EP1954885A1

EP1954885A1 - Temporary soil sheathing apparatus

Info

Publication number: EP1954885A1
Application number: EP06812614A
Authority: EP
Inventors: Seung Deok Baik
Original assignee: SUPPORTEC CO Ltd
Current assignee: SUPPORTEC CO Ltd
Priority date: 2005-11-16
Filing date: 2006-11-15
Publication date: 2008-08-13
Also published as: JP2009516109A; CN101310079B; JP4960969B2; WO2007058464A1; CN101310079A

Abstract

A temporary soil sheathing apparatus supports a set of intermediate bracing beams in a triangular supporting structure during pit excavation work for constructing an underground structure, so that it can satisfactorily support soil pressure. Thus, it is possible to prevent space from being reduced by a complicated supporting structure, reduce construction costs through reduced use of materials, and increase work space to improve productivity. The temporary soil sheathing apparatus simplifies a corner connecting structure, and reinforces ability to withstand the soil pressure transmitted from the bracing beams and wales. Thereby, it is possible to prevent space from being reduced by a complicated supporting structure, reduce construction costs through reduced use of materials, and increase work space to thus improve productivity.

Description

TEMPORARY SOIL SHEATHING APPARATUS

Technical Field

[1] The present invention relates, in general, to a temporary soil sheathing apparatus, and more particularly, to a temporary soil sheathing apparatus capable of increasing ability to withstand soil pressure through structural simplification during pit excavation work for constructing an underground structure. Background Art

[2] As is generally known in the art, in subway construction or in pit excavation work for forming the basement of a building, holes are drilled to a predetermined depth in a designated area, and then vertical piles are sunk into the holes. After the vertical piles are sunk, the ground is partially excavated, and then H-beams and lining boards are installed. After installing the lining boards, the remaining ground is excavated, and bracing beams are repeatedly installed, accompanied with excavation. Therefore, in order to design this temporary structure, the soil pressure and the load acting on each bracing beam must be repeatedly calculated, once for each excavation step, and the bracing beams are installed so as to be able to withstand the maximum soil pressure and load determined thus.

[3] This design and construction requires many bracing beams. In most cases, the bracing beams are densely arranged at intervals between 2 m and 3 m. The dense bracing beams serve as main obstacles that impede the transport of construction materials, the entry and operation of heavy equipment, etc. in the excavated pit, and interfere considerably with form work or reinforcement work when the main structure is subsequently formed. Further, the dense bracing beams inevitably require that a plurality of holes be formed in the main structure, so that they cause a serious problem with respect to the waterproofing of the finished underground structure.

[4] The vertical piles are set up according to various methods, such as a method of using H-beams of steel, a method of using concrete piles in which holes are drilled and filled with concrete, a method of using H-beams together with concrete piles, and a method of using sheet piles. These methods make little difference with respect to the basic principle of drilling holes into the ground, forming piles into a wall, and supporting the load of the ground.

[5] Further, there are other methods: a method of using preflex beams as the vertical piles, and a method of attaching sheet piles to H-piles to increase rigidity.

[6] Meanwhile, among the temporary methods for constructing the underground structure, there is a method of supporting steel piles using earth anchors that does not require the above-described bracing beams.

[7] This method involves drilling a hole at an incline into the ground at the rear of the pile, inserting a steel wire or rod into the hole, anchoring an end of the inserted steel wire or rod using a mechanical method or a chemical method, such as epoxy grouting or cement grouting, and tensioning the anchored steel wire or rod to fix the steel piles.

[8] This temporary method has an advantage in that the problem in that it is difficult to conduct work is mitigated because the constructed structure secures sufficient internal space.

[9] However, this temporary is widely criticized by the public when implemented in a developed urban area because the surrounding private land is encroached upon in most cases, and furthermore, the method costs a great deal.

[10] A method of removing bracing beams crossing an excavated pit from a temporary structure using a truss is disclosed in Korean Utility Model Registration No. 20-258949. This method is expected to be able to be applied in the case in which the ground is excavated to a relatively low depth, wherein H-beams are doubly formed near the surface of land in a lattice shape and are reinforced by vertical beams and raker beams. Thereby, the two-tier truss near the surface of land is made able to withstand the soil pressure.

[11] This method was devised to overcome difficulty in excavation and installation of the main structure due to the bracing beams of the temporary structure, and is regarded as a convenient method in the situation where a wide structure is to be formed in a lower portion of the excavated ground and a narrow structure is to be formed in an upper portion of the excavated ground.

[12] Typically, the bracing beams are primarily used in pit excavation work. During such work, when viewed from the top, the moment is maximized at the central portion in the rectangular area by means of the soil pressure, so that the central portion must have greater bearing capacity than other portions.

[13] Therefore, the central portion requires a lot of central bracing beams. This becomes a factor that increases construction costs and makes the structure complicated. Thereby, the work space is narrowed, thus reducing productivity. Disclosure of Invention Technical Problem

[14] Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a temporary soil sheathing apparatus, in which a set of intermediate bracing beams having a preloading jack in the middle thereof and a triangular supporting structure at opposite ends thereof is installed at an intermediate excavated portion during pit excavation work for constructing an underground structure, thereby increasing the capacity to bear soil pressure through structural simplification.

[15] Another object of the present invention is to provide a temporary soil sheathing apparatus, in which a corner connecting structure is applied to each corner of an excavated portion during pit excavation work for constructing an underground structure, thereby increasing ability to withstand soil pressure through structural simplification.

[16] Another object of the present invention is to provide a temporary soil sheathing apparatus, in which bracing beams are interconnected at each corner of an excavated portion during pit excavation work for constructing an underground structure, thereby forming the bracing beams, to which soil pressure is transmitted, into a truss structure such that the bracing beams behave like one member. Technical Solution

[17] In order to achieve the above objects, according to one aspect of the present invention, there is provided a temporary soil sheathing apparatus, which includes: a set of intermediate bracing beams are is installed across an intermediate portion excavated in a rectangular area during underground pit excavation work, and wales that are integrally connected with opposite ends of the intermediate bracing beam set. Here, the intermediate bracing beam set is provided with a preloading jack at the middle thereof, and is connected with raker beams via first and second connectors on left and right sides of each end thereof, such that the opposite ends thereof form a triangular supporting structure.

[18] According to another aspect of the present invention, there is provided a temporary soil sheathing apparatus, which includes a braced wall that is installed parallel to an excavated portion during underground pit excavation work, a set of bracing beams that are coupled to the braced wall at each corner in the pit excavation work and support soil pressure, and a corner connector having a cross beam that is coupled to each wale, a compression beam that is obliquely connected to one end of the cross beam and is integrally connected to one end of the bracing beam set, and a raker beam that connects one end of the compression beam and another end of the cross beam.

[19] According to yet another aspect of the present invention, there is provided a temporary soil sheathing apparatus, which includes bracing beams that are disposed in rows at predetermined intervals so as to support each corner during underground pit excavation work, and at least one connecting plate that is integrally coupled to any one of upper and lower surfaces of each bracing beam by a coupling means so as to interconnect the bracing beams.

Advantageous Effects [20] According to a first embodiment of the present invention, the temporary soil sheathing apparatus is adapted to simplify the connecting structure of the intermediate bracing beam set and reinforce the ability to withstand the soil pressure transmitted from the braced wall and the wales during rectangular pit excavation work for constructing an underground structure. Thus, the temporary soil sheathing apparatus has a triangular supporting structure that supports the intermediate bracing beam set in the pit excavation work for constructing an underground structure, so that it can satisfactorily support soil pressure. Thus, it is possible to prevent space from being reduced by a complicated supporting structure, reduce construction costs through reduced use of materials, and increase work space to thus improve productivity.

[21] Further, the opposite ends of the intermediate bracing beam set are supported in a triangular supporting structure. Hence, the braced wall to which the soil pressure is actually transmitted can be supported by a wider supporting area compared to existing structures for connecting the intermediate bracing beams, so that it is possible to simultaneously apply an amount of compressive force corresponding to the soil pressure and increase bearing capacity.

[22] According to a second embodiment of the present invention, the temporary soil sheathing apparatus is adapted to simplify the connecting structure in each corner and reinforce the ability to withstand the soil pressure transmitted from the braced wall and the wales during pit excavation work for constructing an underground structure. Thereby, the temporary soil sheathing apparatus can satisfactorily support the soil pressure transmitted to each corner using a simple corner connecting structure during pit excavation work for constructing an underground structure, so that it is possible to prevent space from being reduced by a complicated supporting structure, reduce construction costs through reduced use of materials, and increase work space to thus improve productivity.

[23] According to a third embodiment of the present invention, the temporary soil sheathing apparatus is adapted to interconnect the bracing beams disposed in rows at each corner during pit excavation work for constructing an underground structure. The temporary soil sheathing apparatus integrates the rows of bracing beams at each corner in a truss structure, so that it can uniformly transmit a horizontal load, and thus obtain sufficient durability against a flexural load. Brief Description of the Drawings

[24] FIG. 1 is a schematic top plan view illustrating a temporary soil sheathing apparatus according to a first embodiment of the present invention;

[25] FIG. 2 is a perspective view illustrating an important part in a temporary soil sheathing apparatus according to a first embodiment of the present invention; [26] FIG. 3 is a top plan view illustrating a first connector, which is an important part, in a temporary soil sheathing apparatus according to a first embodiment of the present invention;

[27] FIG. 4 is a top plan view illustrating a connecting structure of a second connector, which is an important part, in a temporary soil sheathing apparatus according to a first embodiment of the present invention;

[28] FIG. 5 is a schematic top plan view illustrating a temporary soil sheathing apparatus according to a second embodiment of the present invention;

[29] FIG. 6 is an enlarged perspective view illustrating part A of FIG. 5;

[30] FIG. 7 is a sectional view illustrating an important part of FIG. 6;

[31] FIG. 8 is a partial top plan view illustrating a modification of the corner connecting structure of FIG. 5;

[32] FIG. 9 is a top plan view illustrating a temporary soil sheathing apparatus according to a third embodiment of the present invention;

[33] FIG. 10 is an enlarged perspective view illustrating part B of FIG. 9;

[34] FIG. 11 is a top plan view illustrating an important part of FIG. 9;

[35] FIG. 12 is a front view illustrating an important part of FIG. 9; and

[36] FIG. 13 is a front view illustrating a modification of FIG. 12.

Best Mode for Carrying Out the Invention

[37] Reference will now be made in greater detail to exemplary embodiments of the invention with reference to the accompanying drawings.

[38] [Embodiment 1]

[39] Referring to FIGS. 1 through 4, a temporary soil sheathing apparatus according to a first embodiment of the present invention includes wales 20 that are integrally coupled to a braced wall (not shown), installed parallel to a vertically excavated portion in a rectangular area during pit excavation work, and that support soil pressure, a set of intermediate bracing beams 100 that traverse long sides of the braced wall and that support the soil pressure transmitted from the braced wall, raker beams 200 that obliquely support the intermediate bracing beam set 100 and the corresponding wale 20 at opposite ends thereof so as to be connected with the intermediate bracing beam set 100 and the corresponding wale 20 in a triangular structure.

[40] More specifically, the intermediate bracing beam set 100 comprises a plurality thereof, and has a structure in which each intermediate bracing beam is connected so as to be integrally coupled to the wales 20 at opposite ends thereof, and is provided with a preloading jack 150 at the middle thereof, thereby having varying ability to withstand the soil pressure.

[41] Each wale 20 may employ a single-layer wale or a multi-layer wale depending on the footprint of the excavated ground, and is preferably pre-stressed so as to match (the moment of) the soil pressure.

[42] Each raker beam 200 is installed obliquely with respect to the intermediate bracing beam 100 and the corresponding wale 20, thereby forming a triangular structure. The raker beam 200 is integrally connected to the intermediate bracing beam set 100 and the corresponding wale 20, respectively, through first and second connectors 310 and 320 at opposite ends thereof. The first and second connectors 310 and 320 have an approximately triangular shape so that they can support the opposite ends of each raker beam 200.

[43] The first connector 310 is interposed between the intermediate bracing beam set

100 and the raker beam 200, and includes a vertical beam 312 that is connected to the intermediate bracing beam set 100, and first and second supporting beams 314 and 316 that are obliquely connected to opposite ends of one side of the vertical beam 312 so as to have a triangular shape.

[44] Further, the second connector 320 is interposed between the raker beam 200 and the corresponding wale 20, and includes a cross beam 322 that is parallel to and in surface contact with the wale 20, and first and second connecting beams 324 and 326 that are obliquely connected to opposite ends of one side of the cross beam 322 and integrally coupled to the other end of the raker beam 200 so as to have a triangular shape.

[45] The cross beam 322 of the second connector 320 is bolted on one side of the wale

20, and the first and second connecting beams 324 and 326 serve to distribute and support the load transmitted from the raker beam 200.

[46] Preferably, the beams of the first and second connectors 310 and 320 each employ a typical H-beam having a web and flanges. At least one first stiff ener 310a is welded to the web of the H-beam for the first connector 310, and at least one second stiff ener 320a is welded to the web of the H-beam for the second connector 320.

[47] Each of the first and second stiffeners 310a and 320a is preferably provided so as to support compressive force at a portion where another member is coupled or force is transmitted.

[48] Further, the cross beam 322 and the vertical beam 312 have end plates welded at opposite ends thereof in order to be connected with the corresponding wale 20 and the intermediate bracing beam set 100, respectively.

[49] Also, the first and second connectors 310 and 320 have first and second reinforcing plates 310b and 320b interposed between the vertical beam 312 and the first supporting beam 314 and between the cross beam 322 and the first connecting beam 324, respectively. Thus, the first and second connectors 310 and 320 are in surface contact with two sides of each of the first and second reinforcing plates 310b and 320b, so that they can increase the ability to withstand compressive force. [50] The wale 20 is preferably provided with a shear key 322a at the position where the compressive force is transmitted. The shear key 322a is connected by high-tensile bolts, and is in contact with one flange of the cross beam 322.

[51] Because the compressive force transmitted to the wale 20 and the force transmitted from the raker beam 200 act in opposite directions, the shear key 322a serves to use the opposing forces to offset each other.

[52] The operation of the temporary soil sheathing apparatus, having this construction, according to a first embodiment of the present invention, will be described below.

[53] The temporary soil sheathing apparatus according to a first embodiment of the present invention is adapted to support soil pressure on an intermediate portion which is transmitted through the braced wall by installing the raker beams 200 for connection with the wales 20 so as to have a triangular supporting structure at opposite ends of the intermediate bracing beam set 100.

[54] At this time, the preloading jack 150 installed at the intermediate portion, preferably at the center, of the intermediate bracing beam set 100 transmits a load in opposite directions. Thereby, the opposite ends of the intermediate bracing beam set 100 apply pressure to the opposite wales 20, and thus transmit compressive bearing force corresponding to the soil pressure to the opposite wales 20.

[55] Further, the compressive force transmitted from the opposite wales 20 is distributed and supported through the raker beam 200 installed on the opposite ends of the intermediate bracing beam set 100 to form a triangular shape, so that stable bearing capacity can be obtained.

[56] The pressure transmitted through each wale 20 is transmitted to the end plates of each cross beam 322, which is in surface contact with a stopper of a corresponding wale 20. In the case in which each cross beam 322 is in contact with the shear key 322a, the compressive force transmitted from each wale 20 acts to oppose the pressure transmitted to the cross beam 322 through the intermediate bracing beam set 100. As a result, these forces can be offset and counteracted by each other, and simultaneously the bearing capacity can be provided by high-tensile bolts.

[57] Further, the raker beams 200 are connected to the intermediate bracing beam set

100 and the opposite wales 20 to form a triangular supporting structure, so that the compressive forces from the opposite wales can be distributed and supported in a more stable way.

[58] Further, the first and second stiffeners 310a and 320a are welded to the webs of the first and second connectors employing H-beams, respectively, so that they can increase rigidity and ability to withstand compressive force. Further, the first and second connectors 310 and 320 are provided with the first and second reinforcing plates 310b and 320b, respectively, so that they can make up for the ability to withstand the compressive force transmitted from the raker beams 200.

[59] [Embodiment 2]

[60] The temporary soil sheathing apparatus according to a second embodiment of the present invention further includes a corner connecting structure employing the triangular supporting structure employed in the temporary soil sheathing apparatus according to the first embodiment of the present invention. In this case, the temporary soil sheathing apparatus can increase the efficiency of use of space and the ability to withstand soil pressure through structural simplification.

[61] The temporary soil sheathing apparatus according to a second embodiment of the present invention further includes a corner connecting structure employing the above- described triangular supporting structure. Referring to FIGS. 5 through 8, the temporary soil sheathing apparatus according to a second embodiment of the present invention includes a braced wall 510 that is installed parallel to a vertically excavated portion during pit excavation work, wales 520 and bracing beam sets 550 that are integrally coupled to the braced wall 510 and support soil pressure, and corner connectors 600 that are provided at corners formed by the braced wall 510 and support the soil pressure transmitted from the braced wall 510.

[62] More specifically, each bracing beam set 550 may be replaced by a strut, and each wale 520 can be pre-stressed so as to match the moment of the soil pressure. Further, each wale 520 may employ a single-layer wale or a multi-layer wale in consideration of the footprint and the depth of the excavated ground.

[63] Each corner connector 600 includes a cross beam 610, a compression beam 620, and a raker beam 630, all of which form a stable structure when pressure is transmitted thereto, i.e. a triangular structure. Here, the cross beam 610 is integrally coupled with the corresponding wale 520. The compression beam 620 is connected to one end of the cross beam 610 and one end of each bracing beam set 550. The raker beam 630 connects the cross beam 610 and the compression beam 620.

[64] The cross beam 610 is fixed to one side of the corresponding wale 520 by means of bolts. The compression beam 620 is connected with each bracing beam set 550 on one side thereof, and transmits the load of the soil pressure, which is transmitted from each bracing beam set 550, to other members. The raker beam 630 serves to distribute and support the load transmitted from the compression beam 620.

[65] Each of the cross beam 610, the compression beam 620, and the raker beam 630 preferably employs a well-known H-beam, to the web of which at least one stiffener 650 is welded.

[66] The stiffener 650 is preferably provided to portions where the members are coupled or where the force is transmitted so as to support compressive force.

[67] Further, the cross beam 610 has end plates 614 welded to opposite ends thereof in order to be connected with the corresponding wale 520.

[68] Also, a reinforcing plate 810 is interposed between the cross beam 610 and the compression beam 620. The reinforcing plate 810 is in surface contact with the cross beam 610 and the compression beam 620 on two sides thereof, so that it can increase the ability to withstand compressive force.

[69] The reference number "602", which has not yet been described, refers to a drain hole for preventing rainwater from collecting in each beam.

[70] As in FIG. 4, each wale 520 is preferably provided with a shear key 615 at a position where the compressive force is transmitted. The shear key 615 is connected by high-tensile bolts, and is in contact with the other side of the cross beam 610.

[71] Because the compressive force transmitted to the wale 520 and the force transmitted from the compression beam 620 act in opposite directions, the shear key 615 serves to use the opposing forces to offset each other.

[72] Although not illustrated, a preloading jack having a cylinder is provided at an intermediate portion of each bracing beam set 550. Preferably, each bracing beam set 550 is provided with corresponding corner connectors 600 having a triangular structure at opposite ends thereof, thereby transmitting compressive force corresponding to the soil pressure from the preloading jack to the compression beams 620 of the corresponding corner connectors 600.

[73] The operation of the temporary soil sheathing apparatus, having this construction, according to a second embodiment of the present invention will be described below.

[74] The temporary soil sheathing apparatus according to a second embodiment of the present invention is adapted to support soil pressure, transmitted through the braced wall 510, through the corner connectors 600, installed between the bracing beam sets 550 and the wales 520 at the corners defined by the braced wall 510.

[75] At this time, the soil pressure on the braced wall 510 is supported by the compressive force transmitted from the bracing beam sets 550 and by the transverse pressure transmitted from the wales 520 at the corners. The compression beam 620 of each corner connector 600 distributes and transmits the pressure, which is transmitted from each bracing beam set 550, to the cross beam 610 and the raker beam 630. As a result, the temporary soil sheathing apparatus can have increased load carrying capacity using a simple structure.

[76] The pressure transmitted through each wale 520 is transmitted to the end plates of each cross beam 610, which is in surface contact with the corresponding wale 520. In the case in which each cross beam 610 is in contact with the shear key 615, the compressive force transmitted from each wale 520 acts against the pressure transmitted to each cross beam 610 through each bracing beam set 550. As a result, these forces can be offset and counteracted by each other, and the bearing capacity can be provided using high-tensile bolts.

[77] Further, the stiffener 650 is welded to the web of each corner connector 600 employing the H-beam, so that it can increase rigidity and the ability to withstand the compressive force. Further, the reinforcing plate is interposed between the cross beam 610 and the compression beam 620, so that it can increase the ability to withstand the compressive force transmitted from each bracing beam set 550.

[78] [Embodiment 3]

[79] The temporary soil sheathing apparatus according to a third embodiment of the present invention further includes a corner connecting structure which is adapted to uniformly transmit horizontal load to thus obtain sufficient ability to withstand a flexural load using bracing beams, disposed in rows at each corner and integrated in a truss structure when pit excavation work for constructing an underground structure is performed.

[80] Referring to FIGS. 9 through 13, the temporary soil sheathing apparatus according to a third embodiment of the present invention includes bracing beams 1100 that are obliquely disposed in rows at each corner when pit excavation work for constructing an underground structure is performed, and that are supported on a braced wall 1010 at opposite ends thereof, and at least one connecting plate 1200 that interconnects upper or lower surfaces of the neighboring bracing beams 1100 using a coupling means.

[81] More specifically, the connecting plate 1200 has a rectangular shape, and is provided with at least one stiffener 1210 that is oriented in a longitudinal direction in order to resist vertical flexural deformation.

[82] The stiffener 1210 is integrally formed at one edge of the connecting plate 1200, or is integrated with the connecting plate 1200 through welding. The stiffener 1210 has the shape of a strip or an L-shaped angle. Although not illustrated, the connecting plate 1200 may employ an H-beam.

[83] FIG. 13 is a front view illustrating a modification of FIG. 12. The connecting plates

1200 are coupled to upper and lower surfaces of each bracing beam 110, respectively. According to the circumstances of a particular site, a plurality of connecting plates 1200 is preferably used in a stacked arrangement. If necessary, the stiffener 1210 can be omitted.

[84] The connecting plates 1200 cause the rows of bracing beams 1100 to be disposed in parallel in a truss structure, and function to uniformly transmit the load without leaning to one side.

[85] Each bracing beam 1100 is connected with wales 1020, which are integrally coupled to the braced wall 1010, at opposite ends thereof. Alternatively, each bracing beam 1100 is connected with the wales 1020 at opposite ends thereof by means of separate structures. [86] The coupling means functions to integrate the connecting plate 1200 and the bracing beams 1100 by means of welding or well-known fastening members using, for instance, bolts 1310 and nuts 1320. When using the fastening members, each bracing beam 1100 and the connecting plate 1200 are provided with a lot of through-holes 1102 and 1202 for fastening the bolts 1310, respectively. The bolts 1310 pass through the through-holes 1102 and 1202, and then are fastened by the nuts 1320.

[87] The reference number "1150", which has not yet been described, indicates a bearing beam that bears the bracing beams 1100 in a transverse direction. At least one bearing beam 1150 is integrally fastened to the lower surface of each bracing beam 1100 by means of the bolts 1310, thereby serving to prevent the bracing beams 1100 from being bent upwards and/or downwards by the load.

[88] The operation of the temporary soil sheathing apparatus, having this construction, according to a third embodiment of the present invention will be described below.

[89] The temporary soil sheathing apparatus according to a third embodiment of the present invention is adapted to interconnect the plurality of rows of bracing beams 1100, which are disposed in parallel at each corner when pit excavation work for constructing an underground structure is performed, using the connecting plates 1200 having a rectangular shape, so that the bracing beams 1100 spaced apart from each other are connected into one structure, thereby behaving in a unified way with respect to a load transmitted from each end thereof. Thus, the load is uniformly transmitted to each bracing beam 1100, and the bracing beams 1100 are prevented from deviating or flexing.

[90] At this time, the connecting plates 1200 are in surface contact with the upper and/or lower surface of each bracing beam 1100, and the through-holes 1102 and 1202 are aligned in a vertical direction. Then, the bolts 1310 pass through the through-holes 1102 and 1202, and are fastened by the nuts 1320. Thereby, the assembly of the temporary soil sheathing apparatus is completed.

[91] When the assembly is completed, the bracing beams 1100 have a truss structure at each corner, defined by the braced wall. Therefore, the bracing beams 1100 react to a transmitted load in an integrated manner, and thereby have sufficient resistance to horizontal flexural load.

[92] Further, the stiff ener 1210 protruding outwards from one surface of each connecting plate 1200 is welded to each connecting plate 1200, so that the bracing beams 1100 can resist upward flexure while the load of each bracing beam 1100 is transmitted.

[93] Meanwhile, when the underground structure is sufficiently stable to prevent the ground from collapsing, the temporary soil sheathing apparatus is disassembled and reused. At this time, the connecting plates 1200 are separated from each bracing beam 1100 by unfastening the bolts 1310 and the nuts 1320. [94] The connecting plates 1200 can vary in size depending on the interval between the rows of bracing beams 1100. Therefore, each connecting plate 1200 is not required to have a fixed size.

Claims

[1] A temporary soil sheathing apparatus, comprising: a set of intermediate bracing beams that is installed across an intermediate portion excavated in a rectangular area during underground pit excavation work; and wales that are integrally connected with opposite ends of the intermediate bracing beam set, wherein the intermediate bracing beam set is provided with a preloading jack at a middle thereof, and is connected with raker beams via first and second connectors on left and right sides of each end thereof, such that the opposite ends thereof form a triangular supporting structure.

[2] The temporary soil sheathing apparatus as set forth in claim 1, wherein each first connector is interposed between one side of the intermediate bracing beam set and one end of each raker beam, and includes a vertical beam that is connected to the intermediate bracing beam set, and first and second supporting beams that are obliquely connected to opposite ends of one side of the vertical beam so as to form a triangular shape.

[3] The temporary soil sheathing apparatus as set forth in claim 1, wherein each second connector is interposed between another end of each raker beam and each wale, and includes a cross beam that is parallel to and in surface contact with each wale, and first and second connecting beams that are obliquely connected to opposite ends of one side of the cross beam so as to form a triangular shape.

[4] The temporary soil sheathing apparatus as set forth in claim 3, wherein each second connector is in surface contact with a shear key, which is provided on each wale.

[5] The temporary soil sheathing apparatus as set forth in claim 3, wherein each of the first and second connectors is an H-beam having a web and flanges, and at least one stiffener is welded to the web in order to increase compressive force.

[6] The temporary soil sheathing apparatus as set forth in claim 1, further comprising a corner connecting structure including: a braced wall that is installed parallel to an excavated portion during underground pit excavation work; a set of bracing beams that are coupled to the braced wall at each corner during the pit excavation work and support soil pressure; and a corner connector, having: a cross beam that is coupled to each wale, a compression beam that is obliquely connected to one end of the cross beam and is integrally connected to one end of the bracing beam set, and a raker beam that connects one end of the compression beam and another end of the cross beam. [7] The temporary soil sheathing apparatus as set forth in claim 6, wherein the raker beam and the compression beam are connected perpendicular to each other. [8] The temporary soil sheathing apparatus as set forth in claim 6, wherein the corner connector is an H-beam having a web and flanges, and at least one stiff ener is coupled to the web. [9] The temporary soil sheathing apparatus as set forth in claim 6, wherein the cross beam and the compression beam have a reinforcing plate integrally coupled therebetween to provide reinforcement. [10] The temporary soil sheathing apparatus as set forth in claim 6, wherein each wale includes a shear key at a position in contact with the cross beam where compression force thereof is transmitted. [11] The temporary soil sheathing apparatus as set forth in claim 1, further comprising a corner connecting structure, including: bracing beams that are disposed in rows at a predetermined interval so as to support each corner during underground pit excavation work; and at least one connecting plate that is integrally coupled to any one of upper and lower surfaces of each bracing beam by a coupling means so as to interconnect the bracing beams. [12] The temporary soil sheathing apparatus as set forth in claim 11, further comprising at least one stiffener that protrudes outwards from one surface of the connecting plate in a longitudinal direction. [13] The temporary soil sheathing apparatus as set forth in claim 11, wherein the coupling means includes: a plurality of through-holes provided to each bracing beam and the connecting plate; bolts passing through the through holes; and nuts screwed onto the bolts. [14] The temporary soil sheathing apparatus as set forth in claim 11, wherein the connecting plate has a quadrilateral shape, is plural in number, and is in a stacked arrangement.