engineering – design and construction / soil mechanics

Design and Construction Steel Referred/deferred Coursework 2013-2014
Your answers must include your workings and results with the correct units. Please submit
your work to the Faculty Office by 5 pm on 19th August 2014.
1. (12%) Two plates in S275 steel are connected with M20 bolts (clearance = 2 mm), as shown in
Figure 1. Check only the adequacy of the cross-section of the plates to resist a design
tension force of 500 kN each.
NEd
NEd
NEd
NEd
140
14
Figure 1: Connection detail showing the dimensions of the steel plates.
2. (a) (28%) A steel compression member pinned at both ends is subjected to a design axial com-pression force, as shown in Figure 2. Verify only the buckling resistance of the mem-ber if a 120x120x10 hot finished SHS section (with dimensions and properties shown
in Figure 2) in S355 steel is used. The Young’s modulus (E) of steel should be taken
as210 000N/mm
2
. The section is class 1.
(b) (5%) Describe the relevance of the section class in carrying out the check in part (a) of this
question. Which term(s) in your calculations is/are dependant on the section class?
h
h
y y
z
z
t
h= 120 mm
t= 10 mm
A= 42.9 cm
2
i = 4.46 cm
NEd
= 1000kN
L= 3m
Figure 2: Compression member (left) and dimensions and properties of the section used (right).
Page 1 of 2
3. (55%) Check the suitability of a 254x146x31 UKB section (with dimensions and properties shown
in Figure 3) in S355 steel loaded as shown in Figure 3. The length of the beam is 4 m. The
Young’s modulus (E) of steel should be taken as210 000N/mm
2
.
The design value of the uniformly distributed load (UDL):p
d
= 15kN/m
The characteristic value of the variable UDL:q
k
= 4kN/m
(Assume that the beam is fully laterally restrained.)
b
h
y y
z
z
t
f
r
t
w
b= 146.1 mm
h= 251.4 mm
t
f
= 8.6 mm
t
w
= 6.0 mm
r= 7.6 mm
A= 39.7 cm
2
Wpl,y = 393 cm
3
I
y = 4410 cm
4
I
z = 448 cm
4
L
Figure 3: Beam (left) and dimensions and properties of the UKB section used (right).
Design and Construction Steel Referred/deferred Coursework Page 2 of 2
BEngCivilEngineering-SoilMechanics-Referred/DeferredCoursework, 2013-2014
1
BEngCivilEngineering
Soil Mechanics
Referred/DeferredCoursework,2013-2014
PleaseanswerALLquestionsandsubmittotheFacultyOfficeFAOMaria
Mavroulidoubythe19
th
August2014Facultydeadline.
DrM. Mavroulidou
July2014
BEngCivilEngineering-SoilMechanics-Referred/DeferredCoursework, 2013-2014
2
1.(a)Anembankmentistobeconstructedusingnatural soil.
a) Whenextractedfromthequarry, thenatural soil hadthefollowing
properties: watercontentw=14%; voidsratioe=0.68; specificgravity
ofthesolidparticles: Gs=2.7.CalculatethedegreeofsaturationSr
, the
bulkdensityr andthedrydensityr
d ofthesoil whenextractedfrom
themine. (9marks)
b) Thesamesoilwillthenbeusedfortheconstructionofanembankment.
The total volume of the embankment after compaction will be
V=50,000m
3
. Thedrydensityofthesoil aftercompactiontoformthe
embankmentwillneedtober
d=1.75g/cm
3
.Calculatethemassofthe
solidparticles, themassofthewaterandhencethetotal massofthe
soilthatwillbeusedforthecompactedembankment. Assumethatthe
watercontentwofthesoilremains14%). (5marks)
c) Thesoilistobetransportedfromtheminetotheconstructionlocation
usinglorriescarrying 6.20tonnesofsoil each(NB1t=1Mg). Taking
intoaccountthetotal massofthesoil tobeusedfortheembankment
(calculatedinb) above) calculate howmanytripsof lorriesof this
capacitywill benecessaryinordertotransporttherequiredsoil mass
fortheembankmentconstruction. (2marks)
d) Consideringthat the total mass of the soil to be usedfor the
embankmenthasnowbeenexcavated, whatisthetotal volumeofthe
excavationontheextractionsite, after theremoval ofthesoil tobe
usedfortheembankment? (4marks)
Total 20marks
2. (a) Asoil sample10cmindiameter wassubject toaconstant head
permeabilitytest. Thetotal headwasmeasuredat twopointsofthe
sampleusingmanometers, oneclosetothetopandanother closeto
the bottom(distance between the points: 108 cm). The first
manometer showedaheadof 198cmandtheother 186cm. The
amount ofwater collectedin15minuteswasQ=1350cm
3
. Calculate
thepermeabilityofthesoil. (7marks)
(b)Afallingheadpermeabilitytestwasperformedonasiltsampleof100
mmindiameter and150mminheight. Two different standpipe
diameterswereused. Measurementsof water level heighthineach
standpipeweretakenatdifferenttimeintervals.Theresultsofthetest
areshowninTable2.Calculatethepermeabilityofthesoil.(10marks)
BEngCivilEngineering-SoilMechanics-Referred/DeferredCoursework, 2013-2014
3
Table2
Waterlevel instandpipe
Standpipediameter
(mm)
Initial level h1
(mm)
Final level h2
(mm)
Timeinterval Dt
(s)
9 1200 840 58
840 600 55
12.5 1200 720 160
720 360 120
(c)Ifthevoidsratioofasandysoilis0.75anditsspecificgravityGs=2.63,
determinethecritical hydraulicgradient of thesoil. (Taketheunit
weightofwatergw=10kN/m
3
). (3marks)
Total 20marks
3. (a)Asoil profileconsistsoftwolayers: alayerofsiltysand6mdeep,
underlainbya5mlayerofsaturatedclay. Thepropertiesofthetwo
layersare:
LayerI(siltysand):
Saturatedunitweightgsat=19kN/m
3
.
LayerII(clay):
Saturatedunitweightgsat=18kN/m
3
Determineandplottheporepressureandthetotal andeffectivestresses
atz=0m, z=2m,z=6mandz=11mdepthforthefollowingtwocases:
(i) thewatertableisatthegroundsurface (6marks)
(ii)thewatertableisat2mbelowgroundsurfacebutthesiltysandis
saturatedwithcapillarywatertoaheightuptothegroundsurface.
(6marks)
(b)Auniformlydistributedloadof70kN/m
2
isappliedtoa3mdeep
layerofclay. Theclayisfreetodrainatboththetopandthebottom.
Thecoefficientofvolumecompressibilitymv oftheclayis0.3m
2
/MN.
Thecoefficientofpermeabilityoftheclayis3x10
-10
m/s.
i)calculatethecoefficientofconsolidationoftheclaylayer (2marks)
ii)calculatethefinal settlementoftheclaylayer (2marks)
iii)calculatethetimewhenthesettlementis20%ofthefinal
settlement (4marks)
Taketheunitweightofwatergw=10kN/m
3
Total 20marks
4. (a)Thecritical statepropertiesofaclayareM=0.89, Γ=3.05, N=3.1
andλ=0.14.Onesampleofthisclayisisotropicallynormallycompressed
inatriaxial apparatus top’=400kN/m
2
. Maintainingthisconsolidation
BEngCivilEngineering-SoilMechanics-Referred/DeferredCoursework, 2013-2014
4
pressure (i.e. without letting the sample swell) the sample is then
subjectedtoastandarddrainedcompressiontest. Calculatethedeviator
stressatfailureandalsothevolumetricstraintofailure.
(9
marks)
(b)Anumber of
drainedandundrainedtriaxial testswerecarriedoutonaclaysoil. The
Table3belowgivesdatafor thestressparametersqf andpf
‘ andthe
specificvolumevfwhenthesampleshadreachedfailureat theircritical
states. Plot the results interms of vf versus pf and qf versus pf
respectively,anddeterminethecritical stateparametersM,λandΓofthe
clay. (11marks)
Table3
Testnumber pf
(kPa) qf
(kPa) vf
1 300 297 1.95
2 610 598 1.80
3 420 411 1.87
4 202 198 2.03
Total 20marks
5. (a) Asampleof clayinatriaxial apparatus issubjectedtoastandard
undrainedcompressiontest. Atthestartofthetesttheporepressure
is200kN/m
2
andthecell pressureis300kN/m
2
.Thesamplefailswhen
thedeviatorstressreachesavalueof62kN/m
2
andtheporepressure
hasincreasedto250kN/m
2
. Drawtotal stressandeffectivestress
Mohr’scirclesfor thesampleat failure. What isthedrainedangleof
frictionoftheclay? (10marks)
(b)Table4givesanextractofresultsfromashearboxtestonadrysand
soil, subjectedtodifferent normal stresslevels. Theresultsshownin
thetablehavealreadybeenprocessedintermsofshear stressesfor
differentnormal stresslevels. Determinetheultimateanglesoffriction
forthesoil. (10marks)
Total 20marks
BEngCivilEngineering-SoilMechanics-Referred/DeferredCoursework, 2013-2014
5
Table4
ShearStress(kPa)
Horizontal
displacement
(mm)
Fornormal stress:
50kPa
Fornormal stress:
100kPa
Fornormal stress:
200kPa
Fornormal stress:
300kPa
0.00 0.00 0.00 0.00 0.00
0.05 8.50 7.67 12.85 37.00
0.55 17.62 22.95 43.21 91.02
1.05 20.58 31.94 58.92 115.51
1.55 23.00 37.93 70.02 132.01
2.05 23.83 42.25 78.91 145.29
2.55 25.03 46.50 86.41 153.88
3.05 25.70 49.51 92.80 160.92
3.56 26.48 51.94 97.34 167.64
4.05 26.85 54.08 100.54 172.16
4.55 26.87 55.90 103.61 175.28
5.05 26.90 57.27 106.84 178.81
5.55 26.99 58.63 108.91 180.11
6.05 27.01 59.80 111.32 184.24
6.55 27.12 60.74 113.25 186.46
7.05 27.12 61.73 114.80 188.99
7.55 27.12 62.48 115.38 189.05
8.05 27.12 63.11 117.78 189.05

:)

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