Experimental Study And Applicatiaon About Static And Dynamic Seepage Test Of Soft Clay Based On HCA

The hydraulic conductivity(k)of clay during the process of compression consolidation,as an important parameter in geotechnical engineering field,has been widely studied.While the influence of dynamic load on soil permeability characteristics is of little concern,which rendering the existing prediction method difficult to be effectively applied in practical engineering.In order to solve this problem,a new seepage permeater based on the 5Hz hollow cylinder apparatus of Zhejiang University(ZJU-HCA)was developed,the seepage tests of spcimens with different consideration conditions were conducted to verify the effectiveness of this new permeater and summarize its advantages.Moreover,a seris of seepage expriments were carried out to investigate the influence of long-term cyclic traffic load on the hydraulic conductivity and permeability anisotropy of the remolded kaolin samples.The main research works are described belowComparing the test results of HCA permeater with the current mainstream seepage device,it can be found that the HCA permeater can effectively measure the hydraulic conductivity of soft clay under different consolidation conditions,and the axial displacement sensor and flexible wall setting owed by this new apparatus can improve the accuracy of measurement to some extent Moreover,the variation of each strain components in different test stages can be accurately read by the HCA permeater,the funcition is conducive to explore the change of void ratio of specimens as well as the relationship between void ratio and hydraulic conductivity under different consolidation circumstanceThe influence of static load on soil permeability was studied,the results can be summarized as follows:1)The meanasured hydraulic conductivity decreased with the increas of the effective consolidation stress under identical consolidation mode,however,although the confining pressure of isotropic consolidation is larger than K0 consolidation and the calculated void ratio is smaller after consolidation,the measured k value is larger on the contrary,which indicates that different consolidation modes have certain influence on soil permeability.2)Several extensively accepted prediction formulas are used to fit the test results and it is observed the empirical formulas considering the limit moisture content of soil are better than others.3)As for the K0 consolidated specimens,the permeability anisotropy ratio rk increases with the increase of effective consolidation stress.The influence of dynamic load on soil permeability was studied,the results can be summarized as follows:1)the vertical k value of different specimens decreased significantly after the cyclic traffic load,the decrease range was relatively 14.46%?16.74%and 17.01%?22.49%under isotropic and K0 consolidation mode.The decreases of k value cannot be explained only from the accumulated strain of soil,which produced by dynamic load.2)For K0 consolidated samples,an increase of about 5.96%-12.50%in the permeability anisotropy ratio after dynamic load is observed,the maximum value appeared where the effective axial consolidation stress was 200 kPa.3)Cyclic load impact on soil permeability characteristics is not only reflected from the cumulative deformation which makes the k value decreases,but also leaded to the internal porosity redistribution on microscopic and the original particle structure destruction,therefore,it is not accurate to establish the permeability prediction model based only on the macro-parameters of soilAccording to the experimental results of HCA on soil properties,the numerical examples of slope analysis considering strength anisotropy and permeability anisotropy are established respectively.The calculation results based on ABAQUS element finite analysis show that the anisotropy of soil strength has a great influence on the final value(such as safety factor and soil deformation);while the permeability anisotropy affects the development law of the important characteristic parameters(settlement and horizontal displacement)in the consolidation process to a greater extent.Specifically,the larger the permeability anisotropy ratio is,the faster the consolidation rate is.Therefore,the permeability anisotropy of soil should be taken into account when relevant to the issue of controling the soil deformation and settlement during construction period.