Lower Gravel Research Articles

Experimental Study of Mechanical Properties and Fracture Characteristics of Conglomerates Based on Mohr–Coulomb Criteria

Gravel is one of the main factors affecting the mechanical properties of conglomerates, which plays a decisive role in crack propagation. In this paper, taking the conglomerate of the Baikouquan Formation in Mahu Sag of Xinjiang as the research object, a three-dimensional model of the conglomerate is constructed by the discrete element numerical simulation method, and the triaxial compression experiment under different confining pressures is simulated. The mechanical properties and fracture morphology of conglomerate are analyzed with gravel content as a variable and verified by laboratory tests. In this simulation, with the increase of gravel content, the compressive strength of the conglomerate decreases, angle of internal friction decreases, and the fractures show different forms. The results show that the gravel morphology, spatial location, and gravel content have an impact on the mechanical properties of the conglomerate. The gravel content affects the formation process of the dominant fracture surface by controlling the distance between gravels so as to control the internal friction angle and it is the main controlling factor for the mechanical properties of the conglomerate. Gravel cracks initiate at the edge of gravel. Stress controls the formation of main cracks under low gravel content, and the influence of gravels under high gravel content makes cracks more discrete and complex.

Study of the durability of self-compacting concrete made from recycled gravel

Research has been carried out in Japan recently with the aim of creating concrete formulations characterized by high workability while being stable in order to adapt concrete to structures with more complex and heavily reinforced sections. (Low segregation, compaction, and bleeding) with strong mechanical properties. The result of this research is self-compacting concrete (SCC), a new type of concrete that can fulfill the aforementioned properties. SCC is distinguished by a high paste volume, a high fines volume, the use of superplasticizers, and a low gravel volume. Due to the increasing demand for aggregates, crushed gravel may be replaced with recycled gravel in the interests of environmental conservation and sustainable development goals. Steel fibers are added to recycled concrete and gravel SCCs to improve their properties. The objective of this research is to examine the durability in the hardened state as well as the physico-mechanical characteristics of self-compacting concrete (SCC) made from recycled concrete gravel. According to the results, the best recycled concrete gravel contains 50%, and the addition of 0.5% fibers improves the properties of these SCCs.

Exploring hydraulic fracture behavior in glutenite formation with strong heterogeneity and variable lithology based on DEM simulation

Glutenite is an important unconventional tight oil and gas reservoir. Due to the glutenite formation with strong heterogeneity and variable lithology which contains a large number of gravels with different sizes, shapes and mineral compositions, the mechanical characteristics of glutenite are more complicated, resulting in more complex fracture morphology. In this paper, a mathematical method for the generation of irregular polygonal gravels is proposed, and the hydraulic fracturing model of glutenite with different gravel characteristics is established based on 2D particle discrete element method. The internal mechanical mechanism of interaction between hydraulic fractures and gravels is first revealed, and the results show that the interaction is mainly affected by the non-uniformly distributed stress field caused by the coordination of deformation of glutenite. The influence of geologic and engineering factors on hydraulic fracture propagation in glutenite is studied. The results show that fracture morpgology in glutenite is mainly affected by injection rate, fracturing fluid viscosity, gravel strength and gravel spatial distribution. High gravel size, low gravel strength, high stress difference, high injection rate and high fracturing fluid viscosity are conducive to the occurrence of gravel penetration. The micro-mechanism of interaction between hydraulic fractures and gravels is mainly affected by the non-uniformly distributed stress field caused by the coordination of deformation of glutenite. This study can provide key technical support and theoretical guidance for oil and gas development in tight glutenite reservoir.

Effects of AMF on plant nutrition and growth depend on substrate gravel content and patchiness in the karst species Bidens pilosa L.

Karst ecosystems represent a typical heterogeneous habitat, and it is ubiquitous with varying interactive patches of rock and soil associated with differential weathering patterns of carbonate rocks. Arbuscular mycorrhizae fungi (AMF) play an important role in regulating plant growth and nutrition in heterogeneous karst habitats. However, it remains unclear how AMF affects the growth and nutrition of plants in heterogeneous karst soil with varying patches and weathering gravel. A heterogeneous experiment with Bidens pilosa L. was conducted in a grid microcosm through patching karst soil with different gravel contents. The experimental treatments included the AMF treatments inoculated with (M+) or without (M-) fungus Glomus etunicatum; the substrate patchiness treatments involved different sizes of the homogeneous patch (Homo), the heterogeneous large patch (Hetl), and the heterogeneous small patch (Hets); the substrate gravel treatments in the inner patch involved the free gravel (FG), the low gravel (LG) 20% in 80% soil, and the high gravel (HG) 40% in 60% soil. Plant traits related to growth and nutrients were analyzed by comparing substrate gravel content and patch size. The results showed that AMF was more beneficial in increasing the aboveground biomass of B. pilosa under the LG and HG substrates with a higher root mycorrhizal colonization rate than under the FG substrate with a lower root mycorrhizal colonization rate. AMF enhanced higher growth and nutrients for B. pilosa under the LG and HG substrates than under the FG substrate and under the Hets than under the Hetl. Moreover, AMF alleviated the limited supply of N for B. pilosa under all heterogeneous treatments. Furthermore, the response ratio LnRR of B. pilosa presented that the substrate gravel promoted the highest growth, N and P absorption than the substrate patchiness with M+ treatment, and the gravel content had a more effect on plant growth and nutrition as compared to the patch size. Overall, this study suggests that plant growth and nutrition regulated by AMF mainly depend on the substrate gravel content rather than the spatial patchiness in the heterogeneous karst habitat.

Study on the Tensile Properties and Application of Gravelly Soil Reinforced by Polypropylene Fiber

Incorporating fibers into gravelly soil is an effective method to prevent the core wall of high earth core rockfill dams (ECRDS) from cracking. In this study, a new type of soil tensile device was used to carry out tensile tests on gravelly soil with different gravel contents and fiber contents. The test results show that as the gravel content increases from 0% to 50%, the improvement in tensile strength decreases from 48.9% to 6.4%, which means the increase in gravel content reduces the improvement in tensile strength significantly. The ultimate tensile strain, tensile strength, and post-peak tensile strength of fiber-reinforced gravelly soil are positively correlated with the fiber content. Combined with the Scanning electron microscopy (SEM) results, the reinforcement effect of the three types of fiber interfaces on the gravel soil is qualitatively analyzed, and the microscopic mechanism of the improvement of the tensile strength of fiber-reinforced gravelly soil is revealed. The energy absorption capacity (EAC) results showed that the lower the gravel content in the soil, the higher the degree of improvement in the EAC value. In practical application, it is recommended to use gravel soil with low gravel content and high fiber content. Finally, a regression model considering the gravel content and fiber content was proposed for fast predicting the tensile strength of the soil. The related results can provide references for the anti-cracking design of the core wall of high ECRDS.

Erosion‐reducing effects of revegetation and fish‐scale pits on steep spoil heaps under concentrated runoff on the Chinese Loess Plateau

AbstractMassive spoil heaps, formed during production and construction activities, have suffered from severe soil erosion, leading to land degradation and damaging the environment. Fish‐scale pits (FSPs) and revegetation (RG) are the most common measures for controlling soil erosion on spoil heaps on the Loess Plateau. To evaluate the effects of FSPs and RG on concentrated runoff erosion, scouring‐erosion experiments were conducted on FSP plots, RG plots, and bare plots (the control) in the field on two types of spoil heaps: low gravel content in soil (LGS) and high gravel content in soil (HGS) at various inflow rates. Mass movement was the main cause of the considerable fluctuations in erosion rate and sharply increased the sediment concentration, which could exceed 800 kg m−3 and cause hyperconcentrated flows. Conversely, the FSP and RG treatments observably reduced the sediment concentration and erosion rate. The erosion‐reducing benefits (ERBs) of both the FSPs and RG treatments were significant. However, the ERB of the FSPs treatment was superior to that of the RG treatment under concentrated runoff, especially high‐intensity concentrated runoff. The ERB of the FSP treatment was on average 78.5% and 80.9% for the LGS and HGS, respectively. The ERB of the RG treatment was on average 36.4% and 56.5% for the LGS and HGS, respectively. The ERBs of the FSPs and RG treatments for the HGS were greater than those for the LGS. Moreover, gravel inhibited concentrated flow erosion. Our results provide important guidance for preventing soil erosion on abandoned spoil heaps in semiarid regions.

Axial resistance of open-ended pipe pile driven in gravelly sand

A full-scale, double-wall, open-ended pipe pile with a diameter, B = 660 mm was densely instrumented with a combination of electrical-resistance and vibrating-wire strain gauges. The test pile was driven into a gravelly sand soil profile to a depth of 30·48 m and then statically and dynamically load tested. The double-wall instrumentation allows independent measurements of the outer shaft, inner shaft (plug) and annulus resistances during a static load test. The residual loads locked in the pile after driving were measured and considered in the correction of the resistance components. The load–settlement curve, load transfer curves and the profile of the unit limit shaft resistance were obtained from the static load test measurements. Two cone penetration test-based methods were used to estimate the resistance of the test pile, which was compared with that obtained from the static load test. Both methods provide good estimates for the unit shaft resistance in sandy layers with low gravel content (<20%), but significantly overestimate the unit shaft resistance mobilised in soil with high gravel content (>30%). The estimated base resistances by both methods match well that measured in the static load test.

Changes in soil properties and soil organic carbon stocks along an elevation gradient at Mount Bambouto, Central Africa

The study was designed to investigate the influence of elevation gradient on soil properties and soil organic carbon (SOC) in the Bambouto Mountain in Western Cameroon and the subsequent consequences of human activities on these SOC contents. Five sites, Bawa, Zavion, Totap, Camp Bororo and Meletan, were selected between 1400 m and 2740 m altitude to conduct the study. Three sampling points per site were allocated and each selected point was sampled using depth increments of 25 cm from the soil surface. The studied soils are characterized by low gravel contents. SOC contents and stock (SOCS) decrease with depth at all sites and increase along the elevation gradient, reaching the highest content (123.67 ± 30.44 g kg−1) at 2100 m a.s.l. Higher SOCS (157.14 ± 23.75 Mg ha−1) were found in 0–25 cm depth at Meletan at 2740 m a.s.l. while the lowest SOCS (86.04 ± 3.19 Mg ha−1) in the same depth was found in Bawa at 1500 m a.s.l. It increased and was significantly correlated with elevation (r = 0.86; p < 0.05), reaching a total of 302.15 ± 34.55 Mg ha−1 at 2740 m a.s.l. The difference might be attributed to longer vegetative growing periods at the high altitude without human interference in comparison with the lower altitude. Amorphous Fe and Al exhibited weak correlations with total SOCS along the altitudinal gradient, implying that their role on the stabilization of SOC might be little. The accumulation and stabilization of SOC is ascribed to clay content, parent material, climate and vegetation, which are controlled by the elevation gradient.

As indústrias do Paleolítico Inferior e Médio associadas ao Terraço T4 do Baixo Tejo (Portugal central); Arquivos da mais antiga ocupação humana no oeste da Ibéria, com ca. 340 ka a 155 ka

Através dos registos geomorfológicos e sedimentares, os rios fornecem relevantes arquivos de mudanças paleoambientais, nomeadamente paleoclimáticas e paleogeográficas. As sucessões sedimentares melhor datadas são as mais importantes, com as idades numéricas dos respetivos dos eventos sedimentares, de fósseis e de materiais arqueológicos, obtidas por uma variedade de técnicas. Os arquivos fluviais do Quaternário fornecidos pelo rio Tejo em Portugal (Baixo Tejo) constituem um importante repositório de dados para estudos da evolução da dinâmica sedimentar e da paisagem, bem como da ocupação humana pré-histórica. O atual estado de conhecimentos resultantes das sucessivas abordagens usando métodos da geomorfologia, litostratigrafia, arqueologia e datação numérica no estudo do Terraço T4 do Baixo Tejo é aqui sintetizado. Este trabalho tem enfoque nos sítios com indústrias do Paleolítico que foram encontradas no Terraço T4, o qual é constituído por uma unidade basal de cascalheiras e uma unidade superior dominada por areias. Os mais antigos artefactos são de rara ocorrência e foram encontrados na unidade de Cascalheiras Inferiores, apresentando formas bifaciais pouco elaboradas que podem ser atribuídas ao Acheulense, com uma idade provável de ca. 340 a 325 ka. Em contraste, os níveis estratigráficos inferiores e médios da unidade de Areias Superiores do T4 apresenta vários sítios arqueológicos que documentam fases sucessivas de um Acheulense evoluído, que foram datados de ca. 325 a 200 ka. Nos níveis estratigráficos dos depósitos do topo do T4 foram encontradas indústrias do Paleolítico Médio e datam, provavelmente, de ca. 165 a 155 ka.

Estimations of soil fertility in physically degraded agricultural soils through selective accounting of fine earth and gravel fractions

Abstract. Soil fertility and organic carbon (C) stock estimations are crucial to soil management, especially that of degraded soils, for productive agricultural use and in soil C sequestration studies. Currently, estimations based on generalized soil mass (hectare furrow basis) or bulk density are used which may be suitable for normal agricultural soils, but not for degraded soils. In this study, soil organic C, available nitrogen (N), available phosphorus (P2O5) and available potassium (K2O), and their stocks were estimated using three methods: (i) generalized soil mass (GSM, 2 million kg ha−1 furrow soil), (ii) bulk-density-based soil mass (BDSM) and (iii) the proportion of fine earth volume (FEV) method, for soils sampled from physically degraded lands in the eastern dry zone of Karnataka State in India. Comparative analyses using these methods revealed that the soil organic C, N, P2O and K2O stocks determined by using BDSM were higher than those determined by the GSM method. The soil organic C values were the lowest in the FEV method. The GSM method overestimated soil organic C, N, P2O and K2O by 9.3–72.1, 9.5–72.3, 7.1–66.6 and 9.2–72.3 %, respectively, compared to FEV-based estimations for physically degraded soils. The differences among the three methods of estimation were lower in soils with low gravel content and increased with an increase in gravel volume. There was overestimation of soil organic C and soil fertility with GSM and BDSM methods. A reassessment of methods of estimation was, therefore, attempted to provide fair estimates for land development projects in degraded lands.

Triaxial shear behaviour of sand-gravel mixtures reinforced with cement and fibre

Results of consolidated-drained and consolidated-undrained triaxial tests conducted on fibre-reinforced cement-treated sand–gravel mixtures are described in present study. The base soils were sand–gravel mixtures containing 30 and 50% gravel content. Cement content was 3% (dry wt.) of sand–gravel mixture and polypropylene fibres 0.012 m in length and 23 μm thick were added at 0.0, 0.5 and 1% (dry wt.) of soil–cement composite. Stress–strain curves besides volume and pore pressure changes, energy absorption and deformability characteristics of the reinforced mixture were evaluated. Mechanical behaviour of the composite was compared with the results of previous studies on fibre-reinforced cement-treated sand in both drained and undrained conditions. According to the results, impact of fibre reinforcement on shear strength of cemented sand–gravel mixture decreased with the increase in gravel content in drained condition. However, for undrained state, the strength was more influenced by the fibres in higher gravel contents. Moreover, increase in gravel content increased the potential of energy absorption and brittleness of the reinforced mixture. Using a single failure envelope for both drained and undrained tests, it was concluded that cohesion intercept was more affected by inclusion of fibres in mixture with lower gravel content.

Spawning and rearing behavior of bull trout in a headwater lake ecosystem

Numerous life histories have been documented for bull trout Salvelinus confluentus. Lacustrine-adfluvial bull trout populations that occupy small, headwater lake ecosystems and migrate short distances to natal tributaries to spawn are likely common; however, much of the research on potamodromous bull trout has focused on describing the spawning and rearing characteristics of bull trout populations that occupy large rivers and lakes and make long distance spawning migrations to natal headwater streams. This study describes the spawning and rearing characteristics of lacustrine-adfluvial bull trout in the Quartz Lake drainage, Glacier National Park, USA, a small headwater lake ecosystem. Many spawning and rearing characteristics of bull trout in the Quartz Lake drainage are similar to potamodromous bull trout that migrate long distances. For example, subadult bull trout distribution was positively associated with slow-water habitat unit types and maximum wetted width, and negatively associated with increased stream gradient. Bull trout spawning also occurred when water temperatures were between 5 and 9 °C, and redds were generally located in stream segments with low stream gradient and abundant gravel and cobble substrates. However, this study also elucidated characteristics of bull trout biology that are not well documented in the literature, but may be relatively widespread and have important implications regarding general characteristics of bull trout ecology, use of available habitat by bull trout, and persistence of lacustrine-adfluvial bull trout in small headwater lake ecosystems.

The effect of increasing gravel cover on forest roads for reduced sediment delivery to stream crossings

AbstractDirect sediment inputs from forest roads at stream crossings are a major concern for water quality and aquatic habitat. Legacy road–stream crossing approaches, or the section of road leading to the stream, may have poor water and grade control upon reopening, thus increasing the potential for negative impacts to water quality. Rainfall simulation experiments were conducted on the entire running surface area associated with six reopened stream crossing approaches in the south‐western Virginia Piedmont physiographic region, USA. Event‐based surface run‐off and associated total suspended solid (TSS) concentrations were compared among a succession of gravel surfacing treatments that represented increasing intensities of best management practice (BMP) implementation. The three treatments were no gravel (10–19% cover), low gravel (34–60% cover), and high gravel (50–99% cover). Increased field hydraulic conductivity was associated with maximized surface cover and ranged from 7.2 to 41.6, 11.9 to 46.3, and 16.0 to 58.6 mm h−1 respectively for the no gravel, low gravel, and high gravel treatments. Median TSS concentration of surface run‐off for the no gravel treatment (2.84 g l−1) was greater than low gravel (1.10 g l−1) and high gravel (0.82 g l−1) by factors of 2.6 and 3.5 respectively. Stream crossing approaches with 90–99% surface cover had TSS concentrations below 1 g l−1. Reducing the length of road segments that drain directly to the stream can reduce the costs associated with gravel surfacing. This research demonstrates that judicious and low‐cost BMPs can ameliorate poor water control and soil erosion associated with reopening legacy roads. Copyright © 2014 John Wiley &amp; Sons, Ltd.

The influence of soil gravel content on compaction behaviour and pre-compression stress

Many arable soils have significant horizon-specific gravel content levels. Just how these influence compaction behaviour, and in particular precompression stress as an important criterion of a soil's susceptibility to compaction, has yet to be sufficiently clarified. This article is intended to contribute towards answering this question.Firstly, three different fine earths, from the “Clay”, “Silt Loam” and “Sandy Loam” soil texture classes were mixed with staggered proportions (0, 10, 20, 30, 40% by volume) of a quartz gravel (the shape of which was subrounded to rounded, average weighted diameter 6mm). Soil core samplers were filled with the mixtures at a typical density for a natural site. In the case of the 30% by volume variant only, in addition to the quartz gravel an angular to subangular limestone gravel with the same size graduation was also used. The tests were supplemented by 20 samples from a natural site; the gravel content of these varied between 0.1 and 23.5% by volume. All of the disturbed and natural samples were adjusted to a water content at a matric potential of −6kPa. Subsequently, an oedometer test was used to apply loads to them in stages (5–550kPa). Precompression stress was calculated using the resulting stress–bulk density functions.While fine earth bulk density remained constant, the staggered addition of quartz gravel led to an increase in the whole soil density after packing, and thus also to a vertical shift in overall stress–bulk density functions. However, the stress–density functions of the fine earth do show that the overall compaction of fine earth decreased as gravel content increased. In the case of low gravel content levels of no more than 10% by volume, the increase in precompression stress (log) in the disturbed samples was, on the whole, very low. In the disturbed samples, however, as gravel content increased precompression stress (log) increased exponentially. Contrary to this, a continuous linear increase in precompression stress (log) could be observed with increasing gravel content in the natural samples. The angular to subangular shape of the gravel only resulted in greater precompression stress (log) in the “Silt Loam”.At gravel-rich sites, gravel content influences soil compaction behaviour and precompression stress very strongly. For this reason, it is essential that it be considered when assessing such sites' risk of compaction damage.

Habitat preference of Common Sandpipers (Actitis hypoleucos) along the River Rába, Hungary

Abstract We investigated habitat preference of Common Sandpipers as part of a monitoring program in the Őrség National Park, Hungary. Field observations were conducted during the summers between 2008 and 2012 along a 47-km long section of the River Rába. During the observations we recorded the number and location of birds on the river bank. We divided the studied area into 1 km long sections and measured the proportion of the visually distinguishable habitat types (water, low gravel and sand bank, vegetation and degraded area) from a digitalized map. Furthermore, we recorded the number of the low banks and the number of bends of the river within each section, as well as the sections’ distance from the closest hydroelectric power plants and human settlements. In 2012 we also performed a detailed habitat mapping, recording the proportion of the vegetation types along the river bank and the number of fishing spots, embankment strengthenings and gravel banks. We tested the correlations between these habitat variables and number of birds present in the river sections. Our results show that Common Sandpipers were observed more frequently in locations which have (1) larger number and area of low gravel and sand banks, (2) less dense vegetation, and (3) lower proportion of degraded habitats. These findings can be taken into account in the conservation management of River Rába

Soil Organic Carbon Assessment at High Vertical Resolution using Closed‐Tube Sampling and Vis‐NIR Spectroscopy

We provide an alternative to standard soil organic carbon (SOC) measurement methods combining percussion drilling with visible and near‐infrared (Vis‐NIR) reflectance spectroscopic analyses at a very high depth resolution on intact soil cores (151 soil profiles; 3‐cm vertical resolution). Using a small but representative subset of the soil cores that we analyzed for SOC content with dry combustion, we developed chemometric models to predict SOC content for the entire dataset. We show that our approach allows for accurate and repeatable measurements of SOC. It provides detailed SOC information at ∼83% lower costs and reduces labor time by ∼85% compared with a traditional approach at the same vertical resolution. The accuracy of spectroscopic predictions is comparable with standard soil analysis techniques, and hence our approach can represent an operational alternative to reference methods of SOC analysis. However, the method is limited to soils with a low gravel content (less than ∼5% gravel).

Clinical study on low-set vacuum aspiration improved the efficacy of calculus removal by percutaneous nephrolithotomy

Objective To investigate the effects of low pressure suction ultrasonic gravel clear stone system in treatment of kidney stone.Methods 80 cases of kidney stones were randomly divided into control group and improved group,each group with 40 cases.Control group used EMS three generations of ultrasonic gravel clear stone system for percutaneous renal mirror lithotripsy,improved group was given the low pressure suction ultrasonic gravel clear stone system for percutaneous renal mirror lithotripsy.A comparative analysis was carried out to the two groups in clear stone time,stones clearance,during the operation,the amount of bleeding,infection,hemorrhage and hospitalization days.Results All patients didn' t appear puncture failure or transit open surgery phenomenon,surgery perform very well.Compared with controls,improved group had a higher clear stone rate (P＜0.05); clear stone time (namely the stoning time from beginning to the end)and the length of time all reduced significantly (P＜0.01); at the same time during the operation,the amount of bleeding was much less than that of control group (P＜0.01).In two groups,the postoperative complications in patients showed no significant difference (P＞0.05).Conclusion Low pressure suction ultrasonic gravel elear stone system can not only help to enhance the efficiency of clearing stone,but also can effectively reduce time of clearing stone and operation time. Key words: Low pressure suction; Kidney stones; Ultrasonic gravel; Retrospective study

Using multiple bed load measurements: Toward the identification of bed dilation and contraction in gravel‐bed rivers

This study examines bed load transport processes in a small gravel‐bed river (Béard Creek, Québec) using three complementary methods: bed elevation changes between successive floods, bed activity surveys using tags inserted into the bed, and bed load transport rates from bed load traps. The analysis of 20 flood events capable of mobilizing bed material led to the identification of divergent results among the methods. In particular, bed elevation changes were not consistent with the bed activity surveys. In many cases, bed elevation changes were significant (1 to 2 times the D50) even if the bed surface had not been activated during the flood, leading to the identification of processes of bed dilation and contraction that occurred over 10% to 40% of the bed surface. These dynamics of the river bed prevent accurate derivation of bed load transport rates from topographic changes, especially for low magnitude floods. This paper discusses the mechanisms that could explain the dilation and contraction of particles within the bed and their implications in fluvial dynamics. Bed contraction seems to be the result of the winnowing of the fine sediments under very low gravel transport. Bed dilation seems to occur on patches of the bed at the threshold of motion where various processes such as fine sediment infiltration lead to the maintenance of a larger sediment framework volume. Both processes are also influenced by flood history and the initial local bed state and in turn may have a significant impact on sediment transport and morphological changes in gravel‐bed rivers.

Predicting habitat preferences for Anthometrina adriani (Echinodermata) on the East Antarctic continental shelf

The comatulid crinoid Anthometrina adriani is well represented among the suspension-feeding megaepibenthos from the continental shelf of the Dumont D'Urville Sea, Antarctica. Nearly 500 specimens were sampled during the Collaborative East Antarctic Marine Census expedition onboard the RV 'Aurora Australis' (December 2007 to January 2008), from 50 of the 87 stations over a 400 km² area. Abiotic environmental factors were measured and an ocean circulation model was used to generate near-bottom parameters. The ecological niche of A. adri- ani was described by using ecological-niche factor analysis and Mahalanobis distances factor analysis. An environmental suitability map (ESM) was developed to map the optimal habitat. A. adriani prefers moderately deep and relatively cold waters with moderate current velocity, and a substrate with low gravel content and biogenic carbonate. The ESM shows 4 optimal regions: the eastern side of the George V Basin, the eastern side of the Adelie Basin, the southern part of the Adelie Bank, and the coastal area between the Astrolabe and Mertz glaciers. The ecological niche for A. adriani appears very narrow, but the species is widely distributed across the Antarctic shelf. It suggests that local changes in limiting factors have a strong local effect on the distribution of this species and that a total eradication of this species from the shelf would need an Antarctic-wide and synchronic change in these essential parameters. Modeling modifications in environmental conditions under different climate change scenarios could help predict the effect of such changes on the distribution of this selective species.

CT Analysis Method for Particular Lithology Reservoir Rock

Core analysis is one of the most necessary means to recognize the geological characteristics of reservoirs. Recently, the oil and gas exploration of particular lithology such as volcanic, conglomerate, mud and carbonate rocks continued to make new breakthroughs. As a result, core analysis for particular lithology reservoir rock is increasingly significant. However, conventional methods of core analyzing have great limitations on particular lithology due to the complex chemical components and variable physical status. In order to obtain accurate experimental data and understand the seepage law of particular lithology, advanced core analysis methods are developed through the application of computed tomography (CT). Through the application of nondestructive CT testing for inner construction of core, and the establishing of CT evaluation criterion for the heterogeneity of particular lithology, the goals of analyzing the features and growth of holes and fractures in core and heterogeneity of core are archived. The evaluation criterion is composed by qualitative evaluation and quantitative evaluation, and gives the corresponding evaluation method and formula. The evaluation criterion provides the basis for CT analysis of particular lithology. The application of CT analysis for 211 cores of particular lithology shows: 1) Most conglomerates develops gravel-edge fractures, growth of the fractures is proportional to the level of gravel and inverse proportional to the degree of compaction. Holes in conglomerate are mainly corroding holes between gravel. The growth of holes is related to the composition of cement and compaction. With the lower gravel level, the number of holes and fractures decline. 2) Most volcanic rocks develop holes; some of them develop big holes or lots of holes. Several volcanic samples contain micro-fractures. The growth of holes and fractures in different volcanic rock categories are equivalent, but the type of holes and fractures are different. This research has opened new experimental means for cores of particular lithology. By increasing the skills of core analysis, this research has increased people’s knowledge of reservoir of particular lithology, and means a lot to oil and gas exploration and development.