Q <sub> 2 </ Sub> Collapsibility Characteristics,

With the implement of exploitation stratagem in the western of our country, project scale is more and more large, simultaneously the project characteristic of the deep loess is more and more attached importance. There have obvious difference of the loess collapsibility between the era of Q₂ and Q₃ in some project practice, so the research of the loess in the era of Q₂ is important and necessary to our in-depth knowledge. In this paper, the increasing humidity deformation characteristic of the loess and fossil soil in the era of Q₂ and the relation between deformation of collapsibility and microstructure have been researched by the indoor experiments which chiefly include following contents:Firstly, according to the indoor experiments' results, separate protracting the curves of p —δ_s, w—δ_s and w—△δ_s, and the increasing humidity deformation characteristic of the loess of L₂,L₃, L₄,L₅,L₆,L₇ and the fossil soil of S₂,S₃,S₄,S₅,S₆, S₇ in the era of Q₂ have been detailed analyzed , discovering the difference of the collapsible deformation between them by the curves, and firstly putting forward the concept of the sensitive saturation and the sensitive part of the normal route of water content, and inducing the relation of the sensitive saturation and the pore ratio in distinct layers of soil.Secondly, we scanned framework grain which conclude the size,the form, the arranging mode and the contacting relation, pore which conclude the size,the form, the structure and the type, cementation structure which conclude the sort existing mode, cementation degree and microstructure type by scanning electron microscope , and we detailed observe and analyze them. We induce and estimate the relation of microscope and collapsible characteristic, and conclude the loess and fossil soil 's microstructure is the inner cause of it's collapsible characteristic.Finally, by the results of experiments, and combining the project practice, we put forward the distinct view of applicability and rationality, which is that the coefficient of collapsibility equaling 0.015 is the loess collapsible characteristic evaluating standard in the era of Q₂ according to Code for building construction in collapsible loess regions (GB 50025-2004).