浅层无砂垫层真空联合水袋堆载预压软基处理研究

针对无砂垫层真空预压后期地基承载力提升有限等问题,为了进一步提高软土地基的承载力,采用Abaqus软件建立无砂垫层真空预压法和无砂垫层真空联合水袋堆载预压法的数值模型,并与现场实际情况进行对比分析,验证了模型的有效性。在大面积吹填土地基内利用可循环利用的水袋替代砂石料作为堆载材料,开展真空联合水袋堆载预压软基处理现场试验。该处理方法施工方便,受外界干扰少,施工成本低,对环境影响小。根据水袋高度调节堆填荷载大小,基本不使用砂石料,水袋堆载卸载方便,真空联合堆载衔接时间短,优化了真空预压联合堆载施工工艺。结果表明:在真空预压1个月后可提前引入水袋荷载,处理后土体在0～2 m深度范围内的平均含水率可降低至43%,土体地基承载力可达到65 kPa。与无砂垫层真空预压法相比,真空联合水袋堆载预压法施工期沉降速率、孔压大,孔隙比、含水率小,沉降量大,土体固结速度快,工后沉降小,土体承载力提高了30%,扩展了真空预压处理技术的应用范围。此法适用于缺乏砂石堆载料或运输相对不方便、工期短、地基承载力要求为50～60 kPa的新近吹填淤泥质土的软基处理工程。

Study on water bag surcharge-combined vacuum preloading without sand cushion for shallow soft foundation treatment

Aiming at the problem that the enhancement of foundation bearing capacity is limited during the later-stage of the vacuum preloading without sand cushion，the software—Abaqus is adopted for establishing numerical model for the method of vacuum preloading without sand cushion and the method of water bag surcharge-combined vacuum preloading without sand cushion，and then a comparative analysis is made with the in situ situation，thus the model availability is verified． Within a large-area dredgefilled foundation，an in situ experiment on the water bag surcharge-combined vacuum preloading without sand cushion for soft foundation treatment is made through adopting the recycled water bag to replace sand and stone material as the surcharging material． The treatment method has the merits of convenient construction，less external interference，low construction cost and little impact on the environment，for which the surcharging load can be adjusted in accordance with the height of water bag，and then no any sand and stone material is basically to be used along with convenient unloading of the water bag surcharge and short joining time for the combination of vacuum preloading with water bag surcharge． Thus the construction technology of the water bag surcharge-combined vacuum preloading is optimized． The result shows that the water bag surcharge can be performed in advance after one month of the vacuum preloading，from which the mean water content of the treated soil mass can be lowered down to 43% within the depth range of 0 ～ 2 m，and then the bearing capacity of the soil foundation can reach to 65 kPa． Compared with the method of vacuum preloading without sand cushion，the method of the water bag surcharge-combined vacuum preloading without sand cushion has the merits of larger settlement rate and pore pressure，less void ratio and water content，larger settlement，fast consolidation speed and less post-construction settlement，and then the bearing capacity of the soil mass is to be increased by 30%，thus the application range of the vacuum preloading treatment technology is to be expanded． This method is applicable for the foundation treatment project of the newly dredge-filled soft foundation of muddy soil with the requirement of the foundation bearing capacity of 50 ～ 60 kPa under the condition of insufficiency of sand and stone material for surcharge or inconvenience of transport and short construction period．