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The objective of this paper is to propose a compaction control method that facilitates the use of expansive soil, as embankment material for highways in humid climates. Three types of expansive soils, utilised as general embankment fill in Southern China, were selected for investigating the physical, compaction, and shear strength properties. The compaction-control method was proposed based on the compaction curve revealed by the dry preparation method, associated with the corresponding soaked California bearing ratio. The site test and long-term monitoring were conducted in an embankment in Ningming, which was filled with compacted expansive soil controlled by the suggested method. The laboratory test results showed that the maximum dry unit weight obtained from the dry preparation method was less than that generated from the moist preparation method, while the optimum moisture content acquired from the dry preparation method was greater and closer to its natural moisture content. The moisture content corresponding to maximum CBR was 2% larger than the optimum moisture content. The in-situ monitoring results presented that the moisture content of the constructed embankment was close to its natural moisture content or plastic limit, the maximum settlement was 70.6 mm, and the maximum horizontal displacement was 20 mm. [ABSTRACT FROM AUTHOR]

• Strength and stiffness of calcareous sand is enhanced by using PFA for chemical stabilization. • The influence of PFA on calcareous sand characteristics are different for varying particle gradation. • The shear strength as well as CBR of calcareous sand is greatly improved when stabilized by PFA. • The test results are useful in determining the optimum content of PFA to be used in a particular calcareous sand with specific particle gradation. The calcareous sand existing at the South China sea is characterized by low shear strength with high compressibility. Associated with particle breakage, foundations built on such problematic soil initiates undrained failure with uneven foundation settlement, unless adequate ground improvement technique is adopted. In this paper, chemical soil stabilization is carried out by applying Polyurethane Foam Adhesive (PFA) to the virgin soil. Improvement of strength and stiffness of the treated soil have been investigated in detail by a series of triaxial consolidation and drainage tests followed by California bearing ratio tests. The effect of particle gradation on the stress–strain curve and CBR values of the stabilized calcareous sand as well as the influence on peak shear stress and shear strength index has been studied. The test results show that the PFA is effective in improving the mechanical properties of calcareous sand. The particle gradation has significant effects on the stress–strain response of the stabilized calcareous sand under different PFA contents. Optimal PFA content for each grading of calcareous sand was proposed. The test results of this work would be beneficial for engineering practice in dealing with the bearing capacity and settlement of foundations involving calcareous sand. [ABSTRACT FROM AUTHOR]