F. Rezaie; H. Nazari; S. Rahmanian; A. R. Shahidi
Abstract
Due to the fast urban developing and construction of surface and sub-surface structures such as several subway lines, requiring the geotechnical studies on these structures is increasingly emphasized. The metropolitan Tehran, in south of the Central Alborz, lying on the set of Quaternary alluvial deposits ...
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Due to the fast urban developing and construction of surface and sub-surface structures such as several subway lines, requiring the geotechnical studies on these structures is increasingly emphasized. The metropolitan Tehran, in south of the Central Alborz, lying on the set of Quaternary alluvial deposits and surrounded by the active seismic faults such as the Northern Tehran fault in the north and the Parchin and Pishva faults in the south requires investigations to determine the bilateral relationship betweenseismic potential of the peripheral active faults andthe geotechnical characteristics of the alluvial deposits. In this study, using field and laboratory data, geotechnical characteristics of the deposits, material of soil horizons, and different parameters of them along the 27 km length of Tehran 7th subway line have been studied by provided software to calculate: bearing capacity, settlement and liquefaction potential. Based on this study, the members C and D of the Tehran alluvial deposits has relatively high resistance value and measured settlement in all areas is limited to 2.5 cm. The data of SPT indicate any likely occurrence of liquefaction of sand layers in the east - central Tehran during a seismic event.
F. Rezaei
Abstract
Behavior of sands under static and dynamic cyclic and monotonous loadings is the most common problem of Geotechnitiens.. This paper presents results of cyclic loading on loose and dense silica and carbonate sands using a modified direct shear box. The laboratory shear box was modified so that the lower ...
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Behavior of sands under static and dynamic cyclic and monotonous loadings is the most common problem of Geotechnitiens.. This paper presents results of cyclic loading on loose and dense silica and carbonate sands using a modified direct shear box. The laboratory shear box was modified so that the lower part of the box was composed of a metal plate with sand grains glued at its surface. Various test parameters such as sand type, sand density, interface conditions, number and form of cyclic loading were studied to explore behavior of soil-soil and soil-structure under naturally occurring loading conditions. Results showed that the two sand types tested demonstrate contraction behavior at the beginning but dilation performance later on. Shear and normal forces decreased during the tests; the decline was larger for carbonate sand than for the silica one. The reduction of shear and normal force increased with decreasing density of sand. This reduction behavior of forces in tests with zero displacement under cyclic loading is similar to the liquefaction phenomena and these results might be applied to evaluate liquefaction problem.
G. Barzegari; A. Uromeihy
Abstract
Development of liquefaction in saturated cohesionless deposits is one of the most dramatic causes of damage in civil structures during earthquakes. The potential damage caused by liquefaction includes: 1) loss of bearing capacity, 2) excessive settlement, 3) lateral spreading, 4) flow failure, and 5) ...
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Development of liquefaction in saturated cohesionless deposits is one of the most dramatic causes of damage in civil structures during earthquakes. The potential damage caused by liquefaction includes: 1) loss of bearing capacity, 2) excessive settlement, 3) lateral spreading, 4) flow failure, and 5) ground oscillation.
The liquefaction susceptibility of a specific deposit is affected by many factors for example, wave-induced liquefaction characteristics, soil type, geological history, confining pressure, permeability, relative density, water content, and properties of the soil grain size.
Chapar-Abad Dam is an inhomogeneous earth-fill dam with height and crest length of 44.5 and 427 meters, respectively. The reservoir capacity is 127 million cubic meters. The dam which is under construction is located about 75 km southeast of UromiehCity, in West-Azerbaijan province. The foundation materials include 60 meters of alluvium deposits overlying the bedrock layers of carbonate units. The abutments consist of carbonate and schistose layers of Precambrian age. In this paper the potential of liquefaction of the site is evaluated according to the SPT results form in-situ tests performed in boreholes driven into the depth of alluvial deposits. Furthermore, recently modified relations of correction factors such as stress reduction factor (rd), earthquake magnitude scaling factor for cyclic stress ratios (MSF), overburden correction factor for cyclic stress ratios (Ks), and the overburden normalization factor for penetration resistances (CN) are presented and used in liquefaction assessment of alluvial foundation at Chapar-Abad Dam. The results indicate the possibility of liquefaction and instability of granular soils during earthquake and any types of strong motions.
