南北导堤地基抗软化加固现场试验

Field Experiment on Subsoil Improvement Against Softening for North and South Guide Dikes

长江口深水航道治理工作南北导堤地基中的软黏土在大风浪作用下,曾因黏土软化而使其上的沉箱发生较大沉降及位移,欲采用排水板预压的加固方案。为验证方案的抗软化能力能否满足要求,在大面积施工前进行此次现场试验与研究。通过对地基的沉降、孔隙水压力一年多的监测及加固前后十字板强度对比试验,其间又经过了几次台风考验,沉箱依然很稳定,以实测数据验证了抗软化加固方案是十分成功的。试验中创新地提出一种新的断面沉降监测方法,并首次将水下自动监测系统放在远离海岸的海底进行长期监测,监测效果非常理想.

The soft clay in the subsoil of the north and south guide dikes was softened under the action of heavy winds and waves and the caissons on the subsoil were settled and displaced greatly. It was therefore planned to improve the soft clay by preloading in combination with plastic drains. To verify whether the planned improvement could meet the requirements of softening resistance, field experiments and research were made before the planned improvement scheme was executed on a large scale. With more than one year＇s monitoring and measurement of the settlement and pore water pressure of the foundation soil and on the basis of the comparative tests of the vane shear strength of the foundation soil before and after the improvement, the measured data proved that the improvement scheme against softening of subsoil was very successful and the caissons installed were very stable though they had experienced a number of typhoons during this period of field experiments. A new innovative method was proposed during the experiments and research to monitor and measure cross sectional settlement. It was also the first time that an underwater automatic monitoring and measurement system was installed on the seabed far away from the shore to carry out long-term monitoring and measurement, which proved very ideal and successful.