3. Use the 2:1 method to determine the change in stress at the top, middle, and bottom of the clay layer that is caused by construction and loading of the foundation. Use these values to Page 1 of 2 calculate the average change in stress for the clay layer that would be predicted using the 2:1 approach. 4. Use Boussinesq's equation (or charts) to determine the change in stress at the top, middle, and bottom of the clay layer that is caused by construction and loading of the foundation. Use these values to calculate the average change in stress for the clay layer that would be predicted by Boussinesq's elastic stress theory, following the approach presented in Equation 8.26 in your text. Compare your answer with the value predicted in Problem 3 - which is more conservative? 5. Calculate the total settlement of the foundation at the end of consolidation of the clay layer, using the average change in stress for the clay layer that would be predicted by Boussinesq's elastic stress theory (your answer from Problem 4). Ignore the effect of compression in the sand layer in your calculations, but don't forget to include the contribution of elastic clay settlement. Give your answer in inches. Lab analysis indicates that the clay is over- consolidated with a maximum past pressure of 1600 psf, a compression index of 0.3, a recompression index of 0.06, and a coefficient of vertical consolidation of 1.4 x 104 in²/sec. 6. Calculate the average degree of consolidation of the clay layer achieved 365 days (1 year) after the start of construction. What is the settlement in inches of the clay layer after 365 days? A 5 foot wide by 25 foot long footing is to be constructed over saturated clay as shown in the profile below. The total load applied at the base of the foundation, including the weight of the foundation itself and all other loads is estimated to be 375 kips. The modulus of elasticity of the clay is 300 ksf. D₁ = 4 ft 5 ft Sand G.W.T. 1 ft 13 ft Clay Rock Qapp = 375 kips (Includes weight of footing & all other loads) Rectangular footing, 5' x 25' Sand: Above G.W.T., partially saturated: Ym = 102 pcf Below G.W.T., saturated: Ysat = 111 pcf Clay: Below G.W.T., saturated: Ysat = 125 pcf e₁ = 0.8 Note: Drawing not to scale 1. Calculate the elastic settlement of the foundation due to elastic compression of the clay layer. Please present your answer in inches, and ignore the effect of compression in the sand layer in your calculations. 2. Determine the initial effective vertical stress at the center of the clay layer prior to construction of the foundation. 3. Use the 2:1 method to determine the change in stress at the top, middle, and bottom of the clay layer that is caused by construction and loading of the foundation. Use these values to Page 1 of 2