December 2000 New Letter

IGS NEWS

A Bulletin of the Indian Geotechnical Society (Chennai Chapter)

Vol.2

AUGUST - DECEMBER 2000

Editor: M. Elangovan

The members of Chennai chapter are requested to contribute technical papers to news bulletin of local chapter as well as parent body.

It has been brought to our notice that the parent body is looking forward technical papers related to earthquake related problems.

The members are requested to send their address with e-mail address. They are also requested to encourage their friends and colleagues to enroll as members of the local chapter as well as parent body.

It is programmed to conduct the annual General body meeting on 18th May 2001.

We look forward your active cooperation.

M. Elangovan

Secretary, IGS Chennai Chapter

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Obituary Dr. S.S. Rao Executive Committee Member IGS Parent Body - New Delhi recently expired in Mumbai. We express our heart felt condolence to the bereaved family. He made commendable contribution in the preparation of BIS code in pile foundation.

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Seminar

One day seminar on “Current Trends in Environmental Geotechnique was held on 11-11-2000 at Muthaiyan Auditorium, Anna University, Chennai - 600 020.

Orgainising Secretary : Mrs. K. Premalatha

Senior Lecturer, Division of Soils Mechanics Foundation, Anna University, Chennai - 600 025.

No. of Participants : 69 No. of Sponsors : 13

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CONTENTS

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LECTURES

Interaction with Educational Institutions

The IGS (Chennai Chapter) has initiated an interaction programme with civil engineering departments of Engineering colleges around Chennai.

On 24-8-2000, a lecture was arranged at Crescent Engineering College, Vandalur. Dr. S.V. Ramaswamy spoke on “ Foundation in Expansive Soil” . Dr. B. Ramanathan, Chairman IGS (Chennai Chapter) presented books worth of Rs. 2000/- to the Civil Engineering Department, on behalf of IGS (Chennai Chapter). Thiru M. Elangovan, Secretary IGS (Chennai Chapter) explained about activities of IGS (Chennai Chapter). Dr. Peer Mohamed, Principal and Dr. Srinivasa Raghavan Head, Civil Engineering Department, Crescent Engineering College arranged the meeting.

The Second Interaction programme was held on 26.9.2000 at Civil Engineering Department, Anna University, Chennai - 25. Dr. B. Ramanathan, Chairman, IGS (Chennai Chapter) presented books on Geotechnical Engineering to the Civil Engineering faculty. A special lecture by Thiru. I.V. Anirudhan on “Geotechnical Engineering in River Management” was also arranged.

The professors, staff, students of Civil engineering Department and Dr. S. V. Ramaswamy and Thiru M. Elangovan, secretary, IGS (Chennai Chapter) attended.

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Congratulations

The Indian Geotechnical Society (Chennai Chapter) warmly congratulate the following members.

K. Rajamani

Promoted as Deputy Director, Highway Research Station, Chennai - 600 025. on 15.3.2000

Dr. K. Ilamparuthi

Deputed to work in the University of Liverpool from 1.10.1999 to 31-10-2000 and also promoted as Professor and Head, Division of Soils Mechanics and Foundation Engineering, Anna University, Chennai - 600 025. from 20-11-2000.

Dr. S.R. Gandhi

Elected as Executive Committee Member, IGS, New Delhi (parent body) 2001-2003.

The IGS (Chennai Chapter) extends warm welcome to the president and other office bearers of IGS (Parent Body) New Delhi.

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TECHNICAL ARTICLES

A Paper on Bhuj Earth quake by Dr. K.S. Rao, Associate Professor, IIT Delhi was published in the IGS News Letter. This paper is reproduced in the current newsletter of IGS Chennai for the benefit of chapter members. (Sorry!!! Not included in the web)

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The letter from Prof. T.S. Ramanathan Ayyar and his comments on the paper by
Mrs. Premalatha is presented

Dear Elangovan,

It was a pleasure for me to receive the IGS News of January - July 2000 of the Madras Chapter. It was nice to see that this news letter which was circulated in the early 1990’s started appearing again. I am also occasionally receiving the information of chapter meetings. It will be nice if a program of major events is prepared earlier and sent, as it will give an opportunity for persons like me to attend. As one of the early members of the chapter as of the first batch of post graduate students of Geotechnical Engineering of the Engineering College, Guindy, under Prof. S. Panchanathan, I cherish very fond memories of those days, Kindly convey my good wishes to all members.

I am enclosing a discussion on paper No. 2 Biotechnical Stabilization by K. Premalatha for publication

Yours sincerely

T.S.R.

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Comments by Prof. T.S. Ramanathan Ayyar

Bio-technical stabilization of slope protection systems has gained increasing acceptance and preference, over concrete or masonry retaining structures and geosynthetic fabrics in environment- conscious societies. Woven mattings of natural fibers like, coir or erosion control mattresses are laid over prepared surfaces and spiked and seeds of grass are laid over it and watered. In due course of time, the grass grows and resists both the movement of soil and arrests the flow velocity of the run off water. In the Western countries, this method is called soil saver and in due course of time, the natural fibre which enriches the nutrients in the soil by its degradation is lost and no harmful materials remain. Jute and coir mattings are extensively used for this purpose, coir being less degradable.

However this application can be adopted only with grass and surface rooted plants and where rainfall in enough for sustaining grass. Deep rooted trees are not applicable. I have come across instances of delayed failures of slopes by the action of deep rooted trees penetrating and disintegrating the hard impervious surfaces of laterite and destroying the cohesion leading to delayed failure. In such cases, the softer horizons below are subjected to seepage, dispersion and piping failures. Also coconut trees planted close to buildings on shallow foundations on lateritic curst are seen to weaken the laterite and cause cracks. Roots of coconut trees also penetrate the shallow drainage systems through joints in stone ware pipes and clog the system if they are in the vicinity. Terzaghi has referred to this phenomenon as the danger posed by the gardener’s hose in slope stability. Details of such failures are given my paper on Long term Stability of Cuts in Laterite Terrain in the IGS-2000. Thus a judicious choice of plants is required for protection of slope cuttings and in close proximity to shallow foundations in hard thin crusts underlain by soft layers.

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