JP4228898B2 - Construction method of underground cavity - Google Patents

Description

  The present invention relates to a construction method for underground cavities, and particularly to a construction method for constructing underground cavities such as tunnels and large cavities for railways and roads at a depth of 30 m or less underground.

  In urban areas such as the Tokyo metropolitan area, the most serious problem is the construction of underground cavities such as tunnels and large cavities for railways and roads at a depth of 30 m or less.

  That is, although there are regional differences, for example, in Tokyo, up to about GL-30m, alluvial and diluvial sand layers are high, groundwater levels are high, and strength is hardly expected.

  Deeper than that, there are many cases of Tertiary unconsolidated sand layer, Dotan Formation with N value around 50. When constructing an underground cavity such as a tunnel in such a Dotan Formation, it is conceivable to construct such an underground cavity by a shield method widely used for constructing a subway tunnel, etc. Has the disadvantage of high construction costs.

  On the other hand, when an underground cavity is constructed by the mountain tunnel construction method (NATM), it can be constructed at a lower cost than the shield construction method. However, when an underground cavity is constructed by such a construction method, it will be described below. There was a problem.

  In other words, when an underground cavity is constructed by the mountain tunnel construction method, there is a concern about the influence of the lowering of the groundwater level due to the excavation of the cavity and the deformation of the natural ground due to the stress release on the surrounding environment.

  In addition, when constructing an underground cavity with such a construction method, auxiliary construction methods such as water stop injection, long tip receiving, and natural ground improvement are required, which not only causes an increase in both construction cost and construction period. It was difficult to completely eliminate the aforementioned risks.

In order to solve such technical problems, the present applicant has developed a construction method for deep underground cavities that can reduce the scale of the auxiliary construction method while reducing the impact on the surrounding environment as much as possible. It has been developed and applied for in Japanese Patent Application No. 2002-293169.
However, the construction method according to this application has the following problems.

  That is, in the construction method according to the previous application, along the side of the underground cavity to be constructed, after forming the continuous walls with water-stopping from the ground to face each other, excavate between the continuous walls, Since a support work is installed along the excavated wall surface to create an underground cavity with a predetermined shape, the impact on the surrounding environment and the scale of the auxiliary method can be reduced, but a continuous wall is formed from the ground. When there are structures that are difficult to relocate, such as existing structures, major transportation facilities, and cultural properties around the ground surface, there is a problem that continuous walls cannot be constructed.

  The present invention has been made in view of such conventional problems, and the object of the present invention is a construction method of an underground cavity that can be constructed without being affected by the structure on the ground surface side. It is to provide.

In order to achieve the above object, the present invention provides a method for constructing underground cavities such as tunnels and large cavities for railways and roads at a depth of 30 m or less below the side of the underground cavities to be constructed. After constructing a shield tunnel in the ground on the extension line and forming a continuous wall with water-stopping property from the inside of the shield tunnel to a predetermined depth so as to face each other, excavating between the continuous walls and excavating A construction method in which a support is installed along a wall surface to form an underground cavity having a predetermined shape, and the continuous wall is composed of a column wall such as a soil cement column having a core material such as H-shaped steel inserted therein. The core material is inserted so that the upper end is deeper than the groundwater level in the ground where the underground cavity is constructed .

  According to the construction method of the underground cavities constructed in this way, a shield tunnel is constructed in the ground of the side upper extension line of the underground cavity to be constructed, and a continuous wall with waterstop is opposed from the inside of the shield tunnel. After forming to a predetermined depth as described above, excavating between the continuous walls and installing a support along the excavated wall surface to form an underground cavity of a predetermined shape, the groundwater outside the continuous wall is continuous It is blocked by the wall and does not affect the excavation of the interior, nor does it cause a drop in groundwater level.

  In addition, the effect of stress release when excavating between continuous walls stays between the continuous walls and the effect on the surrounding environment is also extremely limited. Even when the auxiliary method is adopted, the scale should be greatly reduced. Can do.

  In addition, the continuous wall is constructed from the inside of the shield tunnel to a predetermined depth in the ground of the upper extension line of the side of the underground cavity to be constructed, so it has no influence on the structure on the surface side. In addition, it can be formed without being affected by the structure on the ground surface side.

  When excavating between the continuous walls, a leading work such as fore poling can be provided on the upper side of the excavation cross section.

  The continuous wall can be formed such that the tip is deeper than the construction depth of the underground cavity.

  The underground cavities are tunnels for railways, roads, and the like, and are formed to face each other along the side of the tunnel in which the column row continuous wall is to be constructed, and the ceiling portion is arched between the column row continuous walls. The arch-shaped upper half supporting work is installed on the excavated wall surface so that the columnar row continuous wall becomes the side wall of the tunnel.

  The upper half support can be locked and fixed at both ends thereof to the core material of the columnar continuous wall.

  According to the construction method of an underground cavity according to the present invention, the influence on the surrounding environment is made as much as possible without affecting the structure on the surface side and without being affected by the structure on the surface side. While reducing, the adoption scale of an auxiliary construction method can be reduced.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. 1 to 6 show an embodiment of a construction method for a deep underground cavity according to the present invention.

  The embodiments shown in these drawings are examples in which the present invention is applied to the construction of an underground tunnel 10 for railways or roads. The underground tunnel 10 is constructed at a large depth of about 40 m or less underground.

  In the case of the present embodiment, as shown in FIG. 1, the ground for constructing the underground tunnel 10 has an alluvial and diluvial sand layer A deposited relatively thick on the surface side, and a Tertiary layer B below it. Under the Tertiary layer B, there is a Dotan layer C, and an underground tunnel 10 is constructed in the Dotan layer C.

  When constructing the underground tunnel 10, first, the shield tunnel 11 is constructed as shown in FIGS. The shield tunnel 11 is formed by assembling the segments 11a in an annular shape by a shield machine started from a vertical shaft (not shown).

  A pair of shield tunnels 11 are formed at a predetermined interval so that the tunnel center O having a circular cross section is positioned on the upper extension line on both sides of the underground tunnel 10 (underground cavity) to be constructed.

  In the case of the present embodiment, the pair of shield tunnels 11 are constructed so as to be located in the alluvial and diluvial sand layer A on the ground surface side and substantially parallel at the same depth, and between the shield tunnels 11. The interval is almost the same length as the width of the underground tunnel 10. Each shield tunnel 11 is formed to have the same length as the extension line of the underground tunnel 10 to be constructed.

  When the shield tunnel 11 as described above is constructed, a water-stopping continuous wall 12 is formed from the inside thereof. When the continuous wall 12 is constructed, the inverted segment 11a of each shield tunnel 11 is removed and the ground is excavated so that the continuous wall 12 extends along the extending direction of the shield tunnel 11 over its entire length. Built.

  The continuous walls 12 are formed so that a pair of the continuous walls 12 face each other at a predetermined interval along the side portion of the underground tunnel 10 to be constructed. In the case of the present embodiment, the continuous wall 12 is composed of a columnar wall in which columnar soil cement columns 14 are connected and formed in the horizontal direction. The soil cement column 14 is obtained by injecting a solidifying agent such as cement milk while mixing and stirring the local board, and a core material 16 such as H-shaped steel is inserted therein. ing.

  The soil cement pillar 14 is formed so that the ends of the circular cross section overlap each other in the lateral direction, and the water-stopping continuous wall 12 is formed by solidifying the solidifying agent. As the excavating machine or the like for forming such a column 14, a machine that fits within the diameter of the shield tunnel 11 is used.

  In the case of the present embodiment, the continuous wall 12 is formed so that the tip reaches a depth deeper than the construction depth L of the underground tunnel 10, and the core material 16 extends upward from the lower end, and the upper end is the groundwater level. It is inserted and installed so as to be deeper than WL.

  If the core material 16 is inserted and installed at such a position, the following effects are obtained. That is, after the construction of the underground tunnel 10, when it is necessary to ensure the flowability of the groundwater before and after the continuous wall 12, it is necessary to lose the water stoppage of the continuous wall 12.

  In this case, if the upper end of the core material 16 is made deeper than the groundwater level WL, for example, when the soil cement pillar 14 of the continuous wall 12 is destroyed and the water stoppage is lost, this work is easily performed. You can do it.

  When the formation of the continuous wall 12 as described above is completed, excavation between the continuous walls 12 is performed. In this excavation, for example, a shaft that reaches the construction depth of the underground tunnel 10 is provided in advance at a predetermined location, and the construction site of the underground tunnel 10 is excavated from within the shaft.

  In the present embodiment, prior to excavation of the underground tunnel 10, as shown in FIG. In the state shown in FIGS. 1 to 4, it is assumed that the tunnel is constructed by the normal NATM construction method up to the construction site of the shield tunnel 11.

  The fore-poling 18 is set so that a predetermined length protrudes ahead of the face along the arch shape of the ceiling portion of the underground tunnel 10 with a predetermined interval in the tunnel cross-sectional direction.

  When the forepoling 18 is finished, next, excavation of the cross-sectional space of the underground tunnel 10 is performed. In this embodiment, first, the upper half excavation 20 of the tunnel is performed.

  The upper half excavation 20 is for excavating only the upper side of the substantially semicircular portion of the underground tunnel 10 to be constructed. After the upper half excavation 20 is performed, the continuous wall 12 is cut out.

  In this cutting, as shown in FIG. 6, the side surface of the soil cement column 14 is scraped to expose the core material 16 of the continuous wall 12, and the bracket 22 is fixed to the side surface of the core material 16 by welding. For this purpose, the bracket 22 is used as a base for supporting an upper half support 24 described later.

  In the case of the present embodiment, as shown in FIG. 6, the arrangement pitch of the core material 16 of the continuous wall 12 is different from the arrangement pitch of the bracket 22, that is, the upper half support 24. All of them are not exposed, only the necessary portions facing each other are cut out, and a pair of brackets 22 are fixedly provided at the facing positions with respect to the shaved core material 16.

  In this case, the arch-shaped upper half support 24 is installed on the wall surface excavated by the upper half excavation 20 at the same time as the cutting work of the continuous wall 12 or after this work. The upper half support 24 is formed by bending a steel material in an arch shape, and is formed in a substantially semicircular shape in accordance with the shape of the upper half excavation 20 in this embodiment.

  Both ends of the upper half support 24 installed along the excavation wall surface are fixedly secured to the bracket 22 by welding or the like, whereby the upper half support 24 is connected to the core 22 of the continuous wall 12 via the bracket 22. 16 is supported.

  When the installation of the upper half supporter 24 is completed, as shown in FIG. 5, a sprayed concrete layer 26 is formed on the wall surface excavated by the upper half excavation 20, and the upper half supporter 24 is brought into close contact with the natural ground.

  Next, as shown in FIG. 4, when the lower half excavation 28 is performed so that the lower continuous wall 12 is exposed from the portion where the bracket 22 is provided, one cycle of work is completed. Are sequentially repeated to construct the underground tunnel 10 having a predetermined length.

  Now, according to the construction method of the deep underground cavity constructed as described above, the shield tunnel 11 is constructed in the ground on the side upper extension line of the underground tunnel (underground cavity) 10 to be constructed. 11, after forming the continuous wall 12 with water-stopping to a predetermined depth so as to face each other, excavate between the continuous walls 12 and install the support 24 along the excavated wall 12 surface, Since the underground cavity has a predetermined shape, the groundwater outside the continuous wall 12 is blocked by the continuous wall 12 and does not affect the excavation of the inside, and the groundwater level does not decrease.

  In addition, the effect of stress release when excavating between the continuous walls 12 remains in the range between the continuous walls 12 and the influence on the surrounding environment is also extremely limited. In some cases, for example, a forepoling method 18 is employed. The scale can be greatly reduced, and the construction can be carried out at a lower cost, more safely and without disturbing the surrounding environment as compared with the conventional construction method.

  Furthermore, since the continuous wall 12 constructs the shield tunnel 11 in the ground of the side upper extension line of the underground cavity to be constructed and forms it from the inside of the shield tunnel 11 to a predetermined depth, there is nothing on the structure on the ground surface side. It can be formed without affecting the structure on the surface side.

  In the case of the present embodiment, since the core material 16 such as H-shaped steel is inserted and installed in the continuous wall 12, when the side pressure applied to the continuous wall 12 is large, the core material 16 is earthed. It functions as a material and can effectively counter lateral pressure.

  Further, in this embodiment, the underground cavity is a tunnel 10 for railways, roads, etc., and is formed opposite to the side of the tunnel 10 where the column row continuous wall 12 is to be constructed. Excavation is performed so that the ceiling portion is arched (upper half excavation 20), and an arch-shaped upper half supporting work 24 is installed on the excavated wall surface. It is built to be.

  According to such a configuration, the side wall of the underground tunnel 10 is also used as the continuous wall 12, and the continuous wall 12 extends in the vertical direction of the underground tunnel 10, so that the stability against deformation of the tunnel 10 is very high. growing.

  Further, in the present embodiment, the arch-shaped upper half support 24 is supported by the core material 16 of the continuous wall 12 via the bracket 22. In addition to being able to be received by the material 16, the loading load of the tunnel 10 applied to the upper half support work 24 can also be received by the core material 16, and the scale of the auxiliary method can be further reduced.

  Furthermore, the construction method of the present invention is a construction method that can be employed not only in the construction of a standard section of a tunnel but also in construction of a large-scale cavity such as a railway station part or a widened part. When adopted, the effect is further exhibited.

  According to the construction method of an underground cavity according to the present invention, since it does not affect the structure on the ground surface side, it is effectively utilized when constructing a cavity such as a tunnel at a large depth in a densely populated residential area in an urban area. be able to.

It is sectional explanatory drawing of the construction completion state which shows one Example of the construction method of the underground cavity concerning this invention. It is a cross section of the initial process of the construction method of the underground cavity concerning this invention. FIG. 2 is an explanatory plan view of FIG. 1. FIG. 3 is an explanatory cross-sectional view of a process performed subsequent to FIG. 2. It is a principal part expanded sectional view of FIG. FIG. 6 is an explanatory cross-sectional view of a main part of FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Underground tunnel 11 Shield tunnel 12 Continuous wall 14 Soil cement pillar 16 Core material 18 Fore poling 20 Upper half excavation 22 Bracket 24 Upper half support 26 Sprayed concrete layer 28 Lower half excavation

Claims (5)

In the construction method of building underground cavities such as tunnels and large cavities for railways, roads, etc. at a depth of 30m or less underground,
After constructing a shield tunnel in the ground on the side upper extension line of the underground cavity to be constructed and forming a continuous wall with water-stopping from the inside of the shield tunnel to a predetermined depth, the continuous tunnel It is a construction method that excavates between walls and installs a support along the excavated wall surface to make an underground cavity of a predetermined shape ,
The continuous wall is composed of a column wall such as a soil cement column having a core material such as H-shaped steel inserted therein,
The construction method of the underground cavity, wherein the core material is inserted so that the upper end is deeper than the groundwater level in the ground where the underground cavity is constructed. 2. The construction method of an underground cavity according to claim 1, wherein when excavating between the continuous walls, a receiving work such as fore poling is provided on the upper side of the excavation cross section. 3. The underground cavity construction method according to claim 1 or 2, wherein the continuous wall is formed so that a tip thereof is deeper than a construction depth of the underground cavity. The underground cavity is a tunnel for railways, roads, etc.
The columnar continuous walls are formed to face each other along the side of the tunnel to be constructed, and the columnar continuous walls are excavated so that the ceiling portion has an arch shape. The construction method of an underground cavity according to any one of claims 1 to 3, wherein a semi-supporting work is installed so that the columnar row continuous wall becomes a side wall of the tunnel. 5. The construction method of an underground cavity according to claim 4, wherein the upper half support is engaged and fixed at both ends thereof to the core material of the pillar row continuous wall.

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