Based on our detailed structural characterization, we examine possible relationships between thrust faults and strike-slip faults and thrust-cored folds and depositional units in the Silla Syncline, a 4 km wide fold composed of fine-grained mudstone, coarse sandstone and conglomerate deposits of the Cerro Toro Formation in the Magallanes foreland basin, Chilean Patagonia. The syncline is bounded on its western flank by an asymmetric anticline and on its eastern flank by a broad zone of thrust faults and associated folds, which are oriented sub-parallel to the syncline axis. Deposition of the coarse-grained units of the Silla Syncline appears to have taken place in this structurally defined trough controlled primarily by thrust fault related growth structures flanking the syncline.The syncline and surrounding area have also been deformed by two sets of strike-slip faults, one right-lateral and one left-lateral. The strike-slip and thrust faulting operated contemporaneously for much of their active periods, although it appears that thrust faulting, confined within the fine-grained units, initiated slightly earlier than strike-slip faulting. In addition, younger igneous intrusions at high angle to bedding generally localize along the strike-slip faults. The cross-cutting relationships among the intrusions, strike-slip faults, and flexural slip faults show that all these structures were active during the same period, which extends beyond mid-Miocene.These conclusions support the premise that structures in deep-water sediments are important for understanding not only the deformation of a foreland basin, but also its depositional architecture. 相似文献
This study examines the local geological conditions and soil structure as possible causes of the collapse of the Zümrüt Building
2 February 2004. This catastrophe resulted in 92 fatalities and 35 injuries. This study also examines other views which claim
weak soil structure, elastic and consolidation settlement of soil and excessive groundwater extraction as well as subsidence
resulting from the underground silt erosion as possible factors. Zümrüt Building was constructed on normally consolidated,
low plasticity clay. The underground water table was 30 m in depth. The internal friction angle of soil was 8°–30°, its cohesion
was between 34 and 127 kN/m2 and standard penetration test numbers varied between 11 and 50. The underground water level beneath Zümrüt Building had risen
4.5 m since its construction. Therefore the claim that subsidence resulting from the decrease of underground water level contributed
to the collapse is incorrect. Secondly the settlement, resulting from the filling up of the pores created by the silt receding
with the underground water, was 4.4 mm in total, and attributing this as the primary cause of the collapse is also incorrect.
Soil properties, in situ and laboratory test results showed that the existing and/or expected settlement and the differential
ground settlement in the Zümrüt building vicinity had the potential to cause structural damage. The tensile stresses caused
by differential settlements recorded here are thought to be an indicator, but not the main cause contributing to the collapse
of the building. The Zümrüt Building collapse was due to several compounding mistakes during the construction phase. These
were geotechnical and other project faults and the use of low quality construction materials. The resulting catastrophe caused
92 fatalities, 35 injuries and a material loss of approximately US$7 million. 相似文献
The Bering Sea is a high-latitude, semi-enclosed sea that supports extensive fish, seabird, marine mammal, and invertebrate populations and some of the world's most productive fisheries. The region consists of several distinct biomes that have undergone wide-scale population variation, in part due to fisheries, but also in part due to the effects of interannual and decadal-scale climatic variation. While recent decades of ocean observation have highlighted possible links between climate and species fluctuations, mechanisms linking climate and population fluctuations are only beginning to be understood. Here, we examine the food webs of Bering Sea ecosystems with particular reference to some key shifts in widely distributed, abundant fish populations and their links with climate variation. Both climate variability and fisheries have substantially altered the Bering Sea ecosystem in the past, but their relative importance in shaping the current ecosystem state remains uncertain. 相似文献
The design methods currently used for earth reinforcement are mostly based on deterministic properties of both the soil and
the construction materials used. Nowadays, however, the general trend is designing at a specific degree of reliability. This
is even more true where the raw data such as soil properties exhibit significant variation. Deterministic solutions, in this
case, may not suffice. Therefore, this paper will attempt to use probabilistic formulations thereby modifying the existing
design procedure of reinforced earth retaining walls to account for uncertainties and variabilities. Through a first order
Taylor's series expansion about the mean, the mean and variance of the strip reinforcing components, namely width and length,
are derived in terms of the variations in the soil properties. Design charts that enable estimation of both mean and variance
are developed to avoid extensive partial differentiation involved in the computations. Using appropriate probability distributions
along with the mean and variance, the final design outputs are determined for a selected failure probability by introducing
what is refered to as 'risk index'. The results indicate that the risk index increases with an increase in the coefficient
of variations and a decrease in failure probability. Furthermore, it is shown that in some cases, depending on the variabilities
of the soil properties, the classical design technique produced a relatively high failure probability.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
Rock mass classification is analogous to multi-feature pattern recognition problem. The objective is to assign a rock mass to one of the pre-defined classes using a given set of criteria. This process involves a number of subjective uncertainties stemming from: (a) qualitative (linguistic) criteria; (b) sharp class boundaries; (c) fixed rating (or weight) scales; and (d) variable input reliability. Fuzzy set theory enables a soft approach to account for these uncertainties by allowing the expert to participate in this process in several ways. Hence, this study was designed to investigate the earlier fuzzy rock mass classification attempts and to devise improved methodologies to utilize the theory more accurately and efficiently. As in the earlier studies, the Rock Mass Rating (RMR) system was adopted as a reference conventional classification system because of its simple linear aggregation.
The proposed classification approach is based on the concept of partial fuzzy sets representing the variable importance or recognition power of each criterion in the universal domain of rock mass quality. The method enables one to evaluate rock mass quality using any set of criteria, and it is easy to implement. To reduce uncertainties due to project- and lithology-dependent variations, partial membership functions were formulated considering shallow (<200 m) tunneling in granitic rock masses. This facilitated a detailed expression of the variations in the classification power of each criterion along the corresponding universal domains. The binary relationship tables generated using these functions were processed not to derive a single class but rather to plot criterion contribution trends (stacked area graphs) and belief surface contours, which proved to be very satisfactory in difficult decision situations. Four input scenarios were selected to demonstrate the efficiency of the proposed approach in different situations and with reference to the earlier approaches. 相似文献
The enrichment factor (EF), geochemical index (Igeo), pollution factor (Cf), and pollutant load index (PLI) were calculated using average shale metal concentration values to determine metal pollution in Moryayla and surrounding stream sediments. It was determined that the average concentration values are above the world average shale values. According to the results obtained, the mean accumulation levels of heavy metals in the study area were Mn > Zn > Cu > Pb > As > Cr > Ni > Sb. Considerable degree of enrichment was observed because the elements As, Cu, and Pb are at EF > 5 at locations 47, 53, 70, and 71. The values obtained from the Igeo, Cf, and PLI are a wide range of pollutants (from unpolluted to moderately polluted to extremely polluted to) for the various elements studied. 相似文献