A bridge pier is to be constructed in a riverbed by constructing a cofferdam, as shown in Figure E4.7a. A cofferdam is a temporary enclosure consisting of long, slender elements of steel, concrete, or timber members to support the sides of the enclosure. After construction of the cofferdam, the water within it will be pumped out. (a) Draw the flownet. (b) Calculate the minimum flow rate of a pump required to keep the water level at the base of the excavation. (c) Calculate the porewater pressures at and B. 16.5 ft Sheet piling Water 7.5 ft Water Excavation . 6 ft 5 ft "Silty sand "Keg = 4 x 107 ft/s 6.75 ft Homogeneous, impervious clay

A planned flexible load area (see Figure P7.2) is to be 3 m × 4.6 m and carries a uniformly distributed load of 180 kN/m2. Estimate the elastic settlement below the center of the loaded area. Assume that Df = 2 m and H = . Use Eq. (7.4).

Refer to Figure 7.24. The following data were collected during the field permeability measurement of a confined aquifer using a pumping test. Determine the hydraulic conductivity of the permeable layer. Use Eq. (7.49). Thickness of the aquifer, H = 4.5 m Piezometric level and radial distance of the first observation well: h1 = 2.9 m; r1 = 17.8 m Piezometric level and radial distance of the second observation well: h2 = 1.8 m; r2 = 8.1 m Rate of discharge from pumping, q = 0.5 m3/min