Subgrade Soil Research Articles

Column experiments to study the thermo-hydro-mechanical-chemical behavior of sensitive marine slay subgrade soil treated with lime

Column experiments to study the thermo-hydro-mechanical-chemical behavior of sensitive marine slay subgrade soil treated with lime

Economic and environmental assessment of industrial wastes stabilized clay and sand soil subgrades using experimental and theoretical approaches

The objective of the present study was to increase the strength and stiffness of silty clay and silty sand subgrades for building economic and sustainable asphalt pavements. Advanced cyclic load tri-axial (ACLT) and California bearing ratio (CBR) tests were performed to obtain the experimental and theoretical resilient modulus (MR) of the soil subgrades, respectively. In addition, the impact of the stabilization of the plasticity and compaction characteristics of the soil subgrades was determined. The insight into the mechanism of the stabilization was obtained by determining the mineralogical and microstructural properties of the stabilized soils through X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) tests, respectively. The combined inclusion of 20% brick kiln dust and 20% pond ash resulted in 186% increase in the CBR, 224% increase in the experimental MR, 96% increase in the theoretical MR, 2.07 times higher pavement service life, 23% savings in cost, and 28% reduction in the CO2 emissions associated with pavement construction. The enhancement in the CBR and MR of the soils was attributed to the increased inter-particle friction, improved particle size distribution in stabilized clay and sand, and a concurrent reduction in the plasticity of clay. The study highlights the real-world usage of the ACLT test to get the real MR of soil subgrade rather than the over-estimated theoretical MR. For precise estimation of MR from CBR, a correlation between CBR and experimental MR was established.

Dynamic deformation and meso-structure of coarse-grained saline soil under cyclic loading with freeze-thaw cycles

The cumulative deformation properties of subgrade soil under cyclic traffic loads are critical for optimizing pavement structure design and ensuring long-term highway structural performance. This study aims to investigate the coupling effect of freeze-thaw cycles and cyclic loads on the cumulative deformation behaviors and meso-structure of coarse-grained saline soil (CGSS) subgrade filling in high-cold areas. Dynamic triaxial tests and computed tomography (CT) scanning were conducted to analyze the CGSS under different working conditions. The research focused on the dynamic deformation development and damage evolution under varying freeze-thaw cycles and load amplitudes. The research results show that the cumulative deformation behavior of CGSS under cyclic loading is relatively sensitive to the freeze-thaw process. The cumulative dynamic strain increases as the freeze-thaw cycles, with a critical freeze-thaw cycle number of five. The stable cumulative dynamic strain curve exhibits clear three-stage characteristics when plotted in semi-log coordination, with critical loading cycles at 20 and 1,000. After 10–100 loading cycles, the cumulative strain curve quickly shows failure. The CGSS’s low density and pore regions greatly increase after a freeze-thaw cycle. The rise in dynamic stress amplitude notably affects the bonding between soil particles and crystalline salts. The coupling effect of the freeze-thaw cycle and dynamic activity exacerbates the deterioration of soil structure, resulting in variations in CT values within the scanning layer in the final state.

Results of Laboratory Studies of Strengthening Subgrade Soil with Modifier

Current modern trends in road construction are the increase in traffic intensity and the carrying capacity of motor transport, as well as the expansion of the road network, including local roads. These trends put forward the task of not only increasing the durability of road structures, but also the use of local materials and soils in the construction of highways. Several methods have been developed to strengthen the soils of the road base. A variety of surfactants, modifiers and additives are also produced to strengthen the roadbed. Many of them have not shown their effectiveness in practice. Therefore, there is a need for plenty laboratory and field studies on this topic. Laboratory studies were carried out to investigate the effect of the modifier on the roadbed soil. The type of soil and its maximum density were determined at optimal humidity. Based on this, cement and a modifier were introduced into the soil composition, density and compressive strength were determined. The results of a scanning electron microscope (SEM) were obtained to study the effect of the modifier on the roadbed soil. Laboratory studies and SEM-analysis have shown that the addition of a modifier to the soil leads to an increase in its maximum density, a significant increase in compressive strength and that the modifier serves to improve the binding properties by forming a crystalline bond with cement.

Investigation on shakedown response-behavior of thawed subgrade soils under long-term traffic loading

The shakedown state of the subgrade is crucial for the sustainable design and long-term stability evaluation of pavement structures. In order to characterize the plastic deformation and shakedown behavior of subgrade soil in seasonal frozen regions, cyclic triaxial tests were conducted on the thawed subgrade soil after seven cycles of freeze-thaw. The influences of the numbers of cycle loading, the amplitude of cyclic deviator stress, and the confining stress were considered variables. The evolution features of accumulative plastic strain, accumulative plastic strain rate, and critical dynamic stress were experimentally analyzed. Based on the shakedown theory, the ensuing discoveries were that the accumulative plastic strain response-behavior of thawed subgrade soil was typically divided into plastic shakedown, plastic creep, and incremental collapse under the long-term cyclic loading. Furthermore, the shakedown standard for thawed subgrade soil was also proposed based on the evolution of the accumulative plastic strain rate. The critical dynamic stresses can be obtained by the proposal formula to determine the different plastic deformation ranges.

Prediction of Soil Expansivity with Direct and Indirect Method in Banten Region, Indonesia

Expansive soils are widespread in Indonesia, particularly in Banten Province, causing extensive road damages. The study aimed to predict the soil expansivity of soil subgrade along the damaged road segments in Malingping, Cikeusik-Cibaliung, and Labuan districts. Indirect and direct expansivity predictions were employed to determine soil swelling potential. Indirect expansivity prediction was conducted based on various criteria using the Atterberg limit and grain size distribution. Direct expansivity prediction was conducted using an oedometer apparatus to measure the expansion index according to ASTM D-4829. A dynamic cone penetration test was also conducted to measure CBR values. Various indirect methods showed inconclusive results of swelling potentials, low to very high. The direct method provided more conclusive results, Expansivity Index = 100-167 and swelling values = 9%-18%, thus, categorized as expansive clay (high to very high swelling potential). CBR values were 1.49%-5% which is lower than minimum provisioned CBR (6%).

Experiment on the performance of high-speed railway subgrade with tire debris mixed filling

As an important component of railway track, railway subgrade bears a huge dynamic load from trains. To explore the feasibility and dynamic characteristics of mixed filling of railway subgrade soil with tire debris, a series of large-scale indoor model tests were conducted to compare and analyse the magnitude and distribution of earth pressure, and the cumulative settlement displacement of sleepers, under two different loading conditions (i.e., single-stage cyclic loading and multi-stage cyclic loading). The results demonstrate that under all conditions, the vertical displacement at the sleeper ends is greater than that at the sleeper middle, the vertical displacement at the sleeper end decreases with the increase of static load and frequency, but increases with the increase of amplitude. Additionally, adding tire debris can help reduce the settlement and displacement of the subgrade soil, and the same amount of tire debris has the best effect when mixed in two layers. Moreover, multi-stage cyclic loading can significantly reduce the cumulative settlement of the subgrade soil. Under multi-stage cyclic loading, the settlement displacement at the end of the subgrade soil sleeper is larger than that at the middle of the sleeper, but the difference gradually decreases as the static load increases. It is revealed from the research that tire debris can significantly improve the performance of railway subgrade soil.

Investigation of the discharge performance in infiltration wells based on several soil subgrade models

Heavy precipitation would result in hydrometeorological disasters such as landslides and floods. In general, disasters cause hazardous situations and property loss. Infiltration wells are water and soil conservation techniques that can reduce surface runoff and increase infiltration to mitigate the effects of hydrometeorological disasters. However, evaluations of geotechnical properties have not yet jointly or actively considered these environmental developments. This paper aims to analyse the wide range of soil types against several diameters and depths of the holes. The variation in soil varied from type 1 to 6, containing different properties and consistencies. The holes diameter used are 0.4m, 0.5m, 0.6m, 0.7m, and 0.8m, associated with several depths; 0.5m, 0.75m, 1m, 1.25, and 1.5m. The analysis was conducted with Geostudio SEEP-W in different model variations to obtain the well’s discharge value. The result shows that all the depth depicts similar behaviour of the discharge well. The sand model has the highest value of all categories, with the second place being the sand-clay layer model. In contrast, the clay simulation generates the lowest value of this research. This output offers a strong recommendation between infiltration well structure and soil parameters, which show sand is the most required property to increase the performance of hole infiltration.

Comprehensive Study of Soil Subgrade Reaction Using Different Constitutive Soil Models

Comprehensive Study of Soil Subgrade Reaction Using Different Constitutive Soil Models

Effectiveness of Alccofine, Zycobond, and Terrasil as Clayey Soil Stabilizer: A review

Since the last two decades, India has seen a significant increase in infrastructure development, which has resulted in a rapid increase in pavement construction and structural foundation. Pavements and foundations for structures are generally laid on the soft ground during this process which is highly unfavorable for construction. Clayey soil is a difficult soil to work with because it is cohesive, highly unstable, and prone to volumetric shrinkage, has low shear strength, and is susceptible to moisture. The CBR of these subgrade soils is too low, causing the thickness of the pavement laminas to increase. It creates an undesirable requirement for usage of large number of natural resources. A cost-effective solution would be to convert locally available difficult soil into suitable construction material. So, first method is to ameliorate the properties of the available soil so as to meet the requirements, a process known as soil stabilization. The current study's scope is limited to investigating, the techniques of the stabilization process with respect to the CBR values as the CBR is the most important factor in determining the base material quality for the said purpose. This study compares results from different experiments conducted at different researchers. The effect of Zycobond and Terrasil in combination with Alccofine on clayey soil in various ranges was explored in this paper.

Effect of variations in concrete quality on the crack width in rigid pavement

Cracks pose a significant issue in rigid pavement, leading to substantial damage. The manual mixing and casting of road pavement concrete underscore the importance of concrete quality as a critical parameter. This study investigates crack behavior by varying concrete quality. Loading is performed statically using line loads, shedding light on the impact of concrete quality on crack development. The concrete to be used has a quality fc' of 15 MPa, 25 MPa, and 35 MPa. The fine aggregate used in this study was Lumajang black sand, while the coarse aggregate used was machine crushed stone, and Portland Composite Cement (PCC) was used in all concrete mixes. The reinforcing steel used had a quality fy of 480 MPa, with a reinforcement ratio of ρ=0.010, which was converted to 5-D16 reinforcement. The subgrade density used to support the specimens had a CBR value of 10 %. Specimen dimensions were 2×0.6×0.2 m for length, width, and thickness. Pavement plates, 30 cm thick, were placed on leveled subgrade soil in a steel box set to achieve a 6 % CBR reading. Hydraulic jacks, monitored by a load cell, applied monotonic static loading with 2 kN intervals, reaching a maximum load of 200 kN. Steel tension and plate settlement were measured using a tension sensor and Linear Variable Differential Transformer (LVDT), respectively. A data logger recorded readings, and crack widths were captured by a digital microscope with 0.01 mm accuracy. Experimental results show that low concrete compressive strength values result in larger crack widths, and vice versa. Cracks also occur at earlier loading of concrete quality fc' 15 MPa. In addition, experiments show that the reinforcement stress value has a significant influence on crack width in specimens with low concrete quality

Research on correlation between dynamic resilient modulus and CBR of coarse-grained chlorine saline soil

A large area of coarse-grained saline soil is distributed in saline soil areas, and chlorine saline soil with a high salt content is a typical representative. The dynamic resilient modulus was accurately predicted using the California-bearing ratio (CBR) value to determine the relationship between the dynamic resilient modulus of coarse-grained chloride saline soil and its CBR value. Indoor dynamic triaxial tests and CBR tests were conducted to investigate the evolution of the dynamic resilient modulus (MR) and CBR of coarse-grained chlorine saline soil under the influence of the stress level, water content, and salt content. The test results showed that the dynamic resilient modulus increased with an increase in the confining pressure and bulk stress and decreased as the deviator stress increased; however, the CBR increased with an increase in the corresponding unit pressure. The higher the salt and water contents, the more obvious the influence of stress on the dynamic resilient modulus and CBR value. Under the same stress level, the decrease in the dynamic resilient modulus and CBR gradually increased with increasing salt and moisture content, and the effect of salt tended to be more significant than that of water. Based on the correlation between the dynamic resilient modulus and CBR revealed by the experiment, a more widely applicable model was selected from the existing theoretical models related to CBR for the regression analysis of the test data, and a prediction model of the dynamic resilient modulus based on the CBR value was proposed (MR = 21.06CBR0.52). This prediction model had a high correlation coefficient (R2 = 0.893) and could effectively predict the dynamic resilient modulus of coarse-grained chlorine saline soil using CBR values. The results provide a simple and reliable method for determining the design parameters of a coarse-grained saline soil subgrade.

Characterizing the dynamic resilient modulus of subgrade soil treated by BT-SAP subjected to freeze-thaw cycles

Freeze-thaw (FT) cycles are regarded as a damage effect to the dynamic resilient modulus (MR) of subgrade soil in seasonal frozen regions and improving the resistance on freeze-thaw cycles must be concerned urgently. For this purpose, the bentonite superabsorbent polymer (BT-SAP) was developed as an available admixture to relieve the attenuation of MR of subgrade soil under FT cycles. In order to evaluate the improvement of resistance on FT cycles, a series of dynamic triaxial tests were conducted after various FT cycles. The main influences on MR were investigated including the numbers of freeze-thaw cycles, BT-SAP contents, deviator stress and confining stress. The experimental results indicate that the BT-SAP can delay the attenuation trend of MR that means the resistance on freeze-thaw cycles have been promoted. The ensuing discoveries are that with the increment of BT-SAP content, the sensitivity of the subgrade soil to FT cycles is gradually reduced. Nevertheless, results reveal that a proper content of BT-SAP is recommended as 0.5%, where if the BT-SAP content exceeds 0.5%, the improvement effect of resistance on FT cycles decreases. Moreover, the improved effect caused by BT-SAP can produce a coupling enhancement combining with confining stress, and it also can offset the softening effect due to the deviator stress. For better application and practicability, the high-accuracy empirical model for predicting MR is established and validated. Finally, based on the soil freezing temperature, unfrozen moisture content and moisture distribution characteristics, the mechanism of BT-SAP reducing the freeze-thaw cycle sensitivity is analyzed. The conclusions mentioned above show that employing BT-SAP material is acceptable and significant to improve resistance on freeze-thaw of subgrade soil.

CONSTRUCTION OF SUSTAINABLE ROADS USING THE MIXTURE OF ALKALI-ACTIVATED RICE HUSK ASH AND FLY ASH

Soil stabilization, crucial for enhancing the stability and engineering properties of soil, has been the subject of extensive research utilizing mechanical and chemical methods. This study delves into the challenges faced in traditional soil subgrade stabilization methods, stemming from factors such as soil erosion, inadequate load-bearing capacity, and susceptibility to environmental conditions. These challenges have prompted the exploration of innovative solutions for road subgrade soil stabilization. Our primary motivation stems from the limitations of conventional techniques and the pressing need to address issues like resource exploitation and environmental pollution. Geopolymers, specifically alkaline-activated materials, have emerged as a promising alternative for soil stabilization. This research investigates the effects of geopolymer blended with rice husk ash (RHA) and fly ash (FA) on various geotechnical properties of natural and admixed black cotton soil. The soil is replaced with admixtures ranging from 0% to 30% of blended geopolymer by weight. The study provides a comprehensive analysis, focusing on quantifiable improvements in soil properties through numerical results. The investigations consistently reveal that the application of geopolymer as a soil stabilizer results in notable improvements in the geotechnical properties like index properties, strength properties, resistance to penetration (CBR), etc., of problematic soil. Comparative analysis with traditional methods underscores the superiority of the proposed geopolymer blend, showcasing its innovation, sustainability, and cost-effectiveness. The findings of this study contribute to the advancement of soil stabilization techniques, specifically in the context of geopolymer applications. For future work, this study suggests an in-depth exploration of geopolymer-stabilized soil's long-term durability and environmental impact. Additionally, further research could focus on optimizing the geopolymer blend ratios for varying soil types and environmental conditions.

A laboratory investigation and numerical modeling on fiber reinforced lime and alkaline binder stabilized pavement subgrade soil

The differential settlement and excessive deflection in expansive subgrade soils lead to low volumetric stability upon moisture imbalance and cause severe damage to highway and airport field pavement surfaces. The present paper attempts to strengthen the stability behavior of expansive subgrade soil using an envirosafe alkaline binder (AB) with polypropylene fiber (PLF). AB was produced by combining dry aluminosilicate precursors (steel slag [SS] and sugarcane bagasse ash [SBA]) with a liquid activator (mixture of sodium hydroxide [NaOH] and sodium silicate [Na2SiO3]) in 0.4 water to binder (w/b) ratio. California bearing ratio (CBR) based resilient modulus, shear strength ratio (Sr), and consolidation tests were conducted as performance indicators of expansive subgrade soil reinforced with discrete PLF (0–0.5%) in 6% lime and 6% alkaline binder. The study also proposes the optimal sugarcane bagasse ash-steel slag-PLF dosage in the AB-stabilized subgrade layer. Moreover, mineralogical and morphological studies using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were also carried out to understand the crystalline compounds and micro surface texture of the soil-fiber mixture. It was revealed that AB-fiber-soil exhibits higher interfacial frictional bonding and interlocking density than lime-fiber-soil. Also, 2D finite element analyses were carried out to compare the behavior of subgrade under the influence of vehicular load on the surface. PLF-AB soil mixture shows 72% lower vertical deformation than unstabilized expansive soil. Based on the findings of this study, recommendations for the practical application of stabilizing expansive subgrade soils were proposed.

Mechanism and Application of Soilbags Filled with Excavated Soil in Soft Soil Subgrade Treatment

This research addresses the characteristics of soft soil subgrades treated by soilbags filled with excavated clayey soil. We evaluated of the strength and deformation modulus of soilbags containing excavated soil using unconfined compression tests. In addition, the drainage consolidation characteristics of soilbag-treated subgrades were investigated via model consolidation tests. Furthermore, a practical application included the construction of a 100 m-long rural road subgrade with these soilbags. The field test and numerical simulation results included the surface settlement and pore water pressure during and after construction to validate the effectiveness of the soilbag treatment for soft soil subgrade. The results show that the soilbags significantly enhanced both the strength and deformation modulus of the soft soil, which met the design requirements after the soilbag treatment. The drainage attributes of the soilbag treatment were also found to support the consolidation process of the soft soil subgrade effectively. Notably, the pore water pressure diminished rapidly during the construction interval, which is beneficial to reducing the post-construction settlement. The settlement uniformity of the subgrade is good verification of the superiority of the soilbag-treated subgrades.

Performance evaluation of geosynthetic reinforced marginal material as base layer over weak subgrade

ABSTRACT The availability of quality materials for construction has been an issue in some regions. This scarcity obliged using marginal materials reinforced with geosynthetic materials as one of the quests for sustainability in the pavement industry. In this study, an attempt was made to stabilize the marginal materials by incorporating geosynthetics. The different geosynthetics used in the study are geogrid, geocell, double geogrid, and geocell + geogrid. A series of unreinforced (UR) and geosynthetic reinforced (GR) pavement prototypes were constructed in the laboratory with landslide debris as base material underlain by black cotton soil subgrade. Large-scale cyclic plate load (CPL) tests were performed on test prototypes constructed in the laboratory under cyclic loading following the trapezoidal loading pattern with 0.77 Hz frequency. The efficacy of geosynthetic reinforcement was quantified concerning permanent deformation (PD), resilient deformation (RD), Rut depth reduction (RDR), Traffic improvement ratio (TIR), and reduction in vertical stresses transmitted to the subgrade and reduction in base layer thickness. The test results indicate that the GR significantly reduced the rut depth and improved the traffic capacity. In addition, over all types of GRs, the combination of geogrid and geocell outperformed in terms of permanent deformation and rut depth reduction.

Effect of Initial Conditions on the Pore Structure and Bimodal Soil–Water Characteristic Curve of Compacted Granite Residual Soil

Granite residual soil typically forms complex pore structures and exhibits high water sensitivity due to physical and chemical weathering processes. Changes in initial compaction conditions significantly affect the mechanical and hydraulic properties of in situ granite residual soil subgrades, with these variations fundamentally related to changes in pore structure and soil–water characteristics. This study investigates the pore structure and bimodal soil–water characteristic curve (SWCC) of a compacted granite residual soil through laboratory tests and mercury intrusion porosimetry tests. Nine initial conditions were selected based on potential in situ compaction conditions of subgrades, and their effects on the pore size distribution (PSD) and SWCC were thoroughly analyzed. The results show strong correlations between bimodal pore structure and SWCC. The size and volume of inter-aggregate pores exhibit noticeable changes with initial conditions, affecting SWCC within the low and middle suction range. Conversely, the intra-aggregate pores, which constitute over 60% of the pore structures, remain nearly intact across different initial conditions, resulting in similar SWCCs within the high suction range. As the compaction energy increases, the inter-aggregate pores are compressed and lead to a higher water retention capacity. In addition, as the compaction water content increases, the SWCC becomes less sensitive to compaction energy after the aggregates in the pore structure are fully saturated. Additionally, a three-dimensional bimodal SWCC equation is proposed and validated using test data with an R2 value above 0.98. These findings offer valuable insights for the design and quality control of granite residual soil subgrades.

Study of hydrothermal processes in ice-layers subgrade under constant temperature and dynamic loading

The presence of ice-layers in the subgrade soils makes the hydrothermal state of road subgrade built in island permafrost regions more susceptible to external environmental influences. In order to deepen the study of the ice-layers subgrade, a hydrothermal study of subgrade under constant temperature and dynamic loading was carried out. It was found that dynamic loading can change the temperature, moisture and pore water pressure distribution. Under dynamic loading, the hydrothermal and pore water pressure state of the soil in the upper part of the ice layer changed significantly at the beginning of the test. The application of dynamic loads alters the spatial distribution of pore water pressure in the soil, resulting in pressure differences between different areas, which affects the migration of moisture and ultimately leads to the formation of areas with higher moisture content in the area below the load. However, the reduction in soil temperature will weaken the effect of the load, therefore, the temperature of the soil should be controlled for frozen subgrade with ice-layers to prevent the accumulation of moisture in the soil.

Pine cone ash stabilization of expansive soils

<p>The use of appropriate waste materials to stabilize problematic soils, such as expansive soils that are responsible for geotechnical damage, is a common practice in geotechnical engineering. This study presents the use of pulverized ash from the combustion of pine cone (PC) waste as a stabilizing agent to improve the engineering properties of expansive soils. A series of laboratory tests were carried out to examine the effect of different percentages of pine cone ash (PCA) content (3%, 5%, 7%, and 10%) on the Atterberg limits, swelling potential (Sp), linear shrinkage, compressibility, and unconfined compressive strength (qu) of naturally occurring swelling soils and the PC ash-treated soils. The results showed that PC ash contents of 5% and 7% contributed to a significant reduction in the swelling and shrinkage potential and an improvement in the coarsest texture, brittleness behavior, compaction properties, and compressive strength of the treated soils. Conversely, PC ash contents below 3% and above 7% showed minimal changes in the index and engineering properties of the PC ash-treated soils. In particular, the PC ash content of 5% resulted in optimal mitigation of the poor properties of the treated soils. The use of pine cone ash as a stabilizing agent represents a suitable and complementary subgrade soil material for expansive soils on which lightweight structures are built.</p>