An oil sand pseudo-elastic model for determining ground deformation under large mobile mining equipment

Strain softening of oil sand under dynamic loading from large mining equipment inhibits the ability of the equipment to function at optimal design performance. This paper looks at the findings of dynamic plate load tests, which effectively mimick the loading and unloading action of a shovel track pad. A pseudo-elastic model was proposed based on the results of the dynamic plate load testing to predict the deformation of oil sand under cyclic loading. Both field and laboratory cyclic plate load tests were performed on oil sand materials. The field tests were performed with different plate sizes, or footprints. The load was normalized based on the pressure stiffness concept in units of pressure per unit deformation. FLAC was used to model the field plate load test deformation with the elastic concept. The laboratory tests were performed at room temperature with more control on the load, loading rate, and cycles than possible during the field testing. Tests were conducted using a circular plate of 14.9 cm diameter, at stress magnitudes of 200, 400, 500 and 600 kPa. The plate load tests were conducted for varying loads, holding, and relaxation times of 0, 2, 5 and 10 min respectively for each magnitude of stress. The outcome of laboratory plate load tests show that after frequent cycles, the pressure stiffness (ratio of stress to deformation) converges on a plateau value of 8 kPa/mm. The proposed approach can be used to evaluate oil sands ground performance, enhancing the prediction process for ground deformation under the operation of ultra-class mining equipment.     

Electrical imaging of the groundwater aquifer at Banting,Selangor, Malaysia

A geophysical study was carried out in the Banting area of Malaysia to delineate groundwater aquifer and marine clay layer of the alluvial Quaternary deposits of Beruas and Gula Formations. The Beruas Formation is formed by peat and clayey materials as well as silt and sands, whereas the Gula Formation consists of clay, silt, sand and gravels. Both Formations were deposited on top of the Carboniferous shale of the Kenny Hill Formation. A 2-D geoelectrical resistivity technique was used. Resistivity measurement was carried out using an ABEM SAS 4000 Terrameter. The 2-D resistivity data of subsurface material for each survey line was calculated through inverse modelling and then compared with borehole data. The resistivity images of all the subsurface material below the survey lines show similar pattern of continuous structure of layering or layers with some lenses with resistivity ranging from 0.1 to 50 Ωm. The upper layer shows resistivity values ranging from 0.1 to 10 Ωm, representing a clay horizon with a thickness up to 45 m. The second layer with depth varies from 45 to 70 m below surface and has resistivity values ranging from 10 to 30 Ωm. Borehole data indicate coarse sand with some gravels for this layer, which is also the groundwater aquifer in the study area. The lowermost layer at a depth of 70 m below ground level shows resistivity values ranging from 30–50 Ωm and can be correlated with metasedimentary rocks consisting of shale and metaquartzite.     

Assessment and prediction of contaminant migration in ground water from chromite waste dump

Sukinda chromite valley is one of the largest chromite deposits of the country and produces nearly 8% of chromite ore. It greatly contributes towards the economic development but at the same time deteriorates the natural environment. It is generally excavated by opencast mining method. In the Sukinda mining area, around 7.6 million tons of solid waste have been generated in the form of rejected minerals, overburden material/waste rock and sub-grade ore that may be resulting in environmental degradation, mainly causing lowering in the water table vis-à-vis deterioration in surface and ground water quality. The study conducted in and around one of the chromite mine of the valley reveals that the concentration of hexavalent chromium is found in the water samples of ground and surface water, mine effluents and seepage water. Hexavalent Chromium (Cr⁺⁶) have been found varying between 0.02 mg/l and 0.12 mg/l in mine effluents and 0.03–0.8 mg/l in shallow hand pumps and 0.05 and 1.22 mg/l in quarry seepage. The concentration of Cr⁺⁶ in Damsal nalah, the main surface water source in the area, is found varying between 0.03 mg/l and 0.14 mg/l and a increasing trend, which is in the downstream of mining activities, has been observed. Leachate study clearly shows that the soil lying in the vicinity of mine waste dump shows highest concentration of Cr⁺⁶. Contaminant migration in ground water depends upon various geohydrological conditions of the area. The study shows that aquifer resistivity varies between 15 Ωm to 150 Ωm and aquifer depth varies from 4 m to 26 m below ground level. The ground water flow and mass transport models were constructed with the help of geo-hydrological and geophysical informations using Visual Modflow software. Contaminant migration and path lines for 20 years have been predicted in two layers model of ground water. The study provided an insight into the likely migration of contaminant in ground water due to leaching from overburden dump of chromite ore and will be helpful in making strategic planning for limiting the contaminant migration in the ground water regime in and around the mining areas.     

Multidisciplined investigation to locate the Kentucky shipwreck

A local artifact collector contacted the U.S. Army Engineer District, Vicksburg in the fall of 1994 concerning timbers from a ship protruding from the west bank of the Red River, Louisiana, during the summer of 1994. From historical records it was determined that the shipwreck is that of the Kentucky, which sank in 1865. An investigation integrating archaeological, geological, and geophysical methods was undertaken to determine the location, orientation, and depth of the wreckage. Based on site geology, the shipwreck is expected to lie within a silty sand deposit within 4–8.5 m below the ground surface. The results of probe investigations performed by the archaeologists and borehole data orient the long axis of the ship N57.5E. This orientation conflicts with the geophysical data, which suggest an orientation of N116W. The geophysical surveys identified an anomalous region, approximately 31 m long and 10 m wide, that borders the Red River and an abandoned channel of the Red River. The magnetometer data suggests that the bow of the ship is pointed toward the abandoned channel. This orientation contradicts historical records which have the bow pointing toward the modern Red River. A subsequent underwater investigation by the archaeological contractor discovered a rudder‐related mechanism protruding from the bank of the Red River, confirming the geophysical prediction. All three scientific surveys agree that the wreckage is at a depth 3.8–8.5 m below ground surface and at an inclined position, with a downward slope from the bank of the Red River to the abandoned channel. © 2000 John Wiley & Sons, Inc.*     

Analysis of Rigid Short Caisson with Granular Core Incorporating Nonlinear Interface and Base Responses

It is difficult to construct a conventional shallow foundation in alluvial lowlands because of soft soils and high ground water table. A rigid short caisson foundation with granular core is being proposed for alluvial lowlands. The proposed foundation is analyzed using non-linear hyperbolic stress–displacement responses of homogeneous alluvial deposits. Extensive parametric studies are carried out to study the effects of length ratio (L/d₀), diameter ratio (d/d₀) of granular core with respect to casing, relative stiffness of shaft (α_τ), relative casing base stiffness (α_b), and friction angle of granular material (ϕ_gp) on the load sharing and the settlement of the proposed foundation.     

Diurnal soil water dynamics in the shallow vadose zone (field site of China University of Geosciences,China)

Because of the relatively low soil moisture in arid or semi-arid regions, water vapour movement often predominates in the vadose zone and affects the partitioning of energy among various land surface fluxes. In an outdoor sand bunker experiment, the soil water content at 10 and 30 cm depth were measured at hourly intervals for 2.5 days during October 2004. It was found that the soil moisture reached the daily maximum value (5.9–6.1% at 10 cm and 11.9–13.1% at 30 cm) and minimum value (4.4–4.5% at 10 cm and 10.4–10.8% at 30 cm) at midday (0–1 p.m. for 10 cm and 2–3 p.m. for 30 cm) and before dawn (2–3 a.m. for 10 cm and 4–5 a.m. for 30 cm), respectively. The modified HYDRUS-1D code, which refers to the coupled water, water vapour and heat transport in soil, was used to simulate the moisture and water vapour flow in the soil. The numerical analyses provided insight into the diurnal movement of liquid water and water vapour driven by the gradients of pressure heads and temperatures in the subsurface zone. The simulated temperature and water content were in good agreement with the measured values. The spatial–temporal distribution of liquid water flux, water vapour flux and soil temperature showed a detailed diurnal pattern of soil water dynamics in relatively coarse sand. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Fabrication of dense forsterite–enstatite polycrystals for experimental studies

 A practical and reliable method for the preparation of fine-grained forsterite and forsterite–enstatite polycrystals, in the system MgO–SiO₂, is described. The method employs state-of-the-art techniques from materials science, namely sol-gel synthesis, powder processing and sintering. The resulting dense polycrystalline materials are homogeneously fine-grained (1–2 μm) and uniformly foam-textured. Moreover, they are highly reproducible in composition and microstructure. The enstatite content can be controlled to within ∼1%, in the range 0–50%, and densities up to 98% of theoretical density can be achieved. The method thus yields polycrystalline forsterite–enstatite material suitable for a range of geochemical, petrological and geophysical studies. Received: 19 October 1999 / Accepted: 18 June 2001     

A Solution to the Problem of Predicting the Suitability of Silty–clayey Materials for Cement-stabilization

Major geotechnical problems in construction involving silty–clayey soils are due to their low strength, durability and high compressibility of soft soils, and the swell–shrink nature of the overconsolidated swelling soils. Confronted with these problems, a suitable ground improvement technique is needed, for deep excavations in soft clays, for stability, durability and deformation control. Cement-stabilization is one of the alternatives. An increase in strength and durability, reduction in deformability are the main aims of this method. Conventional cement-stabilization methods are used mainly for surface treatment. However, the use of cement has recently been extended to a greater depth in which cement columns were installed to act as a type of soil reinforcement (deep cement–soil mixing and cement jet grouting). In situ engineering properties of these silty–clayey soils are often variable and difficult to predict. For this reason cement-stabilization methods have a basic target to control the aforementioned engineering properties of these clays so that the properties of a silty–clayey soil become more like the properties of a soft rock such as clayey shale or lightly cemented sandstone. So cement-stabilization of these soils is essential to control their engineering properties and to predict their engineering behaviour for construction. In an effort to predict, classify and study the suitability of silty–clayey soils for cement-stabilization both slaking and unconfined compressive strength tests were carried out on clayey–sand mixtures consisted of two types of clays, kaolin and bentonite. Finally diagrams were prepared to study the variation of slaking and strength due to compaction, curing time and cement percentage and also to predict areas of efficient cement-stabilization.     

Equivalent Continuum Simulations of Geocell Reinforced Sand Beds Supporting Strip Footings

This paper presents an equivalent continuum method for simulating the behaviour of geocell reinforced sand foundation beds, using finite element technique. An equivalent composite model is used for numerically simulating the improvement in the strength and stiffness of sand confined with geocells. Shear strength of geocell encased sand is derived from the additional confining pressure due to geocell using hoop tension theory. The stiffness of geocell encased sand is represented by an empirical equation in terms of the stiffness of the unreinforced sand and the tensile modulus of the geocell material. Numerical simulations of strip footings resting on sand bed are carried out with and without geocell layer, varying parameters like, the dimensions of geocell layer, pocket size, depth of placement of geocell layer and the tensile modulus of the geocell material. The results of numerical analyses are validated with the corresponding experimental results. The comparison between the numerical results and the experimental results is found to be reasonably good. Some significant observations on the mechanism of geocell reinforcement have been presented in this paper.     

Geomorphological analysis of paleo drainage systems and their environmental implications in the desert of Kuwait

 A well-developed drainage network is carved in the hard calcretized and gypcretized gravelly sand of the Pleistocene Dibdibba Formation in northern Kuwait. The present-day aridity suggests that these drainages were developed during pluvial episodes that took place in the post-Pleistocene time and, therefore, are considered as paleo-drainage. Detailed morphometrical analysis of the endoeric drainage systems was performed and the degree of correlation among their different morphometric parameters was investigated. Based on these parameters, the studied drainage basins are statistically grouped into three groups. Such grouping was confirmed by discriminant analysis. The categorical data analysis demonstrated the dependence of these groupings on the surface geology, regional topography, and local geomorphological settings. Infiltration measurements revealed that the drainage bedrocks have a low infiltration rate (<20 cm h^–1), whereas the drainage fill deposits have a relatively high infiltration rate (67–30 cm h^–1). The impact of the drainage system pattern and morphometry on the hydrological conditions is discussed and potential near-surface low salinity to freshwater aquifers is delineated. The role of the studied drainage systems in the occurrence of mobile sand and sand dunes, rainwater harvesting, and land capability are discussed. Received: 8 September 1995 · Accepted: 24 October 1995     

Characterization of a Sedimentary Soft Rock by a Small In-Situ Triaxial Test

To measure the shear strength and deformability of a sedimentary soft rock, a small down-hole in-situ triaxial testing method is developed. The apparatus consists of a triaxial cell and an axial loading device which enables testing at any depth. In this method, a columnar specimen of diameter 90 mm and 285 mm height can be sheared at the bottom of a drill hole. A series of tests were conducted at a 50 m deep experimental cavern. The test gallery is contained in mudstone with some inter-bedded thin sand layers. The tests were done in three different depths in a borehole by a multiple-step loading method. The new testing method was successful to measure stress–strain relation of rock mass. The test results demonstrated that the multiple-step loading method is acceptable in mudstone formation, if an appropriate criterion for load reversal is selected to recognize the instant of failure by stress–strain relation during loading. In addition, different results for mechanical properties of mudstone rock mass were observed in the specimens contained sand layers. It is also concluded that, the same loading method is not successful if a sand layer is located in the middle of the specimen due to large damage induced in early stages of loading.     

Enhanced velocity mixed finite element methods for modeling coupled flow and transport on non-matching multiblock grids

The enhanced velocity mixed finite element method, due to Wheeler et al. (Comput Geosci 6(3–4):315–332, 2002), is analyzed and extended to the problem of modeling slightly compressible flow coupled to the transport of chemical species through porous media, on non-matching multiblock grids. Applications include modeling bio-remediation of heavy oil spills and many other subsurface hazardous wastes, angiogenesis in transition of tumors from dormant to malignant states, transport of contaminants in ground water flow, and acid injection from well bores to increase permeability of surrounding rock. The analysis and numerical examples presented here demonstrate convergence and computational efficiency of this method.     

Interaction of Ribbed-Metal-Strip Reinforcement with Tire Shred–Sand Mixtures

There is a pressing need of finding innovative and beneficial ways of using scrap tires in the construction of various geotechnical structures because a large number of waste tires are generated and discarded every year throughout the world. One example of such geotechnical application is the use of tire shreds mixed with soil as a backfill material for mechanically stabilized earth (MSE) walls. In this paper, we report the results of laboratory pullout tests performed to study the interaction between ribbed-metal-strip reinforcement and tire shred–sand mixtures prepared with various tire shred sizes (9.5 mm in nominal size, 50–100 mm in length, and 100–200 mm in length) and tire shred-to-sand mixing ratios (tire shred contents of 0, 12, 25, 100% by weight). The pullout capacities of ribbed metal strips embedded in tire shred–sand mixtures were obtained for three confining pressures (40, 65, and 90 kPa). The test results showed that the pullout capacity of ribbed metal strips embedded in tire shred–sand mixtures is much higher than that of ribbed metal strips embedded in samples prepared with only tire shreds. Based on the laboratory pullout test results, an equation was developed that can be used to estimate the pullout capacity of ribbed metal strips embedded in tire shred–sand mixtures if the tire shred size, compacted unit weight of the mixture, mean particle size of sand, and vertical effective stress acting at the interface are known.     

Geotechnical Properties of Sandy Seafloors and the Consequences for Dynamic Penetrometer Interpretations: Quartz Sand Versus Carbonate Sand

The societal usage of coastal zones (including offshore wind energy plants, waterway deepening, beach conservation and restoration) is of emerging importance. Sediment dynamics in these areas result in sandy deposits due to strong tidal and wave action, which is difficult to simulate in laboratory geotechnical tests. Here, we present data from in situ penetrometer tests using the lightweight, free-fall Nimrod penetrometer and complementary laboratory experiments to characterize the key physical properties of sandy seafloors in areas dominated by quartzose (North Sea, Germany) and calcareous (Hawaii, USA) mineralogy. The carbonate sands have higher friction angles (carbonate: 31–37°; quartz: 31–32°) and higher void ratios (carbonate: 1.10–1.40; quartz: 0.81–0.93) than their siliceous counterparts, which have partly been attributed to the higher angularity of the coral-derived particles. During the in situ tests, we consistently found higher sediment strength (expressed in deceleration as well as in estimated quasi-static bearing capacity) in the carbonate sand (carbonate: 68–210 g; quartz: 25–85 g), which also showed a greater compressibility. Values were additionally affected by seafloor inclination (e.g., along a sub-aqueous dune or a channel), or layering in areas of sediment mobilization (by tides, shorebreak or currents). The study shows that the differences in in situ measured penetration profiles between carbonate sands and quartz sands are supported by the laboratory results and provide crucial information on mobile layers overlying sands of various physical properties.     

北京市轨道交通基坑工程地表变形特性

根据基坑开挖深度、地层条件的不同,对北京市轨道交通80个明挖顺作法基坑工程实测结果进行统计分析,研究确定北京砂卵石和黏性土地区深基坑开挖引起的周边地表变形规律。研究表明：基坑工程周边地表最大变形的实测结果分布形态为正态分布或半整体分布,地表沉降变形值较大;最大地表沉降的平均值约为砂卵石地区0.11%H（H为开挖深度）,黏性土地区0.20%H;地表变形与桩体向基坑内、外的水平位移值有一定的对应关系;地表沉降随插入比的增大而减小,黏性土地区基坑支撑系统刚度对地表沉降有明显的影响;北京地区基坑工程周边主要影响区约为0.6H或0.7H范围以内。研究成果可对未来北京及其他地区城市轨道交通基坑工程变形大小、安全性的预测和评估、指导基坑工程设计与施工和对防止基坑事故的发生等具有重要意义。     

Hydrogeological conditions and quality of ground waters in northern Banat,Pannonian basin

Geological relationships, hydrogeology and chemical composition of ground water in northern Banat were studied through the period 2000–2004 using the available background data from published and unpublished sources. Northern Banat is the extreme northeastern part of the Republic of Serbia and a geotectonic part of the vast Pannonian depression. The source of domestic and industrial water supply is only groundwater from artesian and subartesian aquifers of Lower Pleistocene (Q₁¹) and Upper Pleistocene (Pl₃²) sand deposits. The ground water, “peculiar” in chemical composition, is the only source of drinking water in the arid area. A notable variation in the chemical composition of artesian waters within the same geotectonic unit (Pannonian basin), abstracted for municipal water supplies of Kikinda, Novi Knezevac and Djala, has attracted attention of these authors. Our paper attempts to interpret the variation in the chemical composition of ground water and the cause of the variation by the interaction of ground water and rocks forming the aquifers on the case example of the water supply sources for the three mentioned towns. With respect to the depth and lithology of the aquifers, we interpret the varied chemical compositions of waters in the mentioned sources as a consequence of natural factors (geological environment), geological relationships and hydrogeological conditions.     

Evaluation of change in subsurface thermal environment due to groundwater flow in the Tokyo Lowland,Japan

Information on the distribution of subsurface temperature and hydraulic heads at 24 observation wells in and around the Tokyo Lowland, the eastern part of the Tokyo Metropolitan area, were examined to make clear the relationship between groundwater and the subsurface thermal environment in the urban area. Minimums in temperature–depth logs due to subsurface temperature increasing at shallow parts were recognized in 21 wells. This fact shows subsurface temperature is affected by ground surface warming in almost all of this area. Deeper than minimums, where the effects of surface warming became relatively small, regional variation is observed as follows: high temperatures are shown in the central part to the southern part, and low temperatures shown in the inland to eastern part. The high temperature area corresponds to an area where the lower boundary of groundwater flow is relatively shallow. This area corresponds also to an area with severe land subsidence resulting from excessive groundwater pumping. It is considered that this high temperature area is formed by the effects of upward groundwater flow affected by hydrogeological conditions and pumping. On the other hand, a comparison between past data (1956–1967) and present data (2001–2003) revealed widespread decreasing temperature in the inland area. This is explained by downward groundwater flow based on an analysis of temperature–depth logs. This fact suggests that subsurface temperature is not only increasing from the effects of surface warming but also decreasing from the effects of groundwater environment change due to pumping.     

大直径钢管桩承载力的非线性分析

推导了砂土地基中闭口管桩的沉桩影响半径以及刚性桩的横向承载力（矩）。通过使用MATLAB程序对单桩轴向刚度的分析,得出了其与桩周单位深度土的等效刚度系数、桩端土的等效刚度系数、钢管桩的壁厚、桩径、桩长、桩身弹性模量等参数之间的一些关系,从而为此类桩的优化设计提供了理论依据。在此基础上通过桩身荷载传递的双曲线函数模型以及相关参数,在已知（假定）桩身压缩量的情况下求出相应的桩顶轴力。     

New data on deep structure, tectonics, and mineralogeny of the Zeya-Bureya Basin

The Zeya-Bureya Basin is a part of the East Asian intracontinental riftogenic belt, which includes oil-and-gas bearing and Mesozoic-Cenozoic sedimentary basins perspective for oil and gas (Upper Zeya, Songliao, Liaohe, North Chinese). The basins are characterized by certain geophysical features: reduced thickness of the Earth’s crust and lithosphere, a higher thermal flow and a raised roof of the asthenosphere. The Zeya-Bureya Basin is composed of Mesozoic-Cenozoic sedimentary-volcanic units, with respect to which the deep structure data are absent. In 2010, geoelectric studies were carried out in this territory using the method of magnetotelluric sounding along the profile Blagoveshchensk-Birokan. These works yielded geoelectric sections down to 2 and 200 km depth. The sedimentary cover is characterized by electric resistivity of 20–50 Ohm m and by thickness of 1700 m. In the section, the Khingan-Olonoi volcanogenic trough is distinct for resistivity of 200–300 Ohm m at a background of 500–1000 Ohm m of the basement rocks. The Zeya-Bureya Basin, in terms of its geophysical characteristics, differs from oil-and-gas bearing basins of the riftogenic belt (thickness of the lithosphere is increased up to 120 km, thermal flow is low, 40–47 mW/m²). The structure of mantle underplating is explicitly seen in the section. The geophysical characteristics close to those of the Zeya-Bureya Depression are typical for gold-bearing structures of the Lower Amur ore district. Nevertheless, manifestations of oil-and-gas bearing potential in particular grabens are possible.     

An ephemeral turbidity maximum generated by resuspension of organic-rich matter in a macrotidal estuary, S.W. Wales

An ephemeral estuarine turbidity maximum (ETM) occurs at high water in the macrotidal Taf estuary (SW Wales, United Kingdom). A new mechanism of ETM formation, due to resuspension and advection of material by flood tidal currents, is observed that differs from classical mechanisms of gravitational circulation and tidal pumping. The flood tide advances across intertidal sand flats in the main body of the estuary, progressively entraining material from the rippled sands. Resuspension creates, a turbid front that has suspended sediment concentrations (SSC) of about 4,000 mg I⁻¹ by the time it reaches its landward limit which is also the landward limit of salt penetration. This turbid body constitutes the ETM. Deposition occurs at high slack water but the ETM retains SSC values up to 800 mg I⁻¹, 1–2 orders of magnitude greater than ambient SSC values in the river and estuarine waters on either side. The ETM retreats down the estuary during the ebb; some material is deposited thinly across emergent intertidal flats and some is flushed out of the estuary. A new ETM is generated by the next flood tide. Both location and SSC of the ETM scale on Q/R³ where Q is tidal range and R is river discharge. The greatest expression of the ETM occurs when a spring tide coincides with low river discharge. It does not form during high river discharge conditions and is poorly developed on neap tides. Particles in the ETM have effective densities (120–160 kg m⁻³) that are 3–4 times less than those in the main part of the estuary at high water. High chlorophyll concentrations in the ETM suggest that flocs probably originate from biological production in the estuary, including production on the intertidal sand flats.