A review of flexible protection in rockfall protection

Natural Hazards - Natural hazards, such as high winds, heavy rains and ice melting, can easily trigger the rockfall which usually leads to great personal injuries and property loss; therefore, the...     

大别山东缘郯庐断裂带造山后左行平移活动时间：锆石LA-ICP-MS U-Pb定年结果的限定

郯庐断裂带在造山阶段之后发生了明显的左行平移活动,但到目前为止对于其发生时间仍存在较大争议。大别山东缘郯庐断裂带内存在一系列花岗质、基性岩脉,其形成与郯庐断裂带左行平移活动密切相关,因而对其形成年龄的测定可以为断裂带左行平移时间提供限定。本次工作在大别山东缘郯庐断裂带内糜棱岩及岩脉中采集了6个样品开展锆石LA-ICP-MS年龄测定。两个花岗质糜棱岩样品均得到了新元古代和印支期两组年龄结果,但并未得到早白垩世年龄结果,可能指示了强烈的构造变形抑制了锆石的生长。与断裂带左行平移活动同期的基性岩墙侵位时间为128 Ma左右;斜切糜棱岩面理的基性岩墙侵位于127 Ma 左右;发生韧性变形形成糜棱岩的二长花岗岩侵位时间为128 Ma左右;仅出现NE向劈理的钾长花岗岩侵位于126 Ma。综合以上结果,大别山东缘郯庐断裂带与下扬子地区存在类似的构造背景,其早白垩世左行平移事件的发生时间为128 Ma之前,之后断裂带在区域伸展背景下转变为正断层活动。     

奥陶系岩溶古地貌恢复及对气藏分布的控制作用——以鄂尔多斯盆地苏里格东区41-33区块为例

苏东41-33区块位于鄂尔多斯盆地中央古隆起的北部南缘,长期沉积间断的风化壳不整合面形成复杂的岩溶古地貌,属苏里格气田东部奥陶系碳酸盐岩气藏的重要勘探区。研究基于钻井、测井、地震及生产动态资料分析,综合运用地球物理法、残厚法和印模法,优选本溪组顶9号煤层和马家沟组马五5灰岩为标志层,深入探讨古地貌单元的恢复依据和划分标准,精细恢复岩溶古地貌形态,并明确岩溶古地貌特征及其对气藏分布的影响。研究表明:苏东41-33区块整体处于二级地貌单元岩溶斜坡之上,奥陶系古风化壳上下地层厚度可划分出上薄下薄、上薄下厚、上厚下薄等5种组合类型,细分古坡地、残丘和沟槽3个三级地貌单元;古地貌总体趋势走向为北高南低,出露层位展布由马五4过渡到马五1。中南部发育连片残丘,北部见小型零星残丘,恢复厚度低于15m,残留厚度超过85m;北部发育2条侵蚀沟槽带,充填厚度大于20m,残留厚度小于45m;古坡地分布范围广泛,周围被古残丘与沟槽所分割,残留厚度介于45m^85m之间,恢复厚度大于10m。古地貌类型对风化壳气藏分布具有明显的控制作用,岩溶残丘及残丘边缘带的古坡地储层叠合厚度增大,溶蚀孔洞充填程度低,主力含气层保存完整且连通性较好,是寻找高产井的目标区,而岩溶古沟槽相对不利于天然气富集,所钻遇气井多为低产或无产能。     

Experiment on Coordinated Observation of Offshore Typhoon in China

The lack of sufficient direct observation data of typhoon fine structure is the main bottleneck that restricts the further development of typhoon discipline and forecasting. This paper briefly introduced the basic information of the National Key R&D Program of China, entitled “Experiment on Coordinated Observation of Offshore Typhoon in China”, which started in early 2019. Firstly, the importance and necessity of the program around the national needs on typhoon-related disaster reduction and prevention were explained. Then, the coordinated observation difficulties and frontiers in the current typhoon discipline situation from the development and improvement of the physical mechanism and key forecasting technologies were shown. The overview of the direct observation instrument and platform, the field campaign and the parameterization techniques related to physical process in typhoon numerical modeling was provided. Finally, the key scientific and technical issues and main research contents of the program were given.     

辽宁盘锦荣兴港作业区MT19钻孔海洋沉积物粒度特征

使用激光粒度分析仪对辽宁盘锦荣兴港MT19钻孔6个样品进行分析,运用福克-沃德（Folk-Ward）图解法计算相关粒度参数并绘制输出粒度频率特征曲线。结果表明：盘锦荣兴港沉积物中黏土(d＜0.004 0 mm)的体积分数最小,平均值为8.49%;粉砂(0.004 0～0.063 mm)的体积分数较大,平均值为38.39%;砂(0.063～2.00 mm)的体积分数变化较大,平均值为53.13%。Shepard沉积物三角形分类图解表明,研究区沉积物类型多属于粉砂质黏土和黏土质粉砂;粒度频率曲线显示,除MT19-2-2号样品为主次三峰型外,其余均为主次双峰型,说明该区域在海进-海退过程中的某些时段沉积环境相似,出现了沉积物粒径组合及大小相似的情况。     

Generalized stress framework for unsaturated soil: demonstration and discussion

The long-lived debate on the principle of effective stress is rooted in the obscure physical significance of stresses. For the sakes of clarifying stress concepts and establishing a reasonable principle of effective stress, unsaturated soil is divided into six phases and the bearing structure of it, named generalized soil structure, is defined based on considering soil as a special structure. Then the essence of effective stress equation, named stress relation equation, is derived according to analysis of interphase interactions and independent-phase equilibrium. The stress relation equation indicates the corresponding relation between two series of stress variables used in mixed and multiphase continuum models, respectively. Furthermore, a reasonable concept of suction stress is redefined to describe interparticle connection properties. Then, a generalized stress framework is constructed by associating stress relation equation with suction stress. After demonstrating the concept of neutral stress, a generalized principle of effective stress is established and the total soil skeleton stress is searched out, which is the predominant stress controlling the strength and deformation of soil. Finally, the collapse phenomenon is analyzed and the time- and spatial-dependent stress frameworks are developed.

     

Evaporation from seasonally frozen bare and vegetated ground at various groundwater table depths in the Ordos Basin,Northwest China

In cold climates, the process of freezing–thawing significantly affects the ground surface heat balance and water balance. To better understand the mechanism of evaporation from seasonally frozen soils, we performed field experiments at different water table depths on vegetated and bare ground in a semiarid region in China. Soil moisture and temperature, air temperature, precipitation, and water table depths were measured over a 5‐month period (November 1, 2016, to March 14, 2017). The evaporation, which was calculated by a mass balance method, was high in the periods of thawing and low in the periods of freezing. Increased water table depth in the freezing period led to high soil moisture in the upper soil layer, whereas lower initial groundwater levels during freezing–thawing decreased the cumulative evaporation. The extent of evaporation from the bare ground was the same in summer as in winter. These results indicate that a noteworthy amount of evaporation from the bare ground is present during freezing–thawing. Finally, the roots of Salix psammophila could increase the soil temperature. This study presents an insight into the joint effects of soil moisture, temperature, ground vegetation, and water table depths on the evaporation from seasonally frozen soils. Furthermore, it also has important implications for water management in seasonally frozen areas.     

The vertical influence of temperature and precipitation on snow cover variability in the Central Tianshan Mountains,Northwest China

Seasonal snow cover in mountainous regions will affect local climate and hydrology. In this study, we assessed the role of altitude in determining the relative importance of temperature and precipitation in snow cover variability in the Central Tianshan Mountains. The results show that: (a) in the study area, temperature has a greater influence on snow cover than precipitation during most of the time period studied and in most altitudes. (b) In the high elevation area, there is a threshold altitude of 3,900 ± 400 m, below which temperature is negatively correlated whereas precipitation is positively correlated to snow cover, and above which the situation is the opposite. Besides, this threshold altitude decreases from snow accumulated period to snow stable period and then increases from snowmelt period to snow‐free period. (c) Below 2,000 m, there is another threshold altitude of 1,400 ± 100 m during the snow stable period, below (above) which precipitation (temperature) is the main driver of snow cover.     

Control factors of DIC in the Y3 seamount waters of the Western Pacific Ocean

An investigation was carried out in the Y3 seamount area of the Western Pacific Ocean in December 2014,and the distribution of dissolved inorganic carbon(DIC) and its relationship with environmental factors in this area were explored.The results show that DIC concentration was higher in the adjacent waters of the Y3 seamount area,and the uplift of DIC isolines at the stations was close to the seamount.Meanwhile,interaction between the North Equatorial Current(NEC) and the Y3 seamount affected the DIC distribution i.e.,the upwelling in the same direction of the NEC was obvious,resulting in a decreasing trend of average concentration of DIC in the 200 m water column from the top to the two side s in this direction but in the cross direction.The DIC concentration increased with the water depth increase,and its distribution was affected by various environmental factors.In the surface water,high temperature was a decisive factor for the decrease of the DIC concentration,but the photosynthesis of phytoplankton showing only a weak influence.In the North Pacific Tropic Water(NPTW),DIC production rate from organic matter decomposition was higher than that of DIC consumption by phytoplankton photosynthesis,leading to a continual increase of DIC.In the North Pacific Intermediate Water(NPIW),organic matter decomposition played a leading role in the increase of DIC.In the deep water,decomposition of organic matter weakened,and the dissolution of CaCO_3 controlled the carbonate system,and DIC had the smallest variation range.     

Research progress of TiO2 photocathodic protection to metals in marine environment

Corrosion protection has become an important issue as the amount of infrastructure construction in marine environment increased.Photocathodic protection is a promising method to reduce the corrosion of metals,and titanium dioxide(TiO_2) is the most widely used photoanode.This review summarizes the progress in TiO_2 photo gene rated protection in recent years.Different types of semiconductors,including sulfides,metals,metal oxide s,polymers,and other materials,are used to design and modify TiO_2.The strategy to dramatically improve the efficiency of photoactivity is proposed,and the mechanism is investigated in detail.Characterization methods are also introduced,including morphology testing,light absorption,photoelectrochemistry,and protected metal observation.This review aims to provide a comprehensive overview of Ti02 development and guide photocathodic protection.