CE 563, Seepage amp; Slope Stability Spring 2012 Homework # 02 Problem 1 (15 pts) For the sheet-pile system with H = 5m, H1 = 4m and H2 = 6m, and...

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CE 563, Seepage & Slope Stability Spring 2012 Homework # 02Problem 1 (15 pts)For the sheet-pile system with H = 5m, H1 = 4m and H2 = 6m, and the four subsoil conditions shownbelow, draw a flow net as accurately as possible. Using the flow net, compute:(a) the seepage per unit length of wall (m3/day), and(b) the porewater pressure (kPa) at Point A. Hydraulic Conductivity (× 10-3 cm/s)Soil Profile Layer 1 Layer 2 kv kh kv kh A 2 2 2 2 B 2 8 2 8 C 8 2 8 2 D 8 8 2 2 H Water2m H1 k1Point A H2 k2Impervious NOTES:(a) A single flownet may be used for profiles A, B and C as long as a clear explanation is provided tosupport the answers. A separate flow net is required for profile D – consider using the SPIRESsoftware as a guide.(b) Make sure that lines are smooth and you really do have squares, where applicable.(c) Label the equipotential lines in a sequential order.(d) Remember that the system geometry must be drawn to scale.Page 1 of 2 CE 563, Seepage & Slope Stability Spring 2012 Problem 2 (15 points)A gravity dam, shown below, is to be constructed to retain a maximum head of 10 meters of water. Theaverage, isotropic hydraulic conductivity of the underlying silty sands is about 2 × 10-4 cm/s and theirsaturated unit weight is about 17 kN/m3. To prevent excessive seepage, two 8-meter sheet piles will beinstalled at the upstream and downstream edge of the dam. As the dam is embedded 2m, the sheet pileswill extend to a depth of 10 meters below the downstream tailwater elevation. For the configurationshown:(a) Draw a flow-net . . . . . try to limit it to 3 flow channels,(b) Determine the amount of seepage, in liters per day,(c) Sketch the distribution of the seepage pressure (i.e. pore water pressure) under the dam betweenpoints A and B. The pressures must be shown in units of kPa or meters head of water,(d) Determine the total uplift force (in kN/m) acting on the gravity dam,(e) If the seepage quantity, determined in (b), is considered excessive, suggest two methods that maybe used to reduce the seepage.25m CONCRETEDAM 10m 2m8m A B 8m 30m Relatively Impervious Problem 3 (10 points)(a) A double packer, permeability test was run in an NX borehole with L = 4 ft and h = 34 ft(Fig. 2-16 in handout). Using an additional pressure of 100 psi, a steady state infiltration rate ofabout q = 11 gallons/minutes was obtained during the test. Assuming that the seepage waspassing into saturated soil, determine the hydraulic conductivity in cm/s. What is the diameter ofa NX hole?(b) A falling head permeability test was conducted using an open 4-inch borehole, 34 feet into an87-foot thick stratum of soil (Fig. 2-18 in Manual). For a 4-inch diameter casing, the water leveldropped 2 feet in 35 minutes. If the mean head during this period was 25 feet, determine thehydraulic permeability of the tested material. How reliable is this computed value? Assignment is due one week after Lecture #7 Page 2 of 2