In the concrete wall mould positioning construction, the construction workers of Concrete wall mould usually use the impact drill to directly drill holes on the floor slab, insert the steel bar head, or directly weld the short steel bars with the length of the wall thickness to the vertical steel bars, and insert the holes The positioning method of the rib tends to damage the wire tube pre-buried in the concrete wall mould , causing the wire tube to be deformed or penetrated, resulting in several points of damage to the threading tube, blockage and exposed steel, affecting the later threading of the tube, when the threading cannot pass through Often, the installation workers will hit the concrete floor slab until the PVC pipe is exposed, cut the deformed PVC pipe, reconnect, then thread and repair, resulting in the destruction of the Concrete wall mould structure; and the positioning short steel bar is directly welded to the vertical steel bar It will destroy the shear resistance and bending resistance of the steel bar, and both methods will cause hidden dangers to the engineering structure.
Soil nail wall-foundation pit support
The specific soil nail quantity, length, location, mesh requirements, etc. are determined according to professional design calculations. The length of soil nails should be 0.5~1.2 times of the excavation depth , the distance between them is 1~2m , and the angle with the horizontal plane is 5 ° ~20 °; the soil nail reinforcement should be HRB335, HRB400 , 16~32mm in diameter, and the borehole diameter should be 70 ~120mm ; grouting strength level is not lower than M10 . The concrete level of the surface layer is not lower than C20 , and the thickness of the protective layer of steel bar should not be less than 20mm .
The construction sequence is: slope repair → hole formation → installation of soil nails → grouting → bundling mesh and reinforcement ribs → shotcrete. Soil nailing should be constructed under conditions that exclude groundwater. The horizontal distance of the concrete sprayer should not be less than 100m , and the vertical distance should not be less than 30m . Selection compressor air flow 9m ³ / min or more, should be able to withstand the conveying pipe 0.8MPa or more pressure.
Bored pile-foundation pit support
The specific pile diameter, pile length, embedded depth, and reinforcement are determined according to the design calculation. The diameter of the cantilever structure pile should not be less than 600mm . The top of the row of piles should be connected by a reinforced concrete crown beam. The width of the crown beam (horizontal direction) should not be less than the pile diameter, and the height of the crown beam (vertical direction) should not be less than 400mm . The concrete strength level of the row pile and crown beam of the pile top should be greater than C20 ; when the crown beam is used as the connecting beam, it can be reinforced according to the structure.
The construction sequence is as follows: drilling rig to make a hole → lifting a steel cage → pouring concrete → crown beam construction. The allowable deviation of pile position is 50mm , and the allowable deviation of verticality is not more than 0.5% . The stiffening stirrups and the main ribs are welded by electric welding, and the spiral stirrups and the main ribs are tied and connected.
Pull anchor-foundation pit support
The specific anchor rod number, diameter, length, position, etc. and embedding depth are determined according to the design calculation. Pull anchors can be combined with row piles. Can also be used in combination with soil nail walls.
The construction sequence is: drilling rig hole → lower anchor cable → grouting → maintenance → anchor installation → anchor rod tension. The allowable deviation of the hole position is not greater than 100mm ; the deflection is not greater than 3% ; the strength of the anchoring section is greater than 15MPa and it can be stretched until it reaches 75% of the design strength . The anchor is anchored between the piles, and the anchoring force is transmitted to the pile body through the steel waist beam.
Foundation pit support-foundation pit support
For the pile-row and slab-wall supporting structure, when the depth of the foundation pit is large, in order to maintain the reasonable force of the wall and control the deformation, it is necessary to add support points. Erecting the support inside the pit is called internal support; setting the support outside the pit is called pulling anchor. Internal support usually has steel structure support and reinforced concrete support. Before the support is dismantled, a reliable force-exchanging member or backfilling should be installed between the main structure and the support.
Steel structure support requirements: the connection of the steel structure support members can be welded or high-strength bolt connection; the waist beam connection node should be set near the support point, and should not exceed 1/3 of the support spacing ; the steel waist beam and the row of piles, underground C20 fine stone concrete should be used for filling between continuous walls ; the joints between the steel waist beam and the steel support should be stiffened.
Reinforced concrete support requirements: the concrete strength level of the member should not be lower than C20 ; the support system should be cast in the same plane as a whole, and the connection point of the waist beam at the corner of the plane of the foundation pit should be designed according to the rigid node. The selection of internal support, plane layout, cross section, node connection, etc. all need to be strictly designed.
Backfill soil layered paving-manual backfill
The thickness and the number of compaction passes of the layered fill of the fill shall be in accordance with the above table. When backfilling in sections, each layer of the joint should be staggered by more than 1m . In winter, the thickness of each layer of backfill should be reduced by 20% to 25% compared with normal construction . The frozen soil content should not exceed 15% , the particle size should not be greater than 150mm , and the particle size of normal temperature backfill should not be greater than 50mm .
Pipeline backfilling-manual backfilling
The lower part of the pipeline is restricted by the pipeline, and mechanical tamping is no longer possible. It is manually squeezed and compacted from below the pipeline; manual tamping on both sides of the pipeline and within 500mm directly above the pipeline avoids damage to the pipeline. It is normal to use mechanical tamping outside 500mm above the pipeline . The backfill soil containing frozen soil shall not be used within 0.5m from the bottom of the trench back to the top of the pipe during the winter .
Earthwork Excavation-Mechanical Excavation
Before excavation, the excavation diagram should be drawn first. The excavation diagram should mark the upper and lower line of the foundation pit, the edge of the cushion, the edge of the foundation, the elevation of the base, the elevation of the deep excavation, the upper and lower mouth lines, and the plane position of all the lines.
When the slope protection form is soil nailing wall, the method of combined excavation with large and small steps is usually adopted. Taking 2 large steps and 6 small steps as an example, first of all, after completing 3 small steps of excavation, then complete 1 large step of excavation to the central area ; then, complete the earth excavation in this order, leaving 300mm soil layer; Finally, manually clear the soil to the bottom of the trough. The layer thickness is determined according to the actual conditions on site and the design scheme of the soil nail wall. Construction in winter must prevent the soil under the foundation from freezing, and loosening or covering should be reserved.
Foundation and foundation
Post-casting of the base raft
teel sheet waterstop, steel mesh, concrete wall mould, steel bar.
According to the thickness of the raft and the position of the water stop, spot welding Φ 12 additional steel bars along the center of the length of the water stop steel plate , with a spacing of 300~500mm .
Connect the additional reinforcement to the upper and lower reinforcement of the raft to fix the water stop plate. The notch of the water stop plate should face the water-facing surface. Cut the steel mesh according to the position of the water stop steel plate and the thickness of the raft, and install the steel mesh on the upper and lower parts of the water stop steel plate. The steel net is located inside the additional reinforcement and is tied to the raft reinforcement.
The formwork is supported on the outside of the expanded metal mesh. The top of the formwork is notched according to the spacing of the steel bars to control the thickness of the protective layer of the steel bar and the spacing of the steel bars. The spacing between the supporting and reinforcing squares is not more than 500mm .
The allowable deviation of the width of the back pouring belt is ± 10mm , and the water stop steel plate is fixed straight.
New type water-stop screw for underground wall
Formwork, water stop screw, dry hard waterproof mortar, expansion agent, cement-based waterproof coating.
Set up the inner formwork of the basement outdoor wall according to the formwork control line. Open holes in the formwork. The openings should be away from the steel bars with a spacing of 400~500mm . Install a new type of middle waterproof. The two ends can be removed and reused. Open a hole in the corresponding position of the outer mold screw and install the outer . Concrete is poured in layers, and the thickness of each layer is not more than 600mm .
Loosen the nut and dismantle the formwork to strengthen the facility Material：s, use a wrench to remove the two ends of the screw to turn around the use part, and remove the formwork. Use a cylindrical brush to clean up the debris in the hole, and spray water to wet it 3 hours before the construction . The micro-expansion dry hard waterproof mortar is flush with the wall. Brush a cement-based waterproof coating on the surface, and sprinkle water for no less than 3d .
The end of the bolt hole is tightly packed, and the waterproof treatment is in place.
Excavation construction of cast-in-situ pile free soil
Before the pile foundation construction, the earthwork was excavated to the bottom of the cushion to construct the concrete cushion. The method of constructing the cushion first and then constructing the pile (which can effectively control the length of the virtual pile and avoid the excavation between the piles). The thickness of the cushion is generally not less than 200mm , and the top elevation of the cushion is 100mm higher than the design pile top . Locate the engineering piles one by one on the completed cushion layer, and the pay-off size is 50mm larger than the design size of the pile .
After cutting the inner cushion concrete by cutting machine and pneumatic pick, support the pile top shape ( 150 ~ 200mm higher than the design pile top elevation ), and pour the concrete of the pile foundation to the top surface of the formwork. The location strengthens the vibration and eliminates the top concrete floating slurry. Remove the formwork to clean the surface of the pile top and the surface of the concrete cushion to meet the requirements of waterproof construction base.
The allowable deviation of the pile top elevation is 20mm , -30mm , and the pile position deviation is ± 30mm .
Sealing with prefabricated cover plate behind the shear wall
Waterproof mortar, prefabricated cover plate, waterproof coiled Material：.
The post-casting belt of the basement shear wall can be constructed by prefabricated cover plate plugging and early backfilling. The sealing cover plate is not less than 200mm wider than the post-casting tape , and the thickness should have the ability of waterproofing and resistance to backfill soil side pressure.
Before and after the installation, the surrounding contact area of the casting belt should be cleaned, and the root waterproof membrane should be protected.
After leveling, install the first cover plate manually or by hoisting the electric hoist. The embedded reinforcement of the cover plate should be welded firmly with the reinforcement of the post-cast belt. The cover plate and the base layer and each other are full of slurry. Install the prefabricated cover plate to the top of the shear wall in sequence. The surface of the cover plate is compacted and smoothed with waterproof mortar.
The prefabricated cover plate is firmly installed and waterproof and reliable.
Construction of jumping floor method of super large area concrete foundation floor
Ready-mixed concrete, formwork and supporting parts, collapsed closing net.
In the construction of large-area foundation concrete rafts, in order to effectively control the internal temperature rise of the concrete to prevent cracks, the concrete can be poured by splitting the tank in the length and width directions.
The division of sub-bins should be determined according to the thickness of raft, structural form, engineering volume, labor force, etc. The general length of sub-bins is not more than 30m . When pouring concrete, the construction can be skipped according to the word "product". The construction in each warehouse should be carried out in accordance with the calculation of thermal engineering. One-time pouring is completed without construction joints; the concrete pouring of the adjacent warehouse should be after the concrete strength of the previous warehouse meets the requirements. For pouring, install a quick and easy closing net at the construction joint to prevent the concrete from falling down.
The temperature measurement points and temperature measurement facilities should be buried in advance during the concrete pouring process, and the surface coverage and maintenance should meet the requirements, and the temperature difference should be controlled within 25 ℃.
The concrete is vibrated and compacted without cracks.
Treatment of the waterproof joint of the root coil
Waterproof membrane, adhesive.
The base root coil is laid flat first and then the facade. The size of the flat coil extending beyond the outer edge of the foundation is not less than 300mm , the lengths of adjacent coils are staggered, and the staggered size is not less than 300mm . After the construction of the concrete foundation is completed, when the facade rolls are laid, the yin and yang corners should be rounded and the diameter should be greater than 50mm . The joints should be uncovered and cleaned, and the damaged parts should be repaired. The adjacent joints of the vertical coil and the upper and lower joints should be staggered by not less than 300mm , and the length of the lap length synthetic polymer coil is not less than 100mm . When laying, the upper part of the coil joint should be pressed down, and the top of the raft guide wall should be waterproof. Additional layer.
The protective layer should be laid in place in time to prevent scratching the waterproof layer.
The waterproof membrane is firmly and tightly paved.
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