JP6574341B2 - Tip resistance force estimation system, press-fitting construction system, and tip resistance force estimation method - Google Patents

Description

  The present invention relates to a tip resistance force estimation system, a press-fitting construction system, and a tip resistance force degree estimation method for estimating tip resistance by pressure input measured during press-fitting of a pile.

Conventionally, a press-in method for statically penetrating a pile into the ground by press input has been mainly used in urban areas because of its advantages such as low vibration, low noise, and temporary installation unnecessary. In construction by such a press-fitting method, construction methods are generally planned based on the results of prior ground investigation. In the case of a plan based on this ground survey, there are many cases where the construction does not proceed as planned due to encountering ground conditions different from the survey results at the time of construction.
On the other hand, the pressure input can be measured during the press-fitting of the pile. The pressure input information includes tip resistance, peripheral surface resistance, and joint resistance. If this information can be separated by some method, it is thought that it will lead to more efficient construction and estimation of ground information. . In particular, it is considered effective to separate the tip resistance from the information.

As a method for extracting the tip resistance from the pressure input, for example, Non-Patent Document 1 describes a method of attaching a measuring instrument such as a load meter to the tip of the pile as in the cone penetration test (CPT).
Further, Patent Literature 1 describes a geological estimation method and a geological estimation system for estimating a tip resistance without attaching a measuring instrument to a pile by using an operation called “punching” during press-fitting.
Further, Patent Document 2 discloses a tip resistance estimation method and an estimation system for a rotary pile that estimate tip resistance from information on pressure input and torque during rotary press-fitting.

JP 2014-177826 A Japanese Patent Laying-Open No. 2015-017493

“Studies on soil classification and converted N values based on PPT data” Yukihiro Ishihara, Nanase Ogawa, Saburo Kinoshita, Kozo Tagaya, Geotechnical Society, Recent Sounding Technology and Ground Evaluation Symposium No. 143, collection of papers pp.85-90, 2009

However, the conventional methods for estimating the tip resistance of piles during press fitting have the following problems.
That is, providing a measuring instrument such as a load cell at the tip of the pile as in Non-Patent Document 1 adds to the cost of the measuring instrument itself and the cost of adding a pile tip structure for providing the measuring instrument to the pile. Cost.
In addition, using such a pile at the construction site requires that the pile equipped with the measuring instrument be pressed in and then pulled out, and that the measuring instrument and the measuring apparatus are connected by bringing the measuring instrument to the site. There is room for improvement in that point.

  Moreover, in the estimation method shown in Patent Document 1 using the operation of “punching” during press-fitting construction, it is not necessary to introduce a costly measuring instrument, but the estimated value becomes discrete in the depth direction. There is a problem that it is not suitable for detecting a thin layer or confirming a supporting force when the press-fitting is completed.

  Furthermore, the method using pressure input and torque during rotational press-fit as shown in Patent Document 2 can extract continuous information in the depth direction, but requires not only pressure input but also torque as an input condition. Therefore, there is a problem that it cannot be applied in the case of press-fitting without rotating.

  The present invention has been made in view of the above-mentioned problems, and the tip that can estimate the tip resistance during press-fitting continuously and accurately in the depth direction without causing additional construction cost and work time. It is an object of the present invention to provide a resistance force estimation system, a press-fitting construction system, and a tip resistance force estimation method.

  In order to achieve the above object, the tip resistance force estimation system according to the present invention calculates the peripheral resistance force degree at each depth at which the tip resistance force degree is obtained from the tip resistance force degree obtained in advance at each depth. From the circumferential surface resistance force calculation unit, the integration unit that calculates the circumferential resistance by integrating the circumferential resistance force level obtained by the circumferential surface resistance force calculation unit, and the obtained pile pressure input, A tip resistance force degree calculating unit that calculates a tip resistance by subtracting the obtained peripheral resistance and obtains a tip resistance force degree based on the tip resistance.

  Moreover, the press-fitting construction system according to the present invention is a press-fitting construction system in which a pile is press-fitted by a press-fitting device using the above-described tip resistance force estimation system, and the depth of the tip of the pile can be sequentially measured in the press-fitting device. Depth measuring means, pressure input measuring means capable of sequentially measuring the pressure input of the pile, and pipe soil length measuring means capable of sequentially measuring the pipe soil length of the pile are provided, and the depth measured by each means The tip resistance force degree is obtained by the peripheral resistance force degree calculation unit, the integrating unit, and the tip resistance force degree calculation unit based on the pressure input and the soil length in the pipe.

  Further, the tip resistance force degree estimation method according to the present invention includes a step of calculating a peripheral surface resistance force degree at each depth at which the tip resistance force degree is obtained from a tip resistance force degree obtained in advance at each depth; A step of calculating the peripheral resistance by adding the surface resistance force, and calculating the tip resistance by subtracting the obtained peripheral resistance from the pressure input of the obtained pile, and calculating the tip resistance force based on the tip resistance. It has the process to obtain | require. It is characterized by having.

In the present invention, the peripheral resistance force degree at each depth at which the tip resistance force degree is obtained is calculated by the peripheral resistance force degree calculation unit from the tip resistance force degree obtained in advance at each depth, and the peripheral resistance force degree is calculated. The tip resistance calculated by subtracting the calculated peripheral surface resistance based on the information on the pressure input of the pile obtained during the press-fitting construction by the tip resistance force degree calculation unit by calculating the peripheral resistance by the integration unit Based on the above, it is possible to obtain the tip resistance force degree. That is, by continuously executing measurements such as depth, pressure input, pipe length, etc. measured during press-fitting work, these measurement data are transferred to the peripheral resistance force calculation unit, integration unit, and tip resistance force calculation unit. By performing arithmetic processing according to the above procedure, the tip resistance during press-fitting can be continuously estimated in the depth direction.
In this case, a measuring instrument such as a load cell used in the prior art is unnecessary, and therefore the construction cost generated by using the measuring instrument without changing the shape and construction procedure of the pile used in normal press-fitting construction. In addition, the tip resistance can be easily and continuously known in the depth direction without increasing the construction period.

Thus, for example, by creating a database in advance by associating the tip resistance force level with the ground information such as soil classification and N value, it is obtained by the calculation process of the estimation method described above from the pressure input information obtained by the normal press-fitting construction. The N value and the soil classification can be easily estimated from the database based on the tip resistance strength.
Further, in the present invention, it is possible to obtain the tip resistance force continuous in the depth direction from the start of press-fitting to the completion of press-fitting, and the processing data can be accumulated. And the supporting force of the pile after press-fit completion can be estimated based on such data of the tip resistance force.

  Further, in the tip resistance force degree estimation system according to the present invention, the peripheral surface resistance force degree calculation unit corrects the tip resistance force degree obtained in advance at each depth based on a change according to a distance from a pile tip. Then, the circumferential resistance force degree may be calculated.

  In this case, in the peripheral resistance force degree calculation unit, for example, according to a general support force equation, a change corresponding to the distance from the pile tip is added to the tip resistance force degree obtained in advance at each depth. Correction can be performed to calculate the peripheral resistance force.

  Further, in the tip resistance force degree estimation system according to the present invention, the peripheral surface resistance force degree calculation unit is configured to obtain the tip resistance obtained in advance at each depth based on information indicating a closed state of a pile tip obtained in advance. The peripheral resistance force degree may be calculated by correcting the force degree.

  In the present invention, in the peripheral surface resistance force calculation unit, for example, according to a general support force equation, correction is performed in consideration of information indicating the closed state of the pile tip with respect to the tip resistance force obtained in advance at each depth. It is possible to calculate the degree of circumferential resistance.

  According to the tip resistance force estimation system, the press-fitting construction system, and the tip resistance force estimation method of the present invention, the tip resistance during press-fitting is continuously and accurately performed in the depth direction without generating additional construction cost and work time. Can be estimated well. Therefore, the estimated tip resistance can be used for estimating geological information and bearing capacity.

It is a figure which shows an example of the outline | summary of the press-fit construction using the tip resistance force degree estimation system by embodiment of this invention. It is the figure which showed the outline | summary regarding the force of the axial direction in a pile. It is a block diagram which shows the structure of a tip resistance force degree estimation system. It is a graph which shows an example of the relationship between the estimated value of tip resistance, the measured value of tip resistance measured with the load cell at the tip of the pile, and the depth.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a tip resistance force estimation system, a press-fitting construction system, and a tip resistance force estimation method according to embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the tip resistance force estimation system 1 according to the present embodiment uses a known press-fitting device 2 that press-fits the pile 4 into the ground by repeatedly raising and lowering the chuck that holds the pile 4. There is a system in which a computer 3 is connected to the press-fitting device 2 in a communicable manner by radio or wire, and the tip resistance force degree is calculated by the computer 3 that has acquired information from the press-fitting device 2. And the ground information of the press-fitting construction location of the pile 4 is estimated based on the tip resistance force degree calculated by the tip resistance force degree estimation system 1.
That is, in this Embodiment, the press-fit construction system which press-fits the pile 4 with the press-fit apparatus 2 using the tip resistance force estimation system 1 is comprised.

  As shown in FIG. 2, the press-fitting device 2 press-fits the ground while applying a press input F to the pile 4. Information input to the computer 3 from the press-fitting device 2 when the pile 4 is press-fitted is the depth z of the tip of the pile 4, the pressure input F, and the soil length h in the pipe, and the depth measurement means 21 and the pressure input measurement means 22, respectively. , And the soil length measuring means 23 in the pipe.

As shown in FIG. 3, the depth measuring means 21 that measures the depth z of the tip of the pile 4 is configured by providing the press-fitting device 2 with a stroke sensor that detects a press-fitting stroke by the press-fitting device 2.
The pressure input measuring means 22 for measuring the pressure input F is configured to measure a pressure input value for press-fitting the pile 4 into the ground by using a hydraulic sensor that detects the hydraulic pressure of the hydraulic drive unit of the press-fitting device 2.
As the pipe length measuring means 23 for measuring the pipe length h, for example, a commonly used wire-type stroke sensor, or an encoder is used to measure the wire feed amount when the weight is lowered in the pile 4 and reaches the pipe soil. It is configured by providing a measuring device or the like in the press-fitting device 2.
Then, the depth z, the pressure input F, and the pipe soil length h are measured in the press-fitting device 2, and these measured values z, F, and h are input to the computer 3 from the press-fitting device 2.

The computer 3 includes a CPU that executes various arithmetic processes described later, a storage unit that stores various control programs executed by the CPU, data, and the like.
The above-mentioned measured values (depth z, pressure input F, and pipe length h) input to the computer 3 are time series data continuously measured during the press-fitting process of the pile 4 and can be correlated with each other. It has become. In the computer 3, time series data of the depth z, the pressure input F, and the pipe soil length h is stored in the attached storage device.

As shown in FIG. 3, the tip resistance force estimation system 1 is configured so that the tip resistance force degree obtained in advance at each depth shallower than the depth (intermediate depths described later) is the circumference at each depth shallower than the depth. Obtained at the depth, a peripheral resistance force calculation unit 11 that calculates the surface resistance force degree, an integration unit 12 that calculates the surface resistance by integrating the peripheral resistance force values obtained by the peripheral resistance force calculation unit 11, and The depth resistance is calculated by subtracting the peripheral resistance obtained by the integrating unit 12 from the pressure input F to calculate the tip resistance at the depth, and dividing this by the tip cross-sectional area taking into account the closed state of the pile tip at the depth. A tip resistance force calculation unit 13 for obtaining a tip resistance force degree.
Here, the peripheral surface resistance force calculation part 11 calculates a peripheral surface resistance force degree based on the change according to the distance from a pile tip according to the general support force type | formula which is mentioned later.

  The CPU of the computer 3 includes the above-described peripheral surface resistance force calculation unit 11, integration unit 12, and tip resistance force calculation unit 13, and is based on time series data of the depth z, the pressure input F, and the pipe soil length h. It functions as a calculation means for calculating the tip resistance force.

Next, a tip resistance force degree estimation method for estimating tip resistance using the tip resistance force degree estimation system 1, that is, a calculation procedure in the CPU of the computer 3 will be specifically described.
First, in the peripheral surface resistance force calculation unit 11, when a pile tip at a depth shallower than the depth (the immediately preceding depth) reaches the depth, calculation is performed at each depth (each intermediate depth) up to the immediately preceding depth. Based on the difference between the depth and the intermediate depth, the peripheral resistance force degree at each intermediate depth is calculated from the tip resistance force degree (peripheral resistance force calculation step). “Each intermediate depth” corresponds to the “each depth” described above.
At this time, the tip resistance and circumferential resistance when the pile tip depth is zero (ground surface) are known amounts (usually both are zero).

Next, the circumferential resistance at the immediately preceding depth is calculated by integrating the circumferential resistance strength at each intermediate depth calculated by the above-described circumferential resistance force calculating step at each intermediate depth up to the immediately preceding depth by the integrating unit 12. (Accumulation step). Specifically, in the integration process, the peripheral resistance force at a depth shallower than the depth is estimated from the tip resistance force estimated at the entire depth shallower than the depth, based on the support force equation described later. To do.
Here, since the circumferential resistance in the minute depth section is approximately zero, the circumferential resistance at the depth is calculated assuming that the circumferential resistance at the immediately preceding depth is equal to the circumferential resistance at the depth.

  Next, the tip resistance force calculation unit 13 subtracts the peripheral resistance at the depth calculated in the integration step based on the information on the pressure input F of the pile 4 measured during the press-fitting work, thereby reducing the tip resistance at the depth. Is calculated. Further, the tip resistance force at the depth is calculated and obtained by dividing the tip resistance at the depth calculated by the tip cross-sectional area at the depth in consideration of the occlusion state (tip resistance force calculation step). That is, since the peripheral resistance in the minute depth section can be ignored, the peripheral resistance estimated by the accumulating unit 12 is regarded as the peripheral resistance at the depth, and this is subtracted from the pressure input at the depth, thereby leading the tip at the depth. Estimate resistance.

In the calculation process described above, the press-fitting device 2 sequentially measures the depth z as the press-in of the pile 4 progresses, and sequentially measures the press-fit F as the depth z increases.
When the time series data of the depth z, the pressure input F, and the pipe soil length h accumulated in the computer 3 is updated during the press-fitting of the pile 4, the tip resistance resistance at the tip position where the pile 4 arrives newly is updated. The degree of force may be calculated, and most of the data string of the tip resistance value corresponding to the change in the depth z during press-fitting may be calculated. During the press-fitting, at least the depth z, the press input F, and the time series data of the pipe soil length h are recorded, and at any time during the press-fitting of the pile 4 or after the press-fitting work is finished, the computer 3 The tip resistance force is calculated.

The computer 3 stores the calculation result of the tip resistance force degree in the attached storage device. The calculation result of the tip resistance force degree is in the form of a data string of tip resistance values corresponding to changes in the depth z plotted as shown in FIG. 4, for example, and includes the tip resistance value at the final depth of the pile 4. FIG. 4 shows data obtained by verifying the validity of the estimation method of the present embodiment by comparing the estimation result of the tip resistance and the measured value of the tip resistance.
In addition, the computer 3 displays the calculation result on the display device 31 (see FIG. 1).

Next, an example of a function (supporting force equation) for calculating the tip resistance force q _b (z) will be described.
Formula (1) formulates a method for estimating the tip resistance (tip resistance force qb (z)) from the pressure input F.
That is, the tip resistance at the depth z is estimated by numerically solving the equation (1) by the calculation procedure executed by the CPU of the computer 3 described above.
Hereinafter, the expression (1) for estimating the tip resistance force qb (z) will be specifically described.

  The press input F (z) during press-fitting is considered to be composed of a tip component (represented by subscript b) and a peripheral surface component (represented by subscript S), as shown in FIG. Each resistance when the pile tip is at a depth z is expressed as Qb (z) and Qs (z), and the pressure input F (z) is expressed by Equations (2) to (7).

Here, in the equations (2) to (7), F (z), Qb (z), Qs (z), qb (z), and h (z) are the pressure input, the tip resistance, and the circumference at the depth z, respectively. The surface resistance, the tip resistance force, and the length of soil in the pipe, a is a coefficient representing the reduction of soil stress around the pile tip, b is a coefficient representing the effect of blockage, and c is a friction fatigue (reduction in circumferential resistance). The coefficient, l is the distance from the tip of the pile, Lp is the circumference of the pile, Do is the outer diameter of the pile, and Din is the inner diameter of the pile. In Expression (4), max (l / Do, 2) ^c represents the degree to which the resistance changes as the relative distance of the piles changes.
Ab and eff are the cross-sectional area of the tip of the pile considering the closed state and expressed by the equation (5), and Ar and eff are the area ratio of the pile considering the closed state and expressed by the equation (6) It is expressed. That is, Ar, eff, Ab, and eff are determined by the length of soil in the pile and the penetration length. IFR is an index representing a closed state, where IFR = 0 represents a completely closed state and IFR = 1 represents a completely unblocked state.

  Further, the tip resistance force qb (z) is a value per unit area of the tip resistance Qb (z). The normal force generated in the minute area dA on the tip surface is expressed as qb · dA, and the friction force generated in the minute area dA on the tip surface of the pile when the pile is rotated is multiplied by the friction coefficient to qb · dA. It is a thing. When this friction coefficient is tan δ, that is, when the friction force is qb · dA · tan δ, δ is the wall surface friction angle.

The tip resistance force degree qb (z) is derived from equation (8) from the relational expression of equations (2) and (3) described above.
Further, since the increment of the peripheral surface resistance Qs can be regarded as zero with respect to the minute depth increment δz, the equation (9) is obtained.

Then, the above equation (1) is derived from the relational expression of the above equations (4) and (9), and this equation (1) is applied as a function of the tip resistance force. That is, the tip resistance force qb (z) can be obtained by numerically solving the equation (1) in consideration of the boundary condition qb (0) = 0.
At this time, a sufficient result can be obtained even if the wall friction angle δ is set as an appropriate constant for each site and implemented as a constant.

As described above, in the tip resistance force estimation system, the press-fitting construction system, and the tip resistance force estimation method according to the present embodiment, as shown in FIG. 3, the depth z, the pressure input F, and the pipe soil measured during the press-fitting construction. By continuously measuring the length h, etc., the measurement data is taken into the peripheral surface resistance force calculating unit 11, the integrating unit 12, and the tip resistance force calculating unit 13 and subjected to the calculation process according to the above procedure. The tip resistance inside can be estimated continuously in the depth direction.
In this case, a measuring instrument such as a load cell used in the prior art is unnecessary, and therefore the construction cost generated by using the measuring instrument without changing the shape and construction procedure of the pile used in normal press-fitting construction. In addition, the tip resistance can be easily and continuously known in the depth direction without increasing the construction period.

  As a result, for example, the tip resistance force degree and the ground information such as soil classification and N value are preliminarily associated with each other to create a database, and the information is obtained by the calculation process of the estimation method described above from the information of the pressure input F obtained by the normal press-fitting construction. Based on the obtained tip resistance force level, the N value and soil classification can be easily estimated from the database.

  Further, in the present embodiment, it is possible to obtain the tip resistance force degree that is continuous in the depth direction from the start of press-fitting to the completion of press-fitting, and the processing data can be accumulated. And the supporting force of the pile 4 after press-fit completion can be estimated based on such data of the tip resistance force.

  As described above, in the tip resistance force estimation system, the press-fitting construction system, and the tip resistance force estimation method according to the present embodiment, the tip resistance during press-fitting is continuously performed in the depth direction without generating additional work cost and work time. Can be estimated efficiently and accurately. Therefore, the estimated tip resistance can be used for estimating geological information and bearing capacity.

  As described above, the embodiments of the tip resistance force estimation system, the press-fitting construction system, and the tip resistance force estimation method according to the present invention have been described, but the present invention is not limited to the above-described embodiments, and departs from the spirit thereof. It is possible to change appropriately within the range not to be.

  For example, in the present embodiment, only the press-fitting work is set as a construction target, but it is also possible to set the rotary press-fitting as a construction target. In the case of rotary press-fitting, torque due to the rotation of the press-fitting device is also subject to calculation as input information, so that it is possible to estimate the tip resistance force with higher accuracy.

In the above-described embodiment, in the peripheral surface resistance force calculation step, the front surface resistance force degree used for calculation of the peripheral surface resistance force degree by the peripheral surface resistance force degree calculation unit 11 is a depth shallower than the depth (the immediately preceding depth). When the tip of the pile at) reaches the depth, the tip resistance force calculated at each depth up to the immediately preceding depth (each intermediate depth) is adopted. Then, the peripheral surface resistance force calculation unit 11 of the present embodiment performs correction in consideration of information indicating the obstruction state of the pile tip obtained in advance with respect to the tip resistance force obtained in advance at each depth. In addition to calculating the surface resistance force level, the peripheral surface resistance force level calculation unit calculates the peripheral surface resistance force level by correcting the tip resistance force level in accordance with the distance from the pile tip. However, it is not limited to these corrections.
That is, in the peripheral surface resistance force calculation unit, an estimation system that does not perform both correction based on information indicating the closed state and correction based on a change according to the distance from the pile tip may be used. A system that performs either correction may be used. Or it is also possible to set it as the system which correct | amends tip resistance force degree using another correction method, and calculates circumferential surface resistance force degree.
That is, the function (supporting force formula) for calculating the tip resistance force q _b (z) shown in the above-described embodiment is an example, and an estimation method using another supporting force formula can be used.

  Further, the press-fitting device is not limited to one using a press-fitting device that takes a reaction force from an existing pile and press-fits the pile into the ground. For example, the reaction force of the press-fitting device may be taken from a weight or an existing structure.

  In addition, it is possible to appropriately replace the components in the above-described embodiments with known components without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Tip resistance force estimation system 2 Press-fit apparatus 3 Computer 4 Pile 11 Circumferential resistance force degree calculation part 12 Accumulation part 13 Tip resistance force degree calculation part 21 Depth measurement means 22 Pressure input measurement means 23 In-pipe soil length measurement means

Claims (6)

A tip resistance force estimation system that estimates the tip resistance force level, which is a value per unit area of tip resistance acting on the tip of the pile when the pile is press-fitted into the ground, for each depth of the pile tip,
From previously obtained tip resistance of the depth shallower the depth than the pile tip circumferential surface acting between the peripheral surface of the pile definitive in each depth to which the tip resistance degree is determined to be said ground A peripheral resistance force calculator that calculates a peripheral resistance force that is a value per unit area of resistance;
An integrating unit for obtaining the peripheral surface resistance by integrating the peripheral surface resistance of obtained by the peripheral surface resistance calculation unit,
Through a compression force sequentially measurable press-fitting force measuring means fitting force of pile definitive in depth of the pile tip obtained using the pile, the pile tip of the net of the circumferential surface resistance obtained by the integration unit calculating a tip resistance definitive depth, and the tip resistive force calculation unit for obtaining the tip resistance degree definitive in depth of the pile tip based on the tip resistor,
A tip resistance force estimation system comprising: The circumferential resistance force degree calculation unit corrects the tip resistance force degree obtained in advance at each depth based on a change in the circumferential resistance force degree according to a distance from a pile tip, and the circumferential resistance force degree. The tip resistance force degree estimation system according to claim 1, wherein: The peripheral surface resistance force degree calculation unit calculates the peripheral surface resistance force degree by correcting the tip resistance force degree obtained in advance at each of the depths based on an index indicating the obstruction state of the pile tip obtained in advance. The tip resistance force degree estimation system according to claim 1 or 2. The tip resistance force degree estimation system according to any one of claims 1 to 3, wherein the tip resistance force degree obtained by the tip resistance force degree calculation unit is used as the tip resistance force degree obtained in advance in the next calculation. A press-fitting construction system for press-fitting a pile with a press-fitting device using the tip resistance force degree estimation system according to any one of claims 1 to 4 ,
Wherein the press-fit device includes a sequential measurable depth measuring means the depth of the pile tip, and the force-insertion force measuring means, and sequentially measurable tract soil length measuring means tube soil length of pile, is provided,
Based on the depth of the pile tip measured by the means, the pressure input, and the soil length in the pipe, the tip resistance force degree is calculated by the peripheral resistance force degree calculation unit, the integration unit, and the tip resistance force degree calculation unit. A press-fit construction system characterized by what is required. A tip resistance force estimation method for estimating the tip resistance force level, which is a value per unit area of tip resistance acting on the pile tip when pressing the pile into the ground, for each depth of the pile tip,
From previously obtained tip resistance of the depth shallower the depth than the pile tip circumferential surface acting between the peripheral surface of the pile definitive in each depth to which the tip resistance degree is determined to be said ground A step of calculating a peripheral surface resistance force which is a value per unit area of resistance ;
A step of determining the circumferential surface resistance by integrating the peripheral surface resistance of,
Through a compression force of pile obtained with the sequential measurable press-fitting force measuring means fitting force of pile, after deducting the circumferential surface resistance was determined to calculate the tip resistance, the pile tip based on tip resistance A step of obtaining a tip resistance force degree at a depth of
A tip resistance force estimation method characterized by comprising:

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