超载预压技术加固高速公路软基的试验研究

为了解超载预压技术对深厚软土的加固效果,结合杭州湾跨海大桥南岸接线高速公路试验段工程,对超载预压技术处理的试验断面进行长达2 a多的现场试验测试。实测结果表明,处理后的路基工后沉降小于15 cm,满足设计要求小于30 cm的标准;深层压缩主要是在排水板范围内的土体中完成的;侧向位移主要发生在16 m以上部位,且7 m以上土体是向加固区内移动的,7 m以下则向加固区外移动;加固后期,加固区表面的断面沉降呈明显的锅底形;孔隙水压力变化在较浅的土层受影响明显,反应灵敏,而深层则反应较慢,孔隙水压力变化不剧烈;原位十字板测试以及室内土性试验结果表明,加固后的土性物理指标有明显的改善,土的工程力学性质有显著增强,说明超载预压排水固结法加固软土地基达到预期的目的,在类似路段中应用是可行的。

EXPERIMENTAL STUDY ON REINFORCED SOFT GROUND OF EXPRESSWAY BY SURCHARGE PRELOADING METHOD

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 effectt,he 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.