Seismic stability of reinforced soil walls under bearing capacity failure by pseudo-dynamic method

In order to evaluate the seismic stability of reinforced soil walls against bearing capacity failure,the seismic safety factor of reinforced soil walls was determined by using pseudo-dynamic method,and calculated by considering different parameters,such as horizontal and vertical seismic acceleration coefficients,ratio of reinforcement length to wall height,back fill friction angle,foundation soil friction angle,soil reinforcement interface friction angle and surcharge.The parametric study shows that the seismic safety factor increases by 24-fold when the foundation soil friction angle varies from 25°to 45°,and increases by 2-fold when the soil reinforcement interface friction angle varies from 0 to 30°.That is to say,the bigger values the foundation soil and/or soil reinforcement interface friction angles have,the safer the reinforced soil walls become in the seismic design.The results were also compared with those obtained from pseudo-static method.It is found that there is a higher value of the safety factor by the present work.

Performance of a Nonwoven Geotextile Reinforced Wall with Unsaturated Fine Backfill Soil

The use of marginal backfills in GSE （geosynthetic stabilized earth） walls has not been recommended by different standards specifications. Restrictions are motivated by the poor hydraulic conductivity of fine soils that are capable of developing of water pressures. However, the use of granular materials can expend the cost of the construction. As a result, local soils, granular or not, have been increasingly used. Unsaturated conditions of fine soils may result in convenient performance even using extensible reinforcements. This paper evaluates the performance of a full scale model of a nonwoven geotextile reinforced wall constructed with fine grained soil backfill. The unsaturated condition was maintained and matric suctions, displacements and reinforcement strains were monitored during the test. Results have shown that the unsaturated condition of the backfill allowed maximum reinforcement peak strain of 0.4 %. For the case of a wrap faced wall on a firm foundation the performance and good agreement between measured strains and factors of safety from limit equilibrium analyses have shown the maintenance of unsaturated conditions as an economical alternative to the use of high quality fill.

Influence of variables related to soil weathering on the geomechanical performance of tropical soils

This paper presents an experimental and analytical investigation of the influence of variables related to soil weathering on the geomechanical performance of sand-silt mixtures containing lateritic soils,i.e.intensely weathered tropical soils with the influence of interparticle bonding.The sand-silt mixtures containing different relative proportions between uniform sand and lateritic soil were produced,and geomechanical soil characterization tests were performed.Based on the results,a transition from a primarily coarse-to a fine-grained prevailing soil structure was found to cause considerable impact on the geomechanical performance of these soils,as evidenced by design variables related to soil mineralogy and size distribution characteristics.Specifically,fines contents of both individual soil particles and soil aggregations were found to correlate with experimental results,while the relative proportion between sesquioxides(aluminum,and iron oxides),and silica,i.e.sesquioxide-silica ratios(SSR^(-1)),facilitated estimates concerning changes in geomechanical performance.Finally,the application of the sandsilt mixtures containing lateritic soil on soil walls reinforced with polymeric strips was also evaluated,further emphasizing the potential advantages of adopting variables related to soil weathering on design guidelines concerning tropical soils.