Keywords: 
• inter-tidal saltmarshes /
• sediment cores /
• compaction /
• Jiangsu coast

Abstract: Tidal salt-marshes represent an important part in a coastal wetland system，and it also becomes a key study objective of land-ocean interaction in coastal zone due to the marked human activities and the sensitivity of the areas in response to global change. Sediment cores as a traditional and primary instrument for studying the sedimentary environments and depositional processes of tidal flat are taken generally by gravity corer in inter-tidal flat. Wherever sediment cores were collected by gravity corer，the length of the cores became shorter than the original length，and this compaction processes take place not only inside the sampling tube but also beneath the bottom of the sampling tube. Nine sediment cores were collected by gravity method in the inter-tidal flat of Wanggang which is located on the central coastline of Jiangsu Province，the depth variations of sampling tube were recorded in situ，and the samples were analyzed for grain size by a laser particle analyzer in laboratory. According to the field records and analysis results indoor，both compactions taking placing inside and beneath the sampling tube are linear process；the compaction ratio inside the sampling tube relate to water content of sediment and sorting coefficient，viz. the higher water content and the worse sorted，the higher compaction ratio. According to the calculated results，the length of the compaction beneath the sampling tube is 11% as much as that inside， the compaction length beneath the sampling tube increases with the increasing of compaction ratio inside，and the function of compaction taking placing beneath the sampling tube is more remarkable.