Abstract: Geosynthetic clay liners (GCLs) are newly used in combination with the vertical barrier wall in waste landfills. One of the critical points of this application is to control the preferential flow in the overlapping area of adjacent GCLs. However, there is still a lack of reliable data. This paper aimed to investigate the influence of the overburden pressure on the equivalent hydraulic conductivity (ko) of the overlapping area with bentonite pastes, to the reference base case in which no bentonite paste was presented. A penetration apparatus with internal dimensions of 1 200 mm×700 mm×700 mm(length×width×height) was presented. The 500 mm long GCL overlap was tested under a combination of the hydraulic head being 1 m and the overburden stress being 10, 25, 50, 100 and 150 kPa, respectively. It was found that: 1) The preferential flow around the overlapping area of GCLs occurred at the initial stage of penetration. The ko of the overlapping zone under an overburden pressure of 10 kPa was 5.6 times greater than that of the GCL due to the existing preferential flow. 2) The ko of the overlapping area decreased with an increase in the overburden pressure. The ko of the overlapping area subjected to a low overburden pressure of 10 kPa was equal to 2.27×10?8 cm/s, while it decreased to 5.93×10?9 cm/s when the overburden pressure reached to 100 kPa. 3) The permeability was significant reduced by the presence of bentonite pastes in the overlapping area. The ko of the GCL overlapping area was lower than that without the bentonite paste, and the value of ko reduced to 5.15×10?10 cm/s when the overburden pressure was as high as 150 kPa.

Key words: geosynthetic clay liner(GCL), overlap, hydraulic conductivity, bentonite, vertical barrier wall