Abstract:The mechanical property of surrounding rocks is the important factor which must be considered in TBM cutter design. At the same time , the factor has a close relation to the overall design of TBM and the feasibility of excavating tunnels with TBM. It is not perfect to select the parameter system whose key parameter is unconfined compressive st rength (UCS) . In the boring process , the rocks below the cutter are exerted on by vertical compres2 sive st ress and sink , and the rocks beside the cutter are compressed in the direction of face and swells. In the de2 formed rocks , the tensile or tensile2shear cracks appear. When the swelling areas between two cutters are superim2 posed , the deformed rocks are separated f rom the face. Under the cutter load , the larger the relative displacement between two point s in the face is , the more advantageous to boring it is. The relative displacement is directly con2 t rolled by elastic modulus ( E) and poisson′s ratio (μ) . To sum up , in addition to UCS , E and μshould be taken into account in TBM cutter design.