Bridges synchronous jack-up is near the abutment excavation of foundation pit pouring concrete as the basis of jack-up bracket temporarily, jack-up stents used seamless steel pipe, seamless steel pipe processing height according to site condition for processing the measured height, upper assure coaxial seamless steel tube placed h-beam surface at the same height, pole placed on top of jack, jack placed on h-beam as beam and beam bottom distribution with composite steel wedge between close contact.
And install the anti-displacement device on the outer side of the abutment or pier column (the height depends on the actual situation of the site).
When the roof is in place, the beam falls and the temporary support column is padded.
In the original abutment, pier support stone lofting, chiseling embedded support stone base groove and grinding flat, modulation of epoxy mortar to put the support stone, support stone welding, and finally put rubber support and leveling, falling beam.

1 jacking process:

And construction preparation in advance (the) of pier abutment area in addition to put jack location to the installation of monitoring equipment, try jack-up (problem feedback and handling) - formal jack-up - first jack-up finish to the placement of temporary support, continues to design position to the placement of temporary supports, landed on the beam to temporary support to installation of prefabricated cushion stone and bearing, cleaning

2. Construction preparation:

After the jacking is completed for the first time, the base surface of pier and cap top shall be cleaned and chipped to remove the raised part of the base surface, and the broken loose concrete residue shall be removed.
In the abutment (pier) presupported temporary steel cushion block part such as the existence of steel head should be cut off and processed to below the surface height of concrete.
Debugging and installation of jacking system: jacking system adopts the dual control of displacement and jacking pressure as the jacking control basis, external data collection takes displacement electronic sensor as the displacement collection, and pressure sensor as the pressure collection.
Single and unified debugging of the normal operation of each control system should be carried out before jacking.
Installation of monitoring equipment: monitoring equipment is the supporting equipment of jacking system, mainly including pressure sensor, displacement sensor and dial indicator.
The installation of displacement sensor should pay attention to the location of the installation must be near the jack position of the support, the nearest distance control to reflect the displacement in the jacking process.
The installation of pressure sensor shall ensure the supporting installation to truly reflect the pressure value of the jack.
At the same time, the dial meter should be installed on the beam floor as an auxiliary displacement control and corrective control measures.
Different personnel rejection inspection of the jacking system before jacking: after the installation of the jacking system, more than two people should be ensured to reject inspection, and the isolation of time and working condition of two people's rejection inspection should be ensured, so as to ensure that the jacking system in the jacking process can truly reflect the situation in the jacking process.
The professional and technical personnel of rejection inspection shall issue the inspection report to the person in charge of on-site construction after the completion of inspection.
Detailed division of labor: prior to jacking, managers and operators participating in jacking shall have a clear division of labor, and the written technical disclosure of the written division of labor shall be made.
Written disclosure shall include organization, division of labor, job responsibilities, emergency channel processing signals, common terms of information channels, and construction prohibition items.
Information feedback and transmission channel check: jacking information transmission tools should be handheld intercom.
Before jacking up, the local unprohibited channels shall be used as information transmission channels.
Check the effectiveness and clarity of each intercom.
And should be clear channel prohibition language, urgent language, urgent language and other key languages.
Safety education and safety protection measures for workers entering the site: ensure the safety education of each jacking personnel before jacking, emphasizing the necessity, rigor, all-staff and responsibility of safety.
Other preparatory work: before jacking, the bridge deck connection of jacking construction office should be disconnected to ensure that support replacement does not affect the structure of adjacent spans. The cast-in-place concrete at the bridge deck should be chipped away first, and then the connection steel bar should be cut off to remove the connection between the two spans. Manual chipping should be used in construction to avoid mechanical damage to the beam body.
Check the jacking bracket set up to ensure its sufficient strength, stiffness and stability. The mid-span deflection of the bracket should be less than 10mm to ensure that the bracket does not collapse, does not tilt, and the settlement is small and uniform when the beam is jacked up.
Before jacking, check the anti - lateral displacement device and limit device carefully.

3 jack-up
3.1 pre-jacking (subject to beam body jacking of 5mm)

The main purpose of pre-jacking is to eliminate the problems that may occur in the jacking system, such as oil leakage in the oil connection, insufficient pressure of the oil pump, etc., and at the same time to eliminate the inelastic deformation that may occur in the jacking process.
Pre-jacking is controlled by jacking from jacking to design load. To ensure that beam body is jacked up synchronously in jacking, unloading should be carried out for more than 5min.
After unloading, the respective control systems and apparent phenomena of the system should be carefully checked. The inspection focuses are: whether there is oil leakage in all oil pipelines, whether there is abnormal phenomenon in the jack, and apparent wear and tear of power supply lines.
After unloading, the steel plate on and off the jack should also be carefully checked for deformation. If necessary, the thickness of the steel plate can be adjusted to meet the jacking requirements.
Carefully check whether the structure under the jack placement position is different from the phenomenon before jacking. If it exists, the formal jacking can be carried out only after the reason is found out carefully. It is strictly prohibited to continue the jacking until the situation is clear.
After unloading, communication meetings should be organized immediately, problems should be coordinated and dealt with in a timely manner, and it is clear that there is no need to re-emphasize and improve the process control of organizational structure, information transmission and feedback, etc.
After all items are checked and found correct, another measuring range can be jacked up, that is, 10cm. Auxiliary support should be added in time after jacking in place.

3.2 in the top

For, the jacking height is required to be large; for the effective travel of the jack, the jacking needs to be changed.
That is to say, the lifting jacks must be carried out in strict accordance with the established scheme. The control contents include the number of steel plates to be raised at the lower part of the jacks, the height and the next jacking height, etc.
In the process of jacking and jacking, if the jacking time is expected to exceed 10min, the beam should be placed on the temporary support at other piers, and it is strictly prohibited to carry out jacking by jack continuous load.
Prior to jacking up, the jacks shall be marked in advance in the position of jacking up. The jacking requirements after jacking up may refer to the pre-jacking part.

3.3 the top reaches the design position

The jacking work can be continued uniformly after the site reconfirms that the jack does not shift and other phenomena.
According to different pier number jacking work needs different jacking cycle to jacking up to the design height, the jacking operation and other procedures in the excessive process should be strictly enforced.
It should be noted that in the jacking process, the jacks shall not reach the maximum travel height of the jacking, and the efficiency reduction of 70% ~ 80% shall be considered.
In the process of jacking up to the design height, spot welding connection should be carried out for temporary support when the temporary support exceeds 20cm to prevent possible instability and side tilt support.
The jacking process shall be carried out in strict accordance with the prescribed hierarchical loading control procedures.

3.4 placement of temporary support

The temporary support placement position should consider the installation width of the new support cushion stone, set aside enough to install the corresponding support cushion stone inlet width.
When the supporting stone is placed, the supporting stone groove should be gouged out in the corresponding position, and the l-shaped Angle steel and the supporting stone reserved steel plate should be welded up and down. After the welding, check the welding seam and repair the edge groove with epoxy mortar.
After a certain strength is formed, support is placed.

3.5 fall beam

In contrast to the jacking procedure, the beam falling procedure should be strictly implemented.
Make sure all temporary supports have been removed and steel pads have been installed before beam falling.
After falling to the fulcrum bearing capacity, attention should be paid to the displacement and pressure sensor data, whether the pier deceleration is consistent, whether the displacement change is consistent, when the difference is too large, the reason should be found out and the beam should be dropped again.

3.6 safe removal and removal of temporary facilities

The demolition and removal of temporary facilities should be safe and orderly, monitored by the same safeguard measures as when jacking up, and the construction safety when finished products are protected and dismantled should be paid attention to.

4. Matters needing attention

Pay special attention to construction safety measures during construction;
The specifications and performance of the bearing into the field should be checked one by one to ensure that the size and performance are appropriate;
The supporting stone must be leveled, and the beam can be dropped after the strength of epoxy mortar is formed.


Key words: bridge synchronous jacking; whole bridge synchronous jacking