Foundation Deformation of Sludge-retaining Dyke for Westlake Dredging Project

摘要

To save the sludge dredged from Westlake in Hangzhou, a sludge reservoir with 1200,000m~3 capacity had been built at the foot of Yuhuang Mountain in 1999. A 18m high earth dam would be constructed on a fishpond. The foundation of the dyke consists of a layer of interbeded silts and clay overlying a basal sand stratum, which will challenge the stability of subsoil during staged loading period. Pay attention to the undesirable geological conditions, three design items are adopted. These items, include: (1) the soft foundation will be improved by vibroflotation gravel columns. (2) the high pressure curtain grouting will prevent the penetration beneath the upstream toe. (3) and geo-textiles will be employed as anti-seepage materials. The field monitoring data during performance period, including foundation vertical and horizontal displacements, pore-water pressures, and underground water movements, showed that: (1) stone pile group with good drainage function accelerated the consolidation and catered the fast earth fill speed. (2) the anti-seepage curtain not only intercepted the underground flows, but also strengthened the weak foundation and restricted effectively the horizontal movement of foundation. (3) the flexibility of anti-seepage geo-textiles on dam face was consonant with the significant deformation of foundation and embankment body. Based on observed information, this paper will evaluate the rationality of original design in detail.