JP4658684B2 - Calculation method of pull-out resistance of knotted piles using support pressure and shear force acting on inclined surface of expanded diameter part, calculation method of indentation resistance, design method of knotted pile, knotted pile - Google Patents

Description

  The present invention relates to a method for calculating a pulling resistance force of a knotted pile using a bearing pressure and a shearing force acting on the inclined surface of the enlarged diameter portion, a method for calculating an indentation resistance force, a method for designing a knotted pile, and a knot It relates to a pile.

  2. Description of the Related Art Conventionally, as a foundation pile that supports the load of a building, a knotted pile having a diameter-expanded portion at the middle or lower end in the longitudinal direction of the foundation pile has been widely used. According to the knotted pile, by providing the enlarged diameter portion, the transmission area of the load from the foundation pile to the ground is increased, so that the vertical support force and the pulling resistance force can be increased.

As a method for evaluating the pulling resistance force of the knotted pile, for example, in Patent Document 1, when the knotted pile is pulled out, the ground directly above the enlarged diameter portion has an effective height that is twice the diameter of the enlarged diameter portion. It is described that a value obtained by multiplying the peripheral area of the cylinder by the shear strength of the ground is designed as the drawing resistance force of the enlarged diameter portion, assuming that the cylinder is sheared into a cylindrical shape.
Japanese Patent Laid-Open No. 2002-21070

  However, in the above-mentioned method for calculating the pulling resistance force of the enlarged diameter portion, the effective height of the shear surface is uniquely set to twice the value of the enlarged diameter portion, so that the difference in diameter between the enlarged diameter portion and the shaft portion is small. In addition, when the difference in diameter between the enlarged diameter portion and the shaft portion is large, there is a problem that the calculated pulling resistance force becomes the same value even though the actual pulling resistance force is different.

  As described above, the method of calculating the pulling resistance force of the knotted pile described in Patent Document 1 cannot always obtain sufficient accuracy, so that the pulling resistance force is underestimated, overdesigned, and costly. In some cases, it becomes expensive, or the pulling resistance force is overestimated, and safety may be impaired.

  Then, an object of this invention is to enable it to calculate correctly the drawing-out resistance of a knot pile.

  The method for calculating the pulling resistance force of the knotted pile according to the present invention is a method of calculating the pulling resistance force of the knotted pile having a diameter-enlarged portion including an inclined surface inclined so that the diameter increases toward the lower side. The ultimate pull-out resistance force borne by the inclined surface is the sum of the vertical downward component of the ultimate shear resistance acting on the inclined surface and the vertical downward component of the ultimate support pressure acting on the inclined surface. It is characterized by calculating based on.

Further, the pulling resistance force of the knotted pile according to the present invention is a method of calculating the pulling resistance force of the knotted pile having a plurality of enlarged diameter portions including an inclined surface inclined so that the diameter increases toward the lower side. , N is the number of the enlarged portions, p _si [kN / m ² ] is the ultimate bearing pressure of the ground near the inclined surface of the i-th enlarged portion, and The ultimate shear resistance is f _si [kN / m ² ], the angle between the inclined surface of the i-th enlarged portion and the vertical direction is θ _i [rad], and the surface area of the inclined surface of the i-th enlarged portion is A _i [m ² ], the limit of the inclined surface of each enlarged-diameter portion obtained by the following equation (1), where β _i is the reduction factor of the resistance force of the ground on the inclined surface of the i-th enlarged-diameter portion The calculation is based on the sum T [kN] of the pulling resistance force.

In the calculation method of the pulling resistance force of the knot pile, when the average N value near the inclined surface of the i-th enlarged diameter portion embedded in the sandy soil is N and the internal friction angle is φ, the above formula ( as extreme Bearing force of _{p si} in 1), the following equation (2) to calculate the ultimate bearing capacity power level _{p si,} ultimate Bearing force of _{p si} calculated by equation (2) is 7500 [kN / ^{m 2} when it is less than, the ultimate bearing capacity force of the calculated, wherein in the case of extreme Bearing force of _{p si} is 7500 [kN / ^{m 2]} or more calculated by ^{(2), 7500 [kN /} m 2] used, the ultimate shear resistance of the above formula (1) as f _si, the ultimate shear resistance of f _si determined as a value that satisfies the following equation (3), ultimate shear resistance force of f _si that said determining 1000 it is less than [kN / ^{m 2]} was said determining electrode If ultimate shear resistance force of _{f si} that the shear resistance of the determined is 1000 [kN / ^{m 2]} or more, if it is 1000 [kN / ^{m 2]} or more, using a 1000 [kN / ^{m 2]} Also good.

Further, the calculation method of the pull-out resistance force of the enlarged diameter portion of the pile with the previous section, the average of the undrained shear strength near the inclined surface of the i-th enlarged diameter portion which is embedded in the cohesive soil was C _U In this case, as the value of the ultimate support pressure p _si in the expression (1), the ultimate support pressure degree p _si is obtained by the following expression (4), and the ultimate support pressure degree p _si calculated by the expression (4) is obtained. When it is less than 7500 [kN / m ² ], the calculated ultimate support pressure degree is when the ultimate support pressure degree p _si calculated by the equation (4) is 7500 [kN / m ² ] or more. 7500 [kN / m ² ], the ultimate shear resistance strength f _si in the above formula (1) is defined as f _si , and the ultimate shear resistance strength f _si is obtained by the following formula (5) and calculated by the formula (5). extreme shear resistance force of _{f si} is smaller than 1000 [kN / ^{m 2]} If you, if ultimate shear resistance of _{f si} calculated by Equation (5) an ultimate shear resistance of the calculated is 1000 [kN / ^{m 2]} or more, using a 1000 [kN / ^{m 2]} May be.
p _si = 6 C _U (4)
f _si = C _U (5)

  Further, the method of calculating the indentation resistance force of the knotted pile according to the present invention is a method of calculating the indentation resistance force of the knotted pile having a diameter-enlarged portion including an inclined surface that is inclined so that the diameter increases toward the upper side. Thus, the ultimate pulling resistance force borne by the inclined surface is the sum of the vertical upward component of the ultimate shear resistance acting on the inclined surface and the vertical upward component of the ultimate support pressure acting on the inclined surface. It calculates based on.

Further, the method of calculating the indentation resistance force of the knotted pile according to the present invention is a method of calculating the indentation resistance force of the knotted pile having a plurality of enlarged diameter portions including an inclined surface inclined so that the diameter increases toward the upper side. there are a number of said radially enlarged portion N, i-th ultimate Bearing force of the p _'si of the ground in the vicinity of the inclined surface of the enlarged diameter portion [kN / m 2], around the inclined surfaces of the ^i-th enlarged diameter portion F ′ _si [kN / m ² ] for the ultimate shear resistance strength of the ground, θ ′ _i [rad] for the angle between the inclined surface of the i-th enlarged portion and the vertical direction, and the i-th enlarged portion When the surface area of the inclined surface is A ′ _i [m ² ] and the reduction coefficient of the resistance force of the ground on the inclined surface of the i-th enlarged diameter portion is β ′ _i , each expansion obtained by the following equation (6) is used. The calculation is based on the sum T ′ [kN] of the ultimate indentation resistance force of the inclined surface of the diameter portion.

  In the method for calculating the pulling resistance, the knotted pile may be a knotted round pile or a knotted wall pile. In the method for calculating the indentation resistance, the knotted pile may be a knotted round pile or a knotted wall pile.

  According to the method for calculating the pulling resistance force and the pushing force calculation method for the above-mentioned knot pile, the force acting on the inclined surface of the enlarged diameter portion is divided into the shear resistance force parallel to the inclined surface and the bearing pressure perpendicular to the inclined surface. Therefore, the drawing resistance force and the pushing force of the enlarged diameter portion can be calculated more accurately.

  Furthermore, the present invention is a design method of a knot pile having a plurality of enlarged diameter portions including an inclined surface that is inclined so that the diameter increases toward the lower side, and by the above-described calculation method of the pulling resistance force of the knot pile. It shall include the design method of a pile with a knot characterized by designing so that the calculated pulling resistance may be more than a predetermined standard resistance.

  Further, the present invention is a design method of a knotted pile having a plurality of enlarged diameter portions including an inclined surface inclined so that the diameter increases toward the upper side, which is calculated by the above-described calculation method of the indentation resistance force of the knotted pile It shall include the design method of the pile with a knot characterized by designing so that the indentation resistance force made may become more than predetermined standard resistance force.

In the above-described method for designing a knotted pile, the knotted pile may be a knotted round pile or a knotted wall pile.
Moreover, this invention shall include the knot pile characterized by the above-mentioned design method of a knot pile.

  Since the pulling resistance force and pushing resistance force of the enlarged diameter portion of the knotted pile can be obtained more accurately, it is possible to prevent excessive design and underestimation of safety, and to reduce costs or improve safety.

  Hereinafter, an embodiment of a method for calculating the pulling resistance force of a knotted pile according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a round pile with a knot that is an object of calculation of pulling resistance. As shown in the figure, the round pile 1 with a knot has a columnar pile shaft portion 2, one or more knot portions 3, and an expanded bottom portion 4, and the upper portion thereof is an underground structure of a building (not shown). )It is connected to the. The node portion 3 and the expanded bottom portion 4 correspond to the expanded diameter portion. In addition, the enlarged diameter part is a part where the pile diameter is constant regardless of the height (referred to as a vertical part) 5 and a part where the diameter changes from the vertical part up and down (referred to as an inclined part). 6 and 7.

  2A is a front cross-sectional view of a knotted wall pile that is an object of calculation of the pulling resistance force, and FIG. 2B is a side cross-sectional view. As shown in the figure, a wall pile 11 having a wall shape is composed of a wall pile body 12, one or more node portions 3, and an expanded bottom portion 4 projecting from the wall pile body 2. The upper part is connected to the building's underground structure (not shown). As in the case of the round pile 1 with a knot, the node 3 and the expanded bottom 4 correspond to the enlarged diameter portion, and the enlarged diameter portion is a portion where the pile diameter is constant regardless of the height (vertical portion) 5) and portions (referred to as inclined portions) 6 and 7 whose diameters change from the vertical portion 5 upward and downward.

The calculation method of the pulling resistance force of the knotted pile according to this embodiment is to calculate the pulling resistance force on the upper side of the enlarged diameter portion with higher accuracy, as will be described below. A similar principle can be used. Therefore, hereinafter, a circular pile with a knot will be described as an example.
In addition, in the calculation method of the drawing-out resistance force of the enlarged diameter part of this embodiment, it calculates without distinguishing the expanded bottom part 4 of a pile lower end, and the node part 3 of a pile intermediate part.

The inventors assumed that the load acting on the knot pile 1 from the ground will be described below, and calculated the pulling resistance of the knot pile 1.
FIG. 3 is a schematic diagram showing the distribution of forces acting around the knotted pile 1 when the pulling force acts on the knotted pile 1 as assumed by the inventors. As shown in the figure, when a pulling force acts on the enlarged diameter portion 4, pressure acts on the node 3 and the inclined surface 8 on the upper side of the enlarged diameter portion 4 from the surrounding ground, and a supporting effect occurs, and the upper inclination A shear resistance acts in a direction parallel to the surface 8 and a supporting pressure acts in a direction perpendicular to the inclined surface 8. Further, a circumferential frictional force acts on the vertical portion 5 in a direction opposite to the pulling force due to the frictional force between the vertical portion 5 and the ground surrounding the knot pile 1. In the lower inclined portion 7, the pulling-out force acts in the direction in which the ground and the lower inclined surface 9 are separated from each other, so that the pull-out resistance force does not act.

As shown in FIG. 3, when the resistance force is distributed in the ground around the jointed pile 1, the pulling resistance force borne by the upper inclined portion 6 is the vertical component of the ultimate support pressure acting on the upper inclined surface 8. And the sum of the vertical direction component of the ultimate shear resistance acting on the upper inclined surface 8. Therefore, the number of the enlarged diameter parts is N, the ultimate bearing pressure degree of the ground near the inclined surface 8 on the upper side of the i-th enlarged diameter part is p _si [kN / m ² ], and the upper-side inclination of the i-th enlarged diameter part. The ultimate shear resistance of the ground near the surface 8 is f _si [kN / m ² ], the angle between the inclined surface 8 on the upper side of the i-th expanded portion and the vertical direction is θ _i [rad], the i-th When the surface area of the upper inclined surface 8 of the enlarged diameter portion is A _i [m ² ], the vertical component of the ultimate support pressure acting on the upper inclined surface 8 of the i-th enlarged diameter portion is p _si A _i sin θ _i. The vertical component of the ultimate shear resistance acting on the inclined surface 8 on the upper side of the i-th enlarged diameter portion is f _si A _i cos θ _i . Accordingly, the total pulling resistance T borne by the upper inclined portion 6 is expressed by the following equation (7).

In consideration of the influence of resistance reduction due to mutual interference between bearing pressure and shear resistance, the ground resistance reduction coefficient β _i was applied. The beta _i varies the inclination angle theta _i of the upper inclined plane 8, generally 0.75 or a value close (about 0.7 to 0.8) is suitable.

Here, in order to calculate the pulling resistance force borne by the upper inclined portion 6 using Expression (7), the values of the ultimate support pressure degree p _si and the ultimate shear resistance force degree f _si are required. A method for calculating the value of has not been established so far. Therefore, the inventor usually examines the N value of the land, the uniaxial compressive strength of the soil, and the like based on the ground investigation and the like based on the ground investigation. From the values such as N value and uniaxial compressive strength obtained by the investigation, the ultimate bearing pressure degree p _si and the ultimate shear resistance force degree f _si were calculated.

Specifically, as a method for calculating the ultimate bearing pressure degree p _si and the ultimate shear resistance degree f _si , the inventors set the N value shown in FIG. It proposes a drainage shear strength, the relationship between the ultimate Bearing force of p _si and ultimate shear resistance of f _si. In the figure, N is the average N value of the ground near the upper slope, _Cu is the average undrained shear strength of the ground near the upper slope, and φ is the internal friction angle of the ground near the upper slope. Is shown. The undrained shear strength is 1/2 of the uniaxial compressive strength of the soil. The internal friction angle can be estimated from the N value or the like.

As shown in the figure, intrinsic Bearing force of p _si in the case of sandy soil is 150 N, and 6C _u in the case of cohesive soil, the upper limit value in the sandy soil and cohesive soil is 7500 [kN / m ² ]. Also, the ultimate shear resistance of _{f si, p si} tan [phi in the case of sandy soil, and _{C u} in the case of cohesive soil, its upper limit is set to 1000 [kN / ^{m 2].}

Hereinafter, the value in each case will be described.
First, as shown in FIG. 4, the ultimate bearing pressure degree p _si in the ground of sandy soil is set to 150 N [kN / m ² ], and this value is determined as follows.
“Ministry of Land, Infrastructure, Transport and Tourism Notification No. 1113” describes the following equation (8) as the allowable stress level q _p of the ground at the tip of the foundation pile. Note that N in the formula is an average N value near the ground near the tip of the foundation pile.
q _p = 150 N / 3 (8)

Here, q _p represents the ultimate bearing strength that the ground can withstand when the indentation force acts on the foundation pile, and p _si in Equation (7) is the maximum against the compressive force of the ground when the pulling force acts on the foundation pile. Represents the degree of compressive stress. Although p _si and q _p are different in the state of the force acting on the pile, that is, pushing and pulling out the pile, this value can be applied because the ultimate support force of the ground does not depend on the direction of the force.

In Equation (8), 150N is the ultimate support pressure, and 150N is divided by 3, which is a so-called safety factor. In equation (8), without the safety factor is the ultimate bearing capacity power level p _si of sandy soil in this embodiment, it decided to use the 150N as its value.

Further, as shown in FIG. 4, for ultimate Bearing force of _{p si} in cohesive _soil, it is set to ^{6C u [kN / m 2]} , this value is determined as follows.
Japanese architecture "building foundation structure design guidelines 2001 revision" of the Society of Author (hereinafter, architecture called Society of design guidelines) as the ultimate tip support force of q _p of the pile in viscous soil, have been described following equation.
q _p = 6C _u (9)

Here, q _p indicates the ultimate bearing strength that the ground can withstand when the indentation force acts on the foundation pile, so that the formula ( As the p _si of 7), the extreme tip supporting force degree q _p of Equation (9) can be used.

As the maximum value of the ultimate Bearing force of _{p si,} it was a 7500 [kN / ^{m 2],} this value is determined as follows. The Ministry of Land, Infrastructure, Transport and Tourism notice states that the maximum N value is 60 (that is, the maximum value of the ultimate support pressure is 150 × 60 = 9000 [kN / m ² ]). 7500 [kN / m ² ]. Here, 7500 [kN / m ² ], which is a value on the safe side of both and widely used by those skilled in the art, is applied.

Next, although the ultimate shear resistance strength f _si in sandy soil was set to p _si tanφ, this value was determined as follows.
The Architectural Institute of Japan design guideline states that “when the supporting ground is sandy soil, tanφ with respect to the internal friction angle φ is the friction coefficient”. Here, the following equation is derived considering the ultimate shear resistance of f _si and the frictional force against the ultimate bearing capacity power p _si. However, since sandy soil is sheared under high pressure and sand particles are crushed, f _si should be set so as to satisfy Equation (10) in consideration of the effect of lowering the internal friction angle φ. It was.

Ultimate shear resistance force of f _si in cohesive soil was C _u, but this value was defined as follows.
When a pulling force is applied to the knot pile, the ground above the expanded portion receives a compressive force in the pulling force direction. At this time, since the surface of the knotted pile is very rough, the soil on the ground near the inclined surface is integrated with the knotted pile and resists the pulling force, causing shear slip in the ground near the boundary of the inclined surface. .

  For this reason, when the shear fracture has occurred inside the ground, the ultimate shear resistance is a value corresponding to the undrained shear strength of the ground. For this reason, the undrained shear strength of the ground can be used as the ultimate shear resistance strength in the present embodiment.

The maximum value of the ultimate shear resistance strength f _si was set to 1000 [kN / m ² ], and this value was determined as follows. In the first place, the undrained shear strength is used as the degree of shear resistance. However, according to this, if the undrained shear strength is large, any value can be used. The AIJ design guideline, if the shear plane between the viscous soil and piles peripheral surface has occurred is decided to use a 100 [kN / m ^2] as the maximum value of the undrained shear strength C _u. This value is the maximum value when shear failure occurs at the boundary between the ground and the pile body surface. In this embodiment, since the shear failure occurs in the ground, the maximum value is 100 [kN / m ² ]. Than can be said. Therefore, in order to ensure safety, an experimental value to be described later is taken into consideration and is set to 1000 [kN / m ² ].

By substituting the ultimate bearing pressure degree p _si and the ultimate shear resistance degree f _si obtained by the above method into the equation (7), the pulling resistance force borne by the upper inclined surface can be calculated. For this reason, the ultimate pull-out of the knot pile is calculated by summing the pull-out resistance force borne by the calculated inclined surface on the upper side of the enlarged diameter portion and the pull-out resistance force borne by the vertical portion of the enlarged diameter portion and the pile shaft portion The resistance force can be calculated.

For example, the Architectural Institute guideline states that the value of the limit circumferential frictional force is τ _s = 3.3 N (upper limit N = 50) for sandy soil and τ _s = C _u (upper limit C) for cohesive soil. _u = 100 [kN / m ² ]). Therefore, the average value of N pile circumferential surface ground in sandy soil to N, in the cohesive soil substitutes average undrained shear strength of pile circumferential surface ground to C _u, by applying the pile circumferential area, with sections The pulling resistance force of the shaft portion of the pile and the vertical portion of the enlarged diameter portion can be calculated. For this reason, the sum of the pullout resistance force of the shaft portion of the jointed pile and the vertical portion of the enlarged diameter portion and the sum of the pullout resistance force of the upper inclined surface is used as the pullout resistance force of the entire jointed pile. Thus, a more accurate pulling resistance can be calculated.

  In addition, although this embodiment demonstrated the case where extraction force acts on a knot pile, the case where pushing force acts on a knot pile can also be considered similarly. FIG. 5 shows the distribution of forces acting around the knotted pile 1 when the pushing force is applied to the knotted pile 1 when the pushing force is acting on the knotted pile, as assumed by the inventors. It is a schematic diagram. As shown in the figure, when a pushing force acts on the enlarged diameter portion 4, pressure acts on the inclined surface 7 on the lower side of the node portion 3 and the enlarged diameter portion 4 from the surrounding ground, and a supporting effect occurs. A shear resistance acts in a direction parallel to the inclined surface 7 and a supporting pressure acts in a direction perpendicular to the inclined surface 7. Further, a circumferential frictional force acts on the vertical portion 5 in a direction opposite to the pushing force due to a frictional force between the vertical portion 5 and the ground surrounding the knotted pile 1. It should be noted that the pulling force acts on the upper inclined portion 6 in a direction in which the ground and the lower inclined surface 9 are separated from each other, so that the pushing resistance force does not act.

  As can be seen by comparing FIG. 3 and FIG. 5, when a pulling force is applied to the knotted pile 1, it works in the opposite direction to the force acting on each part of the knotted pile 1. For this reason, the resistance force when the knotted pile is applied can also be derived by the same principle as when the pulling force is calculated.

Therefore, the number of the enlarged diameter parts is N, the ultimate bearing pressure degree of the ground near the inclined surface 7 below the i-th enlarged diameter part is p ′ _si [kN / m ² ], and the lower of the i-th enlarged diameter part. F ′ _si [kN / m ² ] is the ultimate shear resistance of the ground near the inclined surface 7 on the side, and θ ′ _i [is the angle between the inclined surface 7 on the lower side of the i-th expanded portion and the vertical direction. rad], where the surface area of the lower inclined surface 7 of the i-th enlarged portion is A ′ _i [m ² ] and the reduction factor is β ′ _i , the lower inclined surface 7 of the i-th enlarged portion is The vertical component of the acting ultimate support pressure is p ′ _si A ′ _i sin θ ′ _i , and the vertical component of the ultimate shear resistance acting on the lower inclined surface 7 of the i-th enlarged diameter portion is f ′ _si A ′ _i. cos θ ′ _i . Therefore, the total indentation resistance T ′ borne by the upper inclined portion 6 is expressed by the following equation (11).

_{Here, β 'i, f' si} , p 'si in equation (11) can be used β _{i, f si, p} si in the calculation method of the pull-out resistance force.

  According to the method of calculating the pulling resistance force of the knotted pile according to the present embodiment, the force acting on the inclined surface on the upper side of the enlarged diameter portion is changed to a shear resistance force parallel to the inclined surface and a supporting pressure perpendicular to the inclined surface. Since the calculation is performed separately, it is possible to calculate the pulling resistance force of the enlarged diameter portion more accurately. For this reason, the excessive design by the underestimation of the pulling resistance force and the decrease in safety due to the overestimation of the pulling resistance force can be reduced, and the cost can be reduced or the safety can be improved.

Further, the uniaxial compressive strength of the N value and the soil 4, by using the relationship between the ultimate shear resistance force of f _si, ultimate shear resistance of the N value and the undrained shear strength obtained by the conventional ground survey f _si can be determined. Thereby, it is possible to easily calculate the pulling resistance, and it is possible to reduce the cost and the construction period.

  In addition, when calculating the pullout resistance force, the bottom support of the knot pile did not need to consider the ground support force at the bottom, because the pullout force acts in the direction away from the ground when receiving the pullout force. When calculating the indentation force, the resistance force borne by the bottom of the knotted pile must also be considered. Moreover, although this embodiment demonstrated the case where the pulling-out resistance of a knotted round pile was calculated, the principle of the calculation method of the pulling-out resistance of this invention is applicable similarly to a knotted wall pile.

Here, since the validity of the calculation method of the drawing resistance force of this embodiment was examined using a full-sized knotted wall pile, it demonstrates below.
FIG. 6 is a diagram showing a knotted wall pile which is a test body used in this experiment, and the soil quality and N value of the ground in which the knotted wall pile is embedded. As shown in the figure, this experiment used a knotted wall pile provided with a diameter-expanded portion at the middle and lower end of the wall pile as a test body. The ground in which the experiment was conducted consists of a topsoil layer near the ground surface, a Dotan layer located under the topsoil layer, and a sand layer located under the Dotan layer. The Dotan Formation is clayey ground, and its N value is 50N or more. The knotted wall pile is designed so that the lower end reaches the Dotan Formation, and the node portion and the expanded bottom portion are located in the Dotan Formation.

  FIG. 7 shows a drawing resistance force (hereinafter referred to as “calculated value”) obtained by the above-described calculation method of the drawing resistance force in the node portion and the enlarged diameter portion, and a drawing resistance force (hereinafter referred to as “calculated value”) obtained by experiments. It is a table comparing experimental values). As shown in the table, the calculated value and the experimental value are very close, and the calculated value is lower than the experimental value. As described above, it has been confirmed that the above-described calculation method of the drawing resistance force can accurately evaluate the drawing resistance force of the enlarged diameter portion on the safety side.

It is sectional drawing of the round pile with a node used as the object of calculation of drawing resistance. (A) is front sectional drawing of the knotted wall pile used as the object of calculation of drawing-out resistance, (B) is side sectional drawing. It is the schematic diagram which showed the force which acts on a pile when drawing-out force acts on a knot pile. Is a table showing the N value or the undrained shear strength C _u and ultimate bearing capacity power level p _si and ultimate shear resistance of f _si and values relations. It is the schematic diagram which showed the force which acts on a pile when pushing force acts on a pile with a node. It is a figure which shows the knot pile designed using the design method using the calculation method of the drawing-out resistance of the enlarged diameter part in a knot pile. It is the table | surface which compared the calculated value and the experimental value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Round joint pile 2 Pile shaft part 3 Joint part 4 Expanded bottom part 5 Vertical part 6 Upper slope part 7 Lower slope part 8 Upper slope part 9 Lower slope part 11 Joint wall pile 12 Wall pile body

Claims (16)

It is a method of calculating the pulling resistance force of a pile with a knot having an enlarged diameter part including an inclined surface inclined so that the diameter increases toward the lower side,
The ultimate pulling resistance that the inclined surface bears,
A vertically downward component of the ultimate shear resistance acting on the inclined surface;
A method for calculating the pulling resistance force of a knotted pile, wherein the calculation is based on the sum of the ultimate support pressure acting on the inclined surface and the vertically downward component. It is a method for calculating the pulling resistance force of a knotted pile having a plurality of enlarged diameter parts including an inclined surface that is inclined so that its diameter increases toward the lower side,
N is the number of the expanded portions, p _si [kN / m ² ] is the ultimate bearing pressure of the ground near the inclined surface of the i-th expanded portion, and the ultimate limit of the ground is near the inclined surface of the i-th expanded portion. The shear resistance strength is f _si [kN / m ² ], the angle between the inclined surface of the i-th enlarged portion and the vertical direction is θ _i [rad], and the surface area of the inclined surface of the i-th enlarged portion is A _i [m ² ], when the reduction coefficient of the resistance force of the ground on the inclined surface of the i-th enlarged diameter portion is β _i ,
A calculation method of pulling resistance force of a knotted pile characterized by calculating based on a sum T [kN] of ultimate pulling resistance force of the inclined surface of each enlarged diameter portion obtained by the following formula (1).

The calculation method of the pulling resistance force of a knotted pile according to claim 2, wherein the reduction coefficient β _i is set to a value of 0.7 or more and 0.8 or less. A method for calculating the pullout resistance of the knotted pile according to claim 2 or 3,
When the average N value near the inclined surface of the i-th expanded portion embedded in sandy soil is N and the internal friction angle is φ,
As the ultimate bearing pressure degree p _si in the formula (1),
The ultimate support pressure degree p _si is calculated by the following equation (2):
When the ultimate support pressure p _si calculated by the equation (2) is less than 7500 [kN / m ² ], the calculated ultimate support pressure is
When the ultimate support pressure degree p _si calculated by the equation (2) is 7500 [kN / m ² ] or more, 7500 [kN / m ² ] is used,
_Assuming that the ultimate shear resistance strength in the equation (1) is f _si ,
The ultimate shear resistance strength f _si is determined as a value satisfying the following formula (3):
When the determined ultimate shear resistance strength f _si is less than 1000 [kN / m ² ], the determined ultimate shear resistance strength f _si is 1000 [kN / m ² ] or more. In this case, 1000 [kN / m ² ] is used.

It is the calculation method of the drawing-out resistance of the knot pile according to any one of claims 2 to 4,
When the average of the undrained shear strength near the inclined surface of the i-th enlarged diameter portion which is embedded in the cohesive soil was C _U,
As the value of the ultimate bearing pressure degree p _si in the formula (1),
Determined the ultimate bearing capacity power level p _si by the following equation (4),
If the ultimate support pressure p _si calculated by the equation (4) is less than 7500 [kN / m ² ], the calculated ultimate support pressure is
When the ultimate support pressure degree p _si calculated by the equation (4) is 7500 [kN / m ² ] or more, 7500 [kN / m ² ] is used,
The ultimate shear resistance strength f _si in the formula (1) is determined as f _si by the following formula (5),
When the ultimate shear resistance strength f _si calculated by the formula (5) is less than 1000 [kN / m ² ], the calculated ultimate shear resistance strength f is calculated by the formula (5). _{When si} is 1000 [kN / m ² ] or more, 1000 [kN / m ² ] is used.
p _si = 6 C _U (4)
f _si = C _U (5) It is a method for calculating the indentation resistance force of a knotted pile having an enlarged diameter portion including an inclined surface that is inclined so that the diameter increases toward the upper side,
The ultimate pulling resistance that the inclined surface bears,
A vertically upward component of the ultimate shear resistance acting on the inclined surface;
A calculation method for the indentation resistance force of a knotted pile, wherein the calculation is based on the sum of the ultimate support pressure acting on the inclined surface and the upward component in the vertical direction. It is a method of calculating the indentation resistance force of a pile with a knot having a plurality of enlarged diameter parts including an inclined surface inclined so that the diameter increases toward the upper side,
The number of the enlarged diameter portions is N, the ultimate bearing pressure degree of the ground near the inclined surface of the i-th enlarged diameter portion is p ′ _si [kN / m ² ], and the ground pressure near the inclined surface of the i-th enlarged diameter portion is The ultimate shear resistance is f ′ _si [kN / m ² ], the angle between the inclined surface of the i-th enlarged portion and the vertical direction is θ ′ _i [rad], and the inclined surface of the i-th enlarged portion is the surface area a _{'i [m} ^2], the reduction factor of the resistance force of the ground on the inclined surface of the ^i-th enlarged diameter portion beta' when a _i,
A calculation method of indentation resistance force of a knotted pile, wherein the calculation is based on a sum T ′ [kN] of ultimate indentation resistance force of the inclined surface of each enlarged diameter portion obtained by the following formula (6).

  The method for calculating the pulling resistance force of the knotted pile according to any one of claims 1 to 5, wherein the knotted pile is a rounded pile with a knot.   The method for calculating the indentation resistance force of a knotted pile according to claim 6 or 7, wherein the knotted pile is a rounded pile with a knot.   The method for calculating the pulling resistance force of a knotted pile according to any one of claims 1 to 5, wherein the knotted pile is a knotted wall pile.   The method for calculating the indentation resistance force of a knotted pile according to claim 6 or 7, wherein the knotted pile is a knotted wall pile.   It is a design method of the knot pile which has two or more enlarged diameter parts including the inclined surface inclined so that a diameter may become large in the lower side, Comprising: Pulling out the knot pile according to any one of claims 1 to 5 A design method for a knot pile characterized by designing the drawing resistance calculated by the calculation method of the resistance to be equal to or greater than a predetermined reference resistance.   It is a design method of the knot pile which has two or more enlarged diameter parts including the inclined surface inclined so that a diameter may become large toward the upper side, Comprising: It calculates with the calculation method of the indentation resistance force of the knot pile according to claim 6 or 7 A method for designing a pile with knots, wherein the designed indentation resistance is designed to be equal to or greater than a predetermined reference resistance.   The method for designing a knotted pile according to claim 12 or 13, wherein the knotted pile is a rounded pile with a knot.   The method for designing a knotted pile according to claim 12 or 13, wherein the knotted pile is a knotted wall pile. A knotted pile designed by the knotted pile design method according to any one of claims 12 to 15.

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