I. Pre-requisites for Foundation Construction
Geological Requirements
The foundation of the tower crane must be made of original hard soil, compacted sandy soil or pile foundation caps; direct pouring of the foundation is prohibited in areas with silt, backfill soil, soft and weak soil pits, or underground voids.
The bearing capacity of the foundation must meet the design values specified in the tower crane manual. If the bearing capacity is insufficient, replacement filling or pile reinforcement must be carried out, and a foundation inspection report must be issued.
Drainage Requirements
Drainage ditches with a depth of ≥ 300mm should be excavated around the foundation in advance; additional sump pumps should be installed on sites with high groundwater levels to prevent the foundation from being soaked for a long time and to avoid softening and settlement of the foundation.
Site Load Control
Within 3 meters outward from the edge of the foundation, it is prohibited to stack heavy objects such as steel bars, sand, blocks, and earthwork to avoid lateral pressure causing the foundation to tilt or slide.
II. Standard for Reinforced Concrete Foundation
Concrete strength
The concrete strength grade of the conventional tower crane foundation should not be lower than C35; the pouring and curing should last for no less than 7 days, and the strength should reach 100% of the designed strength before the tower crane can be installed.
Reinforcement and dimensions
The length, width, thickness, and specifications and spacing of the reinforcing bars for the foundation should be strictly constructed in accordance with the original factory drawings of the equipment. No reduction in size or decrease in reinforcing bars is allowed privately.
Sufficient support legs should be set between the reinforcing bars of the upper and lower layers to prevent the bars from sinking or shifting during pouring.
Pre-installed anchor bolts
The positioning frame for the anchor bolts must be firmly reinforced. Coordinates should be rechecked before and after pouring, and the deviation of the center position of the bolts should be ≤ 2mm; the threads of the bolts should be fully protected to prevent contamination by cement and rusting.
A secondary grouting layer is reserved on the top surface of the foundation, and after installing the tower crane base, the grouting should be dense.
