Question

1. A large tank structure 5 m high is to be constructed on the site as shown below on Figure 1. The intention is to fill the tank with water. Determine the vertical total stress, vertical effective stresses and pore water pressure at the centre point of both the clay layer and the sand layer (a) before the tank is constructed (b) immediately after the tank is first filled with water. (c) Many years later assuming the tank remains full of water Ground level = ground water table 5 m high water tank Clay with density 1.6 Mg/m2 4 m Sand with density 1.9 Mg/m 4 m Figure 1 NB: Clay has very low permeability (water travels through it very slowly) and sand has very high permeability (water travels through it very quickly)

Answer 1

1 8olnton m WAler Sand Y1-9 Ma/m3 Huse 9-81 KAm chyY1x/m 16x 10 K31m 1.6x10 N/m 16 KNm Sma larly Y sard Ys14 KNm tamk is construcad AT mid poinro clay 2x 16ENm 32 KNm Beore to tal vartcal strss Pore watir pssuse ax9.81 - 19 62KAm tetalaatin Etech ve ess 2-196)m 12.38AM

At mid point esamd. ttal ahical sas(4x16)+ 2xYsand elay 64+ 2x 19) KNm 102 Nm MPore watu pressre 6 x 9-81 58.86 ENm E eine shass a= retal L02-58C)m 43.14 KNm 2 CPart Immediatly aft tcomstrncion and atr is d At mid point of dlay Since the drainae dlay is mulite su to low pe mlabil Tthe vast ca! be incuasedduu to pore Watir prissur ress ill and Thu Suschar ge in au ases Suddunly (inmudiali ly)

Fotal neatical ass 6x2) turchang 02+ 5x481)N/m s 105 KN/m prssus@xq ) + surhange Mpore watu 19.62+ 5 x9 8) 6 8.67 KNJM fteche etress - 69-67) -Ajm (I05 -la 38 KNm 2- AF mid point Sand Sme dhanage s high parannbi inciase in pore watu atotal wtical shessx16)+2KYaand to due thasi is no pres sure n 2 +surchg 10 a5X9.8 ISI:05 ENm waton pore PYeBBure 6x 9.81 98.89 total A Etechive strass- a M. (iS1.05 -5886) g2-14 KNm

Many yeas latn assumming to Solm A mid peint clay Ate leng Time Se pora watn paLue is dissipakd due to Rurchan) atn is dischanged Avuhial etal) 8105 KNm Csame as m 6) 2 x9.81 Nm 1962 Nm a pecv hess BI 05 -14-62)Nm 61-43N/m A mid point Sand No chang 51-05 ENm a vestieal total Mpore Watin pressnse6X 981.ENm 58 86 KNm SI-05-58.86 )kNm -M= 92. 14 m

S etuten m mSand At mid paint clay Nlacal Crotal) tras F 2 x 16)KN/m watin M pore )2 presure 1 So, Ar Thu top chy layer head =Om head thbotom clay lay +2)- 6 m d ehad at B) watwpreseue = x981 a Jhun, por 29-93 KNm as Etet ne stras talM 2-2943) E 2.57 KNIM

A mid paint samd avehial (total) tras +2 sandl 4x16 +2x 19 - 102 EN/m watn Mpora prastse (6X9-81 2x 9.8)) tepf Sand 17 middle samd - 78 48 EN/ m 102 KN/m-184 23.5 aKN m aEtet stss