The mechanical genesis of the complicated rock mass is because several times of tectonism in pro - period made the structure of rock mass in the right dam foundation damaged seriously and rock mass alteration made its mechanical character more anisotropy . after that the fractures in the right dam foundation slope were stretched at the beginning of the quaternary period because in the period yakouhoushan mountain quaquaversal dome was blowups quickly . at the same time , the valley trenching of lancang river reach to 800 - 1000 meter in altitude at the right bank in nuozadu dam site 导致右岸岩体复杂化的成因是，右岸岩体在早期遭受了多期构造作用和岩体蚀变的基础上，第四纪早期丫口后山穹隆的快速隆起与当时河谷下切至800m 1000m高程这一特殊因素组合引起了右岸岩体沿原有的断裂(裂隙)张开，使地下水等风化营力能够到达坡体较深部位，经过长期的风化卸荷作用，形成了右岸复杂岩体。
