The aim of this paper is to study the engineering characteristics of special land foundations and foundation treatment methods, and to analyze the survey process of digital survey technology in geotechnical engineering. The research uses literature analysis and case study methods to study different types of land foundations in detail. The results show that special foundations such as expansive soils, soft soils and gravel soils have their own characteristics and require different foundation treatment methods. For swelling soils, it can be treated by the methods of foundation replacement, geosynthetic reinforcement and chemical improvement; for soft soils, it can be treated by the methods of pre-drainage consolidation, deep improvement and cantilever foundation design; for gravel soils, it can be treated by the methods of dynamic gravel pile reinforcement. At the same time, remote sensing technology and geological radar technology have wide application prospects in urban underground geotechnical engineering, providing effective technical support for survey and construction parties.