A bridge pile foundation reinforcement structure and method

Abstract

The present invention relates to a bridge pile foundation reinforcement structure and method. The method includes arranging new pile foundations on both sides in the transverse direction of the bridge, with the new pile foundations located outside the original pile foundations; connecting the pile tops of the new pile foundations on both sides to a steel cross beam respectively, and the steel cross beam is provided with extended reinforcement bars; arranging a support frame on the steel cross beam, with a jack arranged at the top of the support frame, and the jack acts on the bottom of the main beam. By jacking up with the jack, the main beam preloads the steel cross beam; arranging pile cap reinforcement bars and formwork around the steel cross beam, connecting the extended reinforcement bars and the pile cap reinforcement bars, implanting reinforcement bars in the pier body on the original pile foundation and connecting them to the pile cap reinforcement bars; pouring the pile cap and curing it to form, with the pile cap covering part of the pier body, and compensating the jack to maintain the original jacking force during the pouring process; removing the formwork of the pile cap, unloading the jack, and removing the support frame. The present invention realizes the simultaneous implementation of temporary and permanent reinforcement of the bridge through the combined force of the steel cross beam and the pile cap, ensures the safety of the bridge structure throughout the process, effectively controls the settlement or deformation of the bridge pile foundation, and avoids quality problems of the bridge.

Description

Technical Field

[0001] The present invention relates to the technical field of bridges, in particular to a bridge pile foundation reinforcement structure and method. Background Art

[0002] Many bridge structures adopt pile-column structures (single pile, double pile, triple pile), with the pile connected to the column, no crossbeam provided at the pile top, a capping beam provided at the column top, bearings provided on the capping beam, and a cast-in-place beam or a precast and then installed beam provided on the bearings. When quality defects such as concrete damage and steel bar exposure occur in the pile foundation after the operation of such bridges, or problems such as extrusion deformation and cracking occur due to the surrounding filling soil, etc., for example, in soft soil foundations, post-construction settlement occurs, the bearing capacity of the ground on the pile cap decreases, the pile cap deflects downward, the force on the original pile increases, resulting in a decrease in the bearing capacity of the pile foundation or bridge deviation, it is necessary to reinforce the pile foundation.

[0003] In the conventional bridge reinforcement process, generally, methods such as wrapping the original pile foundation with reinforced concrete and adding pile foundations and pile caps are adopted. However, during the reinforcement process, the original pile foundation is often disturbed or partially damaged. Moreover, due to the settlement of the added pile foundation and the downward deformation of the pile cap after the settlement of the soil mass below the added pile cap, both will cause an increase in the force on the original pile foundation, resulting in an increase in the force and deformation of the original pile foundation, leading to secondary disasters, which is a relatively dangerous project; in addition, the added reinforcement structure often cannot share the force of the original pile and cannot really play a reinforcement role at the beginning. Only when the original pile is damaged and generates downward deformation, can the added pile foundation, pile cap and other reinforcement structures bear the loads of the superstructure and vehicles, etc. At this time, the bridge pile foundation will have a large settlement or deformation, or a sharp deformation will cause bridge quality problems.

[0004] When the vertical distance between the beam bottom of the bridge and the ground is small, it is difficult or infeasible to add pile foundations directly below the bridge. It is necessary to add piles on the outside of the bridge and construct pile caps. When the transverse width of the bridge deck is large, the span of the pile cap in the transverse direction of the bridge is large. When using a conventional ordinary reinforced concrete pile cap, it is necessary to increase the cross-sectional size of the pile cap, and the downward deflection in the middle span is large. The original pile foundation shares a large part of the gravity of the pile cap, increasing the force on the original pile and the construction difficulty. It is not suitable and new technical solutions need to be studied. Summary of the Invention

[0005] The purpose of the present invention is to provide a bridge pile foundation reinforcement structure and method for the problems existing in the prior art.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect, the present invention provides a bridge pile foundation reinforcement method, including the following steps:

[0008] S1. Set new pile foundations on both sides in the transverse direction of the bridge, and the new pile foundations are located outside the corresponding original pile foundations;

[0009] S2. The pile tops of the new pile foundations on both sides are respectively connected to a steel cross beam, and the steel cross beam is provided with extended reinforcing bars.

[0010] S3. A support frame is arranged on the steel cross beam, a jack is arranged at the top of the support frame, the jack acts on the bottom of the main beam, and the main beam preloads the steel cross beam through the gravity of the support frame and the jacking force of the jack, so as to unload the original pile foundation and the pier.

[0011] S4. Tie bars and formwork of the bearing platform are arranged around the steel cross beam, the extended reinforcing bars are connected to the tie bars of the bearing platform, and reinforcing bars are implanted in the original pile foundation corresponding to the planned bearing platform and / or the pier on the original pile foundation and connected to the tie bars of the bearing platform.

[0012] S5. Pour the bearing platform and cure it to form, the bearing platform covers part of the pier, the oil pressure of the jack is compensated during the concrete pouring process to maintain the original jacking force, and the original jacking force compensation is completed before the concrete initial setting.

[0013] S6. Remove the formwork of the bearing platform, unload the jack, and remove the support frame.

[0014] Adopting a bridge pile foundation reinforcement method of the present invention, the steel cross beam is supported by the new pile foundation, the support frame and the jack are supported by the steel cross beam, and the main beam is supported by the jack to form a temporary reinforcement. Under the condition of unloading the original pile foundation and the pier, subsequent reinforcement is carried out safely. The bearing platform is consolidated by the steel cross beam, and the bearing platform is connected to the original pile foundation and / or the pier to form a permanent reinforcement. The steel cross beam and the bearing platform share the force, combining the temporary and permanent structures, realizing the simultaneous implementation of the temporary and permanent reinforcement of the bridge, ensuring the safety of the bridge structure during the whole process. The steel cross beam is preloaded through the action of the support frame and the jack to establish a permanent resilience force, and at the same time, the new pile foundation is preloaded to make its settlement stable, avoiding the increase of the force on the original pile foundation caused by the settlement of the bearing platform. After the permanent reinforcement is completed, the support frame and the jack of the temporary reinforcement are removed. After the support frame and the jack are removed and unloaded, the steel cross beam has a tendency of upward deformation due to the resilience force. The steel cross beam exists as a hidden beam in the bearing platform, establishing a vertically upward force in the bearing platform to support the pier, sharing the force on the original pile foundation, and at the same time supporting the bearing platform to avoid the increase of the force on the original pile foundation caused by the downward deformation of the bearing platform. Through the connection between the extended reinforcing bars and the tie bars of the bearing platform, the resilience force of the steel cross beam after the removal and unloading of the jack and the support frame is diffused in the bearing platform to avoid stress concentration. This method can effectively control the settlement or deformation of the bridge pile foundation and avoid safety problems of the bridge.

[0015] As a preferred technical solution of the present invention, in step S1, before the construction of the new pile foundation, the soft soil layer is grouted and hardened, and the grouting material can be cement slurry or cement slurry mixed with a quick-setting agent.

[0016] As a preferred technical solution of the present invention, in step S1, the new pile foundation adopts a bored cast-in-place concrete pile, and its steel reinforcement cage extends into the pile cap.

[0017] As a preferred technical solution of the present invention, in step S1, a connecting steel plate and the main reinforcement bars of the pile cap are embedded at the top of the new pile foundation, and the connecting steel plate is used to connect the steel cross beam.

[0018] As a preferred technical solution of the present invention, in step S3, the support frame includes a number of steel pipe columns symmetrically and evenly arranged relative to the mid-span of the steel cross beam, and a jack is arranged at the top of each steel pipe column.

[0019] By adopting this method, through the symmetrical and uniform arrangement of the steel pipe columns and the jacks, when the main beam applies a vertical preloading pressure to the steel cross beam, it is approximately equivalent to the action of a uniformly distributed force, avoiding the concentrated force and stress concentration of the steel cross beam.

[0020] As a further preferred technical solution of the present invention, the bottom of the steel pipe column is welded to the top of the steel cross beam;

[0021] In step S4, a filler is wrapped outside the steel pipe columns corresponding to the top surface of the pile cap;

[0022] In step S5, the pile cap completely wraps the steel cross beam;

[0023] In step S6, after the jacks are unloaded, the filler is removed to form a cutting groove on the top surface of the pile cap, the steel pipe columns in the cutting groove are cut, and concrete is poured to seal to the top surface of the pile cap.

[0024] By adopting this method, the positions of the new pile foundation and the steel cross beam are fixed by the pile cap, and the steel cross beam is completely wrapped to protect it from corrosion.

[0025] As a preferred technical solution of the present invention, in step S4, a layer of pile cap steel bars is arranged between the bottom formwork and the bottom surface of the steel cross beam to form a bottom layer of steel bars, the bottom layer of steel bars fits the bottom surface of the steel cross beam, and a layer of pile cap steel bars is arranged above the steel cross beam to form a top layer of steel bars, and there is a spacing between the top layer of steel bars and the top surface of the steel cross beam.

[0026] By adopting this method, the resilience force of the steel cross beam during the unloading of the pre-pressure is dispersed in the bearing platform through the bottom steel bars and the top steel bars, avoiding damage caused by the concentration of tensile stress or compressive stress around the steel cross beam in the bearing platform, continuously exerting the flexural capacity of the lower edge of the steel cross beam in tension after construction, realizing the coordinated deformation and joint force-bearing of the steel cross beam and the reinforced concrete. At the same time, due to the pre-pressure of the steel cross beam, after the pre-pressure is removed, the steel cross beam has an upward arching tendency, generating a jacking force on the concrete above the steel cross beam in the bearing platform. By setting the spacing between the top steel bars and the top surface of the steel cross beam, the thickness of the concrete on the top surface of the steel cross beam is increased, realizing the dispersion of the jacking force of the steel cross beam on the top concrete of the bearing platform at the top of the bearing platform, and avoiding cracking caused by concentrated force on the top surface of the bearing platform.

[0027] As a preferred technical solution of the present invention, after step S3 and before step S4, the top area of the original pile foundation is backfilled with an isolation layer; in step S6, after the formwork of the bearing platform is removed, a cushion layer is poured at the bottom of the bearing platform, and then the jack is unloaded;

[0028] Alternatively, after step S3 and before step S4, the top area of the original pile foundation is backfilled with an isolation layer, and a concrete cushion layer is poured on the isolation layer to the bottom of the planned bearing platform, and the cushion layer is directly used as the bottom formwork for the subsequent casting of the bearing platform.

[0029] By adopting this method, the isolation layer and the cushion layer isolate surface water and air from infiltrating into the original pile foundation, preventing or slowing down the corrosion of the reinforced concrete at the repaired or unrepaired parts of the original pile foundation below the bearing platform.

[0030] As a further preferred technical solution of the present invention, the isolation layer is made of a water-impermeable material.

[0031] As a further preferred technical solution of the present invention, the water-impermeable material is clay with a small permeability coefficient, with a thickness of 1 m, and is backfilled and compacted in layers.

[0032] As a preferred technical solution of the present invention, after step S5 and before step S6, steel bars are implanted in the pier body above the bearing platform, and a first outer reinforced concrete reinforcement is arranged outside the pier body.

[0033] Adopting this method, on the one hand, the pier body can be strengthened by the first outer reinforced concrete; on the other hand, after step S3 is completed, the load borne by the pier body from the upper part decreases, that is, the vertical pressure decreases, and the pier body generates a rebound elongation deformation. The first outer reinforced concrete is constructed when the pier body is in a relaxed state. During the unloading process of the jack in step S6, the main girder and other upper loads borne by the jack are transferred back to the pier body and the first outer reinforced concrete through the bearing. The pier body and the first outer reinforced concrete can deform together and bear the force synergistically. The load of the main girder can be transmitted to the bearing platform through the first outer reinforced concrete and the pier body, sharing the bearing capacity of the original pile foundation.

[0034] As a further preferred technical solution of the present invention, the thickness of the first outer reinforced concrete is 20 cm - 30 cm, and the bottom surface of the first outer reinforced concrete is connected to the bearing platform.

[0035] As a preferred technical solution of the present invention, the new pile foundation is located outside the vertical projection plane of the bridge deck.

[0036] Adopting this method can effectively increase the span of the bearing platform in the transverse direction of the bridge, and solve the problem that the distance between the bottom of the main girder and the ground is small, and it is difficult to construct pile foundations under the bridge for reinforcement.

[0037] In the second aspect, the present invention also provides a bridge pile foundation reinforcement structure, which is constructed by using the bridge pile foundation reinforcement method described in any one of the above.

[0038] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0039] 1. A method and structure for strengthening bridge pile foundations according to the present invention. The new pile foundation supports the steel cross beam, the steel cross beam supports the support frame and the jack, and the jack supports the main beam to form a temporary reinforcement. Subsequent reinforcement is safely carried out under the condition of unloading the original pile foundation and the pier body. The steel cross beam consolidates the bearing platform, and the bearing platform connects the original pile foundation and / or the pier body to form a permanent reinforcement. The steel cross beam and the bearing platform jointly bear the force, combining the temporary and permanent reinforcements, so as to implement the temporary and permanent reinforcements of the bridge simultaneously, ensuring the safety of the bridge structure throughout the process. Through the action of the support frame and the jack, the steel cross beam is preloaded to establish a permanent resilience force, and at the same time, the new pile foundation is preloaded to make its settlement stable, avoiding an increase in the force on the original pile foundation caused by the settlement of the bearing platform. After the permanent reinforcement is completed, the support frame and the jack for temporary reinforcement are removed. After the support frame and the jack are removed and unloaded, the steel cross beam has a tendency to deform upward due to the resilience force. The steel cross beam exists as a concealed beam in the bearing platform, establishing a vertically upward force in the bearing platform to support the pier body, sharing the force on the original pile foundation, and at the same time supporting the bearing platform to avoid an increase in the force on the original pile foundation caused by the downward deformation of the bearing platform. Through the connection of the extended steel bars and the steel bars of the bearing platform, the resilience force of the steel cross beam after the removal and unloading of the jack and the support frame is dispersed in the bearing platform, avoiding stress concentration. This method can effectively control the settlement or deformation of the bridge pile foundation and avoid safety problems of the bridge;

[0040] 2. A preferred method for strengthening bridge pile foundations according to the present invention. By symmetrically and uniformly arranging the steel pipe columns and the jacks, when the main beam applies a vertical preloading pressure to the steel cross beam, it is approximately a uniformly distributed force, avoiding concentrated force and stress concentration on the steel cross beam;

[0041] 3. A preferred method for strengthening bridge pile foundations according to the present invention. The position of the new pile foundation and the position of the steel cross beam are fixed by the bearing platform, and the steel cross beam is completely wrapped to protect it from corrosion;

[0042] 4. A preferred method for strengthening bridge pile foundations according to the present invention. Through the bottom layer of steel bars and the top layer of steel bars, the resilience force of the steel cross beam during the removal of the preloading force is dispersed in the bearing platform, avoiding damage caused by concentrated tensile stress or compressive stress around the steel cross beam in the bearing platform. After construction, the bending resistance of the lower edge of the steel cross beam in tension is continuously exerted, realizing the coordinated deformation and joint force of the steel cross beam and the reinforced concrete. At the same time, due to the preloading of the steel cross beam, after the preloading force is removed, the steel cross beam has a tendency to arch upward, generating a jacking force on the concrete above the steel cross beam in the bearing platform. By setting the spacing between the top layer of steel bars and the top surface of the steel cross beam, the thickness of the concrete on the top surface of the steel cross beam is increased, realizing the dispersion of the jacking force of the steel cross beam on the top concrete of the bearing platform at the top of the bearing platform, avoiding concentrated force and cracking on the top surface of the bearing platform;

[0043] 5. A preferred method for strengthening bridge pile foundations of the present invention isolates surface water and air from infiltrating into the original pile foundations through the isolation layer and the cushion layer, preventing or slowing down the corrosion of the reinforced concrete at the repaired or unrepaired parts of the original pile foundations below the bearing platform.

[0044] 6. A preferred method for strengthening bridge pile foundations of the present invention can, on the one hand, strengthen the pier body through the first outer-wrapped reinforced concrete, and on the other hand, after step S3 is completed, the bearing capacity of the pier body for the upper load decreases, that is, the vertical pressure decreases, and the pier body generates a rebound elongation deformation. The first outer-wrapped reinforced concrete is constructed under the relaxed state of the pier body. During the unloading process of the jack in step S6, the main beam and other upper loads borne by the jack are transferred back to the pier body and the first outer-wrapped reinforced concrete through the bearing. The pier body and the first outer-wrapped reinforced concrete can deform together and bear the force synergistically. The load of the main beam can be transmitted to the bearing platform through the first outer-wrapped reinforced concrete and the pier body, sharing the bearing capacity of the original pile foundation.

[0045] 7. A preferred method for strengthening bridge pile foundations of the present invention has the new pile foundation located outside the vertical projection plane of the bridge deck, which can effectively increase the span of the bearing platform in the transverse direction of the bridge, solving the problem that the distance between the bottom of the main beam and the ground is small and it is difficult to construct pile foundations under the bridge for reinforcement. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is an elevation view of the bridge pile foundation strengthening structure;

[0047] Figure 2 is Figure 1 side view of;

[0048] Figure 3 is Figure 1 A - A cross-sectional view in;

[0049] Reference numerals in the figure: 01 - original pile foundation, 02 - pier body, 03 - capping beam, 04 - main beam, 05 - bearing, 1 - new pile foundation, 2 - steel cross beam, 3 - steel secondary beam, 4 - bearing platform, 5 - support frame, 51 - steel pipe column, 52 - transverse connecting beam, 53 - diagonal brace, 54 - longitudinal connecting beam, 6 - distribution beam, 7 - jack, 8 - isolation layer, 9 - cushion layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] The present invention will be described in detail below with reference to the accompanying drawings.

[0051] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] Embodiment 1

[0053] As Figures 1 to 3 shown, a method for strengthening a bridge pile foundation according to the present invention, the bridge includes an original pile foundation 01, the original pile foundation 01 is connected to a pier body 02, a capping beam 03 is arranged at the top of the pier body 02, a bearing 05 is arranged on the capping beam 03, and a main beam 04 is arranged on the bearing 05. The method includes the following steps:

[0054] Step 1: As Figure 3 shown, two new pile foundations 1 are respectively arranged on both sides in the transverse bridge direction. The new pile foundations 1 are located outside the corresponding original pile foundations 01, and the new pile foundations 1 are symmetrically arranged along the longitudinal bridge direction on both sides of the original pile foundation 01. There are a total of four new pile foundations 1. Specifically, the new pile foundations 1 adopt bored concrete cast-in-place piles, and their steel reinforcement cages extend into the pile cap. The pile tops of the new pile foundations 1 are treated for pile connection, that is, connection steel plates and pile cap main reinforcement are embedded at the pile tops of the new pile foundations 1. Before the construction of the new pile foundations 1, the soft soil layer is grouted and hardened, and the grouting material can be cement slurry or cement slurry mixed with a quick-setting agent.

[0055] Specifically, the connection steel plate is provided with anchor bars. The length of the anchor bars is 90 cm. The top ends of the anchor bars are bent into an "L" shape and welded to the bottom surface of the connection steel plate. The lower ends of the anchor bars are hooked, and the anchor bars extend into the new pile foundation 1. The connection steel plate is circular, and the diameter of the connection steel plate is 5 cm - 10 cm smaller than the inner diameter of the steel reinforcement cage of the new pile foundation 1.

[0056] The method for embedding the connection steel plate: After the construction of the bored concrete cast-in-place pile is completed, the pile head concrete about 1 m below the bottom surface of the proposed pile cap is chiseled off, and then the bottom layer steel bars located below the connection steel plate are installed and fixed, and then the connection steel plate is installed and fixed thereon. The top surfaces of the same connection steel plate are required to be horizontal, and the connection steel plates on different new pile foundations 1 are required to be at the same elevation. The connection steel plate is located inside the steel reinforcement cage of the new pile foundation 1. Finally, the pile connection formwork is installed, and the pile connection concrete is poured. The elevation of the top surface of the pile connection concrete is flush with the top surface of the connection steel plate.

[0057] Step 2: As Figure 1As shown in the figure, the pile tops of two corresponding new pile foundations 1 on both sides of the transverse bridge direction are welded with a steel cross beam 2 through the connecting steel plates, that is, two steel cross beams 2 are arranged on the four new pile foundations 1. The two steel cross beams 2 are arranged at intervals along the longitudinal bridge direction. Each steel cross beam 2 is arranged in the transverse bridge direction and is located on both sides of the original pile foundation 01 respectively. Specifically, the steel cross beam 2 can be a single H-shaped steel or two H-shaped steels spliced together; several extended steel bars are provided on the steel cross beam 2, and an embedded dynamometer is also provided on the steel cross beam 2 to continuously monitor the stress value of the steel cross beam 2.

[0058] As Figure 2 and Figure 3 shown in the figure, the two steel cross beams 2 are connected by several steel secondary beams 3. The steel secondary beams 3 are used to control the lateral deformation of the steel cross beams 2. In this embodiment, two steel secondary beams 3 and two steel cross beams 2 are used to form a rectangular frame. The top and bottom surfaces of the steel secondary beams 3 do not exceed the height range of the steel cross beams 2.

[0059] Among them, when the steel cross beam 2 conflicts with some of the steel bars of the steel cage where the new pile foundation 1 extends into the bearing platform 4 during installation, the method of cutting off some steel bars or adjusting the positions of the steel bars can be adopted. The steel cross beam 2 and the connecting steel plate are fixed by welding.

[0060] Step 3: Set up a support frame 5 on the steel cross beam 2. As Figures 1 to 3 shown in the figure, the support frame 5 includes several steel pipe columns 51 that are symmetric and evenly arranged relative to the mid-span of the steel cross beam 2. The two ends of the steel pipe column 51 have end sealing steel plates. The bottom of the steel pipe column 51 is welded to the top of the steel cross beam 2. The adjacent steel pipe columns 51 on each steel cross beam 2 are connected by a transverse connecting beam 52 and a diagonal brace 53. The corresponding steel pipe columns 51 between the two steel cross beams 2 are connected by a longitudinal connecting beam 54 to form an integral body, enhancing the stability of the support frame 5 and reducing deformation. A distribution beam 6 is arranged at the top of the corresponding steel pipe columns 51 between the two steel cross beams 2, and a jack 7 is arranged on the distribution beam 6. One jack 7 is correspondingly arranged at the top of each steel pipe column 51. All the jacks 7 act on the bottom of the main beam 04. The main beam 04 preloads the steel cross beam 2 through the gravity of the support frame 5 and the jacking force of the jacks 7, unloading the original pile foundation 01 and the pier body 02.

[0061] Among them, the bottom of the steel pipe column 51 is located inside the bearing platform 4, and the rest of the steel pipe column 51, the transverse connecting beam 52, the diagonal brace 53 and the longitudinal connecting beam 54 are all located above the bearing platform 4.

[0062] In this embodiment, no less than three and an odd number of the steel pipe columns 51 are adopted on a single steel cross beam 2, for example, three, five or seven are adopted. The steel pipe columns 51 are symmetrically and uniformly arranged relative to the center line of the bridge in the transverse direction. By using this method, through the symmetrical and uniform arrangement of the steel pipe columns 51 and the jacks 7, when the main beam 04 applies a vertical preloading pressure to the steel cross beam 2, it is approximately a uniformly distributed force, avoiding the concentrated force on the steel cross beam 2 and the generation of stress concentration.

[0063] After the support frame 5 is installed in place, the steel cross beam 2 bears its weight, that is, a first-stage vertical preloading force F1 is applied to the steel cross beam 2, and the steel cross beam 2 deflects downward.

[0064] The jacks 7 apply a jacking force in stages, that is, a second-stage vertical preloading force F2 is applied to the steel cross beam 2. The steel cross beam 2 continues to deflect downward and preloads the new pile foundation 1, enabling the new pile foundation 1 to complete most of the settlement deformation, reducing the post-construction settlement, and at the same time reducing the bearing capacity of the original pile foundation 01, avoiding the damage of the bridge during the reinforcement process and playing a role in temporary reinforcement.

[0065] The oil pipes of all the jacks 7 on the same pier where the pier body 02 is located are connected in series for synchronous jacking, avoiding uneven force on the main beam 04 and the generation of concrete cracking and damage.

[0066] The maximum value of the sum of the jacking forces of all the jacks 7 is controlled within 50% - 95% of half of the sum of the weights of the main beams 04 of the front and rear spans borne by the pier body 02, and the bottom surface of the main beam 04 is not allowed to be separated from the bearing 05 to maintain the stability of the main beam 04.

[0067] Step 4: Excavate a foundation pit around the original pile foundation 01 to deal with the defects of the part of the original pile foundation 01 below the ground surface. Possible defects include exposed reinforcement and necking down. The original pile foundation 01 can be reinforced by using a second layer of reinforced concrete wrapped around it. The base is grouted to harden the soft soil layer, and the top area of the original pile foundation 01 is backfilled with a replacement layer 8. The isolation layer 8 uses an impermeable material, such as clay with a small permeability coefficient, with a thickness of 1 m, and is backfilled and tamped in layers.

[0068] Apply a third-stage vertical pre-pressure F3 to the steel cross beam 2, where F3 is equal to a part of the gravity of the bearing platform 4 (without considering the gravity of the steel cross beam 2). Let the total gravity of the bearing platform 4 be G. When all the gravity of the bearing platform 4 is borne by the new pile foundation 1, the new pile foundation 1 bears the gravity G of the bearing platform 4. When calculating the force borne by the new pile foundation 1 when the gravity of the bearing platform 4 is jointly supported by the new pile foundation 1 and the original pile foundation 01, the force borne by the new pile foundation 1 is G1, and the original pile foundation 01 bears the gravity G2 of the bearing platform 4 = G - G1. Apply a pre-pressure F3 = G2 to the steel cross beam 2. When there are N steel pipe columns 51, the pressure applied to each steel pipe column 51 is F3 / N, which is evenly distributed. It is realized that after the concrete of the bearing platform 4 is poured, the force borne by the original pile foundation 01 is borne by the steel cross beam 2. When the foundation under the bottom surface of the bearing platform 4 sinks, it is avoided that after the upward bearing force of the ground on the bearing platform 4 decreases due to the foundation settlement, this part of the reduced bearing force is transferred to the original pile foundation 01 to bear, which is beneficial to protecting the defective original pile foundation 01 and avoiding the increase of bridge deformation.

[0069] Among them, when F2 + F3 > the sum of the gravity G5 of (the main beam 04 + bridge deck paving + road surface), preloading measures are taken. Preloading can be carried out on the bridge deck above the corresponding steel pipe columns 51. The gravity of the preloading object is G6, G6 > F2 + F3 - G5, and G6 can be taken as 1.1(F2 + F3 - G5).

[0070] Before construction, conduct structural design and stress calculation on the steel cross beam 2. After the three-stage pre-pressure application to the steel cross beam 2 is completed above, the tensile stress at the lower edge of the steel cross beam 2 < 75% of the allowable tensile stress of the steel, so that the steel cross beam 2 is in an elastic stress state and maintains a certain margin of bearing capacity.

[0071] The structural stress calculation of the steel cross beam 2 and the composite structure stress of the steel cross beam 2 and the bearing platform 4 can be calculated by modeling with software such as structural mechanics or MIDAS.

[0072] Step five: Set up bearing platform steel bars and formwork around the steel cross beam 2. Wrap fillers outside the corresponding steel pipe columns 51 on the top surface of the bearing platform 4. The fillers are made of easily removable materials such as foam plastic or sponge. Connect the extended steel bars and the bearing platform steel bars. Anchor steel bars in the pier 02 and connect the bearing platform steel bars. All the steel bar connections can facilitate the formation of a community after the concrete is poured, coordinate deformation, and jointly bear force. Among them, the thickness of the filler is 5 cm - 10 cm, and the height below the top surface elevation of the bearing platform 4 is 10 cm, that is, the height extending into the bearing platform 4 is 10 cm.

[0073] Among them, a layer of the cap steel bar is arranged between the bottom form and the bottom surface of the steel beam 2 to form a bottom steel bar, the bottom steel bar fits the bottom surface of the steel beam 2, the connecting steel plate is located above the bottom steel bar, and a layer of the cap steel bar is arranged above the steel beam 2 to form a top steel bar, and there is a distance between the top steel bar and the top surface of the steel beam 2. By adopting this method, the rebound force of the steel beam 2 during the pre-stressing process is dispersed in the cap 4 through the bottom steel bar and the top steel bar, so as to avoid the tensile stress or compressive stress of the concrete around the steel beam 2 in the cap 4. Damage, after construction, the bending resistance of the lower edge of the steel beam 2 under tension continues to be exerted, so that the steel beam 2 and the reinforced concrete are deformed in coordination and bear the force together. At the same time, due to the pre-stress of the steel beam 2, the steel beam 2 has a tendency to arch upward after the pre-stress is removed, and a lifting force is generated on the concrete of the pedestal 4 located above the steel beam 2. By setting the distance between the top layer of steel bars and the top surface of the steel beam 2, the thickness of the concrete on the top surface of the steel beam 2 is increased, so that the lifting force of the steel beam 2 on the concrete on the top of the pedestal 4 is dispersed on the top of the pedestal 4, thereby avoiding concentrated force on the top surface of the pedestal 4 and cracking.

[0074] Step six, pour the pedestal 4 and cure it into shape, the pedestal 4 completely wraps the steel beam 2, the pedestal 4 covers part of the pier body 02 or the pedestal 4 covers part of the pier body 02 and part of the original pile foundation 01, during the pouring process, the pedestal bottom formwork will sink under the vertical pressure of the newly poured concrete, the pedestal steel bars will sink and drive the steel beam 2 to deflect downward, and some concrete will directly press on the steel beam 2 and cause deflection, the support frame 5 will deform downward, and the jacking force of the jack 7 will become smaller. At this time, the oil pump should be started to compensate the oil pressure of the jack 7 to maintain the original lifting force.

[0075] Step seven, embedding reinforcement in the pier body 02 above the cap 4, and setting a first outer reinforced concrete reinforcement outside the pier body 02. With this method, the pier body 02 can be reinforced by the first outer reinforced concrete on the one hand, and on the other hand, after the completion of step S3, the upper load borne by the pier body 02 is reduced, that is, the vertical pressure is reduced, and the pier body 02 rebounds and stretches. The first outer reinforced concrete is applied when the pier body 02 is in a relaxed state. During the unloading process of the jack 7 in step S6, the main beam 04 and other upper loads borne by the jack 7 are transferred to the pier body 02 and the first outer reinforced concrete through the support 05 again. The pier body 02 and the first outer reinforced concrete can deform and bear force together. The load of the main beam 04 can be transmitted to the cap 4 through the first outer reinforced concrete and the pier body 02 to share the bearing force of the original pile foundation 01.

[0076] Step 8: Demold the bearing platform 4, and pour a concrete cushion layer 9 at the bottom of the bearing platform 4. By using this method, the surface water and air are isolated from infiltrating into the original pile foundation 01 through the isolation layer 8 and the cushion layer 9, preventing or slowing down the corrosion of the reinforced concrete at the repaired or unrepaired parts of the original pile foundation 01 below the bearing platform 4.

[0077] The jack 7 is unloaded in stages, and the steel cross beam 2 builds up a vertical pre-pressure, that is, an upward resilience force, and there is a tendency to rebound upward. With the staged unloading, the steel cross beam 2 generates an upward jacking force on the bearing platform 4 in stages, preventing or reducing the settlement of the bearing platform 4, realizing the reduction of the force on the original pile foundation 01, and sharing all or part of the upper load of the bridge.

[0078] The unloading of the jack 7 is divided into three steps, with a certain time interval between each step, preferably not less than 6 hours, so as to carry out the next step of unloading after the deformation of the bridge structure is stable, avoiding the sudden deformation of the bridge structure, including:

[0079] 1. Start the oil return of the oil pump of the jack 7, and the unloading value is equal to F3. When there are N jacks 7, the unloading of each jack 7 is F3 / N. The oil pipes of all the jacks 7 are connected in series, and they are unloaded synchronously in stages, and the deck ballast is removed synchronously;

[0080] 2. Start the oil return of the oil pump of the jack 7, and the unloading value is equal to F2. When there are N jacks 7, the unloading of each jack 7 is F2 / N. The oil pipes of all the jacks 7 are connected in series, and they are unloaded synchronously in stages, and the deck ballast is removed synchronously;

[0081] 3. Remove the support frame 5 above the top surface of the bearing platform 4 to complete the unloading of the steel cross beam 2, and the steel cross beam 2 builds up a vertical resilience force.

[0082] Remove the filler to form a cutting groove on the top surface of the bearing platform 4, use oxygen welding to cut the steel pipe column 51 at the bottom of the cutting groove to form a hole, restore the top layer steel bars of the bearing platform 4, and pour concrete into the hole until it seals the top surface of the bearing platform 4. By using this method, the positions of the new pile foundation 1 and the steel cross beam 2 are fixed by the bearing platform 4, and the steel cross beam 2 is completely wrapped to protect it from corrosion.

[0083] For the original pile foundation 01, it can be cut off or not cut.

[0084] A method for strengthening bridge pile foundations according to this embodiment supports the steel cross beam 2 through the new pile foundation 1, supports the support frame 5 and the jack 7 through the steel cross beam 2, and supports the main beam 04 through the jack 7 to form temporary strengthening. Subsequent strengthening is safely carried out under the condition of unloading the original pile foundation 01 and the pier body 02. The steel cross beam 2 consolidates the bearing platform 4, and the bearing platform 4 connects the original pile foundation 01 and / or the pier body 02 to form permanent strengthening. The steel cross beam 2 and the bearing platform 4 share the force, combining temporary and permanent strengthening, realizing the simultaneous implementation of temporary and permanent strengthening of the bridge, ensuring the safety of the bridge structure throughout the process. Through the action of the support frame 5 and the jack 7, the steel cross beam 2 is preloaded to establish a permanent resilience force, and at the same time, the new pile foundation 1 is preloaded to make its settlement stable, avoiding the increase in the force on the original pile foundation 01 caused by the settlement of the bearing platform 4. After the permanent strengthening is completed, the temporary strengthening is removed. After the jack 7 is unloaded, the steel cross beam 2 has a tendency to deform upward due to the resilience force. The steel cross beam 2 exists as a concealed beam in the bearing platform 4, establishing a vertically upward force in the bearing platform 4 to support the pier body 02, sharing the force on the original pile foundation 01, and at the same time supporting the bearing platform 4, avoiding the increase in the force on the original pile foundation 01 caused by the downward deformation of the bearing platform 4. Through the connection of the extended steel bars and the bearing platform steel bars, the resilience force of the steel cross beam 2 after the removal and unloading of the jack 7 and the support frame 5 is diffused in the bearing platform 4, avoiding stress concentration. This method can effectively control the settlement or deformation of bridge pile foundations and avoid safety problems of the bridge.

[0085] Embodiment 2

[0086] A method for strengthening bridge pile foundations according to the present invention is different from Embodiment 1 in that, in this embodiment, after the isolation layer 8 is constructed, a concrete cushion 9 is poured on the isolation layer 8 to the bottom of the proposed bearing platform 4, and the cushion 9 is directly used as the bottom form for the subsequent casting of the bearing platform 4.

[0087] Embodiment 3

[0088] A method for strengthening bridge pile foundations according to the present invention is different from Embodiment 1 or Embodiment 2 in that, in this embodiment, the new pile foundation 1 is located outside the vertical projection plane of the bridge deck.

[0089] Adopting this method can effectively increase the span of the bearing platform 4 in the transverse direction of the bridge, solving the problem that the distance between the bottom of the main beam 04 and the ground is small and it is difficult to construct pile foundations under the bridge for strengthening.

[0090] Embodiment 4

[0091] As Figures 1 to 3 shown, a bridge pile foundation strengthening structure according to the present invention is constructed by using the bridge pile foundation strengthening method according to any one of Embodiments 1 to 3.

[0092] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for strengthening bridge pile foundations, characterized in that, It includes the following steps: S1. New pile foundations (1) are arranged on both sides in the transverse bridge direction, and the new pile foundations (1) are located outside the corresponding original pile foundations (01). S2. The pile tops of the new pile foundations (1) on both sides are respectively connected to a steel cross beam (2), and the steel cross beam (2) is provided with extended reinforcing bars. S3. A support frame (5) is arranged on the steel cross beam (2), a jack (7) is arranged at the top of the support frame (5), the jack (7) acts on the bottom of the main beam (04), and the main beam (04) pre-presses the steel cross beam (2) through the gravity of the support frame (5) and the jacking force of the jack (7). S4. A bearing platform steel bar and a formwork are arranged around the steel cross beam (2), the extended reinforcing bars are connected to the bearing platform steel bar, and steel bars are implanted and connected to the bearing platform steel bar on the corresponding original pile foundation (01) and / or the pier body (02) on the original pile foundation (01) where the bearing platform (4) is to be arranged. S5. The bearing platform (4) is poured and cured to form, the bearing platform (4) covers part of the pier body (02), and the oil pressure of the jack (7) is compensated during the concrete pouring process to maintain the original jacking force. S6. The formwork of the bearing platform (4) is removed, the jack (7) is unloaded, and the support frame (5) is removed.

2. The bridge pile foundation reinforcement method according to claim 1, characterized in that In step S1, the soft soil layer is grouted and hardened before the construction of the new pile foundation (1).

3. The bridge pile foundation reinforcement method according to claim 1, characterized in that In step S1, a connecting steel plate and main bearing platform reinforcing bars are embedded at the pile top of the new pile foundation (1).

4. The bridge pile foundation reinforcement method according to claim 1, characterized in that, In step S3, the support frame (5) includes a plurality of steel pipe columns (51) symmetrically and evenly arranged relative to the mid-span of the steel cross beam (2), and one jack (7) is arranged at the top of each steel pipe column (51).

5. The bridge pile foundation reinforcement method according to claim 4, characterized in that, The bottom of the steel pipe column (51) is welded to the top of the steel cross beam (2). In step S4, a filler is wrapped outside the steel pipe column (51) corresponding to the top surface of the bearing platform (4). In step S5, the bearing platform (4) completely covers the steel cross beam (2). In step S6, after the jack (7) is unloaded, the filler is removed to form a cutting groove on the top surface of the bearing platform (4), the steel pipe column (51) in the cutting groove is cut, and concrete is poured to seal to the top surface of the bearing platform (4).

6. The bridge pile foundation reinforcement method according to claim 1, characterized in that In step S4, a layer of bearing platform steel bars is arranged between the bottom formwork and the bottom surface of the steel cross beam (2) to form a bottom layer of steel bars, the bottom layer of steel bars fits the bottom surface of the steel cross beam (2), a layer of bearing platform steel bars is arranged above the steel cross beam (2) to form a top layer of steel bars, and there is a spacing between the top layer of steel bars and the top surface of the steel cross beam (2).

7. The bridge pile foundation reinforcement method according to claim 1, characterized in that Before step S4 after step S3, the top area of the original pile foundation (01) is backfilled with an isolation layer (8); in step S6, after the formwork of the bearing platform (4) is removed, a cushion layer (9) is poured at the bottom of the bearing platform (4), and then the jack (7) is unloaded. Or, before step S4 after step S3, the top area of the original pile foundation (01) is backfilled with an isolation layer (8), and a concrete cushion layer (9) is poured on the isolation layer (8) to the bottom of the planned bearing platform (4), and the cushion layer (9) is directly used as the bottom formwork for the subsequent pouring and forming of the bearing platform (4).

8. The bridge pile foundation reinforcement method according to claim 1, characterized in that, After step S5 and before step S6, reinforce bars are planted in the pier shaft (02) above the pile cap (4), and a first externally wrapped reinforced concrete reinforcement is provided outside the pier shaft (02).

9. The bridge pile foundation reinforcement method according to any one of claims 1-8, characterized in that, The new pile foundation (1) is located outside the vertical projection plane of the bridge deck.

10. A bridge pile foundation reinforcement structure, characterized in that, The construction is carried out by using the bridge pile foundation reinforcement method according to any one of claims 1-9.

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