JPH051848B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a roadbed construction method using a buried network,
In particular, it relates to a roadbed construction method that is effective when constructing roads, railways, reclaimed land, etc. on soft ground that lacks soil bearing capacity.

[Conventional technology]

As this type of construction method using buried net, the third method is
The one shown in Figure 4 is known. This was proposed by the applicant of this application in Japanese Patent Publication No. 57-39331, in which a fine auxiliary burial net 24 is laid on the surface of soft ground 21 containing mud, and a sand layer 23 is formed on top of it. , a main buried net 25 is laid on the surface of this sand layer 23, and a gravel layer 26 is further laid on top of it.
is formed, thereby constructing the reinforced roadbed 27.

Since the ground 21 of such a roadbed 27 is soft, its own weight (dead load) is reduced as shown in Fig. 4.
When a live load is further applied to the roadbed 27 or as the ground 21 weakens, the deflection further increases. As the roadbed 27 bends, the ground 21 is consolidated and subsides. At this time, pore water in the ground 21 is absorbed into the sand layer 23 through the auxiliary buried network 24 and drained through the sand layer 23. Further, a bending moment acts on the roadbed 27 due to its deflection, but at this time, the tensile resistance of the main buried network 25 and the compressive resistance of the gravel layer 26 counteract this bending moment and are kept balanced. Furthermore, the auxiliary buried network 24 prevents cracks from forming in the lower part of the roadbed 27 when it is bent.

[Problem that the invention seeks to solve]

Although the conventional construction method has the above-mentioned advantages, it also has the following problems. That is, (1) as described above, pore water is absorbed into the sand layer 23 due to consolidation settlement of the soft ground 21, but at that time, the pore water enters the sand layer 23 with soil particles, and the sand layer As a result, the drainage function of the roadbed 27 is reduced, and the progress of consolidation settlement of the soft ground 21 is delayed. Furthermore, if the degree of clogging occurs in different parts of the sand layer 23, differences will occur in the supporting capacity of the soft ground 21 in each part, and over a long period of time, the deflection shape of the roadbed 27 will change and cause problems. That will happen.

(2) From the time of construction of the roadbed 27 on the main underground network 25,
A tensile force is exerted by the deflection, and after the construction of the roadbed, when the deflection of the roadbed 27 progresses due to live load or as the soft ground weakens,
The tensile force increases, and therefore a large number of buried nets must be laid in the roadbed 27.

This invention was made to solve the problems (1) and (2) above, and its purpose is to prevent clogging of the sand layer and promote drainage. Another object of the present invention is to provide a construction method that can minimize the tensile force acting on the main buried net, thereby reducing the number of buried nets to be laid.

[Means for solving problems]

In order to achieve the above object, the present invention lays a filter mat on the surface of soft ground that allows moisture to pass through but does not allow soil particles to pass through, and forms a sand layer on top of the filter mat so that the central part is raised. A roadbed construction method using a buried net is characterized in that a fine auxiliary buried net is laid within a sand layer, a coarse main buried net is laid on the surface of the sand layer, and a gravel layer is formed on top of that.

[Effect]

According to this invention as described above, since the filter mat allows only pore water to pass through, the sand layer is not clogged with soil particles, and the drainage action from the soft ground is promoted. Consolidation settlement is promoted, and the sand layer sinks as the roadbed is constructed, and by the time construction is complete, the top surface of the sand layer becomes horizontal, and the main buried network also becomes horizontal. In other words, the tensile force due to the weight of the roadbed does not act on the buried network, but only when the soft ground subsides or when a live load acts on the roadbed.

〔Example〕

Figures 1 and 2 show an embodiment of the present invention, in which a filter mat 2 that allows moisture to pass through but does not allow soil particles to pass through is laid on the surface of soft ground 1, and a sand layer 3 is placed on top of the filter mat 2 so that the central part is raised. A fine auxiliary buried net 4 is laid in the sand layer 3, a coarse main buried net 5 is laid on the surface of the sand layer 3, and a gravel layer 6 is formed on top of it, and in this way it is strengthened. Build the roadbed 9a.

In this embodiment, a reinforced roadbed 8 is constructed thereon, and this reinforced roadbed 8 includes a lower reinforced roadbed 9a and an upper reinforced roadbed 9b constructed as described above. After constructing the lower reinforced roadbed 9a, sand is spread on it to form a sand layer 10 so that the central part swells, and at this time, an auxiliary buried net 11 is laid in the sand layer 10 in an upwardly curved state. Further, a main buried net 12 is laid on top of the sand layer 10 so as to have the same shape, and a gravel layer 13 is formed by laying gravel on top of the main buried net 12. At that time, the main buried net 14 is laid as necessary.

Furthermore, as shown in FIG. 2, the upper reinforced roadbed 9b
An upper roadbed 15 and a road surface layer 16 are formed on the
This type is used when a road has a long-term use and has a solid structure, and the upper roadbed 15 and the road surface layer 16 may be omitted when a road has a simple structure.

During the construction of the upper and lower reinforced roadbeds 9a and 9b shown in FIG.
sinks, and eventually the upper surfaces of the sand layers 3, 10 become horizontal as shown in FIG. 2, and as a result, the main buried nets 5, 12 also become horizontal. That is, the main buried network 5,
When construction of the upper and lower reinforced subgrades 9a and 9b is completed, no tensile force is applied to 12 due to their own weight, but only when the soft ground 1 begins to sink or when a live load is applied, a tensile force is applied. I will do it.

As the filter mat 2, for example, a cloth-like material made of chemical fiber or the like can be used, and it is desirable to use one having high tensile strength. Similarly, it is desirable that the main buried nets 5, 12 and the auxiliary buried nets 4, 11 have high tensile strength.
Similarly, the main buried nets 5, 12 and the auxiliary buried nets 4, 1
It is also desirable to use a material with high tensile strength, and this is described in detail in Japanese Patent Publication No. 57-39331.

〔Effect of the invention〕

As mentioned above, the present invention involves laying a filter mat on the surface of soft ground that allows water to pass through but does not allow soil particles to pass through, forms a sand layer on top of the filter mat so that the central part is raised, and fine grains are formed in the sand layer. Since the auxiliary buried net is laid, the coarse-grained main buried net is laid on the surface of the sand layer, and a gravel layer is formed on top of that, the sand layer is not clogged and the drainage effect is improved. This promotes consolidation settlement of soft ground,
Stabilization of soft ground can be achieved at an early stage, and the bearing capacity of the soft ground becomes uniform, and there is no need for bearing capacity improvement work, so construction costs can be kept low, and moreover, the above-mentioned The sand layer is formed so that its central part swells, and the main buried net is laid on top of it, so there is no tension on the main buried net until the sand layer sinks due to the weight of the roadbed and the main buried net becomes horizontal. No force is applied, so it is possible to omit the tensile force due to the roadbed's own weight in the design calculations, which makes it possible to minimize the number of main buried nets installed, making it highly economical. This has the advantage that construction work can be carried out.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views showing an embodiment of the inventive method, and FIGS. 3 and 4 are longitudinal sectional views showing the conventional method. 1...Soft ground, 2...Filter mat, 3
...Sand layer, 4...Auxiliary buried network, 5...Main buried network,
6... Gravel layer.

Claims (1)

[Claims] 1. On the surface of the soft ground, lay a filter mat that allows water to pass through but does not allow soil particles to pass through, form a sand layer on top of it so that the central part is raised, and lay a fine auxiliary buried net within the sand layer, A roadbed construction method using a buried net, which is characterized by laying a coarse main buried net on the surface of a sand layer, and forming a gravel layer on top of it.