Study of hydraulic characteristics of aquifer in the path of East-West section of the tunnel line-7 of Tehran subway during mechanized excavation from the aspect of groundwater inflow into tunnel

Remarkable set of features havecaused of widespread applications of artificial ligthweight aggregates. According to their application in various industries, the mechanical properties of these aggregates are important. Due to the absence of bedrock, determination mechanical properties of artificial ligthweight aggregate have special complexity.Ligth expanded clay aggregate (LECA) is the only industrialized ligthweigth aggregates that use in structural concrete in our country at now, which are produced with different density. In this research, to determination the diameter effect on the specific gravity, water absorption, resistance to abrasion, impact and pressure, various tests have been done on four size of structural Leca. Since there is not a standard procedure to determine the elastic modulus of ligthweigth aggregate, the combination of experimental methods and theory of composite material is used to estimate this parameter. With the combination of ligthweigth aggregate and cement-sand mortar (matrix), cylindrical composite specimens with 30% and 40% volume fractions of aggregates were cast and their elastic parameters of them are determined. Then with differential method and using elastic parameters of composite specimens and matrix, elastic modulus of ligthweigth aggregates is calculated. Test results indicate a significant effect of the grain diameter on mechanical propertiesof aggregates which produced with the same condition.