LABORATORY STUDIES ON PREPACKED GRAVEL STRAINERS FOR TUBEWELLS

Abstract

Ground w3 0z of or or&ijbio courco of wztor o ppt ' foz tzigotton, driving and md strial usaow E31oration and o to L a ion• of ground water t3 in fufl G4flg . o Xndio. fait Q . !ice E €r 8 tlottod p pov, Zn the pr000nt r c'U o of tubeioll dovG3opmont, gravel oniolopo of about &nchoo thi cknoca t o foxmcd around the alettcd pipo. G,avol pack it€ fine finetly otobilizod by tatonatoly n*pandtng tho gaol by water . of ng fzom inside and oucking out the tenor material of the aqutfor, by hoivy ping. In this method of development control of the thickness and Sconpecton o' gavol cenot be Over. cisod, ttcorta nt oa of development may often load to onsida rablo yield reduction and sand flovi in the rsoll Gravel strain-ores fobrcoto or lido will be hoe frog oce dif jct tjoa:. Prepa minor at proeont in uoo conoi o of olottod pipe etuck with adhealvo tttodr avol in rna .l t)dcltnose &uch no 3/4 inch. 'hoop► prevent sand eztioctoriiy but ciu.so oucoeotvo head to ooa. P osont v. i!t i. o aid to utudy the of tcacy of coiwea .ones oo c ll oo a propooed typo of popckod of einor rGlativo to *ta corwcntjonei inettu pocks ea to the coot,hoed Ions and ocind floci, In t1 000 otudi.00 an alto.. gothor d ffcont type of porouo pip* ee boon concoLvod and uod inplace of the slotted pipe. The propood type of propockoa gr3vol streinoz la obtainod by fill-Ing and compacting dry g?a oX In the otin lar spaco loft t on . conontr&c.alIy put to bar pipe typo porous pipee giving a pack of ` 3/4* cionr thictcn000. Dow type porous pip* and the prepackod strainer hove ,boon octtrnatod to be cheaper than slotted.pip and the COflVOflt1Ofl:1Et inaitu gravel. masking ropoctively. xparimonto in thin study w o done doing a 3O ( erg ' an ular sector qui `oz' model of. o po. , having /2 inch thick oheet,8 iz a oa in hoiq t o a t 6' r*c a diameter of the ioli. Tht mødol tG a e 1ng in Ground Wato.r Laboratory of U.P, Irrigation earb Institute, Roorkee, and the oxroimonto rsoro carried out there. The model was ømployod by the Xnotituto to car y' out 9Ø pock studios earlier. Studios revealed that the head loss duo to gravel strainer w i rno - In propac ed otrinore ascoipaz'cd to conventional In situgravel pack using € . Vloro drat, don in the well whon propackod strainer roe uocd is due to the greater amount s of frictionalhood loso incurrod no the tvtor has to travel through ouifer bond over longor di of nco. `h:i a extra head boo La oavod when gravel o f larger Chic cnos is ompboyod0 as in conventional inGitu practice ail roverk .eal .or P/A ratio to c pboyod entry of sand into tho pack vies prevented' more effectively. X auggoet9 that cor of of P/A ratio i S iztoro o `fac i.vo to control sand & lorr in otrainors than to greater Chic G cs of packs. Pac c o with collor P/A ratios hoviod ioceo amount of dopor4td nd pac,cod out sand. Dop t of penetrator of sand u,Ao also smaUor in case of pro packed gravel otrnoro as cotiparod to con ntt* al in' aitu pack. Pow unifo ai o of oqui foo :,:r4 oyod P/A ratio of 8.26 and pack thicknoao of 3/4 ado oiy proventod the sand flog into the w U. Thoce etudioc ahoti that øupuit formula can be. employed to analyse the data of op vrimon o on tt labomtory modal of aqui .. Present studies, •suggoot that tore is Ovary nec sn ty of providing i ke packs but the gr v l Tacking be Bono a oido the +iaii to cut corm eli failures duo to tnpropor dovo opant. This suggests the use of light plasticg l r i h can be foznod into is thickness but still tsoight can be Icapt t thin Uito of lifting capacity of the drilling .9 Queetion of pleotic gravel hoc thoroforo to be investigated fully