Page:Professional papers on Indian Engineering (second series).djvu/343

 No. CCCVIII.

CHEAP WELL FOUNDATIONS.

By B. W. BLOOD, Esq., M. Inst. C.E., Exec. Engineer, Rajputana State Railway.

The experience described below is believed to be a novel mode of getting down moderately deep foundations when the soil is not too wet to allow a well to be kept dry.

On the Sambur Nawah Extension of the Rajputana State Railway, the line near Nawah is carried across a bay of the Salt Lake, into which runs, during the rains, a river which drains about 100 square miles of country. The river is one of the largest feeders of the Sambur Lake, and, as may be supposed, at times discharges a very considerable volume of water, which will be passed by a bridge, 40 spans of 20 feet.

The bed of the lake at the site of the bridge is composed of about three feet of a stiff mixture of clay and sand, below which, for about 13 feet, is a kind of quicksand with thin beds of kankar at intervals, till at about 15 to 17 feet a thick band of soft scaly half formed sand- stone is reached. The foundations were to be oval cylinders, 13 and 11 feet major and minor diameters, splayed out at the bottom, and in order to found them upon this hard bed, well steining or tubeing of some kind would be required for the excavated wells to keep out the water and slush. On account of the expense of a regular well steining and carbs, and the delay they would cause, it was decided to adopt a steining of sirpat grass sunk as is done, in their kutcha wells, by the natives of the North-Western Provinces. This steining was made of the long jungle grass, which grows plentifully in that part of the country, formed into a 233