The main thrust of Guilia's research is on the applications of soil mechanics to geotechnical engineering, and deals mainly with underground construction, foundation engineering, and earthquake geotechnical engineering. She has been involved in many infrastructural projects in Italy and the UK, including, monitoring building response to construction of the Jubilee Line Extension in London, the design and construction of Lines 1 and 6 of the Napoli underground and of Line C of the Roma underground, and the design of the foundations, anchor blocks and terminal structures of the Strait of Messina Bridge. She has carried out original research on tunnelling and construction processes, tunnelling induced damage assessment and connected mitigation and remedial measures, and performance based design of geotechnical structures under seismic actions, using a combination of field monitoring and laboratory observations, theoretical analyses, and physical and numerical modelling.

Part of her research is also devoted to topics in fundamental soil mechanics, such as the mechanical behaviour of freezing ground and of granular materials with crushable grains.