JPH0337675B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a system in which a pipe section and a structure may be displaced unevenly in the vertical direction, and a part of the pipe body is joined to the structure. Regarding the structure of short pipes that are fixed to structures, specifically, short pipes that have measures taken to prevent the pipe body from being damaged near the structure even if uneven ground subsidence occurs near the structure. be.

[Conventional technology]

BACKGROUND OF THE INVENTION For pipes connected to water and sewage systems, the ends of the pipes are sometimes buried and fixed in the walls of fixed structures such as manholes and water tanks. Figure 2a shows the short pipe fixed to the structure. A short pipe 1 is joined to a concrete wall surface 2 of a fixed structure, and the next connecting pipe 3 is connected to the enlarged diameter socket of the short pipe 1 via a packing 4, and further pipe bodies are connected one after another. go. Therefore, in the following explanation, the short pipe 1 directly connected to the concrete wall surface 2 will be expressed as the directly connected short pipe 1. The connection between the direct connection short pipe 1 and the connection pipe 3 is allowed to be slightly bent due to the elasticity of the packing 4 and the space available at the enlarged diameter socket, and is generally referred to as a flexible joint. many.

[Problem that the invention seeks to solve]

If piping as shown in Figure 2a is installed on soft ground, the concrete wall 2 of the structure will not sink easily and will remain fixed in place because the foundation construction method is adopted. The pipe side receives a downward load due to ground subsidence, and so-called uneven settlement occurs between the pipe and the structure, causing deformation of the entire pipe. The situation of uneven settlement that occurs here is described in detail in the specification of Japanese Patent Application No. 1982-56596, which was submitted earlier, and extremely large stress is generated in the direct connection short pipe 1. Fig. 2b is a stress distribution diagram in the directly connected short pipe 1 when the above-mentioned uneven settlement occurs. Damage such as cracks occurs to the tube body of No. 1.

Therefore, the present inventors discovered that there is a possibility of causing unequal displacement in the vertical direction between the piping section and the structure, and even if uneven ground subsidence occurs near the structure, the direct connection of short pipes near the structure With the ultimate goal of preventing excessive stress from occurring in the tube and causing damage to the tube, various studies have been carried out and the present invention has been completed.

[Means for solving problems]

In the present invention, in order to suppress damage to a directly connected short pipe installed next to a structure as much as possible, the short pipe has a plurality of laminated structures at least on the side where it is connected to the structure, and the short pipe is inserted into the structure. The main point is that the layers constituting the laminated structure are integrated at the joints provided, and the remaining laminated parts are not integrated with each other, and the outer layer is formed shorter than the inner layer. exists.

[Effect]

A directly connected short pipe connected to a structure has a multilayer structure (two or more layers), and at the joint with the structure at the root of the directly connected short pipe, if there are two layers, an inner layer and an outer layer (if three or more layers, the (all layers) are integrated by means such as mutual adhesion or fusing. Then, the structure and the directly connected short pipe are securely supported. The directly connected short pipe has the innermost layer extending to the farthest position from the structure, and regardless of the number of layers, the outer layer side is always shorter than the immediately adjacent inner layer, so that the leading edge of the innermost layer is connected to the connecting pipe 3. Connected. The stacks of directly connected short pipes other than the fixed joints with the structure, that is, those that protrude outside the structure, are not restrained from each other, and each stack is placed under conditions that ensure free movement with respect to each other. It's just touching. Therefore, it constitutes a type of laminated leaf spring structure, and even if a load is applied to the directly connected short pipe due to uneven ground settlement near the structure and a bending moment is generated, the stress generated in the innermost layer of the directly connected short pipe is constant. The stress is dispersed without being concentrated in one place, and the maximum stress value can be kept relatively small compared to straight short pipes, making it possible to prevent damage to the directly connected short pipes as much as possible.

〔Example〕

An example of a case in which synthetic resin pipes used for water and sewage pipes are continuously connected to structures such as manholes will be described with reference to FIG. 1a.

A directly connected short pipe 1 is embedded and fixed in a concrete wall surface 2 of a structure, and a connecting pipe 3 is inserted into the expanded diameter socket of the directly connected short pipe 1 via a packing 4.

The direct connection short pipe 1 is formed of a three-layer laminated structure, and is composed of an inner layer 1a, an intermediate layer 1b, and an outer layer 1c, and the connection with the connecting pipe 3 is made through an enlarged diameter socket formed in the inner layer 1a. It is done by hand. The total length of each layer is the sum of the length L of the wall-embedded part (common to all layers) and the lengths l ₁ , l ₂ , l ₃ of the protruding parts, and the outer layer is the same as the inner layer. In comparison, they are each formed shorter, and the relationship is l ₃ > l ₂ > l ₁ . In the portion buried in the concrete wall surface 2, the layers 1a, 1b, and 1c of the directly connected short pipe 1 are bonded to each other and integrated. The shape of the pipe end in the illustrated example is such that the diameter gradually expands toward the side facing the concrete wall 2 (the left side in Fig. 1a) because the directly connected short pipe 1
This is to improve the retainability (prevention of slippage) between the concrete wall surface 2 and the concrete wall surface 2, and to allow smooth flow of fluid and smooth insertion of power cables. In the portion protruding from the concrete wall surface 2, the layers 1a, 1b, and 1c are free from each other.

If uneven ground subsidence occurs in the piping section with the above configuration shown in Figure 1a, the concrete wall surface 2
Since the load is applied to the piping portion that does not sink and protrudes from the concrete wall surface 2, stress is generated in the directly connected short pipe 1. The stress distribution generated in the inner layer 1a at this time is
The stress distribution is shown in Figure 1b. That is, inner layer 1
The stress in a is dispersed and lowered, and the location where the maximum stress occurs is not limited to the boundary between the structure and the piping, but is distributed to the boundary between the outer layer and the inner layer. That is, the inner layer 1a is supported like a leaf spring by the boundary part B of the intermediate layer 1b and the boundary part C between the intermediate layer 1b and the outer layer 1c, and compared to the vicinity of the boundary parts B and C and the point A near the structure. Although a large stress is generated, since it is distributed at each point, each stress has a small value when viewed individually, and does not lead to damage to the inner layer 1a.

In the embodiment shown in FIG.
It is not limited to the number of layers, but may be any number of layers as long as it has a structure of multiple layers, such as two layers or four layers. In addition, the protrusion lengths l ₁ , l ₂ , and l ₃ of each layer from the edge of the structure are determined by the characteristics of the pipe body based on the outer and inner diameters of the pipe, the pipe material, etc., the degree of bending and expansion at the joint, the burial depth, and the soil quality. Select a preferred value based on the characteristics of the ground, and set the appropriate length to suit the conditions for burying the pipe. Also, although it is described as a direct-connected short pipe, there are no particular restrictions on its total length.

Stress generated in the tube body under the same conditions for a model using the conventional straight short tube 1 as shown in FIG. 2a and a model using the direct-connected short tube 1 of the present invention as shown in FIG. 1a. In order to make a comparison, we conducted the following experiment.

The length of the pipe protruding from the wall of the structure (effective pipe length of the pipe body) is 90 cm, and the second connecting pipe 3 is 200 cm.
cm, pipe diameter: 170.5 mm, pipe thickness and thickness of each inner and outer layer 9.8 mm, moment of inertia of innermost layer 1a and short pipe 1 1.603×10 ³ cm ⁴ , Poisson's ratio 0.37,
Young's modulus 30000Kgf/cm ² , l ₁ = l ₂ − _{l 1} = ls − l ₂ = 30
cm, and the relative ground settlement was set to 450 mm, and the stress in each model was analyzed. As a result, the maximum stress of approximately 600 kgf/cm ² is generated at the edge of the structure in the case of the conventional straight short pipe, whereas in the case of the inner layer 1a shown in the embodiment of the present invention, A, B in FIG. Approximately each near the boundary point shown in C.
Only a maximum stress of 250 Kgf/cm ² was observed. As a result, the stress distribution was similar to that shown in FIGS. 1b and 2b, and it was numerically demonstrated that the short pipe adjacent to the structure of the present invention disperses and reduces stress.

Although synthetic resin pipes were used in this comparative experiment, the present invention is not limited to synthetic resin pipes, and can be applied to pipes made of any material.

〔Effect of the invention〕

In cases where there is a risk of unequal vertical displacement between piping and a structure, the present invention can be used as a directly connected short pipe to be connected to the structure. This makes it possible to disperse the stress in the intermediate part of the directly connected short pipe, and also to suppress the maximum stress value to a low value. Therefore, it has become possible to greatly reduce the occurrence of damage such as cracks at the boundary with the structure.

[Brief explanation of the drawing]

Figure 1a is a sectional view showing a typical embodiment of the present invention, and Figure 1b is a stress distribution diagram in a short pipe when uneven ground subsidence occurs in the piping section shown in Figure 1a. As an example, FIG. 2a is a sectional view showing a conventional short pipe adjacent to a structure, and FIG. 2b is a graph showing an example of the stress distribution of the short pipe during uneven settlement in FIG. 2a. 1... Directly connected short pipe, 1a... Inner layer, 1b... Intermediate layer, 1
c...outer layer, 2...concrete wall surface, 3...connecting pipe,
4...Patsukin.

Claims (1)

[Claims] 1 A short pipe that is used to connect a pipe that is connected to a structure and has the possibility of being displaced unequally in the vertical direction with respect to the structure to the structure via a short pipe, the short pipe being is composed of a plurality of laminated structures at least on the side that connects to the structure, and at the joint inserted into the structure, the layers constituting the laminated structure are integrated, and the remaining laminated parts are A short pipe adjacent to a structure, characterized in that the outer layer is formed shorter than the inner layer without being integrated with each other.