Support method of earth-retaining construction

Abstract

To provide a support method of earth-retaining construction capable of predicting a preload amount of each part in an earth-retaining structure.SOLUTION: A support method of earth-retaining construction includes: an analysis step of setting a value of a parameter related to earth-retaining timbering or installation of the earth-retaining timbering as a variable, and numerically analyzing a preload amount of a first part in an earth-retaining structure; and a prediction step of predicting the preload amount when the value of the parameter is a specific value, on the basis of the analysis result acquired by the analysis step. The prediction step performs prediction using a regression equation obtained on the basis of the analysis result. The parameter may indicate, for example, the number of timbering, the length of timbering, and cross-section performance of timbering.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for supporting retaining work.

Background Art

[0002] As a method for supporting the wall surface of a ground mass in excavation work, a retaining method using shoring is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional retaining work plan, the preload amount is determined on the assumption that the axial force introduced into the shoring is uniformly transmitted to the retaining wall. However, in a retaining structure where the lengths, cross-sections, and materials of each shoring member are different, the load transmitted from the shoring to the retaining wall during preloading becomes non-uniform. Therefore, it is difficult to accurately predict the preload amount of each part required to suppress the displacement of the retaining wall under such conditions. For example, when setting the preload amount of a retaining shoring, first, the "load per unit width" along the retaining wall is set, and then it is converted into the "load per one shoring". That is, the "load per one shoring" is set on the assumption that the retaining wall is uniformly displaced. However, when the preload is actually applied, non-uniform displacement occurs in the retaining wall, and the shoring axial force as set is not transmitted to the retaining wall (the axial force escapes). In that case, in a subsequent construction stage, the retaining wall is displaced toward the excavation side by more than the planned value. If the preload amount of each part in the retaining structure can be correctly predicted prior to construction, such inconveniences can be avoided.

[0005] Therefore, in one aspect, an object of the present invention is to provide a method for assisting retaining wall construction that can predict the preload amount of each part in a retaining wall structure.

Means for Solving the Problems

[0006] In one embodiment, a parameter value related to the erection of a retaining wall support or a retaining wall support is set as a variable, and an analysis step of numerically analyzing the preload amount of a first part in the retaining wall structure; a prediction step of predicting the preload amount when the parameter value is a specific value based on the analysis result obtained by the analysis step; A method for assisting retaining wall construction is provided, which includes the above steps.

Effects of the Invention

[0007] In one aspect, according to the present invention, the preload amount of each part in the retaining wall structure can be predicted.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0009] FIG. 1 is a plan view exemplifying a retaining structure using a strut, FIG. 2 is a plan view showing a part of the retaining structure, and FIGS. 3 to 3D are longitudinal sectional views of the excavation construction process as seen from above in FIG. 1.

[0010] The retaining structure shown in FIG. 1 is applied when excavating a rectangular region having symmetry with respect to a plane 61 extending in the vertical direction and a plane 62 extending in the horizontal direction in FIG. 1. The region is defined by retaining walls including a retaining wall 40A extending in the vertical direction of FIG. 1 and a retaining wall 40B extending in the horizontal direction of FIG. 1. Also, the retaining structure has symmetry with respect to the plane 61 and the plane 62.

[0011] As shown in FIGS. 1 and 2, the retaining wall 40A is supported by an abdominal lift 30A extending in the vertical direction of FIG. 1, and the retaining wall 40B is supported by an abdominal lift 30B extending in the horizontal direction of FIG. 1, respectively.

[0012] In addition, the abdominal lifts 30A and 30B are supported by cut beams including cut beams 20A and 20B extending in the vertical direction of FIG. 1 and large fire strikes including large fire strikes 10A, 10B, and 10C. As shown in FIG. 1, the large fire strikes 10A, 10B, and 10C connect diagonally between the abdominal lifts 30A and 30B. In FIG. 1, the angles of the large fire strikes 10A, 10B, and 10C with respect to the abdominal lift 30B are θ1, and the angles of the large fire strikes 10A, 10B, and 10C with respect to the abdominal lift 30A are θ2. Note that the extending directions of the large fire strikes 10A, 10B, and 10C are parallel to each other, and in FIGS. 1 and 2, only the angles θ1 and θ2 of the large fire strike 10A are shown.

[0013] As shown in FIG. 2, in this embodiment, jacks 11A, 11B, and 11C are respectively inserted into the large fire strikes 10A, 10B, and 10C to apply preloads.

[0014] In addition, as shown in FIG. 2, in this embodiment, a jack 32 is inserted into the abdominal lift 30B to apply a preload. Also, on the right side of the jack 32 in FIG. 2, the abdominal lift 30B is slidable in the left - right direction of FIG. 2 with respect to the retaining wall 40B. Thereby, the axial (left - right direction of FIG. 2) preload of the abdominal lift 30B by the hydraulic jack 32 also acts on the large fire strikes 10A, 10B, and 10C. Note that by applying a preload to the abdominal lift 30B, the imbalance of the axial force during preloading in the large fire strikes 10A, 10B, and 10C can be suppressed. Specifically, even in the large fire strike 10A with the longest member length and where the axial force is likely to be small during preloading, it becomes easier to ensure the axial force due to the preload on the abdominal lift 30B. However, it is difficult to correctly evaluate this effect by the conventional preload amount setting method that assumes "the load is uniformly transmitted from the shoring work to the retaining wall".

[0015] Next, the process of the excavation construction will be exemplified.

[0016] In the example of the excavation work shown in FIGS. 3 to 3D, before the start of excavation, a retaining wall such as the retaining wall 40A is built (FIG. 3). Next, the ground below the ground surface 41 is excavated to the excavation surface 42 by primary undercutting (FIG. 3A). Next, after installing the support work including the breast wall 30A, a preload indicated by the arrow 31a (FIG. 3B) is introduced into the retaining wall 40A, and the ground is excavated to the excavation surface 43 by secondary undercutting (FIG. 3C). Next, the underground structure B is installed and the support work is disassembled (FIG. 3D).

[0017] Next, the effect of the preload introduced into the breast wall 30B will be described.

[0018] FIG. 4 is a plan view showing a normal retaining structure without introducing a preload into the breast wall. Further, FIG. 5 is a diagram showing the displacement of the retaining wall when a preload is introduced into the breast wall, and FIG. 6 is a diagram showing the displacement of the retaining wall when a preload is not introduced into the breast wall. Steps 1, 2, 3, and 4 in FIGS. 5 and 6 respectively correspond to the process of the excavation work. That is, step 1 corresponds to the state shown in FIG. 3A, step 2 corresponds to the state shown in FIG. 3B, step 3 corresponds to the state shown in FIG. 3C, and step 4 corresponds to the state shown in FIG. 3D.

[0019] Also, the vertical axis of the graphs in FIGS. 5 and 6 indicates the depth from the ground surface 41, and the horizontal axis indicates the displacement of the retaining wall 40A.

[0020] According to the comparison between FIGS. 5 and 6, when a preload is introduced to the abdominal lift 30B (FIG. 5), the displacements of the retaining wall 40A in steps 2 to 4 are respectively suppressed compared to the case where no preload is introduced to the abdominal lift 30B (FIG. 6). Specifically, regarding the displacement amount of the retaining wall 40A, when no preload is introduced to the abdominal lift 30B (FIG. 6), the maximum displacement of the retaining wall 40A shows a value of 22 mm indicated in step 4. On the other hand, when a preload is introduced to the abdominal lift 30B (FIG. 5), the maximum displacement of the retaining wall 40A indicated in step 4 is significantly suppressed. In this case, the maximum displacement of the retaining wall 40A is reduced to a value of 15 mm indicated in step 1. As described above, in the case where no preload is introduced to the abdominal lift 30B (FIG. 6), it is empirically known that the axial force becomes small in the large fire strike 10A with the longest member length. Therefore, if the preload amount is overestimated at the planning stage before construction, it will be a dangerous plan. On the other hand, when a preload is introduced to the abdominal lift 30B (FIG. 5), since the axial force of the large fire strike is ensured, a sufficient preload amount can be expected at the planning stage before construction.

[0021] In this embodiment, the effect of introducing a preload to such an abdominal lift 30B (the second part) can be predicted (evaluated) by a prior analysis (parametric study). For example, the axial forces (preload amounts) introduced to the large fire strikes 10A, 10B, and 10C (the first part) can be analyzed with various parameter values related to the installation of the retaining support work or the retaining support work as variables. At this time, the presence or absence and magnitude of the preload amount introduced to the abdominal lift 30B can also be applied as the values of the parameters. Thereby, for example, it can be grasped in advance that by applying a preload to the abdominal lift 30B, the imbalance of the axial forces during preloading in the large fire strikes 10A, 10B, and 10C can be suppressed. Also, the displacements of the retaining wall as shown in FIGS. 5 and 6 can be analyzed through the axial forces (preload amounts) introduced to the large fire strikes 10A, 10B, and 10C. Thereby, it becomes possible to select a suitable combination of parameter values in advance, and it is possible to numerically analyze in advance the preload amounts of each part in the retaining structure and the displacements of the retaining wall when such a combination of parameters is adopted.

[0022] As parameters corresponding to variables during analysis, parameters related to rockfall retaining supports or the erection of rockfall retaining supports can be widely applied. The attributes of the parameters are arbitrary. For example, the length of the support, the cross-sectional performance of the support, the angle of the support with respect to the wall surface of the rockfall retaining wall, and the preloading amount at the second part in the rockfall retaining structure can be used as parameters. Also, the installation intervals D0, D1, D2, d0, d1, d2, d3, etc. of the supports shown in Fig. 1 can be used as parameters.

[0023] Fig. 7 is a diagram illustrating an analysis model used for parametric study. The analysis model shown in Fig. 7 models the large fires 10A, 10B, 10C, the bulges 30A, 30B, and the surrounding ground 60 shown in Fig. 2. The large fires 10A, 10B, 10C and the bulges 30A, 30B are beam elements, and the ground 60 is a plane strain element, all of which are regarded as elastic bodies. Note that the type of analysis model used in the analysis process is arbitrary and is not limited to the model shown in Fig. 7.

[0024] As described above, the bulge 30B is slidable with respect to the rockfall retaining wall 40B. Therefore, also in the analysis model, the bulge 30B is in a condition of sliding without sharing nodes with the ground 60, and a concentrated load P0 is applied to the end of the bulge 30B. Here, the concentrated load P0 corresponds to the preloading amount introduced by the jack 32. On the other hand, the bulge 30A shares nodes with the ground 60.

[0025] With such an analysis model, for example, the load transfer ratio r can be obtained. Here, let the load transmitted to the rockfall retaining wall 40A through the longest large fire (for example, the large fire 10A corresponding to the first part in Fig. 2) be Pr, and the load transfer ratio r = Pr / P0 is defined.

[0026] Fig. 8 is a diagram illustrating the results of a parametric study using the analysis model of Fig. 7.

[0027] Here, as parameters that are variables in the parametric study, the number of large welds n (n = 3, 4, 5), and the attachment angles θ1 and θ2 of the large weld 10 (Figure 7) were changed, and a total of 24 cases of analysis were performed. The dots shown in Figure 8 indicate the results of each parametric study, and the values on the vertical axis are the analysis results of the load transfer ratio r. Note that in Figure 2, the state where the number of large welds n is 3 is shown. Also, in Figure 7, the state where the number of large welds n is 5 is shown.

[0028] In addition, the values on the horizontal axis of Figure 8 show the regression results of the load transfer ratio r based on the analysis results. This regression result is Regression equation: r = a + b·n + c·sinθ1 + d·sinθ2 (a, b, c, d are constants) shown as. After the regression equation is calculated, it becomes possible to obtain the prediction result of the load transfer ratio r based on the regression equation without individually inputting the combination of parameter values into the analysis model.

[0029] Figures 9 and 10 are diagrams showing analysis examples in the bracing structure using a cut beam. Similar to the case of large welds, analysis by parametric study using the analysis model is possible. Specifically, the results of parametric study in which the combination of parameter values such as the length of the cut beam, cross-sectional performance, and the angles with respect to the wall surface of the bracing wall (for example, θ3 and θ4 shown in Figure 9) are changed can be obtained as analysis results. Also, based on the analysis results, a regression equation can be obtained. After the regression equation is calculated, it becomes possible to predict the preload amount and the displacement of the bracing wall based on the regression equation without individually inputting the combination of parameter values into the analysis model.

[0030] In the example of Fig. 9, the lengths of the cross beams 21A, 21B, and 21C connected to the diaphragms 33 and 34 are different from each other. For this reason, even if the cross-sectional performance is the same, differences occur in the axial forces of the cross beams 21A, 21B, and 21C (the first part). In Fig. 9, the lengths of the arrows 33b etc. towards the dotted line 33a and the arrows 34b etc. towards the dotted line 34a correspond to the magnitudes of the axial forces of the cross beams 21A, 21B, and 21C. The dotted lines 33a and 34a indicate the displacements of the retaining walls at the parts corresponding to the diaphragms 33 and 34. As shown in Fig. 9, the displacements of the retaining walls change corresponding to the axial forces of the cross beams 21A, 21B, and 21C.

[0031] In the example of Fig. 9, based on the analysis results analyzed using the analysis model and the regression equations derived from the analysis results, the lengths, numbers, cross-sectional performances of the cross beams corresponding to the cross beams 21A, 21B, and 21C, the angles of the retaining walls with respect to the wall surfaces (for example, θ3 and θ4 shown in Fig. 9), etc., the axial forces of each cross beam and the displacements of the retaining walls can be predicted in advance. The predicted axial forces can be reflected in the preloading amounts by the jacks 22A, 22B, and 22C during construction.

[0032] In the example of Fig. 10, the cross-sectional performances of the cross beams 23A, 23B, and 23C connected to the diaphragms 35 and 36 are not the same, and the cross-sectional performance of the cross beam 23B is superior to those of the cross beams 23A and 23C. For this reason, even if the lengths (the lengths in the vertical direction in Fig. 10) are the same, differences occur in the axial forces of the cross beams 23A, 23B, and 23C (the first part). In Fig. 10, the lengths of the arrows 35b etc. towards the dotted line 35a and the arrows 36b etc. towards the dotted line 36a correspond to the magnitudes of the axial forces of the cross beams 23A, 23B, and 23C. The dotted lines 35a and 36a indicate the displacements of the retaining walls at the parts corresponding to the diaphragms 35 and 36. As shown in Fig. 10, the displacements of the retaining walls change corresponding to the axial forces of the cross beams 23A, 23B, and 23C.

[0033] Also in the example of FIG. 10, based on the analysis results analyzed using the analysis model and the regression formula derived from the analysis results, the length, number, installation interval, cross-sectional performance of the cut beams corresponding to the cut beams 23A, 23B, and 23C, and the axial force of each cut beam and the displacement of the retaining wall according to the angle with respect to the wall surface of the retaining wall can be predicted in advance. The predicted axial force can be reflected in the preloading amount by the jacks 24A, 24B, and 24C during construction.

[0034] As described above, the method for assisting retaining work of the present invention uses, as variables, the values of parameters related to the erection of retaining supports or retaining supports, and includes an analysis step of numerically analyzing the preloading amount of the first part in the retaining structure, and a prediction step of predicting the preloading amount when the value of the parameter is a specific value based on the analysis results obtained in the analysis step. Therefore, the preloading amount of each part in the retaining structure can be predicted, and an appropriate combination of parameter values can be obtained in advance. In addition, the effect of the retaining structure in the obtained combination of parameter values can be evaluated in advance. Therefore, according to the method for assisting retaining work of the present invention, retaining work can be effectively assisted.

[0035] Although each embodiment has been described in detail above, the present invention is not limited to specific embodiments, and various modifications and changes are possible within the scope described in the claims. Also, it is possible to combine all or a plurality of the constituent elements of the above-described embodiments. For example, the shape of the excavation plane is not limited to that shown in FIG. 1. When the shape of the excavation plane is not rectangular, when the shape of the excavation plane is asymmetric (when there is no axis of symmetry as in FIG. 1), or when the corners of the excavation plane are not right angles, the present invention can also be applied. Further, when the bulging is interrupted in the middle of the retaining wall, or when a plurality of bulging members are stacked and erected (for example, when two H-shaped steels are arranged one above the other and side by side), the present invention can also be applied.

Explanation of Signs

[0036] 10, 10A, 10B, 10C Large fire strike 20A, 20B, 21A, 21B, 21C, 23A, 23B, 23C Cutting beams 30A, 30B, 33, 34, 35, 36 Belly lifters 40A, 40B Ridge retaining walls

Claims

1. An analysis step of numerically analyzing the preload amount of the first part in the retaining structure, using the value of the parameter related to the installation of the retaining support or the retaining support as a variable; A prediction step of predicting the preload amount when the value of the parameter is a specific value, based on the analysis result obtained by the analysis step; A method for assisting in retaining work, comprising:

2. The method for assisting in retaining work according to claim 1, wherein in the prediction step, prediction is performed using a regression equation obtained based on the analysis result.

3. The method for assisting in retaining work according to claim 1 or 2, wherein the parameter includes at least any one of the number of retaining supports, the length of the retaining supports, the cross-sectional performance of the retaining supports, and the angle of the retaining supports with respect to the wall surface of the retaining wall.

4. The method for assisting in retaining work according to claim 1, wherein the parameter includes the preload amount introduced into the second part in the retaining structure.

5. The method for assisting in retaining work according to claim 4, wherein the second part is a belly lift.

Images