Half bridge broadened road and construction method thereof

Abstract

The invention discloses a half-bridge broadened road and a construction method thereof, and relates to the technical field of road extension. The half-bridge broadened road comprises an original road, a broadened road, a U-shaped bearing platform, an enlarged foundation retaining wall, a supporting column and a side slope reinforcing structure. The U-shaped bearing platform comprises a front wall and two side walls, the front side of the front wall is the side close to the mountain, the front ends of the side walls are connected with the front wall, and the upper ends of the side walls are not higher than the front wall. The side wall comprises a high wall section and a low wall section, and the high wall section is located on the side, close to the mountain, of the low wall section. The upper end of the high wall section is higher than the upper end of the low wall section, so that a concave area is formed at the upper end of the low wall section, and one end, close to the mountain, of the bridge deck is placed in the concave area. The enlarged foundation retaining wall is located below the U-shaped bearing platform and supports the U-shaped bearing platform. Compared with the prior art, the half-bridge broadening road and the construction method thereof have the advantages that the original road on the abrupt slope is broadened, and meanwhile, the structural stability can be improved.

Description

Technical Field

[0001] This invention relates to the field of highway expansion technology, and in particular to a method for widening a highway using a half-bridge and its construction. Background Technology

[0002] Currently, in highway widening technology on steep slopes, the unique stress characteristics and insufficient structural stability of pile foundations on steep slopes are common problems. The foundation of a half-bridge, as a crucial component connecting the superstructure and the subgrade, bears the important function of transferring loads. Under load, the foundation and subgrade will experience corresponding stress-strain responses; therefore, it is essential to ensure sufficient bearing capacity, deformation coordination, and overall stability, controlling structural displacement and differential settlement within allowable limits. How to meet the basic requirements of strength, stiffness, and stability, and effectively solve the problem of poor structural stability, is a pressing issue that needs to be addressed in highway widening projects using half-bridges. Therefore, a construction method for half-bridge structures and their slope reinforcement is urgently needed. Summary of the Invention

[0003] The purpose of this invention is to provide a method for widening a road using a half-bridge and its construction, in order to solve the problems existing in the above-mentioned related technologies and improve the structural stability while widening the original road on a steep slope.

[0004] To achieve the above objectives, the present invention provides the following solution: This invention discloses a method for widening a highway using a half-bridge, comprising: The original highway, which was laid on a roadbed on a steep slope; The road is widened, and the widened road is located on the side of the original road away from the mountain, including a bridge deck and a maintenance layer laid on the upper surface of the bridge deck; The U-shaped abutment includes a front wall and two side walls. The front side of the front wall is closer to the mountain. The front ends of the side walls are connected to the front wall, and the upper ends of the side walls are not higher than the front wall. The side walls include a high wall section and a low wall section. The high wall section is located on the side of the low wall section closer to the mountain. The upper end of the high wall section is higher than the upper end of the low wall section, forming a recessed area at the upper end of the low wall section. The recessed area is for the end of the bridge deck closest to the mountain to be inserted. An enlarged foundation retaining wall is provided, which is located below the U-shaped foundation and supports the U-shaped foundation. The support column supports the end of the bridge deck away from the mountain, and includes a pile foundation and a pier fixed on the pile foundation; A slope reinforcement structure includes a reinforcement layer, a greening layer, and a passive net; the reinforcement layer covers the slope, the greening layer covers the reinforcement layer, and the passive net passes through the greening layer and is fixedly connected to the reinforcement layer.

[0005] Preferably, the curing layer includes a cast-in-place concrete layer on the lower side and an asphalt concrete waterproof layer on the upper side.

[0006] Preferably, a dividing fence is fixed to the upper end of the high wall, a guardrail is fixed to the end of the original road near the mountain, and a guardrail is fixed to the end of the widened road away from the mountain.

[0007] This invention also discloses a construction method for widening a highway using a half-bridge, which includes the following steps: S1: Pile foundation construction: After clearing the site, mark out the pile positions and pour the retaining wall. Excavate pile holes layer by layer. The retaining wall is poured in sections and the steel cage is hoisted to ensure verticality. The concrete is poured in layers. S2: Pier construction: Measure and locate the pier position and remove the laitance on the pile top; assemble, hoist and weld the steel cage for reinforcement; install the formwork in sections; vibrate the concrete in layers; remove the formwork and cure after the strength reaches the standard. S3: Enlarged foundation retaining wall construction: Before the construction of the retaining wall, the site is cleared, and the foundation pit is excavated mechanically and the bottom is trimmed manually; after the foundation is accepted, the steel bars are tied and the formwork is installed. After the strength meets the requirements, the formwork is removed, backfilling is carried out, and the foundation is compacted in layers. S4: U-shaped foundation construction: First, take measurements and position the foundation, then pour the foundation walls in sections, expand the foundation retaining wall and foundation, and after the foundation is poured and cured, backfill the back of the foundation in layers and set up blind drains. S5: Slope reinforcement construction: A comprehensive protection method using anchor bolts, wire mesh, shotcrete, grass planting, and passive netting is adopted. First, the slope is cleared, anchor bolts are installed, steel mesh is hung, then shotcrete is applied for reinforcement, and finally, vegetation mats are covered, grass seeds are sown to restore greenery, and passive netting is installed in high-risk areas to intercept falling rocks.

[0008] Preferably, step S1 specifically includes: S11: Remove ground vegetation within the construction area to ensure good visibility of the site; S12: After leveling the site, excavate the pile positions to the bottom elevation of the pile beam. The length and width dimensions should be 100cm larger on each side than the outer diameter of the pile foundation to facilitate formwork and construction. At the same time, drainage ditches should be set up to avoid the impact of rainwater. S13: Before setting out the pile location, check the design data and measure the center of the pile hole according to the control network, which will serve as the center point of the lock hole wall. S14: After the interlocking retaining wall is poured, the surveying team re-measures the pile position and determines four points of the well ring through two vertical radii, and sets control marks for construction verticality control. S15: Pile hole excavation construction: The drilling rig drills along the inner edge of the hole wall. After the drilling rig removes the rock core, the middle rock and the surrounding rock wall form a free surface. Then, a 3cm drilling rig is used to drill 30cm downwards. After that, a crowbar is used to break the middle rock layer and then the slag is removed. S16: The retaining wall construction uses concrete of the same grade as the pile body, mechanically mixed and manually poured, with a section height of 1m. Anti-collapse holes are poured as they are excavated. Reinforcing mesh is added to the soft soil layer. The formwork is removed 24 hours after the initial setting. S17: The steel cage is manufactured in sections, the main bars are rolled with threaded connections, the joint spacing is reasonable, and they are tightened with a torque wrench. After random inspection, the reinforcing bars are welded to make it firm and without defects. S18: The entire transport length is supported to prevent deformation, two-point hoisting maintains verticality, and in case of restrictions, it is hoisted and tied in sections. The top lifting rod prevents floating, and the concrete is poured in layers using a guide pipe.

[0009] Preferably, in step S15, the drilling diameter is 16cm and the drilling depth is 60cm, and the drilling machine is set according to the pile diameter for each pile hole; in step S16, the template splicing should ensure roundness, the wall thickness is 15cm, the upper and lower sections overlap, the first section is made with a locking ring for waterproofing, and the concrete slump is 4-7cm.

[0010] Preferably, step S2 specifically includes: S21: Use a total station to accurately lay out the center of the pier location, and then report to the supervisor for review before construction; S22: Before pier construction, remove the laitance from the top of the pile, clean and keep it moist, and roughen and clean the joints as well. S23: The construction access uses a gantry-type safety ladder, which is assembled in sections, attached to the piers, and fixed with guy ropes; the verticality and stability are checked after each layer is erected, and safety nets and warning signs are set up around the perimeter. S24: The steel cage is centrally fabricated and spliced ​​on site, with the main bars connected by straight threads. Before hoisting, supports are welded on, and two-point hoisting is used. After positioning and correction, the cage is welded and fixed. S25: Remove rust from the standard steel formwork, apply release agent, and use segmented bolts for connection. Ensure precise positioning, seal gaps, and proceed with pouring after acceptance. S26: Pouring should be carried out after the formwork reinforcement is inspected and accepted. Pumping or hopper vibration should be used for layered compaction. Dedicated personnel should monitor the formwork deformation. The number of construction workers should not exceed 3. S27: Remove the formwork after the concrete strength reaches 2.5MPa. During the formwork removal process, collisions are strictly prohibited and a designated person must be in charge of directing the process.

[0011] Preferably, step S3 specifically includes: S31; Clean the ground surface behind the wall, excavate steps to ensure drainage, accurately lay out and verify, and promptly report any abnormalities to the design team. S32: Clear site debris, use machinery to excavate and treat hard rock layers, slope the slope and set up drainage measures, and strictly control its base size and elevation; S33: Re-inspect the bearing capacity and location of the foundation, and proceed with foundation construction after confirming that there are no errors; S34: After the steel reinforcement passes the re-inspection, it shall be tied according to the drawings, tied firmly and a protective layer shall be provided. S35: Formwork construction is carried out afterward: When supporting the formwork, first set up horizontal supports, then set up diagonal braces for fixation, and complete the layout and pre-inspection before installation; S36: Then pour concrete. Before pouring, confirm that the steel bars and formwork have passed the acceptance test, remove debris and water, and pour in layers. Strictly control the drop and layer thickness, and use immersion vibrator. S37: Rebar processing: Fabricate the retaining wall steel cage, remove impurities from the steel bar surface to keep it clean and undamaged; single-sided electric arc welding is used for welding hooks, the welding parts are reasonably staggered, and full binding is used to ensure the stability of the steel mesh structure; S38: Subsequently, a combination of steel pipes and timber formwork was used. The formwork was assembled in sections, and the positioning was adjusted by hanging lines. Steel pipe internal supports and through-wall bolts were installed at the top for fixing. Embedded parts were pre-processed and positioned to ensure convenient and accurate installation later. S39: After the template is installed, pour the concrete. During pouring, strictly control the free fall of the concrete. If the fall exceeds the free fall, set up a chute to divert the excess. The pouring shall be carried out in layers. After the concrete is poured, cover it immediately for moist curing. The curing time shall not be less than 7 days. S310: After the concrete strength reaches the design requirements, backfill the back of the wall with sandy soil that has good permeability and is free of organic matter, or with materials specified in the design.

[0012] Preferably, step S4 specifically includes: S41: Based on the design drawings, perform high-precision measurement and layout of the pile location and the center of the abutment location, and mark the reference axis and edge line of the U-shaped abutment. S42: After the pile foundation strength reaches the requirements, the reinforcement of the pile cap is tied. After the formwork is installed and accepted, the concrete is poured in layers. The U-shaped pile cap is constructed in sections and zones to ensure the quality of joint treatment and overall rigidity. S43: The height of the wall is divided into high and low sections according to the design elevation, and a segmented and layered pouring method is adopted to ensure the stability of the formwork and the compactness of the concrete; S44: After the concrete of the wall reaches the design strength, the backfill soil behind the wall is carried out in layers. S45: After the main structure is completed, construct the auxiliary structures.

[0013] Preferably, step S5 specifically includes: S51: Remove loose soil, dangerous rocks, and weeds from the slope to ensure the working surface is clean and stable; S52: Drill holes according to the design layout, and use pneumatic drills or down-the-hole drills to construct anchor bolt holes. The hole depth is controlled according to the design requirements. S53: Weave φ6~φ8 steel bars into a mesh according to the design spacing, tie it to the slope anchor, and add connecting bars to strengthen the overall integrity if necessary; S54: Use wet spraying process, concrete grade C20~C25, thickness 5~8cm, spray evenly in layers, and control rebound rate; S55: Set up grass seed bags or hang vegetation mats in the sprayed area, and plant drought-resistant slope protection plants in combination with the nutrient soil pre-buried in the sprayed layer to promote vegetation restoration and soil and water conservation.

[0014] Compared with related technologies, the present invention achieves the following technical effects: The U-shaped foundation (with a U-shaped structure) is embedded in the mountain, with its opening facing away from the mountain. The front end of the U-shaped foundation forms the front wall, and the front surface of the front wall is used for soil retention. The side walls are located behind the front wall, perpendicular to it and integrally connected to it, and are used to provide lateral support to the front wall from the rear, transferring the lateral force of the soil on the front wall to the foundation.

[0015] This invention employs a unique design for the U-shaped pier, deviating from the conventional approach of using sidewalls of equal height across all sections. Instead, it creates varying heights at the upper ends of different sections of the sidewalls, resulting in a recessed area at the upper end of the lower sidewall section, which is lower than the adjacent higher sidewall section. Since the upper end of the sidewall is not higher than the front wall, at least a portion of the bridge deck near the mountainside is embedded within this recessed area (i.e., lower than the upper end of the higher sidewall section). Therefore, at least a portion of the bridge deck near the mountainside is lower than the front wall, thereby utilizing the front wall's obstruction of lateral soil flow to reduce the lateral force on the bridge deck and improve the overall structural stability.

[0016] On the other hand, since at least part of the bridge deck is embedded in the recessed area at the end closest to the mountain, it exerts its own weight and the weight of the vehicles above on the U-shaped abutment, making the pressure of the U-shaped abutment on the soil below greater, ensuring the compaction of the soil below, thereby using the self-weight of the bridge deck and the weight of the load on the bridge to suppress the U-shaped abutment, further improving the stability of the U-shaped abutment.

[0017] An enlarged foundation retaining wall is located below and supports the U-shaped foundation, serving to expand the foundation of the U-shaped foundation. It should be noted that the lower surface of the U-shaped foundation retaining wall is U-shaped, irregular in shape, and has a relatively small area, while the lower surface area of ​​the enlarged foundation retaining wall is larger than that of the lower surface of the U-shaped foundation (the meaning of enlarged foundation). Therefore, the enlarged foundation retaining wall is less prone to deformation under pressure compared to the soil below. Thus, this invention, by increasing the contact area with the soil below, makes the pressure distribution of the U-shaped foundation on the soil more uniform, preventing relative flow of soil in different areas due to uneven pressure.

[0018] The supporting columns support the end of the bridge deck facing away from the mountainside and include pile foundations and piers fixed to the pile foundations. The pile foundations are pre-embedded in the soil below, the lower end of the piers is connected to the pile foundations, and the upper end of the piers supports the end of the bridge deck facing away from the mountainside. By using the supporting columns, the road width is expanded by "borrowing space" through the elevated structure, without occupying too much slope or slope toe space. This is especially suitable for steep terrain and confined space, reducing the amount of fill material used and the pressure of spoil disposal, and lowering the difficulty of construction organization.

[0019] Slope reinforcement structures are used to strengthen slopes, intercepting falling debris such as rocks from steep slopes. A slope reinforcement structure includes a reinforcement layer, a greening layer, and a passive netting. The reinforcement layer covers the slope and has a fixed shape, used to stabilize the underlying soil. The greening layer covers the reinforcement layer to improve aesthetics. The passive netting is generally fixed at the bottom of the steep slope, passes through the greening layer, and is fixedly connected to the reinforcement layer; it is used to intercept falling debris such as rocks from steep slopes.

[0020] In summary, this invention combines U-shaped abutments, expanded foundation retaining walls, support columns, and slope reinforcement structures. It not only utilizes the elevated structure to "borrow space" to expand the road width without occupying too much slope or slope toe space, thus reducing the amount of fill material used and the pressure of spoil disposal, and lowering the difficulty of construction organization, but also reduces the lateral forces on the bridge deck and support columns, improves the stability of the overall structure, reduces the risk of rockfall, and enhances the overall aesthetics. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of a construction method for widening a road using a half-bridge, as shown in some examples of the present invention. Figure 2 This is a schematic diagram of a half-bridge widening a road in some examples of the present invention.

[0023] In the diagram: 1-Original highway; 2-Wide highway; 3-U-shaped pier; 4-Enlarged foundation retaining wall; 5-Support column; 6-Slope reinforcement structure. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The purpose of this invention is to provide a method for widening a road using a half-bridge and its construction, in order to solve the problems existing in the above-mentioned related technologies and improve the structural stability while widening the original road on a steep slope.

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Reference Figures 1-2 This embodiment provides a half-bridge widening road, including the original road 1, the widened road 2, the U-shaped abutment 3, the enlarged foundation retaining wall 4, the support column 5, and the slope reinforcement structure 6.

[0028] The original road 1 was laid on a steep slope. The widened road 2 is located on the side of the original road 1 away from the mountainside, and includes the bridge deck and a maintenance layer laid on the upper surface of the bridge deck. The U-shaped abutment 3 includes a front wall and two side walls. The front side of the front wall is closer to the mountainside, and the front ends of the side walls connect to the front wall, with the upper ends of the side walls not exceeding the front wall. The side walls include a high wall section and a low wall section, with the high wall section located on the side of the low wall section closer to the mountainside. The upper end of the high wall section is higher than the upper end of the low wall section, creating a recessed area at the upper end of the low wall section, into which the end of the bridge deck closest to the mountainside is placed. The enlarged foundation retaining wall 4 is located below the U-shaped abutment 3 and supports it. The support column 5 supports the end of the bridge deck away from the mountainside, including pile foundations and piers fixed to the pile foundations. The slope reinforcement structure 6 includes a reinforcement layer, a greening layer, and a passive safety net. The reinforcement layer covers the slope, the greening layer covers the reinforcement layer, and the passive netting passes through the greening layer and is fixedly connected to the reinforcement layer.

[0029] The working principle of this embodiment of widening a highway using a half-bridge is as follows: Widening Road 2 is located on the side of the original Road 1 away from the mountain. The two are set up side by side and can be used for traffic. Thus, the overall traffic width is expanded on the basis of the original Road 1 by setting up Widening Road 2.

[0030] Highway 2 widening adopts a half-bridge design, with one end closer to the mountain supported by the mountain itself, and the other end away from the mountain supported by support pillars 5. Steep slope sections often have narrow terrain, and conventional widening methods require excavation inwards or filling outwards, which not only limits space but also poses challenges such as poor stability of high fill slopes and massive earthwork volumes. The half-bridge utilizes an elevated structure to "borrow" space to widen the road surface, without occupying excessive slope or toe space. This is particularly suitable for steep terrain and confined spaces, reducing the amount of fill material used and the pressure of spoil disposal, while also simplifying construction organization.

[0031] Compared to full-width excavation or high-fill schemes, half-bridges are more adaptable to terrain, eliminating the need for large-scale earthwork balancing and slope protection works, and simplifying the construction process. Furthermore, their structural components (such as precast beams) can be prefabricated in the factory and installed on-site, reducing the impact of steep slopes and inclement weather on on-site pouring operations. This indirectly shortens the construction period and reduces the risk of slope instability and additional costs associated with prolonged construction.

[0032] In the existing technology, the end of the widened road 2 closest to the mountain is directly embedded in the soil of the steep slope, and therefore is affected by the lateral pressure of the soil. Especially when disasters such as landslides occur, the soil will cause huge lateral impacts on the widened road 2, posing a safety hazard of displacement or even cracking of the widened road 2 and the support column 5.

[0033] The U-shaped foundation 3 (with a U-shaped structure) is embedded in the mountain, with its opening facing away from the mountain. The front end of the U-shaped foundation 3 is the front wall, and the front surface of the front wall is used for soil retention. The side walls are located behind the front wall, perpendicular to it and integrally connected to it, and are used to provide lateral support to the front wall from the rear, transferring the lateral force of the soil on the front wall to the foundation.

[0034] This application employs a unique design for the U-shaped pier 3, deviating from the existing approach of using sidewalls of equal height across all sections. Instead, it creates height variations at the upper ends of different sections of the sidewalls, resulting in a recessed area at the upper end of the lower sidewall section due to its lower height compared to the adjacent higher sidewall section. Since the upper end of the sidewall is not higher than the front wall, at least a portion of the bridge deck near the mountainside is embedded within this recessed area (i.e., lower than the upper end of the higher sidewall section). Therefore, at least a portion of the bridge deck near the mountainside is lower than the front wall, thereby utilizing the front wall's obstruction of lateral soil flow to reduce the lateral force on the bridge deck and improve the overall structural stability.

[0035] On the other hand, since at least part of the bridge deck is embedded in the recessed area at the end closest to the mountain, it exerts its own weight and the weight of the vehicles above on the U-shaped pier 3, making the pressure of the U-shaped pier 3 on the soil below greater, ensuring the compaction of the soil below, thereby using the self-weight of the bridge deck and the weight of the load on the bridge to suppress the U-shaped pier 3, further improving the stability of the U-shaped pier 3.

[0036] The enlarged foundation retaining wall 4 is located below and supports the U-shaped foundation 3, serving to enlarge the foundation of the U-shaped foundation 3. It should be noted that the lower surface of the U-shaped foundation retaining wall is U-shaped, irregular in shape, and relatively small in area, while the lower surface area of ​​the enlarged foundation retaining wall 4 is larger than that of the lower surface of the U-shaped foundation 3 (meaning enlarged foundation). Therefore, the enlarged foundation retaining wall 4 is less prone to deformation under pressure compared to the soil below. Thus, this embodiment, by increasing the contact area with the soil below, makes the pressure distribution of the U-shaped foundation 3 on the soil below more uniform, preventing relative flow of soil in different areas due to uneven pressure.

[0037] Support column 5 supports the end of the bridge deck facing away from the mountain and includes pile foundations and piers fixed to the pile foundations. The pile foundations are pre-embedded in the soil below, the lower end of the pier is connected to the pile foundation, and the upper end of the pier supports the end of the bridge deck facing away from the mountain. By setting up support column 5, the road width is expanded by "borrowing space" through the elevated structure, without occupying too much slope or slope toe space. This is especially suitable for road sections with steep terrain and limited space, reducing the amount of fill material used and the pressure of spoil disposal, and reducing the difficulty of construction organization.

[0038] The slope reinforcement structure 6 is used to reinforce slopes, intercepting falling debris such as rocks from steep slopes. The slope reinforcement structure 6 includes a reinforcement layer, a greening layer, and a passive net. The reinforcement layer covers the slope and has a fixed shape, used to compact the underlying soil. The greening layer covers the reinforcement layer to improve aesthetics. The passive net is generally fixed at the bottom of the steep slope, passes through the greening layer, and is fixedly connected to the reinforcement layer, used to intercept falling debris such as rocks from steep slopes.

[0039] In summary, this embodiment combines the U-shaped abutment 3, the enlarged foundation retaining wall 4, the support column 5, and the slope reinforcement structure 6. It not only utilizes the elevated structure to "borrow space" to expand the road width without occupying too much slope or slope toe space, thus reducing the amount of fill material and the pressure of spoil disposal, and lowering the difficulty of construction organization, but also reduces the lateral force on the bridge deck and support column 5, improves the stability of the overall structure, reduces the risk of rockfall, and improves the overall aesthetics.

[0040] In some examples, the curing layer includes a cast-in-place concrete layer on the lower side and an asphalt concrete waterproofing layer on the upper side.

[0041] The cast-in-place concrete layer levels uneven surfaces on the bridge deck, ensuring the smoothness of subsequent waterproofing layers and pavement. It also allows for adjustments to the bridge deck's drainage slope design by varying the thickness of the cast-in-place layer. The asphalt concrete waterproofing layer, as the core waterproofing barrier, prevents rainwater and snowmelt from seeping into the bridge deck, avoiding steel corrosion and concrete carbonation, and is a crucial guarantee of bridge durability. The combined effect of these two layers mitigates the direct impact of vehicle loads on the bridge deck and reduces stress concentration between the pavement and the bridge deck.

[0042] In some examples, a dividing fence is fixed at the top of the high wall, a guardrail is fixed at the end of the original road 1 that is close to the mountain, and a guardrail is fixed at the end of the widened road 2 that is away from the mountain.

[0043] The dividing barrier is used to separate the original highway 1 from the widened highway 2. Guardrail 1 is located on a steep mountain slope, while guardrail 2 is located on a suspended side. Therefore, the impact resistance of guardrail 2 should be higher than that of guardrail 1 to prevent vehicles from running off the side of the bridge deck away from the mountain.

[0044] In some examples, the original road 1 and the widened road 2 have the same angle of inclination, making the side away from the mountain higher than the side closer to the mountain, thereby preventing vehicles from running off the side away from the mountain through the inclination of the road surface.

[0045] This embodiment also provides a construction method for widening a highway using a half-bridge, which includes the following steps: S1: Pile foundation construction: After clearing the site, the pile positions are marked out and the retaining wall is poured. The pile holes are excavated layer by layer. The retaining wall is poured in sections, and the steel cage is hoisted to ensure verticality. The concrete is poured in layers.

[0046] S2: Pier Construction: Measure and locate the pier position and remove the laitance from the pile top; assemble, hoist, and weld the reinforcing cage. Install the formwork in sections, vibrate the concrete in layers, and remove the formwork and allow it to cure after the concrete reaches the required strength.

[0047] S3: Enlarged Foundation Retaining Wall Construction: Before constructing the retaining wall, the site is cleared, and the foundation pit is excavated mechanically and the bottom is trimmed manually. After the foundation is inspected and accepted, steel bars are tied and formwork is installed. After the strength meets the requirements, the formwork is removed, backfilling is carried out, and then the soil is compacted in layers.

[0048] S4: Construction of U-shaped foundation 3: First, take measurements and position the foundation, pour the foundation wall in sections, expand the foundation retaining wall 4 and the foundation, and after the foundation is poured and cured, backfill the back of the foundation in layers and set up blind drains.

[0049] S5: Slope reinforcement construction: A comprehensive protection method is adopted, which includes anchor rods, wire mesh, shotcrete, grass planting, and passive netting. First, the slope is cleared, anchor rods are installed, steel mesh is hung, then shotcrete is applied for reinforcement, and finally, vegetation mats are covered and grass seeds are sown to restore greenery. In high-risk areas, passive netting is installed to intercept falling rocks.

[0050] Since this construction method is used to obtain the aforementioned half-bridge widening of the highway, it also has the corresponding advantages of half-bridge widening of the highway, which will not be elaborated here.

[0051] In some examples, step S1, pile foundation construction, specifically involves: S11: Vegetation clearing and transplanting: Clear ground vegetation within the construction area and transplant it if necessary to ensure good visibility of the site.

[0052] By clearing construction obstacles and ensuring good visibility of the site, it is easier to carry out subsequent surveying, setting out, and mechanical operations accurately; if necessary, vegetation can be transplanted to reduce ecological damage and balance the needs of engineering construction and environmental protection.

[0053] S12: Site leveling and foundation pit excavation: After leveling the site, excavate the pile positions to the bottom elevation of the pile beam, with the length and width dimensions 100cm larger on each side than the outer diameter of the pile foundation to facilitate formwork and construction. Drainage ditches should also be installed to prevent rainwater from affecting the site.

[0054] Leveling the site creates the basic conditions for subsequent construction; the pit size is expanded by 100cm to reserve sufficient space for formwork and personnel operation, improving construction convenience; drainage ditches are set up at the same time to drain rainwater in time and avoid water accumulation affecting the stability of the pit and the progress of subsequent construction.

[0055] S13: Pile location layout and verification: Before the pile location is laid out, the design data should be verified, and the center of the pile hole should be measured according to the control network as the center point of the lock hole wall.

[0056] Verify the design data to ensure consistency with the engineering drawings, and measure the center of the pile hole according to the control network to provide a precise center point for the interlocking wall protection, ensuring accurate pile positioning from the source and reducing the risk of subsequent pile position deviation.

[0057] S14: Pile location re-measurement and control mark setting: After the lock-mouth retaining wall is poured, the surveying team re-measures the pile location and determines four points of the well ring through two vertical diameter lines, and sets control marks for construction verticality control.

[0058] After the interlocking retaining wall was poured, the pile position was re-measured to further verify the accuracy of the pile position; by setting four points of the well ring with vertical diameter and setting control marks, a clear reference was provided for the verticality control of subsequent pile hole excavation, ensuring that the verticality of the pile body complies with regulations.

[0059] S15: Pile hole excavation construction: The drilling rig drills along the inner edge of the hole wall. After the drilling rig removes the rock core, the middle rock and the surrounding rock wall form an open surface. Then, a 3cm drilling rig is used to drill a hole 30cm downwards. A crowbar is then used to break the middle rock layer, and then the slag is removed.

[0060] The drilling rig drills along the inner edge of the borehole wall. Combined with the free surface formed after the rock core is removed, a small drilling rig is used to drill holes and a crowbar is used to break the rock layer. This ensures the quality of the borehole wall formation, while efficiently breaking the rock layer and smoothly removing the slag, thus meeting the excavation needs of the rock geology.

[0061] S16: Retaining wall construction: The retaining wall construction uses concrete of the same grade as the pile body, mechanically mixed and manually poured, with a section height of 1m. Anti-collapse holes are poured as they are excavated. Reinforcing mesh is added to the soft soil layer. The formwork is removed 24 hours after the initial setting.

[0062] Using concrete of the same grade as the pile body ensures that the strength of the retaining wall matches that of the pile body; pouring concrete as it is excavated (1m high section) can support the borehole wall in time and effectively prevent borehole collapse; adding steel mesh to the soft soil layer enhances the bearing capacity of the retaining wall; removing the formwork 24 hours after initial setting ensures the stability of the retaining wall formation and improves the safety of pile hole construction.

[0063] S17: Reinforcing cage fabrication: The reinforcing cage is fabricated in sections, with the main reinforcement bars rolled and threaded together. The joint spacing is reasonable, and the joints are tightened using a torque wrench. After random inspection and approval, reinforcing bars are welded to ensure that the cage is firm and free of defects.

[0064] Sectional manufacturing facilitates processing and transportation; the main reinforcement bars are connected by rolled threads and tightened with a torque wrench to ensure joint strength and connection reliability, and random inspections further tighten quality control; welded reinforcing bars make the steel cage firm and defect-free, ensuring that the steel cage does not deform or sink during hoisting and subsequent concrete pouring.

[0065] S18: Reinforcing cage transportation and hoisting: Support the entire length of the transport cage to prevent deformation, hoist at two points to maintain verticality, hoist and tie in sections when restricted, use top lifting bars to prevent floating, and pour concrete in layers using a guide pipe cassette.

[0066] Full-length support transport prevents deformation of the rebar cage and ensures its structural integrity; two-point hoisting maintains verticality, and segmented hoisting and binding are used when restricted to ensure precise insertion of the rebar cage into the hole; top lifting bars prevent floating and avoid the rebar cage from floating during concrete pouring, ensuring the correct position of the pile rebar; layered concrete pouring lays the foundation for subsequent vibration and compaction.

[0067] S19: Concrete Pouring and Testing: Concrete pouring adopts a combination of tremie pipes and tremie tubes. The bottom 8m uses tremie tubes, and the upper 8m uses tremie pipes. The tremie pipes are made of steel pipes with a diameter of 325mm and a wall thickness of 6mm, connected at both ends by flanges. The tremie tubes are made of rolled 3mm thick steel plates. The tremie tubes are connected to each other and to the tremie pipes by hooks. The distance between the concrete discharge port and the concrete surface should not exceed 2m. Each pouring height should not exceed 0.5m, and the concrete should be compacted in layers using an immersion vibrator. Before the initial setting of each layer, the next layer of concrete is poured, and the previous layer is thoroughly vibrated a second time. After the concrete strength reaches the design requirements, it is tested using ultrasonic testing. If the test report is qualified, the pile is considered complete.

[0068] The combination of tremie pipe and tremie pipe for pouring adapts to different depth requirements (tremie pipe for the lower 8m and tremie pipe for the upper part), and controls the distance between the discharge port and the concrete surface to be no more than 2m and the single pouring height to be no more than 0.5m to avoid concrete segregation; layered vibration and secondary vibration ensure the concrete is dense and reduce defects such as honeycomb and pitting; after the concrete strength reaches the standard, ultrasonic testing is used to accurately check the internal quality of the pile body, and the pile is completed only after it passes the test, ensuring that the final quality of the pile foundation meets the design requirements.

[0069] In some examples, in step S15, the borehole diameter is 16cm and the borehole depth is 60cm. The drilling rig can be set according to the pile diameter for each pile hole. In step S16, the formwork splicing must ensure roundness, the wall thickness is 15cm, the upper and lower sections overlap, the first section is made with a locking ring for waterproofing, and the concrete slump is 4-7cm.

[0070] Depending on the specific needs, those skilled in the art may also select other construction parameters.

[0071] In some examples, step S2, the construction of the pier column, specifically involves: S21: Precise pier location layout: Use a total station to accurately layout the pier center, and report to the supervisor for review before construction.

[0072] The center of the pier is precisely located using a total station to ensure that the pier position is completely consistent with the design and to avoid subsequent deviations. Construction is carried out after the supervisor reviews the information. This dual control further reduces the risk of positioning errors and lays a precise foundation for the construction of the pier.

[0073] S22: Pile top and joint treatment: Before pier construction, remove the laitance from the pile top, clean and keep it moist, and roughen and clean the joint as well.

[0074] Removing the laitance from the top of the pile can remove insufficient concrete and ensure the structural strength of the connection between the pile and the pier; cleaning and moistening the top of the pile and roughening the joint can enhance the adhesion between the pile and the pier, prevent cracks from appearing at the joint, and improve the overall stability of the pier.

[0075] S23: Safety Ladder Erection: The construction access uses a gantry-type safety ladder, which is assembled in sections, attached to the piers, and secured with guy ropes. Verticality and stability are checked after each layer is erected, and safety nets and warning signs are installed around the perimeter.

[0076] The gantry-type climbing ladder is assembled in sections, attached to the pier, and fixed with guy ropes, resulting in a stable structure that meets the height requirements of pier construction. Each layer is checked for verticality and stability, and with the addition of safety nets and warning signs around the perimeter, it can comprehensively ensure the safety of construction personnel going up and down, reducing the risk of falls.

[0077] S24: Reinforcing cage fabrication and hoisting: The reinforcing cage is fabricated centrally and spliced ​​on site. The main bars are connected by straight threads. Before hoisting, supports are welded on. Two-point hoisting is used. After positioning and correction, the cage is welded and fixed.

[0078] Centralized fabrication of the reinforcing cage facilitates unified quality control, while on-site splicing improves construction efficiency. Straight threaded connections of the main reinforcing bars ensure a firm joint. Welding supports before hoisting and two-point hoisting prevent deformation of the reinforcing cage. After positioning and correction, welding fixation ensures that the reinforcing cage is accurately positioned within the pier column and meets the stress requirements.

[0079] S25: Treatment of fixed steel formwork: Remove rust from the fixed steel formwork, apply release agent, and use segmented bolts for connection. Ensure precise positioning, seal gaps, and proceed with pouring after acceptance.

[0080] Applying a release agent to the formwork after rust removal prevents concrete from sticking and ensures a smooth and flat appearance for the piers. The segmented bolt connection facilitates installation and disassembly, provides precise positioning and seals gaps, preventing grout leakage during pouring. Construction can proceed after acceptance, further ensuring that the formwork meets pouring standards and reducing defects in the appearance of the piers.

[0081] S26: Concrete pouring monitoring: Concrete is poured after the formwork and reinforcement are inspected and accepted. Pumping or hopper is used for layered vibration. Dedicated personnel monitor the deformation of the formwork. The number of construction workers shall not exceed 3.

[0082] Pumping or layered vibration of the hopper can ensure the compaction of concrete and avoid quality problems such as honeycomb and pitting. Dedicated personnel can monitor the deformation of the formwork to detect and deal with bulging, displacement and other situations in a timely manner. The number of construction personnel does not exceed 3, which can reduce the congestion of the work surface and reduce safety hazards and construction interference.

[0083] S27: Formwork Removal: Remove the formwork after the concrete strength reaches 2.5MPa. During the removal process, collisions are strictly prohibited and a designated person must be in charge of directing the process.

[0084] Demolding should be done after the concrete strength reaches 2.5MPa to avoid damage to the pier surface due to insufficient strength. During demolding, collisions are strictly prohibited and a designated person should be in charge to protect the pier structure and formwork, while ensuring a safe and orderly demolding process and reducing equipment and structural wear.

[0085] In some examples, step S3, enlarging the foundation retaining wall 4, specifically involves the following construction: S31: Surface clearing and layout verification: Clear the surface behind the wall, excavate steps to ensure drainage, accurately lay out and verify, and promptly report any abnormalities to the design team.

[0086] S32: Site clearing and excavation control: Clear site debris, use machinery to excavate and treat hard rock layers, slope the sides and set up drainage measures, and strictly control the base size and elevation.

[0087] S33: Foundation Re-inspection: Re-inspect the bearing capacity and location of the foundation, and proceed with foundation construction after confirming that there are no errors.

[0088] S34: Reinforcing bar binding: After the reinforcing bars pass the re-inspection, they shall be bound according to the drawings, and the binding shall be secure and a protective layer shall be provided.

[0089] S35: Formwork support construction: When supporting the formwork, first set up horizontal supports, then set up diagonal braces for fixation. The formwork should have sufficient strength, rigidity and stability. Before installation, complete the layout and pre-inspection.

[0090] S36: Concrete Pouring Preparation and Control: Before pouring concrete, confirm that the reinforcement and formwork have passed inspection, remove debris and water, and adopt layered pouring, strictly control the drop and layer thickness, and use immersion vibration.

[0091] S37: Reinforcing Steel Processing Details: When fabricating the retaining wall reinforcing steel cage, the surface of the reinforcing steel should be cleaned of rust, oil, and other impurities to ensure it is clean and undamaged. Hooks should meet design and specification requirements, and welding should be done using single-sided arc welding. Welded parts should be staggered appropriately, and full binding should be used to ensure the stability of the reinforcing steel mesh structure.

[0092] S38: Installation of combined formwork and treatment of embedded parts: Use steel pipe and timber combined formwork, assemble the formwork in sections, adjust the positioning by hanging line, and install steel pipe internal support and through-wall bolts at the top. Embedded parts should be processed and positioned in advance to ensure convenient and accurate installation later.

[0093] S39: Pouring details and curing: After the formwork is installed, pouring is carried out. During pouring, the free fall of concrete is strictly controlled. If the fall exceeds the limit, a chute is set up to guide the flow. Pouring is carried out in layers. After the concrete is poured, it is immediately covered for moist curing. The curing time is not less than 7 days.

[0094] S310: Backfilling behind the wall: After the concrete strength reaches the design requirements, backfill the wall with sandy soil that has good permeability and is free of organic matter, or with materials specified in the design.

[0095] In some examples, the construction of step S4, U-shaped foundation 3, specifically involves: S41: Measurement and layout: Based on the design drawings, perform high-precision measurement and layout of the pile position and the center of the abutment position, and mark the reference axis and edge line of the U-shaped abutment 3.

[0096] High-precision measurement and layout of the pile and abutment center according to the design drawings ensures accurate connection between the U-shaped abutment 3 and the pile foundation, avoiding subsequent structural misalignment; marking the benchmark axis and edge line provides clear reference for the abutment reinforcement binding, formwork installation and other processes, ensuring that the abutment construction meets the design size requirements from the source and reducing the risk of positioning deviation.

[0097] S42: Reinforcement Binding and Concrete Pouring: After the pile foundation strength reaches the requirements, the reinforcement of the pile cap is bound. After the formwork is installed and accepted, the concrete is poured in layers. The U-shaped pile cap 3 should be constructed in sections and zones to ensure the quality of joint treatment and overall rigidity.

[0098] Construction should proceed only after the pile foundation strength meets the standards to avoid affecting the stability of the pier support due to insufficient pile foundation strength; concrete should be poured in layers after the formwork has passed inspection to ensure the concrete is dense and reduce defects such as honeycomb and pitting; the U-shaped pier should be constructed in three sections to precisely control the quality of joint treatment, prevent cracking at the joints, and enhance the overall rigidity of the pier to meet the structural stress requirements.

[0099] S43: Erect Wall Casting: The height of the erected wall is divided into high and low sections according to the design elevation. A segmented and layered casting method is adopted to ensure the stability of the formwork and the compactness of the concrete.

[0100] The wall is divided into high and low sections according to the design elevation to ensure that the height of the wall meets the engineering design standards. The segmented and layered pouring method can not only ensure the stability of the formwork during the pouring process and avoid the deformation of the formwork due to excessive pouring height, but also fully vibrate the concrete to ensure the compactness of the wall concrete and improve the structural strength of the wall.

[0101] S44: Backfilling of soil behind the wall: After the concrete of the wall body reaches the design strength, the soil behind the wall is backfilled in layers.

[0102] Backfilling should be done in layers after the concrete reaches the design strength. This avoids premature backfilling, which could lead to deformation or damage to the wall due to insufficient concrete strength. Layered backfilling ensures soil compaction, reduces later settlement, and provides lateral support for the U-shaped foundation 3, enhancing the overall stability of the foundation.

[0103] S45: Construction of ancillary structures: After the main structure is completed, construct ancillary structures such as expansion joints, supports, abutment caps, bridge deck system, and crash barriers.

[0104] After the main structure is completed, the construction of expansion joints, supports and other auxiliary structures can avoid mutual interference between the main construction and auxiliary construction, and ensure the orderly progress of each process; expansion joints can release structural temperature stress and prevent the abutment from cracking due to thermal expansion and contraction; supports, abutment caps and other components provide stable support for the bridge deck system, and crash barriers ensure traffic safety in the later stage, thus comprehensively improving the function and safety performance of U-shaped abutment 3.

[0105] In some examples, step S5, the slope reinforcement construction, specifically involves: S51: Slope cleaning: Remove loose soil, dangerous rocks, and weeds from the slope to ensure that the working surface is clean and stable.

[0106] Removing loose soil, dangerous rocks, and weeds from the slope removes loose and easily detached materials, eliminating the risk of falling objects during construction. It also keeps the working surface clean and stable, providing a flat and reliable construction foundation for subsequent processes such as anchor drilling and steel mesh laying, and preventing debris from affecting the bonding effect between the reinforced structure and the slope.

[0107] S52: Anchor bolt hole construction: Drill holes according to the design layout, and use pneumatic drills or down-the-hole drills to construct the anchor bolt holes. The hole depth is controlled according to the design requirements.

[0108] Drill holes according to the design positioning to ensure accurate anchor hole location and provide the correct stress points for subsequent anchor installation; use pneumatic drills or down-the-hole drills to adapt to different rock strata conditions and improve drilling efficiency; strictly control the hole depth to meet the design requirements to ensure that the anchor insertion depth meets the standard, so that the anchor can fully exert its anchoring function and enhance the slope's anti-sliding stability.

[0109] S53: Laying of steel mesh: Weave φ6~φ8 steel bars into mesh according to the design spacing, tie it to the slope anchor rod, and install connecting bars to strengthen the overall integrity if necessary.

[0110] By weaving a mesh with φ6 to φ8 steel bars at the designed spacing and binding it to the anchor rods, an overall protective framework for the slope can be formed, dispersing the stress on the slope and preventing local slope collapse. If necessary, connecting bars can be added to further strengthen the integrity of the steel mesh, enhance its collaborative protection capabilities with the anchor rods and the slope, and make the reinforced structure more stable.

[0111] S54: Wet sprayed concrete construction: Wet spraying process is used, the concrete grade is generally C20 to C25, the thickness is 5 to 8 cm, and it is sprayed evenly in layers to control the rebound rate.

[0112] Using a wet spraying process, combined with C20-C25 grade concrete, ensures uniform concrete quality and improves the strength of the sprayed layer; layered and uniform spraying with controlled thickness (5-8cm) allows the sprayed layer to bond tightly with the slope and steel mesh, effectively covering the slope and reducing erosion of the slope by rainwater; controlling the rebound rate saves materials and avoids rebound material affecting construction quality and the working environment.

[0113] S55: Vegetation restoration construction: Set up grass seed bags or hang vegetation mats in the sprayed concrete area, and plant drought-resistant slope protection plants such as bermudagrass and bahiagrass in combination with the pre-buried nutrient soil in the sprayed concrete layer to promote vegetation restoration and soil and water conservation.

[0114] Setting up grass seed bags or hanging vegetation mats, combined with pre-buried nutrient soil within the sprayed concrete layer, provides favorable conditions for plant growth. Planting drought-resistant slope protection plants such as bermudagrass and bahiagrass can quickly restore slope vegetation, utilize plant roots to stabilize the soil, and further enhance slope stability. At the same time, vegetation can reduce surface runoff, playing a role in soil and water conservation, achieving the dual effect of slope reinforcement and ecological restoration, and improving the long-term protection capacity and environmental harmony of the slope.

[0115] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for widening a highway using a half-bridge, characterized in that, include: The original highway, which was laid on a roadbed on a steep slope; The road is widened, and the widened road is located on the side of the original road away from the mountain, including a bridge deck and a maintenance layer laid on the upper surface of the bridge deck; The U-shaped abutment includes a front wall and two side walls. The front side of the front wall is closer to the mountain. The front ends of the side walls are connected to the front wall, and the upper ends of the side walls are not higher than the front wall. The side walls include a high wall section and a low wall section. The high wall section is located on the side of the low wall section closer to the mountain. The upper end of the high wall section is higher than the upper end of the low wall section, forming a recessed area at the upper end of the low wall section. The recessed area is for the end of the bridge deck closest to the mountain to be inserted. An enlarged foundation retaining wall is provided, which is located below the U-shaped foundation and supports the U-shaped foundation. The support column supports the end of the bridge deck away from the mountain, and includes a pile foundation and a pier fixed on the pile foundation; A slope reinforcement structure includes a reinforcement layer, a greening layer, and a passive net; the reinforcement layer covers the slope, the greening layer covers the reinforcement layer, and the passive net passes through the greening layer and is fixedly connected to the reinforcement layer.

2. The method for widening a highway using a half-bridge as described in claim 1, characterized in that: The curing layer includes a cast-in-place concrete layer on the lower side and an asphalt concrete waterproof layer on the upper side.

3. The method for widening a highway using a half-bridge as described in claim 1, characterized in that: A boundary fence is fixed to the upper end of the high wall, a guardrail is fixed to the end of the original road that is closer to the mountain, and a guardrail is fixed to the end of the widened road that is away from the mountain.

4. A construction method for widening a highway using a half-bridge, characterized in that, The method for obtaining a highway widened by half a bridge as described in any one of claims 1 to 3 includes the following steps: S1: Pile foundation construction: After clearing the site, mark out the pile positions and pour the retaining wall. Excavate pile holes layer by layer. The retaining wall is poured in sections and the steel cage is hoisted to ensure verticality. The concrete is poured in layers. S2: Pier construction: Measure and locate the pier position and remove the laitance on the pile top; assemble, hoist and weld the steel cage for reinforcement; install the formwork in sections; vibrate the concrete in layers; remove the formwork and cure after the strength reaches the standard. S3: Enlarged foundation retaining wall construction: Before the construction of the retaining wall, the site is cleared, and the foundation pit is excavated mechanically and the bottom is trimmed manually; after the foundation is accepted, the steel bars are tied and the formwork is installed. After the strength meets the requirements, the formwork is removed, backfilling is carried out, and the foundation is compacted in layers. S4: U-shaped foundation construction: First, take measurements and position the foundation, then pour the foundation walls in sections, expand the foundation retaining wall and foundation, and after the foundation is poured and cured, backfill the back of the foundation in layers and set up blind drains. S5: Slope reinforcement construction: A comprehensive protection method using anchor bolts, wire mesh, shotcrete, grass planting, and passive netting is adopted. First, the slope is cleared, anchor bolts are installed, steel mesh is hung, then shotcrete is applied for reinforcement, and finally, vegetation mats are covered, grass seeds are sown to restore greenery, and passive netting is installed in high-risk areas to intercept falling rocks.

5. The construction method for widening a highway using a half-bridge as described in claim 4, characterized in that: Step S1 is as follows: S11: Remove ground vegetation within the construction area to ensure good visibility of the site; S12: After leveling the site, excavate the pile positions to the bottom elevation of the pile beam. The length and width dimensions should be 100cm larger on each side than the outer diameter of the pile foundation to facilitate formwork and construction. At the same time, drainage ditches should be set up to avoid the impact of rainwater. S13: Before setting out the pile location, check the design data and measure the center of the pile hole according to the control network, which will serve as the center point of the lock hole wall. S14: After the interlocking retaining wall is poured, the surveying team re-measures the pile position and determines four points of the well ring through two vertical radii, and sets control marks for construction verticality control. S15: Pile hole excavation construction: The drilling rig drills along the inner edge of the hole wall. After the drilling rig removes the rock core, the middle rock and the surrounding rock wall form a free surface. Then, a 3cm drilling rig is used to drill 30cm downwards. After that, a crowbar is used to break the middle rock layer and then the slag is removed. S16: The retaining wall construction uses concrete of the same grade as the pile body, mechanically mixed and manually poured, with a section height of 1m. Anti-collapse holes are poured as they are excavated. Reinforcing mesh is added to the soft soil layer. The formwork is removed 24 hours after the initial setting. S17: The steel cage is manufactured in sections, the main bars are rolled with threaded connections, the joint spacing is reasonable, and they are tightened with a torque wrench. After random inspection, the reinforcing bars are welded to make it firm and without defects. S18: The entire transport length is supported to prevent deformation, two-point hoisting maintains verticality, and in case of restrictions, it is hoisted and tied in sections. The top lifting rod prevents floating, and the concrete is poured in layers using a guide pipe.

6. The construction method for widening a highway using a half-bridge as described in claim 5, characterized in that: In step S15, the drilling diameter is 16cm and the drilling depth is 60cm. The drilling machine is set according to the pile diameter for each pile hole. In step S16, the template splicing must ensure roundness, the wall thickness is 15cm, the upper and lower sections overlap, the first section is made with a lock ring for waterproofing, and the concrete slump is 4-7cm.

7. The construction method for widening a highway using a half-bridge as described in claim 4, characterized in that: Step S2 is as follows: S21: Use a total station to accurately lay out the center of the pier location, and then report to the supervisor for review before construction; S22: Before pier construction, remove the laitance from the top of the pile, clean and keep it moist, and roughen and clean the joints as well. S23: The construction access uses a gantry-type safety ladder, which is assembled in sections, attached to the piers, and fixed with guy ropes; the verticality and stability are checked after each layer is erected, and safety nets and warning signs are set up around the perimeter. S24: The steel cage is centrally fabricated and spliced ​​on site, with the main bars connected by straight threads. Before hoisting, supports are welded on, and two-point hoisting is used. After positioning and correction, the cage is welded and fixed. S25: Remove rust from the standard steel formwork, apply release agent, and use segmented bolts for connection. Ensure precise positioning, seal gaps, and proceed with pouring after acceptance. S26: Pouring should be carried out after the formwork reinforcement is inspected and accepted. Pumping or hopper vibration should be used for layered compaction. Dedicated personnel should monitor the formwork deformation. The number of construction workers should not exceed 3. S27: Remove the formwork after the concrete strength reaches 2.5MPa. During the formwork removal process, collisions are strictly prohibited and a designated person must be in charge of directing the process.

8. The construction method for widening a highway using a half-bridge as described in claim 4, characterized in that: Step S3 is as follows: S31; Clean the ground surface behind the wall, excavate steps to ensure drainage, accurately lay out and verify, and promptly report any abnormalities to the design team. S32: Clear site debris, use machinery to excavate and treat hard rock layers, slope the slope and set up drainage measures, and strictly control its base size and elevation; S33: Re-inspect the bearing capacity and location of the foundation, and proceed with foundation construction after confirming that there are no errors; S34: After the steel reinforcement passes the re-inspection, it shall be tied according to the drawings, tied firmly and a protective layer shall be provided. S35: Formwork construction is carried out afterward: When supporting the formwork, first set up horizontal supports, then set up diagonal braces for fixation, and complete the layout and pre-inspection before installation; S36: Then pour concrete. Before pouring, confirm that the steel bars and formwork have passed the acceptance test, remove debris and water, and pour in layers. Strictly control the drop and layer thickness, and use immersion vibrator. S37: Rebar processing: Fabricate the retaining wall steel cage, remove impurities from the steel bar surface to keep it clean and undamaged; single-sided electric arc welding is used for welding hooks, the welding parts are reasonably staggered, and full binding is used to ensure the stability of the steel mesh structure; S38: Subsequently, a combination of steel pipes and timber formwork was used. The formwork was assembled in sections, and the positioning was adjusted by hanging lines. Steel pipe internal supports and through-wall bolts were installed at the top for fixing. Embedded parts were pre-processed and positioned to ensure convenient and accurate installation later. S39: After the template is installed, pour the concrete. During pouring, strictly control the free fall of the concrete. If the fall exceeds the free fall, set up a chute to divert the excess. The pouring shall be carried out in layers. After the concrete is poured, cover it immediately for moist curing. The curing time shall not be less than 7 days. S310: After the concrete strength reaches the design requirements, backfill the back of the wall with sandy soil that has good permeability and is free of organic matter, or with materials specified in the design.

9. The construction method for widening a highway using a half-bridge as described in claim 4, characterized in that: Step S4 is as follows: S41: Based on the design drawings, perform high-precision measurement and layout of the pile location and the center of the abutment location, and mark the reference axis and edge line of the U-shaped abutment. S42: After the pile foundation strength reaches the requirements, the reinforcement of the pile cap is tied. After the formwork is installed and accepted, the concrete is poured in layers. The U-shaped pile cap is constructed in sections and zones to ensure the quality of joint treatment and overall rigidity. S43: The height of the wall is divided into high and low sections according to the design elevation, and a segmented and layered pouring method is adopted to ensure the stability of the formwork and the compactness of the concrete; S44: After the concrete of the wall body reaches the design strength, the backfill soil behind the wall is carried out in layers. S45: After the main structure is completed, construct the auxiliary structures.

10. The construction method for widening a highway using a half-bridge as described in claim 4, characterized in that: Step S5 is as follows: S51: Remove loose soil, dangerous rocks, and weeds from the slope to ensure the working surface is clean and stable; S52: Drill holes according to the design layout, and use pneumatic drills or down-the-hole drills to construct anchor bolt holes. The hole depth is controlled according to the design requirements. S53: Weave φ6~φ8 steel bars into a mesh according to the design spacing, tie it to the slope anchor, and add connecting bars to strengthen the overall integrity if necessary; S54: Use wet spraying process, concrete grade is C20~C25, thickness is 5~8cm, spray evenly in layers, and control rebound rate; S55: Set up grass seed bags or hang vegetation mats in the sprayed area, and plant drought-resistant slope protection plants in combination with the nutrient soil pre-buried in the sprayed layer to promote vegetation restoration and soil and water conservation.

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