Reinforcement Treatment And Settlement Analysis Of Highway Soft Soil Subgrade

With the rapid development of China's economic level and the increasing traffic volume,a large number of highway construction often encounter various geological conditions,especially soft soil,which has become a problem that must be solved in the process of highway construction.Due to the characteristics of soft soil,the soft soil subgrade has low strength and poor stability.Subgrade is the foundation of pavement,so it must have sufficient strength and stability.Therefore,it is very important to reinforce the foundation.If the foundation is not properly treated,the subgrade will have large settlement deformation,which makes the road unable to be used normally.In order to ensure the safety and comfort,the settlement control should be strictly required in the design and construction of the road.On the basis of research at home and abroad,this paper studies and analyzes the reinforcement principle and construction technology of several commonly used treatment methods,and compares and analyzes the application scope,treatment depth,construction progress and construction cost of these treatment methods.Taking Chulaiquan fast access as an example,the distribution of soft soil and the selection of reinforcement methods are described.Then the finite element model is established by selecting the cross section of geogrid and cement mixing pile composite reinforcement.Simulate the whole construction process.In addition,two reinforcement methods,geogrid and cement mixing pile,are studied and analyzed.Finally,the influence of different factors on subgrade settlement is discussed.The conclusions are as follows:(1)Based on the Chulaiquan fast access project,the composite reinforcement of geogrid and cement mixing pile obviously reduces the settlement and lateral displacement of subgrade,and reduces the vertical stress level of soil in the foundation.(2)By numerical simulation of ABAQUS software,two strengthening methods of geogrid and cement mixing pile are analyzed.Through the analysis of geogrid reinforcement,it can be concluded from the analysis results that adding geogrid at the bottom of embankment and 0.5m down from its bottom has little effect on the settlement of subgrade,and obviously reduces the lateral displacement of subgrade.With the increase of geogrid layers,the reduction of lateral displacement of subgrade can be superposed.through the analysis of cement mixing pile reinforcement,it can be concluded from the results that cement mixing pile can effectively reduce the settlement and lateral displacement of subgrade.(3)Based on the ABAQUS software numerical simulation,the different influence factors of subgrade settlement are analyzed.The analysis results of pile modulus,pile spacing and pile length are as follows.The change of pile length has the greatest influence on subgrade settlement,the second is the change of pile modulus and pile spacing.When the pile modulus is large,the influence of increasing pile modulus on subgrade settlement becomes weak,and when the pile spacing is small,the influence of decreasing pile spacing becomes weak.The analysis results of silt layer modulus,silt layer cohesion,silt layer friction angle and silt layer permeability coefficient are as follows.The change of permeability coefficient of silt layer has great influence on subgrade settlement,the change of modulus of silt layer has little influence on subgrade settlement,and the influence of cohesion and friction angle of silt layer on subgrade settlement can be ignored.The analysis results of modulus,cohesion and friction angle of the soil layer below the pile end are as follows.The change of modulus and friction angle has great influence on subgrade settlement,while the change of cohesion has little influence on subgrade settlement.The analysis results of embankment filling rate and embankment construction interval are as follows.Both the filling rate and the interval of embankment construction have great influence on the subgrade settlement,so it is necessary to strictly control the filling rate and the interval of embankment construction.The analysis results of embankment filling height are as follows.The higher the embankment fill is,the greater the settlement of subgrade will be,and the height of embankment fill has a great influence on the settlement of subgrade.Figure [58] table [27] reference [51].