Students are to INDIVIDUALLY complete and submit their responses to: 1. [6 marks] Pick one of the three case histories from Mr. Lostumbo’s Guest Lecture onGeosynthetics. a) Identify and describe the function(s) served by the geosynthetic.b) What properties of the geosynthetic are required to serve that function.c) Describe how you would obtain those parameters.2. [6 marks] The force-displacement results from wide-width tensile tests are given for threegeosynthetics in Figs 1-3. Note that “WARP” refers to the primary load carrying direction and that the “FILL” direction is orthogonal to the WARP direction. a) For GT1 (Fig. 1), explain why the WARP direction is much stronger and stiffer than the FILLdirection. b) For GT1 (Fig. 1), calculate the initial tangent modulus, the tangent modulus from 5-10% strainand the secant modulus at 5% strain. Explain the difference between the 3 modulus parameters for this particular geotextile. c) Calculate and tabulate the maximum tensile strength, strain at failure and secant modulus for 0to 5% elongation for GT1, GT2 and GG1 (Figs 1-3). Report values for the WARP and FILL directions where appropriate. 3. [8 marks] Calculate and tabulate the factor of safety (FS) with respect to reinforcementstrength and pullout resistance for the following reinforced wall. A 6 m high wall (H=6 m) is reinforced with ten (10) layers of equally spaced geosynthetic. The bottom layer (Layer 1) is placed 0.3 m above the toe elevation; the other layers are spaced at 0.6 m apart. The ratio of wall height to reinforcement length (L/H) is 0.7, meaning that the reinforcement length is L=4.2 m long for all layers. The coverage ratio is 100%. The wall embedment depth is equal to zero. The wall has an 8°batter relative to the vertical. The soil materials have the following properties: – Reinforced soil: =20 kN/m3, =34, c=0 – Retained soil: =18.8 kN/m3, =30, c=0 – Foundation soil: =17.3 kN/m3, =28, c=0 The angle of friction between the reinforced soil and the geosynthetic is 23° The long term design strength of the reinforcement is 30 kN/m. Clearly state any other assumptions that you may need to make.
Calculate the initial tangent modulus, the tangent modulus from 5-10% strainand the secant modulus at 5% strain. Explain the difference between the 3 modulus parameters for this particular geotextile.
