(I) process flow

The construction technology of bored pile must be fully supported before the construction of Hefei bored pile, due to different drilling equipment, the construction process is also different. now, taking GPS100 rotary drilling rig as an example, the main construction process is: site leveling → hole position determination → casing embedding → drilling rig in place → drilling into holes → lifting drilling → first hole cleaning → hole inspection → steel cage lifting → pipe down → second hole cleaning → underwater concrete pouring → pipe lifting → pile formation.

Construction of Cast-in-place Pile in Hefei

(II) Main Preparations

1. The construction organization design must be pre-reviewed. Before the commencement of the project, the construction unit shall submit the construction organization design (special construction plan) to the supervision department in advance for review, including the construction method, main technical indicators and control measures. Improve the construction organization design after review by the supervision engineer.

2. must carefully good measurement positioning off. Measurement and positioning is the key to the whole work, in the idea must have enough attention, is related to the accuracy of the hole, drilling verticality and the elevation of the datum. In the specific operation process, the construction unit must strictly follow the requirements of the three-inspection system, communicate with the supervisor in a timely manner, combine with the supervisor's careful review and acceptance, and strictly control the deviation within the scope allowed by the design or specification.

3. The casing and drilling rig must be installed firmly and accurately. The casing has the functions of fixing the pile position, drilling guidance, protecting the orifice and isolating the surface water inside and outside the hole. In the production process, it is required to be strong, durable, not easy to deform, watertight, easy to load and unload, and can be reused. Generally, steel casing with flange is used, which is made of 3~5mm thick steel plate. A stiffening rib is welded on the outer side, middle and lower part of the casing to increase rigidity and prevent deformation. The shape can be made into a whole or two semicircles. When embedding, ensure that the plane position is correct, the deviation shall not be more than 5cm, and 1.0~2.0m higher than the highest water level of construction; The casing buried under water shall be sunk to a stable depth along the guide frame by means of self-weight, water jet, vibration or hammering.

Drilling rig is a support for drilling, lifting reinforcement cage and pouring concreteTo install stable and safe. It should be able to bear the weight of drilling tools and other auxiliary equipment, and have certain rigidity. It is not easy to produce shaking during drilling or other operations. The height is determined by the length of drilling tools and the length of reinforcement frame section, generally 8~12m; The length of the chassis should be determined according to the height stability. The section size of the main stressed members shall be determined by the calculation of the maximum load occurring in the construction, and the safety factor shall not be less.

4. During the drilling process, the hole-forming center must be aligned with the pile position center, and the drilling rig must be kept stable without displacement, inclination and subsidence. When installing in place, the base shall be firmly plugged with sleepers after detailed measurement, and the top shall be fixed stably with cable wind rope, and shall be checked frequently during the drilling process to ensure the level of the rotary table surface and the verticality and aperture of the pile body.