Laboratory Investigation of the Influence of Geotextile on the Stress–Strain and Volumetric Change Behavior of Sand

This paper presents the results of triaxial tests conducted for the investigation of the influence of geotextile on both the stress–strain and volumetric change behavior of reinforced sands. Tests were carried out on loose sand. The experimental program includes drained compression tests on samples reinforced with different values of both geotextile layers (1 ≤ Ng ≤ 3) and confining pressure (\(\upsigma_{\text{c}}^{\prime }\)) varying from 50 to 200 kPa. Tests show that the contribution of geotextile is negligible until an axial strain threshold that range between 2.5% for a confining pressure of 50 kPa to lower than 1% for 100 and 200 kPa confining pressure. At higher values of ε_a, geotextile induces a quasi-linear increase in the stress deviator (q) and volume contraction in the reinforced sand. Tests show a negligible influence of the number of geotextile layers (Ng) on the contribution of geotextile to both stress–strain and volumetric change, when normalized with Ng. Tests also show that the contribution of geotextile to the stress–strain mobilization augments with the increase in the confining pressure, while its contribution to the volume contraction decreases with the increase in the confining pressure. The reinforced soil becomes contracting in the case of 2 and 3 geotextile layers.     

Characteristics of the Mesozoic and Cenozoic Tectonic Stress Fields of the Urumqi-Usu Region, Xinjiang

Based on the study of folds and related conjugate shear joints, the tectonic stress fields of the Urumqi-Usu region to the north of the North Tianshan Mountains have been reconstructed. Furthermore the author discussed the tectonic movements and their dynamic features. The early tectonic movement in the investigated region occurred from the end of the Late Jurassic to the initial stage of the Early Cretaceous, with the maximum (tensile) and minimum (compressional) principal stress trajectories in the tectonic stress field being in E-W and S-N directions respectively; the late tectogenesis took place from the end of the Early Pleistocene to the initial Middle Pleistocene, with the maximum and minimum principal stress trajectories in the late stress field striking in WNW and NE-NNE directions respectively. Through computer-aided simulated calculation by the finite element method and analysis of geological structure, it has been ascertained that the early tectogenesis is a nearly N-S compressive movement and the late one a NE to nearly N-S compressive movement with reverse shear. The dynamic force which caused the tectogeneses came from the movement of the southern major fault, i.e. the North Tianshan Mountains.     

Is there a close spatial relationship between faults and plutons?

Using spatial relationships between individual plutons and faults to support genetic correlations between faulting and magmatism is meaningless since even random magmatic or tectonic processes will result in some plutons adjacent to faults. Our initial analyses of populations of faults and Carboniferous plutons in the Armorican Massif, France and faults and Alleghanian plutons in the southern Appalachians, USA indicate that plutons have broad distributions with respect to faults but with a tendency for plutons to occur away from faults. Maxima of integrated pluton areas occur at 1/4 (Appalachians) and 1/2 (Armorican) of the distance between the average fault spacing in these orogens. Although there is a great need for statistical evaluations of relationships between populations of igneous bodies and structures in a wide variety of settings and crustal depths, our initial studies suggest that faults do not preferentially channel magma during ascent or emplacement and that these are relatively unfocused processes within orogenic belts.     

The Coulomb–Mohr Law and the Change in the Stress–Strain State of a Landslide Prone Mass

Doklady Earth Sciences - The stresses at the points of the ground mass are determined and distributed according to the Coulomb–Mohr law in the main stresses, under compression conditions. The...     

Comparison Between Stress and Strain Quantities of the Failure–Deformation Process of Fennoscandian Hard Rocks Using Geological Information

The aim of this paper was to compare the stress and strain quantities that are related to the failure–deformation process of hard rock. The data used here was obtained from laboratory uniaxial compression tests performed on different types of Fennoscandian hard rocks. The failure–deformation process quantities were compared at each deformation stage and for each single specimen. Moreover, geological information such as the rock origin process and the rock characteristics of the specimens were studied and linked to the stress and strain quantities. The purpose was to investigate the influence of the rock origin process and rock characteristics on these quantities. The main results of this study showed that the normalized crack damage lateral strain (ε _3cd/ε _3p ) and the volumetric strain (ε _crv?ci and ε _v?cd) quantities were strongly affected by the grain size. The normalized and volumetric quantities are weakly dependent on the mineral composition.     

REE Geochemistry and Mineralization Characteristics of the Zudong and Gnanxi Granites, Jiangxi Province

The Zudong and Guanxi granites are original rocks of the ion adsorption-type HREE and LREE deposits in weathering crust of granites. The ΣREE value and LREE/HREE ratio of the Zudong granite are 264 ppm and 0.81-0.24 respectively, and the average Y/ΣREE ratio is 35.8-54.5%. This is mainly due to magmatic crystallization and evolution and deuteric metasomatism (albitization, muscovitization and fluorite-doveritization). These alterations resulted in endogenic mineralizations of yttrium-group REE fluorine carbonates, silicates and arsenates. The Guanxi granite is characterized by LREE enrichment (the average LREE/HREE ratio is 2.43).     

Link between global cooling and mammalian transformation across the Eocene–Oligocene boundary in the continental interior of Asia

Evidence in the world’s ocean current system indicates an abrupt cooling from 34.1 to 33.6?Ma across the Eocene–Oligocene boundary at 33.9?Ma. The remarkable cooling period in the ocean, called the Eocene–Oligocene transition (EOT), is correlated with pronounced mammalian faunal replacement as shown in terrestrial fossil records. For the first time within Asia, a section is magnetostratigraphically dated that also produces mammalian fossils that span the Late Eocene—Early Oligocene transition. Three fossil assemblages revealed through the EOT (34.8, 33.7, and 30.4?Ma) demonstrate that perissodactyl faunas were abruptly replaced by rodent/lagomorph-dominant faunas during climate cooling, and that changes in mammalian communities were accelerated by aridification in central Asia. Three fossil assemblages (34.8, 33.7, and 30.4?Ma) within the north Junggar Basin (Burqin section) tied to this magnetostratigraphically dated section, reveal that perissodactyl faunas were abruptly replaced by rodent/lagomorph-dominant faunas during climate cooling, and that changes in mammalian communities were accelerated by aridification in central Asia. The biotic reorganization events described in the Burqin section are comparable to the Grande Coupure in Europe and the Mongolian Remodeling of mammalian communities. That is, the faunal transition was nearly simultaneous all over the world and mirrored global climatic changes with regional factors playing only a secondary role.     

Microtextural Characteristics and Origin of Dolomites in the Tepearasi Formation, SW of Beysehir-Konya, Turkey

The Tepearasi Formation of the autochthonous Geyikdagi Group in the Central Tauride Belt, SE of Beysehir, is Dogger in age and consists dominantly of massive limestones and greyish dolomites occurring within the middle to upper sections. The total thickness of the dolomitic levels ranges from 100-300 m and laterally extends 500-700 m. Three types of dolomite were distinguished through petrographic analyses: homogeneous, mottled (saddle-crystalline) and joint-filling dolomite, which were interpreted to have formed in two different stages, early diagenetic and late diagenetic. The homogeneous dolomite of the early diagenetic stage is light-coloured and monotonous-textured and shows the form of a dolosparite mosaic. The mottled dolomite formed in the late diagenetic stage is light- to dark-coloured and coarsely granular idiomorphic. The other type of late diagenetic dolomite, described as the joint-filling type, presents a crystal growth pattern from the joint walls towards the centre of the joint space. I     

Stress State of the Earth’s Crust and Seismotectonics of Western Sichuan,China

Geotectonics - The results of using a technology for zoning hazardous faults developed at the Institute of Physics of the Earth based on natural stress data are presented. The source of these data...     

Characteristics of distribution and migration of mercury in the sediment-water interface of Poyang Lake, China

Environmental pollution is one of several essential problems of concern global. Although total mercury concentration in the lake is at trace or even ultra-trace level, it is greatly harmful to human health through food chain by the enrichment in fish, etc…     

Geochemical Characteristics and Origin of Natural Gases in the Qaidam Basin, China

Sixty-five natural gas samples were collected from 19 oil-gasfields in the Qaidam basin, China. The chemical composition and carbon isotope values of the samples were measured, and the geochemical characteristics and origin of the natural gases were studied. The gases can be divided into biogenic gases, sapropelic oil-type gases, mixed type oil-type gases, coal-type gases and mixed gas. The δ13Ci values of the biogenic gases are very small and the C2+ contents of them are very low, ranging from -68.2‰ to -61.8‰ and 0.06% to 0.20% respectively. They have heavy δD and δ13Cco2> showing a CC>2 reduction pathway. They are distributed in the East depression region and derived from the Quaternary source rocks. The sapropelic oil-type gases have small δ13C2 values and high C2+ ranging from -36.6‰ to -28.6‰ and from 33.01% to 47.15% respectively. The mixed type oil-type gases have <5I3C2 values and C2+ contents varying from -28.6‰ to -24.8‰ and from 4.81% to 26.06% respectively. Both sapropelic oil-typ     

Uplift along the western margin of the Deccan Basalt Province: Is there any geomorphometric evidence?

In line with the passive margin landscape evolutionary model in vogue, sustained erosion and long-distance retreat of the Western Ghat escarpment are widely considered to be the results of erosionally-driven isostatic uplift since Tertiary by many workers. Others have postulated or adduced evidence for strong neotectonic activity in the Ghat region. An obvious question in this regard is whether there is any geomorphometric evidence in support of this widespread view? In order to test the hypothesis of ongoing post-rift fexural uplift or neotectonic activity in the western Deccan Basalt Province (DBP), geomorphometric analysis was carried out and commonly used geomorphic indices of active tectonics (GAT) were derived for 30 selected river basins on both sides of the Western Ghat. SRTM-DEM data and ArcGIS were used to derive the indices. Tectonic geomorphic analysis based on five proxy indicators suggests that the differences in GAT indices, both along strike and across the Western Ghat, are statistically insignificant. The index values are nowhere close to the GAT values typically associated with drainage basins affected by active tectonics and deformation. Mapping of the indices reveals lack of discernable trends. The adduced results indicate that the western DBP belongs to the class of relatively low tectonic activity.     

Geochemical Characteristics and Tectonic Setting of the Laohushan Basalts, North Qilian Mountains

The Ordovician Laohushan ophiolite, located in the eastern part of the North Qilian Mountains, is mainly composed of meta-peridotites, gabbros and basalts alternating with sediments. The sediments are mainly turbidites, including sandstones, siltstones, cherts etc. Major elements show that the basalts are subalkaline tholeiites and may be analogous to ocean-floor basalts. Except a few N-MORBs, most of the basalts are E-MORBs as indicated by incompatible element ratios such as (La/Ce)N, La/Sm, Ce/Zr, Zr/Y and Zr/Nb. Negative Nb anomaly is common but negative Zr, Hf and Ti anomalies are quite rare. Based on the geochemical characteristics, it is suggested that the Laohushan basalts were formed in a back-arc basin. εNd (t) of the basalts ranges between +3.0 and +8.9 and (87Sr/86Sr), ranges between 0.7030 and 0.7060, indicating a depleted mantle source which was mixed with more or less enriched mantle components. Furthermore, the petrography of the sandstones and geochemistry of the cherts suggest that the     

Characteristics of Volcanic Rocks in the Shoshonite Province, Eastern China, and Their Metallogenesis

The shoshonite province in eastern China is characterized by extensive distribution (ca. 80000 km2) of Late Jurassic-Early Cretaceous (165-100 Ma) shoshonite series with subordinate high-K calc-alkali series. It was formed in a dominantly tensile stress field. In comparison with their analogues in island arcs and active continental margins in other countries, the volcanic rocks in the shoshonite province have their specific characteristics in petrology, mineralogy and geochemistry as well as related mineralization association, which are the comprehensive reflection of the special composition and structure of the mantle and crust of the province and the special Mesozoic regional tectonic setting.     

Strain and deformation mechanisms in the Variscan nappes of Vendée,South Brittany,France

The Variscan nappes of Vendée (South Brittany, France) were displaced westward through a mechanism of regional subhorizontal ductile shear involving the entire body of the nappes. Ductile shear also affected the upper part of the Silurian footwall, including the rhyolite of Chapelle-Hermier, which was mylonitized and sheared with upward-increasing intensity, as well as the calcalkaline Vendée porphyroids of volcanic and volcanoclastic origin which form a mylonite sheet outlining the major basal thrust zone of the nappes. Nappe displacement was accompanied by a severe extensional strain, estimated at up to 300–400% in both the porphyroids and the rhyolite, and indicating that the deformational history may have involved a gravitational spreading component. Within the mylonitic rhyolite, accommodation of the bulk strain was mainly by solution-assisted mass-transfer, as shown by (1) growth of quartz fibres in low-pressure zones, (2) development of polycrystalline ribbons through continuous growth of quartz grains in pressure shadows and (3) crystallization of muscovite at the expense of the felsitic groundmass. A similar deformation process was probably active in the mylonitic porphyroids at the sole of the nappe, suggesting that pressure-solution flow was an important mechanism in nappe displacement.     

Geochemical Characteristics of the Jinjiazhuang Ultrabasic Rock—Type Gold Deposit in Chicheng County,Hebei Province

The Jinjiazhuang gold deposit occurs in the Zhangjiakou gold field,Northwest Hebei.The ore bodies are mostly hosted in Xiaozhangjiakou ultrabasic rocks dominated by diopsidite.Electron microprobe analyses indicate that the deposit is characterized by the enrichment of some platinum group elements in principal metallic minerals such as chalcopyrite,galena,sphalerite and pyrite,and the presence of millerite,Stable isotope studies show that carbon,sulfur and most of the metallogenic elements were probably derived largely from the host Xiaozhangjiakou ultrabasic rocks and that it is possible that the ore-forming fluid was predominted by meteoric water.     

Age and General Characteristics of the Calimicrobialite near the Permian-Triassic Boundary in Chongyang, Hubei Province

INTRODUCTIONCali microbialites near the Permian-Triassicboundary are a special sedi mentary framework whichis formed on the top of reefs or isolated carbonateplatforms after the end-Permian extinction. Cali mi-crobialite in South China was first found by Lehr-mann (1999) in Bianyang, Guizhou. Al most si multa-neously , Kershawet al .(1999) reported cali microbi-alites in East Sichuan. Discovery of Permian-Triassiccali microbialites in South China has attracted muchattention. Based o…