NUMERICAL SIMULATION OF SEDIMENT TRANSPORT IN DYNAMIC FLOW CONDITIONS

1 INTRODUCTION Rivers as a source of life can at the same time impose devastating conditions on the environment. It is , therefore, imperative to analyse and predict river behaviour for different given conditions and engineering activities. Therefore, the use of simulation tools in this field has become a necessity. Many computational tools for simulation of sediment transport in rivers are now available that can be used for prediction and design under different flow conditions. However, …     

三维层状地基空沟主动隔振分析

基于薄层法在研究层状介质中波的传播问题的高效性、边界单元法处理无限域问题的精确性,结合二者的优点提出三维层状地基薄层法基本解答,建立了基于三维层状半空间薄层法位移基本解答的半解析动力边界元法。该方法可有效的分析多层场地的动力问题,解决土-结构动力相互作用问题。同时分别对粘弹性上软下硬地基及上硬下软地基的三维空沟主动隔振进行了详细的分析。结果表明,两种情况下采用空沟屏障隔振均可以取得一定的隔振效果;同时,地基分层参数对空沟隔振体系的隔振效果影响显著。     

Spoil pile instabilities with reference to a strip coal mine in Turkey: mechanisms and assessment of deformations

With the increasing adoption of the surface mining of coal, problems associated with spoil pile instability, which affects resource recovery, mining cost, and safety and presents environmental hazards, have become a matter of prime concern to mine planners and operators. The study of geotechnical aspects is thus very important in the rational planning for the disposal, reclamation, treatment and utilization of spoil material. A strip coal mine, one of the largest open pit mines in Turkey, is located in Central Anatolia and provides coal to a thermal power station. Coal production is carried out in two adjacent open pits, the Central Pit and South Pit. A large-scale spoil pile instability over an area of 0.3 km² occurred within the dumping area of the Central pit. In addition, small-scale movement occurred in the outside dumping area. This paper outlines the results of field and laboratory investigations to describe the mechanisms of the spoil pile instabilities and to assess deformations monitored over a long period following the failure. Shear test results indicate that the interface between the floor and spoil material dumped by dragline has a negligible cohesion and is the most critical plane of weakness for spoil pile instability. Back analyses based on the method of limit equilibrium and the numerical modelling technique, and observations in the pit revealed that failure occurred along a combined sliding surface consisting of a circular surface through the spoil material itself and a planar surface passing along the interface between the spoil piles and floor. The analyses also indicated that pore water pressure ratios of about 0.25 satisfy limiting equilibrium condition and that rainfall about one month before the failure may be a contributing factor to the instability. Movement monitoring data obtained following the failure over a 1.5-year period suggested that the ongoing deformations were mainly due to compaction of the spoil material. Based on the monitoring data and the results of the analyses, the failure mode of the local instability occurring at the outside dumping area was considerably similar to that of the large instability.     

An Alternative Approach for CO2 Flux Correction Caused by Heat and Water Vapour Transfer

Energy and CO₂ fluxes are commonly measured above plant canopies using an eddy covariance system that consists of a three-dimensional sonic anemometer and an H₂O/CO₂ infrared gas analyzer. By assuming that the dry air is conserved and inducing mean vertical velocity, Webb et al. (Quart. J. Roy. Meteorol. Soc. 106, 85-100, 1980) obtained two equations to account for density effects due to heat and water vapour transfer on H₂O/CO₂ fluxes. In this paper, directly starting with physical consideration of air-parcel expansion/compression, we derive two alternative equations to correct for these effects that do not require the assumption that dry air is conserved and the use of the mean vertical velocity. We then applied these equations to eddy flux observations from a black spruce forest in interior Alaska during the summer of 2002. In this ecosystem, the equations developed here led to increased estimates of CO₂ uptake by the vegetation during the day (up to about 20%), and decreased estimates of CO₂ respiration by the ecosystem during the night (approximately 4%) as compared with estimates obtained using the Webb et al. approach.     

Geotechnical applications in open pit mining

Detailed geotechnical data is often a major unknown factor in open pit design and mining, the lack of which constitutes a significant risk in any mining venture. As geotechnical data is accumulated so the risk of unforeseen conditions reduces, and so safety and productivity can be increased. Previously, most geotechnical work undertaken at open pit mines has focused on the slopes. The work done at Sandsloot open pit situated on the northern limb of the Bushveld Complex, 250 km north east of Johannesburg, however, has involved using geotechnical data for production, as well as slope stability benefits. Solutions to production problems encountered in a rapidly developing open pit are best formulated once some geotechnical control at the pit has been attained. At Sandsloot open pit this was achieved by delineation of geotechnical design zones from a detailed face mapping and drilling programme. Optimum design parameters then were assigned to these zones and geotechnically related problems assessed. This allowed slope management programmes to be initiated, as well as slope optimization of the hangingwall. The latter resulted in an improved slope configuration and an increase in the ultimate angle of the wall by 7°. This resulted in substantial savings, as well as an improvement in safety. In addition, the zones can be used for planning, costing and pit scheduling. The methods have proved successful in optimizing blast fragmentation and thereby loading, crushing and milling rates; in reducing secondary blasting and improving floor conditions; and in reducing drilling, blasting and comminution costs.     

改革开放与地域经济结构变化

笔者系统地分析了1978年以来地域经济结构变化趋势,并运用地理联系率、集中指数、最高与最低水平差距度量其区域经济结构变化规律,阐述了改革开放对地域结构变化所产生的影响及其合理性,归纳为:(1)改革开放的必然性决定地域经济结构变化的合理性;(2)改革开放以来经济地域分布变化复杂,有正反(即平衡和不平衡)两方面的趋势;(3)沿海潜在的区位优势转变为现实优势,以及老工业基地向周边和全国不断扩散是影响经济地域分布变化的两个主导因素;(4)积极的不平衡是地域经济结构优化的前奏;(5)改革开放的长期性决定了地域经济结构的长期性。     

不完美岩浆过程中的微量元素效应

本文综述了国外近年来在不完美岩浆过程中微量元素效应研究方面的进展。在完美平衡过程（平衡部分熔融或者平衡部分结晶）中和在完美分离过程（分离熔融或者分离结晶）中，熔融或者结晶对于高度不相容元素和高度相容元素相对浓度变化的差异悬殊的影响效应是众所周知的。完美分离过程需要满足以下３个条件：（１）每一批次被分离的熔体或者晶体的量趋向于无穷小；（２）晶体与熔体的彻底分离；（３）体系相对于源区物质和残留物质是完     

Prediction of ground vibrations resulting from the blasting operations in an open-pit mine by adaptive neuro-fuzzy inference system

The aim of this study is to predict the peak particle velocity (PPV) values from both presently constructed simple regression model and fuzzy-based model. For this purpose, vibrations induced by bench blasting operations were measured in an open-pit mine operated by the most important magnesite producing company (MAS) in Turkey. After gathering the ordered pairs of distance and PPV values, the site-specific parameters were determined using traditional regression method. Also, an attempt has been made to investigate the applicability of a relatively new soft computing method called as the adaptive neuro-fuzzy inference system (ANFIS) to predict PPV. To achieve this objective, data obtained from the blasting measurements were evaluated by constructing an ANFIS-based prediction model. The distance from the blasting site to the monitoring stations and the charge weight per delay were selected as the input parameters of the constructed model, the output parameter being the PPV. Valid for the site, the PPV prediction capability of the constructed ANFIS-based model has proved to be successful in terms of statistical performance indices such as variance account for (VAF), root mean square error (RMSE), standard error of estimation, and correlation between predicted and measured PPV values. Also, using these statistical performance indices, a prediction performance comparison has been made between the presently constructed ANFIS-based model and the classical regression-based prediction method, which has been widely used in the literature. Although the prediction performance of the regression-based model was high, the comparison has indicated that the proposed ANFIS-based model exhibited better prediction performance than the classical regression-based model.     

Stress Analysis for Rock Mass Failure with Offset Joints

Two-dimensional finite element model was created in this work to investigate the stress distribution within rock-like samples with offset open non-persistent joints under uniaxial loading. The results of this study have explained the fracture mechanisms observed in tests on rock-like material with open non-persistent offset joints (Mughieda and Alzo’ubi, Geotech Geol Eng J 22:545–562, 2004). Finite element code SAP2000 was used to study the stresses distribution within the specimens. Four-noded isoperimetric plain strain element with two degrees of freedom per node, and the three-noded constant strain triangular element with two degree of freedom per node were used in the present study. The results of the present study showed that the tensile stress in the bridge area caused coalescence for specimens with overlapped preexisting cracks (joints) while the coalescence of the secondary cracks, due to shear stress, caused the failure of specimens with non-overlapping cracks.     

L形切口治疗闭合性跟骨骨折的术后疗效及影响因素分析

目的 探讨L形切口治疗闭合性跟骨骨折的术后疗效及影响因素分析。方法 采用回顾性分析研究方法,收集笔者医院自2010年1月~2015年1月收治并行外侧L形切口切开复位内固定术治疗闭合性跟骨骨折的患者临床资料,共150例,其中SandersⅡ、Ⅲ、Ⅳ型各50例,观察术前、术后Bohler角和Gissane角度变化值,术后切口并发症,随访术后Maryland足部评分标准,对可能影响患者术后切口并发症相关变量进行单因素分析,对差异有统计学意义的变量进行多因素Logistic 回归分析。结果 所有患者均完成术后随访,随访时间12~24个月,平均随访时间17个月,以Maryland评分标准进行足部功能评估,优良率为79%,术后切口并发症为16%。结论 L形切口治疗闭合性跟骨骨折SandersⅡ~Ⅳ术后优良率较高,探索影响术后切口并发症的相关因素,发现吸烟、糖尿病、手术时长、受伤至手术时间可使术后切口并发症增加。