The Effect of Moisture Content and the Freeze-thaw Cycle on Loess Tunnel Stability

Seasonal frozen loess tunnel stability is controlled by many factors. To study the effects of water content and freeze-thaw cycles of loess tunnel stability, taking loess in Shanxi Yangqu No. 1 tunnel face as the research object, to do different moisture stability studies on loess tunnel after repeated freeze-thaw cycles. The results show that: (1) by the comprehensive structure potential and structure potential and structure index concept as the theoretical basis, do uniaxial compression test on condition of different water content and different freeze-thaw cycles. The results show that: with th increase of freezing and thawing cycles and water content, the structure index and uniaxial compressive value decrease, which is due to that the structural properties of loess is damaged by water and freeze-thaw cycles. (2)With the increase in the water content of the surrounding rock, wall rock maximum and minimum principal stresses were increased, the tunnel stability coefficient decreases.(3) In condition of same moisture content, the stability factor in tunnel arch and side walls was minimum, indicating that the stress concentration after excavation, soil tends to destroy. The stability factor in tunnel dome was largest, the soil is in a stable condition. With increasing water content in the surrounding rock stability coefficient decreased substantially linear relationship.(4)With the increase of freeze-thaw cycles, the maximum principal stress surrounding rock and minimum principal stresses were increased, stable coefficient decreases. Wall and arch stability factor lower and the magnitude smaller than the dome Vol. 20 [2015], Bund. 9 3904 end of the arch. Hope this paper can provide construction reference in loess distributed area of yangqu even in shanxi.