Question 4 [30 marks Figure Q-4 shows a 7m deep excavation in a 3-layer clay system supported using sheet-pile walls with a single level of struts. The surcharge loading and material parameters indicated on the figure are the unfactored values. Using the unfactored loading and soil parameters in your calculations: (i) Sketch, clearly and legibly, the lateral earth pressure diagram that acts on the sheet-pile wall. Write down the pressure values and equivalent forces at key locations on your diagram. [12 marks] (ii) Calculate the embedment depth D required to maintain wall stability. [3 marks] (11) Calculate the corresponding strut force. [3 marks] (iv) Calculate the theoretical maximum moment in the wall and its depth of occurrence (from the top of the wall). [6 marks] (v) Calculate the factor of safety of the excavation system against basal heave. [6 marks] Please state clearly any assumptions you make. 20 kN/m2 20 kN/m2 14m 2m 3m Upper Clay strut 11= 15 kN/m Sul = 15 kN/m2 4m Middle Clay Y2 = 15 kN/m Su2 = 25 kN/m2 D Lower Clay 16m Y3= 17 kN/m3 Su3 = 35 kPa Dense Sand Figure Q-4 Question 4 [30 marks Figure Q-4 shows a 7m deep excavation in a 3-layer clay system supported using sheet-pile walls with a single level of struts. The surcharge loading and material parameters indicated on the figure are the unfactored values. Using the unfactored loading and soil parameters in your calculations: (i) Sketch, clearly and legibly, the lateral earth pressure diagram that acts on the sheet-pile wall. Write down the pressure values and equivalent forces at key locations on your diagram. [12 marks] (ii) Calculate the embedment depth D required to maintain wall stability. [3 marks] (11) Calculate the corresponding strut force. [3 marks] (iv) Calculate the theoretical maximum moment in the wall and its depth of occurrence (from the top of the wall). [6 marks] (v) Calculate the factor of safety of the excavation system against basal heave. [6 marks] Please state clearly any assumptions you make. 20 kN/m2 20 kN/m2 14m 2m 3m Upper Clay strut 11= 15 kN/m Sul = 15 kN/m2 4m Middle Clay Y2 = 15 kN/m Su2 = 25 kN/m2 D Lower Clay 16m Y3= 17 kN/m3 Su3 = 35 kPa Dense Sand Figure Q-4