Inverkan av valveffekter vid beräkning av jordtryck

Sammanfattning: The load transfer and redistribution phenomenon that occurs through the mobilization of shear stresses in response to relative displacements in granular materials, such as soils, is attributed to the arching effect. The arching effect has a great influence on the behaviour of soils and plays an important role in predicting earth pressure in granular backfills of limited extent, confined by unyielding stationary materials. Unlike geostatic earth pressure, a granular material influenced by arching exhibits a non-linear pressure distribution and exerts a pressure that signicantly differs from the state of pressure obtained under frictionless conditions. The estimation of lateral earthpressure is essential in the engineering practice since it governs the design of many geotechnical structures. A backfill material that is restrained by adjacent structures or placed in a narrow gap between nearby stable materials is partially supported by friction. Depending on the distance between the slip planes, a signicant stress reduction occurs in the backfill. This master's dissertation describes how to estimate the magnitude and distribution of earth pressure exerted by a granular material due to the arching eggect. A finite element simulation, performed in COMSOL 4.4, has been conducted to evaluate the circumstances where a reduction of earth pressure is applicable. Analytical expressions, proposed by Janssen and Terzaghi, are compared to numerical results. A parametric study is undertaken to investigate the effects of various parameters involved in the analytical expressions. The results obtained from the numerical analysis reveal that the confinement of surrounding boundaries, fill properties and wall inclination are crucial factors in predicting the earth pressure exerted by a confined granular material. The numerical results are in good agreement with the analytical expressions for narrow geometries with vertical walls.