A construction method for closing the continuous beam from the middle span to the side span first under complex geological conditions

Abstract

The present application discloses a construction method for closing the continuous beam from the middle span to the side span under complex geological conditions, which includes the following steps: Step 1: Symmetrically construct the main piers, which are successively set as the outer side piers, inner side piers, and middle piers from the side span to the middle span; Step 2: Pour the 0# block at the top of the middle pier; Step 3: Assemble the side span hanging baskets and the middle span hanging baskets on both sides of the 0# block respectively, and symmetrically cantilever cast the continuous beam K1 and K1' segments; Step 4: Move the side span hanging basket and the middle span hanging basket outwards, and successively cantilever symmetrically cast the K2~K17 and K2'~K17' segments; Step 5: Demolish the middle span hanging basket, retain the side span hanging basket, and close the middle span; Step 6: Install a first load-bearing structure for temporarily bearing the Z1'~Z2' segments between the top of the inner side pier and the side span hanging basket; Step 7: Set a first balancing structure between the first load-bearing structure and the top of the outer side pier to balance the eccentric load generated by the cast-in-place concrete on the inner side pier. The present application has the characteristics of short construction period, convenience, quickness, safety, and relatively small investment in material costs.

Description

Technical Field

[0001] The present invention relates to the field of continuous beam construction, and in particular to a construction method for closing the middle span first and then the side spans of a continuous beam under complex geological conditions. Background Art

[0002] During the traditional construction of a continuous beam in water, the construction is usually carried out in the following order: pouring the 0# beam segment at the top of the middle pier, assembling the hanging baskets on the 0# beam segment and symmetrically casting the beam segments in segments in sequence, constructing the cast-in-situ segment of the side span support, constructing the closure segments of both side spans, and finally constructing the closure segment of the middle span.

[0003] During the actual construction process, for the straight segment of the side span in water, it is often necessary to erect a cast-in-situ support on the steel pipe piles that are more than ten meters or more than twenty meters high in the water. The construction period is long, the construction is complex and requires a large amount of steel, and the economic benefit is poor. Moreover, the installation and removal of the cast-in-situ support in water are rather troublesome, and it is difficult to ensure the construction safety, thus affecting the construction safety and progress of the continuous beam. Summary of the Invention

[0004] In order to avoid the installation and removal of the cast-in-situ support in water, the present application provides a construction method for closing the middle span first and then the side spans of a continuous beam under complex geological conditions.

[0005] The construction method for closing the middle span first and then the side spans of a continuous beam under complex geological conditions provided by the present application adopts the following technical solutions:

[0006] A construction method for closing the middle span first and then the side spans of a continuous beam under complex geological conditions includes the following steps:

[0007] Step 1: Symmetrically construct the main piers, which are successively set as the outer side piers, the inner side piers and the middle pier from the side span to the middle span;

[0008] Step 2: Pour the 0# block at the top of the middle pier;

[0009] Step 3: Assemble the side span hanging baskets and the middle span hanging baskets on both sides of the 0# block respectively, and symmetrically cast the continuous beam K1 and K1' segments;

[0010] Step 4: Move the side span hanging basket and the middle span hanging basket outwards, and successively cast the K2~K17 and K2'~K17' segments in cantilever symmetry;

[0011] Step 5: Remove the middle span hanging basket, retain the side span hanging basket, and close the middle span;

[0012] Step 6: Install a first load-bearing structure for temporarily bearing the Z1'~Z2' segments between the top of the inner side pier and the side span hanging basket;

[0013] Step 7: Set a first balancing structure between the first load-bearing structure and the top of the outer side pier to balance the eccentric load generated by the cast-in-situ concrete on the inner side pier;

[0014] Step Eight: Move the side-span hanging basket, and symmetrically cantilever-cast the straight sections Z1' to Z2' of the side span in sequence. During the casting process, adjust the first balance structure to balance the eccentric load on the inner pier caused by the increase in concrete. After the concrete reaches a certain strength, remove the side-span hanging basket, the first load-bearing structure, and the first balance structure.

[0015] Step Nine: Install a second load-bearing structure on the top of the pier body of the inner pier for temporarily bearing the sections Z3' to Z4'.

[0016] Step Ten: Set up a second balance structure between the other side of the top of the inner pier body and the bearing platform of the outer pier to balance the eccentric load on the inner pier caused by the cast-in-place concrete.

[0017] Step Eleven: Construct the section Z4’. During the casting process, adjust the second balance structure to balance the additional eccentric load on the inner pier caused by the concrete.

[0018] Step Twelve: Symmetrically cast the concrete of the two closure sections Z3' simultaneously to close the side span. During the casting process, adjust the second balance structure to balance the additional eccentric load on piers 100# and 103# caused by the concrete.

[0019] Step Thirteen: Remove the loads of the first balance structure and the second balance structure, demolish the temporary structures, and the construction of the continuous beam is completed.

[0020] By adopting the above technical solution, to avoid the erection of the cast-in-place support on the ground during the erection of the straight section of the side span in water, in the construction method of the technical solution disclosed in this application, the middle span is closed first, and then the side-span hanging basket is used to continue walking forward to cantilever-cast the straight section of the side span. Finally, the side span is closed by the cast-in-place support of the inclined corbel of the side pier to complete the construction of the continuous beam.

[0021] In this process, since the middle span is closed first, it causes an eccentric load on the already cast beam sections when casting the sections Z1’ to Z4’, affecting the stability of the middle-span closure section. In severe cases, it may even cause the fracture of the middle-span closure section, posing a safety hazard.

[0022] In the technical solution disclosed in this application, by setting up a first load-bearing structure for temporarily bearing the sections Z1’ to Z2’ and a second load-bearing structure for bearing the sections Z3' to Z4’, a load-bearing system for the sections Z1’ to Z4’ is formed to balance the eccentric load on the already cast beam sections during the construction of the sections Z1’ to Z4’, ensuring the stability of the middle-span closure section.

[0023] In addition, the first balance structure is used to balance the eccentric load of the first load-bearing structure and the sections Z1’ to Z2’ on the inner pier, and the second balance structure is used to balance the eccentric load of the second load-bearing structure and the sections Z3’ to Z4’ on the inner pier to ensure the stability of the inner pier.

[0024] Compared with the traditional construction method of using high scaffolds for the straight section, it avoids the construction of super-high steel pipe piles in the water for the cast-in-place scaffold of the straight section of the side span, and has the remarkable characteristics of short construction period, convenience, safety and relatively small investment in material costs. At the same time, the cast-in-place scaffold of the inclined corbel of the side pier is convenient to demolish, maximizing the economic and safety effects of the construction.

[0025] Preferably, in step six, when installing the first bearing structure, a cantilever beam is constructed on the pier top of the inner side pier, and the side-span hanging basket is connected to the cantilever beam so that the side-span hanging basket can move relative to the cantilever beam.

[0026] By adopting the above technical solution, connecting the cantilever beam with the side-span hanging basket plays a bearing role on the side-span hanging basket and the sections Z1’~Z2’, and balances the eccentric load on the already cast beam sections.

[0027] Preferably, in step seven, when constructing the first balancing structure, a first bearing platform reaction seat is installed on the bearing platform of the outer side pier, a beam end reaction seat is installed on the side of the cantilever beam close to the inner side pier, a first steel strand bundle is installed between the first bearing platform reaction seat and the beam end reaction seat, and a jack for tightening it is installed at the end of the first steel strand bundle.

[0028] By adopting the above technical solution, the first steel strand bundle is tightened by the jack, and the first steel strand bundle is used to balance the torque of the cantilever beam, the side-span hanging basket and the sections Z1’~Z2’ rotating around the pier top of the inner side pier to ensure the stability of the inner side pier.

[0029] Preferably, in step nine, when installing the second bearing structure, an inclined corbel cast-in-place scaffold is erected on the side surface of the top of the inner side pier, and a transverse distribution beam is erected on the inclined corbel cast-in-place scaffold so that the transverse distribution beam extends to the section Z2’;

[0030] Install the side-span closure hanging bracket, with one end of the side-span closure hanging bracket hung on the section Z2’ and the other end supported on the bottom of the transverse distribution beam.

[0031] By adopting the above technical solution, the inclined corbel cast-in-place scaffold provides a erection foundation for the transverse distribution beam. Through the cooperation of the inclined corbel cast-in-place scaffold, the transverse distribution beam and the side-span closure hanging bracket, the bearing effect on the sections Z3’~Z4’ is realized, and at the same time, a casting platform is provided for the section Z3’.

[0032] Preferably, in step ten, when constructing the second balancing structure, a support reaction seat is installed on the other side surface of the top of the inner side pier, a second bearing platform reaction seat is installed on the bearing platform of the outer side pier, a second steel strand bundle is installed between the second bearing platform reaction seat and the support reaction seat, and a jack for tightening it is installed at the end of the second steel strand bundle.

[0033] By adopting the above technical solution, the second steel strand bundle is tightened by a jack. The second steel strand bundle is used to balance the torque of the second load-bearing structure and the rotation of the Z3’-Z4’ segments around the top of the inner pier, so as to ensure the stability of the inner pier.

[0034] Preferably, tracks for connecting with the side-span hanging basket are provided on the cantilever beam.

[0035] By adopting the above technical solution, the arrangement of the tracks is conducive to realizing the sliding connection between the side-span hanging basket and the cantilever beam.

[0036] Preferably, in step twelve, when closing the side span, first tension the temporary horizontal steel cable at the side-span closure, and then pour the concrete of the Z3’ segment.

[0037] By adopting the above technical solution, the Z2’ and Z4’ segments are temporarily rigidly connected to ensure the stability of the Z2’ and Z4’ segments when pouring the concrete of the Z3’ segment.

[0038] Preferably, in step five, water bag counterweights are placed at the mid-span closure to balance the unbalanced loads between the mid-span and the side span.

[0039] By adopting the above technical solution, the unbalanced loads between the mid-span and the side span are counterweighted by water bags, eliminating the need for redundant construction tools and facilitating the on-site selection of the quantity and weight of the water bags according to the actual situation.

[0040] In summary, the present application includes at least one of the following beneficial technical effects:

[0041] 1. To avoid the erection of the cast-in-situ support on the ground during the erection of the straight segment of the side span in water, in the construction method of the technical solution disclosed in the present application, the mid-span is closed first, and then the side-span hanging basket is used to continue walking forward for cantilever casting of the straight segment of the side span. Finally, the side-span closure is completed by the cast-in-situ support of the side pier inclined corbel to complete the construction of the continuous beam.

[0042] 2. By providing a first load-bearing structure for temporarily bearing the Z1’-Z2’ segments and a second load-bearing structure for bearing the Z3'-Z4' segments, a load-bearing system for the Z1’-Z4’ segments is formed to balance the eccentric loads of the Z1’-Z4’ segments on the already cast beam segments during construction, ensuring the stability of the mid-span closure segment.

[0043] 3. The eccentric loads of the first load-bearing structure and the Z1’-Z2’ segments on the inner pier are balanced by the first balance structure, and the eccentric loads of the second load-bearing structure and the Z3’-Z4’ segments on the inner pier are balanced by the second balance structure to ensure the stability of the inner pier.

[0044] 4. Compared with the traditional construction method of using high brackets for the straight section, it avoids the erection of the super-high steel pipe piles in the water for the cast-in-place support of the straight section of the side span. It has the remarkable characteristics of short construction period, convenience, speed, safety, and relatively small investment in material costs. At the same time, the cast-in-place support of the inclined corbel of the side pier is convenient to demolish, maximizing the economic efficiency and safety of the construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram showing the outer side pier, inner side pier, middle pier and trestle structure in Step 1 of the embodiment.

[0046] Figure 2 It is a schematic diagram showing the pouring of the No. 0 block in Step 2 of the embodiment.

[0047] Figure 3 It is a schematic diagram showing the assembly of the side span hanging basket and the middle span hanging basket in Step 3 of the embodiment.

[0048] Figure 4 It is a schematic diagram showing the sequential symmetric cantilever pouring of the K2~K17 and K2'~K17' segments in Step 4 of the embodiment.

[0049] Figure 5 It is a schematic diagram showing the closure of the middle span in Step 5 of the embodiment.

[0050] Figure 6 It is a schematic diagram showing the construction of the first balance structure and the first load-bearing structure in Steps 6 and 7 of the embodiment; showing the pouring of the Z1'~Z2' segments in Step 8.

[0051] Figure 7 It is a schematic diagram showing the construction of the first balance structure and the first load-bearing structure in Steps 9 and 10 of the embodiment; showing the pouring of Z4’ and the closure of the side span in Steps 11 and 12.

[0052] Figure 8 It is a schematic diagram showing the completion of the main beam construction in Step 13 of the embodiment.

[0053] DESCRIPTION OF THE REFERENCE NUMERALS:

[0054] 11. Outer side pier; 12. Inner side pier; 13. Middle pier; 21. Side span hanging basket; 22. Middle span hanging basket; 3. Middle span closure hanging bracket; 4. First load-bearing structure; 41. Cantilever beam; 411. Longitudinal support beam; 412. Transverse support beam; 42. Track; 5. First balance structure; 51. First cap reaction seat; 52. Beam end reaction seat; 53. First steel strand bundle; 6. Second load-bearing structure; 61. Inclined corbel cast-in-place support; 62. Transverse distribution beam; 63. Side span closure hanging bracket; 7. Second balance structure; 71. Inclined corbel steel support; 72. Support reaction seat; 73. Second cap reaction seat; 74. Second steel strand bundle. Detailed implementation manners

[0055] The following further elaborates on this application in conjunction with the Figure 1-8 accompanying drawings.

[0056] The embodiment of this application discloses a construction method for the closure of the continuous beam from the middle span to the side span under complex geological conditions. Referring to Figures 1 to 8 , it includes the following steps:

[0057] Step 1:

[0058] The main bridge piers are constructed symmetrically. From the side span to the middle span, they are successively set as the outer side piers 11 (99#, 104#), the inner side piers 12 (100#, 103#), and the middle piers 13 (101#, 102#). During construction, after the construction of the outer side piers 11 and the inner side piers 12 is completed, a construction trestle is erected to the middle piers 13, and the pile foundation construction is completed. A steel sheet pile cofferdam is installed at the middle piers 13, and the construction of the pile cap and pier body is completed.

[0059] Step 2:

[0060] Temporary consolidations are erected beside the piers 101# and 102#, a formwork system for the casting of the 0# block and the formwork for casting the 0# block are cast-in-place, and the temporary consolidations on both sides of the permanent bridge bearings are cast. The 0# block corresponds to the K0 section in the accompanying drawings.

[0061] The permanent bridge bearings of the piers 101# and 102# are installed, and the upper cover plate and the lower cover plate of the bearing in the permanent bridge bearing are fixed with temporary fixing parts, and the concrete of the 0# block is cast.

[0062] After the concrete reaches a certain strength, the prestressing cables of this stage are symmetrically tensioned.

[0063] Step 3:

[0064] The side formwork and bottom formwork of the 0# block are removed, and the load of the 0# block is transferred to the temporary consolidation for bearing.

[0065] On the side of the 0# block close to the side span, the side span hanging basket 21 is assembled, and on the side close to the middle span, the middle span hanging basket 22 is assembled. The continuous beam K1 and K1' segments are symmetrically cantilever cast. After the concrete reaches a certain strength, the prestressing cables of this stage are symmetrically tensioned.

[0066] Step 4:

[0067] The middle span hanging basket 22 and the side span hanging basket 21 are moved outwards, and the K2~K17 and K2'~K17' segments are successively cantilever cast symmetrically. After the concrete reaches a certain strength, the prestressing cables of this stage are symmetrically tensioned.

[0068] Step 5:

[0069] The middle span hanging basket 22 is removed, and the side span hanging basket 21 is not removed temporarily. The unbalanced load is balanced by placing water bags at the middle span for counterweight.

[0070] Temporarily rigidly connect the beam bodies at the mid-span closure joint, tension the temporary closure steel cables (select the permanent horizontal prestressing tendons to act as them, and they can be directly loaded to the design tensile force after equal strength), and install the mid-span closure hanging bracket 3.

[0071] Select a day with relatively small temperature difference changes, and pour the concrete of the mid-span closure section K18 at the lowest temperature of the day.

[0072] After the concrete of the K18 section reaches a certain strength, remove the temporarily rigidly connected beam bodies, tension all the permanent horizontal prestressing tendons in the temporary closure steel cables, remove the counterweight water bags, remove the temporary consolidation at the tops of the 101# and 102# piers, and release the temporary fixing parts between the upper and lower cover plates of the permanent bearings of the 101# and 102# piers, so that the permanent bearings can move freely.

[0073] Step Six:

[0074] Install the first load-bearing structure 4 between the top of the pier bodies of the 100# and 103# piers and the side-span hanging basket 21. The specific steps are as follows:

[0075] Construct the cantilever beam 41 on the tops of the 100# and 103# piers. The cantilever beam 41 includes a longitudinal support beam 411 installed on the tops of the 100# and 103# piers and a transverse support beam 412 horizontally installed on the top of the longitudinal support beam 411. To ensure the stability of the connection between the transverse support beam 412 and the longitudinal support beam 411, a diagonal support beam is provided between the transverse support beam 412 and the longitudinal support beam 411. To provide a connection for the side-span hanging basket 21, the transverse support beam 412 extends to the K16' section; install the track 42 at the bottom end of the transverse support beam 412, and the side-span hanging basket 21 is slidably matched with the transverse support beam 412 through the track 42.

[0076] The setting of the first load-bearing structure 4 can play a load-bearing role for the side-span hanging basket 21 and the Z1’~Z2’ sections to be poured, balance the eccentric load on the already poured beam sections, and ensure the stability of the mid-span closure section.

[0077] Step Seven:

[0078] Install the first balance structure 5. During installation, embedment parts are set in advance on the bearing platforms of Pier 99# and Pier 104#, and 2 first bearing platform reaction seats 51 are installed on the embedment parts. 2 beam-end reaction seats 52 are installed on one side of the cantilever beam 41 close to the inner pier 12. Correspondingly, 2 groups of first steel strand bundles 53P anchors are installed on the first bearing platform reaction seats 51, and the other ends of the first steel strand bundles 53 are anchored on the beam-end reaction seats 52. A jack for tightening the first steel strand bundles 53 is installed. During the process of pouring the Z1’-Z2’ segments, the first steel strand bundles 53 are tightened by the jack. The first steel strand bundles 53 are used to balance the torque of the cantilever beam 41, the side-span hanging basket 21, and the Z1’-Z2’ segments rotating around the top of the inner pier 12, so as to ensure the stability of the inner pier 12 during the pouring process of the Z1’-Z2’ segments.

[0079] Step Eight:

[0080] Demolish the mid-span closure hanging bracket 3.

[0081] Move the side-span hanging basket 21. The side-span hanging basket 21 moves relative to the cantilever beam 41, and the side-span straight segments Z1'-Z2' are symmetrically cast in cantilever in sequence. During the process of pouring concrete, 2 groups of first steel strand bundles 53 are tensioned in corresponding grades according to the progress of pouring concrete, so as to balance the eccentric load generated by the increased concrete on Piers 100# and 103#.

[0082] After the concrete reaches a certain strength, symmetrically tension the prestressed cables in this stage, and demolish the side-span hanging basket 21, the first load-bearing structure 4, and the first balance structure 5.

[0083] Step Nine:

[0084] Install the second load-bearing structure 6 on the top of Piers 100# and 103#. During installation, an inclined corbel cast-in-place support 61 is erected on the side surface of the top of the main bridge Piers 100# and 103#, and a transverse distribution beam 62 is erected on the inclined corbel cast-in-place support 61, so that the transverse distribution beam 62 extends to the Z2' segment. Install the side-span closure hanging bracket 63, so that one end of the side-span closure hanging bracket 63 is hung on the Z2' segment and the other end is supported on the transverse distribution beam 62. The second load-bearing structure 6 provides a pouring platform for the Z3’ segment, realizes the load-bearing effect on the Z3’-Z4’ segments, balances the eccentric load on the already poured beam segments, and ensures the stability of the mid-span closure segment.

[0085] Step Ten:

[0086] Construct the second balancing structure 7 between Pier 100#, Pier 103# and Pier 99#, Pier 104#. During construction, install the inclined corbel steel brackets 71 on the other side of the top of the piers of Pier 100# and Pier 103# of the main bridge, install 2 bracket reaction seats 72 on the inclined corbel steel brackets 71, set the embedded parts in advance on the pile caps of Pier 99# and Pier 104#, and weld 2 second pile cap reaction seats 73 on the embedded parts. Install 2 groups of second strand bundles 74P anchors correspondingly, and anchor the other ends of the second strand bundles 74 on the bracket reaction seats 72. Install the jacks for tightening the second strand bundles 74, and tighten the second strand bundles 74 through the jacks. The second strand bundles 74 are used to balance the torque of the second bearing structure 6 and the rotation of the sections Z3’~Z4’ around the top of the inner pier 12 to ensure the stability of the inner pier 12 during the pouring of the section Z4’ and the section Z3’.

[0087] Step Eleven:

[0088] Install the pier top bearings on the top of the transverse distribution beam 62 and fix the upper cover plate and the lower cover plate of the bearings in the pier top bearings with temporary fixing parts. Construct the pier top continuous beam section Z4'. During the concrete pouring process, correspondingly tension 2 groups of second strand bundles 74 in grades according to the concrete pouring progress to balance the eccentric load generated by the increased concrete on Pier 100# and Pier 103#.

[0089] Step Twelve:

[0090] Temporarily rigidly connect the beam bodies at the side span closure, and tension the temporary horizontal steel cables. The temporary horizontal steel cables are selected from the permanent horizontal prestressing tendons and can be directly loaded to the design tensile force after equal strength.

[0091] Remove the temporary fixing parts between the upper cover plate and the lower cover plate of the bearings at Pier 100# and Pier 103# to enable the bearings to expand and contract longitudinally. Tie the steel bars, install the prestressing tendons, and symmetrically pour the concrete of 2 closure sections Z3' at the same time. During the concrete pouring process, correspondingly tension 2 groups of second strand bundles 74 in grades to balance the increased eccentric load during the pouring of the side span closure section. After the concrete reaches the strength requirement, remove the temporary rigid connection of the beam bodies, and finally carry out the tensioning and grouting construction of the side span prestressing tendons.

[0092] Step Thirteen:

[0093] Remove the upper loads of 2 groups of first strand bundles 53 and second strand bundles 74, and remove the second bearing structure 6 and the second balancing structure 7; remove the brackets and trestles beside the middle pier 13, etc., and construct other ancillary projects. The construction of the main bridge continuous beam is completed.

[0094] The present application discloses a method for constructing a continuous beam under complex geological conditions by closing the middle span first and then the side spans. The method is to close the middle span first, then use the side span hanging basket 21 to continue moving forward, cantilever cast the straight section of the side span, and finally use the side pier inclined bracket cast-in-place bracket 61 to close the side span to complete the construction of the continuous beam. Compared with the traditional construction method of using high brackets to construct straight sections, it avoids setting up ultra-high steel pipe piles in the water for the straight section of the side span. It has the significant characteristics of short construction period, convenience, safety and low material cost investment. At the same time, the side pier inclined bracket cast-in-place bracket 61 is easy to dismantle, so that the economy and safety of the construction are maximized.

[0095] In this process, it is precisely because the middle span is closed first that an eccentric load is applied to the already cast beam section when casting the Z1'~Z4' sections, affecting the stability of the middle span closure section. In severe cases, it may even cause the middle span closure section to break, posing a safety hazard.

[0096] Based on this, the applicant formed a bearing system for the Z1'~Z4' segments by setting up a first bearing structure 4 for temporarily bearing the Z1'~Z2' segments and a second bearing structure 6 for bearing the Z3'~Z4' segments, so as to balance the eccentric load on the already cast beam sections during the construction of the Z1'~Z4' segments and ensure the stability of the mid-span closure section.

[0097] In addition, the first balancing structure 5 balances the eccentric load of the first bearing structure 4 and the Z1'~Z2' segment on the inner side pier 12, and the second balancing structure 7 balances the eccentric load of the second bearing structure 6 and the Z3'~Z4' segment on the inner side pier 12 to ensure the stability of the inner side pier 12.

[0098] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A construction method for closing the continuous beam from the middle span to the side span under complex geological conditions, characterized in that, it includes the following steps: Step 1: Symmetrically construct the main piers, which are successively set as the outer side piers (11), inner side piers (12) and middle piers (13) from the side span to the middle span; Step 2: Pour the 0# block at the top of the middle pier (13); Step 3: Assemble the side span hanging baskets (21) and middle span hanging baskets (22) on both sides of the 0# block respectively, and symmetrically cantilever cast the continuous beam K1 and K1' segments; Step 4: Move the side span hanging basket (21) and middle span hanging basket (22) outwards, and successively cantilever symmetrically cast the K2~K17 and K2'~K17' segments; Step 5: Remove the middle span hanging basket (22), retain the side span hanging basket (21), and close the middle span; Step 6: Install the first load-bearing structure (4) for temporarily bearing the Z1'~Z2' segments between the top of the pier body of the inner side pier (12) and the side span hanging basket (21); Step 7: Set the first balance structure (5) between the first load-bearing structure (4) and the top of the outer side pier (11) to balance the eccentric load generated by the cast-in-place concrete on the inner side pier (12); Step 8: Move the side span hanging basket (21), and successively cantilever symmetrically cast the side span straight segments Z1'~Z2' segments. During the casting process, adjust the first balance structure (5) to balance the eccentric load generated by the increased concrete on the inner side pier (12). After the concrete reaches a certain strength, remove the side span hanging basket (21), the first load-bearing structure (4) and the first balance structure (5); Step 9: Install the second load-bearing structure (6) for temporarily bearing the Z3'~Z4' segments on the top of the pier body of the inner side pier (12); Step 10: Set the second balance structure (7) between the other side of the top of the pier body of the inner side pier (12) and the bearing platform of the outer side pier (11) to balance the eccentric load generated by the cast-in-place concrete on the inner side pier (12); Step 11: Construct the Z4’ segment, and adjust the second balance structure (7) during the casting process to balance the eccentric load generated by the increased concrete on the inner side pier (12); Step 12: Symmetrically cast the concrete of 2 closure segments Z3' segments at the same time to close the side span. During the casting process, adjust the second balance structure (7) to balance the eccentric load generated by the increased concrete on the 100# and 103# piers; Step 13: Remove the loads of the first balance structure (5) and the second balance structure (7), remove the temporary structures, and the construction of the continuous beam is completed; In Step 6, when installing the first load-bearing structure (4), construct the cantilever beam (41) on the top of the inner side pier (12), and connect the side span hanging basket (21) with the cantilever beam (41) so that the side span hanging basket (21) can move relative to the cantilever beam (41).

2. A construction method for closing the continuous beam from the middle span to the side span under complex geological conditions according to claim 1, characterized in that: In Step 7, when constructing the first balance structure (5), install the first bearing platform reaction seat (51) on the bearing platform of the outer pier (11), install the beam end reaction seat (52) on the side of the cantilever beam (41) close to the inner pier (12), install the first steel strand bundle (53) between the first bearing platform reaction seat (51) and the beam end reaction seat (52), and install a jack for tightening it at the end of the first steel strand bundle (53).

3. A construction method for closing the continuous beam from the middle span to the side span first under complex geological conditions according to claim 2, characterized in that: In Step 9, when installing the second bearing structure (6), erect an inclined corbel cast-in-place support (61) on the side surface at the top of the pier body of the inner pier (12), and erect a transverse distribution beam (62) on the inclined corbel cast-in-place support (61) to extend the transverse distribution beam (62) to the Z2' segment; Install the side span closure hanging bracket (63) so that one end of the side span closure hanging bracket (63) is hung on the Z2' segment and the other end is supported on the bottom of the transverse distribution beam (62).

4. A construction method for closing the continuous beam from the middle span to the side span first under complex geological conditions according to claim 3, characterized in that: In Step 10, when constructing the second balance structure (7), install a support reaction seat (72) on the other side surface at the top of the pier body of the inner pier (12), install the second bearing platform reaction seat (73) on the bearing platform of the outer pier (11), install the second steel strand bundle (74) between the second bearing platform reaction seat (73) and the support reaction seat (72), and install a jack for tightening it at the end of the second steel strand bundle (74).

5. A construction method for closing the continuous beam from the middle span to the side span first under complex geological conditions according to claim 1, characterized in that: A track (42) for connecting with the side span hanging basket (21) is provided on the cantilever beam (41).

6. A construction method for closing the continuous beam from the middle span to the side span first under complex geological conditions according to claim 1, characterized in that: In Step 12, when closing the side span, first tension the temporary horizontal steel cable at the side span closure, and then pour the concrete of the Z3' segment.

7. A construction method for closing the continuous beam from the middle span to the side span first under complex geological conditions according to claim 1, characterized in that: In Step 5, place water bag counterweights at the middle span closure to balance the unbalanced loads between the middle span and the side span.

Images