Hole collapse mainly includes hole collapse and hole collapse. Before and after the collapse of pile foundation, corresponding prevention and treatment methods should be taken according to the actual situation.
1Prevent hole collapse
(1) In the presence of loose strata with larger thickness, in order to avoid collapsing holes in the upper part of the pile foundation, high-pressure rotary jet grouting pile is used to reinforce the upper part of the pile foundation to achieve the purpose of strengthening the foundation or sealing water and preventing seepage.
(2) When the groundwater level is high or water seepage is serious, the hole forming process should be adjusted to wet drilling method in time to eliminate the influence of water seepage on pile foundation hole formation, which can effectively prevent pile foundation hole collapse.
2, hole collapse treatment
(1) When the hole mouth collapses, the protective cylinder can be removed immediately, and the mud in the collapsed hole can be discharged first, and then backfill and tamp with the strong soil around, and bury the protective cylinder again before drilling, or use the long protective cylinder follow-up method for construction.
(2When there are dark holes or loose strata at the bottom of the gully and serious hole collapse occurs, surface grouting can be used to reinforce the strata.
(3) When the hole collapse occurs and the degree of hole collapse is relatively light, it can be used to increase the proportion of mud, improve the performance of mud, change to positive circulation out ballast, increase the head, slow down the drilling speed and other methods, until the collapse section, and then return to normal drilling; When the degree of hole collapse is general, it can be considered to backfill the hole to the collapse site2~3mTo drill again; When the degree of hole collapse is serious, all the holes should be backfilled, and drilling should be carried out after the backfill is deposited dense.
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