Experimental Research On Direct Shear Sichuan-Tibet Railway Permafrost Seasonal Coarse Particles

Sichuan-Tibet region by geographical constraints, Sichuan-Tibet Railway in the construction of the inevitable need to traverse a large number XinDuQiao represented by high-altitude cold area rich water talus slope, riverbed and groove seasonal frozen soil areas. According to existing studies and observations indicate that this type of permafrost slope alluvial material in the season of freezing and thawing can occur slowly slip or flow deformation characteristics of the design of such railway Cut Slope, construction and security operations will be adversely affected. Currently, the construction of Sichuan-Tibet Railway is imminent, it must be water-rich region XinDuQiao foot slope in seasonal frozen soil engineering properties of coarse particles a study as soon as possible. The resulting research will Sichuan-Tibet Railway in the high-altitude cold water talus slope area of survey and design method provides theoretical support for the rich, the rest of the permafrost zone similar parameter selection, line selection and other important guidance and reference.Since XinDuQiao region to alluvial coarse particles mainly permafrost, soil test in accordance with the requirements of the test specimen to produce larger, and therefore can not follow the conventional test methods for carrying out the physical mechanics test requires a special machining suitable test apparatus coarse physical and mechanical parameters of frozen soil. Designed with a diameter of 30cm,20cm height direct shear test case, the wall thickness of the steel tube production 1 cm, the loading system using hydraulic jacks.By interior shear test study 5mm,10mm,20mm,30mm diameter breccia soil and gravel round in natural soil were saturated, natural freezing and thawing, freezing and thawing shear strength under saturated conditions. Process and analyze comparative data, obtained such influence soil moisture, freezing and thawing, particle size, soil and other conditions on the shear strength.This paper has been moisture, freezing and thawing, the particle size, the soil is coarse influence of seasonal frozen soil shear strength XinDuQiao in:when the moisture content increases, the shear strength of coarse grained soil will be reduced; when the particle size increases, the soil coarse grains increased, so that soil shear strength increases; soil only after a freeze-thaw, fine grained soil because the soil frost resistance, shear weakened the coarse grained soil sample shear strength, so the soil shear strength after freezing and thawing of the soil samples than not thaw low shear strength; large under the same conditions, round gravel soil shear strength is always better than brecciated shear strength.