JP2002327438A - Jamming prevention method during casting - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a method for preventing jamming at the time of casting, which can compensate for the shortage of earth and sand at a casting site and can also prevent the solidification of sand grains in a joint portion. SOLUTION: In a construction method for promoting liquefaction of a casting site such as a steel sheet pile by supplying a jet water flow and preventing jamming at a joint portion such as a steel sheet pile,
When the pouring operation is interrupted, bentonite is mixed in the jet water flow in advance, and bentonite is replenished to locations where soil particles have been reduced by liquefaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention promotes the liquefaction of a casting site such as a steel sheet pile by supplying a jet water stream,
The present invention relates to a method for preventing jamming at a joint portion such as a steel sheet pile.

[0002]

2. Description of the Related Art In the driving of steel sheet piles and the like, a joint is connected to an adjacent member through a joint to form a wall surface.
When the casting site is a sandy soil layer, a so-called wedge phenomenon occurs at the joint site regardless of the dynamic construction method or the static construction method. That is,
In the construction procedure here, steel sheet piles are cast while removing the earth and sand clogged in the joint parts such as the steel sheet piles that were pre-pressed downward or sideways with the joint parts such as the next steel sheet piles. It is difficult to eliminate this completely. In particular,
When applied to a fine sand layer with a uniform grain size, the sand particles are dehydrated and solidified inside the joint with the press-fitting of steel sheet pile, etc., increasing the joint resistance and eventually leading to the joint detachment This has adverse consequences (commonly referred to as wedge or jamming phenomena).

[0003] Attempts have been made to use a liquefaction treatment of earth and sand by supplying a jet water stream used for excavation when placing steel sheet piles or the like. However, the problem here is that liquefaction causes small sand particles. Is raised by the water current, and the absolute amount of sediment at the casting site is insufficient. This also causes later land subsidence. In addition, when the casting operation is temporarily interrupted, sand particles having a relatively large specific gravity settle at the casting location, and this solidifies in the joint portion. Therefore, even if the work is resumed afterwards,
The jamming phenomenon occurs and the work becomes impossible.

[0004]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above circumstances, and in preventing jamming using a jet water flow, compensates for a shortage of earth and sand at a casting site.
Moreover, an object of the present invention is to provide a method for preventing jamming at the time of casting, which can prevent the solidification of sand particles in the joint portion.

[0005]

In order to achieve the above object, according to the present invention, liquefaction of a driving point of a steel sheet pile or the like is promoted by supplying a jet water stream, and jamming at a joint portion of a steel sheet pile or the like is achieved. In the method of preventing, at least at the time of interrupting the casting operation, bentonite is mixed in advance in the jet water stream, and the bentonite is replenished to the portion where the soil particles are reduced by liquefaction.

[0006] In this case, as an embodiment of the present invention, it is important to set the supply amount of bentonite in anticipation of the reduction amount of soil particles at the casting site lost by liquefaction.

[0007]

Embodiments of the present invention will be specifically described below with reference to the drawings. In the first embodiment, a case of forming a wall surface using steel sheet piles is described, and in the second embodiment, a case of forming a wall surface using a casing pipe having a joint portion in a steel pipe is described.

(First Embodiment) Here, a joint 2 having an L-shaped cross section is provided on a side edge of a steel sheet pile 1 previously driven, and a joint of a steel sheet pile 1 'at the next stage is provided on the joint. The steel sheet pile 1 'is driven while the 2' is engaged. At this time, a press-fitting machine (so-called still worker) 3 for holding and driving the steel sheet pile 1 'is provided with a clamp. By 4, it is supported on the top of the already driven steel sheet pile 1. In addition, the steel sheet pile 1 ′ is provided with a pipe 5, which is located substantially at the center of the width thereof, for bringing a jet water flow to the lower end of the steel sheet pile on at least one side (if necessary, both sides), for example, a pipe band 6 or the like. The high pressure hose 7 is connected to the upper end of the pipe 5 and connected to the water jet pump 8. The water jet pump 8 includes a hopper 8a
The powder or granular bentonite is supplied from the water to a required amount (an appropriate amount is preset according to the amount of water and the soil properties of the casting location), and is mixed in the supplied jet water stream.
In the drawing, reference numeral 9 denotes a water tank for supplying water to the water jet pump 8, and 10 denotes a submersible pump for taking water into the water tank 9.

In the process in which the steel sheet pile 1 ′ is pressed into the soil by the press-fitting machine 3, the joint portion 2 ′ is moved forward.
It descends while removing earth and sand from the joint part 2 of the adjacent steel sheet pile 1. At this time, a jet water stream in which bentonite is dispersed is supplied from a water jet pump 8 via a high-pressure hose 7 and a pipe 5 to a casting location (the lower end of the steel sheet pile 1 '), and this water stream liquefies the surrounding earth and sand. Then, fine sand particles and soil particles are placed on the sheet pile 1 'and raised along the surface. At this time, the earth and sand in the joint portion 2 is gradually removed by the water flow, and the casting resistance is reduced, so that the jamming phenomenon can be avoided.

[0010] On the other hand, sand particles having a large specific gravity tend to settle, but they mix with the supplied bentonite and maintain appropriate flexibility. Therefore, on the surface of the steel sheet pile 1 'in the soil, a mixed layer A of bentonite and sand grains is formed with a certain fluidity (see FIG. 3). Of course, as a result of using the jet stream, fine sand and soil particles are discharged to the surface of the earth together with the rising water.

For this reason, the absolute amount of earth and sand around the steel sheet pile 1 'becomes insufficient.
Required amount of bentonite (this is set in advance in consideration of the amount of fine sand and soil particles generated by the water flow)
And the remaining mixed layer A with the sand particles having a large specific gravity compensates for the shortage. Therefore, the absorption of water into the soil after the casting causes a necessary tightening phenomenon. When this occurs, a necessary amount can be secured, and problems such as land subsidence caused by leaving a void can be avoided due to lack of earth and sand.

Further, when the work of placing the steel sheet pile 1 'is interrupted (for example, when the addition work of the steel sheet pile is performed), sand particles having a large specific gravity settle in the joint portion 2. At this time, because bentonite is mixed,
Since appropriate flexibility is secured, and consolidation due to sand particles in the joint portion 2 is avoided, the joint portion 2 'is detached from the joint portion 2 when the casting operation is performed again. The jamming phenomenon that can be caused can be avoided.

By the way, when a jet water stream containing no bentonite is used (see FIG. 4), the settled sand particles accumulate in the joint portion 2 and solidify. This will cause a wedge phenomenon.

(Second Embodiment) In this embodiment, a casing tube 11 provided with a pair of joints 12 extending in the longitudinal direction of a steel pipe as shown in FIG. Can be In FIG. 6, the number of the pipes 13 for the water jet is two, which is suitable for soft ground. In FIG. 7, the pipe 13 is branched into four (2 × 2), and is suitable for relatively soft sand ground. In addition, in FIG. 8, the pipe 13 is branched into six (2 × 3) pipes, and is suitable for hard ground.

Here, in the one joint portion 12 of the preceding casing tube 11, the function of avoiding the jamming phenomenon when the next joint casing portion 11 'is engaged when the next casing tube 11' is driven is described above. Since the third embodiment is the same as the first embodiment, it is only illustrated by FIG. 9 and the description thereof is omitted.

FIG. 9 (a) shows the use of a jet water stream containing bentonite according to the present invention, wherein a mixed layer A of sand particles having a large specific gravity and bentonite surrounds the casing tube 11 ', and the mixed layer A is formed. The dispersed state of the sand grains A1 and bentonite A2 in A is schematically shown in FIG.

FIG. 10 (a) shows a situation where a jamming phenomenon occurs when the casting operation is interrupted in a situation where a mere jet stream is used, and after the water is absorbed into the soil. (B) schematically shows the state of the sand grains in which the tightening phenomenon (arrow) around the casing tube 11 'has occurred.

As described above, in any of the embodiments,
The advantage (described in detail in the first embodiment) can be obtained by mixing bentonite into the jet water stream and supplying it to the casting location.

[0019]

As described in detail above, the present invention provides a method for promoting the liquefaction of a driving position of a steel sheet pile or the like by supplying a jet water flow and preventing jamming at a joint portion of the steel sheet pile or the like. In at least, at the time of the suspension of the casting operation, in advance, the bentonite is mixed into the jet water stream, and the bentonite is replenished to the location where the soil particles have been reduced by liquefaction, so as to compensate for the lack of sediment at the casting location, In addition, it is possible to avoid consolidation of sand particles in the joint.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an apparatus for implementing the present invention.

FIG. 3 is a schematic longitudinal sectional view and a transverse sectional view for explaining the function of the present invention.

FIG. 4 is a schematic longitudinal sectional view of a conventional example for comparison with the present invention.

FIG. 5 is a perspective view showing one example of a second embodiment according to the present invention.

FIG. 6 is a front view and a cross-sectional plan view for explaining the functions.

FIG. 7 is a front view and a cross-sectional plan view showing another example.

FIG. 8 is a front view and a cross-sectional plan view showing still another example.

FIG. 9 is also a schematic longitudinal sectional view for explaining a function,
It is a cross-sectional view and a schematic diagram showing the composition of a mixed layer.

FIG. 10 is a schematic vertical cross-sectional view of a conventional example for comparison with the present invention, and a schematic view showing a solidified state of sand particles around a casing tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1 'Steel sheet pile 2, 2' Joint 3 Press-fitting machine (stillworker) 4 Clamp 5 Pipe 6 Pipe band 7 High pressure hose 8 Water jet pump 8a Hopper 9 Water tank 10 Submersible pump A Mixed layer A1 Sand grain A2 Bentonite 11,11 ' Casing tube 12, 12 'Fitting 13 Pipe

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makio Hanedano 1-6-8 Usananami, Gifu City, Gifu Prefecture Dainichi Main Construction Co., Ltd. (72) Inventor Tsuguhiko Shimabukuro 3-, Kandanishikicho, Chiyoda-ku, Tokyo 23 Mukai Construction Co., Ltd. (72) Inventor Isamu Kuramoto 256-shi Ishigami, Kawaguchi City, Saitama Prefecture 54 Kuramoto Foundation F-term (reference) 2D049 FA08 FB03 FB12 FC03 2D050 AA12 BB05 CA04 CB42

Claims (2)

[Claims] 1. A method of promoting liquefaction of a casting site such as a steel sheet pile by supplying a jet water flow and preventing jamming at a joint portion such as a steel sheet pile.
A method for preventing jamming at the time of placing, wherein bentonite is mixed in advance in the jet water flow when the placing operation is interrupted, and the bentonite is replenished to the portion where the soil particles are reduced by liquefaction. 2. The jamming prevention at the time of setting according to claim 1, wherein the supply amount of bentonite is set in anticipation of an amount of soil particles to be reduced at a setting place which is lost by liquefaction. Construction method.