Engineering geological characteristics and bank slope stability in the Jiujiang region along the Yangtze River

Based on comprehensive studies of field geological investigation, geophysical exploration, engineering geological drilling, this paper discussed the stratigraphic structure, karst development, engineering geological characteristics and bank slope stability of bank slope between Hukou and Pengze in the Jiujiang region along the Yangtze River. Both the bankside and polder embankment of the Yangtze River are located in terrace I at the south bank of the Yangtze River. The ground surface is the Quaternary Holocene alluvium, which is a set of lacustrine sediment, with thick silt layer. The foundations of bankside and polder embankment belong to the soft soil layers, which has low engineering bearing capacity, are subject to producing uneven settlement, sand liquefaction and seepage deformation, then resulting in collapse of bankside and polder embankment. Comprehensive analysis suggests that the bank slope stability between Hukou and Furong of Pengze County is poor and the main factors resulting in collapse of Yangtze River bank are: Most polder embankment at the south bank of the Yangtze River is in upstream or head-wave areas, which are seriously scoured by water flow. Bank slope close to the south of the Yangtze River waterway is frequently scoured by the ship wave, causing the steep bank slope and the poor stability. Clayey layer intercalated with thin sand layers in the upper stratum, with fine sand layer at bottom, suggests poor anti-scourability. The saturated soil of beach is during flood season and the low water level of Yangtze River may cause the water exosmosis in flood land induces bank slope instability. For the bank slope mainly consisting of clay, the effective drainage should be strengthened and the slope ratio should be reduced. For the bank slope containing sand layers, protection measures should be constructed in the areas such as sand layers, low water level and variation of water level to prevent scouring and corrosion.