JPS6383313A - Steel sheet pile excellent in separating strength of penetration tip joint section - Google Patents

Abstract

PURPOSE:To obtain the steel sheet pile with a joint which is not destroyed by the compaction of earth in a claw section, when the sheet pile is driven into ground, by local heat-processing a U-formed joint clad base section in a specified length from a penetration tip, and by increasing the strength thereof. CONSTITUTION:The claw base section (n) of the joint section (c) of steel sheet piles A, B is heated at approx. 900 deg.C in a specified length from a penetration tip and is oil-cooled, to enhance its strength. It is desirable that the length to be heated is approx. 50mm or more and 1,000mm or less. When the steel sheet pile B obtained as the result thereof is driven into ground along the previously set steel sheet pile A, then earth in claws engaged with each other is compacted at the lower section, but the strength of the joint claw base section (n) is kept enhanced, and so the joint section (c) is not destroyed by the compaction of earth.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the improvement of steel sheet piles that are widely used in civil engineering works for ports and rivers, and particularly improves the separation strength of joints that mesh and connect with each other. This relates to steel sheet piles that have excellent properties.

[Conventional technology]

As the construction environment for steel sheet piles has become increasingly severe in recent years, it is expected that steel sheet piles with joint shapes suitable for highly efficient construction will be required.

On the other hand, when driving steel sheet piles, the sand that enters the inside of the grip in the fitted state during sheet pile driving becomes gradually dehydrated and solidified as the root length becomes deeper, making driving difficult. If driving continues, the driving energy will turn into a horizontal force, and eventually the grill lugs of the steel sheet piles, which should be in a mated state, will open, causing the steel sheet piles to become uncoupled, causing earth and sand to flow out. This could lead to a dangerous situation.

In particular, in view of the increasing size of civil engineering construction in recent years, the demand for steel sheet piles that are suitable for this purpose and have excellent nine-high strength joint characteristics has become even stronger.

For example, Figures 3 (a) to (,) are a paper on the grill lag resistance when driving steel sheet piles published in Fudo Steel Technical Report, Vol. 17, No. 1 (March 1963), pp. 13 to 20. Fig. 3(b) shows a steel sheet pile B having the same type of steel sheet pile B being fitted with the grips adjacent to the steel sheet pile sheet pile B having a conventional U-shaped grip part that has already been driven. Fig. 3(a) schematically shows the condition of pouring, and shows an example of the relationship between the driving force P and the penetration depth h during pouring. It can be seen that a very large driving force P is required when h is about 6 m.

Considering the reason for this, the SA in the grip of the existing steel sheet pile A shown in Figure 3 (, ) is clogged with soil and sand of a high density depending on the depth, and the next steel sheet pile B is attached to the previous steel sheet pile. When they are fitted and driven in, the density of soil inside the grip is initially small, so some of the soil is removed from the grip opening KA of steel sheet pile A, and the remaining soil is intruded by the fitted steel sheet pile B. As it does so, it is compressed downward by the grip tip.

As driving continues, the soil within the grip becomes dehydrated, leaving almost no voids, and is compressed to the point that it approaches its true specific gravity. The position at which this state occurs varies depending on the soil quality, driving conditions, etc., but in the example shown in Figure 3 (,), the driving force P increases from the point when the tip of the steel sheet pile B passes 6 m, so the steel sheet pile It is thought that the soil density inside the grip of steel sheet pile A below the tip of B is considerably high.

Various countermeasures have been proposed to deal with such problems, but all of them have advantages and disadvantages, and it is far from possible to completely solve the problem.

For example, Japanese Patent Application Laid-Open No. 57-9221 proposes a technique for inserting a closing body into the gap between the claws of a steel sheet pile. It is unavoidable that the construction becomes complicated, and the bottom resistance increases.

Further, Japanese Patent Publication No. 57-32180 describes forming an arcuate recess on the inside of the U section surface of a steel sheet pile joint. Although this technology has a large rotation angle and is easy to construct, it has problems such as meandering of the interconnected steel sheet piles, so it may not be a perfect solution.

On the other hand, the present inventors have already published Japanese Patent Application Laid-Open Nos. 59-106618, 1982-145820, or 6
0-23519, etc., of the U-shaped grig part.
It is proposed that round steel sheet piles be provided with multiple through holes, multiple gaps, or discontinuous protrusions in the school area. By the way, it has been proven that all steel sheet piles with these configurations exhibit excellent effects during construction, but this is a slight disadvantage in manufacturing as it requires additional machining processes such as making holes in the steel sheet piles. It is inevitable that this will happen.

Therefore, the present inventors further investigated and created a steel sheet pile with superior joint separation strength by increasing the strength of the minimum plate thickness at 72 inches of the U-shaped joint and the strength of the nail base. 1982-
This is proposed in No. 76385. FIG. 4 schematically shows the structure of such a joint part, in which the plate thickness of the claw plate base part n is increased by a thickness Ti on both sides.

In addition, Japanese Patent Application No. 60-22155 proposes a steel sheet pile that is increased in thickness from 1 to 4 only on the inner side of the grip at the base of the U-shaped joint to have excellent joint separation strength.

FIG. 5 schematically shows the structure of such a joint portion, in which the thickness of the claw plate base portion n is increased by a thickness Δtn toward the inside of the grip.

However, in any case, such a joint is inevitably disadvantageous in terms of manufacturing costs due to increased weight.

[Problem that the invention seeks to solve]

The present invention provides steel sheet piles that have excellent earth and sand resistance within the grip when engaged and connected, do not cause the joints to separate from each other, do not impair workability like the conventional steel sheet piles mentioned above, and do not increase weight. It is intended to provide.

[Means for solving problems]

That is, the gist of the present invention is to provide a steel sheet pile consisting of a web and a pair of U-shaped joints provided at both ends of the web in the width direction via flanges.
This steel sheet pile is characterized by having increased strength by subjecting the root portion of the U-shaped joint having a diameter of 111 to 10001111 to an extreme heat treatment, and which has an excellent breakaway strength of a special tacked end joint.

[Example/effect]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. First, in order to find a means to completely solve the above-mentioned problems, the following experiments were attempted.

That is, FIG. 6(,) is a sectional view showing the fitted state of the existing steel sheet pile and the poured steel sheet pile B, as in the case of FIG. indicates the U-shaped bottom of the joint, and S indicates the interior of the grip. An earth pressure gauge G was embedded in the bottom part U to measure the horizontal earth pressure.

In addition, Fig. 6(b) is a schematic diagram showing the position of the soil pressure gauge G embedded in the joint U-shaped bottom U of the cast steel sheet pile B, and the soil pressure gauge 01 in the figure is located at 10011 from the embedding tip. Position to,
Earth pressure gauge G2, G3.

Up to G4 and G5, the joints U are each 100B pitch.
It is embedded in the bottom part of the letter U. 1 more with 500 nod pitches
0 soil pressure gauges G are continuously embedded in the bottom U of the U-shape of the joint to learn the behavior of the soil pressure inside the grip Sn.

The steel sheet piles tested were FSP-5L standard 5Y-30, and the thickness at the base of the nail was 9.5B.

FIG. 7 shows the relationship between the soil pressure measured inside the grip S of the poured steel sheet pile B using a soil pressure gauge G in this experiment and the underground position of the tip of the poured steel sheet pile B.

As is clear from Fig. 7, the earth pressure gauges 01 to G5 indicate that as the underground position increases, the earth pressure p1 inside the grip S of the poured steel sheet pile B increases, especially at the lower part of the fitted steel sheet pile B. Embedded soil pressure gauge Gl.

2, it is clear from this measurement result that the earth pressure p1 increases rapidly from the point 15 meters underground when passing through. but,
Earth pressure gauge G6-G embedded with 50011 pitches from G5
Since the earth pressure p1 of n was less than 0.1 kcg/fl12, it was excluded from the diagram.

Further, after that, when the steel sheet piles A and B were pulled out from the fitted state, it was confirmed that the joint claw tips had separated and separated at the lower end surface up to 200 fl from the tip of the root pile. Moreover,
The tip of the joint claw came off and the roots were inserted in nine places.200,5
Measure the cross-sectional hardness of 00゜soow, and in the 8th figure), the nail tip S point, the locking 100 point, the nail plate base part point, the U section part U
When sorted in relation to the joint shape position shown by the dots, it can be seen that the base of the claw plate exhibits the highest hardness, as is clear from FIG. 8 (,). This is thought to be due to the work hardening of the base of the nail plate due to the bending action when the tip of the nail, which functions as a nail shifter, is raised.

When driving steel sheet piles, the reason why joints separate in the earth and sand is that the soil pressure inside the grill is caused by consolidated earth and sand that spreads from the rooting tip to 8001111.
The present inventors will further explain the present invention hereinafter by explaining the fact that a large bending force acts on the base of the claw plate over the entire length, causing the joint to separate due to total cross-sectional yielding.

Figure 1 (,) shows a steel sheet pile with a width W and a height H, which is composed of a web a and a pair of U-shaped joints C provided at both ends in the width direction of the web via flanges. Figure 1 (b) is an enlarged view of the U-shaped joint C of the steel sheet pile.
n represents the thickness of the base of the nail, and LW represents the width of the base of the nail. Figure 1 (C
) is a steel sheet person.

Fig. 1 (d) shows the state in which steel sheet piles A and B are completely connected to each other and are being poured into the earth and sand, and Fig. 1 (d) shows the steel sheet piles A and B completely connected to each other in the earth and sand. This figure shows the state in which the steel sheet piles have been completely poured. In the figure, people are the existing steel sheet piles, B is the steel sheet piles being driven, and La and Lb are the respective steel sheet piles A.

It represents the introduction length from one rooting tip of the base of the nail plate in B.

In the steel sheet pile of the present invention having such a configuration, the width of the base of the claw of the U-shaped joint C shown in FIG. 1(b) is the heat-treated width, and ), the introduction lengths La and Lb of the existing steel sheet pile A and the cast steel sheet pile B can extremely effectively improve the separation strength of the joint at the end of the joist.

That is, such nail root width - 1 introduction length La.

By heat-treating the claw base plate thickness tn within the range of Lb, the bending portion at the time of separation from the joint is strengthened. In this case, the heat treatment conditions are as follows: how much should the breakaway strength be, taking into account the condition of the pouring ground; heat treatment - the width of the nail base of the enclosure; the thickness of the nail base plate tn1; the introduction length La, Lb
need to be selected appropriately. Moreover, the introduction length La, L
By applying the heat treatment described in b to the base of both U-shaped joint claws, the joint separation strength at the tip of the joint is further improved, so it is necessary to select this method in the case of hard ground. be. For example, when driving steel sheet piles on normal sandy ground, the heat treatment conditions include heating to 900°C followed by oil cooling, forced air cooling, water cooling, etc. In this case, the heat treatment range is 1Qtm or more when the nail root width LW is , the nail base plate thickness t3 is the total cross-sectional plate thickness, and the introduction lengths La and Lb are 59 from the joist tip.
It is effective to set the introduction length Lm to 1000111 or more. In this case, setting the introduction length Lm and LbO heat treatment length to 50111 or more and 1000111 or less from the joist tip is equivalent to not performing heat treatment at all if it is less than 50m. This is because it is only a moderate withdrawal strength and has no effect. Moreover, when it exceeds 10100O, it is more than 50n 100011
It is not preferable because the effect of heat treatment in the range of 11 or less is only as good as that of heat treatment, and the working time used for heat treatment is wasted.

Further, as long as the nail root width - 〇 heat treatment range is 10 or more, there is no problem even with the entire nail root.

This fact was obtained through the following experiment. In other words, the steel sheet piles used were U-type 5L type standard BY-
30, the steel sheet pile length was set to 200011fl.

The experiment was conducted using an air-hand release method using local tension. Here, the local tension empty hand release test will be explained with reference to FIG. 2 (,).

In the figure, A and B indicate steel sheet piles that are fitted together, and T indicates a tag plate in which external tensile force is used to replace the earth and sand that is consolidated in the joint and generates internal pressure in the normal earth and sand ground. In this case, the lengths of steel sheet piles A and B are 20001jE, and the tab plate T
In this method, the length of the tab plate T is set to 200 mm, and a tensile load is applied to the tab plate T to cause the joint to separate, and the joint separation strength is evaluated.

The results of the experiment are shown in FIG. 2(b) as the heat treatment length La from the joist tip (in the case in the figure, the tag plate attachment end surface).

It is shown by the relationship between Lb and joint separation strength Pa.

The heat treatment lengths La and Lb from the tips of the joists were the same for both fitted steel sheet piles.

In addition, the nail root heat treatment width is l 5111. The thickness of the base plate of the ti nail was 91 m, and the heat treatment conditions were as follows: heating at 900°C followed by oil cooling.

As is clear from the figure, the heat treatment length Lm from the joist tip
, As Lb increases, the joint separation strength Pa increases (indicated by O mark). In other words, the joint separation strength is improved by improving the material quality of the base portion of the claw plate, which is the bending portion, through local heat treatment, which indicates that the effects of the present invention are being achieved.

However, when the heat-treated length from the tip of the joist is 3011 (indicated by Δ), in the case of 0 length where no heat treatment was performed at all (
The joint separation strength was no different from that shown by the square mark.

In addition, when heat treatment exceeds 100Q+11, the joint separation strength (indicated by 0 mark) improves, but considering the pressure inside the joint when driving steel sheet piles in normal sandy ground, the joint separation strength is 100 Ton/M. If it has this performance, there is no risk of it coming off during pouring. Rather, considering the working time in heat treatment, the efficient heat treatment lengths La, L
It would be better to deal with normal sandy ground by setting b to 1000 cranes.

Next, the effects of the present invention will be illustrated in more detail with reference to a construction example using steel sheet piles according to the present invention.

The steel sheet piles tested were the same as those used in the explanation of Figure 5, F
SP-5L standard 5Y-30, nail base plate thickness tn is 9III
E is used as a comparative example, and the steel sheet pile of the present invention is as follows:
The heat treatment range is the heat treatment length from the tip of the joist La, Lb
was changed as appropriate to 100II and 500111*11000f. In this case, the hardness N value of the sandy ground is measured in advance, and the joint strength Pc of the data shown in Figure 2 obtained in the laboratory experiment is
It was placed on sandy ground suitable for the area. In addition, a nail base heat-treated width of 5 silk and a full thickness nail base plate thickness were used.

Next, at the time of fitting and pouring, the earth pressure inside the grip S3 of the poured steel sheet pile B was measured using an earth pressure gauge G1, as in the case of FIG.

When the steel sheet piles were completely driven at 20 rnt, steel sheet piles A and B were pulled out in the fitted state to observe whether or not joint separation occurred.

The results are summarized in Table 1, and in the case of the steel sheet pile of the present invention, no joint separation was observed at all, and the condition was normal.

Table 1: This is the joist according to the present invention.
This is because the joint separation strength was improved by performing extreme treatment on the base of the U-shaped joint claws up to 0.000 mm.

〔Effect of the invention〕

As explained above, according to the steel sheet pile of the present invention, safety is ensured by improving joint separation performance during fitting and pouring, and furthermore, joint strength can be controlled arbitrarily according to the sandy ground condition at the site. , which is extremely advantageous industrially.

[Brief explanation of the drawing]

FIG. 1 (&) is a diagram showing the shape of the steel sheet pile according to the embodiment of the present invention,
Figure 2 (b) is a detailed diagram of the joint, Figures (e) and (d) are explanatory diagrams during installation in the soil, and Figure 2 (,) is a schematic diagram explaining the joint separation strength evaluation test. (b) is a diagram showing an example of the relationship between the lead-in length from the tip of the joist and joint separation strength. Figure 3 (,) shows an example of the relationship between the depth of the joist at the tip of a conventional steel sheet pile and driving force. Figures 4 and 5 are schematic diagrams illustrating the conventional steel sheet pile, and Figure 6 (,) is an illustration of the steel sheet pile on the same side. A joint view of steel sheet piles showing the embedded state of pressure gauge G, (b) is a schematic diagram showing the embedded position of soil pressure gauge G, and Figure 7 shows the earth pressure in the grill lag of each soil pressure gauge embedded in the cast steel sheet pile. Fig. 8 is a diagram showing an example of the relationship between steel sheet pile cross-sectional hardness and its measurement position, and (b) is a diagram showing the measurement position. It is. a... Web b... Flange C... Joint part U... Joint U-shaped bottom n... Claw plate base tn... Claw root plate thickness Fig. 1 a Web b Flange c: mf Part U Joint U-shaped bottom n: Nail base Fig. 1 (c) (d) Fig. 2 (Q) Fig. 3 (CI) ) Room 4 Figure 6 (Q)

Claims (1)

[Claims] In a steel sheet pile consisting of a web and a pair of U-shaped joints provided at both ends in the width direction of the web via flanges, the claw base of at least one of the U-shaped joints extends between 50 mm and 1000 mm from the embedded tip. A steel sheet pile with excellent breakaway strength at the root end joint, which is characterized by having undergone extreme heat treatment to increase its strength.