8.1 20 ft220 ft-200 ft-Exercise Figure 8.18.1). The concrete has a unit weight of 2.4 Mg/m³(150 lb/ft³). The height of the dam is 67.1 m (220 ft),the crest is 6.1 m (20 ft) wide, and the base is 61 m(200 ft) wide. Note: 1 ft = 0.3048 m.a. What is the average pressure exerted on the rockfoundation in MPa (lb/ft2)? What is the maximumpressure? Explain.b. Refer to the different sedimentary rocks listed inTable 8.1. Using average compressive strength andshear strength values for these sedimentary rockscompare them to the average pressure calculated inpart (a). Are any so low to be of concern? Explain.c. Assume that the pressure from the weight of thedam is dissipated within 30.3 m (100 ft) below therock surface and the full pressure acts over thisdistance. How much settlement will occur in thecenter of the dam because of the gravity force forthe different sedimentary rocks listed in Table 8.1(use average values)?7. Excavation for a gravity dam foundation revealed aunit of poorly cemented sandstone 30.3 m (100 ft)wide (plan view) within a massive dolomite sequence.The dolomite has an E value of 5.5 x 104 MPa(8 x 106 psi) and the sandstone has an E value of6.9 x 10³ MPa (1 x 106 psi).a. What would be the concern if both rocks wereloaded equally by the gravity dam? What would bethe effect on the dam?b. How could this problem be alleviated? Considerboth replacement and strengthening possibilities.8. A 333.3-m (1100-ft) long, horseshoe-shaped tunnelis to be driven through massive granite with a unitweight of 2.72 Mg/m³ (170 lb/ft3). The tunnel is 9.1 m(30 ft) high and 9.1 m (30 ft) wide in cross section(Exercise Figure 8.2). The maximum rock cover abovethe tunnel in the middle of the mountain is 366.5 m(1200 ft). Note: 1 ft = 0.3048 m.15 ft-30 ft-Exercise Figure 8.2a. What is the total overburden stress at the midwaypoint in the tunnel in MPa (psi and psf)?b. Because of arching effects that transfer load aroundthe tunnel opening, the roof or crown of the tunneldoes not commonly support the full overburdenstress, but instead is typically much less. If theroof stress was found to be 0.12 MPa (2500 psf),how many meters (feet) of rock above the tunneldoes this represent? How do you suppose this loadwould be supported in the tunnel?ant to sc. If the tunnel excavation was completed in 80 work-ing days with two shifts per day, how many linealmeters (feet) of tunnel were excavated per day?How many meters (feet) per shift? What was theaverage volume of rock removed per day, per shift?(Hint: Calculate the area of the cross section.)Asd. The tunnel project was bid at $1,878,000. Whatwould be the cost per lineal foot of the tunnel?Rightabutment9. An arch dam transfers much of the water load ontothe abutments (the rock mass on the sides of thedam) (see Exercise Figure 8.3 for a plan view). The Evalue for the concrete is 4.14 x 104 MPa (6 x 106 psi).Exercise Figure 8.3a. What would occur if the abutments were shalewith an E of 2.07 x 104 (3 x 106 psi)?b. What if the abutments were diabase with an E of9.66 x 104 MPa (14 x 106 psi)? Which of the tworocks would be preferred, the shale or the diabase?Explain why.UpstreamDownstream/Leftabutment

Answered: Image /qna-images/answer/e1de3522-ee10-4e0d-be31-a0051940d578.jpg

Exercise Figure 8.1 20 ft 220 ft -200 ft- 8.1). The concrete has a unit weight of 2.4 Mg/m³ (150 lb/ft³). The height of the dam is 67.1 m (220 ft), the crest is 6.1 m (20 ft) wide, and the base is 61 m (200 ft) wide. Note: 1 ft = 0.3048 m. a. What is the average pressure exerted on the rock foundation in MPa (lb/ft2)? What is the maximum pressure? Explain. b. Refer to the different sedimentary rocks listed in Table 8.1. Using average compressive strength and shear strength values for these sedimentary rocks compare them to the average pressure calculated in part (a). Are any so low to be of concern? Explain. c. Assume that the pressure from the weight of the dam is dissipated within 30.3 m (100 ft) below the rock surface and the full pressure acts over this distance. How much settlement will occur in the center of the dam because of the gravity force for the different sedimentary rocks listed in Table 8.1 (use average values)? Ind