Engineering Geological Investigation of dam site of proposed Sunkoshi-2 Hydropower Project, Khurkot area, eastern Nepal

The dam site of proposed Sunkoshi-2 Hydropower Project and its surrounding mainly comprise the Tawa Khola Formation, which is the basal formation of the Bhimphedi Group. Although garnet schist and micaceous quartzite bands are the main rock types; three rock units namely- Schist Unit, Quartzite Unit, and Gneiss Unit were identified. Engineering geological mapping followed by discontinuity survey were carried out. The result exhibited differences in fracture intensity and discontinuity characteristics of rock masses according to rock type. Since joint orientations were found to be consistent over fairly large areas, surface studies of joints were used in predicting subsurface orientations. Rock mass classification was made in line with the Rock Mass Rating System (RMR) and the Dam Mass Rating (DMR) classification for the dam foundation. The rock masses were classified onto fair to good rock classes according to RMR value. Dam foundation analysis regarding stability against sliding using DMR classification helped in selection of suitable dam-axis among two alternatives. Water Quality Standards (2005).

Numerical modelling of dynamic stability of RCC dam

Stability and stress analyses are the most important elements that require rigorous consideration in design of a dam structure. In the current research, dynamic structural stability of a roller-compacted-concrete (RCC) dam was performed. The RCC dam was modeled using the finite element method to investigate the stability against sliding and the structural stability of the body of the dam. The commercially available finite element software (SAP 2000) was used to analyze stresses in the body of the dam and foundation. A linear finite element dynamic analysis was performed. Response spectrum and time history methods were used with different earthquake loads. The response spectrum of the 1995 Aqaba earthquake and a representative elastic-spectrum with smooth plateau for both Operating Basis Earthquake (OBE) and Maximum Credible Earthquake (MCE) were used in this study. The analysis was carried out assuming that no slip will occur at the interface between the dam and the foundation. The greatest tension was found to develop in the rock adjacent to the toe of the upstream slope. The factor of safety against sliding along the entire base of the dam was found to be greater than 1 (FS>1), for both loading conditions.

Study on Stability against Sliding of Seawall Subject to Ice Load and Freezing and Thawing Cycles

The seawall shallow foundation is silty soil in northern coastal area. So the seawall is subject to ice load and freezing and thawing cycles as the temperature variation. It is unfavourable for the stability against sliding of seawall. The experiment of silt soil sample under freezing and thawing cycles has been done to analyze the law of mechanical properties. On this basis the numerical model of seawall with stability against sliding has been established. The calculation results show that the soil strength index decreased under ice load and freezing and thawing cycles. The stability against sliding of seawall would be reduced. Under ice load and freezing and thawing cycles the Mises yield stress reduced, horizontal and vertical displacement would be greater slightly. The stress of the plastic zone would be evenly distributed. The Plastic penetration area does not appear.

Stability Analysis of Tailing Dam under the Action of Seepage

A finite element model of tailings dam model was used to simulate the steady seepage field and analysis the stability under different working conditions. The head contour, velocity, seepage flow and seepage gradient was analyzed. The stability against sliding in this tailings dam was analyzed with the help of the simplified Bishop method which is based on rigid body limit equilibrium coupled with seepage force. The security coefficient under different working conditions was calculated. The analysis result shows that the safety factor meets the specification requirements, and which provides reference for the stability evaluation of tailings dam.

Numerical Analysis of the Impact of the Stope Blasting Vibration on Tailings Dam Stability Based on GeoStudio

In this paper, based on the establishment of the finite element calculating model, the influence of the blasting vibration to tailings dams stability was analyzed in accordance with actual stope blasting vibration monitoring data. The laws of the blasting vibrations impact on tailings dam stability was reached by importing different vibration amplitude of vibration wave intensity. When the blasting vibration acceleration remained under 0.333g and vibration velocity remained under 17.005cm/s, the coefficient of the healthy tailings dam stability against sliding has a increasing trend with the increase of vibration strength. When the vibration acceleration and the vibration velocity reached the maximum value, the coefficient rapidly decline; But the influence of stope blasting vibration on the stability of the risky tailings dams is more significant. The coefficient of stability against sliding had a straight-line decrease to the risky tailings dams. In Engineering, more than 4 times margin is considered to find the control vibration velocity. The value is 4.25 cm/s. An analysis shows that the effect of blasting vibration on healthy tailings dam stability has two sides. When the blasting vibration intensity remains within control vibration velocity, it can be beneficial to the stability of tailings dam. Otherwise it will be harmful.

Research of Effect on the Levee by Drawdown of Caisson Foundation of the North Anchorage of Maanshan Yangtze River Bridge

On account of the north anchorage of Maanshan Yangtze River bridge, the drawdown of caisson foundation may bring about new seepage field of the ground, which make soil consolidate. This paper build two-dimensional plane strain finite-element models of open caisson and the Yangtze River levee, which aim to analyze the effect on the Yangtze River levee by drawdown of the open caisson foundation. Through the seepage analysis of the open caisson foundation and the stability analysis of the slope, this paper obtain the settlement and coefficients of stability against sliding of the Yangtze River levee.

A Three-Dimensional Analysis Method for the Stability against Deep Sliding of Concrete Dam on Rock Foundation with Mud Layers

With the limit equilibrium method for the rigid body, this paper deduces a three-dimensional analysis method for the stability against sliding of concrete dam on rock foundations with mud layers on the basis of the stability against sliding of wedge. The engineering practices show that it is economical and reasonable to apply the method given here to the analysis for the stability of concrete dam foundation with mud layers in the case that the dam axis being not parallel to the strike of mud layers.

Concrete Thermal Stress of Arch Dam in Construction Period of Stability against Sliding of Steep Slope Section

Thermal stress, as one of the most important stress of the arch dam during construction period, strongly influences the sliding stability of the arch dam. To analyze this kind of impact on arch dam sliding stability, numerical modeling of a typical slope dam section from 300-meter-high levels arch dam during construction period was conducted. Based on the rigid body limit equilibrium method, results of the case considering thermal stress as well as those without thermal stress were presented. Detailed comparison with the results of multiple monoliths was also made. In addition, the relevant sliding stability coefficient with the consideration of thermal stress was suggested.