<p>The reuse of biodegradable waste in geotechnical engineering has gained increasing attention as a viable pathway toward more sustainable and cost-effective construction practices, particularly in developing countries where locally sourced alternatives to conventional stabilisers such as lime and cement are urgently needed. Eggshell powder (ESP), generated in large quantities as biodegradable waste from households, restaurants, and poultry facilities, represents one such alternative—low-cost, locally available, and minimally processed. In this study, ESP was added to cohesive and cohesionless soils at proportions of 8.5%, 12%, and 15% by dry weight of soil to examine its effect on shear strength characteristics under standardised laboratory conditions. The cohesive soil, classified as CI (Clay of Intermediate Plasticity, LL = 46.72%, PI = 22.09%) under the Unified Soil Classification System (USCS), was sourced from Matidali, Bogra, while the cohesionless soil, classified as SP (Poorly Graded Sand), was sourced from Gabtoli, Dhaka. Shear strength was assessed using direct shear tests (ASTM D3080) for the sandy soil and unconfined compression tests (ASTM D2166) for the clay. The results showed a strong soil-type dependency in the response to ESP addition. For the cohesionless soil, the internal friction angle increased from <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(29^{\circ }\)</EquationSource> </InlineEquation> (untreated) to a peak of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(38^{\circ }\)</EquationSource> </InlineEquation> at 8.5% ESP, before declining to <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(31^{\circ }\)</EquationSource> </InlineEquation> at 15% ESP. For the cohesive soil, undrained shear strength decreased sharply from 68.11 <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\hbox {kN/m}^{2}\)</EquationSource> </InlineEquation> (untreated) to <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(22.57\,\hbox {kN/m}^{2}\)</EquationSource> </InlineEquation> at 8.5% ESP—a reduction of approximately 67%—with only partial recovery at higher dosages. To the best of the authors’ knowledge, this is one of the first studies in Bangladesh to systematically compare the effect of ESP on both cohesive and cohesionless soils under identical laboratory conditions, providing a directly paired assessment of soil-type dependency—a design consideration that has received limited attention in the existing literature, which predominantly focuses on a single soil type in isolation. The findings highlight that ESP acts as a conditional physical modifier rather than a universal stabiliser: it is beneficial for cohesionless soils within an optimal dosage range but detrimental to cohesive soils when used alone. These results are discussed in the context of recent advances in ESP-based soil stabilisation and their implications for geotechnical practice in Bangladesh and similar deltaic regions.</p>

Eggshell as soil shear strength amplifier for cohesive and cohesionless soils

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2026年6月22日

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MD. Moin Akon,
Khan MD Mohaiminul Islam Shovon,
Asif Alam Chowdhury,
Swarnali Ahmed,
Akram Shakil Turja

摘要

The reuse of biodegradable waste in geotechnical engineering has gained increasing attention as a viable pathway toward more sustainable and cost-effective construction practices, particularly in developing countries where locally sourced alternatives to conventional stabilisers such as lime and cement are urgently needed. Eggshell powder (ESP), generated in large quantities as biodegradable waste from households, restaurants, and poultry facilities, represents one such alternative—low-cost, locally available, and minimally processed. In this study, ESP was added to cohesive and cohesionless soils at proportions of 8.5%, 12%, and 15% by dry weight of soil to examine its effect on shear strength characteristics under standardised laboratory conditions. The cohesive soil, classified as CI (Clay of Intermediate Plasticity, LL = 46.72%, PI = 22.09%) under the Unified Soil Classification System (USCS), was sourced from Matidali, Bogra, while the cohesionless soil, classified as SP (Poorly Graded Sand), was sourced from Gabtoli, Dhaka. Shear strength was assessed using direct shear tests (ASTM D3080) for the sandy soil and unconfined compression tests (ASTM D2166) for the clay. The results showed a strong soil-type dependency in the response to ESP addition. For the cohesionless soil, the internal friction angle increased from \(29^{\circ }\) (untreated) to a peak of \(38^{\circ }\) at 8.5% ESP, before declining to \(31^{\circ }\) at 15% ESP. For the cohesive soil, undrained shear strength decreased sharply from 68.11 \(\hbox {kN/m}^{2}\) (untreated) to \(22.57\,\hbox {kN/m}^{2}\) at 8.5% ESP—a reduction of approximately 67%—with only partial recovery at higher dosages. To the best of the authors’ knowledge, this is one of the first studies in Bangladesh to systematically compare the effect of ESP on both cohesive and cohesionless soils under identical laboratory conditions, providing a directly paired assessment of soil-type dependency—a design consideration that has received limited attention in the existing literature, which predominantly focuses on a single soil type in isolation. The findings highlight that ESP acts as a conditional physical modifier rather than a universal stabiliser: it is beneficial for cohesionless soils within an optimal dosage range but detrimental to cohesive soils when used alone. These results are discussed in the context of recent advances in ESP-based soil stabilisation and their implications for geotechnical practice in Bangladesh and similar deltaic regions.