Geotextile tubes have offered a cost-effective and convenient solution for the treatment of dredged slurry in recent years. Despite their benefits, the dewatering process of this method remains cumbersome and time-consuming. The incorporation of flocculants into dredged slurries has been shown to mitigate the clogging of geotextile tubes, thereby enhancing the efficiency of the dewatering process. To quantify the impact of flocculant addition on the dewatering performance, a series of laboratory tests were conducted to investigate the sedimentation behavior of flocculant-treated river-dredged slurries under filtration of woven geotextiles. The impact of different flocculants is evaluated with the sedimentation rates of dredged slurries, specifically nonionic polyacrylamide (NPAM) and cationic polyacrylamide (CPAM). Results demonstrated that both NPAM and CPAM, at an optimal concentration of around 250 mg/L, could substantially increase the settling rates of slurries when filtered through geotextiles. At equivalent flocculant concentration, NPAM outperforms CPAM in accelerating sedimentation rates. It is also evidenced that adding flocculants can significantly augment the particle size and permeability of slurries. After adding flocculants, the water content and dry density of the final sediments exhibit a more uniform distribution in the vertical direction compared to the original slurry. Furthermore, scanning electron microscopy was employed to analyze the micromorphology of the final sediments treated with different NPAM concentrations. The results showed that the slurries exhibited significant void structure under treatment with the optimal concentration of NPAM, demonstrating the flocculants’ effectiveness in enhancing the dewatering process of river-dredged slurries when filtered with geotextiles.

An accurate description of composite geomembrane-cushion interface behavior is of great importance for stress-deformation analysis and stability assessment of geomembrane surface barrier of rock-fill dam. A series of direct shear tests were conducted to investigate the friction behaviors of interfaces between composite geomembrane and two different permeable cushion materials (crushed stones and polyurethane mixed crushed stones). The shear stress-displacement relationships of the two interfaces show different characteristics and were described by the nonlinear-elastic model and nonlinear-elastic perfectly plastic model, respectively. Then the two models were implemented into the Fast Lagrangian Analysis of Continua in Three Dimensions (FLAC3D) procedure correctly. By verification of a numerical example, numerical calculation results showed a good agreement with the theoretical solutions and test results.

The cushion of a geomembrane surface barrier of a high rockfill dam built on deep overburden is prone to crack and fail because of excessive flexural deformation. This study proposes a geomembrane surface barrier for a high rockfill dam on deep overburden. The proposed geomembrane surface barrier uses polyurethane bonded aggregates as the cushion material. The loading and deformation performance of the barrier system under uniform water pressure was investigated using a self-developed structure model test device. The mechanical and deformation property of each layer of the barrier, and the interaction mode between adjacent layers, were obtained through external videos and internal sensor monitoring. The results demonstrated that the polyurethane bonded aggregate cushion exhibited good adaptability to flexural deformation during the entire loading process and maintained good contact and coordinate deformation with the upper protective and the lower transition layers. The geomembrane surface barrier created using polyurethane bonded aggregates as the cushion material can adapt to the flexural deformation of a high rockfill dam surface on deep overburden.

Based on the direct shear test results of interface between a composite geomembrane and cushion material, nonlinear elastic, perfectly plastic model was used to describe the interface behaviors. The interface model was incorporated into the Geogrid element of a fast Lagrange analysis of continua in three dimensions (FLAC^3D) procedure through a user-defined program in the FISH. Then a geomembrane surfaced rock-fill dam on thick pervious foundation was numerically analyzed using the incorporated model. The numerical results showed that only small tension deformation can be found in the most area of geomembrane on the dam surface. However, large tension deformation of geomembrane appeared close to the anchorage in the peripheral zone of the barrier. The anchorage structure of geomembrane in this area should be carefully designed to avoid tension failure of geomembrane.

An internal geomembrane (GMB)–clay seepage control system is an important form of seepage control structure for rockfill dams. In order to investigate the stress and deformation characteristics of GMB in GMB–clay core-wall rockfill dams (GMCWRD) under different construction and operation conditions, the stress and deformation fields of GMCWRDs were calculated by numerical simulation under a variety of working conditions. The stress and deformation characteristics of the dam and GMB during the impoundment period were investigated, and the influences of the spreading thickness of the clay core-wall and the location of the GMB defects and hydraulic head on the stress and deformation of the GMB were analyzed. The results show that the maximum tensile strain of the GMB upstream of the clay core-wall during the impoundment period occurs at the anchorage of the GMB and the concrete cut-off, with a maximum tensile strain of 2.70%. With the increase in the spreading thickness of the clay core-wall, the maximum tensile stress and strain of the GMB fluctuated. Under the dam construction and foundation conditions in this paper, when the spreading thickness of the clay core-wall was 2 m, the tensile stress and strain of GMB were at the lowest level. As the defect location of the GMB decreases, the phreatic line of the dam gradually increases, and the seepage discharge of the dam and the tensile strain of the GMB gradually increase, with the maximum tensile strain of 3.98%. The maximum deformation of the GMB in each case is much smaller than the maximum elastic deformation range of the selected PVC GMB, and the conclusion of the study provides a certain scientific basis for the design and construction of the seepage control of the core rockfill dam.