Abstract：A new concept of deep excavation for underground structures or foundation of building is set up in order to study the effects of excavation on the surrounding stratum. Many of the deep excavations have proved that the mechanical properties of surrounding stratum，such as relationship of strain and stress，or shear strength of soil，will change in different level at different parts of surrounding stratum，especially when ground water loses during cutting work going on. This will affect the reliability of original design based on the parameters of unexcavated ground. Up to now，how much it will influence the reliability of design due to the property variation of the surrounding stratum is unknown. So a new concept of effect zone of excavation is set up to study the excavation effect on the design. Based on this，the pattern and regulation of the effect zone are studied comparing to the initial ground structure.
