基于DEM的地球与火星格状沙丘对比分析

沙丘是柴达木盆地可类比火星的重要地貌类型,沙丘形态是类火星风沙地貌研究的重要内容。基于数字地形分析（DTA）的方法,采用高程、坡度、坡向及地表复杂程度4个地形计量学指标对火星（北极地区）和地球（柴达木盆地）格状沙丘的地貌形态特征进行定量对比分析。结果表明：（1）两个研究区的高程剖面、坡度、坡向的地理学空间分布格局具有较大相似性;（2）高程、高程梯度、坡度和坡向的直方图相似度指数均大于0.7;（3）不同尺度上的分形维数近似相等,即地表复杂程度相似。用数字地形分析与直方图相似度指数结合的方法,定量或半定量地分析两个研究区沙丘地貌形态的相似性,这对类火星风沙地貌研究中科学选择试验点是一种新的尝试,以期为反演火星风沙地貌的形成与演化提供科学依据。     

Coupling Earth System Model and Integrated Assessment Model

According to the guideline of National Key Research and Development Project, this project aims at developing a world-class Integrated Assessment Model (IAM) in China, which will be used to assess the impacts of climate change on economy system. The objects of this project are to ① Improve the spatial resolution of Earth System Model (ESM); ② Modify the Integrated Assessment Model; ③ Couple the ESM and IAM; ④ Evaluate the impacts of climate change on society and economy. This project will solve two key scientific questions: how to identify the impacts of climate change in the IAM; How much the impacts of climate change on economy in China. Meanwhile, two techniques will be developed to complete the mission of this project: Simulate of small-scale human activities in the EAM and spatial and temporal resolution match of ESM and IAM.     

Chinese Earth Science at Its Turning Point

Since 2010, China has become the second biggest publisher of scientific research papers in the world, but remains far behind the global leadership with regards to the ability of creative innovation. Just like its economy, Chinese science is at a turning point, and the key is to avoid the “Middle-income trap”. Instead of blindly going after quantity of SCI publications, Earth science in China is to address major scientific problems and to perform transition to a new level of innovative researches. This is a written speech to the 4^th Conference on Earth System Science,Shanghai.     

Numerical study on stress states and fabric anisotropies in soilbags using the DEM

Wrapping granular soils in geosynthetic containers, such as soilbags, results in a considerable increase in the bearing capacity due to the effective restraint on the dilatancy of the soil. This paper numerically investigates the stress states and fabric anisotropies in the wrapped soil using the discrete element method, providing a novel perspective for new insights into the reinforcement mechanisms and the development of constitutive relations for soilbags. The two most anticipated loading conditions, namely, unconfined compression and simple shear, are considered, and numerical predictions are compared to experimental results. During unconfined compression, both global and local p–q stress paths evolve linearly, having the same slope until the global failure of the wrapping geosynthetic. Under simple shear, the global stress path approaches the critical state line first and then turns to the compression line of the wrapped soil. Some local loading–unloading stress paths are observed, which may account for the high damping of soilbags during cyclic shear. The reduced fabric anisotropies of the normal and tangential force chains suggest greater confinement from the lateral sides of the geosynthetic container in either loading course. The performance and mechanisms of the soilbag earth reinforcement method, i.e., confinement and interlocking, can be better understood based on these new findings on the stress states and fabric anisotropies.     

Land subsidence and earth fissures due to groundwater withdrawal in the Southern Yangtse Delta,China

Excessive extraction of groundwater has caused severe land subsidence and earth fissures in the Southern Yangtse Delta, China. Based on field data, the temporal and spatial distribution of land subsidence is investigated and the causes for earth fissures are analyzed. The areal distribution of the land subsidence is closely related to the cones of depression in the main exploited aquifers. The compaction of a hydrostratigraphic unit depends on its mechanical behavior, thickness, compressibility, and the piezometric level changing. The primary subsidence layers in Shanghai have been the first aquitard before 1990 and the third confined aquifer since then. But the second aquitard unit was the primary subsidence layer in Changzhou. Earth fissures, trending in several directions, occurred in the Husu tectonic zone. They were mainly caused by differential subsidence and horizontal displacement that resulted from tensile stress and shear stress in units. The majority of fissures in the study area are tensile.     

Assessment and Control of Ore Dilution in Long Hole Mining: Case Studies

Unplanned ore dilution has a direct and large influence on the cost of a stope, and ultimately on the profitability of a mining operation. This paper presents the results of an examination of factors influencing ore dilution in a blasthole stoping environment. For the study, a comprehensive database was established, incorporating information related to the design, construction, excavation and cavity surveys of 172 sequentially mined long hole stope case histories from two orezones. Through a review of the case studies, it was demonstrated that, in addition to stope dimension, the amount of unplanned dilution differed according to stope type. Five stope types were identified, based on their position within a tabular blasthole mining sequence. Measured overbreak varies with stope type, with secondary stopes generating a greater volume of hanging-wall dilution than do primary stopes. Furthermore, a case study is presented to demonstrate the role cablebolts installed in the stope hanging-wall play to control ore dilution. The study illustrates relationships between measured hanging-wall overbreak, cablebolt orientation and stope type.     

湿陷性黄土地区高速公路强夯路基及其特性

西部山区修建高速公路穿越湿陷性黄土地区时面临诸多设计和施工问题。选择国道312线典型湿陷性黄土地基试验段,进行了不同夯击能量的强夯试验。通过对强夯土体室内、外试验结果分析,揭示了强夯前后湿陷性黄土的变化规律,得出:压实度与孔隙比呈线性递减关系;压实度不小于95%时施工含水量的合理范围应控制在11.9%～15.4%,土体分布-1～-5 m;2 000 kN.m、3 000 kN.m、6 000 kN.m强夯的加固深度分别为5～6 m、6～7 m和8.5～10 m,大于加固深度后地基土强度提高不明显。     

Google Earth和ArcGIS 9.2软件在太湖水污染及蓝藻监测数据展现中的应用

利用Google Earth和 ArcGIS 9.2软件对太湖水污染及蓝藻监测数据进行了集成和发布,为形象直观展示太湖生态环境,分析太湖水环境质量及蓝藻空间分布特征提供了很好的技术支持.     

Cost Optimization of Reinforced Earth Walls

This paper deals with optimum cost (objective function) design of geosynthetic reinforced earth retaining walls subjected to static and dynamic loading. The design restrictions are imposed as design constraints in the analysis. Choice of the initial designed length and strength of the reinforcement, which are the elements of the design vectors are made in a way that it forms an initial feasible design vector. Thus the problem is one of mathematical programming. The constraints and the objective function being nonlinear in nature, the Sequential Unconstrained Minimization Technique (SUMT) has been used in conjunction with conjugate direction and quadratic fit methods for multidimensional and unidirectional minimization to arrive at the optimal (minimum) cost of the reinforced earth wall. Optimal cost tables are presented for different combinations of the loading and the developed procedure is validated by taking up an example problem. It has been found from the typical example problem that saving of the order of 7–8% can be made over the conventional design of mechanically stabilized earth (MSE) walls with the aid of design charts.     

地球的时变主惯性矩和变化的自转(英文)

Based on the gravity field models EGM96 and EIGEN-GL04C, the Earth's time-dependent principal moments of inertia A, B, C are obtained, and the variable rotation of the Earth is determined. Numerical results show that A, B, and C have increasing tendencies; the tilt of the rotation axis increases 2.1×10-8 mas/yr; the third component of the rotational angular velocity, ω 3, has a decrease of 1.0×10-22 rad/s2, which is around 23% of the present observed value. Studies show in detail that both θ and ω 3 experience complex fluctua-tions at various time scales due to the variations of A, B and C.