For an unconfined aquifer with uniform rainfall recharge, the initial water table is 10 meters above the bottom confining layer. The rainfall recharge rate is 150 cm/year. The aquifer hydraulic conductivity is 20 m/day. An underground subway is planned to be 7 m above the confining layer. A pumping well is needed in order to lower the water table beneath the subway. If the pumping rate 500 m/day is designed, what is the maximum distance to the subway that the pumping well can be in order to fulfill the dewatering purpose? Land surface Original water table rerlng )reldor ol a ou Subway tunnel 10m abond ol te aidost 7m baba K 20 m/day (not to scale) wofl

For an unconfined aquifer with uniform rainfall recharge, the initial water table is 10 meters above the bottom confining layer. The rainfall recharge rate is 150 cm/year. The aquifer hydraulic conductivity is 20 m/day. An underground subway is planned to be 7 m above the confining layer. A pumping well is needed in order to lower the water table beneath the subway. If the pumping rate 500 m/day is designed, what is the maximum distance to the subway that the pumping well can be in order to fulfill the dewatering purpose? Land surface Original water table rerlng )reldor ol a ou Subway tunnel 10m abond ol te aidost 7m baba K 20 m/day (not to scale) wofl

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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Consider the diagram below. Due to infiltration from the storage pond, waterinfiltrates into the subsurface, passes vertically through the upper (unconfined) aquifer,and vertically through the upper confining layer. Due to regional flow, the flux in theupper confined aquifer follows horizontally towards right. Several monitoring wells aredrilled within this system.The rate of infiltration from the pond is 0.2 meters per day. The hydraulic conductivity ofthe upper aquifer is 0.01 cm/sec. The conductivity of the confining layers is 10−5cm/s.The conductivity of the upper confined aquifer is 0.1 cm/s.ASSUME THAT THE WELLS PROVIDE MEASURES OF HYDRAULIC HEADONLY AT THE BASE OF THE WELL.Consider wells A and B. Assume that the base of these wells is separated by 10 meters.a) Which well would have a higher water level?b) What is the difference in water level in these two wells? Provide your answer incentimeters.
2. An artesian well is pumped at the rate of 25 liters/sec. at observation wells 170m and 340m away the drawdowns noted are 0.83m and 0.67m respectively. The average thickness of the aquifer at the observation wells is 6.5 meters. Compute the coefficient of permeability of the aquifer if the water level was 15 meters before pumping. 340 m 170 m Q= 25 liters normal hyd. grade line 0.83 15m h2 hi impermeable layer t= 6,5 mm Aquifer
The water table in an unconfined aquifer was at 10m below ground level. The bottom of this unconfined aquifer was at 35 mbgl. A 1m width section of this aquifer had a hydraulic conductivity of 34.5m/day and a transmissivity of m2/day(to zero decimal places). A potentiometric surface for a certain confined aquifer was at 10m. This confined aquifer is made of an upper confining layer at 20mbgl and the lower confining layer at 35mbgl. Assume the confining layers have zero thickness. This confined aquifer had a hydraulic conductivity of 34.5m2/day and transmissivity of m2/day (to zero decimal places).
Two identical groundwater pumps are operating 4.2 km apart. Each pump well structure has a tube diameter of 90cm. The original water table has an elevation of 60m and the hydraulic conductivity is 32m/day. However, it is maintained that the maximum drawdown (at the tube) is 14 m. The water table will not change at the midpoint between the two pump wells. If the water source is from a confined aquifer with thickness of 5m: A. Determine the drawdown at a point 0.5 km from the pump. B. Determine the discharge of each groundwater pump in m^3/s.
Q2) A fully penetrating well of diameter 0.3 m is located in an uncontined aquifer of saturated depth 45 m. If the drawdown in the well is 15 m for the discharge of 1200 m³/day and the radius of influence is 300 m, compute hydraulic conductivity?
14. Yuri wants to determine the permeability of an aquifer. The aquifer has a test well 300-mm in diameter with two observation wells. A pumping test was conducted for 24 hours with the discharge being held constant at 5618.7 m^3/day. The first one, 88.43 meters from the test well, has a draw-down of 0.52 meters. The second one, 48 meters from the test well, has a draw-down of 1.48 meters.The static water table penetrates the well to a depth of 27 meters. Determine the radius of influence of the aquifer in meters. Round off to three decimal places.
Three piezometers have been installed in the confined aquifer having a uniform thickness of 4.6 m. and a hydraulic conductivity of 2 x 104 m/s. Be 140m 61m S10m 235m C EL 12292m EL 122.03m E 120.5 Im Aquiclude Aquifer 6m Aquiclude a) Compute the hydraulic gredient. b) Compute the transmissivity in m2/day. c) Compute the flow rate per unit width of the aquifer in liters/day.
A 400 mm diameter test well penetrates 27 m below the static water table. After 24 hours of pumping at 75 liters/sec. the water level in an observation well at a distance of 100 m from the test well is lowered 0.35 m. The other observation well at a distance of 40m from the test well has a drawdown of 0.97 m. Compute the transmissibility of the aquifer in m2/day.
Flow in Wells a) A 30-cm well completely penetrates an artesian aquifer. The length of the strainer* is 25 m. Determine the discharge from the well when the drawdown at the pumping well is 4.0 m. The coefficient of permeability of the aquifer is 45 m/day. Assume the radius of influence of the well is 350 m. *length of strainer = thickness of the aquifer b) A 30-cm well fully penetrates an unconfined aquifer of saturated depth 25 m. When a discharge of 2100 lpm was being pumped for a long time, observation wells at radial distances of 30 m and 90 m indicated drawdown of 5 and 4 m respectively. Estimate the coefficient of permeability and transmissibility of the aquifer. What is the drawdown at the pumping well? *lpm = liters per minute *h = H - s, where H = saturated depth
Problem 3.5 A well of diameter 0.3 m is constructed to the full depth of an unconfined aquifer of thickness of 150 m. The water table is 10 m below the ground surface. A pumping test of 12 m'/hour has resulted a drawdown of 10 m. Assuming ro = 400 m; calculate the coefficient of permeability of the aquifer. If the flow rate increases to 18 m'/hour, and in the absence of any other data, what will be the best estimate for the drawdown in the well?
whe Example. A tube well is 0.46 m in diameter. The unconftncd aquifer is 18 m deep. After drawdown depth of water is 12 m in the well. Soil permeability is 24.5 m/day. Radius of circle of influence is 275m. Calculate discharge of the tube well.
Problem 1. Consider a drainage system that consists of horizontal drains located at an elevation ho above the base of an unconfined aquifer of thickness b 10 m (see Figure 1). The recharge rate is r = 100 mm/yr, and the hydraulic conductivity of the aquifer is K = 1 m/d. The design condition of the drainage system is to avoid ponding at the ground surface. You can ignore the vadose zone for this problem. 1. Obtain the relation between the half-distance between drains, L, and the elevation of the drains, ho. Plot this function over the range of feasible lengths. 2. The cost of each individual drain can be split as the cost of the material (fixed) and the cost of installation (which is assumed to be proportional to the depth b – ho). If the fixed cost is $500 and the installation cost is $100 per meter of aquifer length per meter of depth, can you build a drainage system for less than $1 per meter of aquifer length? If so, what depth ho and spacing 2L would you choose? K= 1 m/day 2L = r…