A single cantilever bridge for V-shaped valleys and its construction method

Abstract

This invention discloses a single cantilever bridge and its construction method for V-shaped valleys. First, tunnels are constructed on both sides of the V-shaped valley. Then, the bottom slab of the tunnel entrance section is excavated downwards to form a working space. Within this working space, the zero-segment is poured. A counterweight section is constructed at the end of the zero-segment furthest from the V-shaped valley, and an anchoring device is installed on the counterweight section to anchor it to the rock mass. Starting from the zero-segment on both sides of the V-shaped valley, the cantilever sections are constructed segment by segment using a formwork system. When the two cantilever sections are constructed segment by segment to the closure section, the closure section is constructed. After the closure section hardens, the formwork is removed from the bridge, and the structure is then hoisted off the bridge deck. Finally, after the bridge deck is cleaned, the bridge's ancillary works are constructed, completing the construction of the single cantilever bridge for the V-shaped valley. This invention eliminates the traditional T-shaped rigid frame bridge piers, achieving single cantilever pouring construction using counterweights and anchoring devices. The span can reach 40m to 200m, shortening the construction period and reducing environmental impact.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering and relates to a bridge spanning a V-shaped valley, specifically a single cantilever construction bridge for a V-shaped valley and its construction method. Background Technology

[0002] Bridges are structures that cross obstacles. In the mountainous southwest of my country, numerous bridges span valleys to accommodate various dense highway and railway networks, inevitably including those crossing "V"-shaped valleys. Due to the significant depth of the bridge deck above the valley floor and the steep slopes on both sides, these terrain conditions generally do not allow for the erection of scaffolding. Using scaffolding for construction carries high risks and is economically unfeasible. Therefore, bridge designs often opt for scaffold-free construction methods, with the bridge directly adjacent to tunnels at both ends. When the span of a bridge across a "V"-shaped valley exceeds 200 meters, arch bridges are often chosen. When the span is less than 40 meters, precast simply supported beams can be used. For spans between 40 and 200 meters, T-shaped rigid frame bridges are primarily chosen for safety and economic considerations. However, this bridge type presents other problems. For example, the required piers are very high, sometimes exceeding 100 meters, and the large cross-sections at the base of the piers can encroach on the valley's floodplain, leading to erosion on the slopes and potential slope collapses, thus compromising the safety of the project. Meanwhile, the construction of high piers is very difficult and costly, making it a last resort. If a new bridge type could be proposed that eliminates the T-shaped rigid frame piers, it would be a very competitive bridge type for "V"-shaped valley landforms. Summary of the Invention

[0003] The purpose of this invention is to provide a single cantilever construction bridge and construction method for V-shaped valleys, which can replace the existing T-shaped rigid frame bridge, thereby reducing costs, improving safety and reducing the impact of environmental damage.

[0004] like Figure 1 As shown, in the prior art, T-shaped rigid frame bridges 100, which are often used when constructing bridges in V-shaped valleys with spans ranging from 40m to 200m, have a central rigid frame pier 110 constructed at the bottom of the V-shaped valley 300. The zero segment is located at the top of the central rigid frame pier 110 and the tunnel entrances on both sides. Construction is carried out simultaneously from the central rigid frame pier and the tunnel entrances on both sides. This invention improves upon the prior art T-shaped rigid frame bridge by eliminating the central rigid frame pier, setting the zero segment at the tunnel entrances on both sides of the V-shaped valley, and installing a counterweight section and anchoring device on the non-cantilever side of each zero segment to balance the unbalanced bending moments on both sides of the zero segment during cantilever casting construction.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A single cantilever construction bridge for V-shaped valleys includes a zero section, a counterweight section, a cantilever section, and a closure section;

[0007] There are two zero segments, which are respectively located inside the tunnel entrances on both sides of the V-shaped valley;

[0008] The outer ends of the two cantilever sections are respectively connected to the two zero sections, and the inner sides are connected by the closing section;

[0009] On each zero segment, a counterweight segment is installed on the side corresponding to the cantilever segment. The counterweight segment is anchored to the rock mass at the bottom of the corresponding tunnel entrance by an anchoring device.

[0010] The present invention also provides a construction method for a single cantilever bridge in a V-shaped valley, comprising the following steps:

[0011] Step 1: Tunnel construction. Tunnel construction is carried out on both sides of the V-shaped valley. The bottom edge of the tunnel entrance section near the V-shaped valley is reinforced.

[0012] Step 2, Excavation of the working space: Excavation is carried out downwards in the reinforced area of ​​the bottom slab of the two tunnel entrance sections, and foundation pit support is carried out simultaneously to form the working space;

[0013] Step 3, Zero Segment Construction: The zero segment is poured in the work space to form two zero segments on both sides of the V-shaped valley;

[0014] Step 4, counterweight section construction: Construct and pour the counterweight section at the end of each zero section away from the V-shaped ditch, and pre-embed anchor bolt sleeves during the pouring process;

[0015] Step 5, Anchoring device foundation construction: At the top of the counterweight section, install the drill rod inside the anchor sleeve, and drill a hole downwards through the drilling rig to the rock bearing layer below the working space to form an anchoring hole; install the anchor rod in the anchoring hole, and then perform grouting to form an anchoring device, anchoring the counterweight section and the rock mass into one unit;

[0016] Step 6, Cantilever Section Construction: Starting from section zero, construct the cantilever sections at the tunnel entrances on both sides of the valley, using hanging baskets to construct the cantilever sections in segments.

[0017] Step 7, Closure Segment Construction: When the two cantilever segments are constructed segment by segment to the closure segment, one hanging basket is moved back, and the other hanging basket is selected to hoist the closure segment rigid frame, adjust the linearity of the bridge, and pour the closure segment to complete the closure.

[0018] Step 8: Remove the hanging basket: After the closure section has hardened, remove the hanging basket on the bridge and then hoist it off the bridge deck;

[0019] Step 9: Bridge Deck Ancillary Construction: After the bridge deck is cleaned, proceed with the construction of bridge ancillary works to complete the bridge construction.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention proposes a single cantilever bridge for V-shaped valleys, eliminating the need for traditional T-shaped rigid frame bridge piers. Utilizing counterweights and anchoring devices, it achieves single-cantilever casting construction, avoiding the engineering risks associated with pier construction and the slope instability problems caused by slope toe erosion due to pier encroachment on the valley's flood discharge area. The span can range from 40m to 200m. Under current technological conditions, considering cost, safety, and construction period, it is the best alternative to traditional T-shaped rigid frame bridge piers. Furthermore, the elimination of piers saves on pier foundation costs, making it a highly competitive bridge type in V-shaped valley topography. It also enriches the types of bridges and has significant engineering value. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a T-shaped rigid frame bridge in the prior art.

[0023] Figure 2 A schematic diagram of a single cantilever bridge constructed over a V-shaped valley in an embodiment of the present invention.

[0024] Figure 3 A structural diagram of a single cantilever construction bridge in an embodiment of the present invention.

[0025] Figure 4.1 This is a schematic diagram of the tunnel construction in step 1.

[0026] Figure 4.2 Schematic diagram of the workspace excavation in step 2.

[0027] Figure 4.3 Step 3: Construction diagram of segment 0.

[0028] Figure 4.4 Schematic diagram of the counterweight section construction in step 4.

[0029] Figure 4.5 Schematic diagram of the anchoring device construction in step 5.

[0030] Figure 4.6 Schematic diagram of cantilever section construction in step 6.

[0031] Figure 4.7 Schematic diagram of the closure section construction in step 7.

[0032] Figure 4.8 A diagram illustrating the removal of the hanging basket in step 8.

[0033] Figure 4.9 Step 9 shows the construction diagram of the completed cantilever bridge.

[0034] 100-T-shaped rigid frame bridge, 110-medium rigid frame pier, 120-bridge, 200-single cantilever construction bridge, 210-section zero, 220-counterweight section, 230-cantilever section, 240-closure section, 250-anchoring device, 251-anchor rod, 260-working space, 270-hanging basket, 300-V-shaped valley, 400-tunnel, 410-tunnel entrance. Detailed Implementation

[0035] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0036] like Figures 1 to 3 As shown, the present invention provides a single cantilever construction bridge 200 for a V-shaped ditch 300, including a zero section 210, a counterweight section 220, a cantilever section 230 and a closing section 240;

[0037] There are two zero segments 210, which are respectively located in the tunnel entrances 410 on both sides of the V-shaped valley 300;

[0038] The outer ends of the two cantilever sections 230 are respectively connected to the two zero sections 210, and the inner sides are connected by the closing section 240.

[0039] On each zero segment 210, a counterweight segment 220 is provided on the side corresponding to the cantilever segment 230. The counterweight segment 220 is anchored to the rock mass at the bottom of the corresponding tunnel entrance 410 by an anchoring device 250.

[0040] As a preferred embodiment, such as Figure 3 As shown, a support (not shown in the figure) is provided at the bottom of segment 210. That is, segment 210 is installed on the tunnel floor at the tunnel entrance 410 via the support, and the weight of the bridge is transferred to the tunnel floor via the support. Segment 210 is supported on the support, and the two ends of segment 210 are the counterweight segment 220 and the cantilever end, respectively. The counterweight segment balances the bending moment around the support generated by the cantilever.

[0041] As a preferred embodiment, the support is mostly a steel ball type support, located in the middle of the bottom plate of segment 210, and vertically supported between the tunnel bottom plate and segment 210 to ensure that the gravity of the structure is transferred to the mountain.

[0042] In a preferred embodiment, the top of the zero segment 210 is flush with the tunnel floor slab inside the tunnel entrances 410 on both sides of the V-shaped valley 300.

[0043] In one preferred embodiment, the counterweight section 220 is a prestressed concrete structure cast from a solid beam, and is connected to the zero section 210 as a whole by internal prestressed steel strands and reinforcing bars (prestressed tendons). More preferably, it can be cast using high-density steel sand concrete to better balance the moment generated by the cantilever section 230, thus ensuring the entire bridge is in a mechanically stable state.

[0044] As a preferred embodiment, such as Figure 3 and Figure 4.5 As shown, the anchoring device 250 includes a set of anchor rods 251 pre-embedded in the counterweight section 220, an anchoring hole opened in the rock mass at the bottom of the tunnel, an anchor rod 251 inserted into the anchoring hole from the set of anchor rods 251, and grouting to fill the area around the anchor rod 251 to form an anchoring structure; the grouting can preferably be epoxy mortar.

[0045] As a preferred embodiment, such as Figure 4.5 As shown, the anchor rods 251 of the anchoring device 250 are a group of anchor rods 251. By passing through the tunnel floor slab with multiple anchor rods 251, the counterweight section 220 is anchored to the mountain (rock mass at the bottom of tunnel 400) as a whole, which is used to balance the unbalanced bending moment generated by the counterweight section 220 and the cantilever section 230 around the support.

[0046] In a preferred embodiment, the anchor bolt 251 is inserted into the rock mass to a depth greater than the thickness or height of the counterweight section 220 itself.

[0047] In a preferred embodiment, the cantilever section 230 is a prestressed concrete structure, internally arranged with prestressed steel strands (prestressed tendons) to ensure the structural stress requirements.

[0048] As a preferred embodiment, the cantilever segment 230 can be a hollow box girder, and the cross-sectional type of the box girder is not limited. Furthermore, the height of the bridge cross-section of the cantilever segment 230 gradually decreases from the zero segment 210 on both sides of the V-shaped valley 300 to the closing segment 240 in the middle of the V-shaped valley 300.

[0049] As a preferred embodiment, the cantilever segment 230 is constructed by precast beam segment splicing or segmental cast-in-place construction using a hanging basket 270. The specific construction method is not limited and is determined according to the actual working conditions on site.

[0050] In a preferred embodiment, the closure section 240 is a cast-in-place or precast box girder, used to connect the two cantilever sections 230 extending from the adjacent tunnel openings 410 of the V-shaped valley 300 into a whole, forming the overall bridge structure.

[0051] like Figures 4.1 to 4.9 As shown, the present invention also provides a construction method for a single cantilever bridge in a V-shaped valley, comprising the following steps:

[0052] Step 1, Tunnel 400 construction, such as Figure 4.1 As shown, tunnel construction will be carried out on both sides of the V-shaped valley 300 (using existing technologies such as blasting, shield tunneling, etc.). The bottom edge of the tunnel portal section near the V-shaped valley 300 will be reinforced. Specifically, the bottom slab of the tunnel portal section can be reinforced with a rectangular frame.

[0053] Step 2, Excavation of the 260mm working space: (e.g.) Figure 4.2 As shown, downward excavation is carried out in the reinforced area of ​​the bottom slab of the two tunnel entrance sections (i.e., within the rectangular frame), and foundation pit support is carried out while excavating, forming a working space of 260. The support method is determined according to the geological conditions, such as steel plate support.

[0054] Step 3, Construction of Segment 0, 210: (e.g.) Figure 4.3 As shown, the zero section 210 is poured in the working space 260 to form two zero sections 210 on both sides of the V-shaped valley 300. Before pouring the zero section 210, the bottom of the working space 260 is excavated to a greater depth, and then concrete is poured to reinforce it, forming the bottom plate of the working space 260.

[0055] The pouring method for section 0, 210 is as follows:

[0056] According to the drawings, supports are arranged on the bottom plate inside the working space 260. Then, the steel cage of segment 210 is tied, prestressed corrugated pipes are arranged, and concrete is poured to form segment 210. When tying the steel cage of segment 210, elongated steel bars are reserved at the end of segment 210.

[0057] Step 4, Construction of counterweight section 220: (e.g.) Figure 4.4 As shown, in each segment 210, a counterweight section 220 is constructed and poured at the end furthest from the V-shaped ditch 300, and 251 sets of anchor bolts are pre-embedded during the pouring process; the construction method of the counterweight section 220 is as follows:

[0058] The counterweight section 220 steel cage is tied in the work space 260 and welded to the reserved elongated steel bar of the zero section 210 to form a whole. Anchor rods 251 are arranged and fitted into the counterweight section 220 steel cage. Concrete is poured to form the counterweight section 220.

[0059] A preferred approach is to use steel grit concrete to increase the weight of the counterweight section 220. This improves the counterweight section 220's ability to balance the bending moment of the cantilever section 230 and reduces the reliance on the anchoring device 250. The anchoring capacity of the anchoring device 250 largely depends on the geological conditions beneath the tunnel. When the geological conditions are good, with a hard rock layer, it can provide a very good anchoring effect. However, when the geological conditions are poor, with a loose rock layer or loose rock mass, the anchor bolt 251 has limited effectiveness, requiring an increase in the weight of the counterweight section 220 to balance the bending moment of the cantilever section 230.

[0060] Step 5, Anchoring device 250 foundation construction: (e.g.) Figure 4.5 As shown, at the top of the counterweight section, the drill rod is installed in the anchor rod 251 set, and the drilling machine drills a hole down to the rock bearing layer below the working space 260 to form an anchoring hole; the anchor rod 251 is installed in the anchoring hole, and then grouting is performed to form the anchoring device 250, anchoring the counterweight section and the rock mass into one piece.

[0061] Step 6, Construction of the 230mm cantilever section: (e.g.) Figure 4.6 As shown, starting from segment 210, the cantilever section 230 of the tunnel entrance 410 on both sides of the valley is constructed, and the hanging basket 270 is used to construct the cantilever section 230 in segments.

[0062] Step 7, Construction of the closure section 240: (e.g.) Figure 4.7 As shown, when the two cantilever segments 230 are constructed segment by segment to the closure segment 240, one hanging basket 270 is moved back, and another hanging basket 270 is selected to hoist the rigid frame of the closure segment 240, adjust the linearity of the bridge, and pour the closure segment 240 to complete the closure.

[0063] Step 8, Remove the hanging basket 270: (as follows) Figure 4.8 As shown, after the closure section 240 is hardened, the hanging basket 270 on the bridge will be removed and then hoisted off the bridge deck;

[0064] Step 9, Bridge deck ancillary construction: such as Figure 4.9 As shown, after the bridge deck was cleaned, the bridge ancillary works were carried out to complete the bridge construction.

[0065] Specifically, the bridge deck ancillary construction includes the construction of ancillary structures such as crash barriers, cable troughs, and streetlights.

[0066] The above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Although the invention has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications, or equivalent substitutions of the technical solutions of the invention do not depart from the spirit and scope of the invention and should be covered within the scope of the claims of the invention.

Claims

1. A construction method for a single cantilever construction bridge for a V-shaped valley, characterized by, The method comprises the following steps: Step 1, tunnel construction, tunnel construction is carried out on both sides of the V-shaped valley, and the bottom edge of the tunnel portal section near the V-shaped valley is reinforced; Step 2, working space excavation: downward excavation is carried out in the reinforced area of the bottom plate of the two tunnel portal sections, and pit support is carried out during excavation to form a working space; Step 3, zero section construction: zero section pouring construction is carried out in the working space to form two zero sections on both sides of the V-shaped valley; Step 4, counterweight section construction: a counterweight section is constructed and poured at one end of each zero section away from the V-shaped valley, and an anchor rod sleeve is pre-buried during pouring; Step 5, anchor device foundation construction: the drill rod is installed in the anchor rod sleeve on the top of the counterweight section, the drill is drilled downward to the rock bearing layer below the working space to form an anchor hole, the anchor rod is installed in the anchor hole, and the anchor device is filled by post-grouting to anchor the counterweight section and the rock mass as a whole; Step 6, cantilever section construction: cantilever section construction is carried out on the tunnel portal of both sides of the valley from the zero section, and hanging basket is used for segmented construction of the cantilever section; Step 7, closure section construction: when the two cantilever sections are constructed to the closure section, one hanging basket is retreated, another hanging basket is selected to hoist the closure section frame, the linearity of the bridge is adjusted, and the closure section is poured to complete the closure; Step 8, remove the hanging basket: after the closure section hardens, remove the hanging basket on the bridge, and then hoist it out of the bridge deck; Step 9, bridge deck auxiliary construction: after the bridge deck is cleaned, the bridge auxiliary works are constructed to complete the bridge construction.

2. The construction method of a single cantilever construction bridge for V-shaped valley according to claim 1, characterized in that: In step 1, the rectangular frame is used to reinforce the bottom plate of the tunnel portal section, and the working space is excavated in the rectangular frame.

3. The construction method of a single cantilever construction bridge for V-shaped valley according to claim 1, characterized in that: In step 3, before the zero section pouring construction, the bottom of the working space is excavated to the super depth, and then the concrete is poured to reinforce the bottom plate of the working space.

4. The construction method of a single cantilever construction bridge for a V-shaped valley according to claim 3, characterized in that: In step 3, the zero section pouring construction method is as follows: According to the drawing requirements, the support is arranged on the bottom plate in the working space, then the zero section reinforcement cage is bound, the prestressed corrugated pipe is arranged, the concrete is poured to form the zero section, and the extension steel bars are reserved at the end of the zero section during the binding of the zero section reinforcement cage.

5. The construction method of a single cantilever construction bridge for V-shaped valley according to claim 4, characterized in that: In step 4, the counterweight section construction method is as follows: The counterweight section reinforcement cage is bound in the working space, and is welded as a whole with the extension steel bars reserved in the zero section, the anchor rod sleeve is arranged in the counterweight section reinforcement cage, and the concrete is poured to form the counterweight section.

6. The construction method of a single cantilever construction bridge for V-shaped valley according to claim 5, characterized in that: In step 4, the counterweight section is formed by pouring the steel sand concrete with high density.

7. The method for constructing a single cantilevered construction bridge for a V-shaped valley according to claim 5, wherein: In step 5, the anchor hole is filled with epoxy mortar for anchoring.

8. The method for constructing a single cantilevered construction bridge for a V-shaped valley according to claim 5, wherein: In step 6, during the cantilever section construction, the prestressed beam is arranged in the top plate of the beam body of the cantilever section, and the prestressed beam tensioning is carried out on the last section after each construction.

9. The method for constructing a single cantilevered construction bridge for a V-shaped valley according to claim 5, wherein: In step 6, the cantilever section adopts the hollow beam with weight reduction function, and the height of the cantilever section bridge section gradually decreases from the zero section on both sides of the V-shaped valley to the closure section in the middle of the V-shaped valley.

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