钱塘江古海塘护坦结构失效机制试验研究

钱塘江古海塘建于明清时期，是钱塘江河口地区防洪御潮的重要屏障。为避免强水动力荷载对古海塘塘基的淘蚀和对塘身稳定性的影响，于古海塘前趾外建有护坦结构。海宁段的护坦多为无相互粘结的靠砌条石结构。为考察该护坦结构的失效机制，采用了波流水槽模型试验。试验揭示，条石覆盖缺失处，护坦易受强涌潮的冲击破坏；临江侧护坦之下的土体易受退潮渗流和纵向水流的冲蚀，并会导致护坦下沉；护坦作为覆盖层可有效保护土体，并可防止土体的瞬时液化和残余液化。

Experimental study of failure mechanism of apron structure of ancient Qiantang River seawall

The ancient Qiantang River seawall, built in Ming and Qing dynasties, is an important barrier in defending the estuary area of Qiantang River against floods and tides. To prevent strong hydrodynamic loads scouring the foundation and lowering the stability of the seawall, the apron structure is built at the front of the ancient seawall. The apron in the Haining region is mostly built by laying unbonded strip stones. To investigate the failure mechanism of such apron, wave and flow flume model tests are performed. It is shown that such apron is vulnerable to the impact by strong tidal bores where the covering stones are missing. The soil under the apron is vulnerable to the erosion by ebb tide seepage and longitudinal current, which leads to the sinking of the apron. As a cover layer, the apron has a good performance in protecting the soil, and can prevent the soil from instantaneous and residual liquefaction.