Dynamic compaction foundation treatment design including effective reinforcement depth determination, interval time, consolidation point arrangement, processing range, etc., before construction should be in the construction site representative on the site to select one or several test areas, trial compaction or experimental construction, determine the design parameters.
(1The limited reinforcement depth of dynamic compaction method should be determined according to field trial compaction or local experience.
(2) The number of ramming of the ramming point should be determined according to the ramming count and ramming volume relation curve of the field trial ramming statistics. The control standard is as follows:
①The average ramming weight of the last two strikes is required:
②The ground around the tamping pit does not have excessive uplift.
③The difficulty of lifting hammer caused by too deep tamping pit.
(3The number of ramming times should be determined according to the nature of the foundation soil, generally using point ramming 2～3 For fine granular soil with poor permeability, the number of ramming times can be increased appropriately. Finally, low energy full ram 2 Times, full rammer can use light hammer or low distance hammer many times ramming, hammer seal phase.
(4The time interval between two rammers depends on the dissipation time of excess pore water pressure in the soil. For good permeability foundation can be rammed continuously, for poor permeability of cohesive soil foundation, the time interval should not be less than 3～4 Weeks.
(5) The plane design of the ramming point should be based on the effective reinforcement depth, and the number of ramming times is arranged by equilateral triangle, isosceles triangle or square. The spacing of the first ramming point should be the diameter of the rammer 2. 5～3.5 Times, the second ramming point is located between the first ramming point; After each ramming spacing can be appropriately reduced. For projects with deep depth or large energy efficiency of single point ramming, the first time ramming point spacing should be appropriately increased.
(6) The scope of dynamic compaction treatment should meet the requirements of building foundation bearing capacity and deformation. Generally, the stress diffusion and influence range of foundation soil should be greater than the scope of building foundation, and the width of each side beyond the outer edge of foundation should be the design treatment depth under the foundation1/2 to 2/3And should not be less than 3m; For liquefied foundation, the treatment width of foundation edge shall not be less than5m; Collapsible loess foundation should comply with the current national standard "Building Code for Collapsible Loess Area". GB 50025 The relevant provisions of.
(7)The bearing capacity characteristic value of dynamic compaction foundation should be determined by field load test, and the reasonable size of pressure plate should be selected according to the effective treatment depth. The size of the platen shall not be less than the effective treatment depth 1/3. The bearing capacity of the underlying layer of dynamic compaction foundation should be reviewed according to the building load and foundation design.
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