JP2021102842A - Estimation system of load bearing capacity of steel pipe pile and steel pipe sheet pile - Google Patents

Abstract

To provide an estimation system for load bearing capacity of a steel pipe pile and a steel pipe sheet pile that allow easy estimation of load bearing capacity of installed steel pipe piles and steel pipe sheet piles.SOLUTION: A load bearing capacity estimation system 28 estimates the load bearing capacity when a steel pipe pile having a steel pipe 2 and a mechanical joint provided on an end part of the steep pile 2 in the longitudinal direction and configured to allow a vertical joint in a retained state with the mechanical joint. The estimation system is provided with: a protection cap 21 having a joint mechanism detachably connectable in a retained state to a pin joint 5 constituting the mechanical joint; a distortion gauge 29 attached on the protection cap 21 and allowing detection of the impact applied on the protection cap 21 upon installation to a support soil layer; and a mobile computer 30 for estimating the load bearing capacity of the installed steel pipe pile based on detected signals with the distortion gauge 29.SELECTED DRAWING: Figure 3

Description

The present invention is a striking method for a steel pipe pile / steel pipe sheet pile having a steel pipe and a joint mechanism provided at the longitudinal end of the steel pipe, which is configured to be vertically spliced by the joint mechanism in a retaining state. The present invention relates to a bearing capacity estimation system that estimates the bearing capacity when the pipe is driven into the support layer.

Steel pipe piles and steel pipe sheet piles are used to construct foundation piles and earth retaining walls for structure installation, landslide prevention piles, and pier foundations. A long steel pipe pile is required to reach the support layer, which is the hard ground under the soft ground, but due to the convenience of manufacturing and transportation, the steel pipe of several meters to several tens of meters manufactured at the factory is required. Pile / steel pipe sheet piles are brought into the site, and a plurality of steel pipe piles / steel pipe sheet piles are connected vertically to form a predetermined length at the site.

As a mechanism for connecting a steel pipe pile and a steel pipe sheet pile, Patent Document 1 proposes a mechanical joint mechanism.

The joint mechanism is formed so that the inward peripheral groove of the outer fitting member and the outward peripheral groove of the inner fitting member have the same groove width, and the outer fitting member and the inner fitting member are fitted to each other. In the state, the inward peripheral groove and the outward peripheral groove are opposed to each other, and the key member built in the inward peripheral groove in advance is extruded to the outward peripheral groove side, and extends over the inward peripheral groove and the outward peripheral groove. By fitting the steel pipe piles together, the pair of steel pipe piles cannot be moved relative to each other in the longitudinal direction of the steel pipe piles.

Such steel pipe piles and steel pipe sheet piles are driven until a predetermined bearing capacity is obtained in the support layer by the striking method. When driving, if the joint mechanism provided on the steel pipe pile / steel pipe sheet pile is directly hit by the hydraulic hammer of the pile driver, the joint mechanism may be deformed and hinder normal connection, so avoid this. A protective cap is used for this purpose. The protective cap has a joint mechanism similar to the joint mechanism provided on the steel pipe pile / steel pipe sheet pile, and is configured to be connectable to the steel pipe pile / steel pipe sheet pile.

By the way, regarding the judgment as to whether or not the driven steel pipe pile / steel pipe sheet pile has a predetermined bearing capacity, conventionally, a worker attaches a recording sheet to the surface of the steel pipe pile / steel pipe sheet pile, and the steel pipe pile / steel pipe sheet pile is used. Write a stroke on the recording paper while moving a writing instrument such as a pencil horizontally for each hit, measure the amount of stroke and rebound based on the written stroke, and estimate this and a predetermined estimate obtained in advance by experiments etc. It was done by the method of estimating the bearing capacity based on the formula. However, since such work of measuring the amount of driving and the amount of rebound requires skill, improvement has been required.

Japanese Patent No. 3336430

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a bearing capacity estimation system for steel pipe piles / steel pipe sheet piles, which can easily estimate the bearing capacity of a driven steel pipe pile / steel pipe sheet pile. And.

The characteristic configuration of the bearing capacity estimation system for steel pipe piles and steel pipe sheet piles for achieving the above-mentioned object includes a steel pipe and a joint mechanism provided at the longitudinal end of the steel pipe, and the joint mechanism provides. It is a bearing capacity estimation system that estimates the bearing capacity when a steel pipe pile / steel pipe sheet pile configured to be vertically connected in a retaining state is driven into the support layer by the striking method, and is removable to the joint mechanism. A protective cap having a joint mechanism that can be connected in a retaining state, a sensor that is attached to the protective cap and can detect the impact given to the protective cap when it is driven into the support layer, and a signal detected by the sensor. Based on the above, it is equipped with a signal processing device that estimates the bearing capacity of the steel pipe pile / steel pipe sheet pile that has been driven in.

If sensors are to be attached to all of the steel pipe piles and steel pipe sheet piles in order to detect the data of the steel pipe piles and steel pipe sheet piles that are actually driven, a large number of sensors are required. On the other hand, if it is attempted to reuse the sensor only for the steel pipe pile / steel pipe sheet pile to be driven, there is a problem that the work cost becomes high because the work of attaching / detaching the sensor is complicated.

As a result of diligent research, the inventors have found that the protective cap is detachable from the steel pipe similar to the steel pipe that constitutes the steel pipe pile / steel pipe sheet pile and the joint mechanism provided on the steel pipe pile / steel pipe sheet pile to prevent it from coming off. When configured with a joint mechanism that can be connected with, as a signal detected by the sensor attached to the protective cap, the same signal as when the sensor is attached to a steel pipe pile or steel pipe sheet pile to be actually driven can be obtained. I got the finding.

The experiments that led to this finding will be described. The inventors hit a steel pipe pile with a sensor 1 m below the upper end and a protective cap with a sensor 1 m below the upper end of the protective cap attached to the steel pipe pile, respectively. An experiment was conducted to hit with force. The sensors are a strain gauge and an acceleration sensor, and the signal obtained from the sensor is input to a PDA (Pile Driving Analyzer) manufactured by PDI (Pile Dynamics. Inc) and analyzed. FIG. 4 is a time history response graph of the pile axial force and velocity when a steel pipe pile with a sensor mounted 1 m below the upper end is hit with a predetermined hitting force (5300 kN). In FIG. 5, the input wave (sum of the pile axial force and velocity × impedance) and the reflected wave (pile axial force and velocity × impedance) created from the time history response graph of the pile axial force and velocity shown in FIG. 4 are shown. The time history stress waveform graph of (difference) is shown. FIG. 6 shows the time history response of the pile axial force and velocity when the protective cap is hit with a predetermined striking force when the sensor is mounted 1 m below the upper end of the protective cap attached to the steel pipe pile. It is a graph. In FIG. 7, the input wave (sum of the pile axial force and velocity × impedance) and the reflected wave (pile axial force and velocity × impedance) created from the time history response graph of the pile axial force and velocity shown in FIG. 6 are shown. The time history stress waveform graph of (difference) is shown. From FIGS. 5 and 7, it can be determined that the stress waveform when the protective cap is hit is substantially the same as the stress waveform when the steel pipe pile is hit. That is, since the signal detected when the sensor is attached to the steel pipe pile itself and the signal detected when the sensor is attached to the protective cap are almost the same, the reliability of the estimated bearing capacity is the same. Can be evaluated as.

In the present invention, since the sensor is configured to be attached only to the protective cap, the above-mentioned problem does not occur.

Since the bearing capacity is estimated based on the signal obtained from the sensor, the reliability of the measurement data is high as compared with the case where the driving amount and the rebound amount are manually measured by the worker. As the sensor, a strain gauge or an acceleration sensor can be preferably exemplified.

In the present invention, it is preferable that the protective cap is made of the same material as the steel pipe.

If the protective cap is made of a material different from that of the steel pipe, the propagation of the impact generated on the driven steel pipe pile / steel pipe sheet pile differs from the propagation of the impact generated on the protective cap, so some correction is required in the estimation formula. Become. According to the above configuration, the estimation formula is not too complicated because the correction is unnecessary.

In the present invention, the joint mechanism is arranged so as to straddle the pin joint, the box joint, the pin joint, and the box joint, and provides a load transmission key that connects the pin joint and the box joint in a retaining state. The joint mechanism is composed of a mechanical joint to be provided, or the joint mechanism is provided on a pin joint, a box joint, an outer surface of the pin joint, and an inner surface of the box joint, and meshes with each other to form the pin joint and the box joint. It is composed of a mechanical joint having a meshing portion for connecting the pin joints in a retaining state, or the joint mechanism is provided on a pin joint, a box joint, an outer surface of the pin joint, and an inner surface of the box joint. It is preferable that the pin joint is composed of a mechanical joint having a screw portion that connects the pin joint and the box joint in a retaining state by screwing each other.

According to the above configuration, since the steel pipe pile / steel pipe sheet pile and the protective cap are connected by a mechanical joint, there is no error that may occur when mounting the sensor for each steel pipe pile / steel pipe sheet pile, so that the accuracy of the obtained signal is eliminated. Is therefore better, and therefore the accuracy of the estimated bearing capacity is better.

In the present invention, it is preferable that the sensor is a strain gauge.

According to the above configuration, an inexpensive strain gauge can be used as the sensor.

In the present invention, it is preferable that the signal processing device is composed of a stationary computer or a portable computer.

According to the above configuration, the signal processor estimates bearing capacity based on the signal detected by the sensor.

Explanatory drawing of steel pipe pile Explanatory drawing of steel pipe pile and protective cap Explanatory diagram of bearing capacity estimation system Time history response graph of pile axial force and velocity obtained from impact test of steel pipe pile Time history stress waveform graph of input wave and reflected wave created from time history response graph of pile axial force and velocity shown in FIG. Time history response graph of pile axial force and velocity obtained from the striking experiment of the protective cap Time history stress waveform graph of input wave and reflected wave created from time history response graph of pile axial force and velocity shown in FIG.

Hereinafter, embodiments of a bearing capacity estimation system for steel pipe piles and steel pipe sheet piles according to the present invention will be described with reference to the drawings. FIG. 1 shows a steel pipe pile 1 as an example of a steel pipe pile / steel pipe sheet pile to which a protective cap according to the present invention can be attached and detached.

The steel pipe pile 1 is connected by a mechanical joint 3 as an example of a joint mechanism provided at the end of the steel pipe 2 in a retaining state and a rotation preventing state. The steel pipe 2 is composed of a spiral steel pipe, a welded pipe such as a UO steel pipe, a seamless steel pipe, a forge welded steel pipe, a cast steel pipe and the like.

The mechanical joint 3 includes a box joint 4, a pin joint 5, a load transmission key 6, and a set bolt 7 provided at the end of the steel pipe 2.

As shown in FIG. 1, the box joint 4 is provided with a single inward groove portion 9 along the circumferential direction on the inner peripheral surface 8 of the box joint 4. The load transmission key 6 is composed of a plurality of arcuate plates divided in the circumferential direction, and the inward groove portion 9 has a depth capable of storing the entire thickness of the load transmission key 6.

The box joint 4 is provided with a through hole 10 communicating with the inward groove portion 9, and a set bolt 7 is arranged in the through hole 10.

As shown in FIG. 1, the pin joint 5 is provided with a single outward groove portion 12 along the circumferential direction at a position of the outer peripheral surface 11 opposite to the inward groove portion 9 provided in the box joint 4. .. The outward groove portion 12 is configured to have a depth capable of storing approximately half the thickness of the load transmission key 6.

When the set bolt 7 is rotated with the pin joint 5 inserted into the box joint 4, the load transmission key 6 stored in the inward groove 9 of the box joint 4 becomes the outward groove 12 of the pin joint 5. It enters and is arranged so as to straddle the inward groove portion 9 and the outward groove portion 12, whereby the box joint 4 and the pin joint 5 are connected in a retaining state.

Further, a plurality of box-side notch recesses 14 are provided at equal intervals on the edge of the outer peripheral surface 13 of the box joint 4 at equal intervals in the circumferential direction. A pin-side notch recess 16 is provided on the edge of the outer peripheral surface 15 of the pin joint 5 at a position facing the box-side notch recess 14 provided in the box joint 4.

A key groove is formed by the box-side notch recess 14 and the pin-side notch recess 16, and by attaching the rotation suppression key 17 to this key groove, the box joint 4 and the pin joint 5 are connected and connected in a non-rotating state. The relative rotation of the two steel pipe piles 1 is prevented. The rotation suppression key 17 is fixed in the keyway by a fixing screw 18 screwed into a screw hole provided in the pin joint 5.

When driving such a steel pipe pile 1 by a striking method, as shown in FIG. 2, a protective cap 21 is used to protect the steel pipe pile 1 from the striking by the hydraulic hammer 20 of the pile driver 19.

When the steel pipe pile 1 is driven, the box joint 4 can be driven so as to be on the front side in the traveling direction, or the pin joint 5 can be driven so as to be on the front side in the traveling direction. In the present embodiment, when the box joint 4 is driven so as to be on the front side in the traveling direction, the protective cap 21 configured to be detachably attached to the pin joint 5 on the rear side in the driving direction will be described.

The protective cap 21 is a member made of the same material as the steel pipe 2. As shown in FIG. 3, the protective cap 21 has a tubular cap joint 22. The inner peripheral surface 23 of the cap joint 22 is formed to have a size that can surround the outer peripheral surface 11 provided with the outward groove portion 12 of the pin joint 5.

The inward groove portion 24 is provided at a position of the inner peripheral surface 23 of the cap joint 22 facing the outward groove portion 12 of the pin joint 5. The cap joint 22 is provided with an opening 25 that communicates with the inward groove portion 24.

As shown in FIG. 4, the protective cap 21 is provided with a retaining key 26 that is arranged so as to straddle the inward groove portion 24 and the outward groove portion 12 and prevents the pin joint 5 from coming off.

The retaining key 26 is composed of a plurality of arcuate plates similar to the load transmission key 6 divided in the circumferential direction.

With the pin joint 5 inserted into the protective cap 21, the retaining key 26 is arranged so as to straddle the inward groove 24 and the outward groove 12 through the opening 25, whereby the protective cap 21 is placed. And the pin joint 5 are connected in a retaining state.

The bearing capacity estimation system 28 according to the present invention is used to estimate the bearing capacity when the steel pipe pile 1 configured in this way is driven into the support layer by the striking method using the protective cap 21.

The bearing force estimation system 28 is attached to the protective cap 21 described above and the outer peripheral surface 27 of the protective cap 21, and the strain gauge 29 as a sensor capable of detecting the impact applied to the protective cap 21 when driven into the support layer, It includes a portable computer 30 as a signal processing device that estimates the bearing capacity of the driven steel pipe pile 1 based on the signal detected by the strain gauge 29.

The portable computer 30 measures the impact applied to the protective cap 21 when driving the steel pipe pile 1 based on the change in the electric resistance of the strain gauge 29, and supports the bearing capacity based on a predetermined estimation formula obtained in advance by an experiment or the like. Is configured to estimate.

In this way, the bearing capacity estimation system 28 can facilitate the estimation of the bearing capacity of the steel pipe pile 1.

In the above-described embodiment, the case where the target for estimating the bearing capacity by the bearing capacity estimation system 28 is the steel pipe pile 1 has been described, but the target for estimating the bearing capacity by the bearing capacity estimation system 28 may be a steel pipe sheet pile. ..

In the above-described embodiment, the case where the protective cap 21 is made of the same material as the steel pipe 2 has been described, but the protective cap 21 may be made of a material different from that of the steel pipe 2. However, in this case, it is necessary to correct the estimation formula due to the difference in materials.

In the above-described embodiment, the case where the sensor capable of detecting the impact applied to the protective cap 21 is the strain gauge 29 has been described, but the sensor may be another sensor, for example, an acceleration sensor. Good.

In the above-described embodiment, the protective cap 21 is detachably attached to the pin joint 5 on the rear side in the driving direction when the steel pipe pile 1 is driven so that the box joint 4 is on the front side in the traveling direction. The case where it is done was explained. However, the steel pipe pile 1 may be driven so that the pin joint 5 is on the front side in the driving direction. Therefore, the protective cap 21 is detachably configured on the box joint 4 on the rear side in the driving direction. You may.

In the above-described embodiment, the case where the joint mechanism is a mechanical joint 3 having a box joint 4, a pin joint 5, and a load transmission key 6 has been described, but the configuration of the joint mechanism is limited to this. Absent. For example, a joint mechanism is provided on a pin joint, a box joint, an outer surface of the pin joint, and an inner surface of the box joint, and meshes with each other to connect the pin joint and the box joint in a retaining state. It may be composed of a mechanical joint having, or is provided on the outer surface of the pin joint, the box joint, the outer surface of the pin joint, and the inner surface of the box joint, and is screwed together to form the pin joint and the box. It may be a mechanical joint having a screw portion for connecting the joint in a retaining state. In any case, the protective cap 21 may be configured to be connectable to the pin joint or the box joint included in these mechanical joints in a retaining state.

In the above-described embodiment, the case where the signal processing device is a portable computer has been described, but the signal processing device may be composed of, for example, a stationary computer.

The above-described embodiments are all examples of the present invention, and the description does not limit the present invention, and the specific configuration of each part can be appropriately modified and designed within the range in which the effects of the present invention are exhibited. is there.

1: Steel pipe pile 2: Steel pipe 3: Mechanical joint 4: Box joint 5: Pin joint 6: Load transmission key 21: Protective cap 28: Supporting force estimation system 29: Strain gauge (sensor)
30: Portable computer (signal processing device)

Claims (7)

A steel pipe pile / steel pipe sheet pile, which has a steel pipe and a joint mechanism provided at the longitudinal end of the steel pipe and is configured to be vertically connected by the joint mechanism in a retaining state, is used as a support layer by a striking method. It is a bearing capacity estimation system that estimates the bearing capacity when driving.
A protective cap having a joint mechanism that is detachable and can be connected to the joint mechanism in a retaining state.
A sensor that is attached to the protective cap and can detect the impact given to the protective cap when it is driven into the support layer.
A bearing capacity estimation system including a signal processing device that estimates the bearing capacity of the steel pipe pile / steel pipe sheet pile that has been driven in based on the signal detected by the sensor. The bearing capacity estimation system according to claim 1, wherein the protective cap is made of the same material as the steel pipe. The joint mechanism is arranged from a pin joint, a box joint, the pin joint, and a mechanical joint having a load transmission key that connects the pin joint and the box joint in a retaining state. The bearing capacity estimation system according to claim 1 or 2, which is configured. The joint mechanism is provided on a pin joint, a box joint, an outer surface of the pin joint, and an inner surface of the box joint, and meshes with each other to connect the pin joint and the box joint in a retaining state. The bearing capacity estimation system according to claim 1 or 2, which is composed of a mechanical joint having. The joint mechanism is provided on a pin joint, a box joint, an outer surface of the pin joint, and an inner surface of the box joint, and is a screw that connects the pin joint and the box joint in a retaining state by screwing each other. The bearing capacity estimation system according to claim 1 or 2, which comprises a joint and a mechanical joint having. The bearing capacity estimation system according to any one of claims 1 to 5, wherein the sensor is a strain gauge. The bearing capacity estimation system according to any one of claims 1 to 6, wherein the signal processing device is composed of a stationary computer or a portable computer.

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