What Is Meant By Clean Clay To Use As Backfill
Soil-bentonite cutoff walls, consisting of excavated in situ soil and bentonite as backfills, are used extensively as vertical barriers for groundwater pollution control. Sand mixed with high-quality natural sodium bentonite (NaB) is commonly used as a research object to investigate the hydraulic and compression properties of soil-bentonite backfills. All the same, pure sand could rarely be found in real weather condition, and natural NaB may not be available readily in some countries such equally China, India, and Turkey. This paper presents a comprehensive laboratory investigation on the compressibility and hydraulic conductivity (m) of soil-bentonite backfills created past simulated in situ soil and low-quality sodium activated calcium bentonite (SACaB). The simulated in situ soils are prepared using sand-natural clay mixtures with sand to natural dirt mass ratios ranging from 0.v to six.0, and the bentonite content (BC) in the base mixture ranges from 0 to 15%. The effect indicates that BC dominates the compression alphabetize (C c ) of the backfill, and a unique human relationship between void ratio at effective vertical compression stress of 1 kPa and compression index is proposed for various types of soil-bentonite backfills. An increase in either BC or clay size fraction (CF) in simulated in situ contributes to reducing k, but the impact of CF in simulated in situ soil on one thousand tends to be insignificant for backfill with BC higher than 6%. A new characteristic parameter based on the concept of void ratio of bentonite (due east b ), named apparent void ratio of clay size fraction (e C ), is adult for predicting soil-bentonite backfills created by in situ soils and bentonites with diverse contents.
1. Introduction
Contaminated sites resulting from industrial development and depression-level waste material disposal are condign increasingly pressing global problems, especially in developing countries similar China and Bharat [1, 2]. The soil-bentonite cutoff walls, consisting of excavated in situ soil, bentonite, and amendment with high sorption chapters equally backfills, are used extensively to command the migration of contaminants in groundwater in both interim and permanent remedial actions in the United States, Canada, Japan, and China.
Sand mixed with high-quality bentonite (east.yard., commercial sodium bentonites and polymer-bentonite composites) equally backfill is commonly used every bit a research object to investigate the engineering properties, such as compressibility, permeability, chemical compatibility, and Earth pressures distribution, of soil-bentonite backfills [three–eight]. Recently, clayey soil–low-quality calcium bentonite (CaB) mixtures have been considered as an culling as backfill when high-quality natural sodium bentonite (NaB) is deficient, only CaB is abundant [9]. In addition, it is reported that the hydraulic conductivity of soil-bentonite backfill is significantly affected by the type of bentonite. The hydraulic conductivity of sand-bentonite backfill using low-quality CaB is unlikely to meet the typical regulatory limit of ten−9 m/s even when the bentonite content is increased to 15% [1]. On the other hand, an approximate 5% of natural NaB in the backfill leads to yielding lower hydraulic conductivity value than 10−nine m/southward [iv–six].
Information technology should be noticed that although either make clean sand or pure dirt could rarely exist institute in real conditions, clean sand-bentonite backfills are by and large used to investigate the performance of the soil-bentonite cutoff wall. To date, very few studies have systematically investigated the influence of in situ soil on the compressibility and hydraulic electrical conductivity of soil-bentonite backfills. Limited studies bear witness that simulating in situ soil with medium (42%) to high (78%) fines content mixed with bentonite-water slurry can exist used as backfill for the slurry-trench cutoff wall without amending bentonite in the base of operations mixture [10]. Withal, the impact of in situ soil (due east.thou., fines fraction and/or clayey-sized fraction) on compressibility and hydraulic conductivity has not been evaluated quantitatively.
In this study, ii types of model soil-bentonite backfills were used to understand the bear on of in situ soil on the compressibility and hydraulic conductivity (thousand). The backfills included (i) sand-bentonite backfills with diverse percentages of bentonite (denoted as SBB) and (2) sand-clay-bentonite backfills with various percentages of natural clay and bentonite (denoted as SCBB). In addition, universal correlation equations were established using void ratio at ' = 1 kPa (e 1) and newly proposed apparent void ratio of clay size fraction (e C ) to predict compression index (C c ) and k of soil-bentonite backfills containing various in situ soil and bentonite, respectively.
ii. Materials and Methods
2.one. Constituent Soils
The soil-bentonite backfills are comprised of sand, natural clay from Nanjing metropolis (denoted as Nanjing clay), and sodium activated calcium bentonite (SACaB). Sand and Nanjing dirt are obtained from Nanjing metropolis, China. The Nanjing clay corresponds to a fluvial deposit. The SACaB is provided by MUFENF mineral processing institute in Zhenjiang Metropolis, Red china. Table 1 shows the basic physical properties and mineralogical compositions of the iii soils used for this report. Based on the Unified Soil Classification System [14], the sand, Nanjing clay, and SACaB are classified as poorly graded sand (SP), low-plasticity clay (CL), and high-plasticity clay (CH), respectively. The result of X-ray diffraction analysis shown in Figure 1 indicates that the ascendant minerals of the Nanjing clay and SACaB are found to exist illite and montmorillonite, respectively. The basal spacing (001) of the bentonite is identified as xv.iv Å, indicating that the SACaB belongs to Ca-bentonite [16]. The SACaB used in this written report represents typical low-quality bentonite with relatively low slap-up index (SI = 16.5 mL/ii chiliad; run into Table one); and therefore, the results could exist compared with those obtained from the backfills using high-quality commercial NaB reported in previous studies.
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| aneX-ray diffraction analysis. 2Mont., montmorillonite. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(a)
(b)
2.two. Preparation of Base Mixture for Backfill
Base mixtures are prepared by mixing a predetermined mass of dry sand, Nanjing clay, and SACaB. Sand-Nanjing clay mixtures are used as representative of false in situ soil. The bentonite content in the base mixture (BC Yard) used for SBB grooming is controlled in the range of iii.five to 15% (dry weight basis); and it is selected to exist 0%, 3.5%, and eight% (dry out weight basis) in the base mixture used for SCBB preparation. The BC Yard is calculated using equation (1). The mass ratio of sand to Nanjing clay ranges from 6 to 0.5 (dry weight basis) in the base mixture of SCBB. The symbol "CBi" denotes an SBB with BC M of i% and the symbol "CBiRj" denotes an SCBB with BC Yard of i% and mass ratio of sand to Nanjing dirt of j. In addition, 1 sand-Nanjing clay mixture is prepared for evaluating the hydraulic conductivity of typical in situ soil in the backfill. The mass ratio of sand to clay of the mixture is ready at 0.5 (dry weight ground), and the mixture is denoted equally R0.five. The proportion of base mixtures for all backfills tested in this written report is presented in Table 2: where m Sand, m Dirt, and g Ben,M are the mass of sand, Nanjing clay, and SACaB in the mixture by dry out weight, respectively.
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| iSBB: sand-bentonite backfill. iiSCBB: sand-clay-bentonite backfill. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
ii.3. Training of Bentonite-Water Slurry
The bentonite-water slurry is prepared by mechanically mixing 10% dry bentonite with 90% tap water (weight ground) for xxx min and left for hydration for 24 h. Later on hydration, the marsh funnel viscosity, density, and filtration of the prepared slurry are measured as per API 13B-1 [17], and the values are 42 s, ane.042 chiliad/cm3, and 10.45, respectively.
ii.iv. Backfill Preparation for Testing
Backfill sample for testing is prepared past mixing the base mixture with the predetermined mass of bentonite-water slurry [nine]. The initial water content of backfill ( ) is controlled to meet the requirement of target slump (−∆H). A −∆H value varying from 100 to 150 mm is adopted to set backfill in the slurry-trench method for soil-bentonite cutoff wall [ane, 6]. The slump is measured according to ASTM C143 [eighteen]. In addition, the specific gravity (G due south ) and liquid limit ( ) of backfills are measured equally per ASTM standards [12, 13]. Information technology should exist noted that cannot be adamant using the percussion method for the false in situ soil (R0.5) and backfill with relatively low bentonite content and Nanjing dirt content, including CB3.5, CB5, CB6, CB3.5R6, and CB3.5R4. The resulting and its corresponding −ΔH, total bentonite content in backfill (BC), distribution of particle sizes, 1000 s, and of all samples for testing are presented in Table iii. The BC value is calculated using the following equation: where chiliad Ben, M and m Base, M are mass of bentonite and imitation in situ soil from base mixture past dry out weight, respectively, and thousand Ben, S is mass of bentonite from bentonite-water slurry past dry weight.
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| iFines fraction, particle size < 75μone thousand. 2Clay size fraction, particle size <2μchiliad. 3ND, cannot be determined. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
2.v. Testing Methods
The oedometer and hydraulic conductivity tests are performed on all samples shown in Table ii. The conventional oedometer tests are conducted based on ASTM D2435 [19]. A pressure of one kPa is used in the preconsolidation stage for 24 h, and the sample is then subjected to incremental loading outset with iii.125 kPa. This is done to avoid soil squeezing through the gap between the sidewall of the oedometer cell and the porous disk [20]. The loading is doubled at each incremental pace until a maximum loading of 800 kPa is reached. The elapsing of each loading is 24 hours.
The falling-caput hydraulic electrical conductivity test in the oedometer is used to decide the hydraulic conductivity (k). The procedure of the falling-caput hydraulic conductivity test in the oedometer is in accord with Bohnhoff and Shackelford [eight]. The examination is conducted after the stop of loading, beginning with loading of 12.v kPa. Tap h2o is used as a permeant liquid. The initial hydraulic gradient is controlled to 30. Caput loss and compression deformation are measured every 8 h to 24 h during the falling-caput process for calculating k value. Permeation is continued until at least four consecutive hydraulic conductivity values are within ±25% of the mean value for g ≥ ane × 10−ten m/s or within ±fifty% for yard < ane × ten−10 m/south according to ASTM D5084 [21].
3. Results and Word
3.1. Compressibility
Figure 2 shows the void ratio (e) and the effective vertical compression stress ( ') compression curves on a semilogarithm scale of sand-bentonite and sand-dirt-bentonite backfills. The upshot indicates that the e-log ( ') compression curves display a significant modify in slope when ' increases from half-dozen.25 kPa to 12.5 kPa. This result is more noticeable with an increment in bentonite content, as shown in Effigy ii(a). Similar results are also observed in remolded natural clays, NaB, and kaolin-bentonite mixtures [twenty, 22]. The effect is attributed to the existence of remolded yield stress in soil nature [23]. Thus, the compression index (C c ) is determined from the linear portion of the e-log( ') pinch bend at the postyield country in this study.
(a)
(b)
Figure 3 shows the human relationship between BC and C c of the backfills tested in this study and previous studies [4–7]. The upshot shows that there exists an approximately linear relationship between BC and C c for sand-bentonite backfills with bentonites having a like range of liquid limit. In addition, C c increases with an increase in bentonite liquid limit for a given BC. The BC-C c relationships of sand/SACaB backfills tested in this written report and sand/NaB backfills reported in previous studies [4–six] are adamant using a Least-Square-Root method; and they tin can be expressed by equation (three) with a coefficient of determination (R 2) of 0.992 and 0.896, respectively:
To understand the influence of in situ soil on C c of soil-bentonite backfill, the human relationship between natural clay content (NC) and C c is presented in Effigy 4. The event shows that C c has a trend for increasing with an increase in NC for a given range of BC. The C c value of the backfills increases linearly with increasing NC and and so reaches a plateau. The growth stage of the NC-C c relationship of the backfills with BC of 6.2 to 6.9% and 12.1 to 12.8% can exist expressed by equation (4) with R2 of 0.922 and 0.937, respectively. In addition, it is found that the slope value of equation (3) for the BC-C c relationship is 16 to 23 times higher than that of equation (4) for the NC-C c relationship, indicating that it is BC that dominates the C c of soil-bentonite backfill:
Information technology has been understood that the compressibility of clay is affected by both soil nature and , which can be described by using a function of void ratio at ' = ane kPa (e i) [23, 24]. Fan et al. [20] report that in that location exists a unique human relationship between e 1 and C c for clay-bentonite backfills with fair bentonite content, as expressed by equation (5). Figure 5 shows the relationship between east ane and C c obtained from the sand-bentonite and sand-dirt-bentonite backfills. It is found that the overall tendency of the e 1-C c relationship for SBB and SCBB is in accord with the proposed equation (five) for dirt-bentonite backfill, except for SSB with BC lower than 10%. The relative accuracy error of C c calculated using equation (v) is within −xviii% to 19%. This result likewise indicates that a sand-bentonite backfill can be regarded equally a granular textile when hydrated bentonite was not able to wrap around sand particles. Under such circumstances, the compression beliefs is controlled by sand particle rearrangement through interparticle slip and rotation, and C c value is generally lower than 0.1 [25]. On the other hand, natural clay in faux in situ soil contributes to filling pore spaces amid sand particles that have not been filled by hydrated bentonite due to low BC, which avoids the formation of the skeletal construction formed by sand particles:
3.two. Hydraulic Conductivity
Figure six presents the human relationship between the void ratio (e) and hydraulic electrical conductivity (k) on a semilogarithmic scale. The event illustrates the due east-log (thousand) relationship is approximately linear. The k values of backfills are generally lower than the recommended limit of 10−nine chiliad/s for engineered barriers, except for the k of CB0R0.five and CB3.5 at loading increments <100 kPa. In add-on, the k of the simulated in situ soil (R0.5) varies from 5.7 × 10−8 to 1.0 × 10−9 m/s, indicating that the addition of bentonite is required fifty-fifty for an in situ soil with a medium to high fines fraction (run into Table 3).
Figure 7 presents the relationship between BC and chiliad corresponding to the void ratio of 0.six to 0.75 in this report and previous studies [3–6, 26]. due east = 0.6 to 0.75 is chosen because the k values corresponding to this range of e are available from these studies, which allows for a comparison of k values among the different backfills. The result illustrates that the m value sharply decreases with an increase in bentonite content when BC M is lower than 5% regardless of the bentonite quality (i.e., NaB or SACaB). The g of SSB tested in this study decreases 1 order of magnitude when BC M increases from five% to xv%, indicating that a further increase in BC results in a express decrease in k. Thus, BC of 6.viii% for the sand-bentonite backfill in this written report is required in society to achieve a thousand lower than the recommended limit of 10−9 yard/s; while a BC of five.8 to 7.2% for the sand-bentonite backfill using conventional NaB results in a m of 10−x m/s. The difference in k for a given BC in Figure 7 tin be attributed to the bentonite quality. The departure in hydraulic conductivity between bentonite clays tin exist attributed to exchangeable metals, cation substitution capacity (CEC), grain size distribution (east.k., clay size fraction), and proportion of minerals in bentonite (e.chiliad., montmorillonite, quartz, cristobalite, and feldspar) [27–29].
To better understand the upshot of in situ soil on the hydraulic electrical conductivity of the backfill, the relationship betwixt incremental clay size fraction due to addition of natural clay (∆CF) and k corresponding to void ratio of 0.6 to 0.75 is presented in Figure 8. The consequence indicates that the impact of in situ soil on hydraulic conductivity depends on BC. The g would testify a significant decrease with increasing ∆CF from the simulated in situ soil when the backfill contains a relatively low corporeality of bentonite; while grand is unlikely to be afflicted past ∆CF from the simulated in situ soil for the backfill with relatively loftier BC. k of the backfill with BC M of 3.5% (i.east., BC = vi.2 to 6.nine%) is approximately i order of magnitude when the clay fraction increases from 3.3% (CB3.5) to 13.ix% (CB3.5R0.5). In contrast, a minimal decrease in m is found regardless of increase in CF from the simulated in situ soil for the backfills with BC K of 8% (i.due east., BC = 12.2 to 12.viii%).
3.3. Estimating k of Sand-Bentonite Blends Using Void Ratio of Bentonite
Kenney et al. [30] develop a feature parameter, void ratio of bentonite (eastward b ), to predict 1000 of the saturated compacted sand-bentonite mixtures. The basic assumption of e b is that sand-bentonite mixture is regarded as an platonic homogeneous mixture, in which sand particle is impermeable, and seepage just exists in hydrated bentonite paste. The proposed e b is defined every bit the ratio of volume of void space to volume of bentonite, which can be expressed by equation (6) or the sand-bentonite mixtures: where and V Ben are the volume of pore water and bentonite, respectively; G s,Ben, G southward,Sand, and Yard southward,M are the specific gravity of bentonite, sand, and sand-bentonite mixture, respectively; BC is the bentonite content; is the density of pore water; and ρ d,M is the dry density of the mixture.
Figure 9 presents the relationship between eastward b and k of sand-bentonite blends in this study and previous studies [4,6,7,30–33] on a logarithmic scale. The maximum eastward b value in this study is xi.iii while those of sand/NaB backfills reported in previous studies [4, 6, 7] vary from 19.5 to 30.six.
The issue illustrates that the e b -one thousand relationship of sand-bentonite blends nether various testing atmospheric condition (e.g., sample preparation, bentonite quality, and bentonite content) generally possess a universal overall trend. The overall trend for the eastward b -k relationship determined using a Least-Square-Root method is expressed past equation (7) with R two of merely 0.16, and a more authentic description of the eastward b -k relationship corresponding to e b ranging from 1 to 66.7 can be expressed by equation (8) using a To the lowest degree-Square-Root method with R 2 of 0.816. In fact, a rational e b -grand human relationship shall be developed based on an platonic sand-bentonite mixture, in which the e b value shall be no more than the costless-swell void ratio of the bentonite (e b,f-s ) [thirty]. Based on that, Castelbaum and Shackelford [32] indicated that a sand-bentonite mixture with e b value lower than approximately 1.four times its corresponding east b,f-s tin can be expected for ideal mixtures; otherwise, it shall exist considered equally a nonideal mixture. The e b -one thousand relationship obtained from sand-bentonite backfills in this study is generally consistent with equation (8) except for the CB3.v sample. 1 possible reason might be a side-leakage during the hydraulic conductivity exam.
Just the results reported by Yeo et al. [four] bear witness a significant divergence from the overall trend for the due east b –k human relationship, which might be due to the fact that the amount of hydrated bentonite (BC 1000 < 5%) is insufficient to fully cover sand particles, resulting in seepage among sand particles:
Considering that the e b value for sand-bentonite backfills is generally lower than three, equation (8) can exist used to predict the k value of sand-bentonite backfills. However, it should exist noticed that in situ soil used for soil-bentonite backfill is not pure sand in practice. As a upshot, equation (eight) is non suitable for predicting a k of soil-bentonite backfill in real condition.
3.four. Proposed Method for Predicting k of Soil-Bentonite Backfills
A large number of methods accept been developed for predicting the hydraulic conductivity of clays and clay-bentonite backfills, in which is an integral index property for representing swell potential and mineralogical composition of soil [xix, 29]. Still, of sand-based soil-bentonite backfill could be questionable especially for backfills with relatively low bentonite content (run across Table iii).
In this study, a new characteristic parameter, named the apparent void ratio of clay size fraction in soil-bentonite backfill (e C ), is developed for predicting chiliad of soil-bentonite backfills on account of the fact that the hydraulic conductivity of natural clays and bentonite clays is significantly affected past liquid limit and soil nature of clay-sized minerals. The concept of due east C originates from the void ratio of bentonite proposed past Kenney et al. [30]. For soil-bentonite backfill with clayey soil in in situ soil, the backfill herein is simplified as an platonic, three-constituent, saturated homogeneous mixture of sand (4.75 mm to 75μm), silt and clay (<75μgrand), and bentonite (hereinafter referred to equally ideal mixture). Base of operations on the concept of e b , it is causeless that all h2o seepages through silt and clay from the in situ soil and hydrated bentonite whereas sand particles themselves are impermeable. In improver, the k of the ideal mixture would be controlled by the hydraulic conductivity of the clay size fraction (<iiμm) in bentonite and in situ soil. Moreover, an empirical coefficient is used to reflect the difference in keen potential betwixt silt and clay from the in situ soil and hydrated bentonite. Hence, eastward C is defined by equation (9) and the method for computing the eastward C value is given by equation (10): where and are the volume of clay size fraction in in situ soil and bentonite, respectively; is the book of water; parameter α is an empirical coefficient reflecting the correlation of great potential betwixt in situ soil and bentonite; is the backfill water content; CF IS and CF Ben are clay size fraction in in situ soil and bentonite, respectively; G due south, IS is the specific gravity of portion of in situ soil that passes the 425 μm sieve; G due south, Ben is the specific gravity of bentonite; LLR is the credible liquid limit ratio, which is obtained from the liquid limit of portion of in situ soil that passes the 425 μm sieve and bentonite; and BC is bentonite content in the backfill, which is available from structure report. A special case in equation (x) is that eastward C =due east b when CF IS = 0 and CF Ben = 100%. In fact, eastward C represents the void ratio that dominates the flow seepage in soil-bentonite backfill, which includes not only the void ratio of bentonite but the void ratio of clay fraction of natural clay in the backfill.
Figure x presents the relationship between e C and k of the soil-bentonite backfills in this written report on a semilog calibration. The outcome indicates that the e C -log(g) relationship for all backfills generally shows a unique linear. The e C -log(g) human relationship determined using a Least-Square-Root method is expressed by equation (11) with R two value of 0.856. To obtain better goodness of fit, a regression assay of the e C -log(k) relationship with eastward C lower than 24 gives equation (12) with a R 2 value of 0.866:
The predictive capacity of equation (xi) for soil-bentonite backfills is evaluated by using published information from sand-bentonite backfill with amendments [5, 6], sand-clay backfill [4], and sand/NaB backfill [7, 26, 34]. The predictive chapters is evaluated using the ratio of measured hydraulic conductivity to predicted hydraulic conductivity (thousand p /k), and the mean (μ), standard deviation (SD), and ranking distance (RD) of the prepare of 1000 p/k [35]. The μ and SD of the set of k p /m are used to point the accurateness and precision (i.e., the amount of dispersion), respectively. A predictive equation possesses a better predictive capacity when the μ value is closer to one and the SD value is closer to 0. The RD value, which gives equal weight to accuracy and precision, is proposed for comparison the predictive capacity of different empirical equations in previous studies [36]. The RD value is given by the following equation:
The result indicates that although equation (12) has a slightly higher R 2 value than that of equation (11), equation (11) shows a better predictive chapters of k for sand-bentonite backfills with subpoena, sand-clay backfills, and sand-bentonite backfills reported in previous studies, as presented in Figure 11. The resulting predictive capacities of equations (eleven) and (12), including the μ, SD, and RD values of the set of m p /k, are presented in Table 4. Regarding equation (eleven), the μ and RD value is closer to i and the SD is closer to 0, indicating that equation (11) is better than equation (12). In addition, the k value predicted using equation (11) generally falls in the range of 1/6 to vi times the measured thou values (data size = 285); and 85% of the ratio of g p to k is within 1/3 to 3. This indicates that a prediction of k of in situ soil-bentonite backfill using equation (xi) is rational [29].
(a)
(b)
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| Equation | Hateful (μ) | Standard deviation (SD) | Ranking distance (RD) |
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| Equation (xi) | i.092 | 0.691 | 0.697 |
| Equation (12) | one.619 | 1.473 | 1.598 |
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Both characteristic parameters e b and e C are developed from the ideal homogeneous mixture, in which sand particle is considered as impermeable material. However, equation (11) is suitable for various types of soil-bentonite backfills, in which in situ soil consists of sand, silt, and clay with various proportions whereas equation (8) could simply exist used nether the condition of pure sand-bentonite backfill. Moreover, all alphabetize properties used for e C calculation are available from conventional lab tests.
4. Conclusions
This study investigates the soil-bentonite backfills that are prepared using sand, natural clay, and a typical commercial sodium activated calcium bentonite. Sand-natural clay mixtures with various proportions are used to simulate excavated in situ soils. The compressibility and hydraulic conductivity are evaluated via a series of oedometer tests and falling-head hydraulic conductivity test in the oedometer. The post-obit conclusions can exist drawn: (1) The impact of in situ soil on the compressibility of soil-bentonite backfills is relatively limited compared with bentonite content. The issue of this written report shows that the compression index tends to increase linearly with increased natural clay content and then reaches a plateau for a given range of bentonite content. At that place exists a unique relationship between void ratio at σ v ' = 1 kPa (e 1) and pinch alphabetize for soil-bentonite backfills containing various in situ soil and bentonite: . (2) The hydraulic conductivity (thousand) of the backfills tested in this study is lower than the recommended limit of ten−9 yard/s, except for two backfills containing a low amount of bentonite and natural clay (CB0R6 and CB3.5 sample). Bentonite content is the ascendant factor in the k value. However, the touch of in situ soil on the g value is considerable for backfill with a relatively low bentonite content (e.thousand., BC = 6.2% to 6.nine%). (3) The void ratio of bentonite provides an constructive method for predicting k of pure sand-bentonite mixtures. A newly proposed method is applied to predict the k values for soil-bentonite backfills containing various in situ soil and bentonite: . The characteristic parameter e C, named the apparent void ratio of dirt size fraction, in the predictive equation represents the void ratio that dominates the flow seepage in soil-bentonite backfill. The predictive chapters of the proposed method is examined by using independent experimental information from this study. The event shows that the predicted k values are more often than not consequent with the measured m value. 85% of the predicted one thousand values fall in the range of i/3 to three times those measured 1000 values.
Data Availability
The information used to support the findings of this study are available from the corresponding author upon request.
Conflicts of Interest
The authors declare that they take no conflicts of interest.
Acknowledgments
The authors are grateful for the fiscal support of the National Key Research and Development Program (2018YFC1803100), the National Natural Science Foundation of Mainland china (51908121 and 41877248), the Natural Science Foundation of Jiangsu Province (BE2017715), the People's republic of china Postdoctoral Science Foundation Grant (2018M642143), and the Key Research Funds for the Key Universities (2242019R20033).
Copyright
Copyright © 2022 Ridong Fan et al. This is an open access commodity distributed under the Creative Commons Attribution License, which permits unrestricted employ, distribution, and reproduction in any medium, provided the original work is properly cited.
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