Experimental research on application of alkali residue-based lightweight soil subgrade filling

The alkali residue (AR) is a waste byproduct generated during the soda production process using the ammonia alkali method, leading to significant environmental pollution in soil, air and water as a result of its extensive accumulation. The proposed technology and method for producing alkali residue-based lightweight soil (A-LS) with AR is designed to facilitate the efficient reuse of AR. The feasibility of the proposed method is substantiated through the indoor trials and field-filling tests. This study involves an experimental analysis to determine the material proportion and preparation method for A-LS. The compressive strength tests, shear tests, CBR tests, dry-wet cycle tests, freeze-thaw cycle tests and field filling tests are conducted to investigate the mechanical properties, durability and road performance of A-LS. The findings demonstrate that the compressive strength, secant modulus, shear strength and CBR increase with the increase of wet density. These properties exhibit an upward trend with the extension of age. A-LS exhibits remarkable resistance to dry-wet and freeze-thaw cycles, boasting excellent durability. A-LS is applied to the X204 bridgehead of Xuwei-Guanyun section of Lianyungang-Suqian Expressway. The field-filling tests demonstrate that A-LS meets the design and specification requirements in terms of the compressive strength, CBR, resilient modulus and deflection. A-LS demonstrates exceptional capacity to absorb significant quantities of AR waste, resulting in a remarkable reduction of 70% in the usage of the ordinary Portland cement. This substantial reduction in ordinary Portland cement signifies a substantial decrease in carbon emissions. A-LS boasts several noteworthy attributes, encompassing simple process, economic and environmental protection, adjustable density and strength, and wide application range. A-LS exhibits a good application prospect.