JP6624443B2 - Freezing method - Google Patents

Description

  The present invention relates to a freezing method for freezing the ground and improving the water stopping performance and the strength performance of the ground.

  Conventionally, a freezing method has been used as a protective method for the purpose of stabilizing the ground, forming a waterproof layer, and the like (for example, see Patent Document 1).

 For example, when constructing a tunnel by excavating the ground with a tunnel machine, especially when constructing a large cross-section tunnel such as a branch / merge section of a road tunnel or a crossover section of a railway tunnel, or opening a segment At times (when the shield tunnel is widened underground), the freezing method is used.

  Here, when a large-scale frozen soil is created, such as when constructing a large section tunnel, or when the ground to be frozen contains viscous soil, the expansion pressure due to the freezing of the ground increases, and the assembled segment ( Excessive load due to the freezing expansion pressure acts on the surrounding structures, etc.), so that the segment bolt may be broken or the segment may be damaged.

  On the other hand, as a measure against the freezing expansion pressure, 1) a method of installing a hot water pipe outside the row of freezing pipes to control the freezing area, and 2) a method of extracting the ground around the frozen soil to reduce the freezing expansion pressure. 3) A method of reinforcing the segment corresponding to the freezing expansion pressure, 4) A method of suppressing the growth of frozen soil by freezing operation control (thinning operation or the like) has been proposed and put to practical use.

JP 2005-264717 A

  However, 1) a method of controlling the freezing area by installing a hot water pipe outside the row of freezing pipes, 2) a method of extracting the ground around the frozen soil to reduce the freezing expansion pressure, and 3) a segment corresponding to the freezing expansion pressure Reinforcement of the method leads to a significant increase in the cost of measures and the construction period. In addition, 4) In the method for suppressing the growth of frozen soil by freezing operation control, there is an inconvenience that the suppression effect is small.

  The present invention has been made in view of the above circumstances, and has as its object to provide a freezing method capable of reliably and easily controlling the freezing and inflation pressure, shortening the construction period, and reducing costs.

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

  The freezing method of the present invention freezes the ground, and in the freezing method of improving the water stopping performance and strength performance of the ground, at the stage where the frozen water in a predetermined area is continuously connected from the start of the freezing operation and the water stopping performance is secured. At an arbitrary timing between the stage where the permafrost wall of the required permafrost thickness is created and the strength performance is ensured, a preliminary excavation of a part of the ground in an area inside with respect to the permafrost wall is characterized in that I do.

 In the freezing method of the present invention, at an arbitrary timing between the stage at which the water stopping performance is secured and the stage at which the strength performance is secured, by excavating part of the ground inside the area of the frozen soil wall in advance. In addition, a part of the freezing expansion pressure can be released, and the freezing expansion pressure can be reduced.

  In addition, by releasing a part of the freezing and expanding pressure at an arbitrary timing between the stage where the water stopping performance is secured and the stage where the strength performance is secured, a sufficiently strong frozen soil wall is formed. It is also possible to reduce the freezing expansion pressure at the specified stage (the freezing expansion pressure when the frozen soil finally reaches the required (maximum) frozen soil thickness).

It is a figure showing an example of the construction method of the tunnel constructed using the freezing method. It is a figure showing an example of a tunnel constructed using a freezing method. It is a figure which shows an example of the tunnel of the branching / merging part constructed using the freezing method. It is a figure showing an example of the construction method of the tunnel constructed using the freezing method. It is the figure used for description of the creation stage of the frozen soil at the time of using a freezing method. In the freezing method of one embodiment of the present invention, at an arbitrary timing between the stage of securing the water stopping performance and the stage of securing the strength performance, it is a diagram showing that a part of the ground inside the frozen soil wall is excavated. is there.

  Hereinafter, a freezing method according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

Here, in the present embodiment, for example, at the time of starting and reaching when constructing a large-section tunnel such as a branching / merging portion of a road tunnel or a crossover portion of a railway tunnel, or at the time of segment opening (during underground widening of a shield tunnel, ) Etc. will be described as using the freezing method.
However, the freezing method of the present invention can be applied to any case where the ground is frozen to form a frozen soil wall (freezing region) in the field of civil engineering and construction.

  First, as shown in FIGS. 1 to 4, when constructing a large-section tunnel such as a branch or a junction of a road tunnel, for example, the main shield 1 and the lamp shield 2 (two pits) are placed in a horizontal direction. At the same time, the underground starting base 3 is constructed while the stabilization of the ground is achieved by forming a ring-shaped or gate-shaped frozen soil wall 5 by the freezing method through the main line shield 1 while maintaining an interval. A plurality of outer shell shields 4 are constructed with a small diameter tunnel excavator so as to surround the main line shield 1 and the lamp shield 2 from the base 3.

  Further, the adjacent outer shell shields 4 are cut open to communicate with each other while the frozen soil wall 5 is formed by using the freezing method, and a permanent lining 6 surrounding the main line shield 1 and the lamp shield 2 is constructed. Then, the ground surrounded by the permanent lining 6 is excavated from the main line shield 1 to communicate with each other, and a large-section tunnel serving as a branching / merging portion is constructed.

  When the frozen soil wall 5 is formed by the freezing method, the freezing pipe 7 and the temperature measuring pipe are installed in the ground, and piping equipment and a refrigerator for circulating and supplying the brine to the freezing pipe 7 are installed. Install instrumentation equipment, etc. in the temperature measuring tube. Then, brine is circulated through the freezing tube 5 to start freezing soil formation. At this time, the underground temperature is measured in real time with a temperature measuring tube, and the progress of the formation of the frozen soil and the maintenance of the frozen soil are grasped, and construction management is performed.

  On the other hand, as shown in FIG. 5, in the freezing method, brine is circulated through the freezing tube 7, and frozen soil is formed around the freezing tube 7 to expand (the frozen soil region 10). The frozen soil on the upstream side in the brine distribution direction is formed first (frozen soil area 11), and the frozen soil on the downstream side is gradually formed (frozen soil area 12), and the frozen soil is connected to form a frozen soil wall having water stopping performance. Further, the frozen soil is formed to a required frozen soil thickness, and the frozen soil wall 5 having a desired strength performance is formed. By maintaining the frozen soil, the frozen soil is further formed inside and outside (the frozen soil area 13 and the frozen soil area 14), and the thickness of the frozen soil wall 5 is increased.

  In addition, the temperature measurement by the temperature measuring tube indicates that the frozen ground regions 11 and 12 having the water stopping performance (securing the water stopping performance) are formed if the region of, for example, the average temperature of −5 ° C. is continuously formed. Can be detected. Further, for example, if the region of the average temperature of −10 ° is continuously formed, it can be detected that the frozen soil wall 5 having the strength performance (securing the desired strength performance) is formed.

  Here, when the frozen soil wall 5 as a bearing wall is constructed in consideration of the strength of the frozen soil, tunnel excavation is generally performed after the frozen soil is formed to a required frozen soil thickness determined by structural calculation. Further, since the freezing expansion pressure increases in accordance with the growth of the frozen soil, the freezing expansion pressure according to the required frozen soil thickness is generated before tunnel excavation.

  On the other hand, in the case where the frozen soil wall 5 is constructed as a water impervious wall in anticipation of the water shielding (water blocking) of the frozen soil, it is sufficient that the frozen soil wall maintaining the continuity is formed, and the thickness of the frozen soil may cause a construction error. Even if you consider it, it is smaller than what is needed for load-bearing walls.

  Focusing on this point, the freezing method of the present embodiment focuses on this point, and illustrates the growth process of the frozen soil in the first stage from the start of operation to the connection of the frozen soil and the water stopping performance, the required frozen soil thickness by the connection of the frozen soil. Is divided into a second stage until the strength performance is ensured and a third stage of the freezing maintenance period.

  Then, at an arbitrary timing from the first stage until the water stopping performance is secured to the second stage where the strength performance is secured, a partial ground inside the frozen soil wall 5 is preliminarily excavated by the ground preliminary excavation process ( Primary excavation).

 That is, the freezing method according to the present embodiment includes a ground excavation step, for example, a part of the tunnel excavation (in the vicinity of the inner segment of the frozen soil wall 5 that secures the water stopping performance) in a range that does not affect the structural stability. By excavating in advance, a part of the freezing expansion pressure can be released and the freezing expansion pressure can be reduced.

  In addition, by excavating a part of the inner ground which secured the water stopping performance in advance, the frozen expansion pressure at the stage where the frozen soil was formed and thickened to form a frozen soil wall having sufficient strength, that is, the final expansion pressure, The freezing expansion pressure at the time when the frozen soil reaches the necessary (maximum) frozen soil thickness can also be reduced.

Incidentally, in an actual study cases, with respect to the maximum freezing inflation pressure 668kN / m ² in the case of not performing primary drilling at the time of the construction of the maximum frozen soil thickness 6.6 m, the maximum freezing inflation pressure by performing primary drilling 369KN / it has been demonstrated that can be reduced to m ^2.

  Therefore, according to the freezing method of the present embodiment, a conventional method of installing a hot water pipe outside the row of freezing pipes to control the freezing area, a method of extracting the ground around the frozen soil to reduce the freezing expansion pressure, Compared with the method of reinforcing the segments corresponding to the expansion pressure and the method of controlling the growth of frozen soil by freezing operation control (thinning operation, etc.), it is possible to control the freezing expansion pressure more reliably and easily, and to shorten the construction period and reduce costs. Becomes possible.

  As described above, one embodiment of the freezing method according to the present invention has been described, but the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1 Main line shield 2 Lamp shield 3 Underground starting base 4 Outer shell shield 5 Frozen soil wall 6 Main lining 7 Freezing tube 10 Frozen area 11 Frozen area 12 Frozen area 13 Frozen area 14 Frozen area

Claims (1)

In the freezing method to freeze the ground and improve the water stopping performance and strength performance of the ground,
At any time between the stage where the frozen soil in the predetermined area is continuously connected from the start of the freezing operation and the water stopping performance is secured, and the stage where the frozen soil wall of the required frozen soil thickness is created and the strength performance is secured, A freezing method characterized by excavating a part of the ground in an area inside the frozen soil wall in advance.

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