Figure 1 shows a vertical cross section through a typical concrete gravity dam with a cut-off trench two key requirements of this kind of a construction are: 1. controlled seepage flow beneath the dam 2. safety against dam failure -gravity dams depend on their mass for stability. they can fail by either sliding or overturning about the toe if the lateral pressures on the upstream become excessive the probability of either type of failure is increased by uplift pressures on the bottom of the dam, especially near the upstream face. therefore, uplift pressures must be known for the designs of safe dams you have been consulted to determine the flow rate of water under the dam and to calculate the uplift pressure at the bottom of the dam. the tasks you need to complete in order to do this are: task a: (i) construct a flow net on figure 1 showing groundwater flow under the dam (4 marks) (ii) calculate how much water is lost under the dam (the dam is 100 m long, soil hydraulic conductivity is 4 x 103 m/s, and reservoir depth is constant at 12 m with a tail water depth of 2 m) (2 marks) (iii) calculate the uplift pressure at point a on figure 1 (2 marks) task b: