Ground excavation method

Abstract

To provide an earth retaining structure and a ground open-cut method, capable of suppressing degradation of timbering effect of struts and capable of realizing efficient open-cut construction, unaffected by installation of timbering to the whole area of an open-cut area, for the large scale open-cut construction of which the open-cut area extends to a wide area.SOLUTION: An earth retaining structure 70 formed upon open-cut of the ground G comprises: a pair of first earth retaining walls 10 that retain at least a pair of excavated wall surfaces forming an open-cut area; and a pair of second earth retaining walls 20 that is arranged in the middle of a span s between the pair of the first earth retaining wall 10 to section the open-cut area, wherein a ground block 40, which is the ground or a ground improvement body, is positioned between the pair of the second earth retaining wall 20, and the second earth retaining wall 20 retains a wall surface of the ground block 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ground excavation method. [Background technology]

[0002] In construction work involving excavation of the ground, various types of retaining walls are constructed along the outer shell of the excavation area, and the ground is excavated (excavated) while struts are erected between the opposing retaining walls. This type of open-cut construction involves constructing a new structure on ground where no existing structures exist, as well as construction where an earth retaining wall is constructed around an existing structure and excavation is carried out while removing the existing structure, for example, to a level deeper than the existing structure.In either case, the new structure is constructed on top of a newly formed bedding.

[0003] For example, Patent Documents 1 and 2 also propose a construction method for an earth retaining structure and an earth retaining construction method in which cutting is performed while erecting struts between opposing earth retaining walls. The construction method of the earth retaining structure described in Patent Document 1 is a construction method that includes the steps of installing a jacking device between the wale at the end of the upper strut and the retaining wall, or between the end of the upper strut and the wale, and using this jacking device to introduce preload into the upper strut; after introducing preload into the upper strut, excavating the area to be excavated to a depth where the lower strut can be installed; installing a jacking device between the wale at the end of the lower strut and the retaining wall, or between the end of the lower strut and the wale, and using this jacking device to introduce preload into the lower strut; and installing diagonal members between the upper strut and the lower strut to make the entire strut into a truss structure. On the other hand, the earth retaining method described in Patent Document 2 is an earth retaining method for construction work in which a new building is constructed by excavating the ground deeper than the lower end of the existing underground outer wall when the groundwater level is higher than the new building floor level, and a water-stopping chemical solution is injected along the outside of the existing underground outer wall from above the lower end of the existing underground outer wall to the embedment position to form a water-stopping chemical solution layer, the existing underground outer wall and pressure plate frame are left in place and the existing underground structure is demolished in advance, the erection of horizontal struts to the inside of the existing underground outer wall and the demolishment of the existing underground structure are repeated in order from the top, the inside of the water-stopping chemical solution layer is excavated at the bottom of the existing underground outer wall, and a concrete wall for an earth retaining reinforcing wall is formed at the bottom of the excavated existing underground outer wall. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-188874 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-233349 Summary of the Invention [Problem to be solved by the invention]

[0005] In large-scale cut-and-cover construction where the excavation area is extensive, the struts naturally become longer, but as the struts become longer, they become more susceptible to buckling, which reduces the support effect of the struts. For example, it is known that when the struts are about 100 m long, the support effect of the struts becomes significantly reduced. Furthermore, in large-scale open cut construction, the next excavation process cannot begin until, for example, multiple struts have been installed in a grid pattern across the entire excavation area. This means that the overall construction speed depends on the speed at which the struts are installed, making it difficult to achieve efficient open cut construction.

[0006] The construction methods and methods for earth retaining structures described in Patent Documents 1 and 2 are basically the same as conventional general cut-and-cover methods in that they involve erecting struts on opposing earth retaining walls and then carrying out excavation, and therefore do not solve the problems associated with struts mentioned above when the excavation area is wide, or the problem of poor efficiency due to the overall construction relying on the installation of struts throughout the entire excavation area.

[0007] The present invention can suppress the decline in the support effect of struts in large-scale cut-and-cover construction where the excavation area covers a wide range, and the cut-and-cover construction is not affected by the installation of struts throughout the entire excavation area, thereby enabling efficient cut-and-cover construction. , earth The object of the present invention is to provide a method for cutting a floor. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the earth retaining structure according to the present invention is as follows: An earth retaining structure formed when excavating the ground, A pair of first retaining walls that retain at least a pair of excavation wall surfaces that form the excavation area; a pair of second retaining walls provided midway along the span of the pair of first retaining walls and separating the excavation area; Between the pair of second retaining walls there is a mass of ground which is the ground or a ground improvement body, and the second retaining wall retains the wall surface of the mass of ground.

[0009] According to this aspect, a pair of second retaining walls that separate the span (excavation area) are provided midway through the span of a pair of first retaining walls that retain at least a pair of excavation wall surfaces that form the excavation area.By doing so, even if the span of the pair of first retaining walls is long, the excavation area can be divided into multiple sections, eliminating the need to wait, for example, for struts to be installed across the entire area of the excavation area before excavation work can be carried out. This makes it possible to excavate each section sandwiched between the first and second retaining walls, or each section sandwiched between a pair of second retaining walls, individually, thereby increasing the overall efficiency of excavation work in the excavation area, and enabling various construction options to be set according to the site, such as excavating part of each excavation section in advance and constructing the structure in advance.

[0010] Furthermore, by not excavating the entire excavation area, but instead leaving the ground mass in the section sandwiched between a pair of second retaining walls in the center, and then excavating the sections sandwiched between the first and second retaining walls on either side of that, it is possible to reduce the amount of rebound compared to excavating the entire excavation area at once.

[0011] In this embodiment, it is not an essential requirement that struts be erected between the first and second earth retaining walls and between the pair of second earth retaining walls. For example, in cases where the ground is relatively hard and high-rigidity earth retaining walls are used as the first and second earth retaining walls, excavation can be performed without the need for struts, and therefore these embodiments are also included.

[0012] Furthermore, the presence of the original ground, ground improvement bodies, and other ground masses between the pair of second earth retaining walls allows these to form a self-supporting, highly rigid earth retaining wall unit as a whole. Therefore, for example, when a strut is erected between the first and second earth retaining walls, the second earth retaining wall can be integrated with the ground mass behind it to form an earth retaining wall that supports one end of the strut.

[0013] In another aspect of the earth retaining structure according to the present invention, A feature of the present invention is that a support structure is erected between the corresponding first retaining wall and the corresponding second retaining wall.

[0014] According to this aspect, by erecting support structures such as wales and struts between the corresponding first and second retaining walls, even if the excavation area is large, for example, it is divided into multiple sections, which prevents the length of the struts erected between the first and second retaining walls from becoming too long, and prevents a reduction in the support effect of the struts.

[0015] Another aspect of the earth retaining structure according to the present invention is as follows: The first retaining wall and the second retaining wall both have an endless shape in a plan view, A feature of the present invention is that a plurality of the supports are erected between the inner peripheral surface of the first retaining wall and the outer peripheral surface of the second retaining wall.

[0016] According to this aspect, a second earth retaining wall, which also has an endless shape in plan view, is located between first earth retaining walls, which have an endless shape in plan view, and a plurality of shoring is erected between the inner circumferential surface of the first earth retaining wall and the outer circumferential surface of the second earth retaining wall, so that a plurality of struts can be erected along the endless shapes between the outer periphery of the second earth retaining wall and the inner periphery of the first earth retaining wall. For example, by first performing excavation and shoring installation (strut installation) inside the endless second earth retaining wall located inside, the second earth retaining wall and its entire interior can be used as an intermediate temporary body, and shoring can be erected between the first earth retaining wall and the intermediate temporary body, making it possible to carry out excavation between the first earth retaining wall and the second earth retaining wall while maintaining balance over the entire excavation area. Here, if the outer shell shape of the excavation area is, for example, rectangular (rectangle or square), the endless shape of the first retaining wall is the same rectangular shape as this outer shell, and the endless shape of the second retaining wall inside it may be, for example, a small rectangle similar to the rectangle of the first retaining wall. Furthermore, even if the endless shape of the first retaining wall is a polygon other than a rectangle, a circle, an ellipse, etc., the endless shape of the second retaining wall inside it may be, for example, a shape similar to the shape of the first retaining wall but of smaller dimensions.

[0017] In another aspect of the earth retaining structure according to the present invention, The second earth retaining wall comprises an earth retaining wall A and an earth retaining wall B arranged at an interval, and a connecting material that integrates the earth retaining walls A and B is attached to the inner or outer peripheral surface of each of the earth retaining walls A and B, When the retaining wall A and the retaining wall B form the second retaining wall having an endless shape in plan view, a connecting material having an endless shape in plan view is attached to the inner surface or outer surface of the second retaining wall having an endless shape in plan view.

[0018] According to this embodiment, the second earth retaining wall comprises earth retaining wall A and earth retaining wall B arranged at a distance from each other, and connecting materials are attached to integrate each of earth retaining walls A and B, so that a highly rigid second earth retaining wall is formed together with the ground mass, which is the ground or ground improvement body, located inside them, and a retaining structure with high construction safety during excavation between the second earth retaining wall and the first earth retaining wall can be formed.

[0019] In another aspect of the earth retaining structure according to the present invention, A temporary pier is arranged above the second retaining wall, and the second retaining wall supports the temporary pier.

[0020] According to this aspect, since the second earth retaining wall supports the temporary pier above it, the second earth retaining wall can also be used as a support member for the temporary pier used by various heavy machinery such as clamshells for excavating the ground and cranes for transporting various materials and equipment, improving workability.Here, a connecting pier is also installed from a part of the first earth retaining wall to the temporary pier.

[0021] Further, one aspect of the ground excavation method according to the present invention is to A ground excavation method for excavating ground, A process A includes constructing a pair of first retaining walls on at least a pair of excavation wall surfaces that form an open-cut area; A process B includes constructing a pair of second retaining walls that are provided midway between the spans of the pair of first retaining walls and that separate the excavation area, and at this time, a ground mass that is the ground or a ground improvement body is placed between the pair of second retaining walls, and the second retaining walls retain the wall surface of the ground mass; The method is characterized by having a step C in which an excavation area A between the corresponding first retaining wall and second retaining wall and an excavation area B between the pair of second retaining walls are individually excavated.

[0022] According to this aspect, a pair of second retaining walls is constructed midway between the span of a pair of first retaining walls that retain at least a pair of excavation wall surfaces that form the excavation area, separating the span, and a ground mass is placed between the pair of second retaining walls.By then separately excavating excavation area A between the first and second retaining walls and excavation area B between the pair of second retaining walls, the construction efficiency of the entire excavation construction in the excavation area can be improved, and various construction options can be set according to the site, such as excavating a portion of each excavation section in advance and constructing structures in advance.

[0023] Another aspect of the ground excavation method according to the present invention is In the step C, In the excavation area A, excavation is performed while erecting supports between the corresponding first retaining wall and second retaining wall, In the excavation area B, excavation is carried out while erecting supports between the pair of second retaining walls.

[0024] According to this aspect, by erecting support structures such as wales and struts between the corresponding first and second retaining walls, even if the excavation area is large, for example, it is divided into multiple sections, which prevents the length of the struts erected between the first and second retaining walls from becoming too long, and prevents a reduction in the support effect of the struts.

[0025] In another aspect of the ground excavation method according to the present invention, In the B step, two pairs of second earth retaining walls are constructed midway through the span of the pair of first earth retaining walls, and the two excavation areas between the corresponding first earth retaining walls and the pair of second earth retaining walls are defined as excavation areas A1 and A2, the excavation areas between the respective second earth retaining walls of the two pairs of second earth retaining walls are defined as excavation areas B1 and B2, and further, the excavation area between the two pairs of second earth retaining walls is defined as excavation area B3, In step C, the central excavation area B3 is excavated first while erecting supports, and an intermediate temporary structure is formed using the supports erected in excavation area B3 and the two pairs of second retaining walls on either side of it, and the excavation areas A1 and A2 on the left and right of the intermediate temporary structure are excavated while erecting supports at the same or approximately the same speed.

[0026] According to this embodiment, two pairs of second retaining walls are constructed midway through the span of a pair of first retaining walls, and the excavation area B3 between the two pairs of second retaining walls is excavated while erecting supports ahead of the other excavation areas, and an intermediate temporary body is formed in the center of the excavation area, and then the excavation areas A1 and A2 on the left and right of the intermediate temporary body are constructed at approximately the same excavation speed, making it possible to carry out balanced construction across the entire wide excavation area. [Effects of the Invention]

[0027] The present invention Land of According to the excavation method, in large-scale excavation construction where the excavation area is wide, the reduction in the support effect of the struts can be suppressed, and the excavation construction is not affected by the installation of struts throughout the entire excavation area, allowing for efficient excavation construction. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 2 is a vertical cross-sectional view showing an example of an earth retaining structure according to the first embodiment, together with a process diagram of an example of a ground excavation method. [Figure 2] 1, is a longitudinal cross-sectional view showing a process diagram of an example of a ground excavation method according to the first embodiment. FIG. [Figure 3] FIG. 10 is a plan view showing an example of an earth retaining structure according to a second embodiment. [Figure 4] FIG. 10 is a vertical cross-sectional view showing an example of an earth retaining structure according to a third embodiment, together with a process diagram of an example of a ground excavation method. [Figure 5] 5 is a longitudinal cross-sectional view showing a process diagram of an example of a ground excavation method according to a third embodiment, following FIG. 4. FIG. [Figure 6]5, is a vertical cross-sectional view showing a process diagram of an example of a ground excavation method according to a third embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, the earth retaining structure and the ground excavation method according to each embodiment will be described with reference to the accompanying drawings. In this specification and the drawings, substantially the same components are designated by the same reference numerals, and redundant explanations may be omitted.

[0030] [Earth retaining structure and ground excavation method according to the first embodiment] First, an example of an earth retaining structure and a ground excavation method according to the first embodiment will be described with reference to Figures 1 and 2. Here, Figure 1 is a vertical cross-sectional view showing an example of an earth retaining structure according to the first embodiment together with a process flow chart of an example of a ground excavation method, and Figure 2 is a vertical cross-sectional view showing a process flow chart of an example of a ground excavation method according to the first embodiment, following Figure 1.

[0031] In the following explanation of each embodiment, the details of excavating ground where there is no existing structure and constructing a new structure are described, but the ground excavation method according to each embodiment can also be applied to excavating ground where there is an existing structure while removing the existing structure and constructing a new structure. Also, in the following explanation, a method of erecting shoring (bracing) between opposing earth retaining walls is described, but if the target ground is hard and the excavation depth is relatively shallow, or if cut-and-cover construction can be performed without the use of shoring, the erection of shoring is not necessary, and the ground excavation method according to each embodiment can also be applied to cut-and-cover construction without erecting shoring, based on the ground conditions and construction conditions.

[0032] The earth retaining structure 70 is, for example, an earth retaining structure that is elongated horizontally in one direction, the Y direction, and is a structure that is formed when excavating the ground G. In the depth direction of the paper (in this example, the short side direction of the excavation area), an earth retaining structure with the same configuration as the illustrated example may be formed, or a simpler appropriate earth retaining structure may be formed.

[0033] Within the excavation area, a pair of first earth retaining walls 10 are constructed in the ground G with a span s in the longitudinal direction Y. Here, the first earth retaining walls 10 can be prefabricated sheet pile walls such as horizontal sheet pile walls and steel sheet pile walls, or cast-in-place walls such as column-type earth retaining walls and diaphragm walls, and column-type earth retaining walls include cast-in-place reinforced concrete column-type earth retaining walls, steel pipe column-type earth retaining walls, and soil cement column-type earth retaining walls (soil cement column-type diaphragm walls, SMW (Soil Mixing Wall) walls) (the above is step A of the ground excavation method).

[0034] A pair of second retaining walls 20 are constructed midway through the span s of the pair of first retaining walls 10 to separate the excavation area of span s, and a ground mass 40, which is the (original) ground or ground improvement body, is placed between the pair of second retaining walls 20, and the wall surface of the ground mass 40 is retained by the pair of second retaining walls 20.

[0035] Here, the length of the span s of the pair of first retaining walls 10 is very long, for example, about 100 m or more, and if continuous struts are erected across the span s, the struts will be prone to buckling, and the supporting effect of the struts will not be fully obtained.

[0036] The second retaining wall 20 extends in the depth direction of the paper, and the integrity of the retaining wall is ensured by multiple stages (three stages in the illustrated example) of connecting members 21 that also extend in the short direction of the excavation area. The connecting members 21 can be made of shaped steel such as channel steel or H-shaped steel, or square steel pipes or steel pipes.

[0037] Here, similar to the first earth retaining wall 10, a prefabricated sheet pile wall, a column-type earth retaining wall, a cast-in-place wall such as a diaphragm wall, or the like can be applied to the second earth retaining wall 20. Furthermore, when the ground mass 40 is a ground improvement body, liquefied treated soil or the like can be applied to this ground improvement body.

[0038] An intermediate temporary body 60 is formed by the pair of second earth retaining walls 20 and the ground mass 40, which separate the span s of the pair of first earth retaining walls 10. The intermediate temporary body 60 may be called a pseudo-island body, since it is a temporary body that exists like an island in the middle of the long span s (this is step B of the ground excavation method).

[0039] A pair of second earth retaining walls 20 constituting the intermediate temporary structure 60 supports a temporary pier 51, and a connecting pier 52 is attached to the temporary pier 51 to allow access from the ground surface behind the first earth retaining wall 10. Various heavy machinery, such as a clamshell (not shown) that excavates the ground G and a crane (not shown) that transports various materials and equipment, moves from the connecting pier 52 to the temporary pier 51, and uses the temporary pier 51 to perform excavation work and transport materials and equipment.

[0040] By having the second retaining wall 20 directly support the temporary pier 51, it is possible to improve the ease of open cut construction in open cut areas with long spans s while eliminating the need to construct a support structure specific to the temporary pier 51.

[0041] An earth retaining structure 70 is formed by a pair of first earth retaining walls 10 and an intermediate temporary structure 60 located midway along the span s thereof.

[0042] By providing an intermediate temporary structure 60 midway along span s, the excavation area of span s is divided into left and right excavation areas A and an excavation area B corresponding to intermediate temporary structure 60.

[0043] In both left and right excavation areas A, the first earth retaining wall 10 and the second earth retaining wall 20 face each other. Therefore, in both excavation areas A, the ground is excavated and shoring 30 consisting of the first stage of wales 31 and struts 32 is erected, followed by the erection of the second stage of shoring 30, excavation of the ground, erection of the third stage of shoring 30, and excavation of the ground in the depth direction, X1, until excavation is completed down to the bedding level. Here, shaped steel materials such as H-shaped steel are used for the wales 31 and struts 32.

[0044] In this cut-and-cover construction, the excavation speeds for the left and right excavation areas A are adjusted to be approximately the same, and construction is carried out while balancing the excavations on both sides, so that the intermediate temporary structure 60 can receive the same amount of pressing force from the left and right struts 32, avoiding problems such as the intermediate temporary structure 60 collapsing due to uneven loads.

[0045] Next, as shown in Figure 2, in the left and right excavation areas A where excavation work has been completed in advance, the foundation K1 shown by the dashed line that constitutes the new structure is constructed, and the skeleton K2 shown by the dashed line that constitutes the new structure is erected in the X2 direction toward the ground. When erecting this skeleton K2, the obstructing supports 30 are removed one by one from the bottom up.

[0046] The pair of second earth retaining walls 20 are supported from the left and right by the upwardly rising skeleton K2. The ground mass (excavation area B) inside the pair of second earth retaining walls 20, which are supported from the sides by the rising skeleton K2, is excavated downward in the X3 direction, and during this process, multiple stages of supports 30A are erected inside the pair of second earth retaining walls 20 (this is step C of the ground excavation method).

[0047] New structures that will form the underground facility are constructed in the left and right excavation areas A, and new structures (not shown) are constructed inside the pair of second retaining walls 20 as well, while the second retaining walls 20 are removed, and by connecting the new structures that have already been constructed in excavation area A with the new structures to be constructed in excavation area B, a new structure that spans the entire excavation area is constructed. Structures such as high-rise or super-high-rise buildings, apartment buildings, and complexes are constructed on top of the new structures that will form the underground facility.

[0048] According to the illustrated ground excavation method, a pair of second earth retaining walls 20 is provided midway along span s of a pair of first earth retaining walls 10 that retain at least a pair of excavation wall surfaces that form the excavation area, dividing the span s. This allows the excavation area to be divided into multiple sections (excavation areas A and B), even if the span s of the pair of first earth retaining walls 10 is long. This eliminates the need to wait for struts to be installed throughout the entire excavation area A and B before starting excavation work. This makes it possible to excavate, for example, excavation area A sandwiched between the first earth retaining wall 10 and the second earth retaining wall 20, and excavation area B sandwiched between the pair of second earth retaining walls 20, separately, thereby improving the efficiency of excavation work in the entire excavation area and enabling various construction options to be set according to the site, such as first excavating one of excavation areas A and B and constructing a structure thereon.

[0049] Furthermore, even if the excavation area is large, since it is divided into multiple excavation areas A and B, the length of the strut 32 erected between the first retaining wall 10 and the second retaining wall 20 does not become too long, and a reduction in the support effect of the strut 32 can be suppressed.

[0050] Furthermore, by not excavating the entire excavation area, but instead leaving the ground mass 40 in excavation area B sandwiched between a pair of second retaining walls 20 in the center, and then excavating excavation areas A on either side of it, it is possible to reduce the amount of rebound compared to excavating the entire excavation area at once.

[0051] [Second embodiment of earth retaining structure and ground excavation method] Next, an example of an earth retaining structure and a ground excavation method according to the second embodiment will be described with reference to Fig. 3. Here, Fig. 3 is a plan view showing an example of an earth retaining structure according to the second embodiment.

[0052] The ground excavation method shown in the example is a method for excavating an excavation area where the excavation area to be constructed is rectangular in plan view and has long spans in both the vertical and horizontal directions. For example, the relatively long horizontal span is about 100 m or more, and the vertical span is also about 80 m or more. Here, the wide excavation area in plan view can be an excavation area of various shapes in plan view, such as a rectangular shape in plan view as shown in the example, a square shape in plan view, a polygonal shape in plan view, a circle in plan view, an ellipse in plan view, or a shape including curved and straight sections that intersect with each other in plan view.

[0053] In this case, a first retaining wall 10 is constructed along the outer shell of the excavation area in an endless shape when viewed from above (in the illustrated example, it is a rectangular frame shape when viewed from above), and inside it, a second retaining wall 20 is constructed in a relatively smaller endless shape when viewed from above (in the illustrated example, it is a rectangular frame shape when viewed from above).

[0054] A ground mass 40 is present inside the second earth retaining wall 20, which has a rectangular frame shape in plan view, and the second earth retaining wall 20 and the ground mass 40 form an intermediate temporary body 60A.

[0055] In the illustrated example, a temporary pier 51 shown by a dotted line is directly supported on the second retaining wall 20, and a bridge pier 52 is erected between the temporary pier 51 and the ground behind a portion of the first retaining wall 10.

[0056] After constructing the first and second earth retaining walls 10 and 20 (intermediate temporary structure 60A), the frame-shaped area between them is designated as excavation area A, and in excavation area A, excavation is carried out up to the floor level by repeating excavation and installation of shoring 30B at each stage, as in Figure 1. Here, in shoring 30B, by installing firestops 33 at the ends of each strut 32, the support area for the strut 32 can be made as wide as possible.

[0057] In addition, at the rectangular corners of the excavation area A, a fire-stopping unit 35 is installed, which is formed by arranging multiple steel structural members, etc. in a triangular shape in a plan view and in a grid pattern, to form an efficient support structure at the corners.

[0058] In the illustrated example, the excavation of the rectangular frame-shaped excavation area A is carried out at the same excavation speed throughout the entire area, and by carrying out the excavation of the excavation area A while balancing it, the intermediate temporary structure 60A in the center can receive the same amount of pressing force from the surrounding struts 32, thereby avoiding problems such as the intermediate temporary structure 60A collapsing due to uneven load.

[0059] Although not shown in the figure, as in Figure 2, a new structure is erected in excavation area A, and the new structure supports the periphery of intermediate temporary structure 60A.In this state, excavation of excavation area B formed by ground mass 40 and installation of support structures are carried out sequentially.

[0060] Finally, by sequentially connecting the new structure that has already been constructed in excavation area A with the new structure to be constructed in excavation area B, a new structure will be constructed that will form an underground facility spanning a wide excavation area that is rectangular in plan view.

[0061] [Earth retaining structure and ground excavation method according to the third embodiment] Next, an example of an earth retaining structure and a ground excavation method according to the third embodiment will be described with reference to Figures 4 to 6. Here, Figure 4 is a vertical cross-sectional view showing an example of an earth retaining structure according to the third embodiment together with a process flow chart of an example of a ground excavation method, and Figures 5 and 6 are vertical cross-sectional views showing the process flow chart of an example of a ground excavation method according to the third embodiment, following Figure 4.

[0062] In the illustrated example, for example, an intermediate temporary structure 60 formed by a pair of second earth retaining walls 20 (earth retaining wall A and earth retaining wall B) and the ground mass 40 between them shown in Fig. 1 is used as a single high-rigidity temporary structure, and two high-rigidity temporary structures are constructed spaced apart on the left and right, with the area between them designated as the area to be excavated first, and a large-scale intermediate temporary structure 60B is formed by the support 30 erected during the excavation first and the high-rigidity temporary structures on the left and right, thereby sequentially carrying out excavation construction of the entire excavation area. Here, the excavation area in the illustrated example may be a long and narrow excavation area that is long in one direction as shown in Fig. 1, or it may be a wide excavation area in a plane, such as a rectangle or polygon in plan view as shown in Fig. 3.

[0063] The area formed by the pair of second earth retaining walls 20 and the ground mass 40 between them is excavation area B1, and excavation area B2 is formed between the two excavation areas B1. Furthermore, excavation areas A1 and A2 are formed between the first earth retaining walls 10 constructed on the outside on the left and right and the second earth retaining wall 20 facing the first earth retaining walls 10.

[0064] In this cut-and-cover construction, the central cut-and-cover area B3 is excavated first, and then the ground is excavated and the supports 30 at each stage are erected in the depth direction X4, and in this process the intermediate temporary structure 60B is formed.

[0065] In the excavation areas A1 and A2 on the left and right of the intermediate temporary structure 60B, excavation work is carried out at approximately the same excavation speed, and the excavation of the ground and the erection of the supports 30 at each stage are carried out in the depth direction, that is, the X5 direction.

[0066] As shown in Figure 5, in the excavation area B3, the foundation K1 that will form the new structure is constructed first, and then the main body K2 is raised toward the ground in the X6 direction, while the second retaining walls 20 on the left and right are supported from the inside by the main body K2.

[0067] In the excavation areas A1 and A2 on the left and right, excavation in the X7 direction up to the floor level is carried out at approximately the same timing as, but delayed from, excavation area B3, and construction is carried out while balancing the excavation of excavation areas A1 and A2 on the left and right of the intermediate temporary structure 60B.

[0068] As shown in Figure 6, new structures are constructed up to ground level in excavation area B3, and then new structures are constructed up to ground level in the left and right excavation areas A1 and A2 with a delay, after which excavation in excavation areas B1 and B2 (and removal of second retaining wall 20) is carried out in the X8 direction.

[0069] During the excavation process of these excavation areas B1 and B2, or after the excavation of these areas B1 and B2 is completed, new structures will be constructed in the excavation areas B1 and B2, and by connecting them to the new structures that have already been constructed in the excavation areas A1 and A2 on the left and right, new structures will be constructed that will form underground facilities spanning a wide excavation area.

[0070] In this excavation method, the excavation areas B1 and B2 are set so that the walls, pillars, etc. of the permanent structure are not located inside the excavation areas B1 and B2, which improves workability when constructing the permanent structure while finally excavating the excavation areas B1 and B2.

[0071] It should be noted that the present invention is not limited to the configurations shown here, and other embodiments may be possible in which other components are combined with the configurations described in the above embodiments. In this regard, the present invention can be modified within the scope of the present invention, and can be appropriately determined depending on the application form. [Explanation of symbols]

[0072] 10: Daiichi retaining wall 20:Second retaining wall 21: Connecting material 30,30A,30B: Shoring 31, 31A: Belly up 32:Surface beam 33: Flint 35: Flint Unit 40: Ground mass 51: Temporary Pier 52: Pier 60, 60A, 60B: Intermediate temporary structure 70,70A,70B: Yamadome structure A, A1, A2, B, B1, B2, B3: Open cut area K1: Basics K2:Structure K3: 1st floor slab G: Ground

Claims

1. A ground excavation method for excavating ground, Step A: constructing a pair of first retaining walls on at least a pair of excavation wall surfaces that form an excavation area; A process B includes constructing a pair of second retaining walls that are provided midway along the span of the pair of first retaining walls and that separate the excavation area, and at this time, a ground mass that is the ground or a ground improvement body is placed between the pair of second retaining walls, and the second retaining walls retain the wall surface of the ground mass; and a C step of individually excavating an excavation area A between the corresponding first retaining wall and the corresponding second retaining wall and an excavation area B between the pair of second retaining walls, In the step C, In the excavation area A, excavation is performed while erecting supports between the corresponding first retaining wall and second retaining wall, A ground excavation method, characterized in that in the excavation area B, excavation is carried out while erecting supports between the pair of second retaining walls.

2. A ground excavation method for excavating ground, Step A: constructing a pair of first retaining walls on at least a pair of excavation wall surfaces that form an excavation area; A process B includes constructing a pair of second retaining walls that are provided midway along the span of the pair of first retaining walls and that separate the excavation area, and at this time, a ground mass that is the ground or a ground improvement body is placed between the pair of second retaining walls, and the second retaining walls retain the wall surface of the ground mass; and a C step of individually excavating an excavation area A between the corresponding first retaining wall and the corresponding second retaining wall and an excavation area B between the pair of second retaining walls, In the B step, two pairs of second earth retaining walls are constructed midway through the span of the pair of first earth retaining walls, and the two excavation areas between the corresponding first earth retaining walls and the pair of second earth retaining walls are defined as excavation areas A1 and A2, the excavation areas between the respective second earth retaining walls of the two pairs of second earth retaining walls are defined as excavation areas B1 and B2, and further, the excavation area between the two pairs of second earth retaining walls is defined as excavation area B3, In step C, the central excavation area B3 is excavated first while erecting supports, and an intermediate temporary structure is formed using the supports erected in excavation area B3 and the two pairs of second retaining walls on either side of it, and the excavation areas A1 and A2 on the left and right of the intermediate temporary structure are excavated while erecting supports at the same or approximately the same speed, a ground excavation method characterized by the above.

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