Sudden settlements in expansive soils often result from local water loss
shrinkage, with four-level responses:
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Mild settlement (<10cm):
Inject high-viscosity mud (45s viscosity) to fill voids.
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Moderate settlement (10–30cm):
Drop graded sand-gravel mixed with quick-setting agent (initial setting in 15min).
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Severe settlement (>30cm):
Adopt grouting pipe shed method to form a 1.2m-diameter reinforcement ring.
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Extreme settlement:
Install backpressure devices at the hole opening combined with freezing for water stop.expansive soil
