A Simplified Calculation Method of Seepage Flux for Slope-Wall Rock-Fill Dams with a Horizontal Blanket

Seepage flux is very important in many hydraulic projects such as in the upper reservoir of a pumped storage power station because of its effect on economic benefits. However, upper reservoirs with a relatively high altitude are generally located above the groundwater level; thus, their leakage is difficult to estimate accurately. Here, using steady seepage theory and Darcy’s law, we propose a simplified calculation method to estimate the leakage of slope-wall rock-fill dams with a horizontal blanket. Using a one-dimensional governing equation for unsaturated seepage flows with the assumption of porous continuous media, formulas are derived for calculating the seepage flux of the dam in a steady state with different groundwater levels, which are mainly divided into two situations: those that are lower or higher than the bottom of the horizontal blanket. Then, two engineering examples are developed to assess the proposed method; the relative errors between the analytical results and numerical results are less than 10%. The results obtained from other analytical methods introduced by other researchers are also compared with our numerical results. The comparison results show that the proposed method is reliable and can be used for the estimation of reservoir leakage in situations where rapid results are needed, such as benefit assessments and safety evaluations.

Microstructure Evolution and Mechanical Properties of Rheocast A319 Aluminum Alloy Using Cooling Slope

A319 aluminum alloys are commonly used in automotive industry due to a combination of good fluidity and mechanical strength. In this present work, cooling slope (CS) rheocasting process was employed to produce A319 billets with near spherical morphology of primary Al phase. The dendritic primary phase in the cast A319 alloy had readily transformed into non-dendritic when the ingots were cast over a cooling plate from pouring temperatures between 620°C and 640°C and with cooling lengths of between 300 mm and 400 mm. The shear driven flow of the solidifying melt on the cooling slope wall promotes heterogeneous nucleation of α-Al phase and subsequent separation from there due to shear driven flow of the solidifying melt produced nearly spheroidal morphology of the primary phase in the microstructure. The results show that the best combination of pouring temperature and cooling length was found to be 630°C and 400 mm respectively. The hardness of the rheocast ingots improved to 85.3 HV from 81.8 HV in as-cast condition.

Mechanical Properties and Tensile Fracture Mechanism of Rheocast A356 Al Alloy Using Cooling Slope

A356 aluminium alloy has a wide applicability in the manufacturing of automotive parts. Cooling slope (CS) rheocasting process has been used in the present work to produce A356 billets having near spherical morphology of primary Al phase. Absence of dendritic primary phase, observed in case conventionally cast A356 alloy, and finer distribution of secondary eutectic Si phase within the matrix establishes the usefulness of the CS casting route. Near spherical primary phase in the rheocast alloy ensures better strength, elongation properties and structural integrity in the produced billets. The liquid melt is allowed to flow through the cooling slope after pouring at 6500C. Rapid heat exchange between the flowing melt and slope wall and the atmosphere facilitates heterogeneous nucleation of α-Al phase on the cooling slope wall. Shear driven flow of the solidifying melt is found responsible for separation of α-Al phase from the slope wall and generation of nearly spherical morphology of the primary phase in the microstructure. Grain refiner addition in the melt leads to enhance the primary α-Al percentage in the microstructure and also aids to the improvement of degree of sphericity and reduction of spheroid size. So, grain refining helps to improve the strength, elongation and fracture properties of rheocast billets further.

Application of Gabion Slope Protection of Nanyang River Channel Regulation in Tianzhen County

Nanyang River channel regulation is one of the major projects for river comprehensive management project in Tianzhen reach of the Nanyang River. According to the geological conditions of ecological restoration, Gabion retaining wall is designed to protect the bed or banks of a stream against erosion. Gabion is made of double twisted hexagonal wire mesh, the thickness of gabion basket and mattress is 50 cm and 30 cm respectively. The slope protection work consists of two parts, the lower part is vertical wall and the upper part is slope wall. The results show that this work can solve the problem of uneven settlement and river scouring, sustain restoration of biodiversity and achieve the harmonious coexistence of humanity and nature.