Essay Example on Phenomenon of stress transformation from yielding part of Soil








Introduction Phenomenon of stress transformation from yielding part of soil onto adjacent rigid part is known to be arching action of soil which is encountered in both underground structures and natural terrains Retaining walls buried pipes culverts under embankments tunnels under loose soil under passes and buried conduits can be categorized as few underground structures affected by arching effect of soil Arching occurs when there is a difference of the stiffness between the installed structure and the surrounding soil If the structure is stiffer than the soil then loads arches onto the structure Otherwise if the structure is less stiff than the soil then loads arches away from the structure Depending on relative stiffness of surrounding soil mass arching phenomenon tends to have both positive and negative impacts on underground structures that s the arching action can be either active or passive Reduction of overall stress transformed on to structure from overlying soil is the foremost positive impact of arching effect

This occurs when surrounding soil around a structure is stiffer than the structure and this is known as active arching Increase of stress transformed to the structure is the foremost negative impact of soil arching which occurs when structure is stiffer than the surrounding soil mass History of development of theories on arching action of soil date back to early 1800 s with findings of French military engineers that only a fraction of total weight of total material above silo was supported by its base and more load was transferred to side walls than expected Development of arching action theory came to a new dimension with Terzaghi s trapdoor tests 1936 and his proposed equations for stresses developed due to arching effect 1943 Terzaghi considered plastic behavior of soil during development of those equations for stress analysis due to soil arching Later many researchers modified Terzaghi's theory and came out with their own experimental results on arching action of soil Finn 1963 Burghignoli 1981 Getzler 1968 were some among those researchers Rather than laboratory and field based experiments computer modelling finite element method Getzler 1920 linear elastic finite element program Rude 1982 discrete element method Sakaguchi and Ozaki 1992 were also have been done on arching action of soil

Problem statement Currently available methods and theories to analyse arching effect of soil on buried structures are inadequate to have better results during analysis of stresses on a structure that is buried or going to be buried in soil and these are relatively time consuming Because during designing of an underground structure it is essential to analysis deflection and ultimate stress that the structure going to undergo during design period of life but results obtained during these analyses are not much relevant to observed field values At present with the development of expressways tunnels buried pipeline systems and culverts there increase a need for accurate and fast way of determining effect of soil arching and stress distribution on buried structure considering arching effect So there arise a need for development of new method to determine real time stress distribution caused by soil arching Significance of the research Since there are no real time analyzing method to determine stresses developed on buried underground structures due to arching effect there arise a need for development of new method to determine stresses with an increase in demand for accurate analysis of stresses developed on buried structures

This research will help to understand how newly developed earth pressure cell can be used to determine real time arching effect stresses and this research will lead studies and analysis on arching effect of soil to a new dimension From this research a real time stress analyzing method can be developed to measure stresses due to arching of soil rather than traditional theoretical calculation methods Scope of the study Scope of this research is to come out with real time analyzing method to determine stresses developed on underground structures considering arching effect of soil with aid of experimental data collected from prototype modelled at laboratory rather than performing experiments at field to overcome time limitation in doing experiment works and cost at field conditions Aims and Objectives of the research Objective of this research is to come out with appropriateness and accuracy of using newly developed earth pressure cells for analyzing and determining real time stresses developed on structures buried under soil considering arching action of soil by doing laboratory experiments on a modelled prototype experiments on buried rigid and flexible pipes Proposed methodology Literature review on various published research articles indexed journals conference papers and books regarding arching effect of soil in past years Understanding theory and effects of arching action of soil need for doing research regarding arching effect Study on how to use recently developed earth pressure cell to determine real time stresses due to arching effect Study and development of a prototype model using buried rigid and flexible pipes at laboratory to determine arching effect Real time data collection from experiments on prototype using earth pressure cells Extrapolation of data to field conditions and analyzing results with available theories

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