WO2022210804A1

WO2022210804A1 - Load test method and analysis system

Info

Publication number: WO2022210804A1
Application number: PCT/JP2022/015727
Authority: WO
Inventors: 一訓稲積; 博文田口; 秀和松原; 通宏中島; 真二西村
Original assignee: 株式会社大林組; 東亜建設工業株式会社; Ｊｆｅスチール株式会社; 株式会社ガンケン; 株式会社シーズエンジニアリング
Priority date: 2021-03-30
Filing date: 2022-03-29
Publication date: 2022-10-06
Also published as: JP2022154205A

Abstract

The present invention minimizes the labor and cost required for a load test. A load test method for a steel pipe pile (12), which was installed while removing crushed rock by using a vibrator (13) to cause the steel pipe pile (12) to vibrate in the vertical direction, thereby crushing a bedrock (11), and supplying a jet of water through a hollow section of the steel pipe pile (12) to a tip end section of the steel pipe pile (12), wherein after a support layer is reached, the supply of the jet of water is stopped, and an accelerometer (19) is used to measure the acceleration of the steel pipe pile (12) when the vibrator (13) has been used as a pressurizing device to apply vibrations to the steel pipe pile (12). The measured acceleration is inputted into an analysis system (20). The analysis system (20) calculates the ground resistance of the bedrock (11) according to an unloading point method in which said acceleration is used.

Description

Loading test method and analysis system

The present invention relates to a load test method for steel pipe piles driven into bedrock, and an analysis system used for the load test.

Known load test methods for evaluating the bearing capacity of foundation piles include static load test methods, dynamic load test methods, and rapid load test methods. For example, in the dynamic loading test method, a rapid loading test with a relative loading time Tr of 5 or more and less than 500 and an impact loading test with a relative loading time Tr of less than 5 are performed. In these loading tests, a hammer driving machine and a monken are used as force applying devices.

In addition, the gunpile method (registered trademark) is known as a method of driving steel pipe piles into bedrock. In the gunpile method, steel pipe piles with reinforced tips are driven directly into the bedrock. Specifically, a vibrator is used to vertically vibrate the steel pipe pile to crush the bedrock, and jet water is supplied to the tip of the steel pipe pile through the hollow part of the steel pipe pile to remove rock crushed powder. Install steel pipe piles.

JP-A-10-153497

However, the method described in Patent Document 1 requires a step of forming a measurement hole near the steel pipe pile, which increases the labor and cost of the load test.

A load test method for solving the above problems is a load test method for a steel pipe pile driven using a vibrator, in which the steel pipe pile is vertically vibrated by the vibrator to crush the rock and crush the steel pipe pile. Jet water is supplied to the tip of the steel pipe pile through the hollow part of the steel pipe pile to drive the steel pipe pile while removing rock crushed powder, and after reaching the support layer, the jet water supply is stopped, and the vibrator is used as a force applying device to obtain the acceleration of the steel pipe pile when vibration is applied to the steel pipe pile, and the ground resistance of the rock is calculated using the obtained acceleration.

According to the present invention, it is possible to efficiently carry out a load test of steel pipe piles.

The figure which shows typically a mode that the steel pipe pile to which one Embodiment of the load test method is applied is driving. FIG. 1 is a block diagram showing a schematic configuration of an analysis system; (a) Graph showing an example of the measurement result of the acceleration of the steel pipe pile, (b) Graph showing the speed of the steel pipe pile based on the acceleration, (c) Graph showing the displacement of the steel pipe pile based on the acceleration, (d) The vibrator is Graph showing the load applied to the steel pipe pile, (e) a graph showing an example of the reaction force of the ground against the steel pipe pile, (f) a graph showing the relationship between the displacement of the steel pipe pile and the ground resistance, (g) the steel pipe in the CASE method The graph which shows an example of the reaction force of the ground with respect to a pile, (h) The graph which shows the relationship between the displacement of a steel pipe pile and ground resistance in CASE method.

An embodiment of the load test method and analysis system will be described with reference to FIGS. 1 to 3. FIG.
As shown in FIG. 1 , in the gunpile construction method (registered trademark), a hollow steel pipe pile 12 with a reinforced tip is driven into a rock 11 by a vibrator 13 . In the gunpile construction method, the rock 11 is pulverized by vibrating the steel pipe pile 12 vertically with the vibrator 13 . At the same time, low-pressure jet water is supplied to the tip of the steel pipe pile 12 through the supply path 14 arranged inside the steel pipe pile 12 to drive the steel pipe pile 12 while removing rock crushed powder. In this embodiment, the hollow portion of the steel pipe pile 12 after driving is filled with a grout material made of a cement-based material such as mortar. In addition, it is not always necessary to fill the hollow portion of the steel pipe pile 12 with the grout material.

The load test method of this embodiment is performed using the vibrator 13 as a force applying device on the steel pipe pile 12 driven by the gunpile method described above. By using the vibrator 13 as a force applying device, a load test equivalent to an impact load test can be performed.

The vibrator 13 has a box 15 , a gripper 16 and a vibration drive source 17 .
The box 15 is suspended by, for example, a crane (not shown). The grip part 16 is supported by the lower end of the box 15 . The gripping portion 16 grips the steel pipe pile 12 by applying a driving force from a gripping drive source (not shown). The vibration driving source 17 is housed inside the box 15 . The vibration driving source 17 of this embodiment is electrically driven. Note that the vibration drive source 17 may be of a hydraulic type. The vibration drive source 17 applies force to the steel pipe pile 12 by vertically vibrating the gripping portion 16 when driven.

A strain gauge 18 and an acceleration gauge 19 are attached to the steel pipe pile 12 . The strain gauge 18 measures strain of the steel pipe pile 12 when vibration is applied from the vibrator 13 . The acceleration measuring device 19 measures the acceleration of the steel pipe pile 12 when vibration is given from the vibrator 13 . Measured values of the strain measuring device 18 and the acceleration measuring device 19 are input to the analysis system 20 . The analysis system 20 is a system for analyzing a load test of the steel pipe pile 12 using the vibrator 13 as a force adding device. A load test is performed before the hollow portion of the steel pipe pile 12 is filled with the grout material, or when the filled grout material is in an unhardened state.

As shown in FIG. 2, the analysis system 20 has an information processing device 21 as a main component.
The information processing device 21 acquires various kinds of information and executes various kinds of processing based on the acquired various kinds of information, programs and various data stored in the memory. The information processing device 21 can be configured as a circuit including one or more dedicated hardware circuits such as ASIC, one or more processors that operate according to a computer program (software), or a combination thereof. A processor includes a CPU and memory, such as RAM and ROM, which stores program code or instructions configured to cause the CPU to perform processes. Memory or computer-readable media includes any media that can be accessed by a general purpose or special purpose computer.

An input device 22 and a display device 23 are electrically connected to the information processing device 21 in addition to the strain measuring device 18 and the acceleration measuring device 19 described above.
The input device 22 includes a keyboard, pointing device, and the like. The input device 22 inputs to the information processing device 21 various information, execution instructions of various processes, and the like.

The display device 23 displays the measurement values of the accelerometer 19, the results of various processes executed by the information processing device 21, and the like. The information processing device 21 has a processing section 25 and a data storage section 26 .

The processing unit 25 executes various processes. The processing unit 25 executes analysis processing when an analysis start operation is performed on the input device 22 .
In the analysis process, the processing unit 25 associates the strain ε input from the strain measuring device 18 and the acceleration a input from the acceleration measuring device 19 for a predetermined period from the analysis start operation for each acquisition timing. Stored in the data storage unit 26 . The processing unit 25 calculates the ground resistance Rsoil of the rock 11 using the stored strain ε and acceleration a. The processing unit 25 of the present embodiment calculates the static resistance component Rw of the rock 11 by the unloading point method, and calculates the calculated static resistance component Rw as the ground resistance Rsoil.

A method of calculating the static resistance component Rw using the unloading point method will be described.
When the load F acts on the steel pipe pile 12, in the opposite direction of the load F, the inertial resistance component Ra (=mass M of the steel pipe pile 12 × acceleration a) of the steel pipe pile 12, and the tip of the steel pipe pile 12 is bedrock. 11 produces a static resistance component Rw and a dynamic resistance component Rv. On the other hand, when the steel pipe pile 12 displaced downward by the load F bounces back against the bedrock 11, the steel pipe pile 12 is in a stationary state. That is, no dynamic resistance component Rv is generated. Therefore, if the reaction force Fsoil from the rock 11 is obtained by subtracting the inertial resistance component Ra from the load F, the reaction force Fsoil at the maximum displacement of the steel pipe pile 12 becomes the static resistance component Rw.

(Procedure of load test)
The load test procedure will be explained. Prior to the load test, target information regarding the steel pipe pile 12 is input to the information processing device 21 through the input device 22 . The target information is information indicating the mechanical properties of the steel pipe pile 12 , such as the Young's modulus of the steel pipe pile 12 , the inner diameter, the outer diameter, the mass M, and the like. The processing unit 25 of the information processing device 21 stores the input target information in the data storage unit 26 .

The load test is conducted after driving the steel pipe piles 12 to a predetermined depth that reaches the bearing layer, and then stopping the jet water supply. In the loading test, first, after the vibrator 13 is driven, the input device 22 is operated to start analysis. By using the vibrator 13 used for driving the steel pipe pile 12 as a force applying device for applying the load F to the steel pipe pile 12 in this way, a force applying device for testing such as Monken becomes unnecessary. .

When an analysis start operation is performed on the input device 22, the processing unit 25 of the information processing device 21 starts analysis processing. In the analysis process, the processing unit 25 stores the strain ε and the acceleration a in the data storage unit 26 . Then, the processing unit 25 calculates the load F acting on the steel pipe pile 12 at each acquisition timing based on the strain ε and the Young's modulus of the steel pipe pile 12 stored in the data storage unit 26, and the processing unit 25 calculates the static resistance component Rw by the unloading point method using the load F, the mass M of the steel pipe pile 12, and the acceleration a.

FIGS. 3(a) to 3(f) are graphs showing an example of the results of actual loading tests.
As shown in FIG. 3(a), the acceleration a obtained in the load test shows a spike-like behavior that changes greatly in a short period of time. Such a spike-like behavior of the acceleration a is obtained by using the vibrator 13 as a force applying device for the steel pipe pile 12 driven into the rock 11 . In FIG. 3(a), the downward acceleration a is indicated by a negative value.

As shown in FIG. 3(b), since the velocity is a value obtained by integrating the acceleration a, it exhibits a smoother behavior than the acceleration a.
As shown in FIG. 3(c), since displacement is a value obtained by integrating velocity, it exhibits a smoother behavior than velocity.

As shown in FIG. 3(d), the load F shows a spike-like behavior more than the velocity and displacement, although not as much as the acceleration a.
As shown in FIG. 3(e), the reaction force Fsoil from the bedrock 11 exhibits spike-like behavior similar to the acceleration a.

FIG. 3(f) is a graph showing the relationship between the ground resistance and the displacement of the steel pipe pile 12, with the reaction force Fsoil from the bedrock 11 being the ground resistance. In FIG. 3(f), the amount of downward displacement is indicated by plus. The ground resistance, as shown in FIG. It shows a similar spike-like behavior. Then, the maximum value at the maximum displacement is calculated as the static resistance component Rw, that is, the ground resistance Rsoil.

The CASE method is known as another method for calculating such ground resistance Rsoil. The CASE method measures an input wave and a reflected wave, and calculates the total ground resistance (static resistance component Rw+dynamic resistance component Rv) based on the measured input wave and reflected wave. Then, the static resistance component Rw obtained by separating the dynamic resistance component Rv from the total resistance is calculated as the ground resistance Rsoil.

FIG. 3(g) shows the reaction force Fsoil of the bedrock 11 calculated by applying the acceleration a shown in FIG. 3(a) to the CASE method. 3(h) shows the relationship between the ground resistance and the amount of displacement of the steel pipe pile 12. As shown in FIG. FIG. 3(g) is shown on the same scale as FIG. 3(e), and FIG. 3(h) is shown on the same scale as FIG. 3(f).

As shown in FIGS. 3(g) and 3(h), in the CASE method, the behavior of the reaction force Fsoil and ground resistance was gentler than those obtained by the above analysis processing. . This is because the dynamic resistance component Rv is calculated using the speed of the steel pipe pile 12 and therefore cannot reflect the spike-like behavior of the acceleration a. As a result, the ground resistance Rsoil calculated by the CASE method was a smaller value than the ground resistance Rsoil calculated by the analysis process.

The inventors compared the ground resistance Rsoil calculated by the above analysis process with the ground resistance Rsoil calculated by a method other than the CASE method. Specifically, a comparison was made with the ground resistance Rsoil calculated using a PDA (Pile Driving Analyzer). PDA is an impact loading test system (manufactured by Pile Dynamics, Inc.), and is a system capable of calculating ground resistance Rsoil with high accuracy. As a result of the comparison, it was confirmed that the ground resistance Rsoil calculated by the above analysis processing was substantially equal to the ground resistance calculated by the PDA.

Effects of the present embodiment will be described.
(1) The load test method described above is a load test method for the steel pipe pile 12 driven using the vibrator 13, and vibrates the steel pipe pile 12 in the vertical direction to crush the bedrock 11 and Jet water is supplied to the tip of the steel pipe pile 12 through the hollow part of the steel pipe pile 12 to drive the steel pipe pile 12 while removing rock crushed powder, and after reaching the support layer, the jet water supply is stopped, and the vibrator 13 is Acceleration of the steel pipe pile 12 is obtained when vibration is applied to the steel pipe pile 12 by using it as a force applying device, and the ground resistance Rsoil of the rock 11 is calculated using the obtained acceleration.

As a result, for example, the process of attaching a force applying device such as a monken to the steel pipe pile 12 and the process of forming a measurement hole near the steel pipe pile 12 become unnecessary. As a result, it is possible to reduce the labor and costs involved in the load test. In addition, since no space is required for waiting the attached force adding device, the space on site can be effectively used.

(2) In the loading test method described above, the ground resistance Rsoil is calculated by the unloading point method using the acceleration a of the steel pipe pile 12 . Thereby, the ground resistance Rsoil of the bedrock 11 can be calculated with high accuracy.

(3) Even if there is unhardened grout material in the hollow portion of the steel pipe pile 12, the influence of the vibration of the steel pipe pile 12 on the grout material is small. Therefore, the load test method described above may be performed when the grout material filled in the hollow portion of the steel pipe pile 12 is in an unhardened state. That is, the load test process and the grout material filling process may be performed at the same time. As a result, the cost related to the load test can be further suppressed.

Although one embodiment of the load test method and analysis system according to the present invention has been described above, the present invention is not limited to the above one embodiment, and can be modified as appropriate without departing from the spirit of the present invention. For example, this embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

- The timing of performing the load test may be before filling of the grout material or after hardening of the grout material.
The method for calculating the ground resistance Rsoil is not limited to the unloading point method, as long as the ground resistance Rsoil is calculated using the acceleration a itself that exhibits a spike-like behavior measured by the accelerometer 19 .

DESCRIPTION OF SYMBOLS 11... Bedrock, 12... Steel pipe pile, 13... Vibrator, 14... Supply path, 15... Box, 16... Grasping part, 17... Vibration drive source, 18... Strain measuring instrument, 19... Accelerometer, 20... Analysis system , 21... Information processing device, 22... Input device, 23... Display device, 25... Processing unit, 26... Data storage unit

Claims

A load test method for a steel pipe pile driven using a vibrator,
The vibrator vertically vibrates the steel pipe pile to pulverize the bedrock and supply jet water to the tip of the steel pipe pile through the hollow portion of the steel pipe pile to remove rock crushed powder while the steel pipe pile is removed. cast,
After reaching the support layer, the supply of the jet water is stopped, and the acceleration of the steel pipe pile is obtained when the vibration is applied to the steel pipe pile using the vibrator as a force adding device,
A load test method for calculating the ground resistance of the rock using the acquired acceleration.
The loading test method according to claim 1, wherein the ground resistance is calculated by an unloading point method using the acceleration of the steel pipe pile.
The load test method according to claim 1 or 2, wherein the load test is performed when the grout material filled in the hollow portion of the steel pipe pile is in an unhardened state.
A vibrator is used to vertically vibrate the steel pipe pile to crush the bedrock, and jet water is supplied to the tip of the steel pipe pile through the hollow part of the steel pipe pile to remove crushed rock powder. An analysis system used for a load test of the steel pipe pile,
an accelerometer for measuring the acceleration of the vibration imparted to the steel pipe pile using the vibrator as a force adding device in a state where the supply of the jet water is stopped;
an information processing device that calculates the ground resistance of the rock using the acceleration; and an analysis system.