黄土高原自然植被下垫面陆面过程参数研究

利用兰州大学半干旱气候与环境观测站的观测资料,分析了黄土高原自然植被下垫面陆面过程相关物理参数.研究了总体输送系数的不同季节平均日变化和频率分布特征,考察了地表粗糙度的变化趋势以及降水的影响.降水正常年份的总体粗糙度为0.009 m,偏干年份总体粗糙度为0.006 m,月平均粗糙度变化与正常年份相比较为平缓,降水通过增加植被覆盖和生长高度,使地表粗糙度增大.对总体输送系数与粗糙度以及总体理查森数的关系分别进行了讨论,在中性层结下黄土高原地区动力输送作用占主导地位,发现动量总体输送系数和奈曼流动沙丘下垫面很接近,而感热输送系数与戈壁下垫面接近.分析了反照率和太阳高度角以及土壤湿度的关系,并拟合得到以这两个物理量为因子的参数化公式.总体上,黄土高原自然植被下垫面的反照率比敦煌荒漠小,而大于长白山松林下垫面,这与3个地区植被覆盖和土壤质地的不同有关.通过对参数化公式模拟效果的检验,发现低太阳高度角下的反照率对土壤湿度和太阳高度角以外的其他因素敏感,而对应高太阳高度角的反照率受土壤湿度和太阳高度角的控制较强.最后,计算了土壤热传导率和热扩散率等土壤热力参数,相同湿度的热传导率比敦煌荒漠要大,并拟合得到热传导率以土壤湿度为自变量的参数化公式.     

美国干热岩"地热能前沿瞭望台研究计划"与中美典型EGS场地勘查现状对比

美国能源部正在实施干热岩“地热能前沿瞭望台研究计划”(FORGE计划)。它是以经典干热岩定义的干热岩勘查开发为约束,通过增强型地热系统(EGS)示范工程建设实践,形成新一代EGS试验平台。美国本着“可复制的结果=巨大的潜力”的理念,实现干热岩勘查开发技术新突破,以满足美国1亿家庭绿色电力供应为实际应用目标。中美典型EGS场地勘查现状对比结果表明：犹他州米尔福德与青海省共和县恰卜恰两个典型EGS场地具可比性,大致处于“并跑”的水平;在天然裂隙系统、原位地应力场、压裂参数获取与压裂方案制定等方面,米尔福德EGS场地有所超前。据此建议有关部门加快青海省共和县恰卜恰EGS场地进入勘查开发阶段,以提高我国干热岩勘查开发技术水平,早日实现EGS工程化。     

基于低空遥感地貌观测的逆断层陡坎研究:以张流沟滩断层陡坎为例

活动断层相关地貌特征的定量研究是揭示古地震和断裂属性的重要依据,其中陡坎地貌是断裂活动的重要地貌响应,是有效识别活动断裂的重要地貌标志。近年来,无人机低空遥感观测技术的不断进步,使得高分辨率地貌数据的快速获取成为现实。本研究利用无人机低空遥感地貌观测技术,对张流沟滩处的断层陡坎附近进行高分辨率数字地形数据的采集。断层陡坎位于张流沟滩河流Ⅱ级阶地上,影像采集范围为800 m×400 m的矩形区域。经过一系列的影像处理,最终获取了目标区地面分辨率为0.1 m的DEM(数字高程模型)数据。基于该DEM数据可以提取到正交于断层陡坎的高程、坡度剖面。利用高程剖面所展示的地形地貌信息,可以提取到陡坎高度为(2.81±0.05) m;利用坡度剖面所展示的坡度曲线特征,可以推断该陡坎至少经历过两次断错活动事件,并且陡坎存在向上“凸起样式”。通过探槽解译,确定该陡坎下伏断裂至少发生过两次活动事件,其中较早的地震事件接近(3.68±0.14) ka B.P.,最晚期的地震活动应为1927年古浪8级地震,两次断裂活动累计垂直位移为(2.80±0.2) m。将以上两种研究方法相比较可以发现,探槽结构分析与低空遥感获取的定量化地貌信息分析结果基本一致,均能够有效揭示古地震期次及累计的同震位移量。最终本研究将探槽揭示的地层单元的沉积、构造信息与陡坎坡度数据特征相结合,提出了基于断层传播褶皱模型的“陡坎凸起”地貌响应样式来解释陡坎存在的向上“凸起样式”。实践证明,利用无人机低空遥感地貌观测技术能够定量、半定量化揭示下伏断裂的活动信息,结合传统断裂研究手段,可以更全面解释活动断层的沉积、构造特征及地形、地貌现象。总的来说,无人机低空遥感地貌观测技术的应用可作为传统古地震研究的辅助手段,并有其独特的方法优势。     

渤海湾盆地干热岩型地热资源有利区位研究

基于沉积盆地型干热岩的基本特征,系统总结了渤海湾盆地干热岩型地热资源选区的地热地质学、地球物理学、地表地热显示、干热岩资源潜力和地质安全性等指标,对渤海湾盆地内主要构造单元干热岩赋存背景进行了分析,建立了适宜于沉积盆地型干热岩勘查选区的评价指标体系。通过层次分析和打分法进行综合评价,结果表明,渤海湾盆地内干热岩勘查的最有利区位为沧县隆起区,次有利区位为济阳坳陷和冀中坳陷,显示厚覆盖盆地内隆起区较坳陷区更为有利,而坳陷区内的次级凸起构造较凹陷构造更为有利。基于上述认识,在有利区位中进一步圈定了沧县隆起、牛驼镇-容城凸起、陈庄凸起和乐亭-昌黎凹陷4个靶区,为渤海湾盆地开展干热岩勘查选址指明了方向。     

A unified constitutive model for unsaturated soil under monotonic and cyclic loading

This study presents a sophisticated elastoplastic constitutive model for unsaturated soil using Bishop-type skeleton stress and degree of saturation as state variables in the framework of critical state soil mechanism. The model is proposed in order to describe the coupled hydromechanical behavior of unsaturated soil irrespective of what kind of the loadings or the drainage conditions may be. At the same time, a water retention characteristic curve considering the influence of deformation on degree of saturation is also proposed. In the model, the superloading and subloading concepts are introduced to consider the influences of overconsolidation and structure on deformation and strength of soils. The proposed model only employs nine parameters, among which five parameters are the same as those used in Cam-Clay model. The other four parameters have the clear physical meanings and can be easily determined by conventional soil tests. The capability and accuracy of the proposed model have been validated carefully through a series of laboratory tests such as isotropic loading tests and triaxial monotonic and cyclic compression tests under different mechanical and hydraulic conditions.

     

The influence of the degree of saturation on compaction-grouted soil nails in sand

A series of large-scale model tests was conducted on compaction-grouted soil nails to study the influence of the degree of saturation on the soil response to compaction grouting and pull-out. The experimental results show that the initial degree of saturation of the soil strongly influences the grout injectability, thus the formed diameter of grout bulb. Subsequently, the diameter of the grout bulb alters the pull-out force, with larger grout bulbs generating higher pull-out forces and exhibiting greater hardening behaviour. Interestingly, the initial pull-out forces are the same for the same grouting pressure, regardless of the initial degree of saturation and the subsequently grout bulb. In addition, some of the main factors influencing the pressure grouting and pull-out of the soil nail, as the initial degree of saturation varies, are as follows. First, the variations in the soil pressure and density with the initial degree of saturation are similar to that of the volume of grout injected, and the compression of the soil induced by pressure grouting exhibits a similar evolution with the initial degree of saturation at different locations. Second, the initial degree of saturation of the soil sample plays a dominant role in the change in suction during pressure grouting and pull-out of soil nail. Third, the horizontal soil pressure derived from the pull-out of soil nail propagates closely in the soil sample of lower initial degree of saturation. The vertical soil pressure induced by the vertical soil dilation and squeezing effect varies in accidence with the initial degree of saturation and the grout bulb.

     

基于SIFT特征检测和密度峰值聚类的太阳活动区自动检测算法研究

太阳活动区是太阳大气中产生各种活动现象的区域,精确地检测和识别太阳活动区对理解太阳磁场的形成机制具有极为重要的科学意义.根据太阳活动区结构较为复杂的特点,基于尺度不变特征变换(ScaleInvariant Feature Transform, SIFT)和密度峰值聚类(Clustering by Fast Search and Find of Density Peaks,DPC)算法的优越性,提出了一种太阳活动区的自动检测和识别方法.首先,对太阳动力学天文台(Solar Dynamics Observatory, SDO)日震和磁场成像仪(Helioseismic and Magnetic Imager, HMI)的纵向磁图进行对比度增强;然后采用SIFT方法提取出全日面磁图中的特征点;最后利用DPC算法将特征点进行聚类,从而自动检测和识别出太阳活动区.研究结果表明, SIFT和DPC算法相结合的方法可以在不需要人工交互的情况下准确地自动检测出太阳活动区.     

地震应急指挥系统关键技术和总体设计

地震应急救灾指挥系统是一项复杂的系统工程,工程内容包括计算机软硬件平台、应急响应系统应用软件（灾害评估、应急对策）开发、数据库（专家知识系统）、3S（GIS、GPS、RS）技术应用、网络、通讯、投影、声像、监控、系统总体集成和有关理论研究,以及基建、场地布局、消防、供电、环境（新风、温、湿度）控制、装饰装修等。本文只从宏观的角度,阐述应急系统的关键技术和总体设计。     

准噶尔盆地腹部永进地区砂岩储层中碳酸盐胶结物特征及其成因意义

准噶尔盆地腹部永进地区不整合面附近砂岩储层中次生孔隙和碳酸盐胶结物相对发育.通过薄片观察、阴极发光、扫描电镜/能谱分析,认为碳酸盐胶结物是研究区砂岩最主要的胶结物成分,其主要类型为(铁)方解石和铁白云石,垂向上含量随深度增加而增加,多集中分布在白垩系和侏罗系之间的不整合面之下约100 m的范围之内.碳、氧同位素分析以及泥岩中各元素测试结果表明,大气淡水通过永进地区白垩系和侏罗系之间存在的角度不整合对其下伏地层物性作用不明显,晚期含铁碳酸盐胶结物和孔隙发育主要与有机酸关系密切.在有机酸作用下,早期发育的碳酸盐胶结物、长石碎屑颗粒以及粘土矿物为晚期碳酸盐胶结物的发育提供了物质基础,而且溶解的物质在酸性流体作用下运移至不整合面附近重新沉淀,造成高孔隙度和高含量碳酸盐胶结物在深度上具有重叠的特征.由于含铁碳酸盐胶结物形成时代晚而且储层未受到其他建设性成岩作用的明显改造,晚期碳酸盐胶结物含量和面孔率呈互相补偿的关系, 表明了晚期碳酸盐胶结物对储层物性的破坏作用.     

Variations of Microbial Communities and the Contents and Isotopic Compositions of Total Organic Carbon and Total Nitrogen in Soil Samples during Their Preservation

Semi-sealed preservation of soil samples at different moisture of 4% and 23%, respectively, was simulated to observe the variations of soil microbial communities and determine the contents and isotopic compositions of the total organic carbon and total nitrogen on the 7th and 30th day, respectively. The results show that during preservation, the quantity of microbial communities tended to increase first and then decrease, with a wider variation range at higher moisture (23%). At the moisture content of 23%, the microbial communities became more active on the 7th day, but less after 30 days, and their activity was stable with little fluctuation at the moisture content of 4%. However, there were no significant changes in the contents and isotopic compositions of the total organic carbon and total nitrogen. During preservation, the responses of soil microbes to the environment are more sensitive to changes in the total nitrogen and organic carbon contents. It is thus suggested that the variations of microbial communities have not exerted remarkable impacts on the isotope compositions of the total nitrogen and total organic carbon.