2024_ENVS3060_Assignment #3

ENVS 3060 Groundwater Assignment #3, Due Mar 13, 2024 Marks are given in brackets beside each question number. Total 75 marks. 1. (5) Classify the soil textural class Soil Sand Silt Clay Textural class 1 45 23 32 2 57 26 17 3 75 7 18 4 92 2 6 5 57 22 21 6 77 11 12 7 85 5 10 8 23 48 29 9 25 51 24 10 55 29 16 2. (10) Calculate the terminal velocity corresponding to the upper size limit of the particles with diameter of 1 um, 20 um, 100 um and 1000 um fractions at 20°C and the particle density of 2600 kg m -3 . 3. (10) Determine the sedimentation time for a soil particle having a diameter of 1 um, 20 um, 100 um and 1000 um and a particle density of 2.6 g/cm 3 . Assume that the sampling was made at the 0.20 m depth and at a temperature of 30 °C. 4. (10) Classify the particles with diameter 1 um, 20 um, 100 um and 1000 um. Calculate the surface area for 100 g of each of these particles. 5. (10 A confined aquifer is 18.5 m thick. The hydraulic head drops 2.99 m between two wells that are 823 m apart. If the hydraulic conductivity of the aquifer is 4.35 m/d, how many cubic meters of water are moving through the aquifer per unit width? 6. (15) An unconfined aquifer has a hydraulic conductivity of 2.3 x 10 -4 m/d. There are two observation wells 348 m apart. Both penetrate the aquifer to the bottom. In one observation well the water stands 9.88 m above the bottom, and in the other it is 7.12 m above the bottom. a. What is the discharge per 100-m-wide strip of the aquifer in cubic meters per day? b. What is the water-table elevation at a point midway between the two observation wells? 7. (10) Draw a flow net for seepage through the earthen dam shown in the figure below. (Hint: assume flow tubes/stream, p = 4 and you are creating f = 20 head divisions). If the hydraulic conductivity of the material used in the dam is 0.22 m/day, what is the seepage per unit width per day?