JP2007239369A - Pile driving construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pile driving construction method for obtaining required tip supporting force without digging a hole for constructing a bored pile down to the ground having a large N value. <P>SOLUTION: This pile driving construction method comprises a hole digging process for digging the ground down to predetermined depth by an auger 25 to form a hole 50, a pouring process for pouring cement milk 51 into the hole 50, a pile insertion process for inserting a pile 10 into the hole 50 in which the cement milk 51 is poured, an installation process for installing a spring hammer 26 at the ground end of the pile 10, and a load loading/measuring process for dropping a drop hammer 27 on the spring hammer 26 from a position having predetermined height to apply load on the pile 10 and measuring tip supporting force of the pile 10 at the same time while the cement milk 51 has fluidity. The load loading/measuring process is repeatedly performed until the measured tip supporting force of the pile 10 becomes target tip supporting force. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pile driving method, and more particularly to a tip supporting force of an embedded pile.

  For example, when building a building in landfill or embankment of soft ground, the concrete foundation is constructed after the piles are built into the ground at predetermined intervals along the shape of the concrete foundation.

  Here, as one of the pile driving methods, a hammering method in which a concrete pile or a steel pile is driven into the ground with a hammer is known. Since this striking method generates vibration and noise during placement, it cannot be constructed where there are buildings in the vicinity, and the pile weight is heavy, so it takes time to transport.

  As another method of pile driving, the auger advanced cement milk rooting method (rooting method) is known. In this root hardening method, a hole is first excavated in the ground with a screw by an auger and cement milk is injected, and then a pile is inserted into the hole.

  Since the rooting method can be installed without vibration and noise, it not only eliminates the above-mentioned problems with the hammering method, but it can also be installed close to existing structures, has a wide range of conformable strata, and can be assembled and disassembled. Because it is simple, it has excellent mobility and economy, it can be installed even on stepped areas and steep slopes, and it can discharge cement milk from the auger tip to restore the ground. .

  In addition, as an auger advance cement milk rooting method, the technique of Unexamined-Japanese-Patent No. 2005-282149 is known, for example.

  Here, the pile built in the ground is required to have a predetermined support force in order to support the building and prevent the uneven settlement. The supporting force can be divided into two types: a tip supporting force supported by the soil just below the bottom surface and a peripheral friction force supported by the ground friction force and adhesive force on the pile peripheral surface. The tip support force is evaluated by a value obtained by multiplying the N value obtained by the ground survey conducted in advance, the pile tip area, and a predetermined support force coefficient (coefficient defined according to the construction method). And it is rare to conduct a pile loading test at the site to determine the actual bearing capacity and verify that this satisfies the required value.

  The N value is the number of hits required to allow a 63.5 kg hammer (weight) to fall freely from a height of 75 cm and allow the sampler to penetrate 30 cm into the soil, and is generally measured every 1 m.

  By the way, in the embedded pile by the root hardening method etc., since the pile is inserted into the hole excavated by the screw with the auger, it is just below the bottom surface like the driven pile by the hammering method etc. in which the pile is placed in the ground. Since the soil cannot be compacted, the bearing capacity coefficient described above is set to a value smaller than that of the hammering method (for example, it is 300 for the pile piles such as the hammering method and 150 for the embedded piles such as the rooting method). The

Therefore, conventionally, in order to obtain the tip supporting force required in the root-capping method, if the tip area is determined by the pile to be used, the N value has to be increased. In other words, there was no choice but to drill a hole that reached deeper and deeper ground in the ground.
JP 2005-282149 A

  However, in such a conventional technique, in order to excavate to a strong ground having a large N value, not only does the cost of excavation itself increase, but also a large amount of earth and sand and mud water accompanying excavation are generated and processed. The cost increases.

  Moreover, since the depth of a hole will become deep and a pile will be inserted in this hole, the length of a pile will become long and the cost required for handling (transportation etc.) of a pile itself and a pile will also become high.

  Therefore, an object of the present invention is to provide a pile driving method capable of obtaining a necessary tip support force without excavating a hole for embedding an embedded pile to the ground having a large N value.

  In order to solve the above-described problems, the pile driving method of the present invention includes a drilling step of drilling the ground to a predetermined depth with a drilling means to form a hole, a pile insertion step of inserting a pile into the hole, It has an installation process for installing a spring hammer on the ground edge, and a loading / measurement process for dropping the load onto the spring hammer from a predetermined height and applying a loading load to the pile and simultaneously measuring the tip support force of the pile. The loading / measurement process is repeatedly performed until the measured tip support force of the pile reaches the target tip support force.

  Further, the pile driving method of the present invention includes a drilling process in which a hole is formed by excavating the ground to a predetermined depth with a drilling means, an injection process in which a hardener is poured into the hole, and a hole into which the hardener is poured. Pile insertion process to insert the pile, installation process to install a spring hammer on the ground end of the pile, and when the hardened material has fluidity, drop the load from the predetermined height to the spring hammer and pile Load and measurement process that measures the tip support force of the pile at the same time as applying a load to the pile, and repeatedly executing the load and measurement process until the measured tip support force of the pile reaches the target tip support force It is characterized by that.

  In a preferred embodiment of the present invention, prior to the execution of the loading / measurement step, a cushioning material for mitigating a drop impact caused by the loaded load is laid on a falling portion of the loaded load on the spring hammer.

  In a further preferred embodiment of the present invention, the pile includes a pile body made of H-shaped steel and a steel plate that is attached to one end of the pile body and envelops the cross section of the pile body. In the pile insertion step, the steel plate is attached. The pile is inserted into the hole so that the end portion becomes the underground end.

  According to the present invention, the following effects can be obtained.

  That is, according to this invention, since the ground located in the underground end of a pile is pressed by applying a loading load to a pile from a perpendicular direction, the front-end | tip support force of a pile increases. And while carrying out the operation | work which increases such a tip support force and the operation | work which measures a tip support force simultaneously, the loading load is added to the pile until it becomes the target tip support force. This makes it possible to obtain the necessary tip support force without digging a hole for embedding piles to the ground with a large N value, and the tip support force is measured simultaneously with the pile driving operation. Therefore, a safer pile can be provided.

  Further, according to the present invention, since it is not necessary to excavate to a strong deep ground having a large N value, it is possible to suppress the excavation cost and the disposal cost of earth and sand and mud accompanying the excavation.

  Furthermore, according to the present invention, since the depth of the hole for installing the pile may be shallow, the length of the pile inserted into the hole can be shortened, and the cost of the pile itself and the handling cost of the pile can be suppressed. Is possible.

  Prior to execution of the loading / measurement process, a shock-absorbing sound when the loaded item falls on the spring hammer is laid on the falling part of the loaded item on the spring hammer by laying a cushioning material to alleviate the drop impact caused by the loaded item. Since the vibration can be greatly reduced and the vibration applied to the surrounding ground can be kept to a minimum, the work restrictions associated with noise and vibration are eased.

  Using a pile with a steel plate that envelops the cross-section of the pile body at one end of the H-shaped steel pile body, in the pile insertion process, the pile is made into a hole so that the end to which the steel plate is attached becomes the underground end By inserting, the pile tip area, which is one element that determines the tip support force of the pile, is expanded, so that a larger tip support force can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described more specifically with reference to the drawings. Here, in the accompanying drawings, the same reference numerals are given to the same members, and duplicate descriptions are omitted. In addition, since description here is the best form by which this invention is implemented, this invention is not limited to the said form.

  FIG. 1 is a perspective view showing a pile used in a pile driving method according to an embodiment of the present invention, FIG. 2 is a schematic view showing a pile driving device for building the pile of FIG. 1, and FIG. 4 is a side view showing a spring hammer attached to a pile driving device, FIG. 4 is a sectional view showing the internal structure of a part of the spring hammer shown in FIG. 3, and FIG. 5 is a pile according to an embodiment of the present invention. FIG. 6 is an explanatory view showing the pile driving process by the pile driving method according to one embodiment of the present invention in order.

  As shown in FIG. 1, a pile 10 used in the pile driving method of the present embodiment is attached to a pile body 10a made of H-shaped steel having a radial cross section of H shape, and one end of the pile body 10a. The steel plate 10b enveloping the cross section of the pile body 10a.

  The pile body 10a has two long plate-like flanges 10a-1 and 10a-1 arranged in parallel to each other, and the long side portion is 90 at the center in the longitudinal direction of the flanges 10a-1 and 10a-1. And a long plate-like web 10a-2 that connects the two flanges 10a-1 and 10a-1 and is connected with an angle of °. Moreover, the steel plate 10b has a disk shape, and through holes 10b-1 are drilled at two locations across the web 10a-2. In FIG. 1, one through hole 10b-1 is not shown because it is hidden by the web 10a-2.

  In this Embodiment, the pile 10 which has the above structure is inserted in a hole so that the edge part to which the steel plate 10b was attached may become an underground end. Details will be described later.

  Here, in this Embodiment, although the steel plate 10b is disk shape, as long as the cross section of the pile main body 10a is enveloped, it can be set as various shapes. Further, the through hole 10b-1 of the steel plate 10b may not be provided. Further, the steel plate 10b itself is not essential, and may be an H-shaped steel to which the steel plate 10b is not attached. Further, the pile is not limited to the H-shaped steel, and various shapes such as a steel material having a cross-sectional shape other than the H shape such as an L-shaped steel, or a steel pipe can be applied.

  Now, as shown in FIG. 2, the lifting machine 20 which is a pile driving device for building the pile of FIG. 1 has a driver seat 21b on the chassis 21a and has a function as an automobile. It has a main body 21 that allows itself to run. At the four corners of the main body 21, the outriggers 22, in which the rods 22 a can be expanded and contracted downward, are attached to be extendable in the lateral direction. During operation, the rod 22a is extended to float the tire 21c from the ground, and the body portion 21 is supported by the four rods 22a, thereby stabilizing the posture of the body portion 21.

  On the chassis 21a, a crane 23 that can be tilted and fixed at an arbitrary angle is provided. And from the upper end of this crane 23, the leader 24 is drooped and attached so that rotation is possible.

  The guide 24 is provided with guide rails 24 a and 24 b over the entire height of the reader 24 at positions opposed to each other in the radial direction. An auger (aperture means) 25 having an auger screw 25a is assembled to one guide rail 24a via a base 29 so as to be movable up and down. Then, an auger suspension wire (not shown) fed from a winch (not shown) installed inside the main body 21 is hung on a wire sheep 28 provided at the upper end of the reader 24 and extended downward. The auger 25 is supported at the end in the vertical direction.

  An auger motor 29a with a speed reducer is incorporated in the base 29, and the auger 25 described above is connected to the output shaft thereof. Inside the auger 25, a cement milk feeding path (not shown) for feeding cement milk as a hardener is formed along the axial direction. The upper end of the cement milk feeding path is connected to a pressure feeding hose extending from the cement milk feeding device via a hose joint (both not shown). Further, the lower end of the cement milk feeding path is a discharge port through which cement milk (hardening material) is discharged. When excavation is completed and the auger 25 is lifted from the hole, the cement milk is simultaneously discharged from the discharge port. The hole wall is prevented from collapsing by filling the hole into the hole.

  On the other guide rail 24b, a spring hammer 26 is mounted on the lower side, and a monken (loading) 27 for hitting the spring hammer 26 is mounted on-site during work.

  As shown in FIGS. 3 and 4, the spring hammer 26 includes a lower casing 26b having a cylindrical lower protective cover 26a opened upward, and a lower protective cover 26a opened downward. And an upper casing 26d provided with a cylindrical upper protective cover 26c that fits with a gap. In the internal space constituted by the lower protective cover 26a and the upper protective cover 26c, for example, seven springs 26f that absorb impact when the monken 27 is hit, which will be described later, have an upper end at the upper casing 26d and a lower end. Are fixed to the lower casing 26b. Note that a damper that attenuates the operation of the spring 26f may be further provided in the internal space.

  A rail cover 26e that is fitted to the guide rail 24b so as to be movable up and down is fixed to the side of the lower housing 26b. Further, below the lower housing 26b, a load cell 30 for measuring the load on the pile head at the time of hitting the monken 27 is disposed on the pile 10 coaxially with the protective covers 26a and 26c.

  A suspension hook 26g is fixed to the upper casing 26d. At the time of work, the tip of a wire (not shown) is hooked on the suspension hook 26g, the spring hammer 26 is lifted by the crane 23, and this is placed on the target pile 10.

  Further, a cushioning material 31 made of, for example, natural rubber is placed on the upper surface of the upper housing 26d at a location where the monken 27 is dropped. The material of the buffer material 31 is not limited to natural rubber, and various materials can be used as long as they can alleviate the drop impact of the monken 27. In the present invention, the mounting of the cushioning material 31 may be omitted.

  As described above, the monken 27 is fitted on the guide rail 24b so as to be movable up and down (free fall) so as to be positioned above the spring hammer 26. The monken 27 is also hooked on a wire (not shown) and lifted up to a predetermined height (for example, a height of 2 m from the cushioning material 31) by the crane 23, and placed on the target pile 10. Drop on the spring hammer 26.

  Thus, in this Embodiment, the spring hammer 26 is installed in the ground end of the pile 10 inserted in the hole, the monken 27 is dropped on the spring hammer 26, and a load is applied to the pile 10, and the tip of the pile 10 is The supporting force is measured. Next, a measuring device 40 that measures the tip supporting force of the pile 10 will be described with reference to FIG.

  Here, as a method of measuring the tip supporting force of the pile 10, there are a static loading method, an impact loading method, and a rapid loading method. The static loading method in which the pile 10 is pressed with a predetermined force takes a long time to obtain the measurement result because the measurement time is long (30 minutes to 2 hours are a plurality of cycles). Moreover, although the impact loading method in which the loading load is directly applied to the pile 10 requires a short analysis time (5 msec), it requires a high level of analysis based on the wave theory, so it still takes time to obtain the measurement result.

  Stanamic, one of the rapid loading methods, burns jet fuel for a short time and dynamically loads the pile using the acceleration of the weight as a reaction force. The measurement time is short (100 msec) and the analysis time is also short. Because it is short (several minutes), measurement results can be obtained immediately. However, the cost for applying a load to the pile is high (million yen per time). Therefore, if the load is applied to the pile a plurality of times, the cost is extremely high and the economic efficiency is deteriorated.

  On the other hand, in the rapid loading method of the present application in which the monken 27 is dropped onto the spring hammer 26, the loading by dropping the monken 27 while maintaining the advantages of stanamic (the advantage of short measurement time and analysis time) as it is. Therefore, the tip support force can be measured at a very low cost (in the present inventor's estimation, tens of thousands to hundreds of thousands of yen per time).

  Now, in FIG. 5, the measuring device 40 includes a load cell 30 that measures the load on the pile head as described above, and an accelerometer 32 that is attached to the pile 10 and measures the acceleration of the pile 10 when hitting the monken 27. Also, a strain gauge 33 that is attached to the pile 10 and measures the degree of distortion of the pile 10 when hitting the monken 27, a displacement meter 34 that optically measures the amount of displacement of the pile 10 when hitting the monken 27, a load cell 30, Measurement values of the accelerometer 32, the strain gauge 33, and the displacement gauge 34 are input via the interface 35, and the computer device 36 calculates the tip support force of the pile 10 based on these measurement values.

  Note that the tip bearing force of the pile 10 can be calculated by obtaining a static load-pile settlement relationship by an established method such as a nonlinear damping method (corrected unloading point method).

  Next, the pile driving method in this Embodiment is demonstrated using FIG. The construction method of the present application is an auger preceding cement milk consolidation method in which the pile 10 is inserted into the hole 50 after the cement milk 51 is injected after the hole 50 is excavated in the ground with the auger 25. The pile 10 to be built becomes an embedded pile.

  First, as a drilling step, the ground 50 is excavated to a predetermined depth with the auger 25 to form a hole 50 for installing the pile 10 (FIG. 6A). At this time, depending on the rock quality, it is better to excavate while applying moderate blow or air.

  Next, as an injection process, cement milk 51 is poured into the excavated hole 50 (FIG. 6B). That is, when the excavation is finished and the auger 25 is pulled up from the hole 50, the cement milk 51 is filled into the hole from the discharge port at the tip of the auger 25. Thereby, the collapse of the hole wall is prevented, and the entire excavated hole 50 is filled with the cement milk 51. In the case of soil that does not stand by itself, the cement milk 51 can be injected while excavating with the auger 25.

  Next, as a pile insertion step, the auger 25 is removed from the hole position, and the pile 10 is inserted into the hole 50 into which the cement milk 51 has been poured (FIG. 6C). Here, in this Embodiment, since the pile 10 provided with the steel plate 10b which encloses the cross section of the pile main body 10a at the one end of the pile main body 10a of H-section steel is used as mentioned above, this pile insertion process Then, the pile 10 is inserted into the hole 50 so that the end to which the steel plate 10b is attached becomes the underground end.

  Subsequently, as an installation step, the leader 24 is rotated 180 °, and the spring hammer 26 is installed on the ground end of the pile 10 as described above (FIG. 6D). At this time, the load cell 30 is disposed between the pile 10 and the spring hammer 26, and the accelerometer 32 and the strain gauge 33 are attached to the pile 10. Further, the displacement meter 34 is set at a predetermined position.

  Then, as a loading / measuring step, when the injected cement milk 51 is in a fluid state (that is, before it has hardened), the loaded monken 27 is dropped from a predetermined height onto the spring hammer 26. A loading load is applied to the pile 10, and at the same time, the tip support force of the pile 10 is measured by a measuring device (see FIG. 5) (FIG. 6E). Note that, as described above, in the rapid loading method of the present application in which the monken 27 is dropped onto the spring hammer 26, since the measurement required time and the analysis time are short, the tip support force as a measurement result can be obtained immediately on site.

  Prior to the execution of the loading / measuring process, it is desirable to lay a shock absorbing material 31 for mitigating the drop impact of the monken 27 on the falling part of the monken 27 in the spring hammer 26 so as to absorb the sound and vibration. .

  When the tip support force of the pile 10 is measured in the loading / measurement step, the loading / measurement step is repeatedly executed until the measured tip support force of the pile 10 reaches the target tip support force.

  That is, when a loading load is applied to the pile from the vertical direction by the monken 27, the ground located at the underground end of the pile 10 is pressed and the target tip support force is obtained. And the value of the front-end | tip support force of the pile 10 when it hit | damages with the monken 27 is obtained immediately in a work site.

  Therefore, a load can be applied to the pile 10 until the target tip support force is achieved while simultaneously performing the operation of increasing the tip support force of the pile 10 and the operation of measuring the tip support force of the pile 10. Thereby, in the embedded pile by the auger preceding cement milk consolidation method, it is possible to obtain the necessary tip support force without excavating the hole 50 for laying the pile 10 to the ground having a large N value.

  In addition, according to verification of this inventor, the target tip support force was able to be obtained by using the pile driving method of this application in the sand ground whose N value is about 10-20. And when the support force coefficient was calculated | required from the obtained front-end | tip support force, it was about 300. By this, by applying this method of construction, it was possible to confirm the tip support force of the same level as the driven pile, although it was an embedded pile.

  And since it is not necessary to excavate with the auger 25 to the strong deep ground where N value is large in this way, it becomes possible to suppress the excavation cost and the processing cost of earth and sand and mud accompanying the excavation.

  Furthermore, since the depth of the hole 50 for embedding the pile 10 may be shallow, the length of the pile 10 inserted into the hole 50 can be shortened, and the cost of the pile itself and the handling cost of the pile can be suppressed. become.

  In addition, if the buffer material 31 is laid in the fall part of the monken 27 in the spring hammer 26 prior to the execution of the loading / measurement process as in the present embodiment, the batting when the monken 27 falls on the spring hammer 26. The sound is greatly reduced, and the vibration applied to the surrounding ground can be kept to a minimum, so that work restrictions associated with noise and vibration are eased. At this time, if the buffer material 31 is thin, noise and vibration increase, but a large load is applied to the spring hammer 26, so the measurable range of the tip support force is expanded. It is better to set as appropriate according to the working environment.

  Furthermore, like this Embodiment, the steel plate 10b was attached by the pile insertion process using the pile 10 provided with the steel plate 10b which encloses the cross section of the pile main body 10a at one end of the pile main body 10a of H-shaped steel. If the pile 10 is inserted into the hole 50 so that the end portion is an underground end, the pile tip area, which is one element that determines the tip support force of the pile 10, is expanded. It becomes possible to obtain.

  Since the steel plate 10b has a through hole 10b-1, the cement milk 51 flows upward from the through hole 10b-1 when the pile 10 is inserted into the hole 50 into which the cement milk 51 is injected. It will be. Thereby, the bottom surface of the hole 50 can be directly supported by the steel plate 10b.

  The pile driving method of the present invention is not limited to the auger preceding cement milk rooting method, but can be widely applied to all embedded piles.

  That is, when a hardener such as cement milk is not used, the pile driving method of the present invention includes a step of drilling the ground to a predetermined depth with a hole drilling means such as an auger (hole drilling step) , A step of inserting a pile into the excavated hole (pile insertion step), a step of installing a spring hammer on the ground end of the pile (installation step), and dropping a load such as monken from a predetermined height onto the spring hammer The process of measuring the tip support force of this pile at the same time (loading / measuring process) at the same time as applying a load to the pile, and loading and measuring until the measured tip support force of the pile reaches the target tip support force The measurement process is repeated.

It is a perspective view which shows the pile used with the pile driving method which is one embodiment of this invention. It is the schematic which shows the pile driving device for building the pile of FIG. It is a side view which shows the spring hammer attached to the pile driving device of FIG. It is sectional drawing which fractures | ruptures a part of spring hammer of FIG. 3, and shows the internal structure. It is explanatory drawing which shows the measuring device which measures the front-end | tip supporting force of the pile in the pile driving method which is one embodiment of this invention. It is explanatory drawing which shows the process of the pile driving | operation by the pile driving method which is one embodiment of this invention later on.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pile 10a Pile main body 10a-1 Flange 10a-2 Web 10b Steel plate 10b-1 Through hole 20 Lifter 21 Main body 21a Chassis 21b Driver's seat 21c Tire 22 Outrigger 22a Rod 23 Crane 24 Leader 24a, 24b Guide rail 25 Auger Hole means)
25a auger screw 26 spring hammer 26a lower protective cover 26b lower casing 26c upper protective cover 26d upper casing 26e rail cover 26f spring 26g hook 27 monken (loading)
28 Wire Sheep 29 Base 29a Auger Motor 30 Load Cell 31 Buffer Material 32 Accelerometer 33 Gauge 34 Displacement Meter 35 Interface 36 Computer Device 40 Measuring Device 50 Hole 51 Cement Milk (Hardening Material)

Claims (4)

A drilling step of drilling the ground to a predetermined depth with a drilling means to form a hole;
A pile insertion step of inserting a pile into the hole;
An installation step of installing a spring hammer on the ground end of the pile;
A loading / measuring step of dropping a loaded load from a predetermined height onto the spring hammer and applying a loading load to the pile and simultaneously measuring a tip supporting force of the pile;
Repeatedly performing the load / measurement process described above until the measured tip support force of the pile reaches the target tip support force,
A pile driving method characterized by that. A drilling step of drilling the ground to a predetermined depth with a drilling means to form a hole;
An injection step of pouring a curing material into the holes;
A pile insertion step of inserting a pile into the hole into which the hardener has been poured;
An installation step of installing a spring hammer on the ground end of the pile;
A loading / measuring step of measuring the tip supporting force of the pile at the same time as applying a loading load to the pile by dropping the loaded load onto the spring hammer from a predetermined height when the hardened material is in a fluid state And
Repeatedly performing the load / measurement process described above until the measured tip support force of the pile reaches the target tip support force,
A pile driving method characterized by that. Prior to the execution of the load / measurement step described above, a cushioning material for mitigating a drop impact caused by the load is laid on the falling portion of the load described above in the spring hammer.
The pile driving method according to claim 1 or 2, characterized in that. The pile includes a pile body made of H-shaped steel, and a steel plate that is attached to one end of the pile body and envelops a cross section of the pile body,
In the pile insertion step, the pile is inserted into the hole so that the end to which the steel plate is attached becomes an underground end,
The pile driving method as described in any one of Claims 1-3 characterized by the above-mentioned.

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