A sand deposit has been identified beneath a site located adjacent to a river. The sand deposit is 30 feet thick and the top of the layer is 24 feet below the ground surface and overlain by a very stiff clay and is underlain by bedrock. The water level has been measured to be at a depth of 30 feet. The standard penetration resistance of the layer has been determined to be 20 blows per foot and a sampler without liners was used; a drill rig with a safety hammer with an efficiency of 60% was used. The length of the drill rod is 5 meters and the borehole diameter is 7.87 inches (200 mm). The design earthquake has been designated as a moment magnitude 7.5 event on a nearby fault and the maximum ground acceleration is expected to be 0.60 g. The wet unit weight of the clay soils is 200 pounds per cubic foot and the wet unit weight of the sand soils is 250 pounds per cubic foot. The sands have 45% fines content according to a grain size analysis. Determine the cyclic stress ratio, CSR. Express your answer in 2 decimal numbers only after the decimal place. (e.g. 0.26).

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A sample of sand is tested in a direct shear device to determine its angle of internal friction. Cross-sec tion dimensions of the shear box are 2.5" by 2.5". The sample is tested at a vertical normal force N of 100 lb and resulted in a maximum horizontal shear force T of 70 lb. (a) Assuming the sand is cohesionless, what is the angle of internal friction of this sand? (b) If a second test is conducted at a vertical normal force of 140 lb, what would be the anticipated maxi mum horizontal shear force T?

Please solve this problem and explain each step clearly, Please explain the theory and show your work clearly, I really want to understand. Thank you