Construction of a composite dam with a masonry spillway across the river Tawa in Madhya Pradesh is in progress. The foundation rock consists of soft stratified sandstone with sandwiched thin shale layers.

The paper describes the studies made in-situ as well as in the laboratory on the soft rock of the spillway foundation. Test results on shear strength, deformability and quality index of the rocks are described in relation to the geological conditions of the dam site.


Construction of a composite dam with a gravity type masonry spillway of about 50 m height, across the river Tawa, is in progress. The site is situated at about a kilometer downstream of the confluence of Tawa with its tributary Denwa in Hoshangabad district of Madhya Pradesh. The paper describes the studies made on the soft foundation rock of the spillway and transitions. The engineering properties like shear strength, modulus of elasticity unconfined compression strength etc. were assessed by conducting in-situ and laboratory tests.

Site Geology

2.0 The foundation rock as revealed by several core borings and exposed trenches consists of Pachmari sandstones of Gondawana age[1] with thin sandwiched layers of shales. Shales vary in thickness from a fraction of centimeter to about 15 cms and occur at varying intervals of depth. An idea about the thickness of shales can be had from fig. 1.

2.1 The layers are dipping upstream with a dip varying from 20° to 25°. Texturally the rocks vary from fine grained to coarse grained. Being a sedimentary formation, layers are erratic and weaker zones are not confined to any particular elevation or part of the foundation.

Preliminary Data

3.0 At the time of planning the present studies, it was known that 1) core recovery was poor (about 60%) when Calyx drilling was used and it had improved to 80 to 95% when diamond core drilling was used.


La construction d’un barrage composé avec un barrage déversoir maçonnaire à travers la riviere Tawa dans Madhya Pradesh est en marche. Le fond rocheux consiste d’un gres faible stratifié, avec des couches schisteuses minces.

La communication dècrit des études faites a la fois in-situ et dans le laboratoire avec la roche faible du fond de dèversoir. Les conclusions des études sur la resistance au cisaillement, deformabilité et l’index de qualité des roches sont decrites comme fonction des conditions géologiques de l’emplacement du barrage.


Das Bauen des zusammengesetzten Damms mit dem gemauerten Wehr über dem Fluss Tawa in Madhya Pradesh schreitet fort. Der Flesboden besteht aus weich geschichtetem Sandstein mit eingelegten dunnen Schiefertonschichte.

Das Papier beschreibt die Versuche die sowohl auf dem Bauplatz als auch in dem Laboratorium über des weichen Fels der wehrgrundung gemacht wurden. Die Untersuchungsergebnisse über Scheffestigkeit, Verformung und qualitätsindex der Felses sind inbezug auf die geologischen Zustande des Bauplatzes beschrieben worden.

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