Seismic response evaluation of base-isolated reinforced concrete buildings under bidirectional excitation

This paper reports on an investigation of the seismic response of base-isolated reinforced concrete buildings, which considers various isolation system parameters under bidirectional near-fault and far-fault motions. Three-dimensional models of 4-, 8-, and 12-story base-isolated buildings with nonlinear effects in the isolation system and the superstructure are investigated, and nonlinear response history analysis is carried out. The bounding values of isolation system properties that incorporate the aging effect of isolators are also taken into account, as is the current state of practice in the design and analysis of base-isolated buildings. The response indicators of the buildings are studied for near-fault and far-fault motions weight-scaled to represent the design earthquake (DE) level and the risk-targeted maximum considered earthquake (MCE_R) level. Results of the nonlinear response history analyses indicate no structural damage under DE-level motions for near-fault and far-fault motions and for MCE_R-level far-fault motions, whereas minor structural damage is observed under MCE_R-level near-fault motions. Results of the base-isolated buildings are compared with their fixed-base counterparts. Significant reduction of the superstructure response of the 12-story base-isolated building compared to the fixed-base condition indicates that base isolation can be effectively used in taller buildings to enhance performance. Additionally, the applicability of a rigid superstructure to predict the isolator displacement demand is also investigated. It is found that the isolator displacements can be estimated accurately using a rigid body model for the superstructure for the buildings considered.     

The paleogeographic significance of Aquilapollenites occurrence in Pakistan

The occurrence of the genus Aquilapollenites in Upper Cretaceous and Neogene sediments of northwestern Pakistan is reported here. Aquilapollenites amplus, Aquilapollenites reductus, and Aquilapollenites sp. occur in the Maastrichtian palynomorph assemblage from an outcrop sample of the Mir Ali section, northern Waziristan. Aquilapollenites medeis in the Neogene Murgha Faqir Zai Formation of the Pishin Basin, Balochistan, is considered a reworked Cretaceous specimen. The Upper Cretaceous sediments of the Asian plate on the Tethys margin are considered to be the source of Aquilapollenites spp. in these samples.     

Multiple growth of garnet,sillimanite/kyanite and monazite during amphibolite facies metamorphism: implications for the P–T–t and tectonic evolution of the western Altai Range,Mongolia

Four amphibolite facies pelitic gneisses from the western Mongolian Altai Range exhibit multistage aluminosilicate formation and various chemical‐zoning patterns in garnet. Two of them contain kyanite in the matrix and sillimanite inclusions in garnet, and the others have kyanite inclusions in garnet with sillimanite or kyanite in the matrix. The Ca‐zoning patterns of the garnet are different in each rock type. U–Th–Pb monazite geochronology revealed that all rock units experienced a c. 360 Ma event, and three of them were also affected by a c. 260 Ma event. The variations in the microstructures and garnet‐zoning profiles are caused by the differences in the (i) whole‐rock chemistry, (ii) pressure conditions during garnet growth at c. 360 Ma and (iii) equilibrium temperatures at c. 260 Ma. The garnet with sillimanite inclusions records an increase in pressure at low‐P (~5.2–7.2 kbar) and moderate temperature conditions (~620–660 °C) at c. 360 Ma. The garnet with kyanite inclusions in the other rock types was also formed during an increase in pressure but at higher pressure conditions (~7.0–8.9 kbar at ~600–640 °C). The detrital zircon provenance of all the rock types is similar and is consistent with that from the sedimentary rocks in the Altai Range, suggesting that the provenance of all the rock types was a surrounding accretionary wedge. One possible scenario for the different thermal gradient is Devonian ridge subduction beneath the Altai Range, as proposed by several researchers. The subducting ridge could have supplied heat to the accretionary wedge and elevated the geotherm at c. 360 Ma. The differences in the thermal gradients that resulted in varying prograde P–T paths might be due to variations in the thermal regimes in the upper plate that were generated by the subducting ridge. The c. 260 Ma event is characterized by a relatively high‐T/P gradient (~25 °C km^?1) and may be due to collision‐related granitic activity and re‐equilibrium at middle crustal depths, which caused the variations in the aluminosilicates in the matrix between the rock units.     

Multilevel Graph Partitioning for Three-Dimensional Discrete Fracture Network Flow Simulations

Mathematical Geosciences - We present a topology-based method for mesh-partitioning in three-dimensional discrete fracture network (DFN) simulations that takes advantage of the intrinsic...     

Plug shaped burrows <Emphasis Type="Italic">Conichnus - Conostichus</Emphasis> from the Late Cretaceous of Bagh Group,Gujarat, western India

Plug-shaped ichnofossils Conichnus conicus, Conostichus broadheadi and C. stouti are found in the intercalated micritic sandstone and sandy allochemic limestone shale sequence of Bagh Group, Narmada district, Gujarat. These ichnospecies occur at two stratigraphic levels and shows distinct morphological features interpreted as resting/dwelling structures of sea anemone. The occurrence of these ichnospecies along with oyster fossils genera like Bosostrea and Indostrea indicate shallow marine environment.     

Spectral Analysis of Magnetic data in the Ajmer-Sambar Sector,North-Central Rajasthan

Ajmer-Sambar sector of Delhi fold belt, North-Central Rajasthan has got importance due to its litho characters, structure, metamorphism, magmatism, migmatisation, metallogeny and rich potential of base metal mineralization. This sector is comprised of Delhi sequence of rocks hosted by the Banded Gneisses Complex (BGC). In view of the significance of this region, ground magnetic survey was conducted along six regional profiles to understand the structural features, magnetic nature of the basement and depth to the basement. Analysis of the magnetic data has clearly identified two magnetic lineaments (a) L1 in WNW-ESE direction that appears to represent litho-contact between Kalyanpura sequences in the south to Anasagar migmatite in the north and (b) L2 in NNW to SSE direction south of Parvatsar which is inferred to be a structural control about which the quartzite rocks of Taragarh Formation culminate. An average depth to basement of 3.7 km is estimated through spectral analysis of magnetic data. The maximum depth of the basin 4.5 km is estimated in central part of the study area. The obtained depth results are in good agreement with the Cummulative Total Intensity Magnetic Anomaly field (CTIMAF) and Deep seismic stuides.     

Stratigraphy and Sedimentology of Middle Jurassic Sequence of Chorar Island,Patan District,Kachchh Basin,Gujarat

Chorar Island exposes ～109 m thick middle Jurassic (Bathonian-Callovian) succession in the eastern most part of the Kachchh Basin, Patan District, Gujarat and is divided into two, Khadir and Gadhada formations. It mainly comprises of mixed siliciclastic-carbonate sediments and limestones; the shales dominate the lower part of the succession while the top of the succession is marked by ferruginous sandstone which also forms the vast, prominent peripheral zone of the Chorar dome. The field and laboratory analysis of the succession reveals nine lithofacies which includes ferruginous sandstone, cross bedded white sandstone, micritic sandstone, allochemic sandstone, sandy micrite, mudstone, sandy allochemic limestone, coralline limestone and shale. The mix siliciclastic-carbonate sediments and ferruginous facies are fossiliferous in nature and display sedimentary structures, like ripple marks, cross- and planar- lamination with biogenic sedimentary structures. Coralline limestone facies comprise of large size (>1m diameter) corals, which are diagenetically modified severely and have lost its original internal structures. The sediment characteristics and associated bioclasts indicates low to moderate wave and current energy in shoreface-offshore subsequently changing to wave dominated shoreface during the deposition of the middle Jurassic sediments of the Chorar Island.     

Robust system size reduction of discrete fracture networks: a multi-fidelity method that preserves transport characteristics

We propose a multi-fidelity system reduction technique that uses weighted graphs paired with three-dimensional discrete fracture network (DFN) modelling for efficient simulation of subsurface flow and transport in fractured media. DFN models are used to simulate flow and transport in subsurface fractured rock with low-permeability. One method to alleviate the heavy computational overhead associated with these simulations is to reduce the size of the DFN using a graph representation of it to identify the primary flow sub-network and only simulate flow and transport thereon. The first of these methods used unweighted graphs constructed solely on DFN topology and could be used for accurate predictions of first-passage times. However, these techniques perform poorly when predicting later stages of the mass breakthrough. We utilize a weighted-graph representation of the DFN where edge weights are based on hydrological parameters in the DFN that allows us to exploit the kinematic quantities derivable a posteriori from the flow solution obtained on the graph representation of the DFN to perform system reduction and predict the later stages of the breakthrough curve with high fidelity. We also propose and demonstrate the use of an adaptive pruning algorithm with error control that produces a pruned DFN sub-network whose predicted mass breakthrough agrees with the original DFN within a user-specified tolerance. The method allows for the level of accuracy to be a user-controlled parameter.     

Role of geophysical and hydrogeological techniques in EIA studies to identify TSDF site for industrial waste management

This paper deals with the importance of integrated hydrogeological, geological and geophysical applications in identifying suitable site for treatment, storage and disposal facility (TDSF) for industrial waste management. The pollution control authorities (Civic body) have a mandate to provide proper TSDF for the industrial zones. One such zone of 2800 acres, established by State Industries Promotion Corporation of Tamil Nadu (SIPCOT) at Perundurai in southern India, is selected to identify suitable TSDF site. The zone is envisaged to cater 22500 MTA (metric tones per annum) of industrial waste generated by 565 units. Hydrogeological and geological setup forms an important criterion in the process of environmental impact assessment (EIA) to establish proposed activity. Hydrogeological, geophysical and socio-economic/ecological studies were carried out to identify suitable TSDF site. Vertical electrical sounding (VES), multi-electrode resistivity imaging (MERI), ground penetrating radar (GPR) scanning, and infiltration tests were performed within the proposed TSDF site of 50 acres land. An inventory of 54 key wells includes depth to water level (varies from 9.7 to 15 m, below ground level) and water chemistry (pH, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, HCO ₃ ^? , SO ₄ ^2? , NO ₃ ^? and F^?) helped in identifying physical environment around (5 km radius) proposed TSDF site. Geophysical and hydrogeological investigations verified with drillings (at 5 locations) within the proposed TSDF site resulted, shallow hard rock at 4.5 m depth, the absence of groundwater, and low infiltration rate (4.3 cm/hour) of soil in the western side (45 acres) of proposed 50 acres land reveals suitability of TSDF site.