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The anisotropy of sand–silt mixtures has not been fully studied in terms of the effects of different grain shapes and silt content. This study investigated the effects on anisotropy in three different sands with various silt contents and grain shapes. The tests performed in this research include 90 hollow cylinder torsion shear tests conducted on three types of sand: Hamadan sand with high angularity, Firoozkuh sand with medium angularity and Tehran sand with low angularity. The samples had silt contents of 0, 15, 30 and 50 per cent. To define the shape criteria in this study, two ratios were defined. The first was roundness, which can be obtained from the ratio of the radius of the corners of the grains to the largest circle that encompasses the entire grain; this ratio is denoted by rr. The second criterion was sphericity, which can be obtained by dividing the smallest pictorial width by the minimum graphical length; this ratio is denoted by rs. Under similar initial effective confining pressures, sand with high roundness and sphericity showed contractive behaviours. An increase in silt content, as well as in the ratios rr and rs, decreased the sample strength. Moreover, increasing these two ratios caused the stress–strain curves to be close to one another.

Construction project is a competitive business with high risk especially in developing countries like Iran which faces with many problems such as delay and time and costs increases. Thus, the first priority here is to determine the causes of prolongation of construction projects and to evaluate their importance. Khuzestan Steel Company (KSC) has made important contribution to the projects in Iran and in turn is required to finish them on time. In this study, an attempt was made to investigate the causes of delay in implementation of construction projects held by this company. Data was collected through questionnaire distributed among the sample including 10 owners, 10 consultants and 15 contractors. Accordingly, participants rated the causes in the questionnaire so the most important priorities of each area were specified using TOPSIS method. The results showed that according to the employers, consultants and contractors' viewpoints, the most important reason for delays in construction projects of KSC is related to the financial matters. Hence, according to the results obtained, causes for delays in the company's projects are largely related to the drilling permits and long administrative cycle to renew them. Besides, continuous production of steel in this company is another reason to delays of construction projects.

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