Seepage Regularity And Slope Stability Evaluation Of Water Diversion Dam-New Liberty Gold Mine

The construction of an earth dam in a high rain forest terrain possesses a significant variation in the mechanical strength of the rock mass forming the dam.Regardless of the high level of improvement in slope stability theory and measures,instability due to embankment is yet a paramount concern to the slope engineers.The essence of this research is to investigate and demonstrate the effect of ground water variation at “significant level” within the Marvoe diversion earth dams as well as to understand the flow dynamics and influence of changing pore pressure profiles within the slope,resulting from installed drainage measures.Groundwater infiltration into the earth dam,has a remarkable influence on the dam inner seepage and on the basic seepage flow theory along with numerical simulations,the amount of flow entering into the upstream and downstream diversion dams at the New Liberty Gold mines are established.The result shows that the remodeling and cementation characteristics due to long term loading results in changes in the microscopic grain structure of the material forming the dam and the water retained in the dam along with the effect of capillarity influences the stability of the dam.By means of numerical simulation,the stability of the starter dam was obtained under the action of the dam overburden weight above the water level and from the numerical analysis results,it is seen that under the action of a load,the factor of safety decreases depicting a quadratic influence rule even with reduction in the water level.The major reason for this phenomenon was such that under the effect of loading the permeability of the top soil reduces,however,when the water enters the dam within compacted region,the unit weight of the rockmass increases thus resulting into greater pore pressures within the dam,thus resulting into decrease in the factor of safety.Depressurization systems are used to lower pore water pressures,which increases the effective stresses and shear strength of the material forming the dam.By means of a conceptual analysis,a much greater understanding as to the current flow dynamics and controlling mechanisms acting within the dam is established and on the basis of the numerical simulations combine with varied assumptions,a clear understanding of the likely flow dynamics within the dam allows for greater focus in future dewatering/depressurization infrastructure and monitoring requirements.The work further establishes the importance of the use of horizontal drains around the perimeter of the starter and ultimate dam of the New Liberty Gold mines,before and at the end of construction and it is seen from numerical simulation that the reduction in pore pressures due to reduction in the water level by means of drains leads to increase in the factor of safety depicting a logarithmic influence rule.The research provides a good theoretical and technical support for the analysis and control flow mechanism of the Marvoe diversion dams and the results have great engineering and geotechnical design benefits on stability as well as to the economic viability of the dam.