The Technology Research On Improvement Of Expressway Subgrade Saline Soil In North Shandong

Saline soil cannot directly be used to fill subgrade because of its special engineering properties. Engineering construction in saline land area needed to improve saline soil qualified as roadbed filler in order to save the engineering costs. The question how to select a technically feasible and economically reasonable improvement programs needed to be addressed.The paper developed the experimental study on inorganic binder improvement of the typical saline soil in north of Shandong province, combined with the construction of the highway from Jinan to Leling. The main work included room soil tests and microstructure analysis of natural saline soil and improved soil, sensitivity analysis of Pavement Deflection based on orthogonal design, economic evaluation of improvement programs based on the theory of value engineering. The following Conclusions had been received:(1)The physical and mechanical properties experimental studies show that, unconfined compressive strength of each ratio increases with the increase of inorganic binding material content in addition to lime improved project, whose unconfined compressive strength reached maximum when mixing lime dosage arrived9%, Each of the ratios of unconfined compressive strength increased programs with prolongation of age. And the coefficients of correlation were above0.9using the logarithmic function fitting. The early strength of cement improved was maximum and the ultimate strength of lime and fly ash (2to1) was supreme. The resilience modulus of cement improved project was the largest when the dosage was same.(2)This article sensitivity analysis between affecting factors, such as modulus and thickness of surface layer, modulus and thickness of base, modulus and thickness of pavement sub base and resilience modulus of road base, and the deflection on the surface of the pavement.The results of range analysis and variance analysis showed that the influence of soil base resilience modulus of the most significant. The primary and secondary relation of the other six variables is:thickness of pavement sub base, the thickness of the base, the thickness of the surface layer, resilient modulus of the surface layer, resilient modulus of pavement sub base, resilient modulus of the base. (3)The economic evaluation of different function indicators was conducted using the theory of value engineering. Regarding the deflection on the surface of the pavement as the objective function,3%lime+3%fly ash improved solution was optimal, followed by3%lime+3%slag improved solution and3%lime+6%slag. Three of the thirty-six improvement programs have a better overall economy in functional indicators of unconfined compressive strength, resilient modulus and surface deflection values. They were the solution of3%lime+3%cement, the solution of3%lime+3%ash and the solution of3%lime+3%slag.