Proposal of a design method for soil-nailed walls and compare it with the conventional design method

In the conventional design method for soil-nailed walls that is based on the FHWA guidance, the nails properties (the length, spacing and diameter of nails) through the excavation depth is usually assumed constant. However, in the design method introduced in the present study (the proposed design method), the nails properties are varied through the excavation depth by step-by-step control of the factor of safety for each row of nails. In the present study, first numerical assumptions are explained and then the numerical modelling methodology is verified through the Clouterre project. Afterwards, the details of the conventional and proposed design methods are described. Next, a parametric study is performed to compare the conventional and proposed design methods. In the parametric study, the effects of the excavation depth, soil density, soil cohesion, surcharge and required factor of safety are investigated. The results of the present study show that the proposed design method compared with the conventional one would decrease on average 30% the nails volumetric density (i.e. the volume of nails divided by the wall area), which is considerable from the economical point of view. Moreover, the results show that the total displacement at the wall crest for the proposed design method is comparatively 10% higher than that of the conventional design method.