Stability Assessment of the Excavated Rock Slope at the Dagangshan Hydropower Station in China Based on Microseismic Monitoring

A high-resolution microseismic (MS) monitoring system was implemented at the right bank slope of the Dagangshan hydropower station in May 2010 to analyse the slope stability subjected to continuous excavation. The MS monitoring system could real-time capture a large number of seismic events occurring inside the rock slope. The identification and delineation of rock mass damage subject to excavation and consolidation grouting can be conducted based on the analysis of tempospatial distribution of MS events. However, how to qualitatively evaluate the stability of the rock slope by utilizing these MS data remains challenging. A damage model based on MS data was proposed to analyse the rock mass damage, and a 3D finite element method model of the rock slope was also established. The deteriorated mechanical parameters of rock mass were determined according to the model elements considering the effect of MS damage. With this method, we can explore the effect of MS activities, which are caused by rock mass damage subjected to excavation and strength degradation to the dynamic instability of the slope. When the MS damage effect was taken into account, the safety factor of the rock slope was reduced by 0.18 compared to the original rock slope model without considering the effect. The simulated results show that MS activities, which are subjected to excavation unloading, have only a limited effect on the stability of the right bank slope. The proposed method is proven to be a better approach for the dynamical assessment of rock slope stability and will provide valuable references for other similar rock slopes.

The Application of Cubic Spline Interpolation Function in Determining Rock Rheological Long-Term Strength

The rheological long-term strength is determined according to the triaxial rheological test data of diabase at the dam area of Dagangshan Hydropower Station. Firstly, based on the stress-strain isochronous curve method and connected the test points with cubic spline interpolation function, the maximum deviation point in the long-term interval is determined as the turning point and established the long-term strength by nonlinear least square method. The results show that this method is consistent with the other methods. Finally, the advantage and disadvantage of this method is analyzed. This method can overcome the randomness of artificial selecting the turning points. Therefore, maximum deviation point method is relatively a reasonable and effective method to determine the rheological long-term strength of rock.

Numerical Simulation of Excavation of Abutment Slope at Left Bank in Dagangshan Hydropower Station

The abutment slope at left bank in Dagangshan hydropower station has complex geological conditions with deep fractures, developed faults and unloading crack. The excavation will influence the stability of the slope. To evaluate the slope stability, the finite element model of this abutment slope was built in this paper to study the deformation, stress and plastic zone distribution of the slope during the excavation. The potential failure location of the slope is forecasted, some suggestions are proposed to be helpful to keep the stability of the slope.

Fracture Characteristics of High Pressure Granite under Unloading Condition

it is already confirmed that the rock mechanical characteristics under unloading condition differ from those under load condition, and the excavation process should be considered to be a typical kind of unloading mechanical behavior. As thus, a series of representative unloading tests and shear strength tests about unloading cracks are performed on hard granite samples from the underground workshop excavation zone in Dagangshan hydropower station in western China, where the surrounding rock is affected by high geo-stress. Based on the tests results, some significant theory research is made.