Spatial analysis of a historical phenomenon: using GIS to demonstrate the strategic placement of Umayyad desert palaces

The Umayyad qusour (desert palaces) are monumental structures built during the reign of the first caliphate of Islam. Usually dismissed as “pleasure palaces” or “hunting lodges,” some scholars are beginning to argue that these prominent structures were strategic interventions in the landscape. Until now, historians have relied mainly on textual, architectural and art-historical analyses of the qusour in order to understand Umayyad state architecture. This research proposes the use of spatial analysis through GIS to lend a new dimension to the discussion. The results of the analysis show that Umayyad qusour are carefully situated at routes of transhumance and water sources. The distribution pattern of the Umayyad qusour is clustered at the outlet of Wadi Sarhan, and there is actually line-of-sight communication between Azraq, Amra, Haranah, Muwaqqar, Umm al Walid, Mushatta, and Qastal. There is also a positive association between Umayyad qusour and their water sources. These results support the argument that the Umayyad qusour were built strategically at perennial water sources in order to monitor routes of transhumance amongst the socio-political centers of the period.     

Mechanical and Elastic Properties of Transversely Isotropic Slate

Planes of weakness like schistosity and foliation affect the strength and deformational behaviors of rocks. In this paper, an attempt has been made to study the elastic and strength behavior of slate rocks obtained from foundation of Sardasht dam site in Iran. Wet and dry specimens with different orientation of foliation were evaluated under uniaxial, triaxial, and Brazilian tests. According to the results obtained, slate mechanically pronounced U-shaped anisotropy in uniaxial and triaxial compression tests. In addition, the degree of anisotropy for the slates tested in current study was relatively high, showing the effect of foliation plane on strength and elastic parameters. It was concluded that stiffness of the samples decrease as the angle of anisotropy reaches 30–40°. This change was more pronounced for wet comparing to dry samples. However, the tensile strength obtained during Brazilian tests indicated that there is no apparent relationship between angle of anisotropy and tensile strength. However, increasing the water saturation decreased the tensile strength of the samples. The calculated elastic moduli referring to different anisotropy angles could be valuable for the design of various engineering structures in planar textured rock masses.     

A modi?ed failure criterion for transversely isotropic rocks

A modified failure criterion is proposed to determine the strength of transversely isotropic rocks. Me-chanical properties of some metamorphic and sedimentary rocks including gneiss, slate, marble, schist, shale, sandstone and limestone, which show transversely isotropic behavior, were taken into consider-ation. Afterward, introduced triaxial rock strength criterion was modified for transversely isotropic rocks. Through modification process an index was obtained that can be considered as a strength reduction parameter due to rock strength anisotropy. Comparison of the parameter with previous anisotropy in-dexes in literature showed reasonable results for the studied rock samples. The modified criterion was compared to modified Hoek-Brown and Ramamurthy criteria for different transversely isotropic rocks. It can be concluded that the modified failure criterion proposed in this study can be used for predicting the strength of transversely isotropic rocks.     

Study of the Engineering Geological Problems of the Havasan Dam,with Emphasis on Clay-Filled Joints in the Right Abutment

Havasan dam site is located in northwest of Iran. The planned concrete dam is to be built on Cretaceous limestone. Faulted and fractured limestone is exposed at the dam abutments and in the reservoir area. Rock mass properties including the deformation modulus and uniaxial compressive strength were calculated using different rock mass classification systems (RMR, Q, GSI and DMR). Laboratory tests indicate that joint filling materials contain clay with low to high plasticity (CL to CH) and low to medium potential swelling pressures. X-ray diffraction analysis confirms that the reason for potential swelling of joint fillings is the existence of clay minerals (such as illite and montmorillonite). The study results about the shear strength of clay-filled joints show that under JRC–JCS condition (laboratory scale), JRC _n –JCS _n (large scale) and normal stress equal to 0.25–4 MPa, the range of shear strength of clay-filled joints will be equal to 0.2–2.17 and 0.14–1.72 MPa. In some areas dissolution along the joints results in high permeability, especially in the right abutment. Three dominant joint sets occur in the exploration galleries which have been excavated in the right abutment. The maximum aperture of these joints varies from 7 to 9 cm, and the joints are typically filled with clay. Preliminary analysis shows that the presence of open joints which will cause seepage of water, combined with the impact of the clay-filled joints and forces acting on the slopes, could lead to slope failures and rock falls. In addition, the assessment of slope stability results in abutments using limited equilibrium method and Swedge software under dynamic and static conditions shows that two wedges formed on the slopes of the abutment by the natural joints are potentially unstable. The rock wedge on the left abutment is smaller but presents higher sliding potential. In addition, there is no probability of planar failure due to the geological condition of the dam abutments. This paper summarizes the site investigation and subsequent analysis, which resulted in a recommendation not to construct this site. We offer some potential mitigation plans to consider if a dam were to be built at this site.     

Petrographic, mineralogy, and geochemistry of coals of Pabedana, Kerman Province, Central Iran

This paper discusses the result of the detailed investigations carried out on the coal characteristics, including coal petrography and its geochemistry of the Pabedana region. A total of 16 samples were collected from four coal seams d2, d4, d5, and d6 of the Pabedana underground mine which is located in the central part of the Central-East Iranian Microcontinent. These samples were reduced to four samples through composite sampling of each seam and were analyzed for their petrographic, mineralogical, and geochemical compositions. Proximate analysis data of the Pabedana coals indicate no major variations in the moisture, ash, volatile matter, and fixed carbon contents in the coals of different seams. Based on sulfur content, the Pabedana coals may be classified as low-sulfur coals. The low-sulfur contents in the Pabedana coal and relatively low proportion of pyritic sulfur suggest a possible fresh water environment during the deposition of the peat of the Pabedana coal. X-ray diffraction and petrographic analyses indicate the presence of pyrite in coal samples. The Pabedana coals have been classified as a high volatile, bituminous coal in accordance with the vitrinite reflectance values (58.75–74.32 %) and other rank parameters (carbon, calorific value, and volatile matter content). The maceral analysis and reflectance study suggest that the coals in all the four seams are of good quality with low maceral matter association. Mineralogical investigations indicate that the inorganic fraction in the Pabedana coal samples is dominated by carbonates; thus, constituting the major inorganic fraction of the coal samples. Illite, kaolinite, muscovite, quartz, feldspar, apatite, and hematite occur as minor or trace phases. The variation in major elements content is relatively narrow between different coal seams. Elements Sc,, Zr, Ga, Ge, La, As, W, Ce, Sb, Nb, Th, Pb, Se, Tl, Bi, Hg, Re, Li, Zn, Mo, and Ba show varying negative correlation with ash yield. These elements possibly have an organic affinity and may be present as primary biological concentrations either with tissues in living condition and/or through sorption and formation of organometallic compounds.     

Implicit structural inversion of gravity data using linear programming,a validation study*

In this study, a regional scale gravity data set has been inverted to infer the structure (topography) of the top of the basement underlying sub‐horizontal strata. We apply our method to this real data set for further proof of concept, validation and benchmarking against results from an earlier forward modelling done elsewhere. Our aim is to carry out implicit structural inversion, i.e., to obtain a geologically reasonable model, without specifically solving for structure. The 2.5D volume of interest is parametrized with homogeneous horizontal prisms and a two‐lithology medium is assumed. A possible regional linear trend and a general floating reference are also inverted for. Using a gridded parametrization, linear programming is used to minimize the L₁ ‐norm of the data misfit, relative to a floating reference. Given a known density contrast between the lithologies, an inversion using linear programming has the intrinsic advantage that a relatively sharp image of the sub‐surface is retrieved instead of a smooth one. The model recovered is almost bi‐modal and its general features seem to be robust with respect to several parametrization scenarios investigated. The floating reference and a linear trend in the data were also retrieved simultaneously. The inversion results, indicating two depressions in the basement, are robust and agree with those obtained earlier based upon detailed 2D forward modelling using many narrow, near‐vertical prisms.     

Shear wave velocity prediction using seismic attributes and well log data

Formation’s properties can be estimated indirectly using joint analysis of compressional and shear wave velocities. Shear wave data is not usually acquired during well logging, which is most likely for cost saving purposes. Even if shear data is available, the logging programs provide only sparsely sampled one-dimensional measurements: this information is inadequate to estimate reservoir rock properties. Thus, if the shear wave data can be obtained using seismic methods, the results can be used across the field to estimate reservoir properties. The aim of this paper is to use seismic attributes for prediction of shear wave velocity in a field located in southern part of Iran. Independent component analysis (ICA) was used to select the most relevant attributes to shear velocity data. Considering the nonlinear relationship between seismic attributes and shear wave velocity, multi-layer feed forward neural network was used for prediction of shear wave velocity and promising results were presented.     

Lithotype discrimination within a gridded model by inverting gravity data

In this paper we present a method which allows delineation of geologic structures in a bi-modal lithotype setting. We propose to use gravity data in combination with a priori information about the density contrast between the two lithotypes. The iterative method uses an objective function with five tunable parameters which need to be set. Using an efficient parameter search, suitable ranges of these are investigated to determine their optimal values, respectively, which in turn, ensures good inversion results.
The approach produces structural images of the subsurface, without the need of an a priori density model; the depth to the top of the inhomogeneity is also retrieved.
Besides synthetic simulations, the methodology has also been applied to a small gravity data set, acquired by the industry over a basinal structure. A consistent, bi-modal image of the bedrock depression is obtained from the data, which, in this case, was the goal. Other potential areas of application include delineation of salt structures and ore deposits.