Analysis Of Affecting Factors For Settlement Deformation And Stability Of Subgrade Under Vacuum Combined Preloading Method

Vacuum combined stacking preloading method is an effective method for strengthening soft soil subgrade.With the improvement of China’s industrialization and construction technology,the vacuum combined stacking preloading method has been widely used in civil engineering.However,this method lags far behind engineering practice in terms of theoretical research,construction technology,design theory,etc.Many theoretical issues have not been resolved satisfactorily,such as the deformation effects-vacuum combined stacking preloading stacking rate-and the stability effects of the roadbed with vacuum degree,velocity of loading and permeability coefficient.Therefore,there is great engineering significance to deeply analyze the effects of the loading rate,vacuum degree and permeability coefficient on settlement deformation and stability in the vacuum combined stacking preloading method.The stability analysis methods used commonly and the calculation formula for the settlement rate were introduced in this paper.Taking the 625 area of the experimental section of the vacuum combined stacking preloaded roadbed treatment project in the first phase development area(Zone A)of the central urban infrastructure construction project in the west of Zhuhai as the engineering background,the whole process of the ground treatment process was tracked on-site.The surface settlement and deep horizontal roadbed displacement were monitored and the settlement deformation characteristics was analyzed.On this basis,the finite element simulated calculation of the subgrade model was compared with the measured data to verify the applicability of the model.Using the verified model,the variation characteristics of the settlement and stability of the vacuum combined stacking preloading subgrade under different loading rate,vacuum degree and permeability coefficient were analyzed:(1)For the settlement deformation of subgrade,different influencing factors showed different sensitivities.The degree of vacuum was the most sensitive to roadbed settlement and deformation and the vacuum degree was directly proportional to the roadbed settlement and deformation.The sensitivity of the permeability coefficient to the subsidence and deformation of the roadbed was second that the greater the permeability coefficient represented the greater the settlement and deformation of the subgrade.The stacking rate showed lowest sensitivity to subgrade settlement deformation.The more layers of stacking produced the greater the subgrade settlement deformation.(2)For the stability of vacuum combined piled preloaded roadbed,among the three influencing factors:the loading rate is the most sensitive to the stability of the roadbed,the stability of the roadbed under the staged loading is the highest;The degree of vacuum is directly proportional to the stability.The greater the degree of vacuum,the higher the stability.The permeability coefficient is the least sensitive to the stability of the subgrade.The permeability coefficient has a nonlinear relationship with the stability of the subgrade,and the dispersion is high.There was certain guiding significance for the practical engineering of affecting factors analysis for the settlement deformation and stability of subgrade in the vacuum combined preloading method.The analysis of affecting factors included velocity of loading,vacuum degree and permeability coefficient could achieve better roadbed treatment effect by arranging the construction sequence reasonably and carrying out stacking construction efficiently and safely.