A microstructural investigation on hydraulic conductivity of soft clay

Abstract

The hydraulic conductivity is a key parameter in geotechnical engineering. It is closely associated to soil microstructure. In practice, consolidation stress, dry density, and natural structure of soil can affect pore diameter and distribution of soil. Thus, to investigate soil hydraulic conductivity, their effects on microstructure and the corresponding hydraulic conductivity were analyzed. The undisturbed soil and the remolded soil with different dry densities were studied by the oedometer tests, hydraulic conductivity tests, and field emission scanning electron microscope (FESEM) tests. The results indicate that the natural structure inside the undisturbed soil is the intrinsic reason that affects hydraulic conductivity. The increase of consolidation stress mainly reduces the number and size of interaggregate pores in terms of provoking aggregation of soil particles. The increase in dry density will fill the interaggregate pores and weaken their connectivity. The area percentage of macropores can be used to reflect the change of soil microstructure. The consolidation stress is the main factor dominating the area percentage of macropores under a high-stress level. A stable intrinsic structure will be developed to inhibit the soil deformation when dry density is 1.4 g/cm3 or above, which helps to restrain the reduction of area percentage and slow down the decrease of hydraulic conductivity. Finally, a brief statistical regression analysis indicates that the area percentage of pores whose diameter larger than 0.4 μm is significantly related to the hydraulic conductivity, which are responsible for seepage in soft clay.