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PERMEABILITAS Yulvi Zaika. SIKLUS HIDROLOGI Muka Air Tanah.

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Presentasi berjudul: "PERMEABILITAS Yulvi Zaika. SIKLUS HIDROLOGI Muka Air Tanah."— Transcript presentasi:

1 PERMEABILITAS Yulvi Zaika

2 SIKLUS HIDROLOGI

3 Muka Air Tanah

4 AQUIFER

5 Dari mana datangnya air tanah

6 Kemana air tanah mengalir?

7 Interaksi air tanah dan air permukaan

8 Aliran  Shallow, unconfined aquifers often follow the same flow patterns as the watershed above them, as seen in the illustration at right. Deeper, confined aquifers may be part of a different flow system.

9 Bagaimana mengeluarkan air tanah?

10 UKURAN BUTIRAN TANAH

11 Porositas

12 TANAH

13 BATUAN

14 Permeabilitas Kemampuan air mengalir melewati tanah

15 KOEFISIEN PERMEABILITAS SoilPermeability Coefficient, k (cm/sec) Relative Permeability Coarse gravel>10 -1 High Sand, clean Medium Sand, dirty Low Silt Very Low Clay<10 -7 Impervious

16 Datum h A = total head W.T. ) h = h A - h B W.T. Impervious Soil pervious Soil h B = total head Seepage Through Porous Media

17 A B Soil Water In ) h =h A - h B Head Loss or Head Difference or Energy Loss hAhA hBhB i = Hydraulic Gradient (q) Water out L = Drainage Path Datum hAhA W.T. hBhB ) h = h A - h B W.T. Impervious Soil ZAZA Datum ZBZB Elevation Head Pressure Head Elevation Head Total Head q = v. A = k i A = k A hh L

18

19 To determine the rate of flow, two parameters are needed * k = coefficient of permeability * i = hydraulic gradient k can be determined using 1- Laboratory Testing [constant head test & falling head test] 2- Field Testing [pumping from wells] 3- Empirical Equations i can be determined 1- from the head loss 2- flow net

20 Water In  h =h A - h B Head Loss or Head Difference or Energy Loss hAhA hBhB A B Datum Porous Stone Porous Stone Seepage Through Porous Media i = Hydraulic Gradient Soil Water out L = Drainage Path L

21 Water In  h =h A - h B Head Loss or Head Difference or Energy Loss ZAZA hBhB A B Datum Porous Stone Porous Stone Seepage Through Porous Media i = Hydraulic Gradient Soil Water out L = Drainage Path L hAhA ZBZB

22 14 ft 3 ft 12 ft In Flow Out Flow 2 ft 4 ft Datum 3 ft 8 ft Piezometer A B C D u = 6 x 62.4 u = 14 x 62.4 No Seepage Buoyancy WsWs WsWs WsWs WsWs WsWs

23 17 ft 3 ft 12 ft In Flow Out Flow 2 ft 4 ft Datum 3 ft 8 ft Piezometer A B C D u = 6 x  u uu u = 17 x 62.4 Upward Seepage Buoyancy + Seepage Force WsWs WsWs WsWs WsWs WsWs

24 10 ft 3 ft 12 ft In Flow Out Flow 2 ft 4 ft Datum 3 ft 8 ft Piezometer A B C D u = 6 x  u u = 17 x 62.4 Downward Seepage Buoyancy - Seepage Force WsWs WsWs WsWs WsWs WsWs Seepage Force

25 3 ft 4 ft 6 ft 12 ft   =110 pcf W.T.  =  =  =  = - = Total Stress Pore Water Pressure Total Stress Pore Water Pressure No Seepage Buoyancy WsWs WsWs WsWs WsWs WsWs u  = u  = u  = u  = Effective Stress  =  =  =  = 1 1  = u  =  = Effective Stress

26 3 ft 4 ft 6 ft 12 ft   =110 pcf W.T = Total Stress Pore Water Pressure No Seepage Buoyancy WsWs WsWs WsWs WsWs WsWs Effective Stress

27 3 ft 4 ft 6 ft 12 ft   =110 pcf W.T = Total Stress Pore Water Pressure No Seepage Buoyancy WsWs WsWs WsWs WsWs WsWs 3 ft 2 Effective Stress

28 3 ft 4 ft 6 ft 12 ft W.T. 4 Total Stress Pore Water Pressure Upward Seepage Buoyancy + Seepage Force WsWs WsWs WsWs WsWs WsWs = Pore Water Pressure 5 ft   =110 pcf Total Stress 4 2 Effective Stress

29 3 ft 4 ft 6 ft 12 ft   =110 pcf W.T = Total Stress Pore Water Pressure Total StressPore Water Pressure 3 ft Downward Seepage Buoyancy - Seepage Force WsWs WsWs WsWs WsWs WsWs Seepage Force Effective Stress

30 3 ft 4 ft 6 ft 12 ft   =110 pcf W.T. 3 ft 4 ft 6 ft 12 ft

31 PERCOBAAN LABORATORIUM Figure 1 is a sketch of the apparatus used to determine the coefficient of permeability in the laboratory. The soil sample should be as close to un- disturbed as possible. While performing the test, one has to maintain a constant water level at the top by adding water at a rate of q for some time interval of t. Then and Q is the volume of water collected in time t from the outlet. The cross- sectional area of the specimen is indicated by A.

32 PERCOBAAN LAPANGAN

33 PERMEABILITY  Porositas mengacu pada kecendrungan material untuk dilewati zat cair melewati pori-pori nya.  Permeabilitas adlah parameter anah penting dalam proyek dimana air mengalir melewati tanah atau batuan seperti alairan yang melewati bawah dam, drainse pada lapisan sabgrade dan timbunan, mengetahui kecepatan sumur dapat teisi kembali dan dewatering untuk struktur yang dekat dengan muka air tanah.  Ada beberapa faktor yang mempengaruhi permeabilitas tanah adalah: 1. visikositas air ( dipengaruhi oleh suhu) 2. ukuran dan bentuk partikel 3. derajat kejenuhan 4. void ratio

34 In construction, if an excavation is to be done below the water table, a dewatering plan needs to be followed. A highly permeable soil will require a pumping system with a comparatively large capacity. A low permeable soil may not require any pumping. In addition, fill material that is highly permeable can usually be placed and compacted immediately, but low permeable fill may require days of drying before being placed and compacted.

35 The fundamental description of permeability is based on the equation q=vA which takes the familiar form similar to river discharge. The variable q is the discharge (Vol/Time), v is the apparent velocity, and A is the area that is related to the geometry of the situation. Now, Darcy's Law describes the factors important in determining the value of v, which is v=ki where k is a constant for the material and is called the coefficient of permeability, and i is the hydraulic gradient which is related to the water pressure. The following table lists some soil permeabilities.


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