Finite Element Analysis of Seepage and Exit Gradient through a Non-Homogeneous Earth Dam without Filter Drain

Abstract

In this study, a slav? program of G?o-Slop? softwar? (S??P/W) was us?d to analyz? th? b?havior of phr?atic lin? along with th? computation of s??pag? flux and ?xit gradi?nt for a non-homog?nous ?arth dam (Hub dam) for two diff?r?nt cas?s, with filt?r drain and without filt?r drain r?sp?ctiv?ly. Th? m?sh?s were compos?d of triangular, squar?, r?ctangular and trap?zoidal typ? of ?l?m?nts. Th? m?sh for cas? filter drain compris?d of 2,297 nod?s, and 2,206 ?l?m?nts, whil? for non-filter drain, 2,283 nod?s, and 2,198 ?l?m?nts w?r? us?d. Th? simulation r?sults r?v?al?d that th? saf?ty of th? Hub dam, at its original d?sign, is not ?ndang?r?d from the s??pag? point of vi?w as th? pr?s?nc? of filt?r drain has a dir?ct ?ff?ct on r?ducing positiv? por? wat?r pr?ssur? within th? dam. Du? to low positiv? por? wat?r pr?ssur? within th? dam for filter drain, th? phr?atic lin? was falling into th? filt?r drain aft?r passing th? cor? with an ov?rall minimum s??pag? flux of 2.113 x 10^-4 ft³/s?c/ft and ?xit gradi?nt at downstr?am to? 0.099 r?sp?ctiv?ly. How?v?r, wh?n th? mod?l was run with sam? g?om?try and mat?rial prop?rti?s without filt?r drain, a v?ry high ?xit gradi?nt was obs?rv?d for (normal and maximum pond l?v?l) sc?narios and th? b?havior of phr?atic lin? was also found abnormal as it cuts th? downstr?am slop? of th? dam. Though th? s??pag? flux was found (28 – 29%) l?ss, but du? to the absence of fr?? passag? within th? dam for th? r?moval of ?xtra wat?r, th? por? wat?r pr?ssur? within th? dam ?sp?cially at downstr?am fac? b?com?s high and l?ads to a slop? failur?. This impli?s that filt?r drain ?sp?cially in ?arth dams plays a pivotal rol? to control th? phr?atic lin? tr?nd and ?xit gradi?nt by r?ducing th? positiv? por? wat?r pr?ssur? within th? dam body and to sav? th? dam from downstr?am slop? failur? r?sp?ctiv?ly.