In Situ Stabilization of Problematic Mixtures in a Failed Roadway Subbase: Fid-Bau Portal

In Situ Stabilization of Problematic Mixtures in a Failed Roadway Subbase

Ding, Jianwen / Shi, Minglei / Liu, Weizheng / Hong, Zhenshun

An engineering failure with serious cracks and heaving in the roadway subbase because of the overuse of phosphogypsum was investigated, and an effective stabilization solution was implemented. For this purpose, mix-proportion design, compaction, expansion, and shrinkage tests were performed on the treated mixture to investigate the engineering properties. Based on the laboratory results, in situ tests were conducted to verify the engineering behaviors of the recycled subbase, which included the static plate load test (SPLT), dynamic cone penetrometer test (DCP), Benkleman beam method test (BBM), and portable falling-weight deflectometer test (PFWD). The test results show that the swelling problem can be controlled by adding lime and fly ash to the problematic mixture at a reasonable proportion. The in situ tests show that the average resilience modulus of the SPLT was 191.5 MPa, which is approximately four times the value before the treatment. The dynamic modulus of the DCP test and PFWD test also indicate an increase of approximately $4 - 5 times$ , and the deflection value of the BBM test was only 37.2 mm after the treatment. The in situ test results show that the recycled subbase can satisfy the roadway requirements and present a good performance. The proposed mix proportion of $6.5 % L + 20 % F + 73.5 % H$ was applied in this problematic subbase. The construction control requirements are outlined in this paper. The treated roadway subbase has worked well for nearly 9 years, which indicates a successful application of in situ stabilization.