Experimental Study On Deformation Of Vibration Drainage Consolidated Soft Soil Under Traffic Load

With the proposal of the Belt and Road Initiative,the east coast economic zones are ushering in a new round of development.As the main soft soil distribution area in China,many projects such as highways have to be built on the soft soil foundation.Those soft soils usually exhibits poor engineering properties such as poor permeability,low strength,high natural water content,etc.Therefore,the treatment of soft soil foundation and the coresspoding settlement deformation behaviors under cyclic traffic load during the operation period have always been the focus of geotechnical engineering.The economic and effective treatment method of foundation soils has become an urgent need.In the traditional soft soil treatment methods,however,static preloading loading method also undergoes a long construction period and not suitable for some projects with specific requirement;the dynamic compaction method will cause a great disturbance to the soft soil and make the foundation soil structure failure.In addition,vacuum preloading and other related methods are limited due to the high cost.The author's research team previously proposed an improved vabraiton drainage consolidation method to strengthen soft soil foundation by applying a vibration load to replace the traditional impact load.Additionally,a vertical drainage system was set to accelerate the water drainage under the vibration load.This method was named as"vibration drainage consolidation method".In this paper,a series of dynamic triaxial tests and dynamic consolidation tests were carried out.In order to analyze the treatment effect of this method and put forward optimization suggestions from two aspects including drainage effect during construction and deformation under cyclic traffic load during operation after construction.The main results are listed below:(1)The vibration drainage consolidation test results showed that the load ratio has a significant effect on the drainage consolidation of soft soil.According to the test results,there is a critical value of load ratio which generates the best drainage effect,and the value of drainage volumn increases with the increasing confining pressure.The vertical deformation of the specimen increases with the increase of load ratio and decreases with the increase of confining pressure.(2)The cyclic stress ratio has a significant effect on the cumulative axial strain under cyclic traffic load for specimens treated with both static load and vibration load.The larger the cyclic stress ratio,the larger is the cumulative axial strain.When the cyclic stress ratio is larger than the critical cyclic stress ratio,the specimen will fail under cyclic load.When the cyclic traffic load is applied to the vibration drainage consolidated specimen,the cumulative axial strain is affected both by the vibration frequency and the cyclic frequency.When the vibration frequency is the same as the cyclic frequency,the cumulative plastic strain is the smallest.The larger the difference between the vibration frequency and the cyclic frequency,the greater is the cumulative plastic strain.(3)Monismith's model is introduced to fit the cumulative plastic strain of the static load treated specimen under cyclic load.According to the results,the relationship between model parameters and cyclic stress ratio and cyclic frequency is established.Based on the analysis of the dynamic triaxial test results of the vibration load treated specimens,the parameters related to the difference of ?f_c-f_v? are introduced to modify the Monismith model.A modified model considering the cyclic stress ratio,cyclic frequency,and frequency difference is obtained.This modified model can predict the cumulative plastic deformation of the vibration load treated soil softs under cyclic traffic load.