JP7344538B2 - spiral pile - Google Patents

Description

The present invention relates to a helical pile that penetrates into the ground using a penetration force that is an external force directed toward penetration.

BACKGROUND ART A spiral pile (also referred to as a spiral pile) in which protruding portions that protrude to both sides of a central axis are spirally provided along the central axis is conventionally known (for example, see Patent Document 1). In addition, as a method for constructing spiral piles, a rotary penetration method is generally used, in which construction is performed by rotating the spiral pile using heavy machinery or the like.

JP 2016-3431 Publication

However, the rotary penetration method requires large-scale construction equipment such as heavy machinery, so there is a problem in that it is difficult to perform construction in narrow spaces. Therefore, there is a need for a helical pile that can be constructed using a small construction machine that performs impact or pressing without applying rotational force to the helical pile.

An object of the present invention is to provide a spiral pile that can be constructed using a construction machine that does not apply rotational force.

One aspect of the present invention includes a spiral portion that protrudes to both sides of a central axis along the direction of penetration into the ground and includes spiral blades along the central axis; It is a spiral pile with a head that receives penetration force as an external force. The spiral portion has a pitch width ratio of 2.0 or more and 7.0 or less, which is the length along the central axis corresponding to a half turn of the spiral divided by the width indicating the outer diameter. When the part receives a penetration force, it penetrates into the ground while rotating around the central axis relative to the ground.

In one aspect of the present invention, the spiral portion has a pitch width ratio of 2.0 or more and 7.0 or less. By setting the pitch width ratio within this numerical range, penetration force can be efficiently converted into rotational force of the spiral pile, and construction can be performed along the pitch without applying rotational force. In other words, the amount of penetration relative to the penetration force can be increased, and the helical pile can be penetrated into the ground with a small penetration force. Furthermore, since construction can be carried out along the pitch, the surrounding ground is less likely to be disturbed and the resistance during pull-out can be increased. For these reasons, construction can be carried out using a small construction machine that performs striking and pressing.

The pitch width ratio is preferably 4.0 or more and 6.5 or less. By setting the pitch width ratio within this numerical range, the resistance during drawing can be further increased.

Another aspect of the present invention includes a spiral portion that protrudes to both sides of a central axis along the direction of penetration into the ground and includes spiral blades along the central axis, and a proximal end of the spiral portion that is open on the proximal side and a distal end thereof. It has a cylindrical shape that is continuous with the side, and when penetrating, it receives a penetration force that is an external force in the direction of penetration, and after penetration, it is a spiral pile with a head that supports the supported structure within the cylinder. be. The spiral portion has a pitch width ratio of 2.0 or more and 7.0 or less, which is the length along the central axis corresponding to a half turn of the spiral divided by the width indicating the outer diameter. When the part receives a penetration force, it penetrates into the ground while rotating around the central axis relative to the ground.

In another aspect of the present invention, the spiral portion has a pitch width ratio of 2.0 or more and 7.0 or less. By setting the pitch width ratio within this numerical range, penetration force can be efficiently converted into rotational force of the spiral pile, and construction can be performed along the pitch without applying rotational force. In other words, the amount of penetration relative to the penetration force can be increased, and the helical pile can be penetrated into the ground with a small penetration force. This makes it possible to perform construction using a small construction machine that performs striking and pressing. Furthermore, the head of a spiral pile has a cylindrical shape with an open base end and a distal end continuous with the base end of the spiral portion. Afterwards, the supported structure is supported within the cylinder. Therefore, the construction work of the supported structure becomes easier, and the construction efficiency can be improved.

It is possible to provide a spiral pile that can be constructed using a construction machine that does not apply rotational force.

FIG. 1 is a side view of a helical pile. FIG. 2 is a top view of the spiral pile. FIG. 3 is a schematic diagram showing an example of a supported structure. FIG. 4 is a schematic diagram showing a spiral pile penetrating into the ground. FIG. 5 is a diagram showing a list of pitch width ratios of model piles used in the test. FIG. 6 is a diagram showing the test results of Test No. 1. FIG. 7 is an enlarged view of the drawing process in FIG. 6. FIG. 8 is a diagram showing the test results of Test No. 2.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a spiral pile disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

Furthermore, in the embodiments described below, expressions such as "spiral," "column," "cylindrical," or "vertical" are used, but these conditions do not have to be strictly satisfied. That is, each of the above expressions allows deviations in manufacturing accuracy, construction accuracy, etc. Further, in the embodiment shown below, a case will be mainly described in which the spiral pile is penetrated into the ground by a blow in the penetrating direction, but it may also be penetrated into the ground by pressing.

First, an example of a spiral pile 10 according to an embodiment will be described using FIG. 1. FIG. 1 is a side view of a helical pile 10. FIG. 1 shows the central axis CL of the spiral pile 10. Further, FIG. 1 also shows a Z-axis indicating the direction of penetration when the helical pile 10 penetrates into the ground. As shown in FIG. 1, the helical pile 10 is penetrated into the ground with the central axis CL aligned in the direction of penetration. Note that this Z-axis may also be shown in other drawings.

As shown in FIG. 1, the spiral pile 10 includes a spiral portion 12 and a head 11. The spiral portion 12 includes a spiral blade 12b that protrudes to both sides of the central axis CL along the direction of penetration into the ground (positive Z-axis direction) and extends along the central axis CL. The head 11 is continuous with the proximal end side (Z-axis negative direction) of the spiral portion 12, and receives a penetration force that is an external force in the penetration direction. The length of the head 11 along the central axis CL is "h3". When the head 11 receives a penetration force, the spiral pile 10 penetrates into the ground while rotating around the central axis CL relative to the ground.

Here, the spiral portion 12 has a pitch width ratio PR of 2.0 or more, which is obtained by dividing the pitch P, which is the length along the central axis CL corresponding to a half rotation of the spiral, by the width W indicating the outer diameter, and It is preferably 7.0 or less. This is because it is thought that if the pitch width ratio PR is set in such a numerical range, the penetration force can be efficiently converted into the rotational force of the spiral pile 10.However, the basis for the preferable numerical range of the pitch width ratio PR and its effects. will be described later using FIGS. 5 to 8.

The head 11 may have a solid shape such as a cylinder or a plate, but as shown in FIG. You can also do it. FIG. 1 shows an inner circumferential surface 11c and an inner bottom surface 11b of the cylindrical head 11. In this way, by making the head 11 hollow, it becomes possible to easily support the supported structure 100 (see FIG. 3) by inserting it, thereby simplifying the installation work of the supported structure 100. can be converted into Note that an example of the supported structure 100 will be described later using FIG. 3.

Further, as shown in FIG. 1, the spiral portion 12 includes a blade 12b and a shaft 12s. The shaft 12s has, for example, a solid cylindrical shape. By making the shaft 12s into a solid shape such as a columnar shape, the strength of the spiral pile 10 can be increased. Note that the shaft 12s may be omitted.

The blades 12b protrude to both sides of the central axis CL and have a spiral shape along the central axis CL. Here, the length of the blade 12b along the central axis CL is "h1", and the length of the shaft 12s along the central axis CL is "h2". Although FIG. 1 shows an example in which the direction of the spiral is clockwise toward the positive direction of the Z-axis, it may also be clockwise.

The helical pile 10 shown in FIG. 1 can be a cast product. By making the helical pile 10 a cast product, the degree of freedom in the shape of the head 11 and the helical portion 12 can be improved. Furthermore, it becomes easy to set the pitch width ratio PR to an arbitrary value.

FIG. 2 is a top view of the spiral pile 10. FIG. 2 corresponds to a diagram of the spiral pile 10 shown in FIG. 1 viewed from the negative Z-axis direction. As shown in FIG. 2, the head 11 has a cylindrical shape with an open upper surface, and has an inner bottom surface 11b at the lower end of an inner peripheral surface 11c.

FIG. 3 is a schematic diagram showing an example of the supported structure 100. In addition, in FIG. 3, a protective fence installed to protect pedestrians etc. from vehicles on a road is illustrated as the supported structure 100, but the supported structure 100 may be a pole that supports a road sign or the like. It may also be a fence foundation, a signboard foundation, etc. installed in places other than roads. Further, although FIG. 3 illustrates a protective fence having two legs, the number of legs may be one, or may be three or more. The spiral piles 10 are penetrated into the ground in advance according to the number of legs of the supported structure 100, and support each leg of the supported structure 100, respectively.

As shown in FIG. 3, a hole GH large enough to accommodate the head 11 of the spiral pile 10 is provided in the ground surface GL of the ground 200. Here, the interval between the legs 110 of the supported structure 100 is, for example, "w1". The helical pile 10 is placed in the hole GH of the ground 200, and the head 11 receives penetration force in the positive direction of the Z-axis, penetrating into the ground 200 to the extent that the head 11 is accommodated in the hole GH. be done. Each spiral pile 10 is penetrated into the ground 200 so that the distance between the respective center axes CL is "w1".

When the penetration of the spiral pile 10 is completed in this way, the legs 110 of the supported structure 100 are inserted into the cylinder of the head 11, and the gap between the legs 110 and the head 11 is filled with mortar, concrete, etc. filled with. That is, the head 11 of the helical pile 10 supports the supported structure 100 within the cylinder after the helical pile 10 penetrates. Note that through holes are provided in corresponding positions of the cylindrical portion of the head 11 and the legs 110 of the supported structure 100, and the head 11 and the legs 110 are connected with bolts or the like after the supported structure 100 is inserted. It is also possible to fasten with a fastener such as a nut.

In this way, the head 11 of the helical pile 10 has a cylindrical shape with the base end open and the distal end continuous with the base end of the spiral portion 12, and when penetrating, the head 11 has a cylindrical shape that is open at the base end and is continuous with the base end of the spiral portion 12. At the same time, after the penetration, the supported structure 100 is supported within the cylinder. Therefore, the installation work of the supported structure 100 is simplified, and the installation efficiency can be improved. Note that after the leg portions 110 are inserted, the holes GH in the ground 200 are filled with a filling material such as non-shrinkage mortar.

FIG. 4 is a schematic diagram showing the helical pile 10 penetrating into the ground 200. As shown in FIG. 4, in order to cause the helical pile 10 to penetrate into the ground 200, a penetration force F, which is an external force in the direction of penetration into the ground 200 (positive direction of the Z-axis), is applied to the head 11. Here, the penetrating force F may be an intermittent external force due to impact, or may be a continuous external force due to pressing.

The central axis CL of the helical pile 10 is along the Z-axis, and the blades of the spiral portion 12 are spiral along the central axis CL, so the helical pile 10 that has received the penetration force F moves around the central axis CL. Rotate to . In the case shown in FIG. 4, since the direction of the spiral is clockwise toward the positive direction of the Z axis, the rotation direction R is also clockwise. Note that when the direction of the spiral is opposite, the rotation direction R is counterclockwise.

In this way, by applying the penetration force F to the extent that the outer bottom surface of the head 11 reaches the bottom surface of the hole GH in the ground 200, the spiral pile 10 penetrates into the ground 200 while rotating around the central axis CL. be done. Here, as described above, if the pitch width ratio PR (see FIG. 1) of the spiral pile 10 is set to 2.0 or more and 7.0 or less, the pitch is as per the pitch (without disturbing the surrounding ground 200). Since it is easy to construct, it is easy to penetrate into the ground 200, and the resistance to pulling out (pulling resistance) can also be increased.

Next, the basis of the preferable numerical range of the pitch width ratio PR (see FIG. 1) will be explained using FIGS. 5 to 8. First, an outline of the test that verified the numerical range of the pitch width ratio PR will be explained. Conventionally, the common method for constructing spiral piles has been the rotary penetration method, in which construction is performed by rotating the pile. In order to carry out the rotary penetration method, it is necessary to apply rotational force to the piles using heavy machinery (such as a backhoe, a mobile small crane with an auger attached, or a pole construction truck), making it difficult to perform construction on narrow residential roads. In some cases, it may be difficult to bring in heavy equipment.

As a construction method other than the rotary penetration method, there is a hammer penetration method that applies impact force to the pile without applying rotational force to the helical pile, but the pitch width ratio of the spiral pile used in the rotary penetration method The PR is often around 1.5, and there are still many unknown points regarding the optimization of the pitch width ratio PR assuming the percussion penetration method. Therefore, using the pitch width ratio PR of the helical pile as a parameter, construction and loading tests were conducted assuming the impact penetration method, and the penetrability and pull-out resistance were measured.

Specifically, model piles with different pitch width ratios PR were pressed against a sand ground tank to which overloading pressure was applied as confining pressure using a loading device, and the relationship between penetration force (kN) and penetration amount (mm) was determined. obtained. Two tests (Test 1 and Test 2) shown below were conducted.

Test No. 1 was a "penetration/withdrawal test" in which the spiral pile was allowed to rotate freely during the penetration process, and the rotation of the spiral pile was fixed during the withdrawal process (corresponding to Figure 6). Specifically, continuous unidirectional loading was carried out using a loading device, and after penetrating 240 mm with a vertically downward pushing force, a 40 mm pullout was performed by applying a vertically upward force. The loading speed during penetration is 23 mm/min, and the loading speed during withdrawal is 8.8 mm/min.

Test No. 2 was a "penetration/pushing test" in which the spiral pile was allowed to rotate freely during the penetrating process, followed by a pushing process in which the rotation was fixed (corresponding to Figure 8).

Specifically, continuous unidirectional loading was performed using a loading device, and after penetration of 200 mm with a vertically downward indentation force, the loading force was once set to 0 kN, and then an additional 40 mm indentation was performed. The loading speed during penetration is 23 mm/min, and the loading speed during pushing is 8.8 mm/min.

The measuring equipment used is as follows. The data logger that acquires data is manufactured by "Kyowa Dengyo Co., Ltd." and has a model of "TDS-303." The load cell that measures the load (penetration force) is manufactured by "Tokyo Sokki Kenkyusho Co., Ltd." and has a model of "TCLP-2B." The contact type displacement meter that measures displacement (penetration amount) is manufactured by "Tokyo Sokki Kenkyusho Co., Ltd." and the model is "TCLP-2B." The capacity of the sand ground tank is 750 mm in diameter and 500 mm in height, and the material of the model ground is silica sand No. 7 with a relative density of 75%.

FIG. 5 is a diagram showing a list of pitch width ratios PR of model piles used in the test. In the model pile, the shaft 12s in the spiral part 12 of the spiral pile 10 shown in FIG. (See the "Schematic Diagram" section in Figure 5). The head 11 functions as an attachment part to the loading device, and receives penetration force and extraction force from the loading device. "h3" is "108 mm" and "h1" is "200 mm". Moreover, the pitch P and width W corresponding to the spiral portion 12 (see FIG. 1) of each model pile are shown in the schematic diagram. In addition, Fig. 5 shows model piles with eight types of pitch width ratio PR, and for reference, two types of model piles: cylindrical (pile name is "pp") and plate-shaped (pile name is "pt"). It shows. In the test, data on a total of 10 types of model piles were obtained. In addition, the width W (see FIG. 1) of each model pile is 32 mm.

The model pile with the pile name "pw1.5" has a pitch P (see FIG. 1) of 48 mm and a pitch width ratio PR (see FIG. 1) of 1.5 (=48/32). "pw1.5" is a general pitch width ratio PR used in the rotary penetration method.

The model pile with the pile name "pw2.5" has a pitch P of 80 mm and a pitch width ratio PR2.5 (=80/32). The model pile with the pile name "pw3.5" has a pitch P of 112 mm and a pitch width ratio PR3.5 (=112/32). The model pile with the pile name "pw4.0" has a pitch P of 128 mm and a pitch width ratio PR4.0 (=128/32). The model pile with the pile name "pw4.5" has a pitch P of 144 mm and a pitch width ratio PR4.5 (=144/32). The model pile with the pile name "pw5.0" has a pitch P of 160 mm and a pitch width ratio PR5.0 (=160/32). The model pile with the pile name "pw5.5" has a pitch P of 176 mm and a pitch width ratio PR5.5 (=176/32). The model pile with the pile name "pw6.5" has a pitch P of 208 mm and a pitch width ratio PR6.5 (=208/32). The model pile with the pile name "pp" has a width W (outer diameter) of 32 mm, a cylinder thickness of 3 mm, and a hollow cylindrical shape with an open bottom, and the pile name is "pp". The model pile of "PT" has a plate shape with a width W of 32 mm.

FIG. 6 is a diagram showing the test results of Test No. 1. Test No. 1 corresponds to the above-mentioned "penetration/withdrawal test". That is, after 240 mm of penetration, 40 mm of extraction was performed. Here, the test results shown in Figure 6 are obtained by conducting the "penetration/pullout test" three times for each model pile shown in Figure 5, and graphing the average value of the three tests for each model pile. . As an exception, the number of "penetration/pullout tests" for model piles with "pw6.5" is two.

The horizontal axis is the penetration force (kN), and the vertical axis is the penetration amount (mm). Below, the graph corresponding to the pile name "pw1.5" shown in Figure 5 is "pw15", the graph corresponding to "pw2.5" is "pw25", and the graph corresponding to "pp" is "pp". Write it like this. Here, the region where the penetration force (horizontal axis) is 0 or more corresponds to the "penetration process", and the region where the penetration force (horizontal axis) is less than 0 corresponds to the "extraction process". Note that the "extracting process" will be described later using the enlarged view of FIG.

As shown in FIG. 6, in each graph, the relationship between the penetration force and the penetration amount is approximately proportional (the penetration force is positive when going to the right, and the penetration amount is positive when going downward, so it falls to the right). When the penetration amount reaches 240 mm, the maximum penetration force is pp, and the minimum penetration force is pt. Furthermore, pw15 has the second largest penetration force after pp, which is about 80% of pp.

Below, in descending order of penetration force, they are pw25, pw35, pw45, pw50, pw40, pw55, and pw65, with pw25 being about 65% of pw15, and pw65 being about 45% of pw15. That is, it can be seen that when the pitch width ratio PR is 2.5 or more, the penetration force can be reduced by 30% or more compared to the case where the pitch width ratio PR is 1.5. From these facts, it can be inferred that even when the pitch width ratio PR is 2.0, the penetration force is reduced more effectively than when the pitch width ratio PR is 1.5. In addition, although FIG. 6 shows the case where the maximum value of the pitch width ratio PR is 6.5, even if the pitch width ratio PR is 7.0, the effect of reducing penetration force is equal to or greater than that of pw40 or pw45. is inferred.

FIG. 7 is an enlarged view of the drawing process in FIG. 6. In the drawing process, the penetration amount is 40 mm from 240 mm to 200 mm. As shown in FIG. 7, in the negative region of penetration force, pw45 has the largest absolute value, and pt has the smallest absolute value. Here, a large absolute value of the penetration force (a large negative value) indicates that it is difficult to pull out, that is, the pulling resistance force is large.

Further, for pw15 to pw65, the absolute value of the penetration force is generally maximum at a penetration amount of 230 mm to 235 mm. In descending order of the absolute value of the penetration force, they are pw45, pw50, pw55, pw40, pw65, pw35, pw25, pw15, pp and pt. pw25 is about twice that of pw15, and pw40 and pw65 are about twice that of pw15. pw55 is about 3 times that of pw15, pw50 is about 3.3 times that of pw15, and pw45 is about 3.5 times that of pw15. In other words, it can be seen that when the pitch width ratio PR is 2.5 or more, the pull-out resistance force can be increased by more than twice as much as when the pitch width ratio PR is 1.5. From these facts, it can be inferred that even when the pitch width ratio PR is 2.0, there is an effect of increasing the pulling resistance force compared to when the pitch width ratio PR is 1.5. Further, when the pitch width ratio PR is 4.0 or more, the pull-out resistance can be more stably increased than when the pitch width ratio PR is 3.5 or less. Furthermore, when the pitch width ratio PR is set to 4.0 or more and 6.5 or less, the pulling resistance can be further increased. Furthermore, when the pitch width ratio PR is set to 4.5 or more and 5.0 or less, the pulling resistance can be further increased. In addition, although FIG. 7 shows the case where the maximum value of the pitch width ratio PR is 6.5, even if the pitch width ratio PR is 7.0, the increase in pulling resistance force is equal to or greater than that of pw35 or pw25. The effect is analogous.

According to the graphs shown in FIGS. 6 and 7, the pullout resistance force of pw15, which has the largest penetration force required in the penetration process, is the smallest, whereas when the pitch width ratio PR increases, the penetration force required in the penetration process is the smallest. The penetration force becomes smaller and the pull-out resistance force becomes larger. From this, pw15 penetrates while breaking (disturbing) the surrounding ground during the penetration process, and a gap is created between the upper surface of the blade 12b in the spiral part 12 (see Fig. 1) and the ground. It is presumed that there is penetration, and as a result, the pullout resistance is thought to be small. On the other hand, when the pitch width ratio PR is large, it is presumed that the penetration force during the penetration process is efficiently converted into rotation, and the penetration is achieved with little disturbance of the surrounding ground. As a result, it is thought that the force required for penetration becomes smaller, a gap is less likely to be formed between the spiral surface of the blade 12b and the ground, and the pulling resistance is increased.

FIG. 8 is a diagram showing the test results of Test No. 2. Test No. 2 corresponds to the above-mentioned "penetration/pushing test". In other words, after the model pile was penetrated 200 mm with freedom to rotate, it was pushed in 40 mm with the model pile fixed in rotation. Here, the test results shown in Figure 8 are obtained by conducting the "penetration/pushing test" three times for each model pile shown in Figure 5, and graphing the average value of the three tests for each model pile. . In addition, as an exception, the number of times of the "penetration/pushing test" is one for model piles of "pw 5.0" and "pw 6.5".

The horizontal and vertical axes are the same as in FIG. 6. Note that, in the positive region of the penetration force, the region where the penetration amount is up to 200 mm corresponds to the "penetration process", and the region larger than 200 mm corresponds to the "pushing process", which is different from FIG. Note that there is no "pulling out process" shown in FIG. Further, below, we will mainly explain the points that are different from Test No. 1 shown in FIG. 6.

As shown in FIG. 8, once the penetration amount reached 200 mm in the penetration process, the penetration force was set to 0, and the model pile was rotated and fixed, and the pushing process was performed until the penetration amount reached 240 mm. When the penetration amount reaches 240 mm through the pushing process, the maximum penetration force is pp, and the minimum penetration force is pt. Furthermore, pw15 has the next largest penetration force after pp, which is about 95% of pp. Below, in descending order of penetration force, they are pw25, pw35, pw50, pw55, pw45, pw40, and pw65, with pw25 being about 85% of pw15, and pw65 being about 70% of pw15.

Here, the rate of increase in the penetration force during the pushing process (penetration force at the completion of the pushing process/penetration force at the completion of the penetration process) increased to about 1.8 times in pw25, compared to about 1.3 times in pw15. . In other words, it can be seen that when the pitch width ratio PR is 2.5 or more, the rate of increase in the penetration force during the pushing process relative to the penetration force during the penetration process is greater than when the pitch width ratio PR is 1.5. In other words, it can be seen that the larger the pitch width ratio PR, the smaller the penetration force in the rotationally free penetration process, that is, the force required for construction. It can also be seen that when the rotation is fixed, it is difficult to penetrate the ground, that is, it is difficult to sink. From these facts, it can be inferred that even when the pitch width ratio PR is 2.0, the effect of preventing sinking is greater than when the pitch width ratio PR is 1.5.

According to pw15 in FIG. 8, the penetration forces in the penetration process and the pushing process do not become step-like with the line of penetration amount 200 mm as a boundary, but form a substantially continuous line. In other words, in pw15, it is presumed that the penetration conditions in the penetration process and the pushing process are almost the same. In other words, in the penetration process of pw15, although it is allowed to rotate freely, it is considered that it penetrates while breaking (disturbing) the ground without almost rotating. For this reason, it is thought that the process is unlikely to be different from the pushing process in which the rotation is forcibly fixed. On the other hand, in the case of the model pile with a large pitch width ratio PR, the lines of the penetration forces in the penetration process and the pushing process are clearly discontinuous with the line of penetration amount 200 mm as the border. The reason why the push-in force required during penetration is small is that the model pile rotates and construction is possible along the pitch, and in the subsequent push-in process, the rotation is fixed, which reduces the resistance force during penetration. is thought to rise in a stepwise manner. Therefore, by increasing the pitch width ratio, the pushing force is efficiently converted into rotation during the penetration process, thereby achieving penetration that does not disturb the surrounding ground. It can be seen that this has the effect of obtaining a large supporting force.

As described above, by setting the pitch width ratio PR to 2.0 or more and 7.0 or less, the penetration force can be efficiently converted into the rotational force of the helical pile 10, and the rotational force cannot be applied. Construction can be carried out along the pitch P, that is, construction can be carried out without disturbing the surrounding ground. That is, the amount of penetration relative to the penetration force can be increased, and the helical pile 10 can be penetrated into the ground with a small penetration force. This makes it possible to perform construction using a small construction machine that performs striking and pressing. In addition, the fact that the ground is not easily disturbed during penetration also means that the resistance force during extraction is increased.

Further advantages and modifications can be easily deduced by those skilled in the art. Therefore, the broader aspects of the invention are not limited to the exemplary embodiments shown and described above. Accordingly, various changes may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

10 spiral pile, 11 head, 11b inner bottom surface, 11c inner peripheral surface, 12 spiral part, 12b blade, 12s shaft, 100 supported structure, 110 leg part, 200 ground, CL central axis, GL ground surface, F Penetration force, GH hole, P pitch, PR pitch width ratio, R rotation direction, W width.

Claims (3)

a spiral portion that includes a blade passing through a central axis along the direction of penetration into the ground, protruding directly from the central axis to both sides and spirally formed along the central axis;
a head that is continuous with the proximal end side of the spiral portion and receives a penetration force that is an external force in the penetration direction;
The spiral portion is
A pitch width ratio obtained by dividing the pitch, which is the length along the central axis corresponding to a half rotation of the spiral, by the width indicating the outer diameter, is 2.0 or more and 7.0 or less, and the head is A spiral pile that penetrates into the ground while rotating about the central axis relative to the ground when receiving the penetration force. The spiral portion is
The helical pile according to claim 1, wherein the pitch width ratio is 4.0 or more and 6.5 or less. a spiral portion that includes a blade passing through a central axis along the direction of penetration into the ground, protruding directly from the central axis to both sides and spirally formed along the central axis;
It has a cylindrical shape with the proximal end open and the distal end continuous with the proximal end of the spiral portion, and when penetrating, it receives a penetrating force that is an external force in the penetrating direction, and after penetrating, it does not support the supported structure. a head supported within a cylinder;
The spiral portion is
A pitch width ratio obtained by dividing the pitch, which is the length along the central axis corresponding to a half rotation of the spiral, by the width indicating the outer diameter, is 2.0 or more and 7.0 or less, and the head is A spiral pile that penetrates into the ground while rotating about the central axis relative to the ground when receiving the penetration force.

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