Soil Bentonite Slurry Trench Cutoff Walls: History, Design, and Construction Practices

Ryan, Christopher R.; Ruffing, Daniel; Evans, Jeffrey

doi:10.1061/9780784484050.010

Cited by 7 publications

(4 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is increasingly common to build barriers around landfills to prevent soil and groundwater contamination [1][2][3]. The application of attapulgite cut-off walls in landfills has attracted more and more attention because of its good adsorption capacity and insensitivity to chemical environments [4][5][6][7][8][9][10][11][12][13]. The final stress of the cut-off wall in the field is usually unknown.…”

Section: Introductionmentioning

confidence: 99%

Stresses and Permeability in Sand–Attapulgite Cut-Off Walls

Zhang,

Zhou,

Rao

et al. 2024

Water

View full text Add to dashboard Cite

The long-term performance of sand–attapulgite cut-off walls in landfills is highly dependent on the permeability of the wall material. Laboratory tests show that the hydraulic conductivity of wall material decreases significantly with the increase in consolidation pressure. Therefore, to accurately estimate the hydraulic conductivity of the cut-off wall in the field, the effective stress must be calculated correctly. In this paper, the ‘modified lateral squeezing model’ is used to calculate the stress distribution of the sand–attapulgite cut-off wall, and the distribution of the hydraulic conductivity of the cut-off wall in the field is calculated based on the stress distribution of the wall and laboratory test results. The results show that the effective stress of the sand–attapulgite cut-off wall in the field increases with the increase in the depth of the wall, and the change in the hydraulic conductivity is the opposite. The effective stress of the cut-off wall is less than 100 kPa. When the wall depth is below 0.5 m, the hydraulic conductivity of the cut-off wall is less than 1.0 × 10−9 m/s. The properties of the in situ foundation soil and the width of the cut-off wall will affect the stress and hydraulic conductivity of the cut-off wall, but the influence on the hydraulic conductivity is very limited, not exceeding one time. Therefore, in the actual construction, special attention should be paid to the anti-seepage measures in the shallow part of the cut-off wall. Our findings are expected to provide a valuable reference for the application of sand–attapulgite cut-off walls in landfills.

show abstract

Section: Introductionmentioning

confidence: 99%

Stresses and Permeability in Sand–Attapulgite Cut-Off Walls

Zhang,

Zhou,

Rao

et al. 2024

Water

View full text Add to dashboard Cite

show abstract

“…However, the chemical compatibility of soil-bentonite cut-off walls with landfill leachate is poor, and its antifouling properties are easily affected by landfill leachate (most importantly, to increase the hydraulic conductivity of the cut-off walls) [6,[12][13][14][15][16][17]. Attapulgite is a clay mineral that is cheap and readily available [18,19], and it seems to be well suited for use in pollution containment barriers [20][21][22][23][24][25][26][27]; it is considered to be a viable alternative to bentonite in landfill cut-off walls [20,21,28]. Some research has experimentally confirmed the technical feasibility of using attapulgite as a landfill cut-off wall material [20,[29][30][31].…”

Section: Introductionmentioning

confidence: 99%

The Chemical Compatibility of Sand–Attapulgite Cut-Off Walls for Landfills

Zhang

RAO

Zhang

et al. 2023

Water

View full text Add to dashboard Cite

Soil–bentonite cut-off walls have been widely used to control landfill pollution but they do not have good chemical compatibility with landfill leachate. Attapulgite can be substituted for bentonite in landfill cut-off walls. However, little is known about the chemical compatibility of attapulgite cut-off walls and leachate. This study experimentally investigated the chemical compatibility of attapulgite cut-off wall specimens with organic and inorganic contaminants and found that a sand–attapulgite cut-off wall has good chemical compatibility with organic contaminants. A CaCl2 solution was used to represent inorganic contaminants, and chemical oxygen demand (COD) was used as an indicator of organic content. The hydraulic conductivity of the cut-off wall initially decreased and then increased to become approximately constant as Ca2+ concentration increased. Changes in COD concentration were divided into a decreasing stage (0–10,000 mg/L) and a constant stage (10,000–40,000 mg/L). The increase or decrease in hydraulic conductivity was by no more than one order of magnitude. The increase in the hydraulic conductivity of the sand–attapulgite cut-off wall is explained in terms of bound water content and pore structure. An increase in Ca2+ concentration decreased the bound water content of the cut-off wall while the CaCl2 solution increased macropore and mesopore volume and decreased small pore volume in the sand–attapulgite cut-off wall. The purpose of this study was to elucidate the chemical compatibility of a sand–attapulgite cut-off wall with organic and inorganic contaminants and to increase the understanding of the interactions between the cut-off wall and the contaminants. The results of this research are informative for improving the application, design, and construction of sand–attapulgite cut-off walls.

show abstract

“…Groundwater pollution caused by landfill leakage has become a major environmental concern worldwide (Han et al, 2016; He et al, 2022; Malmir et al, 2022). The vertical barrier technology has been widely used around world for site contaminant control (Cao et al, 2021; Kui & Xiangping, 2019; Ryan et al, 2022). The principal of this technology is to form a low‐permeability vertical barrier wall to prevent the uncontaminated groundwater from flow into the contaminated aera, so as to prevent contaminant transport with groundwater flow (Cao et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Modelling of contaminant transport in heterogeneous vertical barrier

Shaoyi,

Jiawei,

Peifu

et al. 2023

Water & Environment J

View full text Add to dashboard Cite

Vertical barrier technique is an ideal candidate for site contamination control. In practical application, the characteristic of vertical cut‐off wall is heterogeneous with permeability decreases with depth due to the increasing geostatic stress. In this study, a numerical model was established considering the coupling effect of groundwater flow and contaminant transport considering depth dependent permeability. The results showed that a heterogeneous barrier with variable permeability can reduce the breakthrough time by 63.7% compared to a fixed permeability barrier. The contaminant concentration inside the wall was up to 10 times higher than outside. Shallow leakage occurs where the horizontal migration is dominated by advection. The distribution of pore‐water pressure in the system after the installation of high‐density polyethylene (HDPE) membranes significantly reduced the shallow convective effect by reducing up to 90% pore‐water pressure. Reinforcing the vertical barrier wall using HDPE membrane can effectively prevent the shallow leakage caused by the heterogeneity.

show abstract

Soil Bentonite Slurry Trench Cutoff Walls: History, Design, and Construction Practices

Cited by 7 publications

References 11 publications

Stresses and Permeability in Sand–Attapulgite Cut-Off Walls

Stresses and Permeability in Sand–Attapulgite Cut-Off Walls

The Chemical Compatibility of Sand–Attapulgite Cut-Off Walls for Landfills

Modelling of contaminant transport in heterogeneous vertical barrier

Contact Info

Product

Resources

About