Experimental Study on Permeability of Red Clay as Clay Liner Material for Sanitary Landfill
Abstract: The key to the application of red clay in sanitary landfill is its anti-seepage performance bentonite geosynthetic clay liner for sale. A series of experimental studies on red clay has been carried out through compaction experiments and penetration experiments. The optimum water content of red clay was measured ωopt=26.1%, the maximum dry density ρdmax=1.50g·cm-3 bentonite geosynthetic clay liner manufacturers, and the permeability coefficient k<1.0×10-7cm/s under a certain compaction state high quality bentonite geosynthetic clay liner. The test results show that the selection of reasonable water content and dry density is able to meet the required anti-seepage requirements.
Keywords: sanitary landfill; dry density; optimal water content; permeability coefficient
The key to the construction of a sanitary landfill is anti-seepage. If it is not handled well, it will easily pollute the environment, especially soil and groundwater. At present, there are many anti-seepage treatment technologies and substrate materials used in landfills, such as red clay and synthetic materials . Among them bentonite geosynthetic clay liner for sale, clay has been widely used in landfill cushioning systems due to its strong ability to intercept pollutants bentonite geosynthetic clay liner manufacturers, low permeability and economical price . As a kind of clay, red clay is a kind of high plastic clay formed by carbonate weathering under intense hot weather and red soil.  Its natural water content, liquid limit and plastic limit are very high, and it has high mechanical properties and medium compressibility. When it is applied to sanitary landfills, it has the advantages of a small settlement high quality bentonite geosynthetic clay liner, no cracking and good overall performance. 4]. However, domestic and foreign scholars have less research on their permeability performance, which needs further confirmation from the experiment. Therefore, it is of practical significance to determine the anti-seepage performance of red clay by laboratory experiments bentonite geosynthetic clay liner factory price. The Technical Code for Urban Domestic Waste Sanitary Landfill (CJJ17-2004) stipulates that the permeability coefficient of clay anti-seepage cushion is k<1.0×10-7cm/s and the compaction coefficient is greater than 0.95 . In this regard, this paper explores the anti-seepage performance of red clay by studying and analyzing the results of a large number of laboratory experiments. Among them: the determination of the maximum dry density, the optimal water content bentonite geosynthetic clay liner for sale, and other important parameters according to the “road geotechnical test procedures” (JTGE40-2007); the determination of the permeability coefficient according to the above procedures using the South-55 improved permeation instrument through the variable head test bentonite geosynthetic clay liner factory price.
2 Test section
2.1 Test principle and instrument
2.1.1 Test principle
The permeability coefficient of the contaminant in the clay lining is usually studied by the permeability test bentonite geosynthetic clay liner for sale. The permeability of the soil medium (expressed by the permeability coefficient k) is the main parameter bentonite geosynthetic clay liner factory price, which is expressed by Darcy’s law:
In the formula:
Q——volume flow rate of leachate, cm3/s
A——Infiltration of water area, cm3
V——leachate flow rate, cm/s
i – hydraulic gradient
The penetration test can be divided into the constant head method and the variable head method bentonite geosynthetic clay liner for sale. This experiment uses the variable head method. By continuously observing the head height, the value is obtained by the following formula:
A——measured pipe inner diameter sectional area, cm2
Figure 1 Test device diagram
A——Permeate water area, cm2
Η1——the viscosity coefficient of water at t°C
H1——T1 time pressure tube head, cm
H2——measuring tube head at time t2, cm
2.1.2 Test equipment
One compaction instrument (10cm inner diameter, 12.7cm high), South-55 (improved) permeation instrument, balance (sensing 0.01g), Taiwan scale (weighing 10kg, sensing 5g), metal plate, Bulldozer, ripper, water spray equipment bentonite geosynthetic clay liner for sale, cone funnel, thermometer, watch Vaseline. The South 55 (improved) permeator device is shown in Figure 1.
2.2 Test design and method
2.2.1 Test design
(1) The maximum dry density was obtained by a compaction test. In the clay liner of the landfill, the dry density and compaction of the clay play a decisive role in seepage prevention. Unreasonable dry density directly affects the barrier properties of clay liners bentonite geosynthetic clay liner factory price. Therefore, in the construction of clay liners bentonite geosynthetic clay liner for sale, the choice of dry density of the clay is particularly important. In this test, the ρd-ω curve of the clay sample was obtained by the compaction test to determine the maximum dry density of the soil.
(2) Penetration test Determines the permeability coefficient of clay.
Through the compaction test, we obtained an optimum moisture content of clay of ωopt. In order to obtain a reasonable moisture content range high quality bentonite geosynthetic clay liner, we used a soil sample of different moisture content of ωopt+n×2% (n=0, ±1) for the penetration test bentonite geosynthetic clay liner factory price. In order to better approach engineering practice, we tested the compacted soil sample to ensure its certain degree of compaction.
In addition, for the compacted soil samples, a leachate stock solution (taken from a landfill) and water were used for comparative tests.
2.2.2 Test method
All parameters were obtained according to the “Technical Regulations for Highway Geotechnical Engineering” JTGE40-2007. Among them, the optimum water content and the maximum dry density were measured by a light compaction test method bentonite geosynthetic clay liner for sale. Five compacted soil samples were prepared by adding (minus) 2% to 3% according to the estimated optimal water content, and the relationship between dry density and water content was obtained. According to the variable head penetration test method, the permeability coefficient is divided into three groups of ωopt, ωopt±2%, and the water and leachate stock solutions are used for the comparison test bentonite geosynthetic clay liner manufacturers.
2.3 Test materials
(1) Red clay: Red clay is a kind of high plastic clay formed by carbonated rocks under intense weathering and red soiling under humid and hot weather conditions. The mineral composition is mainly composed of clay minerals, residual rock debris, and free oxides bentonite geosynthetic clay liner for sale. Its natural water content, liquid limit and plastic limit are high, and it has high mechanical properties and medium compressibility.
(2) Leachate: The main pollutants include organic matter, inorganic ions, and nutrients wholesale bentonite geosynthetic clay liner. It has complex composition, high concentration of pollutants, contains certain metal substances, poor biodegradability and high chroma (mostly dark yellow or dark brown).
2.4 Detail processing
In order to reduce the source of error throughout the experimental study, the following key points are noted:
(1) In order to avoid the effects of repeated use of soil samples and drying methods on the maximum dry density and optimum water content of the soil bentonite geosynthetic clay liner for sale. Prepare soil samples by dry soil method (not repeated) and air dry naturally;
(2) The effect of the compaction work consumed to reduce the friction between the soil sample and the wall on the optimum water content and maximum dry density. Evenly coating a layer of petrolatum on the inner wall of the compaction cylinder and the casing wholesale bentonite geosynthetic clay liner;
(3) The residual soil height is controlled below 5mm;
(5) In order to prevent the contact between the red clay and the ring wall, the ring wall and the inner wall of the permeation instrument from affecting the test accuracy high quality bentonite geosynthetic clay liner, a layer of Vaseline is applied inside and outside the ring cutter;
(5) Since the experimental process lasts for a long time, in order to prevent water leakage at the interface of the permeation instrument, the superglue is applied tightly at the joint wholesale bentonite geosynthetic clay liner;
(6) In order to reduce the effect of temperature on the test results, the water does not produce a morning reading of expansion and contraction.
3 Analysis and discussion of test results
3.1 Determination of optimal water content
The relationship between dry density (ρd) and water content (ω) was measured by a compaction experiment bentonite geosynthetic clay liner for sale. On this basis, the least-squares method is used for fitting, and the fitting function bentonite geosynthetic clay liner factory price with the smallest sum of squared deviations is selected. We obtain a functional relationship between dry density y and water content x:
Find the first derivative of x and let dry/dx=0, we can find: x=26.1%, at this time, y=1.50 ie: the maximum dry density is ρdmax=1.50g·cm-3
Figure 2 Relationship between dry density and water content
Figure 3: Permeability coefficient versus time curve bentonite geosynthetic clay liner manufacturers
Optimal water content ωopt=26.1%
Its function relationship is shown in Figure 2.
From the trend of the curve, it can be analyzed as follows:
When the soil moisture content of cohesive soil is small, the intergranular gravity is relatively large high quality bentonite geosynthetic clay liner. Under certain external compaction function, the gravitational force cannot be effectively overcome to make the soil particles move relatively. At this time, the compaction effect is relatively poor; When the water content of the soil sample is increased, the water film is gradually thickened to reduce the gravitational force bentonite geosynthetic clay liner factory price, and the soil particles are easy to move and compact under the same compaction function bentonite geosynthetic clay liner for sale, so the compaction effect is better. However, when the water content of the soil sample increases to a certain extent, free water appears in the pores wholesale bentonite geosynthetic clay liner, and the expansion effect of the combined water film is not large, so the reduction of gravity is not significant, and the free water is filled in the pores, thereby The effect of the movement of the soil particles is prevented, so the compaction effect is lowered.
3.2 Leachate stock solution and water permeability coefficient
In this experiment, six groups of soil samples were compared at the same time. Figure 3 shows the variation of the permeability bentonite geosynthetic clay liner manufacturers coefficient of the clay sample on the leachate stock solution and water with time wholesale bentonite geosynthetic clay liner. Figure 4 shows the change in the permeability coefficient of the clay sample leachate and water with the same water content (ωopt = 26%) over time.
The permeability coefficient of clay sample to water changes with the penetration time. In the initial stage, the permeability coefficient of the soil sample is larger, and the permeability coefficient decreases with the extension of the duration, and finally the stable seepage phase wholesale bentonite geosynthetic clay liner. This is because, under the action of high head, the fine and loose particles in the clay sample migrate under the action of water, blocking the water guiding channel, and the permeability coefficient is lowered. When the migration of fine and loose particles in the soil is completed, the seepage tends to be stable and the permeability coefficient remains substantially unchanged bentonite geosynthetic clay liner factory price.
The k-t curve of the leachate stock solution (Fig. 3(b)) has a trend similar to that of water. In addition to the above reasons (water seepage), the organic matter, heavy metal ions and corrosive substances contained in the leachate can also produce the same retardation. Liang Zhigang , et al., Yu Tianren  and other studies have shown that due to bentonite geosynthetic clay liner manufacturers ion displacement and linkage bond destruction between soil particles high quality bentonite geosynthetic clay liner, the surface of soil particles usually has a negative charge so that heavy metal ions in the leachate are adsorbed on the soil. On the surface of the particle wholesale bentonite geosynthetic clay liner, an electric double-layer structure is formed, resulting in a decrease in the water guiding channel and a decrease in the permeability coefficient. These can be verified in Figure 4.
Figure 4 Curve of permeability coefficient of leachate and water as a function of time
The test results show that the selection of reasonable water content and dry density is able to meet the anti-seepage requirements specified in the specification high quality bentonite geosynthetic clay liner. Through the experimental analysis wholesale bentonite geosynthetic clay liner, the following conclusions can be drawn:
(1) When the water content of red clay is between 24% and 28%, the permeability coefficient K<1.0×10-7cm·s-1 is bentonite geosynthetic clay liner manufacturers feasible as a sanitary landfill liner material;
(2) The clay has a retarding and adsorbing effect on the leachate of the sanitary landfill. Conducive to the anti-seepage of the lining to the landfill leachate.