Use of ‘Limited Life Geotextiles’ (LLGs) for basal reinforcement of embankments built on soft clay

Polymeric technical fabrics have long working lives and are sometimes used in practical situations where a geosynthetic is only needed to be fully functional for a relatively short period of time, e.g. a separator layer beneath a temporary access road. This article concerns the use of ‘Limited Life Geotextiles’ (LLGs), i.e. high specification geotextiles, which are designed on the basis of having a limited working life, as basal reinforcement for an embankment built on soft clay. A method is given for defining the allowable progressive loss of tensile strength of the foregoing basal LLG as a result of improvement of the shear strength of the foundation soil due to consolidation. It is shown that the derived relation between required reinforcement strength and consolidation time (the Time-Strength-Envelope) can be represented by a simple exponential equation. Vegetable fibres are natural candidates for use in the manufacture of LLGs since they are a renewable resource and their degradation with time is accounted for in the design of the LLG. Combinations of vegetable fibres growing in tropical regions which are capable of satisfying the Time-Strength-Envelopes for several embankment slopes are presented.