Pile foundation structure and method for designing pile foundation structure

Abstract

To provide a pile foundation structure capable of reducing negative friction acting on an external pile and an internal pile while suppressing construction cost and the number of processes, and a pile design method.SOLUTION: A pile 4 for supporting a building is buried in the ground of a construction area in a state of reaching a support layer below a consolidation settlement layer in the ground of the construction area where the building is constructed, soil on the upper layer side of the ground of the construction area is removed, and negative friction cut is applied to an external pile 6 which is a pile arranged along the outer peripheral part of the building. A negative friction cut is applied to an inside pile 7 positioned in a corner part E in a plan view among the inside piles 7 being the piles 4 positioned inside the building, and the negative friction cut is not applied to at least a part of the piles 4 of the inside pile 7 positioned other than the corner part E in the plan view.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a pile foundation structure for a building constructed on ground having a consolidated settlement layer where consolidation settlement is in progress, and a method for designing a pile foundation structure. [Background technology]

[0002] Patent Document 1 shows a pile foundation structure in which piles supporting a building constructed on ground with a consolidated settlement layer where consolidation settlement is in progress are buried in the ground of the construction area where the building will be constructed in a state where they reach a supporting layer below the consolidated settlement layer, and the upper layer of soil in the construction area ground is removed.

[0003] In Patent Document 1, it is discovered that when the soil of the ground in the construction area is excavated and removed from the upper layer, making the ground in the construction area less susceptible to consolidation settlement than the ground surrounding the construction area, the negative friction acting on the external piles located on the periphery of the building becomes greater than the negative friction acting on the internal piles located inside the building, and by focusing on this fact, negative friction countermeasures are taken only on the external piles where negative friction acts relatively strongly, thereby reducing construction costs and labor compared to taking negative friction countermeasures on all piles. Patent Document 1 also states that negative friction cuts can be applied to the surface to reduce friction as a negative friction countermeasure for the external piles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-146393 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the inventors of the present application have newly discovered that when the upper layer of soil in the ground of the construction area is removed to make the ground in the construction area less susceptible to consolidation settlement than the ground surrounding the construction area, applying negative friction cuts only to the external piles as described above increases the negative friction acting on the internal piles. In view of this situation, the main objective of the present invention is to provide a pile foundation structure and a design method for a pile foundation structure that can reduce negative friction acting on external piles and internal piles in a balanced manner while keeping construction costs and labor costs down. [Means for solving the problem]

[0006] A first characteristic configuration of the pile foundation structure of the present invention is a pile foundation structure of a building constructed on ground having a consolidated settlement layer in which consolidation settlement is progressing, The piles supporting the building are buried in the ground of the construction area in a state where they reach a supporting layer below the consolidated settlement layer in the ground of the construction area where the building is to be constructed, and the soil on the upper layer side of the ground of the construction area is removed; Negative friction cut is applied to the external piles, which are the piles lined up along the outer periphery of the building, Of the internal piles, which are the piles located inside the building, negative friction cuts are applied to those internal piles located at corners in plan view, while negative friction cuts are not applied to at least some of the internal piles located other than at corners in plan view.

[0007] According to this configuration, when the upper layer of soil in the ground of the construction area is removed to make the ground in the construction area less susceptible to consolidation settlement than the ground surrounding the construction area, negative friction cuts can be applied to the external piles, which have a relatively large negative friction acting on them, thereby reducing the negative friction acting on the external piles. They then discovered that when negative friction cuts are applied to the external piles in this way, the negative friction acting on the internal piles located at the corners in plan view becomes particularly large. By applying negative friction cuts to the internal piles located at the corners in plan view and not applying negative friction cuts to at least some of the internal piles located outside the corners in plan view, they were able to reduce the negative friction acting on the external and internal piles while keeping construction costs and labor hours down.

[0008] The second characteristic configuration of the pile foundation structure of the present invention is that, in addition to the internal piles located at corners in a plan view, negative friction cuts are applied to the internal piles adjacent to the internal piles located at those corners in the direction of the building perimeter.

[0009] It was discovered that, among the internal piles, the pile adjacent to the pile located at the corner in plan view in the direction of the building's periphery has the second largest negative friction acting on it after the internal pile located at the corner in plan view, and that when negative friction cut is applied to the internal pile located at that corner, the negative friction acting on it increases. According to this configuration, by also applying negative friction cut to the internal pile adjacent to the pile located at the corner in plan view in the direction of the building's periphery, it is possible to more effectively distribute the negative friction acting on the internal piles located inside the building, and to reduce the negative friction acting on a large number of piles in an even more balanced manner.

[0010] A third characteristic feature of the pile foundation structure of the present invention is that negative friction cuts are applied only to a partial region in the length direction of the pile.

[0011] According to this configuration, by limiting the longitudinal region of the pile to a partial region where negative friction cuts are applied, the difference in negative friction between piles with and without negative friction cuts can be reduced compared to when negative friction cuts are applied to the entire longitudinal region, and the negative friction acting on a large number of piles can be reduced in an even more balanced manner.

[0012] The characteristic configuration of the design method for pile foundation structures of the present invention is that all of the external piles and the internal piles that are located at corners in a plan view are set as piles to which negative friction cuts are applied, and if the negative friction acting on each of the piles of the building at that time does not become equal to or less than the set value, the internal pile adjacent to the selected internal pile on the side away from the periphery of the building is additionally set as a pile to which negative friction cuts are applied.

[0013] According to this configuration, it is possible to reduce the negative friction acting on the external piles and internal piles while keeping construction costs and labor costs down. [Brief explanation of the drawings]

[0014] [Figure 1] Side cross-sectional view showing the building's pile foundation structure [Figure 2] Plan view showing pile placement [Figure 3] A diagram showing the area where the 16 piles to be verified are located [Figure 4] Graph showing axial force acting on piles [Figure 5] FIG. 10 is a diagram showing the maximum long-term axial force value and the amount of change in axial force over time in Comparative Example 1. [Figure 6] FIG. 10 is a diagram showing the maximum long-term axial force value and the amount of change in axial force over time in Comparative Example 2. [Figure 7] FIG. 10 is a diagram showing the maximum long-term axial force value and the amount of change in axial force over time in Example 1. [Figure 8] FIG. 10 is a diagram showing the maximum long-term axial force value and the amount of change in axial force over time in Example 2. [Figure 9] FIG. 10 is a diagram showing the maximum long-term axial force value and the amount of change in axial force over time in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pile foundation structure and a method for designing a pile foundation structure according to the present invention will be described with reference to the drawings.

[0016] FIG. 1 shows a schematic configuration of a pile foundation structure for a building 1 constructed on ground 3 having a consolidated settlement layer 3B undergoing consolidation settlement. In this pile foundation structure, the upper soil of the ground 3 in construction area A where the building 1 is to be constructed has been removed. Piles 4 are also buried in the ground 3 in construction area A. The piles 4 supporting the building 1 are buried in the ground 3 in construction area A so as to reach a supporting layer 3A below the consolidated settlement layer 3B in the ground 3 in construction area A. The ground 3 in construction area A may be, for example, a recently reclaimed artificial island ground where consolidation settlement is in progress. To remove this ground 3, an amount of soil corresponding to the weight of the building is excavated from the ground 3 in construction area A. Note that in the example shown in FIG. 1, the consolidated settlement layer 3B is shown only between the supporting layer 3A and the building 1, but a consolidated settlement layer 3B may also exist below the supporting layer 3A.

[0017] When excavating and removing the ground 3 in the construction area A as described above, a volume of soil equal to the unloading load of the soil, which is set based on the excess pore water pressure of the consolidated subsidence layer 3B, may be defined as the volume of soil to be excavated, and the soil of this volume may be excavated and removed from the upper layer. Specifically, the volume of soil to be excavated may be a volume of soil with a load equal to or approximately equal to the excess pore water pressure in the clayey layer, which is the consolidated subsidence layer 3B, located above the support layer 3A, or a volume of soil with a load lower than the excess pore water pressure in the clayey layer. The layers above and below the clayey layer, which is the consolidated subsidence layer 3B, are sandy layers, and the support layer 3A is also a sandy layer. The volume of soil to be excavated and removed is calculated taking into account the submerged unit weight for soil below the groundwater level. The excess pore water pressure can be calculated using Terzaghi's one-dimensional consolidation equation, for example. By excavating and removing the soil with a load based on the value of excess pore water pressure calculated in this manner, the excess pore water pressure in the consolidation settlement layer 3B (clay layer) can be dissipated, thereby stopping or reducing the progression of subsequent consolidation settlement.

[0018] In this way, by excavating the ground 3 in construction area A and removing the volume of soil to be excavated, the weight of the ground 3 in construction area A is made smaller than the weight of the ground 3 outside construction area A, thereby reducing the absolute amount of subsidence of the ground 3 in construction area A.

[0019] The piles 4 are supported by the bearing layer 3A of the ground 3 and are therefore considered to be bearing piles. Above the bearing layer 3A in the ground 3 is a consolidated settlement layer 3B, and the piles 4 penetrate through the consolidated settlement layer 3B. Of the piles 4 supporting the building 1, those placed on the outer periphery of the ground 3 in the construction area A are considered external piles 6, and those placed closer to the interior of the construction area A than the external piles 6 are considered internal piles 7. In this embodiment, the external piles 6 are the piles 4 arranged closest to the outer periphery of the construction area A among the multiple piles 4 lined up along two directions that are orthogonal to each other in a plan view. The external piles 6 are arranged in an external region 9 within a set distance from the outer periphery of the construction area A, and the internal piles 7 are arranged in a region (internal region 10) that is more inward than the external region 9.

[0020] When the ground 3 in construction area A is excavated and the volume of soil to be excavated is removed, making the weight of the ground 3 in construction area A less than the weight of the ground 3 outside construction area A and reducing the absolute amount of settlement of the ground 3 in construction area A, it is known that the negative friction acting on the external pile 6 (negative frictional force pulling down on pile 4) becomes greater than the negative friction acting on the internal pile 7, but if negative friction cut is made only on the external pile 6, it is thought that the negative friction acting on the internal pile 7 will increase.

[0021] Therefore, in order to reduce construction costs and labor by limiting negative friction cuts to some of the piles 4, the inventors examined the extent of axial force acting due to negative friction on piles 4 with and without negative friction cuts for several examples (Examples 1 to 3 and Comparative Examples 1 and 2 described below) in which the number of piles 4 with negative friction cuts was different. Incidentally, the design axial force of piles 4 buried in ground 3 where consolidation settlement is expected is calculated as at least the support axial force for supporting building 1 plus the additional axial force due to negative friction. When friction cut is applied as a countermeasure against negative friction, the design axial force is calculated as the support axial force for supporting building 1 plus the additional axial force due to negative friction that acts in a state where friction cut is applied.

[0022] In this verification, as shown in Figures 1 and 2, the rectangular construction area A in plan view was divided into four equal parts, each including one corner, and the piles 4 in the quarter area including one corner (the piles 4 surrounded by dashed lines in Figure 1, and the piles 4 shown by solid lines surrounded by dashed lines in Figure 2) were used as the piles 4 to be verified, and the axial force acting on these piles 4 to be verified (16 piles 4) was determined using the SYS Cam Clay model, etc.

[0023] For the purpose of this study, as shown in Figure 3, the internal area 10 was divided into multiple areas, such as the range of set distance from the external area 9 in the building area A to the internal side being the first internal area 10A, the range of set distance from the first internal area 10A to the internal side being the second internal area 10B, and the range of set distance from the second internal area 10B to the internal side being the third internal area 10C, etc.

[0024] As shown in Figure 3, the stakes 4 to be verified are assigned numbers from 1 to 16, and in Figure 3 and Figures 5 to 8, the assigned numbers are written on the round symbols representing the stakes 4 to indicate the 1st to 16th stakes. Incidentally, the seven external piles 6 in the external area 9 are numbered the first, second, third, fourth, fifth, sixth, and seventh piles, starting from the bottom left of the drawing. The five internal piles 7 in the first internal area 10A are numbered the eighth, ninth, tenth, eleventh, and twelfth piles, starting from the bottom left of the drawing. The three internal piles 7 in the second internal area 10B are numbered the thirteenth, fourteenth, and fifteenth piles, starting from the bottom left of the drawing. The single internal pile 7 in the third internal area 10C is numbered the sixteenth pile.

[0025] Figure 4 is a graph showing the axial force acting on a single pile 4, with the vertical axis of the graph showing the depth (m) of the ground 3 and the horizontal axis of the graph showing the axial force (kN) acting on the pile 4. The graph shows the axial force acting on pile 4 at the time of construction of Building 1 (white circle), one year after construction of Building 1 (white triangle), three years after construction of Building 1 (white square), five years after construction of Building 1 (black circle), ten years after construction of Building 1 (black triangle), 30 years after construction of Building 1 (black square), and 48 years after construction of Building 1 (white diamond). The highest axial force from the time of construction of Building 1 until 48 years after construction is defined as the long-term maximum axial force C, and the highest increase in axial force from the time of construction of Building 1 until 48 years after construction is defined as the change in axial force over time M. In this verification, it is assumed that no consolidation settlement occurs in construction area A after the construction of building 1, and therefore the increase in the axial force change M over time is considered to correspond to the additional axial force due to negative friction.

[0026] Figures 5 to 9 are diagrams showing piles 4 (piles 4 surrounded by thick solid squares) on which negative friction cuts have been applied to the piles 4 (piles 1 to 16) being verified for Comparative Examples 1 and 2 and Examples 1 to 3, and tables showing the maximum long-term axial force C acting on each of the piles 4 (piles 1 to 16) being verified and the change in axial force M over time.

[0027] <Comparative Example 1> Figure 5 shows an example of a verification of a pile foundation structure when negative friction cuts are not applied to all piles 4, and shows a case where negative friction cuts are not applied to any of the piles 4 being verified (pile 1 to pile 16). In this way, when negative friction cuts are not applied to all of the piles 4 being verified, the long-term maximum axial force C and the change in axial force over time M of the external piles 6 (pile 1 to pile 7) located in the external area 9 become large values, and in particular, the long-term maximum axial force C and the change in axial force over time M of the external pile 6 (pile 4) located in the corner E of the external area 9 are the highest, with the long-term maximum axial force C being 19,400 kN and the change in axial force over time M being 13,800 kN.

[0028] <Comparative Example 2> Figure 6 shows an example of a pile foundation structure verification in which negative friction cuts are applied to all of the external piles 6 and negative friction cuts are not applied to all of the internal piles 7. Of the piles 4 being verified, negative friction cuts are applied to all of the external piles 6 (pile 1 to pile 7) and negative friction cuts are not applied to all of the internal piles 7 (pile 8 to pile 16). By applying negative friction cut to all of the outer piles 6 (piles 1 to 7) in this way, the change in axial force over time M for the outer piles 6 (piles 1 to 7) is reduced to 6,000 kN or less, and the long-term maximum axial force C is also reduced to 11,000 kN or less. However, among the inner piles 7 (piles 8 to 12) located in the first inner region 10A, the change in axial force over time M for the inner pile 7 (piles 10) located at the corner E of the first inner region 10A in particular increases to a very large value of 13,600 kN, and the long-term maximum axial force C also increases to a very large value of 18,400 kN.

[0029] Example 1 Figure 7 shows an example of a pile foundation structure where negative friction cuts have been applied to all of the external piles 6 and to the internal piles 7 located at corner E in plan view, and where negative friction cuts have not been applied to the internal piles 7 located other than at corner E in plan view. Of the piles 4 being verified, negative friction cuts have been applied to all of the external piles 6 (pile 1 to pile 7) and the internal pile 7 (pile 10) located at corner E of the first internal area 10A, and negative friction cuts have not been applied to the remaining internal piles 7 (pile 8, pile 9, pile 11 to pile 16). By applying negative friction cut in this manner, the change in axial force M over time for the external piles 6 (pile No. 1 to pile No. 7) and the internal pile 7 (pile No. 10) located at the corner E of the first internal area 10A is reduced to 6000 kN or less, and the long-term maximum axial force C is also reduced to 11000 kN or less. Furthermore, the highest change in axial force over time M among the piles 4 (pile 1 to pile 16) being verified has decreased to 11,800 kN for pile 11, and the highest long-term maximum axial force C among the piles 4 (pile 1 to pile 16) being verified has also decreased to 16,400 kN for pile 11.

[0030] However, although the highest axial force change over time M and the highest long-term maximum axial force C among the piles 4 (piles 1 to 16) under test have decreased, the axial force change over time M and the long-term maximum axial force C of a pair of interior piles 7 (piles 9 and 11) adjacent to the interior pile 7 (piles 10) located in the corner E of the first interior area 10A are relatively high, and the axial force change over time M of these interior piles 7 (piles 9 and 11) has increased to relatively large values ​​of 10,900 kN and 11,800 kN, and the long-term maximum axial force C has also increased to relatively large values ​​of 15,600 kN and 16,400 kN. Therefore, it is considered that there is room for improvement in these piles 4.

[0031] <Example 2> Figure 8 shows an example of a pile foundation structure in which negative friction cuts have been applied to all of the external piles 6, the internal piles 7 located at corner E in plan view, and the internal piles 7 adjacent to those internal piles 7 in the circumferential direction of the building 1, while no negative friction cuts have been applied to the remaining internal piles 7. Of the piles 4 being verified, negative friction cuts have been applied to all of the external piles 6 (pile 1 to pile 7), the internal pile 7 (pile 10) located at corner E of the first internal area 10A, and a pair of internal piles 7 (pile 9 and pile 11) adjacent to those internal piles 7 in the circumferential direction of the building 1, while no negative friction cuts have been applied to the remaining internal piles 7 (pile 8, and piles 12 to 16). By applying negative friction cut in this manner, the change in axial force M over time for all of the external piles 6 (pile No. 1 to pile No. 7), the internal pile 7 (pile No. 10) located at the corner E of the first internal area 10A, and a pair of internal piles 7 (pile Nos. 9 and 11) adjacent to this internal pile 7 in the circumferential direction of the building 1 has been reduced to 6000 kN or less, and the long-term maximum axial force C has also been reduced to 11000 kN or less. Furthermore, the highest change in axial force over time M among the piles 4 (pile 1 to pile 16) being verified has decreased to 10,700 kN for pile 12, and the highest long-term maximum axial force C among the piles 4 (pile 1 to pile 16) being verified has also decreased to 15,100 kN for pile 12.

[0032] Example 3 Figure 9 shows a verification example of a pile foundation structure in which negative friction cuts are applied to all of the external piles 6, the internal piles 7 located at corner E in plan view, and the internal piles 7 adjacent to those internal piles 7 in the circumferential direction of the building 1, and negative friction cuts are not applied to the remaining internal piles 7, narrowing the range in which negative friction cuts are applied to all piles 4. Compared to the case of verification example 2 shown in Figure 8, the range in which negative friction cuts are applied to all of the piles 4 being verified is narrower. Specifically, in the case of Figure 8 (as well as in the cases of Figures 6 and 7), negative friction cuts are applied to the piles 4 from the ground to the bottom end of the consolidated subsidence layer 3B, but in the case of Figure 9, negative friction cuts are applied to the piles 4 from the ground to the top end of the consolidated subsidence layer 3B. By narrowing the range in which negative friction cut is applied in this way, the reduction in the long-term maximum axial force C and the amount of change in axial force M over time in the pile 4 with negative friction cut is smaller, but the axial force borne by the pile 4 with negative friction cut increases accordingly, thereby making it possible to suppress the increase in the long-term maximum axial force C and the amount of change in axial force M over time in the pile 4 without negative friction cut. Although the area where negative friction cuts were applied was narrowed as described above, the highest change in axial force over time M among the piles 4 (pile 1 to pile 16) subject to verification was 9,600 kN for pile 2, which is reduced compared to Example 2 (pile 12 in Figure 8, 10,700 kN), and the highest long-term maximum axial force C among the piles 4 (pile 1 to pile 16) subject to verification was 15,100 kN for pile 2, which is equivalent to Example 2 (pile 12 in Figure 8, 15,100 kN). In this way, the difference in negative friction between piles 4 with and without negative friction cuts could be reduced, and the negative friction acting on a large number of piles 4 could be reduced in an even more balanced manner.

[0033] Next, a method for designing a pile foundation structure of a building 1 constructed on ground 3 having a consolidation settlement layer 3B in which consolidation settlement is in progress will be described. In the design method for the pile foundation structure of building 1, all of the exterior piles 6 and the interior piles 7 that are located at corners E in plan view are set as piles 4 to be subjected to negative friction cut, and if the negative friction acting on each of the piles 4 of building 1 at that time does not fall below a set value, an adjacent interior pile 7 on the side away from the selected interior pile 7 in the direction of the building periphery is additionally set as a pile 4 to be subjected to negative friction cut. The set value can be the value of the long-term maximum axial force C or the value of the axial force change over time M, and it can be considered to select piles 4 to be subjected to negative friction cut so that either or both of the long-term maximum axial force C and the axial force change over time M acting on each of the piles 4 of building 1 fall below the set value.

[0034] When the set values ​​are 12,000 kN for the change in axial force over time M and 17,000 kN for the long-term maximum axial force C, as shown in Example 1 in FIG. 7, all of the outer piles 6 and the inner piles 7 located at the corner E in plan view are selected as piles 4 to be subjected to negative friction cut. Specifically, all of the outer piles 6 (pile 1 to pile 7) located in the outer region 9 are selected, and the inner pile 7 (pile 10) located at the corner E of the first inner region 10A is selected. By selecting piles 4 to be subjected to negative friction cut in this manner, as shown in the table in FIG. 7, the change in axial force over time M of all of the piles 4 (pile 1 to pile 16) to be verified can be set to 12,000 kN or less, and the long-term maximum axial force C of all of the piles 4 (pile 1 to pile 16) to be verified can also be set to 17,000 kN or less.

[0035] Furthermore, if the set values ​​are set to 11,000 kN for the axial force change over time M and 16,000 kN for the long-term maximum axial force C, and if all of the external piles 6 (pile 1 to pile 7) and the internal pile 7 (pile 10) located at the corner E of the first internal area 10A are selected as piles 4 to be subjected to negative friction cut, as in Example 1 shown in Figure 7, and negative friction cut is performed only on these piles 4, there will be a pile 4 that exceeds the set value (pile 11: maximum axial force C is 16,400 kN, axial force change M is 11,800 kN), so the negative friction acting on each of the piles 4 of the building 1 will not be below the set value.

[0036] Therefore, the adjacent internal piles 7 on the side away from the selected internal pile 7 in the direction of the building periphery are added to the piles 4 to be subjected to negative friction cut. Specifically, as shown in Example 2 of FIG. 8, all of the external piles 6 (1st to 7th piles) located in the external region 9 are selected, and the internal pile 7 (10th pile) located in the corner E of the first internal region 10A is selected, and further, the piles 4 (9th and 11th piles) adjacent to the internal pile 7 in the direction of the building periphery are additionally selected. By selecting the piles 4 to be subjected to negative friction cut in this way, as shown in the table of FIG. 8, the axial force change amount M over time of all of the piles 4 (1st to 16th piles) to be verified can be made 11,000 kN or less, and the long-term maximum axial force C of all of the piles 4 (1st to 16th piles) to be verified can also be made 16,000 kN or less.

[0037] Furthermore, if the set value for the axial force change M over time is set to 10,000 kN, as shown in Example 2 of Figure 8, all of the external piles 6 (pile 1 to pile 7) located in the external area 9 are selected, and the internal pile 7 (pile 10) located at the corner E of the first internal area 10A is selected, and further, piles 4 (pile 9 and pile 11) adjacent to the internal pile 7 in the circumferential direction of the building are additionally selected, and negative friction cut is performed only on these piles 4.As a result, there are piles 4 that exceed the set value (pile 8: axial force change M of 10,200 kN, pile 12: axial force change M of 10,700 kN), and therefore the negative friction acting on each of the piles 4 of the building 1 will not be below the set value. Therefore, as shown in Example 3 in Figure 9, negative friction cut is applied to all piles 4 from the ground surface to the upper end of the consolidated subsidence layer 3B, narrowing the range in which negative friction cut is applied. In this way, by adjusting the range in which negative friction cut is applied to the piles 4 and achieving a balance between increasing and decreasing the axial force, it is possible to keep the axial force change M over time to 10,000 kN or less for all of the piles 4 (pile 1 to pile 16) being verified, as shown in the table in Figure 9.

[0038] [Another embodiment] Other embodiments of the present invention will be described below. Note that the configurations of the embodiments described below are not limited to being applied independently, but can also be applied in combination with the configurations of other embodiments.

[0039] (1) In the above embodiment, an example is shown in which an external pile 6 is selected and an internal pile 7 in the first internal area 10A is selected as the internal pile. However, if the negative friction acting on each of the piles 4 of the building 1 does not become less than the set value even after the internal pile 7 in the first internal area 10A is additionally selected, it is also possible to gradually select additional internal piles 7, such as selecting additional internal piles 7 in the second internal area 10B.

[0040] (2) In the above embodiment, the range in which negative friction cut is applied to the pile is exemplified as the range from the ground surface of the pile 4 to the lower end of the consolidated subsidence layer 3B, and the range from the ground surface of the pile 4 to the upper end of the consolidated subsidence layer 3B. However, the range in which negative friction cut is applied to the pile may be changed as appropriate, for example, by positioning the upper end of the range in which negative friction cut is applied to the pile between the ground surface and the consolidated subsidence layer, or by positioning the lower end of the range in which negative friction cut is applied to the pile between the upper and lower ends of the consolidated subsidence layer. [Explanation of symbols]

[0041] 1. Building 3 Ground 3A support layer 3B Consolidation subsidence layer 4 stakes 6 External piles 7 Internal pile A Construction Area E Corner

Claims

1. A pile foundation structure of a building constructed on ground having a consolidation settlement layer in which consolidation settlement is progressing, The piles supporting the building are buried in the ground of the construction area in a state where they reach a supporting layer below the consolidation settlement layer in the ground of the construction area where the building is to be constructed, The upper soil of the ground in the construction area has been removed; Negative friction cut is applied to the external piles, which are the piles lined up along the outer periphery of the building, A pile foundation structure in which, among the internal piles located inside the building, negative friction cuts are applied to the internal piles located at corners in plan view, and negative friction cuts are not applied to at least some of the internal piles located other than at corners in plan view.

2. The pile foundation structure described in claim 1, wherein, in addition to the internal piles located at corners in a plan view, negative friction cuts are applied to the internal piles adjacent to the internal piles located at the corners in the direction of the building periphery.

3. The pile foundation structure according to claim 1 or 2, wherein negative friction cuts are provided only in a partial area in the length direction of the pile.

4. The design method for a pile foundation structure according to claim 1 or 2, A method for designing a pile foundation structure in which all of the external piles and the internal piles that are located at corners in a plan view are set as piles to which negative friction cuts are applied, and if the negative friction acting on each of the piles of the building at that time does not become equal to or less than a set value, the internal pile adjacent to the selected internal pile on the side away from the periphery of the building is additionally set as a pile to which negative friction cuts are applied.

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