Experiment Study On The Cracking Mechanism About Loess In The Tunnelling Environment

The Loess Plateau is one of the areas where geological hazard frequently occurs, theloess slope deformation and failure are more common in geological disasters.Generally theloess slope destruction was due to surface water along the vertical fractures infiltrationchanged slope of soil and groundwater conditions caused by the physical and mechanicalproperties, so research on crack formation mechanism in loess, is the base on study ofgeological disasters in loess.This paper is based on the National Natural Science Foundation“study on the slump mechanism of loess slopes in cave sub-erosion environment”, using theexperimental study the crack formation mechanism in loess.First summarized all kinds of existing research results and opinion about the cause ofloess crack, through field observation found that the loess contraction deformation in theprocess of the moisture content from high to low is the main reason to cause the produce offissure formation, thus set up the topic, carry out experimental study.On the base of remodeling loess without binding under the free boundary condition ofexperiment, the shrinkage characteristics of loess were proved normal shrinkage, shrinkageprocess residual shrinkage, zero shrinkage three different stages, and use the MCG-B modeland the GRO-C model two kinds of formula fitting, to verify the results, this will pave belowloess have outer boundary conditions under the action of dry cracking test.Then under the environment of different temperature and humidity field, applyingdifferent boundary conditions,study the cracking characteristics, determine the crackingprocess along with the time samples’ change rule about the moisture content,crack length andcrack development, and analyzed the crack sample volume change rule, further demonstratethe effect of the different temperature and humidity field to loess craze.Based on the experimental results combined with field investigation, further confirmedthe cracking and the collapse by caves under different temperature and humidity field havegreater effect on the stability of the loess body, also is one of the precondition to cause thedisasters such as landslides, slump.