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The low liquid limit silty soil in the North China plain area is generally unsuitable for direct use as roadbed and slope soil. In order to improve the performance of low liquid limit silty soil, xanthan gum was used as an improver. Through a series of tests, the improvement effect of xanthan gum on low liquid limit silty soil was studied. The test results showed that Xanthan gum as an improver could significantly improve the unconfined compressive strength of silty soil. With the increase in dosage and curing age, the unconfined compressive strength of improved silty soil continued to improve and eventually tended to stabilize. The optimal dosage and curing period were 2% and 7 days, respectively. In addition, Xanthan gum could greatly improve the permeability and disintegration of low liquid limit silty soil. The permeability coefficient of improved silty soil with a content of 0.75% Xanthan gum and a 7-day curing period was 4.73 × 10 −4  m·s −1 , which was only 1.10% of that of plain silty soil at the same curing period. After immersion in water for 12 h, the soil only experienced slight disintegration. The scanning electron microscope image showed that the gel generated by the hydration reaction of Xanthan gum could improve the compactness and integrity of the soil by filling the voids, thus significantly improving the mechanical and hydraulic properties of the low liquid limit silty soil.

The purpose of this study was to assess the performance of high water content clayey sediments at different liquid limits as the clays are treated with cement-based solidifying materials. Three clay samples are obtained from different locations in the Kumamoto Reservoir. Two types of cement-based solidifying agents, namely, ordinary Portland cement and a cement–fly ash binder, were used. Using the initial water content of clay and the mixing amount of the solidifying agent as experimental variables, a cone penetration test was performed on the solidifying agent-stabilized clays to obtain the cone index (qc). The results showed that when the water content to cementitious content ratio (w/AW) was used as a parameter for evaluating the improvement of solidifying agent-stabilized clay, different forms of improvements were observed when different water and solidifying agent contents were used. This implied that the parameter w/AW was not suitable for evaluating the improvement of such clay. A new parameter, K, representing the content of solidifying agent, was introduced to account for the water content. For all sampled clays, the correlation coefficients for the K–ln qc relationship exceeded 0.9. Considering the effect of the liquid limit of the samples, the modified content of the solidifying agent (KL) was introduced to evaluate the cone index of the stabilized soils. It was discovered that the proposed equation unified the assessment of the improvement of the three samples of Kumamoto clayey sediments owing to the new parameter, KL.

Microplastics (MPs) are greatly released into soils in different ways, specifically through mulching practices in irrigated loess soils in northern Iran as the fertile and susceptible soils to water erosion. This study was conducted to examine the effects of Polyethylene (PE) (a common kind of MPs used in mulching farming in loess soils of north Iran), in a Loess soil under an experimental study. A loess soil was collected from 0- 30 cm surface and incubated at two levels of PE (2.5 and 5 % by weight) in two sizes (1-2 mm and >2mm) for 60 days, at 70% of field capacity moisture and temperature of 25-28 ° C. Soils samples were collected in 1, 15, 30, 45 and 60 days after incubation and different soil chemical, physical, mechanical and biological properties were measured. The results showed that soil pH was significantly (P<0.05) reduced by timing (time after incubation), and application rate of MPs. Inclusion of MPs led to increasing bulk density significantly (P<0.05) and also led to reducing aggregation and mean weight diameter (MWD) compared to control soil. The rate of MWD decreasing varied from 79 % to 87 % in different rates of MPs application. Among the mechanical attributes, liquid limit, plastic limit, and plastic index, all were reduced significantly (P<0.05) after mixing up and incubation with MPs. Reducing aggregation and aeration in treated soils compared to control soils, led to lowering soil microbial respiration, especially with timing. As our results about the effects of MPs in loess soils in a few cases were contrary to other soils studied worldwide, further studies are recommended to perform in loess soils in northern Iran, where receive considerable MPs by farming and open landfill practices in the studied region.

The relationship between the compression index and Atterberg limits (liquid limit, plastic limit, shrinkage limit) is well-known. Several equations are found in literature for general correlations or more specifically for correlations considering the state of the soil (e.g. remolded or undisturbed). This paper evaluates different studies considering 250 data points, and relations among the compression index and the liquid limit, index of plasticity, index of shrinkage, soil activity and plasticity ratio are provided. These relations are validated against 12 independent data points. The objective of the research is not to provide a new relation, but it is rather to statistically evaluate the input data used to obtain the new relationships. Therefore, several statistical analyses considering the root mean square error (RMSE), a probabilistic analysis, ranking distance (RD) and ranking index (RI) are performed by taking into account the correlations obtained to quantify the accuracy of each correlation. A Monte Carlo simulation with 100,000 simulations showed that the type of correlation has an influence on the distribution output.

To investigate the influencing factors and mechanisms of shear strength of red clay with a high liquid limit, which was selected at different milepost locations based on the Nanning Bobai Nabu Section Project of the Nanning Zhanjiang Expressway, the basic physical properties of red clay were determined using a liquid plastic limit test, compaction test, inductively coupled plasma optical emission spectrometer (ICP-OES), and X-ray fully automatic diffractometer (XRD). Red clay with a high liquid limit was selected. Furthermore, the direct shear test was used to study the effect of different water contents and compaction degrees on the shear strength. The experimental results demonstrate that under the same compaction degree, the shear stress of the soil sample increases significantly with an increase in normal stress, and the greater the water content, the smaller the shear stress of the soil sample. At 200 kPa, the shear strength of soil samples with 24% water content is 57%, 46%, and 35% of the shear strength of soil samples with 15% water content under different compaction degrees(K) of 86%, 90%, and 93%, respectively. Under the same moisture content, the shear stress of the soil sample shows an increasing trend with an increase in the degree of compaction, and the greater the compaction degrees, the greater the shear stress of the soil sample. The cohesion c and internal friction angle φ of soil samples increase with an increase in the compaction degree, but the increase in cohesion c is also affected by the water content. Under the condition of low water content, the cohesion c of soil samples can be increased by 1.06 times when the water content is 15% and by 0.47 times when the water content is 18%. Under the condition of high water content, the cohesion c of soil samples with 21% water content only increases by 0.3 times, and that with 24% water content only increases by 0.35 times.

This discussion article presents a critical appraisal of three empirical correlations developed via multiple regression analysis and presented in the Kayabali et al. [Geotech Geol Eng 41:4473–4485, 2023. https://doi.org/10.1007/s10706-023-02527-0 ] (the Authors’) investigation for the determination of the soil consistency limits. Specifically, based solely on British Standard (BS) fall-cone (FC) test data, the Authors purport that the correlations given by Equations 2 and 3 of their paper can be used to predict the ASTM rolling-plate plastic limit (i.e., PL RP ), while their Equation 4 can be used to predict the BS FC liquid limit (i.e., LL FC ). The Authors demonstrated that these correlations gave good predictions of the measured LL FC and PL RP water contents (i.e., w L(FC) and w P(RP) , respectively) for 87 fine-grained soils they sourced from different parts of Central Turkey. Employing newly compiled large and diverse consistency limits databases assembled from the published research literature, this discussion article confirms that the Authors’ Equations 2 and 3 generally produce poor w P(RP) predictions for the fine-grained soils comprising these databases, invariably overestimating (often seriously) their measured plastic limit values. Hence, the Discussers recommend that the Authors’ Equations 2 and 3 (being generally unreliable beyond the investigated Turkish soils) should not be used in geotechnical engineering practice. While the Authors’ single-point LL FC method given by their Equation 4 broadly appears as a good w L(FC) predictor for the newly compiled database soils, it is noted that there already exist well-established and standardised single-point LL FC methods.

The present paper presents different approaches which includes plasticity based criteria that helps in distinguish between liquefiable and non-liquefiable soils deposits having fine content. A brief review of the previous work has been mentioned to emphasise on the need of new parameters for liquefaction susceptibility of clayey soils. Clay content, liquid limit and water content are considered as key parameters that helps in liquefaction assessment. Several recommendations proposed by prominent researchers are described here to present wide range of plasticity index, liquid limit and other parameters that affects liquefaction behaviour of clayey soil significantly. But the differences in the range of plasticity index leads to confusion and misperception in determination of liquefaction susceptibility of fine grained soil. One of the high seismic zone site is analyzed using different approach which consider fine content of soil mass. It is found that for a better and proper segregation of the layers Bray and Sancio criteria may be adopted which uses plasticity as one of its input parameter and clearly differentiate site in between liquefiable, non-liquefiable and sites that may liquefy i.e. moderately liquefiable. This summarizes that plasticity is one of the significant criteria which draws a clear differentiating line between liquefiable and non-liquefiable soil deposits.

To improve the mechanical and durability properties of low liquid limit soil, an eco-friendly, all-solid, waste-based stabilizer (GSCFC) was proposed using five different industrial solid wastes: ground granulated blast-furnace slag (GGBS), steel slag (SS), coal fly ash (CFA), flue-gas desulfurization (FGD) gypsum, and carbide slag (CS). The mechanical and durability performance of GSCFC-stabilized soil were evaluated using unconfined compressive strength (UCS), California bearing ratio (CBR), and freeze–thaw and wet–dry cycles. The Rietveld method was employed to analyze the mineral phases in the GSCFC-stabilized soil. The optimal composition of the GSCFC stabilizer was determined as 15% SS, 12% GGBS, 16% FGD gypsum, 36% CS, and 12% CFA. The GSCFC-stabilized soil exhibited higher CBR values, with results of 31.38%, 77.13%, and 94.58% for 30, 50, and 98 blows, respectively, compared to 27.23%, 68.34%, and 85.03% for OPC. Additionally, GSCFC-stabilized soil demonstrated superior durability under dry–wet and freeze–thaw cycles, maintaining a 50% higher UCS (1.5 MPa) and a 58.6% lower expansion rate (3.16%) after 15 dry–wet cycles and achieving a BDR of 86.86% after 5 freeze–thaw cycles, compared to 65% for OPC. Rietveld analysis showed increased hydration products (ettringite by 2.63 times, C-S-H by 2.51 times), significantly enhancing soil strength. These findings highlight the potential of GSCFC-stabilized soil for durable road sub-base applications. This research provides theoretical and technical support for the development of sustainable, cost-effective, and eco-friendly soil stabilizers as alternatives to traditional cement-based stabilizers while also promoting the synergistic utilization of multiple solid wastes.

The compression index C c , is one of the key properties of fine-grained soils. Several correlations exist in the literature linking this parameter to other geotechnical properties such as Atterberg limits, void ratio and porosity. This paper analyzes more than 300 data from the literature plotting C c against liquid limit, LL , plasticity index, PI , shrinkage index, SI , defined as the difference between liquid limit, LL , and the shrinkage limit, SL , plasticity ratio, R p , initial porosity, n 0 . Key words for the literature review analysis were “clays”, “compression index”, “liquid limit”, “plastic limit”, “plasticity index”, “shrinkage index”, “remolded”, “undisturbed” and “correlations”. The C c – LL relationships are considered taking into account the gradient, a , and intercept, b , of the said relationship and plotting several values of the literature to assess their origin. A new relationship between b and a , called Compression Liquid Limit was obtained. Besides, an overview regarding the undisturbed and remolded compression index, C c , as well as the correlation of predicted versus experimental C c values based on two available methods, i.e. the method of Park and Koumoto (J Geotech Geoenviron Eng 130(2):223–226, 2004) and the method of Sharma and Bora (Indian Geotech J 45:225–230, 2015. https://doi.org/10.1007/s40098-014-0128-0 ) is also presented. As a result, the Park and Koumoto (2004) method is capable of predicting approximately with the precision of 1/1.5 to 1.5 the measured compression index using the initial porosity of soil sample, irrespective of the disturbance state of the soil, soil types and clay minerals.

Recently, microbially induced carbonate precipitation (MICP) has been studied as an alternative for the improvement of sand–clay mixtures. However, the cementing uniformity of MICP-treated sand–clay mixtures cannot be guaranteed. In this present study, enzymatic-induced carbonate precipitation (EICP) was used to deal with it. The ions used in kaolin clay was predicted to affect the production rate for calcium carbonate (CaCO3), which was studied using the calcification test. The solidification test was conducted using two different methods (the premixing method and the diffusion method). The permeability, unconfined compressive strength and the content of CaCO3 of treated samples were obtained to evaluate the solidification effect of the EICP method. Moreover, in EICP treatment, the particle aggregation decreased the liquid limit, but the addition of solution increased it. Therefore, there were contrary effects to the soil consistency. In this study, the two types of liquid limits of treated samples were measured with deionized water and 2M-NaCl brine, respectively. The results show that the Al2O3, NaCl and MgCl2 in the kaolin clay had a slight impact on the production rate for CaCO3, while FeCl3 significantly inhibited it. The EICP method can improve sand–clay mixtures and decrease their permeability. Different from MICP, the EICP method can guarantee the uniformity of treated samples. Moreover, the liquid limit of the sample treated with the premixing method decreased, while that of the sample treated with the diffusion method increased firstly and then decreased with the increasing treatment cycles. Different from the deionized water, the pore-fluid chemistry had a larger effect on the liquid limit with 2M-NaCl brine.