A specially assigned person shall check the verticality of the pipe body with a level ruler to ensure that the pipe body is inserted into the groove bottom freely and vertically.
The length and plumpness of the weld shall meet the specification requirements.
Some work without training and do not master some necessary knowledge for grooving construction.
2.2 prevention and control measures (1) before grooving, check the width and perpendicularity of the guide wall and the size of the grab bucket of the grooving machine, deal with any problems found in time, and check whether the grooving machine is in good operation at any time during grooving.
Common defects in grooving quality, staggered joints and out of limit perpendicularity.
When the reinforcement cage is extended, the lateral swing of the reinforcement cage must be avoided, and both ends of the support beam of the lower section must be leveled to keep the cage vertical and ensure the vertical alignment of the upper and lower sections..
(4) Small excavators shall be used for foundation trench excavation.
1.2 prevention and control measures (1) according to the comprehensive design of the project geographical environment, soil layer properties, hydrology, construction mechanical load, mechanical capacity, impact on the surrounding environment and construction progress, a better guide wall form and sufficient buried depth shall be selected, which shall be designed according to the strip foundation according to the code for design of concrete structures and code for design of building foundation, The section division shall be staggered with the groove section to ensure that the surface is flat and the height is consistent, and its height shall be slightly 2 ~ 3cm higher than the original ground to avoid rainwater and spilled mud flowing into the groove.
(8) During the construction process, the heavy load on the ground shall be strictly controlled to avoid the collapse of the tank wall caused by the construction load, shorten the exposure time of the tank wall, timely lower the reinforcement cage and conduit and pour concrete.
Shaking and vibration are inevitable in the lifting process.
The elevation shall be controlled while excavating, and the backfill shall be tamped in layers with jump rammer.
Common quality problems of guide wall: deformation, cracking, sinking and bulging of guide wall.
The subbase shall be compacted with more than 10t roller, and the thickness of reinforced concrete pavement surface shall be more than 20cm to ensure that the bearing capacity meets the construction requirements.
(4) Strictly control the use and management of mud, set up a rain proof sunshade on the site mud box, track the sampling test in the whole process of grooving, take measures such as correction of mix proportion, regeneration treatment or waste treatment according to the test results, and control relevant indicators during grooving, after grooving and before pouring to ensure that the mud indicators meet the construction requirements.
(6) During the construction of access road, the distance to the edge of groove section shall be reserved to ensure that the clear distance is greater than 5m.
(5) Strictly control the stop position of the grooving machine and the driving route of the crane and tank car, lay steel plates beside the guide wall to reduce the contact stress and avoid the inclination, deformation, sinking and cracking of the guide wall.
At the corners of the internal and external corners of the end well, the guide wall shall extend a certain distance outward to avoid insufficient groove section and affecting the construction of reinforcement cage.
It is not allowed to drag on the ground during lifting.
(5) The verticality control shall be strengthened during grooving.
Common quality problems of reinforcement embedded parts: exposed reinforcement, insufficient protective layer and sinking after excavation; Distortion, deformation and dislocation of skeleton; Deviation of embedded parts and dislocation of connectors; Mud is embedded on the inner distribution bar, connector and embedded parts, and the protective layer falls off after welding.
3.2 preventive measures (1) before lowering, find out the paint line on the guide wall, strictly control the position of the jacking machine, and control the elevation of the base with a level or level to ensure its verticality and stability, Check the pipe body injury, the welding quality of connectors, whether the axis of each section is straight after assembly, and whether the clearance between connecting pin and each section affects other processes.
(2) In the weak stratum, the foundation at the bottom of the guide wall can be pre reinforced by vibroflotation, high-pressure suspension spraying, deep mixing and other methods.
The up and down activities of the grab shall be used to brush out the non straightness.
When pouring concrete, raise the pouring elevation to 0.3 ~ 0.5m above the bottom of the guide wall to maintain the stability of the guide wall.
4.1 cause analysis in recent years, the reinforcement cage construction of ground wall has the characteristics of long length, large weight, large flexibility, many joints and high technical requirements.
(2) During lifting, a shoulder beam is set at the top of the reinforcement cage.
Over excavation and under excavation are strictly prohibited.
Each welding point shall be welded firmly, especially at the lifting point.
1.1 cause analysis (1) the guide wall is not deeply embedded, the bottom is not inserted into the undisturbed soil layer, the backfill at the back of the wall is not dense, and no wooden support is added after formwork removal; (2) If the exposure time is too long, it tilts inward and is not parallel to the centerline of the ground wall; (3) Improper and untimely maintenance measures and insufficient concrete curing age lead to cracking; (4) The clear distance between the access road and the guide wall is insufficient, its bearing capacity is insufficient, and it is damaged by crushing and subsidence.
(2) When the wall is not deep, the pipe shall not be bent when lifting the joint pipe as a whole.
The verticality of the grab shall be adjusted by timely adjusting the angle of the arm according to the verticality displayed on the verticality display instrument on the grooving machine.
It is lifted by two machines at multiple points and straightened in the air.
(7) Optimize the construction scheme and strengthen the connection between processes.
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(3) According to the characteristics of the soil layer, the form of the ground wall and the grooving depth in the site, formulate the corresponding grooving scheme, use appropriate machinery, prepare and use mud that meets the site geological conditions and construction conditions, and reasonably arrange the grooving sequence to improve the accuracy and safety of grooving.
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(4) As far as possible, backfill the excavated fresh clay manually, and tamp it in layers with self-made tamping rod or steel chisel to avoid flowing around during concrete pouring.
If the inclination exceeds the limit, it shall be corrected in time and corrected as soon as possible.
Common joint quality problems: the lock pipe and H-shaped steel are unstable, not vertical, skewed, etc., and the concrete flows around.
The reinforcement framework is welded and formed on the fetal membrane.
4.2 prevention and control measures (1) in order to facilitate the stress of reinforcement, facilitate construction and accelerate the wall forming speed, the reinforcement cage shall be processed and hoisted as a whole as far as possible.
(3) When the reinforcement is bound, it shall be fixed with scaffold to ensure its accurate position, no deformation and fragmentation, and ensure the overall stress balance between reinforcement and concrete.
2.1 cause analysis the speed and accuracy of grooving quality are mainly controlled by the grooving machine driver and the inclinometer on the machine.
For the connection between ground walls with different thicknesses, give priority to the construction of a thin one to minimize the disturbance to the adjacent soil mass.
During the lifting process, the position and deflection of the reinforcement cage must be checked and controlled with a lifting wire or theodolite at any time, and corrected in time.
(6) Each time the grab is lowered and lifted, it shall be carried out slowly and uniformly to balance the resistance on both sides of the grab.
(5) After the locking pipe is pulled out, it shall be disassembled, washed and stacked at the designated position for reuse next time.
Sometimes the construction is carried out continuously during the rush period, and the wall protection slurry is unqualified, There are other construction loads or additional stresses nearby during grooving construction.
(3) After lifting in place, timely check whether the pipe body is at the predetermined position, whether it reaches the specified depth and meets the conditions required for joint construction.
Reduce the collision of groove wall and mud oscillation.
The ultrasonic instrument can also be used to conduct random inspection every 3 ~ 5m.
A little carelessness will cause loss due to desoldering, deformation, distortion and fragmentation.
3.1 cause analysis: the filling behind the pipe is insufficient and not dense.
(3) The hoisting process shall be careful and stable, and forced flushing is not allowed to prevent the groove wall from collapsing due to the shaking of the reinforcement cage.
(4) When the reinforcement cage enters the slot, the center of the lifting point must be aligned with the center of the slot section, and then slowly descend.
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Before hoisting, the overall stiffness of reinforcement skeleton and the stress of lifting point shall be simulated and checked with professional software, and the construction personnel shall be provided with detailed technical background.
The pipe shall be placed carefully and gently at a uniform speed.
For special strata, if necessary, use the two drilling and one grasping method to control the perpendicularity.
These human and accidental factors cause unavoidable quality hidden dangers.
(2) Strengthen the training for the driver of the grooving machine, transfer the personnel with high quality, skilled technology, rich experience and strong sense of responsibility, and do not carry out fatigue construction.
The road shall be paved with steel plate when the reinforcement skeleton is made on the fetal membrane, A closed horizontal stirrup shall be arranged every 2.0m to strengthen its integrity and stiffness.
The driver’s level, construction experience and quality awareness directly affect the construction quality.
In order to avoid shaking of the reinforcement cage in the air, two hemp ropes are tied at the bottom and controlled manually.
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