Stability Of Soft Foundation Fill Embankment And Optimization Of Loading Berm Size

Loading berm as one of the soft foundation treatment methods,the features of easy construction and low economic cost make it widely used in the fill embankment with wide terrain or soft foundation treatment failure.In the core problem of how to reasonably determine the loading berm section size,the method based on classical geotechnical theory and engineering experience is somewhat blind;the simplified method of Miyagawa,which ignores the fill shear parameters,is too conservative in its parameter determination and will cause excessive waste of resources.Therefore,in this paper,by reasonably assuming the location of the damage sliding surface of the soft embankment,considering both the fill shear strength parameters and the soft ground shear strength parameters,the simplified Miyagawa safety stability coefficient calculation method is optimized and improved,and its feasibility is verified by geotechnical centrifugal tests and numerical simulations,and the reasonable section size of the loading berm is optimized based on this improved method.The main contents and conclusions are as follows :(1)By reasonably assuming the location of the sliding surface of soft embankment damage and considering both fill and soft soil shear strength parameters based on the Mohr-Coulomb soil strength criterion,the Miyagawa Hayami safety stability factor calculation method was optimized and verified by calculation cases.The results show that the traditional Miyakawa method is too conservative and the error of numerical analysis is more than 50%,and the optimized Miyakawa method is more consistent with the actual project by reducing the error within 10%,which can be a relatively conservative method for calculating the stability coefficient of soft embankments requiring high safety coefficients.(2)Through the geotechnical centrifugal model test,the model of embankment filled directly on soft ground and the model of embankment with loading berm were tested respectively,comparing the test results under different accelerations can be obtained: the safety and stability coefficient obtained by the improved method is closer to the actual engineering situation than the calculation results of the original Miyagawa method;the loading berm can homogenize the stress distribution within the embankment,effectively reduce the rise of soft ground and the uneven settlement of the embankment,and play a good role in It can play a good limiting role in controlling the lateral displacement of the embankment.(3)Through finite element numerical analysis,we simulate the process of plastic deformation of soft foundation embankment and study the influence of soft soil and filler shear parameters on the location of sliding surface of soft foundation embankment.The results show that: the internal friction angle of soft soil has a large impact on the embankment safety and stability coefficient,which cannot be ignored for stability analysis;with the increase of filler shear strength,the embankment plastic deformation zone under the same model extends to the depth of the foundation,and the sliding starting point tends to a region in the middle of the embankment;the safety coefficient increases gradually with the increase of filler shear strength,and the difference of filler shear strength is too large,and the error of Miyagawa method,which ignores its role,is also the larger.Once again,the reasonableness and feasibility of the optimization method are verified.(4)Based on the improvement method,we discuss the reasonable height range and minimum width of the loading berm,study the calculation of the reasonable size of the loading berm under the stability coefficient that meets the specification requirements,and conduct a comparative analysis with the traditional Miyagawa method.The results show that: the berm cross section calculated by considering only the cohesion of soft foundation of the soft embankment is too wide compared with the actual area occupied by the project and the amount of fill soil is large,which wastes too much resources;the optimization method can save more than 30% of the area and fill soil compared with it.