Figure P9.18 shows the soil profile at a site for a proposed office building. It is expected that the vertical stress at the top of the clay will increase by 150 kPa and at the bottom by 90 kPa. Assuming a linear stress distribution within the clay, calculate the consolidation settlement. (Hint: You should divide the clay into five equal layers, compute the settlement for each layer, and then find the total settlement.) Groundwater level is at the top of the clay layer. An oedometer test on a sample of the clay revealed that 90% consolidation on a 20-mm-thick sample occurred in 40 minutes. The sample was drained on the upper and lower boundaries. How long will it take for 50% consolidation to occur in the field?
