Study On Monitoring And Prediction Of Soft Foundation Settlement In Wuxue Section Of Mayang Expressway

Mayang expressway starts from Shanghai-Chengdu(Mazhu section)expressway in the north and reaches hang-rui expressway in the south.It is an important link to improve the layout of Hubei highway network and promote regional economic development.Among them,most of the road sections in Wuxue are located in the hehu accumulation plain area and the river alluvial plain area,and the soft soil is widely distributed.According to the characteristics of soft soil in different areas,the project adopts a large number of soft foundation treatment technologies such as preloading,replacement filling and CFG pile.In order to ensure the quality of soft foundation treatment and subgrade construction and reduce the post-construction settlement of soft soil subgrade,the research on tracking settlement monitoring and settlement prediction of soft soil subgrade was carried out in this project.The following work was mainly carried out:First of all,typical sections(K149 + 509 ~ K152 + 504 huangnai lake farm section,K155 + 820 ~ K159 + 346 alluvial plain section of the north bank of the Yangtze river)were selected for tracking subsidence observation.According to the 280-day settlement monitoring data,choose three typical sections of different processing conditions for settlement changes analysis found that processed K158 CFG pile + 640section(360.8 mm),the largest settlement in the K157 + 590 section of filling processing settlement(232.8 mm)times,directly after the clearance,fill K150 + 610 section settlement minimum(214.4 mm),the section of soft soil foundation treatment effect is up to the engineering requirements;In the process of embankment filling,the settlement increases with the increase of the height of filling,and the settlement changes with the height of filling presents a similar ladder growth trend.Due to the influence of filling load,the settlement rate of roadbed is positively correlated with the filling rate,that is,the faster the filling rate is,the greater the settlement rate is.Secondly,the hyperbolic method,exponential curve method and poisson curve method are respectively used to perform curve fitting and settlement prediction for the settlement changes of three typical sections.The exponential curve method is only accurate when the settlement time is 100 days.When the hyperbola is used to predict the settlement,the K150+610 section with the least disturbance of undisturbed soil is the most ideal,while the K158+640 section with the most damage to the original soil is the worst.Then,three typical sections were selected and the settlement prediction numerical analysis model was established by using FLAC3 D software to simulate the settlement of roadbed.Through comparison,it is found that the simulated value is larger than the measured value and has certain regularity,which also verifies the rationality of thenumerical simulation.Therefore,the numerical model can be used to predict the settlement of the roadbed before construction,so as to provide reasonable Suggestions for the construction scheme.Finally,the settlement prediction hyperbola method,the predicted value of the predicted values and the FLAC3 D numerical simulation method of comparative analysis found that: hyperbola method because according to the measured settlement data to forecast accuracy is higher,and because FLAC3 D numerical simulation based on experimental data and the ideal forecast,without considering the effect of consolidation and secondary consolidation,leading to a lower prediction accuracy.