A method for assessment of excavation damaged zone (EDZ) of a rock mass and its application to a dam foundation case

作者：Wu Faquan; Liu Jianyou^*; Liu Tong; Zhuang Huaze; Yan Changgen

来源：Engineering Geology, 2009, 104(3-4): 254-262.

DOI：10.1016/j.enggeo.2008.11.005

• Excavation disturbed zone (EDZ)
• Unloading strain energy
• Accumulative opening displacement of cracks
• Damage degree
• Borehole camera
• Xiaowan hydropower station

Excavation of slope is an unloading process, and also an energy releasing process when the stress in the rock mass is unloaded, leading to the rebounding deformation towards the free face. And then a zone, namely excavation damaged zone (EDZ), will be formed near the excavation boundary, where the rock is damaged or disturbed and its physical, mechanical and hydraulic properties are greatly changed. This paper is to put forward a new method to quantify the extent and damage degree of the EDZ according to the unloading strain energy which is released in the process of excavation. A simple relationship between unloading strain epsilon and accumulative opening displacement T of cracks, epsilon = dT/dh, is proposed to describe the damage degree of rock mass in the EDZ, where h is the depth variable in normal direction of the open cracks.
This method is used to assess the EDZ of the dam foundation at Xiaowan hydropower station in southwestern China by the accumulative opening displacement curves of cracks along boreholes based on boreholes camera photos. We find that the EDZ can be naturally divided into two sub-zones, i.e. the excavation heavily disturbed sub-zone (EHDZ) and excavation slightly disturbed sub-zone (ESDZ), according to the variation of unloading strain epsilon. Two inflexions of the accumulative opening displacement curve indicate the lower limits of EHDZ and ESDZ respectively.

• 出版日期2009-3-23
• 单位中国科学院地质与地球物理研究所; 中国科学院地质与地球物理研究所兰州油气资源研究中心