Construction technology standard of dynamic compaction Foundation
1 scope of application
This standard is applicable to the construction of foundation reinforcement by dynamic compaction. When the vibration produced by dynamic compaction has an impact on the buildings or structures built or under construction around the site, vibration prevention measures shall be taken when necessary.
2 construction preparation
2.1 main construction equipment
The weight of dynamic rammer is 10-40t, and the bottom form should be round or polygonal. The rammer should be made of cast steel. If the condition is limited, concrete can be filled into steel plate shell. The bottom surface of the rammer should be symmetrically arranged with a number of vent holes with a diameter of 250-300 mm through the top surface, so as to facilitate the rapid discharge of air at the bottom of the pit when the rammer hits the ground and reduces the suction at the bottom of the pit when the hammer is lifted. The hammer bottom area should be determined according to the nature of soil. For sandy soil and gravel fill, the bottom area of 2-4m2 is more appropriate; for general quaternary cohesive civil engineering, it is recommended to use 3-4m2; for muddy soil, it is recommended to use 4-6m2. The value of static grounding pressure at hammer bottom can be 25 ~ 40kpa, while for fine-grained soil, it should be smaller.
2.1.2 lifting equipment
Crawler crane of 15t or above or other special lifting equipment should be selected. When the tonnage of the crane is not enough, the method of adding steel legs can be adopted. The lifting capacity should be 1.5 times of the weight of the rammer. When crawler crane is used, auxiliary gantry can be set at the end of boom, or other safety measures can be taken to prevent the frame from overturning when falling hammer.
2.1.3 decoupler: it is required to have sufficient strength and not produce sliding hook during lifting; the decoupling device is flexible and can keep the hammer falling down smoothly, and the hook is convenient and rapid.