Quasi‐static analysis of elastic behavior for some systems having higher fracture densities

Elastic behavior of geomechanical systems with interacting (but not intersecting) fractures is treated using generalizations of the Backus and the Schoenberg–Muir methods for analyzing layered systems whose layers are intrinsically anisotropic due to locally aligned fractures. By permitting the axis of symmetry of the locally anisotropic compliance matrix for individual layers to differ from that of the layering direction, we derive analytical formulas for interacting fractured regions with arbitrary orientations to each other. This procedure provides a systematic tool for studying how contiguous, but not yet intersecting, fractured domains interact, and provides a direct (though approximate) means of predicting when and how such interactions lead to more dramatic weakening effects and ultimately to failure of these complicated systems. The method permits decomposition of the system elastic behavior into specific eigenmodes that can all be analyzed, and provides a better understanding about which of these specific modes are expected to be most important to the evolving failure process. Copyright © 2009 John Wiley & Sons, Ltd.     

The Importance of Chert in Central Anatolia: Lessons from the Neolithic Assemblage at Çatalhöyük,Turkey

This paper is a presentation of three sources of artifact‐quality chert in Central Anatolia. A previous dearth of research focused on locating and characterizing such raw material sources has incorrectly colored our view of prehistoric economic practices. To remedy this situation, we have conducted a survey of various locales within Central Anatolia to test for the presence of artifact‐quality materials. We make use of Individual Attribute Analysis (IAA) and Energy Dispersive X‐ray Fluorescence (EDXRF) analysis to discriminate among these materials, and suggest their use by the Neolithic occupants of Çatalhöyük through similar analyses of artifactual materials. We argue that the presence and characterization of these new sources allows us to better understand the intricacies of Neolithic practices by illustrating the ways in which the consumption of these materials was variably entwined with the exploitation of other resources, as well as embedded within social relations outside of Central Anatolia. © 2013 Wiley Periodicals, Inc.     

Quantifying climate-induced drought risk to livelihood and mitigation actions in Balochistan

Natural Hazards - Climate change-induced disasters show the highest risk for agriculture and livelihoods in rural areas of developing countries. Due to changing rainfall pattern, the arid and...     

Recycling of abrasives in abrasive water jet cutting with different types of granite

The cost of abrasives has restricted usage of abrasive water jet (AWJ) technology in natural stone cutting applications. However, recycling of the abrasives makes the technology more economical, effective, and environmentally friendly. In this study, significant rock properties affecting the recycling of abrasives in AWJ cutting of granites are investigated. Abrasive mass percentage above 106 μm (AMP_106μm) is considered as a performance criterion in terms of recycling of abrasives since these abrasives can be effectively reused in the rock cutting applications. The study reveals that a considerable amount of used abrasives is in a reusable form. Among the rock properties, the microhardness is statistically determined as the most significant rock property affecting the AMP_106μm. It is also concluded that theAMP_106μm can be explained with high accuracy by the proposed model including the microhardness, the quartz content, and the plagioclase content.     

A precise gravimetric geoid model in a mountainous area with scarce gravity data: a case study in central Turkey

In mountainous regions with scarce gravity data, gravimetric geoid determination is a difficult task that needs special attention to obtain reliable results satisfying the demands, e.g., of engineering applications. The present study investigates a procedure for combining a suitable global geopotential model and available terrestrial data in order to obtain a precise regional geoid model for Konya Closed Basin (KCB). The KCB is located in the central part of Turkey, where a very limited amount of terrestrial gravity data is available. Various data sources, such as the Turkish digital elevation model with 3 ?? × 3?? resolution, a recently published satellite-only global geopotential model from the Gravity Recovery and Climate Experiment satellite (GRACE) and the ground gravity observations, are combined in the least-squares sense by the modified Stokes?? formula. The new gravimetric geoid model is compared with Global Positioning System (GPS)/levelling at the control points, resulting in the Root Mean Square Error (RMS) differences of ±6.4 cm and 1.7 ppm in the absolute and relative senses, respectively. This regional geoid model appears to be more accurate than the Earth Gravitational Model 2008, which is the best global model over the target area, with the RMS differences of ±8.6 cm and 1.8 ppm in the absolute and relative senses, respectively. These results show that the accuracy of a regional gravimetric model can be augmented by the combination of a global geopotential model and local terrestrial data in mountainous areas even though the quality and resolution of the primary terrestrial data are not satisfactory to the geoid modelling procedure.     

Use of joint-growth directions and rock textures to infer thermal regimes during solidification of basaltic lava flows

Thermal contraction joints form in the upper and lower solidifying crusts of basaltic lava flows and grow toward the interior as the crusts thicken. Lava flows are thus divided by vertical joints that, by changes in joint spacing and form, define horizontal intraflow layers known as tiers. Entablatures are tiers with joint spacings less than about 40 cm, whereas colonnades have larger joint spacings. We use structural and petrographic methods to infer heat-transfer processes and to constrain environmental conditions that produce these contrasting tiers. Joint-surface morphology indicates overall joint-growth direction and thus identifies the level in a flow where the upper and lower crusts met. Rock texture provides information on relative cooling rates in the tiers of a flow. Lava flows without entablature have textures that develop by relatively slow cooling, and two joint sets that usually meet near their middles, which indicate mostly conductive cooling. Entablature-bearing flows have two main joint sets that meet well below their middles, and textures that indicate fast cooling of entablatures and slow cooling of colonnades. Entablatures always occur in the upper joint sets and sometimes alternate several times with colonnades. Solidification times of entablature-bearing flows, constrained by lower joint-set thicknesses, are much less than those predicted by a purely conductive cooling model. These results are best explained by a cooling model based on conductive heat transfer near a flow base and water-steam convection in the upper part of an entablature-bearing flow. Calculated solidification rates in the upper parts of such flows exceed that of the upper crust of Kilauea Iki lava lake, where water-steam convection is documented. Use of the solidification rates in an available model of water-steam convection yields permeability values that agree with measured values for fractured crystalline rock. We conclude, therefore, that an entablature forms when part of a flow cools very rapidly by water-steam convection. Flooding of the flow top by surface drainage most likely induces the convection. Colonnades form under conditions of slower cooling by conductive heat transfer in the absence of water.     

iSERVO: Implementing the International Solid Earth Research Virtual Observatory by Integrating Computational Grid and Geographical Information Web Services

We describe the goals and initial implementation of the International Solid Earth Virtual Observatory (iSERVO). This system is built using a Web Services approach to Grid computing infrastructure and is accessed via a component-based Web portal user interface. We describe our implementations of services used by this system, including Geographical Information System (GIS)-based data grid services for accessing remote data repositories and job management services for controlling multiple execution steps. iSERVO is an example of a larger trend to build globally scalable scientific computing infrastructures using the Service Oriented Architecture approach. Adoption of this approach raises a number of research challenges in millisecond-latency message systems suitable for internet-enabled scientific applications. We review our research in these areas.     

Comparison of two snowmelt modelling approaches in the Dudh Koshi basin (eastern Himalayas,Nepal)

Abstract

The glaciers in the Nepalese Himalayas are retreating due to rising temperatures. Lack of data and information on Nepal’s cryosphere has impeded scientific studies and field investigations in the Nepalese Himalayas. Therefore, IRD France and Ev-K2 CNR Italy have conducted the PAPRIKA (CryosPheric responses to Anthropogenic PRessures in the HIndu Kush-Himalaya regions: impacts on water resources and society adaptation in Nepal) project in Nepal with the financial support of the French and Italian scientific agencies. This project aims to address the current and future evolution of the cryosphere in response to overall environmental changes in South Asia, and its consequences for water resources in Nepal. Thus, two hydrological models, the GR4J lumped precipitation–runoff model and the snowmelt runoff model (SRM), were used in the Dudh Koshi basin. The GR4J model has been successfully applied in different parts of Europe. To obtain better results in such a harsh and rugged topography, modifications needed to be made, particularly in the snow module. The runoff pattern is analysed herein both for past years and, in a sensitivity analysis, for possible future climatic conditions (i.e. precipitation and temperature) using the SRM and GR4J modelling approaches. The results reveal a significant contribution of snow- and glacier-melt to runoff, and the SRM model shows better performance in Nepalese catchments than the GR4J model.

Editor D. Koutsoyiannis; Associate editor D. Gerten     

Tunnelling in difficult ground: a case study from Dranaz tunnel, Sinop, Turkey

This paper presents a case study of the instability mechanisms, and the excavation sequence, re-qualification and reinforcement methods adopted to pass through a short segment of a nearly 2-km tunnel built as part of a new 55-km state highway in northern Turkey. The instability problems were encountered during tunnel excavation due to the failure to recognize the fact that alteration in stress field and resulting deformation could cause dilation and increase in the permeability of claystone-shale layers and local fault gouge zones, and in turn significant reduction in shear strength. Change in natural drainage pattern and capillarity exacerbated saturation and the consequent strength reduction. The 92-m³ loose material flowed into the tunnel due to the collapse and caused 2.5 months of delay in completion of the tunnel. Longitudinal and oblique cracks observed in shotcrete were attributed to the reduction in modulus upon saturation, which caused a large cumulative deformation of approximately 110 mm at a section about 30 m behind the collapse face.

It is concluded that early detection or prediction of potentially problematic zones (via probe drilling and monitoring) in tunnelling is of paramount importance, especially through mixed or difficult ground conditions characterized by alternating layers, folding, faulting and localized zones of high water pressure. Because mechanical detection methods cannot be fully relied upon, availability of experienced personnel to predict and deal with such instability problems effectively and promptly is the best insurance for successful completion of tunnelling contracts.