沿海滩涂软土路基堆载预压沉降变形特征与卸载时机研究

Surcharge and Preloading Duration of a Railway Embankment over Coastal Soft Soils

沉降变形与卸载标准是铁路路基堆载预压的主要问题。针对处于沿海滩涂软土路基之上的铁路专用线,采用插塑板与堆载预压相结合的方案进行地基处理,开展了大量的表层沉降、孔隙水压力、分层沉降等观测项目。据实测资料,总结分析了路基表面的沉降规律,并考虑了路基分层沉降与孔隙水压力的变化规律,全面地揭示了整个路基地层的沉降变化特征,运用双曲线合理地预测了工后沉降,且推算出路基整体的固结度,采用工后沉降与地基固结度建立卸载时机判别标准。为堆载预压的卸载时机判别标准研究提供了一种新的思路。

Settlement magnitude and surcharge duration estimations are the main research aspects of the preloading of railroad embankments over soft soils. A railway embankment over the coastal soft soil beach is improved by surcharging with Prefabricated Vertical Drains （PVD）. A geotechnical instrumentation program including surface settlement plates, piezometers and extensometers is also implemented during the construction. The subsurface soft soil settlement and pore water pressure characteristics are summarized from the observed data. The hyperbolic curve fitting method was used in predicting the post construction settlement as well as the degree of consolidation of the soft soils. The relationship between the surcharging loading duration and the post construction settlement as well as the degree of consolidation was established. The results indicate that the surcharging with PVD method effectively improves the coastal soft soils. The surcharging duration can be estimated in accordance with the surface and sub-layer settlement magnitudes, pore water pressures, post construction settlement as well as the degree of con- solidation of soft soils.