The response of subaqueous dunes to floods in sand and gravel bed reaches of the Dutch Rhine

Abstract The branches of the River Rhine in the Netherlands, characterized by a sand–gravel bed in the upstream part and a sand bed in the downstream part of the river system, show migrating dunes, especially during floods. In the last 20 years, these dunes have been studied extensively. High-resolution echo-sounding measurements of these dunes, made with single and multibeam equipment, were analysed for three different sections of the Rhine river system during several floods. This analysis was done to quantify the growth, decay and migration rates of the dunes during floods. In addition, the migrating dunes were used to calculate bedload transport rates with dune tracking. The results of dune growth and decay and migration rate are shown to be very different for the various sections during the various floods, and these differences are related to differences in grain size of the bed and to differences in the distribution of discharge over the main channel and the floodplain. The relations are used to show that the growth and migration rate of dunes, and the calculated bedload transport rates during the rising stage of a flood wave can be predicted from the mobility of the bed material with simple power relations.     

Crustal structure of the continental margin of Korea in the East Sea (Japan Sea) from deep seismic sounding data: evidence for rifting affected by the hotter than normal mantle

Despite the various opening models of the southwestern part of the East Sea (Japan Sea) between the Korean Peninsula and the Japan Arc, the continental margin of the Korean Peninsula remains unknown in crustal structure. As a result, continental rifting and subsequent seafloor spreading processes to explain the opening of the East Sea have not been adequately addressed. We investigated crustal and sedimentary velocity structures across the Korean margin into the adjacent Ulleung Basin from multichannel seismic (MCS) reflection and ocean bottom seismometer (OBS) data. The Ulleung Basin shows crustal velocity structure typical of oceanic although its crustal thickness of about 10 km is greater than normal. The continental margin documents rapid transition from continental to oceanic crust, exhibiting a remarkable decrease in crustal thickness accompanied by shallowing of Moho over a distance of about 50 km. The crustal model of the margin is characterized by a high-velocity (up to 7.4 km/s) lower crustal (HVLC) layer that is thicker than 10 km under the slope base and pinches out seawards. The HVLC layer is interpreted as magmatic underplating emplaced during continental rifting in response to high upper mantle temperature. The acoustic basement of the slope base shows an igneous stratigraphy developed by massive volcanic eruption. These features suggest that the evolution of the Korean margin can be explained by the processes occurring at volcanic rifted margins. Global earthquake tomography supports our interpretation by defining the abnormally hot upper mantle across the Korean margin and in the Ulleung Basin.     

深厚表土层地面注浆加固过程中井壁应变变化规律

分析了深厚表土层地面注浆加固过程中井壁的受力特点,介绍了金桥矿副井表土段地面注浆加固过程中井壁的应变观测结论,提出了深厚表土层井壁外注浆加固工程的井壁安全保证核心技术。     

深层水泥土搅拌桩在基坑支护中的应用

通过介绍水泥与土之间的一系列物理-化学反应,阐述了深层搅拌法加固地基土的原理[1]。结合室内试验及工程实例,介绍了深层水泥土搅拌桩重力式挡墙技术在基坑支护中的应用,对于基坑设计及施工有一定实际意义。     

黄壁庄水库副坝塌坑Ⅳ76+1槽段安全监测

介绍了黄壁庄水库副坝塌坑Ⅳ76+1槽段进行的安全监测设计及根据此设计进行的安全监测实施,根据取得的监测资料解决了一直未能确定的主要变形地层的问题,为水库的加固施工和后期的运行安全提供了一定的依据。     

深基坑复合喷锚支护技术探讨

工程实践表明,复合喷锚支护是一种有效的深基坑支护型式,它可用于土层条件差、安全性要求高、变形控制严格的基坑工程中。复合支护中锚杆为主要受力构件,竖向花管为辅助受力构件,可起到限制、减小土体变形的作用。由于竖向注浆花管的加入,花管及注浆体抗剪作用加强,使基坑的整体稳定性得以大幅度提高。探讨了复合喷锚支护整体稳定性分析方法,建议将滑动区域分为加固土和原土两部分,将锚管注浆形成的注浆体等效为一层加固土,按喷锚支护模型计算复合喷锚支护整体稳定性。     

松潘-甘孜造山带地壳速度结构

位于川西地区的奔子栏——唐克深地震测深剖面以NNE走向穿越松潘——甘孜造山带．根据人工地震记录分析得到的震相走时和相关的振幅信息，确定了该剖面二维P波地壳速度结构．剖面的地壳结构可分为5层，其中第1，2，3层为上地壳；第4，5层为下地壳．上地壳中部普遍存在低速异常带，但龙日坝以北，这一低速带与其上覆的低速基底合为一体．同时，沿剖面的地壳速度结构具有较强的横向变化．据此，可将剖面分为4段，即甘孜——理塘断裂以南、甘孜——理塘断裂至鲜水河断裂、鲜水河断裂至龙日坝断裂和龙日坝断裂以北. 这与区域构造划分基本一致． 地壳厚度沿测线从南西向北东逐渐减薄，即从金沙江畔的62 km减小到黄河附近的52 km． 根据PmP震相分析，莫霍界面深度在鲜水河断裂两侧没有明显变化．全剖面的地壳平均速度较低，为6.30 km/s．奔子栏——唐克剖面揭示了该地区的造山带型地壳上地幔结构特征．鲜水河断裂带位于剖面的中部，该地区的上地壳速度为正异常，而下地壳和上地幔顶部存在负异常．笔者认为，这是一类有利于强震孕育和发生的深部构造环境．      

The crustal fluid evolution and the causes of earthquakes(Ⅲ)

Ｔｈｅｃｒｕｓｔａｌｆｌｕｉｄｅｖｏｌｕｔｉｏｎａｎｄｔｈｅｃａｕｓｅｓｏｆｅａｒｔｈｑｕａｋｅｓ（Ⅲ）ＣＨＡＮＧ－ＦＡＮＧＸＵ（徐常芳）ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｌｏｇｙ，ＳｔａｔｅＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕ，Ｂｅｉｊｉｎｇ１０００...     

Analysis and study of the large earthquake risk in Yanqing-Huailai basin

ＡｎａｌｙｓｉｓａｎｄｓｔｕｄｙｏｆｔｈｅｌａｒｇｅｅａｒｔｈｑｕａｋｅｒｉｓｋｉｎＹａｎｑｉｎｇＨｕａｉｌａｉｂａｓｉｎＣＨＡＮＧＱＵＡＮＬＩＵ（刘昌铨）ＳＨＩＸＵＪＩＡ（嘉世旭）ＭＩＮＧＪＵＮＬＩＵ（刘明军）ＣＨＡＮＧＦＡＬＩ（李长发...     

乌鲁木齐——库尔勒地震转换波测深

利用天然地震转换波研究了天山地区乌鲁木齐－－库尔勒剖面的深部构造特征。地壳中存在５个国煌速度界面，并被数条断裂切割，相应地分为５个构造单元；天山中部的界面均有没和蔼的抬升，在地壳中形成逆部断裂，而地的厚度小于南北两则地区，表明地幔的物质 隆起，有可能造成地壳平均密度增加；天山南缘的和静、巴伦台一带断裂错综复杂，界面严重变形，是未来构造活动比较强烈的地区。