California Bearing Ratio Values Research Articles

Mechanical and Environmental Analysis of Granular Subbase with Fine Crumb Rubber

AbstractThe increasing manufacturing of tires, driven by the automotive sector, has led to various sustainability and waste management issues. Consequently, it is necessary to explore alternatives for the reuse of these wastes. Rubber has demonstrated properties that could make it an attractive material for use as a granular aggregate. The aim of this study is to evaluate the influence of crumb rubber (CR) on the mechanical behavior of a granular subbase (GSB) by replacing fine CR at 10% and 15%. An environmental analysis of the proposal was conducted using the SimaPro tool, and a series of laboratory tests were performed to assess physical and mechanical characteristics. The strength results indicate a decreasing trend as the CR content in the GSB increases. Specifically, in abrasion tests, the natural material showed an average result of 30.86%, while the mixes with 10% and 15% CR exceeded the maximum limit (50%), achieving results of 59.24% and 53.98%, respectively. In terms of the California Bearing Ratio (CBR), only the natural samples compacted at maximum energy exceeded the minimum requirements for low and medium traffic levels (30%). The highest CBR value for samples containing CR was 5%, whereas the natural GSB reached a maximum CBR of 33%. A similar trend is observed in environmental outcomes, with increases of up to 17% in abiotic depletion for the sample with 15% CR. Overall, the environmental analysis suggests that incorporating CR into the GSB could lead to an increase in various environmental impacts.

Application of hybrid modeling to predict California bearing ratio of soil

California Bearing Ratio (CBR) is used to assess bearing capacity, deformation characteristics of roadbed soil, and base layer material in pavement structure. In general, CBR is often determined by laboratory or in-situ tests. However, it is time- and cost-consuming to conduct this experiment because this test requires cumbersome equipment such as a compressor. In this study, two Artificial Intelligence models are developed, including a simple model (Decision Tree Regression, DT) and a hybrid model (AdaBoost - Decision Tree, AB-DT). Using 214 data samples from Van Don - Mong Cai expressway, Vietnam, 10 input variables of the model were considered namely particle composition (content of gravel (X1), coarse sand (X2), fine sand (X3), silt clay (X4), organic (X5)), Atterberg limits (Liquid limit (X6), Plastic limit (X7), Plastic index (X8)), and compaction curve (optimum water content (X9) and maximum dry density (X10)). The developed models were evaluated by using a variety of statistical indicators, including coefficient of determination (R2­­), Root mean square error (RMSE), and Mean absolute error (MAE). The results show that AB-DT model has higher accuracy than the DT model. Moreover, the SHAP value analysis shows that the variable X10 influences the CBR value the most. Thus, it implies that applying the AB-DT model to effectively predict the CBR of the roadbed soil saves time and money for experiments.

Effects of oil palm mesocarp fibers on the physical and mechanical properties of expansive soils

Palm fiber is one of the favorable materials used in stabilization of soft soil in geotechnical engineering projects, nowadays due to its sustainability, less damage of environment, biodegradability, availability and cost-effectiveness in a context of widespread appeal to the world for return to nature by protecting the earth. On the other hand, expansive soils are renowned for their swelling-shrinkage property and these volumetric changes resultantly cause huge damage to civil infrastructures. Likewise, subgrades consisting of expansive soils instigate serviceability failures in pavements across various regions worldwide. This paper presents results of the laboratory evaluation of expansive soils stabilized with oil palm mesocarp fiber (OPMF), with a view to determine its suitability as flexible pavement construction material. The mixtures were subjected to British Standard heavy (modified Proctor) compaction energy to determine their strength characteristics. The samples were subjected to different tests to ascertain their index properties. Varying proportions of OPMF from 1% to 4% were incorporated into the soil samples and the effects were observed based on compaction and California Bearing Ratio (CBR) results. The control samples without inclusion of OPMF achieved the highest Maximum Dry Densities (MDD), the MDDs reduced linearly as the OPMF content increased. Consequently, the CBR values decreased with increase in OPMF. The reduction in MDD ranged from 20.28g/cm3, 18.5 g/cm3, 15.65 g/cm3, 12.53 g/cm3 as the OPMF increased from 1%, 2% to 3%, 4%. and the optimum moisture content remained almost unaffected due to high-absorbent nature of the fibers. With the inclusion of the OPMF, the CBR value under soaked conditions dropped from 5% to 1.8% rendering them very unsuitable for pavement subgrade. It was concluded that the presence of fiber depreciated the engineering properties of the earth materials. Direct application of OPMF in any part of road pavement has been dissuaded.

Investigational Study on the Influence of Sisal Fiber and Rice Husk Ash in the Stabilisation of Clayey Soil

The process of improving and enhancing the engineering qualities of soil so that it can support large loads without failing is known as "soil stabilization" in the realm of civil engineering. The behavior of the soil was examined in the current work at various proportions following the addition of Rice Husk Ash (fixed at 15%) and sisal fiber (varying at 1.5%, 2.0%, and 2.5%; length 40 mm). Various soil properties, such as OMC, MDD, CBR value, and UCS values, were then quantified. Utilizing Sisal Fiber and Rice Husk Ash together can enhance the diverse engineering features of soil, according to the conclusion of this experimental research project. Laboratory tests such Atterberg's Limits, Specific Gravity, Particle Size Distribution, Standard Proctor test, Unconfined Compressive Strength (UCS), and California Bearing Ratio (CBR) were carried out to examine the engineering qualities of the soil and its mixtures. The results showed that the engineering qualities of clayey soil were significantly enhanced by the addition of Sisal Fiber and Rice Husk Ash. As a result, Sisal Fiber and Rice Husk Ash may act as soil stabilizing agents, making clayey soil a better choice for building foundations. All testing were carried out in accordance with Indian standards regulations. Key Words: Compaction test, CBR, UCS, Rice Husk Ash, Sisal Fiber

Analysis of Kinang Jingkion Material as Road Subbase Layer Using Soil Cement Method

This research aims to analyze the California Bearing Ratio (CBR) and Unconfined Compressive Strength Test (UCS) values as road foundation layers using local materials, namely Kinang Jingkion. The soil and Kinang Jingkion materials for the study were taken from the Apalapsili quarry in Yalimo Regency. Additionally, the additive or soil stabilizer used was matos obtained from the testing of soil characteristics, including sieve analysis or gradation, Standard Proctor Test for light density, and liquid limit test. After testing, it was found that the soil from the Apalapsili quarry is granular soil and can be categorized as A-1-a according to SNI 03-6797-2002. Subsequent testing involved CBR and UCS testing on Mix Designs made of soil and cement with concentrations of 4%, 6%, and 8%. Next, additional Mix Designs were created with compositions of Kinang Jingkion, soil, cement at 4%, 6%, and 8%. Further Mix Designs included compositions of Kinang Jingkion, soil, matos at 2%, and cement at 4%, 6%, and 8%. From the UCS testing results, Mix Designs with soil and cement concentrations of 4% and 6% did not meet the compressive strength criteria, with compressive strength values of 9.26 Kg/Cm² and 17.4 Kg/Cm² respectively. According to SNI 6887-2012, the compressive strength value after 7 days of immersion should be within 25-35 Kg/Cm², while other Mix Designs met the criteria of SNI 6887-2012. CBR testing also utilized the same Mix Designs, and the highest CBR result was obtained from the Mix Design with compositions of Kinang Jingkion, soil, cement at 8%, and matos at 2%, with a CBR value of 112%. According to the 2018 Revised General Specifications, a CBR value of 112% indicates a Class A Foundation Layer.

Effect of illite on the mechanical properties of subgrade soil under varying surcharge loads

Due to its non-expanding properties, presence of Illite mineral in subgrade soil is investigated particularly on California bearing ratio (CBR), resilient modulus (MR) and swell potential. Multiple samples of stiff and weak subgrade soils with varying illite percentages were tested under six different surcharge loads ranging from 2.27 to 13.8 kg. Mineralogical analysis is performed using X-ray diffractometer and MR of soil is assessed using Ultrasonic pulse velocity (UPV) technique. Results showed a positive correlation between Illite percentage and both CBR and MR value. The soil with higher Illite content tends to exhibit higher CBR and MR values while those with higher montmorillonite content show lower values even with more Illite content. The CBR and MR values increases from 8.4% to 19 % and 139 MPa–315 MPa for stiff soil and 3.8%–11.7 % and 23 MPa–83 MPa for weak soil, respectively when the surcharge load was increase from to 2.27–13.8 kg. Additionally, a decrease in swell potential was observed from 1.64% to 1.09 % for stiff soil and 1.39%–0.84 % for weak soil with an increase in Illite percentage. The study also developed an improved relationship for predicting resilient modulus based on CBR value, showing a strong correlation with equations developed by many researchers in the past.

EFFECT OF USING LIME AND FLY ASH AS A CEMENT SUBSTITUTE FOR SOIL STABILITY

Subgrade is the lowest layer that receives the load on it if it does not have carrying capacity that is allowed then need for soil stabilization. Chemical soil stabilization is often done with the addition of cement but the use of cement material will cost quite high, it is necessary to alternate other materials for the substitution of cement to reduce the implementation costs incurred. Cement will be replaced as a stabilizing material in this research with additional materials like lime and fly ash. In this research, soil material was taken from the Sentul – Karawang Toll Road Project STA 24+300, with fly ash from PT PUSRI as the stabilization material, and lime material obtained from the market in Yogyakarta. The stabilization material will be used with a fixed lime percentage of 4.2% of the dry weight of the soil, and fly ash at 1.4%, 2.1%, 2.8%, 3.5%, and 4.2% of the dry weight of the soil. The soil samples were tested for physical and mechanical properties, including Standard Proctor and California Bearing Ratio (CBR). All test results were compared to select one variation, which was then designated as the Optimum Mix Design (OMD) sample. The test results of the soil sample + 4.2% lime + 2.1% fly ash yielded a CBR value of 15.52%, indicating an increase of 1078.02% from the initial 1.44%, and were formally designated as an OMD sample. The CBR value satisfies the subgrade requirements, namely >6%.

ANALISIS NILAI CBR SEBAGAI PARAMETER KRITIS UNTUK PERENCANAAN JALAN RAYA

<p><em>Infrastructure development is one indicator of a country's progress that cannot be ignored. Road infrastructure is an important part of the transportation system that connects different locations, facilitates human mobility, and transports goods. In the construction and maintenance of road infrastructure, soil plays a crucial role, so the condition and strength of the soil must be considered. Soil plays a significant role in construction as it serves as the foundation or base for building structures. Soil that has sufficient strength to support road loads will facilitate road construction. This study was conducted to determine the California Bearing Ratio (CBR) value, so that appropriate actions can be taken to construct roads based on local soil conditions. The CBR method is commonly used in soil geotechnical testing for road planning. This method involves laboratory testing of soil samples to determine the California Bearing Ratio (CBR). The results show a CBR value of 22.5%, which falls under the category of very good. This indicates that there is no need for improvement efforts in the construction of the Jl. Panglima Besar Sudirman, Dsn. Bolawen Ds. Tiron Kec. Banyakan Kab. Kediri highway, allowing resources to be allocated to other areas in need of road infrastructure improvements to enhance accessibility and overall regional development.</em></p>

The Effect of Waste Marble Dust and Corncob Ash on the Engineering and Micro-Structural Properties of Expansive Soil for Use in Road Subgrades

This research investigated the effect of Waste Marble Dust (WMD) and Corncob Ash (CCA) on expansive soil's engineering and microstructural properties. Various laboratory experiments were performed on the natural soil to ascertain its characteristics. The corncobs underwent pre-water treatment for fourteen days to remove excess potassium and increase their silica content, resulting in a rise in the silica level from 0% to 50%. At first, only WMD was added to the soil in increments of 5% to 30% using compaction and California bearing tests. The optimum dosage of 15% WMD addition yielded the best result. CCA was then incorporated by the weight of the soil from 2% to 10% in increments of 2% to the first optimum (15% WMD) to obtain the overall optimum for the study (15% WMD and 8% CCA). Stabilization of the natural soil using both materials led to the modification and solidification of the soil mass, evident by the rise in California bearing ratio values from 1.68% to 15.53% and unconfined compressive strength from 41.33 kN/m2 to 174.68 kN/m2. There was also a decrease in the soil's free swell from 120% to 15% as well as reductions in the liquid limits from 56.23% to 36.01% and in the plasticity index from 29.74% to 8.72%, respectively. The microstructural images showed the formation of cementitious compounds in the form of calcium silicate hydrate and calcium aluminate hydrate gels. The findings indicate that using WMD and CCA as a unit has great potential in enhancing engineering properties, like strength parameters and the swell potential of expansive soils.

The Effect of Oil Pollution on the Engineering Properties of Construction Soils in Some Selected Oil Region of Nigeria: A Case Study of Four Oil Towns in Rivers and Delta States

The nature of subgrade as well as basic information of soils for construction purposes is important for engineers, especially civil engineers and the general public. The primary aim of this research work is therefore to access the effect of oil spillage on the engineering properties of soils around the oil producing states of Nigeria. Four communities in two state of the Niger- Delta region of Nigeria were selected for investigation. These communities include Alesa (as sample A) and Aleto (as sample B) in Rivers state and Elume (as sample C) and Mereje (as sample D) in Delta state of the Niger- Delta region of Nigeria. Soil samples from these communities were collected at the subgrade depth of the oil spilled soils and was later subjected to laboratory examination. Important soil properties that were evaluated through laboratory investigation include soil shear strength test using triaxial test where the shear strength parameters were determined to enable evaluation of soil bearing capacity using Terzaghi’s equations. Others include soil strength (CBR) test, soil permeability test, and soil classification test as well as soil compressibility tests or one dimensional consolidation test. The results show that the oil pollution/ spillage have affected the engineering properties of construction soils in the four towns investigated to some degrees. The California Bearing Ratio (CBR) value of the subgrade, the Coefficient of Volume Compressibility,Mv, the Safe Bearing Capacity and the Coefficient of Permeability, K of the investigated soil , all fall below the accepted standard limit for soils to be used for construction purposes. This result will hopefully add to the existing knowledge as well as equipping the government and other relevant agencies for policy and regulatory development for the oil and gas, and construction industries for the sustenance of economic development in Nigeria. Therefore, before any meaningful civil engineering construction works can be done in these communities, the soils within the area will have to be subjected to series of engineering soil tests so as to equip the government and other interesting stakeholders with the requisite knowledge on how to apply appropriate soil remediation and soil stabilization techniques.

Stiffness and Strength of an Artificially Cemented Waste-PET-Shred Reinforced Clay

AbstractThis study explores whether the polyethylene terephthalate bottle shreds (PETBS), could be a viable alternative additive in order to reduce the usage of traditional cement in geotechnical and transportation projects. Through a comprehensive study, clayey soil was stabilized with varying quantities (0.1–1% of solid mass) of PETBS of two different size ranges. Optimal dosages were chosen, followed by additional tests incorporating small amounts of (5, 7 and 10% of solid mass) cement enhancement. After curing periods of 7 and 28 days, California bearing ratio (CBR) tests and ultrasonic pulse velocity (UPV) test results revealed that the addition of PETBS enhanced CBR values and initial shear modulus (G0) in both plain and cement treated samples. Scanning electron microscope (SEM) images also affirmed the improvement of strength at the microstructural level. Notably, PETBS of size 2–4.75 mm exhibited superior performance compared to size 0.42–0.841 mm, with an optimal content range of 0.6–0.8%. It was observed that the addition of PETBS to artificially cemented soil improved CBR values by up to 35%, while also modifying stiffness and brittleness, rendering the soil more ductile. Ultimately, a regression model was proposed to facilitate estimates of CBR and G0 in PETBS-reinforced cemented clay, to accommodate varying PETBS grading and content. The suggested approach promotes cost-effective and eco-friendly solutions by reducing pavement thickness and enhancing soil stability, demonstrating the potential of repurposing PET waste as a sustainable strategy in various engineering projects.

CBR Mapping Prediction from 2D Resistivity Imaging Using Regression Following Archie’s Formula

Indirect geophysical methods are increasingly associated with direct underground methods in investigating the subsurface to address environmental and geotechnical problems and reduce the cost of underground studies. These methods make it possible to explore large areas with acceptable precision, time, and cost. The present study combines the electrical resistivity method with the California Bearing Ratio for exploring an area located west of the Nouakchott port in Mauritania. The study aims firstly to verify that the thickness of the backfill layer must be less than 2 m throughout the entire study area and secondly to map areas with low California Bearing Ratio values (<80%) indicating substandard backfill compaction using 2D Electrical Resistivity Tomography imaging survey and regression. The measured Electrical Resistivity values exhibit a good nonlinear regression with California Bearing Ratio, following Archie's equation. A map of California Bearing Ratio variation was derived from the Electrical Resistivity values, indicating the distribution and variation of soil strength in the study area. The results revealed that the backfill layer did not meet the standards, with approximately 35% of the total area having a California Bearing Ratio value below 80%. The areas with poor compaction requiring treatment were primarily located in the southern sector, followed by the middle and eastern sectors.

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.

Compaction and strength characteristics of lead contaminated lateritic soil treated with eco-friendly biopolymer for use as road foundation material

Reuse of unwanted soil material due to contamination is one of the available alternative to mitigate the depletion of natural construction material like lateritic soil. Lateritic soil can become contaminated as a result of mining activities. However, assessment of such soil for adequate compaction and strength development is a critical requirement for establishing foundation for road pavement failure of which can result in rapid deterioration of structural integrity of pavement. The research paper investigated the efficacy of Gum Arabic biopolymer (GAB) as eco-friendly additive, in enhancing strength development of lead-contaminated lateritic soil (LCLS) for use as foundation material for road pavement. Varying contents of GAB up to 25% of the dry weight of soil in 5% succession was used in treating LCLS. Compaction characteristics, Maximum Dry Density (MDD) and Optimal Moisture Content (OMC), and California Bearing Ratio (CBR) with microstructural analysis of the treated soil were assessed using three distinct compactive efforts: British Standard Light (BSL), West African Standard (WAS), and British Standard Heavy (BSH). With increase in GAB content, there is a corresponding rise in MDD, while OMC decreased across all three compaction efforts. Optimal CBR values were obtained at 10% GAB content across the three compactive efforts. The Scanning Electron Microscopic (SEM) analysis revealed modifications in the surface morphology occurring at the peripheries of clay particles. The R-squared (R2) values of the regression models derived from statistical analysis of all dependent variables revealed that GAB, MDD, OMC and CE (compactive effort) collectively exert considerable significant effect over CBR values. However, the ultimate strength values fall short of the recommended thresholds for sub-base stabilization. This suggests that a GAB content of 10% enhances the characteristics of contaminated lateritic soil. However, it should not be employed as a sole stabilizer; instead, it could be considered as a potential admixture in cement stabilization.

Mechanical properties and field test of lime-soda residue stabilized soil for subgrade

To broaden the sources of subgrade filler and the utilization of Soda Residue (SR), SR was employed to modify clay by adding a small amount of lime for further stabilization, forming a Lime-Soda-Residue-Stabilized Soil (LSRSS). A set of intensive research paths was established, from testing of laboratory mechanical property, mechanism disclosure, and field verification to operational effect. Through Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), and Resilient Modulus (MR) experiments, it was concluded that with the increase in SR content, the UCS, CBR, and MR values of LSRSS showed an increasing trend then followed by a decrease, reaching their peak values, respectively of 0.62 MPa, 65.0%, 78.83 MPa, all at 30% SR content. An optimal proportion was determined for LSRSS as 6% lime, 30% SR, and 70% clay. The UCS, CBR, and MR values of optimal proportion all increased with the increase of compaction degree, but increased first and then decreased with the increase of water content. Their maximum values did not correspond to the OWC of 23% but to 27%, called the compaction water content, which was suitable for application in the actual LSRSS subgrade. Field test results showed that the UCS, CBR, and MR values were 0.85 MPa, 86.5%, and 135.7 MPa, which all were higher than the laboratory values, and the long-term road performance was outstanding. The analysis demonstrates that the better strength and road performance of LSRSS are mainly determined by the superior gradation and the reaction of three materials. The laboratory and field test results collectively provide data evidence for excellent performance and lay a solid foundation for the wider application of the LSRSS subgrade.

Enhancing California Bearing Ratio through Optimized Compaction Efforts: A Study on Alluvial Soils in North India

The quantity of soil required for embankment construction is enormous. Often the soil is brought to the site in dumpers in multiple rounds. This to and from movement of the wagons leads to the deterioration of the existing flexible pavement. In the absence of good earth nearby, using existing soils to act as a subgrade material upon meeting the desired strength and stability characteristics is the need of the hour. The California Bearing Ratio (CBR) is an indicator of soil's strength, which further depends on the degree of compaction of soil. In this study, an effort has been made to find the required compaction efforts to achieve maximum CBR value finding its applicability for both conventional flexible and perpetual pavements. Three different types of alluvial soils in North India were tested for CBR with varying compaction efforts using the modified Proctor test. The effect of mixing different soils was also considered to find the effectiveness of mechanically mixing soils on the required compaction efforts. It was observed that there is a constant upsurge in the CBR of soils upon an increase in the percentage compactive effort up to a certain limit. In the case of clayey soils, the rate of increase is less as compared to the well-graded sands. This study also highlights the effect of mechanical mixing of such soils with sandy soils in desired proportions giving rise to amplified values of CBR ratio of the soil blend. The regression analysis was also conducted to examine a correlation between the compactive effort and CBR values and it was best represented by exponential function for different types of soils.

Improvement of subgrade California Bearing Ratio (CBR) using recycled concrete aggregate and fly ash

The study aims to understand the effect of different admixtures on improving the quality of flexible pavement subgrades. In this paper, recycled concrete aggregates (RCA) and Fly Ash were used as the admixtures in improving the maximum dry density (MDD), swelling potential, and California bearing ratio (CBR) of subgrade soil. The percentages of RCA and fly Ash used were 5%, 10%, and 15%. With the upscaling in fly ash dosage, the optimum moisture content and the California bearing ratio increased. However, the MDD of soil decreased for higher fly ash contents. On the contrary, the optimum moisture content (OMC) of the soil decreased and the MDD and California Bearing Ratio increased with an increase in RCA content. Both RCA and fly ash-treated soil demonstrated lower values of swelling. At 5% dosage, both RCA and fly ash admixtures were found to improve CBR. However, at higher percentages (10% and 15%) of fly ash, the CBR values decreased while in comparison, soil samples performed significantly better in the CBR test with the increasing dosage of RCA. The findings of this research can be used to examine the suitability and effects of recycled aggregate and fly ash on the performance of soil in terms of CBR, particularly when the soil is planned to be used as a subgrade in highways.

Reuse of non-degradable waste PET bottles for ground improvement

ABSTRACT This paper describes California bearing ratio (CBR) tests carried out to investigate the suitability of waste polyethylene terephthalate (PET) bottles for ground improvement. For the studies, quarry dust is used as an infill, and it is prepared at a relative density of 57.6% within the CBR mould with a diameter of 150 mm. Experiments are carried out by embedding cut PET bottles with a diameter of 5.6 cm within the infill to provide cellular confinement in three different configurations, i.e. three-bottle, four-bottle and five-bottle configurations. The effect of bottle height on the performance of the systems is investigated by considering three cell (bottle) heights, viz., 6.6 cm, 9.3 cm and 11.6 cm. To analyse the performance of the cellular confinement, vertical stress distribution below the applied load is determined. It is observed that the performance of the PET bottle embedded system is better when it is placed within the isobar (σz/q) of 0.3. Based on the CBR values and improvement factor, it is observed that a four-bottle configuration with a height of 6.6 cm is effective in sustaining higher loads. The proposed study provides guidelines for using these bottles for stabilising blocked pavements.

Prediction of CBR by Deep Artificial Neural Networks with Hyperparameter Optimization by Simulated Annealing

AbstractThe construction of pavements requires the complete identification of the soils in place and of the added materials. This identification consists in determining the class of the soils and in evaluating their bearing capacity through the California bearing ratio (CBR) index. Obtaining the CBR index is very costly in terms of time and financial resources, especially when it is a large-scale project. It thus leaves prospects of obtaining it by simpler processes; hence, it arises the need to find simpler processes compared to classical processes. This study develops models for predicting the CBR index from physical properties that are less complex to obtain, based on deep neural networks. To achieve this, three databases were used. A first database consists of the proportion of fines, the Atterberg limits and the Proctor references of the soils. A second database uses the methylene blue value instead of the Atterberg limits, and a third database uses only the proportion of fines and the Proctor soil reference. On each of the databases, a deep neural network model was developed using dense layers, regularization layers, residual blocks and parallelization in TensorFlow to predict the CBR value. Each model was formed by combining several deep neural networks developed according to specific architectures. To expedite training, the simulated annealing method was employed to optimize hyperparameters and define the optimal configuration for each network. The predictions obtained are correlated with the true values from 83.6 to 96.5%. In terms of performance, the models have a mean deviation ranging from 3.74 to 5.96%, a maximum deviation ranging from 12.43 to 16.2% and a squared deviation ranging from 0.781 to 2.189. The results suggest that the variable VBS has a negative impact on the accuracy of the networks in predicting the CBR index. The developed models respect the confidence threshold (± 10%) and can be used to set up a local or regional geotechnical platform.

Building MLR, ANN and FL models to predict the strength of problematic clayey soil stabilized with a combination of nano lime and nano pozzolan of natural sources for pavement construction

The current study aims at predicting the strength of the problematic clayey soils treated with combinations of pozzolan of natural sources and lime powder when added as soil additives at a nano scale. Multiple linear regression (MLR), artificial neural networks (ANN) and fuzzy logic (FL) tools were employed in the analytical study. The variables of the present study include the following: nano pozzoaln of natural source (NNP) content, nano lime content (NL), median particle size of NNP, active silica content of NNP (SiO2active), Initial liquid limit (ILL) and initial plastic limit (IPL) of the investigated soils. NNP was added at five percentages, i.e. 0%, 0.5%, 1%, 1.5% and 2%, while NL was added at five percentages, i.e. 0%, 0.3%, 0.6%, 0.9% and 1.2%. Three median particle sizes namely 50, 100 and 500 nm size were studied. Based on the different investigated soils and combinations, 120 soil mixtures were prepared and tested. California bearing ratio (CBR) and plasticity index (PI) were particularly examined. CBR tests were conducted at a soaked condition on specimens compacted to a maximum dry density (MDD) at the optimum moisture content (OMC). PI values were obtained following the Atterberg limits test. Based on the results of the performance criteria of the developed predictive models, it can be concluded that the CBR and PI of the expansive clayey soils can be effectively predicted using ANN and FL techniques. The results obtained by MLR were far from those obtained by both ANN & FL. In addition, ANN tool was slightly more accurate than FL as far as prediction of CBR and PI is concerned. The higher capability of ANN & FL models in predicting CBR & PI values, which generally obtained through time-consuming and expensive tests, could be useful for geotechnical engineers to assess or design a new pavement project. Further, it is recommended to do a re-evaluation of the current study in future, particularly when more data is available in the literature.