Late Quaternary landscapes in Central Australia: sedimentary history and palaeoecology of Puritjarra rock shelter

Puritjarra rock shelter provides a long record of late Quaternary vegetation in the Australian arid zone. Analysis of the sedimentary history of this rock shelter is combined with reanalysis of charcoal and phytolith records to provide a first‐order picture of changing landscapes in western Central Australia. These show a landscape responding to increasing aridity from 45 ka with deflation of clay‐rich red palaeosols (<45 ka) and sharp declines in grassland and other vegetation at 40–36 ka, and at the beginning of the Last Glacial Maximum (LGM) (24 ka). Vegetation in the catchment of the rock shelter recovered after 15 ka with expansion of both acacia woodland and spinifex grasslands, registering stronger summer rainfall in the interior of the continent. By 8.3 ka re‐vegetation of local palaeosols and dunes had choked off sediment supply to the rock shelter and the character of the sediments changed abruptly. Poaceae values peaked at 5.8 ka, suggesting the early–mid Holocene climatic optimum in Central Australia is bracketed between 8.3 and 5.8 ka. Local vegetation was disrupted in the late Holocene with a sharp decline in Poaceae at 3.8 ka, coinciding with an abrupt intensification of ENSO. Local grasslands recovered over the next two millennia and by 1.5 ka the modern vegetation appears to have become established. Copyright © 2009 John Wiley & Sons, Ltd.     

塔中4号油藏渗透率分布的非均质性及渗流方向研究

研究油藏内部油水渗流方向时,主要考虑渗透率影响,引入两个水平方向渗透率比、水平与垂向渗透率比参数来分析。前者反映样品所在储层平面上两个水平方向渗流能力的差异,后者反映样品所在储层水平与垂向渗流能力的差异,并经小柱样测试和全岩心测试两种方法确定两个参数。通过对塔中4号油藏CⅠ油组9口井2306个样品两种渗透率比值分布直方图分析,研究了CⅠ油组渗透率的非均质性及其渗流方向:CI油组储层在水平方向的渗流能力有很大差异,具有明显的方向性。储层垂向渗流能力明显小于水平方向的渗流能力。     

RELAXING ASSUMPTIONS OF PERFECT INFORMATION IN PARK VISITATION MODELS*

Variables related to urban park awareness are identified and methods for relaxing assumptions of perfect information in park use models are discussed. Park awareness is related to park characteristics (age and degree of development of the park), population characteristics (race, age, length of residence, recreation participation), and distance. Park attributes are stronger predictors of both park awareness and use than is distance. These findings parallel similar research on the cognitive aspects of shopping decisions.     

Predicting ground-motion variations at the Turkey-flat test site,California

Results of a single group participating in an international experiment are analyzed. The experiment served to verify computational predictions of the ground-motion variations due to near-surface geological effects at a site established for that purpose by the California Department of Conservation. Based on an acceleration record at a rock location, and geotechnical model of medium, records at the other locations of a nearby sedimentary deposit were predicted. A 2-D finite-difference sensitivity analysis suggested that the lateral wave-propagation effects are negligibly small, and locally 1-D computations are sufficient for the present site. Those computations are compared with observations not available to the authors during the blind prediction. Peak accelerations, peak velocities and RMS accelerations were predicted with errors less than 159%, 114% and 62%, respectively. Maxima of the response spectra were fitted within a factor of 2. The predicted and observed Husid's plots (i.e., the normalized cumulative plots of the acceleration squared) have the correlation coefficients 0.98. The detected misfits do not show any simple relation to the instrument location, component, frequency, or time.     

Integrated approach for identification of potential groundwater zones in Seethanagaram Mandal of Vizianagaram District,Andhra Pradesh,India

Identifying a good site for groundwater exploration in hard rock terrain is a challenging task. In hard rocks, groundwater occurs in secondary porosity developed due to weathering, fracturing, faulting, etc., which is highly variable within short distance and contributing to near-surface inhomogeneity. In such situations topographic, hydrogeological and geomorphological features provide useful clues for the selection of suitable sites. Initially, based on satellite imagery, topographical, geomorphological and hydrogeological features, an area of about 149 km² was demarcated as a promising zone for groundwater exploration in the hard rock tract of Seethanagaram Mandal, Vizianagaram District, Andhra Pradesh, India. A total of 50 Vertical Electrical Soundings (VES) were carried out using Wenner electrode configuration. An interactive interpretation of the VES data sharpened the information inferred from geomorphological and hydrogeological reconnaissance. Ten sites were recommended for drilling. Drilling with Down-The-Hole Hammer (DTH) was carried out at the recommended sites down to 50 to 70 m depths. The interpreted VES results matched well with the drilled bore well lithologs. The yields of bore wells vary from 900 to 9000 liters per hour (lph).     

山东省济宁强磁异常区深部铁矿初步验证及其意义

山东省济宁磁异常是一个重、磁同源体,面积大于100 km2,磁异常峰值为3800nT。钻探验证在孔深1041.57～1796.54m位置发现铁矿体,矿体总厚度74.04～220m,磁性铁平均品位15.89～25.19%。矿石类型有条带状方解磁铁石英岩和条带状磁铁石英大理岩,矿石的主要组成矿物为石英、方解石、磁铁矿、磁赤铁矿、菱铁矿。矿体产于济宁岩群浅变质岩系中,矿床特征与条带状铁建造（BIF）铁矿或鞍山式铁矿有明显区别,铁矿成因类型属与千枚岩、变质中酸性火山岩、大理岩有关的沉积变质型铁矿床。该区铁矿资源潜力巨大。     

Shear strength characterization of municipal solid waste at the Suzhou landfill, China

The current practice of slope stability analysis for a municipal solid waste (MSW) landfill usually overlooks the dependence of waste properties on the fill age or embedment depth. Changes in shear strength of MSW as a function of fill age were investigated by performing field and laboratory studies on the Suzhou landfill in China. The field study included sampling from five boreholes advanced to the bottom of the landfill, cone penetration tests and monitoring of pore fluid pressures. Twenty-six borehole samples representative of different fill ages (0 to 13 years) were used to perform drained triaxial compression tests. The field and laboratory study showed that the waste body in the landfill can be sub-divided into several strata corresponding to different ranges of fill age. Each of the waste strata has individual composition and shear strength characteristics. The triaxial test results showed that the MSW samples exhibited a strain-hardening and contractive behavior. As the fill age of the waste increased from 1.7 years to 11 years, the cohesion mobilized at a strain level of 10% was found to decrease from 23.3 kPa to 0 kPa, and the mobilized friction angle at the same strain level increasing from 9.9° to 26°. For a confinement stress level greater than 50 kPa, the shear strength of the recently-placed MSW seemed to be lower than that of the older MSW. This behavior was consistent with the cone penetration test results. The field measurement of pore pressures revealed a perched leachate mound above an intermediate cover of soils and a substantial leachate mound near the bottom of the landfill. The measurements of shear strength properties and pore pressures were utilized to assess the slope stability of the Suzhou landfill.     

Biaxial test simulations using a packing of polygonal particles

The mechanical response of cohesionless granular materials under monotonic loading is studied by performing molecular dynamic simulations. The diversity of shapes of soil grains is modelled by using randomly generated convex polygons as granular particles. Results of the biaxial test obtained for dense and loose media show that samples achieve the same void ratio at large strains independent of their initial density state. This limit state resembles the so‐called critical state of soil mechanics, except for some stress fluctuations, which remain for large deformations. These fluctuations are studied at the micro‐mechanical level, by following the evolution of the co‐ordination number, force chains and the fraction of the sliding contacts of the sample. Copyright © 2007 John Wiley & Sons, Ltd.     

Influence of Structural Non-Stationarity of Surface Roughness on Morphological Characterization and Mechanical Deformation of Rock Joints

Summary Structural non-stationarity of surface roughness affects accurate morphological characterization as well as mechanical behaviour of rock joints at the laboratory scale using samples with a size below the stationarity threshold. In this paper, the effect of structural non-stationarity of surface roughness is investigated by studying the scale dependence of surface roughness and mechanical behaviour of rock joints. The results show that the structural non-stationarity mainly affects the accurate characterization of the surface roughness of the fracture samples. It also controls the amount and location of the contact areas during shear tests, which in turn affects the mechanical properties and asperity degradation of the samples. It is concluded that for accurate determination of the morphological and mechanical properties of rock joints at laboratory and field scales, samples with size equal to or larger than the stationarity threshold are required. Author’s address: Nader Fardin, Rock Mechanics Group, Department of Mining Engineering, Faculty of Engineering, University of Tehran, P.O. Box: 11365/4563, Tehran, Iran