Modifying lateritic soils, which are widely distributed in humid and rainy regions around the world, for embankment construction is a practical necessity for highway and railway projects. These embankments are susceptible to infiltration of rainfall, wetting and vibration from earthquakes and traffic. Further study is required to investigate the dynamic response characteristics of these embankments under combined action of wetting and vibration. Two scaled-down physical models of embankments were built: one with unmodified lateritic soils, which are typical soils with high liquid limit in central-southern China, and the other with lateritic soils modified with lime at a content of 8%. A self-designed model test system was used to conduct model tests of both embankments under combined action of wetting and vibration. White noise excitation was employed to quantitatively compare the two types of embankments in terms of variations of dynamic properties, such as natural frequency and damping ratio, with wetting degrees. Three types of seismic waves-Chi_Chi, NCALIF and SFERN-were used to quantitatively compare the two types of embankments in terms of variations of dynamic response parameters, including PGA amplification effect, pore water pressure and earth pressure, with wetting degrees and acceleration amplitudes. The test results reveal significant differences in dynamic properties and responses of the two types of embankments. Compared to the unmodified embankment, the damping ratio and PGA amplification factor of the modified embankment are reduced by up to 53.5% and 37.5%, respectively, resulting in an effective mitigation of the combined action of wetting and vibration. Test values of natural frequency, damping ratio, PGA amplification factor, dynamic pore water pressure and dynamic earth pressure of both types of embankments are presented. The research findings provide a theoretical basis for highway and railway construction and for revision of technical specifications in regions with widespread lateritic soils.

Soil with high liquid limit is often encountered in southern China, which is unsuitable for direct use as embankment fill. Current soil reinforcement methods entail high carbon emissions, necessitating mitigation for a low-carbon future. In this study, a reconstituted soil is reconstituted to simulate the soil with high liquid limit from the site of the reconstruction and expansion project for the Zhangshu-Ji'an Highway in Jiangxi, China. This reconstituted soil was reinforced using steel slag, varying in grain sizes and employing two mixing methods. The mechanical characteristics of the pure and reinforced soil were examined by a series of monotonic and cyclic triaxial tests. The results indicate that decreasing the grain size of steel slag increases the monotonic shear strength and leads to a decrease in the permanent strain under cyclic loading, regardless of the mixing methods. The reduction in grain size of steel slag increases the total frictional surface area, thereby enhancing soil strength and resistance to deformation. Compared to the samples by uniform mixing with the steel slag, the samples by layered mixing results in a greater shear strength and a more significant permanent strain, because the concentrated steel slag grains and reconstituted soil particles produce greater friction and more significant compressibility, respectively. Overall, smaller grains of the steel slag by uniform mixing are more effective for reinforcing weak soil with high liquid limit, as it provides a higher monotonic strength and a lower permanent deformation, and reduces rapid energy dissipation under cyclic loading, compared to layered mixing.

The use of basalt fibers, which are employed in various fields, such as construction, automotive, chemical, and petrochemical industries, the sports industry, and energy engineering, is also increasingly common in soil reinforcement studies, another application area of geotechnical engineering, alongside their use in concrete. With this growing application, scientific studies on soil reinforcement with basalt fiber have also gained momentum. This study establishes the effects of basalt fiber on the liquid limit, plastic limit, and strength properties of soils, and the relationships among the liquid limit, plastic limit, and unconfined compressive strength of the soil. For this purpose, 12 mm basalt fiber was used as a reinforcement material in kaolin clay at ratios of 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%. The prepared samples were subjected to liquid limit, plastic limit, and unconfined compressive strength tests. As a result of the experimental studies, the fiber ratio that provided the best improvement in the soil properties was determined, and the relationships among the liquid limit, plastic limit, and unconfined compressive strength were established. The experimental results were then used as input data for an artificial intelligence model. The used neural network (NN) was trained to obtain basalt fiber-to-kaolin ratios based on the liquid limit, plastic limit, and unconfined compressive strength. This model enabled the prediction of the fiber ratio that provides the maximum improvement in the liquid limit, plastic limit, and compressive strength without the need for experiments. The NN results were in great agreement with the experimental results, demonstrating that the fiber ratio providing the maximum improvement in the soil properties can be identified using the NN model without requiring experimental studies. Moreover, the performance and reliability of the NN model were evaluated using 5-fold cross-validation and compared with other AI methods. The ANN model demonstrated superior predictive accuracy, achieving the highest correlation coefficient (R = 0.82), outperforming the other models in terms of both accuracy and reliability.

The problem of subgrade mud pumping under the action of train loads is common and challenging to cure. In order to investigate the occurrence condition and the mechanism underlying the development of mud pumping, the characteristics of 23 groups of soils prone to mud pumping were analyzed. Moreover, findings indicate that most of the soils have the following characteristics: (1) clay content is greater than 2%, and silt content is greater than 20%; (2) the liquid limit ranges between 23 and 75%, and the plasticity index varies between 5 and 42.5; (3) the permeability coefficient is between 3.28 x 10-8 cm/s and 1.39 x 10-4 cm/s; (4) the main mineral components of the mud pumping soils are illite, montmorillonite, and kaolinite; and (5) the saturation of the mud pumping soil is generally greater than 80%. In addition, silty clay was selected to carry out the subgrade mud pumping test. The results show that under cyclic loading, there is an excess pore water pressure gradient in the subgrade soil, which mobilizes the fine particles in the subgrade soil, especially in the upper part of the subgrade soil, to migrate with the water flow, forming mud, and eventually resulting in subgrade mud pumping.

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 selection of structural strength indicators is of utmost importance for slope engineering safety. This paper, with the backdrop of the destruction of high liquid limit clay layers in the Huai River slope, aims to investigate the influence of dry-wet (D-W) cycles on the structural and mechanical properties of undisturbed high liquid limit clay. Through unconfined compression tests, scanning electron microscopy (SEM) tests, and triaxial shear tests, the structural behavior, stress-strain curves, porewater pressure-strain curves, and effective stress paths of undisturbed samples taken at three different angles and reconstituted samples were analyzed under the condition of maximum drying stress with 0 and 1 D-W cycle. Based on the impact of D-W cycles on the effective stress path, the shear failure mode of structurally high liquid limit clay under the influence of D-W cycles was identified. A method for evaluating the anisotropic level of structural clay after experiencing D-W cycles was proposed. The test results show that compared with reconstructed soil, the undisturbed high liquid limit clay with structure is more significantly affected by the D-W cycle. After D-W cycles, the CU shear strength of high liquid limit clay increased significantly. The failure mode transitioned from a hardening-shear dilation mode to a softening-partial shear contraction-partial shear dilation mode. The appearance of the phase transition state (PTS) point may be attributed to the partial action of effective stress on cracks inside the sample, resulting in shear contraction. D-W cycles weakened the structural properties (anisotropy) of high liquid limit clay.

This paper performs the strength properties of bio-enzyme improved high liquid limit soil (HLLS) treated with 4% (by weight) content of cement or lime cured for 28 days. A series of consolidated undrained (CU) triaxial tests and unconfined compressive (UC) strength tests were conducted on plain soil (untreated by cement or lime), cement-treated and lime-treated HLLS specimens improved with different bio-enzyme content (i.e., 0%, 0.2%, 0.4%, 0.6% and 0.8% by weight) to investigate the effect of bio-enzyme content on the strength properties of tested soil. The results indicate that the stress-strain relationship of bio-enzyme improved plain soil specimens exhibit strain-hardening behavior and ductile failure mode. The other specimens exhibit strain-softening behavior and brittle failure mode. Adding 0.6% bio-enzyme, the values of undrained shear strength of CS specimens are about 1.7 times, 1.8 times, and 1.9 times of LS specimens at sigma 3 = 100 kPa, 200 kPa and 300 kPa. The residual strength is about 40.5% on average the peak strength for CS specimens, and 37.0% for LS specimens. The cohesion c increased 258.6% and 220.7%, and the internal friction angle phi increased 38.57% and 39.05% for CS and LS specimens respectively. The UC strength of CS specimen is 1.69 times that of LS specimen. The magnitudes of CU strength, UC strength, cohesion and internal friction angle of three types of soil specimens followed the same increase trend when the bio-enzyme content increased from 0 to 0.6%, and peak values can be observed at 0.6% bio-enzyme content. The use of bio-enzyme to improve the strength behavior of HLLS treated with cement or lime is an innovative and attractive solution in geotechnical engineering. The effectiveness of bio-enzyme in improving the strength of HLLS treated with cement or lime was studied based on a laboratory investigation.Adding cement or lime in HLLS provided a significant increase in strength and strength parameters at a certain bio-enzyme content, where the treatment effect of cement is better than that of lime.The bio-enzyme content of 0.6% can achieve the most economical effect on enhancing the strength and the strength parameters of HLLS improved by 4% cement or lime.

To reuse industrial solid wastes and waste clay with low liquid limit, a kind of soil solidification material by using cement, quicklime and industrial solid wastes such as ground granulated blast -furnace slag (GGBS), silica fume (SF) was developed in this study. Response surface methodology (RSM) based on central composite design (CCD) was used to design the experiment and optimize the mix ratio of GGBS, quicklime and SF under certain cement content conditions (i.e., the content ratio of cement, GGBS, quicklime, and SF was 5: 9.14: 1.7: 2.13). A soil solidification agent named O-QGS was developed to solidify waste clay with low liquid limit. To clarify the solidification mechanism of solidified soil, a series of laboratory experiments such as UCS test, water stability test, and scanning electron microscopy (SEM) test were carried out to capture the mechanical properties, water stability, and microstructure of O-QGS solidified soil and cement solidified soil. For practical purpose of O-QGS, a method for forming prefabricated pile by using O-QGS solidified soil was developed, and a method for strengthening soft foundations with prefabricated O-QGS solidified soil pile was proposed. Based on the results of load tests, the bearing capacity of prefabricated O-QGS solidified soil pile and cement high-pressure rotary jet grouting pile, as well as the composite foundations bearing capacity of prefabricated O-QGS solidified soil pile and cement high-pressure rotary jet grouting pile used for strengthening soft foundations, were analyzed. The feasibility of prefabricated O-QGS solidified soil pile used for strengthening soft foundations was verified in practice. The present study shows that the UCS of O-QGS solidified soil is 7.25 MPa at 28 days, and the water stability coefficient of O-QGS solidified soil is larger than 0.8. Compared with the method of cement highpressure rotary jet grouting pile to reinforce soft foundation, the bearing capacity of prefabricated O-QGS solidified soil pile to reinforce soft foundation is higher, and the cost can be saved by 22.4 %.

Salinity and sodicity greatly influences ongoing physical processes in soils. Organic matter may rehabilitate physical and mechanical properties of soils. Vermicompost as an amendment influences moisture-related parameters including consistency (plastic - PL and liquid limit - LL) and compaction. This study was conducted on soils (sandy-clay-loam) treated with different salinity levels (0.58 (control - irrigation water quality, tap water), 4 and 8 dS m(-1)) to investigate the effects of different vermicompost doses (0% (control), 2.5% and 5% w/w) on soil consistency limits and compaction. The pot experiment was carried out in a total of 27 pots, i.e. 3 (vermicompost doses) x 3 (salinity levels) x 3 (number of replicates). For Proctor compaction properties, maximum dry bulk density (MDD) reduced and optimum water contents (OWC) increased with increasing vermicompost doses under different salinity levels (p < .01). Increasing vermicompost doses under the lowest salinity level (0.58 dS m(-1)) yielded increasing optimum water contents for control (LL = 35.93% and PL = 25.85%). Optimum water contents were determined as 42.19% (LL) and 29.93% (PL) for 2.5% vermicompost dose and as 47.33% (LL) and 36.01% (PL) for 5% vermicompost dose under the lowest salinity level. LL, PL, OWC and MDD were significantly affected by vermicompost x salinity interactions. The highest maximum dry bulk density (1.92 g cm(3)) and the lowest optimum water contents (13.50%) were obtained from 0% vermicompost under the 8 dS m(-1) NaCl level. Mean weight diameter (MWD) values ranged from 0.690 mm for 0% VC treatment under high Na salt level (8 dS m(-1) NaCl) to 0.821 mm for 5% VC treatment under lowest Na salt level (0.58 dS m(-1) NaCl). The correlations between aggregate stability (particle size group 1-2 mm) and optimum water content were 0.647*, 0.587* and 0.598* as compared to correlations of -0.512*, -0.470*, and -0.617** between aggregate stability (particle size group 1-2 mm) and maximum dry bulk density for the 0, 4 and 8 dS m(-1) NaCl levels, respectively. MWD was positively correlated with OWC (0.386*) and negatively correlated with MDD (-0.385*). The greatest (2.39%) and the lowest (0.32%) soil organic matter values were respectively observed in 5% VC under the lowest salinity level (0.58 dS m(-1)) and 0% VC with at high Na salt level (8 dS m(-1) NaCl). It was concluded that vermicompost reduced compaction-induced damage in soils.

Freeze-thaw cycles are prevalent climatic phenomena with substantial effects on soils, leading to alterations in soil strength, stiffness, and hydraulic properties due to disruptions in the soil structure. With the ongoing climate change, weather patterns have grown progressively erratic, resulting in more frequent occurrences of extreme weather events, including heavy snowfall, intense rainfall, and windstorms, even in regions characterized typically with mild climates across the globe. The climate change can potentially threat manmade infrastructure constructed within or upon local soils, regardless of their susceptibility to freezing in temperate climates. The principal objective of this study is to assess the influence of freeze-thaw cycles on the California Bearing Ratio (CBR %) across 12 distinct soils with variations in granulometry and mineralogy. The freeze-thaw cycles resulted in a notable decrease in CBR (%) within the range of 40% to 70%. A strong inverse correlation with D50 was observed regarding the decrease in CBR (%). Nevertheless, it was discerned that the decrease in CBR (%) subsequent to freeze-thaw cycles varied among soil samples sharing identical D50 and liquid limit characteristics. The aim of this study is to enhance our comprehension of how freeze-thaw cycles can impact the bearing capacity of these soils, thereby providing essential insights for predicting their behavior and potential influence on infrastructure in the context of climate change.