| In order to improve the current situation of poor expressway capacity in China,the widely used measures are to renovate existing highways,and most of them use single-sided or double-side widening.China has carried out a lot of in-depth studies on the single-side or double-side widening of highways,but there are few studies on the reserved separation of central dividers.For a more comprehensive evaluation of the working conditions of the subgrade,this paper evaluates the state of the subgrade on the basis of indoor and outdoor tests using dynamic testing equipment,and the finite element software ABAQUS is used to establish the subgrade model to analyze the stability of the existing subgrade.The main contents of this paper are as follows:Firstly,the original soil sample is taken on the existing subgrade for laboratory test.The compaction degree of the roadbed was calculated by the test data,and the influence of the moisture content of the roadbed on the compaction degree and compression modulus is analyzed.Then,using PFWD,GeoGauge soil stiffness/modulus tester and Beckman beam deflection tester to evaluate the bearing capacity of the existing subgrade,respectively obtaining the dynamic resilience modulus and Young’s modulus of the subgrade,and compareding the static rebound modulus obtained by the traditional Beckman beam method.By analyzing the correlation between the static and dynamic modulus of the subgrade and the dynamic and static deflection,it shows that the dynamic and static modulus and the dynamic and static deflection have a good power relationship,which proves that the dynamic modulus and dynamic deflection can be used as the rapid detection and evaluation indicators of the subgrade construction quality modulus and deflection.According to the subgrade deflection evaluation standard and the power model obtained from the field measurement data,the corresponding control standards of the PFWD and GeoGauge soil stiffness/modulus tester are proposed.Thirdly,being combined with the actual expansion and expansion project of the Shi-Xin section of the Huangshi Expressway,the finite element software ABAQUS is used to establish the subgrade model from the filling to the operation for 20 years and the subgrade model of the central separation zone.The numerical simulation is used to analyze the settlement deformation characteristics of the existing subgrade from the filling to the 20-year subgrade and foundation surface.The stability of the roadbed during the widening of the road surface and after several years of operation is analyzed.The differential settlement of the operated subgrade and the reserved subgrade is analyzed.Finally,three countermeasures for the weak subgrade are proposed.The roadbed improvement technology is analyzed in combination with the engineering practice.The effects of the roadbed ash treatment are evaluated by three kinds of testing equipment and numerical simulation.The results show that the road bed ashing treatment is better.The PFWD and GeoGauge soil stiffness/modulus tester can effectively and reliably test and evaluate the subgrade condition. |
