Box Type Minor Bridge on Small Rivers in Alluvial Region

Abstract

Since time immemorial, humankind has been using various techniques to cross the rivers, streams or any depression without closing or obstructing the original flow through a structure called bridge. With the span of time and advancements in civil engineering, several types of bridges have come into existence like wooden, steel, masonry arches, RCC and pre stressed concrete bridges. Indian Roads Congress categorizes three types of the bridges on the basis of length i.e. culverts up to 6.0 m, minor bridges above 6.0 m to maximum 60.0 m length and major bridges above 60.0 m. In present scenario, minor bridges over small rivers has become necessary for development and prosperity of nation as most of the roads have to cross small rivers at several places to connect remotest corner of the country. Bridges, though a manmade structure, over a period become an important part of environment because in most of the cases water flowing below is used for drinking, irrigation and underground recharging. The alluvial region of India spread from Punjab to West Bengal has a peculiar nature because soil is almost soft in nature consisting of mainly sand, clay and silt which is fertile for vegetation. Water retention and its movement condition are high throughout the year. Several type of water bodies which exists in this type of region are pond, small drain, small and medium rivers which drains into the big rivers like Ganga, Yamuna, Ghaghara, Gomati and Sai etc. Since long time, road system on the earthen track and pucca has been introduced for traffic like chart, chariot and motorized vehicle. There were little number of bridges over major rivers i.e. bridge alone to cross over the river Ganga except in few places like Allahabad, Kanpur and Varanasi and over the Ghaghra Algine bridge, Maghighat, Bhatni. Some bridges were constructed over small and medium rivers in medevial period by local rulers and businesspersons, which have now become obsolete. It is found that most of the bridges are of masonry arches wooden and trusses having insufficient water and carriageway. After independence, the road network system has been improved to meet out socio economic needs of people. The new bridges have been constructed with standard road width and sufficient waterway. Study has been conducted for existing new constructed bridge system over small river and alluvial region of Uttar Pradesh to set guidance for future course of action in replacing and providing new bridges to optimize the needs of the people. Bridge system being provided over small & minor rivers for the road network for new and replacement of older bridge at different site is varying from place to place. For this purpose, study has been conducted for sustainable option of minor bridges over small rivers discharge up to 300 m3 /s. It is found that the box type minor bridges are best option on small & minor rivers.