TREATMENT OF EXTREMELY SOFT MUDSTONE ENCOUNTERED DURING CONSTRUCTION OF NAVIGATION CONTROL JUNCTIONSON YUJIANG RIVER,GUANGXI

About 10 navigation control junctions of kiloton-class have been planned on the Yujiang river,Guangxi province.Three junctions,Laokou,Yuliang and Naji,are located in Tertiary basins where.rocks are mainly composed of mudstone.The mudstone is saturated and has the characteristics of low compressive strength,sensitive to environment change and weakly breakage.The mudstone would cause problems in terms of low bearing capacity,excessive deformation,low factor of safety,poor rock mass stability and high requirements for design and construction.Based on the investigation of the mudstones in Naji, Laokou and Yuliang junctions,the characteristics of the mudstones are examined in this paper.Effective evaluation methods and the corresponding engineering strategies for junction construction in the mudstone are put forward.They include assessment of engineering geology conditions,measures for checking criterion for mudstone foundation,foundation mudstone protection,and foundation treatment.