A method for cast-in-place construction of a U-shaped aqueduct body based on a self-propelled trenching machine and the self-propelled trenching machine.

Abstract

This invention relates to the field of aqueduct construction technology, and discloses a method for on-site construction of a U-shaped aqueduct body based on a self-propelled trenching machine, as well as the self-propelled trenching machine itself. It aims to solve the technical problems of poor structural adaptability, insufficient construction stability, difficulty in precision control under complex working conditions, and inefficient construction organization when using conventional bridge mobile formwork for the construction of large-span U-shaped thin-shell aqueducts in the prior art. The invention includes the following steps: S1. Equipment assembly and anti-overturning reinforcement; S2. Pre-stressing and positioning of the formwork structure; S3. Installation of reinforcing steel and prestressed structure; S4. Positioning of the inner formwork anti-buoyancy structure; S5. Concrete pouring and curing; S6. Prestressing tensioning and grouting; S7. Equipment demolding and longitudinal movement through holes; S8. Formwork closing and cyclic construction. The self-propelled trenching machine of this invention, by setting a horizontally opening and closing lower hanging beam and a foldable hydraulic inner formwork structure, enables the formwork to accurately adapt to the complex hyperboloid contour and ultra-large width of the U-shaped aqueduct, solving the structural adaptability problem of conventional formwork.

Description

Technical Field

[0001] This invention relates to the field of aqueduct construction technology, and in particular to a method for cast-in-place construction of a U-shaped aqueduct body based on a self-propelled trenching machine, and the self-propelled trenching machine itself. Background Technology

[0002] In long-distance water conveyance projects, aqueducts are crucial crossing structures traversing valleys, ravines, and other obstacles. Their structural safety, seepage prevention durability, and construction quality directly impact the lifeline safety of the entire project. With the expansion of project scale and the improvement of technical standards, the application of large-span, high-flow-rate, and high-load prestressed concrete aqueducts is becoming increasingly widespread. The Jifucun aqueduct described in this plan has a single span of 30 meters and a design flow rate of 135 m³ / s. It adopts a double-track single-channel design, a U-shaped thin-shell cross-section, and applies longitudinal ring bidirectional prestressing, classifying it as a Class 1 hydraulic structure. Such aqueducts are structurally complex, have high technical standards, and are difficult to construct, posing a significant challenge to traditional construction methods.

[0003] Chinese patent application CN202111592027.0 discloses a bridge construction method for cast-in-place box girder with full-span scaffolding, including the following steps: Step 1: Laying a subbase; Step 2: Erecting a formwork support; Step 3: Installing preloading equipment and performing preloading; Step 4: Installing the steel reinforcement foundation.

[0004] However, the above-mentioned scheme has at least the following technical problems during implementation: The full-span scaffolding cast-in-place method involves erecting dense steel pipe scaffolds at the bottom of the aqueduct as a load-bearing and working platform, and then carrying out formwork installation, rebar tying, concrete pouring, and prestressing construction on them. Although this method is relatively mature, it has significant drawbacks: First, it requires a large amount of scaffolding materials and manpower, resulting in high economic costs; second, the scaffolding erection, prestressing, and dismantling cycle is lengthy, seriously affecting the overall project progress; third, it requires extremely high foundation bearing capacity, and in soft soil, steep slopes, or karst areas, foundation treatment is complex, with a high risk of uneven settlement, seriously affecting the control of the aqueduct's alignment and structural safety; fourth, the large-scale scaffolding system occupies the entire construction surface, severely hindering on-site traffic and material transportation, making construction organization and coordination difficult, and posing significant risks of high-altitude operations and collapse.

[0005] Therefore, there is an urgent need to propose a method for the on-site construction of the U-shaped aqueduct body based on a self-propelled trenching machine, as well as a self-propelled trenching machine. Summary of the Invention

[0006] In view of the above technical problems, this disclosure provides a method for cast-in-place construction of U-shaped aqueduct body based on a self-propelled trenching machine and a self-propelled trenching machine, which solves the technical problems of poor structural adaptability, insufficient construction stability, difficulty in precision control under complex working conditions, and inefficient construction organization when conventional bridge mobile formwork is directly used for the construction of large-span U-shaped thin-shell aqueducts in the prior art.

[0007] According to one aspect of this disclosure, a method for in-situ cast-in-place construction of a U-shaped aqueduct body based on a self-propelled trenching machine is provided, along with the self-propelled trenching machine itself. The self-propelled trenching machine includes a main beam, a nose beam connected to the front end of the main beam, casting legs and a front support leg disposed below the main beam, an upper crossbeam spanning across the main beam, and a horizontally opening and closing lower hanging beam connected to the upper crossbeam. The lower hanging beam carries an outer formwork, and a longitudinally shifting folding inner formwork is disposed on the nose beam. The in-situ cast-in-place construction method for the U-shaped aqueduct body includes the following steps:

[0008] S1. Equipment assembly and anti-overturning reinforcement: Assemble the self-propelled trenching machine at the predetermined assembly site between two adjacent trench piers, and insert multiple high-strength threaded steel bars along the length direction on the anti-vibration block of the pier cap. Use connectors to connect the high-strength threaded steel bars to the bottom structure of the cast-in-place support leg and / or front support leg to form an anchor.

[0009] S2. Preloading and positioning of the formwork structure: The water tank preloading method is used to preload the self-propelled trenching machine and the formwork structure as a whole. The preloading load is 120% of the self-weight of the U-shaped trench structure and the construction load. After the preloading is completed, the elevation of the outer formwork is adjusted and the pre-camber is set according to the monitoring data.

[0010] S3. Reinforcing steel and prestressed structure installation: Tie the U-shaped channel body reinforcing steel skeleton, and simultaneously install longitudinal straight bonded prestressed corrugated pipes and circumferential curved unbonded prestressed steel strands;

[0011] S4. Positioning of the inner mold anti-buoyancy structure: The inner mold is moved longitudinally to the pouring position, and the inner mold is fastened to the nose bridge by the inner mold pressure beam set on the nose bridge to prevent the inner mold from floating during concrete pouring.

[0012] S5. Concrete pouring and curing: Concrete is poured by pumping. The pouring sequence is to advance horizontally in layers from the middle of the U-shaped trough to both ends, and the height difference between the concrete pouring surfaces of the two web plates is controlled to be no more than 30cm. After pouring, heat preservation and moisture retention curing are carried out.

[0013] S6. Prestressing tensioning and grouting: After the concrete strength reaches the design value and the age is not less than 7 days, the prestressed steel strands are tensioned symmetrically in the following order: circumferential tensioning of the first rib, longitudinal tensioning of the second rib, circumferential tensioning of the third rib, circumferential tensioning of the mid-span area, and finally longitudinal tensioning of the remaining ribs. After tensioning is completed, the longitudinal prestressed ducts are grouted.

[0014] S7. Equipment demolding and longitudinal movement through the hole: After the prestressed construction is completed, release the pressure beam, retract the lifting cylinder of the pouring support leg to demold the outer formwork, fold and move the lower hanging beam and outer formwork horizontally, and operate the longitudinal movement cylinder to push the self-propelled trenching machine to the next span construction position.

[0015] S8. Formwork Closure and Cyclic Construction: Lift and pour the support leg in the next span, reverse the operation to close and tighten the lower beam and outer formwork, adjust the formwork elevation, and repeat steps S3 to S7 until the construction of all spans of the U-shaped channel body in a single span is completed.

[0016] In some embodiments of this disclosure, in step S2. Preloading and positioning of the template structure, when the water tank preloading method is used for overall preloading, sandbags are used to construct partition walls at both ends and the middle of the tank to form a water tank. The preloading is carried out in stages according to 60%, 100%, and 120% of the total preloading load until the settlement is stable.

[0017] In some embodiments of this disclosure, during the placement of the inner mold anti-buoyancy structure in step S4, the inner mold cover beam template and support rod are also installed simultaneously. During the concrete pouring process, the inner mold is controlled to float by a combination of pressing the beam and controlling the height difference of the concrete pouring surface on one side to not exceed 30cm.

[0018] In some embodiments of this disclosure, during S5. concrete pouring and curing, the concrete pouring speed is controlled within 30 cm3 / h, and when pouring to the transition area between the bottom plate and the web plate, the pouring speed is slowed down and the material is poured symmetrically and evenly.

[0019] In some embodiments of this disclosure, in step S6. prestressing tensioning and grouting, prestressing tensioning is performed using tensioning equipment, with tension force control as the main method and elongation verification as the method. The tensioning procedure is as follows: initial stress of 10%, 20%, and 100% for five minutes for anchoring.

[0020] In some embodiments of this disclosure, during the demolding and longitudinal movement of the equipment in S7, when the equipment is demolded, the connecting bolts and mechanical locking mechanism between the outer molds are first released, then the folding cylinder of the lower hanging beam is operated to fold the lower hanging beam and the bottom mold, and finally the transverse movement cylinder of the upper crossbeam is operated to open the template.

[0021] In some embodiments of this disclosure, after the construction of a single aqueduct is completed, the method further includes: S9. Disassembly and relocation: The self-propelled trenching machine is disassembled at the landing section of the aqueduct outlet, moved laterally to another trench location and reassembled, and another U-shaped trench body is constructed in reverse order.

[0022] In some embodiments of this disclosure, the precision-rolled threaded steel bar implanted on the pier cap shock-absorbing block has a single bar pull-out force design value of not less than 15 tons, an implantation depth of 500mm, and 200mm exposed for connection with the outrigger.

[0023] A self-propelled trenching machine is applicable to the on-site construction method of U-shaped aqueduct body based on the self-propelled trenching machine, including a main beam mechanism, wherein the main beam mechanism includes a pair of steel box girder main beams and a nose beam connected to the front end of them;

[0024] A support and travel mechanism is provided below the main beam mechanism. The support and travel mechanism includes a casting support leg anchored to the pier cap, a front support leg, and a propulsion trolley located below the main beam.

[0025] The main beam mechanism is connected to the template mechanism, which includes a horizontally openable lower hanging beam connected to the main beam via an upper crossbeam, an outer mold carried by the lower hanging beam, and a foldable hydraulic inner mold set on the nose beam.

[0026] The supporting walking mechanism is connected to the anti-overturning anchoring mechanism, which includes multiple fine-rolled threaded steel bars pre-embedded in the anti-vibration block of the pier cap, and connectors for connecting the fine-rolled threaded steel bars to the cast-in-place support leg or front support leg.

[0027] A pressure beam mechanism is provided on the nose bridge to lock the inner mold and prevent it from floating during concrete pouring.

[0028] In some embodiments of this disclosure, in the anti-overturning anchoring mechanism, each pier cap has 12 precision-rolled threaded steel bars inserted along its length into its anti-vibration block, which are divided into two groups, corresponding to the anchoring positions of the cast-in-place support leg and the front support leg, respectively.

[0029] The beneficial effects of this invention are as follows:

[0030] A highly adaptable and stable specialized construction equipment system was provided. The dedicated self-propelled trenching machine, with its laterally opening and closing lower beam and foldable hydraulic inner mold structure, allows the formwork to precisely adapt to the complex hyperboloid contour and ultra-wide width of the U-shaped aqueduct, solving the structural adaptation problem of conventional formwork. Active anti-overturning and anti-buoyancy reinforcement innovatively incorporates high-strength precision-rolled threaded steel within the anti-vibration blocks of the pier cap, forming a rigid anchor with the trenching machine's outriggers via connectors. This measure, combined with the equipment's own weight and the mechanical locking of the outriggers, constitutes multiple safety guarantees, significantly improving the overall stability and anti-overturning capability of the equipment under extreme conditions such as strong winds and eccentric loading, making it particularly suitable for complex terrains such as high piers and canyons. The integrated inner mold anti-buoyancy design, through a nose beam pressing mechanism, rigidly locks the inner mold to the main beam's nose beam, fundamentally transferring the buoyancy force of the inner mold to the massive main beam system. Combined with a symmetrical and balanced pouring process, this effectively suppresses the risk of inner mold floating during the pouring of U-shaped thin-walled concrete, ensuring structural dimensional accuracy.

[0031] A highly efficient and precise circulating flow construction method has been implemented, eliminating the need for scaffolding and significantly improving work efficiency. The self-propelled and self-supporting mobile formwork technology completely avoids the erection, pre-stressing, and dismantling of large-scale ground-based scaffolding, significantly saving materials and labor time, shortening the construction cycle per span, and achieving standardized and streamlined operations. Refined pre-stressing and deformation control utilize a graded loading water tank pre-stressing method, which can accurately simulate and eliminate inelastic deformation and obtain elastic deformation data, providing a scientific basis for setting the pre-camber for each span, thus effectively ensuring the linear smoothness and design slope of the long aqueduct. Intelligent prestressed construction establishes strict "three-control" tensioning conditions for concrete strength, age, and elastic modulus, and uses intelligent tensioning equipment with dual control of tension force and elongation, performing tensioning according to a scientific sequence (circular first, then longitudinal, symmetrical alternation), ensuring the effective establishment of the prestressed system and structural durability.

[0032] A comprehensive, multi-layered construction quality and safety assurance mechanism was established. Concrete pouring process control stipulated a layered pouring sequence from the middle outwards, strictly controlling the height difference between the two sides, and limiting the pouring speed, effectively avoiding equipment overload and early structural cracks caused by asymmetrical pouring. Environmental and working condition adaptability was ensured by specifying operational restrictions under different wind speeds and equipping the site with a wind speed monitoring and alarm system, improving construction safety in adverse weather conditions. Winter, summer, and rainy season construction measures were proposed, enhancing the universality of the construction method. Regarding coordination with the landing section construction, the construction method clarified the overall sequence of constructing one section of the trench first, followed by dismantling and transferring to another section for construction. This allowed for the efficient operation of the self-propelled trenching machine and the routine construction of the entrance and exit landing sections to be carried out simultaneously without interference, optimizing the overall construction organization. Attached Figure Description

[0033] Figure 1 A flowchart illustrating the construction method of cast-in-place U-shaped aqueduct body;

[0034] Figure 2 A flowchart of the tensioning construction process for the cast-in-place construction of the U-shaped aqueduct body;

[0035] Figure 3 Cross-sectional view of the U-shaped aqueduct body during cast-in-place construction;

[0036] The image shows a tunnel on the left, another tunnel on the right, and an aqueduct connecting the two tunnels in the middle.

[0037] The aqueduct's main structure is a Class 1 building, serving as a crossing structure for the water diversion project's main canal across a valley, connecting the exit of the first tunnel and the entrance of the second tunnel. The main structure, from start to finish, includes: an entrance transition section, an entrance emergency lock chamber section, and an entrance connection section. The aqueduct section comprises 17 segments. The superstructure of each aqueduct segment uses a double U-shaped channel arrangement with uniform cross-sectional dimensions; the substructure, from top to bottom, consists of pier caps, pier bodies, pile caps, and pile foundations. The aqueduct segment is designed with a longitudinal slope...

[0038] Figure 4 A schematic diagram of the main structure of a self-propelled trenching machine under construction conditions;

[0039] Figure 5 This is a schematic diagram of another construction state of the main structure of a self-propelled trenching machine.

[0040] Figure 6 A schematic diagram of the longitudinal section of the self-propelled trenching machine's overall assembly structure;

[0041] Figure 7 This is a schematic diagram of the main beam structure of a self-propelled trenching machine;

[0042] The main beam of the mobile self-propelled trenching machine system consists of a pair of steel box girders. These are divided into three sections, connected by high-strength bolts.

[0043] Figure 8 A schematic diagram of the nose beam structure of a self-propelled trenching machine;

[0044] The equipment has a nose bridge at the front, which is divided into three sections connected by high-strength bolts. The nose bridge serves as a load-bearing structure when the self-propelled trenching machine moves to the next hole, and also acts as the longitudinal track for the front outriggers.

[0045] Figure 9 A schematic diagram of the crossbeam structure of a self-propelled trenching machine;

[0046] The crossbeams are divided into upper crossbeams and lower hanging beams. The upper crossbeam is a box-shaped structure, connected to the main beam by bolts. The lower hanging beams are a welded box-shaped structure. The lower hanging beams are laterally adjustable via a mechanical device mounted on the upper crossbeam. Additionally, the bottom of the lower hanging beams is equipped with a guide device to facilitate adjustment during crossbeam opening and closing, as well as changes in the spacing between the box beams.

[0047] Figure 10 This is a schematic diagram of the longitudinal movement structure of a self-propelled trenching machine;

[0048] The longitudinal movement structure provides longitudinal support for the equipment when it passes through holes and also enables the equipment to move laterally.

[0049] Figure 11 A schematic diagram of the propulsion trolley structure for a self-propelled trenching machine;

[0050] The main function of the trolley is to provide power and support for the equipment when moving longitudinally through the hole. Each trolley is equipped with a longitudinal movement hydraulic cylinder. Slide plates are installed on the upper and lower sliding surfaces of the trolley to reduce friction when the trolley longitudinally pushes the main beam. During longitudinal propulsion of the main beam, the maximum stroke of the hydraulic cylinder is 900mm, and the longitudinal propulsion frame is automatically propelled.

[0051] Figure 12 Schematic diagram of the support leg structure for a self-propelled trenching machine;

[0052] The steel box girder structure with cast-in-place legs is connected to the main beam at the top with high-strength bolts and to the main jacks at the bottom with high-strength bolts. The maximum stress in the cast-in-place state is 4000 kN.

[0053] Figure 13 A schematic diagram of the front outrigger structure of a self-propelled trenching machine;

[0054] The front support leg consists of two independent triangular truss steel box girders connected by a flange in the middle. The front support leg provides auxiliary support through holes during longitudinal movement of the main beam.

[0055] Figure 14 This is a schematic diagram of the external formwork structure of a self-propelled trenching machine;

[0056] The outer formwork consists of a base plate, web plate, ribs, and support rods. The base plate is laid directly on the crossbeams in sections, corresponding to the crossbeams. Each pair of base plates is connected by ordinary bolts along the pin joint direction of the crossbeams. The web plate, ribs, and flanges also correspond to the crossbeams and are installed using formwork supports and bracing installed on the crossbeams.

[0057] Figure 15 This is a schematic diagram of the internal formwork structure of a self-propelled trenching machine;

[0058] The inner mold is a hydraulic inner mold, connected to the nose bridge at the front end, and the rear inner mold frame includes an inner mold template, support system, and folding system. It allows for overall longitudinal movement of the inner mold web through contraction.

[0059] Figure 16 Layout diagram of preloading monitoring points for self-propelled trenching machine;

[0060] The main beam structure of the self-propelled trenching machine is 34m long and is connected by 7 crossbeams in the transverse direction. In order to understand the settlement of the structure after preloading, 9 rows of monitoring points are arranged along the trench direction, with 3 monitoring points in each row, based on the structure of the trenching machine. One monitoring point is set on each of the two main beam structures, and the monitoring point in the middle is set on the crossbeams and the main beam connection structure. The original data of each monitoring point is collected before preloading.

[0061] Figure 17 Anchoring diagram for the support legs of a self-propelled trenching machine;

[0062] To improve the safety factor of the aqueduct superstructure construction and minimize safety risks, it is proposed to add anchoring measures near the contact surfaces of the three sets of outriggers (cast-in-place outriggers, front outriggers, and temporary outriggers) and the pier cap.

[0063] Figure 18 Anchorage diagram of the front outriggers of a self-propelled trenching machine;

[0064] Figure 19 Anchoring diagram for temporary outriggers of a self-propelled trenching machine;

[0065] Figure 20 This is a diagram showing the arrangement of longitudinal prestressing tendons;

[0066] The aqueduct's prestressed system consists of longitudinal and circumferential parts, both tensioned using the post-tensioning method. The longitudinal part uses straight, bonded prestressed steel strands, tensioned at one end, with plastic corrugated pipes as prestressing ducts. The circumferential part uses curved, unbonded prestressed steel strands, tensioned at both ends.

[0067] Figure 21 for Figure 20 Sectional view in direction 2-2;

[0068] Figure 22 for Figure 20 Sectional view in the middle 3-3 direction;

[0069] Figure 23 for Figure 22 Sectional view in the 4-4 direction;

[0070] The components in the diagram are named as follows: 1. Front support leg; 2. Upper crossbeam; 3. Lower hanging beam; 4. Formwork mechanism; 5. Pressure beam mechanism. Detailed Implementation

[0071] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Example 1

[0072] This example discloses a method for in-situ casting of a U-shaped aqueduct body based on a self-propelled trenching machine, and the self-propelled trenching machine itself. (See also...) Figures 1 to 23 ;

[0073] The self-propelled trenching machine includes a main beam, with a nose beam connected to the front end of the main beam. Casting legs and a front support leg 1 are installed below the main beam. Figure 13 As shown, the front support leg 1 consists of two independent triangular truss steel box girders connected by a flange in the middle. The front support leg can be secured to the pier top pad stone via a fastening beam and a fastening beam top rod. The front support leg provides auxiliary support through holes during the longitudinal movement of the main beam. A transverse upper beam 2 spans between the main beams, and the upper beam 2 connects to a transversely opening lower hanging beam 3. Figure 9This is a schematic diagram of the crossbeam structure of a self-propelled trenching machine; the crossbeam consists of an upper crossbeam and a lower hanging beam. The upper crossbeam is a box-shaped structure, connected to the main beam by bolts. The lower hanging beam is a welded box-shaped structure. The lower hanging beams are laterally adjusted by a mechanical device installed on the upper crossbeam. A guide device is also provided at the bottom of the lower hanging beam to facilitate adjustment when the crossbeam is opened and closed, and when the spacing between the box beams changes. The lower hanging beam 3 supports the outer formwork, and a longitudinally sliding folding inner formwork is installed on the nose beam. The in-situ casting construction method for the U-shaped aqueduct body includes the following steps:

[0074] S1. Equipment assembly and anti-overturning reinforcement: Assemble the self-propelled trenching machine at the predetermined assembly site between two adjacent trench piers, and insert multiple high-strength threaded steel bars along the length direction on the anti-vibration block of the pier cap. Use connectors to connect the high-strength threaded steel bars to the bottom structure of the cast-in-place support leg and / or front support leg to form an anchor.

[0075] S2. Preloading and positioning of the formwork structure: The water tank preloading method is used to preload the self-propelled trenching machine and the formwork structure as a whole. After the preloading is completed, the elevation of the outer formwork is adjusted and the pre-camber is set according to the monitoring data.

[0076] S3. Reinforcing steel and prestressed structure installation: Tie the U-shaped channel body reinforcing steel skeleton, and simultaneously install longitudinal straight bonded prestressed corrugated pipes and circumferential curved unbonded prestressed steel strands;

[0077] S4. Positioning of the inner mold anti-buoyancy structure: The inner mold is moved longitudinally to the pouring position, and the inner mold is fastened to the nose bridge by the inner mold pressure beam set on the nose bridge to prevent the inner mold from floating during concrete pouring.

[0078] S5. Concrete pouring and curing: Concrete is poured by pumping, and the pouring sequence is to advance horizontally in layers from the middle of the U-shaped trough to both ends. After pouring, heat preservation and moisture retention curing are carried out.

[0079] S6. Prestressing tensioning and grouting: After the concrete strength reaches the design value, the prestressed steel strands are tensioned symmetrically in the following order: circumferential tension of the first rib, longitudinal tension of the second rib, circumferential tension of the transition section to the mid-span area, and finally the remaining longitudinal tension. After tensioning, the longitudinal prestressed ducts are grouted.

[0080] S7. Equipment demolding and longitudinal movement through the hole: After the prestressed construction is completed, release the pressure beam, retract the lifting cylinder of the pouring support leg to demold the outer formwork, fold and move the lower hanging beam and outer formwork horizontally, and operate the longitudinal movement cylinder to push the self-propelled trenching machine to the next span construction position.

[0081] S8. Formwork Closure and Cyclic Construction: Lift and pour the support leg in the next span, reverse the operation to close and tighten the lower beam and outer formwork, adjust the formwork elevation, and repeat steps S3 to S7 until the construction of all spans of the U-shaped channel body in a single span is completed.

[0082] S2. In the preloading and positioning of the template structure, when the water tank preloading method is used for overall preloading, the water tank is formed by constructing partition walls at both ends and the middle of the tank body with sandbags. The preloading is carried out in stages according to 60%, 100% and 120% of the total preloading load until the settlement is stable.

[0083] S4. During the placement of the inner formwork anti-buoyancy structure, the inner formwork cap beam template and support rod are also installed simultaneously. During the concrete pouring process, the inner formwork is controlled to float by a combination of pressing the beam and controlling the height difference of the concrete pouring surface on one side to not exceed 30cm.

[0084] S5. During concrete pouring and curing, the concrete pouring speed shall be controlled within 30 cm3 / h, and when pouring to the transition area between the bottom slab and the web, the pouring speed shall be slowed down and the material shall be poured symmetrically and evenly.

[0085] S6. In prestressing tensioning and grouting, prestressing tensioning uses tensioning equipment, with tension force as the main control and elongation as the verification. The tensioning procedure is: initial stress of 10%, 20%, and 100% for five minutes, followed by anchoring.

[0086] S7. During demolding and longitudinal movement of the equipment, when demolding the equipment, first release the connecting bolts and mechanical locking mechanism between the outer molds, then operate the folding cylinder of the lower hanging beam to fold the lower hanging beam and the bottom mold, and finally operate the transverse movement cylinder of the upper crossbeam to open the template.

[0087] After the construction of a single aqueduct is completed, the following steps are also included: S9. Disassembly and relocation: The self-propelled trenching machine is disassembled at the landing section of the aqueduct outlet, moved laterally to another trench location and reassembled, and the construction of another U-shaped trench body is carried out in reverse order.

[0088] The precision-rolled threaded steel bars embedded in the anti-vibration blocks of the pier cap have a single pull-out force design value of not less than 15 tons, an embedment depth of 500mm, and 200mm exposed for connection with the outriggers.

[0089] A self-propelled trenching machine is applicable to the on-site construction method of U-shaped aqueduct body based on the self-propelled trenching machine, including a main beam mechanism, which includes a pair of steel box girder main beams and a nose beam connected to the front end of them;

[0090] A support and travel mechanism is set below the main beam mechanism. The support and travel mechanism includes a cast-in-place support leg anchored to the pier cap, a front support leg, and a propulsion trolley set below the main beam.

[0091] The main beam mechanism is connected to the template mechanism 4. The template mechanism includes a horizontally openable lower hanging beam 3 connected to the main beam via an upper cross beam 2, an outer mold supported by the lower hanging beam, and a foldable hydraulic inner mold set on the nose beam.

[0092] The supporting walking mechanism is connected to the anti-overturning anchoring mechanism, which includes multiple fine-rolled threaded steel bars pre-embedded in the anti-vibration block of the pier cap, and connectors for connecting the fine-rolled threaded steel bars to the cast-in-place legs or front legs.

[0093] A pressure beam mechanism 5 is installed on the bridge of the nose to lock the inner mold and prevent it from floating during concrete pouring.

[0094] In the anti-overturning anchoring mechanism, each pier cap has 12 precision-rolled threaded steel bars inserted along its length into its anti-vibration block, which are divided into two groups, corresponding to the anchoring positions of the cast-in-place support leg and the front support leg, respectively.

[0095] Comparative analysis of key construction data in this application and existing technologies:

[0096] The traditional full-span scaffolding method requires 28 days for construction of a single span, but this solution only requires 14 days.

[0097] The linearity control error in the traditional full-span scaffolding method is ±15mm, but in this solution it is only ±3mm.

[0098] The traditional full-span scaffolding method emits 35 tons of carbon per span, but this solution only requires 20 tons per span.

[0099] The traditional full-span scaffolding method requires 50 people per span, but this solution only requires 22 people per span.

[0100] Although some preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0101] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for cast-in-place construction of a U-shaped aqueduct body based on a self-propelled trenching machine, wherein the self-propelled trenching machine includes a main beam, a nose beam connected to the front end of the main beam, casting legs and front legs provided below the main beam, an upper crossbeam spanning between the main beams, the upper crossbeam connecting a horizontally opening and closing lower hanging beam, the lower hanging beam supporting the outer formwork, and a longitudinally shifting folding inner formwork provided on the nose beam, characterized in that... The method for in-situ cast-in-place construction of the U-shaped aqueduct body includes the following steps: S1. Equipment assembly and anti-overturning reinforcement: Assemble the self-propelled trenching machine at the predetermined assembly site between two adjacent trench piers, and insert multiple high-strength threaded steel bars along the length direction on the anti-vibration blocks of the pier cap. Use connectors to connect the high-strength threaded steel bars to the bottom structure of the cast-in-place legs and / or front legs to form an anchor. S2. Preloading and positioning of the formwork structure: The water tank preloading method is used to preload the self-propelled trenching machine and the formwork structure as a whole. After the preloading is completed, the elevation of the outer formwork is adjusted and the pre-camber is set according to the monitoring data. S3. Reinforcing steel and prestressed structure installation: Tie the U-shaped channel body reinforcing steel skeleton, and simultaneously install longitudinal straight bonded prestressed corrugated pipes and circumferential curved unbonded prestressed steel strands; S4. Positioning of the inner mold anti-buoyancy structure: The inner mold is moved longitudinally to the pouring position, and the inner mold is fastened to the nose bridge by the inner mold pressure beam set on the nose bridge to prevent the inner mold from floating during concrete pouring. S5. Concrete pouring and curing: Concrete is poured by pumping, and the pouring sequence is to advance horizontally in layers from the middle of the U-shaped trough to both ends. After pouring, heat preservation and moisture retention curing are carried out. S6. Prestressing tensioning and grouting: After the concrete strength reaches the design value, the prestressed steel strands are tensioned symmetrically in the following order: circumferential tension of the first rib, longitudinal tension of the second rib, circumferential tension of the transition section to the mid-span area, and finally the remaining longitudinal tension. After tensioning, the longitudinal prestressed ducts are grouted. S7. Equipment demolding and longitudinal movement through the hole: After the prestressed construction is completed, release the pressure beam, retract the lifting cylinder of the pouring support leg to demold the outer formwork, fold and move the lower hanging beam and outer formwork horizontally, and operate the longitudinal movement cylinder to push the self-propelled trenching machine to the next span construction position. S8. Formwork Closure and Cyclic Construction: Lift and pour the support leg in the next span, reverse the operation to close and tighten the lower beam and outer formwork, adjust the formwork elevation, and repeat steps S3 to S7 until the construction of all spans of the U-shaped channel body in a single span is completed.

2. The method for cast-in-place construction of the U-shaped aqueduct body based on a self-propelled trenching machine as described in claim 1, characterized in that: In the S2. template structure preloading and positioning, when the water tank preloading method is used for overall preloading, sandbags are used to build partition walls at both ends and the middle of the tank to form a water tank. The preloading is carried out in stages according to 60%, 100%, and 120% of the total preloading load until the settlement is stable.

3. The method for cast-in-place construction of the U-shaped aqueduct body based on a self-propelled trenching machine as described in claim 1, characterized in that: In the S4. In the placement of the inner mold anti-buoyancy structure, the inner mold cover beam template and support rod are also installed at the same time. During the concrete pouring process, the inner mold is controlled to float by a combination of pressing the beam and controlling the height difference of the concrete pouring surface on one side to not exceed 30cm.

4. The method for in-situ casting of the U-shaped aqueduct body based on a self-propelled trenching machine as described in claim 1, characterized in that: In S6. Prestressing tensioning and grouting, prestressing tensioning is performed using tensioning equipment, with tension force as the main control and elongation as the verification. The tensioning procedure is as follows: initial stress of 10%, 20%, and 100% for five minutes, followed by anchoring.

5. The method for cast-in-place construction of the U-shaped aqueduct body based on a self-propelled trenching machine as described in claim 1, characterized in that: In the S7. Equipment demolding and longitudinal movement through hole, when the equipment is demolded, first release the connecting bolts and mechanical locking mechanism between the outer molds, then operate the folding cylinder of the lower hanging beam to fold the lower hanging beam and the bottom mold, and finally operate the transverse movement cylinder of the upper crossbeam to open the template.

6. The method for cast-in-place construction of the U-shaped aqueduct body based on a self-propelled trenching machine as described in claim 1, characterized in that: After the construction of a single aqueduct is completed, the following steps are also included: S9. Disassembly and relocation: The self-propelled trenching machine is disassembled at the landing section of the aqueduct outlet, moved laterally to another trench location and reassembled, and the construction of another U-shaped trench body is carried out in reverse order.

7. The method for cast-in-place construction of the U-shaped aqueduct body based on a self-propelled trenching machine as described in claim 1, characterized in that: The precision-rolled threaded steel bars implanted on the anti-vibration block of the pier cap have a single pull-out force design value of not less than 15 tons, an implantation depth of 500mm, and 200mm exposed for connection with the outrigger.

8. A self-propelled trenching machine, applicable to the cast-in-place construction method of the U-shaped aqueduct body based on the self-propelled trenching machine as described in claim 1, characterized in that, Includes a main beam mechanism, which comprises a pair of steel box girder main beams and a nose beam connected to their front ends; A support and travel mechanism is provided below the main beam mechanism. The support and travel mechanism includes a casting support leg anchored to the pier cap, a front support leg, and a propulsion trolley located below the main beam. The main beam mechanism is connected to the template mechanism, which includes a horizontally openable lower hanging beam connected to the main beam via an upper crossbeam, an outer mold carried by the lower hanging beam, and a foldable hydraulic inner mold set on the nose beam. The supporting walking mechanism is connected to the anti-overturning anchoring mechanism, which includes multiple fine-rolled threaded steel bars pre-embedded in the anti-vibration block of the pier cap, and connectors for connecting the fine-rolled threaded steel bars to the cast-in-place support leg or front support leg. A pressure beam mechanism is provided on the nose bridge to lock the inner mold and prevent it from floating during concrete pouring.

9. The self-propelled trenching machine as described in claim 8, characterized in that: In the anti-overturning anchoring mechanism, each pier cap has 12 precision-rolled threaded steel bars inserted along its length into its anti-vibration block, which are divided into two groups, corresponding to the anchoring positions of the cast-in-place support leg and the front support leg, respectively.

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