the pile foundation of Guoxin Financial Building in Futian Central District of Shenzhen has a diameter of φ1800, φ2000, φ2200 and φ2600mm, mining dth bit ,overburden drilling systems, a pile hole depth of 38 ~ 41mm, a pile bottom bearing stratum of 2m into moderately weathered granite or 0.5m into slightly weathered granite, and a compressive strength of 75 MPa for slightly weathered granite. (2) Pile foundation construction and hole cleaning measures: Sany Heavy Industry SR420II rotary drilling rig is selected for pile foundation construction, 3m pile casing is buried at the orifice, and chemical slurry is prepared from sodium hydroxide powder, sodium hydroxide and CMC. Taking the hole with a pile diameter of 2,600 mm as an example, the upper fill, silty clay, residual soil and strongly weathered rock stratum (about 38 m deep) shall be drilled in two stages according to the diameter of 2,200 mm and 2,600 mm by the rotary drilling bucket. Since the rotary drilling is carried out with static mud without circulation, the drilling speed is fast (about 6 hours), and the mud wave on the hole wall is thin, At this stage, the mud shall be controlled at a specific gravity of 1.08 ~ 1.20 and a viscosity of 18 ~ 20 S. The lower moderately weathered and slightly weathered rock strata are hard and deeply penetrated into the rock. Aliyun Building and Life Building, and has achieved satisfactory results, which should be vigorously promoted. (6) There are a large number of rotary pile construction teams in Shenzhen, and the number of individuals is large. The performance, management level and operation ability of pile drivers are quite different. They are often hastily started, lack of training, and lack of mastery of rotary pile construction technology and operation skills, especially the mastery of drilling mud performance. It is often difficult to achieve the desired results. Therefore, in the specific operation of secondary hole cleaning, the hole cleaning process should be adjusted according to the actual situation. In particular,dth rock bit, if the drilling tool without mud circulation cleaning process is adopted, its practical application has a high technical content. If the sediment at the bottom of the hole cannot meet the design requirements after placing the reinforcement cage and pouring the guide pipe and before pouring the concrete, the mud positive circulation or reverse circulation must be used for secondary hole cleaning. Return to Sohu to see more Responsible Editor:. wt-dthtools.com