Sub: Geotechnical Engineering ed), Construction SN i ZB Is Very Important a a cou in Life CIVE Visit CIVIL Ki GOLI Facchook Page Permeability & Seepage 1. The coefficients permeability of a soil in horizontal and vertical directions are 3.46 and 1.5 m/day respectively. The base length of a concrete dam resting in this soil is 100 m, Whea the flow net is developed for this soil with 1:25 scale factor in the vertical direction, the reduced base length of the dam will be (A)263m (BY 4.00. m ()6.08m — (D)SABm Ans 2. Ina falling head permeability test the initial head of 1.0m dropped fo 0.35 min 3 hours, the diameter of the stand pipe being 5 mm, ‘The soil specimen was 200 ram long and of 100 mun diameter. The coefficient of permeability of the soil is: (A) 4.86 x10" cms (B) 4.86 x 10-%em/s. (©) 4.86 x 105em/s (D) 4.86 x10° cm/s Aas = ees "9 Ga) = 4.86% 10-°mm/s = 4.86% 10-Sem/sAns Ans Ans 6 An unit volume of a mass of saturated soil is. subjected to horizontal seepage, The saturated unit weight is 22 kN/m’ and the hydraulic gradient is 0.3. The resultant body force on the soil mass (a) 198 KN (b) 6.6 kN (©) 12.37 kN (6) 22.97 KN Construction Is Very Important in Life Visit CIVIL Kt GOLT Facebook Page 3 R=VIF FHS 12.37 KN The figure below shows two Mow lines for seepage across an interface between two soil media of different co-efficient of permeability. IFentrance angle 2,=30°, the exit angle ap will be (@) 750° {bj 14.03° - ©) 665" 75.96 6,59 In a constant head permeameter with eross section area of 10 em”, ‘when the flow was taking pkice under a hydraulic gradient of 0.5, the amount of water collected in 60 seconds is 600 ce, The permeability of the soil is (a) 0.002 emis ©) 0.2ems (b) 0.02 ems (d) 20.cm’s 2 k=2em/s Water is flowing through the permeability apparatus as shown i the figure. The coefficient of permeability of the soil is k ms and the porosity of the soil sample is 0.50.Ans Ans: Ans ‘The total head, elevation head and pressure head in metres of water atthe point R shown in the figure are (a) 08, 04,04 (b) 1.2,04,08 (04,004 (a) 1.6,04,12 Hydraulic gradient i= = = 1 Elevation head at R=0 Total head = 1.2~0.8 X(1.0) = 04 Presume head = 0.4-0= 04 Water is flowing through the permeability apparatus as shown in the figure. The coefficient of permeability of the soil is K mvs and the porosity ofthe soil sample is 0.50. Z sample? (AK 2k (B) 23k, 43k O2k&,k (D) 473k, 2/3k Discharge velocity = ki Seepage velocity An open ended steel barrel of 1 m height and 1 m diameter is filled with saturated fine sand having coefficient of permeability of 10? m/s. The harrel stands on a saturated bed of gravel. The time cequired for the water level in the barrel to drop by 0.75 m is, (A) 589s (B) 758. (C) 100s (D) 150s v=Ki 0x1 75secAns ‘Ans 10, ‘Two soil specimens with identical geometric dimensions were subjected to falling head permeability tests in the laboratory under identical conditions, The fall of water head was measured after an identical time interval, The ratio of initial to final water heads for the test involving the first specimen was 1.25. If the coefficient of permeability of the second specimen is S-times that of the first, the ratio of initial to final water heads in the test involving the second specimen is (A) 3.05 (B) 3.80 (C) 4.00 (D) 6.25, kalogt t_ (on), =e, Sa MOLE. = 3.05 a> Pats ‘The flow net around a sheet pile wall is shown in the sketch. ‘The properties of the soil are: permeability coefficient = 0.09 miday (isotropic), specific gravity = 2.70 and void ratio = 0.85. The sheet pile wall and the bottom of the soil are impermeable. The seepage loss (in m3 per day per unit length of the wall) of water is (A) 0.33 (B) 0.38 (C) 0.43 (D) 0.54 Q= KhXE=0.09% 85 x11, The flow net around a sheet pile wall is shown in the sketch, The properties of the soil are: permeability coefficient = 0.09 m/day (isotropic), specific gravity = 2.70 and void ratio = 0.85. The sheet pile wall and the bottom of the soil are impermeable. [ The facior of safety agains! the occurrence of piping failure is (A) 3.55 (B) 2.93 (C) 2.60 (D) 0.39 Ans 26 12, The ratio NIZNd is known as shape factor, where Nf is the number of flow lines and Nd is the aumber of equipotential drops. Flow net is always drawa with a constant bla ratio, where band a are distances between two consecutive flow lines and equipotential lines, respectively. Assuming that b/a ratio remains the same, the shape factor of a flow net will change if the (A) upstream and downstream heads are interchanged. (B) soil im the flow space is changed (© dimensions of the flow space are changed (D) head difference causing the flow is changed Ans: (&) ‘Suresh Sir ~&) Construction 4p, \sVery Important Z, a. CIVIL Ki GOLI in Life Visit CIVIL Ki GOLI Facebook PageAns Mu Ans 15. Ans: 16, ‘The soil profile below a lake with water level at elevation = 0 m and lake bottom at elevation = -10 m is shown in the figure, where k is the permeability coefficient. A piezometer (stand pipe) installed in the sand layer shows a reading of +10 m elevation. ‘Assume that the piezometrie head is uniform in the sand layer, The quantity of water (in m?/s) flowing into the lake from the sand layer through the silt layer per unit area of the lake be sand pipe cok fea wns) (A)15x10% — (B)2.0x 10°* (1Ox10F — (DOS x 10°F KA =10-* x 2 Berens 10m/, A soil has a discharge velocity of 6X 10°7mis and a void ratio of os, velocity is a) 18x 10-%m/s—_by 12 10-7m’s ©) 6x 107% m/s — dy 3x 107s E=05n=45 seepage velocity 1 during a permeability test on a sol seample with fling head permeameter, equal ime intervals ae noted for drop of hea from “hy” to “ha” and again from *h,” to ‘ha’. Then which one of the following relations would hold good? a) AE = Ayltg ) 4 = hak ©) AR = hyhts Ad) ty he) = (ahs) igh A flow net is drawn to obsain a) Scepage, coefficient of permeability and uplift pressure, b) Coefficient of permeability, uplift pressure and seepage quantity ©) Exit gradient, uplift pressure and seepage quantity 0) Exit gradient, seepage and coefficient of petmeabiAns: (c) a Ans Ans A bed of sand eon The value of Darcy's *k’ for upper and lower layers is Ix10“emvsec.and the middle layer is 1x 10° cm’see.The ratio of the permeability of the bed in the horizontal direction to that in the vertical direct 18 of three horizontal layers of equal thickness, a) 10001 2801 ©2001 dIt010 =n04 att = 01428 Banas 728 Due to rise in temperature, the viscosity and unit weight of percolating fluid are reduced t0 70% and 90% respectively. Other things being constant, the change in coefficient of permeability will be a) 20.0% 928.6% ©) 63.0% — d) 77.8% aa Tay Ha = ko =1.2857 = the change is 7.2857 ~ 120.2857 ie 28.6%19, Match List 1 (Plow type) with List IT (low characteristics) and select the correct answer using the codes given below the Transient flow B. Turbulent flow CC. Steady-state flow D. Laminar flow List-1 A. Seepage flow isa function of time B. Hydraulic wradiont varies with square of velocity CC. Flow at low velocity D. Governing equation in2-Dis ky 4 + ky So Codes: A Be D a1243 ba 214 1234 g2 143 am (A) 20. A flow net constructed to determine the seepage through an earth dam which is homogenous but anisowopie, gave four flow channels and sixteen equipotenital drops. ‘The coefficient of permeability in the horizontal and vertical directions is 4,0 x 10~’m/s and 1x 10~?ms respectively. If the storage head was 20m, then the seepage per unit length of dam (in m/s) would be a) 5x 10-7 b) 10x 10-7 ©) 20% 10-7 a) 40% 107 Ans =VEXTO7 X07 x 204 10x 107 mf, 21. Assertion(A): Constani-head permeability test is not used for fine srained soils. Reason (R): The lesser the permeability of the soil, lesser is the discharge. Codes: a) Both A and Ris true and R is the correct explanation of A, b) Both A and Ris tve but R is nota correct explanation of A, ©) Aistrue but R is false. d) Ais false but R is tue.ans: (A) 22. Assertion (A): Permeability continues to decrease with the increase in dry density of a compacted soil Reason (R): Soil particles in water surroundings may be mutually attracted or repulsed Codes: a) Both A and Ris trve and R is the correct explanation of A, b) Both A and Ris tre but R is nota correct explanation of A, ©) Aistrue but Ris false d) Ais false but R rue, Ans: (B) 23, ‘The configuration of flow nets depends upon a) The permeability of the soil b). The difference in the head between upstream and downstream sides ©) The boundary condition of flow d) The amount of seepage that takes place Ans: (©) 24. A flow net for an earth dam on impervious foundation consists of a 4 flow channels and 15 equipotential drops. The full reservoir level is 15m above the downstream water level. Horizontal permeability is 9x 10~%m/s and vertical permeability is 1x 410™%mA, the quantity of seepage through the dam will be a) 36mi’Sim —b) 25 mlisim ©) 20:mlisim — ) 12 misim Ans g-VOR TOP RTO x 15 x 2 =12% 10° m/s = 12x 10-8 x 10 Is =12 ml/s 25. Ina two-layer soil system, the top soil and bottom soil are of same thickness but the coefficient of permeability of the top soil is that of the bottom soil of coefficient of permeability ‘k’. when horizontal flow occurs, the equivalent coefficient of permeability of the system will be a) 2k byLSk ©) 125k d) 12k Ans SR 5k *# Construction SN i Vo Is Very Important a ae cou in Life Visit CIVIL Ki GOLI Facebook Page Suresh sir SBaseeaoes26. A flow net of a coffer dam foundation bas 6 flow channels and 18 equipotenital drops. The head of water lost during seepage is 6m. i? the coefficient of permeability of foundation is 4X10-Sny/min, chen the seepage loss per metre length of dam will be a) 216% 10-day b) 648% 10-2 day ©) 11.52x 10-%m*/day a) 34.56% 10-2m2/day Ans ox 06x £ x 10-5m3 /min 10? = 8x ta m*/day 11.52 x 107? m3 /day 27. ‘The following data were obtained when a sample of medium sand was tested in a constant head parameter Cross-section area of sample: 100m? Hydraulie gradient 210 Discharge collected Weess ‘The coetficient of permeability ofthe sand is a) O.lms b)001m/s ©)1X 104m’) 1X 10° rms Ans 10= kx 10x 100 K=0.01 cm/s = 1x 10-%n/s 28. A Stratified soil deposit has 3 layers of thickness: 2=4, 2,=1, 252 units and the corresponding permeabilites of k= 2, ky= 1. k, units, respectively. The average permeability perpendicular to the bending planes will be a) 4 2 2) 8 aie Ans:29. Match List oil description ) with List -II( Coefficient of permeability mm/s) and select the correct answer using the codes given below the lists: List List-11 A. Gravel Lol B. Clay sit admixtures 2. 10° to 10-* © Loess 3.<10-* D. Homogeneous clays 4. 10-4 to 10° Codes: ABCD a41 32 bi 4 3 2 es 1 23 O14 23 Ans: (4) 30. Consider the following statements: 1, Coarse sand is more than a mill high plasticity clay. ‘The permeability depends on th a times permeable than 3 nature of soil and not on. properties of liquid flowing through soil, 3. Ifa sample of sand and a sample of clay have the same void ratio both samples will exhibit the same permeability. 4, Permeability of soil decreases as the effective stress acting on the soil increases. Which of these statements are correct?” a) Land 2 b)1and 3 tand4 — d)2and3 Ans: (c) 31. Ina falling head permeability test on a soil, the time taken for at the head to fall from fag t0 fy ist, the testis repeated with same initial Nea”, the final head his noted in time ¢/2 . Which one of the following equations gives the relation betweenf’, i andy? a) hahah, b) h=hgTIy c)A'=Ayhy dA’ = Tigh Ans: (€) 32, A soil deposit has three layers having same thickness each but the permeabilities Of the layers are in ratio of 1:2:4 from top ta bottom. What is the ratio of average permeability in the horizontal direction to that in the vertical direction? a) 72 46 ©) 28:24 a)49:36se Construction bya yar S y Yo Is Very Important « CIVIL Ki Gott in Life Visit CIVIL Ki GOLI Facebook Page 33. A soil mass under seepage has a downward flow of water. Which of the following statements are correct with regard {0 stresses at any point in the soil mass? I. Bifective stress is decreased by an amount equal to the seepage force 2. Effective stress is seepage force 3, Total stress will change 4, Total stress will he unaltered increased by an amount equal to the Select the correct answer using the codes given below: a) tand3—b)2and3 ©) Land 4 ) 2and 4 Ans: (d) @ sheet pile wall constructed in a soil having k= 5x 1075 m/s, the difference of the upstream and downstream water levels is 3m. if the flow net drawn for the problem yields 2 as the ratio of number of flow channels, then what is the discharge in unit of m®/s/m length of sheet pile wall? a) 30x10 —b)3.0x 107 e) 15x10 d) 1.5% 107% Ans 5x 10%*3+2= 30x10" 35. Consider the following statements: 1. Permeability of a soil decreases as the effective stress acting. ‘on the soil increases, 2. ‘The presence of organic matter in the soil increases its perineability 3. Entrapped air decreases the permeability of a soil. ‘Which of these statements is/are correct? a) lonly b) Land 2 )2and3— d) Land Ans: (d)36. A homogeneous earth dam is 43m high with 3m as free board and 30m long horizontal filter at the downstream end, a) 0,0004m5/s_b) 0.0036m%/s ©) 0.0039m3/s—d) 20/5 Ans: =34 10-9402 «500 = 20m/s 37. Consider the following stat 1. Void ratio of the soil. 2. Duration of flow. 3. Equivalent diameter ofthe soil grains, 4. Shape of the citele Which of the Statements isare correct? a) 123and4 by 2and 3 only ©)1,3.and4only — d) 3 and 4 only Ans: (©) 38. A soil has a discharge velocity of 5% 10-Tms and a void ratio of 0.50. its seepage velocity will he a) 15x 10-7 mis b) 10x 10-7ms ©) 20% 10-7m’s— d) 30x 10~7m/s Aas oo = 15x 10-7 Me 39. Consider the following statements: 1, The hydraulic head at a point in the soil includes piezomettic hhead as well as datum head 2. Piping in soil occurs when effective pressure becomes equal to 3. Piping in soil oceurs when soil is highly porous. Which of these sta ets islare correct? a) L2and3 — b) Land 2only ©)2and3only — d)2only Ans: (A) 40. Assertion (A): The possibility of piping failure in earth dams is more if black cotton soil isthe foundation material, Reason (R): The highly expansive black cotton soils are the most common soils whatever basalt rock is present. Codes: a) Both A and R are true and R is the correct explanation of A b) Both A and R are true but R is not a correct explanation of A©) Aistrue but Ris false d) Ais false but Ris true Ans: (b) 41. Assertion (A): Flow net is dependent on permeability of soil through which flow is taking place. Reason(R): The flow net is useful in finding the discharge, Codes: a) Both A and R are true and R is the correct explanation of A b) Both A and R are true but R is not « correct explanation of A ©) Ais true but Ris false d) Ais false but Ris tue Ans: (d) 42. A flow net for seepage under a sheet pile wall has my =4, ng= 8 and the permeabilities of soil in the horizontal and vertical directions are : k= 8X 10-Snvsee and ky= 2X 10"Sm/ sec. if the hhead loss through the soil is 2m, the quantity of seepage per meter length of the wall will be a) 2X 10-FPisee Exangs 3 mee = dy ** Construction ©) 8% 10-Fm*/see Ss y Yo Is Very Important a) 16x 10-5350 s Givi. «1 Gor in Life Visit CIVIL Ki GOLI Facebook Page Ans QeVERTOERDRIO x2 x 4x 10-9 MY, 43. ‘Two observation wells penetrating into a confined aquifer are Tocated 1500m apart in the direction of flow. Heads of 50m tand 25m are indicated at these two observation wells. If the coefficient of permeability for the aquifer is 30mvday and its porosity is 0.25, the time of wavel of an inert tracer fom one well to another is a) 7Sdays b) 750d ¢) 1200d 4)3000d Ans eloity 44, IF number of flow channels are 10, number of drops are 6, the total hydraulic head difference is 4m, the length of dam is SOm and the coefficient of permeability is 2x 10™%m/s, the (otal loss of water per day in m? is a) 576 b) 5760 c) 57600 d) 576000Ans: x 109 x5 ~0.6667% 86400 = 57600" / ay 6667" foe 45. A flow line makes angles 60° and @ with the normal to the interface of the soils having permeabilities 3x 10"%m/s. and 1x 10™m/s before and alter deflection. According to the law of deflection of flow Hines atthe interface of the dissimilar soils, the Ais a) 15% »)30” 645° a) 90° Ans: 3x10 _ tan60 Txi0 ~ tand, 8, = 30° 46. The coefficient of permeability of a soil is $x 10-8 em/see for 2 certain pore fluid. If the viscosity of the pore fluid is reduced to half, the co-efficient of permeability will be a) 5x10 em/see b) 10x 10° emisee ©) 25x 10% emisee d) 1.25% 10° emésee Ans: kee # if wis reduce to half,k becomes double 47. According to Darcy's law for flow through porous media, the velocity is proportional 1o a) Elfective stress b) Hydraulic gradient ©) Cohesion ) Stability number Ans: ¢b) Ans 48. A homogeneous anisotropic earth dam which is 20m high constructed on an impermeuble foundation. K, = 4.8 x 10-® m/s and Ky = 1.6 x 108 mis, the water level on reservoir side is at 18m from the base of the dam, Downstream side is dry. It is seen that there are 4 flow channels and 18 equi potential drop in a square flow net drawn in the wansformed dam section, Estimate the ‘quantity of seepage per unit length. QEVTRRTOTRTERIO x 18 10be transformed 1 FS+ in ky and ky direction mallow. The fective (A) ky thy (©) (48 3)" Dy (Kady) Ans: (4) Suresh Sir “fy,” Construction N b |s Very Important S44 CIVIL Kt GOLI in Life Visit CIVIL Ki GOLI Facebook Page