Design and construction method for temporary pushing pier with high bearing capacity in water

Abstract

The invention belongs to the field of bridge construction, and provides an underwater high-bearing-capacity incremental launching temporary pier design and construction method which comprises the following steps that S1, a main trestle serves as a working face, and a branch trestle is built; s2, a branch trestle is used as a first construction platform for construction, multiple rows of steel casings are fixed to a riverbed rock stratum, then a drilling platform is fixed to the upper ends of the steel casings, and a second construction platform is formed; s3, the drilling equipment conducts construction on the steel casings on the second construction platform to form a temporary pier lower structure, the drilling platform on the last steel casing is dismantled after construction is completed, and then the steel casings in the row are pulled out; and S4, the second construction platform is dismantled in a retreating mode, construction of the lower portion of the temporary pier lower portion structure is synchronously completed, after all the construction platforms are dismantled, the temporary pier upper portion structure is constructed, and finally the branch trestle is dismantled. The drilling pile steel casing can be fully reused to serve as a drilling operation platform supporting pile, the construction difficulty is small, and the method adapts to the working conditions of different riverbed flatness, different covering layer thicknesses and different bedrock strengths.

Description

Technical Field

[0001] The invention belongs to the field of bridge construction, and in particular relates to a design and construction method of a temporary underwater high-bearing-capacity jacking pier. Background Art

[0002] Temporary piers, as temporary load-bearing structures for bridge construction, are crucial. Currently, floating installation methods are often used for underwater pier substructures. This involves using a floating crane and a vibratory hammer to drive steel pipe piles. Alternatively, pontoons, drilling rigs, and other temporary structures are used to construct the temporary pier substructure, which is constructed from piles to caps, steel columns, and then bored piles connected to steel pipe columns. When the riverbed is flat, a pre-assembled bottom frame is used. After being lowered using a pontoon and lifting equipment, the steel pipes for the temporary pier substructure are positioned and temporarily secured. A drill is then installed at the top of the steel pipes, mortar anchors are installed, and concrete is poured into the pipes to form the foundation for the temporary pier substructure.

[0003] However, these methods are only technically and economically viable when large pontoons and floating cranes are available for construction, and the construction site has good floating transportation conditions. However, for inland cities where the water system, upstream and downstream, lacks navigational conditions, or where navigation standards are limited and no existing docks are available, the pontoons and floating cranes must be transported to the construction site in sections, and a high-capacity, large-scale lifting platform is required to launch and place them into service. Furthermore, water operations are significantly affected by weather and flood seasons, and construction efficiency is lower than onshore or on construction platforms. Therefore, these solutions are generally technically and economically unsuitable.

[0004] Therefore, when the use of large floating cranes and pontoons is limited or the technical and economic feasibility is poor at the construction site, and a high-bearing-capacity temporary pier substructure must be set up, a temporary trestle and drilling operation platform must be set up as temporary structures for auxiliary pier construction.

[0005] The substructure of the temporary piers is constructed using a pile-cap-steel column structure, but this process is complex and requires the installation of a cofferdam. The integral placement of prefabricated caps places excessively high load-bearing capacity demands on the temporary trestle and platform, and requires the deployment of large-scale lifting equipment, resulting in poor overall technical and economic efficiency. Furthermore, when the substructure of the temporary piers is constructed using bored cast-in-place piles connected to steel pipe piles, there is no standard method to follow for formulating design parameters. The construction method is also incomplete in terms of process settings and construction structure treatment methods, and is poorly adaptable to different geological and riverbed conditions. It requires the installation of a large number of redundant working platform structures, and often requires the segmented casting of bored piles, segmented extension of steel pipe piles, and underwater cutting of steel casings for removal after the pile foundation concrete has solidified. The overall technical and economic efficiency of this construction method needs to be improved, and construction quality control is difficult, making its implementation difficult. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a design and construction method for high-bearing-capacity temporary jacking piers in water, which can fully reuse the bored pile steel casing as the supporting pile of the drilling operation platform, reduce underwater cutting operations by setting the pile foundation pouring buffer section, and at the same time, has low construction difficulty and is adaptable to working conditions with different riverbed flatness, different cover layer thickness, and different bedrock strength.

[0007] The technical solution of the present invention comprises the following steps: S1: Build a main trestle on one side of the existing bridge section, and build a branch trestle on the main trestle. The branch trestle is perpendicular to the main trestle and is located in the direction of the existing bridge section to be extended.

[0008] S2: Construction is carried out with the supporting trestle as the first construction platform. A row of steel casings is fixed on the riverbed rock layer, and the arrangement direction of the row of steel casings is perpendicular to the main trestle. Then a drilling platform is fixed to the upper end of the steel casings to form a second construction platform. Then, multiple rows of steel casings are fixed in sequence on the second construction platform, and the length of the second construction platform is gradually extended until the construction conditions are met.

[0009] S3: The drilling equipment constructs the last row of steel casings on the second construction platform to form the first row of temporary pier substructures. After the construction is completed, the drilling platform on the last row of steel casings is removed, and then the steel casings in that row are pulled out. Each row of steel casings is constructed in turn to form the temporary pier substructure, and the corresponding steel casings are removed.

[0010] S4: After all the steel casings are removed, the temporary pier superstructure will be installed on all the temporary pier substructures, and finally the supporting trestle will be removed.

[0011] Furthermore, in step S2, the bottom of the steel casing extends into the riverbed rock layer by 50 cm to 100 cm.

[0012] Furthermore, in step S2, the upper ends of all steel casings are at the same horizontal plane.

[0013] Furthermore, in step S3, the drilling equipment constructs the last row of steel casings on the second construction platform to form the first row of temporary pier substructures, including the following steps: S31: Use drilling equipment to drill holes into the riverbed rock layer inside the steel casing to the bottom elevation of the bored cast-in-place piles of the temporary pier substructure.

[0014] S32: The steel pipe is inserted into the steel casing, and the upper end of the steel pipe is connected to the upper end of the steel casing with a gap between the steel pipe and the steel casing, and the lower end of the steel pipe extends out of the lower end of the steel casing and enters the drill hole.

[0015] S33: The concrete pouring guide tube is extended into the borehole through the steel pipe pile and concrete is poured.

[0016] S34: After the concrete solidifies, fill the gap between the steel casing and the steel pipe with backfill material to the riverbed surface.

[0017] S35: After the backfill is filled, the steel pipe and the steel casing are disassembled, and finally the steel casing is pulled out.

[0018] Furthermore, in step S32, a plurality of limiting ribs are provided on the lower end of the steel pipe along the circumferential direction, and the limiting ribs are perpendicular to the side wall of the steel pipe.

[0019] Furthermore, in step S32, a reinforced steel sleeve is fixedly sleeved on the lower end of the steel pipe, and a plurality of welding nails are fixed to the reinforced steel sleeve along the circumferential direction, and the welding nails are perpendicular to the side wall of the reinforced steel sleeve.

[0020] Furthermore, in step S32, the lower end of the steel pipe is located at least 3 meters below the steel casing.

[0021] Furthermore, in step S33, concrete is poured to a depth between 0.5 meters and 1 meter below the steel casing.

[0022] Furthermore, in step S2, the drilling platform is connected to the steel casing through a plurality of bracket structures.

[0023] Furthermore, in step S2, a gap of 10 mm to 20 mm is provided between two adjacent corbel structures on the two steel casings.

[0024] The technical solution provided by the present invention has the following advantages compared with the prior art: A main trestle is built on one side of the constructed bridge section, and a branch trestle is built on the main trestle. The branch trestle is perpendicular to the main trestle and is located on one side of the bridge. Construction is carried out with the branch trestle as the first construction platform. A row of steel casings is fixed to the riverbed rock layer, and then a drilling platform is fixed to the upper end of the steel casings to form a second construction platform. Construction is then carried out on the second construction platform, and the above method is repeated to enter the next construction cycle. The length of the second construction platform is gradually extended until the construction conditions are met. The drilling equipment constructs the last row of steel casings on the second construction platform, and then retreats to form a temporary pier lower structure. Wait for the temporary pier lower structure to be completed. After the structural construction is completed, the drilling platform on the last row of steel casings is removed, and then the steel casings in this row are pulled out. The above method is repeated to enter the next construction cycle, and all steel casings are removed in turn. After all steel casings are removed, the temporary pier superstructure is installed on all temporary pier substructures, and finally the supporting trestle is removed. Compared with the existing technology, the present invention does not require large-scale lifting equipment, and can fully reuse steel casings as supporting piles for drilling work platforms. By setting a pile foundation pouring buffer section, underwater cutting operations are reduced. At the same time, the construction difficulty is small, and it is adaptable to working conditions with different riverbed flatness, different cover layer thickness, and different bedrock strength.

[0025] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 The construction of one embodiment of the present invention Figure 1 ; Figure 2 The construction of one embodiment of the present invention Figure 2 ; Figure 3 for Figure 1 Sectional view of the middle AA part; Figure 4 The construction of one embodiment of the present invention Figure 3 ; Figure 5 The construction of one embodiment of the present invention Figure 4 ; Figure 6 This is a construction drawing of a temporary pier substructure according to one embodiment of the present invention; Figure 7 for Figure 6 Cross-section of the middle BB portion; Figure 8 for Figure 6 Cross-section of the middle CC section; Figure 9 for Figure 6 Cross-section of the middle DD part; Figure 10 for Figure 6 Enlarged view of point E in the middle; Figure 11 for Figure 6 Enlarged view of point F in the middle.

[0028] Reference numerals: 1. Main trestle; 2. Support trestle; 3. Steel casing; 4. Drilling platform; 5. Steel pipe; 6. Support ribs; 7. Concrete; 8. Backfill; 9. Limiting bars; 10. Reinforced steel sleeve; 11. Welding nails; 12. Corbel structure; 13. Steel sections; 14. Channel steel; 15. Temporary pier substructure; 16. Anti-tension and anti-compression ring ribs; 17. Limiting steel plates. DETAILED DESCRIPTION

[0029] A specific embodiment of the present invention is described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiment.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the technical solutions of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0031] In the description of the embodiments of the present invention, unless otherwise specified, “a plurality of” means two or more.

[0032] like Figures 1 to 11 As shown, the present invention provides a design and construction method for a high-bearing capacity underwater jacking temporary pier, comprising the following steps: S1: Build a main trestle 1 on one side of the constructed bridge portion, and construct a branch trestle 2 on the main trestle 1. The branch trestle 2 is perpendicular to the main trestle 1 and is located in the direction of the existing bridge portion to be extended.

[0033] S2: Construction is carried out with the supporting trestle 2 as the first construction platform. A row of steel casings 3 is fixed on the riverbed rock layer, and the arrangement direction of the row of steel casings 3 is perpendicular to the main trestle 1. Then, a drilling platform 4 is fixed to the upper end of the steel casings 3 to form a second construction platform. Then, multiple rows of steel casings 3 are fixed in sequence on the second construction platform, and the length of the second construction platform is gradually extended until the construction conditions are met.

[0034] S3: The drilling equipment constructs the last row of steel casings 3 on the second construction platform to form the first row of temporary pier substructures 15. After the construction is completed, the drilling platform 4 on the last row of steel casings 3 is removed, and then the steel casings 3 of this row are pulled out. Each row of steel casings 3 is constructed in turn to form a temporary pier substructure 15, and the corresponding steel casings 3 are removed.

[0035] S4: After all the steel casings 3 are removed, the temporary pier superstructure is installed on all the temporary pier substructures 15, and finally the supporting trestle 2 is removed.

[0036] The present invention does not require large-scale lifting equipment and can fully reuse the steel casing 3 as a supporting pile for the drilling work platform. By setting a pile foundation pouring buffer section, underwater cutting operations are reduced. At the same time, the construction difficulty is small and it is adaptable to working conditions with different riverbed flatness, different cover layer thickness, and different bedrock strength.

[0037] Specifically, the steel casing 3 is directly used as the supporting pile of the drilling operation platform. Considering the stability of the hole wall during the drilling operation, it is advisable to use a steel casing 3 with a diameter not less than 0.4m of the bored pile foundation of the temporary pier substructure 15. The pile body stratum parameters can be corrected and adjusted based on the numerical analysis results of the design supporting pile bearing capacity and the effective bearing surface (considering over-excavation and non-full contact); considering that the steel casing 3 must withstand the local impact load of the pile sinking and the local stability of its compression rod, the ratio of its outer diameter to wall thickness should not exceed ( - steel yield strength (MPa). Under typical operating conditions, a steel casing with a wall thickness of 12mm to 20mm is used. Stiffening plates (the thickness of the plates should not be less than the wall thickness) are installed at the top and bottom of the casing. Double-jointed channel steel is used to connect the steel casing 3, and a 300mm to 500mm gap is set immediately below the corbel to control the bending moment and horizontal displacement of the pile. Double-jointed steel corbels are welded to the steel casing 3 as the main load-bearing beam, and double-jointed steel load-bearing beams are installed as supplementary support points for the Bailey beam.

[0038] The Bailey beam serves as the main longitudinal beam on the corbel structure 12, with the main specification being 321 type Bailey plates (customized Bailey plates can also be used), supplemented by short Bailey plates of 1.5m and 1.0m in length. The steel section 13 is laid on the top surface of the steel casing 3 as a temporary longitudinal load-bearing beam. The selection of the aforementioned load-bearing beams and tie bars is based on the current steel structure design standard (GB 50017-2017) and is designed and calculated, taking into account factors such as structural stress, allowable safe deformation during operation, and initial defects of supporting components. When using a rotary drilling rig for drilling operations, the section modulus of the double corbel load-bearing beam and the main load-bearing beam in the main load-bearing direction should not be less than 4500cm 3 If the project has the conditions for automated processing of steel structures in the factory, the steel composite plate rib structure that meets the bearing capacity can also be used instead; the steel 13 distribution beam is laid on the top of the Bailey beam and the steel casing 3 (the section modulus of the steel 13 distribution beam should not be less than 400cm 3 ), platform panels are laid on the distribution beams (when prefabricated panels are used, the laying sections must be coordinated with the working process sections; 16# to 20# channel steel 14 buckled joints can also be used as platform panels), and the top surface elevation of the platform panels is consistent to form an overall working surface.

[0039] The drilling platform structure based on steel casing 3, such as Figure 3As shown, the structural parameters can be adjusted according to the actual operating calculation conditions of the selected equipment. For example, when the drilling equipment is an impact drill and a pump truck is used for pouring, the Bailey spacing can be increased and the combined structure of the bracket and the cross-connection on the steel casing 3 support pile can be reduced; when the drilling equipment is a rotary drill and a concrete tank truck is used in conjunction with a chute to pour concrete 7, stronger structural parameters are set.

[0040] When constructing the platform, the prefabricated processing structure section of the platform top is first completed at the processing site, and then the top-pushing support trestle 2 is used as the working surface to carry out the bored pile construction of the steel casing 3 supporting piles near the trestle side. After the piles are sunk to the designed position, the pile top elevation is adjusted; the prefabricated processing structure section and the steel casing 3 supporting piles with the corrected elevation are then welded together using connecting steel plates (the structural joint between the brackets is set based on the design allowable deformation and the design allowable construction error under the calculated working conditions, generally 10mm to 20mm, not more than 30mm; when the actual deformation exceeds the reserved structural joint width, the brackets can be converted into limit constraints after contact, and the direction setting should be consistent with the water flow direction), and then the Bailey beam, load-bearing beam and platform panel are installed; finally, the completed steel platform structure is used as the working surface to construct the next row of steel casing 3 supporting piles and the upper structure, and the above-mentioned construction steps are repeated until the working conditions for constructing the first row of temporary pier substructure 15 bored piles are met.

[0041] The overall construction procedure is to construct the temporary pier substructure in the jacking direction according to the following process flow: remove the top steel beam and platform panel of the first row of steel casings of the temporary pier substructure working platform (this process is not required for the first row) → drill and clean the hole with a rotary drill rig → position and fix the steel pipe → pour concrete for bored piles → press back filler construction → remove the first row of steel casings and superstructure → construct the next row of bored piles according to the above process until the construction of the current temporary pier substructure is completed (the working platform system based on the steel casing is dismantled simultaneously) → remove the jacking support trestle at the current temporary pier substructure → construct the remaining temporary pier substructures according to the above process.

[0042] After the removal of the top steel beam 13 of the first row of steel casing 3 supporting piles and the platform panel, the conditions for the retreat-type water-flow construction of the temporary pier substructure 15 are met. According to the technical standards, a rotary drilling rig (impact drilling rig) is used to carry out the pilot hole construction. After completing the routine procedures such as hole cleaning and hole inspection, the steel pipe 5 piles are temporarily fixed, such as Figure 3 and Figure 6As shown, the steel pipe 5 piles of the jacking drilling platform are sunk on the top surface of the steel casing 3 through temporary support ribs 6, and the support ribs 6 are welded to the steel casing 3. Limiting ribs 9 are welded on the support ribs 6 to control the positioning plane error of the steel pipe 5 piles to be less than 35mm. Limiting cross steel bars are set at the bottom of the steel pipe 5 piles, forming a double limit with the limiting ribs 9 to ensure that the plane position and verticality of the steel pipe 5 piles meet the construction control requirements throughout the construction process. The steel pipe 5 is assembled as a whole before hoisting, and its various structural plates are also prefabricated before hoisting. The whole is hoisted and temporarily fixed to the top of the steel casing 3. Then, according to the relevant technical standards, the guide tube is inserted into the steel pipe 5 pile to pour the bored pile concrete 7.

[0043] In the embodiment provided by the present invention, in step S2 , the bottom of the steel casing 3 extends into the riverbed rock layer by 50 cm to 100 cm to ensure that the steel casing 3 is stably fixed.

[0044] In the embodiment provided by the present invention, in step S2, the upper ends of all the steel casings 3 are at the same horizontal plane.

[0045] It can be understood that the upper ends of the steel casings 3 are on the same horizontal plane in order to ensure that when the drilling platform 4 is installed, the upper end surface of the drilling platform 4 is horizontal, and further ensure that the construction conditions meet the requirements.

[0046] When adjusting the upper end of the steel casing 3, if it is lower than the height required for construction, the height is increased by welding other steel casings 3. If it is higher than the height required for construction, the height is lowered by cutting the steel casing 3.

[0047] Optionally, two adjacent steel casings 3 are connected via a channel steel 14 .

[0048] In the embodiment provided by the present invention, in step S3, the construction method of the temporary pier substructure 15 includes the following steps: S31: Drill holes into the riverbed rock stratum in the steel casing 3 to the bottom elevation of the bored pile of the temporary pier substructure 15 by means of a drilling device.

[0049] S32: The sediment in the borehole is treated and the hole formation is inspected. After the inspection is qualified, the steel pipe 5 is inserted into the steel casing 3. The upper end of the steel pipe 5 is connected to the upper end of the steel casing 3 through the supporting rib 6, and there is a gap between the steel pipe 5 and the steel casing 3. The lower end of the steel pipe 5 extends out of the lower end of the steel casing 3 and enters the borehole.

[0050] S33: The concrete pouring conduit is extended into the borehole through the steel pipe 5 and concrete 7 is poured.

[0051] S34: After the concrete 7 solidifies, fill the gap between the steel casing 3 and the steel pipe 5 with backfill material 8 to the riverbed surface.

[0052] S35: After the backfill material 8 is filled, the supporting ribs 6 are removed and the steel casing 3 is pulled out.

[0053] Optionally, the supporting ribs 6 are connected to the steel casing 3 through an arc-shaped plate, including but not limited to a welding connection or a detachable bolt connection.

[0054] Optionally, a limiting steel plate 17 is provided at one end of the supporting rib 6 away from the steel casing 3 .

[0055] Optionally, the backfill material 8 is sand, gravel, soil or concrete 7. The specific selection needs to be determined in combination with the design drawings, geological survey report and construction specifications.

[0056] Optionally, concrete 7 should be made of highly fluid underwater fine aggregate concrete 7, with a slump expansion of no less than 550mm. Considering operational efficiency requirements, the time interval allowed for steel casing 3 removal must be minimized. Therefore, concrete 7 must possess a certain early strength, with a grade of no less than C30. Accelerators may be added as needed based on operational efficiency requirements. The storage capacity of concrete 7 should meet the following requirements: after the first batch of concrete 7 is placed in the hole, the depth of the conduit embedded in the concrete 7 must be no less than 1m and no more than 2.5m. Before pouring concrete 7, a water-blocking plug must be installed in the conduit. Once the funnel is filled with the initial batch of concrete 7, the underwater concrete 7 pouring process begins. After the ball is removed, the concrete 7 must be poured continuously without pause to ensure that the entire pile is poured before the concrete 7 begins to set. During the concrete pouring process, a dedicated person must measure the concrete 7 surface elevation, accurately calculate the depth of the conduit embedded in the concrete 7, and strictly ensure that the concrete 7 pouring height is below the bottom of the steel casing 3.

[0057] The gaps between the steel pipe 5, the steel casing 3 and the borehole are densely filled with backfill material 8. The backfill material 8 uses a permeable material that can well transmit the force and has negligible cohesion, such as yellow sand, pebble soil, etc.; the steel pipe 5 is backfilled to the original riverbed surface to improve the axial compressive bearing capacity and pull-out bearing capacity of the steel pipe 5 and reduce the calculated compressive length of the steel pipe 5 pile, thereby improving the overall stability of the structure. An overfill of no more than 10% is set based on the diameter and wall thickness of the steel casing 3 and the previous drilling records and inspection results.

[0058] To ensure the pouring quality of the gap between the steel pipe 5 pile and the drilled hole and to allow sufficient space for concrete 7 to flow back, the guide tube is raised to a height of 0.5m to 1.0m from the bottom of the steel pipe 5 during the pouring process and then no longer raised. Once the pouring height reaches the designed elevation, the guide tube is removed all at once. Underwater concrete 7 should be poured continuously without pauses. Intervals for removing the guide tube should be minimized. The pouring time for each pile should not be too long, and should ideally be completed within 3 hours.

[0059] 24 hours after the bored pile concrete 7 is poured, the temporary supporting ribs 6 of the steel pipes 5 are welded and cut, and the upper structures such as the corbels and load-bearing beams that are no longer in use are removed. Then the construction of the next row of temporary pier substructures 15 begins, and the next construction cycle begins. When the upper supporting components of a row of steel casings 3 supporting piles are removed, the steel casings 3 are pulled out using pile pulling equipment. In this way, backward construction is implemented, and the drilling platform structure that will no longer be used is dismantled while the temporary pier substructure 15 is constructed. The main load-bearing structure diagram of the construction conditions of the last row and the first row of temporary pier substructures 15 is shown in the figure below. Figure 4 and Figure 5 As shown, the construction of the remaining jacking drilling work platforms and the jacking temporary pier lower structure 15 is carried out in a flow-line manner according to this construction process until the construction of all the jacking temporary pier lower structures 15 is completed.

[0060] The final selection of the construction parameters of the working platform and the temporary pier substructure 15 upper structure can be determined by the setting principles and recommended value ranges in the aforementioned technical scheme in combination with the current specifications and standards and relevant technical manuals, and will not be repeated here; the temporary pier substructure 15 lower structure must calculate the single pile bearing capacity required for the platform support pile based on the most unfavorable working conditions of the jacking temporary pier substructure 15 construction, and determine the required bearing capacity of the steel pipe 5 and the bored cast-in-place piles implanted therein based on the most unfavorable stress conditions of each temporary pier substructure 15 during the entire jacking process, and then determine the specific construction parameters such as the drilling depth, pouring length and planting depth of the bored cast-in-place piles of the temporary pier substructure 15 according to the single pile bearing capacity requirements according to the following calculation method.

[0061] The bottom elevation of the steel casing 3 support piles is determined by taking the greater of the required depth for the platform support pile's design single pile bearing capacity and the corresponding depth of the pile bottom entering the rock stratum at 0.5m. Since these are temporary structural support piles with a service life of two to three months and no flood control design requirements, a calculated bearing capacity enhancement factor is set. Steel casing 3 support piles are typically supported in strongly or fully weathered rock strata. Their rock penetration depth does not meet the structural requirements for the ratio of pile diameter to rock embedment depth. Therefore, the axial compressive bearing capacity of a single pile supported in the soil should be considered. This can be calculated using the following formula. Geotechnical parameters are taken from the geological survey report: .

[0062] Where: ——For short-term temporary piles without flood control requirements, the bearing capacity improvement coefficient is calculated as 1.3.

[0063] —Steel casing circumference (m).

[0064] —Number of soil layers.

[0065] —The thickness of each soil layer within the range of steel casing entering the riverbed (m).

[0066] -and The corresponding standard value of friction resistance between each soil layer and the pile side (kPa).

[0067] —Standard value of the bearing capacity of the soil at the pile end (kPa). Considering that there is still bored pile guide hole construction below, it is not in a triaxial compression state and there is an open surface, so the smaller value of 1000kPa should be taken here.

[0068] —are the influence coefficients of vibration pile driving on the pile side friction resistance and pile end bearing capacity of each soil layer. Taking into account the pile diameter and the type of riverbed cover layer, the value is 0.5 to 1.1 according to the technical standards. The smaller value is taken for clay soil, and the larger value is taken for sandy soil, gravel soil, etc.

[0069] — Cross-sectional area of ​​pile end (m 2 ), including the expanded bottom structural area such as stiffening arc plates.

[0070] —The soil plug effect coefficient at the pile end is taken as 0.3 to 0.4.

[0071] The axial compressive bearing capacity of the designed single steel pipe pile 5 is calculated based on the assumption that the pile is embedded in the bedrock. The calculation formula is as follows. Except for parameters with special instructions, the calculation coefficients are based on the technical standards. Considering the synergistic force of the friction resistance between the inner and outer walls of the steel pipe pile, the side friction resistance enhancement coefficient is set: ).

[0072] Where: ——Taking into account the synergistic force of the friction resistance of the inner and outer walls of the steel pipe pile, the side friction resistance improvement coefficient of the bored cast-in-place pile is taken as 1.5.

[0073] ——End resistance coefficient, take 0.6.

[0074] ——Cross-sectional area of ​​pile end (m 2 ), including the cross-sectional area of ​​the bottom expansion structure such as the arc-shaped stiffening plate.

[0075] ——Taking into account the backflow of concrete voids and the absence of vibration conditions, take 80% (kPa) of the standard value of the uniaxial compressive strength of the pile end concrete.

[0076] ——The lateral resistance coefficient of pile concrete is taken as 0.05.

[0077] ——Circumference of the outer wall of the steel pipe (m).

[0078] ——Effective embedment depth of supporting piles (m), taking into account the actual embedment depth of steel pipe piles in concrete including the thickness of poor quality scum, the effective embedment depth is the actual embedment depth minus 1m.

[0079] ——The lateral resistance coefficient of the backfill material. The backfill material can be yellow sand, crushed stone soil or pebble soil, and its value is 0.8.

[0080] ——The sum of the thickness of the retrieved filler and the thickness of the pile head with slag (1m) (m).

[0081] ——The standard value of the backfill material side resistance is 80kPa.

[0082] The axial compressive bearing capacity of a single bored pile embedded in the steel pipe 5 is calculated based on the bored pile embedded in the bedrock. The calculation coefficients are based on technical standards except for special parameters. The geotechnical parameters are based on the geological survey report: 。

[0083] Where: ——The end resistance coefficient is determined based on factors such as rock strength and rock crushing degree, and is taken as 0.4 to 0.6.

[0084] ——Cross-sectional area of ​​pile end (m 2 ).

[0085] ——Standard value of saturated uniaxial compressive strength of rock at pile end (kPa).

[0086] ——The i-th layer value.

[0087] ——The lateral resistance coefficient of the i-th rock layer is determined according to factors such as rock strength and rock crushing degree, and is taken as 0.03 to 0.05.

[0088] ——Pile circumference of each soil or rock layer (m).

[0089] ——The thickness of the pile embedded in each rock layer (m).

[0090] —Number of rock layers, excluding strongly weathered and fully weathered layers.

[0091] - Side resistance coefficient of the covering soil, the value of which should be based on the pile end Determine, here take 0.2 to 1.0, when <2MPa, =1.0, 2MPa≤ <15MPa, =0.8, when 15MPa≤ <30MPa, =0.5, when >30MPa, =0.2.

[0092] ——The thickness of each soil layer below the bottom surface of the foundation or the local scour line (m).

[0093] ——The standard value of the lateral resistance of the i-th layer of soil on the pile side (kPa), the backfill (yellow sand, crushed stone soil or pebble soil) layer is 80kPa.

[0094] ——The number of soil layers, backfill layers and strongly weathered and fully weathered rock layers are all considered as soil layers.

[0095] A welded nail is set at the lower end of the steel pipe 5 to enhance the integrity of the steel pipe pile and the bored pile, reduce the settlement of the steel pipe pile, and control the relative displacement between it and the concrete. As a shear connector, a cylindrical head welded nail is preferably used. The shear bearing capacity design value of a single shear connector should be determined by the following formula: .

[0096] Where: ——Elastic modulus of concrete (N / mm²), here taken as 30000N / mm².

[0097] ——Cross-sectional area of ​​cylindrical head welding nail rod (mm²).

[0098] ——Design value of concrete compressive strength: when the concrete grade of bored pile is C30 underwater, take 14.3N / mm².

[0099] ——The design value of the ultimate tensile strength of cylindrical head welding nails must meet the requirements of the current national standard "Cylinder head welding nails for arc stud welding" GB / T 10433 (N / mm²), and 320N / mm² is taken here.

[0100] The construction parameters of each bearing capacity unit of the temporary pier substructure should match each other, and the number of welding nails set should be based on the total bearing capacity required. 总 Sure, 总 = 0.6 to 0.7 ≤ . Number of welding nails n= 总 / By rounding off and considering the structural requirements, the settlement and pull-out bearing capacity of the steel pipe can be further controlled, the linear control requirements of the jacking process can be ensured, uneven settlement of the substructure of each temporary pier that affects the safety of the jacking construction can be avoided, and the pipe piles can be prevented from being broken and pulled out during the flood season.

[0101] In the embodiment provided by the present invention, in step S32 , a plurality of limiting ribs 9 are provided at the lower end of the steel pipe 5 along the circumferential direction, and the limiting ribs 9 are perpendicular to the side wall of the steel pipe 5 .

[0102] The limiting ribs 9 cooperate with the supporting ribs 6 to form a double limiting measure to ensure that the construction error of the steel pipe 5 pile is within the design allowable range.

[0103] In the embodiment provided by the present invention, in step S32 , the lower end of the steel pipe 5 is fixedly sleeved with a reinforced steel sleeve 10 , and the reinforced steel sleeve 10 is fixed with a plurality of welding nails 11 along the circumferential direction, and the welding nails 11 are perpendicular to the side wall of the reinforced steel sleeve 10 .

[0104] The steel pipe 5 is equipped with welded anti-pulling and compression ring ribs 16 at an elevation of 1.0m above the top surface of the bored pile. These ribs bear the deadweight of the backfill material 8, thereby increasing the pull-out bearing capacity of the pile foundation. A reinforced steel sleeve 10 with a thickness not less than the wall thickness of the steel pipe 5 is installed at the bottom of the steel pipe 5. The installation range is reasonably selected based on the calculated arrangement range of the rivets 11. Multiple layers of rivets 11 are installed on the reinforced steel sleeve 10, and each layer of rivets 11 is evenly arranged along the arc-shaped reinforced steel sleeve 10. This serves to reduce the displacement between the temporary steel pipe 5 pile and the concrete 7, control settlement, and ensure the linear control requirements of the steel box girder jacking construction. At the same time, it can increase the pull-out bearing capacity of the steel pipe 5.

[0105] In the embodiment provided by the present invention, in step S32, the lower end of the steel pipe 5 is located at least 3 meters below the steel casing 3 to ensure that the steel pipe 5 is fixed after the concrete 7 is poured. If the depth is not enough, it will lead to poor stability of the steel pipe 5, thereby reducing the supporting strength of the temporary pier substructure 15, posing a safety hazard to the construction.

[0106] In the embodiment provided by the present invention, in step S33 , the concrete 7 is poured to a depth between 0.5 meters and 1 meter below the steel casing 3 .

[0107] A 1m gap is set between the bottom of the steel casing 3 support pile and the top surface of the designed bored pile as a reserved buffer section for pouring. The over-pouring length of concrete 7 is controlled at 0.5m and shall not exceed 1.0m to prevent underwater cutting operations when pulling out the steel casing 3, ensuring that the subsequent steel casing 3 can be directly pulled out and recycled.

[0108] In the embodiment provided by the present invention, in step S2 , the drilling platform 4 is connected to the steel casing 3 via the corbel structure 12 .

[0109] Optionally, the plurality of corbel structures 12 are prefabricated integral corbel structures.

[0110] In the embodiment provided by the present invention, in step S2 , a gap of 10 mm to 20 mm is provided between two adjacent corbel structures 12 on two steel casings 3 .

[0111] The specific construction method is: The first step is to use the existing main trestle 1 as the working surface and construct the supporting trestle 2 in a continuous manner along the jacking direction.

[0112] In the second step, construction is carried out with the supporting trestle 2 as the first construction platform, a row of steel casings 3 are fixed into the riverbed, and the bottom ends of the steel casings 3 are inserted into the rock layer. After the elevation adjustment is completed, a prefabricated integral bracket structure 12 is installed above each steel casing 3, and the upper structure of the drilling platform 4 is installed on the bracket structure 12 to form a second construction platform. Then, construction is carried out on the second construction platform, and the above method is repeated to enter the next construction cycle, gradually expanding the area of ​​the second construction platform, and the top of the last fixed row of steel casings 3 is not closed, reserving a drilling operation surface.

[0113] The third step is that when the second construction platform meets the construction requirements of the temporary pier substructure 15, on the second construction platform, a hole is drilled in the steel casing 3 to the bottom elevation of the bored pile of the temporary pier substructure 15 by means of drilling equipment, and then the sediment in the hole is treated and the hole is inspected. After the inspection is qualified, the steel pipe 5 is fixedly supported on the steel casing 3 through the temporary support ribs 6, and the limiting ribs 9 and the limiting ribs 9 are set to assist in limiting, so as to ensure that the construction error of the steel pipe 5 pile is within the design allowable range. After the pile top elevation is adjusted, the butt welding stiffening pile head structure is completed, and the bored pile structure of the first row of steel pipes 5 is completed. The above method is repeated to enter the next construction cycle until the last row of steel casings 3 is pulled out, that is, the bored pile structure of all steel pipes 5 is completed, and the demolition construction of the second construction platform is also completed. Then, the first construction platform (supporting trestle 2) is used to complete the parallel connection of the temporary pier substructure 15 and the construction of the upper load-bearing beam and the sliding beam, forming a functionally complete jacking temporary pier substructure 15 and then the support trestle 2 is demolished.

[0114] The last step: repeat the third step, and carry out continuous construction until all the second construction platforms are dismantled, all the upper structures of the jacking temporary piers are completed, and all the jacking supporting trestle bridges 2 are dismantled.

[0115] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0116] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and exemplary embodiments. They can be applied to a variety of fields suitable for the present invention. Further modifications will be readily apparent to those skilled in the art. Therefore, the present invention is not limited to the specific details and illustrations shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims

1. A design and construction method for a high-bearing capacity temporary jacking pier in water, characterized in that: The following steps are involved: S1: constructing a main trestle (1) on one side of the constructed bridge portion, and constructing a branch trestle (2) on the main trestle (1), wherein the branch trestle (2) is perpendicular to the main trestle (1), and the branch trestle (2) is located in the direction of the existing bridge portion to be extended; S2: Construction is carried out using the supporting trestle (2) as the first construction platform, a row of steel casings (3) is fixed on the riverbed rock layer, and the arrangement direction of the row of steel casings (3) is perpendicular to the main trestle (1), and then a drilling platform (4) is fixed to the upper end of the steel casings (3) to form a second construction platform, and then multiple rows of steel casings (3) are fixed in sequence on the second construction platform, and the length of the second construction platform is gradually extended until the construction conditions are met; S3: The drilling equipment constructs the last row of steel casings (3) on the second construction platform to form the first row of temporary pier substructures (15). After the construction is completed, the drilling platform (4) on the last row of steel casings (3) is removed, and then the steel casings (3) of the row are pulled out. Each row of steel casings (3) is constructed in turn to form the temporary pier substructure (15), and the corresponding steel casings (3) are removed. S4: After all the steel casings (3) are removed, the temporary pier superstructure is installed on all the temporary pier substructures (15), and finally the supporting trestle (2) is removed.

2. The design and construction method of a high-bearing capacity underwater temporary pier as claimed in claim 1, characterized in that: In step S2, the bottom of the steel casing (3) extends into the riverbed rock layer by 50 cm to 100 cm.

3. The design and construction method of a high-bearing capacity underwater temporary pier as claimed in claim 1, characterized in that: In step S2, the upper ends of all the steel casings (3) are at the same horizontal plane.

4. The design and construction method of a high-bearing capacity underwater temporary pier as claimed in claim 1, characterized in that: In step S3, the drilling equipment constructs the last row of steel casings (3) on the second construction platform to form the first row of temporary pier substructures (15), including the following steps: S31: Drilling a hole into the riverbed rock layer in the steel casing (3) to the bottom elevation of the bored pile of the temporary pier substructure (15) by means of a drilling device; S32: inserting the steel pipe (5) into the steel casing (3), with the upper end of the steel pipe (5) connected to the upper end of the steel casing (3), and a gap being provided between the steel pipe (5) and the steel casing (3), and the lower end of the steel pipe (5) extending out of the lower end of the steel casing (3) and entering the drill hole; S33: The concrete pouring conduit is extended into the drilled hole through the steel pipe (5) and concrete (7) is poured into the hole; S34: After the concrete (7) solidifies, backfill (8) is filled into the gap between the steel casing (3) and the steel pipe (5) until it reaches the riverbed surface; S35: After the backfill material (8) is filled, the steel pipe (5) and the steel casing (3) are disassembled, and finally the steel casing (3) is pulled out.

5. The design and construction method of a high-bearing capacity underwater temporary pier as claimed in claim 4, characterized in that: In step S32, a plurality of limiting ribs (9) are provided at the lower end of the steel pipe (5) along the circumferential direction, and the limiting ribs (9) are perpendicular to the side wall of the steel pipe (5).

6. A method for designing and constructing a temporary underwater pier with high bearing capacity as claimed in claim 4 or 5, characterized in that: In step S32, a reinforced steel sleeve (10) is fixedly sleeved on the lower end of the steel pipe (5), and a plurality of welding nails (11) are fixed to the reinforced steel sleeve (10) along the circumferential direction, and the welding nails (11) are perpendicular to the side wall of the reinforced steel sleeve (10).

7. The design and construction method of a high-bearing capacity underwater jacking temporary pier according to claim 4, characterized in that: In step S32, the lower end of the steel pipe (5) is located at least 3 meters below the steel casing (3).

8. The design and construction method of a high-bearing capacity underwater temporary pier as claimed in claim 4, characterized in that: In step S33, the concrete (7) is poured to a depth between 0.5 m and 1 m below the steel casing (3).

9. The design and construction method of a high-bearing capacity underwater temporary pier as claimed in claim 1, characterized in that: In step S2, the drilling platform (4) is connected to the steel casing (3) via a plurality of bracket structures (12).

10. The design and construction method of a high-bearing capacity underwater temporary jacking pier according to claim 9, characterized in that: In step S2, a gap of 10 mm to 20 mm is provided between two adjacent corbel structures (12) on two steel casings (3).

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