JP2019039144A - Foundation structure of structure, and foundation method of structure - Google Patents

Abstract

To provide an inexpensive foundation structure when constructing a structure on soft ground.SOLUTION: A foundation structure of a structure 2 constructed on soft ground 1 comprises a plurality of small diameter piles 3 placed in the soft ground 1, an inclusion 4 disposed above the plurality of small diameter piles 3, and a foundation 20 of a lower structure of the structure 2 constructed on the inclusion 4. As a result, in the case of constructing the structure 2 on the soft ground 1, the foundation structure of the structure 2 can be constructed inexpensively.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a foundation structure of a structure constructed (constructed) on soft ground and a foundation construction method for the structure.

  There are the following Patent Document 1 and Patent Document 2 as the basic structure of the structure constructed on the soft ground. The basic structure of the structure of Patent Document 1 includes a plurality of support piles placed in a soft layer, and a sandbag interposed between the bottom surface of the structure and the pile heads of the plurality of support piles. And a material. The basic structure of the structure of Patent Document 2 includes a plurality of piles embedded in a loose saturated sandy layer, and a sandbag as a solid material filled between the foundation and the pile of the structure. is there.

JP 2005-307594 A Japanese Unexamined Patent Publication No. 2016-23451

  When constructing a structure on soft ground, it is important to construct the basic structure of the structure at a low cost.

  The problem to be solved by the present invention is that when a structure is constructed on soft ground, the foundation structure of the structure that can be constructed at a low cost and the foundation construction method of the structure. It is to provide.

  The foundation structure of the structure according to the present invention is a foundation structure of a structure constructed on soft ground, and is arranged on the heads of a plurality of small-diameter piles placed in the soft ground and a plurality of small-diameter piles. It is characterized by comprising an inclusion provided and a foundation of a substructure of a structure constructed on the inclusion.

  In the basic structure of the structure of the present invention, the small-diameter pile is preferably a pile having a diameter of 100 mm to 300 mm.

  The foundation of the structure of the present invention is preferably such that the foundation is a direct foundation.

  In the foundation structure of the structure of the present invention, the small-diameter pile is a pile having a diameter of 100 mm, the foundation of the lower structure of the structure is a direct foundation, and a plurality of small-diameter piles with respect to the area of the bottom surface of the direct foundation The ratio of the total head area or the total cross-sectional area is preferably 6.1% or more.

  In the foundation structure of the structure of the present invention, the small-diameter pile is a pile having a diameter of 300 mm, the foundation of the lower structure of the structure is a direct foundation, and a plurality of small-diameter piles with respect to the area of the bottom surface of the direct foundation The ratio of the total head area or the total cross-sectional area is preferably 28.4% or more.

  In the basic structure of the structure of the present invention, it is preferable that the inclusion is a group of sandbags.

  The basic structure of the structure of the present invention is a structure in which a sandbag group is constructed by laying a sandbag body in which a plurality of sandbags are surrounded by a high-strength material at a predetermined width and a predetermined depth, and laminated at a predetermined height. It is preferable that

  In the basic structure of the structure of the present invention, the height of the sandbag group is preferably 100 mm to 1000 mm.

  The foundation method of the structure of the present invention is a foundation method for a structure constructed on soft ground, and includes a step of placing a plurality of small-diameter piles in the soft ground and an overhead of the plurality of small-diameter piles. A step of disposing an object, and a step of constructing a foundation of a substructure of the structure on the inclusion.

  In the foundation construction method for the structure of the present invention, the small-diameter pile is preferably a pile having a diameter of 100 mm to 300 mm.

  In the foundation construction method of the structure of the present invention, the foundation is preferably a direct foundation.

  In the foundation construction method of the structure of the present invention, the small-diameter pile is a pile having a diameter of 100 mm, the foundation of the lower structure of the structure is a direct foundation, and a plurality of small-diameter piles with respect to the area of the bottom surface of the direct foundation The ratio of the total head area or the total cross-sectional area is preferably 6.1% or more.

  The foundation construction method of the structure of the present invention is such that the small-diameter pile is a pile having a diameter of 300 mm, the foundation of the lower structure of the structure is a direct foundation, and a plurality of small-diameter piles with respect to the area of the bottom surface of the direct foundation The ratio of the total head area or the total cross-sectional area is preferably 28.4% or more.

  In the basic construction method of the structure according to the present invention, it is preferable that the inclusions are a group of sandbags.

  In the foundation construction method of the structure of the present invention, a group of sandbags lays a sandbag body in which a plurality of sandbags are surrounded by a high-strength material at a predetermined width and a predetermined depth, and is laminated at a predetermined height. It is preferable that

  In the foundation construction method of the structure of the present invention, the height of the sandbag group is preferably 100 mm to 1000 mm.

  INDUSTRIAL APPLICATION When constructing a structure on a soft ground, this invention can provide the basic structure of the structure which can construct | assemble the basic structure of the structure at low cost, and the basic construction method of a structure.

FIG. 1 is a schematic vertical cross-sectional view showing an embodiment of a foundation structure of a structure according to the present invention. FIG. 2 is a schematic front view showing a sandbag. FIG. 3 is a schematic plan view (schematic view taken in the direction of arrow III in FIG. 2) showing the sandbag. FIG. 4 is a schematic view showing a sandbag. (A) is a schematic plan view. (B) is a vertical cross-sectional schematic diagram (BB cross-sectional schematic diagram in (A)). FIG. 5 is an overall perspective explanatory view showing an analysis model when a study on the required number of small-diameter piles (the ratio of the total head area or total cross-sectional area of a plurality of small-diameter piles to the area of the bottom surface of the direct foundation) is performed. . FIG. 6 is a partial vertical cross-sectional explanatory view showing the analysis model of FIG. FIG. 7 is an explanatory diagram (an explanatory diagram viewed from the direction of the white arrow in FIGS. 5 and 6) showing the arrangement state of the small-diameter piles examined in the analysis models of FIGS. (A), (B), (C), (D) is explanatory drawing which shows the arrangement | positioning state of the small diameter pile whose diameter is 100 mm. (E), (F) is explanatory drawing which shows the arrangement | positioning state of the small diameter pile whose diameter is 300 mm. FIG. 8 is an explanatory diagram (graph) showing the results (relative relationship between the vertical load and the vertical displacement (subsidence amount)) in the analysis models of FIGS. It is. FIG. 9 is an explanatory view showing a test body of a 1/10 scale shaking table model experiment when the height (thickness) of the crust group of inclusions is examined. (A) shows the case where the height of the sandbag group is 0 mm and the case where the height is 60 mm (actual size 0.6 m). (B) shows the case where the height of the sandbag group is 60 mm (actual size 0.6 m) and 100 mm (actual size 1 m). FIG. 10 is an explanatory diagram (graph) showing the results of investigation (relative relationship between the maximum input acceleration and the maximum response acceleration at the pier top end position) in the test body of the shaking table model experiment of FIG.

  Hereinafter, an example of a basic structure of a structure according to the present invention and an embodiment (example) of a basic construction method of the structure will be described in detail with reference to the drawings.

(Description of configuration of basic structure of structure according to embodiment)
Hereinafter, the structure of the foundation structure of the structure based on this embodiment is demonstrated. As shown in FIG. 1, the basic structure of the structure according to this embodiment is applied when the structure 2 is constructed on the soft ground 1. The foundation structure of the structure according to this embodiment includes a plurality of small-diameter piles 3, inclusions 4, and a foundation 20 that is a lower structure of the structure 2.

  As shown in FIG. 1, the soft ground 1 has a soft layer 11 laminated on a high-quality support layer 10. For this reason, the soft ground 1 consists of the soft layer 11 whose surface layer ground on the ground surface GL side is soft. The layer thickness of the soft layer 11 is, for example, 10 m to 15 m. Here, the N value of the support layer 10 is, for example, about 30 or more. On the other hand, the N value of the soft layer 11 is, for example, about 5 or less. The N value is one index indicating the hardness of the ground. Note that the N value of the support layer 10 may not be about 30 or more, and the N value of the soft layer 11 may not be about 5 or less.

  In this example, the structure 2 is a bridge applied to a railway or a roadway. As shown in FIG. 1, the bridge structure 2 includes a lower structure foundation 20, an intermediate structure bridge pier 21, and an upper structure bridge girder 22. The foundation 20 is a direct foundation in this example. The foundation 20 of the structure 2 and the lower part (lower end part) of the bridge pier 21 are embedded in the soft layer 11 of the soft ground 1.

  In this example, the small-diameter pile 3 is a pile having a diameter of about 100 mm (about 0.1 m) to about 300 mm (about 0.3 m). The small-diameter pile 3 is a pile such as a steel pipe pile, a wooden pile, or a mortar pile. The structure, shape, material, etc. of the small diameter pile 3 are not particularly limited. The required number of small-diameter piles 3 are embedded in the soft layer 11 of the soft ground 1. The tip (lower end) of the small-diameter pile 3 does not reach the support layer 10 in this example. Note that the tip (lower end) of the small-diameter pile 3 may be driven into the support layer 10 according to the situation of the soft layer 11.

  As shown in FIG. 1, the inclusion 4 is disposed directly on the heads of the plurality of small-diameter piles 3. Thereby, the lower surface of the inclusion 4 is directly mounted on the pile head surface (upper end surface) of the plurality of small-diameter piles 3. On the inclusion 4, the foundation 20 of the substructure of the structure 2 is directly constructed. Thereby, the bottom surface of the foundation 20 is directly placed on the upper surface of the inclusion 4. Inclusions 4 are embedded in the soft layer 11 of the soft ground 1. The inclusion 4 transmits the load of the structure 2 to the plurality of small-diameter piles 3 equally or substantially uniformly.

  In this example, the inclusion 4 is a group of sandbags made of an inexpensive material. As shown in FIG. 1, the sandbag group of the inclusions 4 is constructed by laying sandbag bodies 40 at a predetermined width and a predetermined depth and at a predetermined height. In this example, the clay body 40 is laminated in three layers. The clay body 40 may be laminated in one layer, two layers, four layers or more. Moreover, the sandbag 40 is laminated | stacked alternately by the upper and lower sides right and left in this example. In addition, the clay body 40 may be laminated as it is without being alternately left and right.

  As shown in FIGS. 2 and 3, a plurality of sandbags 40, in this example, nine sandbags 41 are surrounded by a high-strength material 42. Nine sandbags 41 are arranged flatly in three vertical and horizontal directions. In this example, the plan view shape of the clay body 40, that is, the shape seen from above, is substantially square. The height (thickness) HA, depth DA, and width WA of the sandbag 40 are about 150 (about 0.15 m) to about 300 (about 0.3 m) mm, about 1000 mm (about 1 m), and about WA in this example. 1000 mm (about 1 m). Note that the shape of the sandbag 40 in plan view may be other than a substantially square shape, for example, a rectangular shape. In addition, the high-strength material 42 is a geotextile (strong synthetic fiber) in this example.

  As shown in FIGS. 4 (A) and 4 (B), the earthenware 41 is made by filling an earthen bag 44 in an earthen bag 43. In this example, the plan view shape of the sandbag 41 is substantially square. The plan view shape of the sandbag 41 may be a rectangular shape other than a substantially square shape, for example. In this example, the sandbag 41 is a normal sandbag. That is, the sandbag 43 is made of a synthetic resin sheet, and the filling material 44 is made of earth or sand. For this reason, the sandbag 41 is made of an inexpensive material. Thereby, the inclusion 4 which is a sandbag group is inexpensive.

(Description of the basic construction method of the structure according to the embodiment)
Hereinafter, the basic construction method of the structure according to this embodiment will be described. As shown in FIG. 1, the foundation construction method for a structure according to this embodiment includes the following first step, second step, and third step.

  First, a necessary number of small-diameter piles 3 having a diameter of about 100 mm (about 0.1 m) to about 300 mm (about 0.3 m) are placed and buried in the soft layer 11 of the soft ground 1 (first step). . In addition, since detailed description of the small diameter pile 3 was demonstrated in detail in the said foundation structure, it abbreviate | omits.

  Next, the inclusion 4 is directly disposed on the head of the plurality of small-diameter piles 3 (second step). In addition, the detailed description of the sandbag group which is the inclusion 4, the sandbag body 40 which constitutes this sandbag group, the sandbag 41 which constitutes this sandbag body 40 and the high-strength material 42 has been described in detail in the above-mentioned basic structure. So it is omitted.

  Then, the foundation 20 of the lower structure of the structure 2 is directly constructed on the inclusion 4 (third step). In addition, since detailed description of the structure 2 and the foundation 20 was demonstrated in detail in the said foundation structure, it abbreviate | omits.

(Explanation for studying the required number of small-diameter piles)
Hereinafter, the examination implementation regarding the required number of small-diameter piles (the ratio of the total head area or the total cross-sectional area of a plurality of small-diameter piles to the area of the bottom surface of the direct foundation) will be described with reference to FIGS. This examination is based on the following simulation conditions for the pile diameter and pile layout that have the same performance as sandy ground with N value of 30 which can be regarded as direct support ground in railway design standards. ,It was conducted.

  In addition, the head area of a small diameter pile is an area of the pile head surface (upper end surface) of a small diameter pile. The cross-sectional area of the small-diameter pile is the area of the surface obtained by cutting the small-diameter pile perpendicularly to the longitudinal axis of the small-diameter pile. Here, the small-diameter pile has a uniform or substantially uniform shape in the longitudinal direction. For this reason, the head area of the small-diameter pile and the cross-sectional area of the small-diameter pile are equivalent or almost equivalent.

  FIG. 5 and FIG. 6 are an overall perspective explanatory view and a partial vertical cross-sectional explanatory view showing an analysis model when a study on the required number of small-diameter piles is performed. FIG. 7 is an explanatory diagram showing an arrangement state of small-diameter piles examined in the analysis models of FIGS. 5 and 6. FIG. 8 is an explanatory diagram (graph) showing the result of studying the arrangement state of the small-diameter piles of FIG. 7 in the analysis models of FIGS. 5 and 6.

  In FIG. 5 and FIG. 6, 1 </ b> A is a simulated soft ground that simulates the soft ground 1. The width W, the depth D, and the layer thickness H of the simulated soft ground 1A are 20.8 m, 20.8 m, and 7 m. In the simulated soft ground 1A, as shown in FIG. 6, a simulated soft layer 11A is laminated on a simulated support layer 10A. In this example, the simulated support layer 10A is sandy soil having an N value of 30 and a layer thickness H2 of 2 m. On the other hand, the simulated soft layer (surface soil) 11A is a soft viscous ground having an N value of 5 and a layer thickness H1 of 5 m in this example.

  5 and 6, 3S and 3L are simulated small-diameter piles having a pile length H4 of 4.5 m and diameters of 100 mm and 300 mm. The examination was carried out under the conditions in which the plurality of simulated small-diameter piles 3S and 3L were placed (inserted) into the simulated soft layer 11A of the simulated soft ground 1A. Note that the tips (lower ends) of the simulated small-diameter piles 3S and 3L reach the simulated support layer 10A of the simulated soft ground 1A. That is, the tip surfaces (lower end surfaces) of the simulated small-diameter piles 3S and 3L are directly placed on the upper surface of the simulated support layer 10A of the simulated soft ground 1A. As a result, the height H3 from the pile head surface (upper end surface) of the simulated small-diameter piles 3S and 3L to the simulated ground surface GLA of the simulated soft ground layer 11A of the simulated soft ground 1A is 0.5 m.

  5 and 6, reference numeral 20 </ b> A denotes a loading plate that simulates the foundation (direct foundation) 20 of the structure 2. The height x width of the loading plate 20A is 1.8 m x 1.8 m. The plate thickness of the loading plate 20A is not particularly defined. The loading plate 20A is placed on the simulated ground surface GLA corresponding to the pile heads of the plurality of simulated small-diameter piles 3S, 3L. Then, the relationship between the vertical load and the vertical displacement (the amount of settlement) was examined by a static analysis in which the loading plate 20A was forcedly displaced by 100 mm vertically at a load of 1000 steps.

  The arrangement | positioning state of the several simulated small diameter pile 3S, 3L examined is shown in FIG. Here, in FIG. 7, the center of the middle simulated small-diameter piles 3S, 3L among the plurality of simulated small-diameter piles 3S, 3L coincides with or substantially coincides with the center of the loading plate 20A.

  FIG. 7A shows a case (A) in which simulated small-diameter piles 3S having a diameter of 100 mm are arranged with a total of nine vertical and horizontal three pieces in a center-to-center S1. FIG. 7B shows a case (B) in which simulated small-diameter piles 3S having a diameter of 100 mm are arranged with a total of 25 vertical and horizontal 5 pieces in a center-to-center S1. FIG. 7C shows a case (C) in which simulated small-diameter piles 3S having a diameter of 100 mm are arranged with a total of 49 vertical and horizontal 7 pieces in a center-to-center S1. FIG. 7D shows a case (D) in which simulated small-diameter piles 3S having a diameter of 100 mm are arranged with a total of nine vertical and horizontal three pieces in a center-to-center S2. FIG. 7E shows a case (E) in which simulated small-diameter piles 3L having a diameter of 300 mm are arranged with a total of nine vertical and horizontal three pieces in a center-to-center S2. FIG. 7 (F) shows a case (F) in which simulated small-diameter piles 3L having a diameter of 300 mm are arranged with a total of 13 centers S3 and S4.

  The center-to-center S1 is three times the diameter of the simulated small-diameter pile 3S and is 300 mm. The center-to-center S2 is 9 times the diameter of the simulated small-diameter pile 3S and 3 times the diameter of the simulated small-diameter pile 3L, and is 900 mm. The center-to-center S3 is 800 mm. The center-to-center S4 is 566 mm.

  In addition to the case of FIG. 7, the simulated small-diameter piles 3 </ b> S and 3 </ b> L are not arranged, the ground condition is a viscous soil with an N value of 5 and the ground condition is a sandy soil with an N value of 30 (H) was carried out. Case (H) is a case that is a target for ground improvement.

  As a result of the examination of each case, the relationship between the vertical load and the vertical displacement (settlement amount) of each case is as shown in FIG. In FIG. 8, the case (A) is indicated by a thin two-dot chain line. Case (B) is indicated by a dashed line. Case (C) is indicated by a thick two-dot chain line. Case (D) is indicated by a thin broken line. Case (E) is indicated by a dashed line. Case (F) is indicated by a thick broken line. Case (G) is indicated by a thin solid line. Case (H) is indicated by a thick solid line. In FIG. 8, the vertical axis indicates the vertical load, and the unit is [kN]. The horizontal axis indicates the vertical displacement (settlement amount), and the unit is [mm].

  Here, the area of the loading plate 20A is assumed to be A (square meter), the total head area of the simulated small-diameter piles 3S and 3L, or the total cross-sectional area a (square meter). The ratio of the total head area or the total cross-sectional area of the plurality of simulated small-diameter piles 3S and 3L to the area of the loading plate 20A is p = a / A. From FIG. 8, in the case (B) and the case (F), the relationship between the vertical load and the vertical displacement (subsidence amount) is substantially the same as that of sandy soil having an N value of 30. The ratio p of the total head area or total cross-sectional area of the plurality of simulated small-diameter piles 3S, 3L to the area of the loading plate 20A is p = 6.1% in case (B) and p = 28.4 in case (F). %. The ratio p of the total head area or total cross-sectional area of the plurality of simulated small-diameter piles 3S, 3L to the area of the loading plate 20A in this analysis model is the plurality of small-diameter piles relative to the area of the bottom surface of the actual foundation (direct foundation) 20 The total head area or the total cross-sectional area ratio of 3 coincides or almost coincides.

  As a result, in the case of the small-diameter pile 3 (3S) having a diameter of 100 mm in the actual foundation structure and the foundation method of the structure, a plurality of small diameters with respect to the area of the bottom surface of the foundation (direct foundation) 20 of the structure 2 The ratio of the total head area or the total cross-sectional area of the pile 3 (3S) is preferably 6.1% or more. Further, in the case of the small-diameter pile 3 (3L) having a diameter of 300 mm, the ratio of the total head area or the total cross-sectional area of the plurality of small-diameter piles 3 (3L) to the area of the bottom surface of the foundation (direct foundation) 20 of the structure 2 is 28.4% or more is preferable.

(Explanation of examination of height of inclusion 4)
Hereinafter, the implementation of the study on the height (thickness) of the crust group of the inclusions 4 will be described with reference to FIGS. 9 and 10. This examination was conducted by a 1/10 scale shaking table model experiment.

  FIG. 9 is an explanatory view showing a test body of a 1/10 scale shaking table model experiment when the height (thickness) of the crust group of inclusions is examined. FIG. 10 is an explanatory diagram (graph) showing the results of investigations on the test specimen of the shaking table model experiment of FIG.

  9A and 9B, 1B is a simulated soft ground simulating the soft ground 1. FIG. Reference numeral 10 </ b> B is a simulated support layer that simulates the support layer 10. 11B is a simulated soft layer imitating the soft layer 11. GLB is a simulated ground surface.

  9A and 9B, reference numeral 2B denotes a 1/10 scale pier model for the actual pier 21 and the foundation (direct foundation) 20 (see FIG. 1). The height of the pier model 2B, that is, the height H5 from the top surface (top surface) of the top end of the pier model 2B directly to the bottom surface of the foundation is 412 mm (0.412 m). The height H6 from the top surface (top surface) of the pier model 2B to the top surface of the foundation is 362 mm (0.362 m). As a result, the height from the top surface to the bottom surface of the direct foundation of the pier model 2B is 50 mm (0.05 m). Further, the width W2 and depth of the bottom surface of the direct foundation of the pier model 2B are 300 mm (0.3 m) and 300 mm (0.3 m).

  9A and 9B, reference numeral 4B denotes a 1/10 scale sandbag model with respect to a real sandbag body 40 (see FIG. 1). The width W3, the depth, and the height (thickness) of the one-stage crust model 4B are 390 mm (0.39 m), 390 mm (0.39 m), and 200 mm (0.2 m).

  9A and 9B, WB is a weight placed on the top end of the pier model 2B. The weight WB has a plate shape. The width, depth, height, and weight of one weight WB are 330 mm (0.33 m), 330 mm (0.33 m), 30 mm (0.03 m), and 25 kg. The three weights WB are placed in a state of being overlaid on the upper surface (top surface) of the top end of the pier model 2B. The height H7 and weight of the three weights WB are 90 mm (0.09 m) and 75 kg. The three weights WB simulate the bridge girder 22 of the structure 2. The three weights WB add a weight of 75 kg to the top end of the pier model 2B.

  In FIGS. 9A and 9B, the horizontal arrow on the lower side indicates the input location of acceleration. The height H8 from the upper surface of the direct foundation of the pier model 2B to the acceleration input location is 100 mm (0.1 m). Moreover, the horizontal arrow on the upper side indicates the response location of acceleration at the top end position of the pier model 2B. The height H9 from the acceleration input location to the acceleration response location is 250 mm (0.25 m).

  9A and 9B, C1 of the pier model 2B is a case in which the bottom surface of the direct foundation of the pier model 2B is directly installed on the upper surface of the simulated support layer 10B. C2 of the pier model 2B is a case in which a three-stage crust model 4B is installed downward from the upper surface of the simulated support layer 10B and the bottom surface of the direct foundation of the pier model 2B is installed directly on the upper surface of the three-stage crust model 4B. It is. C3 of the pier model 2B is a case in which the three-stage crust model 4B is installed in the simulated soft layer 11B, and the bottom surface of the direct foundation of the pier model 2B is installed directly on the upper surface of the three-stage crust model 4B. As for C4 of the pier model 2B, the five-stage crust model 4B is installed in the simulated soft layer 11B, the lower surface of the five-level crust model 4B is directly installed on the upper surface of the simulated support layer 10B, and the pier model 2B. This is a case in which the bottom surface of the direct foundation is directly installed on the upper surface of the five-stage crust model 4B.

  As a result of a shaking table test for each of the cases C1, C2, C3, and C4 under the conditions shown in FIGS. 9A and 9B, the maximum input acceleration and the pier sky of each case C1, C2, C3, and C4 are obtained. The relationship with the maximum response acceleration at the end position is as shown in FIG. In FIG. 10, the case C1 is indicated by a circle. Case C2 is indicated by a triangle. Case C3 is indicated by a square. Case C4 is indicated by X. In FIG. 10, the vertical axis indicates the maximum input acceleration (Response Acc), and the unit is [gal]. The horizontal axis indicates the maximum response acceleration (Input Acc) at the pier top end position, and the unit is [gal].

  As shown in FIG. 10, as an overall tendency from case C1 to case C4, although the response acceleration increases until the input acceleration is about 400 gal, the response acceleration shows a peak after that. As a result, as in the case C1 in which the pier model 2B is installed on the simulated support layer 10B, in the cases C2, C3, and C4 in which the pier model 2B is installed via the sandbag model 4B, the direct foundation of the pier model 2B is lifted. It has been confirmed that there is a seismic isolation effect due to.

  In addition, as for the value of the response acceleration indicating the peak, the value of the case C4 in which the five models of the sandbag model 4B are installed is slightly lower, but the other cases C2 and C3 are the same values as the case C1. ing. Thereby, it was confirmed that the bearing capacity performance of the pier model 2B provided with the sandbag model 4B is equivalent to the bearing capacity performance of the pier model 2B on the simulated support layer 10B.

  From the above, the sandbag group of inclusions 4 under the conditions that the height (thickness) of the sandbag group of the actual inclusions 4 is 0.6 m and 1 m has performance equivalent to that of the high-quality support layer 10. is there.

(Explanation of effect of embodiment)
The basic structure of the structure and the basic construction method of the structure according to this embodiment are configured as described above, and the effects thereof will be described below.

  Since the foundation structure of the structure and the foundation method of the structure according to this embodiment are such that a small-diameter pile 3 which is an inexpensive member is placed in the soft ground 1, the structure 2 is constructed on the soft ground 1. In this case, the basic structure of the structure 2 can be constructed at a low cost.

  In the foundation structure of the structure and the foundation construction method according to this embodiment, the inclusion 4 is disposed on the head of the plurality of small-diameter piles 3 and the substructure of the structure 2 is placed on the inclusion 4. The foundation 20 is constructed. As a result, the foundation structure of the structure and the foundation construction method of the structure according to this embodiment can transmit the load of the structure 2 to the plurality of small-diameter piles 3 through the inclusions 4 evenly or substantially equally. . Thereby, the foundation structure of the structure which concerns on this embodiment, and the foundation construction method of a structure can prevent the destruction of the ground just under the foundation 20 with the inclusion 4, and can obtain high earthquake resistance.

  Since the foundation structure of the structure according to this embodiment and the foundation construction method of the structure use a small-diameter pile 3 having a diameter of 100 mm to 300 mm, when constructing the structure 2 on the soft ground 1, The basic structure of the structure 2 can be constructed at a lower cost.

  Since the foundation structure of the structure and the foundation construction method according to this embodiment use (apply) the foundation directly as the foundation 20 of the lower structure of the structure 2, the improvement of the seismic performance of the structure 2 Can contribute. That is, the direct foundation 20 is lifted during an earthquake, and an effect similar to the seismic isolation characteristic in which the seismic action input to the bridge pier 21 of the intermediate structure of the structure 2 and the bridge girder 22 of the upper structure reaches its peak can be expected. . As a result, it is possible to contribute to the improvement of the earthquake resistance of the structure 2 that is a bridge applied to railways and roadways.

  In the foundation structure of the structure and the foundation construction method according to this embodiment, a small-diameter pile 3S having a diameter of 100 mm is used, and a direct foundation is used (applied) as the foundation 20 of the structure 2. The ratio of the total head area or the total cross-sectional area of the plurality of small-diameter piles 3S to the area of the bottom surface is 6.1% or more. Thereby, the foundation structure of the structure according to this embodiment and the foundation construction method of the structure have the same level of performance, that is, support of the soft layer 11 on which the plurality of small-diameter piles 3S are placed, as well as the high-quality support layer 10. Power is obtained.

  As a result, the foundation structure of the structure according to this embodiment and the foundation construction method of the structure require a sufficient supporting force of the supporting ground by placing a plurality of small-diameter piles 3S in the soft layer 11. The direct foundation can be used (applied) as the foundation 20 of the structure 2 that is a bridge applied to railways and roadways. That is, the foundation structure of the structure and the foundation construction method according to this embodiment provide the necessary bearing force when the foundation is directly used (applied) to the soft ground 1 composed of the soft layer 11 whose surface ground is soft. There is no need to excavate or improve the surface ground for the purpose of securing. Thereby, since the foundation structure of the structure and the foundation construction method of the structure according to this embodiment are to directly construct a foundation by placing a plurality of small-diameter piles 3S in the soft layer 11, the surface layer ground The cost can be reduced as compared with the case where the foundation is directly constructed by excavation or ground improvement. Moreover, the foundation structure of the structure and the foundation construction method of the structure according to this embodiment can directly construct the foundation at a low cost even when the soft layer 11 is thick.

  In the foundation structure of the structure and the foundation construction method according to this embodiment, a small-diameter pile 3L having a diameter of 300 mm is used, and a direct foundation is used (applied) as the foundation 20 of the structure 2. The ratio of the total head area or the total cross-sectional area of the plurality of small-diameter piles 3L to the area of the bottom surface is 28.4% or more. Thereby, the foundation structure of the structure and the foundation construction method of the structure according to this embodiment are configured so that the soft layer 11 in which a plurality of small-diameter piles 3L are driven is equivalent in performance to the high-quality support layer 10, that is, the support. Power is obtained.

  As a result, the basic structure of the structure and the foundation construction method of the structure according to this embodiment are as follows. When the direct foundation that sufficiently requires the supporting force of the supporting ground is constructed on the soft ground 1 as described above, the soft ground 1 By placing a plurality of small-diameter piles 3L in one soft layer 11, it can be constructed at a low cost.

  The basic structure of the structure and the basic construction method of the structure according to this embodiment can be reduced in cost because the inclusion 4 is a group of sandbags made of an inexpensive material.

  The foundation structure of the structure according to this embodiment and the foundation construction method of the structure are composed of nine clay 41 since the nine clay 41 are surrounded by a high-strength material 42 to form the clay 40. The sandbag 40 can be used as one unit, and it is easier to handle than when using one sandbag 41 as one unit. As a result, in the foundation structure of the structure and the foundation construction method according to this embodiment, the clay body 40 composed of nine sandbags 41 is laid at a predetermined width and a predetermined depth and laminated at a predetermined height. Thereby, the sandbag group of the inclusion 4 can be constructed efficiently.

  In the basic structure of the structure and the basic construction method of the structure according to this embodiment, nine clay 41 are surrounded by a high-strength material 42 to form a clay body 40. The clay body 40 has a predetermined width and a predetermined width. It is laid in the depth and stacked at a predetermined height to constitute a sandbag group of inclusions 4. As a result, the basic structure of the structure and the basic construction method of the structure according to this embodiment are laminated vertically by appropriately selecting the friction coefficient of the high-strength material 42 of the clay body 40 laminated vertically. The coefficient of friction between the sandbags 40 can be adjusted as appropriate, and the coefficient of friction between the sandbags 40 stacked one above the other can be partially changed, so that high earthquake resistance can be obtained.

  In the foundation structure of the structure and the foundation construction method according to this embodiment, since the height of the earthen body 40 is 200 mm, by laminating the earthen body 40 in three layers, four layers, and five layers, 600 mm , 800 mm and 1000 mm high, that is, the inclusion 4 having the same performance as the high-quality support layer 10 can be efficiently applied.

(Description of example other than embodiment)
In the above-described embodiment, the structure 2 is a bridge applied to a railway or a roadway. However, in the present invention, the structure may be a structure other than a bridge applied to a railway or a roadway, such as a building (building structure).

  Moreover, in the said embodiment, the height of the earthen body 40 shall be 200 mm, this earthen body 40 is laminated | stacked up and down with 3 layers, 4 layers, and 5 layers, and the group of earthen soil whose height is 600 mm, 800 mm, and 1000 mm. That is, an inclusion is provided. However, in the present invention, the height of the sandbag 40 may be other than 200 mm (for example, 50 mm, 100 mm, etc.).

  In this case, the height of the sandbag group, that is, the height of the inclusions is the height of the sandbag 40 × the number of the sandbags 40 stacked. In addition, the height of the sandbag group, that is, the inclusion is preferably, for example, 100 mm to 1000 mm.

  In addition, this invention is not limited by the said embodiment.

DESCRIPTION OF SYMBOLS 1 ... Soft ground 1A, 1B ... Simulated soft ground 10 ... Support layer 10A, 10B ... Simulated support layer 11 ... Soft layer 11A, 11B ... Simulated soft layer 2 ... Structure 2B ... Pier model 20 ... Foundation (direct foundation)
20A ... Loading plate 21 ... Pier 22 ... Bridge girder 3 ... Small-diameter pile 3S ... Simulated small-diameter pile 3L ... Simulated small-diameter pile 300mm in diameter 4 ... Inclusion (group of soil)
4B ... Soil models 40 ... Soil bodies 41 ... Soil pads 42 ... High strength materials (geotextile)
43 ... Soil bag 44 ... Filling material C1, C2, C3, C4 ... Case of pier model in 1/10 scale shaking table model test D ... Depth of simulated soft ground DA ... Depth of sandbag GL ... Ground Surface GLA, GLB ... Simulated ground surface H ... Simulated soft ground layer thickness H1 ... Simulated soft layer thickness H2 ... Simulated support layer thickness H3 ... Simulated small-diameter pile height from pile head surface to simulated ground surface H4 ... Pile length of simulated small-diameter pile H5 ... Height from the top of the pier model to the bottom of the foundation directly H6 ... Height from the top of the pier model to the top of the foundation directly H7 ... of three weights Height H8: Height from the top surface of the direct foundation of the pier model to the acceleration input location H9: Height from the acceleration input location to the acceleration response location HA ... Height of the sandbag (thickness)
S1, S2, S3, S4 ... Center-to-center W ... Width of simulated soft ground W2 ... Width of direct foundation of pier model W3 ... Width of sandbag model WA ... Width of sandbag body WB ... Weight

Claims (16)

The basic structure of the structure built on soft ground,
A plurality of small-diameter piles placed in soft ground,
Inclusions disposed above the plurality of small-diameter piles;
A foundation of a substructure of the structure constructed on the inclusion;
Comprising
The basic structure of the structure. The small-diameter pile is a pile having a diameter of 100 mm to 300 mm.
The basic structure of the structure according to claim 1. The foundation is a direct foundation,
The basic structure of the structure according to claim 1 or 2, characterized by the above-mentioned. The small-diameter pile is a pile having a diameter of 100 mm,
The foundation of the substructure of the structure is a direct foundation;
The ratio of the total head area or the total cross-sectional area of the plurality of small diameter piles to the area of the bottom surface of the direct foundation is 6.1% or more.
The basic structure of the structure according to any one of claims 1 to 3. The small-diameter pile is a pile having a diameter of 300 mm,
The foundation of the substructure of the structure is a direct foundation;
The ratio of the total head area or the total cross-sectional area of the plurality of small diameter piles to the area of the bottom surface of the direct foundation is 28.4% or more.
The basic structure of the structure according to any one of claims 1 to 3. The inclusion is a group of sandbags,
The basic structure of the structure according to any one of claims 1 to 5, wherein The group of sandbags is formed by laying a sandbag body in which a plurality of sandbags are surrounded by a high-strength material at a predetermined width and a predetermined depth, and laminated at a predetermined height.
The basic structure of the structure according to claim 6. The height of the group of sandbags is 100 mm to 1000 mm,
The basic structure of the structure according to claim 7. It is a basic construction method for structures built on soft ground,
A process of placing a plurality of small-diameter piles in soft ground;
Disposing inclusions above the plurality of small-diameter piles;
Building a foundation of the substructure of the structure on the inclusion;
Comprising
A basic construction method for structures. The small-diameter pile is a pile having a diameter of 100 mm to 300 mm.
The foundation construction method for a structure according to claim 9, wherein: The foundation is a direct foundation,
The foundation construction method for a structure according to claim 9 or 10, characterized in that: The small-diameter pile is a pile having a diameter of 100 mm,
The foundation of the substructure of the structure is a direct foundation;
The ratio of the total head area or the total cross-sectional area of the plurality of small diameter piles to the area of the bottom surface of the direct foundation is 6.1% or more.
The foundation construction method for a structure according to any one of claims 9 to 11, wherein The small-diameter pile is a pile having a diameter of 300 mm,
The foundation of the substructure of the structure is a direct foundation;
The ratio of the total head area or the total cross-sectional area of the plurality of small diameter piles to the area of the bottom surface of the direct foundation is 28.4% or more.
The foundation construction method for a structure according to any one of claims 9 to 11, wherein The inclusion is a group of sandbags,
The foundation construction method for a structure according to any one of claims 9 to 13. The group of sandbags is formed by laying a sandbag body in which a plurality of sandbags are surrounded by a high-strength material at a predetermined width and a predetermined depth, and laminated at a predetermined height.
The foundation construction method for a structure according to claim 14, wherein: The height of the group of sandbags is 100 mm to 1000 mm,
The foundation construction method for a structure according to claim 15, wherein:

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