Design method for steel pipe piles, steel pipe piles, and construction method for steel pipe piles
The steel pipe pile design with a slip layer on the inner surface addresses the challenge of incorporating impermeable soil layers, ensuring efficient and cost-effective construction by preventing tip blocking and contamination diffusion.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NIPPON STEEL METAL PROD CO LTD
- Filing Date
- 2024-12-25
- Publication Date
- 2026-07-07
Smart Images
Figure 2026112939000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a design method for steel pipe piles, steel pipe piles, and a construction method for steel pipe piles.
Background Art
[0002] For example, when constructing a steel pipe pile in soil contaminated with specific harmful substances or the like, a technique is known in which a steel pipe pile having an opening at the tip is used, and the water stoppage property is ensured by the soil of the viscous soil layer (impervious layer) taken in through the opening (see, for example, Patent Document 1). In this technique, the soil of the taken-in viscous soil layer separates between the soil of the contaminated aquifer layer taken into the steel pipe pile and the ground located below the viscous soil layer, preventing the contaminants present in the contaminated aquifer layer near the ground surface from diffusing into the lower layer.
[0003] Also, by ensuring the water stoppage property in the viscous soil layer, a water channel can be formed inside the steel pipe pile to prevent the groundwater contained in the confined aquifer layer from gushing out from the pile head. This technique is a useful technique that can prevent the diffusion of contaminants and the gushing out of groundwater without using a casing pipe or the like, and can simplify the pile construction process.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] By the way, when there is a relatively hard ground such as a gravel layer in a layer shallower than the viscous soil layer, the tip may be blocked by the hard ground before the viscous soil layer is taken in. In the above technique, the soil is stirred using an auger screw, or the soil taken into the steel pipe pile is removed using a hammer club or the like. However, such work is time-consuming and expensive, and cannot be easily carried out.
[0006] Therefore, the present invention aims to provide a steel pipe pile design method, a steel pipe pile, and a steel pipe pile construction method that can more easily and reliably incorporate an impermeable soil layer into the inside of the steel pipe pile, thereby ensuring watertightness inside the steel pipe pile. [Means for solving the problem]
[0007] [1] A method for designing a steel pipe pile to be driven into ground in which a first aquifer, an impermeable layer, a second aquifer, and a supporting layer are stacked in order from the surface side, the method comprising a steel pipe pile design step of designing the steel pipe pile such that a slip layer layer is provided on the inner surface of the steel pipe pile. [2] The steel pipe pile design method according to [1], comprising a ground structure acquisition step of acquiring the ground structure into which the steel pipe pile penetrates, wherein in the steel pipe pile design step, the steel pipe pile is designed such that the slip layer layer is provided on the inner circumferential surface of the steel pipe pile in a range corresponding to the depth from the tip of the steel pipe pile to the upper end of the impermeable layer. [3] A method for designing a steel pipe pile according to [1], comprising a ground structure acquisition step for acquiring the structure of the ground into which the steel pipe pile penetrates, wherein in the steel pipe pile design step, the steel pipe pile is designed such that the slip layer is provided on the inner circumferential surface of the steel pipe pile in a range corresponding to a depth from the tip of the steel pipe pile to at least a portion of the impermeable layer. [4] The slip layer contains bituminous material, the design method for steel pipe piles according to any one of [1] to [3]. [5] The steel pipe pile is a rotating pile having a cylindrical portion formed by a steel pipe and a blade joined to the end face on the tip side of the cylindrical portion, the design method for a steel pipe pile according to any one of [1] to [3]. [6] The steel pipe pile is a rotating pile having a cylindrical portion formed by a steel pipe and a helical vane joined to the outer surface of the cylindrical portion, the design method for a steel pipe pile according to any one of [1] to [3]. A steel pipe pile designed according to the steel pipe pile design method described in any one of [7], [1], to [3].
[0008] [8] A construction method for driving a steel pipe pile into ground in which a first aquifer, an impermeable layer, a second aquifer, and a supporting layer are stacked in order from the surface side, the method comprising: providing a slip layer on the inner surface of the steel pipe pile before driving the steel pipe pile; taking in the soil of the first aquifer into the steel pipe pile through an opening formed at the tip of the steel pipe pile; taking in the soil of the impermeable layer into the steel pipe pile through the opening; and bringing the tip of the steel pipe pile to the supporting layer. [Effects of the Invention]
[0009] According to the above configuration, by providing a slip layer on the inner surface of the steel pipe pile, the first aquifer is smoothly incorporated into the steel pipe pile. This prevents the tip of the steel pipe pile from becoming blocked when the soil of the first aquifer is incorporated into the steel pipe pile, and ensures watertightness inside the steel pipe pile by incorporating the soil of the impermeable layer into the steel pipe pile. [Brief explanation of the drawing]
[0010] [Figure 1] This is a partial cross-sectional view of a steel pipe pile according to an embodiment of the present invention. [Figure 2] This diagram shows the composition of the ground where the steel pipe piles are to be installed, and the steel pipe piles of this embodiment. [Figure 3] This figure schematically illustrates a method for constructing steel pipe piles according to an embodiment of the present invention. [Figure 4] This diagram shows other forms of steel pipe piles. [Modes for carrying out the invention]
[0011] Figure 1 is a partial cross-sectional view of a steel pipe pile according to an embodiment of the present invention. The steel pipe pile is a pile that is driven into the ground where, for example, a contaminated aquifer, an impermeable layer, a non-contaminated aquifer, and a supporting layer are stacked in order from the surface side.
[0012] As shown in Figure 1, the steel pipe pile 10 of this embodiment has a cylindrical portion 11 formed from a steel pipe and a blade 12 joined to the end face of the tip of the cylindrical portion 11, and is a rotary pile that is driven into the ground by rotary press-fitting using a construction machine (not shown). The shaft diameter of the cylindrical portion 11 can be, for example, 100 mm or more and 1600 mm or less. The steel pipe pile 10 is an open-end rotary pile, with an opening 13 formed at its tip. By matching the amount of penetration per rotation during rotational penetration to the helical pitch of the blades 12, the steel pipe pile 10 can be driven into the ground while drawing soil into the interior of the steel pipe pile 10 through the opening 13 at its tip without disturbing the ground.
[0013] A slip layer SL is provided on the inner surface of the steel pipe pile 10. The slip layer SL is a layer formed by a slip layer, which is a circumferential friction reducing material. The slip layer is formed from a material containing a low-friction material such as bituminous material (asphalt). The slip layer SL may be provided by applying the slip layer, or by attaching a sheet formed from the slip layer. Furthermore, in order to protect the surface of the slip layer SL, a surface protective material such as a nonwoven fabric may be provided on top of the slip layer SL.
[0014] The steel pipe pile 10 can be removed by rotating it in the reverse direction. In other words, the steel pipe pile 10 of this embodiment can be removed without using a casing to separate the pile from the ground.
[0015] Next, the design method for steel pipe piles according to this embodiment will be described. The steel pipe pile design method of this embodiment includes a ground structure acquisition step of acquiring the ground structure on which the steel pipe pile 10 will be constructed, and a steel pipe pile design step of designing the steel pipe pile based on the acquired ground structure.
[0016] The ground composition acquisition process performs known ground surveys such as boring surveys to acquire the composition of the ground, such as the depth of the formation boundary and the N value. Through the ground composition acquisition process, for example, a ground composition as shown in FIG. 2 can be obtained. Note that the composition of the ground may be acquired using known boring data without performing a ground survey.
[0017] In the steel pipe pile design process, the steel pipe pile 10 is designed based on the boring data obtained from the ground survey. Specifically, the specifications of the steel pipe pile (length, pile diameter, diameter of the tip blade, etc.) are determined by known methods. Also, in the steel pipe pile design process, the steel pipe pile is designed such that a slip layer SL is provided on the inner peripheral surface of the steel pipe pile 10. Specifically, in the steel pipe pile design process, the position where the slip layer SL is provided in the longitudinal direction of the steel pipe pile 10 is determined.
[0018] FIG. 2 is a diagram showing the composition of the ground where the steel pipe pile is constructed and the steel pipe pile of the present embodiment. The steel pipe pile 10 shown in FIG. 2 is a steel pipe pile 10 designed by the steel pipe pile design method of the present invention, and a steel pipe pile 10 provided with a slip layer SL on the inner peripheral surface. As shown in FIG. 2, in the ground of the present embodiment, a contaminated aquifer L1 (the first aquifer), an impervious layer L2, an uncontaminated aquifer L3 (the second aquifer), and a support layer L4 are laminated in order from the surface side.
[0019] In the steel pipe pile design process, the steel pipe pile 10 is designed such that the slip layer SL is provided in a range corresponding to the depth from the tip of the steel pipe pile 10 to the upper end of the impervious layer L2 (the depth of the contaminated aquifer L1) on the inner peripheral surface of the steel pipe pile 10. If the depth of the upper end of the impervious layer L2 is D, the slip layer SL is provided in the range of D from the tip of the steel pipe pile 10.
[0020] Next, the construction method of the steel pipe pile using the steel pipe pile 10 of the present embodiment will be described. Figure 3 is a schematic diagram showing a construction method for a steel pipe pile according to an embodiment of the present invention. In this embodiment, a steel pipe pile 10 is driven into the ground where a contaminated aquifer L1, an impermeable layer L2, a non-contaminated aquifer L3, and a supporting layer L4 are stacked in order from the surface side.
[0021] Here, the contaminated aquifer L1 is an aquifer containing pollutants such as specific hazardous substances. The impermeable layer L2 is located below the contaminated aquifer L1 and substantially blocks the flow of groundwater between it and the uncontaminated aquifer L3. Examples include a cohesive soil layer composed of clay. However, the impermeable layer L2 does not necessarily have to be a completely impermeable layer; for example, it may be a semi-impermeable layer defined as "a layer with a thickness of 1 meter or more and a permeability coefficient of 1 micrometer per second or less, or a layer with equivalent or greater water-blocking effectiveness." The uncontaminated aquifer L3 is a confined aquifer that does not contain pollutants because it is separated from the contaminated aquifer L1 by an impermeable layer L2. The ground may also include additional layers on the surface side of the contaminated aquifer L1, and between the contaminated aquifer L1, the impermeable layer L2, the uncontaminated aquifer L3, and the supporting layer L4.
[0022] In the ground conditions described above, when a steel pipe pile 10 is driven into a supporting layer L4 such as bedrock below the uncontaminated aquifer L3, it is necessary to prevent the contaminants contained in the contaminated aquifer L1 from mixing with and diffusing into the uncontaminated aquifer L3 by penetrating the impermeable layer L2. For example, if a closed-end rotary pile, i.e., a rotary pile without an opening at its tip, is used, there is a concern that the soil of the contaminated aquifer L1 will be pushed through the impermeable layer L2 and into the uncontaminated aquifer L3 by the penetration of the rotary pile, and that contaminants will diffuse as the soil of the contaminated aquifer L1 mixes with the uncontaminated aquifer L3.
[0023] In this embodiment, as described below, a steel pipe pile 10 which is an open-end rotating pile is used, and the soil from the impermeable layer L2 is incorporated into the inside of the steel pipe pile 10 in addition to the soil from the contaminated aquifer L1, thereby preventing the soil from the contaminated aquifer L1 from mixing with the uncontaminated aquifer L3.
[0024] Specifically, as shown in Figure 3(a), the steel pipe pile 10 is first driven into the ground from the ground surface, and the soil S1 of the contaminated aquifer L1 is taken into the interior through the opening at the tip of the steel pipe pile 10. Here, because a slip layer SL is provided on the inner surface of the steel pipe pile 10, the friction on the inner surface is reduced to 1 / 5 to 1 / 10. As a result, the contaminated aquifer L1 is smoothly taken into the interior of the steel pipe pile 10. Furthermore, because the area D where the slip layer SL is provided (see Figure 2) corresponds to the depth D of the contaminated aquifer L1 (the depth of the upper end of the impermeable layer L2), the entire contaminated aquifer L1 in the depth direction is smoothly incorporated into the steel pipe pile 10.
[0025] Furthermore, the steel pipe pile 10 is driven in, and as shown in Figure 3(b), the soil S2 of the impermeable layer L2 is taken into the interior through the opening at the tip of the steel pipe pile 10. In this way, if the soil S2 of the impermeable layer L2 is taken into the interior of the steel pipe pile 10 in addition to the soil S1 of the contaminated aquifer L1, then even when the tip of the steel pipe pile 10 reaches the uncontaminated aquifer L3, as shown in Figure 3(c), the soil S2 of the impermeable layer L2 separates the soil S1 of the contaminated aquifer L1 from the uncontaminated aquifer L3, thus preventing the diffusion of pollutants into the uncontaminated aquifer L3. After that, as shown in Figure 3(d), the tip of the steel pipe pile 10 is brought to the support layer L4, and the construction is completed.
[0026] Here, whether the tip of the steel pipe pile 10 has reached the impermeable layer L2 can be determined from the magnitude of the rotational torque required to drive the steel pipe pile 10 into the ground (hereinafter also referred to as the construction torque). Since the construction torque has a high correlation with the N value of the ground, if the N values measured in advance differ between the contaminated aquifer L1 and the impermeable layer L2, it can be determined that the tip of the steel pipe pile 10 has reached the impermeable layer L2 by the change in construction torque accompanying the change in N value. Furthermore, the construction torque also changes depending on the soil type of the ground. That is, even if the N values of the contaminated aquifer L1 and the impermeable layer L2 are similar, the construction torque will be smaller for the impermeable layer L2, which has a smaller permeability coefficient, compared to the contaminated aquifer L1, which has a larger permeability coefficient. Therefore, it can be determined that the tip of the steel pipe pile 10 has reached the impermeable layer L2 by the change in construction torque that reflects the change in soil type.
[0027] As described above, the open-end rotating steel pipe pile 10 can take in soil from the opening at its tip. However, if the ground is hard, the tip will be blocked by the taken-in soil, preventing further soil from being taken in. In the above example, if a slip layer SL is not installed on the inner surface of the steel pipe pile 10, the tip of the steel pipe pile 10 will be blocked when it takes in soil S1 from the contaminated aquifer L1, and as a result, the soil from the impermeable layer L2 will not be taken in. Consequently, the steel pipe pile 10 may reach the uncontaminated aquifer L3 with the soil S1 from the contaminated aquifer L1 exposed at its tip. To prevent this situation, in the above example, a slip layer SL is provided on the inner surface of the steel pipe pile 10 to facilitate the intake of soil from the contaminated aquifer L1, thereby preventing the tip from being blocked when the soil S1 from the contaminated aquifer L1 is taken into the steel pipe pile 10. This ensures that even when the ground beneath the contaminated aquifer L1 is hard, the soil S2 of the impermeable layer L2 is reliably incorporated into the steel pipe pile 10, preventing the pollutants from the contaminated aquifer L1 from spreading to the uncontaminated aquifer L3.
[0028] According to the embodiment described above, the impermeable layer L2 soil S2 taken in through the opening at the tip of the steel pipe pile 10, which is an open-end rotating pile, separates the soil S1 of the contaminated aquifer L1 taken into the inside of the steel pipe pile 10 from the uncontaminated aquifer L3, thereby preventing contaminants contained in the soil S1 of the contaminated aquifer L1 from mixing with the uncontaminated aquifer L3. As a result, when constructing a steel pipe pile 10 in ground containing a contaminated aquifer L1, the diffusion of contaminants can be prevented without using a casing pipe, and the pile construction process can be simplified.
[0029] Furthermore, by providing a slip layer SL on the inner surface of the steel pipe pile 10, the contaminated aquifer L1 is smoothly incorporated into the steel pipe pile 10. This prevents the tip of the steel pipe pile 10 from becoming blocked when the soil S1 of the contaminated aquifer L1 is incorporated into the steel pipe pile 10. Furthermore, by providing the slip layer SL in a portion of the steel pipe pile 10 corresponding to the depth D of the contaminated aquifer L1, rather than providing it along the entire length of the steel pipe pile 10, the manufacturing cost of the steel pipe pile 10 having the slip layer SL can be reduced.
[0030] Furthermore, by using a rotating steel pipe pile 10, the construction torque can be detected, allowing the steel pipe pile 10 to be driven in while confirming the ground structure. For example, if the impermeable layer L2 is thought to be thinner than investigated beforehand, necessary measures can be taken.
[0031] In the above embodiment, the steel pipe pile 10 is a rotating pile having a blade 12 joined to the end face at the tip, but it is not limited to this. For example, it may be a rotating pile having a cylindrical portion 11A formed of a steel pipe and a helical blade 12A joined to the outer circumferential surface of the cylindrical portion 11A, as shown in Figure 4. It is also applicable to steel pipe piles (driven piles) consisting only of a cylindrical portion without blades.
[0032] Furthermore, in the above embodiment, the slip layer SL is provided on the inner surface of the steel pipe pile 10 in a range corresponding to the depth from the tip of the steel pipe pile 10 to the upper end of the impermeable layer L2, but it is not limited to this. For example, the slip layer SL can be provided on the inner surface of the steel pipe pile 10 in a range corresponding to the depth from the tip of the steel pipe pile 10 to at least a part of the impermeable layer L2. In other words, the construction range of the slip layer SL can be extended to a range corresponding to the depth of the lower end of the impermeable layer L2. This makes it possible to smoothly incorporate the contaminated aquifer L1 and the impermeable layer L2 into the interior of the steel pipe pile 10. [Explanation of Symbols]
[0033] 10...Steel pipe pile, 11...Cylindrical section, 12...Wings, 13...Opening, L1...Contaminated aquifer (first aquifer), L2...Impermeable layer, L3...Non-contaminated aquifer (second aquifer), L4...Supporting layer, SL...Slip layer.
Claims
1. A design method for steel pipe piles to be driven into ground in which a first aquifer, an impermeable layer, a second aquifer, and a supporting layer are stacked in order from the surface side, A method for designing a steel pipe pile, comprising a steel pipe pile design step of designing the steel pipe pile such that a slip layer layer is provided on the inner circumferential surface of the steel pipe pile.
2. The process includes a ground structure acquisition step to acquire the structure of the ground into which the steel pipe pile penetrates, The steel pipe pile design method according to claim 1, wherein in the steel pipe pile design step, the steel pipe pile is designed such that the slip layer layer is provided on the inner circumferential surface of the steel pipe pile in a range corresponding to the depth from the tip of the steel pipe pile to the upper end of the impermeable layer.
3. The process includes a ground structure acquisition step to acquire the structure of the ground into which the steel pipe pile penetrates, The steel pipe pile design method according to claim 1, wherein in the steel pipe pile design step, the steel pipe pile is designed such that the slip layer layer is provided on the inner circumferential surface of the steel pipe pile in a range corresponding to a depth from the tip of the steel pipe pile to at least a portion of the impermeable layer.
4. The design method for steel pipe piles according to any one of claims 1 to 3, wherein the slip layer contains bituminous material.
5. The steel pipe pile design method according to any one of claims 1 to 3, wherein the steel pipe pile is a rotating pile having a cylindrical portion formed by a steel pipe and a blade joined to the end face on the tip side of the cylindrical portion.
6. The steel pipe pile design method according to any one of claims 1 to 3, wherein the steel pipe pile is a rotating pile having a cylindrical portion formed by a steel pipe and a helical vane joined to the outer surface of the cylindrical portion.
7. A steel pipe pile designed by the steel pipe pile design method described in any one of claims 1 to 3.
8. A construction method for driving steel pipe piles into ground in which a first aquifer, an impermeable layer, a second aquifer, and a supporting layer are stacked in order from the surface side, A step of providing a slip layer on the inner surface of the steel pipe pile before the steel pipe pile is driven in, A step of taking the soil from the first aquifer into the steel pipe pile through an opening formed at the tip of the steel pipe pile, The process of taking the soil of the impermeable layer into the interior of the steel pipe pile through the opening, The process of bringing the tip of the steel pipe pile to the support layer, Construction methods for steel pipe piles, including [specific details omitted].