JP4974364B2 - Pile burying method - Google Patents

Description

  The present invention relates to a method of burying an existing pile, and more particularly to a method of burying an existing pile without discharging excavated residual soil to the ground during pile construction.

  One approach to environmental problems in construction is to reduce industrial waste generated during construction and dismantling. Although there are a wide range of targets for industrial waste reduction, disposal of excavated soil generated during pile construction has been cited as one of them in the field of building foundation structures, which has become a major social issue.

  The piles currently in use are mainly (1) ready-made concrete piles, (2) cast-in-place concrete piles, and (3) steel pipe piles for economic reasons (1) ready-made concrete piles and (2) cast-in-place piles. The construction results of have increased. For the piles of (1) and (2) above, the mainstream of the construction method is a method of excavating the ground beforehand and installing the pile material in it, and a large amount of excavated residual soil is generated with the construction. Yes.

  In addition to the above social demands for environmental problems in recent years, it is expected that costs related to industrial waste disposal will increase due to a decrease in industrial waste disposal sites. Development of pile embedding methods that reduce or eliminate excavated soil is becoming active.

The following methods have been developed to reduce excavated soil until now.
(a) Driving pile method for driving ready-made concrete piles and steel pipe piles
(b) Consolidation digging method
(c) Steel pipe pile method with tip blade
(d) Ready-made concrete pile method with tip blade
(e) Double auger Nakabori pile method The pile pile method (a) above is a method of construction by driving or pressing the pile material into the ground using a hammer or the like, but there are noise and vibration problems. Since the construction area is limited, it cannot be expected much in the future as a method for reducing or eliminating excavated soil.

Regarding the consolidation tip digging method (b) above, JP-A-07-293850 discloses:
“Auger head equipped with a conical surface expanding upward and a spiral surface having a crust edge at the periphery is attached to the lower end of a vertical straight cylindrical casing, and on the outer peripheral surface near the lower end of the casing. A compaction shoe having a diameter larger than the outer diameter of the pressure edge is fixed, and a vertical protrusion is fixed to an outer peripheral surface other than the lower end portion of the casing, and a rotational force is applied to the upper end portion of the casing. The auger head is screwed into the ground while applying the pressure, and the inner peripheral surface of the hole that the auger head expands into the soil is further expanded while being consolidated with the above-mentioned compaction shoe to form a cylindrical consolidated soil wall And supplying rotational energy to the auger head and the compaction shoe while reducing the rotational friction by sliding the top surface of the protrusion provided on the casing along the inner peripheral surface of the compacted soil wall. To form a hole with a vertical cylindrical surface in the soil Together, characterized in that to prevent the collapse of the bore inner surface by the compaction soil walls, no dumping method of constructing foundation piles. (Claim 6),
Is disclosed.
However, this construction method allows the device to penetrate while consolidating the excavated soil without discharging the excavated soil, so the ground reaction force acting on the compaction shoe and the frictional force acting on the peripheral surface of the casing during rotation are large, and the casing rotates. An excessive load is applied to the driving device.
For this reason, the ground conditions to which this method can be applied are limited to soft ground, and are not versatile.
JP 07-293850 A

In the steel pipe pile method with tip blades of (c) above, the lower pile steel pipe with a spiral steel blade welded to the tip of the steel pipe is rotated by a full swirler or the like, and the wedge effect of the tip blades is used to achieve a predetermined depth in the ground. This is a method of repeatedly installing the upper pile steel pipe that does not have blades at its upper end, welded and connected, and then repeatedly press-fitted.
Apart from this, JP-A-9-49229 discloses:
It is divided into a hollow cylindrical part in the section from the upper end to the axial middle part and a tip part of the section from the intermediate part to the lower end, the cylindrical part is a steel pipe, and a hollow in which a spiral protrusion is formed on the outer periphery The pile with a vertical shape whose outer diameter decreases from the cylindrical part side to the tip is rotated in the direction in which the spiral ridges advance during press-fitting, and the soil around the tip part is removed. There is disclosed a steel pipe pile method with a spiral ridge that is installed directly in the ground or by being pressed into the surrounding ground while being press-fitted by a digging method or a digging method.
These steel pipe pile methods with blades at the tip and the steel pipe pile method with spiral ridges are construction methods that are widely applicable from large foundations of heavy structures to relatively lightweight foundations such as houses. Because it is buried and not used repeatedly, it is not possible to equip a steel pipe pile tip with an expensive excavation head, and even if an auger with an auger head that excavates the ground is used, until a predetermined support layer is reached When there is a solid stratum called an intermediate layer, it is often difficult to work to penetrate the intermediate layer, and since it is a steel pipe pile, the frictional force on the peripheral surface of the pile is reduced and the material cost is reduced. However, it is not expensive enough to be used except for residential use.
Moreover, the ready-made concrete pile method with a tip blade of the above (d) is a method of attaching a steel blade to the tip of a ready-made concrete pile, similarly to the steel pipe pile method with a tip blade of the above (c). Similarly, there are problems such as limited ground conditions for construction and material costs of blades, and there are few construction results (Patent Documents 3 and 4).
JP 9-49229 A JP 2001-248157 A JP 2002-081059 A

The double auger Nakabori pile construction method of (e) above is disclosed in JP 2005-248439 A,
“A casing and an auger with a drilling head attached to the tip and a tapered shape at the tip are inserted and placed at the inside of the casing at the point where the pile is buried. Start up separately and proceed with excavation while rotating in opposite directions, and temporarily lift and leave a part of the excavated earth and sand, and after excavating to a predetermined depth, lift the auger to the ground. The pile is built, the gap between the casing and the pile is filled with excavated earth and sand, then the casing is lifted to the ground, and the entire amount of earth and sand left on the ground is backfilled inside the cavity and the pile where the casing is lifted A method of burying piles without leaving soil on the ground. (Claim 1),
It is.
This method of burying piles can reduce the size of the pile driving machine and reduce the cost burden related to construction, such as using a small auger with a small capacity. However, it is necessary to discharge the sediment to the ground and leave it on the ground temporarily. In addition, after the casing is lifted, it is necessary to backfill the earth and sand into the donut-shaped hollow portion and the hollow portion of the existing pile, so that the work efficiency is not always good. Moreover, since the outer peripheral part of the pile is backfill excavated soil, its density is small. For this reason, since the pile peripheral surface frictional force is small, the vertical load supporting force of a big pile cannot be obtained.
JP 2005-248439 A

As described above, the existing construction methods have problems such as limited ground conditions, high costs, reduced support performance, vibration and noise, and have not yet been established as excavation residual soil reduction methods.
The present invention has been devised to solve these problems, and the pile reaches a predetermined support layer by using a special casing for a ready-made pile having a relatively low material cost. By making a solid stratum called an intermediate layer easily penetrated, the pile peripheral surface friction force is increased to increase the vertical load bearing capacity of the pile, and the pile material cost is reduced while the excavated residual soil is reduced or zero. It is an object of the present invention to provide a pile-free soil burying method that makes it possible to do so.

According to the first aspect of the present invention, a drilling head is mounted at the tip and a pre-made pile to be embedded and a peripheral ground having a volume corresponding to the volume of cement milk to be injected are laterally compacted and continuously tapered. The excavation is continued while rotating in the opposite direction each of a casing composed of a cylindrical portion and an auger disposed on the inside of the casing and having a drilling bit at the tip, and after the excavation to a predetermined depth, the auger Pull up to the ground, and at this time or after that, inject the cement milk into the sand in the casing and stir, lay the pile in the casing, then lift the casing to the ground, and bury the pile without soil It was decided.
In the invention according to claim 2, when the casing is pulled up to the ground, it is swung up and down to promote the downward movement of the soil cement between the casing and the peripheral wall of the pile.
In the invention according to claim 3, when the casing is pulled up to the ground, the soil cement moves downward between the casing and the peripheral wall of the pile through the hole for discharging the soil cement formed in the tapered portion of the casing. It was decided to promote.

According to the invention according to claim 1, since the surrounding ground having a volume corresponding to the volume of cement milk to be buried and the volume of cement milk to be injected is compacted to the side, the pile material cost is reduced. The pile peripheral surface friction force can be increased to increase the vertical load supporting force of the pile, and the remaining excavation soil can be reduced or reduced to zero.
Further, the excavation is carried out while rotating the casing with the excavation head attached to the tip and the auger disposed inside the casing and having the excavation bit at the tip in opposite directions, and excavating to a predetermined depth; Therefore, it is possible to easily penetrate a solid formation called an intermediate layer before reaching a predetermined support layer, and to construct a pile with high accuracy at low cost, canceling the reaction torque acting on the base machine and the leader. Can be operated smoothly.
According to the invention concerning Claim 2 and Claim 3, in addition to the effect of the invention concerning Claim 1, the soil cement between a casing and a pile surrounding wall can be smoothly guided below.

  The present invention requires at least filling by adding up the actual volume of the ready-made pile, that is, the volume excluding the volume of the hollow portion of the hollow ready-made pile to be placed and the volume of cement milk to be injected, by the tapered portion of the casing. The ready-made pile and the cement milk are filled into the space created by compacting and compacting the surrounding ground corresponding to the volume to the side, thereby burying the ready-made pile without soil.

The soil to be excavated varies widely depending on the region, and since it is clay or gravel, the mixing ratio of cement milk and soil to be injected must be adjusted appropriately according to this property There is.
On the other hand, the amount of excavated soil is determined by the excavation diameter of the excavation head attached to the tip of the casing, and the actual volume of the ready-made concrete pile is determined by the pile to be embedded.
For this reason, the internal diameter of the cylindrical part of a casing is changed according to the filling amount of cement milk.
As a result, the excavated soil can be embedded in a ready-made concrete pile without being discharged to the ground even temporarily.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a pile-free soil burying method according to the present invention will be described in detail based on the drawings.
There are ready-made concrete piles, shell steel pipe concrete piles, steel pipe piles, etc. as pre-built piles to be buried, but in this example, in consideration of economic efficiency, ease of construction with no soil, etc. A pile is used.
FIG. 1 schematically shows the construction procedure of the present invention. From the left, in order from the left, the excavation process for excavating to a predetermined depth while compacting the periphery of the ground to the side, mixing and stirring the cement milk and excavated soil 3 shows a mixing stirring step, a pile building step in which a pile is built in a slurry-like soil cement that has been mixed and stirred, and a casing drawing step in which the casing is pulled out.
FIG. 2 is an enlarged view of the excavation casing and the tip of the ready-made concrete pile.
In FIG. 1, only the excavation process is illustrated for the excavation head 3, and illustration is omitted in other processes.

  1 and 2, 1 is a casing for excavation, 2 is an auger, 3 is an excavating head, 4 is an excavating bit, 5 is an agitator, 6 is a hollow ready-made concrete pile, 7 is a double auger equipped with an internal and external propulsion mechanism An internal propulsion mechanism of the excavator, 8 is a tapered portion of the excavating casing 1, 9 is a closing plate, and 10 is a support layer.

A method for burying a ready-made concrete pile in the ground reaching the support layer by placing a ready-made concrete pile having a length of 10 m using this excavator will be described as an example.
Since the ready-made concrete pile 6 reduces the degree of compaction of surrounding soil and saves the driving energy of the casing 1 for excavation, it is desirable to use a ready-made pile as hollow as possible in order to reduce the volume.
Thus, the hollow ready-made concrete pile 6 has a length of 10 m, an outer diameter of 500 mm, and a wall thickness of 80 mm in consideration of the structure load and the conditions of the ground where the pile is placed.

The excavating casing 1 is a cylindrical steel pipe having a wall thickness of 20 mm, and the tip portion is formed as a tapered portion 8 with a reduced diameter toward the tip in order to consolidate the surrounding ground to the side, and the angle is a load on the excavator. It is determined in consideration of smooth excavation and efficient ground consolidation.
In this embodiment, it is inclined about 20 degrees with respect to the axis of the excavating casing 1.
3 is an excavation head. The height h is 200 mm, and the thickness is greater than the wall thickness 20 mm of the excavation casing 1 body. The excavation head 3 is arranged to excavate the ground in cooperation with an auger excavation bit, which will be described later, when it rotates counterclockwise.

Although not shown in the drawings, the taper portion 8 is formed with a discharge hole for discharging a soil cement, which will be described later, from the inside of the excavation casing 1 downward in the circumferential direction. During the excavation, the excavation casing 1 is propelled while rotating into the ground. Therefore, the excavation soil enters the excavation casing 1 from the discharge port in the initial stage. It gradually stops entering due to earth pressure.
The formation of the discharge port is effective for discharging the soil cement downward from the inside of the excavation casing 1 when the excavation casing 1 is pulled out.
What is indicated by a broken line 9 in FIG. 2 shows a closing plate for closing the discharge hole and preventing the excavated soil from entering the excavating casing 1 during excavation.
The closing plate 9 has an upper end pivotally attached to the casing 1 body, and is closed by earth pressure from below during excavation, and is opened when the excavation casing 1 is pulled up. .

The excavation diameter of the excavation casing 1, that is, the inner diameter d ₂ of the excavation head 3, allows the soil cement described later to pass through between the inner peripheral surface of the excavation head 3 and the outer peripheral surface of the hollow ready-made concrete pile 6 when the casing 1 is pulled up. Te, to smoothly discharged from the interior of the drilling casing 1 downward, it is desirable to set 100mm about than the outer diameter d ₁ of the hollow pre-cast concrete pile 6 large. For this reason, in this embodiment, it is set larger by 130 mm.
The casing 1 for excavation of this invention forms the taper part 8 following the cylindrical excavation head 3, and the cylindrical steel pipe is connected to this.
When drilling casing 1 having the structure is excavation is pressed into the ground, a cylindrical inner diameter d ₂ of the diameter of the drilling head _3, the columnar body height is 10m of excavated soil is the drilling casing 1 while being taken, the surrounding ground located outside the drilling head 3 is guided outward along the tapered portion 8, and be compacted to a casing outer wall position of the inner diameter d _3.
As a result, a space not occupied by the excavated soil is created in the excavating casing 1. This space is effectively used to embed the hollow ready-made concrete pile 6 and cement milk in the casing 1 in a state of non-draining soil that does not discharge excavated soil to the ground surface.

Here, the capacity of the space to be newly created in the present invention will be described.
As a result of conducting a soil survey in advance at the construction site, the soil is a loam layer over a depth of 0.4 to 5.0 m from the ground surface, a shirasu layer at a depth deeper than 5.0 m, and an N value of 13 m. It was found to be over 30 in depth. Based on the results of this survey, the following matters were determined.
1. Pile to be buried Pile diameter 500mm, wall thickness 80mm, length 10m
2, Excavation diameter Pile diameter + 130mm 630mm
3. Capacity of excavated soil to be accommodated in the casing (expected to increase 10% of the actual excavated soil)
3.43 m ³
4. Capacity of cement milk to be injected (W / C = 60%)
0.49 m ³ (volume ratio of excavated soil: cement milk = 7: 1)
5. Actual capacity of hollow ready-made concrete piles
1.06m ³
6. Space capacity to be newly created (4 + 5 above)
1.55m ³
7. Total capacity of 3 and 6 above
4.98m ³

Among the casings for excavation that are planned, the smallest one that can accommodate the total capacity of 4.98 m ³ is an inner diameter of 800 mm and a capacity of 5.02 m ³ .
Therefore, the thing of this size is selected as the casing 1 for excavation actually used.
As explained above, the drilling diameter d ₂ of the casing by embedded the pile diameter is cylindrical inner diameter d ₃ of the casing is determined by the injection volume of the actual volume and cement milk pile to be embedded.
Accordingly, as a form of specifically implementing the present invention, a plurality of types in 100mm units outside diameter d ₁ of the pile, drilling diameter d ₂ of the casing corresponding to Kakusoto径d _1, corresponding to each drilling diameter d ₂ A plurality of types of casing cylindrical inner diameters d ₃ may be prepared, for example, d ₃ = 800 mm and d ₃ = 900 mm corresponding to a plurality of types, for example, d ₂ = 630 mm.
Thus, when d ₃ is changed with respect to the same d ₂ , the space capacity of the selected casing is remarkably large with respect to the total capacity of the above 7, and a gap can be formed between the hollow ready-made concrete pile and the ground soil. is there. In such a case, the hollow ready-made concrete pile tip is closed and the excavated soil or the like is not filled in the hollow portion, or soil generated in other construction work in the field is used.

In FIG. 1, 2 is an auger which has the excavation bit 4 in the front-end | tip.
The upper end of the rotating shaft of the auger 2 and the upper end of the excavating casing 1 are rotated in opposite directions by rotating the auger rotating shaft forward and rotating the casing backward in a double auger type excavator equipped with an independent propulsion mechanism. The excavation head 3 of the excavation casing 1 and the excavation bit 4 at the tip of the auger 2 cooperate to reliably excavate a solid ground such as intermediate gravel ground. .
The auger 2 has a spiral blade fixed to the rotating shaft in a right-handed direction, and the upper end of the spiral blade is set at a position lower than the upper end of the excavating casing 1. With this configuration, the excavated soil moves upward in the excavation casing 1 by the spiral blades, but remains in the excavation casing 1 and is not discharged to the outside and left on the ground.
The excavation casing 1 with the excavation head 3 attached to the tip and the auger 2 disposed inside the casing 1 and having the excavation bit 4 at the tip are advanced in excavation while rotating in the opposite directions. Since the excavation is performed to a depth, it is possible to construct a pile with high vertical accuracy, and to cancel the reaction torque acting on the base machine and the leader and to make the operation smooth.

This excavator incorporates a swivel mechanism (not shown).
When excavated to a predetermined depth, as shown in FIG. 1, the swivel mechanism is driven to reverse the auger 2 so that the excavated soil is not discharged from the upper end of the excavating casing 1, and the swivel mechanism is driven from the tip of the rotating shaft. Pull out the auger 2 while discharging cement milk.
Next, the stirring device 5 in which the stirring blade pieces are spirally planted on the rotating shaft is inserted while rotating up and down to mix the excavated soil in the excavating casing 1 and the injected cement milk.・ Stir.
The blending of the cement milk is determined according to the ground conditions and design conditions as described above.
Thus, by mixing and stirring the excavated soil and cement milk in the casing 1, a highly reliable soil cement can be constructed adjacent to the inner and outer walls of the hollow ready-made concrete pile 6 to be press-fitted thereafter. .
And since a high intensity | strength area | region can be largely formed compared with the above-mentioned conventional construction method in the pile surrounding surface ground compared with the above-mentioned conventional method, a big friction support force can be obtained in a pile surrounding surface.
In this embodiment, the auger 2 and the stirring device 5 are configured separately, but if the upper half of the spiral blade of the auger 2 shown in FIG. The excavation and mixing / stirring can be performed in the same apparatus without exchanging both apparatuses.

At the stage where the mixing and stirring of the excavated soil and cement milk is completed, the stirring device 5 is pulled up, and the hollow ready-made concrete pile 6 is coupled to the inner propulsion mechanism 7 of the double auger excavator having the upper and lower independent propulsion mechanisms. Then, it is press-fitted into a slurry soil cement and built.
At this time, the soil cement is also filled into the hollow ready-made concrete pile 6.

After building the hollow ready-made concrete pile 6, the casing 1 for excavation is pulled up.
At this time, the excavating casing 1 is swung up and down while rotating in the right direction so that the soil cement can easily slip through between the inner peripheral surface of the excavating head 3 and the outer peripheral surface of the hollow ready-made concrete pile 6. It is preferable to discharge smoothly from the inside of the casing 1 downward.
After pulling out the casing, check the vertical and horizontal position of the pile. If the pile is displaced from the specified position, readjust the pile head.
At this stage, since the soil cement located inside and outside the hollow ready-made concrete pile 6 is in a slurry state, a part of the cement milk penetrates into the surrounding ground.
As a result, the cement milk is subsequently solidified at the outer periphery of the hollow ready-made concrete pile to become concrete, and the surface thereof is systematically integrated with the surrounding ground.

As described above, the pile-free soil burying method of the present invention is such that the surrounding ground having a volume corresponding to the volume of the ready-made concrete pile to be embedded and the cement milk to be injected is laterally tightened by the tapered portion 8 of the excavating casing 1. Once consolidated and consolidated, the cement milk is then solidified at the outer periphery of the buried hollow ready-made concrete pile to become concrete, and the pile peripheral surface friction force can be increased to increase the vertical load bearing capacity of the pile.
In addition, since excavation surplus soil is not discharged to the ground surface during excavation work, it is not only necessary to backfill excavation surplus soil in the ground, improving the efficiency of pile burial work, and reducing excavation residual soil Or since it becomes possible to make it zero, the generation of industrial waste itself can be eliminated.

The construction procedure of this invention is shown typically. It is an enlarged view of the front-end | tip part of a ready-made concrete pile.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing for excavation 2 Auger 3 Excavation head 4 Excavation bit 5 Stirrer 6 Hollow ready-made concrete pile 7 Inner propulsion mechanism of double auger excavator provided with internal and external independent propulsion mechanisms 8 Tapered portion of excavation casing 9 Closure plate 10 Support layer

Claims (3)

  A drilling head is attached to the tip, and it is composed of at least a prefabricated pile to be buried, a tapered portion that is compacted by compacting the surrounding ground with a volume equivalent to the volume of cement milk to be injected, and a cylindrical portion continuous to the taper portion. The casing and the auger disposed inside the casing and having an excavation bit at the tip of the casing are rotated in the opposite directions to proceed with excavation. After excavating to a predetermined depth, the auger is lifted to the ground. A method in which cement milk is poured and stirred into the earth and sand in the casing at or after that, a pile is built in the casing, and then the casing is pulled up to the ground, and the pile is buried without draining.   The pile according to claim 1, wherein when the casing is pulled up to the ground, the pile is swung up and down to promote the downward movement of the soil cement between the casing and the peripheral wall of the pile. A method of burying with soil removal.   When the casing is pulled up to the ground, the downward movement of the soil cement between the casing and the pile peripheral wall is promoted through the soil cement discharge hole formed in the tapered portion of the casing. A method for burying a pile according to any one of claims 1 to 2 without soil.

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