Bubbles Transportation In Cohesive Soil With Its Influence On Permeability

Being different from unsaturated soil,gassy soil contains bubbles which are larger than pores of the soil.Although a number of some researches on saturated or unsaturated soil have been conducted in recent years,any investigation into gassy soil still remains few and any specialized experimental setup for investigating consolidation and permeability of gassy soil is rarely seen.With a newly developed multifunction device for test of consolidation,permeability measurement and gas-injection experiment,the fundamental premise of this research is to study the bubbles transport process in soil and its impact on permeability of soil by investigating a kind of soft clay in the west of Hangzhou.This research consists of four parts as follows:(1)On the foundation of previous research,a newly developed multifunction device is proposed for test of consolidation,permeability measurement and gas-injection experiment.Without limitation or drawback of water-gas separation and sealing,the device is easily assembled to accommodate a wide variety of the tests.Test reliability of the device is validated by the implemented test for consolidation and permeability measurement of saturated soil,which indicates that the experimental results of the new device are in accordance with that of conventional device.(2)Consolidation test is implemented with the newly developed device.Variation of settlement of soil,pore pressure on the bottom of soil and permeability coefficient is investigated under different consolidation pressure.Experimental results show that pattern of changes in settlement over time is consistent under different levels of consolidation pressure and effect of saturation of soil or stiffness of sensors on pore pressure on the bottom of the soil is lagged.Based on empirical formulas,relationship between permeability coefficient and void ratio is also obtained in this research.(3)Gas-injection test is implemented with the newly developed device.Firstly,remolded soil is consolidated under certain consolidation pressure,and then gas-injection experiment is implemented by adding different air pressure.Experimental results indicate that either higher air pressure or less consolidation pressure is profitable to shorten the penetration time of gas through the soil,speed up the process of drainage and increase the permeability of soil.(4)Combined test of consolidation and gas-injection is implemented with the newly developed device.Remolded soil is consolidated under different pressure and simultaneously injected gas with different air pressure.During the process of consolidation and gas-injection,penetration time of gas through the soil,drainage,deformation and permeability coefficient.Experimental results reveal that either higher air pressure or less consolidation pressure is profitable to shorten penetration time of gas through the soil,speed up the process of drainage and increase the permeability of soil.Besides,impact of consolidation pressure on experimental results is greater than that of air pressure.