Variability of levee failure mechanisms subject to heavy rainfalls,case studies in Taiwan

In this study, the failure mechanisms for Chiuliao 1st Levee and Gueishan Levee in Taiwan were re-examined comprehensively considering the uncertainty of different parameters. Results have shown that for Chiuliao 1st Levee, the slope sliding failure has a higher coefficient of variation (COV). For Gueishan Levee, retaining wall sliding and overturning failure have higher values of COV instead. It can also be found that the scouring depths affect the stability of the levee significantly, therefore, a protecting system for the backfill material may be necessary to increase the stability of the levee effectively.     

Observed characteristics of atmospheric ducts over the South China Sea in autumn

The observed characteristics of lower atmospheric ducts over the South China Sea(SCS) were analyzed based on Global Position Systerm(GPS) radiosonde data collected four times daily during autumn open cruises from 2006 to 2012.Duct occurrence,thickness,and strength over the SCS were about 40%,150-m thick,and 8 M units,respectively,which were larger than during the summer monsoon period.Most ducts occurred at heights 1 500 m and these ducts easily trap electromagnetic wave clusters with wavelengths 2 m.Diurnal variation of the SCS ducts appeared evident.They occurred more often at midnight at higher altitudes(about 1 100 m),with a thickest layer of about 145 m and less frequently during the evening at lower altitudes(about 800 m),with a thinnest layer of about 125 m.Moreover,ducts during the daytime at a mean height of about 900 m,with the greatest strength of about 10 M units.Furthermore,all duct variables observed over the SCS in autumn decreased from north to south.These findings are useful not only in the design of radar and communication systems,but also for evaluating possible effects of anomalous propagation on meteorological radar and military applications.     

The dominant driving force for supercontinent breakup: Plume push or subduction retreat?

Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth's geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have been considered: the push by mantle plumes from the sub-continental mantle which is called the active force for breakup, and the dragging force from oceanic subduction retreat which is called the passive force for breakup. However, the relative importance of these two forces is unclear. Here we model the supercontinent breakup coupled with global mantle convection in order to address this question. Our global model features a spherical harmonic degree-2 structure, which includes a major subduction girdle and two large upwelling(superplume) systems. Based on this global mantle structure,we examine the distribution of extensional stress applied to the supercontinent by both subsupercontinent mantle upwellings and subduction retreat at the supercontinent peripheral. Our results show that:(1) at the center half of the supercontinent, plume push stress is ～3 times larger than the stress induced by subduction retreat;(2) an average hot anomaly of no higher than 50 K beneath the supercontinent can produce a push force strong enough to cause the initialization of supercontinent breakup;(3) the extensional stress induced by subduction retreat concentrates on a ～600 km wide zone on the boundary of the supercontinent, but has far less impact to the interior of the supercontinent. We therefore conclude that although circum-supercontinent subduction retreat assists supercontinent breakup, sub-supercontinent mantle upwelling is the essential force.     

Water system characteristics of Karst river basins in South China and their driving mechanisms of hydrological drought

Natural Hazards - It is common knowledge that drought is considered one of the most damaging natural disasters in terms of economic costs, societal problems, and ecological impacts. In this study,...     

A model for the representation of emergency cases

The aim of this paper is to propose a location model of earthquake emergency service depot on the basis of hybrid multi-attribute decision-making method. The advantage of the proposed method is that practical mixed uncertainty of location decision information is considered, and the corresponding factors that affect the location of transfer stations are contained. To solve the location problem, a hybrid multi-attribute decision procedure without information transformation is developed. Besides, a novel weighting method and aggregation process is given. Finally, a numerical example is provided to show the feasibility and validity of the proposed method.     

综合物探法在砂岩型铀矿中深部找矿中的实践与分析——以新疆昭苏盆地为例

为了探查新疆昭苏盆地砂岩型铀矿的异常信息,选择可控源音频大地电磁测量、高精度磁测和土壤氡气测量三种物探方法,并简要介绍各方法的工作原理。通过分析昭苏盆地的地质特征、物性特征和本区的找矿难点,对昭苏盆地综合物探数据所蕴含的信息进行地质-物探综合解译。实践证明:可控源音频大地电磁测量对低阻和高阻体均有良好的电性响应,可以划分地层、推断断裂构造;高精度磁测可以推断氧化还原界面,辅助解释断裂构造;土壤氡气测量可辅助解释断裂构造,对地下铀矿体有指示作用,三种方法的技术特性相互补充,提高了物探解释的准确性。突破了伊犁盆地以往600 m的找矿深度,并以电性稳定的中阻厚层、磁测异常、氡异常偏高晕和峰-谷状曲线作为预测标志,解决了深埋藏条件下赋矿地质体的圈定难点,在昭苏盆地砂岩型铀矿中、深部找矿工作中取得了良好的效果。     

Research on Creep Deformation and Control Mechanism of Weak Surrounding Rock in Super Large Section Tunnel

Geotechnical and Geological Engineering - In order to solve the difficulties of creep deformation of surrounding rock in super large section tunnel, taking Letuan tunnel of Binlai expressway, a...