JP7197258B2 - freezing method - Google Patents

Description

The present invention relates to a freezing method.

BACKGROUND ART Conventionally, as a protective work for stabilizing the ground, forming a waterproof layer, etc., a freezing construction method has been used in which a load-bearing wall or a water cutoff wall is formed from frozen soil walls (see, for example, Patent Document 1).

On the other hand, when constructing a load-bearing wall by the freezing method, the required frozen soil thickness is determined by performing structural calculations. In addition, the load is normally separated from the earth and water pressure, the vertical earth pressure of the acting earth pressure is the total earth pressure, and the horizontal earth pressure is the static earth pressure considering some freezing expansion pressure (for example, see Non-Patent Document 1) ).

JP-A-2005-264717

Geotechnical Society: Geotechnical Practice Series 31 "Survey, Design and Construction of Ground Improvement - From Detached Houses to Artificial Islands -", pp. 160-170, 2013

On the other hand, freezing expansion pressure should act on the actual frozen soil, but conventionally, the freezing expansion pressure is not quantitatively determined, but it is included in the total soil pressure in the vertical earth pressure and in the static earth pressure in the horizontal earth pressure. The required frozen soil thickness was calculated simply as

However, in the case of construction using the freezing method at great depths, which has been increasing in recent years, there are cases where the frozen soil thickness calculation results are excessively safe if the total earth pressure is used as the vertical earth pressure and the stationary earth pressure is used as the horizontal earth pressure. was there. In addition, when freezing cohesive soil that generates a large freeze expansion pressure, the frozen soil thickness calculation result may be dangerous if the freeze expansion pressure is not taken into consideration.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a freezing construction method that enables calculation of the required frozen soil thickness with higher accuracy, taking into consideration the freezing expansion pressure.

In order to achieve the above objects, the present invention provides the following means.

The freezing method of the present invention is a freezing method for constructing a structure while forming a frozen soil wall on the ground, and the load acting on the frozen soil wall is the loosening earth pressure, the water pressure, and the freezing expansion pressure. It is characterized in that the required frozen soil thickness is set based on the calculated result .

In the freezing construction method of the present invention, it is possible to calculate the necessary frozen soil thickness more accurately by considering the freezing expansion pressure, and to realize construction of a rational freezing construction method.

It is a figure which shows an example of the construction method of the tunnel constructed using a freezing construction method. It is a figure which shows an example of the construction method of the tunnel constructed using a freezing construction method. It is a figure which shows an example of the tunnel constructed using a freezing construction method. It is a figure which shows an example of the tunnel of a branch/confluence|merging part constructed using a freezing construction method. It is a figure which shows an example of the construction method of the tunnel constructed using a freezing construction method. It is the figure which compared the difference of the concept of calculation of the required frozen soil thickness of the conventional and this invention. FIG. 10 is a diagram used in the explanation of an example in which the necessary frozen soil thicknesses of the conventional method and the present invention were obtained for actual fields.

Hereinafter, a freezing method according to an embodiment of the present invention will be described with reference to FIGS. 1 to 7. FIG.

Here, in this embodiment, for example, when constructing a large cross-section tunnel such as a branch / confluence part of a road tunnel or a connecting line part of a railway tunnel, ) will be explained assuming that the freezing method is used.
However, the freezing expansion pressure calculation method of the freezing construction method of the present invention is applicable to all cases where the freezing construction method is used in the field of civil engineering and construction.

First, as shown in FIGS. 1 to 4, when constructing a large cross-section tunnel such as a branching/merging section of a road tunnel, for example, a main line shield 1 and a ramp shield 2 (two guide shafts) are placed laterally. In addition to constructing in advance with an interval between them, through the ramp shield 2, the underground shaft 3 is constructed while stabilizing the ground by forming the frozen soil wall 6 by the freezing method. Construct a starting base 4 with a circumferential shield of . A plurality of outer shell shields 5 are constructed by a small-diameter tunnel boring machine so as to surround the main line shield 1 and the ramp shield 2 from the starting base 4. - 特許庁

Furthermore, as shown in FIGS. 2 and 5, while forming the frozen soil wall 8 using the freezing method, the adjacent outer shell shields 5 are cut open to communicate (freezing pipe 9, cut portion 10), the main line shield 1, the ramp A permanent lining 7 surrounding the shield 2 is constructed. Then, the ground surrounded by the permanent lining 7 from the main line shield 1 is excavated and connected to construct a large-section tunnel that serves as a branch/merge section.

Here, in the conventional freezing method, as shown in Fig. 6(a), the freezing expansion pressure is not quantitatively obtained, but is included in the total earth pressure for vertical earth pressure and static earth pressure for horizontal earth pressure. The necessary frozen soil thickness was calculated simply. For this reason, when applying the freeze construction method at great depths, there were cases where the frozen soil thickness calculation results were excessively safe when the total earth pressure was used as the vertical earth pressure and the stationary earth pressure was used as the horizontal earth pressure. . In addition, when freezing cohesive soil that generates a large freeze expansion pressure, there is a possibility that the frozen soil thickness calculation result will be dangerous if this freeze expansion pressure is not taken into account.

On the other hand, in the freezing method of the present embodiment, as shown in FIG. 6(b), as the loads acting on the frozen soil, loose soil pressure, water pressure, and freeze expansion pressure are taken into consideration, and the necessary frozen soil thickness is calculated. did.

As a specific example, an example of deep underground widening construction will be described with reference to FIG. 7 and Table 1.
As shown in Fig. 7, in this case, clay layers existed in the upper and lower parts, and it was predicted that the freeze expansion pressure would increase.
Under these circumstances, when the required frozen soil thickness was calculated using the conventional method, as shown in Table 1, it was confirmed that the required frozen soil thickness on the upper side was on the dangerous side, and that on the lower side it was excessively on the safe side.
On the other hand, when the freezing method of this embodiment is used, that is, when the necessary frozen soil thickness is calculated in consideration of the loose soil pressure, water pressure, and freeze expansion pressure as the load acting on the frozen soil, both the upper and lower portions are moderately safe. was confirmed to be The validity of the necessary frozen soil thickness calculated by the method according to the present invention has been confirmed by FEM analysis.

Therefore, according to the freezing method of the present embodiment, it is possible to calculate the necessary frozen soil thickness more accurately in consideration of the freezing expansion pressure, and it is possible to implement a rational freezing method.

Although one embodiment of the freezing method according to the present invention has been described above, the present invention is not limited to the above one embodiment, and can be appropriately modified without departing from the scope of the present invention.

1 Main Line Shield 2 Ramp Shield 3 Underground Shaft 4 Departure Base 5 Shell Shield 6 Frozen Earth Wall 7 Permanent Lining 8 Frozen Earth Wall 9 Frozen Pipe 10 Cutout

Claims (1)

A freezing method for constructing a structure while forming a frozen wall on the ground,
A freezing method, wherein a necessary frozen soil thickness is set based on a calculation result in which loose earth pressure, water pressure, and freezing expansion pressure are applied as a load acting on the frozen soil wall.

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