Vol.:(0123456789) 1 3 Innovative Infrastructure Solutions (2021) 6:41 https://doi.org/10.1007/s41062-020-00408-6 TECHNICAL PAPER Experimental and numerical studies of three‑layered unreinforced and geosynthetic‑reinforced soil slopes Kingshuk Jana 1  · Suman Hazari 1  · Sima Ghosh 1 Received: 27 June 2020 / Accepted: 16 November 2020 © Springer Nature Switzerland AG 2020 Abstract This paper presents both experimental and numerical studies of three-layered reinforced soil slopes consisting of one sandy layer sandwiched between two cohesive–frictional soils. Geosynthetic reinforcements are provided at the interfaces. Small- scale shaking table tests are performed to evaluate diferent stability parameters like horizontal deformation, root-mean-square acceleration amplifcation factor, and crest deformation of the slope. Water content, base shaking acceleration, frequencies, and quantity and type of reinforcements are varied to perform the tests. The inclusion of reinforcements increases the strength of the slope enormously which is represented in the paper in terms of diferent parameters. Geogrid reinforcement is found to be better in comparison with geotextile reinforcement. To verify the results obtained from the present experimental study, a numerical model is developed using PLAXIS 2D and the acceptability of the study is discussed. Keywords Layered slope · Cohesive–frictional soil · Sand · Shaking table · Geosynthetic reinforcement · PLAXIS 2D Introduction Slopes are the exposed ground surface which stands at an angle with the horizontal. The stability of slope is one of the major concerns and trending research topics in geotech- nical engineering for designing highway embankments, earth dams, etc. Slopes which are stable under static load- ing condition may not be stable under seismic loading due to the incorporation of extra added inertia force. In such situations, either the slope is to be fattened, embankment soil is to be replaced by higher strength soil, or the soil is to be reinforced by introducing reinforcements. The use of geosynthetics is one such method. The advantage of the use of geosynthetics is manyfold. In addition to the increase in strength of the slope soil, it also absorbs seismic energy and waves and transmits lesser energy to the next upper soil and so on. The study of slope under static loading conditions is done by several researchers [1–4]. But to understand the response of slopes under seismic loading condition, Clough and Pirtz [5] have performed the frst well-documented shak- ing table study on model rockfll dams and concluded that earth-fll dams are very much resistant to earthquake due to their fexible nature. Seed and Clough [6] have studied the earthquake-resistant dams and concluded that due to earth- quake the upper portion of the slope undergoes settlement, whereas base soil undergoes sliding. Hong et al. [7] has performed shaking table tests on fve-nailed model slopes and showed that the nails could improve the seismic resist- ance of steep slopes signifcantly. Nova-Roessig and Sitar [8] have performed a centrifuge model test and observed that the dynamic behavior of soil slopes reinforced with geosynthetics and metal grids depends on the backfll den- sity, slope inclination, reinforcement stifness, and spacing. Koga and Matsuo [9] have conducted 1-g shaking table tests of earth embankments located on saturated sandy ground and revealed that the soil response and damage extent of an embankment are strongly afected by input motion char- acteristics. Wartman et al. [10] has compared the sliding response of deformable clay masses and a rigid block on an inclined plane subjected to cyclic motion. This study found that the rigid block procedure should not be used in cases when the computed tuning ratio (ratio of the predominant * Sima Ghosh sima.civil@nita.ac.in Kingshuk Jana kingshukjana4@gmail.com Suman Hazari sumanhazari22@gmail.com 1 Department of Civil Engineering, NIT Agartala, Agartala, India