25th February 2018
THE de MONTOMORENCY BRIDGE ACROSS THE
JHELUM RIVER AT KHUSHAB.
The de Montmorency Bridge which was opened by the Governor. of Punjab, Sir Geoffrey de Montmorency on April 25th, 1931, forms a combined railway and road connection across the Jhelum River on the Sargodha-Khushab Branch line of the N. W. Railway. On the completion of the rail-cum-road bridge across the Chenab River at Chiniot (which is expected to be ready in March 1932) and with the railway bridge at Kalabagh (opened to traffic on 10th August 1931) an alternative route from Lahore to Waziristan was available.
The
bridge consists of 15 spans, each 159 feet center to center of piers: with a
clear span of 144 ft.
Paper By CAPTAIN J. R. SIMPSON, R.E., ASTT.
EXECUTIVE ENGINEER,
NORTHWESTERN RAILWAY.
Standard of loading.
The de Montmorency Bridge is designed to carry a single line of broad-gauge railway to M. L. Standard Loading of 1926, which is equal-valent to a train hauled by two locomotives of 22} ton axle load, and for the roadways, British Engineering Standard 10-unit highway load, which is equivalent to a ten-ton axle load followed by 4.5-ton axle loads spaced 10 feet apart.
Foundation of piers.
The piers and wells are brick-in-cement mortar well foundations. Twin octagonal well foundations were employed, and they were sunk to an average depth of 90 ft. The wells, piers, guide bunds, and approach banks were built by the Construction Branch, N. W. Railway, Mr. A. Latif Sheikh, B.A., B.Sc., being the Executive Engineer, and are not dealt with in this paper.
Discharge of river.
The discharge of the river varied from a minimum of 300 cusecs. in the cold weather to a maximum of about 5,50,000 cusecs during the monsoon.
Girders.
The spans are made up of half-through
type truss duplicated trusses and were designed and erected by the
bridge division of the Northwestern Railway. The details of the design
were approved by the Consulting Engineers, Messrs. Rendel Palmer & Tritten,
Westminster, London. The steel work has been largely made
up of railway spans re-leased from the Kaiser-i-Hind bridge across the Sutlej
River at Ferozepur.
In all, 6752 tons have been used in
the superstructure, 27 percent of this being of new material which
includes 6 new trusses manufactured by a construction firm in India. The
work entailed closing over half a million rivets in the field.
The second-hand material was dealt
with in the bridge department workshop at Jhelum. the girders being
strengthened and remodeled there as required. Each span was
assembled in the yard at Jhelum to ensure correct fabrication before
being sent to the site for erection. As the main girders are duplicated,
separate arrangements were necessary for the erection of inner
and outer girders.
The weight of each pair of inner
girders without flooring was 130 tons.
Temporary staging in all cases was
founded on sandalwood piles 35 feet long. Sixteen piles are being used
for the staging, grouped under the center of each span. Most of the piles were
extracted by inverting the pile driver and suspending it from the
main girders above, the pile driver driving against a yoke attached to
the piles. During the monsoon, some of the piles were extracted by
making fast one end of a rope to the pile and the other end to the
main girders.
and allowing the next flood to scour out the bed and free the pile.
Labor.
With the method of girder erection
described, assembling and riveting each pair of girders occupied 7 days;
launching, hitting, and riveting cross girders another 7 days, each pair of
inner girders being completed in a fortnight. About 350 men were
employed in an ordinary way and 100 of these were semi-skilled men. With double the above labor,
and working from both ends of the
bridge, it was found possible to
double this Work through the monsoon of 1930, the highest flood experienced in
l'5 feet of the maximum flood for the last 40 years.
Cost.
Work was completed at Rs. 200 a ton.
With new steelwork, the cost would not have been less than Rs. 350
per ton.
Staff.
The design, fabrication of girders at Jhelum, and girder erection in the field, were carried out under the supervision of Mr. W. T. Everall. O.B.E., M. Inst., C.E, Deputy Chief Engineer, Bridges. Executive Engineer, Bridges, was responsible for the girders in Jhelum, girder erection in the field, and several of the interesting features employed in the work.
