A construction method for a newly-built open-cut tunnel to cross an existing operating tunnel in parallel above it

Abstract

The present invention provides a construction method for a newly-built open-cut tunnel to cross an existing operating tunnel in parallel, belonging to the technical field of architectural engineering design and construction. During the construction process of the newly-built tunnel, a method of strictly controlling the single unloading volume + counterweight load compensation + strictly dewatering as required + automatic monitoring is adopted to reduce the adverse impact on the lower existing tunnel during the construction period, and a retaining structure + anti-floating bracket is adopted to meet the overall anti-floating requirements, so as to achieve the purpose of ensuring the safe operation of the lower existing tunnel throughout the whole process stage.

Description

Technical Field

[0001] The invention belongs to the technical field of building engineering design and construction, and particularly relates to a construction method for a new open-cut tunnel to parallelly cross an existing operating tunnel. Background Art

[0002] With the continuous development of urbanization, in order to meet the needs of the growing traffic pressure in the core areas of the city, the urban municipal and transportation systems also need to be continuously upgraded accordingly. Underground projects such as municipal and subway tunnels have also quietly formed lines and networks. In new construction projects, it is inevitable to encounter situations where existing tunnels are crossed, especially in soft soil areas where the existing tunnels below need to be operated uninterruptedly. The excavation of the foundation pit of the new tunnel above has a great impact on the structural safety and operational safety of the tunnel directly below. In existing actual engineering cases in soft soil areas, considering that they may be subject to construction risks and limitations on the development of prefabricated technology, most existing cases are cases of crossing existing operating tunnels. There are very few cases of new open-cut tunnels parallel to existing operating tunnels. Therefore, further research is needed on the scheme of parallel crossing existing tunnels.

[0003] In engineering cases across existing tunnels, the following methods are usually used:

[0004] 1. Full reinforcement + temporary support followed by grid excavation method: Before construction, full reinforcement is first performed, and then a temporary support structure is used to grid the soil within the excavation range. After excavating each grid to the base, the structure is promptly rebuilt. After the structural concrete reaches the designed strength, adjacent grids are excavated until the construction is completed. The advantage is that the single excavation volume can be controlled by refining the grid size to reduce the impact on the lower tunnel; the disadvantage is that the risk of temporary support construction directly above is relatively high, and this method has high requirements for the vertical clearance between the two projects.

[0005] 2. Large excavation method after pipe curtain reinforcement: construct pipe curtain starting and receiving working wells on both sides of the existing tunnel, use small pipe jacking machinery to construct circular or rectangular steel pipes above the existing tunnel, and fill the steel pipes with reinforced concrete after the construction is completed to form a steel-concrete composite pipe curtain with a certain rigidity. When excavating the foundation pit at the top, use the rigidity of the pipe curtain to resist the uplift deformation of the foundation pit excavation, so as to protect the existing operating tunnel. The advantage is that the high-strength pipe curtain can appropriately increase the excavation working surface; the disadvantage is that the pipe curtain working well needs to be set up, the construction period is long and the cost is high, the rigidity of the pipe curtain is limited, and most of them still need to adopt block excavation + counterweight compensation measures.

[0006] The problems existing in the parallel overcrossing of the existing tunnel mainly include: 1. During the construction of the new open-cut tunnel, the existing tunnel directly below needs to operate normally, and the large-scale unloading and loading in the upper part have a great impact on the structural safety and operation safety of the lower tunnel; 2. The dewatering construction of the upper foundation pit has a great impact on the safety of the lower tunnel; 3. The construction period of the conventional in-situ casting method is relatively long, and the "time-space effect" of the long-term exposure after the foundation pit excavation is obvious, which is not conducive to the safety of the lower tunnel; 4. The construction of the upper new tunnel changes the anti-floating state of the existing tunnel below, and it is necessary to pay attention to the adverse effects on the anti-floating of the existing tunnel during the whole construction process and after operation; 5. During the whole construction process, the lower tunnel needs to operate normally, and strong measures need to be taken to ensure the structural safety and operation safety of the existing tunnel. Summary of the Invention

[0007] In view of the technical problems existing in the prior art, the present invention provides a construction method for a new open-cut tunnel parallel overcrossing an existing operating tunnel, which is applicable to a large-span, small clear distance, and long-distance parallel open-cut foundation pit directly above the existing operating tunnel. During the construction process of the new tunnel, the method of strictly controlling the single unloading volume + counterweight load compensation + strictly dewatering according to demand + automatic monitoring is adopted to reduce the adverse effects on the lower existing tunnel during the construction period, and the method of retaining structure + anti-floating bracket is adopted to meet the overall anti-floating requirements, so as to achieve the purpose of ensuring the safe operation of the lower existing tunnel in the whole process stage.

[0008] The technical solution adopted by the present invention is: a construction method for a new open-cut tunnel parallel overcrossing an existing operating tunnel, including the following steps:

[0009] Step 1: Construct the retaining structure, capping beam, water retaining wall, and foundation reinforcement of the foundation pit of the new tunnel. The retaining structure is located on both sides of the existing operating tunnel. A capping beam is arranged on the retaining structure, and a water retaining wall is arranged on the capping beam. The foundation reinforcement is located between the two retaining structures and above the existing operating tunnel. During the construction process of the new tunnel, the whole process and automatic real-time monitoring of the lower existing operating tunnel are carried out;

[0010] Step 2: Divide the excavation area of the foundation pit of the new tunnel into several middle block areas and side block areas. The middle block areas are located in the middle of the foundation pit and arranged in a row, and the side block areas are located on both sides of the middle block areas. Each side block area is adjacent to two middle block areas;

[0011] Step 3: Excavate the first layer of soil in layers and sections, and construct the first support. The first support acts at the center elevation of the capping beam;

[0012] Step 4: Construction of the middle block area: Excavate the soil in the middle above the existing operating tunnel to the base. After the middle foundation pit is excavated to the base, construct the cushion layer and waterproof layer. After the cushion layer and waterproof layer meet the design requirements, carry out the hoisting and backfilling construction of the prefabricated component A on it, and apply the counterweight A;

[0013] Step 5: Construction of the side block area: After the automated monitoring data of the existing operating tunnel is stable, construct the corresponding side block areas on both sides of the middle block area respectively; after the foundation pit is excavated to the base, construct the cushion and waterproof layer. After the cushion and waterproof layer meet the design requirements, carry out the hoisting and backfilling construction of precast component B on it, and apply counterweight B.

[0014] Step 6: Complete the connection of the post-cast strengthening belt of the floor slab between different precast components A and precast component B. The post-cast strengthening belt is poured with high-strength compensated shrinkage concrete; the gap between precast component B and the retaining structure is filled densely with plain concrete of the same grade, and then construct the anti-floating corbels. The anti-floating corbels are reliably connected to the retaining structure in the form of embedded steel bar connectors or post-inserted reinforcing bars.

[0015] Step 7: Symmetrically complete the hoisting and backfilling construction of precast component C, and promptly construct the side wall waterproof layer. Precast component C is installed on precast component B.

[0016] Step 8: Backfill the waste pit densely with cohesive soil.

[0017] Step 9: Demolish the first support, hoist and backfill precast component D. Precast component D is installed on precast component A and precast component C.

[0018] Step 10: Demolish the replacement support, and then complete the backfilling construction of the foundation pit and the waste pit.

[0019] Step 11: Under the guidance of the automated monitoring results of the existing operating tunnel, gradually remove counterweight A, counterweight B and counterweight C during the construction period.

[0020] Furthermore, in Step 1, a safety distance is reserved between the bottom of the foundation reinforcement and the top of the existing operating tunnel.

[0021] Furthermore, the initial load of counterweight A should be reasonably selected according to the requirements of the design scheme and the results of the automated monitoring of the lower existing operating tunnel, and then adjusted reasonably according to the changes in the information-based monitoring data.

[0022] Furthermore, the initial load of counterweight B is reasonably selected according to the requirements of the design scheme and the results of the automated monitoring of the lower existing operating tunnel, and then adjusted reasonably according to the changes in the information-based monitoring data.

[0023] Furthermore, in Step 8, after the waste pit is backfilled densely, install a replacement support between precast components C, and set a reinforced concrete force transfer belt at the waste pit position between precast component C and the retaining structure.

[0024] Furthermore, precast component A is provided with a U-shaped opening reserved for the replacement support, and the reserved opening is post-cast and closed with high-strength compensated shrinkage reinforced concrete after the replacement support is demolished.

[0025] Further, along the construction progress direction, first complete the construction of 4 - 6 intermediate block areas, and then carry out the construction in the order of one intermediate block area and one side block area on each side.

[0026] Further, the segmented length of the prefabricated component D matches the lengths of the prefabricated components A and C.

[0027] Further, the steel bar connections between the prefabricated components A, B, C, and D all adopt the method of grouting sleeves.

[0028] Further, the prefabricated components A, B, C, and D all adopt anti - seepage concrete, and at least one external waterproof layer is provided on their soil - facing surfaces.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. The present invention adopts the excavation process of small segments and small blocks to minimize the single - time excavation unloading volume. After the bottom slab is backfilled, load compensation is immediately carried out by applying counterweights, and the size of the counterweights is determined comprehensively according to the design requirements and the stability of the monitoring data.

[0031] 2. In order to reduce the adverse effects during the foundation pit excavation, the present invention utilizes the "time - space effect" principle. All components adopt prefabricated precast components, which can achieve rapid assembly and backfilling, so as to achieve the purpose of reducing the long - time exposure of the foundation pit.

[0032] 3. The present invention uses the foundation pit retaining structure + anti - floating corbels to ensure that the anti - floating effects on the existing tunnel below during the construction process and operation of the upper tunnel can meet the specifications and safety requirements. The connection form between the anti - floating corbels and the retaining structure can adopt the method of embedding steel bar connectors inside the retaining structure or post - implanting steel bars later.

[0033] 4. During the construction process of the upper tunnel, the present invention adopts the method of full - process automated structural monitoring + video operation monitoring for the lower operating tunnel, real - time monitors the structural safety status and operation status of the tunnel, and guides the on - site construction in real - time according to the stability of the monitoring data.

[0034] 5. The present invention realizes the purpose of safe, economic, and smooth construction of the upper newly - built tunnel while ensuring the safe operation of the lower existing tunnel. Description of the Drawings

[0035] Figure 1 is the flowchart of the embodiment of the present invention;

[0036] Figure 2 is the construction drawing of the retaining structure and the foundation after reinforcement of the embodiment of the present invention;

[0037] Figure 3 Construction drawing after the middle part of the foundation pit of the embodiment of the present invention is excavated to the base

[0038] Figure 4 Construction drawing of the middle structure backfilling and counterweight application of the embodiment of the present invention

[0039] Figure 5 Construction drawing after the side floor backfilling and counterweight application of the embodiment of the present invention

[0040] Figure 6 Construction drawing after the floor slab and anti-floating bracket construction of the embodiment of the present invention are completed

[0041] Figure 7 Construction drawing after the side wall backfilling of the embodiment of the present invention

[0042] Figure 8 Construction drawing after the replacement strut and force transfer belt construction of the embodiment of the present invention

[0043] Figure 9 Construction drawing after the roof slab construction of the embodiment of the present invention is completed

[0044] Figure 10 Status diagram after the construction of the embodiment of the present invention is completed

[0045] Figure 11 Construction process drawing of the foundation pit support setting and excavation block construction of the embodiment of the present invention

[0046] Figure 12 Construction drawing of the foundation pit replacement strut setting and floor slab post-cast strengthening belt setting of the embodiment of the present invention

[0047] Figure 13 Position relationship drawing of the roof slab block with the floor slab and side wall of the embodiment of the present invention

[0048] Figure 14 Reinforcement connection drawing of joint ① of the embodiment of the present invention

[0049] Figure 15 Waterproof joint schematic diagram of joint ① of the embodiment of the present invention

[0050] Figure 16 Reinforcement connection drawing of joint ② of the embodiment of the present invention

[0051] Figure 17 Waterproof joint schematic diagram of joint ② of the embodiment of the present invention

[0052] Figure 18 Reinforcement connection drawing of joints ③ and ④ of the embodiment of the present invention

[0053] Figure 19Schematic diagram of waterproof joint of joint ③ in the embodiment of the present invention. Detailed implementation manners

[0054] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] An embodiment of the present invention provides a construction method for a newly-built open-cut tunnel to cross an existing operating tunnel in parallel, as Figure 1 shown, which includes the following steps:

[0056] Step 1: Construct the retaining structure, capping beam, water retaining wall, and foundation reinforcement of the foundation pit of the newly-built tunnel. As Figure 2 shown, the retaining structure is located on both sides of the existing operating tunnel. A capping beam is provided on the retaining structure, and a water retaining wall is provided on the capping beam. The foundation reinforcement is located between the two retaining structures and above the existing operating tunnel. A safety distance is reserved between the bottom of the foundation reinforcement and the top of the existing operating tunnel. During the construction process, the elevation of the bottom of the foundation reinforcement is strictly controlled to ensure safety. Dewatering wells, ground drainage ditches, etc. are set according to actual engineering needs. During the construction of the newly-built tunnel, the existing operating tunnel below is monitored in real time throughout the process and automatically. Since the retaining structure needs to participate in anti-floating during the operation period, it should be designed and constructed according to the permanent structure design standard. When constructing the steel reinforcement cage of the retaining structure, connecting steel bar couplers, etc. for the later anti-floating corbels, etc. should be embedded, or the connection can also be achieved by post-implanting steel bars later.

[0057] Step 2: Divide the excavation area of the foundation pit of the newly-built tunnel into several middle block areas and side block areas. The middle block areas are located in the middle of the foundation pit and arranged in a row. The side block areas are located on both sides of the middle block areas. Each side block area is adjacent to two middle block areas. Design in blocks and construct one block at a time to minimize the single excavation and unloading volume as much as possible.

[0058] Step 3: Excavate the first layer of soil in layers and sections, and construct the first support. The first support acts at the center elevation of the capping beam. The first support can be a steel pipe support or an assembled concrete support according to theoretical calculations to save the total construction period after excavation and unloading.

[0059] Step 4: Construction of the middle block area: Excavate the soil in the middle above the existing operating tunnel to the base. When necessary, quickly spray and mix the slope surface to ensure the safety of the temporary slope. As Figure 3As shown. The width and length of the preliminary foundation pit block excavation should be determined comprehensively according to the design risk assessment requirements and the size of the prefabricated components. During the foundation pit excavation process, the groundwater should be pumped down or drained openly. After the middle foundation pit is excavated to the base, the cushion layer and waterproof layer should be constructed immediately. The cushion layer is implemented with early-strength plain concrete. After the cushion layer and waterproof layer meet the design requirements, the prefabricated component A is quickly hoisted and rebuilt on it, and the counterweight A is applied in time. The longitudinal section of the prefabricated component A is in the shape of an inverted T, and two counterweights A are placed symmetrically on it. As shown Figure 4 As shown. The initial load of counterweight A should be reasonably selected according to the requirements of the design plan and the results of automated monitoring of the existing operating tunnel below, and then reasonably increased or decreased according to the changes in the information monitoring data. During the prefabrication of prefabricated component A, interfaces should be reserved and embedded for adjacent and upper components according to the design node requirements. The interface position should be strictly located and well protected before connection construction to ensure reliable connection in the later stage.

[0060] Step 5: Construction of side block areas: After the automated monitoring data of the existing operating tunnel is stable, the side block areas corresponding to both sides of the middle block area shall be constructed respectively; after the foundation pit is excavated to the base, the cushion layer and waterproof layer shall be constructed immediately. The cushion layer shall be implemented with early-strength plain concrete. After the cushion layer and waterproof layer meet the design requirements, the prefabricated component B shall be hoisted and rebuilt on it quickly, and the counterweight B shall be applied in time. Figure 5 and Figure 6 As shown. The longitudinal section of the prefabricated component B is in the shape of a straight line, on which a counterweight B is placed. The initial load of the counterweight B is reasonably selected according to the requirements of the design scheme and the results of the automated monitoring of the existing operating tunnel below, and is subsequently reasonably increased or decreased according to the changes in the information monitoring data. The two counterweights B should make the existing operating tunnel as balanced as possible to avoid excessive eccentric loading on one side. During the prefabrication construction of the prefabricated component B, interfaces should be reserved and embedded for adjacent and upper components according to the requirements of the design nodes. The interface positions should be strictly positioned, and protection should be done before the connection construction to ensure reliable connection in the later stage.

[0061] Step 6: Complete the connection of the post-cast reinforcement belt of the bottom plate between different prefabricated components A and B. The post-cast reinforcement belt is cast with high-grade compensating shrinkage concrete; the gap between prefabricated component B and the enclosure structure is filled with the same-grade plain concrete, and then the anti-floating corbel is constructed. The anti-floating corbel is reliably connected to the enclosure structure in the form of pre-buried steel bar connectors or embedded steel bars. Figure 6 and Figure 12 As shown. During the prefabrication of prefabricated component B, interfaces should be reserved and embedded for adjacent and upper components according to the design node requirements. The interface positions should be strictly positioned and well protected before connection construction to ensure reliable connection in the later stage. The steel bar connection between prefabricated component B and prefabricated component A at node ① adopts grouting sleeve, such as Figure 14Before the construction of the anti-floating corbel, attention should be paid to the flange and overlap length of the bottom plate waterproof layer toward the side wall to ensure that the full waterproofing requirements can be met.

[0062] Step 7: Complete the hoisting and reconstructing of prefabricated component C symmetrically, and construct the side wall waterproof layer in time. Prefabricated component C is installed on prefabricated component B. Figure 7 As shown. The steel bar connection between the bottom plate of prefabricated component C and prefabricated component B adopts grouting sleeve, as shown in Figure 16 As shown. During the prefabrication construction of the assembled component C at node ②, interfaces should be reserved and embedded for the upper and lower components according to the design node requirements. The interface positions should be strictly positioned and well protected before the connection construction to ensure reliable connection in the later stage.

[0063] Step 8: After the joints between prefabricated components C and B have reached the designed strength and the waterproof layer has been constructed as required, the fertilizer trough is backfilled with clay soil to make it dense. For relatively deep foundation pits, a replacement brace is set up between prefabricated components C, and a reinforced concrete force transmission belt is set up at the fertilizer trough between prefabricated components C and the surrounding structure to ensure a rigid transition of force transmission between the replacement brace and the surrounding structure. Figure 8 and Figure 12 As shown. During the prefabrication of prefabricated component A, a U-shaped opening should be reserved for the replacement support according to the replacement support setting spacing. After the replacement support is removed, the reserved opening is sealed with high-grade shrinkage compensation reinforced concrete. If the foundation pit is shallow, the replacement support may not be used according to the actual calculation results of the project. In this embodiment, replacement supports and force transmission belts are used.

[0064] Step 9: After the replacement support and force transmission belt meet the design requirements, remove the first support, hoist and reconstruct the prefabricated component D, and install the prefabricated component D on the prefabricated component A and prefabricated component C. Figure 9 As shown. At nodes ③ and ④, the steel bars of prefabricated component D, prefabricated component C, and prefabricated component A are connected by grouting sleeves, as shown in Figure 18 As shown. During the prefabrication of prefabricated component D, interfaces should be reserved and embedded for the lower components according to the design node requirements. The interface positions should be strictly positioned and well protected before connection construction to ensure reliable connection in the later stage. Prefabricated component D can choose the on-site casting method according to the difficulty of on-site construction and construction conditions. If the cast-in-place scheme is adopted, the relevant supporting nodes need to be comprehensively considered and matched.

[0065] Step 10: After the connection between prefabricated component D and prefabricated component A and prefabricated component C reaches the design strength, remove the replacement support and then complete the backfill construction of the foundation pit and fertilizer trough. If the tunnel is located under the municipal road, the backfill material and compaction degree must meet the relevant requirements of the municipal road subgrade.

[0066] Step 11: Under the guidance of the automated monitoring results of the existing operating tunnel, gradually remove the counterweights A, B, and C during construction.Figure 10 as shown

[0067] During construction, along the construction progress direction, first complete the construction of 4 - 6 middle block areas, and then construct in the order of one middle block area and one side block area on each side. As shown in the appendix Figure 11 in And so on, for flow - through construction, to avoid the situation of large - scale excavation to the foundation at the same cross - section position.

[0068] The prefabricated component D is the top plate of the new tunnel structure. The segmented length can be comprehensively considered according to factors such as site conditions, construction machinery, hoisting capacity, transportation, and construction convenience, but the segmented length should match the lengths of the prefabricated components A and C. As shown Figure 13 as shown. The prefabricated component D can also adopt the cast - in - place scheme in combination with the actual site conditions. If the cast - in - place scheme is adopted, the top supporting nodes of the prefabricated components A and C connected to this component need to be considered for matching adjustment.

[0069] The steel bar connection of the main nodes between each prefabricated component adopts the grouting sleeve method. The sleeve and grouting material both need to use high - quality performance materials. The sleeve generally uses high - quality carbon structural steel, and the grouting material should have properties such as large fluidity, early strength, high strength, and slight expansion to ensure the effect of "equivalent to cast - in - place". The specific connection details are as shown in Figure 14 and the appendix Figure 16 and the appendix Figure 18 . To ensure the waterproof effect at the nodes and realize the function of full - package waterproofing for the underground tunnel, it is necessary to strengthen the waterproof treatment of the connection nodes of each component. In addition to using impermeable concrete for each prefabricated component itself, it is also necessary to set at least one external waterproof layer on the soil - facing side of each prefabricated component and strengthen the treatment at the nodes. The waterproof strengthening details of each main node are as shown in Figure 15 and the appendix Figure 17 and the appendix Figure 19 .

[0070] The above has described the present invention in detail through embodiments, but the content described is only an exemplary embodiment of the present invention and cannot be considered as limiting the implementation scope of the present invention. The protection scope of the present invention is defined by the claims. All those who utilize the technical solutions described in the present invention, or those skilled in the art inspired by the technical solutions of the present invention, within the essence and protection scope of the present invention, design similar technical solutions to achieve the above - mentioned technical effects, or make equivalent changes and improvements to the application scope, etc., should still fall within the patent coverage protection scope of the present invention.

Claims

1. A construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel, characterized in that, It includes the following steps: Step 1: Construct the retaining structure, capping beam, water retaining wall, and foundation reinforcement of the new tunnel foundation pit. The retaining structure is located on both sides of the existing operating tunnel. A capping beam is set on the retaining structure, and a water retaining wall is set on the capping beam. The foundation reinforcement is located between the two retaining structures and above the existing operating tunnel. During the construction of the new tunnel, the whole process and automatic real-time monitoring of the lower existing operating tunnel are carried out; Step 2: Divide the excavation area of the new tunnel foundation pit into several middle block areas and side block areas. The middle block areas are located in the middle of the foundation pit and arranged in a row. The side block areas are located on both sides of the middle block areas, and each side block area is adjacent to two middle block areas; Step 3: Excavate the first layer of soil in layers and sections, and construct the first support. The first support acts at the center elevation of the capping beam; Step 4: Construction of the middle block area: Excavate the soil in the middle above the existing operating tunnel to the base. After the middle foundation pit is excavated to the base, construct the cushion and waterproof layer. After the cushion and waterproof layer meet the design requirements, carry out the hoisting and backfilling construction of prefabricated component A on it, and apply counterweight A; Step 5: Construction of the side block area: After the automatic monitoring data of the existing operating tunnel is stable, construct the corresponding side block areas on both sides of the middle block area respectively; after the foundation pit is excavated to the base, construct the cushion and waterproof layer. After the cushion and waterproof layer meet the design requirements, carry out the hoisting and backfilling construction of prefabricated component B on it, and apply counterweight B; Step 6: Complete the connection of the post-cast strengthening belt of the bottom slab between different prefabricated component A and prefabricated component B. The post-cast strengthening belt is poured with high-strength compensated shrinkage concrete; the gap between the prefabricated component B and the retaining structure is filled densely with plain concrete of the same grade, and then the anti-floating corbels are constructed. The anti-floating corbels are reliably connected to the retaining structure in the form of embedded steel bar connectors or implanted steel bars; Step 7: Symmetrically complete the hoisting and backfilling construction of prefabricated component C, and construct the side wall waterproof layer. Prefabricated component C is installed on prefabricated component B; Step 8: Backfill the fat pocket densely with cohesive soil; Step 9: Remove the first support, hoist and backfill prefabricated component D. Prefabricated component D is installed on prefabricated component A and prefabricated component C; Step 10: Remove the replacement support, and then complete the backfilling construction of the foundation pit and the fat pocket; Step 11: Under the guidance of the automatic monitoring results of the existing operating tunnel, gradually remove counterweight A, counterweight B, and counterweight C during the construction period.

2. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 1, characterized in that, In Step 1, a safety distance is reserved between the bottom of the foundation reinforcement and the top of the existing operating tunnel.

3. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 1, characterized in that, The initial load of counterweight A should be reasonably selected according to the requirements of the design scheme and the results of the automatic monitoring of the lower existing operating tunnel, and then adjusted reasonably according to the changes in the information monitoring data.

4. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 1, characterized in that, The initial load of counterweight B is reasonably selected according to the requirements of the design scheme and the results of the automatic monitoring of the lower existing operating tunnel, and then adjusted reasonably according to the changes in the information monitoring data.

5. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 1, characterized in that, In Step 8, after the fat pocket is backfilled densely, a replacement support is erected between the prefabricated component C, and a reinforced concrete force transfer belt is set at the fat pocket position between the prefabricated component C and the retaining structure.

6. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 5, characterized in that, The prefabricated component A is provided with a U-shaped opening reserved for the replacement strut, and the reserved opening is post-cast and sealed with high-strength shrinkage-compensating reinforced concrete after the replacement strut is demolished.

7. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 1, characterized in that, Along the construction progress direction, the construction of 4-6 middle block areas is completed first, and then the construction is carried out in the order of one middle block area and one side block area on each side.

8. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 1, characterized in that, The segmented length of the prefabricated component D matches the lengths of the prefabricated components A and C.

9. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 1, characterized in that, The steel bar connections between the prefabricated components A, B, C, and D all adopt the method of grouting sleeves.

10. The construction method for a newly built open-cut tunnel to cross an existing operating tunnel in parallel according to claim 1, characterized in that, The prefabricated components A, B, C, and D all adopt anti-seepage concrete, and at least one external waterproof layer is provided on their soil-facing surfaces.

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