Soaked California Bearing Ratio Tests Research Articles

Utilization of waste face masks to reinforce magnesite mine tailings for sustainable subgrade construction

The disposal of magnesite mine tailings (MMT), a by-product of magnesite mining, raises significant environmental concerns due to its adverse effects on soil, water and air quality. Likewise, the improper disposal of used face masks exacerbates environmental burdens. The innovative use of polypropylene fibres (PPF) derived from disposable face masks to reinforce. This study explores the compaction and strength characteristics of PPF-MMT composites with varying fibre content to develop a sustainable composite for subgrade construction. The findings indicate that the addition of PPF increases optimal moisture content and decreases maximum dry density. Shear strength analysis reveals a linear failure envelope for both MMT and PPF-MMT, with initial angle of internal friction improvement at lower PPF content (0.25% and 0.5%) but a decline at higher contents (0.75% and 1%). Importantly, PPF-MMT consistently exhibits a unique strain-hardening behaviour across all stress levels, distinguishing it from MMT, which only transitions to strain-hardening at higher stresses. Under vertical load, MMT shows contraction, while the PPF-MMT composite initially contracts but later dilates due to increased fibre-MMT interaction during horizontal displacement. Furthermore, California bearing ratio (CBR) tests demonstrate increased dry CBR with PPF, reaching a peak of 33.85% at 0.5% fibre content. The soaked CBR tests affirm the remarkable durability of PPF-MMT, maintaining significantly higher values than MMT even after 60 days of soaking. The study concludes that 0.5% fibre content as optimum dosage.

Natural Gradient Boosting for Probabilistic Prediction of Soaked CBR Values Using an Explainable Artificial Intelligence Approach

The California bearing ratio (CBR) value of subgrade is the most used parameter for dimensioning flexible and rigid pavements. The test for determining the CBR value is typically conducted under soaked conditions and is costly, labour-intensive, and time-consuming. Machine learning (ML) techniques have been recently implemented in engineering practice to predict the CBR value from the soil index properties with satisfactory results. However, they provide only deterministic predictions, which do not account for the aleatoric uncertainty linked to input variables and the epistemic uncertainty inherent in the model itself. This work addresses this limitation by introducing an ML model based on the natural gradient boosting (NGBoost) algorithm, becoming the first study to estimate the soaked CBR value from this probabilistic perspective. A database of 2130 soaked CBR tests was compiled for this study. The NGBoost model showcased robust predictive performance, establishing itself as a reliable and effective algorithm for predicting the soaked CBR value. Furthermore, it produced probabilistic CBR predictions as probability density functions, facilitating the establishment of reliable confidence intervals, representing a notable improvement compared to conventional deterministic models. Finally, the Shapley additive explanations method was implemented to investigate the interpretability of the proposed model.

Experimental Analysis on the Stability of the Soil Using Medical Waste

Abstract: Due to pandemic and other health care activities, there is an increase in generation of Medicine and Medical waste also Out of which 85% of Hospital waste disposed are general non-hazardous waste that can be recycled and reused. On the other hand, there is a need in increasing the strength of the sub-grade economically. Therefore attempts has been made to recycle the medical waste and are used as a soil stabilizer material to increase the strength of the sub-grade. In this project, Medical waste such as Plastic flakes and Expired tablets are used as a stabilizer. The effect of stabilization using these materials were evaluated by carrying out standard laboratory tests. The tests have been done for both natural soil and stabilized soil with a combination of 1% of expired medicine (GLIMI DM PLUS) with different proportion of plastic flakes such as 0.25%, 0.5%, 0.75% and 1%. A series of Standard proctor compaction test and Soaked California Bearing ratio test were done for both natural soil and soil with stabilizers. The test results shows that there is an improvement in the strength of the soil when adding medical waste and furthermore increase in the proportion of the medical waste causes gradual decrease in the strength of the soil. Thus adding medical waste at a certain amount increase the stability of the sub-grade.

Mapping the Physical Properties of Soils and the California Bearing Ratio (CBR) Value for Different Soil Types: A Case Study in the Bukit Kemuning and Pugung Tampak Areas

It is widely accepted that soil is a mixture of mineral constituents that have accumulated over time. The physical characteristics of soil vary according to the mineral and organic matter content and the process of formation. The soil`s unique characteristics have been the subject of research in the field of civil engineering, which has continued to evolve to the present day due to the land`s requirement for civil engineering construction, such as road paving. As a result, the current study sought to determine the similarity of soil samples based on their physical properties and California Bearing Ratio (CBR) values, as well as the relationship between the soil`s physical properties and CBR values. To our knowledge, there is hardly little research in the literature investigating the topic under our investigation. Furthermore, we also mapped the physical characteristics and CBR values of numerous distinct soil samples using a Geographical Information System (GIS). This study concentrated on the West Lampung Regency, specifically the area between Bukit Kemuning in Central Lampung and Liwa in West Lampung, along the lines of Bukit Kemuning, Liwa, and Krui, all the way to the Lampung – Bengkulu province border. The soil samples from the area were taken for two tests: the unsoaked CBR test and the soaked CBR test. The results of the tests show that a 31-kilometre distance does not result in a significant difference in soil properties, which are generally similar except in clay-rich areas. Furthermore, the results of the laboratory analysis show that the amount of water in the soil sample affects the Liquid Limit (LL), Plastic Limit (PL), Maximum Dry Density (MDD), and CBR values; the lower the plastic limit value, and thus the lower the CBR value, the less water in the soil. The implications of the current findings are also discussed.

Analysis of soil subgrade bearing capacity for clay using laboratory testing data

Road construction failures are often caused by unsupported subgrade classification. The purpose of this study was to determine the bearing capacity of subgrade on clay using test data in the laboratory. The contribution of this study can later be a recommendation in the use of subgrade types of clay and alternative uses. One of the properties of land strength associated with roads in the California Bearing Ratio (CBR). The method used is soil physical testing and CBR testing. The soil sample used was undisturbed soil in the subgrade in Minas District, Siak Regency, Riau Province. The result showed that the clay studied was non-organic Sandy Lean Clay CL) with low plasticity based on the USCS classification table. 2.681 specific gravity, water content 29,94%, liquid limit 33.64%, plastic limit 23,67% and plasticity index 9.97%. Soaked CBR test results obtained 4.21% and included in the medium classification. The use of this type of clay soil for subgrade with the bearing capacity of CBR classification needs to be pursued with alternative improvements and soil reinforcement that can increase the CBR value to a minimum of 6%.

Predicting soaked CBR of SC subgrade from dry density for light and heavy compaction

Laboratory California Bearing Ratio (CBR) test is an arduous and lengthy process to determine the CBR strength of the soil. CBR value of subgrade soil plays an important role in the design of flexible pavement. CBR strength of soil can be determined in dry/unsoaked condition and in soaked condition. Soaked CBR value of the subgrade is usually preferred for designing flexible pavements as it gives the CBR strength of subgrade soil under worst case scenario of a pavement being submerged under water for a minimum period of 4 days during floods. Generally, in the lab soaking of the prepared specimen is done for a period of 96 h or 4 days in case of soaked CBR test. While constructing a pavement lot of CBR tests have to be carried out on the subgrade soil at different locations along the length of the pavement. As conducting soaked CBR test requires minimum of 4 days, this will result in lot of delay in the execution of project and ultimately will result in increase in cost of construction. Thus the objective of the present experimental work is to correlate by means of Simple Linear Regression Analysis (SLRA), the soaked CBR value of SC (Clayey Sand) soil with the dry density (DD) of SC soil attained using light and heavy compaction. So that based on the empirical correlations, soaked CBR strength of the subgrade soil consisting of SC soil can be easily predicted from the DD of the subgrade soil without actually conducting the CBR test in the laboratory. Also in this study, an effort has been made to investigate the effect of varying compaction energies on the soaked CBR strength of the SC soil.

Pemanfaatan Geopolimer Abu Terbang Sebagai Pozzolanic Tanah Lempung Untuk Material Tanah Dasar Perkerasan

California Bearing Ratio (CBR) is one of a method for determining soil bearing capacity. Extraction of industrial disposal to be used as material for road pavement construction is still lacking. This research aims to determine changing CBR values due to the fly ash addition in clay under conditions with or without curing and soaked. Samples curing for 28 days were done in two conditions firstly, curing in mold and wrapped with plastic. Secondly, wrapped with plastic off mold. Looking at the CBR test results, plasticity index, density and specific gravity (Gs) is decreased. The addition of fly ash rises the value of the optimum water content (OMC). CBR value increased due to the addition of fly ash, a significantly increase occurred in the fly ash addition by 15%. Curing method uses different CBR values, where curing using mold has a high CBR value. In soaked CBR test, the CBR value varies due to the characteristics of the fly ash and clay which absorbed water. Water absorption varies depend on the percentage of the mixture of fly ash content and clay. The width variance of moisture content with OMC, because water absorption, affect to value of CBR. Samples with moisture content is more close to OMC the CBR value is more bigger

Experimental Investigation on the Behaviour of Glass Fibre-Reinforced Cohesive Soil for Application as Pavement Subgrade Material

Proctor compaction and California bearing ratio (CBR) tests were performed on glass fibre-reinforced cohesive soil to investigate its suitability as a subgrade material. The effects of varying fibre content, fibre length, compacted moisture content and soaking period on CBR and secant modulus were investigated. The test results indicate marginal variation of MDU and OMC with glass fibre reinforcement. Unsoaked CBR test was conducted on specimens compacted at optimum moisture content (OMC) and at 2% wet and dry sides of OMC, whereas soaked CBR test was conducted only on specimens compacted at OMC. CBR value increases with penetration depth up to 5.08 and 7.62 mm under unsoaked and soaked conditions, respectively. Both CBR and secant modulus increase with fiber content and fiber length at any compacted state. They decrease on either side of OMC, and also with increasing soaking period. The reinforcement benefit increases with increasing fiber content up to 0.75% for any fiber length and testing condition. The maximum enhancement in CBR are 2.77 and 2.85 times with 0.75% fibre reinforcement of 20 mm length, under unsoaked and soaked conditions, respectively. Using the glass fibre-reinforced soil in the subgrade may cause reduction of pavement thickness up to 25% even for a traffic value of 150 msa.

Influence of Maximum Particle Size, Fines Content, and Dust Ratio on the Behavior of Base and Subbase Coarse Aggregates

Unbound aggregate base and subbase layers are the main load-bearing layers in a pavement structure. Size and shape properties of these aggregate materials should be controlled to ensure proper workability during construction and improved performance for pavement longevity. The effects of gradation, maximum particle size, fines content (percentage passing the No. 200 sieve), and dust ratio on the quality of aggregates were investigated by performing many soaked California bearing ratio tests on a crushed limestone material. The dust ratio represents the amount of fines content divided by the amount of minus No. 40 sieve material. The dust ratios studied were 0.4, 0.6, and 1.0. Two gradations commonly used in Illinois, with maximum particle sizes of 1 in. and 2 in., were studied to analyze the effect of fines content with respect to maximum particle size in the gradation. A typical range of fines contents (i.e., 5%, 8%, and 12%) was also considered. The results show that the gradation, dust ratio, and fines content should be taken into account in the selection of aggregate properties for stability requirements. Aggregates with larger maximum size particles provide high strength, and they are not affected as much as aggregates with smaller maximum size particles by an increase in fines content. The aggregates with smaller maximum size particles provide lower strength. It was also concluded that samples with a dust ratio of 1.0 do not necessarily result in an aggregate material with low strength.

Improvement in Bearing Capacity of a Soft Soil by Addition of Fly Ash

Soft soils are not suitable for use in runway and highway construction due to their undesirable characteristics such as poor grading, low strength, and excessive plasticity, tendency to shrink or swell. By stabilizing such soils with appropriate agents, their engineering properties can be improved. One of the stabilizing agents is Class C fly ash. The paper aimed to study the bearing capacity improvement of a soft soil (from Elmadağ area) by using Class C fly ash (from Soma Thermal Power Plant). In the experimental study, index properties of soft soil and fly ash stabilized samples are determined. Then modified Proctor compaction, soaked California Bearing Ratio, and Unconfined Compressive Strength characteristics of the samples are investigated. During the study, the stabilized soil samples are prepared at different fly ash contents, i.e., 0%, 3%, 5%, 7%, and 10%. The samples are subjected to soaked California Bearing Ratio tests after 0, 7, and 28 days of curing. In addition to California Bearing Ratio tests, Unconfined Compressive Strength tests with 0, 7, and 28 days of curing are performed. In order to observe microstructures of samples, Scanning Electron Microscope-Energy Dispersive X-ray analysis are performed. The results of the study show that bearing capacity of Elmadağ soft soil can be improved substantially and swell can be reduced significantly by using Class C fly ash.