an intra-lattice improvement body 12 provided in the intra-lattice ground 81 surrounded by the boundary improvement body 11.

[0070] <Second embodiment: Liquefaction safety factor (F L Method for determining the specifications of the lattice-shaped improved body using the The second embodiment is a method for determining the specifications of the lattice-shaped improved body 1. More specifically, the method for determining the specifications of the lattice-shaped improved body 1 of the second embodiment uses the liquefaction safety factor (F L The specifications of the lattice-shaped improved body 1 are determined using the value of the lattice-shaped improved body 1. Examples of the specifications of the lattice-shaped improved body 1 include the spacing between the improved bodies that make up the lattice-shaped improved body 1, the rigidity of the improved bodies, and the depth of the improved bodies.

[0071] 7 is a flowchart showing the main steps S10A, S11A, S12A, S13A, and S14A of the method for determining the specifications of a lattice-shaped improved body according to the second embodiment. The method for determining the specifications of a lattice-shaped improved body 1 according to the second embodiment uses a geomechanical model 100M (see FIG. 4) based on the flowchart shown in FIG. 7 to determine the safety factor (F L value) and calculate the safety factor (F L The specifications of the lattice-shaped improved body 1 are determined based on the fact that the value of the lattice-shaped improved body 1 is less than 1.

[0072] The method for determining the specifications of the lattice-shaped improved body 1 of the second embodiment has steps S10A, S11A, S12A, S13A, and S14A as main steps. Of these, steps S10A, S11A, S12A, and S13A are the same as steps S10, S11, S12, and S13, respectively, included in the method for evaluating the ground 100 of the first embodiment. Therefore, detailed explanations of steps S10A, S11A, S12A, and S13A will be omitted. The method for determining the specifications of the lattice-shaped improved body 1 of the second embodiment performs steps S10A, S11A, S12A, and S13A, thereby determining the liquefaction safety factor (F L value).

[0073] The equivalent repeated shear stress (τ d ), there is a possibility that liquefaction may occur in the ground 81 within the grid, or there is a possibility that liquefaction may not occur. Therefore, in step S14A, the equivalent repeated shear stress intensity (τd ) to evaluate whether or not there is a possibility of liquefaction of the ground 81 within the grid.

[0074] Specifically, the liquefaction safety factor (F L It is determined whether the non-liquefaction condition is satisfied (S14A). The non-liquefaction condition is expressed by the following formula (17). Specifically, F L Determines whether the value is greater than 1.0.

number

[0075] Liquefaction safety factor (F L If the liquefaction safety factor (F L If the non-liquefaction condition is not met (S14A: NO) because the value of ≈1 is less than or equal to 1, the specifications of the lattice-shaped improved body set in step S121 cannot be adopted as the specifications of the lattice-shaped improved body. Therefore, steps S12A and S13A are carried out again.

[0076] <Second embodiment: Actions and effects> First, as a comparative example, the problems with the method described in Patent Document 1 will be described. Next, the differences between the method described in Patent Document 1 and the method for determining the specifications of the lattice-shaped improved body 1, which is the second embodiment, will be described. Furthermore, the problems and differences with the method described in Patent Document 2 will also be described. Then, the effects of the method for determining the specifications of the lattice-shaped improved body 1, which is the second embodiment, will be described.

[0077] <Patent Document 1> The first issue with the method proposed in Patent Document 1 is that the simplified evaluation formula cannot be used when the prerequisite factors, such as the rate of soil stiffness reduction, the rigidity of the liquefied layer, and the wall thickness of the improved body, are different. In other words, the method proposed in Patent Document 1 lacks versatility. The method proposed in Patent Document 1 may not adequately evaluate the stresses from unimproved ground outside the grid. The second issue with the method proposed in Patent Document 1 is that it does not include an evaluation of the stresses acting on the improved body. As a result, the method proposed in Patent Document 1 may not adequately examine the cross-section of the improved body. The third issue with the method proposed in Patent Document 1 is that, without reference to simplified evaluation methods or existing guidelines, liquefaction assessment requires finite element analysis (3D effective stress analysis, total stress analysis, and equivalent linear analysis). Determining the optimal grid spacing and improved body specifications requires a significant amount of time and effort.

[0078] The method proposed in Patent Document 1 involves an analysis that includes the grid spacing, the rigidity of the improved body, and the height of the liquefied layer as parameters, but does not include the rigidity and rigidity reduction rate of the liquefied layer, which vary depending on the location and geology. Using the correction coefficients obtained from this analysis due to the grid-like ground improvement, the equivalent shear stress ratio during an earthquake that occurs in the ground within the grid-like improvement is reduced, and F L On the other hand, the method for determining the specifications of the lattice-shaped improved body 1 of the second embodiment utilizes a geomechanics model 100M that introduces the relationship between the shear stiffness reduction rate and shear strain (G / G0-γ relationship) of the intra-lattice ground 81 and the lattice-shaped improved body 1. The method for determining the specifications of the lattice-shaped improved body 1 of the second embodiment uses the shear stress intensity (τ d , τ s ) and F L This method differs from the method proposed in Patent Document 1 in that it judges liquefaction based on the value and examines the stress of the lattice-shaped improved body 1.

[0079] <Patent Document 2> The method proposed in Patent Document 2 calculates the equivalent stiffness of the improved body and the liquefied layer ground, which have completely different stiffness and properties. This calculation is cumbersome. Furthermore, the method proposed in Patent Document 2 does not take into account the influence of the non-liquefied layer deposited below the liquefied layer. Furthermore, the method proposed in Patent Document 2 is unable to evaluate the stress exerted by the unimproved ground outside the grid when liquefaction countermeasures are implemented using a grid-like improved body.

[0080] The method proposed in Patent Document 2 essentially considers the partially improved ground as an assembly of unit periodic structures, and calculates the stiffness of these unit periodic structures based on mathematical homogenization theory. This is then used as the equivalent stiffness of the entire partially improved ground to calculate the liquefaction strength and deformation amount. On the other hand, the method for determining the specifications of the lattice-shaped improved body 1 of the second embodiment utilizes a geomechanical model 100M that uses the stiffness (ground spring) of the extra-lattice ground 82 and the intra-lattice ground 81, and the stiffness (shear spring) of the lattice-shaped improved body 1. The method for determining the specifications of the lattice-shaped improved body 1 of the second embodiment then calculates the shear stress intensity (τ d , τ s ) and F L This method differs from the method proposed in Patent Document 2 in that it judges liquefaction based on the value and examines the stress of the lattice-shaped improved body 1.

[0081] In contrast to the above-mentioned conventional techniques, the method of determining the specifications of the lattice-shaped improved body 1 according to the second embodiment includes a first determination step (S121) of setting the specifications of the lattice-shaped improved body 1 surrounding the intra-lattice ground 81 including the area where liquefaction is expected, a second determination step (S122) of setting a geomechanical model 100M including model components simulating the lattice-shaped improved body 1 and model components simulating the intra-lattice ground 81, and calculating the equivalent repeated shear stress (τ d ) and the third determination step (S123a) of obtaining the equivalent cyclic shear stress (τ d ) to evaluate whether liquefaction of the ground 81 in the grid will occur or not. L The fourth step (S13A) determines the liquefaction safety factor (F Land a fifth determination step (S14A) of evaluating the liquefaction of the intra-lattice ground 81 using the calculated liquefaction coefficient (σ) and the calculated liquefaction coefficient (σ) values. In the fifth determination step (S14A), the second determination step (S122), the third determination step (S123a), the fourth determination step (S13A), and the fifth determination step (S14A) are repeated while changing the specifications of the lattice-shaped improved body 1 in the first determination step (S121) until the results of the evaluation of the liquefaction of the intra-lattice ground 81 satisfy the predetermined conditions.

[0082] According to the method for determining the specifications of the lattice-shaped improved body 1 of the second embodiment, the intra-lattice ground 81, which is the object of evaluating the possibility of liquefaction, is simulated as a geomechanical model 100M. Then, using this geomechanical model 100M, a liquefaction safety factor (F L In order to obtain the value of the equivalent cyclic shear stress (τ d ) is obtained. The geomechanical model 100M makes it easier to reflect parameters that are ground characteristics. Furthermore, the geomechanical model makes it possible to suppress an increase in the calculation load. Therefore, according to this method, it is possible to obtain the liquefaction safety factor (F L The specifications of the grid-like improvement body 1 can be determined based on the evaluation results of the ground 100 based on the value.

[0083] <Third embodiment: Liquefaction safety factor (F L Method for determining the specifications of the grid-like improved body using the allowable stress of the grid-like improved body) The third embodiment is also a method for determining the specifications of the lattice-shaped improved body 1. The effects of earthquakes also extend to the lattice-shaped improved body 1. In other words, the lattice-shaped improved body 1 must be able to withstand the input of seismic motion without being damaged. Therefore, the method for determining the specifications of the lattice-shaped improved body 1 in the third embodiment sets the condition for determining the specifications of the lattice-shaped improved body 1 as whether or not liquefaction will occur, and also sets the condition that the lattice-shaped improved body 1 will not be damaged by the input of seismic motion and will continue to maintain its function of suppressing liquefaction.

[0084] More specifically, the method for determining the specifications of the grid-shaped improved body 1 according to the third embodiment is based on the liquefaction safety factor (F L value) and shear stress intensity (τ S ) is used to determine the specifications of the grid-shaped improved body 1. In other words, in the second embodiment, the liquefaction safety factor (F L In the previous embodiment, the specifications of the grid-shaped improved body 1 were determined using only the liquefaction safety factor (F L In addition to the shear stress (τ S ) is also used to determine the specifications of the lattice improvement body.

[0085] Therefore, according to the method for determining the specifications of the lattice-shaped improvement body 1 of the third embodiment, it is possible to determine the specifications of the lattice-shaped improvement body 1 that can suppress the occurrence of liquefaction of the ground 81 within the lattice and can continue to maintain its function of suppressing liquefaction even when seismic motion is input.

[0086] Fig. 8 is a flowchart showing the main steps S10B, S11B, S12B, S13B, S14B, and S15B of the method for determining the specifications of a lattice-shaped improved body according to the third embodiment. The method for determining the specifications of a lattice-shaped improved body 1 according to the third embodiment uses a geomechanical model 100M (see Fig. 4) based on the flowchart shown in Fig. 8 to determine the safety factor (F L value) and the shear stress generated in the grid-like improvement body 1. Then, the safety factor for liquefaction (F L The specifications of the lattice-like improved body 1 are determined based on the fact that the value of the lattice-like improved body 1 is greater than 1 and that the shear stress generated in the lattice-like improved body 1 is below the allowable value (for example, within the short-term allowable stress level).

[0087] The method for determining the specifications of the lattice-shaped improved body 1 according to the third embodiment has steps S10B, S11B, S13B, S14B, and S15B as its main steps. Of these, steps S10B, S11B, and S13B are the same as steps S10, S11, and S13, respectively, included in the method for evaluating the ground 100 according to the first embodiment. Step S14B is the same as step S14A included in the method for determining the specifications of the lattice-shaped improved body 1 according to the second embodiment. Therefore, detailed explanations of steps S10B, S11B, S13B, and S14B will be omitted.

[0088] In addition to steps S121, S122, S123a, and S124, step S12B further includes step S123b, which calculates the shear stress intensity (τ s ) is obtained. Step S123b may be performed after step S123a and before step S124. These shear stress intensities (τ s The calculation to obtain the shear stress (τ d ) is an iterative calculation, similar to the calculation to obtain the shear stress intensity (τ s ) can be obtained.

[0089] In step S14B, the liquefaction safety factor (F L If it is determined that the value) is greater than 1 and the non-liquefaction condition is met (S14B: YES), the next step S15B is executed.

[0090] In step S15B, the shear stress intensity (τ s ) is equal to or less than the allowable stress. The allowable stress is a value that is set in advance. The allowable stress can be set according to the strength of the lattice-shaped improved body 1, etc. The shear stress (τ s If the shear stress (τs If the stress level is not below the allowable stress level (S15B: NO), it is determined that the lattice-shaped improved body 1 will no longer be sound due to the input of seismic motion, and steps S12B, S13B, and S14B are performed again.

[0091] <Third embodiment: effects> In the method for determining the specifications of the lattice-shaped improved body 1 according to the third embodiment, in the third determination step (S123), the equivalent repeated shear stress intensity (τ d ) is obtained (S123a), and the shear stress intensity (τ s ) and further obtain (S123b). The method of determining the specifications of the lattice-shaped improved body 1 according to the third embodiment is to calculate the shear stress intensity (τ s ) further has a sixth determination step (S15B) of determining whether the lattice-shaped improved body 1 is an allowable value. The method of determining the specifications of the lattice-shaped improved body 1 is carried out when the result of the evaluation regarding the liquefaction of the ground 81 in the lattice in the fifth determination step (S14B) is found to satisfy the predetermined condition, and the shear stress intensity (τ s ) repeats the second determination step (S122), the third determination step (S123a, S123b), the fourth determination step (S13B), the fifth determination step (S14B) and the sixth determination step (S15B) while changing the specifications of the lattice-shaped improvement body 1 in the first determination step (S121) until a determination result is obtained that the lattice-shaped improvement body 1 is an acceptable value.

[0092] According to the method for determining the specifications of the grid-shaped improved body 1 of the third embodiment, the liquefaction safety factor (F L In addition to the evaluation results of the ground 100 based on the shear stress (τ s ) can be taken into consideration when determining the specifications of the lattice-shaped improved body 1. As a result, it is possible to determine the specifications of the lattice-shaped improved body 1 that will not be damaged even when subjected to earthquake motion and can continue to maintain its function of suppressing liquefaction.

[0093] <Fourth embodiment: horizontal displacement (D i ) to evaluate the ground The fourth embodiment is a method for evaluating the ground 100. In the method for evaluating the ground 100 of the first embodiment, a liquefaction safety factor (F L In the evaluation method of the ground 100 according to the fourth embodiment, the liquefaction safety factor (F L value) instead of the horizontal displacement of the i-th layer (D i ) or maximum horizontal displacement of the ground surface (D cy ) is used as an index for evaluating the ground 100.

[0094] FIG. 9 is a flowchart showing the main steps S10C, S12C, and S13C of the fourth embodiment of the evaluation method for the ground 100. The evaluation method for the ground 100 of the fourth embodiment uses the geomechanical model 100M (see FIG. 4) based on the flowchart shown in FIG. 9 to obtain the equivalent cyclic shear strain (γ). Then, the horizontal displacement (D i ) and the maximum horizontal displacement of the ground surface (D cy ) is obtained.

[0095] The fourth embodiment of the method for evaluating the ground 100 includes steps S10C, S12C, and S13C. Step S10C of conducting a ground investigation is the same as step S10 of the first embodiment, and therefore a detailed description thereof will be omitted.

[0096] After step S10C, the equivalent cyclic shear strain (γ) acting on the intra-lattice ground 81 is obtained (S12C). As with the method of the first embodiment, the method of the fourth embodiment also uses a geomechanical model 100M (see FIG. 4) that represents the evaluation object including the intra-lattice ground 81 as an aggregate of multiple spring elements. First, the specifications of the lattice-shaped improved body 1 are set (S121). Next, the physical properties of the intra-lattice ground 81, the extra-lattice ground 82, and the lattice-shaped improved body 1 are set, and the geomechanical model 100M is set (S122).

[0097] Next, using this geomechanical model 100M, the equivalent cyclic shear strain (γ) for each depth in the in-grid soil model 81M is obtained (S123Ca). For example, the equivalent cyclic shear strain (γ) may be obtained by applying the corrected N value (Na) and cyclic shear stress ratio (τd / σz') of the ith layer to the graph in Figure 10.

[0098] Then, it is determined whether the obtained equivalent cyclic shear strain (γ) satisfies the convergence condition (S124). If the convergence condition is satisfied (S124: YES), the process proceeds to the next process (S13C) using the equivalent cyclic shear strain (γ). If the convergence condition is not satisfied (S124: NO), steps S122, S123Ca, and S124 are performed again.

[0099] In addition, in the ground 100, the horizontal displacement of the i-th layer (D i ), the process may proceed to the next step (S13C) after the convergence condition is satisfied (S124: YES).

[0100] On the other hand, if you want to obtain the maximum horizontal displacement (Dcy) on the ground surface, you need to calculate the horizontal displacement (D i ) is required to obtain the horizontal displacement (D i Steps S122, S123Ca and S124 may be repeatedly performed until a .times. ...

[0101] Next, the horizontal displacement of the i-th layer (D i ) is obtained (S13C). The horizontal displacement (D i ) is expressed by the following formula (18).

number

[0102] In step S13C, the maximum horizontal displacement (Dcy ) can be obtained. cy ) is expressed by the following formula (19).

number

[0103] By executing the above steps S10C, S12C, and S13C, the horizontal displacement (D i ) and maximum horizontal displacement (D cy ) can be obtained.

[0104] <Fourth embodiment: effects> The evaluation method of the ground 100 according to the fourth embodiment includes a first evaluation step (S121) of setting specifications for the lattice-shaped improved body 1 surrounding the intra-lattice ground 81 including the area where liquefaction is expected, a second evaluation step (S122) of defining a geomechanical model including model components simulating the lattice-shaped improved body and model components simulating the intra-lattice ground, a third evaluation step (123Ca) of obtaining the equivalent cyclic shear strain (γ) using the geomechanical model 100M, and a third evaluation step (123Ca) of calculating the horizontal displacement (D) occurring in the intra-lattice ground 81 using the equivalent cyclic shear strain (γ). cy and a fourth evaluation step (S13C) of obtaining a result of the evaluation.

[0105] This method prepares a geomechanical model 100M including a model component that simulates the grid-like improved body 1 to be evaluated and a model component that simulates the intra-grid ground 81. Then, using this geomechanical model 100M, the horizontal displacement (D i ) is obtained. According to the geomechanical model 100M, the parameters of the ground properties are horizontal displacement (D i) can be more easily reflected in the calculation results. Furthermore, the geomechanical model 100M makes it possible to suppress an increase in the calculation load. Therefore, according to this method, the ground 100 can be evaluated while reflecting the parameters that indicate the characteristics of the ground 100 and suppressing an increase in the calculation load.

[0106] Fifth embodiment: Maximum horizontal displacement of the ground surface (D cy ) to determine the specifications of the lattice-shaped improved body> The fifth embodiment is a method for determining the specifications of the grid-like improved body 1. More specifically, the fifth embodiment is a method for determining the specifications of the grid-like improved body 1, which is based on the maximum horizontal displacement (D cy ) to determine the specifications of the lattice-shaped improved body 1.

[0107] As shown in Figure 11, the method for determining the specifications of the grid-like improved body 1 according to the fifth embodiment has steps S10D, S12D, S13D, and S14D as its main steps. Of these, steps S10D, S12D, and S13D are the same as steps S10C, S12C, and S13C, respectively, included in the ground evaluation method according to the fourth embodiment. Therefore, detailed explanations of steps S10D, S12D, and S13D will be omitted.

[0108] Step S14D is the maximum horizontal displacement of the ground surface (D cy ) to identify the degree of liquefaction, and a process of determining whether the identified degree of liquefaction satisfies the liquefaction evaluation index.

[0109] First, the maximum horizontal displacement of the ground surface (D cy ) to identify the degree of liquefaction. For example, the maximum horizontal displacement (D cy The relationship between the maximum horizontal displacement (D) and the degree of liquefaction can be exemplified as shown in Table 1. cy ) is applied to Table 1 to determine the degree of liquefaction. [Table 1]

[0110] Then, it is determined whether the identified degree of liquefaction satisfies the liquefaction assessment index. The liquefaction assessment index may be one selected from the "degree of liquefaction" in Table 1. For example, if "minor" is selected as the liquefaction assessment index, the liquefaction assessment index may be satisfied when the result of the process of identifying the degree of liquefaction is "none" or "minor."

[0111] The liquefaction assessment index is the maximum horizontal displacement of the ground surface (D cy ) can be set as the numerical value itself. For example, the maximum horizontal displacement (D cy ) is less than 0.05" may be set.

[0112] Maximum horizontal displacement of the ground surface (D cy ) satisfies the non-liquefaction condition (S14D: YES), the specifications of the grid-shaped improvement body 1 set in step S121 are adopted as the specifications of the grid-shaped improvement body 1. On the other hand, the maximum horizontal displacement (D cy ) does not satisfy the non-liquefaction condition (S14D: NO), the specifications of the lattice-shaped improved body 1 set in step S121 cannot be adopted as the specifications of the lattice-shaped improved body 1. Therefore, steps S12D and S13D are carried out again.

[0113] <Fifth embodiment: effects> The method for determining the specifications of the lattice-shaped improved body 1 according to the fifth embodiment includes a first determination step (S121) for setting the specifications of the lattice-shaped improved body 1 surrounding the lattice ground 81 including the area where liquefaction is expected, a second determination step (S122) for setting a geomechanical model 100M including a model component simulating the lattice-shaped improved body 1 and a model component simulating the lattice ground 81, and a third determination step (S123Da) for obtaining the equivalent cyclic shear strain (γ) using the geomechanical model 100M, and an equivalent cyclic shear stress intensity (τ d ) to calculate the maximum horizontal displacement (D cy ) and the fourth determination step (S13D) to obtain the maximum horizontal displacement (D cyand a fifth determination step (S14D) of evaluating the liquefaction of the intra-lattice ground 81 using the lattice-shaped improvement body 1. In the fifth determination step (S14D), the second determination step (S122), the third determination step (S123Da), the fourth determination step (S13D), and the fifth determination step (S14D) are repeated while changing the specifications of the lattice-shaped improved body 1 in the first determination step (S121) until the result of the evaluation of the liquefaction of the intra-lattice ground 81 satisfies the predetermined conditions.

[0114] According to the method for determining the specifications of the lattice-shaped improved body 1 of the fifth embodiment, the intra-lattice ground 81, which is the object of evaluating the possibility of liquefaction, is simulated as a geomechanical model 100M. Then, using this geomechanical model 100M, the maximum horizontal displacement (D cy ), the equivalent cyclic shear strain (γ) acting on the ground 81 within the grid is obtained. The geomechanical model 100M makes it easier to reflect parameters that are ground characteristics. Furthermore, the geomechanical model 100M makes it possible to suppress an increase in the calculation load. Therefore, according to this method, it is possible to calculate the maximum horizontal displacement (D cy The specifications of the grid-like improvement body 1 can be determined based on the evaluation results of the ground 100 based on the above.

[0115] Sixth embodiment: Maximum horizontal displacement of the ground surface (D cy ) and a method for determining the specifications of the grid-like improved body using the allowable stress of the grid-like improved body> The sixth embodiment is also a method for determining the specifications of the grid-like improvement body 1. More specifically, the sixth embodiment is a method for determining the specifications of the grid-like improvement body 1, which is based on the maximum horizontal displacement (D cy ) and the shear stress intensity (τ s ) is used to determine the specifications of the grid-like improvement body 1. In other words, in the sixth embodiment, the maximum horizontal displacement of the ground surface (D cy ) was used to determine the specifications of the grid-like improved body 1. However, in the sixth embodiment, the maximum horizontal displacement of the ground surface (D cy ) and the shear stress intensity (τs ) is also used to determine the specifications of the lattice-shaped improved body 1.

[0116] Fig. 12 is a flowchart showing the main steps S10E, S12E, S13E, S14E, and S15E of the method for determining the specifications of the lattice-shaped improved body 1 according to the sixth embodiment. The method for determining the specifications of the lattice-shaped improved body 1 according to the sixth embodiment uses a geomechanical model 100M (see Fig. 4) based on the flowchart shown in Fig. 12 to calculate the maximum horizontal displacement (D cy ) and the shear stress intensity (τ s ) and obtain the maximum horizontal displacement (D cy ) satisfies the non-liquefaction condition, and the shear stress intensity (τ s The specifications of the grid-like improved body 1 are determined on the condition that the stress (stress) is within the allowable value (for example, within the short-term allowable stress).

[0117] Steps S10E and S13E of the method for determining the specifications of the lattice-shaped improved body 1 of the sixth embodiment are the same as steps S10C and S13C of the ground evaluation method of the fourth embodiment. Furthermore, step S14E of the method for determining the specifications of the lattice-shaped improved body 1 of the sixth embodiment is the same as step S14D of the method for determining the specifications of the lattice-shaped improved body 1 of the fifth embodiment. Therefore, detailed explanations of the specific contents of steps S10E, S12E, S13E, and S14E will be omitted.

[0118] The method for determining the specifications of the lattice-shaped improved body 1 according to the sixth embodiment is to determine the shear stress intensity (τ s The specific content of this step S123Eb is the same as that of step S123b in the third embodiment. Therefore, a detailed description of step S123Eb will be omitted.

[0119] In step S14E, the maximum horizontal displacement of the ground surface (D cyIf it is determined that the non-liquefaction condition is satisfied (S14E: YES), step S15E is carried out. The specific content of step S15E is the same as step S15B in the third embodiment. Therefore, a detailed description of step S15E will be omitted.

[0120] <Sixth embodiment: effects> The method for determining the specifications of the lattice-shaped improved body 1 according to the sixth embodiment is to determine the shear stress intensity (τ s ) further includes a sixth determination step (S15E) for determining whether the grid-like improved body 1 is an allowable value. In the third determination step (S123E), the equivalent repeated shear stress intensity (τ d ) is obtained (S123Ea), and the shear stress intensity (τ s The method for determining the specifications of the lattice-shaped improved body 1 is to obtain a result that the evaluation result regarding the liquefaction of the ground 81 in the lattice in the fifth determination step (S14E) satisfies the predetermined condition, and to obtain a shear stress intensity (τ s ) repeats the second determination step (S122), the third determination step (S123E), the fourth determination step (S13E), the fifth determination step (S14E) and the sixth determination step (S15E) while changing the specifications of the lattice-shaped improvement body 1 in the first determination step (S121) until a determination result is obtained that the lattice-shaped improvement body 1 is an acceptable value.

[0121] According to the method for determining the specifications of the grid-shaped improved body 1 of the sixth embodiment, the horizontal displacement of the ground surface (D cy In addition to the evaluation results of the ground 100 based on the shear stress intensity (τ s ) can be taken into consideration when determining the specifications of the lattice-shaped improved body 1. As a result, it is possible to determine the specifications of the lattice-shaped improved body 1 that will not be damaged even when subjected to earthquake motion and can continue to maintain its function of suppressing liquefaction.

[0122] The method for determining the specifications of the grid-like improved body 1 is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the present invention.

[0123] <Variation 1> For example, as a prerequisite for determining the specifications of the lattice-shaped improved body 1, it may be assumed that the extra-lattice ground 82 has already liquefied. If it is assumed that the extra-lattice ground 82 has already liquefied, some ingenuity may be required to handle the stress that the extra-lattice ground 82 exerts on the boundary improved body 11. As shown in Figure 13, there is a method for treating the stress that the extra-lattice ground 82 exerts on the boundary improved body 11 as a load (shear stress intensity) due to earth pressure and water pressure that occurs during an earthquake due to the extra-lattice ground 82. The load due to earth pressure and water pressure is calculated as the shear stress intensity (τ S2 ) can be treated as this shear stress (τ S2 ) can be obtained by a calculation other than that using the extra-grid soil model 82M. S2 ), the geomechanics model 100MA does not need to include the extra-grid ground model 82M. That is, as shown in Fig. 13, the geomechanics model 100MA includes a boundary improvement body model 11M, an intra-grid improvement body model 12M, an intra-grid ground model 81M, and a non-liquefaction layer model 9M.

[0124] FIG. 14 is a flowchart of the evaluation method of the ground 100 according to the first modification. The evaluation method of the ground 100 according to the first modification includes setting a simple analysis model (S122F) and calculating the shear stress intensity (τ S ) (S123F) is different from the evaluation method for the ground 100 of the first embodiment, variant 1. The other steps in the evaluation method for the ground 100 of the first embodiment are the same as those in the evaluation method for the ground 100 of the first embodiment, variant 1, and therefore detailed explanations will be omitted.

[0125] First, in step S122F, the physical properties of the intra-grid ground 81 and the lattice-shaped improved body 1 are set, and the geomechanical model 100MA (see FIG. 13) is also set. As described above, the geomechanical model 100MA does not include the extra-grid ground model 82M.

[0126] In this case, the geomechanical model 100MA uses the shear stiffness matrix ([K S ]).

number

[0127] Furthermore, the geomechanical model 100MA uses the axial stiffness matrix ([K N ]).

number

[0128] Next, in step S123F, the shear stress intensity (τ S ) is obtained. The shear stress intensity (τ S ) is the first shear stress (τ S1 ) and the second shear stress (τ S2 ) and the sum of. Therefore, step S123Fb is the first shear stress intensity (τ S1 ) (S123F1) and the second shear stress (τ S2 ) (S123F2) and the first shear stress (τ S1 ) and second shear stress (τ S2 ) (S123F3).

[0129] First, the first shear stress (τ S1 In step S123F1, the first shear stress intensity (τ S1 ) can be obtained.

[0130] Next, the second shear stress (τ S2 ) is obtained (S123F2). The second shear stress (τ S2 Two methods are given below as examples of calculation methods for obtaining .

[0131] < Second shear stress (τ S2 ) calculation method 1> Second shear stress (τ S2 ) may be obtained using the design guidelines described in the following documents: The Building Center of Japan, Better Living, "Design and Quality Control Guidelines for Improved Ground for Buildings," 1st Edition, Japan, The Building Center of Japan and Better Living, November 30, 2018, pp. 126-127.

[0132] According to this document, when an earthquake occurs, the second shear stress intensity (τ S2 ) can be defined as the sum of an increasing component and an oscillating component. The increasing component is shown by the following equation (22). The oscillating component is shown by the following equation (23). Equations (22) and (23) are citations of equations (10.6.1) and (10.6.2) described on page 126 of the above-mentioned document.

number

number

[0133] < Second shear stress (τ S2 ) calculation method 2> Second shear stress (τ S2 ) may be obtained using another design guideline described in the following document: Ministry of Construction, Public Works Research Institute, Earthquake Resistance Technology Research Center, Dynamic Soil Research Laboratory et al., "Liquefaction Countermeasures Design and Implementation Manual (Draft)," Japan, March 1999, pp. 120-124.

[0134] On page 120 of this document, a flowchart is given for calculating the soil water pressure in a given layer. According to this flowchart, the second shear stress (τ S2 ) may be obtained.

[0135] Furthermore, this document also states that the second shear stress intensity (τ S2 ) is defined as the sum of a gradual increase component and an oscillatory component. The gradual increase component is shown by the following equation (24). The oscillatory component is shown by the following equation (25). Equations (24) and (25) are quoted from "Table - Explanation 4.8.4 Hydraulic Pressure Calculation Method" on page 123 of the above document.

number

number

[0136] And the shear stress (τ S In step S123F3, the first shear stress intensity (τ S1 ) to the second shear stress intensity (τ S2 ) is added. As a result, the first shear stress (τ S1 ) and second shear stress (τ S2 ) the total shear stress (τ S ) can be obtained.

[0137] <Effects of Modification Example 1>

[0138] In the evaluation method for the ground 100, which is variant example 1, the second evaluation step (S122F) defines a geomechanical model 100M using shear spring elements that constitute model components that simulate the lattice-shaped improvement body 1, and shear spring elements and axial spring elements that simulate the intra-lattice ground 81. According to this method, the geomechanical model 100M is composed of multiple shear spring elements. The geomechanical model 100M composed of shear spring elements can reduce the calculation load for obtaining the equivalent cyclic shear stress intensity (τd) acting on the intra-lattice ground 81.

[0139] The third evaluation step (S123F) uses the geomechanical model 100M to calculate the first shear stress (τ s1 ) and a step (S123F1) of obtaining a second shear stress intensity (τ s2 ) and a step (S123F2) of obtaining a first shear stress (τ s1 ) to the second shear stress (τ s2 and (S123F3) adding This method makes it possible to easily incorporate into calculations for ground evaluation the load acting on the lattice-shaped improved body 1 due to the ground 100 existing outside the lattice-shaped improved body 1. As a result, it is possible to evaluate the ground 100 taking into account the load when the outside of the lattice-shaped improved body 1 liquefies.

[0140] The technique of Modification 1 is an application of the first embodiment to the load acting on the lattice-shaped improved body 1 due to the extra-lattice ground 82. The technique of Modification 1 can also be applied to each of the second to sixth embodiments.

[0141] <Variation 2> The geomechanics model 100MA of the first modification did not include the out-of-grid ground model 82M. For example, as in the first embodiment, a geomechanics model 100M including the out-of-grid ground model 82M is used, and the second shear stress intensity (τ s2 ) may be used to obtain an index for evaluating the ground 100.

[0142] FIG. 15 is a flowchart of the evaluation method of the ground 100 according to the second modification. The method of determining the specifications of the grid-like improved body 1 according to the second modification is to calculate the shear stress intensity (τ S ) (S123G) is obtained. The other steps in the ground evaluation method of Modification 2 are the same as those in the method of the first embodiment, so detailed explanations will be omitted.

[0143] In step S123G included in step S12G, the shear stress intensity (τ s The shear stress intensity (τ s ) is the first shear stress (τ s1 ) and the second shear stress (τ s2 ) and is the sum of.

[0144] First, the first shear stress (τs1 In this step S123G1, the first shear stress (τ s1 ) is obtained. The calculation method may be the same as step S123F1 in the embodiment. Next, the second shear stress intensity (τ s2 ) is obtained (S123G2). This step S123G2 is the same as step S123F2 in Modification 1. Then, in step S123G3, the first shear stress intensity (τ s1 ) and the second shear stress intensity (τ s2 ) together.

[0145] <Action and effect> The second evaluation step (S12G) of the evaluation method for the ground 100 is defined by shear spring elements that constitute a model component simulating the lattice-like improved body 1, shear spring elements and axial spring elements that constitute a model component simulating the intra-lattice ground 81, and shear spring elements and axial spring elements that constitute a model component simulating the extra-lattice ground 82 that exists outside the lattice-like improved body 1. The model components simulating the grid-shaped improved body 1 are configured with shear spring elements, the model components simulating the in-grid ground 81 are configured with shear spring elements and axial spring elements, and the model components simulating the out-grid ground 82 are configured with shear spring elements and axial spring elements. This also allows the geomechanics model 100M to be used to calculate the liquefaction safety factor (F L This can improve the accuracy of the calculation to obtain the value.

[0146] The third evaluation step (S123G) uses a geomechanical model to estimate the first shear stress (τ s1 ) and the process (S123G1) of obtaining the second shear stress intensity (τ s2 ) and a step (S123G2) of obtaining the first shear stress (τ s1 ) to the second shear stress (τ s2 and (S123G3) adding This method also makes it possible to easily incorporate into calculations for ground evaluation the load acting on the lattice-shaped improved body 1 due to the extra-lattice ground 82 existing outside the lattice-shaped improved body 1. In other words, it is possible to perform a ground evaluation that takes into account the shear stress intensity obtained using the geomechanics model 100M that includes model components that simulate the extra-lattice ground 82 existing outside the lattice-shaped improved body 1, and the shear stress intensity caused by the liquefied extra-lattice ground 82.

[0147] The technique of Modification 2 is an application of the first embodiment to the load acting on the lattice-shaped improved body 1 due to the extra-lattice ground 82. The technique of Modification 2 can also be applied to each of the second to sixth embodiments.

[0148] <Variation 3> For example, as shown in Figure 16, the geomechanical model 100MC may be composed of a boundary improvement body model 11M, an intra-grid improvement body model 12M, an intra-grid ground model 81M, and an extra-grid ground model 82M. In other words, the geomechanical model 100MC does not need to include the non-liquefaction layer model 9M. In this case, the geomechanical model 100MC is represented by the shear stiffness matrix shown in equation (26) and the axial stiffness matrix shown in equation (27).

number

number

[0149] <Effects of Modification 3> A non-liquefaction layer 9 exists below the lattice-shaped improved body 1 and the intra-lattice ground 81. In the second evaluation step (S122), a geomechanics model 100M is defined by shear spring elements constituting model components that simulate the lattice-shaped improved body 1 shallower than the non-liquefaction layer, shear spring elements and axial spring elements that simulate the intra-lattice ground 81 shallower than the non-liquefaction layer, and shear spring elements and axial spring elements that simulate the extra-lattice ground 82 that exists outside the lattice-shaped improved body 1. The geomechanics model 100M includes model components that simulate the lattice-shaped improved body 1 that exists shallower than the non-liquefaction layer and the intra-lattice ground 81. As a result, it is possible to evaluate the ground 100 without taking into account the influence of the non-liquefaction layer.

[0150] <Other variations> For example, in the model of the first embodiment, the lattice-like improvement body 1 includes a boundary improvement body 11 and an intra-lattice improvement body 12. For example, as shown in FIG. 17, the boundary improvement body 11 may include only a boundary improvement body region 11E.

[0151] The model simulating the ground 100 is not limited to one employing multiple spring elements SE as shown in FIG. 4. For example, as shown in FIG. 18(a), a geomechanics model 102E may employ multiple plane strain elements. The model in FIG. 18(a) includes a liquefied layer region 8E and a non-liquefied layer region 9E. The liquefied layer region 8E is composed of a plane strain element 11P simulating the boundary improvement body 11 and a plane strain element 81P simulating the intra-grid ground 81. The non-liquefied layer region 9E is composed of a plane strain element 9P simulating the non-liquefied layer 9.

[0152] As shown in Figure 18(b), the geomechanics model 103M may include multiple spring elements and multiple beam elements. The model in Figure 18(b) simulates the axial stiffness of the intra-lattice ground 81 using spring element 81S2. Furthermore, the model in Figure 18(b) simulates the shear stiffness of the boundary improvement body model 11Ma, the intra-lattice ground model 81Ma, and the non-liquefaction layer model 9M using beam elements 11B, 81B, and 9B, respectively. The beam elements 11B, 81B, and 9B can also reflect parameters representing the characteristics of the boundary improvement body model 11Ma, the intra-lattice ground model 81Ma, and the non-liquefaction layer model 9M, respectively. The bending stiffness of the beam elements 11B and 81B can also be treated as infinite, as appropriate.

[0153] Furthermore, when the direction of the earthquake external force F is considered as shown in Fig. 6, an out-of-plane wall 11a that is out-of-plane with respect to the earthquake external force F and an in-plane wall 11b that is in-plane with respect to the earthquake external force F can be defined. Therefore, as shown in Fig. 19, the geomechanical model 104M may be composed of an out-of-plane wall direction model 105M related to the out-of-plane wall direction and an in-plane wall direction model 106M related to the in-plane wall direction. Furthermore, a three-dimensional geomechanical model 104M may be constructed by connecting the out-of-plane wall direction model 105M and the in-plane wall direction model 106M with multiple shear spring elements 104S.

[0154] <Example of an extended geomechanical model> The ground evaluation method of this embodiment can be applied to more complex geomechanical models. Figure 20 is a plan view of improved ground 70, in which an improvement body 71 is provided on ground 72. The shape of the improvement body 71 in plan view is what is known as a lattice shape. In this modification, a force F70 acting in the right direction on the page acts on the improvement body 71 shown in Figure 20.

[0155] First, the ground 72 is divided into an extra-lattice ground 721 that is not surrounded by the improved body 71, and an intra-lattice ground 722 that is surrounded by the improved body 71. If a force F70 is defined as acting in the right direction on the page, the improved body 71 is divided into two parts depending on the direction of this force F70. The improved body 71 has an inner lattice wall 711 and an outer lattice wall 712.

[0156] The cross-sectional shape of the lattice plane inner wall 711 is a rectangle including a long side and a short side. The long side of the lattice plane inner wall 711 is parallel to the direction of the force F70, and the short side of the lattice plane inner wall 711 is perpendicular to the direction of the force F70. The lattice plane inner wall 711 defined in this way has a large second moment of area and a large resistance to the force F70. In other words, it can be said that the lattice plane inner wall 711 is difficult to deform due to the force F70.

[0157] The cross-sectional shape of the lattice plane outer wall 712 is also a rectangle including a long side and a short side. The long side of the lattice plane outer wall 712 is perpendicular to the direction of the force F70, and the short side of the lattice plane outer wall 712 is parallel to the direction of the force F70. The lattice plane outer wall 712 defined in this way has a smaller second moment of area than the lattice plane inner wall 711, and therefore has a smaller resistance to the force F70. In other words, it can be said that the lattice plane outer wall 712 is more easily deformed by the force F70 than the lattice plane inner wall 711.

[0158] Three regions are then defined based on the direction of force F70. First, the improved ground 70 has a region along the direction of force F70 where no improved body 71 is provided and where only unimproved ground 72 is present. This region is referred to as the lattice outer surface 720. Next, the improved ground 70 has a region along the direction of force F70 that includes the outer-lattice ground 721, the lattice surface inner wall 711, and the inner-lattice ground 722. This region is referred to as the lattice surface inner surface 700. Finally, the improved ground 70 has a region along the direction of force F70 that includes the outer-lattice ground 721, the lattice surface outer wall 712, and the inner-lattice ground 722. This region is referred to as the lattice surface outer surface 710.

[0159] Figure 21 shows a geomechanical model 70M that uses multiple spring elements to represent the ground 72 and the improved body 71 shown in Figure 20. Figure 21 shows the geomechanical model 70M that corresponds to a portion of the area shown in Figure 20. The geomechanical model 70M shown in Figure 21 includes structural plane mechanical models that correspond to the multiple structural planes shown in Figure 20.

[0160] The ground mechanical model 70M also includes a mechanical model corresponding to the extra-lattice ground 721. Specifically, the lattice exterior surface mechanical model 720M shown in Fig. 21 corresponds to the lattice exterior surface 720 shown in Fig. 20. The lattice interior surface mechanical model 700M shown in Fig. 21 corresponds to the lattice interior surface 700 shown in Fig. 20. Similarly, the lattice exterior surface mechanical model 710M shown in Fig. 21 corresponds to the lattice exterior surface 710 shown in Fig. 20.

[0161] These mechanical models include unimproved ground spring elements 72S that represent unimproved ground, and improved body spring elements 71S that represent the improved body 71.

[0162] For example, no improved body 71 is provided on the lattice exterior surface 720. Therefore, the lattice exterior surface mechanical model 720M is composed of only the unimproved ground spring elements 72S.

[0163] The lattice plane inner structural surface 700 includes an extra-lattice ground 721 and an inner lattice wall 711. Therefore, the lattice plane inner structural surface mechanical model 700M includes a model region 721M representing the extra-lattice ground 721 represented by unimproved ground spring elements 72S, and a model region 711M representing the inner lattice wall 711 represented by improved body spring elements 71S. For example, the model region 711M representing the inner lattice wall 711 includes a plurality of improved body spring elements 71S connected in the direction of the force F70. This represents that the inner lattice wall 711 is less likely to deform in response to the force F70.

[0164] The lattice plane exterior surface 710 includes an extra-lattice ground 721, a lattice plane exterior wall 712, and an intra-lattice ground 722. Therefore, the lattice plane exterior surface mechanical model 710M includes a model region 721M representing the extra-lattice ground 721 represented by unimproved ground spring elements 72S, a model region 722M representing the intra-lattice ground 722 represented by unimproved ground spring elements 72S, and a model region 712M representing the lattice plane exterior wall 712 represented by improved body spring elements 71S. For example, the model region 712M representing the lattice plane exterior wall 712 is represented by one improved body spring element 71S in the direction of force F70. This indicates that the lattice plane exterior wall 712 is more easily deformed than the lattice plane interior wall 711 in response to force F70.

[0165] Furthermore, the lattice exterior structural surface mechanical model 720M, the lattice interior structural surface mechanical model 700M, and the lattice exterior structural surface mechanical model 710M are connected to one another in a direction intersecting with the force F70. This connection is also indicated by the unimproved ground spring element 72S or the improved body spring element 71S.

[0166] For example, the lattice plane exterior structural surface mechanical model 720M and the lattice plane interior structural surface mechanical model 700M are connected by an unimproved ground spring element 72S. The lattice plane interior structural surface mechanical model 700M and the lattice plane exterior structural surface mechanical model 710M are connected by an unimproved ground spring element 72S and a spring element 71S representing the improved body 71. Specifically, the improved body spring elements 71S constituting the lattice plane interior structural surface mechanical model 700M include those connected to the improved body spring elements 71S of the lattice plane exterior structural surface mechanical model 710M and those connected to the unimproved ground spring elements 72S of the lattice plane exterior structural surface mechanical model 710M. The improved body spring elements 71S constituting the lattice plane interior structural surface mechanical model 700M that are connected to the improved body spring elements 71S of the lattice plane exterior structural surface mechanical model 710M are connected by the improved body spring elements 71S. The improved body spring elements 71S constituting the lattice plane inner structural surface mechanical model 700M, which are connected to the unimproved ground spring elements 72S of the lattice plane outer structural surface mechanical model 710M, are connected by the unimproved ground spring elements 72S.

[0167] For the ground 72 provided with an improved body 71 shown in the geomechanics model 70M in Figure 21, the ground evaluation method described in detail in the embodiment can be used to evaluate the ground while reflecting parameters that indicate the characteristics of the ground and suppressing an increase in calculation load. [Explanation of symbols]

[0168] 1...Grid-shaped improvement body, 8...Liquefaction layer, 9...Non-liquefaction layer, 11...Boundary improvement body, 12...Intra-grid improvement body, 81...Intra-grid ground, 81a...Liquefaction area, 100M, 104M...Geomechanical model.

Claims

1. A first evaluation step of setting specifications for a grid-like improvement body surrounding the ground within the grid including the area where liquefaction is expected; a second evaluation step of defining a geomechanics model including a model component simulating the grid-like improvement body and a model component simulating the intra-grid ground; Using the geomechanical model, the equivalent repeated shear stress intensity (τ ｄ ) or equivalent cyclic shear strain (γ); The equivalent repeated shear stress (τ ｄ ) to evaluate whether liquefaction of the ground in the grid will occur or not. Ｌ value), or the horizontal displacement (D ｃｙ and a fourth evaluation step of obtaining a ground surface roughness.

2. In the second evaluation step, a shear spring element constituting a model component that simulates the lattice-shaped improvement body; The method for evaluating ground according to claim 1 , wherein the ground mechanical model is defined by shear spring elements and axial spring elements that simulate the ground within the grid.

3. The third evaluation step includes: The first shear stress (τ ｓ１ ) and The second shear stress intensity (τ ｓ２ ) and The first shear stress (τ ｓ１ ) to the second shear stress (τ ｓ２ 3. The method for evaluating ground according to claim 2, further comprising the step of adding:

4. In the second evaluation step, a shear spring element constituting a model component that simulates the lattice-shaped improvement body; shear spring elements and axial spring elements constituting a model component that simulates the ground within the grid; The ground evaluation method according to claim 1, wherein the ground mechanics model is defined by shear spring elements and axial spring elements that constitute model components that simulate the extra-lattice ground that exists outside the lattice-shaped improvement body.

5. The third evaluation step includes: The first shear stress (τ ｓ１ ) and The second shear stress intensity (τ ｓ２ ) and The first shear stress (τ ｓ１ ) to the second shear stress (τ ｓ２ 5. The method for evaluating ground according to claim 4, further comprising the step of adding:

6. A non-liquefaction layer exists below the grid-like improved body and the ground within the grid, In the second evaluation step, a shear spring element constituting a model component that simulates the lattice-shaped improvement body; shear spring elements and axial spring elements constituting a model component that simulates the ground within the grid; 2. The method for evaluating ground according to claim 1, wherein the geomechanical model is defined by a shear spring element and an axial spring element that constitute model components that simulate the non-liquefaction layer.

7. A non-liquefaction layer exists below the grid-like improved body and the ground within the grid, In the second evaluation step, a shear spring element constituting a model component simulating the lattice-shaped improved body shallower than the non-liquefaction layer; Shear spring elements and axial spring elements that simulate the ground within the grid shallower than the non-liquefaction layer; 2. The method for evaluating ground according to claim 1, wherein the ground mechanical model is defined by shear spring elements and axial spring elements that simulate the extra-grid ground existing outside the lattice-shaped improvement body.

8. The ground evaluation method described in claim 1, wherein the lattice-shaped improvement body is composed of a boundary improvement body surrounding the intra-lattice ground and an intra-lattice improvement body provided in the intra-lattice ground surrounded by the boundary improvement body.

9. 2. The ground evaluation method according to claim 1, wherein the lattice-shaped improved body is composed only of a boundary improved body surrounding the ground within the lattice.

10. The lattice-shaped improved body is composed of a boundary improved body surrounding the intra-lattice ground and an intra-lattice improved body provided in the intra-lattice ground surrounded by the boundary improved body, The ground evaluation method described in claim 1, wherein the intra-lattice improved bodies include in-plane improved bodies whose long sides of the cross section are aligned with the direction of the external force, and out-of-plane improved bodies whose short sides of the cross section are aligned with the direction of the external force.

11. A first determination step of setting specifications for a grid-like improvement body surrounding the ground within the grid, including the area where liquefaction is expected; a second determination step of setting a geomechanical model including a model component simulating the lattice-shaped improved body and a model component simulating the ground within the lattice; Using the geomechanical model, the equivalent repeated shear stress intensity (τ ｄ ) or equivalent cyclic shear strain (γ); The equivalent repeated shear stress (τ ｄ ) to evaluate whether liquefaction of the ground in the grid will occur or not. Ｌ value), or obtain the equivalent repeated shear stress intensity (τ ｄ ) to calculate the horizontal displacement (D ｃｙ a fourth determination step of obtaining The liquefaction safety factor (F Ｌ value) and the horizontal displacement (D ｃｙ A fifth determination step of evaluating the liquefaction of the ground in the grid using at least one of the following: A method for determining the specifications of a lattice-shaped improvement body for liquefaction countermeasures, wherein the second, third, fourth and fifth determination steps are repeated while changing the specifications of the lattice-shaped improvement body in the first determination step until the results of the evaluation regarding liquefaction of the ground within the lattice in the fifth determination step satisfy predetermined conditions.

12. The shear stress intensity (τ ｓ ) further comprises a sixth determining step of determining whether the grid refinement is an acceptable value; In the third determination step, the equivalent repeated shear stress intensity (τ ｄ ) and the shear stress intensity (τ ｓ ) and further obtain In the fifth determination step, the result of the evaluation regarding the liquefaction of the ground in the grid satisfies the predetermined condition, and in the sixth determination step, the shear stress intensity (τ ｓ 12. A method for determining specifications of a lattice-shaped improved body for liquefaction countermeasures as described in claim 11, wherein the second determination step, the third determination step, the fourth determination step, the fifth determination step, and the sixth determination step are repeated while changing the specifications of the lattice-shaped improved body in the first determination step until a determination result is obtained that the lattice-shaped improved body is an acceptable value.

Images