Reg. IVo. :
Question Paper Code
:
B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 20 1 t.
Foudh Semester Civil Engineering CE 2251
-
SOIL MECHAMCS
(Regulation 2008) Time : Three hours
Maximum i 100 marks Answer ALL quesdons. Assume suitable data if found necessarv_
PARTA-{1Ox2=20Earks) Determine tlle aaximum possible voids iatio for a uniformiy graded sand of perfectly spherical grains-
What is a Zero Air Voids line? Draw a Compaction curve and show the Zero Ab Voids line. What is a quick sand? How would you calculate the hydraulic gradient required to create quick sand cotditions in a sample of 6ard? For a homogeneous earth dam 52m high a_nd 2m free board, a flow net was constructed alrd follo$ring results were obtained : Number of potential drops = 25 Number of flow channels = 4.
Calculate the discharge per metle length of the dafi-if the co-effrcient of perrtreability oI tlle dam rnatedal is 3 x 10 -5 m/see.
5.
Write down t}Ie use of influence charts-
6. \{hat 7.
are lsochrones?
How will you
fird the shear strength
of cohesionless soil?
8.
List out the grpes of sheal tests based on drainage'
9.
What are different factors of safety used in the stab-ilty of slopes?
10_
What is a stability number? i\rhat are the uses of stability charts?
PARTB-(5x 16= 80 marks) 1 1
. lal
(bl
12.
la)
An earthen embanlment of 106 m3 volume is to be constructed with borrow pits irarked A, B and C havisg soils with void ratios of 0'90' i,So ttta f.go, respectively- The cost of excavation and tiansporting the soil is Rs 0.r5, Rs o.23 a\d Rs O'18 per m3, respectivelyCalculate the volume of soil to be excavated from each pit which borrow pit is the most economical? {Take G = 2'65)' Or A 1abo.atory compaction test on soil having specific- gravity. equal 2.67 gave a maximum dry unit wei8ht of 17 8 kN/m3 and a sa conteit of 15 per cent. Detersine the degree of saturation' coltent and peicentage air voids at the maximum dry unit wei What would be theoretical maximum dry unit weight cores to zero air voids at the optjztufi water conteEt? A louqdation tredch is to be excavated in a stratum of stiff clay, 1 thick, underlaifl b5r a bed of coarse safld [Fig-1]' In a trial borel the ground water was observed to rise to ai elevation of 3 5m b grou;d suiface. Determine the depth upto which an excavation 6e safely- caried out without the dalger of t]le bottorE becol unstable under the a-rtesian pressure in the sand stratum' specific $avity of clay particles is 2.75 and the void ratio is 0 B' If excavation is to be carried out safely to a depth of 8m, ho{' should the water table be lowered in t}le vicinity of tie trench?
Fig.1
Or (b)
The following data were recorded
,.
in a constant
head
Intemal diameter of pennea&eter = Z.Scm Head lost over a sample length of 18cm
= 24.7cm
Quantity of water collected in 60 Sec 626 = ml Porosity of the soil s arnple \ as 44ya
i3.
(a)
cdcurare the coeflicienl 0f permeabi.liry of the soir. Arso deterrnine trte discharge velocjty and se;page velocity durjns the;;* -'.-.*-. consolidometer resr on a 20 mm ll..a llbgralory thick samDie of saturated clay taken from a site
reached.in.r 0'mii"u;;"';";*:,".,;: or.5 ., thiclmess ar rhe site for 50% ;3? '"Tfi:li.il.,l.o"l#,J?i compresiio" ,r irr.*.i".i.lrij""l rhe rop. whar is rhe tjme *qrir.a r* :liv,lojySldsconsoljdation if rhe layer r,u" d.utf" JJrue;,r"J,J; "rr"u"iliiTl iil"l, loy: :; smgle
Jl
drainage.
Or (b]
(a)
Ii,i.1.ffi,""
various components of a set emenr? How are rhese
*i.;
A vane, 10 em long and, g cn.l in d;r
;:ffi',:TI' :ffi ::.L1,.J:1,"1fi I "' " to 4s N rD when ;"#' rncreased failure took prac.. #;";*itl,,yriJi#l ro compretery remoutd rhe *ii-rb;,.;;;"ril 311:!-Tfl"- 11*at"sa torque of _t8 r
r,
uonoo,'ii
"u
N_m. Calculale u," ..rr."i.r-.iiil :i1:,T1",::.,.19 LEJ me narurat and remouldF.t states and also tn" u"1". oi ifr; 'rt sensitivity
Or (b)
Describe the triaxial shear- test. What are the advantages of triaxial shear test over the direct shear test?
(a)
ml, T.. differenl tjpes of slope faijures? Discuss the various methods for improving the stabiliry of slopes.
(b)
.
Or Al1 embaalonent 10 @ high is inclined at 35" to the horizontal. A stability analysis by the method of sli"." g"r" ,i,"'f"U.*;"iL?'J"",
Dr =900kN,xI =420kN,IU =200kN If the length of the failure arc is 23.O m, find the lactor of safety. The Soil has c=20kN /m) and g=15" .
55240
