Group Resistance Of Recycled Plastic Pin In Sustainable Slope Stabilization

Abstract

Slope failure is a common phenomenon in areas with slope constructed on high plasticity clay and shallow slope failure is predominant in North Texas. The cumulative maintenance cost of minor slides is equal or greater than major landslides. But, cost associated with post failure maintenance can be reduced significantly if an appropriate stabilization method is adopted. Thus, selection of appropriate and economically viable slope stabilization method has got great importance for the geotechnical engineers. Recently, a new approach of shallow slope stabilization technique is introduced using Recycled Plastic Pin (RPP). RPP used in shallow slope stabilization should pass beyond the slip surface to pin the sliding surface with the stiff soil. An extensive study based on the field performance of RPP installed for shallow slope stabilization was carried out by Loehr and Boders in Missouri, and Khan in Texas. In most of the cases, the horizontal displacement of RPP reinforced slope was about 3 inches both in Missouri and in Texas. The field investigation of the RPP reinforced slopes leads researchers to develop two new design protocols. They are limit resistance method by Loehr and Boders and performance based method by Khan. The limit resistance design method did not consider the effects of creep of RPP. This limitation was taken into account and a new performance based design method is proposed by Khan. But, instead of considering group resistance of RPP, only resistance of single RPP is considered in performance based method. Thus, the objective of this study is to determine the group resistance of RPP in sustainable slope stabilization. To attain the goal, number of RPP required forming an effective group at different spacing is determined. In order to fulfill the objective, an extensive study has been conducted based on numerical modeling and supported by field data. Thereby, a new design chart is proposed considering group resistance of RPP, where maximum horizontal displacement and flexural stress of RPP are taken into account. Parametric study is carried out to determine the variation of resistance between group of RPP and single RPP at different loading condition, soil strength parameters, spacing and depth of slip surface, where the horizontal displacement of single RPP and group of RPP is determined and plotted graphically. The graphical representation shows the difference of resistance between group of RPP and single RPP with increasing load, soil strength, spacing and depth of slip surface. Thus, the design charts for group of RPP at different spacing are developed considering different types of soil for different slope, where the horizontal displacement and/or flexural stress is shown with increasing applied load. Similar conditions of Interstate 70-Emma Site, as presented in the literature by Loehr and Borders is plotted on developed design chart for 4-ft deep slip surface. The interpolated horizontal displacement according to the developed design chart for RPP at 3-ft spacing is 0.51 and is in good agreement with Interstate 70-Emma Site. Finally, a multiplication factor is introduced to establish a relationship between the developed design charts to performance based method.