Laboratory Validation of Ultra-Soft Soil Deformation Model     

Myint Win Bo  Victor Choa  Kai Sin Wong  Arul Arulrajah 《Geotechnical and Geological Engineering》2011,29(1):65-74

Ultra-soft soil with high moisture content will experience large strain deformation under one-dimensional compression with little or no gain in effective stress. Such deformation behaviour does not comply with Terzaghi’s effective stress gain theory. The e-log s_v^￠ \sigma_{v}^{\prime } relationship of ultra-soft soil is non-linear with large compression index in the first order of log cycle. This paper proposes three compression indices (C_c1^* C_{c1}^{*} , C_c2^* C_{c2}^{*} and C_c3^* C_{c3}^{*} ) for stresses covering three log cycles. Good prediction of settlement magnitude is possible with these newly proposed compression parameters for ultra-soft soil. In addition, implicit finite difference model applying the large strain theory is also proposed and validated with results from laboratory measurements. The time factor curves for ultra-soft soil with large strain compression are also proposed and validated.  相似文献   

Landslide susceptibility mapping of Tevankarai Ar sub-watershed,Kodaikkanal taluk,India, using weighted similar choice fuzzy model     

Sujatha  E. Ramani  Rajamanickam  Victor 《Natural Hazards》2011,59(1):401-425

This paper deals with the landslide susceptibility zonation of Tevankarai Ar sub-watershed using weighted similar choice fuzzy method in a GIS environment. There has been a rapid increase in landslide occurrences in the Kodaikkanal town and area surrounding the town specially in the settlements around the town and road links leading to and from the town. This necessitates a detailed study of slope instability problems in this area. It is observed that these incidences occur frequently during the monsoon and summer showers. Rainfall is identified as the prime triggering factor. Eleven physical factors that cause instability are identified as causative factors from the field investigations and landslide occurrences. Land use pattern, slope gradient, curvature and aspect, weathering index which are evaluated from the weathering ratios of different chemical constituents of the three major lithological variations, soil type, hydraulic conductivity of soil and soil thickness, geomorphology, drainage, and lineament have been utilized to prepare the spatial variation. A weighted similar choice fuzzy model which ranks a set of alternatives by identifying the similarity between the outcome of alternatives and outcome of ideal alternatives is used to rank the causative factors. Each causative factor is classified into sub-categories and rated based on their effect on stimulating the landslide event using qualitative judgment derived from field studies and landslide history. The prepared thematic maps of causative factors are integrated, utilizing the GIS software Arcmap. The outcome has projected the low, moderate, high, and very high landslide susceptibility zones. The high-hazard and very high-hazard areas fall in the northwestern part characterized by croplands and agricultural plantations, while the moderate hazard zones are seen in prominent settlements and low-hazard zones are observed in the sparse settlements and zones of less agricultural activity. The model is verified using the relative landslide density (R) index, and the susceptibility map is found to be consistent with the mapped landslide incidences. The results from this study illustrate that the use of weighted similar choice fuzzy method is suitable for landslide susceptibility mapping on regional scale in growing hill towns as Kodaikkanal town.  相似文献   

GIS based landslide susceptibility mapping of Tevankarai Ar sub-watershed, Kodaikkanal, India using binary logistic regression analysis   总被引：5，自引：0，他引：5  

Sujatha E RAMANI  Kumarvel PITCHAIMANI  Victor Rajamanickam GNANAMANICKAM 《山地科学学报》2011,8(4):505-517

Landslide susceptibility mapping is the first step in regional hazard management as it helps to understand the spatial distribution of the probability of slope failure in an area.An attempt is made to map the landslide susceptibility in Tevankarai Ar subwatershed,Kodaikkanal,India using binary logistic regression analysis.Geographic Information System is used to prepare the database of the predictor variables and landslide inventory map,which is used to build the spatial model of landslide susceptibility.The model describes the relationship between the dependent variable(presence and absence of landslide) and the independent variables selected for study(predictor variables) by the best fitting function.A forward stepwise logistic regression model using maximum likelihood estimation is used in the regression analysis.An inventory of 84 landslides and cells within a buffer distance of 10m around the landslide is used as the dependent variable.Relief,slope,aspect,plan curvature,profile curvature,land use,soil,topographic wetness index,proximity to roads and proximity to lineaments are taken as independent variables.The constant and the coefficient of the predictor variable retained by the regression model are used to calculate the probability of slope failure and analyze the effect of each predictor variable on landslide occurrence in thestudy area.The model shows that the most significant parameter contributing to landslides is slope.The other significant parameters are profile curvature,soil,road,wetness index and relief.The predictive logistic regression model is validated using temporal validation data-set of known landslide locations and shows an accuracy of 85.29 %.  相似文献   

Quantitative assessment of landslide hazard along transportation lines using historical records   总被引：2，自引：1，他引：1  

Pankaj Jaiswal  Cees J. van Westen  Victor Jetten 《Landslides》2011,8(3):279-291

In this paper, a quantitative landslide hazard model is presented for transportation lines, with an example for a road and railroad alignment, in parts of Nilgiri hills in southern India. The data required for the hazard assessment were obtained from historical records available for a 21-year period from 1987 to 2007. A total of 901 landslides from cut slopes along the railroad and road alignment were included in the inventory. The landslides were grouped into three magnitude classes based on the landslide type, volume, scar depth, and run-out distance. To calculate landslide hazard, we estimated the total number of individual landslides per kilometer of the (rail) road for different return periods, based on the relationship between past landslides (recorded in our database) and triggering events. These were multiplied by the probability that the landslides belong to a given magnitude class. This gives the hazard for a given return period expressed as the number of landslides of a given magnitude class per kilometer of (rail) road. The relationship between the total number of landslides and the return period was established using a Gumbel distribution model, and the probability of landslide magnitude was obtained from frequency–volume statistics. The results of the analysis indicate that the total number of landslides, from 1- to 50-year return period, varies from 56 to 197 along the railroad and from 14 to 82 along the road. In total, 18 hazard scenarios were generated using the three magnitude classes and six return periods (1, 3, 5, 15, 25, and 50 years). The hazard scenarios derived from the model form the basis for future direct and indirect landslide risk analysis along the transportation lines. The model was validated with landslides that occurred in the year 2009.  相似文献   

Preliminary Evidence for Iodate Reduction in Bottom Waters of the Gulf of Mexico During an Hypoxic Event     

Piers Chapman  Victor W. Truesdale 《Aquatic Geochemistry》2011,17(4-5):671-695

The distributions of iodate and total inorganic iodine concentrations in the waters on the Texas?CLouisiana shelf in April, June, and August 2004 are described. Iodine?Csalinity graphs show three-end-member mixing involving onshore and offshore surface waters and deep offshore water. The April survey showed simple mixing on the surface, but in the later surveys, iodate concentrations were often much lower than predicted by the mixing curve while those for total inorganic iodine were higher. This demonstrated both iodate reduction in the water and iodide addition, although individual samples did not show equivalent speciation changes. Hydrographically, the system consists of the estuaries of the Mississippi and Atchafalaya rivers as they spill onto the shelf. The waters are stratified seasonally by a robust halocline, leading to hypoxia in the bottom waters from the combined effect of restricted downward diffusion of oxygen and the sinking of the luxuriant growth of phytoplankton induced by riverine nutrient supply. The distributions of iodate and total inorganic iodine are, therefore, interpreted in terms of water?Csediment interaction as the shelf shoals to the north.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987111000594     

Victor D. Mats  Tatiana I. Perepelova 《地学前缘(英文版)》2011,2(3):349-365

A new model is suggested for the history of the Baikal Rift,in deviation from the classic two-stage evolution scenario,based on a synthesis of the available data from the Baikal Basin and revised correlation between tectonic-lithological-stratigraphic complexes(TLSC) in sedimentary sections around Lake Baikal and seismic stratigraphic sequences(SSS) in the lake sediments.Unlike the previous models,the revised model places the onset of rifting during Late Cretaceous and comprises three major stages which are subdivided into several substages.The stages and the substages are separated by events of tectonic activity and stress reversal when additional compression produced folds and shear structures.The events that mark the stage boundaries show up as gaps,unconformities,and deformation features in the deposition patterns. The earliest Late Cretaceous-Oligocene stage began long before the India-Eurasia collision in a setting of diffuse extension that acted over a large territory of Asia.The NW-SE far-field pure extension produced an NE-striking half-graben oriented along an old zone of weakness at the edge of the Siberian craton.That was already the onset of rift evolution recorded in weathered lacustrine deposits on the Baikal shore and in a wedge-shaped acoustically transparent seismic unit in the lake sediments.The second stage spanning Late Oligocene-Early Pliocene time began with a stress change when the effect from the Eocene India-Eurasia collision had reached the region and became a major control of its geodynamics.The EW and NE transpression and shear from the collisional front transformed the Late Cretaceous half-graben into a U-shaped one which accumulated a deformed layered sequence of sediments.Rifting at the latest stage was driven by extension from a local source associated with hot mantle material rising to the base of the rifted crust.The asthenospheric upwarp first induced the growth of the Baikal dome and the related change from finer to coarser molasse deposition.With time,the upwarp became a more powerful stress source than the collision,and the stress vector returned to the previous NW-SE extension that changed the rift geometry back to a half-graben. The layered Late Pliocene-Quaternary subaerial tectonic-lithological-stratigraphic and the Quaternary submarine seismic stratigraphic units filling the latest half-graben remained almost undeformed.The rifting mechanisms were thus passive during two earlier stages and active during the third stage. The three-stage model of the rift history does not rule out the previous division into two major stages but rather extends its limits back into time as far as the Maastrichtian.Our model is consistent with geological, stratigraphic,structural,and geophysical data and provides further insights into the understanding of rifting in the Baikal region in particular and continental rifting in general.  相似文献   

The study of metal contamination in urban topsoils of Mexico City using GIS   总被引：1，自引：0，他引：1  

María Teresa Rodríguez-Salazar  Ofelia Morton-Bermea  Elizabeth Hernández-Álvarez  Rufino Lozano  Victor Tapia-Cruz 《Environmental Earth Sciences》2011,62(5):899-905

This research presents and discusses information concerning the spatial distribution of heavy metals (Pb, Cu, Zn, Ba, Co, Cr, Ni and V) in the urban environments of Mexico City using geographical information system and statistical analysis. Superficial soil samples (n = 146) were analyzed. The highest contamination indices were found in the north and center zone of the metropolitan area. In contrast, the surrounding rural fields show a lower impact grade. The higher concentrations of Pb, Cu, Zn and Ba were observed as being related to high vehicular traffic, nevertheless other elements such as Co, Cr, Ni and V do not show anthropogenic influence and their content can be attributed to the parental rock. The results are compared with previous surveys carried out in 2003 in order to evaluate temporal deposition trends. No changes were found on reported concentrations except for Cu and Zn, whose concentration has increased in later years. The results suggest that spatial distribution analysis and results in comparison with previous studies could be useful for the management and sustainable development of the metropolitan area of Mexico City.  相似文献   

Surficial geophysical deduction of the geomaterial and aquifer distributions at Ngor-Okpala local government area of Imo State, South Eastern Nigeria     

Obianwu I. Victor  Chimezie C. Innocent  Akpan E. Anthony  George N. Jimmy 《Central European Journal of Geosciences》2011,3(4):368-374

Twenty seven vertical electrical sounding (VES) profiles surrounding four known traverses were obtained in Ngor-Okpala local government area of Imo state to examine the subsurface geomaterials and the associated groundwater potential. The VES data, constrained by borehole data, provided useful information about the subsurface hydrogeologic and lithologic conditions. From the validated interpretation, the area assessed has loamy soil, medium grained sands, well-sorted medium-grained/gravelly sands and river sand as the lithologic succession from top to the bottom of the depth penetrated. The aquifers in the area were found in the medium-grained sands and well-sorted medium-coarse-grained sands. The aquifer depth for all-season groundwater that would be devoid of draw-down can be found at a depth range of 42–50 m. The resistivity maps of selected depths exhibit sharp resistivity changes at depth due mainly to undulating subsurface topography. A map of the distribution of the kσ-values shows that good quality groundwater can be found in most parts of the area.  相似文献   

Geology and geochemistry of Iberian roofing slates     

Victor Cárdenes  Alvaro Rubio-Ordoñez  Carmela Monterroso  Lope Calleja 《Chemie der Erde / Geochemistry》2013

This article analyzes the geochemical and mineralogical composition of the roofing slate deposits of the Iberian Peninsula. Most roofing slate deposits are found on Middle and Upper Ordovician terrains, although there are also deposits in the Ediacaran, Cambrian and Devonian terrains. Samples of slate were taken in most of the active quarries of the Iberian Peninsula, and being analyzed by X-ray Diffraction and Fluorescence. Each lithotect or slate productive formation has its own specific proportions of major and trace elements, being able to differentiate between them by using these relationships. This fact is particularly interesting in geological exploration and prospecting, as it allows knowing exactly the slate lithotect, and also for restoration work in the architectural heritage, due to the ability of identifying the source of the original slate tiles.  相似文献   

The age and composition of the pre-Cenozoic basement of the Jalisco Block: implications for and relation to the Guerrero composite terrane     

Victor A. Valencia  Kevin Righter  Jose Rosas-Elguera  Margarita López-Martínez  Marty Grove 《Contributions to Mineralogy and Petrology》2013,166(3):801-824

The Jalisco Block is thought to be part of the Guerrero terrane, but the nature and age of the underlying crystalline basement are largely unknown. We have collected a suite of schists, granitoids, and weakly metamorphosed marine sediments from various parts of the Jalisco Block including Atenguillo and Ameca, Mascota and San Sebastián, Cuale, Puerto Vallarta, Punta Mita, Yelapa, and Tomatlán. The schists range in age from 135 to 161 Ma, with many exhibiting Proterozoic and Phanerozoic zircon ages. The granitoids range in age from 65 to 90 Ma, and are calc-alkaline compositionally—similar to granitoids from the Puerto Vallarta and Los Cabos batholiths. The Jalisco granitoids also experienced similar uplift rates to granitoids from the regions to the north and south of the Jalisco Block. The marine sediments yield a maximum depositional age of 131 Ma, and also contain a significant zircon population with ages extending back to the Archean. Granitoids from this study define two age groups, even after the effects of thermal resetting and different closure temperatures are considered. The 66.8-Ma silicic ash flow tuff near Union de Tula significantly expands the extent of this Cretaceous–Paleocene age ash flow tuff unit within the Jalisco Block, and we propose calling the unit “Carmichael silicic ash flow tuff volcanic succession” in honor of Ian Carmichael. The ages of the basement schists in the Jalisco Block fully overlap with the ages of terranes of continental Mexico, and other parts of the Guerrero terrane in the south, confirming the autochthonous origin of the Jalisco Block rather than exotic arc or allochthonous origin. Geologic data, in combination with geochronologic and oxygen isotopic data, suggest the evolution of SW Mexico with an early 200–1,200-Ma passive margin, followed by steep subduction in a continental arc setting at 160–165 Ma, then shallower subduction by 135 Ma, and finally, emplacement of granitoids at 65–90 Ma.  相似文献