1. Construction preparation stage. Before the project starts to break ground, it is necessary to have on-site geological investigation data, so as to prepare for the review of the construction drawing and the basis for the preparation of the construction technical scheme, organize and arrange the construction technological process and safety technical indicators and measures, and formulate relevant early warning treatment schemes for hidden dangers existing on the site to avoid or reduce the safety and quality problems in the construction process. At the same time, according to the site environmental inspection "three links and one leveling" and the preparation of temporary facilities, master the distribution of underground pipelines and structures in the surrounding area of the site. Configure the model and quantity of construction machinery and equipment according to the convenience of the construction site and the engineering quantity plan, and ensure that the machinery and equipment have relevant appraisal certificates. The purchase and entry of construction materials should strictly control the quality and check the source. 2. Construction process stage. The construction sequence of independent foundation is as follows: foundation excavation → foundation pit finishing → plain concrete cushion → foundation pile cap → foundation beam and column → backfill soil. The pouring sequence is "first transported, last transported". (1) Earthwork excavation and side protection. Before earthwork excavation, put away the foundation sideline and earthwork excavation line, and lead them to the place outside the foundation pit that will not be destroyed. When excavating, pay attention to the 2mm thick soil layer reserved at the bottom, and dig it when pouring the cushion after checking the groove to prevent the basement from being disturbed by long-term exposure. When excavating a foundation pit, if it is found that the soil layer does not conform to the geological report, or if it is found that there are bad foundations, such as underground ditches, underground rises, hidden ponds, tombs and civil air defense facilities, it shall immediately notify the personnel of the geological exploration department, design institute and other relevant departments of the construction unit to study and solve them on the spot. During earthwork excavation, the construction surveyors strictly control the elevation, and it is forbidden to overbreak. Earthwork adopts large excavation and natural sloping, and rainwater or surface water is collected in the collecting well through drainage, and then discharged out of the pit by submersible pump. (2) Foundation cushion construction. After the foundation trench inspection is completed, remove the surface floating soil and disturbed soil, leaving no water, and immediately carry out the construction of cushion concrete. The cushion concrete must be vibrated and compacted, and the surface is flat. It is forbidden to dry the foundation soil. When the C1 concrete cushion is cast, a set of standard test blocks shall be retained, and the test blocks shall be supervised by the personnel of the supervision company and sent to the laboratory for maintenance. Before the cushion is poured, the earthwork should be trimmed, and the elevation of the foundation pit should be marked with bamboo sticks. First sign it in the foundation pit with bamboo, and then measure its elevation with a leveling ruler. In the process of plain concrete pouring, the overall elevation will be measured based on the tops of these bamboo sticks. In concrete construction, surveyors should control the whole process of construction. (3) Fabrication and installation of steel bars. Learn and be familiar with the construction drawings and designated atlas, understand the reinforcement structure of constructional columns, ring beams and joints and the practices of various ministries, and determine the reasonable segmentation and lap joint positions and installation order. Steel bars shall be provided with factory quality certificates and test reports, and different models, steel grades and specifications shall be re-examined, and can only be used if they meet the design requirements and relevant standards. After cold drawing, the length of Grade I steel is extended to a general small cold drawing, and the steel bars shall not be cracked, rusted, damaged or free from pollution. If particles are found, they shall not be used. Calculate the accurate blanking list according to the construction drawing, plan the blanking according to the length of steel, and strengthen the recheck of the middle size to make the best use of it. According to the requirements of the construction layout and the binding order, the quantities of different models, specifications and sizes are stacked and hung with signs. Before binding, the sundries in the template and the floor mortar ash of the wall should be cleaned, and the horizontal elevation lines should be played on the template. When binding the reinforcement of foundation column, the joints of stirrups should be staggered on the longitudinal reinforcement at the four corners, and the intersection of stirrup corners and longitudinal reinforcement should be firmly fastened. When binding stirrups, the binding buckles should be splayed. Tie the foundation beam, tie it after the formwork is supported, draw a line on one side of the formwork according to the stirrup spacing, and then put the stirrup into the stressed steel bar. When binding, stirrups should be reinforced vertically and staggered along the direction of reinforced bars. The binding joints between the stressed steel bars should be staggered and fastened with iron wires at the center and both ends. When processing steel bars, they shall not be sawed and placed randomly, and the oil, dirt and floating rust on the steel bars shall be cleaned before use. Steel bars shall be kept clean after binding. (4) Formwork construction. First of all, the formwork and its support must comply with the following provisions: to ensure the accuracy of the shape, size and mutual position of various parts of engineering structures and components. It has sufficient bearing capacity, rigidity and stability, and can reliably bear the dead weight and lateral pressure of new concrete and the load generated in the construction process. Simple structure, convenient assembly and disassembly, convenient for binding and installation of steel bars, pouring and curing of concrete and other requirements. The joints of the formwork should not leak slurry. Wood molds and supporting systems should be made of materials that are not easy to deform, light in weight and good in toughness, and rotten, brittle and moisture-prone wood should not be used. Secondly, in the installation of foundation column formwork, it is necessary to ensure that the foundation column formwork is composed of side formwork, column hoop and support. Before installation, the sundries in the foundation column and steel bar should be cleaned up, and the side formwork should be installed first and then the column hoop should be installed to fix it. In order to ensure the stability of the formwork, the formwork should be fixed with horizontal braces and scissors. When the formwork is dismantled, the bearing formwork can only be dismantled when the concrete strength can ensure that its surface and edges and corners are not damaged by formwork removal. Dismantled templates should be cleaned up and transported in time, meanwhile, the sundries on the templates should be cleaned up, the isolation agent should be painted, and the templates should be sorted and stacked neatly. (5) Concrete pouring. Before pouring, check the mechanical equipment to ensure the supply of water, electricity and raw materials, and master the weather changes. Check the elevation, position and section size of the formwork, whether the support and the fixation of the formwork are reliable, and whether the specifications, quantities and installation positions of the steel bars comply with the design. Clean up the sundries in the formwork and the oil stain on the steel bar, and water it to moisten it, but there shall be no water. When pouring the foundation column, pay attention to the distance between the vibrator and the formwork, and avoid the collision between the steel bar and the formwork. When pouring, it should be transported from the mixing place to the pouring place with the least number of reprints and the shortest time. When using the vibrator, it should be inserted and tamped in an orderly way, without missing vibration. The duration of each vibrating should make the concrete surface appear laitance and not sink. When pouring, always observe the formwork to prevent the expansion of the formwork. When vibrating concrete for foundation beam, the inserting distance of vibrators is generally about 4mm, and the vibrating time should make the surface of concrete appear laitance and not sink. For reinforced dense parts, measures should be made to ensure smooth distribution and vibrating compaction. When pouring, we should always observe the reinforcement and formwork, and take immediate measures to deal with any deformation or displacement. After the concrete is vibrated, the surface should be smoothed with a grinding plate. After pouring, concrete curing should be carried out, that is, covering and watering. Before the strength reaches 1.2N/mm2, it is not allowed to trample and install masonry on it. (6) Earthwork backfilling. Due to the current situation of the project, the foundation backfill is divided into one backfill, and the natural soil is used for layered compaction. When filling the soil, the compaction quality of the edge should be guaranteed. Before backfilling, clean up the sundries and rubbish such as tree roots and wood in the pit, drain the accumulated water in the hole and pit, clean the silt and sand, block the shoulder-load hole with fine stone concrete, and ensure that the strength of the wall and concrete reaches certain requirements, so as not to be damaged during earthwork backfilling before backfilling. When backfilling, tamping should be one tamping and half tamping, and tamping should be connected, row by row and criss-crossing, and the so-called "water tamping" method of sinking soil by water pouring is strictly prohibited. In the process of filling, backfill soil shall be carried out according to the design requirements, soil quality, moisture content and backfill specifications in each process such as soil taking, soil spreading and compaction. While doing the above work, all construction links must be strictly constructed to ensure the smooth progress of earthwork backfilling project. To sum up, the construction technology of civil independent foundation is widely used and popularized in civil construction in China because of its strong adaptability, low cost and simple construction. As a hidden project, the construction process is usually underground, so it is difficult to monitor the construction process and check the construction results, and every construction link may have quality hidden dangers. Therefore, it must be taken seriously.
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