Author(s)

Tian Kaijie ¹, Chen Kai ¹

Affiliation(s)

¹ Business School, University of Shanghai for Science and Technology, Shanghai, China

Corresponding Author

Chen Kai

ABSTRACT

Shallow in-situ solidification combined with deep cement mixing columns is widely used to control differential settlement behind bridge abutments, yet the mix proportion and stiffness of the solidified layer are still usually chosen by experience. Taking a bridge project in East China as the background, this study tests the mechanical properties of in-situ solidified soil in the laboratory, proposes a mix design method based on the water–cement ratio index, and uses a numerical model to quantify how the modulus and thickness of the solidified layer affect settlement, so that the recommended parameters balance effectiveness and cost. The tests show that the water–cement ratio index — the water–cement ratio divided by the liquid limit — correlates almost linearly with the reciprocal of the unconfined compressive strength (UCS), so soils of different types can be placed in one calibration system; a water–cement ratio of 1.5 is recommended. Strength grows with cement content and curing age (the 14 d value reaches about 80% of the 28 d value) and drops exponentially as the water content rises. Replacing part of the cement with activated mineral powder (6% cement + 2% activated mineral powder) raises the 28 d strength by about 19.3% without lowering the 90 d resilient modulus, so strength and stiffness improve together. The numerical results are less encouraging for simply stiffening the layer: raising the modulus from 60 MPa to 140 MPa cuts the total settlement of the solidified zone by only about 3.3% (less than 1% in the non-solidified zone), whereas each additional metre of thickness reduces it by about 1.68 mm, roughly 5%, which makes the settlement-control efficiency per unit cement consumption about 5–6 times higher. Settlement behind the abutment is evidently governed by the underlying soft clay, and the modulus of the solidified layer is not the controlling variable. In practice, the recommended mix proportion should be used to secure strength and durability, deformation should be adjusted by thickening the layer within equipment limits, and the remaining settlement should be handled through the column parameters.

KEYWORDS

Bridge abutment back; In-situ solidification; Solidified soil; Water–cement ratio index; Unconfined compressive strength; Compressive resilient modulus

CITE THIS PAPER

Tian Kaijie, Chen Kai. Experimental Study on Mechanical Properties of In-situ Solidified Soil and Modulus Effect of the Solidified Layer in Composite Foundation behind Bridge Abutments. Journal of Civil Engineering and Urban Planning (2026). Vol. 8, No.2, 149-161. DOI: http://dx.doi.org/10.23977/jceup.2026.080216.

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