Transport rate of calcareous sand in unidirectional flow

This paper examines the transport of calcareous sand in unidirectional flow and its prediction through existing sediment transport models. A flume experiment of four sand samples collected on Oahu, Hawaii, provides 29 sets of sediment transport data in the bed-form and suspended transport stages. The measured transport data are compared with direct predictions from four energy-based transport models developed for siliceous particles. Corrections for the grain-size, fall velocity, and critical velocity of calcareous sand based on recent research are applied to the models and the results are compared with the direct calculations and measured data. The comparison illustrates the important role particle shape plays in the transport of calcareous sand. All four sediment transport models give consistent predictions and good agreement with the majority of the measured data. Two of the models respond positively to the corrections in both the bed-form and suspended transport stages indicating that such an approach may provide an interim solution for the transport of calcareous sand.     

马槽滩磷矿区的矿体形态特征及合理勘查工程间距

马槽滩磷矿区矿体形态复杂,底板起伏不定,多年来勘查工程间距不断改变,因此用多种方法讨论了合理工程间距.探采对比和数理统计学方法求得控制资源量的合理工程间距分别为200m×150m和200m×100m;控制半变异函数的变程亦为200m×100m,均与现行规范相吻合。但沿走向和倾向的变异相同,因此建议用正方形网格进行勘查更为合理,间距为150m×150m。     

A three dimensional model of muckpile formation and grade boundary movement in open pit blasting

Summary Formulation and case studies of a three dimensional kinematic model are presented. Thein situ overburden geometry can be simulated accurately and various initiation patterns of blasts can be modelled. The overburden geometry, hole patterns and explosive distribution are all explicit model inputs. Because the effect of explosive properties, rock mass condition and inter-row delay are very difficult to measure in terms of blast performance, these are represented in the model by control parameters which are left for calibration using field data. The output of the model is a three dimensional muckpile shape of any cross section and a contour map of grade distribution within the muckpile. Two case studies are presented which have shown that the model is a valuable tool for optimizing production blasting as well as for controlling grade dilution during blasting.     

Deriving airborne laser scanning based computational canopy volume for forest biomass and allometry studies

A computational canopy volume (CCV) based on airborne laser scanning (ALS) data is proposed to improve predictions of forest biomass and other related attributes like stem volume and basal area. An approach to derive the CCV based on computational geometry, topological connectivity and numerical optimization was tested with sparse-density, plot-level ALS data acquired from 40 field sample plots of 500–1000 m² located in a boreal forest in Norway. The CCV had a high correspondence with the biomass attributes considered when derived from optimized filtrations, i.e. ordered sets of simplices belonging to the triangulations based on the point data. Coefficients of determination (R²) between the CCV and total above-ground biomass, canopy biomass, stem volume, and basal area were 0.88–0.89, 0.89, 0.83–0.97, and 0.88–0.92, respectively, depending on the applied filtration. The magnitude of the required filtration was found to increase according to an increasing basal area, which indicated a possibility to predict this magnitude by means of ALS-based height and density metrics. A simple prediction model provided CCVs which had R² of 0.77–0.90 with the aforementioned forest attributes. The derived CCVs always produced complementary information and were mainly able to improve the predictions of forest biomass relative to models based on the height and density metrics, yet only by 0–1.9 percentage points in terms of relative root mean squared error. Possibilities to improve the CCVs by a further analysis of topological persistence are discussed.     

水力劈裂对岩体中自然裂纹的影响研究

建立了求解自然裂纹和水力裂纹扩展的扩展有限元法,对裂纹附近区域的节点采用广义形函数,并采用线增函数消除混合单元,以提高裂纹附近的精度。引入水力劈裂的非耦合模型,即假设裂纹中的水压力为均布力;用砂浆法（线段-线段接触法）结合增广型拉格朗日乘子法处理受压裂纹段的接触条件。并通过算例分析了以下内容：计算了受压裂纹和裂纹面分布均布水压力的水力裂纹的应力强度因子,并与解析解进行了比较,结果表明,提出的方法具有很高的精度;模拟了水力裂纹对自然裂纹面的影响,并分析了自然裂纹面上的接触力和接触状态。     

滑坡及危岩(崩塌)防治工程措施选择与工程设置

滑坡和危岩（崩塌）治理工程措施较多，措施组合可变性大，每种工程措施都有其相应的应用条件，不宜性、适宜性和最佳配置组合。治理工程措施选择应充分考虑治理工程功能性的具体要求、在不同工况条件下的安全性及耐久性、工期要求和投资的经济性以及后期维护的要求、工程岩土体性质及其蓄水后的变化、场地条件、施工技术条件、地方材料资源等具体制约因素以及环境保护的要求。在三峡水库区二期地质灾害防治工程国家级验收总结的基础上，对滑坡与危岩（崩塌）常用防治工程措施（排水、削方减载、回填压脚、抗滑桩、重力式抗滑挡墙、预应力锚索、格构锚固、拦石墙等）的工程适用条件、工程设置及不宜性进行了详细的分析，并提出工程设置应考虑及注意的问题。     

Quaternary colluvium in west-central Anatolia: sedimentary facies and palaeoclimatic significance

The Quaternary colluvial aprons in Lake Eğirdir area, Taurus Mountains, consist of steep coalescent fans, up to 17–20 m thick and 350–450 m in plan-view radius, and the sedimentary succession comprises four lithostratigraphic divisions. The basal red–brown colluvium consists of a chaotic, bouldery fan-core rubble covered with bedded, openwork to matrix-rich gravel, whose deposition is attributed to rockfalls and cohesive debrisflows, with minor grainflows and sheetwash processes. The middle part of this division contains interbeds of early Pleistocene tephra. The overlying light-grey colluvium consists of bedded gravel with numerous palaeogullies and its deposition is attributed to waterflow, rockfalls and cohesive debrisflows. The younger, medium-grey colluvium consists of stratified pebbly sand interspersed with cobble/boulder gravel and its deposition is attributed to sheetwash processes accompanied by rockfalls and wet snowflows/slushflows. A bulk-pollen radiocarbon date indicates Late Würm age. The youngest, yellow–grey colluvium consists of bedded, mainly pebbly and openwork gravel, whose deposition is attributed to dry grainflows, rockfalls and minor cohesive debrisflows. Based on the sedimentary facies assemblages and available isotopic dates, the four colluvial divisions are correlated with the following stages of the region's climatic history: (1) the latest Pliocene to Early Pleistocene stage of warm–humid climate with pronounced phases of drier conditions; (2) the Late Pleistocene stage of colder climate, with alternating phases of higher and lower humidity; (3) the last glacial (Würm) stage of coldest climate; and (4) the Holocene stage of warm semi-arid climate. It is concluded that colluvial depositional systems bear a valuable proxy record of climatic changes and regional geoclimatic differences.     

阿尔泰可可托海伟晶岩中弧形石英白云母层的成因及意义

石英白云母层时常紧贴伟晶岩侵入体的边界出现且平行边界延伸。但是在新疆阿尔泰可可托海伟晶岩型稀有金属矿区伟晶岩体中石英白云母层出现了三种不同类型的弧形起伏,这些弧形形态仅用矿物的定向生长是难以解释的。弧形石英白云母层具有统一的"背地性"指向(弧形凸起顶端一律朝上)并且越靠近伟晶岩侵入体的顶部弧形凸起越明显,在侵入体侧部边界的石英白云母层不存在弧形凸起形态。这些形态特点与浮力作用下形成的形态具有可比性,暗示浮力与弧形石英白云母层间存在密切的成因联系。石英白云母层与石英钠长石层的间隔出现指示伟晶岩浆中挥发分含量的周期性增加。挥发分含量的周期性增加导致了挥发分不断加入未固结的剩余岩浆中并向伟晶岩体顶部上升,逐步在伟晶岩侵入体的顶部形成了弧形石英白云母层。弧形石英白云母层的大量出现不仅说明伟晶岩侵入体规模较大,也暗示存在有利的挥发分保存环境,对伟晶岩型稀有金属矿产的形成和稀有金属找矿预测起到非常重要的作用。     

窑洞外形特征对结构抗震性能影响研究

调查发现山西北部农村地区农居窑洞多是独立式土坯窑洞,结构主要受力体系是土坯砌体砌筑拱结构,其建造无统一标准,外形样式存在差异。由于拱结构的内力分布对外形尺寸变化比较敏感,为研究窑洞外形特征对结构抗震性能影响,建立相应的有限元模型进行计算分析,对比不同外形特征窑洞在地震作用下的损伤情况,并结合历史震害,指出窑洞结构的薄弱位置。研究结果表明覆土较厚的窑洞容易损伤,连拱孔数较多窑洞的两侧位置更容易发生破坏,拱的曲线形状对结构抗震性能有一定影响,合理拱曲线窑洞的抗震性能优于一般形状窑洞。