Study On Mechanical Properties Of Loess-Like Compacted Soil

In recent years, the fundamental facilities in northwest areas gained more and more attention with the switch of the economic policies of government. Therefore, how to construct on the backfill becomes a big problem for all the engineers and researchers due to its special topography characteristic. For all the backfill structures, the compact quality of backfill foundation is the key point to ensure the realization of indexes of backfill, such as strength, stiffness and safety and further meet the safety requirements of the superstructure. The construction water content and degree of compaction after compacted are the normal indexes to check the quality of backfill in all compaction standards.The degree of compaction is defined as the ratio of the maximum dry density tested in site and laboratory compaction test. However, the calculation of construction degree of compaction may have big errors. The accuracy of measurement of dry density should be considered first which need to pay more attention. Therefore, the study of effect of compaction effort on the mechanical properties of backfill has significant meaning for engineering use.The loessy backfill in Lvliang, Shanxi was tested in this study to investigate the effects of water content and compaction effort on the void ratio and compressibility coefficients of unsaturated or saturated compacted backfill, shear strength, cohesion and friction angles. The conclusions are drawn out as follow. (1) With the increase of compaction effort, the maximum dry density is increased while the optimum water content is decreased. And with the increase of compaction effort, the increment of maximum dry density becomes smaller.(2) With the increase of water content, the void ratio decreased, i.e., the compressibility coefficient increased. With the pressure increased, the difference of compressibility between soil samples with different water content becomes smaller. Under the same water content and vertical pressure, with the increase of compaction effort, the void ratio decreased. The relationship between the compressibility coefficient and compaction effort is affected by the water content. The compressibility coefficient is the smallest at the optimum water content while the compressibility coefficient decreased with the increase of compaction effort beside both side of optimum water content.(3) With the increase of water content, the shear strength decreased while increased with the increase of compacted effort. After the soil sample saturated, the shear strength decreased sharply and the decrement of shear strength increased with the decrease of water content. With the increase of water content, the cohesion decreased. The compacted effort has certain effects on the cohesion but does not show any relationship. Generally, the friction angle decreased with the increase of water content. With the increase of compacted effort, the friction angle increased monotonously.