Experimental Study On The Physical Mechanics Properties Of The Surrounding Rock Of Shanxi Yangqu No.1Highway Loess Tunnel

Shanxi Yangqu NO.1highway loess Tunnel in the research background, this paper elicitsthe physcico-mechanical properties and mechanics index of the loess in YangQu NO.1highway loess Tunnel through experimental research on the loess under the conventionalconditions and freezing-thawing cycles. It builds up a strength degradation mode of theshearing strength of the loess in YangQu NO.1highway loess Tunnel based on moisturecontent and freeze-thaw cycles. By using the finite element software (MIDAS/GTS), the paperconducts numerical simulation for Tunnel construction process and studies on the stability ofsurrounding rocks in different moisture content and different natural freeze-thaw cyclecondition. The main work of the paper is as follows:（1） Researches on direct shearing experiments and consolidation tests on loess of differentmoisture contents show that the cohesion and internal friction angle of high moisture contentloess both get decrease along with the increase of moisture content; moisture content impactsmore to cohesion than to internal friction angle; when moisture content reaches to plastic limitmoisture content, the decreasing speed of cohesion slows down; along with the increase ofmoisture content, the compression coefficient of loess moisture content increases while thecompression modulus decreases.（2） Freeze-thaw cycle experiments under different cycles show that loess appears to havedegradation along with the increase of freeze-thaw cycles; the paper analyses on thedegradation mechanism and concludes that soil mass of higher moisture content sustainsseverer freeze-thaw damage; freeze-thaw cycles slightly reduces moisture content, lowersliquid limit and basically leaves plastic limit unchanged.（3） Through freeze-thaw cycle experiments, direct shearing and consolidation tests, the paper analyses the effect of freeze-thaw cycles to cohesion, internal friction angle modulus ofcompression compressibility coefficient. Test results show that under the condition of the samemoisture content, along with the increase of number of freeze-thaw cycle, the viscosity of loesscohesion obviously decreases, the internal friction angle amplifies slightly, the compressibilitycoefficient amplifies and modulus of compression decreases. To soil mass of higher moisturecontent of the soil, the bigger of change value, the more violent of the deterioration. The paperestablishes a loess strength degradation model which reflects the freeze-thaw cycle indexesand moisture content with the test data, and adopts independent test data to verify theexactness of model.（4） By using the finite element software (MIDAS/GTS), the paper conducts numericalsimulation for tunnel construction process and introduces the strength criteria calculationstability parameters of surrounding rocks of Moore Coulomb. Researches show that with theincrease of rock moisture content, the horizontal and vertical displacements increase rapidly,and the stable coefficient of surrounding rocks decreases. In the same the moisture contentconditions, the horizontal and vertical displacements of surrounding rocks both increase alongwith increase of freezing-thawing cycles. The decrease of the stable coefficient of surroundingrocks indicates the greater threat of high moisture content and freezing-thawing cycles to thestability of surrounding rocks.