软土路基真空-堆载预压沉降变形特征及卸载时机研究

Study on Settlement Deformation Behavior of Soft Soil Subgrade under Vacuum-surcharge Preloading and Unloading Occasion

针对处于沿海滩涂软土路基之上的铁路专用线,采用真空-堆载联合预压的方案加固路基地基,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,分析了地基表面的沉降规律,并考虑了地基分层沉降与孔隙水压力的变化规律,全面揭示了整个地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,且推算出地基整体的固结度;采用工后沉降与地基固结度建立卸载时机判别标准。结果表明:真空-堆载联合预压的处理方案有效地加固了沿海滩涂软土地基;全面考虑地基表面沉降、分层沉降及孔隙水压力,并采用工后沉降与地基固结度相结合的方式,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。

For the special service railway on soft soil subgrade in coastal beach,the subgrade was reinforced by vacuum-surcharge preloading scheme and subject to large amount of observations,including surface subsidence,pore water pressure and layered settlement.Based on the measured data,this paper analyzed the surface subsidence law of subgrade and,with the consideration of the change laws of the layered settlement thereof and the pore water pressure therein,disclosed the settlement change features of the whole subsoil formation comprehensively.Moreover,the post-construction settlement was predicted by hyperbola reasonably and the overall degree of consolidation of the subgrade estimated,then by use of the both,the criteria judging unloading occasion was developed.The results show that the disposal scheme of vacuum-surcharge preloading reinforces the soft soil subgrade in coastal beach effectively; the comprehensive consideration of surface subsidence,layered settlement and pore water pressure,and the use of combination of post-construction settlement and foundation consolidation degree,offer a new idea for the study of criteria for unloading occasion.