Abstract: Argillaceous slate is a typical soft rock which is commonly encountered in urban Changsha area. The stratigraphic and lithologic characteristics of the slate might also be the main sources of the construction safety hazard. This paper presents a case study of the deep excavation project within the argillaceous slate soft rock. The subsurface lithology is briefly introduced and an improved design of the original soldier pile with the ground anchor is also presented. The deformation analysis was performed at the location with least safety factor. The construction monitoring data indicates that the deformation of the excavated area was satisfactory.

Key words: Soft Rock, Argillaceous Slate, Deep Excavation Optimization