Engineering Characteristics of Weak Subsoil in Coastal Area and Reforcement Effectiveness Using Cement-mixed Pile
The southeastern coastal region of China presents deep and complex soft foundations characterized by high groundwater levels,considerable thickness of muddy soft soils,and low foundation strength,posing challenges in foundation treatment and control of settlement deformations.Leveraging the foundation reinforcement project of the Shanshan high speed railway,this study carried field test and laboratory tests to analyze the engineering characteristics of soft soils in coastal area.A method involving cement mixing piles for foundation treatment was proposed,alongside optimization of mix ratios and construction schemes.Following treatment,the efficacy of reinforcement was assessed through quality inspections of the piles.The Results reveal a shear strength of 28.7 kPa for the soft soil foundation in coastal area,with groundwater levels buried at depths ranging from 1.2～2.0 m.The presence of muddy soft soil layers significantly impacts the formation of cement soil piles.Based on the engineering properties of soft soil foundations,construction adopts the"four-stirring and four-spraying"pile forming process,with a water-cement ratio of 0.55,a cement-sand ratio of 0.40,and a cement content of 20%.Through field coring tests and composite foundation load tests,the strength of cement soil ranges from 0.520～2.953 MPa.Furthermore,the increase in foundation settlement gradually diminishes with growing loads.The maximum settlement value of the cement mixing pile composite foundation is 7.48 mm,with a foundation bearing capacity of 180 kPa.Both the pile strength and foundation bearing capacity adhere to specification requirements.
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