JPS58207416A - Steel pile for hard ground - Google Patents

Abstract

PURPOSE:To drive a steel pile into hard ground without causing the crushing or abrasion of the tip portion of the pile by attaching a shoe made of a steel material having a high strength and a high wear resistance to the tip of the pile body. CONSTITUTION:A shoe 5 made of a steel material having a high strength and a high wear resistance, e.g., high-carbon and high-manganese steel or blister steel, is welded to the tip of a pile body 1, for example. The preferred high-C and high-Mn steels are preferably ones containing 0.50-1.20wt% C and 10-20wt% Mn and having a tensile strength of 75kg/mm.<2> or more, which is subjected to work hardening. When a cemented steel is used, the preferred steels are ones containing 0.5% or more carbon and having a Vickers hardness of 400 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel pile for hard ground that is used by being driven into hard ground.

Piles that are driven into hard ground, that is, hard ground or rock with an N value of over 50 in a standard penetration test, have traditionally been reinforced using the following method.

■ Increase the thickness of the pile tip (2) as well as the thickness of the other parts (1) (Figure 1).

■ Weld the reinforcing plate (3) to the pile tip (2) (Figure 2).

■ For steel pipe piles, weld the cross plate (4) inside the pipe at the pile tip (2) (Figure 6).

However, although these methods can somewhat improve the rigidity of the tip of the pile, they also pose the following problems.

■ Although the rigidity of the pile tip improves, the pile driving efficiency (speed) decreases because the cross-sectional area of the tip increases.

■ Since there is no improvement in the hardness of the pile tip, the above method is effective in preventing crushing and wear of the pile tip due to pile driving.

(2) Piles with complicated tip shapes, such as steel sheet pile piles, cannot be reinforced using the above method.

■ Because rolled steel piles have a certain amount of residual strain, they cannot be expected to have sufficient strength, and when driven into hard ground, this residual strain causes the steel pile to collapse.

This invention was made to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a steel pile for hard ground that does not cause crushing or wear at the tip of the pile even when driven into hard ground. It is something.

The gist of this invention is a steel pile for hard ground, in which a shoe is formed of a steel material with high strength and wear resistance, and the shoe is attached to the tip of the pile body.

Embodiments of the present invention will be described below with reference to the drawings.

(5) A shoe, and the shoe (5) is attached to the pile body (1).
The shoe (5) and the pile body (1) form a steel pile for hard ground. The shoe (5) is made of a steel material with high strength and wear resistance, and the steel material may be high carbon, high manganese steel or carburized steel. As a high carbon high manganese steel,
C component is 0.50 to 1.20 wt%, Mn component is 10
~20 wt%, a tensile strength of 75 (- or more) and work hardening is preferable. The actual piles shown in Figures 5 and 6 were manufactured and tested in greenschist along with H piles made of ordinary steel (5S41).The actual piles with shoes made of steel in this range were found in greenschist. This is based on the results that the ordinary steel H pile could not be driven due to local buckling, whereas it could be driven into the pile quickly.

Table 1 The difference as mentioned above is that high carbon, high manganese steel has the property of being significantly hardened by processing, and the tip of the pile made of high carbon, high manganese steel is processed by hammering and cutting during driving, and the surface layer becomes significantly hardened. In order to improve wear resistance, high carbon high manganese steel was originally
This is because it has twice the strength. The degree of hardening of the tip of the pile due to impact from driving and cutting is shown in Table 2.1
That's right.

Table 2: Butt or fillet welding can be used to attach the shoe to the pile body. This is because, as shown in Table 6, when actual piles with shoes attached by butt or fillet welding were actually driven in, good results were obtained in all cases. In the figure, (6) indicates a welded part.

No. 6 When surface-carburized steel is used as a shoe, the surface layer must have a Vickers hardness of 400 or more or a carbon content of 0.5.
% or more is preferable. The reason why this range is preferable is that the actual piles shown in Figs. 9, 10, and 11 are manufactured by carburizing in the process shown in Fig. 7, and the hardness distribution is as shown in Fig. 8, and the actual piles shown in Figs. Greenschist (-axial compressive strength qu = 500 Ks = f/i) with H steel piles made of steel
When we drove the carburized pile into the pile, it was possible to drive it quickly, but as shown in Figure 12, the tip of the normal steel H steel pile had significant wear, and the plate thickness at the tip This is based on the result that the metallurgy decreased, which caused local buckling and made it impossible to drive. In FIGS. 9 to 11, the mesh portion (7) represents the carburized portion, and the other portion (8) represents the carburized portion.

The above difference is that by carburizing, carbon penetrates into the interior from the steel surface, and the closer to the surface the higher the carbon content, but the interior is made of mild steel, and as a result, the surface layer has a lower resistance. This is because it has excellent wear resistance, and the pile as a whole has good toughness and impact resistance. The degree of decrease in plate thickness with each driving extension is as shown in FIG.

Since surface hardening by carburization prevents a decrease in plate thickness, it can be seen in the figure that the decrease in plate thickness is greater as the Vickers hardness is less than 400, and the degree of wear is extremely increased.

Although it is possible to carburize the entire steel pile, it is possible to reduce costs by carburizing only the shoe and welding it to the pile body. Shoes that have been carburized will have an increased amount of carbon and will have poor weldability, but if a special chemical is applied to the welding area, carburization of that area can be prevented, so there is no problem with welding it to the pile body. The cross-sectional shape of the t/-4° shoe is the same as the cross-sectional shape of the pile body, and is tapered so that the cross-sectional area decreases toward the tip. This is because the driving resistance in hard ground is dominated by the pile tip resistance rather than the frictional resistance of the pile circumferential surface, and the penetration speed increases as the energy per unit area of the pile tip increases, that is, the impact energy of no. If so, the smaller the cross-sectional area of the tip, the faster the purchasing speed can be. The height of the shoe is preferably about 20% to 50% of the width of the pile body. This is because it has been experimentally confirmed that this range is effective against local buckling.

The tip of the shoe may be smooth as shown in FIG. 14, or may be uneven as shown in FIG. 15. Providing unevenness at the tip of the shoe has the effect of making it easier to drive the pile. In addition,
High-carbon, high-manganese steel shoes are manufactured by pouring molten steel into molds. As the pile body, steel shapes such as H steel, steel pipes, or steel sheet piles can be used.

As explained above, in this invention, the shoe is formed from a steel material with high strength and wear resistance, and the shoe is attached to the pile body, so there is no possibility of wear or local buckling even if the shoe is driven into hard ground. This has the effect of allowing efficient driving work.

[Brief explanation of drawings]

Figure 1 shows a steel pipe pile in which the thickness of the tip of the pile is greater than that of the other parts; (a) is a longitudinal cross-sectional view, and (b) is a vertical cross-sectional view.
is a plan cross-sectional view. Figure 2 shows a steel pipe pile with a reinforcing plate welded to the tip of the pile; (a) is a longitudinal cross-sectional view, (b)
is a plan cross-sectional view. FIG. 3 shows a steel pipe pile in which a cross plate is welded into the pipe at the tip of the steel pipe pile, where (a) is a longitudinal sectional view and (b) is a plan sectional view. FIG. 4, FIG. 5, and FIG. 6 show examples of steel piles for hard ground according to the present invention. Figure 4 shows a steel pile with a shoe welded to the tip of the H steel; (a) is a side view, (b) is a front view, (
C) is a plan sectional view. Figure 5 shows a steel pile with a shoe welded to the tip of a steel pipe, with (a) being a longitudinal sectional view and (b) being a plan sectional view. FIG. 6 shows a steel pile with a shoe welded to the tip of a steel sheet pile, in which (a) is a side view, (b) is a front view, and (C) is a plan sectional view. FIG. 7 is a process diagram of the carburizing treatment, and FIG. 8 is a graph showing the hardness distribution of the carburized shoe. FIGS. 9, 10 and 11 show an embodiment of a steel pile for hard ground according to the present invention, which is equipped with a carburized shoe. FIG. 9 shows a steel pile in which a shoe is welded to the tip of a steel pipe, (IL) is a side view, and (b) is a plan sectional view. FIG. 10 shows a steel pile with a shoe welded to the tip of the H steel, in which (a) is a front view and (b) is a plan sectional view. FIG. 11 shows a steel pile in which a shoe is welded to the tip of a steel sheet pile, in which (a) is a front view and (b) is a plan sectional view. 12th
The figure is a sketch of an H steel pile that has locally buckled, and Figure 16 is a graph showing the degree of decrease in plate thickness for each driving extension. FIGS. 14 and 15 are explanatory views showing the shape of the tip of the shoe, with (a) being a front view and (b) being a side view. 1...Pile body, 5...-Shoe, 6...Welding department agent Patent attorney Mitsuru Kimura Akakake-ζ 9a9 8th, Furu 1, Yu ψ Fig. 9 Ryo 10 mouth Fig. 11 (0) (CI)
(0) Figure 12 Sasa Figure 13 Figure 14 (b) (a) Rod 15 Figure (b) (a)

Claims (1)

[Claims] A steel pile for hard ground, characterized in that the shoe is formed of a steel material with high strength and wear resistance, and the shoe is attached to the tip of the pile body.