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.     

一种非饱和土表层蒸发过程的预测方法

探索了一种由土壤基本物性指标、气象数据预测非饱和土表层蒸发过程的方法。通过土壤基本物理性质（颗粒分布、土粒相对密度、干密度）预测出土-水特征曲线（SWCC）,进而得到土壤气相对湿度与含水率的关系,采用Penman-Wilson模型预测出了非饱和土表面的蒸发曲线。通过该方法,只需实地采取土样,获取其基本物理性质,由任意时刻土壤的含水率及气象数据就能预测出该时刻土表的蒸发速率。采用自制的自动蒸发测量系统进行浅层土蒸发试验,得到了蒸发曲线,与预测结果进行比较发现预测蒸发过程与实测结果一样皆由临界含水率和风干含水率将其分为3个阶段：稳定阶段、减速阶段和残余阶段,且蒸发量吻合,证明了所提出方法的准确性和实用性,对工程界估计土表蒸发量,确定水流量边界有重要意义。     

感潮河网二维水流-输运耦合数学模型

感潮河网水流不仅受径流、潮汐动力的双重影响,还常受水闸调度等人类活动的影响,水动力条件极为复杂。针对水闸调度影响下感潮河网复杂水动力及其伴随物质输移扩散模拟,提出了考虑水闸调度并集成输运对流项的水流-输运通量耦合求解器,建立了基于非结构网格Godunov格式的二维水流-输运耦合数学模型。采用具有时空二阶精度的MUSCL-Hancock预测-校正格式,结合变量重构限制器技术,在保证计算精度的同时避免了数值振荡。运用斜底三角单元网格表达水闸线状地形,并通过地形调整模拟了水闸启闭过程。算例研究表明,该模型计算精度高,可有效模拟水闸调度影响下感潮河网水流运动及污染物输运过程,具有较好的推广应用价值。     

A mathematical model for predicting coupled heat and water movement in unsaturated soil

An investigation was conducted to develop a comprehensive moisture model for predicting non-isothermal moisture conditions in soils. An extensive literature review indicated that a model based on the Philip and de Vries equations for non-isothermal moisture movement and heat conduction would give the best results. By using numerical methods, the implicit finite difference approximations to the moisture movement and heat-transfer equations were programmed for computer solution of water content and temperature in the soil with time. Validation studies indicate that the moisture model can be used to predict accurately moisture conditions in the soil. The model was validated by using hydraulic data from laboratory studies conducted on soil columns compacted with AASHO A-3 and AASHO A-4 soil. The application of the moisture model to the study of non-isothermal moisture movement in the field is demonstrated. The influence of parameters such as water table depth, precipitation, and soil hydraulic properties on soil moisture content are shown by use of the moisture model. The model is shown to be applicable to a wide range of boundary conditions and that it predicts the moisture-temperature regime with time in soils utilizing climatic input data.     

A new tectonic model for the Laurentia−Avalonia−Baltica sutures in the North Sea: A case study along MONA LISA profile 3

We present a new model for the lithospheric structure of the transitions between Laurentia, Avalonia and Baltica in the North Sea, northwestern Europe based on 2¾D potential field modelling of MONA LISA profile 3 across the Central Graben, with constraints from seismic P-wave velocity models and the crustal normal incidence reflection section along the profile. The model shows evidence for the presence of upper-and lower Palaeozoic sedimentary rocks as well as differences in crustal structure between the palaeo-continents Laurentia, Avalonia and Baltica. Our new model, together with previous results from transformations of the gravity and magnetic fields, demonstrates correlation between crustal magnetic domains along the profile and the terrane affinity of the crust. This integrated interpretation indicates that a 150 km wide zone, characterized by low-grade metamorphosis and oblique thrusting of Avalonia crust over Baltica lower crust, is characteristic for the central North Sea area. The magnetic susceptibility and the density across the Coffee Soil Fault range from almost zero and 2715 kg/m³ in Avalonia crust to 0.05 SI and 2775 kg/m³ in Baltica crust. The model of MONA LISA profile 3 indicates that the transition between Avalonia and Baltica is located beneath the Central Graben with a ramp–flat–ramp geometry. Our results indicate that the initial rifting of the Central Graben and the Viking Graben was controlled by the location of the Caledonian collisional suture, located at the Coffee Soil Fault, and that the deep crustal part of Baltica extends further to the west than hitherto believed.     

A high strain‐rate constitutive model for sand and its application in finite‐element analysis of tunnels subjected to blast

The paper presents a constitutive model for simulating the high strain‐rate behavior of sands. Based on the concepts of critical‐state soil mechanics, the bounding surface plasticity theory and the overstress theory of viscoplasticity, the constitutive model simulates the high strain‐rate behavior of sands under uniaxial, triaxial and multi‐axial loading conditions. The model parameters are determined for Ottawa and Fontainebleau sands, and the performance of the model under extreme transient loading conditions is demonstrated through simulations of split Hopkinson pressure bar tests up to a strain rate of 2000/s. The constitutive model is implemented in a finite‐element analysis software Abaqus to analyze underground tunnels in sandy soil subjected to internal blast loads. Parametric studies are conducted to examine the effect of relative density and type of sand and of the depth of tunnel on the variation of stresses and deformations in the soil adjacent to the tunnels. Copyright © 2012 John Wiley & Sons, Ltd.     

Basin shape and sediment architecture in the Gun Supersequence: A strike‐slip model for Pb–Zn–Ag ore genesis at Mt Isa

Sequence‐stratigraphic correlations provide a better understanding of sediment architecture in the Mt Isa and lower McNamara Groups of northern Australia. Sediments record deposition in a marine environment on a broad southeast‐facing ramp that extended from the Murphy Inlier in the northwest to the Gorge Creek, Saint Paul and Rufous Fault Zones in the southeast. Depositional systems prograded in a southeasterly direction. Shoreline siliciclastic facies belts initially formed on the western and northern parts of the ramp, deeper water basinal facies occurred to the east and south. The general absence of shoreline facies throughout the Mt Isa Group suggests that depositional systems originally extended further to the east and probably crossed the Kalkadoon‐Leichhardt Block. Fourteen, regionally correlatable fourth‐order sequences, each with a duration of approximately one million years, are identified in the 1670–1655 Ma Gun Supersequence. Stratal correlations of fourth‐order sequences and attendant facies belts resolve a stratigraphic architecture dominated by times of paired subsidence and uplift. This architecture is most consistent with sinistral strike‐slip tectonism along north‐northeast‐oriented structures with dilational jogs along northwest structures as the primary driver for accommodation. Although reactivated during deformation, the ancestral northwest‐trending May Downs, Twenty Nine Mile, Painted Rocks, Transmitter, Redie Creek and Termite Range Fault Zones are interpreted as the principal synsedimentary growth structures. Sinistral strike‐slip resulted in a zone of long‐lived dilation to the north of the May Downs/Twenty Nine Mile and Gorge Creek Fault Zones and a major basin depocentre in the broad southeast‐facing ramp. Subordinate depocentres also developed on the northern side of the ancestral Redie Creek and Termite Range fault zones. Transfer of strike‐slip movement to the east produced restraining or compressive regions, localising areas of uplift and the generation of local unconformities. Northwest‐ and north‐northeast‐oriented magnetic anomalies to the south and west of Mt Isa, identify basement heterogeneities. Basement to the south and west of these anomalies is interpreted to mark intrabasin siliciclastic provenance areas in the Gun depositional system. Pb–Zn–Ag deposits of the Mt Isa valley are interpreted as occurring in a major basin depocentre in response to a renewed phase of paired uplift and subsidence in late Gun time (approximately 1656 Ma). This event is interpreted to have synchronously created accommodation for sediments that host the Mt Isa deposit, while focusing topographically and thermobarically driven basinal fluids into the zone of dilation.