JPS60219319A - Steel sheet pipe excellent in disjoining strength of joint part - Google Patents

Abstract

PURPOSE:To prevent breakage of a claw root part and disjoining of a joint due to a pressure generated resulting from an increase in density of earth in a grip with the progress of hammering, by a method wherein the strength of the claw root part of a U-shaped joint part is increased over that of the minimum thickness part of the flange of a steel sheet pile. CONSTITUTION:A pair of U-shaped joint parts (c) are attached to opposite ends in the direction of width of a web through the medium of a flange part (b) to form a steel sheet pipe. The strength of a claw root part (n) of the U-shaped part (c) is increased over that of a minimum thickness part (f) of a flange part. This, when a pressure is increased resulting from an increase in density of earth in a grip with the progress of hammering, causes the minimum thickness part (f) of the flange to be yielded before the claw root part (n), being the weakmost part of the grip, is yielded, resulting in prevention of disjoining of a joint.

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 in particular to the separation of joints that engage and connect with each other. This relates to steel sheet piles with excellent strength.

[Prior art and problems]

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 soil that invades the inside of the grip in the fitted state during sheet pile driving becomes gradually dehydrated and solidified as the root depth becomes deeper, making it difficult to drive. If driving continues, the driving energy will turn into a horizontal force, and eventually the grip 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 such as causing

In addition, the back earth pressure when used for earth retention, water shielding, etc. is as follows:
The demand for steel sheet piles with excellent high-strength joint properties suitable for larger civil engineering construction projects has become even stronger in recent years, as the weight increases in proportion to the depth.

For example, Figure 1 is from the Fudo Steel Technical Report, Volume 17, No. 1 (Showa 4).
March 2013) This is shown in the paper on grip resistance during driving of steel sheet piles published on pages 13 to 20, and is a steel sheet pile with a normal OU type grip part that has already been driven. This is an example showing the relationship between the driving force P and the penetration depth h of the same type steel sheet pile B that is being driven with the grips fitted together in contact with AKIII. It can be seen that a large driving force P is required.

Considering the reason for this, the inside of the grip sA of the existing steel sheet pile A is clogged with earth and sand of high density depending on the depth, and when the next steel sheet pile B is fitted into the previous steel sheet pile A and driven,
Initially, the density of soil inside the grip is small, so some of the soil is removed through the grip opening KA of the steel sheet pile A, and the remaining soil is moved downward by the tip of the grip as the fitted steel sheet pile B enters. Compressed.

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 1, the tip of the steel sheet pile B is at 2
Since the driving force P becomes large after passing 0 m, it is considered that the soil density in the grill lag of the steel sheet pile A below the tip of the steel sheet pile B becomes significantly higher.

In order to deal with such problems, various countermeasures have been proposed, but all of them have advantages and disadvantages, and do not completely solve the problem.

For example, Japanese Unexamined Patent Publication No. 57-9221 proposes a technique for inserting a closing body into the gap between the claws of a steel sheet pile, but this method makes it difficult to actually attach and remove the closing body. It is unavoidable that the construction becomes complicated, and the bottom resistance increases.

Further, Japanese Patent Publication No. 57-32180 describes that four arc-shaped parts are formed inside the U-shaped bottom surface of a steel sheet pile joint. Although this technology has a large rotation angle and is easy to construct, it has many problems such as meandering of the interconnected steel sheet piles, so it may not be a complete solution.

On the other hand, the present inventors have already published Japanese Patent Application No. 57-216864,
Patent Application No. 18059/1982 or Patent Application No. 130/1982
No. 273, etc., proposes a steel sheet pile in which a plurality of through holes, a plurality of gaps, or a discontinuous convex portion are provided in the U-shaped bottom of the pU-shaped grip portion. By the way, it has been proven that all of the 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.

In view of the current situation, the following experiments were attempted in order to find a means to completely solve the above problems.

That is, as in the case of FIG. 1, FIG. 2 is a cross-sectional view showing the fitted state of the existing steel sheet pile A and the cast steel sheet pile B, and in the figure n
indicates the base of the claw, and f indicates the minimum plate thickness of 7 runs. In order to understand the deformation behavior of the joint of the existing steel sheet pile A, the inventors determined the point n of the base of the claw at a depth of 20 m. A strain gauge was attached to each of the points f and the minimum plate thickness of the flange, and the amount of strain in the horizontal direction was measured.

FIG. 3 shows the relationship between the amount of strain measured in the joint deformation behavior of the existing steel sheet pile A and the driving force of the poured steel sheet pile B in this experiment.

As is clear from Fig. 3, as the driving force P of the fitted steel sheet pile B increases, the compressive strain at point n and the tensile strain at point f increase. The measurement results show that the amount of strain increases rapidly from the point of passing, and that the point n reaches a yield strain state earlier than the point f, causing plastic deformation.

Further, when the steel sheet piles A and B were subsequently pulled out in the fitted state, it was found that the grip was clogged with solidified earth and sand, and the pressure inside the grip had increased considerably. If this situation progresses, it is estimated that it will lead to accidents such as joint separation.

In other words, the density of soil inside the grip during fitting driving is not high in proportion to the depth, and the soil solidified into concrete may generate high pressure inside the grip, and the steel sheet piles that should be in the fitted state may The base of the claw of the U-shaped joint yields first. The mechanism by which the tips of the claws, which should function as the claws and hooks, rise up and cause the mutually interlocking and connected U-shaped joints to separate has been clarified.〇 [Object of the Invention] Book The invention provides a steel sheet pile that has excellent earth and sand resistance within the grip when engaged and connected even under such severe conditions, does not allow the joints to separate from each other, and does not impair the workability of conventional steel sheet piles. It is intended to.

[Structure of the invention]

That is, the gist of the present invention is that 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 7 rungs, the strength of the minimum plate thickness of the flange is This steel sheet pile has excellent separation strength of the joint part, which is characterized by increasing the strength of the claw base of the shaped joint part.

The present invention will be described in detail below with reference to the drawings.

Fig. 4 shows the width W consisting of the web a and a pair of U-shaped joints C provided at both ends in the width direction of the web via seven run parts.
1 shows a steel sheet pile with a height H, and furthermore, the detailed drawing of the joint C includes the minimum plate thickness of the flange f1 the base of the claw n1 the height of the claw d
1 claw plate thickness g1 flange minimum plate thickness 1 (, claw plate base plate thickness t
Dimensions and shapes such as n% nail bottom plate thickness tu, angle θ1 between flange b and nail bottom e, angle between nail bottom e and nail), angle θ2 with surface 8, grip/opening width, etc. It is. In the steel sheet pile of the present invention having such a configuration, the strength at the base of the claw is made thicker than the strength at the minimum thickness of the flange, as described earlier with reference to Figs. 1 and 2 when driving the steel sheet pile. As the horizontal force increases as the driving force increases, this is to ensure that the minimum plate thickness part f of the flange yields before the base part n of the claw plate, which is the weakest part of the grip, yields.

In other words, when the minimum plate thickness part f of the flange first yields and deforms, it shifts to rotational bending deformation that involves the tip of the claw, and eventually the tip of the claw is prevented from rising up and becomes strong due to mutual engagement. This prevents the joint from coming off at all.

In this case, as a means to increase the strength of the claw base part more than the strength of the minimum plate thickness of the flange, for example, the minimum plate thickness part f of the flange is made thinner than the nail plate base part n, and the tip part of the claw is It is also possible to cause this phenomenon to occur, or it is also possible to cause this phenomenon by lowering the yield stress of the 7 rung part than the yield stress of the base of the nail plate, and the method that is advantageous for manufacturing can be selected as appropriate. You can.

When the hardness of the flange minimum thickness section is Hvf and the hardness of the claw plate base section is Hvn, the flange minimum thickness section strength is t.
In addition, the nail base strength can be expressed as fX4■ and t□XJ ball i, and when expressed in this way, the relationship between the two must satisfy tfX: 〉1.0.

In this case, the flange minimum thickness part strength ′JfctfX lesson i
Also, the reason why the nail root strength can be expressed as tnX JFi is that the bending moment when the entire cross section of the minimum plate thickness part f is plastic is approximately -t" f X Hvf
X±−3, 3
This is because X Hvn X L -ment Mn is approximately expressed as - and 3 This is because the strength is increased.

The steel sheet pile of the present invention can be applied to any shape as shown in FIG.
It exhibits a remarkable effect when used with a size in the range of 0 rtanXH from 85 trlIn to 225 mm.

〔Effect of the invention〕

As explained above, according to the steel sheet pile of the present invention, it is possible to prevent the joint from separating when driving the fitting together, improving construction efficiency, and since the structure is simple, it is easy to increase or decrease the thickness or hardness during manufacturing. Moreover, it can be carried out economically, so it is extremely advantageous industrially.

〔Example〕

Next, the effects of the present invention will be illustrated in more detail with reference to Examples.

Example 1 The chemical components are shown in Table 1, and the mechanical properties are shown in Table 2.

The basic dimensions and shapes of the U-shaped steel sheet piles tested are shown in Table 3. Only the thickness t1 of the Franz f section and the thickness tn of the n section at the base of the nail are 7 to 11, respectively. .5 kaku and 8 pus ~ 12. The steel sheet piles that have been completely fitted and placed are pulled up as they are, and the locking length t on the hook surface S is determined at the position shown in Fig. 5. It was measured. In this case, if the locking length before pouring is tOs, the locking length after pouring is tl, and the locking length change amount is Δt, the locking length change amount Δ1=10−11.

FIG. 6 is a plot of the relationship between the amount of change Δt in the hooking length of the hook surface 8 and the thickness 11 of the flange f section/thickness 1n of the n section of the hook base based on the measurement results.

In other words, an increase in the amount of change Δt in the pawl locking length indicates that the pawl hook surfaces S that have been engaged with each other are approaching the detached state, and when the plate thickness ratio exceeds 1.0, the pawl hook surfaces The amount of change in locking length Δt is as small as 1 mm to 4 cm, indicating that the claw does not come off.

Example 2 As in Example 1, for U-shaped steel sheet piles having the chemical composition and basic dimensions and shapes shown in Tables 1 and 3, the thickness t4 of the flange f part and the thickness tn of the nail base n part were 10.5 am. , and the cross-sectional hardness Hvf of the flange f part and the cross-sectional hardness Hvn of the nail base n part were varied within the range of 160 to 185. The sheet pile was pulled up as it was, and the locking length t on the claw hook surface S was measured at the position shown in FIG. In this case, if the locking length before pouring is to, the locking length after pouring is tl, and the locking length change amount is Δt, the locking length change amount Δt=1.
-1. It is expressed as

Figure 7 is a plot of the relationship between the variation Δt of the pawl locking length of the slope S of the pawl portion and the cross-sectional hardness Hvf of the flange f section/the cross-sectional hardness Hvn of the n portion of the nail base based on the measurement results. be. That is, an increase in the amount of change Δt in the claw locking length indicates that the claw hook surfaces 8 that have been engaged with each other are approaching the detached state, and when the hardness ratio exceeds 1.0, the claws are locked. The length change amount Δt is as small as 1wn to 41 stitches.

This clearly indicates that the flannel portion yields first, suppresses the lifting of the tip of the claw, and causes the claw to be rolled up, preventing the joint from separating.

[Brief explanation of the drawing]

Fig. 1(a) is a diagram showing an example of the relationship between the tip penetration depth and driving force of a conventional steel sheet pile, Fig. 1(b) and (c) are explanatory diagrams of the aspect of the steel sheet pile on the same side, and Fig. 2 The figure is a Vr side view of the fitted steel sheet pile A and the poured steel sheet pile B, and Figure 3 shows an example of the relationship between the driving force of the fitted steel sheet pile B and the amount of strain at the joint of the existing steel sheet pile A. 4(a) is a sectional view showing the dimensions and shape of the steel sheet pile according to the present invention, FIG. 4(b) is a detailed explanatory view of the joint part,
FIG. 5 is a sectional view of the locking length measurement position, and FIG.
FIG. 7 is a diagram showing an example of the relationship between the change in pawl locking length and the pawl base plate thickness/flange plate thickness in the steel sheet pile according to the present invention and the conventional steel sheet pile. It is a diagram showing an example of the relationship between nail base hardness/flange hardness. a... Waep b... Franz C... Joint part d... Claw height e... Claw part s tu... Claw plate thickness g... Claw blade thickness k... Grip Opening width S...Claw hook surface n...Claw plate base f...Flange minimum plate thickness C1tl-1101), 0/X 4WMLF:d Fig. 1 ((1) A Fig. 2 Fig. 3 Figure ``ρ; Fitting irA arrow, anti-β, snoring force x 10' (T
on-yn) Figure 5 3 V) γ

Claims (1)

[Claims] Kueb and Kueh! In steel sheet piles consisting of a pair of U-shaped joints installed at both ends in the width direction via flanges, the strength of the minimum plate thickness of the flange is increased and the strength of the claw plate base of the U-shaped joint is increased. Steel sheet piles with excellent separation strength at joints.