Experimental Study And Fem Analysis Of Geosynthetic Reinforcement

Up to now, the geosynthetic reinforcement mechanism is still not very clear; design method is not maturated; and theoretical research lags behind engineering practice, to some extent, which hinder the application of geosynthetics. Therefore, it is necessary to make further researches on geosynthetic reinforcement.(1) Systematic triaxial compression tests are made for the sand reinforced by various national geosynthetics. Comprehensive investigations into the interaction characteristics are also made between sand/lime fly ash and various national geosynthetics by direct shear tests and pull out tests, which can help choosing geosynthetic type and understanding the geosynthetic reinforcement mechanism; (2) This paper is also firstly systematically presents the results of a comprehensive investigation into the interaction characteristics between lime fly ash and various national geosynthetics;(3) By non-linear FEM, the influence of the modulus of geosynthetics, the thickness of the soft ground and the width of the foundation on the effectiveness of geosynthetic reinforcement are also studied;(4) The main conclusions are as followed: ( Geotextiles are likely to be suited for projects allowing high displacement, polyester warp knitting geogrids and oriented geogrids for projects allowing medium displacement, glass fiber geogrids for projects allowing low displacement and geonets for secondary projects. ( The confining effect of fill material to act on different kinds of geosynthetics varies largely, which must be considered. ( Lime fly ash is light in unit weight; high in shear strength and pull out coefficient, so it is an ideal fill material. ( Geosynthetics make the shallow soft ground become "relative overlaying crust", hence geosynthetics improve the stability of the soft ground. ( There are at least three kinds of different distribution of the friction force of the interface between geosynthetics and the soft ground. When the width of the foundation is smaller, the friction force is firstly increased from zero at the central area of the foundation, then decreased to zero at the edges of the foundation, hence there is a peak; when the width of the foundation and the thickness of the soft ground is larger, the frication force is almost zero from the central area of the foundation to a certain distance, then increased, at last decreased to zero at the edges of the foundation, therefore there is a peak; and when the width of the foundation is larger and the thickness of the soft ground is smaller, the friction force is firstly increased from zero at the central area of the foundation in the negative direction, then decreased to zero, so there is a negative peak, then increases in the positive direction, eventually decreased to zero at the edges of the foundation, hence there is a positive peak. ( When the width of the foundation is smaller, geosynthetics must be placed under the entire foundation; when the width of the foundation is larger, geosynthetics may be placed for certain width at the edges of the foundation.