Frozen soil support structure and its formation method

Abstract

To provide a frozen soil support structure and a method of forming thereof, when constructing a skeleton, which is an underground structure, by drilling holes inside or on the side of frozen soil, which can achieve both suppression or deterrence of thawing of frozen soil caused by heat transfer from the support structure and securing of bearing capacity for supporting the frozen soil by the support structure.SOLUTION: The present invention is a frozen soil support structure 100 in which frozen soil 20 is constructed inside ground G, a reaction body 40 is provided inside or on the side of the frozen soil 20, and a part of the frozen soil 20 is supported by a part of the reaction body 40. Between the reaction body 40 and the frozen soil 20, a laminate 80 of a first heat insulating material 50 that resists the axial force acting from the frozen soil 20 and a bag body 60 containing a hardened filler 70 is interposed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a frozen soil support structure and a method for forming the same. [Background technology]

[0002] When constructing underground structures in ground deeper than groundwater, various ground improvement methods are sometimes applied as auxiliary methods to prevent groundwater eruption and soil collapse during excavation using open cut or shield methods, and freezing methods are sometimes used as ground improvement methods. Ground improvement methods include a method in which the original ground and cement are mixed to create an improved ground, and a freezing method, but the freezing method freezes the original ground containing groundwater to create hard, impermeable frozen soil, which allows for safe construction of underground structures, and is known as an environmentally friendly ground improvement method because no improved soil is left in the ground after construction is completed by thawing the frozen soil. When using freezing methods to construct underground structures, after the frozen soil is laid, excavation is performed inside the frozen soil and on the sides of it to construct boreholes. Similar to the installation of retaining supports when using general open-cut construction methods, the frozen soil is supported from the borehole side at specified depths while the borehole is constructed in the depth direction.

[0003] However, since the object of support is frozen soil, unlike when supporting general ground, when heat is transferred from the supporting materials (temporary materials, walls of the permanent structure, etc.) supporting the frozen soil to the frozen soil, the heat transfer parts in the frozen soil will melt, and there is a risk that the initial improvement strength of the frozen soil will decrease due to cross-sectional defects and a decrease in strength of the frozen soil. Therefore, a measure to suppress the heat transfer from the support member to the frozen soil can be considered by placing a heat insulating material between the frozen soil and the support member. Commonly applied heat insulating materials (materials with a thermal conductivity of, for example, less than 0.1 W / mK) include glass wool and Styrofoam (registered trademark), which is an extruded polystyrene foam. However, such heat insulating materials generally have a compressive strength of, for example, 0.2 N / mm 2The compressive strength of these materials is low, at around 1.63 W / mK or less, and it is difficult to say that they have sufficient compressive strength to withstand the soil-water pressure (axial force) acting from the rear ground through the frozen soil. Therefore, although it is possible to suppress heat transfer to the frozen soil, issues may arise such as the inability to secure the support force that is originally expected of support members. If one were to try to use mortar or wood, which are common materials with relatively high compressive strength, it would be difficult to suppress the melting of the frozen soil, as the thermal conductivity of cement is around 1.63 W / mK and that of wood is around 0.12 W / mK, both of which are higher than the thermal conductivity of insulating materials. For the above reasons, when constructing the main body of an underground structure by drilling holes inside or beside the frozen soil, it is desirable to have a frozen soil support structure and a method for forming the same that can both suppress or prevent the melting of the frozen soil caused by heat transfer from the support structure and ensure the supporting capacity of the support structure to support the frozen soil.

[0004] Here, Patent Document 1 proposes a freezing expansion pressure reducing structure constructed in the ground between the area scheduled for freezing and an existing structure. This freezing expansion pressure reducing structure is formed of a deformation absorbing wall that, when the area scheduled for freezing freezes and expands, a part of it undergoes plastic deformation to absorb the expansion pressure and prevent an increase in added stress on the existing structure, and the deformation absorbing wall has a wall structure constructed by filling the ground with treated soil mixed with beads.

[0005] Meanwhile, Patent Document 2 proposes a freezing method for the starting and reaching parts of a thrust pipe, which the thrust pipe passes through. This freezing method involves placing a segment containing a coiled cooling pipe, which is inserted into a bag and can be penetrated by the thrust pipe, in the natural ground at the starting or reaching part of the thrust pipe, then filling the bag with a solidifying material to expand the bag and project it together with the cooling pipe into a hollow part formed in the natural ground, and then circulating brine through the cooling pipe. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-279985 [Patent Document 2] JP 2004-332295 A Summary of the Invention [Problem to be solved by the invention]

[0007] The freezing expansion pressure reduction structure described in Patent Document 1 makes it possible to reduce the freezing expansion pressure during frozen soil construction, and the freezing method described in Patent Document 2 makes it possible to support the frozen soil using bags that have been expanded by filling them with a solidification material; however, with either technology, it is difficult to achieve both the melting of the frozen soil due to heat transfer from the support structure that supports the frozen soil and the securing of the supporting capacity of the support structure to support the frozen soil.

[0008] The present invention aims to provide a frozen soil support structure and a method for forming the same, which can suppress or prevent the melting of frozen soil caused by heat transfer from the support structure and ensure the bearing capacity of the support structure to support the frozen soil when drilling holes inside or beside the frozen soil to construct the main body of an underground structure. [Means for solving the problem]

[0009] In order to achieve the above object, one aspect of the frozen soil support structure according to the present invention is to A frozen soil support structure in which frozen soil is constructed inside the ground, a reaction body is present inside or on the side of the frozen soil, and a part of the reaction body supports a part of the frozen soil, A laminate consisting of a first insulating material that resists the axial force acting from the frozen soil and a bag containing hardened filler is interposed between the reaction body and the frozen soil.

[0010] According to this aspect, in a support structure in which a part of a reaction body inside or on the side of the frozen soil supports a part of the frozen soil, a first insulation material that counters the axial force (soil water pressure) acting from the frozen soil is interposed between the structure and the frozen soil, so that melting of the frozen soil caused by heat transfer from the support structure can be suppressed or inhibited, and the supporting force for supporting the frozen soil can be secured. In addition, by using a bag containing a hardened filler, when the filler hardens and the bag expands, the laminated body adheres tightly while absorbing the unevenness of the surface of the frozen soil, and a support structure capable of transmitting the axial force acting from the frozen soil to the structure can be formed. Here, the "reaction body" includes various forms such as underground structures made of reinforced concrete (RC (Reinforced Concrete)) or steel concrete (SC (Steel Concrete)), as well as tunneling mobile bodies for constructing underground structures such as shield tunneling machines and tunneling machines in the jacking method.

[0011] Another aspect of the frozen soil support structure according to the present invention is The method is characterized in that frozen soil is laid inside the ground, a borehole is constructed inside or beside the frozen soil, a structure serving as the reaction body is constructed inside the borehole, and a part of the structure supports a part of the frozen soil.

[0012] According to this aspect, the structure constructed inside the frozen soil or inside a borehole located to the side of the frozen soil serves as a reaction body, and a first insulating material is interposed between the structure and the frozen soil, thereby forming a support structure capable of transmitting axial force acting from the frozen soil to the structure. Here, the "structure" that supports part of the frozen soil is, as mentioned above, a component part (side wall, etc.) of an underground structure made of reinforced concrete or reinforced concrete. Examples of the SC construction include a form in which concrete is filled inside a steel shell such as a steel segment.

[0013] In addition, "the borehole is constructed inside or beside the frozen soil" includes both a form in which a borehole is constructed inside the frozen soil and a form in which a borehole is constructed in the ground beside the frozen soil. The former form includes an example in which a borehole is constructed while excavating inside the frozen soil, and support members such as wales and struts are installed at predetermined depths during the construction of the borehole, and the axial force supported by the support members is supported by the structure constructed in the borehole via the laminate. On the other hand, an example of the latter form is when connecting and widening a main line tunnel and a ramp tunnel constructed underground, constructing a shaft extending vertically below one of the tunnels, constructing a group of large-section circular propulsion boxes in a vertical plane below this shaft as the starting and arrival base for the propulsion boxes, and constructing a large-section widening section inside the group of propulsion boxes while excavating the inside of the group of propulsion boxes from above.When excavating the inside of the group of propulsion boxes from above, frozen soil is constructed and when the end structure of the large-section widening section is constructed on the side of the frozen soil, the structure is constructed on the side of the frozen soil.

[0014] Another aspect of the frozen soil support structure according to the present invention is The first insulation material is a honeycomb board having a plurality of hexagonal hollow bodies, and the axial direction of the hexagonal hollow bodies is in the direction supporting the frozen soil.

[0015] According to this aspect, the first insulating material is a honeycomb board, and the axial direction of the hexagonal hollow bodies forming the honeycomb board extends in the direction supporting the frozen soil, so that the axial force acting from the frozen soil can be transmitted to the skeleton via the first insulating material with high supporting performance. Here, specific forms of the honeycomb board include a form that includes only a plurality of hexagonal hollow bodies, and a form in which both ends of the plurality of hexagonal hollow bodies are sandwiched between, for example, two flat plates.

[0016] Another aspect of the frozen soil support structure according to the present invention is The first insulation material is formed from a plurality of divided insulation materials, and each divided insulation material is stacked in the direction connecting the reaction body and the frozen soil.

[0017] According to this aspect, the first insulation material is formed of a plurality of divided insulation materials, and the divided insulation materials are stacked in the direction connecting the reaction body such as a building frame and the frozen soil, so that the thickness of the first insulation material can be changed according to the gap between the reaction body and the frozen soil, and the first insulation material can be installed closely in the gap between the reaction body and the frozen soil. Here, when the divided insulation materials have a trapezoidal side shape with a tapered surface, the divided insulation materials can be stacked in a wedge shape, and a stacked structure in which the divided insulation materials are pressed against each other can be formed.

[0018] Another aspect of the frozen soil support structure according to the present invention is A second insulating material is arranged on a wall surface of the frozen soil, and the bag body abuts against the frozen soil by being crushed by the laminate.

[0019] According to this aspect, since the second insulating material is disposed on the wall surface of the frozen soil, it is possible to suppress a part of the frozen soil from melting due to a rise in temperature of the region of the frozen soil on the side of the borehole when the borehole is constructed. Furthermore, since the bag body abuts against the frozen soil by squashing the second insulating material with the laminate, when the laminate is formed, the bag body penetrates into the uneven side surface of the frozen soil, and the side surface of the frozen soil can be effectively supported by the laminate.

[0020] In another aspect of the frozen soil support structure according to the present invention, The reaction body includes at least cast-in-place concrete.

[0021] According to this aspect, even if the reaction body such as a structural body contains at least cast-in-place concrete, the first insulation material forming the laminate can suppress heat transfer from the cast-in-place concrete to the frozen soil, thereby preventing the frozen soil from melting, and can suppress the transfer of cold heat from the frozen soil to the cast-in-place concrete, thereby preventing frost damage, in which water freezes due to cold heat during the hardening process of the poured cast-in-place concrete, resulting in poor hardening.

[0022] In addition, one aspect of the method for forming a frozen soil support structure according to the present invention is to Process A involves laying frozen soil inside the ground, and A step B of disposing a reaction body inside or beside the frozen soil, and when disposing the reaction body, a first insulating material and a deflated bag body are interposed between the reaction body and the frozen soil; The method is characterized by having a process C of supplying a filler material into the inside of the bag body and hardening it, inflating the bag body to abut against the frozen soil, and forming a laminate of the first insulation material and the bag body containing the hardened filler material to support the frozen soil.

[0023] According to this embodiment, in step B, a laminate of the first insulating material and the bag in an unexpanded state is interposed between the reaction body and the frozen soil, and in step C, a filler is supplied inside the bag and hardened to expand the bag to form a laminate, which supports the frozen soil. By interposing the first insulating material between the reaction body and the frozen soil against the axial force (frozen soil pressure) acting from the frozen soil, it is possible to suppress melting of the frozen soil due to heat transfer from the support structure, and it is possible to ensure the supporting force for supporting the frozen soil. Furthermore, by using the bag containing the hardened filler, when the filler hardens and the bag expands, the laminate comes into close contact with the frozen soil, and a support structure capable of transmitting the axial force acting from the frozen soil to the building frame can be formed.

[0024] In another aspect of the method for forming a frozen soil support structure according to the present invention, The step B is characterized in that a borehole is drilled inside or beside the frozen soil, and a structure serving as the reaction body is constructed inside the borehole.

[0025] According to this embodiment, a reaction body, that is, a structural body, is constructed inside the frozen soil or inside a borehole located to the side of the frozen soil, and a first insulating material is interposed between the structural body and the frozen soil, thereby forming a support structure capable of transmitting axial force acting from the frozen soil to the structural body.

[0026] In another aspect of the method for forming a frozen soil support structure according to the present invention, The step B is characterized in that after the borehole is constructed, a second insulation material is disposed on the wall surface of the frozen soil, and the structure is constructed to the side of the second insulation material.

[0027] According to this aspect, by disposing a second insulation material on the wall surface of the frozen soil, it is possible to prevent the area of ​​the frozen soil on the borehole side from rising in temperature when the borehole is constructed, and thereby prevent part of the frozen soil from melting.

[0028] Another aspect of the method for forming a frozen soil support structure according to the present invention is to The method is characterized in that the B step and the C step are treated as a set and are repeated in the depth direction of the ground using a reverse winding method.

[0029] According to this embodiment, by carrying out a reverse winding method in which steps B and C are treated as one set and are repeated multiple times in the depth direction of the ground, the construction of boreholes in the depth direction and the construction of underground structures can be made efficient. This effect becomes more pronounced as the depth increases, and construction safety can be guaranteed by the stable support of the frozen soil by part of the structure. Effect of the Invention

[0030] According to the frozen soil support structure and its formation method of the present invention, when drilling holes inside or to the side of the frozen soil to construct the main body of an underground structure, melting of the frozen soil caused by heat transfer from the support structure can be suppressed or prevented, and the supporting capacity of the support structure to support the frozen soil can be ensured. [Brief description of the drawings]

[0031] [Figure 1] A longitudinal cross-sectional view showing an example of a frozen soil support structure according to an embodiment, showing a state in which the frozen soil and a part of a structure constructed in a borehole to the side of the frozen soil are supporting a part of the frozen soil. [Diagram 2] FIG. 2 is a diagram showing an example of a laminate constituting a frozen soil support structure according to an embodiment, illustrating a state in which the bag body is not inflated. [Diagram 3] An oblique view showing the structure of an example of a divided insulation material that constitutes a first insulation material. [Figure 4] FIG. 2 is a diagram showing an example of a laminate constituting a frozen soil support structure according to an embodiment, illustrating a state in which a bag body is inflated. [Diagram 5] 1 is a process diagram of an example of a method for forming a frozen soil support structure according to an embodiment. FIG. [Figure 6] 5, a process diagram of an example of a method for forming a frozen soil support structure according to an embodiment of the present invention. [Figure 7] 6, this is a process diagram of an example of a method for forming a frozen soil support structure according to an embodiment. [Figure 8] 7, a process diagram of an example of a method for forming a frozen soil support structure according to an embodiment of the present invention will be described. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, a frozen soil support structure and a method for forming the same according to an embodiment will be described with reference to the accompanying drawings. In this specification and the drawings, substantially identical components are designated by the same reference numerals to avoid redundant description.

[0033] [Frozen soil support structure according to the embodiment] First, an example of a frozen soil support structure according to an embodiment will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a vertical cross-sectional view showing an example of a frozen soil support structure according to an embodiment, showing a state in which the frozen soil and a part of a body constructed in a borehole on the side of the frozen soil support structure are supporting a part of the frozen soil. Fig. 2 and Fig. 4 are views showing an example of a laminate constituting the frozen soil support structure according to an embodiment, respectively showing a state in which the bag body is not inflated and a state in which the bag body is inflated. Furthermore, Fig. 3 is a perspective view showing a structure of an example of a divided insulating material constituting the first insulating material.

[0034] Figure 1 shows a borehole 10 being constructed on the right side of frozen soil 20 laid in the ground G, a structure 40 (an example of a reaction body) being constructed inside the borehole 10, and a frozen soil support structure 100 being formed in the gap S between the frozen soil 20 and the structure 40.

[0035] Here, Figure 1 and Figures 5 to 8 referred to below all illustrate a certain height range at an intermediate depth of frozen soil 20 that has been constructed on ground G, and therefore in Figure 1 etc., frozen soil (not shown) extends further above, below, and to the left of the illustrated frozen soil 20, and a structure (not shown) extends further above the illustrated structure 40.

[0036] In the illustrated example, the borehole 10 is constructed on the side of frozen soil 20 laid in the ground G, but the borehole may be constructed inside the frozen soil 20 .

[0037] The construction of the underground structure in the illustrated example is outlined below. First, in this construction example, frozen soil is constructed on the side of the gable frame at the end of the widening section, which is an underground structure, by connecting and widening a main line tunnel and a ramp tunnel (not shown) that are constructed underground. In this construction, for example, a vertical shaft is constructed that extends vertically below the ramp tunnel, and a group of circular large-section propulsion boxes that house the main line tunnel and the ramp tunnel inside are constructed within a vertical plane, with the lower part of this shaft serving as the starting and arrival base for the propulsion boxes (not shown).

[0038] A steel shell for the widening section is formed by constructing a group of multiple large cross-section jacking boxes adjacent to each other along the extension direction of the main line tunnel and the ramp tunnel, and the reverse winding method is applied to excavate the inside of the steel shell from top to bottom (extending the borehole downward) to construct the underground structure that is the widening section. When constructing this borehole, frozen soil is constructed as an auxiliary construction method on the side of the gable frame at the end of the widening section, and a frozen soil support structure 100 is applied when construction is carried out while supporting the frozen soil on the side at each specified depth according to the downward extension of the borehole. Note that the illustrated example illustrates the reverse winding construction method, but it goes without saying that the forward winding construction method may be applied as another construction method.

[0039] As shown in Figure 1, on the side of the frozen soil 20, boreholes 10 are constructed downward at regular depths using a reverse winding method, and after excavation to the certain depth is completed, a structure 40 (for example, the gable structure of the widening section described above) is constructed up to a depth close to the certain depth.

[0040] The skeleton 40 is a steel concrete (SC) skeleton in which a plurality of hollow steel shells 41 are stacked in the depth direction at a certain height, shear reinforcement bars 42 are arranged at intervals in the depth direction inside the steel shells 41, and a cast-in-place concrete body 44 is arranged inside the steel shells 41. A grout injection pipe 43 is also arranged inside the steel shells 41 to fill the gap S between the frozen soil 20 and the skeleton 40 with backfill grout 35. In other words, the steel shells 41 also serve as a formwork when constructing the cast-in-place concrete body 44. Here, the skeleton may be an RC skeleton in addition to the SC skeleton shown in the figure.

[0041] The steel shell 41 of the structure 40 constructed in accordance with the construction step of the borehole 10 and the steel shell 41 of the structure 40 constructed below it are connected to each other via welds 45 .

[0042] After drilling the borehole 10 to a predetermined depth on the side of the frozen soil 20, and before constructing the skeleton 40, the side surface 21 of the frozen soil 20 facing the skeleton is covered with the second insulating material 30. Here, glass wool or the like can be used as the second insulating material 30.

[0043] When the borehole 10 is constructed, the side 21 of the frozen soil 20 is heated from the borehole 10 side, which may cause the area of ​​the frozen soil 20 on the side 21 side to melt; however, by covering the side 21 with the second insulation material 30, the melting of the frozen soil 20 can be suppressed.

[0044] The skeleton 40 is constructed with a gap S between it and the frozen soil 20. A laminate 80 made of a first insulating material 50 and a bag 60 containing hardened filler 70 is disposed in this gap S. Here, grout such as mortar is used as the filler 70. In the illustrated example, the laminate 80 is installed below each of the skeletons 40 that are connected to each other at a certain height.

[0045] After the structure 40 has been constructed, for example after several days have passed, the gap S between the upper layer 80 that was constructed in the previous excavation step and the layer 80 constructed in the current excavation step is filled with backfill grout 35.

[0046] As described below, when the bag 60 containing the filler 70 is filled with the filler 70 and expands, the bag 60 crushes the second insulating material 30 in the opposing position and comes into contact with the side surface 21 of the frozen soil 20. The side surface 21 of the frozen soil 20 has an uneven surface, but the deformable bag 60 can fit closely to the uneven surface of the side surface 21 while expanding.

[0047] As the filler 70 filled in the bag 60 hardens, the back surface of the laminate 80 is supported by the structure 40, forming a frozen soil support structure 100 that supports the frozen soil 20.

[0048] Here, the main body 40 extends in a band-like shape in the depth direction of the paper in Figure 1, and the bag body 60 is also in a band-like shape having approximately the same length as the main body 40, and multiple first insulating materials 50 are arranged continuously in the longitudinal direction of the bag body 60.

[0049] Each frozen soil support structure 100, which is arranged at a predetermined interval in the depth direction, supports the frozen soil 20 by applying a support reaction force P to the frozen soil 20 as a wall that receives soil-water pressure acting from the ground behind the frozen soil 20.

[0050] Here, on the side of the structure 40 opposite the frozen soil 20, at a depth position similar to that of the stack 80, a strut support (not shown) is installed, and a supporting force P' is applied to the structure 40 from the strut support.

[0051] Next, each component of the laminate 80 will be described. As shown in FIG. 2, an engagement pin 48 is provided on the surface of the body 40 facing the gap S in the steel shell 41. A first insulating material 50 is disposed below the engagement pin 48 so as to abut against the steel shell 41. Meanwhile, an eyelet hole 61 of the bag body 60 in a deflated state before expansion is engaged with the engagement pin 48. A filling port member 62 for filling a filler from inside the steel shell 41 is provided at an end of the bag body 60. The tip of the filling port member 62 penetrates the steel shell 41 and protrudes into the inside, and an injection pipe (not shown) is attached to the thread groove at the tip of the filling port member 62 so that grout is injected. For example, a grout bag or the like is applied as the bag body 60.

[0052] The first insulation material 50 is formed from multiple (three in the illustrated example) divided insulation materials 51, and each divided insulation material 51 has rigidity to withstand the axial force acting from the frozen soil 20 and also has insulating performance.

[0053] As shown in FIG. 3, the divided heat insulating material 51 is formed of a honeycomb board in which two flat plates 53 sandwich both ends of a plurality of hexagonal hollow bodies 52 arranged side by side.

[0054] The X direction, which is the axial direction of the hexagonal hollow body 52, is the left-right direction supporting the frozen soil 20 in Figs. 2 and 3 (the direction connecting the structure 40 and the frozen soil 20).

[0055] Since the divided heat insulating material 51 includes a plurality of hexagonal hollow bodies 52 with the axial direction being the direction in which the frozen soil 20 is supported, the divided heat insulating material 51 can have the rigidity to resist the axial force acting from the frozen soil 20 and the expansion pressure when the filler 70 is filled into the bag body 60. For example, the plane compressive strength of a honeycomb board is 1.6 N / mm 2 The plane compressive strength of conventional insulation materials such as Styrofoam (polystyrene foam) and Aeroflex (registered trademark, special elastomer) is about 0.2N / mm 2 This results in a component with significantly higher compressive strength than the conventional method.

[0056] Here, the divided insulation material 51 (the hexagonal hollow body 52 and the flat plate 53 that constitute it) is made of, for example, polypropylene resin, and has a thermal conductivity of about 0.065 W / mK, which is significantly lower than the thermal conductivity of about 0.1 W / mK that is generally accepted as a thermal insulation material. Therefore, the divided insulation material 51 is a thermal insulation material with high compressive strength.

[0057] In addition, in addition to the example shown in the figure, the divided insulation material may also be in a trapezoidal shape when viewed from the side.If this shape is applied, each divided insulation material can be installed by inserting it into a wedge shape, thereby preventing the divided insulation materials from shifting relative to each other.

[0058] A first insulation material 50 is formed by stacking a plurality of divided insulation materials 51, each having rigidity against the axial force acting from the frozen soil 20 and having thermal insulation performance, in the direction supporting the frozen soil 20, and after placing a deflated bag body 60, as shown in Fig. 4, the inside of the bag body 60 is filled with a filling material 70 to inflate the bag body 60, so that the bag body 60 comes into contact with the side surface 21 of the frozen soil 20 while crushing a part of the second insulation material 30. Here, a material that hardens due to the cold and heat of the frozen soil 20 may be used for the filling material 70.

[0059] As a construction method, after the installation of the bag body 60 is completed as shown in Fig. 2, cast-in-place concrete body 44 is cast on-site inside steel shell 41 to construct structure 40. Next, filler 70 is filled into bag body 60 from inside structure 40, and when filler 70 hardens, a frozen soil support structure 100 is formed, as shown in Fig. 4, in which the back side is supported by structure 40 and the front side of bag body 60 abuts against frozen soil 20 to provide support force P.

[0060] In order to shorten the construction period as much as possible, even when the frozen soil support structure 100 is formed and the next step of constructing a borehole is attempted to be started while the concrete forming the cast-in-place concrete body 44 is still in the hardening process and at a high temperature of, for example, about 60°C, the presence of the first insulation material 50 between the frozen soil 20 and the main body 40 allows the heat of the cast-in-place concrete 44 to be transferred to the frozen soil 20 via the laminate 80, suppressing or preventing part of the frozen soil 20 from melting.

[0061] Furthermore, the first insulation material 50 suppresses the transfer of cold heat from the frozen soil 20 to the cast-in-place concrete body 44, thereby suppressing or preventing frost damage, which is a cause of poor hardening of the cast-in-place concrete body 44.

[0062] [Method of forming a frozen soil support structure according to an embodiment] Next, an example of a method for forming a frozen soil support structure according to an embodiment will be described with reference to Fig. 5 to Fig. 8 and Fig. 1. Here, Fig. 5 to Fig. 8 and Fig. 1 are process diagrams of an example of a method for forming a frozen soil support structure according to an embodiment, in order.

[0063] The method of forming a frozen soil support structure in the illustrated example involves sequentially excavating the ground G to the side of the frozen soil 20 from above using a reverse winding method to construct boreholes 10, constructing a structure 40 in the boreholes 10, and forming a frozen soil support structure 100 to support the frozen soil 20. This method of forming a frozen soil support structure involves the process of constructing the structure 40, which is an underground structure extending to a predetermined depth, by repeating multiple sets of the construction of the boreholes 10 and the structure 40 and the formation of the frozen soil support structure 100 in the depth direction of the ground G.

[0064] When constructing the borehole 10, frozen soil 20 is applied to the ground on the side of the construction area (on the left side in the illustrated example). The frozen soil 20 is applied, for example, by extending a plurality of freezing pipes diagonally vertically downward or vertically upward from the above-mentioned ramp tunnel (not shown) and circulating brine (antifreeze) through the freezing pipes.

[0065] The frozen soil 20 to be constructed on the ground G has a length longer vertically than the structure 40 to be constructed, and is wide enough to withstand soil and water pressure from the rear, and is constructed to an extent that it can prevent groundwater from seeping into the construction area when the borehole 10 is constructed (this is the end of Process A).

[0066] 5 shows a state in which the construction of the borehole 10 to a certain depth is completed, the construction of the skeleton 40 is completed, the frozen soil support structure 100 is formed to support the frozen soil 20 while applying a bearing force P to the frozen soil 20, and a bearing force P' is applied from a braced support structure (not shown) to the side of the skeleton 40 opposite the frozen soil. From this state (the bedding state shown by the dashed dotted line), in order to construct the skeleton 40 at a deeper depth, the ground G is excavated and the borehole 10 is constructed in the Y direction extending to the bedding surface shown by the solid line.

[0067] As shown in Fig. 5, by constructing a borehole 10 on the side of the frozen soil 20, a side surface 21 of the frozen soil 20 is exposed to the borehole 10. In order to prevent this exposed side surface 21 from being heated from the borehole 10 side and melting the area of ​​the frozen soil 20 on the side surface 21 side, the exposed side surface 21 is covered with a second insulating material 30 as shown in Fig. 6.

[0068] 6, the lower end of the steel shell 41 constituting the already constructed upper structure 40 is connected to the upper end of the steel shell 41 constituting the structure 40 to be constructed below via a welded portion 45, and the steel shells 41 are stacked downward in sequence. When constructing the steel shells 41, a gap S is provided between the steel shells 41 and the frozen soil 20 to install the stacked body 80.

[0069] Next, as shown in Figure 7, steel shells 41 are stacked up to near the floor surface of the borehole 10, and multiple shear reinforcement bars 42 are arranged at intervals in the depth direction inside the steel shells 41.Furthermore, a first insulating material 50 and a deflated bag body 60 are installed on the side facing the gap S below the steel shells 41 (this is process B).

[0070] Next, as shown in FIG. 8, a cast-in-place concrete body 44 is placed inside the steel shell 41 to construct the structure 40, and a filler 70 is filled inside the bag body 60 to expand the bag body 60, and the filler 70 hardens to form a laminated body 80 (this is process C).

[0071] As shown in Figure 1, a laminate 80 whose back surface is supported by a main body 40 provides a bearing force P to the frozen soil 20, and a bearing force P' is provided to the side of the main body 40 opposite the frozen soil 20 from a braced support structure (not shown).

[0072] Thereafter, backfill grout 35 is filled into the gap S via a grout injection pipe 43, whereby the frozen soil 20 is supported by the frozen soil support structure 100, and the structure 40 is constructed to a predetermined height.

[0073] Steps B and C are treated as one set, and by repeating this set up to the design depth using the reverse winding method, the structure 40 that supports the frozen soil 20 with the frozen soil support structure 100 is constructed.

[0074] In addition, the present invention is not limited to the configuration shown here, and may be implemented in other embodiments in which other components are combined with the configurations and the like of the above-mentioned embodiment. In this regard, the present invention may be modified within the scope of the gist of the present invention, and may be appropriately determined according to the application form.

[0075] For example, the illustrated example shows an example of constructing a body, which is an example of a reaction body, on the side of the frozen soil, but the reaction body may be a moving body such as a shield tunneling machine. For example, a shield tunneling machine is driven into a frozen soil development area, a worker excavates a part of the frozen soil in front of the cutter head of the shield tunneling machine to form a working space, and the worker enters the working space and replaces the cutter bit attached to the cutter head underground. In this case, a support such as an H-shaped steel is installed between the cutter head and the frozen soil in front, and a laminated body 80 can be interposed between the tip of the support and the frozen soil. After the underground replacement of the cutter bit, etc. is completed, the working space is filled with liquefied treated soil from inside the shield tunneling machine, and excavation by the shield tunneling machine is resumed. [Explanation of symbols]

[0076] 10: Borehole 20: Frozen soil 21: Side 30: Second insulation material 35: Backfill grout 40: Structure (underground structure, reaction body) 41: Steel shell 42: Shear reinforcement 43: Grout injection pipe 44: Cast-in-place concrete 45: Welded section 48: Engagement pin 50: First insulation material 51: Split insulation material (honeycomb board) 52:Hexagonal hollow body 53: Flat plate 60: Bag (grout bag) 61: Eyelet hole 62: Filling port member 70: Filler (grout) 80: Laminate 100: Frozen soil support structure G: Ground S: Gap P: Supporting capacity P': Bearing capacity from braced beam support

Claims

1. A frozen soil support structure in which frozen soil is constructed inside the ground, a reaction body is present inside or on the side of the frozen soil, and a part of the reaction body supports a part of the frozen soil, A frozen soil support structure, characterized in that a laminate consisting of a first insulation material that counteracts the axial force acting from the frozen soil and a bag body containing hardened filler is interposed between the reaction body and the frozen soil.

2. The frozen soil support structure described in claim 1, characterized in that frozen soil is constructed inside the ground, a borehole is constructed inside or beside the frozen soil, a structure serving as the reaction body is constructed inside the borehole, and a part of the structure supports a part of the frozen soil.

3. The frozen soil support structure according to claim 1 or 2, characterized in that the first insulation material is a honeycomb board having a plurality of hexagonal hollow bodies, and the axial direction of the hexagonal hollow bodies is the direction in which the frozen soil is supported.

4. The frozen soil support structure according to any one of claims 1 to 3, characterized in that the first insulation material is formed from a plurality of divided insulation materials, and each divided insulation material is stacked in the direction connecting the reaction body and the frozen soil.

5. The frozen soil support structure described in any one of claims 1 to 4, characterized in that a second insulating material is arranged on a wall surface of the frozen soil, and the bag body abuts against the frozen soil by the second insulating material being crushed by the laminate.

6. The frozen soil support structure according to any one of claims 1 to 5, characterized in that the reaction body includes at least cast-in-place concrete.

7. Process A involves applying frozen soil inside the ground; A step B of disposing a counterforce body inside or beside the frozen soil, and when disposing the counterforce body, a first insulating material and a deflated bag body are interposed between the counterforce body and the frozen soil; A method for forming a frozen soil support structure, comprising: a step C of supplying a filler material into the inside of the bag body and hardening it, inflating the bag body to abut against the frozen soil, and forming a laminate of the first insulation material and the bag body containing the hardened filler material to support the frozen soil.

8. The method for forming a frozen soil support structure according to claim 7, characterized in that in step B, a borehole is drilled inside or beside the frozen soil, and a body serving as the reaction body is constructed inside the borehole.

9. The method for forming a frozen soil support structure described in claim 8, characterized in that in step B, after the borehole is constructed, a second insulation material is arranged on the wall surface of the frozen soil, and the main body is constructed to the side of the second insulation material.

10. A method for forming a frozen soil support structure as described in any one of claims 7 to 9, characterized in that a reverse winding method is used in which the B process and the C process are set as one set and are repeatedly performed in the depth direction of the ground.

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