Numerical Simulation of Sand Fill to Allow Operation of Pile Driving Rigs on Peaty Soil

[摘要] Construction sites in undeveloped areas underlain with a thick peat bed require some preparation, usually surcharging with sandy soil. In such conditions, the buildings are erected on pile foundations. To ensure safe operation of pile driving rigs, method statements must specify a minimum sand fill thickness. Numerical simulation of the sand fill was performed in PLAXIS 2D software to establish the required fill thickness over peat. The analysis was performed for sphagnum peat, the samples of which had been taken from undeveloped wetlands. Peat shear strength was determined with a standard vane and was found to be 6 to 10 kPa. Strain and strength properties were calculated on the basis of laboratory tests. To estimate the strength properties, a laboratory unit was built to include a peat sample box measuring 0.5×0.5×0.5 m, a stamp and a linkage system. The pressure applied to the peat was assumed within the range of 12.5 to 35 kPa. Upon load application, a four-bladed vane was submerged into the peat through a hole in the stamp to carry out a torsion shear test. Using the results of sample testing in the laboratory unit, the values of the internal friction angle for sphagnum peat were obtained. A Soft Soil model was used for peat in the numerical simulation. Peat thickness was assumed within the range of 2 to 6 m, and shear resistance - 6 to 10 kPa. The analysis was performed for the most common models of drop hammer and static pressure pile driving units. The design criterion was the minimum sand bed thickness at which peat bearing capacity was ensured. In addition, the maximum soil settlement was estimated that would allow normal operation of pile driving equipment.

[发布机构] Northern Federal University Named after M.V. Lomonosov (NArFU), Severnaya Dvina Emb. 17, Arkhangelsk; 163002, Russia^1

[关键词] Construction sites;Internal friction angle;Load application;Normal operations;Shear resistances;Strength property;Torsion shear tests;Undeveloped areas