Mechanical and hydraulic behaviour of overlapped geosynthetic clay liners under differential settlement

Flow through overlapped Geosynthetic Clay Liners (GCLs) under differential settlement is investigated. A numerical model is validated against published data. Due to slippage, the overlap width decreases from d o = 151 mm to full separation ( d = 0) as vertical differential settlement Δ increases from 0 to 185 mm. The overburden stress on the overlap can also drop to 20%-40% of its initial value due to arching. The transmissivity of the interface between overlapping GCL panels increases as the overburden stress decreases for both good- (≥400 g/m bentonite in overlap) and poor-quality overlaps (<400 g/m). Good overlap transmissivity decreased from ∼1 × 10 −9 to ∼2 × 10 −12 m 2 /s (m 3 /s/m) as effective stress increased from 2 to 250 kPa. Poor overlap transmissivity was one to two orders of magnitude higher than good overlaps. By linking these stress–transmissivity relationships with modelled overburden stress and overlap slippage, overlap transmissivities were estimated at various levels of differential settlement below the overlap. Results show that the leakage through GCLs with a 150 mm overlap increases by over two orders of magnitude as Δ increases from 0 to 180 mm. An overlap of 300 mm significantly reduces leakage compared to a 150 mm overlap. • First numerical model to simulate GCL overlap slippage and overburden pressure loss under differential settlement. • First empirical relationship established between leakage through GCL overlaps and overburden stress using 66 data points. • First coupled hydro-mechanical method to evaluate leakage through GCL overlaps at varying levels of differential settlement.