Unsoaked California Bearing Ratio Research Articles

Impact evaluation of polypropylene fibres on the engineering behaviour of Siwalik clay

In the Kashmir region of Pakistan, the presence of Siwalik clays engenders serviceability issues to the infrastructure causing substantial loss of property. In this study, an attempt has been made to address these issues using polypropylene fibres (PPFs) as a sustainable modifier. These fibres were used in five different proportions, namely 0.25, 0.5, 0.75, 1 and 1.25% as partial replacement of base soil to analyse their impact on the engineering behaviour of matrices. Classification, compaction, indirect tensile, unconfined and triaxial compression, swell potential, consolidation and California bearing ratio (CBR) tests were conducted on controlled as well as reinforced-clay samples for comparative analyses. The maximum improvements were observed in unconfined compressive strength (109%), tensile strength (300%), cohesion (13%), friction angle (110%), soaked CBR (800%) and un-soaked CBR (550%). Besides, the reduction in swelling strain by 92% was also recorded corresponding to 1 kPa effective vertical stress. The capital cost analyses showed that PPFs reduced the costs of backfill behind the retaining wall and foundation soil beneath isolated footing by 21 and 44.5%, respectively. Moreover, the modifier had no adverse effect on the aqueous media. Conclusively, PPFs can be used as sustainable modifiers leading to a potential solution for serviceability issues.

Geotechnical appraisal of failed sections of some highway pavements in parts of Northcentral Nigeria

Purpose The purpose of this study was to investigate the likely causes of failure of some sections of road pavements in Ajaokuta, Northcentral Nigeria. This was achieved through a geotechnical assessment of subgrade soils in affected areas. Design/methodology/approach The methods entailed field and laboratory methods and statistical analysis. Subgrade soil samples were retrieved from a depth of 1,000 mm beneath the failed portions using a hang auger. The soils were analyzed for natural moisture content (NMC), Atterberg limit (liquid limit, plastic limit and linear shrinkage), grain size distribution, compaction and California bearing ratio (CBR), respectively. Findings The results of the geotechnical tests ranged from NMC (12.5%–19.4%), sand (84%–98%), fines (2%–16%), LL (16.0%–32.2%), PL (17%–27.5%), LS (2.7%–6.4%), PI (2.5%–18.4%), maximum dry density (1756 kg/m2–1961 kg/m2), optimum moisture content (13.2%–20.2%), unsoaked CBR (15.5%–30.5%) and soaked CBR (8%–22%), respectively. Pearson’s correlation coefficient performed on the variables showed that some parameters exhibited a strong positive correlation with r2 > 0.5. Research limitations/implications Funding was the main limitation. Originality/value Comparing the results with Nigerian standards for road construction, and the AASHTO classification scheme, the subgrade soils are competent and possess excellent to good properties. The soils also exhibited very low plasticity, a high percentage of sand, high CBR and low NMC, which implies that it has the strength required for road pavement subgrades. The likely causes of the failures are, therefore, due to the use of poor construction materials, technical incompetence and poor compaction of sub-base materials, respectively.

Evaluation of citric acid-treated natural fibres as sustainable additives for improving expansive soil performance in highway construction

This study addresses the evaluation of citric acid-treated natural fibres as sustainable additives for improving soil performance in highway construction. A series of tests were conducted on the soil to assess its baseline properties. The natural soil exhibited a Plasticity Index (PI) of 30 and Linear Shrinkage of 12%, along with a Liquid Limit (LL) of 65 and Plastic Limit (PL) of 35. Additionally, the fines content (<0.075 mm) and sand content (0.075–4.7 mm) were determined to be 79.6% and 20.4%, respectively. The soil's mineral composition included Quartz (5%), Orthoclase (3–5%), Montmorillonite (2.6%), and Illite (18.2%), with key components identified through chemical analysis: SiO2 (52.721 wt%), Fe2O3 (16.132 wt%), and Al2O3 (15.202 wt%). Subsequently, a range of tests were performed with varying additives to assess their impact on the soil's engineering properties. The sample containing 6% Sawdust (SD) additive exhibited notable improvements in multiple aspects. This sample achieved a maximum dry density (MDD) of 1856 kg/m³, surpassing the control (1900 kg/m³) and the 10% Rice Husk Ash (RHF) sample (1698 kg/m³). Furthermore, the 6% SD sample demonstrated enhanced Unconfined Compressive Strength (UCS) of 320 kPa, as opposed to the control's 121 kPa. Triaxial shear strength followed a similar pattern, peaking at 41 kPa for the 6% SD sample. The California Bearing Ratio (CBR), the 6% SD sample showcased significant improvements, achieving 41% for Unsoaked CBR and 36% for Soaked CBR. These results outperformed the control (25%) and the 4% RHF sample (37%). Additionally, the hydraulic conductivity of the 6% SD sample was notably lower at 4.98 ×10–8 cm/s compared to the control (3.35 ×10–8 cm/s) and the 4% RHF sample (4.58 ×10–8 cm/s). The Coefficient of Volume Change (Mv) further supported the superior performance of the 6% SD sample with a value of 0.6, indicating reduced settlement potential compared to the 4% RHF sample (Mv: 0.7). Based on the results, the 6% Sawdust (SD) additive consistently demonstrated the most favourable engineering properties for the expansive clay soil. hence, it is recommended that the 6% SD sample be considered as an optimal choice for enhancing subgrade material, leading to improved performance and sustainability in highway construction.

INTEGRATED GEOLOGY AND ENGINEERING GEOLOGICAL PROPERTIES OF LATERITIC SOIL AT ITA – ONIYAN AREA, SOUTHWESTERN NIGERIA

This study investigates the geology and the engineering geological properties of lateritic soil of Ita – Oniyan area of Ondo state, Southwestern, Nigeria. Twenty soil samples were collected from twenty test pits at depth of about 1.0m and were air–dried for two weeks and, thereafter were subjected to laboratory analyses which include natural moisture content, particle size analysis, consistency limits, linear shrinkage, specific gravity, standard compaction, shear strength, and unsoaked California Bearing Ratio (CBR) tests. Results showed that the natural moisture content of the soils ranged from 7% to 28%, the liquid limit ranged from 30.2% to 69.1%, the plastic limit ranged from 17.5% to 43.4%, while the plasticity index ranged from 8.6% to 36.9%. The soils were grouped into CL (low plasticity), CI (medium plasticity), and CH (high plasticity). Linear shrinkage ranged from 3.7% to 11.9%. Grain size analysis gave coarse contents varying from 30.4% to 98.1% and fine contents from 27.4% to 86.9%. The unsoaked CBR ranged from 18% to 72%, for compaction, MDD ranged from 1482kg/m3 to 1981kg/m3, and OMC from 13.7% to 32.5%. Geologic mapping showed that the major rock types in the study area were biotite gneiss, charnockite, quartzite and granite parent rocks from which the soil was formed. The soil samples are made up of lateritic soil with high clay content mainly illite, since the soil samples in the study area have poor engineering properties therefore the soil needed to be stabilized to improve their engineering properties.

Soil strength improvement by reinforcing soil with geotextiles

In recent times, geosynthetic products are widely utilized in the construction sector and particularly in the field of Geotechnical Engineering. Geosynthetics are the synthetic products used mainly within the soil to perform various functions. In this paper, an attempt has been made to utilize Woven geotextiles (WG) and Non-woven geotextiles (NWG) as reinforcement within soil to enhance the strength of subgrade soil. 2 types of coarse-grained soil, soil with high fines content and soil with low fines content were utilized in the experimental work. WG and NWG were placed at varying depths of H/5, 2H/5, 3H/5 and 4H/5 from top of the soil specimen (where H is the height of soil specimen), to find the enhancement in soaked & unsoaked California Bearing Ratio (CBR) strength of soil with respect to that of unreinforced soil. Based on the experimental results, improvement in CBR strength of soil reinforced with geotextile and the ideal location of placement of geotextile within the soil thickness varied according to the soil type and this may be attributed to the presence of varied percentages of fines within soil. Also, the soil reinforced with WG was observed to be more effective in terms of strength gain as compared to that of soil reinforced with NWG. Improvement in CBR strength of subgrade soil reinforced with geotextiles leads to reduced pavement thickness thus resulting in a cost-effective construction.

A Study on Crushed Coconut Shells as Stabiliser to Soil

Road construction over soft subgrade soil is a major issue affecting cost and scheduling of highway projects. Many techniques have been conducted to strengthen the highway soil subgrade. One of them are using additives such as coconut shells, rice husk ash, stone dust, and fly ash. to strengthen the soil. The strength of the subgrade is commonly expressed as California Bearing Ratio (CBR). In this study, the crushed coconut shells (CCS) of 65 mm to 10 mm ranges of size was mix with the laterite soil. A series of unsoaked CBR test were conducted with an addition of 1, 2, 3, 4, 5, 6, 7 and 8% of CCS to determine the strength of the stabilized laterite soil. The laterite soil is classified as sandy SILT of high plasticity (MH) according to British Standard Classification System (BSCS). The results show that the CBR values of the stabilized soil increase with an increasing percentage the CCS. The stabilized soil with 4% CCS is the highest CBR value, 27.5%. The CBR% then decreasing as further additional of CCS %. The stabilised soil with an 8% CCS content had the lowest CBR value at 5.25%, which is lower than the unstabilised laterite soil’s CBR value. It is concluded that the additions of CCS have greatly improved the soil strength with the increment increase of CBR value. Hence CCS has a good potential for upgrading the CBR value of subgrade soil.

Investigation of Soil Sample Using Triaxial Test and Detailed CBR Test

California Bearing Ratio (CBR) value of subgrade is utilized in accordance with IRC recommendation.in order to create flexible pavements. A crucial soil parameter for the design of flexible pavements and runways at airports is the California Bearing Ratio (CBR) value. It might also utilize to calculate the soil's subgrade reaction via correlation. It is among the most significant engineering characteristics of soil for designing road subgrade. CBR value is depend upon optimal dry density (MDD), maximum moisture content (MC), and other variables liquid limit (LL), plastic limit (PL), plasticity index (PI), moisture content (OMC), and type of soil, soil permeability, etc. Additionally, the soil's condition—whether it's damp or not—affects the value. The method of determining CBR is quite drawn-out and time-consuming. This study aims to link the soaked or unsoaked CBR value with the MDD, OMC, LL, PL, PI along with triaxial of various soil samples collected from Qila Road in Aligarh, Uttar Pradesh, India.

Sustainable Binary Blending for Low-Volume Roads—Reliability-Based Design Approach and Carbon Footprint Analysis

The utilization of industrial by-products as stabilizers is gaining attention from the sustainability perspective. Along these lines, granite sand (GS) and calcium lignosulfonate (CLS) are used as alternatives to traditional stabilizers for cohesive soil (clay). The unsoaked California Bearing Ratio (CBR) was taken as a performance indicator (as a subgrade material for low-volume roads). A series of tests were performed by varying the dosages of GS (30%, 40%, and 50%) and CLS (0.5%, 1%, 1.5%, and 2%) for different curing periods (0, 7, and 28 days). This study revealed that the optimal dosages of granite sand (GS) are 35%, 34%, 33%, and 32% for dosages of calcium lignosulfonate (CLS) of 0.5%, 1.0%, 1.5%, and 2.0%, respectively. These values are needed to maintain a reliability index greater than or equal to 3.0 when the coefficient of variation (COV) of the minimum specified value of the CBR is 20% for a 28-day curing period. The proposed RBDO (reliability-based design optimization) presents an optimal design methodology for designing low-volume roads when GS and CLS are blended for clay soils. The optimal mix, i.e., 70% clay blended with 30% GS and 0.5% CLS (exhibiting the highest CBR value) is considered an appropriate dosage for the pavement subgrade material. Carbon footprint analysis (CFA) was performed on a typical pavement section according to Indian Road Congress recommendations. It is observed that the use of GS and CLS as stabilizers of clay reduces the carbon energy by 97.52% and 98.53% over the traditional stabilizers lime and cement at 6% and 4% dosages, respectively.

A comparative study of stabilising collapsible soil using different types of biopolymers

This paper presents a comprehensive study of using xanthan gum (XG), sodium alginate (SA) and gelatin (G) to stabilise collapsible soil. Modified Proctor, one-dimensional collapse, unconsolidated-undrained triaxial and California bearing ratio (CBR) tests were conducted to estimate the engineering characteristics of the untreated and treated soil. Additionally, x-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were utilised to demonstrate the changes in the microstructure of the treated samples. It was found that biopolymers decreased the maximum dry density and increased the optimum water content. The results also indicated that a 4% content of XG, SA and G significantly reduced the collapse index by 96, 95 and 82%, respectively. Shear tests showed that biopolymers slightly reduced the internal friction angle and significantly increased the cohesion intercept, which led to shear strength improvement. The results also indicated that 4% XG-treated, 4% SA-treated and 4% G-treated samples exhibited higher shear strengths by 145, 106 and 73%, respectively, than the untreated samples under the same conditions. The findings also indicated that when the soil was mixed with a 4% concentration of XG, SA and G, the unsoaked CBR value increased by about 185, 157 and 141%, respectively.

Utilization of coal fly ash to enhance the bearing capacity of road base

Coal is responsible for the generation of around 38 percent of the power that is used throughout the entire planet. In the last two decades, there has been a rise in the number of chances for recycling and usage of fly ash from coal combustion due to its hydrophobic and cementitious properties. However, there is still limited commercialization of coal fly ash (CFA) in road construction. The focus of this research is to determine the bearing capacity of a CFA-treated crusher run used as a road base course. In order to determine the appropriate percentage of CFA, the crusher run was mixed with various percentages of Class F CFA, including 10%, 15%, 20%, and 25%. The proctor Compaction test (PCT), soaked and unsoaked California Bearing Ratio (CBR) tests, and Unconfined Compressive Strength Test (UCST) were then used to evaluate the bearing capacity of the CFA-treated crusher. The result shows that as the percentage of CFA increased, the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) decreased compared with the control specimen. The soaked and unsoaked CBR of the CFA-treated crusher run with 20% CFA increased by approximately 32% and 26% respectively that of the control specimen. Therefore, it is proven that utilization of CFA up to 20% into crusher run could enhance the bearing capacity of the road base.

Effect of sodium silicate and cement on the improvement of engineering properties of organic soil

The study is aimed at evaluating the effect of adding sodium silicate and cement to organic soil. Geotechnical properties of organic soil are determined before and after the addition of the stabilizing materials, which in this case are cement and sodium silicate. The results obtained after treatment were analyzed and evaluated to determine whether the strength values reached are adequate for strong subgrades for pavement, and airports construction. Organic soil samples used in this study were obtained from Kayseri Free Area in Turkey. Index properties and geotechnical properties of organic soil, which was identified as sample P, were determined and this formed the reference upon which strength improvements of each mix design sample were obtained. Optimum moisture content and maximum dry density of the soil and the various mixes were obtained using standard proctor test. Unconfined compressive tests (UCS), California bearing ratio (CBR), and Falling head permeability tests were used to determine geotechnical properties. UCS tests were conducted on air cured samples for 1, 7, and 28 days. Soaked and unsoaked CBR samples were tested after 1, 7 and 28 days. Hydraulic conductivity was determined using the falling head permeability test. From the experiments, sodium silicate and cement were seen to improve the strength of organic soil and provide acceptable subgrade strength and CBR values. CBR and UCS tests indicated that longer curing periods improved strength even more. Higher values were obtained for 7 days cured samples than for 1-day samples with the highest values being obtained for 28 days cured samples. Design mixes with higher cement and sodium silicate compositions gave the highest values of strength. In conclusion, sodium silicate and cement give positive results when it comes to stabilizing organic soil.

The Effect of Diatomaceous Earth Addition on CBR Values of Glee Geunteng Soil in Aceh Besar, Aceh Province, Indonesia

The soil which is the platform often used for construction activities needs the strength to resist loads. However, its physical and mechanical properties are sometimes naturally limited and this implies there is a need for improvement and stabilization. Therefore, this study uses diatomaceous earth, which is a natural pozzolanic material classified as a type of Supplementary Cementing Materials (SCM), as an additive. The chemical stabilization was conducted by mixing the soil with stabilizing materials such as cement, lime, fly ash or others that have the ability to change the chemical composition and combination of soil. It is important to note that diatomaceous earth has similar properties as other pozzolanic materials such as fly ash and metakaolin powder and this is the reason it is expected to function as a soil stabilizing agent needed to improve soil properties. This study was conducted using the soil from Glee Geunteng in Peukan Bada as well as the diatomaceous earth obtained from Lambeureunut Village, Aceh Besar Regency, Aceh Province, Indonesia. The main purpose was to determine the California Bearing Ratio (CBR) value of the Glee Geunteng soil mixed with diatomaceous earth at 5, 10, 15, and 20% dry weight of the soil. The CBR test consisted of unsoaked CBR, soaked CBR testing at 4 days, and swelling properties of CBR with a variety of diatomaceous earth mixtures. Glee Geunteng soil was classified as A-6 Group Index 3 based on the AASHTO soil classification and as the SC (silty clay) soil according to the USCS classification. The results showed that the unsoaked CBR value reduced from 35.96% for the natural Glee Geunteng soil to 31.65% for the soil mixed with 20% diatomaceous earth material. A similar trend was observed for the soaked CBR value with a reduction from 15.57% to 6.98%. The decrease in CBR value was perceived to be caused by the very small silica content (SiO2 ) in diatomaceous earth material with 42.09% compared to the 86% in the material obtained from another source in the previous research by Hidayati.

The Effect of CKD and RAP on the Mechanical Properties of Subgrade Soils

The construction of pavement layers on subgrade soil with good characteristics decreases the thickness of these layers, which in turn lowers the cost of building and maintaining roadways. However, it is impossible to avoid constructing pavements on unsuitable subgrade due to a number of limitations. Using conventional additives like lime and cement to improve subgrade properties results in additional costs. As a result, utilizing by-products (cement kiln dust and reclaimed asphalt pavement) in this field has benefits for the environment, economy, and technology. Large amounts of cement kiln dust (CKD), a by-product material, are produced in Portland cement factories. On the other hand, large amounts of reclaimed asphalt pavement (RAP) are accumulated as a result of the rehabilitation of old roads. This paper discusses using CKD and RAP to improve the characteristics of poor subgrade layers by conducting a series of Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) tests on samples of natural soil and soil stabilized with different percentages of CKD and RAP with different curing times to investigate their impacts on soil properties. The curing was carried out by wrapping the stabilized samples with several layers of nylon and then placing them in plastic bags at room temperature. The compaction results illustrated that the addition of CKD increases OMC and decreases MDD, in contrast to RAP, which decreases OMC and increases MDD. The addition of CKD and RAP led to a significant and unexpected increase in the CBR values. The results show that the soaked and unsoaked CBR values improve from 3.4% and 12.1% for natural soil to 220.1% and 211%, respectively, after adding 20% CKD and curing the samples for 28 days. Also, the addition of 25% RAP to soil-20% CKD blend increased the soaked and unsoaked CBR values to 251% and 215%, respectively. All the additions resulted in a significant reduction in swelling.

The stabilization effect of peat soil using an effective microorganism reviewed from CBR Value

The behavior of peat soil's physical characteristics and the mechanism are extremely influenced by the decomposition degree. This study aims to know a physique range alteration and mechanism of the peat soil fibrous reviewed from the enhanced value of California Bearing Ratio (CBR) after it is stabilized using Effective Microorganism (EM). The volume of EM inserted and combined are 20% and 40% that ripened for 14 and 21 days. Then the peat soil and EM are mixed with water content close to original peat soil volume. The results showed that the most significant change in peat soil's physical characteristics and the mechanism is 40% EM solution with maximum decomposition rate occurs at the 14-days ripening period. The fiber content is reduced from 60% to 52%, and decomposition rate 0% fiber/day to 0.57% fiber/day, and the increased value of unsoaked CBR 3.28% to 7.47% and 3.01% to 6.11% in wet conditions.

A comparative study of red brick powder and lime as soft soil stabilizer.

Background: The role of soil in building construction is to support the loads above it. Different types of soil with poor mechanical properties require more attention. Therefore, more effort is needed to stabilize the soil by improving its properties. These improvements are intended to modify soil properties to improve engineering performance, such as strength, decrease in compressibility and permeability. This study aimed to compare the potential of lime and brick powder as stabilizers based on the California Bearing Ratio (CBR) values. Soil stabilization can be defined as modifying the soil properties by chemical or physical means to improve its engineering efficiency. The main objectives of stabilizing soil are increasing its bearing capacity, resistance to weathering processes, and permeability. Methods: This work did laboratory tests with disturbed and undisturbed soil samples. The proportions of lime or red brick powder additives are 0%, 5%, 10%, and 15% of the soil sample. From the results of the laboratory tests, the soil type obtained is MH (low plasticity silt) as per the Unified Soil Classification System (USCS). Results: This study showed that soft soil could be improved by adding lime and red brick powder as a soil stabilizer. In both soaked and unsoaked CBR tests, there was an increase in the CBR value for each proportion of the mixed additives. However, the red brick powder addition (15%) has significantly increased the CBR value. Conclusions: The soil sample mixed with 15% red brick powder had the highest Maximum Dry Density (MDD), about 5.5% over untreated soil. The increment of lime to 15% has increased the CBR soaked by 61% in relation to untreated soil. The increment of red brick powder to 15% has increased the CBR unsoaked by 73% in relation to untreated soil.

A Comparative Study of the California Bearing Ratio Value of Subgrade Made by Stone Dust and Natural Sand with Coarse Aggregate

Resources of engineering materials (sand) used for construction activities are limited, so some other materials should be introduced by changing the sand. Stone dust produced from Stone Crushing Zone appears as a problem for effective disposal. Stone dust can be replaced by sand which is used as a fine aggregate in construction work. In this study, the main concern is to find an alternative to sand. Replacement of normal sand by stone dust will work both solid waste minimization and sand recovery. Stone dust is one of the alternatives to sand which can meet the demand of fine aggregate. In the engineering practice, the properties of existing sub-grades are required for the construction of the earth, thereby improving density and strength of the subgrade. A series of California Bearing Ratio (CBR) tests have been conducted for determination of soaked and un-soaked CBR by using the stone dust as a fine aggregate blended with 10 mm and 20 mm size Coarse Aggregates (CA). A detailed comparison is made for the findings of the CBR tests conducted on samples prepared using natural sand (as a fine aggregate) blended with 10 mm and 20 mm size coarse aggregates.

Prediction of Strength and CBR Characteristics of Chemically Stabilized Coal Gangue: ANN and Random Forest Tree Approach.

Coal mining waste in the form of coal gangue (CG) was established recently as a potential fill material in earthworks. To ascertain this potential, this study forecasts the strength and California Bearing Ratio (CBR) characteristics of chemically stabilized CG by deploying two widely used artificial intelligence approaches, i.e., artificial neural network (ANN) and random forest (RF) regression. In this research work, varied dosage levels of lime (2, 4, and 6%) and gypsum (0.5, 1, and 1.5%) were employed for determining the unconfined compression strength (UCS) and CBR of stabilized CG mixes. An experimental study comprising 384 datasets was conducted and the resulting database was used to develop the ANN and RF regression models. Lime content, gypsum dosage, and 28 d curing period were considered as three input attributes in obtaining three outputs (i.e., UCS, unsoaked CBR, and soaked CBR). While modelling with the ANN technique, different algorithms, hidden layers, and the number of neurons were studied while selecting the optimum model. In the case of RF regression modelling, optimal grid comprising maximal depth of tree, number of trees, confidence, random splits, enabled parallel execution, and guess subset ratio were investigated, alongside the variable number of folds, to obtain the best model. The optimum models obtained using the ANN approach manifested relatively better performance in terms of correlation coefficient values, equaling 0.993, 0.995, and 0.997 for UCS, unsoaked CBR and soaked CBR, respectively. Additionally, the MAE values were observed as 45.98 kPa, 1.41%, and 1.18% for UCS, unsoaked CBR, and soaked CBR, respectively. The models were also validated using 2-stage validation processes. In the first stage of validation of the model (using unseen 30% of the data), it was revealed that reliable performance of the models was attained, whereas in the second stage (parametric analysis), results were achieved which are corroborated with those in existing literature.

GEOTECHNICAL PROPERTIES OF LIME AND BAMBOO STEM ASH STABILIZED SOILS FOR ROAD CONSTRUCTION IN SOUTH-WESTERN NIGERIA

The state of any road layer today and in the future is primarily dictated by the soil beneath its foundation, and knowing enough about the Engineering qualities of soil and the sub-soil condition is crucial in foundation design. This research looked at the geotechnical qualities of soils stabilized with Lime-and-Bamboo Stem Ash (BSA) mixture. Soil samples were obtained from each state in the study area and transported to the laboratory, where they were stabilized with 6% lime and 0 to 10% BSA. California Bearing Ratio (CBR), Compaction, Unconfined Compressive Strength (UCS), and Triaxial tests were performed on the combined samples. The local additive was also subjected to a chemical examination. The results showed that BSA additive has a high SiO2 content. As BSA content increases, all strength properties (Maximum Dry Density (MDD), CBR, UCS, Cohesion (C), Shear strength (S) and Angle of Internal Friction (ϕ)) increase and reached peak at 6% BSA content, thereafter decrease; however, Optimum Moisture Content (OMC) decreases. The peak values are 2475 kg/m3, 58.53%, 45.32%, 638.9 kN/m2, 137 kN/m2, 290.57 kN/m2 and 41° for MDD, soaked CBR, unsoaked CBR, UCS, C, S and Ø respectively. After going through the process, almost all of the unsuitable soil samples became suitable for use as pavement layer materials. As a result, a mixture of 6% lime and 6% BSA content is strongly recommended for soil improvement, particularly for road construction in South-Western Nigeria.

Application of Soft Computing Techniques in Modelling of Soaked and Unsoaked California Bearing Ratio

In this study, author attempted to establish a correlation between soil physical parameters and California Bearing Ratio of lateritic soils using advanced mathematical techniques such as the Support Vector Machine (SVM), Random Forest (RF), M5 tree, multiple linear regression, and Artificial Neural Network. A total of 480 soil samples were collected and separated into a data set using training and validation of the generated models based on the main soil parameters of Liquid Limit (LL), Plastic Limit (PL), Natural moisture content (NMC), Specific gravity (GS), Fines (F), Gravel, and Sand. The Principal Component Analysis (PCA) was used to minimize the dataset's huge dimension, and the approximate sum of the first four principal components (PC) captured 88 percent of the variability in the response variable with just 12% information loss. The RMSE values of 21.6, 21.23, 295.67, 7.03, 14.54 and 24.43,24.59,326.49,8.63,17.71 are from the MLR, ANN, MS Tree, RF, and SVM models for SCBR and USCBR values, respectively. For SCBR and USCBR, random forest (RF) yielded the lowest values of 7.03 and 8.63, respectively. Similarly, the R values range from 0.1 to 0.94 and 0.01 to 0.92, indicating that the anticipated and real SCBR and USCBR are related. The Random Forest Model for SCBR and USCBR was shown to be the best by the correlation coefficient values, while the MS tree model for SCBR and USCBR was determined to have the lowest coefficient of determination R2. As a result, it can be concluded that Random Forest provided the best Soaked and Unsoaked CBR model based on the dataset, while MS tree provided the poorest model. The model is a valuable tool for evaluating the subsurface indices of a civil engineering site at the preliminary planning stage before final structural design for the substructures, as the anticipated soil parameter values are within permitted accuracy.

Evaluation of the Effect of RAP and Lime on Geotechnical Properties of Clayey Soil

Abstract: Road network plays a large role in the rapid development of the economy of a country, providing connectivity to remote areas for various transportation activities. India ranks second in the world in terms of length of road network after the United States. The major road network in the urban locality consists of bituminous pavements periodically resurfaced during maintenance. From the milling process, reclaimed asphalt pavement (RAP) is obtained. Additionally, RAP can be used for the utilization of recycled asphalt pavement (RAP) materials in subgrade soil. Reclaimed Asphalt Pavement (RAP) is being used in this case study to stabilize the subgrade soil collected from Crop Research Center (CRC), Govind Ballabh Pant University, Tanda Range, Uttarakhand (29°01'09.7"N, 79°28'55.9"E). To conduct the experimental program, a variable amount of RAP percentages viz., 5, 10, 15, and 20%, and different percentages of lime i.e., 2, 4, 6, and 8% were mixed with natural soil. Based on gradation, Standard Proctor Test (SPT), Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), and Specific gravity, the characteristics of RAP-soils with added lime were evaluated. For soil mixture including 10% RAP and 4% lime, a maximum MDD of 19.04 and a percentage increase in compaction of 11.93% was observed. OMC value was observed as 11.35%, which further decreased as RAP content increased. Due to RAP containing coarse aggregate, a higher CBR value was obtained due to the harder sample surface. For all soil mixers of 15% RAP and 4% lime, unsoaked CBR and soaked CBR values were found to be 31.39% and 18.69% respectively. Percentage increases in their respective CBR values were 868.83% and 662.86%. for every percentage of lime variation, maximum CBR was obtained at 15% RAP, and maximum CBR value for soaked CBR was obtained for soil with 15% RAP and 2% lime, whereas for unsoaked CBR, it was obtained for soil with 15% RAP and 4% lime. Maximum UCS values of 412.45 kN/m2 , 606.81 kN/m2 and 857.62 kN/m2 were observed on 3rd, 7th and 14th days for soil mix with 15% RAP and 4% lime, with percentage increase of 291.17%, 249.40% and 387.78% respectively. Based on the results of the study, RAP materials can be effectively used in the soil subgrade, sub-base, and base of flexible pavements, reducing the cost of construction. Keywords: Reclaimed Asphalt Pavement (RAP), Lime, CBR, SPT, UCS, OMC, MDD.