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Abstract Combining with an engineering case of soft ground treatment about the experimental segment of expressway of the south shore connecting line of Hangzhou Bay spanning bridge，the technology of surcharge preloading is studied. To comprehend the treatment effect，the in-situ monitoring has been conducted for more than two years. The following results can be drawn. The post-construction settlement is less than 15 cm，meeting the design requirement that the post-construction settlement should be less than 30 cm. The deep compression of soft soil mainly occurs in the scope of the prefabricated vertical drains. The horizontal displacement of soil mainly takes place in the range below the roadbed with depth of 16 m；and the direction of the horizontal displacement below the roadbed with depth of 7 m points to the improvement area，but the one between 7–16 m below the roadbed deviates to outside of improvement area. In the preloading anaphase，the cross-section settlement appears obvious pot bottom shape；and the pore water pressure changes obviously and sensitively in the shallow soil layers，but the one in deep region responds slowly. The results of both vane shear test and laboratory soil test show that the physical properties of soil have been improved obviously after improvement；and the engineering mechanical properties have also been strengthened obviously. These indicate that the surcharge preloading method is very effective for treatment of the soft clay ground of the ordinary expressway section and feasible in the similar road segments in this area.
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Received: 06 July 2006
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