6585844966

ESOPT

State-of-the-art report

Penetration testing in India

M.D. Desai, G.R.S. Jain, Swami Saran & P.K. Jain

SEMMaRY. Ihree typ as of penetration tests are being freouently used. Ihe Standard penetration test has been ln use sińce early fifties and varlous factors affectlng the results like overburden, slze of borę, and depth of penetration bave been studledi and varlous oorrelations have been bzought out. By uslng a flve percent bentonlte slurry in water, sedimentatlon and sand bolllng ln bores oould be successfully avol ded.

In Dynamie Gono Penetration tests, two sizes of cones are gcnerally adopted. Oones with 60° apex anglo are found to piovide least resl stance. and thus adopted. Ihe 50 mm dla. cone is driven dry. It helps ln reoonnai ssance studies for enabling selective detali ed in-situ testing or sampling for typ i cal soil profil es. Ihe 65 mm cone is used both dry and with bentonlte slurry. In the latter, friction on driving rods is elirai-nated and the results are morę representatlve of the strata penetrated and provlde comparable Yalues to N in Standard Penetration Tests.

Ihe Static cone tests are freąuently used fbr determining bearlng capadty of deep fbotings. A detalled study on plles indicated that frictlonal resl stance is about 2 percent of the point resl stance.

Ihere are fbur Indian Standards on Penetration tests and over five other Co des on foundatlons spec! fy their use with guidelines for the lnterpretation of data.

1. IHTRDDUCTION

Penetration tests. apart from their use in zoutine soli eiplorations, are increaslngly being used fbr estlo&tlng the bearlng capadty of fbotings, plles and caissons. Advantage of uslng pen^-tration tests is obvious. Ihey are easy to perfbun and reflect the properties of substrata reasonably wdl fbr most of the avil Bigg. Works.

The field load tests are though the most direct and preferable raethod fbr determining the bearlng capadty of fbotings but are not practicable on most of the Jobs due to the elaborate naturę of the tests and oost. Determination of bear-ing capadty from soli properties is possible but prerequl d tes are soli samples. Ihe dlfficulty and ezpense of extractlng undisturbed samples from borę holes, particularly in case of non-coheslve strata, and the lmpossibility of deallng with gravels, ln a way limits the scope of this approach.

Indian Sub fentinent has three dlstlnct earth features which are as unlike in their phydcal as ln thdr geological characters. Biese are the trlangular plateau of the Peninsula. the mountain-eous region of the Himaliayas which borders India to the West, North and Bast, and the Great Indo-Oangetic Plain of the Punjab & Bengal soperatlng the two fbnner areas (Wadia, 1944).

Ihe soil of the Peninsula, for the greater part, is of resldual naturę.

Ihe great alluvial mantle of Korth India, oonstituting one of the largest alluvial deposlts was formed of debrls brought down by the iivers fzom the higher grounds. Ihe residual solls of the Peninsula show ątdte a variety both in thdr texture and in thdr minerological oomposition. Ihey al® exibit a great deal of varlatlon ln depth, oondstency, colour etc.

However, the solls of India, s> far as thdr geolog!cal peculiarlties are ooncerned, show far less regi°ⁿal vad-atlon than those ln other oountries. Ihese soils differ condderably from the soli of Euorpean oountries which are largely of post-Gladal growth.

Ihe alluyial solls of the vast Indian Gangetic Plains likewlse differ from Penlnsular solls and from the major!ty of European solls in havlng undergone but lit tle pedo genie erolution sińce thdr deposition by rlver ag®cy.

India is fuli of high mountalns, deep and extended valleys, rlver bałt deposlts, large plains and ooastal lands. Due to yarlous five year development piana, many sophi sticated structures are ooming up all over.

And, we need qulck and reliable soli esploratlon techniques. Kost of the present metnods of analyds in the field of Fbundatlon Ehgineerlng are still based on indirect tests and penetrometers have fairly established thcinselves as one of the widely accept-ed techniąue (Indian Standards, 63,