Evaluating land subsidence by field survey and D-In SAR technique in Damaneh City, Iran

Based on the data from piezometers, well logs, geophysical surveys and the interferometric synthetic aperture radar（In SAR） technique, this study investigates the main causes of land subsidence in Damaneh City, Iran. The size, openings and direction of fissures were measured by micrometer and compass. The locations of fissures and wall cracks were determined by GPS. The geoelectrical data were used to determine the composition, thickness, depth and shape of lower parts of the aquifer. Groundwater fluctuations were evaluated by available piezometers. The In SAR technique was used to measure land deformation from space and to map the dense changes of surface displacements. The results indicate that the main cause of ground subsidence is the decline of groundwater heads and changes in composition and thickness of compressible lacustrine sediments. The subsidence map obtained from the radar data of ASAR sensor of ENVISAT satellite shows that the subsidence zone is mainly in northern city that is underlain by very thick fine sediments. The subsidence rates from March to December 2005 and from July 2011 to January 2012 are 6.7 and 7.0 cm/a, respectively. The results also show good correlations among the formation of earth features, decline in groundwater head and thickness of fine-grained sediments. We recommend that the groundwater withdrawal for agricultural and industrial sectors should be restricted and urban expansion in the northern part of the city should be constrained.

Modeling of Land Subsidence in the South Pars Gas Field (Iran)

The objective of this study is to predict the subsidence of the South Pars gas field at the end of production period. With respect to the notable reservoir thickness, significant pressure drop due to extraction and high areal extent of the South Pars gas field there is a high subsidence potential in this field. In order to determinate the maximum land subsidence and subsidence profile of the South Pars gas field, at first, the reservoir compaction was estimated based on the thickness of the reservoir, the pressure drop in the reservoir and the uniaxial compaction coefficient of the reservoir rock, and then the effect of the reservoir compaction on the field surface was modeled with the use of analytical and semi-numerical methods. The compaction of the reservoir at the end of production period was estimated to be about 0.48 m. Both of the subsidence modeling methods show similar results and predict that the maximum subsidence will reach about 0.6 m at the end of production period.

Discontinuous rock slope stability analysis by limit equilibrium approaches–a review

Slope stability is one of the most important topics of engineering geology with a background of more than 300 years.So far,various stability assessment techniques have been developed which include a range of simple evaluations,planar failure,limit state criteria,limit equilibrium analysis,numerical methods,hybrid and high-order approaches which are implemented in two-dimensional(2D)and three-dimensional(3D)space.In the meantime,limit equilibrium methods due to their simplicity,short analysis time,coupled with probabilistic and statistics functions to estimate the safety factor(F.S),probable slip surface,application on different failure mechanisms,and varied geological conditions has been received special attention from researchers.The presented paper provides a review to limit equilibrium methods used for discontinuous rock slope stability analyses with different failure mechanisms of natural and cut slopes.The article attempted to provide a systematic review for rock slope stability analysis outlook based on limit equilibrium approaches.