gelling concentration 应该是胶凝浓度的意思,具体还应参考研究背景。concentration一词为浓度之意,gelling则是指物质具有的凝胶现象。相关资料可以看一下国外相关文献,如:
Modelling the settling of suspended sediments for concentrations close to the gelling concentration[J]. Continental Shelf Research, 2011, 31(10): S106–S116.