| The large-scale construction of freeway in our country began in the 1990’s, and continues to this day. The old roads cannot meet the traffic demand, need to renovation and expansion to increase capacity. Based on expansion projection of west hub interchange acceleration/deceleration lane extend engineering of Liujing Freeway in Guangxi, this paper makes a research on technical difficulties of expansion project in high liquid limit soil area. The main works of this paper are as follows:(1) The physical properties of high liquid limit soil in the project area are studied by experiment. According to local situation, a physical improvement plan of high liquid limit soil by mixed with gravel is proposed, and the physical properties of modified soil are tested. Designed three plans of embankment filling by high liquid limit soil, gravel improvement, gland method, the geotextile reinforced method, sandwich method and et al. are applied comprehensively. Then the subgrade quality of test road is tested, the result shows that filling the high liquid limit soil without improved in the lower layer of subgrade through gland method is feasible.(2) Analyzed the influence of different load positions to the stress of pavement structure, and the influence of differential settlement of subgrade to the stress of pavement structure by a finite element model, demonstrates the necessity of established roadbed model in the finite element model. Thereafter, applied the load in the most unfavorable load position on the pavement, and analyzed the vertical shear stress and horizontal bending tensile stress of pavement structure, and vertical shear stress and axial tensile stress of pull rod. It is discussed that the influence of the inner stress of pull rod and pavement structure with different diameter, length, distribution density of pull rod. Study on the suitable step sizes in pavement conjunct, and propose the suggested sizes of surface course and base course. The influence of stress of pavement conjunct with different properties of geotextile is also discussed.(3) Considering the problem of insufficient strength of old pavement, propose different improved plans of traffic flow, and put forward different plans of pavement conjunct, and compare the merit and demerit of various plans. |
