Compacted laterite and bentonite, as well as a mixture of the two, are strongly impermeable and can effectively prevent the migration and diffusion of contaminants. This study explored the feasibility of employing a laterite/bentonite mixture as a vertical barrier in landfills, tailings ponds, or sites contaminated by heavy metals. Permeability tests using chemical solutions of different concentrations and compression tests were performed on mixed bentonite/laterite samples with different dry densities and mixing ratios. The permeability and consolidation characteristics were verified using scanning electron microscopy. The hydraulic conductivity of the laterite samples decreased with increased dry density, and the hydraulic conductivity of the mixed-soil samples decreased with increased bentonite content. Adding bentonite significantly improved seepage control performance. The hydraulic conductivity of the pure laterite was 4.7 × 10−7 cm/s, whereas that of the laterite sample mixed with 20% bentonite was 1.6 × 10−8 cm/s. The compacted laterite with a dry density of 1.5 g/cm3 was demonstrated to satisfy the permeability specifications to serve as a landfill seepage control system. When the concentration of the heavy metal or salt solutions increased, the laterite flocculation increased, and the hydraulic conductivity decreased. The laterite in the mixed soil samples substantially affected these characteristics, particularly decreasing the hydraulic conductivity. As the concentration of the chemical solutions increased, the yield stress of the compacted samples and the compression index decreased, and the compression performance improved. These findings indicate that chemical solutions significantly affect the hydromechanical behavior of a laterite/bentonite mixture used as an engineered barrier.

Effects of chemical solutions on the hydromechanical behavior of a laterite/bentonite mixture used as an engineered barrier

Assessment of the influence of copper and zinc on the microstructural parameters and hydraulic conductivity of bentonites on the basis of SEM tests.

Study on the microscale structure and anti-seepage properties of plastic concrete for cut-off walls modified with silica fume: Experiment and modelling

The effects of potentially toxic metals (copper and zinc) on selected physical and physico-chemical properties of bentonites.

Insight into barrier mechanism of fly ash-bentonite blocking wall for lead pollution in groundwater

Studies on the chemical compatibility of soil-bentonite cut-off walls for landfills.

Permeability of soil-bentonite cut-off wall backfill material

The invention discloses modified sludge, a preparation method of the modified sludge and a construction method of the modified sludge used as a covering soil material. The modified sludge consists ofsludge from sewage plants, sulphoaluminate cement and lime. Meanwhile, the invention also discloses the preparation method of the modified sludge and the construction method of the modified sludge used as the covering soil material. Daily covering soil or middle-layer covering soil can be formed quickly through reactions and can be used as the covering soil material after being cured for 24 h, besides, the strength and permeability of the covering soil can completely meet the engineering mechanics property requirement for covering soil. Besides, the permeability coefficient in the covering soil in landfill bodies can be increased later, so that the probability of production of middle-layer stagnant water can be reduced, after modification treatment of the sludge, the volume is not increased notably, and the storage capacity of a landfill cannot be occupied.

Modified sludge, preparation method of modified sludge and construction method of modified sludge used as covering soil material

Extensive attention has been paid to the treatment and disposal of dredged material, and there is a need to clarify the feasibility of recycling dredged material by using it as backfill in soil-bentonite vertical cutoff walls. By setting the dredged material in the Baimao storage yard of Meiliang Bay in Taihu Lake and bentonite as the research objects, this paper studied the influences of bentonite content, confining pressure and pore size distribution on the permeability of dredged material-bentonite backfills. According to the test results, from the perspective of medium-term and short-term permeability, it is feasible to recycle dredged material by using it as backfill in a vertical cutoff wall. The permeability of the dredged material-bentonite soil mixture decreases with increasing bentonite content, but the degree of decrease is not significant. At the same time, the higher the confining pressure is, the smaller the variation in hydraulic conductivity with bentonite content. The permeability of the soil mixture decreases with increasing confining pressure, and the range of reduction is within a certain order of magnitude. Moreover, the confining pressure has a similar impact on the decrease in the permeability of the soil mixtures with different bentonite contents. The hydraulic conductivity of the dredged material-bentonite mixture decreases because the addition of bentonite changes the pore size distribution and reduces the porosity and characteristic pore size D50 of the soil mixture.

The permeability of dredged material-bentonite backfills.

The disclosure discloses a speed limiting type flowable quick soil strength detection apparatus and a detection method. The detection apparatus includes a framework, a pressing apparatus passing through a top of the framework, and a liquid speed limiting apparatus in the framework. The detection method includes the steps of: pressing down the pressing apparatus so that a detection tube is pressed into to-be-detected soil, and then resetting the pressing apparatus; recording a soil depth entered before and after the detection tube is pressed into the soil; and multiplying the soil depth by an elastic coefficient of an elastic component to obtain a force when the detection tube pierces the soil, and then dividing an area of a cross section where the detection tube contacts with the soil, to obtain a pressure when the soil is pierced, that is, a compressive strength of the soil. The disclosure is simple in structure, may read a compressive strength of soil just by a pressing operation, may implement site measurement, and has a reliable data result and a small error.

Jiang Pengming

Papers

Studies on the chemical compatibility of soil-bentonite cut-off walls for landfills.

Permeability of soil-bentonite cut-off wall backfill material

Modified sludge, preparation method of modified sludge and construction method of modified sludge used as covering soil material

The permeability of dredged material-bentonite backfills.

Speed limiting type flowable quick soil strength detection apparatus and detection method