Experimental Study On The Microstructure Of Clay In Changchun Subway Line2Construction Layer

Structural properties of soil have an important impact on its engineeringproperties, and soil’s microstructure and macroscopic properties are inextricablylinked. Engineers usually focus on the clay’s macroscopic properties and neglect theinfluence of clay’s microstructure. In this article, the reserve object is Changchun claywhich is dug from the construction layer of Changchun Subway Line2. Themicrostructure of Changchun clay is analysed through experimental study. The mainconclusions of this article include:(1) Based on XRD test, the main mineral composition is quartz, feldspar,kaolinite, illite and chlorite. SEM can be used to show the microstructure ofChangchun clay.(2) The contact relations of cohesive soil particle before consolidation areside-side, side-face; whereas after consolidation the contact relations is transition forthe side-face, face-face. Due to the consolidation, particles contact more closely andpores trend to be homogeneous.(3) Quantitative analysis of clay’s microstructure is conducted based on SEMtests, MIP tests and digital image processing. The analysis show that: the particles aremutually closer contact after consolidation; porosity decreases gradually, the range ofpore size and pore size distribution is reduced, the quantity of medium pores andmacropores decline, pore area and pore area distribution range also decline. Themicrostructure of clay samples, taken from horizontal section and vertical sectionrespectively, show the same variation law under the influence of consolidationpressure. But the pore size, pore quantity and pore area of clay samples fromhorizontal section change much more quickly. Therefore, Changchun clay soil isanisotropic at micro scale.(4) After3D reconstruction of Changchun clay, the3-dimansional porosity canbe obtained. In the consolidation process, the porosity decrease significantly andparticles contact closer. With the increasing of consolidation pressure, the porositydrop rapidly. The original microstructure quickly change into a new and more stable structure. The combination of SEM graph analysis and MIP test can reveal thevariation of clay’s microstructure in the consolidation more comprehensively.