A combined structure and construction method of a second lining steel bar hanger for a large-span cavern

Abstract

The invention discloses a combined structure and construction method of a second lining steel bar hanger of a giant-span cavern, the combined structure comprising: a steel bar skeleton, the bottom of which is fixed to the second lining structure of the invert and the short side wall, and the top of which is connected to the L-shaped welding steel bar through an extended suspension anchor rod; the extended suspension anchor rod is connected to the anchor rod and anchor cable of the arch joint support structure system through a steel sleeve, an anchor spraying support primary support layer is arranged inside the anchor rod and the anchor cable, a spraying waterproof layer is arranged inside the anchor spraying support primary support layer, and a square steel plate water stop ring is arranged at the intersection of the spraying waterproof layer and the extended suspension anchor rod. The invention utilizes the anchoring capacity deep in the surrounding rock and the tensile strength of the anchor rod steel bar, effectively controls the engineering quality defects such as the easy large deformation and instability of the steel bar skeleton under the giant span and the exposed steel or insufficient thickness of the protective layer during the pouring process, and provides a safe and efficient construction method for the second lining structure of the giant span.

Description

Technical Field

[0001] The invention relates to the technical field of building structures, and in particular to a combined structure of a second lining steel bar hanger for a giant-span cavern and a construction method. Background Art

[0002] There is no clear standard for dividing the span of underground caverns at home and abroad. According to convention and relevant experience, underground caverns with a span of not less than 20 meters, such as highway tunnels with three or more lanes in a single hole, railway tunnels, subway stations, underground oil storage depots, main power plant buildings of hydropower stations, underground water-sealed caverns, etc., are all called ultra-large span tunnels, which poses technical difficulties in excavation support and secondary lining structure construction that cannot be underestimated.

[0003] In recent years, with the development and utilization of underground space, the continuous improvement of mechanization level and the emergence of large-scale equipment, more and more large-section underground caverns have been built or are being built at home and abroad to meet different usage functions. The span is gradually developing towards giant spans. For example, the ice rink in the city of Gjovik in Norway has a span of 61m and a height of 25m; the excavation span of the crossing line section at both ends of the Badaling Great Wall Station is 32.7m, which is also the largest span traffic tunnel in China. This type of super-large giant cavern is not only extremely difficult to construct and has high excavation risks, but also the steel bars of the secondary lining structure are difficult to stabilize themselves during installation, and are prone to noodle-like instability. In addition, after pouring, there are construction quality problems such as insufficient thickness of the steel protection layer or exposed steel bars, which cause great troubles and safety hazards to the construction. Summary of the invention

[0004] The purpose of the present invention is to provide a combined structure and construction method of a second lining steel bar hanger for a giant-span cavern, which utilizes the anchoring capacity deep in the surrounding rock and the tensile strength of the anchor steel bars to effectively control the engineering quality defects such as large deformation and instability of the steel skeleton under the giant span, exposed steel or insufficient thickness of the protective layer during the pouring process, and provides a safe and efficient construction method for the second lining structure of the giant span.

[0005] To achieve the above-mentioned purpose, the specific technical scheme of a large-span cavern secondary lining steel bar hanger combined structure and construction method of the present invention is as follows:

[0006] A combined structure of a secondary lining steel bar hanger for a giant-span cavern comprises: a steel bar skeleton, the bottom of which is fixed to the secondary lining structure of an invert and a short side wall, and the top of which is connected to an L-shaped welding steel bar through an extended suspension anchor rod; the extended suspension anchor rod is connected to the anchor rod and anchor cable of the arch joint support structure system through a steel sleeve, an anchor-sprayed support primary support layer is arranged on the inner side of the anchor-sprayed support primary support layer, a sprayed waterproof layer is arranged on the inner side of the sprayed waterproof layer, and a square steel plate waterstop ring is arranged at the intersection of the sprayed waterproof layer and the extended suspension anchor rod.

[0007] A construction method for a large-span cavern secondary lining steel bar hanger composite structure comprises the following steps:

[0008] Step 1: Processing threads on the ends of anchor rods and anchor cables;

[0009] Step 2: adopt the partial excavation method, use the arch joint support structure system's anchor rods and anchor cables to support while excavating, and spray concrete to form the anchor spray support primary support layer to complete the underground space cavern with a huge span;

[0010] Step 3, starting from the center line of the section, the suspension anchor steel bars are connected at intervals in an annular direction through a threaded connection process of a steel sleeve;

[0011] Step 4: Apply a sprayed waterproof layer on the inner side of the primary support layer of the anchor spraying support of the giant span cavern, weld a square water-stop steel plate in the middle of the extended suspension anchor rod, and apply cement crystal coating at the connection between the extended suspension anchor rod and the sprayed waterproof layer;

[0012] Step 5: construct the secondary lining structure of the inverted arch and the short side wall and the steel skeleton composed of the annular main reinforcement, longitudinal distribution reinforcement and plum blossom-shaped tension reinforcement;

[0013] Step 6: erect the steel skeleton of the arch and the remaining side wall secondary lining structure;

[0014] Step seven: pour concrete for the remaining side walls and arch secondary lining structure to complete the closure of the mega-span cavern secondary lining structure.

[0015] The advantages of the large-span cavern secondary lining steel bar hanger combined structure and construction method of the present invention are:

[0016] 1) Make full use of the anchoring capacity deep in the surrounding rock and the tensile strength of the anchor steel bars, effectively control the engineering quality defects such as large deformation and instability of the steel skeleton under the giant span, exposed steel or insufficient thickness of the protective layer during the pouring process, and provide a safe and efficient construction method for the giant span secondary lining structure;

[0017] 2) For the erection of the secondary lining steel frame for caverns with super-large spans or huge spans of more than 30 meters, the secondary lining steel bar construction can be carried out quickly and effectively to ensure the construction quality;

[0018] 3) It provides a safe and efficient construction method to prevent instability during the erection of the secondary lining reinforcement in large-span caverns, greatly reduces construction risks, and effectively controls engineering quality defects such as large deformation of the reinforcement skeleton and exposed steel or insufficient thickness of the protective layer during pouring, and has strong applicability;

[0019] 4) Through the combined hanger of "anchor suspension and steel skeleton", the anchoring capacity in the deep surrounding rock and the strong suspension tension of the anchor are fully utilized. Under the joint action of the self-bearing capacity of the steel frame and the auxiliary anchor suspension, the stiffness deformation of the secondary lining steel bars themselves is controlled, and the protection and control measures for the deformation of the steel skeleton relying solely on the secondary lining formwork trolley are reduced. The formwork trolley support system is optimized, the loss of manpower and working hours is reduced, time and space are saved, and the cost is saved, which has good economic efficiency;

[0020] 5) The construction process is clear and the operation is simple. It can realize large-scale mechanized operations and is highly feasible under the conditions of super-large spans or huge span caverns. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the suspension anchor rod extension after the anchor spraying support of the present invention is completed;

[0022] Figure 2 It is a schematic diagram of pouring the secondary lining of the invert and the short side wall in advance according to the present invention;

[0023] Figure 3 It is a schematic diagram of secondary casting after the suspension anchor rod of the present invention is combined with the steel bar skeleton;

[0024] Figure 4 It is a schematic structural diagram of the combined hanger of the arch steel bar skeleton and the suspension anchor rod of the present invention.

[0025] In the figure: 1. Anchor rod; 2. Anchor cable; 3. Anchor spraying support primary support layer; 4. Spraying waterproof layer; 5. Square steel plate water stop ring; 6. Secondary lining structure; 7. Steel skeleton; 8. Extended suspension anchor rod; 9. Arch secondary lining structure; 10. Steel sleeve; 11. L-shaped welding steel bar. DETAILED DESCRIPTION

[0026] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of the combined structure and construction method of the second lining steel bar hanger of a large-span cavern of the present invention in conjunction with the accompanying drawings.

[0027] like Figures 1 to 4As shown, it shows a combined structure and construction method of a second lining steel bar hanger for a huge-span cavern of the present invention, which is suitable for dark excavated caverns supported by anchor spraying, and the span of the cavern can reach 30m to 100m. A combined hanger structure type combined with a steel bar skeleton 7 is used under the huge-span cavern through anchor suspension to ensure the stability of the second lining steel bar skeleton erection process. Through the anchor suspension method, one end of the anchor rod 1 is anchored deep in the surrounding rock, and the other end passes through the anchor pad and nut, and the exposed length is determined according to the thickness of the second lining structure; the position of the action point of the suspension anchor rod is determined according to the size of the cavern span and the deadweight of the steel bar skeleton, so that the anchor rod can evenly bear the deadweight tension of the steel bar; the second lining steel bar skeleton adopts large-diameter main bars and connecting reinforcement bars to form a whole skeleton, improve the overall stability of the second lining steel frame skeleton during installation, prevent the "noodle-like" deformation of the steel bar, and ensure the construction quality of the second lining.

[0028] Specifically, the composite structure of the present invention includes: an extended suspension anchor rod 8 and a steel skeleton 7, and also includes an anchor rod 1 and an anchor cable 2 of the arch joint support structure system, an anchor spraying support primary support layer 3, a sprayed waterproof layer 4, a square steel plate water stop ring 5, a secondary lining structure 6 of the inverted arch and the short side wall, an arch secondary lining structure 9, a steel sleeve 10 and an L-shaped welding steel bar 11. Among them, the longitudinal and circumferential spacing of the extended suspension anchor rod 8 is determined by combining the spacing of the anchor rod 1 and the anchor cable 2.

[0029] Furthermore, the bottom of the arch reinforcement skeleton 7 is fixed together with the inverted arch and the secondary lining structure 6 of the short side wall, and the top is connected to the L-shaped welding reinforcement 11 through the extended suspension anchor 8 to achieve the second lining reinforcement of the huge span cavern in place. The circumferential main reinforcement of the arch reinforcement skeleton 7 is a large diameter reinforcement with a diameter greater than 28 mm.

[0030] Furthermore, the extended suspension anchor rod 8 is connected to the anchor rod 1 and anchor cable 2 of the arch joint support structure system through a steel sleeve, and the exposed ends of the anchor rod 1 and anchor cable 2 are provided with threads, so that the sleeve extended anchor rod is connected to the anchor rod 1 and anchor cable 2 through thread thread processing in the later stage of construction. An anchor spraying support primary support layer 3 is set on the inner side of the anchor rod 1 and the anchor cable 2, and the anchor spraying support primary support layer is formed by concrete spraying to form a giant span underground space cavern. In addition, one end of the anchor rod 1 is anchored deep in the surrounding rock, and the other end passes through the anchor pad and the nut. During the initial support, the exposed part of the thread is specially protected by a protective sleeve after the anchor pad is installed.

[0031] Furthermore, a sprayed waterproof layer 4 is provided inside the anchor sprayed support primary support layer 3, and a square steel plate water stop ring 5 is provided at the junction of the sprayed waterproof layer 4 and the extended suspension anchor 8. The connection between the extended suspension anchor 8 and the sprayed waterproof layer 4 is painted with cement crystal coating to strengthen the thickness of the sprayed waterproof layer 4 and increase the waterproof ability of the connection.

[0032] Furthermore, the arch annular main reinforcement, longitudinal distribution reinforcement and extended suspension anchor 8 are welded together by L-shaped auxiliary welding reinforcement 11 (same diameter as the annular main reinforcement), using double-sided welding with a length of not less than 5d to form an integral hanger assembly structure.

[0033] The invention also discloses a construction method of a large-span cavern secondary lining steel bar hanger combined structure, comprising the following steps:

[0034] Step 1: Before the construction of anchor rods 1 and anchor cables 2 of the arch joint support structure system, the ends of anchor rods 1 and anchor cables 2 are processed with threads so that sleeves can be used to extend anchor rods 1 later. After the initial support and installation of anchor pads, the exposed parts of the threads are specially protected with protective sleeves.

[0035] Step 2: According to the geological conditions and the span of the cavern excavation, a reasonable partial excavation method is adopted. The arch joint support structure system's anchor rods and anchor cables are used to support the excavation while supporting, and concrete is sprayed to form the anchor-sprayed support primary support layer 3 to complete the underground space cavern with a huge span.

[0036] Step 3: After the excavation of the giant-span cavern is completed, the suspension anchor reinforcement is extended by threading connection technology of steel sleeve 10 at circumferential intervals of 2.4 to 3.6 m starting from the center line of the section. The longitudinal spacing of the suspension anchor is 1.2 to 3.6 m. The connection length is determined according to the thickness of the secondary lining and is extended to the circumferential force-bearing main reinforcement of the free surface.

[0037] Step 4: Apply a sprayed waterproof layer 4 on the inner side of the primary support layer 3 of the anchor spray support of the giant span cavern, weld a square waterstop steel plate 5 in the middle of the extended suspension anchor rod, apply cement crystal coating on the connection between the extended suspension anchor rod and the sprayed waterproof layer 4, and increase the thickness of the sprayed waterproof layer 4 to enhance the waterproof ability of the connection.

[0038] Step five, construct the secondary lining structure 6 of the invert and the short side wall and the steel skeleton 7 composed of the annular main reinforcement, the longitudinal distribution reinforcement and the plum blossom-shaped tension reinforcement, first tie the steel skeleton 7 and then pour the concrete secondary lining structure 6, and roughen the construction joints.

[0039] The annular main reinforcement of the reinforcement skeleton 7 of the arch portion is made of large-diameter reinforcement with a diameter of 28 mm or more.

[0040] Step six, erect the steel skeleton 7 of the arch and the remaining side wall secondary lining structure, the arch annular main reinforcement, longitudinal distribution reinforcement and extended suspension anchor 8 are welded together with L-shaped auxiliary welding steel bars 11 (same diameter as the annular main reinforcement), double-sided welding is adopted, and the length is not less than 5d, to form an integral hanger composite structure.

[0041] The longitudinal and circumferential spacings of the extended suspension anchor rods 8 are determined by combining the spacings of the anchor rods and anchor cables of the arch joint support structure system.

[0042] Step seven, pouring concrete of the remaining side walls and the arch secondary lining structure 9 to complete the closure of the mega-span cavern secondary lining structure.

[0043] The invention discloses a combined structure and construction method for the second lining steel bar hanger of a giant-span cavern, which fully utilizes the anchoring capacity deep in the surrounding rock and the tensile strength of the anchor steel bar, effectively controls the engineering quality defects such as large deformation and instability of the steel bar skeleton under the giant span, exposed steel or insufficient thickness of the protective layer during pouring, and provides a safe and efficient construction method for the second lining structure of the giant span; for the erection of the second lining steel frame of a giant-span cavern with a super-large span of more than 30 meters or a giant span cavern, the second lining steel bar construction can be carried out quickly and effectively to ensure the construction quality; it provides a safe and efficient construction method for preventing the instability of the second lining steel bar erection process of the giant-span cavern, greatly reduces the construction risk, and effectively controls the large deformation of the steel bar skeleton and the exposed steel during pouring. Or insufficient thickness of protective layer and other engineering quality defects, it has strong applicability; through the "anchor suspension and steel skeleton" combined hanger, the anchoring capacity in the deep surrounding rock and the strong suspension tension of the anchor are fully utilized, and under the joint action of the self-bearing capacity of the steel frame and the auxiliary anchor suspension, the stiffness deformation of the secondary lining steel bars themselves is controlled, and the protection and control measures for the deformation of the steel skeleton relying solely on the secondary lining formwork trolley are reduced, the formwork trolley support system is optimized, the loss of manpower and working hours is reduced, time and space are saved, and the cost is saved, which has good economy; the construction process is clear, the operation is simple, and large-scale mechanized operation can be realized, and it is highly feasible under the conditions of super-large span or giant span caverns.

[0044] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description here should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A construction method for a large-span cavern secondary lining steel bar hanger combined structure, characterized in that A combined structure of a second lining steel bar hanger for a large-span cavern is used, and the combined structure comprises: The steel frame (7) is fixed to the secondary lining structure (6) of the invert and the short side wall at the bottom, and is connected to the L-shaped welding steel bar (11) at the top through the extended suspension anchor rod (8); The extended suspension anchor rod (8) is connected to the anchor rod (1) and the anchor cable (2) of the arch joint support structure system through a steel sleeve, an anchor spraying support primary support layer (3) is arranged inside the anchor rod (1) and the anchor cable (2), a spraying waterproof layer (4) is arranged inside the anchor spraying support primary support layer (3), and a square steel plate water stop ring (5) is arranged at the intersection of the spraying waterproof layer (4) and the extended suspension anchor rod (8); The construction method of the large-span cavern secondary lining steel bar hanger combined structure comprises the following steps: Step 1: Processing threads on the ends of anchor rods and anchor cables; Step 2: adopt the partial excavation method, use the arch joint support structure system's anchor rods and anchor cables to support while excavating, and spray concrete to form the anchor spray support primary support layer to complete the underground space cavern with a huge span; Step 3, starting from the center line of the section, the suspension anchor steel bars are connected at intervals in an annular direction through a threaded connection process of a steel sleeve; Step 4: Apply a sprayed waterproof layer on the inner side of the primary support layer of the anchor spraying support of the giant span cavern, weld a square water-stop steel plate in the middle of the extended suspension anchor rod, and apply cement crystal coating at the connection between the extended suspension anchor rod and the sprayed waterproof layer; Step 5: construct the secondary lining structure of the inverted arch and the short side wall and the steel skeleton composed of the annular main reinforcement, longitudinal distribution reinforcement and plum blossom-shaped tension reinforcement; Step 6: erect the steel skeleton of the arch and the remaining side wall secondary lining structure; Step seven: pour concrete for the remaining side walls and arch secondary lining structure to complete the closure of the mega-span cavern secondary lining structure.

2. The construction method of a large-span cavern secondary lining steel bar hanger combined structure according to claim 1 is characterized in that: One end of the anchor rod (1) is anchored deep in the surrounding rock, and the other end passes through the anchor plate and the nut.

3. The construction method of a large-span cavern secondary lining steel bar hanger combined structure according to claim 1 is characterized in that: The connection between the extended suspension anchor rod (8) and the sprayed waterproof layer (4) is painted with cement crystal paint to increase the thickness of the sprayed waterproof layer (4).

4. The construction method of a large-span cavern secondary lining steel bar hanger combined structure according to claim 1 is characterized in that: In step three, the longitudinal spacing of the suspension anchors is extended by 1.2 to 3.6 m. The connection length is determined according to the thickness of the secondary lining and is extended to the annular main reinforcement on the free surface.

5. The construction method of a large-span cavern secondary lining steel bar hanger combined structure according to claim 1 is characterized in that: In step five, the steel bar skeleton (7) is firstly tied, and then the concrete secondary lining structure (6) is poured, and the construction joints are roughened.

6. The construction method of a large-span cavern secondary lining steel bar hanger combined structure according to claim 1 is characterized in that: In step six, the arch annular main reinforcement, longitudinal distribution reinforcement and extended suspension anchor rods are welded together using L-shaped welding steel bars and double-sided welding.

Images