Experimental Study On Differential Settlement Of Expressway Subgrade Widened By Solidified Soil

The differential settlement control at the junction of old and new roadbed is one of the technical difficulties in highway reconstruction and expansion.If the differential settlement value is too large,the subgrade will be destroyed,the pavement structure will be affected,the use quality of the road will be reduced,and even the driving safety will be endangered.Aiming at the above problems,this paper,based on the Changsha-Zhuzhou expressway reconstruction and expansion project,uses the solidified soil to fill and widen the roadbed,adopts the means of field investigation,laboratory test,numerical simulation and field test to study the differential settlement and deformation law of the solidified soil widen the expressway roadbed.The main research results are as follows:(1)Based on SEM scanning electron microscope,the interaction process of "curing agent,soil-inorganic mixture" was analyzed,and the action mechanism of curing agent improved soil was proved.The optimal mixture ratio of solidified soil was determined to be 94∶6∶0.02 by orthogonal multi-factor tests.Compared with plain soil,the strength of solidified soil at 7d,28 d and 90 d increases by 20%,66.67% and 107.69%,respectively,the water stability coefficient at90 d increases from 80% to 90%,and the frost tolerance index increases from 55% to 65%.(2)Based on FLAC,the interaction model of new and old subgrade foundation is established Based on 3D finite difference software,the differential settlement and deformation law of new and old subgrade(including ordinary subgrade and solidified soil subgrade)under the influence of subgrade widening width and filling height,subgrade compression modulus,driving load and other factors are studied.The sensitivity order of each influencing factor is:subgrade compression modulus M > widening width L > filling height H;the optimal mix proportion solidification method proposed in this paper is adopted Compared with ordinary subgrade filler,the differential settlement can be reduced by 50.15% ～ 58.71% under the same condition.(3)Through field test,the settlement and deformation characteristics of widened subgrade with solidified soil are studied,and the reliability of numerical calculation results is verified;Two stages of settlement process of widening subgrade with solidified soil in construction period are proposed,namely,rapid settlement period and stable settlement period;Based on the settlement monitoring data of Huanghua interchange of Changsha Zhuzhou expressway,the accuracy of logitics model to predict the long-term settlement of widened subgrade is verified.