Armoured Tank Movement at Suratgarh, Rajasthan, India
|Main Client||Indian Army Corps of Engineer|
|Material Used||StrataWeb® geocells|
|Application||Load bearing application with confinement to facilitate heavy tank movement over loose soil, with high ground water.|
|Project Period||March 2012|
The Armoured Engineer Regiment, Rajasthan had a critical problem of running its tracked heavy armoured tanks on loose, fine sand, resulting in delayed movements and drills. The area is low lying, sometimes in quick sand-type conditions with constant seepage from the surrounding canals. Weights of the various categories of tanks ranged from 14 tonnes to 50 tonnes.
Objective And Solution
The soil was loose fine sand resulting in slow and dusty movement of the heavy weight tanks. The problem was compounded with seepage from nearby canals. With due considerations to time and cost, StrataWeb® SW35 of 150mm depth was recommended along with local sand as infill. Importation of better quality infill would have increased costs and logistic problems with tangible benefits and hence local sand was used instead, quite effectively. Each StrataWeb® panel was interconnected with high strength cable ties.
StrataWeb panels used were of size 2.6 m X 5.6 m. The 5.6 m length was placed parallel to the traffic movement. The cells were filled with the in-situ sand with the help of a JCB and also manually. The tanks were immediately run over both StrataWeb stretch as well the untreated portions beyond.
Movement over the portion over which the StrataWeb was laid was fast and smooth with barely any sand dispersion behind the tracks. However over the untreated portion, the tracks kicked up the sand and caused severe rutting. The speed was also impaired and the traction engine was strained.
The Mechanics of StrataWeb®
Cross Section of StrataWeb® geocell
StrataWeb® geocells filled with cohesionless material form rigid mats capable of distributing imposed loads over a larger area.
When a vertical pressure q₀ is exerted on the non-cohesion fill within the StrataWeb®, lateral stresses are generated. Since all the StrataWeb® cells are filled with non-cohesive material, deflection of the StrataWeb® walls are negligible. Hence the lateral stresses thus generated equal to about (k₀ * q₀) in all cells, where k₀ is the “at rest” earth pressure coefficient for the in-filled non-cohesive soil. This increases shear strength of the confined soil within the geocells, and lateral stresses are generated in congruent cells as reaction.
This effect creates a stiff mattress which contributes to distributing the load over a larger area. Hence the pressure below the StrataWeb® system, p is lower than what they would be through a conventional load transfer system. Hence heavy loads are spread and can be safely transmitted onto weak foundation soils without distress.
StrataWeb provides a quick and successful solution for heavy vehicular movement in loose soils. Even when the water table is high and the CBR is low, StrataWeb® geocells have successfully proved capable to take heavy loads without distress.