Large-span weak surrounding rock underground cavern dome excavation supporting method

Abstract

The invention provides a large-span weak surrounding rock underground cavern dome excavation supporting method, and belongs to the technical field of underground cavern construction. The method comprises the following steps that a construction channel is arranged on a top arch layer; excavating and supporting a middle pilot tunnel along the central axis of the dome of the cavern; constructing a first ring beam at the skewback part of the dome of the cavern; first top beam construction is conducted on the front top arch part of the construction channel, a first top beam is connected with a first ring beam, and the stress condition is ensured; expanding excavation supports on the two sides are started, expanding excavation is conducted along the center line of the cavern, and excavation support of a middle pilot tunnel and construction of a second ring beam and a second top beam are conducted in sequence; an avoiding structure is arranged at the crossed part of the first crown beam and the second crown beam; and after the second top beam is formed, expanding excavation supporting of the remaining part is symmetrically conducted in a staggered mode, and after excavation is completed, the second ring beam is immediately constructed to form a stress whole. The technical problem that the safety coefficient is low during construction in the prior art can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of underground cavern construction, and in particular to a method for excavating and supporting a dome of a large-span soft surrounding rock underground cavern. Background Art

[0002] At present, large-span underground caverns with weak surrounding rock are a type of building structure, usually located underground, suitable for fields such as transportation, mining or storage. Its characteristics are: large span, which means that the width and length of the cavern are large, and it can accommodate large equipment or vehicles, such as trains, mine cars, etc., without the need for intermediate support columns. Therefore, special consideration needs to be given to the stability of the surrounding rock during design and construction. Engineering technical requirements, in order to ensure safety, usually require the use of advanced support technologies such as anchors, shotcrete, etc., to enhance the structural stability of the cavern. In addition, methods such as segmented excavation and water level control may be used during the construction process to reduce the impact on the surrounding rock. Application scenarios, this type of cavern is widely used in places such as subway tunnels, mines, underground storage and large underground parking lots.

[0003] In the related art, during the excavation of a large-span underground cavern dome, the applicant found that deformation or collapse is prone to occur underground, and the safety factor during construction is low. Summary of the invention

[0004] The present application discloses a method for excavating and supporting a dome of an underground cavern with a large span and weak surrounding rock, so as to solve the technical problem of low safety factor during construction in the related technology.

[0005] The present application provides a method for supporting the dome of a large-span soft surrounding rock underground cavern, which adopts the following technical solution: A method for excavating and supporting a dome of a large-span soft surrounding rock underground cavern comprises the following steps: A construction channel is set up in the top arch layer, and excavation and support of the construction channel are carried out. The excavation is carried out forward along the axis of the construction channel until the dome of the cavern is reached; the middle guide hole is excavated and supported along the central axis of the dome of the cavern until the designed section is reached; the first ring beam is constructed at the arch seat of the dome of the cavern, and the first ring beam adopts a reinforced concrete structure and uses prestressed anchor rods to apply tension; the first crown beam is constructed at the top arch of the construction channel, and the first crown beam is connected with the first ring beam to ensure the stress condition; the expansion and support on both sides are started, and the expansion and support are carried out along the center line of the cavern, and the excavation and support of the middle guide hole, the construction of the second ring beam and the second crown beam are carried out in sequence, so that the first crown beam and the second crown beam form a "cross" structure; an avoidance structure is set at the intersection of the first crown beam and the second crown beam, so that the first crown beam and the second crown beam do not interfere with each other; after the second crown beam is formed, the remaining part is expanded and supported by staggered symmetry, and the second ring beam is constructed immediately after the excavation is completed to form a stress-bearing whole.

[0006] Preferably, the width and height of the construction channel are no more than 5m.

[0007] Preferably, the cross-sectional width of the middle guide tunnel is not less than 5m and the excavation height is not more than 8m.

[0008] Preferably, the cross-sectional dimensions of the first ring beam are not less than 1m×1m.

[0009] Preferably, the diameter of the prestressed anchor rod is 32 mm, the length is 9 m, the prestressed tension is 10 KN, and the arrangement spacing between adjacent prestressed anchor rods is 50 cm.

[0010] Preferably, the setting of the avoidance structure includes the following steps: a avoidance member is provided at the intersection of the first crown beam and the second crown beam, a first accommodating groove is opened on the avoidance member, and the first accommodating groove is used for the first crown beam to be embedded; second accommodating grooves are also provided on both sides of the avoidance member on the first accommodating groove, and the second accommodating grooves are used for the second crown beam to be embedded at one end away from the second ring beam.

[0011] Preferably, the setting of the avoidance structure includes the following steps: a clamping piece is provided on the inner side wall of the second accommodating groove, and the clamping piece is elastically slidably provided on the inner side wall of the second accommodating groove, the clamping piece is used to avoid the second crown beam when the end of the second crown beam is embedded in the second accommodating groove, and prevent the second crown beam from escaping from the second accommodating groove when the second crown beam is clamped in place.

[0012] Preferably, the clamping member includes a clamping portion and an elastic portion, and the setting of the clamping member includes the following steps: a clamping groove is provided on the inner side wall of the second accommodating groove, the elastic portion is provided in the clamping groove, and the clamping portion is connected to the elastic portion; the clamping portion has a switchable first state and a second state, and when the clamping portion is in the first state, the elastic portion is in a natural state and drives part of the clamping portion to extend out of the clamping groove and abut against the other inner side wall of the second accommodating groove; when the clamping portion is in the second state, the elastic portion is in a compressed state, and the clamping portion is completely located in the clamping groove.

[0013] Preferably, when forming the second crown beam, a first abutment slope is provided near the end of the second crown beam; a second abutment slope is provided on the clamping portion and is slidably and abuttably cooperates with the first abutment slope; during the axial movement of the first abutment slope along the second accommodating groove, the first abutment slope and the second abutment slope are slidably and abuttably cooperated, so that the clamping portion switches from the first state to the second state, until the first abutment slope is clamped into place, and the clamping portion automatically switches back from the second state to the first state, and locks the end of the second crown beam in the second accommodating groove.

[0014] Preferably, an arc-shaped matching surface is provided at a portion of the clamping portion away from the second abutting inclined surface, and the arc-shaped matching surface is matched with the curvature of the outer wall of the second crown beam.

[0015] The present invention has the following advantages and beneficial effects: 1. Through phased support design, the surrounding rock is gradually reinforced, reducing the risk of collapse. The excavation sequence of the construction channel and the middle guide tunnel effectively controls the disturbance to the surrounding rock and maintains the stability of the overall structure. The construction of the first ring beam, the second ring beam, the first crown beam and the second crown beam ensures the interconnection of the entire support system, improves the bearing capacity and deformation resistance of the structure, and thus reduces the safety hazards caused by uneven settlement or external loads; 2. The construction method of zoned excavation and staged support allows operations to be carried out simultaneously in different areas, improving overall construction efficiency and shortening the project period. Clear construction steps (such as channel excavation, ring beam and crown beam construction, etc.) and reasonable sequence arrangement reduce the waiting time between processes and improve the continuity and fluency of construction; 3. The setting of the avoidance structure enables the first crown beam and the second crown beam to be normally installed on the same plane, and the first crown beam and the second crown beam do not interfere with each other, both of which can play a bearing effect, thereby improving the stability and coordination of construction and installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a schematic diagram of the construction layout of some embodiments of the present application. Figure 1 ; Figure 2 This is a schematic diagram of the construction layout of some embodiments of the present application. Figure 2 ; Figure 3 It is a schematic diagram for showing the installation of prestressed anchor rods in some embodiments of the present application; Figure 4 is a schematic diagram for illustrating the arrangement of the avoidance structure in some embodiments of the present application; Figure 5 is a schematic diagram for showing the clamping portion in a first state in some embodiments of the present application; Figure 6 It is a schematic diagram for showing the relative sliding state between the clamping portion and the second crown beam in some embodiments of the present application; Figure 7 is a schematic diagram for showing the clamping portion in the second state in some embodiments of the present application; Figure 8 It is a structural schematic diagram for showing the clamping part of some implementations of the present application.

[0018] The markings in the figure are: 100, construction channel; 200, first ring beam; 210, prestressed anchor rod; 300, first crown beam; 400, second ring beam; 500, second crown beam; 510, first abutting slope; 600, avoidance structure; 610, avoidance member; 611, first accommodating groove; 612, second accommodating groove; 6121, snap-fit ​​groove; 620, snap-fit ​​member; 621, snap-fit ​​portion; 6211, second abutting slope; 6212, arc-shaped mating surface; 622, elastic portion. DETAILED DESCRIPTION

[0019] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0020] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0021] In the related technology, currently, large-span soft rock underground caverns are an important building structure, widely used in transportation, mining, storage and other fields. Its design features are that the cavern has a large width and length, can accommodate large equipment or vehicles, such as trains and mine cars, and does not require intermediate support columns. However, this design places higher requirements on the stability of the surrounding rock.

[0022] During the construction process, especially during the dome excavation stage, underground caverns are prone to collapse. The main reasons include the following: 1. Physical characteristics of surrounding rock: Low strength and high plasticity: Weak surrounding rock usually has low compressive strength and is difficult to withstand the load generated during excavation. During excavation, plastic deformation of the surrounding rock is likely to occur in stress concentration areas, leading to local instability.

[0023] Deformability: When subjected to external forces, the soft surrounding rock has a strong ability to deform and is prone to flow or slip under continuous loads, which makes it impossible for the surrounding rock to effectively support the structure during dome excavation.

[0024] 2. Changes in stress state: Stress redistribution caused by excavation: During the excavation of the dome, the stress state around the surrounding rock will change significantly. After excavation, the deadweight and lateral pressure of the top rock layer are redistributed, which may lead to insufficient bearing capacity in some areas and increase the risk of collapse.

[0025] Stress concentration: In the absence of proper support, stress concentrations may occur in local areas of the surrounding rock, especially below the vault, which are most susceptible to damage and thus collapse.

[0026] 3. Improper construction method: Excavation method: Rapid or large-scale excavation may result in the support capacity of the surrounding rock not being restored in time. Traditional excavation methods fail to take into account the need for gradual release and support, increasing the risk of collapse.

[0027] Timing of support installation: If the installation of support structures (such as anchors, shotcrete, etc.) is not synchronized with the pace of excavation, the surrounding rock will be exposed to gravity and lateral pressure without support and will be prone to collapse.

[0028] In summary, the physical properties of the surrounding rock, changes in stress state, improper construction methods, external environmental factors and insufficient monitoring during dome construction all lead to an increased risk of collapse. The existence of these problems urgently requires the development of new technical solutions to improve the construction safety of large-span underground caverns with weak surrounding rock, to ensure the smooth progress of the project and the safety of personnel.

[0029] In view of this, some embodiments of the present application provide a method for excavating and supporting a dome of an underground cavern with a large span and weak surrounding rock.

[0030] See also Figures 1 to 8 In some embodiments, a method for supporting the dome of a large-span soft surrounding rock underground cavern comprises the following steps: S1: Setting and excavation support of construction channel 100: Set the construction channel 100 in the top arch layer of the cavern to ensure that the width and height of the channel meet the passage requirements of the construction equipment. For example, the width and height of the construction channel 100 are not more than 5m. Excavate along the axis of the construction channel 100, using segmented support to gradually excavate forward until the dome of the cavern is reached. During the excavation process, support materials such as anchors and shotcrete should be used to enhance the stability of the surrounding rock.

[0031] S2: Excavation and support of the middle guide tunnel: The middle guide tunnel is excavated along the central axis of the dome of the cavern to ensure that the excavation width meets the design requirements. During the excavation process, the support plan needs to be adjusted according to the real-time monitoring results to maintain the stability of the surrounding rock. For example, the cross-sectional width of the middle guide tunnel is not less than 5m and the excavation height is not more than 8m.

[0032] S3: Construction of the first ring beam 200: The first ring beam 200 is constructed at the arch seat of the dome, using a reinforced concrete structure, and the cross-sectional dimensions should meet the design standards. During the construction process, tension is applied through prestressed anchor rods 210 to enhance the bearing capacity of the ring beam and ensure its effective combination with the surrounding rock. Exemplarily, the cross-sectional dimensions of the first ring beam 200 are not less than 1m×1m. Furthermore, the diameter of the prestressed anchor rod 210 is 32mm, the length is 9m, the prestressed tension is 10KN, and the arrangement spacing between adjacent prestressed anchor rods 210 is 50cm.

[0033] S4: Construction of the first crown beam 300: The first crown beam 300 is constructed at the top arch of the construction channel 100. The first crown beam 300 should be connected with the first ring beam 200 to form an effective force-bearing system. During construction, it should be ensured that the connection point between the crown beam and the ring beam is in a reasonable force-bearing state.

[0034] S5: Excavation and support on both sides: Start the excavation and support on both sides, expand the excavation along the center line of the cavern, and then carry out the excavation and support of the middle guide tunnel, the construction of the second ring beam 400 and the second crown beam 500. During this process, ensure the timely installation of the support structure to maintain the stability of the surrounding rock and avoid the risk of collapse caused by large-scale excavation.

[0035] S6: Formation of a cross-shaped structure: An avoidance structure 600 is provided at the intersection of the first crown beam 300 and the second crown beam 500 to ensure that the two do not interfere with each other when they intersect, thereby preventing stress interference between them. The design of the avoidance structure 600 should take into account the stress state in actual construction to ensure the safety of the structure.

[0036] S7: Excavation and support of the remaining part: After the construction of the second crown beam 500 is completed, the remaining part is excavated and supported by using a staggered symmetrical method to ensure that there is sufficient support structure to support the surrounding rock after each excavation. After the excavation is completed, the second ring beam 400 is immediately constructed to form an overall force-bearing structure and enhance the stability of the cavern.

[0037] In this way, by setting up the construction channel 100, gradually excavating and supporting in sections, the stress state of the surrounding rock can be effectively controlled and the risk of collapse can be reduced. The design of the first ring beam 200 and the second ring beam 400 is helpful to form a solid support frame and improve the overall anti-deformation ability of the cavern.

[0038] At the same time, during the dome excavation process, real-time monitoring and timely support measures effectively reduced the disturbance to the surrounding rock during the construction process, ensured the safety of workers, and improved the safety factor of construction. In addition, the setting of the avoidance structure 600 avoids interference between the first crown beam 300 and the second crown beam 500, further improving safety. In addition, the use of a reasonable construction sequence and method, such as staggered and symmetrical excavation support, enables construction in different areas to be carried out simultaneously, shortening the construction period. The strategy of segmented excavation and support reduces the risks caused by large-scale excavation and improves the continuity and efficiency of construction.

[0039] In summary, the above excavation support method not only improves the construction safety and efficiency of large-span soft surrounding rock underground caverns, but also provides guarantees for the economy and environmental friendliness of the project. These advantages make this construction method have broad prospects and value in practical applications.

[0040] In some embodiments, Figure 1 , Figure 4 As shown, the configuration of the avoidance structure 600 includes the following steps: A avoidance member 610 is provided at the intersection of the first crown beam 300 and the second crown beam 500, and a first accommodating groove 611 is provided on the avoidance member 610, and the first accommodating groove 611 is used for the first crown beam 300 to be inserted. Exemplarily, the avoidance member 610 is configured as an installation base, which provides an installation foundation for the installation of the first crown beam 300 and the second crown beam 500.

[0041] At the same time, second accommodating grooves 612 are provided on both sides of the first accommodating groove 611 on the avoidance member 610 , and the second accommodating grooves 612 are used for inserting an end of the second crown beam 500 away from the second ring beam 400 .

[0042] Exemplarily, one second crown beam 500 is provided on each side of the first crown beam 300, and the ends of each second crown beam 500 are respectively embedded in the second receiving grooves 612 on both sides of the first receiving groove 611. At the same time, one end of the second crown beam 500 away from the second receiving groove 612 is welded or bolted to the second ring beam 400.

[0043] In this configuration, since the end of the second crown beam 500 is embedded in the second receiving groove 612 , the second crown beam 500 does not interfere with the first crown beam 300 , so that the second crown beam 500 and the first crown beam 300 are connected stably when each of them bears the dome.

[0044] In some embodiments, the avoidance member 610 is installed on the dome by a plurality of temporary anchor rods. The temporary anchor rods can be removed when the next excavation is performed.

[0045] In some embodiments, Figure 1 , Figure 4 As shown, the configuration of the avoidance structure 600 includes the following steps: A clamping member 620 is provided on the inner side wall of the second receiving groove 612, and the clamping member 620 is elastically slidably provided on the inner side wall of the second receiving groove 612. The clamping member 620 is used to avoid the second crown beam 500 when the end of the second crown beam 500 is inserted into the second receiving groove 612, and to prevent the second crown beam 500 from escaping from the second receiving groove 612 when the second crown beam 500 is inserted into place. Exemplarily, the lower end and one side of the second receiving groove 612 are both opened, and the end of the second crown beam 500 is inserted into the second receiving groove 612 in the following manner: first align the end of the second crown beam 500 with the lower end opening of the second receiving groove 612, and then slide the end of the second crown beam 500 vertically upward into the second receiving groove 612.

[0046] After such arrangement, when the end of the second crown beam 500 needs to be installed in the second receiving groove 612, the end of the second crown beam 500 is first moved vertically upward from the lower end opening of the second receiving groove 612, and when the end of the second crown beam 500 approaches the clamping member 620, the clamping member 620 will avoid the end of the second crown beam 500, so that the end of the second crown beam 500 can pass through the clamping member 620 and be normally clamped in place. After being clamped in place, the clamping member 620 can limit the position of the second crown beam 500, so that the end of the second crown beam 500 is not easy to slide out of the second receiving groove 612, thereby improving the convenience and stability of the end of the second crown beam 500 being installed in the second receiving groove 612.

[0047] In some embodiments, reference Figure 4 , Figure 5 The clamping member 620 includes a clamping portion 621 and an elastic portion 622, and the configuration of the clamping member 620 includes the following steps: A clamping groove 6121 is provided on the inner side wall of the second receiving groove 612, and the elastic part 622 is provided in the clamping groove 6121, and the clamping part 621 is connected to the elastic part 622. Exemplarily, the clamping groove 6121 and the second receiving groove 612 are perpendicular to each other and communicated. Further, the elastic part 622 is configured as a spring, one end of the spring is connected to the inner end wall of the clamping groove 6121, and the other end is connected to one end of the clamping part 621 located in the clamping groove 6121. At the same time, the clamping part 621 is configured as a clamping block.

[0048] At the same time, the clamping portion 621 has a switchable first state and a second state. When the clamping portion 621 is in the first state, the elastic portion 622 is in a natural state and drives part of the clamping portion 621 to extend out of the clamping groove 6121 and abut against the other inner wall of the second accommodating groove 612; when the clamping portion 621 is in the second state, the elastic portion 622 is in a compressed state, and the clamping portion 621 is completely located in the clamping groove 6121.

[0049] In this configuration, since the clamping portion 621 has a switchable first state and a second state, the position of the clamping portion 621 can be adaptively changed as the end of the second crown beam 500 is embedded. For example, when the end of the second crown beam 500 is not embedded in the second receiving groove 612, the clamping portion 621 is in the first state and blocks the entrance passage of the second receiving groove 612. However, when the end of the second crown beam 500 needs to be embedded in the second receiving groove 612, the clamping portion 621 can be adjusted to the second state, so that the end of the second crown beam 500 can enter the second receiving groove 612 normally without being blocked by the clamping portion 621, and the end of the second crown beam 500 can finally be in the clamping position in the second receiving groove 612.

[0050] In some embodiments, reference Figure 5~Figure 7When the second crown beam 500 is formed, a first abutting inclined surface 510 is provided near the end of the second crown beam 500; a second abutting inclined surface 6211 that slidably contacts and cooperates with the first abutting inclined surface 510 is provided on the clamping portion 621; during the axial movement of the first abutting inclined surface 510 along the second receiving groove 612, the first abutting inclined surface 510 and the second abutting inclined surface 6211 slidably contact and cooperate, so that the clamping portion 621 switches from the first state to the second state, until the first abutting inclined surface 510 is clamped in place, and the clamping portion 621 automatically switches back from the second state to the first state, and locks the end of the second crown beam 500 in the second receiving groove 612.

[0051] On this basis, when the end of the second crown beam 500 needs to be embedded in the second accommodating groove 612, the end of the second crown beam 500 is aligned with the lower end opening of the second accommodating groove 612, and then the end of the second crown beam 500 is pushed from bottom to top, so that the end of the second crown beam 500 enters the second accommodating groove 612 and gradually approaches the clamping portion 621. When the first abutting slope 510 on the end of the second crown beam 500 is fitted with the second abutting slope 6211 on the clamping portion 621, the end of the second crown beam 500 continues to move vertically upward. At this time, the first abutting slope 510 will apply a thrust to the second abutting slope 6211, so that the second abutting slope 6211 will avoid the end of the second crown beam 500 after receiving the thrust, that is, the entire clamping portion 621 will gradually move from the second accommodating groove 612 into the clamping groove 6121. At this time, the clamping portion 621 will switch from the first state to the second state, making room for the end of the second crown beam 500 to pass through, and the clamping portion 621 in the second state will be completely in the clamping groove 6121, and the elastic portion 622 is in a compressed state at this time.

[0052] After the end of the second crown beam 500 completely passes over the clamping groove 6121, the end of the second crown beam 500 no longer contacts the clamping portion 621. Under the compressive elastic force of the elastic portion 622, the clamping portion 621 will change from the second state to the first state again. At this time, the wall surface of the clamping portion 621 away from the second abutting inclined surface 6211 will serve as the installation basis for the end of the second crown beam 500 to be in the clamping position, that is, the wall surface of the clamping portion 621 away from the second abutting inclined surface 6211 will contact the end of the second crown beam 500, so that the end of the second crown beam 500 cannot be moved out again in the embedding direction, thereby allowing the end of the second crown beam 500 to be stably in the clamping position in the second accommodating groove 612.

[0053] Exemplarily, in order to enhance the relative sliding effect between the first abutting slope 510 and the second abutting slope 6211 , a polytetrafluoroethylene layer is coated on either the first abutting slope 510 or the second abutting slope 6211 , thereby reducing the friction resistance between the first abutting slope 510 and the second abutting slope 6211 .

[0054] In some embodiments, in combination Figure 8 , an arcuate mating surface 6212 is provided at the portion of the clamping portion 621 away from the second abutting inclined surface 6211, and the arcuate mating surface 6212 is adapted to the curvature of the outer wall of the second crown beam 500. In this arrangement, since the shape of the second crown beam 500 is an arcuate shape adapted to the dome, the portion of the clamping portion 621 away from the second abutting inclined surface 6211 is provided as the arcuate mating surface 6212, so that the second crown beam 500 and the clamping portion 621 are in contact without affecting the installation of the rest of the second crown beam 500, thereby improving the adaptability of the second crown beam 500 when it is installed in the second receiving groove 612.

[0055] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for excavating and supporting the dome of a large-span soft surrounding rock underground cavern, characterized in that: The following steps are involved: A construction channel (100) is arranged in the top arch layer, excavation and support of the construction channel (100) are performed, and excavation is performed forward along the axis of the construction channel (100) until the dome position of the cavern is reached; Excavating and supporting the middle pilot hole along the dome centerline of the cavern until the designed section is reached; A first ring beam (200) is constructed at the arch seat portion of the dome of the cavern, wherein the first ring beam (200) adopts a reinforced concrete structure and uses prestressed anchor rods (210) to apply tension; A first crown beam (300) is constructed at the top arch portion of the construction channel (100), wherein the first crown beam (300) is connected to the first ring beam (200) to ensure stress conditions; Starting the excavation and support on both sides, excavating along the center line of the cavern, and sequentially carrying out the excavation and support of the middle guide tunnel, the construction of the second ring beam (400) and the second crown beam (500), so that the first crown beam (300) and the second crown beam (500) form a "cross" structure; An avoidance structure (600) is provided at the intersection of the first crown beam (300) and the second crown beam (500) so as to prevent the first crown beam (300) and the second crown beam (500) from interfering with each other; After the second crown beam (500) is formed, the remaining portion is excavated and supported symmetrically with staggered spacing, and the second ring beam (400) is constructed immediately after the excavation is completed to form a force-bearing whole.

2. A method for excavating and supporting a large-span soft surrounding rock underground cave dome according to claim 1, characterized in that: The width and height of the construction channel (100) are no greater than 5 m.

3. The method for excavating and supporting the dome of a large-span soft surrounding rock underground cavern according to claim 1, characterized in that: The cross-sectional width of the middle guide tunnel is not less than 5m and the excavation height is not more than 8m.

4. The method for excavating and supporting the dome of a large-span soft surrounding rock underground cavern according to claim 1, characterized in that: The cross-sectional dimensions of the first ring beam (200) are not less than 1m×1m.

5. The method for excavating and supporting the dome of a large-span soft surrounding rock underground cavern according to claim 1, characterized in that: The prestressed anchor rod (210) has a diameter of 32 mm, a length of 9 m, a prestressed tension of 10 KN, and an arrangement spacing of 50 cm between adjacent prestressed anchor rods (210).

6. A method for excavating and supporting a dome of a large-span soft surrounding rock underground cavern according to any one of claims 1 to 5, characterized in that: The configuration of the avoidance structure (600) comprises the following steps: A avoidance member (610) is arranged at the intersection of the first crown beam (300) and the second crown beam (500), and a first accommodating groove (611) is provided on the avoidance member (610), wherein the first accommodating groove (611) is used for the first crown beam (300) to be embedded; Second accommodating grooves (612) are also provided on both sides of the first accommodating groove (611) on the avoidance member (610), and the second accommodating groove (612) is used for an end of the second crown beam (500) away from the second ring beam (400) to be embedded.

7. A method for excavating and supporting a large-span soft surrounding rock underground cave dome according to claim 6, characterized in that: The configuration of the avoidance structure (600) comprises the following steps: A clamping piece (620) is provided on the inner side wall of the second accommodating groove (612), and the clamping piece (620) is elastically slidably provided on the inner side wall of the second accommodating groove (612). The clamping piece (620) is used to avoid the second crown beam (500) when the end of the second crown beam (500) is embedded in the second accommodating groove (612), and to prevent the second crown beam (500) from escaping from the second accommodating groove (612) when the second crown beam (500) is clamped in place.

8. The method for excavating and supporting the dome of a large-span soft surrounding rock underground cavern according to claim 7, characterized in that: The clamping member (620) comprises a clamping portion (621) and an elastic portion (622), and the provision of the clamping member (620) comprises the following steps: A clamping groove (6121) is provided on the inner side wall of the second accommodating groove (612), the elastic part (622) is arranged in the clamping groove (6121), and the clamping part (621) is connected to the elastic part (622); The clamping portion (621) has a switchable first state and a second state. When the clamping portion (621) is in the first state, the elastic portion (622) is in a natural state and drives a portion of the clamping portion (621) to extend out of the clamping groove (6121) and abut against the other inner side wall of the second accommodating groove (612); When the clamping portion (621) is in the second state, the elastic portion (622) is in a compressed state, and the clamping portion (621) is completely located in the clamping groove (6121).

9. A method for excavating and supporting a large-span soft surrounding rock underground cave dome according to claim 8, characterized in that: When forming the second crown beam (500), a first abutment inclined surface (510) is provided near the end of the second crown beam (500); A second abutment inclined surface (6211) is provided on the clamping portion (621) and is slidably and abuttingly matched with the first abutment inclined surface (510); During the axial movement of the first abutting inclined surface (510) along the second receiving groove (612), the first abutting inclined surface (510) and the second abutting inclined surface (6211) are slidably abutted against each other, so that the clamping portion (621) switches from the first state to the second state. After the first abutting inclined surface (510) is clamped in place, the clamping portion (621) automatically switches back from the second state to the first state, and locks the end of the second crown beam (500) in the second receiving groove (612).

10. The method for excavating and supporting the dome of a large-span soft surrounding rock underground cavern according to claim 8, characterized in that: An arc-shaped matching surface (6212) is provided at a position of the clamping portion (621) away from the second abutting inclined surface (6211), and the arc-shaped matching surface (6212) is adapted to the curvature of the outer wall of the second crown beam (500).

Images