People have a high demand for housing construction, but houses are always affected by some factors in the process of construction, and there are always defects in the construction quality, which affects the overall quality of the building, which is not only a problem in housing design and construction materials, but also part of the reason in construction supervision and construction technology.
To make the housing construction have high quality, we should start from the construction technology. The precast pile construction of reinforced concrete is very important in the whole project, and if its construction technology is not controlled well, the construction quality will not be good. This construction technology itself has more advantages, will not be affected by groundwater, will not be affected by moisture, and has a strong load force, this technology has been applied in many construction projects.
1 Precast pile construction preparation stage
1.1 Fabrication of precast piles
For the precast pile production, it can be made in the factory or in advance at the construction site, depending on the actual situation of the construction, which can facilitate the construction and save time and cost. If you use shorter prefabricated piles, it is best to prefabricate in the factory, so that transportation is more convenient; there are 10M less square piles are also best to prefabricate in the factory, as well as the pipe Zhuang, prefabricated in the factory will be more convenient.
If the square pile is very long, it has to be made at the construction site, and the pipe pile of the square pile still has to be made in the factory to ensure the quality of the prefabricated pile, which also means that the prefabricated work of the template should be done. In the pre-knowledge suit for prefabrication, to maintain the straightness of the pile surface, in the production of the pile size and the quality of the template to ensure that the pile surface distance also have control, can not have bonding, and do a good job of painting the isolation layer operation.
Then the main reinforcement should be used to connect the steel skeleton, and the best way to weld the skeleton is by butt welding, and special treatment should be given to the pile top and pile tip reinforcement.
1.2 Transportation of prefabricated piles
After making the prefabricated piles, the piles should be placed for a period of time to ensure that the strength of the piles can reach the design strength requirements, and after reaching the design standard, the prefabricated piles can be transported and piling can be carried out, so that the prefabricated quality of the piles can be guaranteed, and the prefabricated piles will not be damaged during transportation, so that the construction quality can be guaranteed when applied to the construction.
If you need to lift prefabricated piles, it is necessary to prepare in advance, and do a series of inspection and processing work, all up to standard before transport. When lifting the pile must be smooth, can not be impact or vibration, each lifting point to ensure that the force at the same time, if there is no ring, according to the pile tying points and the number to determine, and according to the length of the pile to find the most suitable lifting method, in short, to ensure that the pile is subject to minimal damage.
2 Pile driving construction technology analysis
2.1 Piling equipment
The first is the pile hammer. In the choice of pile hammer, you can use the drop hammer, vibratory hammer and steam hammer, which is made of cast iron, mainly using wire rope or strong rope, and then hook it on the winch, and then through the pile frame inverted rod to raise it to the appropriate height, and then let it fall freely, prior to the pile top of the blow.
And the main working principle of steam hammer is based on compressed gas such as high pressure steam as the main power to strike the pile. Next is the pile frame, which plays a supporting role for the pile hammer and the pile body, and can guide the direction and smoothness of the pile when driving the pile, so that the pile hammer can strike the pile body. The composition of the pile frame is relatively simple, with a chassis, spreader bars and lifting equipment.
2.2 Piling sequence
The piling sequence directly affects the quality and construction speed of the pile foundation. The piling sequence should be reasonably determined based on the density of the piles (pile spacing size), the specifications and length of the piles, the design elevation of the piles, the working surface arrangement, and the construction period requirements.
According to the density of piles, the piling sequence is generally divided into three kinds: piling section by section, piling from the middle to all around and piling from the middle to both sides.
When the pile driver is in position, the pile frame should be vertical and smooth, and the centerline of the guide bar should be consistent with the piling direction. When the pile starts to be driven, the hammer distance should be controlled and a short distance and light blow should be used; after the pile is stabilized at a certain depth in the soil, the pile should be driven with the specified distance.
The principle of pile driving is heavy hammer and low blow, so that the impact of the hammer on the pile head is small and the rebound is small, and the pile head is not easily damaged, and most of the energy is used to overcome the frictional resistance of the pile body and soil and the resistance of the pile tip, and the pile can be sunk into the soil faster.
2.4 Piling quality requirements and measurement records
If the final penetration of end-bearing pile is not greater than the design penetration value, the design elevation of pile end can be used as reference; if the elevation of friction pile end reaches the design elevation range, the penetration can be used as reference. The deviation of the pile position of the driven pile must be in accordance with the relevant quality control regulations.
The bearing capacity of the pile is to be tested if it meets the requirements. Piling project is a hidden project, the construction should do a good job of each pile observation and records, which is the basis for the acceptance of the project inspection quality.
2.5 Analysis of common problems in piling construction
First of all, the pile body rebound serious, pile hammer leap back problem in the choice of pile hammer, if the hammer quality is light can cause such problems, the lighter the pile hammer caused by the pile hammer leap back is also greater. In the process of pressing, if the pile tip encounters a hard obstacle in the stratum that is difficult to overcome, the pile body rebound problem will occur.
Second, the pile body is interrupted pile body has a large bending convex belly, pile body production, local concrete strength is not enough, in the sinking pile tip encounter obstacles such as solitary stone or hard soil layer, repeated excessive impact, increase the drop distance, etc. may cause the pile body fracture.
Once again, the pile top broken when piling, pile top directly by the impact of the hammer will produce high local stress, if the concrete protection layer is too thick, pile top reinforcement mesh configuration is not appropriate, the pile center axis and pile top plane is not perpendicular, the pile top is not flat and other quality problems will cause the pile top broken.
Finally, pile twisting, displacement, tilting pile tip quadrilateral cone production deviation, pile centerline and pile tip do not overlap production, pile body and pile cap and pile hammer are not in the same vertical line of construction operations, pile frame tilt, pile tip encounter solitary stone and other reasons can cause pile twisting, displacement, tilting.
3 Pile foundation static compression pile construction technology
Static pile construction technology is a new exploration of pile construction technology, which has been widely promoted and used in the construction of engineering foundations in China, and the quality of engineering construction is strongly guaranteed. This construction process mainly uses static pressure for construction. This static pressure construction technology has many excellent features, it has no vibration, no noise, and evenly presses the pile into the soil. This construction technique is mainly used in the environment of homogeneous soil and the nature of the foundation is required to be soft.
Its working principle is to use the counterweight and self-weight of the pile press frame, by the pulley, pressurized wire rope, pressure beam, through the winch traction, the entire pile press gravity on the top of the pile, so as to overcome the friction between the foundation soil and the pile sinking, so as to achieve the purpose of precast pile sinking.
In the construction, attention should be paid to the appropriateness of the pressing method. The pile pressing construction generally adopts the construction method of section-by-section extension and section-by-section pressing, which fully ensures the quality of construction.
The application of reinforced concrete precast piles in housing construction can effectively ensure the stability of the building structure and improve its seismic capacity.
However, special attention should be paid to the production process and transportation process of precast piles and the final application process, to protect the pile body from receiving any damage, to grasp the main points of each control in the construction process, combined with the needs of the construction period.
At the same time, pay attention to the safety of the construction process, and for the actual situation of the site environment to develop a reasonable construction plan to ensure that the quality of housing construction can meet the construction standards.