JP7100434B2 - Foundation structure of structure and foundation construction method of structure - Google Patents

Description

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

The following Patent Documents 1 and 2 are the basic structures of structures constructed on soft ground. The basic structure of the structure of Patent Document 1 includes a plurality of support piles cast in a soft layer and a clay sac interposed between the bottom surface of the structure and the pile heads of the plurality of support piles. It is equipped with materials. The foundation structure of the structure of Patent Document 2 includes a plurality of piles buried in a loose saturated sandy layer and an earthen bed as a solid material filled between the foundations of the structure and the piles. be.

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

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

The problem to be solved by the present invention is to establish a basic structure of a structure and a basic construction method of the structure, which can inexpensively construct the basic structure of the structure when the structure is constructed on soft ground. To provide.

The foundation structure of the structure of the present invention is a foundation structure of a structure constructed on soft ground, and is arranged above a plurality of small-diameter piles cast in the soft ground and a plurality of small-diameter piles. The inclusions are provided and the foundation of the substructure of the structure built on the inclusions, and the inclusions store granular substances such as earth and sand in a high-strength synthetic resin bag. The bag-shaped pile head laying material is surrounded by a high-strength geotextile and integrated as a bag-shaped pile head laying body, and the integrated bag-shaped pile head laying body is laid without gaps in a predetermined width and a predetermined depth. It is characterized in that it is laminated at a predetermined height.

As the basic structure of the structure of the present invention, it is preferable that the small-diameter pile is a pile having a diameter of 100 mm to 300 mm.

In the basic structure of the structure of the present invention, it is preferable 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 substructure 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. It is preferable that the ratio of the total head area or the total cross-sectional area is 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 substructure 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. It is preferable that the ratio of the total head area or the total cross-sectional area is 28.4% or more.

In the basic structure of the structure of the present invention, the height of the laminated bag-shaped pile head laying material is preferably 100 mm to 1000 mm.

The foundation construction method of the structure of the present invention is a foundation construction method of a structure constructed on soft ground, and is a step of placing a plurality of small-diameter piles in the soft ground and overhead of the plurality of small-diameter piles. It includes a step of arranging inclusions and a step of constructing the foundation of the substructure of the structure on the inclusions. The stored bag-type pile head laying material is surrounded by a high-strength geotextile and integrated as a bag-type pile head laying body, and the integrated bag-type pile head laying body is laid without gaps in a predetermined width and a predetermined depth. , It is characterized in that it is laminated at a predetermined height.

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

In the foundation method for the structure of the present invention, it is preferable that the foundation is a direct foundation.

In the foundation method of the structure of the present invention, the small-diameter pile is a pile with a diameter of 100 mm, the foundation of the substructure 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 are used. It is preferable that the ratio of the total head area or the total cross-sectional area is 6.1% or more.

In the foundation method of the structure of the present invention, the small-diameter pile is a pile with a diameter of 300 mm, the foundation of the substructure 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 are used. It is preferable that the ratio of the total head area or the total cross-sectional area is 28.4% or more.

In the basic construction method of the structure of the present invention, it is preferable that the height of the laminated bag-shaped pile head laying material is 100 mm to 1000 mm.

INDUSTRIAL APPLICABILITY When constructing a structure on soft ground, the present invention can provide a foundation structure of a structure capable of constructing a foundation structure of the structure at low cost, and a foundation construction method of the structure.

FIG. 1 is a schematic vertical cross-sectional view showing an embodiment of a basic 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 showing the sandbag (schematic view taken along the line III in FIG. 2). FIG. 4 is a schematic view showing sandbags. (A) is a schematic plan view. (B) is a vertical cross-sectional schematic diagram (B-B line sectional schematic diagram in (A)). FIG. 5 is an overall perspective explanatory view showing an analysis model when 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) was examined. .. FIG. 6 is a partial vertical cross-sectional explanatory view showing the analysis model of FIG. FIG. 7 is an explanatory diagram showing the arrangement state of the small-diameter piles examined in the analysis models of FIGS. 5 and 6 (explanatory diagram seen from the direction of the white arrow in FIGS. 5 and 6). (A), (B), (C), and (D) are explanatory views showing an arrangement state of small diameter piles having a diameter of 100 mm. (E) and (F) are explanatory views showing the arrangement state of the small-diameter pile having a diameter of 300 mm. FIG. 8 is an explanatory diagram (graph) showing the results (relative relationship between the vertical load and the vertical displacement (sinking amount)) of examining the arrangement state of the small-diameter piles of FIG. 7 in the analysis models of FIGS. 5 and 6. Is. FIG. 9 is an explanatory diagram showing a test piece of a 1/10 scale shaking table model experiment when the height (thickness) of the sandbag group of inclusions was examined. (A) shows the case where the height of the sandbag group is 0 mm and the case where the height of the sandbag group 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 the case where the height is 100 mm (actual size 1 m). FIG. 10 is an explanatory diagram (graph) showing the results (relative relationship between the maximum input acceleration and the maximum response acceleration at the top position of the pier) of the test body of the shaking table model experiment of FIG.

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

(Explanation of the structure of the basic structure of the structure according to the embodiment)
Hereinafter, the configuration of the basic structure of the structure according to this embodiment will be described. As shown in FIG. 1, the basic structure of the structure according to this embodiment is constructed 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 which is a substructure 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. Therefore, the soft ground 1 is composed of a 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. The N value of the support layer 10 does not have to be about 30 or more, and the N value of the soft layer 11 does not have to be about 5 or less.

Structure 2 is, in this example, a bridge applied to a railroad or a roadway. As shown in FIG. 1, the structure 2 of the bridge has a foundation 20 of the substructure, a pier 21 of the intermediate structure, and a bridge girder 22 of the superstructure. Foundation 20 is, in this example, a direct foundation. The foundation 20 of the structure 2 and the lower portion (lower end portion) of the pier 21 are buried 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, for example, 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. A plurality of small-diameter piles 3 are buried in the soft layer 11 of the soft ground 1 by placing a required number of them. The tip (lower end) of the small-diameter pile 3 does not reach the support layer 10 in this example. Depending on the situation of the soft layer 11, the tip (lower end) of the small-diameter pile 3 may be driven into the support layer 10.

As shown in FIG. 1, the inclusions 4 are directly arranged above the heads of a plurality of small-diameter piles 3. As a result, the lower surface of the inclusions 4 is directly placed on the pile head surface (upper end surface) of the plurality of small-diameter piles 3. The foundation 20 of the substructure of the structure 2 is directly constructed on the inclusions 4. As a result, the bottom surface of the foundation 20 is directly placed on the upper surface of the inclusions 4. The inclusions 4 are buried in the soft layer 11 of the soft ground 1. The inclusions 4 transmit the load of the structure 2 evenly or substantially evenly to a plurality of small-diameter piles 3.

The inclusions 4 are, in this example, sandbags made of inexpensive materials. As shown in FIG. 1, the sandbag group of inclusions 4 is formed by laying sandbags 40 in a predetermined width and a predetermined depth and laminating them at a predetermined height. The sandbag 40 is laminated in three layers in this example. The sandbag 40 may be laminated with one layer, two layers, four layers or more. Further, in this example, the sandbags 40 are vertically stacked alternately on the left and right. The sandbags 40 may be laminated as they are without being staggered from side to side.

As shown in FIGS. 2 and 3, the sandbag 40 is formed by surrounding a plurality of sandbags 40, in this example, nine sandbags 41 with a high-strength material 42. The nine sandbags 41 are arranged flat by three vertically and horizontally. The plan view shape of the sandbag 40, that is, the shape seen from above, forms a substantially square shape in this example. The height (thickness) HA, depth DA, and width WA of the sandbag 40 are, in this example, about 150 (about 0.15 m) to about 300 (about 0.3 m) mm, about 1000 mm (about 1 m), and about. It is 1000 mm (about 1 m). The shape of the sandbag 40 in a plan view may be a rectangular shape, for example, other than a substantially square shape. Also, the high-strength material 42 is, in this example, geotextile (strong synthetic fiber).

As shown in FIGS. 4A and 4B, the sandbag 41 is formed by filling the sandbag 43 with the filling material 44. The plan view shape of the sandbag 41 is almost a square shape in this example. The shape of the sandbag 41 in a plan view may be, for example, a rectangular shape other than a substantially square shape. Further, as the sandbag 41, a normal sandbag is used in this example. That is, the sandbag 43 is made of a bag made of a synthetic resin sheet or the like, and the filling material 44 is made of earth and sand or the like. Therefore, the sandbag 41 is made of an inexpensive material. As a result, the inclusions 4, which are sandbags, are inexpensive.

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

First, a plurality 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). .. Since the detailed description of the small diameter pile 3 has been described in detail in the above-mentioned foundation structure, it will be omitted.

Next, the inclusions 4 are directly arranged above the heads of the plurality of small-diameter piles 3 (second step). A detailed description of the sandbags 4 as inclusions 4, the sandbags 40 constituting the sandbags, the sandbags 41 constituting the sandbags 40, and the high-strength material 42 has been described in detail in the above-mentioned basic structure. Therefore, it is omitted.

Then, the foundation 20 of the substructure of the structure 2 is directly constructed on the inclusions 4 (third step). The detailed description of the structure 2 and the foundation 20 will be omitted because they have been described in detail in the above-mentioned foundation structure.

(Explanation of examination and implementation of the required number of small-diameter piles)
Hereinafter, the study and implementation of 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. 5 to 8. In this study, under the following simulated conditions, the pile diameter and pile arrangement will be as good as the sandy ground with an N value of 30, which can be regarded as a direct foundation support ground in the railway design standard. ,It was conducted.

The head area of the small-diameter pile is the area of the pile head surface (upper end surface) of the 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 perpendicular 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. Therefore, the head area of the small-diameter pile and the cross-sectional area of the small-diameter pile are equal to or almost the same.

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

In FIGS. 5 and 6, 1A is a simulated soft ground simulating the soft ground 1. The width W, depth D, and 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, the simulated soft layer 11A is laminated on the simulated support layer 10A. In this example, the simulated support layer 10A is a 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 land with an N value of 5 and a layer thickness of H1 of 5 m in this example.

In FIGS. 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 study was carried out under the condition that the plurality of simulated small-diameter piles 3S and 3L were placed (inserted) in the simulated soft layer 11A of the simulated soft ground 1A. 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 surface (lower end surface) of the simulated small-diameter piles 3S and 3L is 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 layer 11A of the simulated soft ground 1A is 0.5 m.

In FIGS. 5 and 6, 20A is a loading plate simulating the foundation (direct foundation) 20 of the structure 2. The length 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 specified. The loading plate 20A is placed on a simulated ground surface GLA corresponding to a plurality of simulated small-diameter piles 3S and 3L pile heads. Then, the relationship between the vertical load and the vertical displacement (sinking amount) was examined by static analysis in which the loading plate 20A was forcibly displaced 100 mm vertically by loading in 1000 steps.

FIG. 7 shows the arrangement state of the plurality of simulated small-diameter piles 3S and 3L examined. Here, in FIG. 7, the centers of the simulated small-diameter piles 3S and 3L in the middle of the plurality of simulated small-diameter piles 3S and 3L coincide with or substantially coincide with the center of the loading plate 20A.

FIG. 7A is a case (A) in which simulated small-diameter piles 3S having a diameter of 100 mm are arranged with three vertical and horizontal piles, a total of nine piles, and an intercenter S1. FIG. 7B is a case (B) in which simulated small-diameter piles 3S having a diameter of 100 mm are arranged with 5 vertical and horizontal piles, 25 in total, and S1 between the centers. FIG. 7C is a case (C) in which simulated small-diameter piles 3S having a diameter of 100 mm are arranged with seven vertical and horizontal piles, a total of 49 piles, and an intercenter S1. FIG. 7 (D) is a case (D) in which simulated small-diameter piles 3S having a diameter of 100 mm are arranged with three vertical and horizontal piles, nine in total, and S2 between the centers. FIG. 7 (E) is a case (E) in which simulated small-diameter piles 3L having a diameter of 300 mm are arranged in a total of nine in each of three vertical and horizontal lines with an intercenter S2. FIG. 7 (F) is a case (F) in which simulated small-diameter piles 3L having a diameter of 300 mm are arranged with a total of 13 piles and 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 shown in FIG. 7, the case (G) in which the simulated small-diameter piles 3S and 3L are not arranged and the ground condition is cohesive soil with an N value of 5, and the case where the ground condition is sandy soil with an N value of 30 are used. (H) was carried out. Case (H) is a case that is the target of ground improvement.

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

Here, the area of the loading plate 20A is A (square meter), and the total head area or the total cross-sectional area a (square meter) of the simulated small-diameter piles 3S and 3L. The ratio of the total head area or the total cross-sectional area of a plurality of simulated small-diameter piles 3S and 3L to the area of the loading plate 20A is defined as p = a / A. From FIG. 8, in the case (B) and the case (F), the relationship between the vertical load and the vertical displacement (sinking 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 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 = 6.1% in the case (B) and p = 28.4 in the case (F). %. The ratio p 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 in this analysis model is the number of small-diameter piles to the area of the bottom surface of the actual foundation (direct foundation) 20. It is or almost the same as the ratio of the total head area or the total cross-sectional area of 3.

As a result, in the case of the small-diameter pile 3 (3S) having a diameter of 100 mm in the actual foundation structure of the structure and the foundation construction 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 and implementation of height of inclusions 4)
Hereinafter, the study and implementation of the height (thickness) of the sandbag group of the inclusions 4 will be described with reference to FIGS. 9 and 10. This study was carried out by a 1/10 scale shaking table model experiment.

FIG. 9 is an explanatory diagram showing a test piece of a 1/10 scale shaking table model experiment when the height (thickness) of the sandbag group of inclusions was examined. FIG. 10 is an explanatory diagram (graph) showing the results of the examination in the test body of the shaking table model experiment of FIG.

In FIGS. 9A and 9B, 1B is a simulated soft ground simulating the soft ground 1. Reference numeral 10B is a simulated support layer simulating the support layer 10. Reference numeral 11B is a simulated soft layer that imitates the soft layer 11. GLB is a simulated ground surface.

In FIGS. 9A and 9B, 2B is a 1/10 scale pier model with respect to the actual pier 21 and foundation (direct foundation) 20 (see FIG. 1). The height of the pier model 2B, that is, the height H5 from the upper surface (top surface) of the top end of the pier model 2B to the bottom surface of the foundation directly is 412 mm (0.412 m). The height H6 from the upper surface (top surface) of the top end of the pier model 2B to the upper surface of the foundation directly is 362 mm (0.362 m). As a result, the height from the upper 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 the 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).

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

In FIGS. 9A and 9B, the WB is a weight placed on the top 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 so as to be overlapped on the upper surface (top surface) of the top end of the pier model 2B. The height H7 of the three weights WB and the weight are 90 mm (0.09 m) and 75 kg. The three weights WB simulate the bridge girder 22 of the structure 2. These three weights WB add a weight of 75 kg to the top of the pier model 2B.

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

In FIGS. 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 the three-stage sandbag model 4B is installed below the upper surface of the simulated support layer 10B, and the bottom surface of the direct foundation of the pier model 2B is directly installed on the upper surface of the three-stage sandbag model 4B. Is. C3 of the pier model 2B is a case in which the three-stage sandbag model 4B is installed in the simulated soft layer 11B, and the bottom surface of the direct foundation of the pier model 2B is directly installed on the upper surface of the three-stage sandbag model 4B. In C4 of the pier model 2B, the five-stage sandbag model 4B is installed in the simulated soft layer 11B, the lower surface of the five-stage sandbag model 4B is directly installed on the upper surface of the simulated support layer 10B, and the pier model 2B is further installed. This is a case where the bottom surface of the direct foundation is directly installed on the upper surface of the 5-stage sandbag model 4B.

As a result of performing a shaking table test for each of the above cases C1, C2, C3 and C4 under the conditions of FIGS. 9A and 9B, the maximum input acceleration of each of the cases C1, C2, C3 and C4 and the pier ceiling The relationship with the maximum response acceleration at the end position is shown in FIG. In FIG. 10, 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. Further, 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 position of the top of the pier and the unit is [gal].

As shown in FIG. 10, the overall tendency from case C1 to case C4 is that the response acceleration increases up to about 400 gal, but the response acceleration has peaked after that. As a result, in the same way as 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 clay sac model 4B, the direct foundation of the pier model 2B rises. It was confirmed that there is a seismic isolation effect.

Regarding the value of the response acceleration indicating the peaking, the value of the case C4 in which the sandbag model 4B is installed in five stages is slightly lower, but the values of the other cases C2 and C3 are the same as those of the case C1. ing. From this, it was confirmed that the bearing capacity performance of the pier model 2B on which the sandbag model 4B was installed can be said to be 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 has the same performance as that of the high-quality support layer 10 under the conditions that the height (thickness) of the sandbag group of the actual inclusions 4 is 0.6 m and 1 m. be.

(Explanation of the effect of the embodiment)
The foundation structure of the structure and the foundation construction method of the structure according to this embodiment have the above-mentioned configurations, and the effects thereof will be described below.

Since the foundation structure of the structure and the foundation construction method of the structure according to this embodiment are to drive a small diameter pile 3 which is an inexpensive member into 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 low cost.

In the foundation structure of the structure and the foundation construction method of the structure according to this embodiment, inclusions 4 are arranged overhead of a plurality of small-diameter piles 3, and the substructure of the structure 2 is placed on the inclusions 4. It builds the foundation 20. As a result, in the foundation structure of the structure and the foundation construction method of the structure according to this embodiment, the load of the structure 2 can be uniformly or almost evenly transmitted to the plurality of small diameter piles 3 via the inclusions 4. .. As a result, in the foundation structure of the structure and the foundation construction method of the structure according to this embodiment, the inclusions 4 can prevent the ground immediately below the foundation 20 from being destroyed, and high seismic performance can be obtained.

Since the foundation structure of the structure and the foundation construction method of the structure according to this embodiment use a small-diameter pile 3 having a diameter of 100 mm to 300 mm, when the structure 2 is constructed on the soft ground 1, the structure 2 is used. 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 of the structure according to this embodiment directly use (apply) the foundation as the foundation 20 of the substructure of the structure 2, the seismic performance of the structure 2 is improved. Can contribute to. That is, the direct foundation 20 can be expected to have an effect similar to the seismic isolation characteristic in which the direct foundation 20 is lifted at the time of an earthquake and the seismic action input to the pier 21 of the intermediate structure of the structure 2 and the bridge girder 22 of the superstructure reaches a plateau. .. As a result, it can contribute to the improvement of seismic performance of the structure 2 which is a bridge applied to railways and roadways.

In the foundation structure of the structure and the foundation construction method of the structure 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, and the direct foundation 20 is used. It is assumed that 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 of the foundation is 6.1% or more. As a result, in the foundation structure of the structure and the foundation construction method of the structure according to this embodiment, the soft layer 11 in which a plurality of small-diameter piles 3S are placed is supported with the same performance as that of the high-quality support layer 10. Power is gained.

As a result, the foundation structure of the structure and the foundation construction method of the structure according to this embodiment require sufficient supporting force of the supporting ground by driving 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, which is a bridge applied to railways and roads. That is, the foundation structure of the structure and the foundation construction method of the structure according to this embodiment provide the required bearing capacity when the foundation is directly used (applied) to the soft ground 1 composed of the soft layer 11 whose surface layer ground is soft. There is no need to excavate or improve the surface ground for the purpose of securing. As a result, since the foundation structure of the structure and the foundation construction method of the structure according to this embodiment are to drive a plurality of small diameter piles 3S into the soft layer 11 to directly construct the foundation, the surface layer ground is constructed. The cost can be reduced compared to excavating or improving the ground to directly build the foundation. 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 layer thickness of the soft layer 11 is thick.

In the foundation structure of the structure and the foundation construction method of the structure 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, and the direct foundation 20 is used. It is assumed that 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 of the foundation is 28.4% or more. As a result, in the foundation structure of the structure and the foundation construction method of the structure according to this embodiment, the soft layer 11 in which a plurality of small-diameter piles 3L are placed is supported with the same performance as that of the high-quality support layer 10. Power is gained.

As a result, as described above, the foundation structure of the structure and the foundation construction method of the structure according to this embodiment are soft ground when a direct foundation that requires sufficient bearing capacity of the supporting ground is constructed on the soft ground 1. By driving a plurality of small-diameter piles 3L in the soft layer 11 of 1, it can be constructed at low cost.

In the foundation structure of the structure and the foundation construction method of the structure according to this embodiment, the cost can be reduced because the inclusion 4 is a sandbag group made of an inexpensive material.

The foundation structure of the structure and the foundation construction method of the structure according to this embodiment are composed of nine sandbags 41 because nine sandbags 41 are surrounded by a high-strength material 42 to form a sandbag 40. The sandbag 40 can be used as one unit, and it is easier to handle as compared with the case where one sandbag 41 is used as one unit. As a result, in the basic structure of the structure and the basic construction method of the structure according to this embodiment, the clay sill 40 composed of nine clay sac 41 is laid in a predetermined width and a predetermined depth and laminated at a predetermined height. As a result, the soil group of inclusions 4 can be efficiently constructed.

In the foundation structure of the structure and the foundation construction method of the structure according to this embodiment, nine clay sac 41 are surrounded by a high-strength material 42 to form a clay sac 40, and the clay sac 40 has a predetermined width and a predetermined width. It is laid in the depth and laminated at a predetermined height to form a soil group of inclusions 4. As a result, the foundation structure of the structure and the foundation 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 vertically laminated clay shell 40. The coefficient of friction between the soil containers 40 can be appropriately adjusted, and the friction coefficient between the vertically stacked soil containers 40 can be partially changed, so that high seismic performance can be obtained.

In the basic structure of the structure and the basic construction method of the structure according to this embodiment, since the height of the earthen body 40 is 200 mm, the earthen body 40 is laminated up and down with three layers, four layers and five layers to be 600 mm. , 800 mm, 1000 mm high soil sac group, that is, inclusions 4 having performance equivalent to that of a good quality support layer 10 can be efficiently constructed.

(Explanation of examples other than the embodiment)
In the above 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 road, for example, a building (building structure).

Further, in the above-described embodiment, the height of the sandbag 40 is set to 200 mm, and the sandbag 40 is vertically laminated with three layers, four layers, and five layers, and the sandbags have heights of 600 mm, 800 mm, and 1000 mm. That is, inclusions are provided. However, in the present invention, the height of the sandbag 40 may be a height other than 200 mm (for example, 50 mm, 100 mm, etc.).

In this case, the height of the sandbag group, that is, the inclusions is the height of the sandbag 40 × the number of layers of the sandbag 40. The height of the sandbag group, that is, the inclusions is preferably 100 mm to 1000 mm, for example.

The present invention is not limited to the above embodiment.

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 ... Bridge pier model 20 ... Foundation (direct foundation)
20A ... Loading plate 21 ... Pier 22 ... Bridge girder 3 ... Small diameter pile 3S ... Simulated small diameter pile with a diameter of 100 mm 3L ... Simulated small diameter pile with a diameter of 300 mm 4 ... Inclusion (sandbag group)
4B ... Sandbag model 40 ... Sandbag body 41 ... Sandbag 42 ... High-strength material (geotextile)
43 ... Soil bag 44 ... Filling material C1, C2, C3, C4 ... Case of pier model performed in 1/10 scale shaking table model experiment D ... Depth of simulated soft ground DA ... Depth of soil sac GL ... Ground Surface GLA, GLB ... Simulated ground surface H ... Simulated soft ground layer thickness H1 ... Simulated soft layer layer thickness H2 ... Simulated support layer 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 surface of the top of the pier model to the bottom of the foundation directly H6 ... Height from the top of the top of the pier model to the top of the foundation directly H7 ... Three weights Height H8 ... Height from the top surface of the direct foundation of the pier model to the acceleration input point H9 ... Height from the acceleration input point to the acceleration response point HA ... Height (thickness) of the earthen body
S1, S2, S3, S4 ... Between centers 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 (6)

It is the foundation structure of the structure constructed on soft ground.
Multiple small-diameter piles placed in soft ground,
The inclusions arranged above the heads of the plurality of small-diameter piles and
The foundation of the substructure of the structure built on the inclusions and
Equipped with
The inclusions are made by integrating a bag-type pile head laying material in which granular substances such as earth and sand are stored in a high-strength synthetic resin bag as a bag-type pile head laying body surrounded by a high-strength geotextile. Molded pile head laying body The bag type pile head laying body adjacent to a predetermined width and a predetermined depth is laid without gaps and laminated at a predetermined height.
The basic structure of the structure characterized by that. The stacked bag-shaped pile head laying bodies were laid so that the upper and lower bag-shaped pile head laying bodies were laid in a staggered manner.
The basic structure of the structure according to claim 1. The bag-shaped pile head laying body at the bottom layer has a one-to-one correspondence with the small- diameter pile.
The basic structure of the structure according to claim 1 or 2, characterized in that. It is a foundation method for structures constructed on soft ground.
The process of driving multiple small-diameter piles in soft ground,
The process of arranging inclusions above the heads of a plurality of the small-diameter piles,
The process of constructing the foundation of the substructure of the structure on the inclusions,
Equipped with
The inclusions are made by integrating a bag-type pile head laying material in which granular substances such as earth and sand are stored in a high-strength synthetic resin bag as a bag-type pile head laying body surrounded by a high-strength geotextile. The type pile head laying body The bag type pile head laying body adjacent to a predetermined width and a predetermined depth is laid without gaps and laminated at a predetermined height.
A foundation construction method for structures characterized by this. The stacked bag-shaped pile head laying bodies were laid so that the upper and lower bag-shaped pile head laying bodies were laid in a staggered manner.
The foundation construction method for the structure according to claim 4. The bag-shaped pile head laying body at the bottom layer has a one-to-one correspondence with the small- diameter pile.
The basic construction method for a structure according to claim 4 or 5, characterized in that.

Images