I. Engineering background
A expressway Bridge is located in Zhejiang Province. The superstructure of the bridge is a continuous hollow slab beam with prestressed concrete simply supported first and then the structure. The span arrangement is 4× 16m, and the total length of the bridge is 68.4m.. The deck layout is 0.5m (guardrail)+19m (driveway) +0.75m (guardrail)+1.5m (median) +0.75m (guardrail)+19m (driveway) +0.5m (guardrail), and the total width of the bridge is 40.5m. The substructure of the bridge adopts pile pier and bored pile foundation.
Abutment back is the key part connecting abutment and subgrade, which is related to the stability of abutment and the comfort and safety of driving. Strengthening the back well of abutment is related to the quality of highway bridge and the driving safety of vehicles.
Present situation of main diseases of bridges
According to the description of the inspection unit, the bridge mainly has the following diseases:
1, the influence of back earth pressure, the settlement of the fill itself, the damage of the back wall and the local buckling, cracking and damage of the beam.
2. Due to the pushing and squeezing of the backfill behind the abutment and the uneven settlement of the foundation, the slope protection in front of the abutment is seriously cracked and separated from the abutment cap.
3. The bearing steel plate is corroded, and most of the bearing rubber is sheared, which is mainly due to subgrade settlement and abutment sliding forward under the action of horizontal force behind abutment, resulting in shear deformation of bearing rubber along the bridge direction.
4. The joint width of the expansion joint on the damaged side of the back wall is almost zero, which is in a "stuck" state.
Third, the reinforcement scheme and technology
1, reinforcement scheme
1) chisel away the cracked and badly damaged abutment ear back wall, keep the original steel bar, plant φ 16, make the new and old concrete form a whole, and pour concrete one grade higher than the original design.
2) Due to the failure of bridge expansion joint, its normal performance is affected. This time, the bridge deck pavement within the construction scope will be poured again.
3) Abutment bearings are severely deformed, and local bearings are hollow. In this reinforcement, the bearings on both sides are lifted and replaced synchronously.
Reinforcement treatment behind abutment: In order to reduce the influence of soil pressure and soil slip behind abutment on abutment pile foundation, the abutment is reinforced this time, and the specific schemes are as follows: Scheme 1, grouting reinforcement behind abutment, grouting the subgrade behind abutment with sleeve valve pipe within the range of 10m; Scheme 2 (recommended scheme), the abutment is reinforced with lightweight foam concrete, and the replacement depth is 50cm below the original ground line.
Main construction technology
1) The construction sequence of some structures to be chiseled out of this bridge is: deck pavement → slab → abutment back wall and ear wall. All bridge deck chiseled components are mainly small components, which are manually chiseled by air compressor, rather than removed by large machinery, so as to ensure that all components are removed without damaging the original structural components. Safety protection net should be set around the chiseled area, which can not only play a certain protective role, but also prevent the broken concrete fragments from falling. In the process of chiseling the bridge deck, the dividing line between bridge deck concrete and beam slab concrete should be made clear, and the beam slab concrete should be avoided as far as possible to prevent the beam slab from breaking during lifting. Broken concrete blocks should be transported to a fixed place in time for stacking and unified treatment. The original structural reinforcement shall be retained as far as possible for the bottom plate, abutment back wall and ear wall. If the original structural reinforcement is damaged, it should be repaired and strengthened by planting reinforcement.
2) The rear wall of the ear is reinforced with φ 16 rebar planting, and concrete with higher grade than the original design is poured.
3) Grouting of sleeve valve tube at the back of abutment: The basic construction process of sleeve valve tube grouting method can be divided into the following steps: protecting the wall with mud to form holes, pouring casing materials, setting sleeve valve tube and fixing the tube to stop grouting, grouting and so on.
Its technological process is as follows: setting the hole position → moving the machine to the hole position → rechecking the hole position → drilling to the design depth → making a hole-forming record → rechecking the hole depth → lowering the sleeve valve tube (sleeve material, sleeve valve tube and sealing) → lowering the zinc tube (grouting head and pipeline connection) → mixing → opening the grouting machine → sucking the slurry (mixing slurry) → lifting the tube step by step → ending.
4) Replacement and filling of foamed concrete at abutment back: foamed concrete is a kind of lightweight filling material with a large number of closed pores, which is fully foamed by mechanical means, fully and evenly mixed with cement slurry and other admixtures in a certain proportion, then poured by pumping system and naturally cured. Technological process, the production process of foam concrete includes foam preparation, foam concrete mixture preparation, pouring, maintenance and inspection. Cleaning at the grass-roots level → Determining the thickness and height points according to the design or drawings → Watering and wetting → Making foam concrete → Casting and molding according to the construction sequence → Maintenance → Inspection and finished product protection.
5) Overall jacking replacement of bearing: technological process, construction preparation → beam top elevation retest, jacking height determination → scaffolding and working platform erection → connection debugging of CNC synchronous jacking system → installation of jack and displacement sensor → jacking → lifting to design elevation → garbage removal at pier top → bearing replacement → jack oil return, unloading of synchronous jacking system → bearing replacement completion → bearing vacancy inspection → scaffold removal and site cleaning.
Verb (abbreviation of verb) conclusion and suggestion
Combined with a bridge engineering example, this paper mainly puts forward targeted reinforcement measures and methods for the diseases existing in abutment back, hoping to provide some reference for the construction and reinforcement of abutment back.
The detailed information of "Abutment Back Wall Disease and Maintenance and Reinforcement Scheme" is available in Zhong Da Consulting & Building Link, and all relevant building construction information you want is available.
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