Experimental Study Of The Engineering Properties Before And After Compaction Of Subgrade Loess

Loess, a special soil widely distributing in northwest area of China, is often used as road foundation filling element and foundation soil during the large-scale highway construction of this area. For a long time, various geological disasters always occur in the process of construction and operation of the highway in loess area due to the special engineering property of loess. Therefore, it is of great practical significance to study the physical properties, the strength properties and the collapsibility of loess for preventing and dealing with the geological disasters of loess foundation. The studies and main fruits are as follows:Firstly, changes of the particulate component, pore characteristic and microstructure of the intact loess and the compacted loess are contrasted by the way of grain-analysis and SEM. From the analysis and observation, it could be seen that the surface cementation of conglomeration peels, grain becomes thinner; the original grain framework of the loess is destroyed, the flocculate cline-cementation structure and plank-macrospore cline-cementation structure turns to be embedded structure and pile-up structure, and the structure of loess becomes compacted.Secondly, the changing rules of the intact loess are analyzed through the structure strength test. Strength properties and sensitivity of water of the intact loess and the compacted loess are analyzed through the unconfined compression strength test, shear strength test and the spot loading test on the condition of natural water content and saturation moisture content. The results show that shear strength and bearing capacity are improved evidently, but the sensitivity of water is depressed greatly.Finally, through collapsibility studies on intact loess and compacted loess, the relationship between intact loess collapsibility and pressure and water content are analyzed, in which the mathematic formulation among compactness, dry density, void ratio, modulus of compression, and collapsibility coefficient are concluded and the collapsibility mechanism of loess is analyzed synthetically.