Today I'm going to talk about the preparation work before foundation pit excavation. Let's have a look.
Field reconnaissance investigation
1. Understand the natural conditions such as topography, landform and climate of the construction site.
2. Consult the geological survey report to understand the distribution, formation age and physical and mechanical properties of the soil layer within the pile-forming depth of the construction site.
3. Understand the groundwater level, water quality and its changes in the construction site.
4. Understand the man-made and natural geological phenomena in the construction site area, such as earthquakes, karst rocks, mineral rocks, gutang, hidden banks, underground structures and obstacles.
5. Understand the location, distance, structural nature, current situation and current use of adjacent buildings.
6. Understand the distribution, distance, buried depth, service life, pipe diameter and structure of underground pipelines (gas pipes, water pipes, sewer pipes, cables, etc.). ) near the pile sinking area.
technical reserve
1. Preparation of construction scheme. Before construction, the construction scheme should be worked out, and the pile-forming machinery, pile-forming method, construction sequence and protective measures for adjacent buildings or underground pipelines should be defined.
2. Construction progress plan. Determine the pile foundation construction plan according to the overall project schedule, which should include the schedule plan, labor demand plan and material and equipment demand plan.
3. Formulate measures such as quality assurance, safety technology and civilized construction.
4. Carry out process pile test. In order to determine the reasonable construction technology, pile testing should be carried out before construction to determine the process parameters.
Mechanical equipment preparation
Before construction, the corresponding mechanical equipment should be selected according to the designed pile type and soil conditions, and the pile should be tested.
Site preparation
1. Clear the obstacles on site. Before piling, it is very important to remove the overhead and underground obstacles that hinder the construction, such as poles, wires passing through the construction area, foundations of old buildings or other underground structures.
2. The site is leveled. Pile foundations of high-rise buildings are usually closely spaced piles. Before the pile driver enters the site, the whole work area must be leveled to ensure the verticality of the pile driver and facilitate its smooth walking.
For precast piles, whether hammering, static pressure or vibration piling, the self-weight of piling machinery is relatively large. When the site is leveled, gravel with a certain thickness (generally about 200mm) should be laid to improve the bearing capacity of the foundation surface in direct contact with the piling machinery and prevent the uneven settlement of the piling machinery from affecting the verticality of piling. The general crawler pile driver requires the bearing capacity of foundation to be 100 ~ 130 kPa. If the paving of gravel still cannot meet the requirements, the method of paving walkway slab (also called subgrade box) can be adopted to reduce the pressure on foundation soil.
For cast-in-place piles, the site should be leveled according to different pore-forming methods. If manual excavation is used, the excavated earth-moving road should be considered when leveling the site; Mud tanks and drains should be considered when using bored piles. In recent years, Shanghai and other big cities have carried out the hard ground construction method of bored piles, that is, first make concrete hard ground in the construction area of bored piles, and at the same time arrange mud pools, grooves and drainage ditches, and then drill holes at the pile site to form piles. This method makes the mud discharge orderly, realizes civilized construction and greatly improves the construction efficiency. During the construction of immersed cast-in-place piles, the site leveling requirements are similar to those of precast driven piles. Because of the need to hammer or vibrate when sinking the pipe, the pile driver also has higher requirements for the bearing capacity of the foundation soil.
I believe that after the above introduction, if you want to have a worry-free foundation pit project, everyone has a certain understanding of these four preparations. Welcome to Zhong Da for more information.
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