Chapter 16, Problem 16.12P

What is deposition of sediments and how this occur and how can this be managed? (Short essay)

Assume that concentration is directly proportional to flow rate (i.e., C=KQ). Determine and plot the pollutograph [mg/L vs. min] and the sedimentgraph [kg/sec vs. min] for a total sediment load of 1150 tons for the following runoff hydrograph. [Hint: you need to determine a value for K with units of mg/sec/(cfs)2].   Time (min) Flow Rate (cfs) 0 30 60 90 120 150 180 0 45 190 375 285 95 0   As a check, determine and report the total sediment load from the sedimentgraph.

Refer to Figure 7.28. For the construction of an airport, a large fill operationis required. For the work, the average permanent load, (p), on the claylayer will increase by about 70 kN/m2. The average effective overburdenpressure on the clay layer before the fill operation is 95 kN/m2. For the claylayer, which is normally consolidated and drained at top and bottom, H = 5 m, Cc = 0.24, e0 = 0.81, and cv = 0.44 m2/mo.a. Determine the primary consolidation settlement of the clay layer causedby the additional permanent load, (p).b. What is the time required for 90% of primary consolidation settlementunder the additional permanent load only?c. What temporary surcharge, (f), will be required to eliminate the entireprimary consolidation settlement in 6 months by the precompressiontechnique?

A double wall sheet pile coffer dam retains a height of water 9 m on one side. A flow net constructed for this structure, driven into a pervious deposit overlain by an impervious ledge, consists of five flow channels and fifteen potential drops. The length of the coffer dam is 90 meters. If the coefficient of permeability of the pervious deposit is 10^–2 mm/s.Determine the seepage in cubic meters per day.

Q. Solve this seepage problem.

An earth dam requires 1 million cu.m. of soil compacted to a void ratio of 0.80. In the vicinity of the proposed dam, three borrow pits were identified as having suitable materials. The cost of purchasing the soil and the cost of excavation are the same for each borrow pit. The only cost difference is transportation cost. The table below provides the void ratio and the transportation cost for each borrow pit. PLEASE COMPLETE SOLUTION 1. Compute the volume of soil if taken from borrow pit C.2. Compute the transportation cost of the soil if taken from borrow pit B.3. Which borrow pit would be the most economical?

H2 = 0.3’                      h = 1.25’  H1 = 0.2’                      d = 1.5”  H = 0.5’                        D = 4”  Ksand = 0.000075 ft/min Ksilt = 0.0038 ft/min Determine: Determine the total flow of water q. Find the equivalent permeability for the soil.

A reservoir has an initial capacity of 45,000 acre-ft, with an average annual inflow of 63,000 acre-ft and a sediment inflow of 180 acre-ft/yr. The useful life of the reservoir is when only 20% of the capacity remains. (a) Assuming the sediment capture rate is unchanged and equal to that of the new reservoir, what would be the lifetime of the reservoir? (b) What are the percentage capture efficiencies when the reservoir is at 100% and 20% capacities?

Given: rw = 0.25 m, rs = 0.35 m, de =4.5 m, cv 5 cvr = 0.3 m2/month, kh/ks 5 2, and Hc = 9 m. Determine: The degree of consolidation for the clay layer causedonly by the sand drains after six months of surchargeapplication