JPS59219588A - Method of ground liquefaction countermeasure construction ofburied duct - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a construction method for preventing ground liquefaction in buried pipelines.

Loose sandy ground, such as reclaimed land or alluvial land, is known to liquefy during earthquakes. When this liquefaction occurs, the sandy ground has a specific gravity between that of water and saturated sand (1,0 to 2,0).
The pipes exhibit similar behavior, and construction methods such as compaction construction, displacement construction, crushed stone drain construction, etc. are used to prevent liquefaction by increasing the resistance to liquefaction by making the pipe thicker. However, when applying these construction methods to underground pipelines with long construction lengths, the construction costs are quite high, and
This is often difficult in practice. Therefore, there is a need for a more economical construction method to prevent ground liquefaction for buried pipes.The present invention eliminates the drawbacks of the conventional T-method drip method, The purpose of this invention is to provide an economical ground liquefaction countermeasure method for buried pipes that can prevent pipes from floating up.

The ground liquefaction countermeasure construction method for buried pipelines of the present invention includes, prior to burying the pipeline, a weight is installed below the pipeline burial position, and the weight is
When the pipe is buried, it is connected to the pipe by a weight connecting member and resists the buoyant force acting on the pipe.
〉) The details will be explained with reference to the embodiment diagrams below.1. Figure 1 shows the construction of the present invention.
In the figure, S indicates sandy ground (loose ground), Coke clay layer, and R indicates bedrock, indicating a situation where the pipe is buried in loose ground that is prone to liquefaction.1 indicates a buried pipe. 2 is the main body of the weight, 3 is a connecting member for the weight, 4 is attached to the pipe in advance,
This is a band that has a metal fitting with a weight on the bottom.

Figure 2 is an enlarged view of the part where the weight is connected to the pipe (top view of the pipe)
The symbols are the same as in Figure 1.

The body of the weight is made of concrete or cobblestones surrounded by a net, and its weight is calculated assuming that the specific gravity of liquefied sand is between that of water and saturated sand (1.0 to 2.0). It is determined to balance the buoyancy force.

Prior to burying the pipeline, the weight will be installed below the location where the pipeline will be buried. Therefore, when the pipe is buried, it is connected to the pipe by the connecting member of the weight. A variety of wire ropes, chains, and rod pipes can be used as connection members for the weight, and they can be connected to the weight mounting bracket at the bottom of a bunt that has been attached to the pipe in advance, or tied down by directly connecting the pipe. (size and weight of the weight), spacing between the positions of the weights (construction pitch)
etc. are appropriately determined by calculation in relation to the pipe type and in balance with the buoyancy acting on the pipe. Table 1 shows calculation examples of the relationship between construction pitches for several types of pipes (in the case of large weights and concrete pipes).

The weight is a cube, and its size is shown in the table by the length of one side.〇Table 1 Table 2 shows an example of calculating the maximum bending stress of a pipe with a bolt when a buoyant force acts on the pipe. Table 2 From Table 2, when the construction pitch is 5 m to 20 m, the maximum bending stress is the same as that of steel. It is shown that it is safe below the yield stress of . .

Next, we will discuss experiments that confirmed the effectiveness of the construction method of the present invention.

In an earthen tank with a length of 3 m, a width of 1 m, and a height of 0.5 m,
A model pipe with a diameter of 60 mm and a diameter of 60 mm was buried, instruments were placed, and the inside of the soil tank was liquefied by increasing the volume to 1 ml on a shaking table.

Figure 3 is a side view showing the situation of the model pipe-ground system in the experiment.
5 is an earthen tank, and 1' is a model pipe. Figures (,) are without countermeasures, and Figure (b) is a model pipe 1' with a weight W tied to it so that the specific gravity of the entire pipe is 2.0, and countermeasures have been taken using the construction method of the present invention. The position of the pipe body after liquefaction is as shown in the pipe body displacement diagram (top view of the pipe) in Figure 4. In the case of no countermeasures, the model pipe 1' would have completely floated, but when the construction method of the present invention is applied, In this case, the pipe body 1' remained in its original position despite the ground subsidence, demonstrating the effectiveness of the countermeasures. In FIG. 4, (,) shows the results before liquefaction, (b) shows the results without countermeasures, and (C) shows the results when the construction method of the present invention is applied.

By applying the construction method of the present invention described above, unlike conventional measures to prevent ground liquefaction, it is possible to economically prevent buried pipes from floating when the ground becomes liquefied.

[Brief explanation of the drawing]

Figure 1 is a detailed explanatory diagram (side view) of the present invention, Figure 2 is an enlarged view of the part where the weight is connected to the pipe (pipe pressure surface view), and Figure 3 is a model experiment of the construction method of the present invention. Figure 5 is a model pipe-ground system situation diagram (side view) and a diagram (pipe pressure surface diagram) showing the displacement of the pipe body due to liquefaction in the experiment. S: Sand ground, C: Clay layer, R: Bedrock, 1: Buried pipe, 2
: Weight main body, 6: Weight connecting member, 4: Band, 1': Model tube, 5: Earthen tank, W: Weight. Agent Patent Attorney Mitsuro Kimura 1st Prisoner Figure 2 Figure 3 Figure 4 Procedural Amendment (Method) % Formula % 1 Indication of Case Patent Application No. 1982-92352 2 Title of Invention Ground liquid of buried pipe Relation to the case of the person making the amendment Patent applicant name (412) Nippon Kokan Co., Ltd. 4 Agent Address: 21-19-5 Toranomon-chome, Minato-ku, Tokyo 105 Date of amendment order August 10, 1982 day (Shipping date: Showa 5)
(August 30, 2008) 6. Column 7 for a brief explanation of the drawings in the specification subject to the amendment. Contents of the amendment.

Claims (1)

[Claims] Prior to burying the pipe, a weight is installed below the pipe burying position, and when the pipe is buried, the weight is connected to the pipe by a connecting member of the weight to resist the buoyant force acting on the pipe. Ground liquefaction countermeasure construction method for buried pipelines