山体轰然倒塌

正大地震可以产生造山作用,但是也可以触发滑坡从而消磨自然景观。根据2008年汶川地震的分析表明,滑坡毁坏了更多的地形,高于地壳抬升的方量。多山地带的地形演化被最简单地看作地形建造的构造过程与地形破坏并带走沉积物的侵蚀过程之间的竞争。在构造活动的山脉,这些侵蚀过程主要包括陡峭河流的下切和物质输送、以滑坡和冰川磨损形式的大规模物质输送。每种作用的贡献随时间而变化,受气候的变化而不同。当构造抬升的过程超过侵蚀过程时,造山带生长;当两者平衡时,造山带保持稳定;而当侵蚀超过抬升     

胶东地区前孙家-洼孙家断裂南段构造控矿规律及找矿研究

胶东西北部是我国重要的金矿聚集区,矿床主要受断裂构造控制。前孙家-洼孙家断裂是研究区内主要控矿断裂。依据该构造南段前孙家、金华山两个金矿的岩石、构造、矿体分布、矿化蚀变等特征,对两矿区的构造控矿型式、构造控矿规律进行了探讨,认为该区成矿热液活动具有多期性。成矿预测表明前孙家矿区4号脉的深部可能存在盲矿体,2号脉在深部有一定的延伸;金华山矿区1号脉的下盘可能存在与1号脉平行的雁列脉矿体;1号脉、2号脉在深部应有交汇,可作为重点找矿位置。     

不同结构离岸式潜堤消浪效果试验研究

在某保滩促淤工程中,应用了离岸式潜堤技术。为了验证其不同结构形式的消浪效果,通过物理模型试验,对斜坡堤、大圆筒以及板桩直立堤的3种潜堤断面,在3种不同水位、波高作用下的消波效果作观测比较,并对其结果进行分析研究,旨在为工程设计和建设提供科学依据。     

平面应变条件下原状黄土侧向卸载变形与强度特性分析EI北大核心CSCD

基于平面应变改造后的西安理工大学真三轴仪,在不同围压条件下对不同含水率黄土进行了侧向卸载平面应变试验,研究了平面应变条件下原状黄土的卸载强度、变形特性以及原状黄土的破坏方式。研究结果表明:不同固结围压条件下,各含水率原状黄土的侧向卸载应力-应变曲线均为硬化型,近似呈理想塑性曲线。剪切过程中,黄土的侧向与竖向变形呈非线性变化,侧向应变的发展要快于竖向应变,体积变形均为体胀。侧向卸载条件下土的破坏应变要比平面应变竖向加载和常规三轴试验小得多。黄土的卸载破坏强度与含水率、围压和球应力状态密切相关;随着含水率的增大,黏聚力衰减明显,内摩擦角略有减小。侧向卸载条件下,原状黄土呈剪胀滑移破坏形式。     

单轴压缩下含层理加锚岩石力学特性研究EI北大核心CSCD

为分析锚固方式和层理对加锚岩石力学特性影响规律,采用相似材料预制含层理岩石,室内钻取0°和90°层理标准试件,以45号钢加工而成的螺杆模拟锚杆,分别对试件进行端部锚固和全长锚固,从而得到不加锚杆、端部锚固、全长锚固3种试件,而后在MTS815岩石力学试验系统上对试件进行单轴压缩试验分析其变形、强度特征。结果表明:锚杆可提高岩石的强度,且层理方向和锚固方式影响其对强度的提高幅度。层理相同的加锚试件,全长锚固下岩石的抗压强度提高幅度大于端部锚固岩石;同一锚固方式下,90°层理加锚试件的单轴抗压强度提高幅度大于0°层理加锚试件。锚固方式不同,加锚试件的破坏形式亦有所差别。根据锚固方式不同,可将破坏形式分为剪切拉伸和剪切错断2种。锚固方式对加锚试件锚杆失效模式无影响,二者均表现为岩体与灌浆界面滑脱,但全长锚固与端部锚固所不同的是,全长锚固锚杆与岩石粘结长度更大,粘结强度更高,失效时可带出更多、更厚的岩石碎屑。     

The changes of pigment contents and their environmental implications in the lake sediments of Ny-(A)lesund, Svalbard, the Arctic

According to palaeoclimatic and modern instrumental data, numerous studies have indicated that the Arctic climate has undergone a significant warming during the past 100 years, and this may lead to significant impact on the fragile lake ecosystem. In this study, we collected a lake sediment core from the Ny-(A)lesund of Svalbard and determined the concentrations of four pigments including chlorophyll derivatives, total carotenoids, oscillaxanthin and myxoxanthophyll in the sediments. Combined with other physical and chemical proxies such as calcium carbonate, total organic carbon, biogenic silicon etc., we have reconstructed the historical changes of lacustrine primary productivity in Ny-(A)lesund, especially for the past 100 years. The results showed that during the period of Little Ice Age (LIA), the climate was unfavorable for the growth of the lake algae, and thus the lacustrine productivity declined. This result was supported by the relatively low contents of pigment and biogenic silica in the sediments. In contrast, the contents of total organic carbon (TOC) and sediment pigments increased significantly in the upper 5 cm (~1890AD), reflecting the rapid growth of the lake algae, thus the great increase of lacustrine primary productivity, corresponding to the warming climate after LIA. However, the biogenic silica in the upper sediments still had a relatively low level, and this might be related to the growth competition with other algae species. Over the past 100 years, the ratio of Osc/Myx in the sediments decreased continuously, indicative of durative increase of myxoxanthophyll in blue-green algal pigments, and this might imply that the human activity had enhanced the nutrition level of the lake in the Arctic region.     

Blasius方程中临界值的分析估计

证明了流体力学边界层理论中著名的Blasius方程的一个新性质,它在二维平板流的研究中具有重要的作用,由此建立它的积分形式,并给出方程中的临界值βc的分析估计。     

黄河站与斯瓦尔巴群岛

斯瓦尔巴群岛自然资源丰富,17世纪时期,斯瓦尔巴群岛附近海域渔业发达,渔民已经开始在这里捕杀鲸鱼、海豹、海象等海洋生物。由于长期过量的捕杀,到18世纪末期,渔业开始衰落。斯瓦尔巴群岛各个岛屿上储存着丰富的煤炭资源,附近海域蕴藏着丰富的石油资源。     

Diffraction of plane SH waves by a semi-circular cavity in half-space

This paper presents a closed-form solution for diffraction of plane SH waves by a semi-circular cavity in half-space by using wave function expansion method. Accuracy of the solution is checked by the displacement residual and stress residual along the boundaries. Numerical results show that there are notable differences for response amplitudes between a semi-circular cavity and a whole-circular cavity in a half-space.     

西南极南设得兰群岛地层对比与划分

对南设得兰群岛基岩区进行地质调查和研究,恢复其地层层序与演化过程.通过野外考察和资料收集,对比分析了前人年代学、地球化学、古地磁学、古生物学、地层学等方面的研究成果,将南设得兰群岛地层划分为24个岩石地层单元,建立了南设得兰群岛中—新生代火山-沉积地层层序和年代学格架.研究表明;南设得兰群岛火山活动早白垩世—早中新世总...