Long Term Mechanical Property of Cement Treated Loam Used in Road Embankment-Paper

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The study examined the long-term strength of cement-treated loam used in a large highway embankment in Shizuoka, Japan. Nine years after construction, researchers drilled an undisturbed core through about 18 m of fill. The embankment contained approximately 414,000 m³ of material and reached a maximum height of about 40 m. Strength was assessed using unconfined compression tests at roughly 2 m intervals, alongside soil-hardness and needle-penetration tests at closer intervals. Phenolphthalein was used to assess cement mixing and alkalinity.<br /><br />The core was generally well cemented below the surface-soil layer, and phenolphthalein indicated alkaline material throughout the sampled depth. Unconfined compressive strengths exceeded the design strengths across the core. Strength was generally higher where water content was lower and dry density was higher. The soil-hardness test provided reasonable strength estimates below about 2,000 kN/m², while needle-penetration estimates showed substantial scatter.<br /><br />At approximately 18 m depth, below the groundwater level, average strength after nine years was 1,553 kN/m², about 1.2 times the average measured after 56 days. This gain was relatively modest compared with some reported results for other cement-treated soils. The authors suggest that groundwater exposure, including possible calcium leaching, may have influenced long-term strength, but the available data were insufficient to identify the main causes. Strength differences may also reflect soil variability and cement-dosing practices during construction.<br /><br />Overall, the embankment’s treated loam remained stronger than its design requirements after nine years, but its long-term strength increase was limited. Further investigation is needed to clarify the effects of groundwater, soil and binder characteristics, and construction conditions.

Keywords

cement-treated loam

highway embankment

long-term strength

unconfined compression

soil-hardness test

needle penetration

phenolphthalein

groundwater exposure

calcium leaching

Shizuoka Japan