Laboratory Tests On Consolidation Behavior Of Marine And Backswamp Soft Soils Under Vibration Drainage Conditions

Soft soils are widely distributed all over the world.Due to different genesis,the soft soils of different sedimentary facies have different physical and mechanical properties.In addition,the structures of soft soils are different in different regions.On the basis of dynamic drainage consolidation technique,this paper attempts to replace the impact load with the cyclic vibration load,and puts forward the vibration drainage consolidation technique to reinforce the soft soils in Lianyungang and Zhenjiang,and compares with the drainage effect under static load.Through the tests of vibration drainage consolidation of marine and backswamp soft soils,the consolidation characteristics of soft soils with different sedimentary facies are analyzed in the consolidation process.Optimization tests of the backswamp oft soil are carried out under the method of vibration drainage consolidation to analyze the suitable technical parameters for improving the drainage effect.Tests of backswamp soft soil with different confining pressures are studied to research dynamic response under vibration drainage consolidation.The research contents are shown as follows:(1)Consolidation characteristic analysis of marine and backswamp soft soils.On the basis of the basic physical and mechanical index analysis of marine and backswamp soft soils,a series of laboratory tests are conducted by a self-developed dynamic consolidation oedometer to research consolidation characteristic.Drainage response of marine and backswamp soft soils is researched by applying static load firstly then dynamic load as well as exerting static load and dynamic load simultaneously on the early stage of the test;The marine and backswamp soft soils are used to produce low disturbed soil and reconstituted soil to study the impact of disturbance degree;Reconstituted backswamp soil is used to research moisture content influence under vibration drainage conditions.The soft soils are applied to the rectangular waveform,triangle waveform and sine waveform to analyze influence of the consolidation efficiency;it is analyzed that the axial accumulative strain and drainage volumetric strain of marine and backswamp soft soils vary with time.The results show that: it has good effect for the consolidation drainage of soft soil by exerting static load then the dynamic load in the early stage of the tests;The lowerdisturbance degree of soft soil,the higher is the consolidation efficiency;With the increase of water content,vibration load can significantly improve the efficiency of drainage consolidation of soft soil;The vibration load in the form of rectangular can produce larger drainage volumetric strain and axial accumulative strain;Under the same confining pressure,frequency and load conditions,When the displacement volume is stable,the consolidation time of backswamp soft soil is shorter than marine soft soil.(2)Analysis on the effect of vibration drainage consolidation of backswamp soft soil.tests are conducted on backswamp soft soils by changing the initial static load,step static load duration,the initial time of vibration load and vibration load frequencies to study effect of drainage consolidation.According to the axial accumulative strain and drainage volumetric strain,reasonable parameters of vibration drainage consolidation method are determined.The results show that: the initial static load,step load duration and the starting time of vibration load have a significant effect on the axial accumulative strain and drainage volumetric strain;In the consolidation process of soft soil,it has different effects on soft soil consolidation to change the frequencies of vibration load.(3)Analysis of dynamic response of backswamp soft soil under different confining pressures.The static loads and vibration loads of different frequencies are applied to backswamp soft soil to analyze the drainage volumetric strain,axial accumulative strain and drainage volumetric strain rate after 24 hours of drainage consolidation under different confining pressures.The results show that confining pressure and frequency have important influence on the consolidation of soft soil.