Discovery of an ice cave in the Yatude Valley, Langhovde, Dronning Maud Land, East Antarctica

A circular hole was discovered on the downstream side of a glacier dam in the Yatude Valley, Langhovde, East Antarctica, during the 2005–2006 austral summer. The opening of this hole is the first opportunity enabling us to observe the interior of the dam. The opening led to a large cave in the dam, raising the possibility of meltwater drainage through the dam. The Yatude Valley is an approximately U-shaped fluvial valley. The valley floor has been incised to form a box-shaped inner valley that contains fluvial terraces and large boulders upon the valley floor. The origin of these features can be explained by a large amount of running water; however, we consider it unlikely that a regular current has flowed through this site for a long period. Instead, it is more likely that large quantities of lake water have been periodically discharged due to collapse of the glacier dam or spilling out through a tunnel channel within the cave. The discovered hole and the ice cave are key features in understanding the historical development of the Yatude Valley in relation to the melting history of the Antarctic ice sheet.     

Numerical investigation of hydraulic characteristics and prediction of cavitation number in Shahid Madani Dam's Spillway

The prediction of the probability of cavitation occurrence to prevent serious damages in the spillways is the major concern for hydraulic engineers. In this research, the three-dimensional model of Shahid Madani Dam’s spillway was simulated with the Flow 3D software and by the comparison of numerical model results with the experi-mental data, the probability of occurrence of the cavitation phenomenon has been investigated. The flow parameters including pressure, velocity, and water depth were calculated for three different flow rates of 495 m3/s, 705 m3/s and 2 205 m3/s respectively. The Renormalization Group (RNG) turbulence model was used to simulate current turbulence. Comparison of simulation results for pressure, velocity and water depth with the results of the experimental model with two statistical indices Root Mean Square Error (RMSE) and Coefficient of Determination (R2) showed that the numerical simulation results are in good consistency with experimental model. However, simulation results indicated that at any flow rates with a return period of 1 000 years, probable maximum flood and designed flow rates, the cavitation number is not lower than the critical cavitation number; Therefore, it is predicted that the cavitation phenomenon in Shahid Madani Dam’s spillway will not happen.     

溢洪道高边坡控制爆破施工

本文分析了单响药量和起爆网络对爆破振动的影响,结合控制爆破技术进行了振速监测,通过爆破监测估算出该地区爆破振动衰减规律,用以指导溢洪道开挖施工,保证了泄洪洞的安全。     

Towards a universal optimization of the performance of sand storage dams in arid and semi-arid areas by systematically minimizing vulnerability to siltation: A case study in Makueni,Kenya

Sand storage dams are hydraulic retention structures that increase the volume of coarse sediments in seasonal sandy streams by exclusively blocking the bedload transport during runoff events. However,siltation of fine grain particles, which are transported as part of the suspended load, is a major factor causing sand storage dams to perform poorly. Therefore, this study aimed to evaluate the hydrological performance and cost-efficiency of 30 sand storage dams. This study also aimed to increase the understanding of critical factors which may affect the performance and lead to siltation of sand storage reservoirs. The analysis was based on a physical survey of 30 sand storage dams that were built in onestage in southeastern Kenya. Most of the study sites had the capacity to produce sand. However, the reservoirs suffered from severe siltation, which caused generalized low annual yields, reduced supply capacities, and low cost-efficiency. It is argued that the main factors for the poor performance were the high inter-and intra-annual variability of bedload transport, which coupled with the construction of onestage spillways, led to siltation of the reservoirs. Thus, large volumes of fine grain particles accumulated in the reservoirs during runoff events with bedload layer heights lower than the height of the one-stage spillways. To systematically maximize the robustness to the inherent variability of bedload transport, and ensure optimal performance levels by systematically minimizing siltation, spillways should be built in stages of reduced height. Thus, the lower the stage height, the higher the probability of maximizing the accumulation of coarse sediment. It is estimated that a multi-stage construction process with stage heights of 20 cm would have produced a performance 26 times higher. This implies that the 30 reservoirs would have had the capacity to supply 8516 people as compared to the current supply capacity of 330 people. Improvements in the performance of sand storage dams can greatly assist attempts to link this technology with income-generating activities for agropastoralists in arid and semi-arid areas.