JP2005113612A - Method for construction management of rotary press-in steel pipe pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method effective for construction management of a rotary press-in steel pipe pile with an opened or closed end, which steel pipe pile has a blade having an excavating edge at its front end. <P>SOLUTION: According to the method for the construction management of the rotary press-in steel pipe pile 1, the work for pressing the steel pipe pile into the ground is controlled while a penetration resistance Rp is obtained by the equation: Rp=ä(cosθ-αsinθ)(Ht-Qwh)+(sinθ+αcosθ)Lb}/ä(1+γ)(sinθ+αcosθ)+α(Dp'/Dw')(cosθ-αsinθ)}. In the equation, Rp represents the penetration resistance which is received by a pile press-in part, θrepresents an angle of the blade to the face perpendicular to an axial center of the pile, α represents a coefficient of friction between the ground and a steel plate, Ht represents a value obtained by replacing the torque applied to the pile front end with a horizontal force on an action circular of the blade of the outer part of the pile, Lb represents an upper load applied to the pile front end, Dp' represents a diameter of the action circular of the pile press-in part, Dw' represents a diameter of the action circular of the blade of the outer part of the pile, Qwh represents a horizontal resistance of the ground which is received by the cutting edge, and γ represents a drag coefficient of the vertical cutting edge. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a blade having an outer diameter larger than the outer diameter of one or more piles fixed to straddle the outer surface of the lower end of the pile used for the foundation of a building structure or the like or the outer periphery of the pile and the inner periphery of the pile. It is related with the method of carrying out construction management of the press-fitting work into the ground of the open end or closed end rotary press-fit steel pipe pile provided with.

As a method of installing a pile as a foundation pile in the ground, a hammering method, a press-in method, and a rotary press-in method are implemented. In the batting method, a construction management method has been developed in which the pile construction is managed by assuming the pile support force from the impact penetration resistance at the time of construction when placing the pile in the ground. Further, in JP-A-5-163727, in the drill pile method belonging to the rotary press fitting method, a spiral rib is formed on the outer periphery of the pile tip, excavation teeth are attached to the lower end of the pile, and a small diameter with the lower end of the pile being an open end. There has been disclosed a method for managing the construction of pile driving by detecting the rotational torque of a driving device for rotationally penetrating a steel pipe pile into the ground during construction for rotationally penetrating the steel pipe pile into the ground.
JP-A-5-163727 JP 2001-193063 A

  However, recently used rotary press-fit steel pipe piles also have a larger pile diameter, an outer diameter larger than the outer diameter of the pile fixed to straddle the outer periphery and the inner periphery on the outer surface of the lower end of the pile or the lower end of the pile, Whereas it is an open or closed pile with blades with excavating blades at the tip, the rotary penetrating steel pipe pile introduced in the prior art forms a spiral rib on the outer periphery of the pile tip, and at the bottom of the pile Since the drilling teeth are attached and the bottom end of the pile is a small diameter, the mechanism of penetration of both into the ground is different, so the prior art construction management method is used for the construction management of rotary press-fit steel pipe piles as described above Was not applicable.

  The present invention has an outer diameter larger than the outer diameter of one or more piles fixed to the outer surface of the lower end of the steel pipe pile or fixed to the lower end of the steel pipe so as to straddle the outer periphery of the pile and the inner periphery of the pile. It is another object of the present invention to provide a construction management method effective for construction management of an open-end or closed-end rotary press-fit steel pipe pile provided with a blade having an excavating blade at the tip.

In order to solve the above-mentioned problem, the first invention of the present invention is a construction management method for rotary press-fit steel pipe piles that is fixed to the outer surface of the lower end of the pile or straddles the outer periphery of the pile and the inner periphery of the pile at the lower end of the pile. In the construction management method of an open-end or closed-end rotary press-fit steel pipe pile having an outer diameter larger than the outer diameter of one or more piles to be fixed and having a blade having a drilling blade at the tip, the following formula is used. The press-fitting operation of the steel pipe pile into the ground is controlled while obtaining the penetration resistance Rp.
Rp = {(cosθ−αsinθ) (Ht−Qwh) + (sinθ + αcosθ) Lb} /
{(1 + γ) (sin θ + α cos θ) + α (Dp ′ / Dw ′) (cos θ−α sin θ)}
Rp: Penetration resistance received by the pile press-in part ("Pile press-in part" is the area where the pile body is located at the lower end)
θ: Angle of blade made perpendicular to the axis of the pile center axis α: Coefficient of friction between ground and steel plate Ht: Value obtained by replacing the torque acting on the tip of the pile with the horizontal force on the working circle of the blade on the outer side of the pile Lb: Overhead load acting on the pile tip Dp ': Diameter of the working circle of the pile press-in part Dw': Diameter of the working circle of the blade on the outer side of the pile Qwh: Horizontal resistance of the ground received by the cutting edge γ: Resistance coefficient of the vertical cutting edge

The second aspect of the present invention is the construction management method for a rotary penetrating steel pipe pile according to the first aspect of the present invention, wherein the found area of the blade outside the pile is Aw, the found area of the pile press-fit portion is Ap, When the efficiency is e (0 <e ≦ 1) and the correction coefficient determined by the penetration amount of the rotary press-fit steel pipe pile is d, the tip support force Qu of the pile is obtained by the following formula.
Qu = (Rp / d) × {1 + e (Aw / Ap)}

The third aspect of the present invention is characterized in that, in the construction management method for a rotary penetrating steel pipe pile according to the first aspect of the present invention, the leading end pull-out strength Qup of the pile is determined by the following equation.
Qup ≧ Rp−Lb

  According to the configuration of the present invention, the pile diameter is larger than one or more pile outer diameters fixed to the outer surface of the lower end of the pile or fixed to the lower end of the pile so as to straddle the outer periphery of the pile and the inner periphery of the pile. In the construction process of rotary press-fit steel pipe piles that are open end piles or closed end piles with blades having a large outer diameter, each parameter is measured and recorded, and during construction, all measurable data is recorded on the ground, By inputting these measurement data into the proposed calculation formula entered in the proposed computer, the penetration resistance can be calculated easily and reliably. As a foundation pile, the quality and performance guarantee as designed is carried out with high accuracy. It is possible to provide a foundation pile having a high pile supporting capacity and a high pull-out strength at the pile tip.

  An embodiment of the present invention will be described with reference to the drawings. FIGS. 1A and 1B show an embodiment of a rotary press-fit steel pipe pile 1. The rotary press-fit steel pipe pile 1 is larger than the pile diameter on the outer surface of the lower end portion of the pile 2, a spiral blade 3 having an excavating blade 4 is installed at the tip, and the lower end surface 5 of the pile is open. 2 (a) and 2 (b) show another embodiment of the rotary press-fit steel pipe pile 1, in which a lower end of the pile 2 is cut out in a spiral shape, and a spiral shape having a drilling blade 6 at the tip thereof on the surface thereof. The blades 7 are installed so as to straddle the outer periphery and the inner periphery of the pile 2.

  1 and 2 of the embodiment shown in FIG. 1 and FIG. 2, the spiral blades 3 of the rotary press-fit steel pipe pile 1 and the spiral shape along the p-axis center line p-axis passing through the intermediate point in the width direction of the outer portion of the pile 2 of the pile 2 When the outer portions of the piles 2 of the blades 3 and 7 are unfolded on a straight line and placed in a vertical plane, the angle of the blade formed with the plane perpendicular to the center axis of the pile is represented as a straight line of length L with θ. FIG. 3 shows the relationship between the non-excavated surface on the p-axis line in the steady state and the spiral blades 3 and 7.

  FIG. 4 is an analysis of the force acting on the outer portion of the pile 2 of the spiral blades 3 and 7 and the pile press-fit portion at the lower end of the pile body 2.

  FIG. 5 is a vector diagram showing the mechanical state acting on the outer portions of the spiral blades 3 and 7 shown in FIG. 4 and the pile press-fit portion at the lower end of the pile 2.

The symbols in the present invention are as follows.
A: Found area when Dw is effective Aw: Found area of the blade outside the pile Ap: Found area of the pile press-in part ("Pile press-in part" refers to the lower end of the pile and Ap is the pile diameter at the lower end of the pile The area of a circle with a diameter of.
Dw ′: diameter of the working circle of the outer blade of the pile = {2 × (Dw ² −Do ² )} / {3 × (Dw ² −Do ² )}
Dp ′: diameter of the working circle of the pile press-fit portion = (2/3) Do
Do: Pile outer diameter Dw: Pile outer diameter Ht: Torque acting on the pile tip is replaced by horizontal force on the action circle of the blade outer portion = Tb / (Dw ′ / 2)
L: Blade length on working circle = πDw ′ / cos θ
Lt: Upper load acting on the pile head Lb: Upper load acting on the pile tip = aLt
Pw: Propulsive force Fw: Friction force acting on the blade upper surface = αPw
Fp: friction force acting on the pile press-fit portion = αRp
Rp: Penetration resistance received by the pile press-in part Qu: Pile tip support force Qup: Pile tip pull-out strength Qwh: Horizontal resistance of ground receiving the blade tip Qwv: Vertical tip resistance = γRp
S: penetration amount Tt: torque acting on pile head Tb: torque acting on pile lower end = aTt
α: Friction coefficient between ground and steel plate θ: Angle of blade made perpendicular to pile central axis φ: Ground friction angle γ: Vertical cutting edge resistance coefficient η: Penetration angle a: Pile tip of loading load Lt and torque Tt D: Correction factor determined by the amount of penetration when the pile is stopped e: Effective rate of blades outside the pile

From the vector diagram of FIG.
Fp = α (Dp ′ / Dw ′) Rp (1)
Fw = αPw (2)
The balance formula of this force is as follows.
Ht−Qwh = α (Dp ′ / Dw ′) Rp + Pwsinθ + αPwcosθ (3)
Rp−Lb + Qwh = Pwcos θ−αPwsin θ (4)
From equation (3),
Ht−Qwh−α (Dp ′ / Dw ′) Rp = Pw (sin θ + α cos θ) (5)
From equation (4)
Rp−Lb + Qwh = Pw (cos θ−α sin θ) (6)
If Pw is eliminated from the equations (5) and (6),
{Ht−Qwh−α (Dp ′ / Dw ′) Rp} (cos θ−αsin θ) =
(Rp−Lb + Qwh) (sin θ + α cos θ) (7)
When Rp is derived from the equation (7),
(Ht−Qwh) (cos θ−α sin θ) −α (Dp ′ / Dw ′) (cos θ−α sin θ) Rp = (sin θ + α cos θ) Rp− (Lb−γRp) (sin θ + αcos θ)
{(1 + γ) (sin θ + α cos θ) + α (Dp ′ / Dw ′) (cos θ−α sin θ)}
Rp = (Ht−Qwh) (cos θ−α sin θ) + Lb (sin θ + α cos θ)
Thus,
Rp = {(cosθ−αsinθ) (Ht−Qwh) + (sinθ + αcosθ) Lb} /
{(1 + γ) (sin θ + α cos θ) + α (Dp ′ / Dw ′) (cos θ−α sin θ)}
(8)
The following formula is obtained.

As shown in the above equation (8), the penetration resistance Rp is expressed by a coefficient α, a and a horizontal cutting edge resistance Qwh.
The blade inclination angle θ determined by the shape, the diameter Dp ′ of the working circle of the pile press-fit portion, the diameter Dw ′ of the working circle of the blade outside the pile, the coefficient γ, the torque Tt measured as a record item of construction management, and These parameters are calculated based on the load Lt. These parameters can be measured at any time for the open / closed piles on the ground at the stage before construction or during the construction process. .

The formula to calculate the tip bearing capacity Qu of the pile is
Qu = (Rp / d) × {1 + e (Aw / Ap)} (9)
However, as shown in this equation (9), the tip support force Qu of the pile is the coefficient α, a and the horizontal cutting edge resistance Qwh, the blade inclination angle θ determined by the shape, the working circle of the pile press-fit portion Diameter Dp ′, the outer area Aw of the pile outer blade, the outer area Ap of the pile press-fit portion, the diameter Dw ′ of the working circle of the outer blade of the pile, the coefficient γ, and the measurement items are measured. These parameters are calculated from the torque Tt and the loading load Lt, and these parameters can be measured at any time for the open and closed piles on the ground before construction or during construction. Can be performed with high accuracy. The correction factors e and d are given as a function of the penetration angle η, and the fluctuation range is 0 <d ≦ 1, 0 <e ≦ 1, and these values are used to calculate the tip of the pile from equation (9) The supporting force can be estimated.

The formula for calculating the pull-out strength Qup of the pile is
Qup ≧ Rp−Lb (10)
However, as shown in the equation (10), the tip pull-out strength Qup of the pile is the coefficient α, a and the horizontal blade edge resistance Qwh, the blade inclination angle θ determined by the shape, and the action of the pile press-fit portion. The diameter Dp ′ of the circle, the diameter Dw ′ of the working circle of the blade outside the pile, the coefficient γ, the torque Tt measured as the record items of the construction management, and the overload Lt are calculated. Since it is possible to measure open and closed piles at any time on the ground before construction or in the construction process, quality assurance of foundation piles can be performed with high accuracy.

(A) (b) One Embodiment of the rotary press-fit steel pipe pile of this invention is shown. (A) (b) Other embodiment of the rotary press-fit steel pipe pile of this invention is shown. The relationship figure of the non-excavation surface and blade | wing on the p-axis line of a steady state is shown. It is the figure which analyzed the force which acts on the pile press-in part of the outer side part of a pile of a blade | wing and the lower end of a pile. It is a vector diagram which shows the mechanical state which acts on the outer side part of a blade | wing and the pile press-fit part of the lower end of a pile.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation press-fit steel pipe pile 2 Pile 3 Blade 4 Excavation blade 5 Pile lower end surface 6 Excavation blade 7 Blade

Claims (3)

One or more piles with an outer diameter that is fixed to the outer surface of the lower end of the pile or is fixed to the lower end of the pile so as to straddle the outer periphery of the pile and the inner periphery of the pile. In the construction management method of an open-end or closed-end rotary press-fit steel pipe pile with blades having a rotation, it is characterized by controlling the press-fitting work of the steel pipe pile into the ground while obtaining the penetration resistance Rp obtained by the following formula Construction management method for press-fit piles.
Rp = {(cosθ−αsinθ) (Ht−Qwh) + (sinθ + αcosθ) Lb} /
{(1 + γ) (sin θ + α cos θ) + α (Dp ′ / Dw ′) (cos θ−α sin θ)}
Rp: Penetration resistance received by pile press-in part θ: Angle of blade made perpendicular to the center axis of pile α: Friction coefficient of ground and steel plate Ht: Torque acting on pile tip is on action circle of blade on outer part of pile Value replaced with horizontal force Lb: Overload applied to the pile tip Dp ': Diameter of the working circle of the pile press-fit portion Dw': Diameter of the working circle of the blade on the outer side of the pile Qwh: Horizontal resistance of the ground received by the cutting edge γ: Vertical cutting edge resistance coefficient The found area of the outer blade of the pile is Aw, the found area of the press-fitted portion of the pile is Ap, the effective rate of the outer blade of the pile is e (0 <e ≦ 1), and is determined by the amount of penetration of the rotary press-fit steel pipe pile The construction management method for a rotary press-fit steel pipe pile according to claim 1, wherein when the correction coefficient is d, the tip support force Qu of the pile is obtained by the following formula.
Qu = (Rp / d) × {1 + e (Aw / Ap)} The construction management method for a rotary press-fit steel pipe pile according to claim 1, wherein the pull-out strength Qup of the tip of the pile is determined by the following formula.
Qup ≧ Rp−Lb

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