This paper presents briefly some research works involved in the field of soil mechanics and rock mechanics and some part of actual monitoring results on problems of the high earth-rock cofferdam in deepwater, the stability analyses of rock foundation of the gravity dam and the high rock excavated slope of ship lock, the most challenging works in the civil engineering construction at TGP.

The high cofferdam, an earth rock dam with the height of about 90m, two concrete cut-off walls inserted at the body, is formed by dropping the weathered granite in deep water (60m depth), and its density is quite loose. The stress and strain in walls are very complicated and the construction work is also very difficult. Nevertheless, the practical result is very well, even beyond the expected.

The high rock slope of permanent ship lock has been excavated in rock mass, with the maximum height of 170m. The concern is focused on the displacement and stability of the rock slope, as the deformation of slope is very much related to the safety of ship lock operation. Different kinds of tests in field and numerical analysis are performed during the design, construction and even operation period. The analysis results are proved to be reliable by the actual deformation measurements during ship lock excavation.

The stability of rock foundation of the gravity dam has been comprehensively studied by means of the rock mechanical tests, numerical analysis and the large scale of geological mechanics model test. The actual situations of the dam are working well up to now.

All those results are very important to Three Gorges Project, and also will be significant to other dams as well.