Vertical cutoff walls serve as a primary engineering treatment for the containment of contaminated sites, functioning as essential physical barriers to intercept the migration of hazardous plumes. Compared to traditional soil-bentonite slurry walls, composite cutoff walls provide superior hydraulic reliability and chemical attenuation, yet their integrity and performance in vertical configurations, particularly in unsaturated states, remain poorly understood.
This study investigates the initial 4-month consolidation and desiccation behaviors of a geomembrane-soil-bentonite cutoff wall under unsaturated conditions at a municipal solid waste landfill, using an innovative ''locking joint'' sensor installation method to monitor the evolution of water content, pore pressure, horizontal stress and temperature. Results reveal a pronounced depth-dependent desiccation stratification, where the shallow zone becomes unsaturated within 10 days and horizontal stresses drop below 20 kPa across all depths, significantly lower than saturated barriers. The typical stress distribution and desiccation-induced shrinkage led to GMB-backfill interface detachment, functioning as preferential flow paths and causing synchronous pressure jumps during rainfall periods.
The findings underscore wall's structural vulnerability under drying conditions and provide optimization strategies to enhance its long-term service performance.

Composite cutoff wall,Soil-bentonite,desiccation cracking,Field test,Membrane-backfill interface