JP5867301B2 - Pipe pile and its construction method - Google Patents

Description

  The present invention relates to a pipe pile such as a steel pipe pile used in a civil engineering field such as a harbor structure, a bridge foundation and a building foundation, and a construction method thereof.

In recent years, piles used for harbor structures, bridge foundations, building foundations, etc. have a high tip support force and workability, as well as a large resistance to pulling when placed on the ground (hereinafter referred to as “pullout resistance”). )) Is required.
Conventionally, as a pile with increased pulling resistance, in a rotary press-fit pile having a pile support plate processed with a steel plate or the like having a spiral shape at the tip of the pile, the outer shape of the pile support plate is in contact with the outer periphery of the pile support plate. There is known a rotary press-fit pile characterized in that a support plate outer peripheral steel plate bent so as to match is provided so as to protrude in both the upper and lower directions of the pile support plate (for example, Patent Document 1).

However, such a rotary press-in pile has a pile support plate with a spiral shape, etc., so it is basically necessary to construct it by the rotary press-in method, and without applying rotational force such as striking method or vibration method. When applying the pile driving method to be constructed only by force, the pile support plate becomes resistance and cannot be easily placed on the ground.
Further, in the rotary press-fit pile, the problem is that the cost becomes high due to the processing cost of the pile support plate and the application of the rotary press-fit method.

  In addition, as another pile, a pulling resistance mechanism formed of a horizontal plate and a reinforcing plate is protruded at the lower end of the steel pile, and the lower part of the steel pile is placed on the filler placed in the expanded hole in the supporting ground. Also, a drawing resistance pile characterized by burying the drawing resistance mechanism is known (for example, Patent Document 2).

The pull-out resistance is to secure the pull-out resistance by integrating the pull-out resistance mechanism and the filler placed in the expanded bottom hole portion in the supporting ground by associating them.
However, the work of embedding steel piles and the work of filling fillers around steel piles are troublesome and are not economical. Moreover, in the pile shape as shown in FIG. 1 (B) of Patent Document 2, the driving pile method such as the hammering method or the vibration method causes a large resistance during construction, leading to an increase in construction cost.

  Furthermore, as a technique for increasing the pulling resistance, the inner and outer winding plates having the required thickness and width are respectively wound and fixed on the inner peripheral wall surface of the tip of the ready-made pile. The friction resistance reduction technology is also known. (For example, Patent Document 3)

In this technology, the frictional resistance of the stratum acting on the outer peripheral wall surface of the pile acts only on the outer winding plate, and the frictional resistance of the stratum acting on the inner peripheral surface of the pile acts only on the inner winding plate. Since it concentrates only on the front-end | tip part and hardly acts on other inner and outer wall surfaces, it can improve driving performance and can improve the workability to hard ground.
However, no particular consideration has been given to securing the pulling resistance of the piles, and it is considered difficult to secure the pulling resistance necessary for harbor structures, bridge foundations, building foundations, and the like.

  Further, a steel pipe pile including a straight straight portion having a cylindrical shape and a tapered portion that is continuous with one end of the straight portion and has an outer diameter and an inner diameter that taper in a direction away from the one end. There is also known a technique that enables an increase in the vertical resistance force (for example, Patent Document 4).

The steel pipe pile used in this technology can obtain a larger support force on the outer peripheral surface of the tapered portion whose outer diameter and inner diameter taper in the direction away from one end, and can reduce resistance during pile construction. Can be widely used in various construction methods.
However, in harbor structures, bridge foundations, building foundations, etc., it may be necessary to have a larger pulling resistance in addition to a large tip support force. Is not particularly taken into consideration, and in some cases, sufficient pulling resistance may not be obtained.

JP 2000-352047 A Japanese Patent Laid-Open No. 5-140930 JP-A-61-250223 Japanese Patent No. 4635114

  The problem to be solved by the present invention is that a pipe pile that can be constructed by various driving pile methods such as a hammering method and a vibration method without requiring an auxiliary method, and that can secure a high tip support force and a pulling resistance force, and this pipe pile Is to provide a construction method using

  In order to solve the above-mentioned problems, the present inventors have obtained the following technical knowledge as a result of various theoretical and experimental studies.

(A) By attaching a cylindrical cover part to the outer peripheral surface of the straight part on the pile tip side, the area of the pile tip part is widened, and a high tip support force can be secured compared to a normal pile without a cover part. .
Moreover, the high pulling-out resistance force by an anchor effect can be ensured by the said cover part.
Furthermore, by attaching the cover part to the pile body so that the axis thereof is collinear with the axis of the straight part, the entire pile has an axisymmetric shape. Eccentricity does not occur, and workability is improved.

(B) The said cover part shall have the taper surface which an outer peripheral surface side tapers gradually as it goes in the direction of the pile front end side, and the inner peripheral diameter on the pile head side becomes larger than the outer peripheral diameter of the said straight part. In the case of the structure formed as described above, the projected area in the horizontal direction is further expanded, and therefore a sufficiently large tip supporting force can be secured even with a small penetration length.

The present invention has been completed based on such technical knowledge, and the gist thereof is as follows.
That is, in order to solve the above-mentioned problem, the pipe pile of the present invention includes a straight portion formed in a straight cylindrical shape and a pile portion of the straight portion on an outer peripheral surface of an end portion of the straight portion on the pile front end side. A cylindrical cover portion functioning as a pulling resistance attached to cover the tip side, and the cover portion is at least an end on the pile head side of the ends of the pile head side and the pile tip side The inner peripheral diameter of the straight portion is formed larger than the outer peripheral diameter of the straight portion, the pile tip side of the straight portion is inserted on the inner peripheral surface side, and the axis thereof is collinear with the axis of the straight portion Attached to the straight portion, the cover portion has a tapered surface with an outer peripheral surface side gradually tapering in the direction of the pile tip side, and the cover portion has an inner peripheral diameter of the end portion on the pile tip side of the straight portion. Formed smaller than the outer diameter of the part And attached to the straight portion in a state where the inner peripheral surface of the pile tip side and the outer peripheral surface of the end portion of the straight portion on the pile tip side are in contact with each other, and each pile tip side of the straight portion and the cover portion An end portion of the cover portion is opened , and a plate-shaped closing member that closes the opening of the upper end portion of the cover portion is disposed on the upper end side of the cover portion .

In the present invention, the pipe pile can be placed on the ground by a hammering method in which the pipe pile is hammered and driven.
Moreover, the said pipe pile can be driven in the ground by the vibration construction method which gives a vibration to this pipe pile.
Alternatively, the pipe pile can be placed on the ground by a press-fitting method that applies a pushing force to the ground to the pipe pile.
Furthermore, the pipe pile can be driven by a medium excavation method in which the pipe pile is buried while excavating the ground with an excavation rod having an excavation head inserted into the space inside the straight portion.
In addition, when the pipe pile is driven using the hammering method, the vibration method, the press-fitting method, or the Nakabori method, the pipe pile is sprayed while water is sprayed to the outer peripheral surface of the straight part and the cover part. May be placed on the ground.

(A) According to the pipe pile according to the present invention, a cylindrical cover part functioning as a pulling resistance is provided on the outer peripheral surface of the straight part on the pile tip side, and at least a part of the inner peripheral surface of the cover part is a straight part. Since it is attached in a state of being in contact with the outer peripheral surface of the pile, the area of the pile tip portion is widened, and a high tip support force can be secured compared to a normal pile without a cover portion, and by the anchor effect by the cover portion High pulling resistance can be obtained.

(B) Moreover, since the pipe part which concerns on this invention is attached to this pile main body so that the axis line may be on the same straight line as the axis line of a straight part, the pipe pile concerning this invention becomes an axially symmetrical shape as the whole pile. The eccentricity does not occur when the axial force is transmitted during construction, and the workability is further improved.

(C) The cover portion has a tapered surface with the outer peripheral surface side gradually tapering in the direction of the pile tip side, and the inner peripheral diameter on the pile head side is larger than the outer peripheral diameter of the straight portion. In the case of the configuration, since the horizontal projected area is further expanded, a high circumferential frictional force suppressing effect is obtained at the time of construction, and the workability is further improved. Moreover, even if it has little penetration length, the tip supporting force equivalent to or more than a normal pile (straight pile which does not form a taper) can be exhibited. Furthermore, the pulling resistance is greatly improved by the anchor effect.

BRIEF DESCRIPTION OF THE DRAWINGS The 1st Embodiment of the pipe pile which concerns on this invention is shown typically, (a) A partially broken front view, (b) is a bottom view. It is the same perspective view. It is a perspective view showing typically the state where the closure member was provided in the pipe pile of a 1st embodiment of the present invention. In the pipe pile of the 1st Embodiment of this invention, it is a perspective view which shows typically the state which provided the rib. The 2nd embodiment of a pipe pile concerning the present invention is shown typically, (a) A partially broken front view, (b) is a bottom view. It is the same perspective view. A 3rd embodiment of a pipe pile concerning the present invention is shown typically, (a) A partial fracture front view, (b) is a bottom view. It is the same perspective view. In the pipe pile of the 2nd Embodiment of this invention, it is a perspective view which shows typically the state which provided the rib. In the pipe pile of the 2nd Embodiment of this invention, it is a perspective view which shows typically the state which provided the obstruction | occlusion member. It is a perspective view which shows typically the straight pile which does not have the cover part which concerns on this invention. It is explanatory drawing at the time of performing the calculation by the theoretical solution, when prescribe | regulating the outer periphery diameter and height of the upper end side of a cover part about the pipe pile in the 1st and 2nd embodiment which concerns on this invention. It is a graph which shows the experimental result in an Example.

Hereinafter, with reference to a figure, the pipe pile concerning the present invention is explained in detail.
FIG.1 and FIG.2 shows 1st Embodiment of the pipe pile which concerns on this invention, The pipe pile 1 of this embodiment is the straight part 2 formed in the cylinder shape extended linearly, The straight portion 2 includes a cover portion 3 attached to the outer peripheral surface of the end portion on the pile tip side.

The straight portion 2 is a long circular tube having a substantially circular cross section made of a material such as steel. In the case shown in FIGS. 1 and 2, the straight portion 2 extends in the vertical direction, the lower end side is the pile front end side, the upper end side has a pile head side, and has the same inner diameter and an outer diameter D ₁ respectively over the entire length of axial length.
Here, it is desirable that the straight portion 2 has a perfect circular cross section. By setting the cross-sectional shape to a perfect circle in this way, it is possible to prevent the eccentricity from occurring during the construction and the axial force transmission during service.

The cover part 3 functions as a pulling resistance of the pipe pile 1 and is formed of a material such as steel into a cylindrical shape having a substantially circular cross section whose inner and outer diameters do not change over the entire length in the axial direction. ing. And the edge part side of the pile front end side of the said straight part 2, ie, the lower end part side, is inserted in the inner peripheral surface 3a side, and the several rib mentioned later is in the state which covered the outer peripheral surface of the pile front end side of the straight part 2. It is attached to this straight part 2 via.
The cover portion 3 of this embodiment is formed so that the axial length is shorter than the straight portion 2 and the inner peripheral diameter is larger than the outer peripheral diameter D ₁ of the straight portion 2. . For this reason, the cover portion 3 protrudes outward from the outer peripheral surface of the straight portion 2 over the entire length in the axial direction, while between the inner peripheral surface 3a of the cover portion and the outer peripheral surface of the straight portion 2. Spaces are formed and are not in contact with each other.

Here, like the straight part 2, the cover 3 preferably has a perfect circular cross section in order to suppress eccentricity during construction and during axial force transmission during service.
In addition, the amount of overhang from the straight portion 2 of the cover portion 3 can be arbitrarily set depending on the construction location or the like, but basically, as the amount of overhang of the cover portion 3 is larger, the pulling resistance of the entire pipe pile is increased. Power increases.
Furthermore, the upper and lower end surfaces of the cover portion 3 are flat surfaces extending in a direction orthogonal to the axial direction of the cover portion 3, and the upper end side, that is, the end surface on the pile head side, has resistance to earth and sand in the tensile direction. Thus, it contributes to the improvement of the tensile resistance, and the lower end side, that is, the end face of the pile tip side enlarges the contact area with the surrounding earth and sand and contributes to the improvement of the tip support force.

Furthermore, the cover part 3 is attached to the straight portion 2 as its axis L ₂ is the axis line L ₁ of the straight portion 2 and on the same straight line.
Thus, the cover portion 3, by attaching to the axis L ₁ of the axis L ₂ and the straight portion 2 of the cover portion 3 is collinear, the symmetrical shape with the axis of the whole Kankui As a result, the entire pipe pile is less likely to be eccentric during construction and when transmitting axial force during service.

  In this embodiment, as shown in FIG. 1A, the mounting position of the straight portion 2 of the cover portion 3 is slightly different from the lower end portion of the straight portion 2 on the pile head side (upper end portion). The position is close to the side. Accordingly, the lower end surface of the cover portion 3 and the lower end surface of the straight portion 2 do not coincide with each other, and a part of the outer peripheral surface of the lower end portion of the straight portion 2 is exposed to the outside.

Further, the cover part 3 and the straight part 2 are connected to each other by the above-described plurality of ribs disposed in the space between the inner peripheral surface 3a of the cover part 3 and the outer peripheral surface of the straight part 2. Has been.
Each of these ribs is a plate-shaped member that is formed of a highly rigid material such as a steel plate and has substantially the same axial length as that of the cover portion 3, and has the same plate width. One end side of each rib in the plate width direction is fixed to the inner peripheral surface 3a of the cover portion 3, and the other end side is fixed to the outer peripheral surface of the straight portion 2 by various means such as welding. As a result, the cover portion 3 is held by these ribs in a state where the axis L2 thereof is always on the same straight line as the axis L1 of the straight portion 2.
In this embodiment, a total of four ribs are provided, and each rib is arranged at a position that forms an angle of 90 degrees around the axis of the pipe pile in plan view, as shown in FIG. 1 (b). It is installed. However, the number of ribs and the arrangement position in the space can be arbitrarily set.

When the pipe pile 1 having the above-described configuration is driven into the ground, it can be constructed using various known construction methods, such as hydraulic hammers, diesel hammers, and monkens that are commonly used in civil engineering work. It can be applied to a hammering method in which a pile is driven into the soil with a driving machine such as a machine.
Moreover, the vibration construction method which places this pipe pile 1 in the ground by the vibration by the vibro hammer with which the pile head of the pipe pile 1 was mounted | worn can be applied.
Furthermore, a nozzle capable of jetting high-pressure water is attached to the pile tip portion of the pipe pile 1, and the pile is driven to the support layer while water is sprayed from the nozzle in the driving direction to cut the ground. It can also be applied to the jet method.
Alternatively, it can also be applied to the water jet combined vibration method in which the pipe pile 1 is driven to the support layer by using the vibration by the vibratory hammer and the water jet from the nozzle (water jet). There is an advantage that noise and vibration due to placing can be reduced, and further, the amount of soil discharged can be suppressed.
Furthermore, if necessary, the peripheral surface portion of the pipe pile 1 can also be filled with a fluidized solidifying material such as cement milk to increase the peripheral frictional force of the pipe pile 1, thereby reducing the pulling resistance force. Further improvement can be achieved.

  Moreover, the press-fitting method which pushes this pipe pile 1 in a ground by giving the pushing force with respect to the ground with the static load by oil_pressure | hydraulic to the pipe pile 1 to be embed | buried using the drawing-out resistance of the existing pile can be used. In addition, the auger excavation with the auger excavation head at the tip and the simultaneous press-fitting method in which the auger excavation and the press-fitting of the pipe pile are performed simultaneously, or the auger excavation and the press-fitting of the pipe pile 1 after the advance excavation with the advance excavation head Various press-fitting methods such as the so-called simultaneous core press-fitting method for performing the above-mentioned can be applied. In the case of these press-fitting methods, the aforementioned water jet may be used in combination.

Furthermore, it is also possible to apply the intermediate excavation method in which the pipe pile 1 is buried while excavating with an excavation rod having an excavation head at the tip.
In this case, cutting using the above-described water jet can be used in combination, and the peripheral surface of the pipe pile 1 is filled with a fluidized solidifying material such as cement milk through the nozzle to solidify the root. May be.

  The pipe pile 1 can also be applied to a rotary press-fitting method using an all-around turning machine. In this case, the aforementioned water jet may be used in combination, and a drilling bit may be provided at the tip of the pipe pile 1.

In the pipe pile 1 having the above-described configuration, since the cylindrical cover portion 3 is attached to the outer peripheral surface of the lower end portion that is the end portion of the straight portion 2 on the pile tip side, the area of the tip portion of the pile is widened and high tip support is provided. Power can be secured.
Furthermore, since the said cover part 3 protrudes outward from the outer peripheral surface of the straight part 2, this cover part 3 exhibits the anchor effect with respect to the ground, and, thereby, high pulling-out resistance can be ensured as the whole pipe pile. .
In particular, in the case of the pipe pile of this embodiment, since the soil of the ground enters into the space formed between the inner peripheral surface 3a of the cover portion 3 and the outer peripheral surface of the straight portion 2, a larger tip It becomes possible to obtain a supporting force and a pulling resistance force.

And since the said cover part 3 protrudes rather than the outer peripheral surface of the straight part 2, since a space | gap can be generated between the outer peripheral surface of the straight part 2, and the ground, the ground and the straight part 2 at the time of construction are obtained. Friction with the outer peripheral surface of can be suppressed.
In particular, as in this embodiment, larger than the outside diameter D ₁ inner circumference and outer diameter D ₂ of the straight portion 2 of the cover portion 3, the cover portion 3 protrudes greater from the outer peripheral surface of the straight portion In the case where the ground has a large construction resistance due to circumferential friction, since the gap can be further expanded between the outer circumferential surface of the straight portion 2 and the ground, the effect of suppressing the construction resistance is improved.

In the first embodiment, as means for attaching the cover portion 3 to the straight portion, a plurality of ribs are provided in the space between the inner peripheral surface 3a of the cover portion 3 and the outer peripheral surface of the straight portion 2, and these The structure which fixedly connected the cover part 3 and the straight part 2 via the rib is employ | adopted.
However, as a means for attaching the cover portion 3 to the straight portion, other configurations can be used. For example, as shown in FIG. 3, the straight portion 2 is inserted into the inner peripheral surface of the cover portion 3. Then, plate-like blocking members 10 and 11 are attached to the upper end surface side and the lower end surface side of the cover part 3 respectively, and the space between the inner peripheral surface of the cover part 3 and the outer peripheral surface of the straight part 2 is closed. A configuration can be used. In addition, about this obstruction | occlusion member, you may make it provide only in an upper end side or only a lower end side instead of upper and lower both end surfaces like FIG.
Furthermore, as shown in FIG. 4, the closing member and the rib of the first embodiment may be used in combination. In this case, when only one of the closing member or the rib is employed. In comparison, the rigidity of the pipe pile tip can be dramatically improved.

  Thus, when the blocking member is provided, the blocking member is not expected to have an effect of clogging soil between the cover portion and the straight portion as in the configuration in which only the rib is provided as in the above embodiment. Since a large pulling resistance and tip support force can be stably and reliably generated on the plate surface, there is an advantage that the functionality and reliability as a pile are enhanced. In addition, in the case of a closing member, the resistance to the ground is increased compared to a state in which soil is clogged between the cover portion and the straight portion in the configuration in which only the rib is provided, so that the pulling resistance force and the tip supporting force are increased. Becomes even larger.

  On the other hand, when the blocking member is provided, when the pipe pile is placed on the ground, resistance is received on the lower surface side of the blocking member, so that the workability is considered to be inferior compared to the configuration in which only the rib is provided. However, in the ground where the construction resistance due to peripheral surface friction is large, the presence of this blocking member can surely push out the soil etc., so that the gap between the outer peripheral surface of the straight part and the ground can be further expanded. Become. Therefore, the effect of suppressing the friction between the outer peripheral surface of the straight portion and the ground, that is, the peripheral surface friction can be obtained to the same extent as that of the configuration having only the rib.

5 and 6 show a second embodiment of the pipe pile according to the present invention, and the pipe pile 4 of this embodiment has the same basic configuration as that of the first embodiment. ing. That is, the straight part 5 formed in the shape of a cylinder extending in a straight line, and the cover part attached to the outer peripheral surface of the end part of the straight part 5 on the pile tip side so as to cover the pile tip side of the straight part 5 6 is provided.
The straight portion 5 has substantially the same configuration as that of the straight portion 2 of the first embodiment and has the same operational effects, and thus detailed description thereof is omitted. Moreover, in the case of what is shown in FIG.5 and FIG.6, the lower end side of the pipe pile 4 is a pile front end side, and the upper end side is a pile head side.

The cover portion 6 is formed in a cylindrical shape that functions as a pulling resistance of the pipe pile 4, and the lower end side of the straight portion 5 is inserted into the inner peripheral surface 6 a side, and the pile tip side of the straight portion 5 It is attached to this straight part 5 so that the outer peripheral surface of this edge part may be covered.
The cover portion 6 has an axial length shorter than that of the straight portion 5, has a uniform thickness over the entire length of the axial direction, and is constructed as a symmetrical shape with respect to the axis of the entire pipe pile. In order to suppress the eccentricity of the entire pipe pile at the time of transmission of axial force during operation, the axis L ₂ is attached to the straight part 5 so as to be collinear with the axis L ₁ of the straight part 5.
Further, the upper and lower end surfaces of the cover portion 6 are flat surfaces extending in a direction orthogonal to the axial direction of the cover portion 6, and the upper end side, that is, the end surface on the pile head side is resistance to earth and sand in the tensile direction. Thus, the tensile resistance is improved, and the end surface on the lower end side, that is, the end side of the pile tip side, enlarges the contact area with the surrounding earth and sand to improve the tip supporting force.

Moreover, the said cover part 6 is formed in the tapering cylindrical shape from which an outer peripheral diameter and an inner peripheral diameter become small gradually as it goes to the direction of a pile front end side, and the outer peripheral surface 6b side and the inner peripheral surface 6a side are pile tip ends. The taper surface gradually tapers in the direction of the side.
Here, as the cover portion 6, a member formed with the tapered surface by using a method of pressing a metal plate such as a steel plate little by little by roll bending or a dedicated die can be used.

Further, the cover portion 6, the inner circumference of the pile head side, while being larger than the outside diameter D ₃ of the straight portion 5, the inner circumference of the end portion of the pile tip side (lower end portion) However, it is formed to have substantially the same diameter as the outer peripheral diameter D ₃ of the straight portion 5.
And the inner peripheral surface 6a side of a lower end side is joined to this straight part 5 by various means, such as welding, in the state which contact | abutted the outer peripheral surface of the pile front end side of the straight part 5 which is the same outer peripheral diameter as an inner peripheral diameter. ing.
Therefore, the cover portion 6, the entire outer peripheral surface 6b is an end of the pile head side of the cover portion 6 of the outer periphery diameter D ₄ of the (upper end portion) as a maximum, projecting from the outer peripheral surface of the straight portion 5 outwardly It is in a state.

  In this embodiment, as shown in FIG. 5A, the mounting position of the cover portion 6 on the straight portion 5 is slightly piled from the end (lower end) of the straight portion 5 on the pile front end side. The position close to the head side is such that the lower end surface of the cover portion 6 and the lower end surface of the straight portion 5 do not coincide with each other, and a part of the outer peripheral surface on the lower end side of the straight portion 5 is exposed to the outside.

The pipe pile 4 having the above configuration can be driven into the ground basically using the same construction method as that of the first embodiment, and can obtain the same effects as those of the first embodiment. it can.
However, in the pipe pile 4 of the second embodiment, the taper surface gradually tapered toward the pile tip side on the outer peripheral surface 6b side of the cover portion 6 is formed. The taper surface provides the effect of suppressing peripheral surface frictional force during construction, and this has the advantage that the workability is further improved.
Furthermore, since the cover portion 6 has a mode in which the entire outer peripheral surface 6b that is a tapered surface is projected outward from the outer peripheral surface of the straight portion 5, the horizontal projection area is further expanded, As a result, even with a small penetration length, the tip support force is equivalent to or better than that of normal piles (straight piles without taper), especially when penetrating into a hard support layer. Is advantageous.
And since the cover part 6 protrudes greatly from the outer peripheral surface of the straight part 5 as it goes to a pile head side, the anchor effect by this cover part 6 improves further, and a drawing-out resistance improves markedly.

In the first and second embodiments, the cover portions 3 and 6 are attached to the straight portions 2 and 5 from the end of the straight portions 2 and 5 on the pile tip side. Although it is set to a position slightly closer to the pile head side, the lower end surfaces of the cover portions 3 and 6 and the lower end surfaces of the straight portions 2 and 5 do not necessarily coincide with each other, but such a configuration is not necessarily required.
In general, the ground becomes harder as the depth becomes deeper, and the deeper the layers, the higher the vertical support force and the pulling resistance can be obtained. It is desirable to make it close.

7 and 8 show a third embodiment of the pipe pile according to the present invention, and the pipe pile 7 of this embodiment has the same basic configuration as the first and second embodiments. A straight portion 8 formed in a linearly extending cylindrical shape, and a cylinder that is attached to an outer peripheral surface of an end portion of the straight portion 8 on the pile tip side and functions as a pulling resistance of the pipe pile 7 And a cover 9 having a shape.
The straight portion 8 has substantially the same configuration as that of the straight portion 2 of the first embodiment, and has the same operational effects, so detailed description thereof will be omitted. Moreover, in the case of what is shown in FIG.7 and FIG.8, the lower end side of the pipe pile 7 is a pile front end side, and the upper end side is a pile head side.

The cover portion 9 has an end (lower end) side on the pile tip side of the straight portion 8 inserted on the inner circumferential surface 9a side, and the straight portion 8 covers the outer peripheral surface on the pile tip side. 8 is attached.
Further, the axial length is shorter than the straight portion 8 and is formed to have a uniform thickness over the entire length of the axial direction, and the shaft at the time of construction or operation as a symmetrical shape with respect to the axis as the entire pipe pile In order to suppress the eccentricity of the entire pipe pile at the time of force transmission, it is attached to the straight portion 8 so that the axis L ₂ is collinear with the axis L ₁ of the straight portion 8.
Further, the upper end surface and the lower end surface of the cover portion 6 are flat surfaces extending in a direction orthogonal to the axial direction of the cover member 6 to improve the tensile resistance force and the tip support force, respectively.

And this cover part 9 is formed in the tapering cylindrical shape from which an outer peripheral diameter and an inner peripheral diameter become small gradually as it goes to the direction of a pile tip side, and, thereby, the outer peripheral surface 9b side and the inner peripheral surface 9a side are The taper surface gradually tapers as it goes to the lower end side.
As the cover portion 9, as in the second embodiment, the taper surface is formed using a method of pressing a metal plate such as a steel plate little by little by roll bending or a dedicated die. Can be used.

Further, the cover portion 9 is formed such that the inner peripheral diameter on the pile tip side is smaller than the outer peripheral diameter D ₅ of the straight portion 8, and a part of the inner peripheral surface 9 a of the cover portion 9 and the straight portion 8 The straight portion 8 is joined to the straight portion 8 by various means such as welding while being in contact with the outer peripheral surface of the lower end portion.
On the other hand, the inner peripheral diameter on the pile head side is formed larger than the outer peripheral diameter D ₅ of the straight portion 8, whereby the outer peripheral surface on the pile head side is the end on the pile head side of the cover portion 9. The outer peripheral diameter D ₆ of the portion (upper end portion) is maximized, and the portion protrudes outward from the outer peripheral surface of the straight portion 8.

In this embodiment, as shown in FIG. 7 (a), the cover portion 9 has an inner peripheral diameter at the height of the substantially middle stage (substantially the center in the axial direction length) on the inner peripheral surface 9a side. The outer diameter of the straight portion 8 is substantially the same as that of the straight portion 8, and is in contact with and joined to the lower end portion of the straight portion 8 in the middle stage.
Therefore, the cover portion 9 has the height of the contact position with the straight portion 8 as a boundary, the lower side from the corresponding contact position is lower than the lower end portion of the straight portion, and the upper side from the contact position is the straight portion. It will be located above the lower end. The position where the outer peripheral surface 9a of the cover portion 9 projects outward from the outer peripheral surface of the straight portion 8 is higher than the height of the contact position with the trait portion 8 because of the thickness of the cover portion 9. It is located on the lower side (see FIG. 7A).

The pipe pile 7 having the above-described configuration can be driven into the ground basically using the same construction method as the first and second embodiments, and the pipes of the first and second embodiments. The same effect as a pile can be obtained.
However, in the pipe pile 7 of this 3rd Embodiment, since the inner peripheral diameter of the pile tip side of the cover part 9 is formed smaller than the outer peripheral diameter of the said straight part, the said 1st and 2nd Compared to the case of the embodiment, the amount of earth and sand flowing into the inner peripheral surface of the straight portion 8 from the front end side during construction can be reduced. Thereby, since the front-end | tip obstruction | occlusion in the pipe pile 7 can be suppressed, the resistance of the ground with respect to driving of the pipe pile at the time of construction can be reduced, and there exists an effect which improves workability more.

Further, the pull-out resistance force after installation, for example, when the outside diameter D ₅ of the straight portion 8 is the same as the outside diameter D ₃ of the straight portion 5 of the second embodiment, the pile end of the cover portion 9 by the end of the side of the outer periphery diameter D ₆ of the (upper part) the same as the outside diameter D ₄ of the upper end portion of the cover portion 6 of the second embodiment, the Kankui 4 of the second embodiment Since the same pulling resistance can be obtained, a high pulling resistance can be obtained in addition to the excellent workability as described above with a relatively simple configuration.

  In the second and third embodiments, nothing is arranged for the end portion (upper end portion) on the pile head side of the cover portions 6 and 9, and the cover portion only by the rigidity of the cover portions 6 and 9. 6 and 9, but, for example, like the pipe pile 4 of the second embodiment shown in FIG. 9, between the inner peripheral surface 6 a of the cover portion 6 and the outer peripheral surface of the straight portion 5. The cover portion can be reinforced by providing ribs 14 made of a material such as steel for reinforcing the cover portion 6.

  In the second and third embodiments, the inner peripheral surfaces 6a and 9a of the cover parts 6 and 9 are exposed from the openings on the upper ends of the cover parts 6 and 9, but FIG. As in the case of the pipe pile 4 of the second embodiment shown in Fig. 2, a plate-shaped closing member formed of a material such as steel on the upper end side of the cover portion 6 in order to close the opening at the upper end portion of the cover portion 6 The rigidity of the cover part can be increased by arranging 15 or the like. Alternatively, the rib and the closing member may be used in combination.

Here, in the pipe pile provided with the cover portion having the tapered surface as in the second and third embodiments, when the closing member is provided on the upper end surface of the cover portion, there is no closing member. Even if the space on the inner peripheral surface side of the cover portion does not clog as in the configuration, there is an advantage that a large pulling resistance force can be stably and reliably generated by the plate surface of the closing member.
In the case of the pipe piles of the second and third embodiments, the closing member exists only at the upper end portion of the cover portion having a tapered surface, so that the closing member becomes a resistance at the time of placing. Therefore, high workability can be obtained without changing the presence or absence of the blocking member.

  Note that the amount of protrusion of the cover portions 6 and 9 from the straight portions 5 and 8 in the second and third embodiments can be arbitrarily set depending on the construction location, etc. It is the same as in the case of the first embodiment that the pulling resistance as the entire pipe pile increases as the amount increases.

By the way, as shown in FIG. 11, in the case of a pipe pile having a simple configuration in which the cross-sectional shape is a perfect circle shape and the tip is open, when used as a tip support pile, the soil flowing into the pipe pile is used. The resistance due to blockage contributes greatly. In this case, in order to completely close the tip of the pipe pile, it is widely known that as a general physical property, it is necessary to be rooted in the support layer more than five times the outer diameter of the pipe pile.
The pipe piles 1, 4, and 7 of the first to third embodiments have a perfect circular cross section at the tip and an open end as in the pipe pile 20 of FIG. 11. Therefore, the pipe piles 1, 4, 7 of the first to third embodiments need to be embedded in the support layer at least five times the outer peripheral diameters D ₁ , D ₃ , D ₅ of the straight portions 2, 5, 8. There is.
In this case, with respect to the cover portions 3, 6, and 9 of the first and second embodiments, D ₂ and D ₄ that are the outer diameters of the upper end portions, and axial lengths (heights) H ₁ and H ₂ , H ₃ are determined as follows.

FIG. 12 is a diagram for explaining a concept established in the ground field called main earth pressure theory.
When constructing the pile on the ground, the outer peripheral diameters D ₂ , D ₄ , D ₆ of the upper ends of the cover parts 3, 6, 9 of the first to third embodiments are the straight parts 2, 5, 8 is different from the outer peripheral diameters D ₁ , D ₃ , and D _5, and a gap is generated between each of the straight portions 2, 5, and 8 and the inner peripheral surface of the ground of the support layer.
However, in order to obtain the pulling resistance, it is necessary to return the ground of the support layer above the cover portions 3, 6, and 9 of the first to third embodiments after the construction.
In that case, the total amount of ground to be returned is derived from the main earth pressure theory.

As described above, the penetration amount of the pile into the support layer is five times the outer diameter of the straight portions 2, 5, and 8 of the first to third embodiments. In that case, the total amount of ground flowing in due to the main earth pressure must be larger than the total amount of the generated voids.
Here, taking the case of the pipe pile 4 according to the second embodiment as an example, the total amount of voids is determined by (5D ₄ −H ₂ ) × (D ₄ −D ₃ ) / 2 from FIG.
On the other hand, the total amount of ground flowing in due to the main earth pressure is 1/2 × (5D ₃ −H ₂ ) × (5D ₃ −H ₂ ) × Tan (45 ° − (φ / 2)) (where φ is The internal friction angle of the ground).
After that, if the expression is expanded sequentially, finally,
D ₄ + H ₂ Tan (45 ° − (φ / 2)) <D ₃ (1 + 5 Tan (45 ° − (φ / 2)))
It becomes.
Here, since it is known that φ is a maximum of 45 ° as a physical property of the ground,
D ₄ + H ₂ <D ₃ (1 + 5 Tan (45 ° − (45 ° / 2)))
That is, it is desirable that D ₄ and H ₂ exist in a range where D ₄ + H ₂ <3.071D ₃ is satisfied.
At this time, D4> D3.
As for the Kankui 1 of the first embodiment, the outside diameter D ₂ of the cover portion 3 of the embodiment first, outside diameter D of the upper end portion of the cover portion 6 of the second embodiment _{When 4} is the same, the same expression is established in relation to D ₁ , D ₂ , and H ₁ .
Furthermore, for the Kankui 7 of the third embodiment, the outside diameter D ₆ of the cover portion 9 of the embodiment of the third, outside diameter D of the upper end portion of the cover portion 6 of the second embodiment _{When 4} is the same, the same formula is established in relation to D ₅ , D ₆ , and H ₃ .

In order to confirm the effect of the present invention, the ratio (expansion ratio) between the outer peripheral diameter of the upper end portion of the cover portion and the outer peripheral diameter of the straight portion in the pipe pile according to the present invention, and the cover portion like the pipe pile of the present invention An experiment was conducted to investigate the relationship with the pulling resistance ratio (%) for a normal straight pile without slag.
In this experiment, as Kankui the present invention, enlarged ratio between the outer diameter D ₄ and the outer diameter D ₃ of the straight portion 5 of the upper end of Kankui 4 (cover 6 according to the second embodiment D ₄ / D ₃ ), a straight portion 5 shown in FIG. 11 and a straight pile 20 of approximately the same shape and size, and a numerical experiment using the finite element method was performed for each to determine the pulling resistance. The drawing resistance ratio is a ratio of the drawing resistance of the pipe pile 4 according to the second embodiment to the drawing resistance of the straight pile 20.
The results are shown in FIG.

Figure 13, for Kankui 4 according to the present invention, the outside diameter D ₄ of the upper end portion of the cover portion 6, the ratio between the outer diameter D ₃ of the straight portion 5 (diameter ratio) horizontal axis D 4 _/ D ₃ The drawing resistance ratio, which is the ratio between the drawing resistance of the pipe pile 4 according to the present invention and the drawing resistance of the straight pile 10 of the comparative example, is shown as the vertical axis.
In FIG. 13, the pulling resistance of the pile is 10% of the outer peripheral diameter D ₃ of the straight portion 5 when the pile is pulled vertically upward after the pile is constructed (penetration construction) on the ground (stratum). This is the resistance when
The drawing resistance ratio is the drawing resistance of the pipe pile 4 according to the present invention when the drawing resistance of the straight pile 10 of the comparative example is 1.0. That is, the drawing resistance ratio is defined as the ratio between the drawing resistance of the pipe pile 4 according to the present invention and the drawing resistance of the straight pile 10 of the comparative example.

From the results shown in FIG. 13, it can be seen that the pulling resistance ratio of the pipe pile 4 according to the present invention is much larger than the pulling resistance ratio of the straight pile 10 of the comparative example (that is, the pulling resistance ratio is 1). This proved that the pipe pile according to the present invention can obtain a high pulling resistance.
Further, from FIG. 13, the pull-out resistance ratio, the outside diameter D ₄ of the upper end portion of the cover portion 6, the ratio between the outer diameter D ₃ of the straight portion 5 (diameter ratio) D 4 _/ D ₃ positively correlated It can be seen that there is a relationship.
That is, the outside diameter D ₄ of the upper end portion of the cover portion 6, the ratio between the outer diameter D ₃ of the straight portion 5 (diameter ratio) larger the D 4 _/ D _3, to obtain a large pull-out resistance it can.
Therefore, it was found that the material cost can be reduced by reducing the number of piles, and that the construction cost can be reduced at the same time, contributing to the shortening of the construction period.

1, 4, 7 Pipe pile 2, 5, 8 Straight part 3, 6, 9 Cover part L ₁ Axis of straight part L ₂ Axis of cover part

Claims (6)

A straight portion formed in a cylindrical shape extending linearly, and a cylinder functioning as a pulling resistance attached to the outer peripheral surface of the end portion of the straight portion on the pile tip side so as to cover the pile tip side of the straight portion A cover portion having a shape,
The cover part is formed such that an inner peripheral diameter of at least the end part of the pile head side of the end parts of the pile head side and the pile tip side is larger than an outer peripheral diameter of the straight part, and the inner peripheral surface side The pile tip side of the straight part is inserted, and the axis is attached to the straight part in a state where it is collinear with the axis of the straight part,
The cover part is a tapered surface that gradually tapers as the outer peripheral surface side goes in the direction of the pile tip side,
The cover portion is formed such that the inner peripheral diameter of the end portion on the pile front end side is smaller than the outer peripheral diameter of the straight portion, and the outer peripheral surface of the inner peripheral surface on the pile front end side and the end portion on the pile front end side of the straight portion Attached to the straight part in a state where
The ends of the straight ends and the respective pile front ends of the cover portion are opened ,
A pipe pile characterized in that a plate-shaped closing member that closes the opening of the upper end portion of the cover portion is disposed on the upper end side of the cover portion .   The pipe pile construction method according to claim 1, wherein the pipe pile is driven on the ground by a hammering method in which the pipe pile is hammered and driven.   A pipe pile construction method according to claim 1, wherein the pipe pile according to claim 1 is placed on the ground by a vibration method for applying vibration to the pipe pile.   A pipe pile construction method according to claim 1, wherein the pipe pile according to claim 1 is placed on the ground by a press-fitting method for applying a pushing force to the ground to the pipe pile.   The pipe pile according to claim 1 is driven by a medium excavation method in which the pipe pile is buried while excavating the ground by a drill rod having a drill head inserted into the space inside the straight portion. Pipe pile construction method.   The pipe pile construction according to any one of claims 3 to 5, wherein the pipe pile is placed on the ground while water is sprayed onto the outer peripheral surfaces of the straight portion and the cover portion in the pipe pile. Method.

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